Light Metals 2021

Efficient operation of the red mud settling and washingSettling and washing system is a key operational goal for an alumina refinery. The concentration of soda in thickener underflow and the dosage of flocculant have great influence on the production cost of alumina. SAMI has developed an intelligent control system for red mud settling and washing, which can monitor the data of thickener online in real time through data mining, optimization of control strategy, and other methods to realize automatic intelligent control. The intelligent control system has been built, deployed, and tested into operation for about two years in an alumina refinery in China. The results show that the consumption of flocculant is reduced by 15%, the concentration of discharged soda is reduced by 16~36%, and the economic benefit is remarkable.

Plant volume controlPlant volume control is a challenge for all alumina refineries because it involves complex mass and energy balances with numerous variables and conflicting goals. For instance, maximizing tank levels means increased production, but tank overflows mean safety risks and unnecessary cleaning expenses; increased water in red mud filtration means better caustic recovery, but higher costs in water evaporation. Bayer process refineries have a large number of equipment and tanks in which caustic liquor flows and many parameters vary dynamically. Therefore, it is necessary to have well-established control limits, plant volume parameters, and targets to allow daily routines of caustic cleaning and maintenance. This paper presents the development in CBA’s alumina refinery, regarding the tools to support teams to make important decisions in volume control and management system created to support weekly and annual planning.

In the process of alumina production using Bayer process technology, organic impurities (like oxalate) can enrich along the production process, which may bring in some serious problems. For example, the mother liquor will thicken, the viscosity will increase, and the sedimentation performance of the red mud will decrease, if the organic impurity content is high. Calcium aluminate hydrate, as one process intermediate product, has small particle size, and a large specific surface area, which has obvious adsorption potential. It has practical significance to study the adsorption and removal of organic in sodium aluminate solution by Tricalcium aluminate hexahydrateTricalcium aluminate hexahydrate (TCA) (TCA). Based on the above statement, the efficiency of TCA on the oxalate removal was investigated. Besides the influence of different prepared condition for TCA was also investigated using orthogonal experimentOrthogonal experiment method.

The desulfurizationDesulfurization of high-sulfur bauxiteHigh-sulfur bauxite via flotationFlotation is more difficult than conventional sulphide, since the finely disseminated sulphide in the high-sulfur bauxite can lead to excessive particle entrainment, increase of froth, and low separation efficiency. Acidification of high-sulfur bauxite resulting in changes in mineral surface properties is one of the main reasons for this. RegulatorsRegulator could be used to adjust the mineral surface properties and pulp properties to improve flotation efficiency. The effects of several regulators on the flotation desulfurization were systematically investigated in this work. The results indicate that the regulators have great impacts on the desulfurizationDesulfurization efficiency. Sodium silicate could significantly reduce the sulphur content of concentrate from 0.90 to 0.29% and increase the concentrate recovery by more than 10%. Zeta potential results prove that sodium silicate can eliminate the effect of acidification on flotationFlotation desulfurization.

Zinc is one of several impurities in alumina products. To reduce zinc in Bayer liquor, a novel method using organic additivesOrganic additive was proposed. An orthogonal experimentOrthogonal experiment methodology was applied to explore the interactions between different impacts. L9 (33) orthogonal experiments were designed to optimize the process parameters such as temperature, retention time, and dezinc agent (species and dosage). The results show that the optimum experimental conditions are: temperature 80 °C, retention time 2 h, and dezinc agent dosage 0.4 gpl. Based on the experimental results and in line with theory, it is concluded that the temperature has the main influence, followed by dezinc agent dosage, and then retention time. The impact of organic additiveOrganic additive on the content of organics in the Bayer liquor was also investigated. Results show that the organic additives had little effect on the organic content in Bayer liquor, which implies that these additives have great application potential in alumina refineries for impurity control.

Using an effective collectorCollector is often the key to improving the flotation recoveryFlotation recovery of valuable mineral concentrates. China’s diaspore-type bauxite is a refractory ore, since silicate minerals, such as kaoliniteKaolinite, are often closely embedded with diasporeDiaspore. Propyl gallate (PG) is an effective and novel collector of diaspore. Detailed flotation behaviors of diaspore and kaolinite with PG and traditional collector sodium oleate (NaOL) were investigated in this work. The effects of stirring speed, aeration volume, slurry pH, and collector dosage on the flotation recovery of the two minerals were discussed. The results show that, compared with the traditional collector NaOL, PG had better collection and selectivity for diaspore since the collectorCollector PG could increase the hydrophobic difference of diaspore and kaolinite than NaOL. Under the optimal flotation conditions: 1600 r/min of stirring speed, 60 mL/min of aeration volume, 60 mg/L of PG dosage, and slurry pH 9, the flotation recoveryFlotation recovery of diaspore and kaoliniteKaolinite are 88.5% and 23.4%, respectively.

Silicate minerals (such as kaoliniteKaolinite) are common gangues in diasporeDiaspore type bauxite, which are easy to be mudding and adhered to the diaspore surface in the flotation system, thus affecting the flotation recovery. Fluid flow enhancement with agitation is one of the more effective ways to improve the dispersion of aluminum–silicate minerals and reduce flotation entrainment. Whether high shear agitationHigh shear agitation could also change the surface propertiesSurface properties of mineral particles was investigated through dispersion experiment of diaspore and kaolinite slurry in this paper. The results show that a high turbulence environment was beneficial to enhance the mass transfer of reagents and change the surface properties of mineral particles. With the increase of stirring strength, the contact angle and zeta potential of two minerals were increased at the same dispersant dosage, and the dispersion of two minerals was further improved.

The iron oxide (typically 20–50%) contained in bauxite residueBauxite Residue (BR) (BR) can be recovered as pig iron. But this is not economically viable due to the low market price of pig iron. Silicon rich iron alloys have higher value than pig iron, and BR typically contains 5–15% silicon oxide. To increase the value of the produced metal, it is attempted to maximise the silicon content of iron alloys produced from BR. This option has been explored with experiments and thermodynamic Thermodynamics models (FactSage) focusing on BR from one legacy site and three alumina refineries, obtaining a maximum of 17 wt.% Si in experimentally produced alloys. The paper discusses the thermodynamics around the results and looks at the influence of slag viscosity.

Remediation of bauxite residue (BR) represents an important requirement in some applications aiming to the residue of large-scale utilization such as agronomic applications. The high operational cost of chemical neutralization is one of the main impediments for using this technology in ameliorating BR’s traits such as high alkalinity and sodicity. This study applied a biotechnological approach to neutralize the BR using biogenic sulfuric and citric acids, produced by the bacterium Acidithiobacillus thiooxidansAcidithiobacillus thiooxidans and by the fungi Aspergillus nigerAspergillus niger, respectively, in comparison to their ACS reagent grade equivalents. Batch tests containing BR (20% w/v) mixed with acidic solutions had solid (XRD, XRF, and SEM) and liquid (pH, EC, and ICP-OES) phases evaluated separately. Results showed that the biogenic H2SO4 was more effective in partial BR neutralization (final pH ~ 8) and sodium content decreasing (~35%), indicating the potential of this biotechnological route in the BR remediation prior utilization.

Red mudRed mud is an alkaline waste generated in the industrial production of alumina. Direct storage in the open air will cause great harm to the environment. The secondary utilization of red mud is of great significance to environmental protection. In this experiment, acid leachingAcid leaching treatment on red mud to recover ironIron, aluminumAluminum, and titaniumTitanium in red mud were carried out by using three different leaching agents of sulfuric acid, hydrochloric acid, and phosphorus-sulfuric mixed acid. The effects of leaching agent type, reaction time, leaching temperature, liquid-solid ratio, mechanical stirring speed, and other factors on the leaching effect of three metal elements were investigated by single factor experiments. Experimental results show that 25% sulfuric acid solution is the most suitable as the leaching agent. When the leaching temperature is 90 °C, the liquid-solid ratio is 10:1, the leaching time is 150 min, and the mechanical stirring speed is 300 rpm, the leaching effect of the three metal elements is the best.

Bauxite residueBauxite Residue (BR) (BR) has being extensively investigated as a secondary source of raw materials such as iron, titanium, and rare earth elements (REE). However, the enrichment and recovery of particular elements are not a straightforward process, especially when it is present in the finest particle’s fractions (−150 μm). BR fines usually contain Fe, Si, Ti, Al, Ca, Na, Zr, V among other elements locked up into complex mineral phases. Hydrometallurgical and pyrometallurgical routes used for BR beneficiation usually show higher recovery efficiency but prohibitive costs. On the other hand, gravity concentration methods are one of the oldest and economical ore processing operations, but its efficiency is not clear when tailings are handled. This work describes an exploratory investigation considering three gravity devices—Wilfley shaking table, spiral concentrator, and Knelson centrifugal concentrator handling BR fines. The main goal was to evaluate gravimetric methods as a pre-concentration step to improve BR interesting elements grade prior its extraction. Knelson centrifugal concentrator was found to have a greater selectivity over the Wilfley table and the spiral concentrator.

AnodizingAnodizing is the most common method for producing corrosionCorrosion resistant layer coatings for aluminumAluminum alloys. It is possible to use anodizing with most commercial aluminum alloys to increase material corrosion resistance, but often the brittle, passive oxide layer formed during anodization does not adhere well to the material, reducing effectiveness, and overall compatibility. Therefore, it is important for the compatibility and effect of anodization to be studied for any newly developed alloys. Recently developed eutectic Al–Ce alloys offer advantages like high castability, limited or no heat treatment requirements, and high-temperature strength retention. In this work, Al–Ce alloys are shown to have good compatibility with current processes and may exhibit improved adhesion of passivated layer because intermetallic phases anchor the anodized product to unconverted bulk. The source of these phenomena and their effect on material corrosion and layer adhesion properties of Al–Ce alloys will be discussed and compared with results from common commercial aluminum alloys.

Traditional Al alloys Al-Sm alloys have shown tremendous potential in the aerospace industry due to their attractive properties such as ductility, fracture toughness, and fatigue resistance. However, modern aerospace applications call for next-generation Al alloys with a stringent combination of properties such as high strength, low density, and excellent environmental stability. In that sense, we studied highly driven Al-Rare-Earth (RE) alloys under far-from-equilibrium conditions to investigate the possible effects of cooling rate on the expected microstructure, thus mechanical properties. Al94Sm6 was produced using a copper wheel melt spinner. XRD analysis showed the Sm is entirely trapped within the Al matrix. The heat-treated specimens resulted in the formation of the nanocrystalline Al4Sm phase embedded in the Al matrix, with a two-step precipitation sequence. The hardness values determined by nanoindentation Nanoindentation shows that the initial supersaturated solid solution has 3.83 GPa hardness, while the heat-treated ones have 3.34 GPa. The mechanisms behind this extreme strength and ductility through solute trapping, and subsequent heat-treatments were discussed in detail using a combined study of micromechanical characterization, nanoindentation Nanoindentation, electron microscopy, XRD, and DSC.

Due to the high processability and good service characteristics, 7XXX series aluminum alloys 7XXX alloyshave found wide application in building and construction, in particular in bridge structures. The main disadvantage of these alloys is increased susceptibility to stress corrosion cracking of semi-finished products and welded joints. To increase the safety and competitiveness of bridges made of these alloys, an improvement of alloys is required, providing increased corrosion resistance Corrosion resistance. Achievement of improved complex of properties for the alloys is possible due to balanced alloying of alloys with small additions of transition metals Transition metals, which provide high strength indices with high corrosion resistance. This paper presents the results of studies of extrusion profiles and welded joints from Al–Mg–Zn system alloy with small additives of transition metals. It has been shown that the introduction of Co leads to an increase in the strength characteristics and corrosion resistance of profiles and welded joints of the alloy7XXX alloys type 7005.

The dissimilar welding of Al/Cu is widely used in power industry systems because it realizes satisfying mechanical and electrical properties with low cost. As the key factor influencing the property of welds, the formation of Al/Cu intermetallic compoundsIntermetallic compounds has attracted much attention. In this study, liquid–solid reaction between Al and Cu is realized at different temperatures, producing various intermetallic compoundsIntermetallic compounds (IMCs) which are mainly Al2Cu and AlCu. With morphology observation, the dependence of IMC formation on reaction temperature is determined. With the increase of reaction temperature, the thickness of Al2Cu keeps increasing while it finally reaches a stable state for AlCu IMC. Based on the diffusionDiffusion theory, the inner formation mechanism of these IMCs is discussed. The formation of Al2Cu is controlled by the diffusionDiffusion of Cu and Al in the melt, which is enhanced with high temperature. AlCu formation, on the other hand, is simultaneously affected by the diffusionDiffusion of Cu and Al across the Al2Cu, which displays different kineticsKinetics.

Ongoing development of Al–Si cast alloysAl cast alloy leads to an increased usage of alloying elements to fulfill different property demands. This new complexity of composition may lead to the formation of various phases, of which some are desired and others unwanted. In the present case, a model Al–Si alloy was developed on a laboratory scale and analyzed. The idea behind the alloy was to reduce die sticking while increasing its mechanical properties by adding the transition metals Cr, Mn, and Mo. Special attention was given to the formation of phases rich in the above mentioned elements. During permanent mold experiments, an unintended formation of a phases rich in the added elements was discovered. Recommendations on how to avoid the formation of this phase are given as well.

It is well known that the strengthening of 6000 series aluminumAluminum can be achieved via billet heating, direct extrusionExtrusion and subsequent water or air quenching. The metallurgical characteristics of the Al–Mg–Si alloy system renders it relatively quenchQuench insensitive thus allowing billet preheating and the heat of extrusion to substitute for a separate, more expensive solution heat treat step. However, the linkage of direct extrusion to the quench comes with a risk of quench interruptions that, under certain conditions, can reduce the localized strength of the extrusion. These localized areas reduce the consistency in performance and therefore it is desirable to minimize these strength variations. The work presented in this paper is intended to better understand two key inputs to these quench interruptions (i.e. quench delay time and alloy chemistry) with the goal of making the process more robust.

Laser beam powder bed fusion (LB-PBF) process is an attractive additive manufacturingAdditive Manufacturing (AM) (AM) technology that is applicable for numerous metallic alloying systems. Recently, aluminium (Al) alloys such as AlSi10Mg and Scalmalloy have received a lot of attention from AM processes because of their promising mechanical propertiesMechanical properties. This study endeavours to investigate and develop suitable heat treatmentHeat treatment processes to optimize the mechanical properties of these Al alloys by LB-PBF and provide a better understanding of their process-structure–property relations. The effects of heat treatments on the microstructureMicrostructure have been studied using optical microscopy as well as microhardness measurements. Furthermore, the uniaxial tensile properties of both alloys have been tested in various heat treatmentHeat treatment conditions. LB-PBF Scalmalloy shows a hardening mechanical response relative to its initial as-built (AB) properties while LB-PBF AlSi10Mg alloy shows a softening mechanical behaviour as compared with its AB condition.

Hybrid material structures do offer the possibility of combining different material properties and thus meeting diverse functional requirements in one single component. Here, particular attention should be paid to the transition zones between both metallic compound partners. These transition zones need to show homogeneous and materially bonded structures to ensure ideal transmission of particular amount of thermal energy and to prevent failure of component due to heat variations which may cause debonding effects. With this respect, an innovative process for producing hybrid components has been developed in which a powder metallurgical route is combined with semi-solid formingSemi-solid metal forming technology. The aluminium alloy AlSi7Mg0.5 (A357) is heated up into the semi-solid state and subsequently formed into a porous copper green bodyGreen bodies. In order to analyse the connection mechanisms, copper green bodies of varying densities were manufactured, resulting into different qualities of joint metallic components. The paper deals with produced thermal properties of components manufactured this way.

FrictionFriction, wearWear resistance, and microstructural evolution of nanocrystallineNanocrystalline (NC) (NC) aluminumAluminum during sliding were investigated using molecular dynamics (MD) simulations. The effect of Zr dopantsDopant and twinningTwinning has also been explored and it was found that doped NC Al sample and twinned NC Al sample exhibited better wear resistance and smaller friction force than pure NC Al sample. This trend was found to be correlated with higher hardness and higher strength of the doped NC Al sample and twinned NC Al sample. More grain growth in pure samples was found after wear, as compared with doped samples and twinned samples. We have determined the mechanisms of grain growth in NC Al and the main mechanism is grain boundary (GB) migration induced by emission of dislocations. Additional grain growth mechanisms found in the pure NC Al samples are disconnection-mediated GB migration and a so-called dissociation of low-angle GBs. Dislocation emission and GB migration were suppressed in both doped and twinned samples.

The feasibility of using laser direct energy deposition (DED) additive manufacturingAdditive Manufacturing (AM) (AM) to synthesize a commercial, aluminum-manganese alloyAluminum alloys of the 3000 series was evaluated by comparing the microstructures of AM and direct-chill (DC) cast alloys. The purpose of this work was to establish a baseline for accelerating Al alloy discovery using combinatorial materials synthesis. Feedstock alloy powder was prepared by mixing pure metal element or binary alloy powders via ball-milling and fabricating bulk samples using laser DED AM. Compositional accuracy of both powder feedstock and laser DED AM samples was controlled within 10% of the target. The effect of homogenizationHomogenization on the evolution of second-phase particles as a function of temperature and time was found to be similar in both laser DED AM and DC-cast materials.

In the present study, the effect of solidification time on the grain size, mechanical properties, hardness, static contact angle, and corrosion resistance of A206-T7 aluminum alloy was investigated. To study the effect of solidification time, a step sand casting, with varying section thickness, was made. Microstructural analysis was performed using optical microscopy images, and morphology and elemental composition of the samples were studied via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis, respectively. Contact angle (CA) measurements were performed on the fully polished specimens using a goniometer. Potentiodynamic polarization experiment was performed to study the corrosion resistance of the samples. The casting process was also simulated by use of a commercial software. The conclusion drawn from the simulation process shows that larger thickness allows for higher solidification time. The experimental results for the physical properties of the samples are consistent with the process simulation results. The experimental results indicate that by increasing casting thickness, the average grain size increases from 80 to 124 µm. Wetting study shows that CA values range between 71° and 87°. Corrosion experiment reveals a correlation between solidification time and corrosion resistance of the A206 samples. It was found that the corrosion current nearly decreases by 73% when section thickness increases from 0.75 to 2 in. indicating that the dominant corrosion mechanism in this alloy is presumably intergranular corrosion.

The combination of the conventional forming processes rolling and extruding enables the continuous production of cross-sectional aluminumAluminum long products. Due to its continuity, the combined forming processCombined processes is more efficient compared to its conventional alternatives. The combined rolling and extrusion process is at an early stage of maturity. The production of pure aluminum wire is state of the art. For the production of complex cross-sections, a better understanding of the material flow within the process is necessary. This paper describes the results of numerical and experimental investigations regarding the material flow of the combined rolling and extrusion process. The finite elements method was used to simulate the material flow within the process. The simulated results were compared to an experimental visioplastic examination of the process. The results of the visioplastic examination show some specific material flow characteristics linked to the combined rolling and extrusion process. The results of the numerical simulation and the experimental investigations are in good agreement. The finite elements method can be used to reproduce the material flow within the examined process and its specifics.

6xxx series aluminumAluminum alloys are used in various sectors ranging from the automotive industry to structural applications. A wide range of usage areas requires materials characteristics. In order to meet customer requirements, R&D activities should be conducted in an industrial environment. Development studies can be managed with computer aided simulationSimulation techniques first to reduce the number of trials which negatively affects productivity. In this study, simulationSimulation and modelling have been utilized to develop a holistic approach for forecasting critical performance characteristics without committing excessive experiments. At the same time, verification of real life outputs was also carried out within the scope of the study.

Lightweight metal matrix nanocompositesMetal Matrix Nanocomposites (MMnC) (MMnC) could offer distinct advanced properties to light metals due to inherent high temperature stability, high strength, high stiffness, and wear resistance. Production processes have to consider that the movement of particles in the nanoscale range differs from that in the micro and mesoscale range. NanoparticlesNanoparticle show a slight aggregation behaviour in the casting process compared to larger particles. Here a Lagrangian framework was developed to calculate the conservation equation of momentum for nanoparticle taking into account surface and body forces that act on the particle. Thermophoretic and Brownian forces which play a dominant role in the motion of nanoparticles were implemented to analyse the distribution of nanoparticles in low pressure die castingLow Pressure Die Casting (LPDC) simulations. Strategies to simulate nanoparticle tracking in low pressure die casting were proposed. Verifications were carried out to investigate the motion behaviour using benchmark simulations. The developed model was employed to conduct low pressure die casting simulation and the computational simulation of nanoparticle distributions could be utilized to compare to experimental results from low pressure die casting processes determined by transmission electron microscopy.

The aim of this paper is to determine regimes of thermomechanical processing of the 5181 alloy (Al–Mg–Sc system with 0.03% Sc) for preservation of 40% improved strength compared with 5083. The influence of cold work degree in the range of 30–70% and annealing regimes on mechanical properties of the 5181 sheetsSheets are investigated. The condition for achieving the required strength advantage over 5083 alloy is to ensure partially un-recrystallized structure in the 5181 sheets. It is shown that cold work degree has a significant effect on the recrystallization rate during annealing. With a decrease of the cold work degree, the softening of 5181 sheets shifts towards the areas of higher annealing temperatures and the softening curve becomes flatter. This allows precise control of theHigh-strength high strength-elongation balance. Preferable fields of application for 5181 alloy are marine and automotive applications due to attractive combination of strength properties and cost.

Aluminum-silicon (Al–Si) based alloys Rare earth mischmetal are prominently used in the transportation industry, due to their impressive strength, great castability, and lightweight properties. Small additions of magnesium (Mg) can improve the mechanical properties through precipitation of strengthening intermetallics such as Mg2Si. However, the poor thermal stability Thermal stability of Mg2Si restricts the use of Al–Si–Mg alloys, such as A356, to only lower temperature applications (i.e. less than ~170 °C). With the growing demand for increasing fuel efficiency amongst the transportation industry (achieved through elevating the operating pressure and temperature of combustion engines), it is necessary to investigate methods of improving the thermal stability Thermal stability and mechanical properties of the well-established A356 alloy. Addition of rare earth (RE) to Al alloys can improve the thermal stability Thermal stability through precipitation of fine Al-RE intermetallics. Thus, this paper characterizing the effects that RE mischmetal has on the elevated temperature strength and ductility of the A356 alloy. The precipitation of AlSiRE and Al20Ti2RE intermetallics in the RE modified A356 alloy resulted in a 133% increase in the yield (YS) and tensile (UTS) strength at 250 °C and a 158 and 268% increase in YS and UTS at 300 °C. Moreover, the T6 A356+3.5%RE alloy retained more than 50% of its strength when increasing the temperature from 250 to 300 °C.

Ultrasonic melt processingUltrasonic melt processing (USP) (USP) technique was used to study the effect of Zr addition on the structure refinement and mechanical propertiesMechanical properties of hypereutectic binary alloy in three different alloys (Al–SiAl–Si alloy, Al–FeAl–Fe alloy, and Al–NiAl–Ni alloy) as potential alternatives to the Al–Si eutectic system especially for high-temperature applications. Mechanical properties of these alloys were controlled through both structure refinement by USP and also Al3Zr nano-precipitation hardening. Significant refinement of primary intermetallics was achieved under USP during the Al3Zr formation in solidification process. The residual Zr in the aluminium solid solution enabled precipitation hardening at 450 °C. As a result, the tensile properties, especially ductility, were considerably improved at room and elevated temperatures. The mechanical properties were analyzed with respect to the volume fraction of intermetallic phases. Electrical conductivity was measured to better explore their potential applications. The effects of alloying elements and structural changes on the mechanical behaviour and electrical conductivity were discussed.

The aluminum alloysAluminum alloys containing magnesium and silicon as main alloying elements have been found to be amenable to recycling. During the recycling process, calciumCalcium is found as a trace element or through deliberate addition. The addition of calciumCalcium may influence the corrosion properties of the alloy via changes like microstructureMicrostructure and compositional chemistry. This study investigates the potential effects of added calciumCalcium, heat treatment, and deformation on the corrosionCorrosion behavior of 5xxx and 6xxx alloys using standard corrosion evaluation techniques, like Tafel, linear and cyclic polarization. The addition of trace calcium has affected the microstructureMicrostructure of 6xxx alloy, but it does not show significant changes to corrosion behavior and repassivation behavior of both alloys. The change in microstructure has altered the pit forming mechanism in both, but it is predominantly shown in 6xxx alloy. Although the 5xxx alloy shows decreased corrosionCorrosion potential and increased sensitization time the corrosion rates are comparable.

RetrogressionRetrogression forming and reaging (RFRA) is a new warm-formingWarm-forming process designed to produce automotive structural components from high-strength aluminumAluminum alloys. A scientific approach is described to determine appropriate RFRA conditions for AA7075-T6 and is applied to laboratory-scale forming experiments. The concept of reduced time is used with the activation energy of retrogression measured for AA7075-T6 to predict appropriate times and temperatures for retrogression forming. Conditions recommended for AA7075-T6 are retrogression at 200 °C for 3 to 12 min while forming at strain rates of up to 10–1 s−1. The recommended reaging heat treatment to fully restore strength to the T6 condition after retrogression forming is 120 °C for 24 h. These RFRA conditions were successfully applied in laboratory-scale experiments to form AA7075-T6 Alclad sheet and produce a final strength equivalent to the T6 condition. Data from tensile tests provide flow stresses and tensile ductilities across the range of conditions appropriate for RFRA.

Aluminum alloysAluminum alloy have become prominent materials for additive manufacturing (AM) owing to their high specific strength and the opportunities provided by AM for fabricating parts with complex geometries. Many efforts have been devoted recently to developing novel high-strength aluminum alloys compatible with AM processes. However, the fatigue performance of these alloys needs to be thoroughly understood before being deployed in critical load-bearing applications. It is well known that build orientationBuild orientation affects the microstructureMicrostructure and defects of the AM parts, which then dictates their fatigue performance. Accordingly, this study investigates the fatigue behaviorFatigue behavior of ScalmalloyScalmalloy (Al-Sc-Zr) in different build orientations fabricated via laser beam powder bed fusionLaser Beam Powder Bed Fusion (LB-PBF) (LB-PBF) AM process. The anisotropy in fatigue behavior and failure mechanisms associated with the variation in micro-/defect-structure of LB-PBF Scalmalloy are addressed and discussed.

In this study, AA6082 and AA6005 aluminium alloys were joined using different rotation speeds (1200, 1500, and 1800 rpm) and feed rates (70,110, and 150 mm/min). Microstructures of welding joints were examined by an optical microscope and a scanning electron microscope (SEM). The surface fractures and possible welding defects were scanned via SEM. The best mechanical properties were obtained when conical helical shape stirrer pins were used.

The work presents a study on alloys of the Al-Mg system (5–6 wt%) strengthened with Al3Er particles. The introduction of Al3Er particles into the Al-Mg melt was carried out using master alloys, a mechanical mixer. In addition, when casting into the chill mold, the melt was subjected to vibration treatment before solidification. The structure of the alloys obtained in the cast state of both initial (without particles) and containing particles was studied using metallography methods, i.e. optical and scanning electron microscopy. Analysis of the mechanical propertiesMechanical properties of the alloys under loading was carried out. It was revealed that the introduction of Al3Er particles does not affect the average grain size and hardness, but increases the ductility of the 1550 alloy.

Al–Fe–NiAl–Fe–Ni alloy eutectic alloys have high potential for being alternative aluminum alloys for various electronic and electrical applications instead of conventional low-conductivity Al casting alloys. Furthermore, the addition of Zr and Sc up to 0.3–0.6 wt% improves the hardness for high temperature applications, which is a result of the finer Al–Fe–Ni eutectic structure, and precipitation hardeningPrecipitation hardening of Al3Zr and/or Al3Sc nanoprecipitates. Thus, the aim of the present contribution is to analyze the microstructure features changes in an Al-1.75Fe–1.25Ni eutectic alloy upon different cooling rates during solidificationSolidification. The features of Al–Fe–Ni eutectics and intermetallics were studied quantitatively, and the mechanical properties and electrical conductivityElectrical conductivity were measured.

Commercial aluminum alloysAluminum alloys are unusable above ~250 °C (523 K, which is 56% of the absolute melting point of aluminum, Tm = 933 K), due mainly to the rapid coarsening/dissolution of their fine strengthening precipitates. The recently developed L12-strengthened alloys exhibit, however, a significantly better coarsening resistance at high temperatures. In this study, we present a new class of L12-strengthed aluminum alloysAluminum alloys based on the Al–Mn–Zr–Er system, which exhibits an exceptional combination of high-creep and high coarsening resistance at 300 °C. The microstructure of the isochronally peak-aged alloys has been studied over relevant length scales utilizing scanning electron microscopy (SEM) and local-electrode atom-probe (LEAP) tomography, in parallel with microhardness measurements. Compressive creep experiments are performed to determine the creep threshold stresses of these alloys at 300 °C.

Quantitative analysis of the dispersion of hollow particles in aluminum alloyAluminum alloy matrix syntactic foamSyntactic foam is important because it influences the mechanical properties and deformation behavior of the foam. To this end, three-dimensional analysis can provide more clear results than can two-dimensional analysis. In this study, aluminum-magnesium alloy matrix syntactic foams were manufactured through stirring casting. The cenosphere dispersion and wear behavior were investigated using micro-computed tomographyComputed tomography. In addition, the cenosphere-added A3M syntactic foam was surface-treated with wire-brushing to investigate the effect of surface treatment on the wear characteristics and behavior changes. The wear tests were performed at a vertical load of 50 N and a linear speed of 0.5 m/s for a sliding distance of 500 m. The addition of the cenosphere particles led to a change in wear behavior from adhesive to abrasive and reduced the coefficient of friction. The brushing surface treatment reduced the wear rate of the A3M syntactic foamSyntactic foam and effectively suppressed the delamination phenomenon.

The use of high strength, lightweight aluminumAluminum alloys in high-tech applications such as aerospace, as well as in the emerging field of electric vehicles, is an integral part of our society’s push towards high energy efficiency. However, solidificationSolidification processing of such alloys, especially fusion welding and additive manufacturing, remains challenging due to solute segregations and, ultimately, solidification cracking. Recently the use of refractory nanoparticles in hot crack susceptible aluminumAluminum alloys showed great potential to mitigate cracking during solidificationSolidification. This work investigates the solidificationSolidification mechanisms for aluminumAluminum alloy (AA) 7075 treated with a low volume fraction nanoparticles. Using Differential Scanning Calorimetry (DSC), we showed a significant deviation in the solidificationSolidification behavior of nano-treated alloys from their commercial counterparts and found evidence of the underlying mechanisms in the microstructure of the material.

Grain refinement is a promising strategy for improving wearWear resistance of metals, but in Al, previous studies have often shown undesirable wear-induced grain growth. Here, we investigated tribological properties and microstructural evolutionMicrostructural evolution during sliding of ultra-fine grainUltra-Fine Grains (UFG) (UFG) aluminumAluminum prepared by accumulative rolling bonding and by physical vapor deposition (PVD). The wear-induced grain refinement was observed for the first time in UFG Al and we have identified a transition from grain growth to grain refinement as a function of the mean contact stress. According to the observations from transmission electron microscopy, the mechanism underlying the microstructural evolution is dynamic recrystallizationDynamic recrystallization. We have also found that the PVD-grown UFG Al was the most wear-resistant among all the samples, even though it was not the hardest one. This finding means that hardness and grain size alone are not sufficient to predict trends in wear resistance.

In commercial Al–Fe–Si foil stock alloysAl–FeSi–foil-alloys, mechanical properties such as strength and ductility are influenced by the materials microchemistryMicrochemistry. This study covers the general relation of microchemistry and the potential final softening behavior of aluminum foil, as described in the literature. In this paper, the focus lies on the evolution of solute content and microchemistry through different experimental homogenizationHomogenization practices for two 8xxx alloys with varying Fe and Si contents. The solute level, dispersoid phase volume fraction, and phase morphology of precipitated particles are investigated. The experimental results show a major temperature dependency of the solute content during homogenization.

There is continuing interest to develop lightweight and strong alloys for the aerospace sector. The advent of 3D printing has spurred a search for alloys developed for these processes. One such alloy of interest is the Al–10 wt%Si–0.45 wt%Mg–0.4 wt%Sc that has been developed and used in laser powder bed 3D printing. This study is focused on characterizing the microstructuresMicrostructures of the atomized Al-10 wt%Si–0.45 wt%Mg–0.4 wt%Sc alloy to provide a basis for understanding the microstructural evolution of this alloy during processing. The atomized powders were separated into four size ranges. Each range was quantitatively characterized by determining its dendritic length scale and hardnessHardness. Mean spacing values from 1.5 μm to 5.5 μm could be associated with hardnesses from 105 HV to 120 HV, with higher hardness related to lower spacing. The 3D Si growth morphologies were found to fall into two distinct groupings. The first was a mixture of skeletal Si plates and in-plane Si rods for the largest particle sizes. The second grouping was related more specifically to powders with <125 μm in size. A prevalence of Si fibers was noted for this specific group. These observations were compared to those of previous works performed on eutecticEutectic morphologies of Al–Si and Al–Si–Mg alloys.

Conventional extrusionExtrusion of aluminumAluminum alloy 7075AA 7075 is limited to 1–2 m/min in order to avoid surface tearing and cracking. An emerging technique called Shear Assisted Processing and Extrusion (ShAPE) wasShear Assisted Processing and Extrusion (ShAPE) used to extrude aluminum alloy 7075 tubing at a speed of 7.4 m/min without inducing surface defects. The faster extrusionExtrusion speed is attributed to the unique flow characteristics inherent to the ShAPE process compared to conventional extrusion. Tubes with inner diameter of 10 mm, outer diameter of 12 mm, and length of 2 m were extruded at temperatures ranging from 340 to 466 °C. Tensile testing was performed per ASTM B557-15 with strain measured using digital image correlation. An ultimate tensile strength of 565 ± 4.6 MPa, yield strength of 496 ± 8.7 MPa, and elongation of 16.4 ± 1.0% were measured for extrusions made at 362 °C and heat treated to a T6 condition with extended aging.

Shear Assisted Processing and Extrusion (ShAPE) wasShear Assisted Processing and Extrusion (ShAPE) used to fabricate thin-walled AA6063 tubing with improved mechanical properties compared to conventional extrusion. Namely, tensile properties for ShAPE extrusions after T5 heat treatment far exceed conventional T5 properties and are on par with T6 tensile properties. Die rotational speed did not affect tensile properties, although increased extrusion speed did lead to moderate increases in elongation.

6XXX alloys (AlMgSi) are of great importance for the automotive industry and lightweight design. Currently, more than 100 different compositions (different levels of alloying elements, different magnesium: silicon ratios, trace elementsTrace elements,…) of the alloy 6082 are known, showing big differences in mechanical and corrosion properties. Especially high-alloyed 6082, 6061, and 6066 have a significant quench and corrosion susceptibility. In this study, quench ratesQuench rate between 1 and 200 °C/s were applied to study the effect on mechanical and corrosion properties. Different magnesium and silicon levels were analyzed as a function of quench rate and aging parameters. It has been found, that in most cases a higher strength can be achieved with a hot quench medium. Possible explanations are the lower viscosity with a better heat transfer coefficient, furthermore, a hot quench medium could act as a pre-aging heat treatment.

This paper deals with a technology for producing long products from aluminium and aluminium alloysAluminium alloys by combined rolling-extrusion methodCombined rolling-extrusion method. Compared to conventional methods (rolling and extrusion), the combined method combines both processes, which simultaneously occur in one deformation zone. This technology considerably reduces the footprint of equipment, ensures a rather high quality, and allows manufacturing products from a large number of aluminium alloys. This paper provides process diagrams, as well as the results of manufacturing long products from 5000 series alloys.

ExtrusionExtrusion is a solid-state metal forming process that utilizes heat and excessive deformation to shape materials with constant cross sections. In this forming mechanism, microstructureMicrostructure evolves to variants of fibrous and equiaxed grains with the effects of deformation and recrystallization mechanisms. Besides mechanical properties, weldingWelding capabilities and corrosionCorrosion resistance of 6XXX series of aluminum alloys also affected from extrusionExtrusion process. In this study, changes on microstructureMicrostructure and mechanical properties that triggered from extrusionExtrusion process parameters were investigated to gain knowledge about weldingWelding and corrosionCorrosion behavior for 6XXX series aluminum alloys.

Over the past decade, NASA Langley has led development of the Integrally Stiffened CylinderIntegrally Stiffened Cylinders (ISC) (ISC) Process, a near-net-shape, flow-formingFlow-forming technology. This innovative process is being evaluated for launch vehicle and commercial aircraft manufacturing. A thick-walled, cylindrical preform is flow-formed using a single operation into a thin-walled barrel with integral longitudinal stiffeners. The one-piece, stiffened barrels offer a direct replacement for conventional multi-piece, welded, or riveted structures. A cost-benefit analysis for launch vehicle cryogenic propellant tanks estimated that the ISCIntegrally Stiffened Cylinders (ISC) process offers up to a 50% reduction in manufacturing costs and a 10% reduction in mass. NASA, the European Space Agency (ESA), and industry partners have teamed to manufacture 3 m (10-ft.) diameter aluminum ISCs. The intent is to demonstrate the commercial viability of the process at a scale relevant to the commercial launch and aircraft industries. Development activities will be presented, including process scale-up, formability assessment, and mechanical propertyMechanical properties testing.

Arc welding of dissimilar high-strength aluminumAluminum alloys is a major challenge in the automotive and aerospace industries due to differences in intrinsic material parameters and compositions. However, successful joiningJoining can lead to desirable combinations of material properties. To solve this problem, nanoparticles were loaded into AA6061 and AA7075 filler wires to fabricate nano-treated fillers, which were used to successfully weld AA6061 and AA7075. Neither weldment exhibited defects such as hot tearing or crater cracking, and both weld metals were observed to contain equiaxial grains smaller than 30 µm. The principal mechanisms behind the observed microstructures originate from nanoparticle interactions during the welding process, as they affect the solidification behavior of the weld metal and modify eutectic secondary phases that traditionally lead to dendritic grain morphologies. The promising results of these dissimilar high-strength aluminum alloy welds show nano-treated fillers have much potential in welding systems that are traditionally difficult to weld.

This paper analyzes the mechanism of “thermal characteristicsThermal characteristic” on the electrochemical process of industrial aluminum electrolysis. The basic principle and control model of optimizing the thermal characteristics of aluminum reduction cellAluminium reduction cell, by taking the adjustment of the energy flowEnergy flow as a variable, are proposed. This enables a “decouplingDecoupling” of the real-time control parameters of aluminum electrolysis (metal level and cell voltage) and the control target. A new concept of “output side energy savingOutput side energy saving” is put forward. Through the stable control of superheat and the effective collection and utilization of the dissipated heat from the reduction cell, the energy saving goals of “Input Side” and “Output Side” are realized at the same time. In addition, the adjustment of the energy flow at the output makes the electrolytic aluminum plant realize flexible production. This study has the potential to increase the energy efficiency of aluminum electrolysis from the actual 50% to more than 58%.

Due to the continuous uprising trend in raw material prices, Aluminium-LME meltdown, and consequent shrinking profitability margins, low amperage smelters are facing many challenges. To overcome the challenges a path defining initiative has been undertaken to bring down the specific power consumption and to improve productivity. To meet this objective, we earmarked ten pots for a pilot study. A Booster-Rectifier dedicated for these ten pots was installed. Some measures were taken, such as: change in busbars system, change in anodes dimensions, change in anode ring, larger cathode blocks and collector bars, new lining, increased current, and use of PLC pot controllers. This approach has not only the potential to consolidate the business viability of our operations, but also the outcome of this R&D can be accommodated in any other smelter of world. This paper will discuss the performance of ten new modified potsModified pot, benefits in voltageVoltage drop and way forward.

In aluminium electrolysisAluminum electrolysis cells, the interface between molten metal and electrolyte is animated by surface wavesWave. It is well known that there is a permanent deformation of the bath-metal interfaceBath-Metal Interface (BMI) (BMI) due to the magnetohydrodynamic force in the cell. RaftsRaft of agglomerated alumina may float on the BMI. A mathematical model was developed to describe the transport of these rafts by surface waves on the BMI. In this study, we examined the impact of the BMI deformation to the mass transport by waves. The mathematical model is validated by a low temperature physical model. Laboratory experiments with rigid objects driven by regular surface waves were performed for a range of amplitude and frequencies. Two immiscible fluids are used to model the electrolysis cell, the interface between water and silicone oil is animated by regular wavesWave. Theoretical model predictions of the object drift motion are compared with the experimental data.

Current reduction cell control strategies rely on pot-wide parameters such as the cell voltage to determine control actions. In an effort to reduce spatial variations in cell conditions, model-based control approaches have been proposed in conjunction to measurements of anode current distributions for estimationEstimation and control, such as calculating control actions for various locations in the cell. However, the lack of a dynamic anode settingAnode setting model suitable for control purposes has seen the proposed estimators and controllers only suitable for use during idle shift periods. This paper discusses the important mechanisms driving the pickup of individual anode currentIndividual anode current, and present simulations showing the evolution of key control parameters. An application of online estimation of key process variables including anode-to-cathode distance and dissolved alumina concentration during anode setting was also provided.

SuperconductorSuperconductor busbarsBusbar have reached industrial readiness. Superconductors are conducting direct current with extremely high densities of more than 50 kA/cm2 with zero losses. Due to their low space requirements, high current carrying capacity, and utmost efficiencyEfficiency, superconductor busbars will find their place in the aluminiumAluminium industry. The paper introduces the technical basis of superconductors and continues with technical and economic advantages. Five different use cases are illustrated with information about technical limits, energy efficiency, and economic performance. Experiences out of installations are shared. The presented use cases are: Main busbars between rectifiers and potroom Interconnection busbarsBusbar between potrooms and to standby rectifiers Magnetic field compensation with minimum space and power requirements DC connection between potline and power plant or grid connection point Superconducting magnetic field shielding—permanent or mobile. Investment costs are indicated as well as costs for maintenance, operation and total cost of ownership for various timelines. A breakeven can be achieved by case between 1 and below 10 years.

TheCoupled SPH-DEM model optimization of powder injection is a source of concern for several fields such as the agri-food industry, metallurgy, and ore extraction. Several physical mechanisms intervene during the injection of a granular material into a liquid: solid mechanics, fluid mechanics, heat transfer, and phase change. Since a powder is a discrete material, the model presented in this article uses the discrete element method (DEM). It is coupled to the “smoothed particle hydrodynamics” (SPH) method to simulate the liquid. A sub-model is used to calculate the heat transfer and the associated mechanical effects (sintering, coagulation). The phase change is integrated into the model to consider the solicitation of the liquid. Validation of the results is achieved with the injection of particles cooled with liquid nitrogen in a liquid at room temperature. The experiments were filmed with a high-speed camera to track each particle during the impact with the liquid surface.

In this work, an individual anode currentIndividual anode current measurement system is installed to monitor the aluminum smelting process in a case study involving power reduction and restoration. In this study, anode current signals, together with the line current and cell voltage, were obtained at a high sampling rate to ensure the dynamic features in the process are captured. It is observed that the cell exhibits “battery” behaviors on stopping the electrolysis process due to the anodes having surface intermediates that have not been transformed into the final gaseous products. It is also found that the currents carried by anodes after the experiment are different from the ones before due to the changed hydrodynamic forces. The analysis results provide more fundamental understandings of the aluminum reductionAluminum reduction process and can aid the cell operations such as power modulation.

Carbon dustCarbon dust refers to carbon particles, originating from carbon inputs into the smelting process like anodes, that float on top of the bath, below anodes or suspended in the bath. The phenomenon has a deleterious effect on the specific energy consumption of cells and can lead to anode deformations, hot cells out of the process window and stoppage of cells. Trials were conducted in the TRIMET Hamburg Smelter focusing on the effect of dust at anode changes. The conditions were chosen to be best and worst practice as assessed by a visual carbon dust assessment in the tap hole. Contrasting with published literature, there was no relation in the experiments between spikeSpike formation and carbon dust in anodes after 8 h. Anodes set in cells with a high carbon level in the tap hole did not behave differently when compared to anodes with a low carbon dust content in the tap hole. Samples obtained from the frozen bath layer underneath the anodes showed carbon contents in the range of 0.0315–6.29%.

Two AP18 pots were put into hibernationHibernation state from a normal production state for a period of 4 weeks. They were then woken up and successfully transitioned back to their normal operation. During the hibernation period, the pots were operated at normal line current and the bath temperature maintained around 840–860 °C. This paper presents the pot thermal behavior and responses to different phases of the hibernation process from transitioning into a hibernation state, maintaining a stable sleep state, to waking up and transitioning back to a normal production state. Special adjustments were necessary for each phase during the hibernation process. Interesting observations, unanticipated events, and effective countermeasures are also presented and discussed.

CVG Venalum, a state-owned primary aluminium plant, was commissioned in 1979, taking advantage of cheap and clean hydro energy in the Guayana region in the south of VenezuelaVenezuela. This paper describes the rise and fall of this aluminium plant from its commissioning with P-19 pots, Reynolds design, 150 KA, improved with hydro aluminium technology so as to provide higher performance, an expansion project with a fifth line hydro aluminium 230 KA, until 2009, when CVG Venalum aluminium production began to decline because of an energy crisisEnergy crisis, as CORPOELEC (a state-owned power corporation) suffered from the same issues as the rest of the country’s industrial parks: lack of investment and economic mismanagement, leading finally, after a decade of steadily declining production, to the shutdown of the plant in March 2019 because of the country’s blackout.

In this paper, the problem of the rapid rise of cathode voltage dropCathode Voltage Drop (CVD) (CVD) in an aluminum smelter enterprise is analyzed and addressed. Among the factors that lead to the increase of the CVD caused by the long-term unstable power supply loadUnstable Power Supply Load, the reduction of the conductive area of the cathode due to the increase of sludge, crusts, and the growth of side ledge was the main reason, and the sodium penetration and expansion were also inevitable. The CVD could be significantly reduced by adjusting the parameters reasonably and clearing the sludge and crusts on the cathode’s surface of the cells manually, but it was not easy to recover to the initial value. To keep the CVD stable over the long term, it was key to stabilize the controlling parameters, and ensure that the cathode surface temperature was slightly higher than the temperature of the liquid bath.

Using low voltageLow voltage technology is an effective measure to realize energy saving and consumption reduction of aluminum electrolysis cells. After reducing the cell voltage, the energy balanceEnergy balance must be adapted to low voltage technology. The authors took 200 kA aluminum reduction cellAluminum reduction cell as an example. The heat distribution challenge was evaluated from actual measurement results and calculations under the operating conditions of the low-voltage aluminum electrolysis cell. At 0.76 A/cm2 of anode current density, the total heat lossHeat loss of cell was predicted to be equivalent to 1.223 V, calculated as electric voltage, in which the anode area heat loss was 0.758 V, accounting for 62% of the total heat loss. The cathode area heat loss was 0.465 V, accounting for 38% of the total heat loss. Electrolysis temperature, bath and pad level, the consumption of alumina, anode gross consumption, and anode net consumption on the heat balance were also reported.

A new integrated energy-saving technology characteristic with protruding cathode blocks and high conductivity cathode collector bars was tested in 300 kA electrolysis cells. In order to maintain the normal operation at super low voltage, the technical parameters and operation management were optimized. Gauging was improved in anode changing and appropriate energy compensation was carried out, the heat loss and contact voltage drop were reduced as much as possible, and all the equipment was maintained in time. Under the determined process conditions, the cells ran efficiently and stably, the electrolyte superheat was kept in moderate range, the cell side ledge was kept at appropriate thickness, no sludge agglomerated on the bottom surface, and no carbon dust accumulated on the electrolyte surface. The following economic technological indexes of the test cells were achieved, the average voltage was 3.714–3.783 V, the current efficiency was 91.09–92.05%, and the DC power consumption was 12080–12246 kWh/tAl.

Several changes during our latest increases of cell productivity had a significant impact on cell resistance behavior and general cell performance. Lower anode–cathode distance and/or anode size enlargement have led to a significant drop in bath volume. At the same time, more alumina must be dissolved in a context of higher current density. Alumina dissolution and dispersion through the cell became an issue and the level of instabilityInstability has risen. Along with increasing instabilityInstability, mucky cells became more frequent. Changes in control algorithms were needed to face this new reality and bring back cell performance to its former level or even improve it. InstabilityInstability procedure has been modernized in order to discriminate high- and low-frequency instabilities. Alumina feedingAlumina feeding procedure needed to be more robust against instabilityInstability and be independent from instabilityInstability procedure. Results from implementation at Alma plant are presented.

The latest intergovernmental panel on climate change update includes a methodology to estimate perfluorocarbonPerfluorocarbon (PFC) (PFC) emissions generated during reduction cell start-up. Alcoa has sampled PFC emissions to estimate tier 3 PFC emission slope from aluminum cell operation including cell start-up, for low and high voltage PFC emissionsHigh voltage PFC emissions. Results obtained show that cell start-up methodology will impact the PFC emission slope. Thus, some aluminum smelters will have similar PFC emission slope coefficients for cell start-up and older cell in operation, while others will have different PFC emission slope coefficients for start-up and older cell. Based on this, Alcoa smelters in Canada have put in place a procedure to analyze and use different slopes or integrate both results into one slope depending on the number of pots started during a given period.

This paper focuses on steel–aluminum welding technology and full-section welding technology for large section worksLarge section works, mainly used in aluminum reduction industry. Direct welding between steel and aluminum would easily form brittle chemical compoundsCompound and cracks. Research in this paper showed that proper transition metalTransition metal as brazing filler metal, with heat inputHeat input management during the welding process could effectively restrain the compound formation and reduce cracks tendency as well. Factors that influence the compound formation have been found from numerous tests, through which we can get good welding joints with shear strength above 110 MPa. In view of current shortcomings of traditional repair methods about large section works during aluminum reduction process, this paper comes up with a welding technology by which the joints can have the equal property of the base metals. It adapts to large section welding between steel and steel, and between aluminum and aluminum. Actual practice proves that it already has fulfilled the requirements of wide application.

The emission of fluorine from aluminium smelters to the atmosphere remains a serious environmental concern and requires special considerations during Gas Treatment Centre (GTC) engineering phase for greenfield or creeping projects. In order to achieve the lowest emission of Hydrogen Fluorine (HF), Fives has developed several innovations and demonstrated their benefits at industrial scale: (1) An alumina recirculation gas scrubber named OZEOS designed to allow adjustments of the alumina residence time optimizing the HF adsorption. (2) Fives patented process of alumina CascadeCascade with specific air gravity conveyor ensuring an improved scrubbing efficiency in very warm areas. (3) A dedicated flow-control valve installed at pots outlet ducts allowing the adjustment of the pot gas suction with cell operation requirements. (4) A digitalDigital solution combining multi-location measurements of hydrogen fluoride (potroom and stack). The current paper describes the R&D works, the industrial implementation, and the industrial results obtained thanks to these innovations.

The number of RUSAL’s cells with unshaped, eco-friendly materials of the thermal insulation and part of the refractory—materials that can be recycled in the amount of no less than 80%—has been increased up to 1,600. Because of said materials’ lower density and recycling, it is possible to reduce the amount of SPL requiring landfilling. The paper elaborates on technologies to both expand and improve pyrolysis products from carbon raw materials, so that products from lignite, charcoal,Charcoal and grass culmsGrass culms for cell lining can be used as thermal insulation in cells with unshaped lining materials. The paper provides the results of researching both earlier-tested and new unshaped carbon materials. New materials are compared with earlier-tested and conventional lining materials, in terms of efficiency and performance. Additional information is given about the use of such materials, including equipment for their installation. Autopsy results are provided for different-age cells lined with unshaped materials.

This article studied the harmlessness of SPLSPL. The generation, composition, and toxicological characteristics of SPL are introduced. Under the conditions of no strong acid, no strong alkali, and normal temperature, by leaching and chemical reaction, the harmful substances such as cyanide and fluoride in slurry are transformed into nontoxic products. The technical principle and experimental results of the wet acid-free treatmentWet acid-free treatment process of SPL are expounded. The process is described in detail, and the industrial applicationIndustrial application results of wet acid-free technology in SPLSPL are introduced.

When a process modification evolves a new, or a partly unknown, material, it is very important to establish a good basis for the material characteristics. If a material sample is available, it is possible to measure various material parameters and characterize the material perfectly. An accurate measurement of only a few material parameters will allow for a better selection of the necessary process steps for the product handlingMaterial handling and selection of the right storage equipment. In this paper, different ways to characterize powder and bulk material are introduced. A system to select the right storage and handling equipment is discussed.

A potline for the production of aluminium typically comprises several hundred electrolytic pots with one or two large centralized gas treatment centers Gas Treatment Center (GTC)(GTCs) located in the middle of the courtyard. Due to the mixing of the process gases before entry to the large centralized GTC, the corresponding average fluoride content in the enriched alumina Aluminais distributed back to each pot. However, since pots are behaving differently each with unique HF evolving dynamics, a different approach is explored with dedicated Pot Integrated Abart (PIA) modules where the adsorbed fluoride is recovered back to the same pot. The PIA concept integrates with the pot controllers to optimize the feed of alumina by demand into the gas adsorption reactors. The PIA concept also includes a high degree of prefabrication into container-sized modules that are designed to be suspended directly from the potroom columns.

A portable analyzer for monitoring the aluminumAluminum chemistry in production cells is presented. With the portable battery-powered device, trace element concentration analysis can be obtained within 45 s of manually extracting a liquid metal sample from the cell. The device uses laser-induced breakdown spectroscopy (LIBS)Laser-Induced Breakdown Spectroscopy (LIBS) to directly analyze the composition of the liquid metal, down to concentrations of approximately 10 ppm for a range of elements. We compare the performance of the portable analyzer with conventional off-line laboratory analysis of cast process samples. In addition to the significant time savings and reduced chance of human error, we show that direct analysis in the liquid metal is particularly advantageous in the case of trace elements that display significant segregation upon solidification, such as silicon.

Alumina dissolutionAlumina dissolution is one of the most important processes in the Hall-Héroult process. In this work, video recording using a high-speed camera and a see-through cellSee-through cell and electromotive force (emf) based alumina sensor measurements were performed during the addition of alumina and throughout the entire dissolution process. These methods can reveal crucial information about the alumina–bath interaction and the variation of the alumina concentration during the dissolution process. The sensor data reflecting the actual dissolved alumina in the melt are interesting itself, but especially so when analyzed together with the alumina–bath interaction obtained from the see-through cell.

Aluminium electrolysis involves feeding of alumina into a cryolite-based bath. Water originating from alumina as well as from air reacts with fluorides and results in HF evolution. Untreated HF gas is a significant environmental and economical issue. HF is, however, effectively adsorbed in (primary) alumina before being fed back to the cell as secondary alumina, thereby recycling the fluoride. As alumina is fed to the cell, it forms a raft, delaying the dissolution process and linked to several operational challenges. The goal of the current work is twofold; first, water content is investigated in a lab-scale setting, aiming to explain raft porosity, ultimately causing it to float rather than disperse in the bath. Secondly, the evolution of HF is investigated for different alumina in industrial measurements performed at Alcoa Mosjøen, aiming to identify correlations between gas evolution and alumina properties.

Inert anodesInert anodes for aluminium production can be made of ceramics, metals, or a mixture of those (cermets). Regardless of the type of anode, the surface will be an oxide. With high enough anode potential, the surface oxide will be decomposed upon formation of the corresponding fluoride, eventually leading to a catastrophic defect. The reversible voltage for decompositionDecomposition was calculated for anode materials based on Ni, Fe, Cu, Co, and Cr in terms of the activities of alumina and aluminium fluoride at 960 °C and at 800 °C. Cu is the most promising candidate, when based on the decomposition voltage alone. It was found that the risk of failure was higher at low temperature, partly because low-melting bathsLow-melting bath have high activity of aluminium fluoride, and partly because it will be challenging to maintain high enough activity of alumina, even in a “slurry cell” where the bath consists of a suspension of tiny alumina particles. Based on a simplified model for the conditions inside the diffusion layer at the anode, it was estimated that the alumina particles in the slurry cannot be larger than 5–10 microns.

The liquid metal refining industry has a demand for new technologies operated at low energy consumption and environmental impact nowadays. This work addresses an approach for Al purification and extraction from scrapScrap in a thin layer of the multiple-capillary molten saltMolten salt electrochemical system. The two types of single-capillary cells with quasi-reference electrodes were used to study the kinetics of aluminiumAluminium reduction and dissolution in a narrow (Ø x length) 1 × 1 and 1 × 5 mm channel filled with liquid LiF-AlF3 or equimolar NaCl-KCl with the AlF3 addition at 850 °C. A multiple-capillary Al refineryRefinery process can be designed to significantly reduce the specific energy consumption. The new refinery process can be performed at high current densities. The single-capillaryCapillary electrolysisElectrolysis can be used for kinetics studies. Thin-layer cells should be operated at a thickness no more than 5 mm to compensate the high resistance which may vary in the range from 0.7 to 2.5 Ω at this capillary length. The 64LiF-36AlF3 melt can be used as an electrolyte for the thin-layer electrolysis due to the high electrical conductivity, the wide potential window between Al and Li reduction, and the low liquidus temperature.

In aluminum production process, the control of alumina concentration is very important for the cell steadily running with higher current efficiency. Usually, the identification and control of alumina concentration are achieved by shifts of overfeed periods and underfeed periods. The alumina concentration target is usually controlled as much as possible between a range. In this paper, a number of industrial trials, testing, and data mining analysis reveal some relationships between the alumina concentration and current efficiency, and some relationships between alumina concentration and temperature, as well as some relationships between the alumina concentration and perfluorocarbon (PFC) emissions and anode effects. Then, a method for obtaining an optimal target range of alumina concentration and a new control strategy of alumina feeding is provided to aluminum production process for higher current efficiency and lower emissions as well as lower energy consumption.

Alumina dissolution is of first concern in modern electrolysis cells. The rate of dissolution strongly depends on the physical and chemical conditions in the cryolitic melts. In this work, the alumina dissolution rate has been measured with the gravimetric methods in NaF-AlF3-CaF2-Al2O3 systems. To evaluate the influence of the additives and the superheat, a parametric study has been conducted. A wide range of additive content has been studied to meet industrial conditions. Thus, bath compositions with different liquidus temperatures, in the range from 924 to 970 ℃, were used to dissolve alumina at fixed superheat. Results show consistency with physicochemical expectations so that the additive content decreases the alumina dissolution rate and the superheat increases this rate. The experimentally obtained correlations can help to adjust the parameters taking into account their effect on the dissolution.

Dr. Alton Tabereaux retired from Alcoa a long time ago, but never quit working in the aluminum industry. He continues to be active in smelting technology advancement, and in serving the aluminum industry and particularly the light metals community. He is world renowned not only for his technical contributions to aluminum smelting technology but equally important for his dedication to teaching and training younger generations, providing consultancy and technical support to operations. He serves the light metals industry with a unique technical background and knowledge in areas from environment protection, helping to stewardship government policies, to strengthening aluminum society. In this special tribute session, I am honored to renew our learning of Alton and his major technical achievements—looking back from his very early career as a young scientist at Reynolds Metal Co to later becoming a world renown industry icon.

Perfluorocarbons (PFCs) doPerfluorocarbons (PFC) not affect stratospheric ozone depletion; however, they have extremely long atmospheric lifetimes. They are very stable because of the strength of the carbon–fluorine bond, one of the strongest in organic chemistry, and it is because of their inertness that PFCs are powerful greenhouse gases (GHGs). CF4 has a global warmingGlobal warming potential (GWP) over 100 years 6,630 times more potent than CO2, whereas C2F6 and the lesser known C3F8 have GWPs of 11,100 and 8,900, respectively. The high GWP of atmospheric PFCs led to an increase of public concern about the effects of their accumulation in the earth’s atmosphere in the 1990s. At that time significant PFCs were only considered to occur during ‘anode effectsAnode effects’ (AEs) in the aluminum industry. There was a renewed worldwide concern about greenhouse gases which focused attention on PFC emissions from aluminum smeltingAluminum smelting. In response, aluminum producers initiated aggressive programs to decrease both the frequency and duration of AEs at most smelters globally. International voluntary programs to reduce AE frequency and duration proved to be exceptionally successful as PFC emissions were reduced in ten countries by 31%–78% relative to 1990 levels; the overall average reduction in PFCsPerfluorocarbons (PFC) for countries was 46%. This paper provides a historic overview of the discovery of PFCs, and highlights some of the first investigators in every phase of the journey to understand, measure, account for, and reduce the emission of these potent GHGs.

Modern aluminium production cells are pushed to the limits of high amperage at the lowest possible energy consumption. The linear MHDMHD stability theory conditions of small amplitude wave perturbation, fixed magnetic field and electric current distribution, and the neglect of large horizontal circulation velocities are not valid in large cells. The program MHD-VALDIS is specifically designed to perform the full magnetic field update at all time steps in an economic and efficient way. The additional Lorentz force from the interaction of the full time dependent vertical magnetic field Bz and the horizontal currents in liquid metal leads to a possibility to discover new types of instabilities in the low anode–cathode distance (ACD) conditions. The analysis for a generic 500 kA cell is presented, demonstrating the limitations of the linear stability estimates and the full nonlinear time dependent modelling to permit MHDMHD stability.

The hundreds of aluminum reductionAluminum reduction cells within an aluminum smelter are typically operated in an individual fashion. It is known that reduction cells from a single potline can have different behavior and performance depending on their different lining design, historical performance and/or setpoints for bath chemistry, temperature and electrical resistance. The pot operational state is generally characterized by a limited set of pseudo real time indicators and different variables, such as bath chemistry or temperature, manually sampled at low frequency, where consecutive samples can be separated by a few days. Smelting operators have designed process controlProcess control systems and reaction procedures to cope with process variations, while not always acknowledging the cyclic variations characterizing the pot state. This paper sheds some light on cyclic operation parameters variations and how it can impact negatively control actions taken by the control system or the pot operators.

The newly developed modelling technique of alumina dissolutionAlumina dissolution is implemented into the specialised software to treat the industrial cell operation practices of the anode changes. Alumina feeding at regular intervals requires optimization for the feed amount and timing intervals in situations where the MHD driven large-scale circulation experiences abrupt restructuring. The alumina particles of various sizes are traced accounting for their inertia, drag in the turbulent flow, the electrolyte layer shape, and the electromagnetic force at the location. The large-scale circulation is essential to achieve the desired uniform alumina composition over the whole cell, while the local bubble evolution contributes to the turbulence level and the enhanced dissolution of the particles. Individual particles gradually dissolve in the dependence of the local turbulent diffusion and the instantaneous concentration level below the saturation. The newly developed modelling technique is applied to illustrate possible optimization of the cell performance at arbitrary location in a potline

Computer controlComputer control of aluminum reduction cellsAluminum reduction cells started in the early 1960s, first for energy input by anode beam movement and alumina feedingAlumina feeding by monitoring the change of cell resistanceCell resistance with alumina concentration. Invention of point breaking/feeding in prebake cells, combined with continuous overfeeding and underfeeding of alumina, brought alumina concentration to 2–3%, an optimum for cell performance until today. Bath chemistry also became computer controlled by automatic feeding of AlF3. From these fundamentals, as the computer speed and capacity increased, the computer controlComputer control became more sophisticated and intelligent in reaction to alumina quality, cell conditions, and cell operation routines, with the aim to achieve constant target parameters in every cell of a potline. Prediction and practical elimination of anode effects reduced perfluorocarbon (PFC) emissions to a minimum. In this paper, we trace the prebake cell computer controlComputer control from the beginnings to the most recent applications of artificial intelligence and Industry 4.0.

By applying fundamental data and developing simplified correlations while assuming uniform conditions in the cells, the aluminium industry has been able to design better cells and steadily improve the environmental performance, energy, and faradaic efficiencies. However, with the high capital and operating costs of the technology’s retrofits aimed at increasing the productivity of installed capacity, the retrofitted cells have not always been able to sustain their previous environmental standards and production efficiencies. Hence challenges have emerged, with it becoming evident that the changed “physics” such as those contributing to magneto-hydrodynamic stability, alumina dissolution, electrolyte mixing, spatial heat generation and its transfer can all contribute to the deterioration in some of the key performance indicators and operating cost factors. Advancing the technology further is likely to be reliant on developing the design operating and control practices that solve these challenges.

After the successful development and operation of the 6 HAL4e test cells at the Årdal research Centre starting in 2008, HydroHydro decided in 2015 to build an industrial pilot plant. The site chosen is on KarmøyKarmøy island in Norway, on the very same, cleaned site where the Karmøy Søderberg plant once operated. The 60-cells plant is called the Karmøy Technology PilotKarmøy Technology Pilot (KTP), or KTP for short. The HAL4e cell development program’s ambition included step improvements in energy consumption and environmental friendliness. These innovations span many aspects of cell technology, environment protection, infrastructure, and operation, like low cell resistivity, PAH-free linings, low-energy cell preheat and start-upStart-up, low specific energy consumption, low-anode effect rate and duration, low fluoride emissions, low CO2 emissions, automated cell operations, and many more. This paper summarizes the preparation and start-up activities and also presents some operating results of the first two years of operation.

Electricity cost is one of the main determinants of the competitive structure of an aluminium smelter. Over the past few years, ALRO Group, the biggest industrial power consumer in Romania, has completed ambitious projects to reduce specific energy consumption. To reach the next level, in 2018, ALRO mandated Rio Tinto Aluminium Pechiney (RTAP) to supply AP12 Low EnergyLow energy technology. To guarantee smooth technology transferTechnology transfer and validation and achieve step-change performance the AP Technology™ standard “cell development cycle” approach was used. ALRO and RTAP worked together as a team to execute specific activities such as a measurement campaign, modelling, risk analysis, readiness assessment, on-site and remote support, data analytics, Go/No Go. This article presents this project, which achieved a significant reduction in specific energy consumption, along with some of the supporting activities and tools.

RUSALRUSAL is in phase 2 of upgrading its Søderberg technologySøderberg technology. After a successful upgrade in the Krasnoyarsk smelter, new designs (EcoSøderberg) are now being deployed across the Bratsk, Irkutsk, Novokuznetsk, and Volgograd smelters. The EcoSøderberg includes: energy-efficient cathode; point feeding; innovative gas removal system (without burners) where CO-to-CO2 after-burning occurs under the skirt; anode paste/SHP based on eco-pitch (low PAHs); continuous digital control over the environmental performance of cells, including pot-without-seal warnings; new potroom vehicles with automated control; shorter pot tending operations; and two-stage exhaust gas treatment. The above helped to reduce benzo(a)pyrene emissions by more than 60%. Other emissions reduced to the average of pre-baked technologies, or even lower. Low (compared to conversion to PB) upgrade costs and considerable improvements in cell performance should be noted. RUSALRUSAL continues its efforts to minimize/ ‘reduce to zero’ PAH and other emissions and develop a fully automatic system for environmental control.

In 1886, Charles Hall and Paul Héroult invented the process of alumina reduction, which is called the Hall-Héroult process. The principle of the Hall-Héroult process is the same, even today, but the production technology has changed tremendously. Renukoot Smelter is one of the leading aluminium producers. Over the years, we have improved the smelter performance by successfully implementing several fundamental changes. This low amperage plant upgraded the smelting operations massively by carrying out innovative solutions, incorporating modernization programs, using varying dimensions of collector bars. By successfully implementing these initiatives, low amperage pots are now comparable to modern high amperage pots in parameters like voltageVoltage drop, both in the cell and cell connections. In this paper, one of the most notable innovations, stepped collector barsStepped collector bar to improve performance, will be described in detail.

Reduced fossil carbonFossil carbon footprint is currently a hot topic in the metal-producing industries. Replacement of fossil carbon with bio-based equivalents is thus an important topic also for the primary aluminium industry. Several challenges related to biocarbonBiocarbon have been discussed in the literature as the quality and performance of carbon materials made from bio-based sources tend to be inferior to the fossil-based materials, unless they undergo expensive treatments for adaptation to the aluminium industry. The most likely successful scenario appears to be a gradual introduction of biocarbon into the fossil-based carbon materials already being used. Strategies being considered include replacement of the fossil binder material with a bio-based binder as well as introducing small amounts of bio-cokeBio-coke (charcoal) in the production of carbon anodes and ramming paste. The current paper reviews research works on candidate bio-based carbon materials in the aluminium industry. The sustainability of biocarbon with respect to availability is also discussed.

Trondheim aluminium courseTrondheim aluminium course, which has been organized from the start by Professor Harald Øye, took place for the first time in 1981 when it was given by Warren Haupin to participants from Norway. The success of this course led to the organization of an international course in 1982, which was given by several international experts to participants from 14 countries. Since then the course took place every year except in 2015, which was a difficult time for the aluminium industry and in 2020 due to the pandemic travel restrictions. 2933 participants from 58 countries have attended the course in 40 years. Participants were from aluminium smelters, suppliers to the smelters, universities and research institutions. Experienced lecturers from many different countries and lively interaction with participants, including group discussions on smelter problems, have contributed to the success of the course. Lectures presented basics and fundamentals of aluminium electrolysisAluminium electrolysis, practical knowledge of potline operation and control as well as a review of technological progress and innovations in aluminium reduction technology. In the last few years, an optional 1-day visit to Hydro’s Sunndal Smelter at the end of the course enhanced the learning experience. The course has played an important role in connecting research to practice and in putting the industrial production on scientific basis through attendees that carried this knowledge to their smelters. This paper reviews the most important subjects covered in the course during the last 40 years.

From 1990 to 2000, Harald A. Øye supervised work to establish a model of the chemistry of the melt from the electrolyte that goes into the porosity of the carbon cathodeCarbon cathode blocks during start-up and operation of Hall–Héroult cells. The model was effectively complete by 1995. The work had two parts, where the first was laboratory-scale testing and the second was analysis of industrial cathode materials from cells. In Part I, the laboratory-scale electrolysisElectrolysis, a comprehensive test program was run by visiting scientist Philippe Brilloit with tests of a range of carbon materials and electrolyte compositions, and operation from less than 1 h to a few days. In Part II, industrial cells, Lorentz Petter Lossius collected cores from cathodes from cells stopped after 10 days to 2534 days. The understanding built with the laboratory-scale results was applied to interpret the chemical processes occurring through the lifetime of industrial cathodes. Briefly, in a new cell a sodium front (metallic Na) will move from the electrolyte side down into the cathode carbon. Electrolyte will follow, as melt in the pores in the carbon. Chemical changes will occur after a pattern of dynamic change downward and over time. This was described with a set of model chemical equations and thermodynamic calculations that supported the observed changes. The paper recounts key analysis experiences with focus on the development of the sample preparation, the XRD method, and supplemented with later experiences with newer analysis methods.

In order to be able to assess the rate of heat transfer between a new anode and an anode butt, it is critical to measure the interface thermal contact resistanceThermal contact resistance between them. For that purpose, a lab experiment has been set up and tests have been carried out to record the thermal response of the system after a cold anode block is put in contact with a hot anode block. Finally, a model of the same system has been developed in order to identify the value of the thermal contact resistance that permits to reproduce the experimental thermal response.

Emirates Global Aluminium (EGA), initially Dubai Aluminium (DUBAL), started operation in 1979 in its Jebel Ali smelter in Dubai, which consisted of three potlines of 360 Kaiser P69 cells operating at 150 kA by 1982. In 1990/1991, the fourth potline was started with improved lining, called D18 Technology, used also in relining of Potlines 1 to 3. This allowed amperage increase and improved potlifePotlife, which reached approximately 2600 days using anthracitic blocksAnthracitic blocks at 192 kA in 1997. Subsequent DUBAL expansions with CD20/D20 Technology started in 1996–2006, using 30% graphitic blocksGraphitic blocks whose best average life was 2150 days. These were replaced by graphitized blocksGraphitized blocks in the second generation, with best life of 1880 days. The newer EGA homegrown technologies, DX, DX +, and DX+ Ultra, first started in 2005 as five DX demonstration cells and since 2008 deployed on large scale at EGA with recent DX+ Ultra in ALBA Potline 6. These technologies use graphitized and impregnated graphitized blocksGraphitized blocks, the former having first-generation average life of 1780 days and the latter 1950 days. In 2015–2018, the D18 potlines were modernized to D18+ Technology having 100% graphitic blocksGraphitic blocks. These are being replaced with graphitized blocksGraphitized blocks in the second generation. The change of cathode grade was to permit amperage and pot productivity increase. In this paper, the evolution of cathode blocks, their performance, and potlifePotlife, across all pot technologies at EGA will be presented. This includes different collector barCollector bar designs from round to rectangular cross section and the transition to copper inserts.

The extent to which the carbon cathodeCarbon cathode is wetted by molten electrolyteElectrolyte or molten aluminiumAluminium metal is important for understanding the cathode wear during aluminium electrolysis. The present paper reports on a laboratory study of the wettability of four different carbon materials using the immersion–emersion technique. The effect of polarization of the carbon cathode on the wettability was also included in the study. The measurements demonstrated that the carbon material is poorly wetted by the molten electrolyte or the metal. After polarization of the carbon in the cathodic direction, the cathode became quickly wetted by the molten electrolyte. The presence of aluminium during the experiments resulted in enhanced wettability by the molten electrolyte. The carbon materials were analyzed by microscopy after the experiments and formation of Al4C3 was observed on the surfaces of the materials. The role of sodium in relation to enhanced wettability by molten electrolyte is discussed.

Albras has improved its anode performance at pots in terms of noise after anode change, anode current pick up, anode set modifierSet modifier, anode consumption in cells, and anode qualityAnode quality, aiming to improve the gross and net carbon, following the continuous amperage increase. Optimization of anode change was done testing a new anode set modifierSet modifier, analyzing the size and duration of the modifier to maintain the stability. Moreover, anode performance was monitored by anode voltage dropVoltage drop, reducing the power energy and improving the current efficiency. Anode consumption was monitored measuring the butt thickness and burn-off rate, looking to optimize the anode life in the cell reducing the anode cost. Anode qualityAnode quality was checked during the weekly audit between carbon and potline assessing the anode parameters, such as crack, and pots parameters, such as quality of the anode cover material.

COVID-19COVID-19 has caused a global pandemicPandemic since December 2019. It has impacted not only the wellbeing of human society but also has been damaging to the global economy. This has imposed severe threats and challenges on businesses. The British government has launched aid schemes to combat the new scenarios developed as a result of the pandemic. This paper aims to assess the impact of COVID-19 on foundriesFoundries in the UK. Recorded responses from a detailed survey of the British foundries were analysed and short- and long-term action plans for the foundries are suggested. The current status, challenges, and future direction of the UK foundries are discussed. An opinion for the use of additive technologies with business model innovation for the de-centralised foundries is presented.

AluminiumAluminium multilayerMultilayer packagingPackaging systems have in recent years become increasingly popular due to their performance related to food preservation. These material systems often consist of two or more layers of organic material (PP, PE, PET, etc.) and a layer of aluminium. Until recently, there has not been any environmentally friendly technique for separation of these materials so that aluminium could be recycled with a satisfactory metal yield. This paper presents laboratory-scale experiments where steamSteam (i.e. water vapour) at elevated temperature and pressure has been shown to liberate the organic layers from the aluminium. The results show different types of organic material behave differently and that the aluminium does not oxidize significantly at least up to 3 h of treatment at 174 °C and 8 bar pressure.

One of the problems when recycling aluminium is its oxidation and consequent metal loss. This is especially critical for the thin sheet/foil materials used for food packaging applications. Compacting the scrap into briquettes may partly reduce such losses in addition to facilitate transport and storage. Shredded aluminium materials of different thicknesses (15–300 $$\mu $$ μ m) were compacted into cylindrical briquettes of 4 cm diameter, each weighing 20 g by uniaxial pressure or moderate-pressure torsion. A subset of briquettes and chips was subsequently oxidized at 650 $${}^{\circ }$$ ∘ C, while a subset was left untreated. Finally, all samples were re-melted under molten protective salt flux. Compacting reduced the specific oxidation during the heat treatment and promoted the coalescence and yield for the heat-treated materials. Both effects were most significant for the thinnest foil in the study (15 $$\mu $$ μ m). The material thickness influenced the porosity and surface roughness of the resultant briquette as well as the pressure required to reach a given bulk density.

OxidationOxidation of aluminumAluminum alloys during production is a well-known problem and contributes to significant metal losses. As small additions of CO2CO2 in the oxidizing atmosphere has proven to inhibit the oxidation rate for high-Mg(≥5wt%) aluminum alloys, the present study has aimed at evaluating its effect on alloys with varying Mg concentration in combination with other alloying elements (Si and Mn), i.e. Al alloys 5182 (AlMg4.6Mn0.4) and 6016 (AlSi1.2Mg0.4). Experiments were performed byDifferential Scanning Calorimetry (DSC) DSC-TG (Differential Scanning Calorimetry–Thermogravimetric AnalysisThermogravimetric Analysis (TGA)) using three different cover gases, i.e. (i) 80% synthetic airSynthetic air and 20% argonArgon, (ii) 99.999% argon, and (iii) 4% CO2CO2, 20% argon and 76% synthetic air while monitoring the mass change and heat flux at 750 °C for 7 h. A significant inhibiting effect was observed for alloy 5182 during exposure to CO2, with a mass loss of -0.3%, when compared to the results obtained for synthetic air and argon having mass gains of 11.21% and 1.67%, respectively. The thickness of the oxide layer was also influenced and decreased stepwise from synthetic air, to argon and CO2CO2. A similar effect was observed to a lesser extent for alloy 6016 due to the lower Mg concentration, decreasing the mass gain from 2.45% when heated in synthetic air to 1.61% in argon and 0.7% in CO2. The thickness of the oxide layer decreased in argon and increased to almost similar thicknesses in synthetic airSynthetic air and CO2. The lower mass gain in CO2 proves that CO2 has an inhibiting effect on the oxidationOxidation rate even for low-Mg alloys.

Chemical compositionChemical composition analysis using sampling practices in as-cast aluminum alloys are not accurate enough. Optical emission spectrometry (OES) analyses of samples taken at specified milling depths do not match the desired nominal composition due to segregationSegregation phenomenon. Moreover, macrosegregation profiles within samples cast with current molds often exhibit significant variations. Various types of molds have been tested in the past to solve this problem, but none have had a satisfactory outcome. This paper presents research on a novel mold with an insulated periphery designed to yield more accurate sampling tests. The results from samples made with the insulated periphery moldInsulated periphery mold show segregation profiles with good reproducibility. A value close to the nominal composition was observed at 6–7 mm milling depth. The reproducibility of segregation profiles is correlated to one-dimensional solidification, minimizing surface segregationSegregation areas, and melt convection.

We report on automated analysis of the trace element content of liquid metal, implemented in a casthouse of a primary aluminumAluminum smelter. The automated analysis involves robotic sampling from transport crucibles followed by direct measurement of the chemical content of the liquid metal using laser-induced breakdown spectroscopy (LIBS)Laser-Induced Breakdown Spectroscopy (LIBS). Experiments were carried out on-site over a period of several months, sampling over 200 crucibles and comparing the LIBSLaser-Induced Breakdown Spectroscopy (LIBS) analysis with conventional laboratory spark-OES analysis of solid samples collected from the same crucibles. We discuss the predictive power of LIBSLaser-Induced Breakdown Spectroscopy (LIBS) analysis for different elements, confirming that automated analysis of the molten metal can replace manual laboratory analysis for process control for many common trace elements.

Quality assurance of incoming material is a critical parameter to prevent an increasing reject rate during subsequent production. All unacceptable products caused by impuritiesImpurities involve rework or rejection, which directly lead to production losses. Aluminum containing silicon will impact the fluidity of the molten alloy. According to the content of some impurities, silicon metalSilicon metal can be divided into different grades. INALUM uses silicon metal grade 441 to produce foundry alloy A356.2Foundry Alloy A356.2 with a maximum iron content of 0.12 wt%. An unidentified silicon source will impact impurity content, such as iron (Fe). Although still unable to identify the distribution of iron content in each bag, several programs have been developed. In this work, a new method with high accuracy of characteristic material with compositeComposite and homogeneity testsHomogeneity test has been proven to reduce the reject rate of products and is discussed to seek opportunities to expand a more complex method using machine learning.

In the cast houseCast house, from the raw materials to the finished products, aluminium undergoes a series of treatments ranging from furnace charging and alloying, degassing, filtration, and castingCasting. One common denominator between all these treatments is that molten metal must be transferred in a way or another. Sometimes the transferTransfer method is obvious but there are many occasions where there are different methods available. Open launders, covered launders, pouring, multi-level launders are common open channel methods for transferring molten metal. Gravity siphoning, aspiration siphoning, and pressure siphoning are less common but increasingly used in the industry. All have different influences on molten metal temperature, oxidation, and cleanliness. The purpose of this paper is to compare different molten metal transferTransfer methods and provide guidelines to select and size the most appropriate method according to the process requirements.

The established industry standards for assessing the cleanliness of aluminum melts are PoDFA (Porous Disc Filtration Apparatus) andPorous Disc Filtration Apparatus (PoDFA) LiMCA (Liquid Metal CleanlinessMetal cleanliness Analyzer) analyses. PoDFA provides the necessary qualitative and quantitative differentiation between the inclusions present in the molten metal, but it is slow and subject to human biases. LiMCA provides real-time data without sufficient differentiation, limiting its usefulness for metal quality and process control. Complementary solutions are in demand that can provide similar quality results as PoDFA at the speed of LiMCA. With the Automated Metal Cleanliness Analyzer (AMCA), an alternative solution is suggested that combines the strengths of both established approaches by standardized on-site sampling and automated image analysis for real-time quality control. The present study shows a validation of the image analysis method by replicating the main cleanliness indicator of PoDFA in real industry samples at high precision.

The filtrationFiltration of molten metal using ceramic foam filtersCeramic Foam Filter (CFF) (CFF) is a purification method often used by the aluminum industry to meet the increasing demands the melt quality. CFFs are in most cases produced by the replica method using polyurethane foam templates, which are coated with a ceramicCeramic slurry of targeted composition before being sintered into its final structure. Despite the key role of CFFs in view of metal cleanliness, there are only a few quality parameters for their evaluation. In the present study, an overview of the different material properties essential for CFFs, suitable measurement methods, and their limitations are presented. The focuses of this work are the different densities of ceramic foams and the thermal expansion coefficient measured by dilatometry, as well as the filter porosities and microstructure measured through mercury intrusion porosimetry and computer tomography, respectively. Moreover, elastic (Young’s Modulus) and mechanical properties (compressive strength) are discussed.

Particles and inclusions are commonly removed from molten aluminium with the use of Ceramic Foam FiltersCeramic Foam Filters (CFFs) (CFF). The mechanical properties of CFFs are of great importance not only during transportation, storage, and mounting, ut also in view of securing the integrity of the filters during operation. Data on the compression strengthCompression strength of CFFs at room temperature are available in the literature, but this is not the case for their performance under operating conditions. The main aim of the present study has therefore been to develop an experimental procedure enabling compression testing of CFFs submerged in molten aluminium at operating temperature, i.e. when exposed to actual casthouse conditions. The effect of temperature and holding time was investigated with tests performed at room temperature, at operating temperature with varying duration of filter sample preheating and submerged in molten aluminium. The developed procedure for the measurement of the compression strength for samples submerged in aluminium showed realistic and reproducible data in comparison with previous studies and testing at room temperature. The filter tested was a commercial 30 ppi Al2O3-based CFF, which as expected revealed a significant decrease in compression strength for the filter samples submerged in aluminium. The weakened structure of the ceramic foam is believed to be due to a reaction occurring between the CFF and the molten aluminium. Additionally, the exposed filter samples also exhibited a less brittle behaviour compared to the unexposed samples, indicating that even a softening of the ceramic structure had taken place.

Grain refinement of aluminiumAluminium and its alloys is a common industrial practice. Fine equiaxed, grain structure leads to improved castability, strength, machinability, formability, and good surface finish. FiltrationFiltration is one of the widely used technologies to remove inclusionsInclusions from the melt. Ceramic Foam FiltersCeramic Foam Filter (CFF) (CFFs) are commonly used to clean the aluminium melt before the casting process. However, at a high inclusion load and with grain refinerGrain refiner addition, reduced filtration efficiency is well known to occur. In the current work, the filtration behaviour of CFFs with three different levels of inclusions and grain refiner has been systematically studied in plant scale pilot trials at Hydro’s reference centre in Sunndalsøra, Norway. The results show that oxide films capture grain refiner particles. Grain refiners tends to agglomerate heavily with inclusions at higher inclusionInclusions content. These heavy and compacted small clusters are more likely to be released from the CFFCeramic Foam Filter (CFF) during the filtrationFiltration process. A little effect from grain refiner addition on filtration efficiency is observed when the level of grain refiner and chips addition is relatively low or when both are high, but not with high grain refiner addition with middle level of inclusion load. The threshold of the grain refinerGrain refiner addition effect is further discussed in this paper.

Filter boxesFilter box for ceramic foam filtersCeramic foam filter in Aluminum casthouses are typically preheated by gas-fired systems, as they are faster and more versatile than existing electrical preheating solutions. The Drache Flow Heater is a next-generation electrical preheating systemPreheating system which has the efficiency of a gas-fired system, combined with the ease of use of an electrical system. In this paper, a brief introduction to the technology of the Flow Heater is given. A comparison is made between the Flow Heater, a gas-fired preheating system, and existing electrical heating solutions, showing the individual advantages of each system. Performance data for preheating ceramic foam filters with the Drache Flow Heater is shown. Furthermore, an outlook on the future development of the Flow Heater system is given.

Aluminum smelting results in extremely high greenhouse gas emissions. Recycling of aluminum alloyAluminum alloy is a key issue for decreasing the carbon footprint of aluminum products. To recycleRecycle aluminum scrap, impurity elements such as silicon, copper, etc., will become an obstacle. In this study, removing impurity elements from casting aluminum alloy which includes silicon higher than 7% was attempted by using a fractional crystallizationFractional crystallization method with electromagnetic stirringElectromagnetic Stirring (EMS) (EMS). EMS was implemented during cooling from the liquid phase to the solid–liquid coexistence temperature. Then the semi-solid aluminum slurry was obtained. After that by squeezingSqueezing aluminum slurry, α-aluminum phase particles and the liquid phase were separated, and the number of α-phase particles was increased by applying EMS. The Si contains in α-phase was less than 2.0%. After squeezing, Si contains could be reduced from the original material.

Nature Alu produces high-purityHigh purity aluminium (4N4N or 99.99% and more) using a process known as Fractional Crystallisation. The idea of starting such a company was initiated a few years ago when two retired metallurgical engineers saw an opportunity for a North American-based 4N4N aluminium producer. A team was built and the design of a purification equipment began. Resources from research centers were used to help improve the process parameters. A pilot plant was built to test the equipment in real production size. Using results from experiments made with the pilot plant helped streamline the whole production process and optimize the full-size plant layout and budget. The plant is starting production in Q3 2020. The purpose of this paper is to present the many interdependent steps and actions required to achieve the goal of opening a production plant starting with a project idea, including technology development, financing, and project management.

New results on grain refinementGrain refinement of aluminiumAluminium are presented by using the efficiency concept, which is a powerful tool to compare the nucleationNucleation efficiency of different grain refiners. This involves the calculation of nucleation sites per unit volume, which gives much more information about nucleation than intercept grain size. The different methods of measuring efficiency are discussed. Optifine, a high-efficiency grain refiner, has been on the market for almost 10 years. When Optifine is implemented at cast houses, the grain refiner additions can be minimised, using the growth restrictionGrowth restriction effect that titanium in liquid solution imposes on the first nucleated aluminium crystals. The efficiency concept is utilised in our grain refinement test method to accurately calibrate the performance of each batch of Optifine. Decreased grain refiner additions are beneficial for many reasons, e.g. lower cost, fewer impurities leading to defects, enhanced surface quality, and less blocking of filters.

Using a 1D upward solidification device with indirect to direct chill transition, the as-cast grain structures of an AA6060 alloy were evaluated for different Al-Ti-B grain refinerGrain refiner types and addition rates. Through consideration of the individual and combined effects of heterogeneous nucleation and grain growth restrictionGrowth restriction, a method is provided to reduce the grain refiner addition rate by at least 50%, whilst maintaining the desired grain structure. Scanning electron microscopy (SEM) characterisation was carried out on the microstructures of each grain refiner, and the size distributions of TiB2TiB2 particles were compared. The grain refining efficiency of AMG’s TiBAl Advance is demonstrated to surpass that of other grain refinersGrain refiner tested. TiBAl Advance is suggested to introduce a greater number density of nucleation sites on which free growth of α – Al could be expected to prevail. However, supplementary work is necessary to explain the exact mechanism.

Grain refinersGrain refiner are used in the aluminumAluminum DC castingDC casting process to refine the cast structure. On the other hand, high levels of TiB2 particles and other inclusions from the grain refiner can cause clogging of the melt filter. Improvement of the grain refinementGrain refinement effectiveness is required in order to reduce the addition level of grain refiners. The grain refiner manufacturer AMG developed “TiBAl Advance”, which is a high-performance Al-3Ti-1B (mass%, following is the same) grain refiner. TiBAl Advance has passed a special casting test to provide grain refiners with a high grain refinement efficiency. However, the reason why it shows such high grain refinement effectiveness is yet to be clarified. In this work, the grain refinement effectiveness of TiBAl Advance was compared to that of conventional grain refiners. In addition, the TiB2 agglomerateAgglomerate size distributions were measured in each refiner and applied to the new UACJ model for grain size prediction. TiBAl Advance was demonstrated to have superior grain refinement effectiveness compared with other conventional grain refinersGrain refiner. Furthermore, the predicted grain size from the new UACJ model agreed well with the experimental results. Based on these results, it was estimated that the superior grain refinementGrain refinement effectiveness of TiBAl Advance is due to the smaller size of TiB2 agglomerates, and consequently greater number of heterogeneous nuclei available for any given volume fraction of TiB2.

Ultrasonic melt treatmentUltrasonic melt Treatment (UST) (UST) using a single sonotrode source in a launder is an efficient way to treat a large-volume melt. One key parameter is the melt processing temperature. Melt processing temperature affects the acoustic pressure generated by the sonotrode, which ultimately defines the cavitationCavitation development as well as the resulting acoustic streaming. Experimental results also show that processing temperature affects intermetallic number density and the final grain size. This work presents a numerical model covering acoustic cavitation, flow (including acoustic streaming), and heat transfer in direct-chill (DC) casting, to better understand this process. The UST effectiveness is quantified through the size of the high-pressure acoustic region and the melt residence time, a result reflected in experimental grain size data. The output of this work is useful for optimizing the selection of process parameters for UST DC castingDC casting.

Residual stressResidual stress development during the manufacturing process of powertrain components, such as engine blocksEngine block, is a primary source of premature failure. Residual stressResidual stress may induce in-service dimensional instability and crack formations, which poses challenges for developing high-efficiency engines. Hence, adopting a reliable approach for accurate prediction and characterization of residual stressesResidual stress plays a vital role in efficient stress management. Advanced numerical techniques using versatile finite element methods are viable tools for stress analyses. The current study develops a numerical model of the residual stressResidual stress evolution in engine blocksEngine block during the casting procedure. To determine proper modelling and process parameters, the simulationModelling and simulation was initially conducted on a simplified standard geometry. Then, the casting process of an I6 bore-chilled sand-cast engine blockEngine block was simulated in ANSYSTM. The results revealed that there was a positive correlation between the predicted residual stressesResidual stress and neutron diffraction data, specifically in the engine block’s axial orientation.

High-pressure castingHigh-Pressure Die Casting (HPDC) (HPDC) is an increasingly important production process for large, thin-walled components. When geometries combine large thin areas with volumetric regions, defects due to misrunsMisrun, cold shutsCold shut, air pockets, and porosityPorosity can occur in close proximity and influence each other. Simulation-based process optimization requires a combined modeling approach to capture these errors fully coupled. To address this task, a multi-phase fully coupled mold filling and solidification methodology has been developed. Liquid melt and gas are treated as compressible fluids separated by a sharp volume-of-fluid interface. Reduced melt flow due to solidification is achieved by a mushy-zone model. The methodology allows the simultaneous simulation of reduced melt flow, air compression, and porosity formation due to gas evaporation and volume shrinkage. The ability to address these defects with one combined modelling approach was validated by casting trials using a specially designed geometry for thin-walled aluminum HPDC applications.

Owing to recent global warming, the global village is experiencing changes in climate and environment not experienced by regions. In order to solve these problems, automobile weight reduction and energy-saving automobile development are continuously being promoted; environmental regulations for automobiles are greatly strengthened worldwide. In order to cope with such reinforced environmental regulations, various studies for eco-friendly energy-saving are rapidly progressed, focusing on the automobile industry. As the need for weight reduction is increasing, materials that are in the spotlight include aluminum, magnesium, and plastics [1–3]. The A356 alloy is a representative of Al–Si-based alloy; it is an age-hardening type alloy according to the precipitation of the phase and is a vital alloy material that is increasing in usage, which can give changes in mechanical properties according to the shape control of Si particles through the T6 heat-treatment process [4–8]. The forging process is a manufacturing process, including the shaping of metal through harming or pressing. And then its compressive forces are delivered with a hammer or die. Forging is often classified according to the temperature at which it is performed as cold or hot forging. In this paper, a wheel for a commercial vehicle was fabricated by performing molten metal forging through a multi-cavity using a semi-solid A356 alloy. Moreover, this study was conducted to secure excellent mechanical properties through the development of a multi-cavity process rather than a conventional one-cavity process.

The stability of the continuous casting process is dependent on tight control of a multitude of parameters. Even slight fluctuations within the defined production process window of crack sensitive wrought aluminum alloys are potentially detrimental. However, for certain parameters the extent to which their variance can be reduced is severely limited. For that reason, the continuous casting process for AA7075AA7075 rolling slabs is modeled using MAGMA CCMAGMA CC. Model assumptions are validated experimentally in an industrial DC castingDC casting pit. Different mold and cooling conditions as well as casting temperatures are simulated and their effect on the stress distribution in the slab is investigated. Criteria are developed to assess the tendency towards casting defectsCasting defects, such as center cracks due to process parameter fluctuation. The findings are used to identify potential for process optimization.

Traditional aluminum Aluminum direct-chill rolling ingot Ingot casting uses a fixed mold bore opening (MBO) that is optimized to cast an ingot that is flat in the steady-state region under particular conditions. A fixed MBO mold is chosen as a compromise between cast speed and amount of ingot butt swell. The APEXTM Casting APEX System has controllable rolling faces that allow the MBO to change dynamically during casting. The mold can optimize the shape of the ingot over a wide range of casting parameters from cast start to end. This expands the traditional limits on speed with a fixed MBO. With the ability to cast faster and increase pit productivity, internal metallurgical properties such as macrosegregation Macrosegregation and porosity Porosity can become the limiting factor for speed. Comparisons of metallurgical data from ingots cast at different speeds up to 120 mm/min with the APEX™ Casting System will be discussed and compared with other technologies.

This work focuses on the effects of ultrasonic melt treatmentUltrasonic melt Treatment (UST) (UST) during direct-chill (DC) casting on the temperature distribution across the billet, sump profile, and the resulting microstructure. Two AA6008 billets were cast; one was treated with UST in the hot top while the other was not. To determine the temperature distribution along the billet, multi-point temperature measurementsTemperature measurement were made across the radii of both billets. The sump profile was also analyzed through macrostructure analysis, after Zn was poured into the sump, while structure refinementStructure refinement was quantified through grain-size measurements. A numerical model of ultrasound-assisted DC castingDC casting is validated using the temperature measurements. As an outcome, this study provides information on the extent to which UST affects the sump profile and the corresponding changes in the microstructure. The knowledge gained from this study paves the way towards optimization of UST parameters in DC casting.

Vertical direct chill (VDC) casting is commonly used to produce slabs and billets from wrought aluminiumAluminium alloys. The fact that the VDC is not a continuous process and moulds must be prepared for the next batch decreases the productivity of the process. Alternatively, horizontal direct chill (HDC) casting simplifies the process and allows a continuous production. The casting speedCasting speed in the HDC casting is easier to control and can be optimized for different alloys by changing the speed. This study focuses on investigating the effects of casting speed on the macrostructure of 6082 aluminium billets with 60 mm diameter. A demo-scale casting unit was used and the casting speed was changed from 310 to 385 mm/min. Changes in surface condition, macrocracks, microporosity, and diameter of the billets were investigated. Surface quality of the billets became better with the increasing casting speedCasting speed, while diameter of the billet expands. Furthermore, centreline cracks appear at the casting speed of 355 mm/min.

The hot rolling of large ingots is the predominant process for producing plate, sheet, and foil. During the hot rolling of aluminum/magnesium alloys, edge crackingEdge cracking tends to dramatically increase with increasing magnesium concentration, often resulting in significant unplanned scrap generation. It has been observed that significant cracking most frequently occurs in the start-up region of the ingot, which prompted the current investigation into the impact of casting conditions on edge crackingEdge cracking. By taking samples from the start-up and steady-state regions of AA5182 ingots and subjecting them to different simulated pre-heat rates, we were able to observe a noticeable difference in liquation and void formation behavior on the ingot surface. For a given casting condition, there appears to be a threshold pre-heat rate beyond which significant void formation occurs. Our investigation indicates that the start-up region of DC castDC casting ingots has a lower threshold temperature, thus leading to increased edge crackingEdge cracking.

Reducing gas-shrink porosity is a topical issue in the production of large slabs made of aluminum-magnesium alloys by direct chill casting. To do this, various methods of influencing the melt are used, both during the preparation and during the crystallization of slabs. Currently, due to the growing demand for slabs of large cross-sections for rolling and cutting and stricter requirements for final products, research on reducing porosity is widely used in the industry. The paper presents data obtained from the study of porosity in slabs of aluminum-magnesium alloys produced by direct chill casting at the Pilot casting complex (PCC) of the company OK RUSAL. the dependence of porosity morphology on the alloy composition, size, and technological parameters of casting are presented. The main causes of porosity are considered, and metallographic images of the distribution of pores along the slab cross-section are presented.

It is well known that residual stressesResidual stresses are quite common in castings and they emerge due to uneven cooling conditions. Nowadays, the development of atomistic modelling techniques has allowed for the in-depth investigation of the solidification process mechanics as well as the distribution of residual stresses in the simulation domain. In this study we have performed three-dimensional molecular dynamicsMolecular Dynamics (MD) simulations to investigate the evolution of residual stresses during homogeneous nucleation in pure aluminiumAluminium as well as their distribution over the simulation domain. A simulation box containing 1 million aluminium atoms placed on the sites of a face centred cubic (FCC) lattice has been melted and subsequently quenched under various cooling ratesCooling rate. The potential energy as well as the formation of grains has been monitored during quenching stages. Moreover, the present analysis is expanded to the distribution of the grain size and the number of grains as a function of the cooling rate. Finally, the obtained results suggest that the cooling rate significantly affects the distribution as well as the final magnitude of residual stressesResidual stresses in the solidified structure.

Industry 4.0 and digitalizationDigitalization are common themes in aluminium producers’ strategies. However, the actual penetration of such applications varies and there is a lack of common terminology. In this article, we first establish a framework around different types of applications seen in the aluminium industry, specifically the carbon areaCarbon area, consisting of: (1) Measuring and managing data (2) Sensing and diagnosing (3) Simulating and creating a “twin” (4) Automatic process optimizationProcess optimization (5) Robotics and autonomous operation. We then review what we see currently existing in the market, discussing some of the early implementations of optimization products through anode and rod tracking, and presenting what we currently see under development both within Metso Outotec aluminium and amongst our peers, such as other technology vendors and producers’ in-house technology departments. Currently, there are four interesting avenues emerging: (1) Advanced process simulations enabling effective debottlenecking, e.g., in the rod shop (2) Continued development of overall process optimizationProcess optimization in the carbon areaCarbon area, using data sensors and analytics to further optimize anode quality. Still missing, though, is the critical real-time feedback loop from potlines (3) Predictive maintenancePredictive maintenance applications particularly for equipment-intensive areas such as the rodshop or vibrocompactors. (4) Increased autonomous operations, reducing the need for manual labour in hazardous areas. All of these have their base in understanding which process parameters need monitoring, and hence which sensors should be installed. In addition, embarking on this journey requires certain investments into analytics capabilities, i.e., people and/or software which are able to do the necessary number crunching.In summary, we believe digitalizationDigitalization is starting to make great strides in the industry at the moment. Hindering this movement, however, is still a conservative mindset approach from the industry particularly in new greenfield investments—where arguably adding new features would be far easier than when doing retrofits. We’d encourage more cooperation between technology vendors, EPCMs, and aluminium producers to work together in this field.

Over the last 10 years, FivesFives has developed a comprehensive carbon digital chain to reduce anodeAnode production costs and to better control the cost impacts to the reduction line. This solution, called “AMELIOS Suite”, is built using three packages that cover the whole value chain: green anode, baked anode, and anode usage. These packages can be implemented in existing or new smelters to benefit customer with lower net carbon consumption and maximum use of the carbon below stubs. Using an anode tracking system in combination with the existing online anode resistivity analyser MIREA and the newly implemented SOFIA butts scanning system, it allows us to create an anode ID card with all the key production parameters. This data, uploaded in the smelter knowledge management system, allows us to understand how anodeAnode characteristics impact the potline and therefore fine tune the process parameters to optimize carbon production.

Electrical resistivity (ER) measurements for anodes have been around for more than 50 years. These measurements, as well as any other voltage drop measurement methods on green or baked anodes, can be used for quality control (QC). However, correlations between these QC criteria, especially on green anodes, and their behavior in the pots have not been established. It is difficult to determine absolute pass/reject thresholds, and hence the benefits are hard to quantify. However, it is possible to use those methods for process control and monitoring. A non-destructiveNon-destructive technique (NDT) measurement method of ER based on the 4PP technique was developed by Alcoa for that purpose. It can be used on both green and baked anodes. The development and the capabilities of the equipment for pitch optimization of the green anode is described. Observations on QC for green and baked anodes are also discussed based on the results obtained during the development and trial experiments.

The world economy is keeping manufacturers of all products under continuous pressure to lower costs and improve quality. In addition, low metals prices are driving primary producers of aluminum to optimize their processes to stay competitive and profitable in a very tight market. In order to assure optimum technical and financial performance of the carbon plants and anode block manufacturing, aluminium manufacturers are moving forward in the adoption and integration of Industry 4.0Industry 4.0 technologies as part of their roadmap to the aluminium plant of the future. This paper will present an overview of where current modern aluminium smelters are with their connectivity and readiness for Industry 4.0Industry 4.0 integration and will explore the current technologies as they are being applied and as they may be applied in the future to the handling, cleaning, inspection, and tracking of anode blocks through the anode manufacturing process.

In the early 2000s, the first industrial-scale Rhodax® process green anode plant (GAP) was started. More than 15 years later, the latest version of this technology was successfully commissioned to produce anodesAnode at a higher production rate and for a higher amperage pot. The experience accumulated during this time contributed to an evolution of the technologies, allowing us to meet today’s challenges: more stringent environmental requirements that limit emissions, reduced operator noise exposure, higher GAP operation availability, and stable anode quality. It was also an opportunity to implement the use of digitalDigital technologies to enhance the Rhodax® and the pre-heating screw performance, monitor and maintain operation performance with advanced process control solutions. This paper summarizes the key lessons learnt from the latest project and the performance achieved. It also presents the innovations implemented that open the door to new remote services for equipment performance and process stability enhancements.

The market is becoming increasingly competitive and as a result, capital investments for projects are becoming increasingly difficult to justify. In some instances, the “do nothing” solution may impact a plant ability to maintain a stable and reliable operation. Therefore, an alternative approach must be taken to solve the problem in a cost-effective manner. Alcoa Deschambault faced this challenge when new process conditions resulted in their existing anode stub holeAnode stub hole cleaningCleaning machine failing to adequately clean anodes. Manual cleaning was implemented to allow the anodes to properly mate with the yoke, but this led to ergonomics issues for the operators. This paper will elaborate on the approach taken to optimize a solution and overcome obstacles so that a cost-effective alternative to manual cleaning could be implemented.

A continuous and consistent supply of carbon anodes is required to produce aluminium. Manufacturing of carbon anodes happens in three equally critical stages: green anodeGreen anode production, anode baking, and anode rodding. At Aditya Aluminium (Hindalco Industries Ltd) anode baking is carried out in an open top ring-type furnace constructed of high alumina refractory materials. The productivity of the anode baking furnaceAnode baking furnace is dependent on operation and maintenance practices’ and anode quality is dependent on process parameters and their optimization. The behavior of key baking parameters was analyzed to determine the impact of deteriorating refractory condition on productivity and baked anodeBaked anode quality. This paper describes the study of some of the practices followed in order to sustain the productivity and quality of baked anodeBaked anode in the furnace.

The electrical current densityCurrent density and distribution pattern between the anode and cathode is of fundamental influence on potnoise and current efficiencyCurrent efficiency, also on cathode wear and pot-life, and potentially for low-voltage anode effect. The reduction of harmful peak current densities can be achieved by controlling the electrical contact resistance ECR of the iron to carbon connections in the anode and cathode assemblies through selective use of conductive nails and altering the iron connection contact area. ANSYS and Maxwell optimization software are used to alter the ECRs to improve the uniformity of current density on the anode and cathode active surfaces, and to reduce horizontal current vectors and magnetic force magnitude in the metal pad. Voltage drops are modeled to predict potential energy savings. Scenarios of increased amperage with reduced anode to cathode distance ACDAnode to Cathode Distance (ACD) are modeled to predict increased aluminum production while maintaining thermal balance and acceptable magnetic force distribution.

Hydro Aluminium has reviewed reactivity analysis with an in-house Hydro-developed thermo gravimetric analysis (TGA) system. The TGA system has PID-regulated temperature control with a thermocouple sensor placed inside the test piece and runs with continuous logging of the mass loss to better than 0.01 wt%/min sensitivity. This system has been in use since 1990 to determine routine and research reactivity properties, including burnoff and collected dust, but has seen only limited use for advanced testing of anode reactivity. The anode reactivity analysis is used to quantify the risk of anode surface burnoff and the risk of dusting in the cell, both carboxy and from oxygen in air. Dusting and burn off impacts the cell operational performance and are followed by electrolysis as key anode quality parameters for optimal electrolysis operation. Reactivity causes anode carbon surface erosion and risk of carbon dusting in the electrolysis cell. The paper describes current work with the Hydro TGA system. The reporting of results is now aligned and harmonized with industry practice; the analysis precision has been determined and examples are given how the good precision supports research in anode and coke reactivity. The study also aimed to see if the TGA system has the potential to gather more information and the system has been tested with several temperature setpoints and TGA profile analysis.

In the aluminum industry, repairing anode rods, instead of replacing them with new rods, is increasingly being preferred as it reduces production costs. This work discusses an attempt to weld the anode yoke using friction stir welding. The traditional welding creates an air gap at the welding interface resulting in an additional voltage dropVoltage drop. The parameters affecting this welding method were studied. It includes welding speed, friction pressure, forging pressure, and materials type. The results obtained proved that the welded yoke pin samples have better mechanical properties, with the tensile strength of the welded joint increasing from 182 to 271 MPa and electrical samples equivalent to those of the original steel casting without welding. The results show that not only the new voltage dropVoltage drop had decreased, but additional improvements are achieved with a better contact pressure at steel/carbon interface. It decreases the cast iron thickness as a result of easily replacing the deteriorated pins with new ones. Consequently, it improves the energy efficiencyEnergy efficiency of the process.