Light Metals 2015

Problem of bauxite grade declining is now becoming a global scenario. That is why, for many years, scientists have been studying the problem of bauxite beneficiation. Complex mineralogy of bauxite, high content of alumina and process limitations often make traditional beneficiation techniques ineffective.The use of different kinds of radiation jointly with sorting techniques has been intensively studied in Russia, that resulted in development of new direction of beneficiation — X-Ray sorting. Currently this is a separate direction of beneficiation widely and selectively applied for lump separation of different ore types, including bauxites. This can be used for reduction of silica content and carbonate/sulfur removal in bauxites. The paper shows feasibility to use this technique for improvement of quality of hard to beneficiate bauxites located in the Urals, Russia and analyzes applicability of this method to other bauxites of the world.

High-sulfur bauxite is being paid more and more attention due to the decreasing grade for traditional ore in China. There is rich high-sulfur bauxite with low-median grade in Chongqing, which is being treated with Bayer process with dressing. But there still exist excess impurities of sulfur and iron in the alumina product. The effect of surface density, particle size, temperature and time on the roasting desulfurization process was studied. The optimized roasting conditions are as follows: 750 °C, 60 minutes, the surface density of 7.6 kg / m2 and the particle size from 147 μm to 177 μm for the ore. Under these conditions, residual sulfur in the roasted ore is lower than 0.4%, which can meet the requirements of alumina production. Meanwhile, the digestion performance of the roasted ore improves. Roasting desulfurization might be one of methods for treating high-sulfur bauxite with low-median grade, and better technical and economic results might be attained when it is used to treat high-sulfur bauxite with organic and / or goethite impurites.

To increase the proportion of lower grade bauxite in the utilized feed and also the possibility of increasing A/S ratio (Al₂O₃ to SiO₂ mass ratio) in the plant feed (4.66), some investigations have been carried out on improving A/S ratio of Elburz Bauxite, especially lower grade ones, by gravitational method and flotation. To evaluate heavy media separation, heavy liquids with different specific gravities in the range of 2.8–3.4 (g/cm3) have been used on various size fractions of this bauxite with initial A/S ratio between 1.3–8.5. A special specific gravity can produce the concentrates (in sunk fractions) with the A/S ratios and productivities which can economically be used as plant feed . Pilot plant tests also carried out on a 25t sample of Bauxite with a A/S ratio of 2.0 and concentrate A/S and recovery in DMS tests were 3.40 and >40%, respectively

The Alumina Rondon project consists of a bauxite mine, beneficiation plant and an alumina refinery, along with its associated logistics. It will be installed in the Rondon do Para municipality in the Para state — northern Brazil. The refinery production capacity is three million tons of alumina per year. For this production, 12 million tons of ROM will be beneficiated, resulting in 8 million tons of washed bauxite. The beneficiation process will occur in a single line plant at 1.500 tons per hour. During the early stages of the project engineering, a characterization study was conducted. Such a study consists in the evaluation and quantification several key aspects of the material needed to proper equipment sizing. To confirm the values of the laboratory scale studies, an industrial scale test was done in the operating bauxite beneficiation plant installed in the Mirai municipality located in the state of Minas Gerais — southeast Brazil. The test was done with two bulk samples obtained from two pilot scale mines. The main aspects evaluated were: product loss, product contamination and effects of residence time in the scrubber.

A novel self-stirring tubular reactor driven by pressure energy used in bauxite digestion process is presented originally in this paper. This reactor combines the advantages of autoclaves and conventional tubular digestion equipment, it can restrain scale at high temperature and high pressure and intensify mass and heat transfer. Stirring of the novel reactor only needs the pressure energy of the liquid. Performance of self-stirring reactor driven by pressure energy was studied in this paper. High-speed photography was adopted in the paper to research the effects of various factors on rotating speed in the self-stirring reactor driven by pressure energy. The results demonstrated that fluid pressure has the most outstanding effects on stirring speed of the novel reactor, and the effects of fluid density and viscosity on stirring speed are minor.

Based on the actual production data of gibbsite refinery in Vietnam, prediction model of heat transfer coefficient is established due to the mechanism of heat transfer, which is validated by actual production data. The results show that the predicted and the actual ones are in good conformity. The main factors affecting the heat transfer coefficient are analyzed, and the main measures to control the scale are put forward. It can help to arrange the cleaning period, ensure the digestion technical indexes, and stabilize production process.

In this paper, a study was made on digestion behavior of sulfur in high-sulfur bauxite. It was investigated that the effects of temperature, time, lime dosage and initial caustic concentration on digestion behavior of sulfur. The results show that sulfur in high-sulfur bauxite goes into solution mostly in the form of S2”; the digestion rates of sulfur increase at first and then decrease with the increase of lime dosage; the digestion rates of sulfur increase with the increase of temperature, initial caustic concentration and digestion time; in this experiment, the process conditions for getting higher digestion rate of alumina and lower digestion rate of sulfur are temperature 260 °C, digestion time 60 min and lime dosage 13%, under these conditions, digestion rates of alumina and sulfur are respectively 84.16% and 40.04%). And research results reveal both S2− and S₂O₃2− in solution can be removed completely by wet oxidation in digestion process.

The presence of sulfate and carbonate ions in the aluminate liquors results in the creation of scale on heat exchange surfaces during heating and evaporation. As inhibitor the liquid silicone polymers of siliconate type was used. Inhibitor is added directly into the substance. The effect of inhibitor concentration on the degree of sulfate and carbonate sediments encrustation of heat exchange surface of evaporator equipment was found. The results obtained in pilot and industrial conditions showed that with increasing concentration of inhibitor the speed of encrustation slows down. Complete cessation of encrustation achieved with the addition of inhibitor in the liquor is evaporated in amount of about 35 ppm. The results of using the inhibitor are expressed in steam consumption reduction for evaporation and grow capacity.

Bauxite slurry and heated caustic liquor are fed into digestion reactors for alumina extraction. The main parameter of the reactor output, the A/C (alumina/caustic) ratio is adjusted manually through the bauxite flow, based on laboratory analyses that are made to calibrate the system every two hours. Since many variables interfere in the A/C ratio, such as bauxite and liquor composition and scaling process, the measurements have low reliability, making this control not effective. This case focuses on Fuzzy technology application in a bauxite digester in order to control the bauxite slurry.The software does not require phenomenological knowledge to control the A/C ratio and uses empirical rules to estimate it. By anticipating production variances, the process variability was reduced by 50%, which saved 3.2% of the steam used for caustic liquor heating.

In the digestion process of diasporic bauxite, due to precipitation of silicon and titanium compounds, a hard, dense mineral fouling are formed at the digestion device wall, causing heat transfer coefficient decrease. The phases of mineral fouling were analyzed by X-diffraction analysis, infrared spectroscopy, scanning electron microscopy and thermal analysis. In view of mineral characteristics of Chinese high silica and hard to digest diasporic bauxite, the mineral composition and microstructure of the silicon titanium mineral fouling have been analyzed. The mineral fouling prevention and removal methods have been studied. Using bauxite slurry pre-desilication and pre-detitanation we can effectively reduce and prevent the mineral fouling formation; and application of acid leaching can soften the hard and dense silicon titanium mineral fouling, and by high pressure water washing, the mineral fouling can be easily washed away.

High calcium/aluminum ratio (C/A=12:7) is one of the main problems which inhibit the development of lime sinter process. Decrease the C/A of clinker is studied in this paper. 12CaO•7Al₂O₃ (C₁₂A₇) and CaO•Al₂O₃ (CA) were synthesized at 1350 °C by analytical pure reagents. The phase composition of sinters was analyzed by XRD and the alumina leaching experiments were carried out. The results show that the optimal alumina leaching ratio of C₁₂A₇ and CA are 93.40% and 73.18%. The leaching experiments of the mixture of C₁₂A₇ and CA with different proportions were carried out. The alumina leaching ratio of the mixture reaches 91.12% when the content of C₁₂A₇ is 40% (in mass). Above this proportion, the alumina leaching ratio increases little. The results show that the existence of C₁₂A₇ can promote the leaching property of CA.

The three-dimensional multiphase flow in a large-scale seed precipitation tank stirred with multiple Intermig impellers was simulated by CFD method. The flow field, solid particles distribution and power consumption were numerically analyzed by adopting Eulerian Granular Model (GEM) and standard k-ε turbulence model. The tank was improved by lengthening the lowest impeller and adopting sloped baffles which largely promoted the solids suspension and fluid mixing. In the original tank, the maximum of relative solid concentration difference in the whole tank was less than 5% at the minimum rotational speed of 4.8r/min. Although the lowest lengthened impeller cost more power, the minimum rotational speed could be down to 3.8r/min. So in the improved tank, about 40% power could be saved to achieve the same mixing effect. The results have important meaning to industrial design and optimization.

There is lots of heat and water vapor in alumina calciner gas. Almost all alumina refineries exhaust the gas that is about 150 degree C directly. A method was provided to recover both sensible heat and latent heat at the same time using the patented equipment. The thermal balance was calculated. Hot water can be obtained, which can be used to wash aluminum hydroxide and residue. And the exhausted gas after recovering would be below 70 degree C.

All commercial Smelter Grade Alumina (SGA) is produced by Calcination of Aluminium Hydroxide in Alumina Refineries. The Aluminium Hydroxide, or Hydrate, is precipitated from a super saturated solution and classified into fine seed and coarse product for Calcination in rotary kilns or stationary calciners.Over the past 40+ years significant technology changes/shifts has taken place in Refineries and Aluminium Smelters, the only customer for SGA. The drivers for these changes were and still are Economy of Scale, Energy Efficiency and/or improved Environmental performance.Following an introductory review of the major technology changes/shifts that has taken place, the associated challenges in SGA quality is reviewed. Emphasis will be on Alumina properties from Calcination in Rotary Kilns and Gas Suspension Calciners (GSC) at low or high temperature onwards into Smelting, such as: Particle Size, Strength and Dust Generation & Management, HF Generation and Capture, Alumina Feeding and Dissolution. Finally the impact of major chemical impurities will be discussed. The current SGA quality requirements beyond consistency are summarized with a view to optimization of the available Hydrate Precipitation and Calcination technology. Future SGA quality requirements are discussed from a Calcination point of view as the intermediate processing step between the Refiner and the Smelter, including its potential constraints or drawbacks.

Calcination is the last step in the production of alumina from Bauxite. In modern refineries this step is carried out in stationary calciners, such as Circulating Fluidized Bed (CFB), Gas Suspension (GSC) or Fluid Flash (FF) Calciners. These technologies have been available for over 40 years, and are thus very far matured. The technologies have developed substantially and many boundaries have been pushed, sometimes close to the theoretical limit. Yet the development has not stopped and new concepts and technologies are being explored. In this paper the authors discuss, from a supplier perspective, what was driving the design in the past, at present and possibly in the future, and also what the challenges typically encountered are.

This paper aimed at studying the carbonation process — the core process of “Calcification-Carbonation”, and a venturi carbonation reactor to process calcified residue was innovatively designed and produced. The simulated calculations for dynamic characteristics of gas-liquid-solid three-phase flow were discussed under different superficial gas velocities. Results showed: with the increase of gas velocity, gas holdup increased and solid holdup decreased slightly. Fluid turbulence intensity and collision and coalescence of bubbles were enhanced with the increase of gas velocity, which was beneficial to the mass transfer and reaction among gas, liquid and solid. The measured values agreed well with the simulated calculations obtained by CFD, which indicated that it was feasible to use this model to simulate the gas-liquid-solid three-phase flow field in this reactor and the results of numerical simulation were reliable. The above results provided a theoretical basis for the design of the reactor under a high temperature and a high pressure.

Bayer process of alumina production involves generation of considerable mud tonnage (1.5 – 3 t of red mud per 1 ton of alumina) with high content of scandium and rare earth metals up to 120 g/t and 1500 g/t respectively. Scandium is difficult-to-obtain and expensive element (oxide price – 99.9–99.99% is between USD 4 000 – 5000 per kg). The main applications are the high quality alloys, high temperature ceramics, luminescent materials, dielectrics.In frames of creation of ecologically friendly technology to utilize red mud, RUSAL is developing process of scandium concentrate recovery based on the carbonization leaching of scandium. This process allows improvement of the efficiency of red mud processing by scandium recovery and partial caustic removal with alkali recycling to the process. This technology excludes the acids effluents and can be easily implemented into existing process circuit. This paper presents the results of the laboratory trials of red mud processing with scandium concentrate generation, as well as the data on the pilot unit to produce scandium concentrate at one of the alumina refineries in Russia.

Results of using of Outotec’s technological solution for liquid and solid phase separation for processing of aluminum raw material to alumina and chemical products are shown. Laboratory test work simulating Outotec SUPAFLO thickener with alumina production sludge showed that capacity can be increased at least in 1,3 times while reducing flocculant consumption in 3 times compared with existing technology. High density of thickened product and low solids content in overflow were achieved. Pressure filters, vacuum filters and capillary ceramic disk filters using in Outotec technological flowchart for red mud and amorphous aluminum hydroxides filtration and washing allow getting product with required chemical composition with 21–80% residual moisture level and 35–280 kgDS/m2 ∙h capacity.

The Alumina Rondon refinery will have a production capacity of 3.0 million tons of smelter grade alumina per year. For this production, approximately, 11.0 million tons of bauxite Run of Mine (RoM) will be necessary. This bauxite must be washed prior being fed in the refinery, and so, the beneficiation plant will dispose 3.0 million tons (dry basis) of bauxite reject. The moisture of this material, at the moment of disposal, may vary from 88% to 25%, depending on the dewatering method. The moisture is a conditionant to the disposal, ranging from discharging the pulp in tailing ponds or back filling mined areas with mechanical dewatered reject.This study evaluated different ways of treatment, handling and disposal of the reject. The comparison was made in terms of Capital Expenditure (CapEx) and Operational Expenditure (OpEx). The compared indicator is the Net Present Value of the accumulated Free Cash Flow (FCF). This comparison allows to evaluate the best financial solution for the life of the project. The evaluated scenarios included combinations between ways of dewatering the reject (natural settling, thickening, supperfloculaltion and pressfiltering) and ways of diposing it (tailing ponds, heightened tailing ponds and mine back fill). The superflocculation option has the lowest CapEx while back filling mined areas with press filtered reject saves 30% of the value of the base case scenario: direct disposal in tailing ponds without previuos thickening.

Currently, production of stable pelletized materials for blast furnace remains a major challenge for iron and steel metallurgy. The use of red mud with a low content of alkaline elements allows intensifying sintering processes of agglomerate and making pellets from ores and concentrates of ferruginous quartzite. Structural studies have shown that the beneficial effect of low alkaline red mud occurs at the stage of melts in high temperature sintering zone.RUSAL ETC in cooperation with MISIS develops a process for introduction into sintering mixture of sintering aids on the basis of red mud to improve the agglomerate quality and to raise capacity of sintering machines. For the production of pellets a process is in development for activation of bentonite clay with Bayer red mud aimed to raise iron content in sintered pellets, to reduce consumption of expensive natural bentonite and to improve quality of sintered pellets.A complex of laboratory and plant investigations has been conducted; the results obtained testifying viability of introduction of sintering aid and complex binding agent on the basis of red mud at enterprises of iron and steel metallurgy for the production of agglomerate (sinter) and iron ore pellets.

The key parameters for the effective control of settlers and washers are interface and mud level. Manual measurement of these is risky and labour intensive. Using Smartdiver, it is now possible to automatically track suspended solids and density within the entire profile of the vessel, providing more accurate measurement of interface and mud levels that are easily integrated with a control system.Using this data, control strategies of varying complexity from standard feedback to feed forward and model predictive control can be employed, resulting in significant reduction in overflow suspended solids with minimum flocculant consumption.Enhanced control of mud level can increase underflow density resulting in less liquor passing to washers in the case of settlers, whilst improving the efficiency of washers within a CCD circuit. Increased underflow density in tailings thickener will reduce the volume of slurry entering the tailings dam, subsequently increasing its lifespan.By optimizing the performance of settlers, washers and tailings thickeners, significant cost and environmental benefits can be achieved with the use of Smartdiver.

With the rapid development of the electric power industry in China, the amount of fly ash discharged is growing day by day, which brings great harm to the production industry and people’s living conditions. In this article, hydro-thermal method and alkali fusion -hydro-thermal method have been used to prepare 4A zeolite from coal fly ash. The results indicate that the optimum conditions (calcination temperature 850°C, ratio of silicon to aluminum in raw material 0.8, alkalinity of NaOH 2.5mol/L, the aging time 6h, crystal temperature 90°C and crystal time 24h), the specific surface area of the prepared zeolite is 605.6m2/g. The synthesized 4A zeolite has a uniform particle size with a narrow distribution. Its shape is cube and in rules, and all its properties are close to 4A zeolite purchased in the market.

One of the process stages of kaolin clay processing to alumina is solid-liquid separation process after HCl leaching with subsequent washing of silica residue. Our laboratory studies have shown that of existing equipment most efficiently for this task pressure filter can be used. Slurry after hydrochloric leaching is amenable to filtration under 5 bar pressure with good parameters, in spite of material being fine (relatively d₅₀ = 17 µm). Type of filter media has no significant influence.The main process parameters were established in the lab scale using press filter with washing. It was also noted that after fourfold washing, filter capacity (by filtrate) was reduced from 2.5–3 to 0.3–0.6 m3/(m2∙h). Study of these phenomena by means of XRD and Electron Microscopy analysis showed that the reason is gelation of amorphous silica while рН of washing water approaches 7.

Enormous emphasis is placed on the specific energy consumption from the refining of alumina from Bauxite. The current spread of specific energy consumption of the industry varies from 7 GJ/tonne to 21 GJ/tonne. Energy consumption is highly technology specific with digestion and calcination accounting for sixty percent of refinery thermal energy consumption. With Greenfield projects placing a high importance on fuel consumption in order to make their projects viable, careful selection of the technology will have an immediate impact on the energy consumption and in turn the fuel consumption which could ultimately determine the financial viability of the refinery throughout the lifetime of the project. This paper seeks to analyze the energy consumption requirements for different digestion and calcination configurations, such as single vs split stream digestion along with alternative methods of final stage heating; as well as calcination technology options and also their impact on the financial viability of the refinery itself.

The role of sustainability is becoming more pre-eminent in the development of projects in the mining and minerals industry, including the Bauxite and Alumina industry. However the relationship between sustainability criteria and their applicability to the Bauxite and Alumina industry is not always clear. In addition it may appear at times that implementing sustainability criteria negatively affects project economics. A previous paper addressed sustainability in the Bauxite & Alumina industry, reporting guidelines, sustainable development goals, and corporate sustainability targets [1]. It also discussed bauxite deposit quality criteria and sustainability, and concluded that quality criteria for the evaluation of a bauxite resource span economic, environmental and social aspects, and concluded that economic and environmental aspects (in some cases social aspects) are often intertwined. Put differently: economically more attractive deposits are also more attractive in environmental terms (sometimes in social terms).The current paper builds on these results and explores the relationship between sustainability and ten key design criteria for alumina refineries in the context of applicable Global Reporting Initiative (GRI) sustainability performance indicators.

Calcium-silica residue is the leaching residue of the lime sinter process which is used to extract alumina from low-grade bauxite or fly ash. The major phases of this residue are dicalcium silicate and calcium carbonate, and the minor phases are aluminates. A large amount of calcium-silica residue is produced because of the high material flow of lime sinter process and most of it is stockpiled. The main contents of the residue, CaO and SiO₂, are the same as the main contents of ceramic glass. Therefore, the production of ceramic glass using calcium-silica residue as the main raw materials, B₂O₃ as fluxing agent and P₂O₅ as nucleation agent is reported on in this paper. XRD and DSC are used to analyze the property of the ceramic glass. The results show that the flexural strength and corrosion resistance of the ceramic glass obtained through a melting method are better.

Fly ash is a very important unconventional aluminum resource in which the alumina content comes up to 40 ~ 60% in part of China. It has great economic and environmental value to exploit the recycling method of fly ash and produce high value-added multi-alumina products. In this paper, preparation of pseudo-boehmite by using Inner Mongolia Datang fly ash sintering clinker has been investigated. After a series of processing under optimized conditions (dissolution at 80°C, 60min, liquid solid ratio 4:1, first stage desilication 120min, 170°C, sodium silicon slag 100 g/l, sec-stage desilication 120 min, 90°C, CaO content 15 g/l), the silica ratio of the solution reaches up to 838, which conforms to the requirement of the industry. The pore volume of the seed precipitation product reaches 0.8291cm3/g, which is almost the same with standard sample. The Na₂O content of pseudo-boehmite prepared is below 0.3%, which can meet the sodium content requirements of general catalyst.

Motivated by an increased focus on recycling of aluminium alloys, for which elements like Mn, Fe and Si tend to increase, a comprehensive investigation of the softening behavior during annealing after cold rolling of Al-Mn-Fe-Si alloys has been carried out. It is clearly demonstrated that the kinetics and final microstructure are the result of a delicate balance between processing conditions and microchemistry. In general, at the same processing condition, more and finer dispersoids, whether preexisting or formed during annealing (concurrent precipitation) strongly affect the kinetics and either mainly suppress recrystallization or give coarse non-equiaxed recrystallized grains. Faster softening kinetics is observed at large deformations and conditions less affected by dispersoids, together with equiaxed fine grains. The precipitation behavior before the completion of recrystallization is accelerated by high solid solution levels of Mn, large deformations and high temperature. However, even with a strong supersaturation of Mn in solid solution, annealing at high temperature accelerates recrystallization so that it is mainly completed before substantial concurrent precipitation take place, giving a fine equiaxed grain structure. Moreover, annealing treatments at low heating rates produce more inhomogeneous microstructures than isothermal annealing.

The hot deformation behavior of 7150 aluminum alloys micro-alloyed with 0.12% Zr and 0.11% V was investigated using uniaxial compression tests conducted at various temperatures and strain rates. The results show that the flow stress levels increase significantly due to the additions of 0.12% Zr and 0.11% V. The activation energy for hot deformation has generally been treated as a constant value for a given material in literature. Using revised Sellars’ constitutive analyses, the activation energy of a material is considered as a function of deformation temperature and strain rate. It is found that the activation energies of all three 7150 alloys decrease with increasing deformation temperature and increasing strain rate. The activation energies of the alloy containing 0.12% Zr are remarkably increased compared with the base alloy at most deformation conditions studied. The 0.11% V addition generally increases activation energies at the majority of deformation conditions, except at low temperatures and at low strain rates. Comparing the activation energy maps over all the deformation conditions applied for three alloys, the effects of micro-alloying of Zr and V on the plastic deformation under specific deformation conditions can be better understood.

Controlling the microstructure developed during hot rolling is of great importance to controlling final material properties. Changes in processing parameters and chemical composition alter the recovery-recrystallization-grain-growth processes that control microstructure evolution. To better understand these processes in two Al-Mg alloys, cylindrical specimens were subjected to hot compression at temperatures from 300 to 500°C with a fixed strain rate of 1.0 s−1. Upset specimens were immediately quenched by He gas to preserve their deformed microstructures. Specimen sections were then annealed to separate the dynamic and static components of microstructure evolution. Specimen microstructures were characterized by optical and electron microscopy. Grain size and the degree of recrystallization were measured as functions of specimen chemistry, compression-test conditions and annealing conditions. The experimental results are interpreted to better understand the mechanisms of microstructure evolution and to evaluate new paths to microstructure refinement during hot rolling.

The paper presents the results of the mechanical properties of AlMgSiCu aluminum alloys with vanadium in an amount of 0.1 and 0.2 wt.%. During solutioning heat treatment and aging which were compared with those for the material without the addition of copper. The reference material was 6xxx alloy without copper and vanadium. Analysis of the structure of the transmission electron microscope (TEM with EDS) revealed the role of vanadium in the heat treatment process.During the aging, in addition to precipitation of the phases Al₂Cu and Mg₂Si, the finely vanadium and vanadium-iron phases was observed. The size and distribution vanadium phases were also dependent on the chemical composition of the alloy. It was found that in AlMgSuCu alloys with vanadium clearly relies Rm and Rp0,2, the additive vanadium in an amount of 0.2 wt.%. increases elongation almost doubled. The optimum heat treatment parameters was determined for states T6, T61, T64 and T7.The information on the role of vanadium in the process of strengthening of precipitation are sporadic [3–6]. It is only known that vanadium acts as a grain refiner and also lowers the conductivity and raises the temperature of recrystallization [4,5]. Investigation of the effect of vanadium in an amount of 0.1% in the alloy 6063 [6] found that the kinetics of vanadium accelerates precipitation of phase β′ and β″, which in turn will have an impact on strength and yield strength of the material after aging.

It has been reported that ultimate tensile strength of commercial 7075 alloy is improved up to about 1 GPa by high-pressure torsion (HPT), which is one of the typical methods of severe plastic deformation. In the present study, Al — (8, 10) % Zn — 2 % Mg — 2 % Cu — 0.25 % Cr — (0, 1) % Fe alloys, in mass %, were prepared by high-pressure die-casting (HPDC) or by gravity casting (GC) to study the effect of process conditions before HPT process on the mechanical properties after HPT. The tensile strength of the alloy HPTed at 2 GPa was increased up to 900 MPa, irrespective of process conditions before HPT. On the other hand, the process conditions affected the tensile elongation; the specimens prepared by HPDC show higher ductility than those by GC. This result is related to size and distribution of second-phase particles.

In order to assess the influence of the solution heat treatment temperature in the mechanical and electrical properties of AA6201 drawn wire, samples were solution heat treated at different temperatures (both above and below the solvus limit), quenched, deformed and artificially aged, so as to reproduce the actual wire manufacturing conditions. The relation between the mechanical and electrical properties of the rod and the solution heat treatment temperature was thus obtained, focusing primarily on the practical impact and consequences of such temperature variations regarding the attainable final product properties. It was observed that a minimum solution heat treating temperature of 510°C is desirable in order to reach the optimal conditions for the final product. Failure to reach such temperature leads not only to lower mechanical properties of the wire, but also reduces the elongation to fracture of the rod.

We have calculated liquidus projections in the typical sections of the Al-Ni-Fe-Mn-Si system up to: 9% Ni, 3% Fe, 3% Mn, and 3% Si (%wt). We have identified concentrations of elements enabling primary crystallisation of the Al₃Ni, Al₉FeNi, Al₃Fe, Al₆(Fe,Mn), and Al₁₅(Fe,Mn)₃Si₂ intermetallic phases. We have demonstrated close agreement of the experimental data and calculated data. Primary crystals of two phases — Al₉FeNi and Al₆(Fe,Mn) will most likely form during casting to metal moulds in the area of nickalyn compositions. Primary crystallisation of the Al₃Ni and Al₁₅(Fe,Mn)₃Si₂ phases is possible only at higher Ni and Si concentrations respectively, while formation of the Al₃Fe phase requires slow solidification achieved through casting to expendable moulds.

In this work, performed in close collaboration with PACCAR and Magna International (Stronach Centre for Innovation, SCFI), a 6xxx series aluminum alloy was used for the development of an A-pillar cover for the cab of a typical heavy-duty Class-8 truck. The use of Al alloy for the A-pillar cover represents an approximately 40% weight savings over its steel or molded fiberglass composite counterpart. For the selected Al alloy, a small amount of cold work (5% tensile strain), following prior hot-forming, was found to significantly improve the subsequent age-hardening response. The role of solutionizing temperature and rate of cooling on the age-hardening response after paint-bake treatment were investigated. For the temperature range selected in this work, higher solutionizing temperature correlated with greater subsequent age-hardening and vice-versa. However, the age-hardening response was insensitive to the mode of cooling (water quench vs. air cooling). Finally, a two-step forming process was developed where, in the first step, the blank was heated to solutionizing temperature, quenched, and then partially formed at room temperature. For the second step, the pre-form was reheated and quenched as in the first step, and the forming was completed at room temperature. The resulting A-pillars had sufficient residual ductility to be compatible with hemming and riveting operations that occur during downstream cab assembly.

Because of the evolution of structural requirements for some aircraft components, which are required for longer life time and high temperature conditions operation (up to 90 000 hours at up to 250°C), developing an accelerated ageing process becomes essential to observe and understand the ageing of aluminum alloys and predict the influence of such process on the mechanical behaviors of these alloys under temperature. The alloy considered in this study is an as cast Al-Si-Cu-Mg aluminum alloy. In this presentation, microstructures and mechanical properties of the material in its initial non-aged state are compared to those obtained after different ageing treatment. Changes in mechanical properties are related to changes in terms of precipitation through precipitate size. Higher temperature conditions accelerate the ageing phenomenon and thus enable us to reach an infinite ageing state from which, with a time — temperature equivalency, we will be able to build a computer model of accelerated ageing.

The growing demand for increasingly more cost and energy effective electronics components is a challenge for the manufacturing industry. To achieve higher thermal conductivity in telecom components, an aluminum alloy with a composition of Al-2Si-0.8Cu-0.8Fe-0.3Mn was created for rheocasting. Yield strength and thermal conductivity of the material were investigated in the as cast, T5 and T6 heat-treated conditions. The results showed that in the as-cast condition thermal conductivity of 168 W/mK and yield strength of 67 MPa was achieved at room temperature. A T5 treatment at 200°C and 250°C increased thermal conductivity to 174 W/mK and 182 W/mK, respectively, while only a slight increase in yield strength was observed. Moreover, a T6 treatment resulted in similar thermal conductivity as the T5 treatment at 250°C with no significant improvement in yield strength. Therefore, the T5 treatment at 250°C was suggested as an optimum condition for the current alloy composition.

Vehma/Cosma Engineering a Division of Magna International, the U.S. Department of Energy and Ford Motor Company initiated the Multi Materials Lightweight Vehicle (MMLV) Project in 2012. The goal was to design and build prototype vehicles, maintaining donor vehicle architectural space in an effort to reduce mass relative to a 2002 baseline vehicle target. The result of this study was a 23.5% reduction in vehicle weight compared to the current donor vehicle.This paper reviews the mass reduction and performance of aluminum high pressure vacuum die cast (hpvdc) body structure components, integral to the lightweight BIW architecture of a C/D segment an aluminum-intensive vehicle. Selected stiffness, durability and crash requirements are assessed. The BIW structure incorporates aluminum castings and extrusions, as well as aluminum and steel sheet, assembled using structural adhesive bonding and a variety of joining technologies. No other body structure in high volume production incorporates this combination of materials and joining processes. The eight hpvdc aluminum castings in the MMLV body structure were specially designed to maximize crash performance and assembly costs (part count reduction), offsetting the differential in material cost relative to steel construction.

High-strength aluminum alloy sheet materials are of interest to automobile manufacturers for components that can significantly reduce vehicle mass. But, the practical application of these materials is limited by low formability. Warm forming offers a potential means to overcome this limitation. The warm-forming behavior of an AA7075-T6 sheet material is investigated using direct electrical resistance to rapidly heat material for tensile testing. These experiments probe the potential to use rapid heating from the hardened T6 condition to form under retrogression conditions that provide ductilities significantly better than those possible at room temperature. The key advantage of this approach is the possibility to recover nearly full strength by reaging after warm forming, which may be possible through the paint-bake cycle alone. The development, implementation, and validation of the direct electrical resistance heating tensile testing system are discussed. The results of tension tests and retrogression-reaging experiments are presented.

In the present research activity EN AW 7068 alloy samples have been analyzed, from morphological and mechanical point of view. Extrusion process has been employed for the alloy production. As industrial routine, following the manufacturing the alloy has been submitted to different thermal treatments. Thermal treated samples have been extracted by cutting procedures and the obtained samples, have been submitted to standard laboratory preparation and then to morphological and mechanical characterization. Some preliminary SEM analysis reveal the presence of secondary particles. The secondary phase grains are mostly uniformly distributed in both longitudinal and transverse sections. Moreover, especially in the longitudinal section, the grains appear organized along parallel lines to the extrusion direction. According to the EDS analysis results these particles are prevalently made of Al, Cu, Zn and Mg. With the goal to achieve the dissolution of Cu-rich phases, two new solution heat treatments were performed at 470°C for 48 h and at 470°C for 24 h. Effectively, the new solution heat treatments have allowed to reach the dissolution of Cu-rich phases and secondly allowed to obtain a more homogeneous microstructure, especially for as regard the microstructure of cross section. So these thermal treatments could be adopted to dissolve Cu-rich phases that are deleterious for the mechanical properties.

To remain competitive, wrought aluminum alloys should offer the customer improved mechanical properties, achieved through recycling. To ensure this, it is necessary to organize a scrap yard with different material streams, each with a proper and well-controlled chemical composition, and to develop the software for calculating the proper combination of material streams that is essential for achieving the required alloy composition. An algorithm was developed for calculating the optimum combination of material streams for providing the standard composition of the pre-melting mixture, the required mechanical properties of the alloy and the minimum cost of production within the entire processing chain. It does not favour in advance the formulation of alloys with an increased amount of scrap, but selects a solution based on the optimum cost of production. The algorithm is also useful for tailoring recycling-friendly compositions of wrought aluminum alloys and for optimizing the production technology.

The microscale deformation of an Al-Mg alloy with a bimodal grain size distribution, consisting of coarse grains (CGs) and ultrafine grains (UFGs) is studied through finite element methods. Procedurally generated models are created to characterize the behavior of this micro structure at different scales. The mechanical response of individual grains is represented through crystal plasticity laws, which include accommodations for solute and grain size strengthening effects. These effects are quantified through multiscale models allowing for experimental calibration. Additionally, the behavior of grain boundaries is included through cohesive interface models. Using these techniques, grain scale deformation is characterized, load distribution between the two phases is examined, and the roles of crystal anisotropy and interface accommodation are considered.

Findings from quasi-static and impact loading of aluminum (AA6082-T6) and magnesium (AZ31B-F) circular extrusions when subjected to crush and cutting modes of deformation are presented. Circular cross sectional extrusion geometry with a thickness of 1.5 mm, a diameter of 62 mm, and lengths equal to 300 mm were selected. Dynamic loading resulted from impact with a dropping mass of 57 kg at a velocity of 7 m/s. Under cutting deformation, the aluminum alloy extrusions generated lengthy chips ahead of the cutter followed by stable formation of petalled cut side walls. The magnesium extrusions, illustrated the formation of small chips and sides walls which often, although not consistently, fractured. Energy dissipation was noted to be greater and the deformation more stable for the aluminum extrusions. Under a cutting deformation mode, energy dissipation of 0.621 – 0.684 kJ for the magnesium extrusions was found compared to 1.20 – 1.23 kJ for the aluminum extrusions.

Numerical simulation is used to improve the productivity and optimize casting process in today’s foundry. The accurate estimation of heat transfer coefficients (HTC) at the metal-mold interface is essential to simulate casting solidification processes. In this work, a 5-step casting mold was employed with section thicknesses of 2, 4, 8, 12, 20 mm. Wrought aluminum alloy 7075 was squeeze cast under an applied pressure of 60MPa in a hydraulic press. By placing the type-K thermocouples at different locations of each step in the mold, the casting-die interfacial IHTC in the 5-step casting were evaluated from the measured temperatures by applying the polynomial curve fitting method. The results from the estimation indicated that the wall thickness of squeeze cast wrought aluminum 7075 significantly influenced the value of IHTC. The peak IHTC value increased as the step thickness increased.

Al-Mg-Si-Cu alloys exhibit natural aging, which negatively influences artificial aging. Additions of trace elements have been recently shown to eliminate this effect: At room temperature quenched-in vacancies are trapped by trace solutes in the ppm range and natural aging is supressed, while at higher temperatures these vacancies are released and artificial aging is promoted. In this study we determine an optimum in chemical composition and solution heat treatment temperature for Sn and In-doped Al-Mg-Si-Cu alloys. Automated thermodynamic calculations coupled with a statistical evaluation of influencing parameters on solubility of Mg, Si, Cu, Sn and In were used to find maximum strengthening potential and dissolved trace element content. Theoretical predictions are compared to aging experiments. The method enables detailed and rapid analysis of a wide compositional and temperature space in multicomponent systems.

This research was focused on refining the microstructures of Al-5Fe alloy by increasing cooling rate during solidification and adding alloying elements. Under the condition of near-rapidly solidification, the primary Al₁₃Fe₄ phase was refined to the order of magnitude of 10 microns. Adding silicon to the alloy resulted in changes to the morphologies of the primary phase from starlike pattern to polygonal and firework-like patterns. The addition of silicon and cerium gave rise to further refinement in both primary and eutectic iron-rich phases to a significant extent.

Many of the aluminum casting alloys used today are based on the Al-Si eutectic system because it imparts to the alloy excellent feeding ability and resistance to hot tearing. However, strengthening of these alloys by precipitation hardening is limited to a few alloying elements; and therefore, it is desirable to find an alternative eutectic system that would become the basis for a new generation of aluminum casting alloys with higher strength. Towards this end, the Al-Ni, the Al-Fe, and the Al-Fe-Ni eutectic systems are investigated. In this, the first of two papers, the casting ability and tensile properties of these three eutectic compositions are measured and compared to those of the Al-Si eutectic. Based on these comparisons, it is concluded that all three eutectic compositions are viable alternatives to the Al-Si eutectic.

Based on their casting ability and tensile properties, the Al-Ni, Al-Fe, and Al-Fe-Ni eutectic systems have been shown to be potential alternatives to the Al-Si eutectic system for fabricating aluminum casting alloys. The micro structure of these eutectics consists of long fibers within an essentially pure aluminum matrix and it has been envisioned by many that modifying the micro structure by breaking down these fibers would lead to enhanced tensile properties. In this, the second of two papers, a method for effective modification of the micro structure of these eutectics is described and the resulting micro structures and tensile properties of the modified alloys are characterized. It is found that the ultimate tensile strength and yield strength of the modified alloys are lower than those of the unmodified alloys, but their ductility is higher.

The influence of solidification conditions on the microstructure of Al-Si-Cu alloys was examined using two molds: an endchill mold that provided different cooling rates along the solidification axis, and a sand mold comprising different fins. Melt hydrogen, Sr, Ti levels were also varied. In all 24 alloys/135 conditions were investigated. Statistical analysis of porosity data for end-chill mold samples showed good fits for percentage porosity, and average/maximum pore area/pore length response parameters. At low solidification times, pores nucleated predominantly in intergranular regions, were mostly elongated, and occurred along the grain boundaries. Probability of pore nucleation in interdendritic regions increased at higher solidification times, and pores were more rounded. In sand castings, hydrogen levels of ~0.3 ml/100g produced extremely large pores, even at high cooling rates. For sound castings, proper melt degassing and preheating of the sand mold are essential to ensure against occurrence of reaction porosity along the casting surface.

The microstructure and tensile properties of as cast Al-20%Si-1.5%%Ba hyper-eutectic alloys are presented. All sample alloys in as cast condition showed\ microstructure that is comprised of an almost primary Si free Al-Si eutectic. The eutectic silicon appears as flake/fiber in morphology and assumes the width of flake/fiber in the range of sub-micron. The alloys show a very high ductility of about 7% and exhibit UTS of 130 MPa.

Grain refinements were an effective method to improve the mechanical properties of aluminium alloy, and heterogeneous nucleation was widely applied in industry to achieve a grain-refined. In this study, grain refinement behavior of 55%Al-Zn-1.6%Si alloy by Al-Ti-B was investigated. In order to obtain the microstructure in situ, high-temperature liquid quenching by stainless steel pipe was used to capture the sample snapshots. Then, the effect of Al-5Ti-0.2B on the alloy was analyzed by microstructure, solid fraction and grain size. Our results show that the grain size of 55Al-Zn-Si alloy decreased after the Al-5Ti-0.2B addition to some extent, and in order to understand the effect of refinement, it was necessary to analyze the mechanisms of Ti in 55Al-Zn-Si alloy. Meanwhile, during the process of solidification, the solid fraction of 55Al-Zn-Si alloy was further increased with the temperature decreasing, and the result was consistent with our calculation of phase diagram. Finally the reactions were identified using calculation of phase diagram.

As fuel price increases, automobile industries are looking for more fuel efficient cars with less carbon emissions and high crashworthiness. Accordingly, this has necessitated for further research into the formability of Al 6xxx series alloys that have low weight and high strength properties. Since Al 6xxx series alloys are used in automotive panels, their formability characterization is essential. Hence, it is important to study the Forming Limit Diagram (FLD) which predicts the limit strains which in turn, can be imposed safely during forming. The present work manly focuses on determining the Forming Limit Diagrams of Al6061-T6 alloy experimentally. The measurement of limit strains was accomplished using Digital Image Correlation Technique. The Hill — Swift model was used to predict FLD theoretically and a good agreement was found with the experimental results. Experimental results show that the use of appropriate formability parameters and reasonable processing methods can improve formability of Al6061-T6 alloys.

Though warm and hot sheet forming operations enhance the limited formability of aluminium alloys, the high cost and low production rates make them unfit for the demanding automotive sector. A non-isothermal stamping approach, referred to as hot blank — cold die (HB-CD), promises a fast/economic alternative while overcoming the limited formability issues of the material. This, however, necessitates characterizing and modeling the complex material behavior over a wide range of temperatures and strain rates, which is the prime focus of this work. Detailed mechanical testing, aided by digital image correlation (DIC), is carried out on an automotive-grade 5182 aluminium alloy sheet. A phenomenological model is developed and is shown to successfully capture the isothermal behavior of the material over the full temperature/strain rate range for HB-CD stamping.

The plastic instability phenomenon Portevin-Le Châtelier effect (PLC) was investigated in a Rheocast Al-Si-Cu alloy. The effect of strain rate under as-cast, solution treated and water quenched as well as artificially aged conditions was studied. Tensile tests were conducted at room temperature at different strain rates ranging from 10–5 to 10–1 (1/s). The nature and type of PLC effect were identified and analyzed. The results showed that the PLC effect changed with strain rate. Heat treatment of the material, widened the range of strain rates exhibiting PLC as well as changed the nature of the PLC effect.

Aluminum alloy AA7075 sheets were deformed at room temperature at strain-rates exceeding 1000 /s using the electrohydraulic forming (EHF) technique. A method that combines high speed imaging and digital image correlation technique, developed at Pacific Northwest National Laboratory, was used to investigate high strain rate deformation behavior of AA7075. For strain-rate sensitive materials, the ability to accurately model their high-rate deformation behavior is dependent upon the ability to accurately quantify the strain-rate that the material is subjected to. This work investigates the objectivity of software-calculated strain and strain rate by varying different parameters within commonly used commercially available digital image correlation software. The results show that except for very close to the time of crack opening the calculated strain and strain rates are consistent and independent of the adjustable parameters of the software.

The microstructures and the bending performance in rolling direction (RD) and transverse direction (TD) of an AA6016-T4P automotive sheet were investigated. The surface necking forming mechanism together with the initiation and propagation of shear bands during bending were studied in detail. The results indicated that no macro-crack formed in both RD and TD specimens after 180o bending, but RD specimen exhibited inferior bendability compared with TD specimen, showing more severe surface necking. The anisotropy of surface necking in the AA6016-T4P sheet was caused by special crystallographic texture, rather than grain shape and spatial distribution of the constitute particles. The total volume fraction of Goss_ND90, R, P, and Cu orientations was almost twice as that of Goss orientation in the AA6016-T4P sheet, resulting in the facilitation of the initiation and propagation of shear bands in the RD specimens. Two bundles of shear bands intersected at the surface where strain localized, forming the surface necking, so RD direction had more severe surface necking than TD direction.

Al-Zn-Mg base alloys prone to show hydrogen embrittlement (HE) when exposed and deformed under hydrogen related atmosphere. To suppress HE of the Al-Zn-Mg base alloys, the addition of copper is reported to be effective. However, the role of copper on the suppression of HE has not been fully cleared. In the present study, hydrogen in the deformed microstructure was visualized by means of hydrogen microprint technique together with mass spectrometry. Using HMT, it was revealed that hydrogen was released preferentially from grain boundaries, slip lines, and intermetallic particles. The tendency of hydrogen trapping around the particles was prominent in the Al-Zn-Mg alloys containing copper. In contrast, hydrogen was released mainly from localized slip lines and grain boundaries in the Al-Zn-Mg alloy without copper. The difference of hydrogen trapping state in the microstructure could be related to HE sensitivity of Al-Zn-Mg base alloys.

In the current research, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to determine the structural stability of nanostructured Al-5.7wt.%-Ni mechanically alloyed (MA) eutectic alloy powders. DSC traces were employed to determine the variation in the amount of stored energy and dislocation density as a function of milling conditions. SEM imaging was employed to investigate the degree of structural stability against grain growth as a function of the isothermal heating of MA milled powder. TEM was utilized to investigate the influence of isothermal heating on the MA nanoscale structured powders resistance to coarsening. It was found that the increasing the milling energy (RPM, ball-to-powder-ratio and time) resulted in increasing the amount of stored energy as well as increasing the dislocation density, which increased the susceptibility for grain growth.

The Al-Zn-Mg-Cu alloys have been widely used as aircraft structure materials because of their high strength to density ratio. These alloys in the T6 temper are known to be highly susceptible to stress corrosion cracking (SCC). In the present investigation, a comprehensive study on the effect of RRA treatment on the strength and corrosion properties of AA 7049 aluminium alloy has been made. The retrogression heat treatment is varied from 2 min to 60 min at temperatures between 1800C and 2400C; the re-aging treatment was done for 24 hours at 1200C. Within the scope of this investigation, the results indicate that, the susceptibility for corrosion can be decreased by subjecting the alloy for RRA treatment. It is found that the grain boundary precipitate coarsening and enrichment of copper in the grain boundary precipitate are the factors responsible for improvement in reducing susceptibility to SCC.

Al 5xxx alloys can become sensitized to intergranular corrosion (IGC) and stress corrosion cracking (SCC) because of the precipitation of intergranular β phase (Al₃Mg₂) when exposed to elevated temperature for sufficient time. In this study, ASTM G67 mass loss tests of Al 5083 H131, H116 and Al 5456 H116 aged at 323 K and 343 K for different times were conducted. The average grain size and grain boundary thickness of the three alloys were obtained from Electron Backscattered Diffraction (EBSD) images, and the classical nucleation theory was used to predict the precipitation behavior. Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to characterize Al 5083 H116 aged at different temperature for different times. Scanning Electron Microscopy (SEM) images of Al 5083 H131 etched for different times were used to evaluate the corrosion behavior of different grain boundaries.

Al-Mg-Si alloys are widely used in cast, wrought and extruded form. A characteristic property of these alloys is the negative effect of natural pre-aging at room temperature on artificial aging. Minor additions of Sn suppress the adverse effect of room temperature aging due to controlled buffering of quenched-in excess vacancies at low temperatures. In this study we evaluate the buffering performance of Sn in the temperature range between 5 and 45 °C. This is investigated for two Sn-added AA6061 alloys with systematic variation in their Mg-, Si- and Cu-content, for comparison the natural aging kinetics of a Sn-free alloy is studied. In general a strong dependence of hardening kinetics on temperature and on chemical composition is observed. Results of aging kinetics are discussed in terms of common clustering theories and the temperature dependent trapping effect of Sn on excess vacancies.

Minor alloying elements had been used to modify the solidification process leading to improve mechanical performance of Aluminum casting alloys. However, difficulties in balancing strength, ductility and the subsequent precipitation strengthening heat treatment remain. In this study, use of nano-structured silanols based on partially-condensed polyhedral oligomeric silsequioxanes (POSS-silanol) was examined. The silanols react with active aluminum surface to form stable Si-O-Al bonds, while cage-like POSS core enables control of subsequent solidification process leading desired mechanical performance. Specifically, trisilanol phenyl POSS modifier was added to the casting alloy A4047. Using standard casting approach, a highly refined fine fibrous of eutectic Al-Si formed instead of the irregular flakes, which lead to a significant improvement in its ductility while improve the tensile strength as compared to the unmodified A4047. This newly developed approach was expanded to other heat-treatable casting aluminum alloys with specific interest on changes in the eutectic Al-Si microstructure.

The effects of LiOH, Na₂MoO₄, and BTA on the corrosion behaviors of copper and copper-nickel alloy in 60% LiBr solution was studied by AC impedance measurements. Results indicated that LiOH, BTA, and Na₂MoO₄ could inhibited the corrosion of copper and copper-nickel alloy in LiBr solution respectively. When they were used together, the inhibition efficiency was higher than that of used one of them. They behaved a synergistic effect on inhibiting the corrosion of copper and copper-nickel alloy in 60% LiBr solution. It presented that when the concentration of LiOH, Na₂MoO₄ and BTA was 0.10mol/L, 150mg/L and 150mg/L, respectively, they behaved the highest inhibition efficiency on the corrosion of copper and copper-nickel alloy in 60% LiBr solution.

The influence of strontium, bismuth, lead and tin alloy, magnesium and other alloying components on the microstructure evolution of superficial films of aluminum and its alloys was researched using an X-ray electron spectroscopy. It was established that the alloying additives are surface-active materials and concentrate mainly in the surface layer, with partial oxidation together with aluminum. The chemical composition and properties of the formed film influence the properties of products based on doped alloys, in particular, powders, when used for different purposes. The correlation was determined between the level of hydrogen discharge from the alloy composition as well as the solution рН during interaction of aluminum, magnesium powders and their alloys with water, NaOH solution (рН = 11) and HCl (рН = 3). It was established that the aluminum powders alloyed with bismuth are the most reactive ones, and the powders alloyed with strontium are the least reactive ones.

Both titanium (Ti) and lanthanum (La) can improve the quality of hot-dip 55%Al-Zn-Si coating. However, the authors found that the dross problem was very serious when titanium and lanthanum coexisted in the bath. In order to reveal the cause of this phenomenon, different contents of Ti were added into the 55%Al-Zn-Si-La bath to study its influence on the dross formation. The results indicated that La promotes the formation of Si-rich τ₅ (Fe₂Al₈Si or α-AlFeSi) phase in the bath while Ti has no influence on the Fe-Al phase. Furthermore, it was also found that the addition of Ti into the 55%Al-Zn-Si-La bath would lead to the precipitation of TiAl₃ and Ti₂Al₂₀La type of intermetallic compounds, both of which are insoluble and become part of the dross, therefore increase the amount of dross in the bath.

This paper present the results of electrolytic nickel composite coatings manufacture. The process was conducted in Watts-type solutions with the addition of finely dispersed hard ceramic particles of alumina (Al₂O₃) in concentrations of 50 and 100 g/l. The coatings were produced on aluminum alloys 2xxx and 5xxx series. Morphology, structure and microhardness of the obtained composite coatings were examined. The corrosion resistance of coatings was investigated in the neutral salt spray test (NSS) and by electrochemical methods. The results of Taber abrasion resistance test were also given. Based on the overall results of studies, a varying effect of nickel sulfate and Al₂O₃ concentration in bath on the properties of composite coatings deposited on aluminum alloys was stated.

In the present investigation, pure cerium ingots were added to Al-8% Si alloy melt to study its effect on the microstructure and cooling curve parameters. The melt treated alloy was solidified against sand base, stainless steel, brass, and copper chills to study the effect of chilling. Ce treated alloys solidified against sand base resulted in refinement of the eutectic silicon along with the formation of Al-Si-Ce ternary intermetallic compound. Addition of Ce to alloys solidified against chills resulted in the complete modification of eutectic silicon. Thermal analysis results revealed that the nucleation temperatures of eutectic silicon decreased on addition of cerium to the chilled alloys due to the synergistic effect of chilling and cerium addition. The degree of modification achieved was higher due to the decrease in the formation of Ce intermetallics at higher cooling rates.

The impact that various water treatment additives and contaminants might have on aluminum ingot casting heat transfer was evaluated using laboratory heat transfer measurements simulating ingot quench waters. These included: oil in water, corrosion inhibitors and various dissolved solids. Test samples were prepared and submitted as blind samples for heat transfer and cooling rate studies to the Center for Heat Treating Excellence at Worchester Polytechnic Institute. Demineralized water was used as a baseline for comparison to waters containing either additives or contaminants. Heat transfer (BTU’s/ft2 hour oF) and Cooling Rate (oF / sec) over a range of 900oF to 150oF was measured. The heat transfer curves captured the entire boiling range from film, through nucleate to convection. Changes in heat transfer or cooling were plotted against the baseline as well as untreated supply water. The results from this work were used to help prioritize maintenance and operational practices at an industrial casting plant and to minimize shifts in heat transfer caused by previously unmonitored water components.

Manufacturers of rolled materials are always striving to reduce the costs associated with production—be they time, material, or waste. This is especially true with the manufacture of next-generation particle-reinforced materials, such as those used in high-value automotive components. Process variables such as temperature, roller speed, and plate dimensions, among others, all affect strength, ductility, and anisotropy of the hot rolled plate. Manipulation of the thermo-mechanical processing (TMP) parameters can help to optimize mechanical properties, which would reduce waste and improve quality. A parametric study was conducted via ANSYS and LS-DYNA to numerically simulate symmetric hot rolling. The TMP parameters have been varied to characterize how geometric and material properties confer a mechanical response for single-pass isothermal rolling. This approach to virtual processing represents a means by which manufacturers can lower the time, material, and scrap costs associated with developing new, high-value components. Conditions that minimize edge cracking as predicted by a ductility model are presented.

In the Direct Flame Impingement (DFI) process, oxy-fuel flames directly heat the moving metal strip. The resulting heat transfer can be up to ten times higher than in conventional fuel fired furnaces. Characteristic of the process is that the material temperature rises very quickly within a compact furnace body. The DFI process is successfully applied in the steel industry, for example to boost productivity in continuous steel galvanizing lines. Linde has performed several DFI aluminium strip annealing tests in its pilot plant laboratory. These results predict that the technology would play an important role in the aluminium industry. One important example is annealing of Auto Body Sheet. The paper will discuss the DFI technology and its applications in the Aluminium Industry, hardware, lab facilities, and results.

The increasing use of lightweight materials, such as aluminum alloys, in auto body structures requires more effective surface cleaning and texturing techniques to improve the quality of the structural components. The present work introduces a novel surface treatment method using laser interferometry produced by two beams of a pulsed Nd:YAG laser operating at 10Hz of frequency to clean aluminum surfaces, and meanwhile creating periodic and rough surface structures. The influences of beam size, laser fluence, wavelength, and pulse number per spot are 1]. Aluminum surface cleaning to remove oxides and contaminations is required prior to the welding and joining processes. Without proper surface preparation, seams and joints are susceptible to increased wear, degradation and, in some cases, catastrophic failure. There are many methods to remove aluminum surface oxides. Mechanical method [2] is one prevalent method due to its relative low cost. It typically uses blasting media or abrasive materials that are applied directly to the surface. Chemical stripping [3] is another widely used cleaning method. An advantage of this method is the ability to more easily remove all traces of surface oxides and contaminations regardless of shape or surface features. Although the chemical stripping method is effective, the cost associate with environmental protection, hazardous-waste management is high.High-energy laser pulses can also be used for surface cleaning [4,5]. The mechanism is mainly due to the surface melting and ablation when the metal surface subjected to very short laser pulses (nanoseconds to milliseconds range) with high peak intensities, as well as the laser-induced shocks [6]. It’s a non-contact process without abrasion and chemical impact. The controllability offered by laser enables high-precision removal of surface oxides and contaminations in the range from sub-micrometers to several millimeters. All types of organic and inorganic impurities can be removed from the surface. This paper introduces another method for aluminum surface processing using laser interference patterning. The interface pattern is produced by two beams of high-energy laser pulses. Like the conventional laser cleaning method, surface oxides and contaminations are likely to be removed. Meanwhile, periodic structures can be formed on the surface due to the periodic intensity distribution of the laser interference patterns. This method offers the capability to control the surface texture.

As part of a large investment plan, Novelis, world leader in aluminium rolled products, has installed and commissioned at their facilities in Pindamonhangaba (São Paulo State) a new High Speed Single Coat (double faces) Coil Coating Line for Aluminium Coated End Stock.The line was supplied by FATA Hunter, Division of FATA S.p.A. (Italy) and started commercial operations in the second semester of 2014.The line, operating at 300 m/min, is capable of producing painted coil of 0.18–0.35 mm thick and 1,250–1,780 mm wide aluminium strip for production of Can Stock for the beverage industry.The most advanced technologies were utilized in the design of the individual equipment, and their integration in continuous high quality and process control allow the production of superior coated end stock coating for the beverage industry.

Nowadays, energy consumption has been proposed as one of the major indexes in evaluation of community development. For this purpose, different types of heat recovery systems have been designed and built. One of these systems is a fixed-bed regenerator (FBR) that has widespread applications in energy industries such as glass and aluminum. In aluminum melting furnaces such systems can be utilized to preheat air by absorbing heat from flue gases from the combustion chamber which results considerable fuel consumption in the furnace. Due to the high temperature application of such systems in aluminum furnaces, the packing must be constructed from ceramic with very low thermal conductivity and the mechanism of heat transfer will be convection and radial conduction inside the spherical packing. This paper presents the results of the mathematical modeling and simulation studies of a fixed bed regenerator filled with spherical shape packing made from alumina with different diameters. For the modeling purposes two mathematical models have been considered; simplest convection model and more complex radial conduction model inside the packing particles. For evaluation of the model and to study the effect of different parameters such as gas mass flow rate, period time and ball diameter on the performance of the system, an experimental setup has been designed and built. The results clearly show that decreasing of gas mass flow rate, period time and packing diameter increase the system efficiency.

The strain components (shear strain, strain in rolling direction), equivalent strain and deformation of elements through sheet thickness in symmetric / asymmetric rolled AA 7075 Al alloy sheets were quantified using finite element method (FEM) with taking into account the deformation histories. The FEM results showed that positive and negative shear strains can be formed after a single-pass rolling and the total shear strain in the middle thickness of asymmetric rolled sheet (asymmetric ratio: 1.25) can be greatly increased compared to that of symmetric rolled sheet for the introduction of severe plastic shear deformation, so as to improve the equivalent strain. Using the engraved-mark experimental method the FEM results were verified to be consistent. Moreover, it can be found that much more shear bands will be introduced through the thickness of asymmetric rolled sheet, especially in the middle layer, indicating that asymmetric rolling greatly favors to through-thickness deformation accumulation.

A project has been undertaken at Trimet Aluminium SE to improve grain refinement of extrusion alloys involving three stages. The first stage comprised making small scale tests using the Opticast method on 4kg melts at the MQP laboratory in Stockholm. In stage two testing was carried out on the R&D casting pit at Trimet in Essen where single billets were cast from a 1.2t furnace. The small scale tests predicted that grain refiner addition rate could be reduced by 88% and the results of the subsequent R&D and production tests confirmed that this was possible however the actual addition rate used for the trial was 0.16kg/t representing a reduction of 68%. The results of the third stage of the project, involving making full casts of 6060 billets on a production casting pit then evaluating these in terms of grain size, metallography and subsequent performance during extrusion, are reported.

Conventional transmission electron microscopy and x-ray diffraction techniques have been applied to study the microstructure of heavily wire-drawn and annealed samples of pure Al metal. Samples wire drawn (60% of the original value) have been found to be comprised of columnar grains with heavily distorted crystal structure and to exhibit a strong <111> texture. Thus drawn samples after annealing appear free of columnar granular structure and show re-crystallized grains. Electron diffraction studies from thus re-crystallized grains are presented to evaluate the resulting annealing texture.

The vaporizing foil actuator (VFA) is a novel tool for impulse-based metal working operations. In this work, it has been used for impact welding of aluminum flyer sheets to high-strength steel and magnesium plates. Aluminum alloy 6061 sheets of 0.81 mm thickness were launched to velocities in excess of 800m/s and found to weld to both the target materials investigated: HSLA A588 steel and AM60B magnesium alloy. Grooved as well as flat target plates were utilized. Welding with grooved target plates was found to be not very robust as the weld samples came apart during sectioning. However, the flat targets welded successfully, and during mechanical testing, failure was found to occur outside the joint. The weld interface morphology for each material system and configuration has been shown. Some improvements to the grooved-target experimental configuration are also demonstrated.

Zirconium added to aluminium alloys may under suitable conditions form metastable cubic precipitates Al₃Zr, which pin moving grain boundaries and thus shift recrystallization to higher temperatures. Twin-roll cast AA3003 aluminium alloy cold-rolled to 5 and 1 mm was subjected to several annealing steps in order to find ideal conditions for precipitation of Al₃Zr phase. Mechanical properties were monitored by microhardness measurement and microstructure was observed by light microscope and transmission electron microscope. Annealing to 450 °C with slow heating rate has been used to produce Al₃Zr precipitates. This heat treatment also influenced presence of other phases like cubic α-Al(Mn,Fe)Si. The main mechanisms influencing microhardness were hardening by Al₃Zr precipitates, softening by recovery and recrystallization and depletion of the solid solution from the major alloying elements.

The SY600 High Amperage Aluminum Reduction Pot Technology was developed by CHINALCO. The 600 kA pilot pots were started in August 2012 and were operated at 600 kA and 3.777 volts during the testing stage. The technical strategies of 600 kA pot technology were researched by SAMI, which meanwhile completed engineering designs. In this article the flow field of such a 600 kA pot was studied using a simulation and validated by on-site measurements. The results show that the 600 kA pot has a relatively low metal flow and high MHD stability.

High capacity, low energy consumption, SY600 aluminum reduction cell technology has been developed by CHINALCO. Starting with research from 2007, this technology aims at a current intensity of 600kA with a target of low D.C. power consumption. Following the SAMI SY series cell development methodology and using numerical simulation modeling, low ACD energy-saving cell industrial experiments and operation acknowledge, the new design criterion is established for low energy 600kA cell technology. This article presents major technical developments of the SY600 technology with focus on new busbar design, reduction of horizontal current in metal, lining with low voltage heat balance design, and cell bottom shell upward restraint. The startup of a 600kA pilot plant with 12 prototype cells in 2012 and the main performances are also described in this paper.

Five DX+ demonstration cells were started up during July-August 2010 in Dubai Aluminium (DUBAL) Eagle demonstration section and were shutdown in January 2014 in order to provide space for five DX+ Ultra low energy demonstration cells. This paper describes the characteristics and performance of DX+ cells during the entire period of their operation from starting cell amperage of 420 kA to 460 kA at shutdown. A new cell control system based on standard PLC (Programmable Logic Controller) was developed on these demonstration cells and successfully transferred to the industrial DX+ cells in EMAL Potline 3. During the whole period of operation, the cell metal production was increased by 228 kg/cell-day and the specific energy consumption was reduced by 0.29 kWh/kg Al while the current efficiency was maintained at 95 %. This was achieved through process optimization, revised work practices coupled with cell control strategies and anode design changes. After shutdown, autopsies were carried out to predict life expectancy of these cells.

The 38 cells of the Arvida Aluminum Smelter-AP60 Technological Center were started at the end of 2013. This successful start-up has established a new benchmark for the primary metal aluminum industry in terms of productivity, robustness, environmental performance and CAPEX/OPEX benefits. The cell start-up methodology was fine-tuned using process data analysis and specific R&D instrumentation. An in-depth measurement activity was performed during the different phases of cell start-up to characterize the mechanical behavior of shells, superstructures and busbars, thus allowing characterization of the robustness of the mechanical cell design. In parallel, measurements were taken to evaluate the cell lining performance and cell stability. After six months of operation, the robustness of the cell technology and the operational and environmental results have opened the way for improved performance and amperage increase.

Over the past four decades there has been continual development of the original D18 potlines at DUBAL to increase their efficiency and productivity. Amperage has increased by 37 % to 205 kA, the number of cells has increased by 44 % to 520 and individual cell production has increased by 47 % to 1549 kg/cell-day. Specific energy has also reduced from 15.96 to 14.79 DC kWh/kgAl and PFC emissions have reduced by 74% recently to 95 CO₂eq kg/t Al.To make the next step in improving DUBAL’s productivity and economic competitiveness, a completely new cell design, D18+, was developed to modernise the original potlines. After construction of seven D18+ test cells in 2012, the new design has achieved its key objectives with current efficiency of 95.1 %, specific energy of 12.64 DC kWh/kgAl and PFC emissions of 5 CO₂eq kg/tAl. Work has now begun for full implementation in the D18 potlines.

EMAL started up the first cell of Potline 3 on 11 September 2013. Several challenges had to be overcome for the technology transfer from five DX+ demonstration cells at DUBAL to a Potline of 444 cells starting up at 440 kA. Among these were: first time implementation of plant-wide PLC based control system, management of large Gas Treatment Centers with capacity greater than 2 million Nm3/h and management of the longest Pot Feed System. Separate teams were organized for pot preparation and preheat, bath-up and early operation and normal operation. The last cell was started up on 13 June 2014, completing the start-up at an average rate of 11.26 cells per week with an impeccable safety record and no pot failures. Several process improvements during the start-up were made in preheat, bath-up; early operation and alumina feed control. This paper describes the challenges faced and improvements made during Line 3 start-up

This paper puts forward a new aluminum reduction cell shell technology, specifically a pre-stressed shell. The technology was developed in order to solve the breakage of aluminum reduction shell caused by large deformation. The work is based on pre-stressing technology research and application in the field of steel structures. By pre-stressing the shell cradle, the technology significantly improves the cell structural performance, increases structure safety, reduces materials consumption and is beneficial to prolong the cell life. This paper introduces the design method (force analysis and experimental research), detailed measurements of the pre-stressed shell and gives the application example.

This paper gives the analysis of the volatility of primary aluminium prices within the period of 1967–2013 in nominal and real terms and underlines the economic problems of aluminium smelters activity.The production process flow diagram of aluminium cluster, consisted of alumina bearing feedstock mine, alumina refinery, primary aluminium smelter, processing plant and power station, is proposed. An economic model of aluminium cluster functioning with minimal risks in regards with market volatility and financial-economic crises is developed.

Life Cycle Assessment (LCA) methodology is emerging as a standardized reference for assessing the comprehensive environmental impact from any product or process. This holistic approach considers all steps related to the product/process life, from cradle to grave. As an aluminum producer, Rio Tinto Alcan (RTA) recently applied this method to assess its relative performance compared to the industry average, with a specific focus on its GHG (Greenhouse Gas) emission intensity. As a smelting technology supplier, RTA is now deploying a simplified approach based on LCA principles to assess technology performance. Combined with specific accounting techniques, this should allow for more efficient designs, both from an environmental and financial perspective. This paper illustrates, through some examples on product and process assessments, how this philosophy can be used to design and operate sustainable technology solutions in a systematic way.

This paper focuses on the global warming potential (GWP) of primary aluminum production analyzing the hotspots of greenhouse gas (GHG) emission. The major GHG emission of primary aluminum production is caused by aluminum smelting. Inert anodes or non-consumable anodes are considered as a solution to mitigate GHG emission of the Hall-Héroult process.A comparative cradle-to-gate life cycle assessment (LCA) was conducted to estimate the environmental impact of primary aluminum production considering conventional and inert anode smelting, including the production technology of the anodes themselves as well as the influence of the energy mix used to produce the electrical power.

The Aluar Aluminum Primary Aluminium Smelter is composed of two potlines with Aluar cell technology (400 pots PFPB type at 200 kA) and two potlines with AP18 cell technology (384 pots PFPB type at 220 kA). Sampling of roof emissions is done with a 32 cassette arrangement according to EPA14A method for total fluoride (gaseous and particulate phase) emission control and monitoring. Following the guidelines of the methodology the cassettes are placed along the roof monitor of the 8 potrooms that form the 4 potlines.From a total of 1651 values of total fluoride concentrations (822 for Aluar type potlines and 829 for the Pechiney type potlines) obtained from monthly measurements from September 2012 to May 2014, several statistics analysis were made in order to study the variability of fluoride emission in both technologies. The effect on the results of the run time sampling period was examined (24, 32 and 40 hours), which concluded that there were no significant differences were found between periods. In order to optimize our resources, the feasibility to alternate sampling between potrooms and its impact on long term fluoride specific emissions was also investigated for each type of potlines. Also enabled us to validate a recognizable correlation between pot hooding quality and fluoride emissions, which is presented is a separate 2015 TMS paper.

This paper describes briefly the main tasks and methods that have led to lower total anode effect (AE) duration at Nordural smelter. Anode effect is a phenomenon which occurs when alumina concentration is low in the electrolyte and eventually increases the resistance in the pot, making instability, less aluminum production and increases PFC emissions [1]. Despite a current increase, substantial reduction of total anode effect (AE) duration has been achieved at Nordural smelter over the last three years with simple tasks that could be implemented in most smelters. The main reason for the reduction of total AE duration at Nordural is shorter reaction time among operators, analysis of AE root causes, physical experiments in pot control, prioritizing of procedures and statistical analysis as a measure of the gain of each process or control change.

It is well established that maintaining magneto hydrodynamic stability over the life of an aluminium reduction cell is important for achieving optimum performance, and this includes having balanced cell current distribution. Dubal operates at the leading edge of current density, thanks to a state of the art control algorithm which also maintains low PFC emissions. As part of a continuing performance enhancement programme, we have been investigating temporal and spatial changes in cell conditions due to routine activities such as anode set, which can impose uneven distribution of current between operating anodes. During these investigations, we have found the occasional formation of traces of background anthropogenic PFC gases, namely tetrafluoride and hexafluoroethane, commonly referred to as non-AE PFC emissions. Further insights into the causes are presented from these studies.

Perfluorocarbons (PFCs) evolved from aluminum electrolysis pots during periods when pot voltage is below eight volts are considered non-anode effect (NAE) PFC emissions, consistent with current PFC measurement protocols. NAEPFC emissions occur from all commercial smelters, regardless of plant size or technology type. This work uses historical estimations to illustrate the potential impact of including NAEPFC emissions across a portfolio of location and technology specific PFC inventories and discusses technical considerations regarding the current measurement protocol and potential modifications to include NAEPFC emissions.

Impurities in the electrolyte of an aluminum reduction cell are known to affect current efficiency and other aspects of potroom operation. Traces of phosphorus and sulfur are generally present in the cells and their behavior is of interest due to their known adverse effect on the process of aluminum production In this study, data analysis was performed on the phosphorus concentration and different process parameters registered during the three years of daily measurements at the Alcoa Fjarðaál smelter. Experimental samples taken during power outages were also collected and analyzed for the sulfur and phosphorus concentrations in the bath.High bath height was found to be correlated with higher phosphorus concentration in the metal. Moreover, there is a very strong negative correlation between superheat and phosphorus in the metal. Elemental analysis shows an increase of the phosphorus and sulfur concentration during power outages.

The anode cover material (ACM) is necessary to control the top heat losses of aluminum electrolysis cells, to decrease the fluoride fumes emissions and to prevent air burn of carbon anodes. In order to understand the behavior of the ACM and anode crust at operating conditions, samples of these materials are taken from an industrial electrolysis cell in the side channel, center channel and between anodes. Their chemical compositions are analyzed by X-ray diffraction while the temperatures inside the crust are validated by temperature measurements. The reactions occurring in the ACM and anode crust are then determined by thermodynamic equilibrium calculations. Concentration gradients of chiolite (Na₅Al₃F₁₄), cryolite (Na₃AlF₆), Na₂Ca₃Al₂F₁₄, and Al₂O₃ are observed in the anode crust, implying a variation of the cryolite ratio and melting temperature of the crust. The thermodynamic analysis describes the state and behavior of the anode crust in aluminum electrolysis cells.

The frozen bath layer on the sidewalls of aluminum reduction cells plays a crucial role in the process of aluminum production. The stability of the freeze layer is more and more at risk with the trend of increasing line current.We present a non-intrusive thermal based method with which the continuous monitoring of the sidewall freeze is possible. The foundation of this method is a special arrangement of thermocouples, which are embedded in the sidewalls of operating cells. The method is able to follow the thermal load of the sidewalls and feeding the measured signals into a simplified mathematical model, and an estimate of the changing thickness and shape of the freeze layer can be obtained.We give a comparison of freeze profiles measured with traditional mechanical probing and our novel method. The continuous change of the protective freeze layer throughout specific events in the cell is also discussed.

In the Hall-Héroult process, alumina dissolution rate is dependent on a number of process variables. One major variable is the superheat, especially in modern reduction cells which operate at low cell voltage. During the cell operation, routine practices and abnormalities give rise to energy imbalance at different parts of the cell, and consequently local superheat variations. This leads to variations in local alumina dissolution rate, and affects process efficiency and performance. This paper presents a method for monitoring local cell conditions by estimating the rate constant of alumina dissolution and alumina concentration using the extended Kalman filter. The method employs a combined mass balance and cell voltage model, which estimates the effective local superheat-dependent dissolution rate constant and local alumina concentration from individual anode current, cell voltage, alumina feed rate and anode-cathode distance. The results are verified with alumina concentration and superheat measured during an experiment conducted in an industrial cell.

By using the see-through cell, the dissolution phenomenon of alumina in the cryolite electrolyte was clearly visible. In this paper, the dissolution processes of primary and secondary alumina in typical aluminum bath were shown and the dissolution rates were compared as well as the temperature fluctuations during dissolution. Both the video and temperature measurements confirm the three key steps of the dissolution process: fast dissolution upon feeding, crust formation and sludge dissolution. And the dissolution rate in each step is very different. Secondary alumina displays a quite different dissolution behavior from primary alumina. Meanwhile, the dissolution rate of secondary alumina is much faster than that of primary alumina. The mechanism for alumina dissolution under the influences of MOI, LOI, surface area, absorbed fluorine and carbon content was also discussed.

Primary testing for producing Al-Sc alloy by electrolysis of Sc₂O₃ dissolved in a cryolite bath containing molten aluminum was performed. A lab-scale cell consisted of graphite anode and aluminum cathode located on the bottom of corundum crucible. A graphite current lead to the aluminum cathode was also served as a stirrer. Molten cryolite NaF-AlF₃ or KF-AlF₃, or their mixture with cryolite ratio in a range of 1.3–2.3 was used as a solvent for Sc₂O₃. Electrolysis was carried out in the sodium cryolite with composition similar to conventional electrolyte at 980 °C and in the low-melted sodium and potassium-cryolite-based-electrolytes with cryolite ratio 1.3 and 1.5 at 750, 800 and 850 °C. The cathode current density impact on the composition of producing alloys was studied. The alloy’s and electrolyte’s composition was analyzed with SEM EDX and ICP methods. A uniform distribution of scandium throughout the Al-Sc alloy matrix for all studied samples was observed.

Alcoa has conducted multi-year concept validation, pilot and full-scale demonstration studies to assess the technical feasibility of an energy efficient, horizontal gas-flow, co-current in-duct scrubber. The in-duct scrubber was designed and developed with the aim to significantly reduce capital expenditures and operating costs while providing >90% reduction of SO₂ emissions from aluminum smelters, anode bake furnaces, coke calciners and industrial boiler exhausts.Pilot scale parametric testing of various spray nozzle types and configurations has been conducted to optimize the final scrubber design using a liquid solution for SO₂ scrubbing. More recently, a full scale commercial unit has been installed and is currently operating with SO₂ removal efficiencies greater than 92%. The scrubber treats the exhaust gases from an anode baking furnace with flows ranging between 120,000 and 150,000 cubic feet per min (cfm), liquid to gas (L/G) ratios ranging from 10–12 gallons/1000 acf (actual cubic feet) and an overall pressure drop across the scrubbing unit at or below 1.5 inch w.g. (water gauge). Future testing of this unit will entail detailed evaluation of the system’s capability in removing fine particulates.

Roofline wet scrubbers are employed at aluminum smelters to provide significant reduction in fluoride emissions from the potrooms. Roofline wet scrubbers are most useful at locations that have emission performance constraints owing to hooding efficiency limitations or pot technology issues that increase fluoride losses to the potroom. Unfortunately, roofline wet scrubbers are quite cost intensive to install, operate and maintain, which intensifies scrutiny regarding the value of these systems. This talk will present in-plant data showing real-time continuous monitoring of wet scrubber HF capture efficiency and the impact of work practices on the efficiency of the roof scrubbers for capturing gaseous fluoride from aluminum smelter potroom rooflines.

Presented is a solution of advanced measurement equipment for fugitive emissions through roof vents. Developed is an innovative mobile roof monitoring system that is tested for two years in several potrooms and presents many opportunities in terms of technical advancement as well as operation improvement. The system comprises of a climate controlled shuttle that is mounted on a rail track. It fundamentally complies with government rules for HF emissions and complies with both Alcan method 3010–09 and US EPA method 14/14A. The system eliminates safety risks associated with a hot and contaminated atmosphere and with the extreme working height. It has absolutely no co-activity with the process and costs less than a catwalk. The complete rail system and climate controlled shuttle are easy to maintain. The advanced features are: a multi-axis air speed profiling with real time recording (useful for sampling point selection that can be modified considering either seasonal change for collection efficiency or changes in regulations , and used even for building design validation), isokinetic sampling, concentration profiling and integrated reporting with active diagnostic. The platform is adaptable to integration of other pollutants such as SO₂, PM2.5 or others, for multiple sensors and with on-board IR instruments.

EPA Method 14A is one of the most widely used methods for measurement of total fluoride (gaseous and particulate phase expressed as Ft) emissions through roof monitors in aluminium primary smelters. In order to obtain the Ft concentration emitted from the potroom, several cassette arrangements are placed in predetermined locations and later removed from the roof monitor for the analysis of each run.Because Aluar operates a total of 8 potrooms and this kind of environmental testing is costly and elaborate, an alternative approach is required to keep monitoring the emissions on a daily basis. A robust and cost effective option is to identify those pots that are missing at least one hood simultaneously due to operational and/or maintenance practises. This paper presents the development of tests with the purpose to find a correlation between Ft concentration measured with EPA method 14A and the sum of pots with at least one hood opened, as well as to establish a theoretical factor to relate the amount of pots in such condition to specific emissions in potrooms where we use the original Aluar type PFPB end-to-end cells. It was estimated that during normal operation an increase of 0.03 kg of Ft per (metric) ton of aluminium produced (equivalent to 0.36 kg Ft per hour) is added to the current Ft emission per pot with one hood opened.

Reliably achieving target fluoride roof vent emissions remains a challenge for many smelters. Since they contribute up to 40% of the overall roof vent emissions, anode change operations are often targeted for improvements and more specifically the contribution from the spent anode butts. Over the last few years, Rio Tinto Alcan has therefore pursued an ambitious R&D program to understand the physical phenomena involved. Several conceptual solutions were consecutively designed and tested, including different types of enclosed butt boxes.These initial tests concluded that the efficiency of such solutions is very sensitive to the design of the seals, and this has therefore been the focus of the most recent work. This paper provides an update on the latest development of a new covered pallet device, including the latest measurement campaign, prototyping and industrialization steps for it to be efficiently applied in smelters.

The GTC of the AP60 potline has reached full operation at the end of 2013, treating gases from 38 pots. This paper will overview Fives most advanced and eco-designed scrubbing technology built around the Ozeos scrubbing modules with integrated reactors. The AP60 GTC has five modules: four are equipped with conventional bags and one equipped with extended surface bags. The GTC is also provided with state of the art fresh alumina distribution system allowing overfeed into a module that handles more gas flow (ex: module with extended surface bags) and capability to operate in Cascade feed mode during the summer time. Great care was given to the ID fan selection and noise abatement to meet very stringent requirements (the smelter being located amid a residential area). The paper will finally present the scrubbing performance obtained during the first year of operation and the comparison in performance of the modules equipped with extended surface bags versus conventional bags.

Today, pot gas emissions are well treated by modern Gas Treatment Centers (GTC), with efficiency rates close to 99.8%. However, stack emissions only represent a very small amount of the total HF emitted by smelters. Indeed, HF is mostly originated from potrooms where in most smelters no specific treatment is provided to limit pollutants.This paper presents several solutions from Fives to eliminate two of the main sources of HF emissions in potrooms:Emissions from opened pots. The normal draft cannot maintain a negative pressure in pots, which results in fumes emission. Fives developed boosted suction systems installed in the latest smelters.Emissions from butts stored in potrooms, before being transferred to the rodding shop. Fives developed a solution to confine butts, until being treated at the rodding shop.A test campaign has been performed in the ALRO smelter in Slatina, Romania. Presented are the achieved HF reductions and a CAPEX and OPEX case study.

Many aluminium smelters currently choose amperage increase as a way to boost production over costly new plants. However, the increased pot amperage gives higher gas temperatures and higher gas flows to the Gas Treatment Centers (GTCs). The higher gas flows give capacity problems for the existing GTC’s and high gas temperatures (above 115°C) lead to poor scrubbing efficiency in the dry scrubbers. For more than seven years Alstom has successfully developed and tested heat exchangers to cool the pot gas including self-cleaning heat exchangers that has been in continuous operation for 6 years.In December 2013, Alba awarded Alstom a contract to supply and install heat exchangers and more filter capacity to existing GTCs installed at Potline 4. This marks a breakthrough for the heat exchanger technology that enables Alba to increase the amperage with low HF emissions. In addition, this opens up the possibility of the development of technologies to utilize 25 MW of thermal energy from the pot gas. Sea water desalination, electricity production, absorption chillers or preheating/drying of raw materials are assessed for utilizing the waste heat.

Agglomerates in the Hall-Héroult cell reduce the alumina dissolution rate and affect the stability of the process. Alumina agglomerates have been thoroughly studied, however their formation is not completely understood yet. This study focuses on the behavior of powders on the surface of a liquid, in an attempt to shed light on how alumina powder enters the electrolytic bath, as it could influence the formation of agglomerates. The ability of an object to float on the surface of a liquid could be determined by analyzing the force balance. Besides liquid properties, the shape of the object, bulk density and contact angle were analyzed. Beyond the analysis of single particles, the condition of floating of particle agglomerates was also examined, which could lead to the deeper understanding of the behavior of powders on a liquid surface and to a more accurate modeling of alumina feeding into the bath.

The injection and the dissolution of alumina in the molten cryolite are crucial steps of the Hall-Héroult process because of their impact on the cell efficiency and stability. A better understanding of the dissolution can support the scientists to optimize the energy consumption of the electrolysis process. This requires the study of the dissolution kinetics of alumina experimentally. In order to follow the evolution of the alumina concentration with good precision after its injection, a semi-automatic mechanical sampling system has been developed. The computer controlled system is able to take molten bath samples at around 1000°C for later chemical and microstructural analysis. The appropriate operation of the sampling system required the resolution of several problems, like the choice of appropriate dimensions and material suitable for a very destructive environment. In the present paper, the design process, including problems and solutions, of a semi-automatic molten cryolite sampling system is presented.

A phenomenological model for the creation and transport of anodic gas bubbles in Hall-H´eroult cells has been developed, following a multiscale approach. The essential features of the modelling framework are reviewed and discussed in the present paper. The model covers the generation of molecular gas species through Faradays law, subsequent bubble nucleation, and the evolution of macroscopic bubbles which are treated by a volume of fluid model. Recently, the modelling framework has been extended to include several complex phenomena such as surface tension and wetting, bath chemistry, and variable flow properties. The modelling framework has currently been applied to a laboratory scale electrolysis cell setup. The results demonstrate that the essential properties are well represented over a large range of experimental conditions by the proposed approach.

Recently, there are efforts to change bath chemistry used for aluminium electrolysis, in order to decrease operation temperature, cell voltage, etc. Such modifications have a significant impact on the whole Hall-Héroult process, including the composition, the structure, and the thermal properties of the protecting side ledge. Consequently, the heat balance of the cell can be shifted and thus the optimal parameters of the cell operation can be modified. This paper presents some observations and a few results obtained with side ledge of a semi-industrial cell, operating with modified bath composition. Results show that the main components of the continuous phase in the side ledge remain the cryolithe mixed with some chiolite. However, the apparition of new compounds increases the inhomogeneity, resulting in a slight decrease of the thermal conductivity of side ledge.

The effects of LiF and MgF₂ addition to the electrolyte on current efficiency were investigated during aluminium electrolysis using base NaF-AlF₃-Al₂O₃-CaF₂ system at 980°C in laboratory scale. The electrolysis was performed with a cryolite ratio of 2.5 and with 4% Al₂O₃ and 5% CaF₂. The duration of each electrolysis experiment was 4 h with a graphite anode and a cathodic current density of 0.85 Acm−2. Additions of LiF up to 5 wt% were found to improve the current efficiency. Additions of MgF₂ had a positive effect on current efficiency. The effects of KF and LiF on the cathode process were studied using the same system. The alkali metals concentration including K, Na and Li in deposited aluminium were analyzed as a function of the cathodic current density. Results are presented from a study of the influence of electrolyte composition and cathodic current density on current efficiency and cathode process.

Several features in the aluminium electrolysis depend on wetting between anode carbon and bath, such as bubble size, gas coverage at the anode, “bubble overvoltage”, and the conditions during anode effect. The present paper describes the relevant theory concerning wetting, and factors concerning the choice of method of measurement are discussed. The selected method is based on the immersion-emersion technique, which was adapted for use at high temperature and presence of fluorides, and with polarisation of the sample. The method is based on continuous monitoring of the force acting on a sample which moves into or out from a liquid. There are no restrictions concerning the state of the solid surface. The preferred type of sample is shaped as an inverted cup with thin walls to minimise the ratio between buoyancy and surface tension force. The method was tested using different combinations of solids and liquids at room temperature.

An apparatus for determination of wetting angles, based on the immersion-emersion technique and adapted for use at high temperature, was used for measuring the wetting between cryolitic melts and samples consisting of standard anode carbon. Anodic polarisation of the sample and the alumina concentration were the more important factors. Polarisation strongly improved the wetting if the melt was low in alumina, and the effect persisted for a while after the current was turned off. Increasing the alumina concentration to near saturation brought about a dramatic change from non-wetting to good wetting. The advancing angle of wetting was normally larger than the receding angle, while the opposite was observed in some experiments with aqueous solutions of ethanol and sodium fluoride. The latter effect has interesting consequences for the motion of gas bubbles, and the results also demonstrate that it is necessary to be careful in the selection of liquids and materials for physical modelling of aluminium cells.

In the context of global climate change and Hydro’s focus on reducing its greenhouse gas footprint, Hydro’s Primary Metal Technology (PMT) department has been focusing on low energy pot development for the last decade. Disclosing some of the development is meant as one of Hydro’s contributions to the industry’s effort in reducing greenhouse gas production. This paper presents Hydro’s PMT experiences with the use of external potshell insulation. It presents its early uses as a tool to improve pots having cold spots, to a solution for maintaining a cathode free from bottom deposits on pots where heat input is sharply decreased, opening the door to cheap retrofitting of smelters for low energy consumption. The authors also mention recent development where external insulation is becoming part of pot design, which, along with other efforts in reducing voltage drops, allows stable pot operation below 12kWh/kg.

With the increase in market’s demand and the development of technology, high amperage electrolytic cells in China have become widely used. In recent years, over 40 prototype cells each operating around 420 kA have been constructed. With different electricity prices in different regions and hence different cell heat balance requirements, a wide variety of lining design were tested, each having its advantages and disadvantages. This study aims to analyze and compare each lining design components in terms of cell productivity, energy efficiency, lining life and safety aspects in order to identify the most pertinent and rational design.

Energy saving is one of the greatest challenges in the aluminum industry. In an effort to determine viable ways to improve pot design and reduce energy consumption, an Alumar team conducted a benchmark study with its sister plant (Mount Holly) and found a slight difference in the anode rod assembly design that showed a significant saving potential. Changes of the copper rod dimensions and improved welding techniques were the main improvement characteristics.

The automation of modern aluminum plants together with the introduction of robotics is not a current trend but potentially a future factor able to reduce OPEX, boost productivity growth and improve HSE performance.If increased productivity is one of the biggest reasons in justifying the use of automation, then improving operator safety is undoubtedly the number one priority driving the automation of arduous industrial operations. Many physical and rather dangerous tasks in pot-lines are still required to be carried out by a floor operator. The manual manipulation of pot hoods required for anode changing is a good example. The Embedded Service Robot (ESR) is an additional tool of the Pot Tending Machine (PTM) designed and developed to assist the pot-room operators during this operation and further safeguard them against the hazards of the smelter environment. The ESR is based on industrial robotics and driven in automatic, semi-automatic or manual mode. It is able to perform many different duties with limited impact on PTM cycle time.

Ramming paste around cathode blocks of Hall-Héroult electrolysis cells is considered a critical step to avoid premature infiltration and maximize the useful life of cells. To optimize the uniformity of compaction and make the task easier, this operation is typically assisted by equipment commonly called Pot Ramming Machines.Lately, STAS has concluded a development project with the objective to offer the industry an alternative to the commercial systems available, with improved performances and innovative characteristics. The emphasis has been to deliver better operability, up-to-date quality control, easier mobility and maintenance, and improved capability in terms of compaction.This paper presents a summary of the development work from prototyping through the selection of operating parameters, the qualification of compaction and the design and manufacturing of a full scale Pot Ramming Machine now available to the industry.

Managing and maintaining an Aluminium Smelter at its optimum is a challenging job. Only a mistake, like inferior joint on the anode, bad anode, sleepy operator or bad pot tending process can disrupt a pot. Once done, it may take months for a pot to recover from such a disruption and get back to its most productive stage again. Nowadays a modern smelter has more pots running at higher amperage. The operational team needs to use these pots and manage their performance in order to reach an excellent operational result. In this paper we will discuss the need for equipment that gives a constant predictable performance as well as real time feedback on this performance of people and equipment to the management. We see this is the way forward to change industry operational know how from a reactive behavior into a knowledge based pro-active behavior. In this paper, a helping hand to the aluminium industry is offered form an unusual perspective.

This paper will review the process and technology trends in bath treatment plants. Indeed, over the past 10 years, potline needs have evolved from fine bath towards coarse bath product size, leading to the introduction of new milling technologies. Moreover, due to more stringent environmental constraints, hot bath continuous cooling processes are nowadays frequently required. As an illustration of these trends, two recent references in the Middle East will be presented: one 62 tph cold bath treatment plant featured with a gravity discharge autogenous mill and one 40 tph hot bath treatment plant featured with an apron cooling conveyor.

Standard work aims to ensure that reliable analysis methods are available. ISO standards are commercially important and are recognised and used by suppliers and customers around the world. Reliable analysis enables the suppliers to describe their materials using common standards for well-established material properties, and the standards are a support for smelters when evaluating and comparing sources of materials.ISO Technical Committee 226 maintains 110 standards on sampling and analysis covering smelter grade alumina, smelter grade fluorides, pitch, petroleum coke and solid carbon bodies including anodes and cathodes. The main work is done through dedicated work groups, one for each of the material groups. The need for modernisation of the standards is continuous as instruments improve and raw materials change. The paper will describe the committee, the work groups, current projects and ISO work in general. The paper is co-authored by Convenors and technical experts from the work groups. Aims of this paper are; to interest potential technical experts to participate in committee projects, and to encourage metal producing companies to support the important work that their participating staff makes within the committee.

In 2014, Alouette acquired a system to monitor the on-line anode current on two pots. This system, developed and supplied by WIT, reports all anodes current and the pot voltage for every second of operation. The following paper describes some of the resulting improvements that apply to the process control of the aluminum electrolysis cell.Current monitoring of the anodes easily indicates the generation of localized anode effects (AE) prior to their propagation into a “voltage triggered” AE. Basic concepts, algorithms, results and optimization to improve the detection rate are discussed in the first part of the paper.Moreover, AE are directly influenced by the alumina distribution in the cell. A better understanding of the dissolution patterns based on the feeder’s position was achieved by using the monitoring system.

Long term measurement campaigns were conducted at Hydro Aluminium’s Reference Centre in Årdal. The work comprised high frequency measurements of all individual anode current loads in three test cells. Typical patterns of current load as a function of the anode age are presented and discussed. Middle-aged anodes showed increased current fluctuations, which could be related to the anode setting pattern. The current load started increasing when the anode slots had worn away. This is apparently explained by a decreasing anode-cathode distance. It was possible to provoke local anode effects (AE) at one or more individual anodes by manipulation of the alumina feeders. Such AEs were detected as sudden drops in the current without significant increase in the cell voltage. All observed general AEs were initiated on old anodes where the slots had worn away.

Aiming a new view at pot feed cycles and to learn about the anode effect’s peculiarities, the cell voltage was analyzed in the frequency domain through its power spectrums and the patterns were classified statistically at different stages of cell feeding. The results show that the power during the overfeed and underfedd remained at a low amplitude without drastic changes. A power increase was seen as the pots got closer to anode effect, even when, in the time domain, its behaviors were similar to normal operation. This analysis method fulfilled its purpose of providing both new information about the alumina feed cycles and a characteristic behavior near to the anode effect.

The anode currents provide a wealth of information on the aluminum reduction cell, especially in sub-regions in the cell. The online signals are usually measured by voltage drops along anode rods and Hall voltage near anode rods. However, measurements by these methods require that contacts be attached to anode rods or use of costly Hall sensors. An experiment on measurement of online anode currents at anode beam was carried out on 400kA cells. The results are presented and preliminarily analyzed in the paper. The study of the anode current is of great importance for improving the pot control and operation.

Globally, aluminium smelter’s focus has been on the energy reduction and in this context cathode lining is one of the key areas of research. The design and the material modifications of cathode and collector bar have shown potential for reducing the cathode voltage drop, also it results in improved current distribution in the metal region. Such modifications have been reported mostly for the higher amperage cells, where heat dissipation is much sought as compared to the lower amperage heat conservative cells. Hence, these modifications may have detrimental impact on the thermal balance of a low amperage cell and should be carefully evaluated. The present work focuses on the simulation studies, for understanding the effect of various modifications in the design and the material of cathode and collector bar, on voltage drop and thermal balance of an 85 kA cell. Simulations have been performed using a 3D thermo-electric model, validated with the plant measurements. This study depicts that the collector bar modification have substantial impact on the thermal balance of a low amperage cell.

Prolonged changes in electrical input to aluminum reduction cells are generally undesirable, but may be imposed, either intentionally or otherwise. In either case the smelter personnel must react so as to minimize disruption to the process. One concern with respect to such changes is maintaining the protective frozen ledge on the cell walls. The depth of the molten metal pad is one process variable commonly used as a countermeasure or enabler for electrical changes. Limited changes to power input can often be accommodated by increasing or decreasing metal depth, while keeping bath depth constant. This changes the wet area for heat transfer to the ledge around the interior periphery of the cell cavity. This paper presents simple analytical expressions for maintaining ledge by changing metal height to balance changes in cell power.

UC RUSAL remains one of the world’s leaders in primary aluminium producing eight percent of total world output in 2013. In 2012, following the global industrial trends, Management initiated several technical projects with the goal to decrease power consumption in all reduction technologies used. Below are the major measures:1.Energy balance adjustment to reduce heat generation by a stage-by-stage decrease in the anode-cathode distance (ACD) down to the Limit values, resulting in the specific power consumption has decreased by 300 DCkWh/t.2.The introduction of slotted anodes for the PB cells at the Krasnoyarsk and Irkutsk smelters decreasing specific power consumption by an average of 200 DCkWh/t.3.Advanced energy-saving cathode designs are currently tested with a potential for decreasing 300 DCkWh/t or more.The rest of this paper will describe how these projects decreased the specific power consumption in all RUSAL smelters between 2013 and 2014.

Many smelters are seeking for pathways to achieve breakthroughs in reducing energy consumption and increasing productivity for survival in difficult situations of high power cost and low metal price. Some smelters realize that transformational changes are required for them to progress to a desired future state. These changes can be implemented in one or more of many areas such as Operation procedures, Processes, Systems, Organisational structure, Culture, Work design and so on. Change often inevitably faces resistance from either individuals or groups of people. However, resistance is manageable. This paper discusses the aspects of change management and process management in some smelters during the implementation of changes in Operation and control systems. Implementation of changes including practice and operators’ decisions during anode setting was selected as a case study. The results indicate the importance of work design modification and effective feedback in operational quality improvement.

A suite of efficient modelling tools is critical to continuously improve the performance and robustness of aluminium electrolysis cells. Rio Tinto Alcan has developed a suite of chained models to provide a good electrical balance in busbar configuration, satisfactory MHD stability in the cells, and thermal balance ensuring the ledge protection of the lining. This paper presents a high level model which calculates all magnetic, electrical, thermal fields as well as liquid velocities and ledge formation, all in 3D. First developed in 2005 by EPFL, follow-up work has improved mesh quality and performance, to give more reliable and accurate results. This MHD-TE model is now in an industrial form, using a qualified material database. Its capability to provide the measured values has been demonstrated on AP Technology pots. Cell designs can be better optimized to balance local effects observed on upstream/downstream sides, corners or end walls.

DUBAL has extensive experience with electrical preheat of cells and continuously works on preheat optimization. Previously, preheat improvements were made by trial and error on real cells. Recently DUBAL developed a mathematical model of cell preheat which helps to optimize preheat parameters. This paper focuses on development of the DUBAL cell preheat model in ANSYS and model validation on DX+ cells. Detailed measurements of temperatures and voltage drops were carried out throughout the cell preheat. The model is three dimensional and transient. It represents a quarter of the cell and predicts the evolution of temperature distribution, heat loss and voltage drops in different parts of the cell, including graphite preheat bed. Different configurations of graphite preheat bed were modelled and verified in practice during EMAL Potline 3 start-up.

A software application based on the full MHD model of the aluminium electrolytic production cell is used to predict the liquid metal surface instability in a commercial Trimet operated potline. The results are compared with the electric current distribution variation in time over the anodes obtained from the measurement of magnetic fields by wireless sensors. The model incorporating full 3d busbar configuration predicts a critical instability excitation frequency 0.0259 Hz, which compares to the measured frequency of 0.0254 Hz. The mathematical software permits to analyse the sensitivity to the pot individual features like ACD, anode loads, ledge shape, bottom wear and busbar irregularities. The ability to monitor continuously the electric current distribution to high accuracy helps to control disturbances and to visualise the cell interior with the help of this numerical tool.

A lab-based electrolytic-cell is designed to analyze the effect of external magnetic field on bubble evolution underneath an anode surface. Buckingham Pi theorem is used to provide a complete list of dimensionless parameters for a typical cell configuration.

A water model of the lab scale electrolysis cell presented previously has been constructed to investigate bubble coalescence and movement under a surface with varying inclination. Bubble generation is simulated by passing N₂ gas through a porous ceramic plate representing the anode. Experiments have been performed with three different liquids; tap water, and tap water mixed with ethanol or NaCl, aiming primarily to study the influence of varying surface tension at different anode inclinations and gas flow rates. Gas bubble behavior is tracked using a high speed camera. A strong dependence upon fluid properties is observed when considering the gas flow behavior with respect to bubble size, velocities and flow pattern in general. The results indicate that only the NaCl solution is able to reproduce the self-organized state expected from corresponding electrolysis experiments. Results indicate that this feature is mainly due to different wetting behavior of the different fluids considered.

Laboratory scale transparent aluminum electrolysis cells were used to study anodic bubble behavior, including bubble layer thickness, bubble shape and coverage at the anode bottom surface, and the resultant cell voltage drop in a very similar environment to real industrial cells. The observation was conducted using two transparent cells, one with side-view and the other with a bottom-view cell design. For the side-observation experiment, the evolution of bubble layer thickness and bubble rising process were studied. In the bottom-observation experiment, bubble behavior was investigated on both unslotted and slotted anodes. Cell voltage was simultaneously recorded for a quantitative investigation of its relevance to bubble coverage. It was found that the cell voltage drop is very consistent with bubble coverage, with a high voltage drop corresponding to a high bubble coverage. The coverage of anodic gas bubbles decreases with the increase of current density. These phenomena were observed on unslotted and slotted anodes. The comparison of unslotted anode and slotted anode indicated that the slot significantly reduces the cell voltage drop, voltage drop fluctuations and bubble coverage.

The use of copper inserts in collector bars has been tested in the booster section of one line. The impact on the metal velocity field, metal deformation, cell magneto-hydrodynamic state and operational data has been computed for a Reference cell and for the “Copper insert” cell. In-situ measurements in the collector bars and numerous other measurements were performed to evaluate the impact after 6 months operation. The model and measurements show a very good agreement and the results are very promising.

Traditional carbon anode technology relies on the natural flow of gases from under the anodes during the aluminum reduction process. The anode gas bubbles generated on the bottom surface of carbon anodes during electrolysis are non-conductive and thus increase energy consumption as they increase the electrical resistance in cells. The use of single and multiple bottom anode slots across the entire bottom surface of prebake anodes is now a widely accepted practice to quickly divert anode gases into bottom slots to allow amperage creep. The slots have the potential to save about three percent of the energy required in the process depending on the number and design of slots. It has now been demonstrated in this work that vertical non-continuous slots can also be formed in-situ in self-baking VS Søderberg anodes by vertically inserting four rows/or layers of multiple aluminum plates into the top surface of the anode during charging anode carbon paste to cells. Extended plant tests confirm that these multiple slots significantly reduce the electrical resistance, lower the cell voltage, and thereby reduce the cell energy consumption in VS Søderberg cells; for example, the pot noise was found to be reduced 40%, (0.04–0.05 V) compared with traditional low noise Søderberg cells; pot noise was reduced by 80% (-0.200 V) when compared to high noise Søderberg cells.

Different operational parameters are known to influence cell stability like ACD, ledge toe position and metal level.

A three-dimensional (3-D) model was developed to study the influence of cathode shape on current density, electromagnetic force and metal heave in 300 kA aluminum reduction cell. The new design is inclined cathode surface that makes horizontal current density in the metal pad as small as possible so as to simultaneously minimize power consumption. Results show that compared to plane cathode, cathode with 4.5° inclination can decrease 44.7 pct of horizontal current density. Cathode with 4.5° inclination and cylindrical protrusions can decrease 32.5 pct of horizontal electromagnetic force and 1.36 cm of metal heave in the metal pad.

Clarification of the underlying chemistry and physics is critical for understanding the “double W” wear pattern of the carbon cathode observed in Hall-Héroult cells. Many studies have pointed out that aluminium carbide formation on the cathode surface is the dominating process that determines the cathode wear. However, the mechanisms of aluminium carbide formation on the carbon cathode surface are still not well clarified. In this study, previous work on cathode wear mechanism is summarized. The region between molten aluminium and the carbon cathode is considered as a small “local electrolysis cell” involving the aluminium pad, a bath film, an aluminium carbide layer, and the carbon cathode. The aluminium carbide formation rate is proportional to the current through the “local electrolysis cell” which is obtained by applying Ohm’s law to the current and voltage of the electro-chemical reaction. A model is established for calculating the aluminium carbide formation rate as well as the cathode wear rate.

In recent years, a new process to weld aluminum bus bars has been developed, tested and used industrially, permitting significant productivity gains both in terms of time and manpower savings. ESW (new aluminum bus bars welding process) offers among others advantages the possibility to modify or repair bus bars in magnetic field of an operating smelter with minimum power shutdown time (about 20 minutes per full bus bar section weld).

The electrolysis expansion of semi-graphitic cathode blocks was studied in (Na, K) cryolite-alumina melts. A self-made modified Rapoport apparatus was used to study the effects of CR (cryolite ratio) and KR (potassium cryolite content divided by the total amount of potassium cryolite and sodium cryolite) on the expansion. The empirical formula linking CR, KR and expansion was obtained from the experiment results. When CR is in the range between 1.4 and 3.0, KR 0.1 and 0.5, the formula can be used to reveal the relationship between electrolysis expansion of semi-graphitic cathode and melts composition. On this basis, the ternary isotherm diagram refer to electrolysis expansion is also drawn. From this diagram, the electrolysis expansion of semi-graphitic cathode in low temperature electrolyte containing potassium can be directly obtained, which corresponds to the different electrolyte compositions; conversely, the electrolysis expansion of semi-graphitic cathode can be designed as expected through selecting the appropriate CR and KR according to the ternary isotherm diagram. This has some help on choosing the components of low temperature electrolyte containing potassium.

China is the largest producer and consumer of carbon cathode blocks and ramming pastes. Various grades and qualities of carbon cathode materials are now produced and used in China, among them some have reached the world advanced levels with regards to the qualities. The present paper describes the raw material selection, production equipment, standards and specifications of the carbon cathode materials in China. Although the carbon cathode materials are overall over-supplied, the demand for high quality graphitized blocks and environment friendly ramming pastes is increasing. The application of graphitized cathode blocks in 300kA and 400kA potlines in Wanji Aluminum and the development of high density graphitized blocks in Shanjin Carbon are simply introduced respectively. As the pressure on energy saving, productivity and environment is increasing, graphitized cathode blocks and cold ramming pastes are becoming more and more popular, which will in return promote the Chinese aluminum smelting industry to new level.

During air-slip direct chill casting of aluminum alloys, uneven or low air pressure areas at the surface of the porous graphite ring mold, can cause the metal to stick to the graphite ring and produce traces along the billets called vertical drags (VD). To prevent this type of defect, it would be an advantage to decrease the wettability of the graphite ring. It has been shown that nanostructured surfaces can have hydrophobic properties, and a question is whether the same effect can be achieved for molten metals. A TiO2 nanowire structure is proposed to cover the casting ring, and the wetting behavior of such a structure has been studied, and compared to the wetting at a regular graphite ring surface by the dispensed sessile drop method. The results showed that the nanostructured surface very strongly de-wets metal droplets.

In DC casting of aluminum alloys, thermal strains can cause cracks during and after solidification and rejection of the ingot. Previous numerical models have simulated strain and stress in rounds, but less attention has been paid to slabs. To study residual stresses as a function of rectangular ingot aspect ratio and absolute ingot size, a 3D finite element model is used with simplified dynamic thermal boundary conditions. In industrial practice, a wiper is sometimes placed below the mold to isolate the lower part of ingot from cooling water, and that effect is also simulated. Stresses throughout the process start-up are predicted; the surface is first under tension, and later in compression, while the center has the opposite history. Results indicate decreasing stress magnitudes with the addition of a wiper. Also, placing the wiper closer to the mold will further reduce the residual tension in ingot center, but, if the wiper is too close, the ingot surface temperature will rebound and the surface may begin to remelt. A height limit of wiper position is determined to prevent the surface remelting. Larger ingots and slabs with larger aspect ratios are found out to have a higher overall tension level.

A fully transient numerical model of the direct chill casting process is used to examine the influence of casting parameters on the macrosegregation of alloy 7050. The casting speed and secondary cooling boundary condition were varied. The secondary cooling was altered by placing a wiper to divert the free-falling water away from the solidified metal surface. Both the casting rate and wiper placement affect the sump depth and shape, and therefore influence the level of macrosegregation, especially at the centerline. The sump depth and level of macrosegregation increased with the casting rate, while placing the wiper nearer the mold could decrease negative centerline segregation.

The increased demand for aluminum as a primary structural metal stems from a quest in automotive, aerospace, and marine industries to be more energy efficient and sustainable. This unprecedented demand drives aluminum casting methods towards increased productivity looking to, cast larger ingots faster. The unfortunate consequence of this approach is an enhanced variation of metallurgical properties over the cross section of slab ingots. Rolling slab ingots of AlCu4.5 using a typical Direct-Chill casting technique have been cast and sectioned for analysis. This alloy allowed us to compare our results with the available literature and to elucidate the marked differences in spatial variation of microstructure and composition found in radial and lateral symmetry castings. In an attempt to couple conventional theory with our results, sump and temperature profiles were measured in-situ and modeled using a commercial finite element analysis software package. The combination of experimental and modeling results indicate that the variations in the cooling parameters through the cross section are largely responsible for the spatial variances in metallurgical properties, pointing to a possible refinement of DC casting parameters.

Ingot casting machines are commonly used in the aluminium industry for producing various shapes of ingots, including special shapes such as deoxidizing cones.Typical molten metal mould filling systems include casting wheels or oscillating feeding bowls that are prone to dross buildup and somewhat difficult to adjust. An automated flexible ingot mould filling system has been designed and installed to improve filling consistency and minimize metal spills outside the moulds. This filling system allows for flexibility of production equipment, enabling the use of different moulds or casting different alloys having different flow characteristics without changing the filling system.

There is great incentive for improving the energy efficiency of aluminum melting and holding furnaces. Many factors affect the amount of energy required to melt scrap aluminum, but the influence of each factor can be difficult to quantify. The effect of each factor on the flow of material and energy can be calculated by developing a system model of the process. The most effective model utilizes the fundamental laws of mass and energy conservation, along with empirical relationships developed from plant observations. This paper describes the procedure for developing an Excel model for a 113,000 kg (250,000 lb) side well furnace melting 120.5 kg/min (7200 kg/hr, 15,900 lb/hr) [1]. Simulations were carried out with the aid of specially-developed Excel add-in programs. The results were used to optimize the firing rate for minimizing the specific energy requirement, and quantifying the use of special energy-saving techniques.

A numerical model using the commercial software ANSYS Fluent was previously established for one of Hydro Aluminium’s furnaces at the Rolling Mill plant in Karmøy, Norway, to analyze heat transfer conditions in the 35-ton casthouse furnace. The model was extended to evaluate a low temperature oxy-fuel burner technology different from the burners currently used today. It incorporates gas flow, chemical reactions, conduction, convection and radiation along with latent heat release. A steady state model with a heat sink was used to attain representative furnace conditions before switching to transient calculation. The focus of this work is to look at the influence of possible turbulence models and combustion models for this setup. Results confirm clear differences between the applied turbulence models and combustion models.

Since its introduction to the aluminum industry in 1998, the Rotary Flux Injection technology has been implemented in cast houses worldwide for replacing chlorine for metal treatment in furnaces. Using a rotary impeller to inject salt into furnaces maximizes shearing and reduces the concentration of alkali/alkaline earth impurities as well as the non-metallic inclusion content in the melt. This equipment also provides efficient mixing of molten aluminum to eliminate thermal gradients and to improve the alloying ingredient dissolution and homogenization.

Hess & Brondyke’s studies of molten metal explosions proved molten aluminium could explode upon contact with moisture and various substrates. Over forty years later, their findings have been mostly forgotten. This paper will review Hess & Brondyke’s findings as well as other studies with a special attention to the various specific substrates that upon contact with molten metal generate an explosion. I argue that Hess & Brondyke’s research is still valid today and if followed will result in a decrease in the number of molten metal explosions occurring in our industry.

Continuous flue gas composition measurements (CO, CO2, O2, H2) were made for three rotary aluminum melt furnace heats, with air/oxy/gas combustion. In many cases, during rotary furnace aluminum melting, furnace atmosphere conditions become increasingly reducing (higher CO and H2, lower CO2) as the heat progresses. This suggests that aluminum is being oxidized.For these three heats, the measured flue gas CO, CO2 and H2 compositions were utilized, with C, H and O balance equations, to calculate instantaneous aluminum oxidation rates throughout the heat.For medium gauge clean scrap (clean crushed wheels), calculated aluminum oxidation rate is zero. For dross, calculated total aluminum oxidation loss is 0.5%, based on aluminum tap weight, for both 50% O2 combustion and 90% O2 combustion. Instantaneous aluminum oxidation rates are highest at the end of the heat, corresponding to higher temperatures.

In essence, only a small fraction of the heat supplied to the conventional aluminum casting (holding) furnaces is used up for its main purpose — alloying and maintaining the metal set point temperature. As the metal introduced to furnace is most often already in the molten phase, most of the energy supplied via open fire burners is usually lost through the furnace walls, door openings and the flue gas. In this theoretical study, fire-tubes are immersed in the metal as an alternative for the conventional open fire burners. Using the Finite Volume Method (FVM), Computational Fluid Dynamics (CFD) models, with heat transfer and combustion incorporated, are developed for both design options, using the commercial code StarCCM+. Thermodynamic analyses are adapted in making a comparison between both designs. In both options, the non-premixed flame (heat source) is simulated using the Eddy Break Up (EBU), 3-step reaction models. The participating media radiation models are adapted for a comprehensive estimation of the radiation heat transfer within the furnace. Turbulence within the flame is modeled using the standard K-epsilon model. Results show that the immersed fire tube improved the furnace’s thermal efficiency.

The development of a multi stage filter comprising a ceramic foam filter applied in a first chamber operating in cake mode; grain refiner added in a second chamber and a cyclone deployed in a final chamber to ensure removal of oxides and agglomerates arising from grain refiner addition was presented in TMS 2008. The first industrial prototype, installed at Trimet Aluminium at Essen in Germany, demonstrated that liquid metal could pass through the cyclone successfully without excessive turbulence or splash. Initial difficulties in achieving the desired flow rate through the cyclone were overcome by increasing the head height difference to 150 mm and a flow rate of >20t/hr was achieved in testing on a sow casting station and reported at TMS 2011. The most recent results of trials carried out on the Research Casting pit at Trimet were measurements of the metal cleanliness achieved were made are presented.

Electromagnetic fields can influence the behavior of liquid metals in commercial Ceramic Foam Filters (CFF’s). In the present study 9 inch industrial CFF’s of high grade with 50 and 80 pores per inch (ppi) have been investigated. The main objective was to prime the 9 inch industrial scale CFF’s with a standard aluminum casting alloy (3XXX — alloy) by the use of various magnetic field strengths (max. 0.12 T) induced by a coil. The obtained results were compared with reference gravity experiments. The influence of the electromagnetic Lorentz forces on the obtained results was calculated with 2D Finite Element Modeling (FEM) using the COMSOL® software. The fluid flow characteristics inside the CFF were considered and are part of another publication within the group.

JW Aluminum identified the need to quantify inclusion loads in its molten metal in an effort to deliver higher quality products to its customers. The inclusion detection system had to be able to identify and quantify potential sources of inclusion related defects as well as the benefits from process improvements. This paper describes the validation of principle and measurements made before the final decision to purchase a MetalVision MV20/20 ultrasonic inclusion analyzer. The initial practical experience after purchasing the system obtained is also discussed.

At the TMS conference in 2013 the paper Ultrasonic Degasing and Processing of Aluminum was presented (Rundquist & Manchiraju, Ultrasonic Degasing and Processing of Molten Aluminum, 2013). The focus of the paper was the removal of dissolved hydrogen from molten aluminum using Ultrasonics. In this paper we will present a brief overview of the earlier work. Our continued work using ultrasonics in molten aluminum both in the foundry and continuous casting has demonstrated that not only were we removing hydrogen efficiently from molten aluminum but there was a significant reduction in inclusion levels as well. The main focus of this paper will be to present the effectiveness of the ultrasonic degassing process at removing hydrogen and inclusions from the molten aluminum. Such inclusions include oxide films, carbides, refractories etc… Data from both the continuous casting and foundry process(s) will be presented and discussed. Finally, based on the ideas advanced in the previous sections, conclusions will be drawn on the overall ability of ultrasonic processing of molten aluminum along with the improvements in casting quality.

CFFs are used to filter liquid metal in the aluminum industry. CFFs are classified in grades or pores per inch (PPI), ranging from10–100 PPI. Their properties vary in everything from pore and strut size to window size. CFFs of 80–100 PPI are generally not practical for use by industry, as priming of the filters by gravitational forces requires an excessive metal head. Recently, co-authors have invented a method to prime such filters using electromagnetic Lorentz forces, thus allowing filters to be primed with a low metal head.In the continuation of this research work, an improved experimental setup was developed in the present study to validate previous results and to measure the permeability of different filters, as well as a stack of filters. The study of permeability facilitates estimation of the required pressure drop to prime the filters and the head required to generate a given casting rate.

The quantitative methods for controlling and predicting the level of Si modification in EN AC-46000 aluminum cast alloys were examined using thermocouples (thermal analysis) and optical microscopy (image analysis). A wide range of Sr, from 35 to 500 ppm, was added to the alloy. The alloys were cast using three different molds providing different cooling rate and consequently varied microstructure coarseness. Large difference in nucleation and growth temperature of unmodified and modified alloy was found irrespective of coarseness of microstructure. The depression in growth temperature of eutectic Si found to be strongly correlated to content of modification agent as well as modification level. Thermal analysis technique was realized as a non-biased, accurate and inexpensive approach for on-line prediction of Si modification level in the EN AC-46000 alloy cast under different cooling rate.

A kind of Al-5Ti-0.3C master alloy with uniform microstructure has been prepared using a new technology. The pre-nucleating TiC particles with an average size of about 0.3µm are dispersed homogeneously in the a-Al matrix.This new Al-5Ti-0.3C master alloy has great refining performance on aluminum alloys. It is found that the average grain size of 6063 alloy can be reduced from 3000µm to 40µm by the addition of the prepared Al-5Ti-0.3C master alloy and the refining efficiency does not fade obviously within 60 min. Furthermore, the mechanical properties and corrosion resistance of 6063 alloy are also improved. The ultimate tensile strength and hardness of the 6063 alloy can be largely improved from 170MPa, 35 to 271MPa, 81.7, respectively. In addition, the corrosion resistance is also enhanced largely. Finally, the possible mechanisms are also discussed.

Particle settling and stratification in aluminium processing operations are of importance for cast house performance and product quality as they influence important factors such as furnace cleaning frequency, and design of launder troughs and inline equipment.Analytical analyses of settling generally refer to Stokes’ law describing the motion of a solid sphere in a liquid but neglect the dominating factor of thermal convection. A new option to monitor particle concentrations at different melt depths based on LiMCA technology was utilized to study particle settling within AMAP, the Open Innovation Research Cluster for Non-Ferrous Metals at RWTH Aachen University.This paper reports the initial results obtained with the new LiMCA method in trials in a laboratory crucible furnace. The results are analysed with respect to the influence of particle size on settling kinetics and stratification and are compared to the above mentioned theoretical calculations.

The LiMCA measurement principle has proven to be a robust approach for measuring solid inclusions in molten aluminium in various industrial conditions thus providing a quality indicator for metal cleanliness of aluminium alloys.Improvements in electronics, equipment configuration and data processing have made the LiMCA much more usable in industrial process environments. This paper reviews some of these advancements and how they affect the ability to use LiMCA in industrial environments. New perspectives on further improvement of the technology for the next generation LiMCA III will be presented.

Following the initial molten metal quality studies with the MetalVision Inclusion Analyzer1,2, the need for more robust molten metal treatment equipment and methods was identified. Through Rapid Improvement Events and other Six Sigma techniques, systematic changes were introduced and closely monitored. Significant improvements were made in melting, degassing and filtration that resulted in the ability to adapt the production process to varying raw material types. The changes made are discussed as well as their effects on the molten metal quality measurements.. Implementation challenges and the follow up control ensuring uniform and consistent sustainable benefits are also discussed. Data is presented proving that final product quality has improved as measured by in plant non-conformances and the goal of zero customer returns and complaints.

Market trends caused a reduction in the spread between recycled and prime aluminum starting in 2013. This required JW Aluminum to be responsive to changes in raw material pricing. The ability to rapidly respond to changing raw material markets, depends on a full understanding of the effects raw material has on the JW Aluminum production process. To facilitate a better understanding, JW Aluminum recently purchased a Metalvision MV 20/20 inclusion analyzer that was used extensively to study the effects of raw materials on molten metal quality. As part of the 6-Sigma DMAIC process1, experiments were designed using critical variables and controlled Key Process Inputs. The principle outputs were obtained from the MV 20/20 and final product quality evaluations. The study showed that raw materials has a statistically significant effect on molten metal quality. As a result of this study, Lean Rapid Improvement events were held that significantly altered the way in which JW Aluminum melts and processes its raw materials2.

Aluminum alloy castings are becoming commonplace for critical applications in the automotive and aerospace industries where materials failure is not an option. Tight control over the cleanliness of the melt (mitigation of solid particle inclusions and dissolved gases) and microstructure must be achieved. Very few techniques exist that can quantitatively measure inclusion levels in-situ. The use of laser-induced breakdown spectroscopy (LIBS) has shown promise as a technique to quantify solid particles, wanted and unwanted, in aluminum melts. SiC particles were added to pure aluminum and analyzed with LIBS, and traditional metallography. An algorithm, based on the Nalimov test, was used to differentiate between LIBS signal from the matrix and particles. Initial tests show a linear relationship between SiC concentration and LIBS signal.

LiMCA is the reference technique available today for on-line measurement of inclusions in molten aluminium. With LiMCA a glass sampling tube is immersed in molten aluminium and metal is alternatively pumped and rejected in this tube. By construction, LiMCA gives access to inclusions ranging from 20 to maximum 300 µm (which is the sampling hole size). Commercially available tubes have the sampling hole located 50 mm under the surface of molten metal. In this work elongated tubes have been assessed in order to measure inclusions deeper in the melt. The paper illustrates the work done to validate the elongated tubes, by measurements done in crucibles and launders. The need for elongated electrodes is also discussed. This work provides a methodology for the measurement of inclusions at different depths into the melt, or for the measurement in locations with difficult access.

The electromagnetic forces in an induction furnace deform the free surface of a molten aluminum bath into a dome shape. The deformation may also be affected by the oxide skin present at the free surface. A structured light technique was used to measure the free surface deformation and its variations in a laboratory scale induction furnace, as a function of operating parameters — current intensity and liquid metal filling inside the crucible. A numerical model capable of taking into account the strong electromagnetic — hydrodynamics coupling was developed to simulate the electromagnetic stirring phenomena. The Volume Of Fluid (VOF) method was applied to model the free surface deformation. A comparison of the measured and the calculated dome shapes is presented.

The challenge has always been to melt aluminum at it’s highest recovery. As the aluminum industry has developed over the past 60 years the value of the aluminum and the view of the oxidation products has changed from one that was thrown away to one that we look to completely recycle. Aluminum melting generates dross. Dross removal carries out free aluminum. Minimizing these two realities has been the charge of companies developing systems for our industry. The last 60 years has marked real progress in these areas and continues move forward successfully.

Aluminum and its alloys have experienced significant increases in their usage in the automotive industry for the past few decades. Large quantity of aluminum is being produced everyday with huge waste such as dross and chips. Due to environmental and cost issues, production of aluminum via recycling is increasingly becoming a must for further expansion. However, technologies for aluminum recycling are far from perfection, in particular for machining chips. In this work, machining chips of aluminum alloy A380 were collected from computer numerical control (CNC) machines and then cleaned. The cleaned chips were thermally recovered with two fluoride-containing fluxes and one fluoride-free flux. The recovery rate of the recycled metal was determined based on weight measurements. The results of tensile testing, microstructure analysis and chemical composition evaluation indicate that the quality of the recovered metal is comparable to die-cast A380.

Rio Tinto Alcan (RTA) produces Value-Added Aluminium Products (VAP) with very tight chemical composition specifications for addition ingredients and trace elements in order to meet the final product requirements for the client. The control and the certification of the alloy chemical composition rely on the utilization of the spark atomic emission spectrometry (Spark-AES) or commonly named Optical Emission Spectroscopy (OES). This technique, used by the cast house operation personnel, must be calibrated using a combination of appropriate spectroscopic Certified Reference Materials (CRM) with very tight chemical composition which are referenced to wet chemical analysis methods. This paper presents the production and certification process applied by RTA at Arvida Research and Development Center to certify the composition of CRMs. The analytical procedures and methods from classical wet chemistry to modern instrumental techniques are used to produce global and individual certificate of analysis for every CRM disc.

More scrap from Automotive Body Sheet (ABS) alloys will soon be entering the North American recycle stream. Some of this scrap will enter from end of life automobiles (post-consumer scrap) while more immediately, scrap will be generated at the automotive stamping plants (post-manufacturing scrap). Current projections show that the recycle rate of post-manufacturing scrap could be of the order of 30,000 tons per year. Unfortunately of the 4 major alloys used in ABS, none are 100 % compatible for use as a feed stock for one of the other ABS alloys. In fact most of the alloys are only moderately compatible with the other ABS alloys. This creates a risk in the recycling of these postmanufacturing materials back into the same alloys if contamination is not closely controlled or dealt with in another manner. Methods to minimize risk from post-manufacturing scrap to the cast house will be discussed.

The value of pilot anode testing for evaluating raw materials, anode recipes and mixing/forming changes has been well documented in previous studies. Since early 2013, RÜTGERS and Rain CII have invested significant effort into developing a new pilot anode facility at Castrop-Rauxel, Germany. With the ability to mix and form paste at temperatures up to 300 °C and bake anodes at temperatures up to 1300 °C, this new facility is now being used actively across a wide range of carbon raw material R&D projects. Pilot-scale anode results will be presented to expand on previously reported work on low-PAH binder systems along with tests on different quality CPC raw materials. The good reproducibility of the pilot anode process allows better correlation of raw material properties and processing parameters on anode quality with a well targeted testing program.

In the context of degrading coke quality, Rio Tinto Alcan has implemented different measures to maintain and even improve anode quality. Over the last twenty years, coke vibrated bulk density (VBD) has decreased and its variability has increased. In order to cope with this challenge, a separation process based on coke density was developed. High density particles are used in medium and coarse fractions, whereas low density particles are crushed and used as fines. Use of a coke separator has resulted in an increase of baked anode density (BAD) by ~0.015 g/cm³. Furthermore, the BAD variation upon use of different cokes was reduced. Different phases of the technology development (from laboratory experiments to industrial implementation) and results from six years of operation are presented.

The use of a vertical mill for the grinding of anode coke is well accepted in the Aluminium industry. One of the raw materials, calcined petcoke (CPC), is sourced from different parts of the world with different properties. As the ground product must have constant properties, the grinding process must be adjusted accordingly.Adding of crushed butts into the grinding mill is a process step which may become more important in future. In this paper these implications on the grinding process using the vertical mill are described.

Petroleum coke, used in anode manufacture has some porosity which tends to absorb pitch into the pores during green paste mixing. This is becoming more important as the sources for higher quality petroleum coke decrease and lower quality petroleum cokes with higher porosity must be used. A theoretical formula of pitch absorption coefficient has been deduced from the formula for the density of an aggregate mixture. Variations on the absorption coefficient and porosity were studied as a function of particle size of petroleum coke, mixing temperature, mixing time and the pitch content in the paste. The pitch absorption coefficient is found to be between 0.3 and 0.8. The information obtained may be useful in optimization of the pitch level in use of cokes with various absorption coefficients.

The objective of this work is to develop a rapid and nondestructive machine vision sensor to predict Vibrated Bulk Density (VBD) of coke aggregate samples based on their surface textural characteristics obtained by imaging. This information could be useful for ultimately making real-time process adjustments to reduce green anode variability. Coke samples from different sources and sieved in a number of size classes were investigated individually and in blends. Wavelet Texture Analysis (WTA) was used to extract textural features of coke samples, and these were related to their VBD using Partial Least Squares (PLS) regression. It is shown that WTA captures variations in coke size and source and leads to good VBD predictions.

Optimizing the composition of the calcined coke aggregate blend used in anode manufacture is important from several aspects, including production of high density anodes, reducing binder pitch requirement, and/or minimizing problems such as cracking or dusting. Plots of aggregate density as a function of composition have been experimentally determined for a number of carbon plants using the Y-blender method. Important experimental considerations will be discussed and representative results given.

Changes in the quality of green cokes available for the production of pre-baked carbon anodes used in the production of aluminum are stimulating the development of a better understanding of the thermodynamic behavior of cokes. Impurity content and crystallite sizes (over a wide range of temperature) are of particular concern. No thermodynamic model currently exists for the precise prediction of the enthalpy and entropy of cokes that can be applied to industrial processes. The present model uses a simplified structure for coke crystallites for the production of predictive calculations that can potentially incorporate the impact of various impurities. The thermodynamic properties of coke crystallites as functions of temperatures, crystallite sizes and hydrogen/sulfur contents are presented in this work. Examples of key applications of the present model are: the calculation of dehydrogenation/desulfurization curves of cokes with constrained L _c and of the gaseous composition of volatile species emanating from heat treated cokes.

Carbon anodes, regularly consumed in primary aluminum production, are made of calcined petroleum coke, coal tar pitch, and recycled materials. The properties of calcined coke depend on the source of crude oil and the calcination conditions. Similarly, pitch properties depend on the coal tar source and the manufacturing process. Different calcined coke and pitch mixtures are commonly used in anode manufacturing to meet various regulations and/or due to economics and availability. This makes it hard to maintain the anode quality. Calcined coke and pitch are placed in silos and used when required for production. It is hard for the industries to track the source of raw materials used in their daily recipes. This article presents an approach to trace back the details of the use of particulate raw materials with a custom-made software, which takes into account the type (mass flow or funnel flow) of silos. Such tracking can help identify the causes of problems and maintain/improve anode quality.

Anode manufacturing is an important step during the production of primary aluminum, and baking is the costliest stage of the anode manufacturing process. The industrial challenge resides in obtaining a good anode quality while keeping the energy consumption, environmental emissions, and cost to minimum.A dynamic process model has been developed for horizontal anode baking furnaces. It covers all important phenomena such as fuel combustion, generation and combustion of volatiles (tar, methane, and hydrogen), air infiltration, and heat losses to the atmosphere and the foundation. The model was built using two coupled sub-models of the flue and the pit and was validated using the plant data. It simulates the dynamic behavior of the furnace and gives a prediction of its operation and performance. In this article, the modelling approach will be described, and the results of a number of case studies will be presented.

Having acquired a brown field manufacturing site in 2012, Century Aluminum, US, (Century) set about building a state-of-the-art aluminium anode manufacturing plant in Vlissingen, NL, meeting the latest environmental, safety and operational standards.Realised in less than one year, the new fume treatment system (FTS), comprising three regenerative thermal oxidisers (RTO) in combination with wet desulphurization technology, ensures the most cost-effective solution and lowest exhaust gas emissions values.Lowest CAPEX and OPEX costs were the primary considerations for this FTS configuration — the first ever on a baking furnace worldwide.This paper describes the evolution of the FTS design, the technical and commercial benefits of this solution, and how it was successfully integrated into the new anode production facility in record-breaking time.

In 2013, Century Aluminum carried-out large investment to restart an anode production facility in The Netherlands to produce world class anodes for parent aluminum smelters. Along with the partial refractory refurbishment of the existing baking furnace, the project included the upgrade of the firing equipment to comply with new local stringent regulation for NOx emission.Fives Solios was selected to implement its latest control system (HeliosRT) featured with clean and efficient injection technology.Few months only after the furnace start-up, the plant reached stable operation and production target and welcomes the performances of the new firing system.

Aluminum production requires the use of carbon anodes. Anode quality influences strongly the cell stability, energy consumption, green house gas (GHG) emissions, and production cost. Current practice for anode quality evaluation (visual inspection and analysis of a core taken from the top of a small number of anodes produced) gives limited information.A simple and non-intrusive technique has been developed to measure the electrical resistivity distribution in industrial anodes with the objective of using it for on-line quality control in the paste plant to eliminate defective green anodes. This helps avoid the unnecessary baking of substandard anodes and reduces energy consumption and GHG emissions. The technology could ultimately be used also for baked anodes. The electrical resistivity is a distinctive characteristic of anode quality, and its distribution indicates anode homogeneity. In this article, the measurement technique will be explained and results will be presented which demonstrate its use for the determination of anode quality.

Throughputs and anode quality requirements for vibrocompactors are continuously increasing. Meanwhile, properties of raw materials are decreasing and expectations for cleaner and safer working environments are higher. A few years ago, Fives developed a new generation of vibrocompactors called “XELIOS”. Its first industrial implementation was done on a demanding site with the highest throughputs and solicitations. Reliability had to be improved.This paper introduces the latest developments done, based on operations feedback from the Gulf area:•Environment and Health conditions have been improved to comply with new expectations and process parameters•Overall Equipment Efficiency has been increased thanks to dedicated monitoring, on site measurements and off line models leading to an improved mechanical design•New features have been added to meet highest requirements i.e. increase of green anode density and easy monitoringToday 21 formers are installed.

Continual capacity creep and expansion of the smelter without proportional increase in Carbon Plant production capacity has resulted in the baked anode requirement at Dubai Aluminium (“DUBAL” — known as EGA Jebel Ali Operations) exceeding its Baking Furnace capacity. The additional anode demand was satisfied by procuring the shortfall from the international market at a premium.In order to limit DUBAL’s dependence on third parties, the baking furnace productivity was increased by ~14% by operating the furnaces with shorter fire cycles. Operating the furnaces with shorter fire cycles resulted in an increase in anode temperature variation across the pits. To address this variation, several flue wall design changes were incorporated into the rebuild plan for the upcoming rebuild of Anode Baking Furnace #4 (ABF 4).In 2013, after achieving an average flue wall life of 184 heats, ABF 4 was successfully rebuilt with minimal production losses while incorporating design changes to increase productivity and improve heat distribution within the pits. This article describes DUBAL’s kiln rebuild strategy and the execution of Kiln 4 rebuild while integrating design changes.

In aluminum industry, carbon anodes are consumed continuously during alumina reduction in the electrolysis cells. Anodes are made of calcined coke, butt, and recycled anode particles and pitch as the binder. Green anodes are baked in large furnaces where they attain specific properties in terms of density, mechanical strength, and electrical conductivity. Baking is an important and costly step in carbon anode production. The proper operation of the furnace provides the required anode quality.Mathematical modeling allows the prediction of the heating profile of anodes during baking. Taking into account all the relevant phenomena, a 3D transient mathematical model was developed to simulate the different stages of the baking process in the furnace. The predictions give a detailed view of the furnace operation and performance. In this article, the 3D model is described, and the results on the impact of various parameters on furnace behavior are presented.

Monitoring anode mechanical strength is increasingly important in production and operation of carbon anodes in high amperage cells due to higher crack driving forces. To achieve a better understanding of the directional crack resistance of the anode, a laboratory testing rig has been developed and installed at Hydro Aluminium Primary Metal Technology. The rig consists of a high-precision testing machine and a Hydro-developed measurement system which calculates the Young’s modulus of elasticity, the tensile strength, the fracture strain and the fracture toughness. The equations of the physical parameters are derived from a finite element modelling of the specimen loadings, and are implemented in a Hydro developed laboratory software which computes the values from load-deflection data and transfers the parameters to a database. The paper outlines this method including the sample preparation machine.

Carbon anodes constitute a substantial part of the cost during the electrolytic production of aluminum. The industry tries to minimize the consumption of anodes by improving their quality. Therefore, a clear understanding of the impact of the quality of raw materials as well as process parameters on anode properties is important.The plants have a large collection of data, which is complex and difficult to analyze using conventional methods. In this article, linear multivariable (LMA), partial least square regression (PLS), and artificial neural network (ANN) analyses are presented and compared as tools to predict the influence of different parameters on anode properties. Published laboratory data have been processed using Matlab software to carry out the analyses. The results clearly show that ANN is the best tool for prediction purposes. Unlike other methods, ANN can handle nonlinear complex relations even if a well-defined relationship is not available.

EMAL is a primary aluminium smelter with an annual production capacity of 1.32 million tonnes of aluminium. It has 756 cells operating at 385 kA and 444 cells operating at 450 kA. The prebake carbon anodes required for the operation of these cells are produced in two captive carbon plants. For its anode production, EMAL procures calcined petroleum coke from multiple sources. The properties of baked anodes produced during the last two years were analyzed to find correlations between baked anode properties with coke characteristics and process parameters. The analysis show that baked anode properties and anode performance are influenced by raw material properties and process parameters. The understanding gained through the analyses helps in adjusting the process parameters and selection/blending of cokes to produce optimum quality baked anodes that perform well in the cells.

Pilot test anodes were designed by Hydro Aluminium for laboratory studies using controlled blends of <2 mm aggregate from two single source cokes. Spatial and imaging methods were used to characterise anode surfaces with respect to consumption, density, pore distribution and real active area before and after electrolysis. The methods include X-ray computed tomography (CT), confocal microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). It was found that during electrolysis, the electrolyte does not completely wet the carbon inside large pores on the surface. Hence, even large pores do not contribute to the electrochemically active surface area. Large grains of isotropic cokes and anisotropic sponge cokes are consumed at approximately the same rate, and bubble coke in anisotropic sponge cokes are consumed at a slower rate than the bulk material. This is due to higher resistivity through the bubble coke.

Carbon anode, used in the Hall-Héroult process, is subject to both air oxidation and carboxy gasification by CO₂. These reactions are considered as being the main causes of dusting phenomenon in the electrolysis bath. More precisely, it is believed that CO₂ and O₂ preferentially attack the baked pitch (pitch coke) resulting in detachment of coke and butt particles in the form of dust. The present work aims at elucidating this phenomenon by studying the air and CO₂ reactivities of the prebaked carbon anode and also of its constituents. The air and CO₂ reactivities were evaluated using thermo-gravimetric analysis and the standard reactivity test of R&D Carbon, ISO Standard 12981-1. The microstructural features of the samples, i.e. real density, crystallite size and specific surface area, were measured. The reactivity of the anode and its constituents was assessed separately and their effect on dusting phenomenon was discussed.

The anode with under-calcined cokes have better component homogeneity and smaller carbon consumption in aluminum electrolysis. In this study, three types of petroleum cokes were calcined at 800, 900, 1000 and 1100 °C, respectively. The content of S and volatiles of cokes were measured against the calcining temperature. The air/CO₂ reactivity, electrical conductivity, density, porosity, compressive/shear strength of the bench-scale anode sample made by these cokes were optimized as a function of calcining temperatures. In addition, the L_C value and real density of cokes were tested to show calcining level of the cokes. Based on the results above, the optimum calcining level of cokes for the prebaked anodes was obtained.

The effects of anode current density, electrolysis temperature and KF addition in electrolyte on the consumption of prebaked anode during aluminum electrolysis was investigated in a closed laboratory cell. The current density varied from 0.75 to 1.1 A/cm2, the electrolysis temperature varied from 930 to 960 °C with modified electrolyte composition. KF content varied from 0 to 4 wt% in the electrolyte of the industrial composition. Electrolysis durations was 2 h, the distance between the electrodes was 35 mm. The total consumption of anode, the amount of carbon dust and the amount of carbon gasification were determined under the operating conditions similar to the industrial application. It is established that the increased current density and the KF addition reduces the anode consumption, but the consumption increases again when the current density is more than 0.9 A/cm2. The anode consumption increases with increasing electrolysis temperature.

In the production of aluminum from conventional prebaked Hall-Héroult electrolysis cells, anodes have to be replaced on a regular basis. The anode rod assemblies, which are submitted to multiple heating/cooling cycles, tend to deform over time, and attacks from HF gas and liquid bath erode the stubs to a different extent at each cycle. Following the anode butt recycling stage, the stubs have to be inspected to determine if the anode rod assemblies are still suitable for another run in the pot or if they require repairs. STAS has recently completed the development of a 3D measuring system allowing the measurement of hexapods and the likes. The proposed system allows multiple measurements to be taken at once. Stub lengths, erosion profiles, diameters, straightness and others can all be monitored. In addition to anode rod fitness for sealing, the system allows to keep statistics on the rod population.

The prediction of the air gap at the cast iron to carbon interface in the anodic assemblies as well as its closing and pressure build-up during the operation remain a complex task. It is therefore very difficult to predict the electrical performance of anodic assemblies. This main difficulty comes from the evolution of the thermophysical and thermo-mechanical properties of the microstructure mapping during these stages. To overcome this difficulty, a natural approach is to characterize this mapping of microstructures.In this paper, the creep properties at high temperature of the cast iron connector are determined using this approach. The results show highest creep strength of the pearlitic and white cast irons below 475–550°C compared with the ferritic microstructure. With the temperature, the creep deformation increases but above 550°C a graphitization in the pearlitic and white cast irons contributes to their growth, which is comparable or exceeds the creep rate.

The electrical resistance of an electrolytic cell requires a voltage drop of about 4.5 V for a current of 300 kA of which 7% is attributable to the anode assembly. Reducing this voltage drop is one of the most challenging research topics for the aluminum industry. Over the past decades, there has been much research on the minimization of this loss using the same assembly configuration. In this work, a new approach, which consists of inserting elements into the carbon paste during the anode production, was developed. This approach would provide a significant reduction in the voltage drop mainly through the improvement of the contact quality at the anode connection and the current distribution in the anode. Laboratory tests simulating the baking as well as the operation of small-scale assembly were carried out to estimate the resistance. The results demonstrate that it is possible to decrease the resistance at the anode connection under the conditions similar to those used by industry.

The properties of steel stubs change with each operational cycle of the Hall-Héroult process at high temperatures due to a carburization that occurs in carbon containing environments. The operability of carburized steels and its impact on the performance of the anodic assembly can be determined by evaluating the properties of new and recycled stubs. The chemical composition, mechanical, creep and thermo-physical properties were investigated to evaluate their changes regarding operational cycle and take into account in a numerical model for the assessment of their impact on the thermo-mechanical behavior of the anode, evolution of air gap between the anode and the cast iron connector, and voltage drop.The first results show that the initial carbon content of the new stub 0.2% increases up to 1.1% after 2–3 years of operational cycles and accompanied by cardinal microstructure changes that contributes to change of thermal expansion, tensile and creep strength, elongation and specific heat.

The effect on the high temperature oxidation behavior of partially substituting Cu by M, with M = Sn, Ag, V, Nb, Ir, Ru, Ta, in mechanically alloyed Cu-Ni-Fe anode was investigated. Characterization of the as-milled and consolidated powders was achieved through a combination of XRD, SEM and EDX mapping. On the basis of TGA experiments performed at 700°C under oxygen and subsequent SEM-EDX analyses, substitution of Cu by Nb, Ru, Ir, Sn and Ag leads to the formation of thinner Cu oxide layers at the surface of the electrode. However, except for M = Nb, chemical segregation was observed in the bulk alloy.

NiFe₂O₄ ceramic based inert anodes were fabricated by a two-step cold-pressing sintering process. The bubble behavior of NiFe₂O₄ ceramic based inert anodes was investigated in a two-compartment see-through quartz cell. Anodic overvoltage and potential decay curves on the inert anodes were measured by using the steady state and current interruption technique. The results show that the electrolytic gas evolution for NiFe₂O₄ inert anodes, including bubble nucleation, growth, coalescence, growth again, migration and escaping, lasts for 79s and the escaping bubble size is about of Φ4mm×2mm. While gas evolution lasts for 102s of carbon anodes with larger releasing bubbles. When current densities are 0.6, 0.8, 1.0 and 1.2A/cm2, the anodic overvoltage of NiFe₂O₄ anodes are 0.189 V, 0.270 V, 0.309 V and 0.359 V, respectively. After adding small amount of MnO₂, V₂O₅, and TiO₂, a minor reduction in anodic overvoltage of NiFe₂O₄ anodes can be obtained.

Grey relational analysis was a data processing method used to sort out the correlation extent of effect factors in a system with uncertain information. In the paper, it was applied to evaluate the effect of operating parameters on corrosion rates of inert anodes in aluminum electrolysis. The corrosion rates of 5%Ni-NiFe₂O₄ cermet anodes were investigated as a function of some operating parameters. To reach a better understanding of the corrosion mechanism, the behavior of the anodes was observed under some designated conditions, such as in pure cryolite solvent, high current densities, and varying cathode surface areas. It was confirmed that low alumina concentration and high temperature were detrimental. The experiment results showed that grey relational analysis was an innovative data process method used to rank the corrosion extent of effect factors in the corrosion processes.

Twin roll casting is a highly cost and energy-efficient way to produce aluminium strip directly from liquid aluminium. The limiting step in increasing productivity is heat removal from the melt and solidification which must be finalized before the material reaches the roll gap. A simple heat balance model is used to evaluate the role of the decisive components for heat removal with a special focus on transversal temperature variations. Especially the design of the melt distribution system proved to be important for the reduction of transversal variations. Hydro’s tip design provides a more homogeneous melt temperature along roll width than standard designs and hence allows lower furnace temperatures as well as higher casting speeds leading to reduced energy consumption and higher productivity.

A single roll caster equipped with a scraper was designed and assembled. The effect of the scraper was investigated. A constant load of 1 N/mm was sufficient to push the scraper. The surface that did not contact to the roll was scribed by the scraper. The thickness distribution was improved. The heat transfer between the roll and the strip became greater and the strip was sufficiently cooled. A strip of 5182 aluminum alloy could be cast at the speed up to 40 m/min. Center line segregation did not occur, and no difference was found between the two surfaces after cold rolling.

Aluminium alloys produced by twin-roll casting exhibit inherently existing features due to distinctive solidification behaviour encountered during casting. Contrary to fine intermetallic particles observed at the outermost surface, centerline segregations enriched in solute elements reside at the mid-plane of cross-section. These morphological and compositional discrepancies are affected by casting parameters and resultant heat extraction due to separating force exerted by solidifying metal. In that respect, materials produced with different set of casting parameters were exposed to different thermo-mechanical processes to elucidate recrystallization and grain-growth behaviour inherited by initial as-cast microstructure. Microstructures were investigated by employing metallographic techniques throughout downstream processes. Complementary studies were performed by electrical conductivity measurements, tensile tests, micro-hardness tests and corrosion tests. Results show that microstructural properties of as-cast sheet can be tailored with defined combination of casting parameters. This also results in different material properties to evolve as they are exposed further annealing and rolling operations.

A conventional process chain for the manufacturing of steel-clad aluminum strips using roll bonding comprises many auxiliary operations. These steps include the surface preparation of steel and aluminum strips as well as heat treatment for an interfacial diffusion control. Twin-roll casting provides an efficient alternative way to join these metals. In this process a thin solid steel strip is fed between two revolving rolls together with an aluminum melt. The melt solidifies rapidly to a thin layer which is subsequently deformed in the roll gap. For a comparison of the mechanisms and conditions of joining using these two methods, a series of experiments of roll bonding at a temperature near the melting point of aluminum were carried out. The minimal hot deformation strain necessary for a satisfying bonding quality was identified. The results of roll bonding experiments and twin-roll cast trials related to clads’ microstructure and mechanical properties were compared.

A vertical type tandem twin roll caster and a vertical type twin roll caster equipped with a scraper were proposed to cast clad strip. The vertical type tandem twin roll caster can cast a three or five — layer clad strip, and the vertical type twin roll caster equipped with a scraper can cast two — layer clad strip. In this paper, the casting parameters that affect the clad ratio, bonding of the strips and re-melting of the layers are investigated.

In order to fabricated high strength aluminum sheets with reasonable cost, several Al-Mg and Al-Zn-Mg-Cu alloy strips were successfully fabricated by the twin roll casting with a proper operating condition. The strips had good workability during subsequent warm/cold rolling processes due to the fine cast structure. The final annealed sheets have good mechanical properties at ambient temperature. The tensile strength and elongation of annealed Al-10wt%Mg sheet are about 400MPa and 30%, respectively. The tensile strength and yield strength of Al-Zn-Mg-Cu alloy sheet after the aging at paint baking condition (180oC × 30min) are 480MPa and 350MPa, respectively. The developed aluminum alloy sheets have a superior strength to commercial aluminum alloy sheets used for automotive body structures.

Twin roll casting is a combined solidification and deformation process and the material flow is thereby more complex than in many other casting processes. A modelling approach is presented including heat and fluid flow coupled with stresses and deformations. A Coulomb friction law is applied and by iterations on the mechanical conservation equations the parts of the cast surface that are either in slip or sticking mode against the roll shell are determined and tangential forces are calculated. Results like the total roll force and the forward slip on the strip are available from the model. Generally the model approach is applicable to both aluminium and magnesium casting with the appropriate material characteristics. In this study a 2D finite element simulation on the twin roll casting of a 1050 alloy is performed and the calculated roll force and forward slip are compared with results from industrial TRC processing trials.

In this study, the effect of copper addition on microstructural evolution, mechanical and corrosion properties of twin roll cast (TRC) AlFeMnSi alloy system mainly used in container foil applications was investigated. Microstructural characterization studies were conducted on as-cast, homogenization annealed and final products by employing optical and scanning electron microscopes. The mechanical properties of the samples obtained from compositional were determined at the thickness of final product by tensile and Erichsen tests. Addition of Cu improved mechanical properties and formability performance of the foil products with the contribution of final annealing parameters. Corrosion properties were also improved as compared to those of the AlFeMnSi alloys having lower Cu content.

Finstock materials having different chemical compositions produced by TRC have been widely used in heat exchanger systems. Al-Mn alloys produced with TRC technique are also used as fin materials in various brazing applications. With the addition of zinc, these alloys are utilized as sacrificial materials to protect tube material. Alloy chemistry and casting parameters primarily dictate the stoichiometry and morphology of microstructural constituents in TRC strip.Motivation of this study is to prolong the corrosion resistance of fin material by tailoring microstructure of as-cast strip during casting process. This was accomplished by decreasing the magnitude of centerline segregation instead of altering overall composition of the alloy.Casting parameters were altered to gain better control over the microstructural constituents. Microstructure of as-cast strip and end product were characterized through entire thicknesses. Magnitude of CLS was correlated with variants of casting parameters. Results were supported by electro-chemical potential measurements and salt-spray tests.