Light Metals 2017

The latest CFB Calciners were installed in green field Alumina Refineries. Because of the pressure of cost reduction, a low capital expenditure needs to be achieved. At the same time, an outstanding performance is expected regarding energy consumption, product quality and availability. It is obvious that these contradictory demands are running into a conflict, if the conventional technology is only reproduced. New developments are required to achieve these challenging market demands. This paper describes how solutions were developed, proven and tested and expands on possible future improvements. Examples of new developments are described. Further, it is shown how these targets are achieved with new large calciners installed in a new green field alumina refinery. These new features are considering a steady continuous operation. At the same time product quality and energy consumption are improved.

Alkaline aluminosilicates are of significant interest for metallurgical and chemical industries. They are widespread in countries like Russia, USA, China, Canada, Venezuela, Mexico, Iran, etc. and can present a viable alternative to bauxites. Complex and waste-free alkaline aluminoslilcates processing technology into alumina, soda ash and cement was developed in VAMI institute in 20th century from idea till successful realization at several industrial facilities in Russia, operating till now with competitive production cost of alumina. Russian Alumina refineries are using feedstock with unique high alumina content (Al₂O₃ 26–28%) whereas there are other nepheline sources in Russia and in other counties of lower quality (Al₂O₃19–22%) and their processing results in more cement produced per tonne of alumina. An economical beneficiation technology has been developed that opens the possibility for more efficient industrial processing of comparatively poor aluminosilicate raw materials in Russia and the rest of the world.

The BauxiteBauxite from North Brazil is characterized by a geological profile with different layers. The differences among these layers are percentage of bauxite constituents (gibbsite, kaolinite and hematite). Nowadays, only one layer is used for alumina production by Bayer process, the commercial or crystallized bauxite. This work intended to characterize and to ore dress crystallized bauxite (CB), amorphous crystallized (MB) and nodular bauxite (MNB) from Pará to make them usable in the Bayer process. The ore dressingOre dressing was developed by mechanochemical activationMechanochemical activation with an alkaline reagent in different concentrations and conditioning time. After ore dressing, the samples were submitted to characterization by X-ray diffraction (XRD), X-ray fluorescence (XFR) and rheological characterization. CB and MB ore dressing products were characterized by an increase of mass ratio Al₂O_3available/SiO_2reactive and it was observed that the total silica of MNB, after ore dressing, decreased around 13%. These results were a strong indication that these bauxites could be used in the Bayer process.

The high-temperature digestion process is well applied in china for alumina production from diaspore, and digestion is the critical process for alumina plant. The present study attempts to extract alumina from diaspore using a synthetic caustic liquor. The effect of important parameters such as digestion temperature and caustic concentration were investigated and the process conditions were optimized using surface response methodology (RSM) based on central composite design (CCD). The different influence of digestion parameters on equilibrium molar ratio was compared, and the optimum condition for extraction of alumina from diaspore was identified. The model equation developed using RSM software shows good agreement with the experimental data, with a correlation coefficient (R2) ≥0.96. The characterization of sample before and after digestion was determined by X-ray diffraction (XRD).

The research on lime sintering process to treat low grade bauxite becomes the hotspot, because it can realize dry sintering and decrease the energy consumption. But during the sintering process the existence of MgO, which is trace element and contained in lime, will lead to the phase formation from 12CaO·7Al₂O₃ (C₁₂A₇) to 20CaO·13Al₂O₃·3MgO·3SiO₂ (Q phase) whose alumina leaching property is worse than the former. The alumina leaching ratio decreases obviously. The double parameter model is used to calculate the thermodynamic data of the quaternary compound, and the formation law of alumina-containing phases is obtained by Factsage software. The results indicate that low temperature and high lime addition are benefit to the formation of C₁₂A₇. The Q phase is found in clinker when sintering temperature is 1325 °C. The content of Q phase increases obviously when the temperature is higher than 1400 °C.

LeachingLeaching behavior of aluminaAlumina of smelting reduction calcium aluminate slagCalcium aluminate slag based on high-iron red mud composition was investigated. Alumina of calcium aluminate slag was leached using sodium carbonate solutions (Na₂CO₃ abbr., Na₂O_c). The effects of Na₂O_c concentration, reaction temperature, reaction time, liquid-solid ratio on the leachingLeaching rate of alumina were investigated and its leaching kineticsKinetics was studied as well. The results show that the optimum conditions of leaching is reaction temperature of 75 °C, Na₂O_c concentration of 100 g L−1, reaction time of 100 min, liquid-solid ratio of 4.5:1. The leaching rate of alumina is 83.7% under the optimum conditions. It is found that the leaching process can be satisfactorily represented by fitting with Avrami equation. The apparent activation energy of leaching pro cess and the feature parameter of Avrami equation are determined to be 11,844 kJ mol−1 and 0.0983, respectively, the leaching process is inner-difussion controlled.

Security disposal and comprehensive utilization of bauxite residues are of great significance to the world alumina industry due to environmental protection requirement and waste materials recovery. The security disposal and utilization technologies for bauxite residue will be shown and discussed in this paper. The dry stacking technology for Bayer residues by the drum or pressure filters has been applied widely in the Chinese refineries from 10 years ago. Magnetic separation dressing of high iron content red mud for iron ore concentrates has been put into industrial operations in China for more than 5 years. The residue from sintering process is able to be used for red mud pool dam construction and Soil Modifiers for high acidic soil areas for neutralizing and adsorbing the harmful heavy metal compounds in the soil. The high caustic Bayer residues could be applied for such construction materials as foamed ceramics and glass ceramics etc. The further utilization possibilities and potentials in the future are outlined in the steelmaking, construction, agriculture and environmental industry etc.

The alumina production Bayer process generates 0.7–2.0 ton of Bauxite ResidueBauxite residue (BR) and an average of 1.0 ton of CO₂ per ton of alumina produced. The direct use of exhaust gases to react and reduce the alkalinity of BR may allow a triple gain: improving the storage conditions, opening a range of new applications for BR and sequester from 16 to 102 kg of CO₂ per ton of alumina. This paper shows a lab scale long term program to measure the effects of adding different percentages of Ca and Mg salts followed by carbonationCarbonation in order to precipitate the alkalinityAlkalinity precipitation on stable compounds. The main goal is to decrease the stabilization pH to facilitate the reuse. The processed material was analyzed periodically to monitor the appearance of carbonates. The pH of the suspension was monitored for 400 days after the reaction to evaluate the buffer effect. X-ray diffraction and scanning electron microscopy were used to analyze the reacted material.

In the process of calcification-carbonization, the alkali and aluminum in the mid-low grade bauxite and red mud can be recovered. Aluminum is obtained in the form of low-concentration sodium aluminate solution which is comparatively difficult to reuse. In this paper, the low-concentration sodium aluminate solution was reused to prepare tricalcium aluminate and went back to the Calcification-Carbonization process instead of lime. When processing gibbsite and diasporic bauxite with Calcification-Carbonization method, the effect of calcium aluminate on dealkalization and dealumination was investigated. The results show that the alumina-silica ratio of these two ores can be both reduced to 0.70, and the sodium alkali content can be reduce to less than 0.50%. It indicates that it’s feasible to use calcium aluminate replacing lime. The proposal well solved the problem that aluminum is difficult to recycle at low concentrations and enhances the effectiveness and cleanness of Calcification-Carbonization process which has an extensive prospect.

Red-mud, the residue generated from the Bayers processing of bauxite ore in Jamaica was subjected to a low temperature reduction process. Hematite (~60 m%) was reduced to magnetite employing a gas based mixture of CO, CO₂ and N₂ as a diluent. Extensive thermodynamic study was conducted to identify the stability region for magnetite. ‘Optimal conditions’ for the gas-phase reduction were determined to be: a processing temperature of 540 °C ± 10 °C, partial pressures CO_(g) and CO_2(g) each of 0.070 atm (bar) ± 0.001 atm (bar)/inert diluent-gas: N_2(g), for a conversion-time of 30 min. Mathematical model for reduction based on unidirectional diffusion is also formulated in this paper.

Bauxite ore residue is a hazardous byproduct derived from alumina production, containing iron, titanium, aluminum and other valuable metals. The feasibility of an integrated technological route for recovering titanium from bauxite ore residue was verified in this study. Titanium-bearing iron concentrate was first recycled through magnetic separation process, and titanium was further leached from the non-magnetic material derived from the upper-stream process by using sulfuric acid. The effects of magnetic intensity on the recovery of iron, and the effects of H₂SO₄ concentration, leaching temperature, leaching time and liquid to solid ratio on the leaching of titanium have been investigated. The results showed a magnetic concentrate with total iron grade of 56.39% and TiO₂ content of 8.66% was obtained under a two-stage magnetic separation process (intensity: 0.8 and 0.2 T, respectively), and magnetic recoveries of iron and titanium attained 55.79 and, 17.37% respectively. 96.36% TiO₂ was subsequently leached from the non-magnetic material under the optimal conditions of sulfuric acid concentration of 8 mol/L, leaching temperature of 70 °C, leaching time of 120 min, and liquid to solid ratio of 8.

The novel calcification-carbonation method was proposed to process the diasporic red mud discharged from Bayer process alumina plant. In this study, Batch experiments were performed to evaluate the potential effects of important parameters such as temperature, amount of CaO added, CO₂ partial pressure and carbonation cycles on the recovery of alkali and alumina. The results showed that 78.74% alumina was recovered from the diasporic red mud with decreases in the mass ratios of Al₂O₃ to SiO₂ (A/S) from 1.27 to 0.27. The Na₂O content in the processed red mud was less than 0.3 wt%, and it can be used as a construction material.

The polymer flocculants and dewatering additivesDewatering additives have been applied to separation of Red Mud for thirty years. In recent years, it is pointed out that the additives is related to the presence of other ions. The experimental results show that the effect of mud dewatering and mud compaction will affect the production capacity and purity of product. The potential of using water absorbing polymer or synthetic dispersant to change the rheological property of the slurry is also summarized in the end. The combination of these effects, with the new bio polymer to improve the primary pour into the washing bath of the overflow liquid clarity and recovery of sodium hydroxide is also researched.

A novel method was developed to prepare activated alumina via spray pyrolysis of aluminum chloride solution. In this paper, activated alumina was obtained by spray pyrolysis in tube furnace with aluminum chloride solution as raw materials in different temperatures. X-ray diffraction (XRD), scanning electron microscope(SEM) and the specific surface area analysis were used to characterize the spray pyrolysis products, respectively. XRD results showed that the crystal phase composition of activated alumina can be controlled through adjusting pyrolysis temperature. The crystal structure of γ-Al₂O₃ in the products conformed to the requirements of the index of activated alumina. Most of pyrolysis products were porous structure which the particle size was around 5 μm under scanning electron microscope. With the activated alumina were examined by specific surface area analysis, the products existed as inkbottle-shaped and parallel-plate pores. Pyrolysis products more conformed to the requirements of activated alumina after examined by XRD, SEM, and the specific surface area.

A novel method was developed to prepare aluminium via fluidizing chlorination with untraditional aluminum resources as raw materials. The main steps in this method were: alumina transformed into aluminium chloride through fluidizing chlorination; aluminium chloride reacted with NaOH solution for aluminium hydroxide and NaCl; NaOH and Cl₂ were recycled from NaCl solution by electrolytic process. The new process for preparing aluminium resources by fluidizing chlorination method was proposed to realize efficient separation of the valuable components in non-traditional aluminum resources such as fly ash or low grade bauxite, silicon in untraditional aluminum changed into SiCl₄ in fluidizing chlorination which could be used as raw materials for high purity Si products. Furthermore, the tailings emission of this process was quite lower than that of Bayer process. This paper mainly introduce the principle of this new process, the thermodynamics of fluidizing chlorination is analysis as well.

Technology for processing aluminum raw materials derived from the sintering method enables produce the aluminum hydroxide in the form of pseudoboehmite directly in the production cycle from processing aluminate liquors. Pseudoboehmite was prepared by carbonation. Pseudoboehmite dewatering capacity was of 20–200 kg/h m2. Studies on the properties of carbonation pseudoboehmite showed that its properties are similar to the same product obtained in other ways. At the same time, pseudoboehmite from aluminate liquors has lower specific surface area, includes other modifications of aluminum hydroxide, and other features. The dried pseudoboehmite under normal conditions has a high porosity, and can be used in the matrix for the zeolite Y containing hydrocarbon conversion catalyst to produce a catalyst of suitable attrition resistance and catalytic activity for use in fluid cracking systems etc.

Processes of chemical alumina preparation of high alumina content fly ash raw materials are put forward in order to solve the problems of bauxite resource shortage in China and high value application of fly ash. High white aluminum hydroxide and Pseudoboehmite can be obtained by sintering process with the precipitation and carbonate decomposition. 4A zeolite is prepared through the pre-roasting and synthesis process, and activated aluminium oxide is prepared through the acid leaching and pyrolysis method. Typical experiments for preparing different kind of chemical alumina products are presented as well. Whiteness, porosity, pore volume, crystalline and other key parameters of chemical alumina products determined by XRD and ASAP match the industry requirements well.

Soda-lime sintering process and lime sintering process are the research focus on utilization of low-grade alumina recently. The latter process can realize dry-sintering process and its energy consumption is relatively lower. However, its sintering temperature is up to 1350 °C, which is unfavorable to industrial production. Based on lime sintering method, a novel process of alumina production from low-grade bauxite containing sulfur or fly ash is carried out in this paper. The phase of alumina transforms from 12CaO·7Al₂O₃ (C₁₂A₇) to 4CaO·3Al₂O₃·SO₃ (C₄A₃S), whoseCalcium sulphoaluminatealumina leachingAlumina leaching property is better, through decreasing sinter temperature and time and adjusting the content of CaSO₄ of the raw materials of lime sintering process. The main phases of the clinker sintered at 1250 °C are C₄A₃S and silicon dioxide. Its leaching ratio reaches 89% after 10 min reaction, and the conditions of leaching temperature and sodium carbonate’s concentration are lower than that of C₁₂A₇.

In the alumina production process through the dominant commercial Bayer process red mud, which is not consumable and causes serious environmental challenges is produced. Alternative sustainable process for bauxite treatment to alumina is the Pedersen process, which was patented in 1920s and was in operation in Norway for many years before closing down due to economic reasons. In this process, bauxite is smelted and reduced, which yields pig iron and a calcium aluminate slag. Alumina is further produced from the slag through a hydrometallurgical process. In the present study, different bauxites with different chemical compositions are smelted with lime and reduced by coke. The smelting reduction is studied through chemical analysis and microstructural study. It is shown that complete separation of iron from the slag is possible and in addition the process is effective for partial separation of the other impurities such as Ti, Si, V, from the Al₂O₃-containing slag.

The method of $$ {\text{G}}_{{{\text{R}},{\text{Ca4Al2SO1}}0 {\cdot} 1 2 {\text{H2O}}}}^{\text{o}} = \sum {{\text{G}}_{\text{oxide}}^{\text{o}} } + \sum {{\text{G}}_{\text{R}}^{\text{o}} } $$ was used to estimateEstimation the Gibbs free energyGibbs free energy of calcium hydroaluminosulfateCalcium hydroaluminosulfate$$ (3{\text{CaO}} {\cdot} {\text{Al}}_{2} {\text{O}}_{3} {\cdot} 3{\text{CaSO}}_{4} {\cdot} {\text{nH}}_{ 2} {\text{O, }}3{\text{CaO}} {\cdot} {\text{Al}}_{2} {\text{O}}_{3} {\cdot} {\text{CaSO}}_{4} {\cdot} 12{\text{H}}_{ 2} {\text{O)}} $$ and Ca₃Al₂(OH)₁₂, then to calculate the Gibbs free energies of desulfurization reaction that lime interacts with sodium sulfate in sodium aluminate solution. To make judgments about reaction direction, the correctness of calculation was validated by experimentsExperiment. ThermodynamicThermodynamics calculation and XRD phase identification indicate that $$ 3{\text{CaO}} {\cdot} {\text{Al}}_{2} {\text{O}}_{3} {\cdot} 3{\text{CaSO}}_{4} {\cdot} {\text{nH}}_{ 2} {\text{O}} $$ and $$ 3{\text{CaO}} {\cdot} {\text{Al}}_{2} {\text{O}}_{3} {\cdot} {\text{CaSO}}_{4} {\cdot} 12{\text{H}}_{ 2} {\text{O}} $$ can be generated in the procces of desulfurization. With the reaction time to extend the calcium hydroaluminosulfate decomposition, the $$ 3{\text{CaO}} {\cdot} {\text{Al}}_{2} {\text{O}}_{3} {\cdot} 3{\text{CaSO}}_{4} {\cdot} {\text{nH}}_{ 2} {\text{O}} $$ has been characterized. The thermodynamic behavior of adding lime to desulfurization in the sodium aluminate solution was discussed.

The synthesis rate of calcium hydroaluminosulfate, which has an important effect on desulfurization and desilicon in alumina production, was studied in this research; Based on the analysis of the two-level multifactor test, the reaction temperature (°C), reaction time (min), Na₂SO₄ concentration in solution (g/L) and total alkali concentration (g/L). It is important to emphasize the significant factors that affect the synthesis of calcium hydroaluminosulfate have been screened out. Taking the significant factors as the study object, and by the central composite experimental design and response surface analysis to simulate the synthesis process of calcium hydroaluminosulfate, a prediction model of the synthesis rate of calcium hydroaluminosulfate has been got. The technological conditions are obtained by optimization as that: reaction temperature 75 °C, reaction time 65 min, Na₂SO₄ concentration in solution 40 g/L and total alkali concentration 45 g/L. Under this condition experiment, synthesis rate of calcium hydroaluminosulfate obtained was 69.72%, with the small difference from model prediction value 70.24%. This illustrates that the prediction model and the optimized process conditions can be used to guide the experiment and production.

A comprehensive and accurate thermodynamic database for Al 6xxx series alloy encompassing Al-Mg-Si-Cu-Fe-Mn-Cr has been developed based on the critical evaluation and optimization of all the available literature data and new phase diagram experiment. Based on this database, the thermodynamic calculations are performed to understand the phase evolution during casting, homogenization, and final tempering process. In particular, the equilibrium phase fraction diagrams of all the possible precipitate phases are mapped in the composition range of 0–1.1 wt% Mg and 0–0.7 wt% Si at different processing temperatures. The influence of the variation of minor alloying/impurity elements such as Cu, Fe, Mn, and Cr to the amount of each type of precipitates is also taken into account. Considering conventional Al processing technologies from casting, homogenization, extrusion, and final age-hardening stages, the calculation results will be interpreted for logical Al alloy design.

Aluminum alloys with low Young’s ModulusYoung’s Modulus have not been well studied. This study offers properties and production methods of an Al-Ca alloy. Here, an Al-Ca alloy with a small amount of Fe addition was prepared by Direct-Chill (DC) casting, extrusionExtrusion and rollingRolling, microstructureMicrostructure and mechanical properties were investigated after every process. Low Young’s Modulus of less than 55 GPa and increased yield strength was achieved when adding heat treatment after extrusion and rolling.

3004 aluminum alloys have received wide range in automotive, packaging and building industries due to it is high strength, high corrosion resistance and good machinability. Besides, 3004 alloys commonly produced by Direct Chill Casting method. Furthermore, Twin Roll Casting method which is an alternative of traditional method, came forward in recent years. In the present work; 3004 aluminum alloys were prepared by twin roll casting. Aiming for high strength and good bendability, alternative thermo-mechanical processes were done in laboratories using laboratory mill and furnace. Mechanical tests were performed for indicating the required temper designation. Characterization of the samples was accomplished through metallographic investigation in order to examine the effect of process parameters and examining the morphology. In addition to this, Vickers micro-hardness, electrical conductivity tests and bending tests were performed on the samples for the characterization.

TiB₂ particles are dispersed into aluminum alloys to improve their mechanical properties. The TiB₂ particles are produced in situ by chemical reactions of a mixture of K₂TiF₆ and KBF₄ salts with aluminum and are subsequently dispersed in the aluminum alloys as reinforcement. Through adjusting the processing chemistry by adding different alloying elements, TiB₂ particles can be tailored to desired morphologies and sizes. The results are discussed in view of interfacial energy and heterogeneous nucleation of aluminum grains in solidification.

An aluminum (Al) matrix hybrid composite reinforced with yttrium tungstate (Y₂W₃O₁₂) and aluminum nitride (AlN) is synthesized by high energy ball milling followed by compaction and sintering. Y₂W₃O₁₂, a negative thermal expansion material (−7.1 × 10−6/K), is chosen as one of the reinforcements to lower the coefficient of thermal expansion (CTE) of the composite. AlN is added to the composite in order to improve the strength and thermal conductivity of the composite. X-ray diffraction patterns of the milled powders as well as sintered composites reveal the presence of only Al, AlN and Y₂W₃O₁₂ peaks indicating no chemical reaction between the matrix and reinforcement during milling and sintering. The scanning electron micrograph shows fairly uniform dispersion of reinforcement in the matrix. Hardness, elastic modulus and CTE are measured by Vickers hardness test, nanoindentation test, and dilatometry, respectively. It is observed that a composite with high hardness, high Young’s modulus and low CTE can be obtained by adding 15 wt% AlN and 30 wt% Y₂W₃O₁₂ into the Al matrix.

A series of large crystals of α-Al(Mn,Fe)Si with different content of manganese, iron and silicon have been analyzed using microprobe, X-ray diffraction, pycnometer (density) and electrical devices (electrical resistivity and Seebeck coefficientSeebeck coefficient). The cubic phase α-Al(Mn,Fe)Si had a density varying from 3520 to 3620 kg/m3. When iron was increased from 1.9 to 20.8 wt%, the content of silicon was reduced from 10.7 wt% to 8.6 wt%. The phase had a low electrical resistivity, 2 × 10−6 Ωm. Large crystals of α-AlMnSi had a large Seebeck coefficient, viz. 42 µV/K, the crystal containing some iron gave a slightly lower value, 34 µV/K. All the crystals were n-type semiconductors. A new model for α-AlMnSi has been proposed, where Si-atoms are connected in hexagonal rings around 0,0,0 and ½,½,½. The rings are linked by Mn and Si atoms, all covalently bondedCovalent bonding. According to this model, the ideal α-AlMnSi crystals have 24 Mn, 18 Si and 96 Al-atoms in the unit cell. Fe + Al can substitute for Mn + Si atoms in the unit cell. Vacancies can form on Mn-sites.

This paper compares the castability of the near eutectic aluminum-cerium alloy system to the aluminum-silicon and aluminum-copper systems. The alloys are compared based on die filling capability, feeding characteristics and tendency to hot tear in both sand cast and permanent mold applications. The castability ranking of the binary Al–Ce systems is as good as the aluminum-silicon system with some deterioration as additional alloying elements are added. In alloy systems that use cerium in combination with common aluminum alloying elements such as silicon, magnesium and/or copper, the casting characteristics are generally better than the aluminum-copper system. In general, production systems for melting, de-gassing and other processing of aluminum-silicon or aluminum-copper alloys can be used without modification for conventional casting of aluminum-cerium alloys.

Ultrasonic melt processing is a promising technique for microstructural refinement in castings. Several mechanisms have been proposed for the observed effects, including cavitation-induced nucleation, activation of substrates and fragmentation. Until now, however, real-time experimental observations which could clarify any of the above mechanisms are very limited. For the first time we directly observed the fragmentation of primary crystals formed in alloys by ultrasonic cavitation. The primary crystals were extracted from real Al alloys and subjected to ultrasonic processing in water with in situ high-speed filmingIn situ high speed filming. The recordings of fragmentation of the primary crystals allowed us to observe the different mechanisms of fragmentation, depending on the mechanical properties and morphology of the primary crystals. The collapse of cavitation bubbles in water is less violent than that in liquid aluminum due to the lower cavitation threshold, viscosity and surface tension. Therefore the fragmentation mechanisms for the primary crystals observed in water should also be present for the same primary crystals in the more violent cavitation situation in liquid aluminum.

For A356 alloy, solidification with relative lower cooling rate will result in coarse grain size and lower mechanical properties. In this case, Al5Ti1B mater alloy was not the effective one to refine the A356 alloy. In present study, the effective grain refiner for A356 alloy was developed. Experimental results showed that the equiaxed grains were obtained with modified A356 alloy, rather than the dendritic grains of A356 refined by Al5Ti1B master alloy. Compared to the A356 alloy refined by 0.2 wt%Al5Ti1B, the yield strength, ultimate tensile strength and elongation of modified A356 alloy were increased by 4 MPa, 30.6 MPa, and 4.5% respectively. The value of yield strength, ultimate tensile strength and elongation of modified A356 alloy were 182.3 MPa, 278.3 MPa and 8.2%. The significant improvement of mechanical properties was ascribed to the effective nucleation of α-Al and the morphology evolution of eutectic Si.

OEMs manufacturers of aluminum based safety components for automotiveAutomotive sector are used to require low percentage of Fe as contaminant, since it can be responsible of very high brittle microstructure due to formation of acicular Fe-compounds. Lowest Fe percentage is achieved by alloying primary aluminum, instead of secondary aluminum obtained on recyclingRecycling marketplace. On the other hand, any aluminum alloysAluminum alloys fabricated starting from primary aluminum achieves very high environmental impact, due to very high CO₂ equivalent emitted during the early extractive stage. In order to reduce total global warming potential of finished components, recycling alloys would be preferred, but metallurgy solutions are necessary to control Fe-contaminants. According to recent advancements, Fe-compounds in recycled aluminum could be controlled throughout semisolidSemisolid processes, where the stirring phase of a semisolid slurry would produce fragmentation Fe-compounds. In this work, investigation about key process parameters has been performed to correlate microstructural features to mechanical properties in presence of Fe-compound. Among various process parameters, stirring time and solid fraction are most important key parameters to control to obtain fine globular microstructure. Tensile tests have been performed showing promising results (yield strength about 300 MPa and ultimate tensile stress about 330 MPa). Stirring stage in semisolid process allows reduction of average size of Fe-compounds, thus producing an increase in percentage elongation and toughness, namely the main requirements in automotive sector for widespread use of low-cost and low-environmental impact aluminum alloys.

An integrated casting-extrusion is proposed as a novel method for producing profiles of light alloys at low cost and high efficiency. Such a process has multiple advantages, including use of solidification heat, removing the multiple steps in conventional processes and eliminating casting defects. Integrated cast-extrusion experiments have been carried out using an AA6082 aluminium alloy, under usual casting conditions and 360 °C extrusion temperature. Experimental results revealed that deformation structure dominated in the as-cast-extruded state with a uniform microstructure and that, upon heat treatment, a uniform distribution of Mg₂Si precipitations was obtained. EBSD measurements showed that, after T6-5h heat-treatment, a fine grain structure with an average grain size of 75 µm and well developed high angle grain boundaries was successfully achieved. The hardness of the alloy reached to 116 HV after 5 h aging at 180 °C, which is comparable to that reported for the same alloy processed by conventional routines.

The aim of the present work was to investigate the metallurgical parameters controlling porosity formationPorosity formation in Al–Si–Cu alloys, through a study of the microstructural characteristics of directionally solidified 319.2 alloys as a function of iron content, Sr addition (250 ppm), and solidification rateSolidification rate. The iron levels selected varied from 0.12 to 0.8 wt%, and cover the range of Fe levels found in commercial casting alloys. The use of an end-chilled mold provided different solidification rates along the height of the same casting, with DAS values that varied from ~15 to 85 μm, corresponding to levels of 5, 10, 30, 50 and 100 mm above the chill end. The amount of iron present in the alloy affects the size of the beta-iron Al5FeSi platelets and their distribution, particularly at low solidification rates. Addition of strontium leads to fragmentation of co-eutectic or post-eutectic beta-iron platelets.

The successful industrial modelingModelingof wroughtWrought alloysaluminumAluminum alloys with the desired combination of properties is based on finding the surjective and inverse correlation T(C, PP) ↔ P between the properties, P, of the final product and the different technological paths T(C, PP) capable of providing it (and vice versa). Here, C represents the chemical composition of the alloy and PP is the processing parameters. The algorithm presented in this work is based on the functional equivalency of two different technological paths, T1 and T2, able to provide the same combination of properties, written as P(T1) = P(T2), where P(T1) and P(T2) represent the properties obtained using the various paths T1 and T2 in vector space. The selection of the best among the functionally equivalent technological paths, T, was performed by applying the minimum-cost criterion. The cognitive computingCognitive computing of the real data confirmed the promising industrial potential of such a modeling for high-strength and recycling-friendly wrought aluminum alloysWrought alloys.

The microstructureMicrostructure of an Al–Si–Mn–Fe alloy was determined using SEMSEM and Tof-SIMSTof-SIMS. The trace elements detected were chlorides and a minute content of fluorides. Potassium was found in large cracks along boundaries. Sn was found on the surface of α-Al(Mn,Fe)Si, on grain boundaries and as separate particles. Small Pb-Sn particles were detected close to grain boundaries. The α-Al(Mn,Fe)Si-particles were 1–5 μm in size and gave pronounced Mn- and Fe-peaks in Tof-SIMS, while silicon did not. SEM-analysis showed that the phase had the composition (wt%): 59Al-12Si-17Mn-12Fe. Separate Tof-SIMS analyses of the matrix and these particles showed that the particles were sputtered at a slower rate than the matrix. The sensitivity factor (S _x/Al ) was lower in the particles as compared to the matrix. These observations were explained by the fact that intermetallic phases are substantially harder that the Al-matrix, and that the Si-atoms and a fraction of the Mn and Fe atoms are covalently bonded in α-Al(Mn,Fe)Si-particles.

Aluminum foil produced with prescribed thermomechanical processing route develop oxide film. Alloy chemistry and annealing practices, particularly its duration and exposed temperature, determine the characteristics of the oxide film. The magnitude and characteristics of the oxide film may impair surface features leading to serious problems in some applications, such as coating, printing and in some severe cases failure in formability. Therefore, it is important for the rolling industry to be able to monitor the oxide formation on the foil products and quantify its thickness. Well known methods to measure an oxide thickness that is in the order of nanometer, require meticulous sample preparation techniques, long duration for measurements and sophisticated equipment. However, in this study, a simple and rapid grazing angle attenuated total reflectance infrared (GA-ATR-FTIR) spectroscopic method combined with chemometrics multivariate calibration has been developed for the oxide thickness determination which is validated with x-ray photoelectron spectroscopy (XPS). 3000 and 8000 series aluminum foil materials which were produced by twin roll casting technique were used in this study. Foil samples were annealed at various different temperatures and annealing times in a laboratory scale furnace. Immediately after collecting GA-ATR-FTIR spectra, the 3000 series alloy samples were sent to a laboratory where XPS reference oxide thickness measurements had been performed. Partial Least Squares (PLS) method was used to develop a multivariate calibration model based on FTIR spectra and XPS reference oxide thickness values in order to predict the aluminum oxide thickness. The correlation coefficient of XPS reference oxide thickness values versus grazing angle ATR-FTIR based PLS predicted values was found as 0.9903 the standard error of cross validation (SECV) was found to be 0.29 nm in range of 4.9–14.0 nm for Al₂O₃. In addition, the standard error of prediction (SEP) for the validation set was 0.24 nm with the model generated with three principal components (PCs).

Every pound of aluminum or aluminum alloys cast and sold is certified to meet The Aluminum Association Inc. registered limits or other specified composition limits. Certification of aluminum and aluminum alloys to specified composition limits is typically done using Spark-Atomic Emission Spectrometry (Spark-AES) following the procedures in ASTM International (ASTM) E716 Standard Practices for Sampling and Sample Preparation of Aluminum and Aluminum Alloys for Determination ofChemical CompositionChemical compositionby Spectrochemical Analysis and ASTM E1251 Standard Test Method for Analysis of Aluminum and Aluminum Alloys by Spark–AES. Spark-AES laboratories at major aluminum production facilities normally have excellent analytical practices and follow strict quality control protocols to provide the best results possible. However, every measurement has an associated uncertainty and the measurement of composition using Spark-AES is no exception to the rule. This paper provides a brief discussion of:1.The uncertainty inherent in the elemental analysis of aluminum and aluminum alloys by Spark-AES.2.The benefits of using guard bands to set internal operating limits, which are offset from specified composition limits.3.A model of the risk for sale of out-of-specification product based on the analysis uncertainty relative to the specified composition limits.4.The main sources of uncertainty of Spark-AES and their potential causes.

Most industrial products have (challenging) 3D shapes, many of them require traceability and individual marking. Although some laser marking systems on the market have 3D capabilities, they require the 3D shape to be loaded in the laser controller and the part to be precisely located. However, many industrial processes requiring direct part identification cannot fulfill those precise positioning requirements. To overcome these limitations, a 3D laser marker with integrated 3D imaging system was developed. This imaging system obtains the 3D image of the piece, and then the laser controller starts the marking process so that the focus fits on the part surface. The whole 3D data acquisition and transfer takes less than 3 s. This solves the problem of part positioning and simplifies the integration, while also providing 3D data of the surface that can be used for quality control.

Arconic Spectrochemical Reference Materials, formerly Alcoa Spectrochemical Standards, has been a leading producer of certified reference materials (CRMs) used by the aluminum industry for more than 70 years. Arconic offers more than 320 catalog alloys as well as custom specification alloys, all of which are produced by casting techniques that minimize or substantially eliminate both macro and micro segregations. The alloy compositions are certified for up to 28 elements using two or more independent analytical methods; most commonly Spark-AES, ICP-AES, and GD-MS; and rigorous statistical analysis to ensure the accuracy of the final composition certification, the chemical and physical uniformity, and the performance of the CRMs in use. The Arconic Spectrochemical Reference Materials’ process is ISO Guide 34, ISO 17025, and ISO 9001 accredited. This paper describes the production, analysis, and certification techniques used by Arconic Spectrochemical Reference Materials for the production and certification of CRMs.

This work features a characterization of AA7050 strip produced for the first time in a single deformation step via large strain extrusion machining (LSEM), which has emerged as an alternative method to produce AA7050 strip. The resultant LSEM plate or sheet microstructure is promising for applications where SCC and exfoliation cracking resistance are important. LSEM has been shown to produce grains with a lower aspect ratio than conventional hot rolling, which has been linked to SCC resistance. In addition, LSEM grains have a different orientation relative to the strip direction, which may result in an improvement in exfoliation cracking resistance as compared to hot-rolled strip.

There is an on-going effort to control Fe bearing intermetallic formation during solidification in direct chill (DC) casting of dilute Al alloy billets from recycled material sources, as these insoluble Fe intermetallics control the downstream processing conditions and final properties of the processed products. This paper investigates the influence of molybdenum (Mo) and grain refiner combined additions on Fe bearing intermetallic formation during casting of a 6063 Al alloy. In particular, the grain size and intermetallic phase content of the samples have been characterised using various microscopies and X-ray diffractometry. An intermetallic phase extraction technique has been used to facilitate measurement of the three-dimensional morphology and chemistry of the different Fe intermetallics present, with changes rationalized in terms of the effect of trace additions. Both “α_c-AlFeSi” and “β-AlFeSi” are observed in all the castings. After the addition of Al-5Ti-1B grain refiner to the base alloy, β-AlFeSi was predominated in the casting. Further addition of Mo to the grain refined alloy promoted α_c-AlFeSi in the casting. The possible mechanisms for these effects are discussed.

The homogenization treatment of 7075 aluminium alloy slabs is required for ensuring the technological properties for later processing. This usually has two stages. The soaking time in the second stage has an important influence. In order to evaluate the influence of this parameter, the homogenization, solution heat treatment, quenching and ageing treatment were simulated in the laboratory at various homogenization soaking time between 4 and 24 h. The evolution of the eutectic structures in the as-cast and homogenized 7075 aluminium alloy were investigated by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), differential scanning calorimetry (DSC) and tensile test. The results demonstrate that from many standpoints (mechanical properties, microstructureMicrostructural evolution etc.) the complete dissolution of all soluble phases ends before the limit of 20 h that is considered as standard all over industry.

Quench factor analysis has been widely used to describe how precipitation in quenching affects the development of properties of aluminum alloys in subsequent aging treatment. To minimize the amount of effort and time, Jominy end quench was used to conduct quench factor analysis. The author applied Jominy end quench test to Al–5%Cu–0.4%Mn alloy, followed by different artificial aging time, and Rockwell hardness was measured along the length of the samples. Quench factor analysis was conducted with measured data. Critical time at different temperatures of Al–5%Cu–0.4%Mn was calculated with the kinetic parameters and 400 °C was demonstrated to be the sensitive temperature. In addition, the effect of quenching rate on aging was studied and the strengthening effects of precipitation during quenching and aging were compared. The results revealed that with decreasing quenching rate, the peak aging time and the hardness of as-quenched increased, whereas the peak hardness decreased.

Young’s modulus of metallic materials is one of the most important mechanical properties in controlling structural design. The increase of Young’s modulus in cast aluminium alloys is attractive for lightweight structures. In the present investigation, the Young’s modulus of an Al–Si–Mg–Cu alloy reinforced with TiB₂ and Mg₂Si phases was investigated under different heat treatment processes, including T4, T6, T7 and O. The microstructural evaluation and mechanical properties of the developed Al–Si–Mg–Cu alloys were examined by X-ray diffractometer (XRD), scanning and high resolution transmission electron microscopes (SEM and HRTEM), ultrasonic pulse technique and tensile test. The results revealed that the alloys, in all heat treatment conditions, mainly consist of Si, Mg₂Si and TiB₂ phases, which are responsible for the increase of Young’s modulus. HRTEM micrographs showed the formation of incoherent, clean and smooth interfaces between aluminium matrix and TiB₂ particles. The alloys with over 90 GPa Young’s modulus are still castable for making shaped castings. In comparison with the conventional aluminium alloys that have Young’s modulus at a level of 70 GPa, 30% increase of Young’s modulus can be achieved by the developed alloys.

The request for aluminium with enhanced properties, such as an improved resistance to intergranular corrosion for the 6XXX alloys has risen in the past years. In the past years there have been investigations on the IGC behaviour of 6XXX extrusion alloys, but no studies about the behaviour of rod are known to the authors of this paper. In this article, the IGC behaviour of 6082 rod will be investigated. The rods were produced by TRIMET in Castelsarrasin with a continuous casting and rolling process. They were subsequently, in the labs of TRIMET, homogenised, drawn with final area reduction of 53%, annealed and heat treated. The samples were than tested according to the VW PV 1113 for ICG of 6XXX alloys, a test used on extruded profiles, permitting a comparison of the results. Results indicate that chemical composition and process parameters have a strong influence to the corrosion sensitivity of this material.

Streaking is a common surface defect on architectural extrusions. The current study investigates the effect of processing parameters and thermomechanical history on the surface finish of a streaked AA6060 extrusion. Streaked profiles were intentionally produced via extrusion using a die with internal geometry deliberately designed to produce thermomechanical variation in specific regions of the profile geometry. Extrusions were conducted at various ram speeds and the profiles were given an anodization pre-treatment process to reveal streaking in the designated regions. Thermomechanical variation was analyzed using the “ALE” code HyperXtrude®. The surface profile and roughness of the treated and mill finish extrudates were analyzed using optical profilometry. The presence of the streaks were associated with strain rate variability as determined by the die geometry, independent of the ram speed. The streaked regions of the profile were found to be more recessed compared to the bulk regions.

In this study, an AlMg₈Si₉Cu₁₀Zn₁₀ (in wt%) alloy is fabricated with a high volume fraction of coarse secondary phases, which is higher fraction than in the conventional piston alloys. Ingots are cast in a permanent mold after an ultrasonic melt treatment for 60 s at the temperature range of 750–700 °C. Microstructure of AlMgSiCuZn alloyAlMgSiCuZn alloy consists of Si, Zn, Mg₂Si, Q-Al₅Cu₂Mg₈Si₆, and θ-Al₂Cu phases. By the heat-treatmentHeat-treatment at 440 °C, Q-phase at the vicinity of blocky Mg₂Si phase grows and the roundness of the second phases increases with respect to the heat-treating time. Compared with the as-cast specimen, room-temperature ultimate compressive strength of the heat-treated specimens increases. However, maximum compressive stress at 350 °C is slightly decreased by heat treatment. The formation of fine clusters increases the ultimate compressive strength, while the spheroidization of bulky secondary phases during heat treatment deteriorates the ultimate compressive strengths.

Al–Zn–Mg–Cu alloysAl-Zn-Mg-Cu alloys are widely used in aged-hardened condition for aircraft applications because of their high strength, adequate fracture toughness, stress corrosion cracking resistance and good machinability. In this study the effect of interrupted quenching (I.Q.) from solution temperature to 25–225 °C on subsequent artificial ageing was studied. Hardness measurements, tensile tests and instrumented impact tests were used to characterize the mechanical properties of Al–Zn–Mg–Cu plates. The results indicate that a high hardness can be reached directly after I.Q. for medium I.Q. temperatures. Compared to standard water quenching, the results showed that hardening kinetics and the age hardening response during artificial ageing can be enhanced for I.Q. at medium artificial ageing temperatures, but are reduced at high temperatures. I.Q. at high temperatures affects subsequent artificial ageing via the formation of precipitates, which contribute less to hardening but consume a significant amount of solute.

In this paper an analytical yield criterion for description of the plastic behavior of face-centered cubic single crystals is presented. The new criterion is written in terms of the generalized invariantsGeneralized Invariants of the stress deviator proposed by Cazacu and Barlat (Int J Eng Sci 41:1367–1385, 2003 [1]), specialized to cubic symmetry. The octahedral projections of the yield surfaces for different crystal orientations according to the new model are presented, and compared with the yield surfaces according to the regularized Schmid law (Bishop and Hill, in Lond Edinb Dublin Philos Mag J Sci 42:1298–1307 (1951) [2], Darrieulat and Piot, in Int J Plas 12:575–612 (1996) [3]).

Prior studies of cast AA7050 mechanical property are sparse, and only include the as-cast condition. In order to generate data for simulation of stress development in direct chill (DC) casting, compression tests were performed on AA7050 specimens in both as-cast and homogenized conditions in the temperature range of 20–500 °C at strain rates from 10−4 to 10−2 s−1 to a strain of 0.5. Results from test specimens having round and square cross-sections were compared to each other and to published tensile data. The round specimens are preferred due to less cornering effect. The flow stress-strain data is fit to the Ludwik equation to generate constitutive relations for the flow stress as a function of strain, strain rate and temperature. The microstructural changes from as-cast to homogenized structures lowers the flow stress of AA7050 with the removal of harder eutectic microconstituent. This effect is most significant at an intermediate temperature (200 °C) and decreases with increasing temperature.

Evolution of texture components during deformation of lightweight aluminum alloy sheet under different strain paths is studied by analyzing the evolution of element rotation calculated using a rate-dependent crystal plasticity finite element model. Based on a stability criteria proposed by Ali et al. (Light Metals 2016. Wiley, London, pp. 159–162, 2016), data from cold rolling, shear and compression simulations is analyzed to determine stable texture components. The predicted stable texture components, for the same microstructure, for rolling, shear and compression using the stability criteria are in-line with experimental observations. Further analysis of simulated data yields a simpler methodology that stable texture components are those that are aligned with the loading direction. Using this methodology, stable textures under rolling, shear and plane-strain compression are analytically identified and the results show an excellent conformity to experimental data. This new methodology can be included in robust non-texture based phenomenological modelling to predict texture evolution in engineering design problems.

In order to improve the mechanical properties of aluminium alloys used in automotive powertrain at elevated temperatures, the chemical composition of Al–Si–Cu–Mg alloys is modified by addition of transition elements. In comparison with the commonly used EN-AC-42000 alloy, the new aluminium alloy can significantly improve tensile properties at elevated temperatures. Microstructural investigation revealed that tuning of chemical composition can refine the strengthening phases and increase their volume fractions in the aluminium alloy. SEM observation demonstrated the existence of well distributed phases in the microstructure of the Developed alloy. As a result of microstructural modification, yield strength of Developed alloy is enhanced versus Base alloy (EN-AC-42000). The multiple strengthening mechanisms are responsible for the property improvement.

We observed that non-heat treatable Al–Fe–Mn alloy foils exhibit an increase in strength and a decrease in elongation due to low temperature annealing treatment subsequent to cold rolling. In this study, we investigate the effects of alloying elements on this anneal-hardening behavior. The alloys without alloying element of iron were not hardened by low temperature annealing treatment. On the other hand, the anneal-hardening behavior was observed only in Al–Fe based alloys containing manganese or chromium. These results are similar to “hardening by annealing” reported on severe plastic deformation of metal.

The impact extrusionImpact extrusion process of aluminumAluminum is an important manufacturing method for production of semi-finished products. Actually AlMgSi (EN AW 6xxx) alloys are impact extruded in a soft state (0 condition), however a heat treatment on the final products is needed to generate a high ductility and strength (T6 condition). Through this heat treatment distortions on the final product could occur and new process routes have to be developed. The purpose of this study is to compare mechanical properties and corrosion resistance of different process routes to be able to optimize industrial processes. In this work the deformation resistance, heat generation during deformation, strength and corrosion resistance as a function of thermomechanical processingThermomechanical processing and microstructure were analyzed.

CobaPress™ process is a hybrid process of castingCasting and forgingForging leading to the manufacturing of high integrity/critical safety components and sub-assemblies for the automotive industry. Throughout this process, the main objective consists of the elaboration of an aluminum alloy with yield strength of 300 MPa and at least 8% of elongation. The use of Thermocalc© simulations allowed us to set up with annealing temperatures and chemical composition. Channel dieChannel die experiments have been carried out to study sub-structure evolution for a fixed temperature and different strain rates. Observations on EBSDEBSD have been made in order to characterize recovery and/or recrystallizationRecrystallization. Apart from the fact that sub-structuration improves yield strength and ultimate tensile strength, fatigueFatigue life is much greater than AS7G03 usually used through the CobaPress™ process.

AA6061 alloy is one of the most widely used aluminum alloy in modern aerospace and automotive industries due to low cost, good formability and high specific strength. Most of aluminum structural components experience dynamic loading, which leads to fatigue failure. Since studies on the strain-controlled fatigue behavior of these alloys are very limited, this study was aimed to evaluate the strain-controlled cyclic deformation behavior of an extruded 6061 aluminum alloy and determine the fatigue life under varying higher strain amplitudes. The stress-strain responses exhibited essentially symmetric responses with slight Bauschinger effect. A slight cyclic hardening occurred at high strain amplitudes (0.8–1.2%) within the first ten cycles, and then cyclic stabilization follows until failure. It had longer fatigue life which can also be described by the Coffin–Manson law and Basquin’s equation. Crack initiated from the specimen surface and crack propagation was characterized by fatigue striation-like features at lower strain amplitudes.

Technological changes driven to solve the energy problems existing in the world today, offer a key opportunity for sciences related to the selection of materials. Specifically for production industries and handling biofuel, it is crucial the effectiveness of materials against corrosion, so in recent years the increase is denoted in corrosion studies of metallic alloys applied in these industries. The aim of this work is to study the corrosion behavior of aluminum-magnesium alloys, using potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) tests in ethanol (99.5% v/v) at room temperature, evaluating the effects of microstructure and percentage of magnesium addition. Furthermore, the mechanisms involved in corrosion are proposed, compared to the different theories suggested by other authors.

This paper presents the warm pressing as an alternative powder metallurgy approach to conventional press-and-sinter or hot working (e.g., extrusion, forging) consolidations of Al powders into complex near-net-shape parts with required mechanical properties. In this study gas-atomized Al powders (A1050 and A6061) with various particle sizes were consolidated by uniaxial pressing, with minimum plastic deformation induced, at temperatures of 22 and 430 °C, respectively. The materials pressed at 22 °C showed poor strengths, ductility and electrical conductivity. The properties were improved markedly when pressing temperature increased to 430 °C and reached values comparable to A1050 and A6061 materials fabricated by conventional powder and ingot metallurgy approach. Similarly, the properties of the materials pressed at 22 °C were improved after annealing at 300 °C for 2 h. This indicated the formation of sufficiently strong interfacial bonding between native oxide layers on adjacent Al powder particles (i.e., grains) when processing temperature increased to 300 °C. With interfacial bonding established, the fracture mechanism changed from brittle to ductile character.

It is a well-known phenomenon in aluminum industry that alumina powder, fed into the electrolyte, tends to stay afloat on the surface of the bath. This hinders dispersion and direct contact of most of the powder with the electrolyte, therefore delays dissolution. In addition, large clusters of alumina particles sintered together during raft formation might lead to the agglomerate piercing through the bath-aluminum interface, which should be avoided. Since the interference between raft formation and alumina dissolution is significant, it deserves more attention. Several experiments were conducted in a small carbon crucible in which cryolitic bath was melted and alumina of different properties was fed. The injections were recorded by a video camera above the bath. The spreadingSpreading of the powder on the surface, the infiltration of powder by the bath as well as the disintegration or the sinking of the raft was observed and the results analyzed.

The Bayer process, storage and transport of smelter grade alumina (SGA) together contribute to the unique particle size distribution of the SGA as received in a gas treatment facility or in a reduction cell hopper. Pore size distribution analyses of alumina fractions indicate that the +125, +90 to −125, +63 to −90 and +45 to −63 μm particles possess similar total pore volumes. The total pore volume of −45 μm particle size fraction, however, was found to be approximately 15% lower than the remaining bulk. Having earlier studied the evolution of pore size distribution in the bulk SGA during fluoride scrubbing, this work examines the interplay between particle and pore size distributions, with focus on the impact of fines on scrubbing efficiency in a smelter GTC.

Smelter grade alumina (SGA) is the preferred agent for recovering HF from pot exhaust gases since the alumina also serves as feed to the electrolysis process, thereby allowing return of the recovered fluoride to the process. This alumina-based recovery loop includes sulfur that evolves from cells as SO₂ and that is co-adsorbed on SGA that is not completely saturated by HF. Previously, Dando and Lindsay (Light Met Miner Met Mater Soc 527–531, 2016, [1]) reported on the competitive adsorptionAdsorption of HF and SO₂ on smelter grade alumina by investigating the temporal breakthrough behavior of both HF gas and SO₂ gas to quantify the mechanisms behind adsorption of both gases on the same particle of alumina. In this paper follow-on work is presented where this research data is translated into an empirical formulaEmpirical formula that can be used by engineers and technologists. Examples are given of applications that may be practical in making predictions on the removal of SO₂ by alumina in a dry scrubber.

HF regeneration due to submicron fluoride particles trapped inside the filter cloth reacting with the humidity in the pot gas is one likely mechanism that explains why the HF emissions increase with gas temperature and humidity in the dry scrubbers. A significant temperature effect is observed and gas cooling is in many smelters today necessary to keep the emissions under control. The GE heat exchanger (HEX)Heat exchanger (HEX) technology is one of the technologies that are now built and operated in full scale several places in the world. Results from the first full scale GTCGas treatment center (GTC) installation document the positive effect of the cooling for the AbartAbart GTC technology installed. The HEX cools the temperature with more than 25 °C down to less than 110 °C and HF emissions in the range 0.2–0.3 mg/Nm3 are measured at ambient temperatures higher than 40 °C, and high humidity.

Handling and conveyingConveying of powderous material needs a detailed knowledge of the powder properties itself combined with the knowledge how the conveying and handling effects the powder properties. Ideally there is no measurable effect on the powder. For intermediate storage in the plant and Material Distribution SystemsMaterial distribution system alongside the pot room these effects need to be considered. In this paper the influence of various parameter of pneumatic conveyingPneumatic conveying on the material properties is described. Comprehensive tests have been done to evaluate the influence of changes in conveying parameters on the material and vice versa. This paper concludes technical features presented on earlier TMS Annual Meetings and compares them with results from practice. In order to improve the handling behaviour of poorly-flowing fine-particle bulk materials, these can be mixed with a suitable coarse-particle and free-flowing solid. On the other hand, the flow characteristics of a coarse material are worsened by the particle attrition and/or fracture occurring during the handling. To determine these effects in more depth for Alumina tests have been undertaken with systematically varied material compositions. These data are compared with material data from other industries with the aim to give general conclusions for the material handling.

Anode effectsAnode effect (AE) are considered a nuisance for aluminium production due to the numerous negative impacts that they generate in an electrolysis cell. Previously, great efforts have been deployed to minimize the occurrence of this event. Using online anode current monitoring, Alouette introduced an algorithm to detect abnormalities prior to an AE, allowing sufficient time to apply a corrective action before its occurrence. Several sets of strategies were tested to evaluate the best approach to correct the situation without generating additional problems in the cells. Finally, individual anode currents measurements were connected to the cell control system of two pots to automatically launch preventive treatment of AE. A decrease in the total number of anode effects along with an increased cell stability is noticeable. Other indicators, such as anodic incidents, alumina dosage and metal purity were also compared to make sure that no deterioration in the cell conditions occurred over time.

EGA’s Jebel Ali smelter hot metal production has increased above 1 million tons per annum since 2010 and produced a record 1,045,255 tons in 2015 and with forecast total production of 1,065,280 tons for 2016. Jebel Ali Potrooms has also strived to minimize its environmentalEnvironment impact with significant effort to reduce the three main sources of GHGGHGemissionsEmissions; power consumption, anode carbon and CO₂e emissions from AE PFC’s (anode effect perflurocarbons). Specific energy has decreased from 14.82 DC kWh/kg to 14.29 DC kWh/kg, net carbon has reduced from 0.434 t/t Al to 0.423 t/t Al and AE PFC emissionsEmissions have reduced from 0.263 CO₂e/t Al to 0.071 t CO₂e/t Al. This has resulted in reducing annual GHGGHG emissions by 798,065 CO₂e tons and was achieved despite increasing annual hot metal production by 63,266 tons since 2010. This achievement demonstrates EGA’s vision for operational excellence and continuing efforts to minimise its environmental footprint.

Most laboratory systems investigating the aluminium production process utilize a single anode set-up. When approaching alumina depletion under constant current conditions in such a system, the potential will increase to high levels (>10 V) and initiate an anode effect and perfluorocarbon generation. However, it has been discovered by industrial measurements that perfluorocarbon generation may also occur at normal cell voltages. With the use of a two-anode setup in parallel with an electronic load this phenomena was investigated in the laboratory. The results indicate that as long as the rest of the cell can acquire the extra load, partial passivation of one or more anodes is possible and can be accompanied by small amounts of PFCPerflurocarbons (PFCs) evolution (0–3 ppm mol CF₄). Individual anode potentials can be highly elevated, albeit the changes get buried in the total cell voltage. Only when the total load becomes too large the voltage rises abruptly and substantial amounts of PFC can be produced (≫1000 ppm mol CF₄).

The recent finding of continuous background PFC co-evolutionPFC co-evolution during apparently normal operations of large operating smelting cells has raised the question as to whether or not these arise from a different reaction mechanism since they occur at similar cell voltages to what is considered to be below the threshold when calculating greenhouse gas emissions emanating from cells. The analysis presented from this combination of studies suggest that all PFC emissions are triggered by the anodeAnode reactionspotentialAnode potentials approaching that necessary for COF₂(g) formation, with the intermediate formed on the electrode surface decomposing to release an increased amount of CO(g) as well as CF₄(g) according to the overall reaction1$$ {\text{Al}}_{ 2} {\text{O}}_{ 3} + 2 {\text{Na}}_{ 3} {\text{AlF}}_{ 6} ( {\text{l)}} + 9/ 2 {\text{C}} = 4 {\text{Al}} + 3 {\text{CO(g)}} + 3/ 2 {\text{CF}}_{ 4} ( {\text{g)}} + 6 {\text{NaF}} $$ Because of the difference in kinetics of discharge of the two anions, and the extra thermal energy necessary to satisfy the overall enthalpy, partial passivation of the electrode surface can occur when it is under cell voltage control. The situation also applies to individual anode in large cells and therefore gives rise to PFC co-evolution through spatial variations. As the spatial changes propagate the same process leads to a full anode effect in the operating cell.

The most typical thermal insulating materials used in the cathode lining in aluminium electrolysis cells are Moler, calcium silicate, or vermiculite. The thermal insulation is important for the overall thermal and dimensional stability of the cell. The chemical stability of the thermal insulating materials is important, especially in cases where the refractory layer above the thermal insulation layer becomes fully penetrated by sodium vapour. The chemical degradation of thermal insulating materials by sodium vapours has been investigated in a laboratory test resembling the environments in the cathode lining. The exposed materials were investigated with respect to changes in the microstructure and chemical and mineralogical composition by a combination of optical and electronic microscopy and powder X-ray diffraction. These investigations revealed different reaction patterns for the three materials and the formation of new mineralogical phases were identified. Finally, these findings were compared with chemical reactions with sodium based on computational thermodynamics.

Dimensional stability of materials used in aluminiumAluminium electrolysis cells are important for stable cell operation. The observed compression of insulating liningsLining from autopsies of industrial cells are in many cases much higher than would be expected from laboratory creepCreep tests of the corresponding materials. Creep in compression of three commercial insulating materials for aluminium electrolysis cells, produced from diatomite, perlite and calcium silicate, respectively, has been studied. The creep rates were measured versus temperature and load on as received materials, after additional heat treatment, and materials contaminated with KF and NaF. Refiring the as received materials resulted in a substantial decrease in the creep rate.

To investigate cathode wear, an autopsy of a shutdown aluminium electrolysis cell was conducted. The original lining consisted of a fully impregnated and graphitized carbon block and the cell was shut down after 2461 days operation. The cell was cleaned down to the surface of the carbon cathodeCarbon cathode, revealing the profile of the cathode wear. Generally, the cathode wear was uneven across the cell with typical potholes. At a finer length scale, the wear was characterized by small “pitholes” resembling wide shallow pitting corrosion. Samples of the cell lining were obtained by drilling cylindrical samples at different locations in the cell. These samples were analysed with respect to phase composition and microstructure by a combination of X-ray computed tomography, optical and electron microscopy. The findings are discussed in relation to the current understanding of the underlying mechanism(s) for cathode wear.

Aluminum smelters generate a considerable amount of spent potlining (SPL), which results from the chemical and mechanical degradation of carbon, refractory and insulating materials used to isolate them from a high-temperature and chemically aggressive process of electrolysis. The specific amount of generated SPL is 18–40 kg/t Al, and it depends on the life of the cell, which varies from 5 to 7+ years. Besides considerable expenses for cell relining, SPL has a negative impact on the environment due to fluorine compounds and cyanides, and for this reason it is classified as a hazardous waste. There are two most evident ways of minimizing the above negative impact from SPL: a decrease in the amount of SPL, and SPL re-processing, including SPL neutralization and the production of sub-products such as fluorine, carbon and aluminosilicates. These materials can either be used in-house or sold to third parties. This paper covers RUSAL’s efforts aimed at developing and implementing a technology to recycle and re-process SPL.

Spent pot liningSpent pot lining (SPL) is a well-known waste product from the aluminium electrolytic cell. The SPL generation rate is approximately 1–1.5 million tons per annum, and this is a significant environmental burden to the aluminium industry. Previous reports indicated that more than half of the total amount of SPL generated is stored in lined/ unlined sites/buildings, waiting for further treatment. At the University of Toronto, the Process Metallurgy and Modelling Group (PM2G) is working extensively to understand the chemistry of SPL and find alternate applications of SPL. Some of the potential applications of SPL conceptualized at the University of Toronto are: (a) as a flux in the non ferrous industry, (b) as an alternate to coal in ironmaking blast furnaces. Experimental and mathematical modelingMathematical modeling techniques have been used to test these ideas, and the results are discussed in detail.

Aluminum smelting potlines usually have a big number of cells, producing aluminum in a continuous and complex process. Analytical monitoring is essential to increase the industries’ competitive advantage, however, during their operation, some cells share similar behaviors, therefore forming clusters of cells. These clusters rely on data patterns that are usually implicit or invisible to operation, but can be found by means data analysis. In this work we present two clustering techniques (Fuzzy C-Means and K-Means) to find and cluster the cells that present similar behaviors. The benefits of clustering are mainly in the simplification of potline analysis, since a large number of cells can be summarized in one single cluster, which can provide richer but compacted information for control and modelling.

Due to the multivariate nature of the aluminium electrolysis process, the usual univariate control algorithms coupled with the low visibility of the process used in the aluminium industry intrinsically causes control errors resulting in suboptimal process controlProcess control. A trend in the industry consists in applying multivariate statistical process control with specific responses to the cause of variations. Such a system in the form of a BathBathTemperatureTemperature and ChemistryChemistry Control Module (BTCM) was developed to be used in conjunction with state-of-the-art STARprobeTM measurements of electrolyte properties, providing the ability to respond quickly to causes of abnormalities detected from the immediate synchronous bath measurements. This paper presents the system and results from a smelter’s pilot section.

There is a constant effort from aluminium producers to reduce energy consumption of the Hall-Héroult cells in order to decrease cost and environmental fingerprint. Among others, slotted anodesSlotted anode were introduced in order to promote faster evacuation of the electrically isolating anode gas bubblesBubble and thus diminish their contribution to the total cell voltageCell voltage. A bubble layer simulatorSimulator was developed to reproduce cell voltage fluctuations, caused by the dynamics of anode bubbles. Results of simulations show that the slots cut in the right position and direction can reduce both the amplitude of fluctuations and the average cell voltage. This impact is even higher for new, almost horizontal flat anode bottoms. It is also revealed that the slots are acting mainly as a simple bubble sink, but they also contribute to the acceleration of the bubble layer as well and thus their role in the momentum exchange between liquid and gas must be taken into account.

Due to the nature of the process, aluminium smelting can have many issues/abnormalities/problems. One type is systematic issuesSystematic issues, which are those that occur on multiple pots simultaneously and can result in prolonged issues across a potline if not identified early. However, detecting and identifying these issues can be a difficult task for smelter engineers and management, particularly when information sources are not recorded, integrated and available in a centralised location. In addition, they are often not displayed in a way that is convenient for tracking and identifying systematic problems. For example, an increasing trend in cryolite ratio (CR) on all pots can be difficult to spot if graphical CR trends are only displayed for individual pots, or worse, in a tabulated format. This paper presents two case studies in detecting systematic issues in smelting process using the Generation 3 process controlProcess control system that highlights the importance of a centralised dataCentralised data location and appropriate data presentationData presentation. The cause of the systematic issues and the actions taken to manage the impact will also be discussed.

New statistical models were developed to predict the behavior of industrial potlines. A first model, based on a multiple linear regression analysis, predicts the instability (cell noise) of P155 potlines and is used as a tool to investigate drifts. An example of the usefulness of such a model is presented. A second model that predicts the current efficiency was built using a similar approach. It is based on 10 years of data from 30 potlines. The non-linearity of the relationship between current efficiency (CE) and anode-cathode-distance (ACD) was investigated and confirmed during the course of this study. These current efficiency and instability models provide new ways to anticipate potline performance and to conduct gap analysis.

The relationship between the content of sodiumSodium in the metal in aluminium production cells and the current efficiencyCurrent efficiency (CE) (CE) was analysed, using available theory and experimental data. The sodium concentration as well as the CE varies with the bath composition (the bath ratio) and the cathodic overvoltageCathodic overvoltage. The mentioned parameters are all functions of the same type of ratio between the activities of sodium fluoride and aluminium fluoride, thus enabling an internally consistent and quantitative description. The “ideal” relationships between the sodium concentration in the metal, the CE, and the cathodic overvoltage are illustrated. It is suggested that the sodium content in the metal can indeed be used as an indicator of the cell performance. However, it is necessary to use adequate sampling and analysis techniques. The exact cell conditions during sampling should be taken into account as well, such as the bath composition and the overfeeding/underfeeding cycle.

Based in Mumbai, India, Gharda Scientific Research Foundation (GSRF) is working to produce aluminium chloride and primary aluminium via carbochlorination of bauxite followed by electrolysis step. In this paper, a literature review of the chloride route based on published literature and concept proof experiments in various small setups are discussed. Bauxite was chlorinated with calcined petroleum coke in an externally heated small bubbling fluidized bed reactor. Aluminium chloride thus produced was purified by reductive distillation in a small setup and used for aluminium chloride electrolysis in a 50 L cell. The study aimed to generate scale up data for optimizing the chloride conversion, recovery and purity as well as electrolysis efficiency. The findings are used for process scale up to a kg scale setup and then to a larger demonstration plant. Presently, GSRF is operating a demonstration plant for carbochlorination of bauxite.

Chloride is considered one of the most important contaminants in cryolitic electrolyte system for aluminum smelting, and yet at the same time, chloride salts such as NaCl, MgCl₂ and others have also been chosen for potential additives to change the electrolyte physical chemical properties for smelting efficiency improvement. This paper studied the chloride stability in the cryolitic electrolyte system. The behavior of NaCl and MgCl₂ was investigated when there is a moisture present with or without electrolysis or when there is anode effect. HCl will be generated along with HF during a normal electrolysis even when chloride in the electrolyte is at a low level. CF₃Cl gas is generated along with CF₄ and C_xF_y when anode effect occurs. The results confirm that even though chlorides (NaCl/MgCl₂) are considered the most important contaminants, the level of the contaminants remains relatively low in the smelting electrolyte without obvious accumulation over time.

Thermochemically CO should be the dominant product and various theories have been proposed to explain the electrochemical dominance of CO₂. Following publication of the proposed correlation between current efficiency and cell gas composition by Pearson and Waddington [1], smelting operators have considered the presence of high amount of CO to be a direct indicator of poor cell performance. However substantial deviations occasionally occur in the gas composition [2, 3] yet the rigour of correlations and reaction mechanismsReactions mechanisms interpretation have not been questioned. As a consequence of anode gas composition trends associated with large multi-electrode smelting cells, and aided by supplementary data, the mechanistic interpretation for the formation of CO and CO₂ during aluminium electrowinning has been re-analysed. The data indicates interfacial heat transferHeat transfer to satisfy the entropic energy plays an important role in determining the proportions of the gas.

Good busbar design is of paramount importance for aluminium reduction cell performance. Busbar design impacts cell magnetohydrodynamic (MHD) stability, without which it is difficult to achieve high current efficiency and low energy consumption, since instabilities enhance the rate of back reaction and make pot control more difficult. Many aspects of busbar design and MHD stability are still grey areas where cell designers do not have full confidence because MHD criteria are still rather qualitative. EGA has developed cell design capabilities, including busbar design. During the last six years, EGA has developed about ten busbar designs for new and retrofit potlines. In some cases, the constraints led to sub-optimal busbar design for cell stability in practice. This experience enhanced our understanding of busbar design, MHD modelling and measurements, which we share in this paper. We also discuss criteria for busbar temperature, current density and vertical magnetic field distribution.

In a Hall-Héroult electrolysis cellHall-Héroult electrolysis cell for aluminum production, understanding hydrodynamic phenomena induced by the magnetic field is very important for process stability and performance. The mathematical modeling of the flow of liquid aluminum and the electrolytic bath under operational conditions involves solving two systems of equations for two immiscible stratified fluidsStratified fluids where the movement is primarily due to the anodic bubles and the electromagnetic forces. Because of the flow recirculation, dissimilar cell length scales in three directions and the magnetic field effects, the turbulence estimation for flow modeling is not straightforward. In this study, numerical simulations are conducted in order to investigate the applicability of Large Eddy SimulationLarge Eddy Simulationturbulence modelsTurbulence model to adequately represent the magnetohydrodynamicMagnetohydrodynamic turbulence in the electrolysis cell.

Liquid metal batteriesLiquid metal batteries (LMB) are candidates for large-scale energy storage in a national energy grid. The attraction of the liquid batteries lies in the fast kinetics at liquid metal-electrolyte interfaces, simple assembly and recycling, while the major difficulties to implementation are their sensitivity to liquid motion and operation at elevated temperatures. The concept of liquid metal battery bears a close similarity to aluminium electrolytic production cells. The two liquid layer magnetohydrodynamic effects can be projected to the three liquid layer self-segregated structure of the batteries. The trend for commercial electrolysis cells is to increase their size instead of operating a large number of parallel small ones. Our aim is to develop a numerical model for the three density-stratified electrically conductive liquid layers using 3D and shallow layer approximation accounting for specific magnetohydrodynamic effects during periods of battery charge/discharge. A possibility to reuse infrastructure of an old aluminium electrolysis potline for a large scale liquid batteries facility is discussed.

Two innovations presented by the authors recently at ICSOBA conferences allow to very significantly reducing both the cathode and the busbar voltage drop (Dupuis in A new aluminium electrolysis cell busbar network concept, 2015; Dupuis in New busbar network concepts taking advantage of copper collector bars to reduce Busbar weight and increase cell power efficiency, 2016). This paper combines the usage of those two innovations with the usage of the new anode stub hole design presented at the Aluminiun of Siberia conference (Dupuis in Presentation of a new anode stub hole design reducing the voltage drop of the connection by 50 mV, 2016) to come up with a very low energy consumption cell design.

Contact resistanceContact resistance between cathodeCathode block and cast iron plays an important role for the ohmic resistance of the cathode system and hence for the cathode voltage dropCathode voltage drop (CVD). Investigations of the standard dove-tail cathode slotCathode slot design showed poor electrical contact in the bottom of the slot and small contact area on the cathode wings. Different thermo-mechanical properties of carbon cathode block, cast iron, and steel collector bar resulted in displacements relative to each other after rodding, during cooling and handling. To mitigate this effect without changing materials or procedures, different slot geometries were modeled with respect to preheating and casting. By introducing anchoring grooves for the cast iron at the bottom corners of the slot, bottom contact was achieved: Lab tests proved that voltage drop between cathode slot bottom and cast iron decreased significantly. Subsequent field trials showed a CVD reduction of 20 mV.

The still on-going productivity improvement realized in potlines outlines the importance of the tending crane availability rate, which results from both their reliability and their easiness to repair. In the field of the crane electrical insulation monitoring—essential for ensuring operator safety and avoiding equipment damage, it is now expected that preliminary incidents being quickly tracked and fixed, in order to minimize the investigation time. This paper presents the new version 4.0 of the Fives ECL CANDI™ monitoring system. It deals with a new modular architecture, which allows its implementation on green field projects as well as on retrofitting ones; it also focuses on the evolution of the scanning which brings faster results. It finally presents the information the operating or maintenance people will benefit thanks to a thoroughly redesigned human-machine interface and new data transmission capabilities.

TRIMET Aluminium SE operates the Essen aluminium smelter with 3 potlines in Germany. On April 12th 2016 a smoke alarm in the substation triggered an emergency shutdown of the whole plant. The smoke alarm was triggered by a short circuit on a 21 kV bus bar. While potline II and III could be restarted within 2 h, the damaged bus bar had to be removed, separating potline I from the redundant high voltage power supply and fixing it on a single 220 kV transformer. When potline 1 was able to be restarted, the 220 kV transformer was found to have an insulation fault. An emergency bus bar replacement was welded in place and potline I could be re-energized after 5 h 50 min and 30 s. Due to the immediate steps taken in the potrooms, any pot loss could be prevented and the potline was back to normal operation in 12 h.

Unlike pot-to-pot cathode busbars, often protected by the potroom working floor (or gratings), risersRisers are usually exposed to accidental collisions with pot tending machine tools, anode assemblies, crucibles and even heavy vehicles. The tap end corner risers of several pots located immediately after the passageways of the Baie-Comeau Smelter’s Potline D had been damaged throughout the years, which led to the mechanical failure of a considerable amount of the welded plates connecting said risers to the passageway liaison conductors. The retrofit of damaged pot-to-pot conductors is traditionally based on welding techniques, often requiring bypass bridges or potline shutdowns. In the fall of 2015, an integrated Alcoa-Hatch multidisciplinary team succeeded to safely replace one of these risers, without production downtime or auxiliary conductors, by resorting to bolted connectionsBolted Connections in lieu of standard welded joints. This unique piece of equipment has been operating consistently within target for about 10 months.

This paper comes up with a new baking approach, high temperature gas bakingGas baking technology, based upon aluminium cells characteristics and raw material properties. Research achievements have been widely used in actual practice after numerous laboratory and industry tests. It turns out that, high temperature gas, as heating media, is able to ensure uniform surface temperature distribution of cathode lining. What’s more, it reduces the possibility of paste and carbon blocks oxidation damage during baking process. Its good baking results create favorable condition to prolong cells’ s service life. This approach is also proved to be energy-saving, safe and environment friendly.

In March 2012, EGA started seven test cells to validate its new D18+ cell technology. Designed with the latest technological advances to upgrade the original D18 potlines, the test cells quickly met their design targets with specific energy of 12.75 DC kWh/kg Al and AE frequency less than 0.02/cell/day. After successful validation, a project was commenced in August 2015 to upgrade the original D18 potlines to the newly developed D18+ cell technology. Unlike previous capacity expansion at EGA, the D18+ project required construction within the existing potrooms, which continued to operate while the upgrade was underway. Despite the challenges involved, full conversion of Potline 1 was successfully achieved ahead of schedule and without injury. Through increased amperage to 235 kA and higher efficiency EGA’s production capacity will be increased by 23 kt per annum. Further conversion of 272 cells to D18+ in Potline 3 will commence in September 2016.

ALBRAS needed to align its operation with the follow-up methodology used by Hydro Aluminium, its majority owner. To achieve this goal, ALBRAS decided to standardize its potline production information by installing Hydro’s APICS system. A tight integrationSystems integration with the underlying pot control systems was needed to replace their supervision HMI by APICS’s one. To design an interface to integrate both systems and install it in the running control systems without disturbing the smelters’ operations was a challenge. In this paper the interface solution provided to integrate APICS with two different versions of the SCORE supervision and control system, installed in all four smelters at ALBRAS, will be presented. Challenges will be discussed, the defined interface solution will be detailed and the results along with some lessons learned will be presented.

After successful development and industrial implementation of DX and DX+ Cell Technologies, EGA Technology Development launched several initiatives to lower CAPEX and cell energy consumption. The result is DX+ Ultra Technology, which is installed in five demonstration cells in the Eagle Section of Potline 5 Eagle at DUBAL (EGA Jebel Ali Operations), which were started up in March to May 2014 at 450 kA. The main new features of DX+ Ultra Technology are: reduced cell-to-cell distance as well as proprietary novel-design split anode risers, collector bar copper inserts and cathode flexes. More than one year of excellent performance at 455 kA with 95 % current efficiency and net specific energy consumption of 12.8 kWh/kg Al has confirmed that the technology is ready for industrial implementation. DX+ Ultra Technology has been selected for Alba’s Potline 6Alba Potline 6 expansion. Further optimization of the cells is underway to deliver best-in-class technology to the client. This includes larger busbar cross-sections for even lower energy consumption.

Today, in the electrolysis area of modern aluminium smelters, treatment of pot gas emissions has been drastically improved by the latest generation of dry scrubbing technologies, with efficiency rates close to 99.8%. As a consequence, stack emissions now only represent a very small amount of the total fluorides emitted over the entire smelter. Most of the HF is released to the atmosphere directly from the potroom, where in many smelters no specific treatment is provided to limit emissions related to pot maintenance activities (pot hoods opening, spent anodes removal, etc.). FIVES SOLIOS now proposes a solution to eliminate emissions coming from hot spent anodes stored in potroom thanks to an Anode Inert Tray (AIT) designed to confine anode butts. This paper presents the results of the industrial first of class AIT, developed conjointly between FIVES SOLIOS and FIVES ECL and which has been operated by ALRO for several months.

In the present work, previous studies carried out by the Norwegian aluminium industryAluminium Industry and research centres with the aim of recovering heat from aluminium production off-gas, are reviewed. The main challenge in improving heat recoveryHeat recovery is the foulingFouling phenomena, which is due to the presence of particulate matter and corrosive gases in the off-gas. Fouling can occur due to particle deposition, condensation of corrosive acids and scalingScaling reactions, which in turn can build up hard layers, particularly, on heat exchanger surfaces. The review focuses primarily on fundamental studies (theoretical and experimental), which address off-gas composition characterization, particle size distribution and particle deposition phenomena in laboratory and industrial environments. Moreover, it presents commercial concepts already implemented in industry applications. Upcoming activities in regards to the scaling phenomena, which include the design of a cold-finger for laboratory and industrial measurements, as well as mathematical modelling using CFDCFD, are also discussed.

Positioned in British Columbia on the west coast of Canada, Kitimat smelter is in operation for more than 60 years. A new era has started with the modernization of the smelter using the AP40 smelting technology. AP40 technology has already been successfully used in the Alma (Canada) smelter enabling operation above 400 kA. The new Kitimat potline, with its 384 pots, started production mid-2015 and reached full capacity in March 2016. The robust start-up has been successfully concluded with a performance test achieving 96.1% Current Efficiency and 12,800 kWh/t of Specific Energy Consumption. Thanks to new AP40 potline, the Kitimat production increases by about 48% to 420,000 tons annually while the smelter’s overall emissions have been halved. Kitimat smelter is now one of the most efficient, greenest and lowest-cost in the world.

The purpose of this study is to investigate the effect of adding the Al–Ti–B grain refiner to the aluminum twin roll casting. The authors analyzed the microstructure of the as-cast strip produced by the twin roll castingTwin roll casting based on several casting conditions. The results showed that the amount of the TiB₂ particles and the temperature gradient in the solidification area are the key factors for enhancing the effect of the grain refiningGrain refining. Additionally, this study simulated the behavior of the TiB₂ particles in the aluminum melt. The temperature distribution of the aluminum between the twin rolls was also calculated. The authors clarified the relationship between the grain refiner particles and the temperature gradient for the grain refining effect during the twin roll casting.

In twin-roll castingTwin-roll casting of aluminiumAluminium the content of alloying elements is limited due to the formation of segregationsSegregation mainly at the centerline and the surface of the strip. Their appearance, size and localization have a major influence on the final product quality. AlFeSiAlFeSi alloys are well suited for this investigation as they are alloyed with iron far beyond solubility. In casting experiments, casting speed is altered stepwise while all other casting parameters are not actively changed. Naturally roll and strip temperatures are increasing while separation force and strip thickness are reducing when casting speed is increased. Basically with increased casting speed the liquid and semi-solid sump is growing and contact time of the strip with the water-cooled roll is reduced. Hence both factors influencing segregation behavior, namely solidification conditions and deformation of the sump, are changing during the experiments. Experimental investigation is supported by process simulation in Alsim.

High magnesium containing aluminum alloysHigh magnesium aluminum alloy are preferred in applications where high strength and good formability are of importance. However, enhanced Mg content in AlMg alloys leads to increased solidification range which makes these systems difficult to be produced by twin-roll castingTwin-roll casting. In this study, AlMg alloys were produced by twin-roll casting with different Mg contents up to 5.2 wt% and processed to obtain soft annealed 1 mm thick samples. The effect of Mg content on the microstructural evolution during twin-roll casting as well as downstream processes and mechanical properties of soft annealed 1 mm thick samples was investigated. Addition of Mg leads to coarser grain structure in as-cast strips and finer grain structure after intermediate annealing as well as soft final annealing. At the same time, enhanced Mg content provides higher yield and tensile strengths as well as lower elongation.

The formation of strips at twin-roll castingTwin-roll casting depends on the state of the roll surface. The processing conditions, which are characterized by high metal-tool interface temperatures and compression stresses, provoke stickingSticking between the cast material and the rolls. This effects changing of the tool’s topography, impairment of the strip’s surface quality and interference of its flatness. In the scope of this study the evolution of roll’s topography at twin-roll casting of 3 mm thick strips of aluminum alloysAluminum alloys EN AW-1070 and EN AW-6082 without any release agents was experimentally analyzed using laboratory casting unit. The effect of repetitive tool’s self-cleaning during processing of the EN AW-6082 alloy was observed, whereas aluminum of technical purity showed intensive sticking on the roll surface. In the last case micro-profiling of the tool’s surface is not more efficient and release agents have to be used for improvement of the strip’s formation conditions.

Continuous casting of aluminum sheet products has so many advantages due to its short production route. These advantages can be listed as low production cost, low investment cost and short delivery time. However, this method has some technical insufficiencies that are mostly related with quality issues. These disadvantages can be listed as low alloy range, mechanical properties and surface quality. The most critical issue is surface quality. To improve casted sheet surfaceAs Cast sheet surface quality, cold mill performance of continuous cast coils and final surface properties; some operational applications are needed to guarantee for a sustainable process parameters and repeatable measuring method. With this work, it is aimed to evaluate the surface quality in terms of surface roughness changes with casting and cold rollingCold rolling operations. Besides material’s roughness, change in casting shell and work roll roughnessRoll roughness, in-going material roughness and planning parameters of casting and cold rolling operations are involved.

The manufacturing of thin aluminium-steel clad strips by means of twin-roll casting is a prospective trend of the progress in the light metals sheet production. The resulting composite possesses high bonding strength due to the presence of a continuous thin layer of intermetallic phases at the bonding interface of metallic constituents. At the same time, for the application of twin-roll cast clads, the evaluation of their properties is of great importance. In order to determine the behavior of twin-roll cast aluminum-steel clad strips under loading, monotonic tensile and fatigue tests were carried out. Therefore, strips in the as-cast condition as well as after a heat treatment, stimulating the growth of the intermetallic phases, were subject for the characterization. In addition, the specimen’s fracture surfaces were analyzed using scanning electron microscopy to obtain information on the type of fracture, the location and source of the crack nuclei.

M-HPDC is an In-Mold manufacturing process combining High Pressure Die Casting (HPDC) and Injection Molding (IM) within one manufacturing plant. The biggest influence within a metal-plastic-bond realized by micro bracing is ascribed to a suitable temperature management in the die. Therefore a suitable temperature control concept for a sample die, made to manufacture an overlap shear tensile sample, will be presented. In order to investigate the temperature influence, the die provides several options to influence the actual temperature. A number of independent cooling circuits, an alternating temperature management unit and a contour adapted heating cartridge are integrated. Besides that, the temperature within the joining area can be raised by exchangeable die inserts for the usage of either an inductor or a heating ceramic. For the purpose of quantification, the temperature will be monitored by thermocouples close to the actual cavity surface. The die concept and first results of the simulative approaches will be shown.

The porosities and intermetallic phases in a high pressure die cast Al–Mg–Si–Mn alloy was investigated using 3D X-ray computed tomography with different scanning resolutions. The experimental results demonstrated the porosityPorosity level and phase detection of dependency upon voxel sizes. The porosity levels were 0.4, 0.5 and 0.8% and the intermetallic phases were 0.3, 0.4 and 0.6% when the same casting sample was scanned at 15 μm/vox, 7.2 μm/vox and 2.1 μm/vox, respectively. However, the structural parameters should be assessed to determine the necessary and/or possible image quality, weighing factors such as scan time, field of view, and voxel sizes.

The cooling of castings especially heavy steel castings was usually very slow and nonuniform after solidification, which results in low production efficiency and great residual stress or deformation. Furthermore, great thermal gradient appears across their thick sections and between the thick and thin areas, which may cause significant residual stress or deformation or even cracks. So as to solve this dilemma, we come up with a new method to make the riser useful and realize the castings rapid, inside-out and uniform cooling. It was named the post solidification intensive riser cooling technology (PSIRC). In this paper, the effect of PSIRC was investigated for three different alloys GS38 carbon steel, H13 alloy steel and A356 aluminium alloy by using stress frame castings. The results show that PSIRC could improve production efficiency and temperature uniform of the castings made of these three materials. For the improvement of cooling rate, it ranks from GS38 carbon steel, H13 alloy steel to A356 Al alloy. While for improving temperature uniform, the order is A356 Al alloy, GS38 carbon steel and H13 alloy steel. The effect of PSIRC mainly depends on the thermal conductivity of castings, high thermal conductivity means more cooling efficiency.

Aluminum alloys are widely used in the automotive field, for the excellent relationship between mechanical strength and lightness. In the recent years, the request for cleaner, lighter and more powerful engines, has led to the design of components subjected to higher thermo-mechanical stresses. Demanding exercise conditions can imply the presence of different properties that are never fulfilled by a single, homogeneous material. Various solutions have been developed using composites, surface modification techniques and Functionally Graded Material (FGM). This study has applied FGM concept to the traditional casting technology, in order to obtain a more performing product. To reach this goal, two different alloys were sequentially poured by gravity casting, each one delivering locally its properties to a specific volume of the casting. Beyond the morphological and microstructural analysis of the contact interface between the two alloys, the mechanical testing has shown promising results for future applications.

The modification level (ML) of A356, A319, and A413 Al–Si alloys was investigated via thermal analysis (TA) and microstructural investigation. The modification treatment was carried out using different levels of Sr in the form of Al-10 wt% Sr master alloy. The melt was poured into three different types of molds to give different cooling rates (CRs) to simulate the actual casting conditions. Increasing the level of Sr improved the ML of the eutectic Si. Slower CRs required higher additions of Sr to produce the same ML obtained from the higher CRs. An attempt was made to assess the ML at the high CRs with the aid of the TA parameters measured at the slow CR. Thermal analysis was found to provide successful quantitative measure for the modification level in A356. In A319 and A413, thermal analysis could provide successful quantitative measure of ML when the ML was below 4.0. It could provide only qualitative indication of the occurrence of modification when the ML was 4–6. The latter findings were found independent of cooling rate.

Diluted, mild or flameless oxyfuel combustion has shown in the past years huge successes as an optimization tool for different high temperature applications. This innovative combustion technology has a lower flame temperature, more uniform temperature distribution and low concentrations of oxygen as well as nitrogen inside the furnace, leading to low fuel consumption and very low NO_x levels. In this work we analyze the optimization processes of different types of rotary and reverberatory furnaces (fix, tiltable) with Messer Oxipyr® burners, which led to impressive savings, dross reduction and ecological improvements for the customers. A review of the available literature, on this topic, is also given.

New Zealand Aluminium Smelters Limited (NZAS)Zealand Aluminium Smelters Limited (NZAS) manufactures the highest purity primary aluminiumAluminium ingot, high quality extrusion billet and rolling slab products. In 2011, NZAS installed Zmag’sZmag MagStir™ into a 50T casting furnace. MagStir utilises Zmag Permanent Magnetic Circuit, the world’s first, proprietary permanent magnet-based technology for contactless stirringStirring in the bath. Agitation of casting furnaces during alloying to achieve elemental dissolution and temperature control is the key part of furnace preparation and when performed in an efficient manner, it can give significant savings in fuel and alloying costs and increased throughput. In 2016, NZAS added MagStir to two more casting furnaces and achieved significant improvements in temperature control during all phases of furnace preparation. This paper is a case study on the benefits of stirring in general, specific benefits observed using Zmag’s MagStir at NZAS as well as lessons learned in the operation of the systems over 5 years.

Energy efficiencyEnergy efficiency is a critical issue for all manufacturing sectors. In the present paper the energy efficiency of UK foundriesUK foundries was assessed. In the context of this research 80 foundries were studied, 60 were contacted and 10 were visited. General energy data were collected using structured questionnaires, interviewing energy managers and process operators. A number of foundries are operating to a good standard, by employing energy managers and regularly auditing; they are in control of their process and working rigorously to improve their efficiency. Simultaneously though, smaller foundries have not adjusted to the new market demands and are not operating in the most energy efficient manner. Important barriers to energy efficiency in these foundries include lack of knowledge on auditing methods, poor knowledge in managing energy consumption, the inefficiency of individual process steps, production disruptions, aging equipment, personnel behavior, inadequate maintenance and lack of investment, automation and research.

Nowadays, the most important problem is the high cost of casted products. Foundries are increasing the use of secondary sources to reduce their raw material costs. Continuous caster edge milled swarf has a large potential as a possible new secondary source. Usually this swarf has a high amount of oil ingredient and low density. These properties lead this material as a low quality and low recovery rate source. To solve this problem some of the companies try to reduce oil usage, some of them changing the oil type. However especially for reverberatory melting furnaces the density must be higher than molten aluminum density. We will evaluate the chip briquetting solutions to improve melting efficiencyMelting efficiency for chipsChips. Also we will be conducting the density and oil amount results together with edge miller oil usage, swarf oil amount, cyclone filter parameters, pressing parameters, oil reduction methods and melting efficiency of briquetting.

On site Hot Dross Processing systems (HDP) can offer a method for significant environmental savings with on site aluminum recovery. HDP often can eliminate the remelting of the recovered sows or at worst take advantage of the retained heat in the poured off sow. The most advantageous systems offer productive end use of the dross oxides and aluminum fines left in the residual materials after the aluminum is recovered. All of these systems offer significant environmental advantages over pan cooling or dross pressing of materials that simply change the form of the aluminum and require further off site rotary salt furnace processing. There are four HDP systems that will be reviewed in this paper. Hot dross stirrersHot dross stirrers plus dross coolers/size separatorsHot dross rotary furnace operationsTAHA hot dross mixer, cooling and sizing

For successful and consistent casting on ingot DC casting systems, metal heat loss has to be reduced. Metal heat loss is directly influenced by casting trough/launder design and material selection. To assist in developing solutions to reduce metal heat loss from furnace to casting table, a CFD modeling program was developed for heat loss analysis from furnace spout to casting station. The influence of the degasser, CFF units, and automated metal level controls are all included in the program to improve accuracy. Case studies are reported to reveal the influence of refractory geometry and material selection on metal heat loss. It is shown that when the main launder refractory material is changed from REF-1 to REF-2, heat loss is ~15.0 °C less at start and ~3.5 °C less at run cast at a ~136 kg/min flow rate. A trough/launder with a V-Shape cross section has less heat loss than a trough/launder with a U-Shape cross section as a result of increased metal flow due to reduced cross section area and the reduced metal contact surface area. The reasonable agreement between our modeling results and field measurements show that the developed casting process modeling program can be used to analyze refractory/insulation materials and trough/launder geometry designs.

In the past, numerical modeling and measurements in the field have provided insight into direct chill castingDirect chill casting of sheet ingotsSheet ingot and helped identify critical parameters to achieve successful cast start-ups. The control of these critical parameters is of key importance to maximise performance and throughput of the cast house as well as to meet stringent client requirements. Among these key parameters, management of liquid metal temperature, at start of cast, is critical in regard to casting performance. This paper presents several process variables influencing direct chill casting performance such as ingot recovery, false start and ingot quality.

The objective of this study is to analyze bleed-outs in Horizontal Direct Chill (HDC) casting process by using a finite element model (FEM). HDC casting machines for aluminium are made for continuous casting with typical duration from 3 to 20 days according to the equipment manufacturer. Reduced duration due to technical difficulties affects capacity, productivity and cost. In order to improve understanding of the operation and the effect of alternative casting parameters an FEM model was developed for a 36 bar HDC machine installed in the Alcoa Fjardaal casthouse. SimulationsFEM simulation were done for alternative inlet metal temperatures, cooling water temperatures, cooling water flow rate and casting speed with the focus on extracting information about potential bleed out conditions of a cast bar. Physical measurements were done on the HDC under real casting conditions and compared with the results of the numerical simulation showing good agreement with the measured results.

A novel method based on the use of a turbulent jet has recently been proposed to minimize the degree of centerline segregation in Direct-Chill (DC) casting of aluminum ingots. The functionality of this method relies on the ability of the jet to re-suspend solute poor grains which have settled to the bottom of the molten pool. To date, the presence of these grains has mostly been acknowledged by theory and post-mortem observations. Herein are reported results of a series of experiments designed to allow the sampling of grains in DC cast ingots with and without the use of a turbulent jet. Analysis of the shape and chemical composition of the samples are reported.

Recent investigations have suggested important benefits in using a turbulent mixing jet impinging into the molten pool of a continuously cast Al4.5Cu ingot [1]. It was for example demonstrated that such jet can significantly modify the macrosegregationMacrosegregation patterns found in large castings. One possible reason put forth for this modification is the ability of the jet to suspend sedimented grains from the ingot centerline. In this study, we propose a model to optimize the re-suspension of grains through the use of an engineered jet. We have recently completed series of full scale experiments using a variety of jet powers for Al4.5Cu ingots. In this study we completed a blind study of a new alloy (AA3104) cast under different conditions in order to validate the robustness of our model. Results confirm the potential of a turbulent jetTurbulent jet to mitigate the degree of centerline segregation in DC cast products for a relatively broad range of alloys.

In direct chill casting of aluminum alloys, negative macro segregation of eutectic elements and positive macro segregationMacro segregation of peritectic elements can occur at the center of the slab. It is very important to investigate the mechanism of these macro segregations because they influence the mechanical and chemical properties of the wrought products. The authors have performed a two-dimensional measurement of the macro segregation by optical emission spectroscopy, and important characteristics of this phenomenon were observed. They are explained qualitatively and quantitatively by our proposed hypothesis, the partially swept solute model. The model assumes that the sump flow penetrating into the mushy zone will sweep out the enriched or diluted liquid solute until the critical solid fraction $$ f_s^{\ast} $$ is reached, when the dendrite arms begin to sufficiently entangle with each other, making it difficult for the sump flow to penetrate into the mushy zone. Then, the ordinary solidification process continues. In case of severe segregation, the microstructureMicrostructure at the center of the slab becomes a granular crystal because the enriched or diluted solute in front of the solidification interface is swept out by the penetration flow and dendrite growth is inhibited.

This work presents results of preliminary investigations concerning the effect of ultrasonic vibrationsUltrasonic vibration on the solidification structure and hot-tearing susceptibilityHot-tearing susceptibility of 6000 series aluminum alloys in high-speed direct chill casting processes. A pilot DC caster was used to produce billets of 82–97 mm in diameter. Ultrasonic vibrations were introduced directly into the mold through a high-amplitude ceramic sonotrode, the tip of which was positioned at different distances from the melt crystallization front. The cast billets were then investigated for the microstructureMicrostructure and hot tearing susceptibility. It is shown that the ultrasonic treatment leads to a significant reduction in hot tearing susceptibility, and at the same time to a rise in mechanical properties of the alloys. The results suggest that at least two ultrasonic effects contribute to these improvements. The first one is cavitationCavitation which results in forming more refined and uniform microstructure of alloys. The second one is acoustic streamingAcoustic streaming which is responsible for macro agitation of melt in the sump. This causes the liquid-solid system to approach an equilibrium state that results in increasing the fraction of eutectic phase solidified at the grain boundaries of α-Al phase.

For many years now, ultrasonic melt treatment (UST) has proven itself to promote grain refinement in aluminium alloys. The current work presents cavitation-aided grain refinement obtained on commercial AA6082AA6082 DC-cast billets. Grain refinement was achieved while applying UST in the crucible away from the sump, prior to casting. Since in high strength alloys, Zr and Ti are commonly present as alloying elements for anti-recrystallization and corrosion resistance properties, their as well as UST parameters influence on the microstructureMicrostructure are studied and presented. Primary Al₃(Zr_1–x–y, Ti_x, Si_y) intermetallics were found in the centre of the α-Al grains. This suggests that UST may have forced the nucleation and refinement of primary intermetallics influencing the subsequent solidification process when Al₃(Zr_1–x–y, Ti_x, Si_y) act as nucleation sites.

In previous investigation [1] has demonstrated the wide variation of grain size found through the cross-section of a Direct-Chill (DC) cast ingot due to the location-dependent solidification rate inherent to the process. Recently we have demonstrated [2] that the use of a turbulent jetTurbulent jet as a metal entrance method has the potential to significantly reduce grain size and its variability upon location. We herein report a series of experiments investigating the influence of jet power on the grain size and distribution in Al4.5Cu DC cast ingots. Our findings indicate that significantly increasing the jet power does not appreciably decrease the grain size. Instead, a threshold jet power required for grain refinementGrain refinement is anticipated, beyond which only marginal improvements are anticipated.

Ultrasonic treatment was conducted to study its effect on the size and morphology of the α-Al phase of the A356 Al–Si–Mg alloy. Treatments were carried out in the temperature range from 700 to 614 °C, i.e. from above the liquidus temperature (619 °C) to semisolid temperatures. The treatment times varied from 15 to 180 s. The results showed that ultrasonic treatment could control the alloy microstructure when applied in the liquid or semisolid states, and was most efficient when applied at a few degrees above the liquidus temperature, e.g., 620 °C, where globule size of 57 μm and roundness between 0.62 and 0.70 were obtained. Ultrasonic treatment times in the order of 15–30 s were sufficient to dramatically refine the size and alter the morphology of the α-Al phase. The refining effect observed in samples treated in semisolid state was due to solid fragmentation and dispersion, while in the liquid state, refining occurred most likely as a result of activation of non-equilibrium nucleation events which was confirmed from experimental simulations performed using succinonitrile polymer.

Al–Ti-B grain refinersGrain refiner are used as a grain refining agents in twin-roll casting. Although Al₃Ti particles in the rod dissolve, principal inoculant of TiB₂ remains undissolved and initiate heterogeneous nucleation. TiB₂ particlesTiB2 particle with higher density than liquid Aluminum are in tendency to settle as they are released from the melting grain refiner rod. Experimental studies showed that Ti concentration varies at different depth of the liquid metal in the launder. As samples were gathered from the bottom, not only the chemical content, but the metallographic analysis of the samples clearly exhibited that melt at the bottom of the launder heavily bear TiB₂ particles and oxides. The trajectories of the particles upon revealing from different position of the depth and their settlement were also simulated in finite element analysis (FEA) and experimental findings were confirmed.

Grain refining is an important technology in the modern aluminum foundry, since it provides several advantages to mechanical behavior and integrity of castings. In this chapter, thermal analysis of the A319 alloys was studied for the purpose of obtaining precise and repetitive cooling curvesCooling curve and hence accurate thermal analysis parametersThermal analysis parameters. The main casting parameters such as cooling rateCooling rate, alloy composition, and grain refinerRefiner level were considered and evaluated. The results showed that the cooling conditions during thermal analysis need to be suitable to rapidly reach equilibrium between the solidifying melt and the mold. The time parameters gave better control of grain refining than temperature parameters since they spread over wide ranges. The variation of SiSi and CuCu levels resulted in composition-related changes of the thermal analysis parameters. It was also found that the sensitivity of the thermal analysis parameters to the variation of grain refiner level was highly impaired at slow cooling rates of 0.27–0.40 °C/s.

Initiation and growth mechanisms of peritectic coupled growthCoupled growth (PCG) structures have been reviewed to clarify parameters that play a significant role in PCG formation and stability. Three important alloys of Fe–Ni, Ni–Al and Ti–Al have been studied to reveal mechanisms contributing to PCG formation. Types of PCG, the stability of lamellar coupled growth and their morphological behavior are strongly dependent on G/V ratio (G: thermal gradient, V: growth rate), lamellar spacing and composition. Analogy between peritectic coupled growth (PCG) and eutectic coupled growth (ECG) is also a point of interest in this study. Further investigations in Ni–Al and Cu–Sn are necessary to clarify the PCG formation (nucleation/growth mechanism) in conventional G/V versus composition diagram.

Explosions of molten aluminum and water are a very serious safety risk in aluminum casthouses. Although prevention of these explosions is of paramount importance, understanding the overpressure resulting from an explosion is important for worker protection and to the design of blast-proof control rooms and protection of other equipment. Overpressure has traditionally been assessed using a simplistic principle of decreasing overpressure with distance, which neglects the significant, complex interactions of the blast wave with walls and other bodies, resulting in regions of high overpressure not captured using simpler hand calculations. Computational fluid dynamics (CFD) modeling presents a method to analyze the problem in three dimensions. Blast analysis of a full casthouse with a conventional commercial CFD code can be time-prohibitive. This chapter presents a methodology to predict overpressure due to a molten aluminum-water explosion in a casthouse using a new manycore CFD solver—EXN/Aero developed by Envenio Inc. Results for a casthouse explosion are presented to demonstrate the use of this analysis in developing explosion-proof designs for control rooms and other equipment.

Sow casting in Aluminerie Alouette Inc have undergone many optimization projects in the past few years. In the cycle time critical path, actual pouring of the metal in the moulds from the crucibles remained one of the most important parts. This operation was done manually, leading to variability in duration as well as for sow weight. Sow caster capacity is a function of the average weight of the sows and a reduction of the standard deviation can help improve the average weight hence the capacity. A formula was developed to predict the quantity of metal transferred in function of the crucible tilt angle and an algorithm was built to optimize the pouring time. Implementation of the program was made in a very short time frame and the results show that a reduction of the pouring time as well as the weight standard deviation was obtained.

The current trend in all industries is to maximize operation time while lowering production costs. To achieve this goal, manual tasks, such as data monitoring, are being transferred to automated systems and carried out by them. Radio Frequency Identification (RFID) technology is one of these alternatives, in which electromagnetic fields are used to automatically identify and track objects. The present paper will elaborate on the possible RFID applications for the aluminum industry using examples from a project currently being executed at the Alcoa Deschambault and Baie-Comeau smelters. The implementation of an RFID system in a metal environment and the major factors that need to be considered during the design will be described. This paper will also describe the field tests performed by the Casthouse and Potroom sectors and the methods used to improve metal time management and personnel safety.

Parts traceabilityTraceability is becoming more and more important in many industries. Among others, automotive, military, aeronautics and medical industries have strict rules on parts traceability. Different marking technologies can be used to meet these requirements. Durability and reliability of the marking is very important. Also important is the automation of the marking process to avoid any human error in the procedure. Improved traceability is possible with lasers as compared to stickers and ink jet marking. A powerful, quick acting laserLaser is now available but safety of the installation in an existing process is essential and it is one of the main design criteria. A successful integration of an equipment providing laser, ink jet and micro-percussion in an existing production line was made while complying to all safetySafety and cycle time requirements.

Pressurized ladles, being closed, minimize aluminum dross due to oxidization and conserve energy required for ladle preheating. Design of pressurized ladles is not addressed by ladle design standards such as AISE Technical Report No. 9. This paper presents a design-by-analysis methodology for structural integrity assessment of pressurized ladles using finite element analysis and guidelines of ASME Boiler and Pressure Vessel Code. Transient temperatures in the ladle shell during preheating and aluminum charging/discharging are estimated and validated against site measurement data. Thermal loads are then combined with gravity loads (ladle self-weight and molten metal charge) and ladle internal pressure at different pressurization, lifting, and metal pouring stages. The resultant stresses and deformations in the ladle are compared with the ASME allowable limits against plastic collapse, thermal ratcheting and fatigue failures. This paper demonstrates the robustness of design-by-analysis methodology for integrity assessment of ladles under non-standard conditions.

The frequency and severity of molten metal explosionsExplosions in our industry has increased over the past decade. This paper considers if recent technology advances in direct chill casting processes resulted in our industry downplaying this hazard. Through analysis of past research studies, molten metal incident reporting data and review of the recent explosion that destroyed the Noranda Aluminium cast house. The causes of molten metalMolten metal explosions are considered and explored. I argue that recent molten metal explosions could have been prevented if the past research studies’ conclusions were adopted as best practices.

Increased demand for wrought aluminum products has put pressure on suppliers to increase the amount of recycled material used in the production stream. While this has financial and ecological benefits, even single-source scrap streams never exhibit the composition profile of the original product. The corresponding accumulation of so-called “tramp” elements such as iron, chromium, and vanadium can have an impact on the secondary phase intermetallic particles formed during Direct-Chill (DC) casting. In order to better understand the influence of increased concentrations of certain tramp elementsTramp elements, an AA3104 ingot has been cast with an increased level of iron compared to the standard. The secondary phase particles have been analyzed as a function of position using a deep-etch technique and compared to grain size and macrosegregation profiles.

Used beverage can scrap (UBC)Used beverage can scrap (UBC) bales can be remelted in state of the art multi-chamber furnaces. Following the recycling of baled UBC scrap in multi-chamber furnaces, a laboratory scale process route was developed for thermal pre-treatmentThermal pre-treatment and submerged meltingSubmerged melting of the scrap. In the present work, UBC scrap types with different densities and level of contamination are compared. The scrap types were thermally pre-treated in different atmospheres up to 823 K (550 °C) and subsequently melted by submerging in a salt-free laboratory process. Melting was performed in pure aluminum at 1023 K (750 °C) under protective argon atmosphere to exclude the influence of thermolysis gases and atmosphere. The impact of remaining organic contamination and oxidation products after thermal pre-treatment on dross formationDross formation were described. Results of SEM EDX analysis, as well as thermochemical calculations, were used to explain reactions between solid scrap and the liquid aluminium melt to improve recycling efficiency.

In a rotary furnace for aluminium recyclingAluminium recycling and dross treatment, a salt flux is added which protects against oxidation and captures non-metallic impurities. Furthermore, the salt has to promote the coalescenceCoalescence of the metal drops in the dross. This work investigates the coalescence of molten aluminium for different types of scrap. One hundred discs were stamped from aluminium alloy sheets with and without coating. They were melted, covered in NaCl–KCl–Na₃AlF₆ molten salt, in an induction furnace at 790 °C. The solidified aluminum droplets were extracted by leaching the salt with water. The fraction of coalesced drops and the average diameter were determined to evaluate the coalescence efficiency. The effect of various de-coatingDe-coating temperatures was studied. The results show that the coalescence is negatively affected by coating. Long holding times has no effect. Complete coalescence off all discs are achieved with uncoated scrap. The drops coalesce if the temperature of the combustion reaction for the coating is attained.

In order to remove impurities in scrap aluminum alloys, hence increasing their value, a laboratory-scale high shear processing (HSP)High shear processing (HSP) unit for mixing the molten alloy was developed, which makes it possible to remove iron-based contaminants using physical conditioning, at relatively low cost. In order to make this technology applicable in the industrial environment, we are now investigating the scale-up of HSP by using computer simulation. The computational research quantitatively predicts a variety of key features of fluid flow, which determine the feasibility of the scale-up. These include the mass flow rate through the mixing head, the effective agitation of the melt in the bulk crucible, and the shear rate that can be achieved. Based on the configuration of HSP that we review in this paper, we predict that it is feasible to achieve a factor of four scale-up in the volume of liquid alloy treated.

Recycling is a sustainability strategy that enables environmental savings as well as energy and cost reduction. Sustainability and reduced energy consumption requirements demand that Al–Si alloys are recycled by re-melting. Industries that use cast Al–Si alloys are increasing, leading to more consumption of these alloys that in turn leads to more scrap. Unfortunately, when cast Al–Si alloys are recycled, detrimental microstructuresMicrostructure combined with reduction in the mechanical properties occur. In this work, the limitations of recycling of cast Al–Si scrap are discussed. To overcome some of these limitations, centrifugal castingCentrifugal casting was adopted and the effect of the centrifugal speed was investigated. The microstructure of Al–Si alloys with high recycled content produced by centrifugal casting using different parameters was studied. The independent variables are the centrifugal speed and scrap material mix. The microstructure of the recycled cast Al–Si alloys was observed to improve by centrifugal casting, resulting a graded microstructure from inner to outer surface of the casting. The centrifugal separation is shown to be a promising method for controlling the Fe-rich enormous structures and the porosity present in the recycled Al–Si alloys.

Castability and tensile properties of recycled cast Al–Si alloys are affected by the presence of high iron content. The present study demonstrates a promising scope of better recyclability by engineering the intermetallicIntermetallics β-phase that present in cast Al–6 wt%Si model alloy systems with as high as 2 wt%Fe. ThermodynamicThermodynamic modelling interplay between Si and Fe concentration on the formation of the β-phase and the solidification behaviour of this hypoeutectic Al–Si alloy has been explored. It has been demonstrated that suitable heat treatment alters the morphology of the β-phase and simultaneous addition of Cu improves the strength. Based on the experimental evidences, the mechanism behind the solid-state morphological changes of beta phase has been proposed. Experimental results and thermodynamic calculations suggest that Cu content of more than 2 wt% marginally increases the yield of beta phase; however, at 4 wt%Cu the solid solution strengthening improve the strength of solutionized alloy.

The majority of RUSAL’s Russian smelters have to deal with challenges that are created by blending and calcining green cokes with varying chemical and physical properties and, especially, the problem is associated with high-sulfur cokes. It has been widely reported in the literature that desulfurization, which occurs during petroleum cokePetroleum cokecalcinationCalcination, negatively affects coke quality. To assess the risks of desulfurization and its influence on the coke physical structure, the RUSAL Krasnoyarsk Aluminum Smelter has run several experimental trials regarding the calcining of petroleum coke in an industrial rotary kiln at different temperatures. This paper discusses the physical changes in calcined coke with different sulfurSulfur contents in an industrial rotary kiln where the real density and carboxy reactivity of high-sulfur coke are shown to be extremely dependent on the temperature of calcination and non-predictable from 1200 to 1350 °C.

Today there is a growing trend towards the use of higher melting binder pitches in the manufacture of prebaked anodesAnode binder. Although 110–115 °C softening point Mettler (SPM) pitches are still the dominant quality for prebaked anodes, the use of 120 M pitches is growing and some anode producers are even using 130 M pitches on a routine basis. Due to their increased coking value, higher softening point pitches provide several property benefits over standard binders and total PAH levels are lower. Binders up to 150 M can be still produced with conventional distillation technology and processing as well as storage of these binders should be achievable in modern paste plants with relatively minor upgrades. Today’s generation of paste mixers are already capable of processing carbon paste up to 250 °C. The paper gives an overview of binder properties in the range of 112–150 M and presents the results of pilot anode testingPilot anode testing with these binders.

Aluminium smeltersAluminium Smelters are tightening bulk densityBulk density specifications for Calcined Petroleum CokeCalcined petroleum coke while refiners are sacrificing green coke densities at the cost of outputs. Previously, Apparent Density using mercury was popular for defining CPC density. But after AD testing was discontinued owing to environmental issues arising out of mercury usage, each smelter has come out with its own Bulk Density measurement method and specs. The industry specifies Vibrated Bulk Density, Tapped Bulk Density and that too, on a different size fraction viz. (1–2) mm, (−8 + 14) mesh, (−20 + 35) mesh, crushed and uncrushed particles etc. The calciners are confused and GOA CARBON LTD. has made an attempt to analyze various Bulk Densities on different size fractions using crushed/uncrushed basis, to explore, if there exists, a co-relation internally, among all the densities and in particular with mercury AD.

Thermal desulfurization (TDS)Desulfurization of petroleum cokePetroleum coke during calcination is a well-known phenomenon which results in a significant decrease in bulk density. In 2011, Rain Carbon began experimenting with TDS in a shaft calciner and some results were unexpected, particularly an increase in real density. This paper reports on the results of extensive work to explore the fundamental differences between TDS in shaft calciners and rotary kilns. Pilot anode studies have been completed to explore the potential of using TDS coke from shaft calciners in anode production. The attraction is both commercial and environmental. High sulfurSulfur (S) cokes are readily available and cheaper than low S cokes and removing SO₂ during calcination is more efficient than removing SO₂ from potroom flue-gas streams to meet emission limits.

The primary aluminium metal production carbon anode is a high volume product even on the global scale, which can benefit from optimising the aggregate packing. The general impression from literature is that the industry employs relatively simple methods for particle sizing, modified and enhanced by specific knowledge about the materials in question. The study lists examples of current and possible methods for measurement and control. A common approach is techniques based on sieving, like the Fuller curves: $$ Cumulative\,\% \,finer\, than = \sqrt {(particle \,diameter/maximum \,particle \,diameter)} \cdot 100\% $$ The packing of a given particle size distribution is substantially affected by surface roughness and particle shape, factors that normally is addressed only empirically if at all. The focus is on carbon anode production for aluminium metal reduction, but a comparison is made with other industries.

Rain Carbon completed its 20th global CPC round robin (RR)Round Robin (RR) in 2016 with five CPC samples covering a wide range of chemical and physical properties as well as both rotary kiln and shaft calcining technologies. Twenty-three labs participated in the RR and the paper summarizes repeatability and reproducibility data for the different test methods. Particular emphasis was given to bulk density testing. Pilot anodesPilot anode testing were prepared with each coke to examine the relationship between coke bulk densityCoke bulk density, anode density and other anode physical properties. The study generated some interesting findings with respect to bulk densities measured on naturally occurring coke particles. As coke particle size increases, particle shape has a greater influence on the bulk density result. An alternative envelope density test gives a more reliable indicator of anode density. The paper also provides an update on a new ASTM bulk density test being developed.

The anodic reaction of aluminium electrolysisAluminium electrolysis cells leads to the formation of CO₂ bubbles, which partly screen the anode surface and leads to an increase in the cell voltage. An advantage of these bubbles is that the formation and release contribute to the stirring of the electrolyte, however, the screening of the surface increases the irreversible energy losses. The voltage and current oscillation due to the bubble evolution during electrolysis for different anode materials have been determined in a laboratory cell. The effect of coke sulphur content and grain sizes were investigated. Anodes with finer coke fraction showed lower oscillations than coarser fraction equivalents. Additionally, the influence of current density on the amplitude of the anode potentials was measured. A 64% increase of current density caused an increase of anode potential oscillations from 79 to 170%.

INALUM has been using high Sulphur and low Sulphur coke with 60:40 ratios since 2004. Furthermore, some efforts have been done to increase anode quality, such as Blaine Number Stabilization, Butt Cleaning Improvement, and Cone Crusher Utilization. By controlling the fine fractions output in green paste mixing, the Blaine number variance was reduced by 5%. In the other hand, the butt quality also become a serious factor to anode quality, and to overcome this problem, better butt cleaning process was used to reduce the impurities. The impurity was reduced and stabilized in the level below 150 ppm from the specification of 300 ppm. In green paste mixing, coarser material also affected the green paste product. Coarse material composition should reach at least 5%, nevertheless the existing hammer mill cannot provide. Hence, INALUM has installed the Cone Crusher equipment to increase the coarse material up to 10%. Finally, by performing those improvements have increased the RRO₂ by 2.5% and RRCO₂ by 0.74%.

Carbon anodes are presently produced from petroleum-derived cokeCoke and coal tar pitch. Upon consumption of these anodes, some 1.5 t CO₂/t Al are generated. This considerable footprint could be reduced by using biomassBiomass-derived coke. It was suggested to manufacture coke from biomass char. However, the corresponding cokes typically contain undesired oxidation catalysts (alkali and alkaline earth metals), are high in oxygen (reducing carbon available for electrolysis), have undesired isotropic texturesTexture, and also have low bulk densities. In order to avoid these shortcomings, a new approach was studied: coking of biomass-derived oils from a fast pyrolysisPyrolysis process yielding lower-oxygen oil. The corresponding cokes are very low in undesired impurities (sulphur, vanadium, and nickel). Levels of oxygen, alkali and alkaline earth metals are acceptable. Using appropriate conditions, cokes with desired anisotropic textures can be produced.

To improve a low flue wall life, a natural gas purged infrared pyrometer system was implemented to replace original thermocouples based temperature measurement systems on firing system, in 1991. Flue wall life increased to be over 100 cycles, on Pechiney furnaces, by preventing flue walls overheating. Anodes baking quality is adequate for two burners ramps fire technology. Some problems had to be corrected over time as they appeared: calibration drift, pinched injector tubes, frosted pyrometers lenses, etc. Pyrometers and thermocouple measurement technologies can both successfully bake anodes to specifications, but original cost, ease of operation, and maintenance, and effect on refractory may favour one system over the other, depending on the plant situation.

As part of the continuous work in improving anode quality at Hydro Aluminium, series of pilot scale anodes have been manufactured with systematic changes in coke type and green paste production including recipe. The anodes also support M.Sc., Ph.D. and PostDoc work in programs supported by Hydro and the Norwegian Research Council. In addition to regular analysis, the pore, void and grain distribution has been investigated using Micro X-ray Computed Tomography (µCT). This non-destructive 3D imaging is now implemented at a cost to allow larger numbers of samples, and a methodology has been developed by SINTEF that yields surprising sharp detail, suited to interpret important structural factors for relatively large anode volumes of 10–130 mm diameter. Given a better cost to information yield than image analysis and mercury porosimetry, Hydro will continue to support academic work with CT analysis. Examples will be shown of baked anodes before and after electrolysis testing plus crack patterns after mechanical testing.

The quality of prebaked carbon anodes, consumed in electrolysis during the primary aluminum production, has an important impact on the cell performance. The anode quality depends on the raw material quality and operating conditions in the anode plant. Development of simple, quick, and inexpensive techniques and tools for anode quality control will help industry identify the source of problems and take the necessary corrective actions rapidly. In this article, different quality control tools developed to find the wettability of cokeCoke by pitchPitch, effect of mixing on coke particle size distribution, metallic impurity content, optimum vibration time, pitch content in green anode, and the measurement of green and baked anode electrical resistivities are presented. In parallel, data analysis using the artificial neural network (ANN), a powerful statistical tool for such applications, provides complementary information on quality and process. This article also presents the potential utilization of ANN in quality control.

A continuous measurement of the flow inside the flues of baking furnaces is still a challenge that has not been solved. As a substitute, the draft is measured in one position of each flue to determine the existence of a volume or flow. Knowing the real flow would be of the essence for a more accurate and optimized control of the combustion inside the furnace. A mathematical model for flow detectionFlow detection, based on fuzzy logics was developed to determine the actual flow in each flue. With the introduction of this flow detection module, each flue in a furnace is continuously evaluated. The on-line mathematical model calculates the actual flow in each flue by correlation of the relevant process data available in the firing system. As a result, the baking process is further optimized for lowest emissions and best fuel efficiency. The paper illustrates the mathematical approach and shows the results.

A hard carbon build-upCarbon build-up layer often forms on the flue wall surface in anode baking furnacesAnode baking furnace. The layer accumulates over thermal circles and needs to be mechanically removed regularly to ensure sufficient space for the anodes between flue walls. The underlying mechanisms are still unknown and the extent of the carbon build-up varies from plant to plant. The build-up on the flue wall, taken from an autopsy of an open top furnace, has been examined. Microstructure and phase compositions of the carbon build-up, especially towards the refractory interface, were studied by optical microscopy, X-ray computed tomography (CT), SEM/EDS, and XRD. Pyrolytic carbonPyrolytic carbon was found to be the main part of the carbon build-up layer in addition to packing coke particles. The transport of silicon from the refractory material, condensating on the flue wall surface, is found as nucleation sites for the formation of carbon build-up. Formation mechanisms of the carbon build-up are proposed with reaction schemes supported by thermodynamic calculations.

Crack propagationCrack propagation in carbonCarboncathodeCathode used in the aluminium industry has been investigated through flexural tests on notched specimens. The main parameters of interest were the geometrical evolution of the crack and the stress intensity factorStress intensity factor at the tip ends. The latter, in the case of interfacial fracture in two-dimensional geometries, can be related to normal (mode I) and shear (mode II) stresses. In this work, a new methodology has been applied which optically measures the crack tip displacement field by Digital Image CorrelationDigital image correlation. The stress intensity factors derived from the experimental data are consistent with results available in the literature. Furthermore, the preliminary results showed that characterizing the mode I (opening) only is somehow challenging due to the heterogeneity of such carbonaceous materials.

The refractory liningRefractory lining in anode baking furnacesAnode baking furnace is exposed to harsh chemical environment and thermal cycling. Spent refractory lining from an anode baking furnace after 4000 days in operation was investigated. Variation in the density and porosity across the bricks revealed that carbon build up in pores had taken place towards the anode side. The spent refractory bricks were investigated with respect to chemical and mineralogical composition by X-ray diffraction and electron microscopy. No significant change in the mineralogical composition across the brick could be detected by X-ray diffraction. Fluoride was not found in the bricks, while traces of sodium was shown to accumulate together with other impurities in the bricks. The changes in the chemical and mineralogical composition across the bricks are discussed in relation to possible chemical reactionsChemical reactions taking place during anode baking.

Baked anodes quality control is still mostly based on core sampling and characterization. Only a small proportion of the production can be tested by this method due to the costly, time consuming, and destructive nature of the analytical techniques. Furthermore, the core properties are not necessarily representative of those of the whole block. A rapid and non-destructive method for anode quality control based on vibrationVibrationmodal analysisModal analysis is proposed. A number of baked anodes produced under different conditions at the Alcoa Deschambault smelter were selected. These were excited mechanically at different locations and the vibration signals of the blocks were measured by accelerometers. Principal Component Analysis (PCAPCA) was used to cluster the vibration modes of the anodes. It is shown that the proposed approach allows detecting and distinguishing different types of anode internal defects. Some of the tested anodes were cut and imaged in order to confirm the results visually.

During the production of aluminium from conventional prebaked Hall-Héroult electrolysis cells, anodes have to be replaced on a regular basis. The anode rod assemblies, which are submitted to multiple heating/cooling cycles, tend to deform over time. Moreover, attacks from HF gas and liquid bath erode the stubs to a different extent at each cycle. The stubs thus require regular inspectionInspection to determine if they need to be repaired. Repair costs are often very expensive and difficult to follow and forecast. In 2016, STAS commissioned its new ASIS3D for the 3D analysis of stubs in any configuration (like hexapods). All anode rods in the rodding shop are automatically inspected in less than 30 s. A work order is automatically generated for each anode rod that needs to be repaired, after which it is registered in the database and printed on the anode rod. This paper describes the industrial performances of the ASIS3D.

Carbon-cast ironCast iron electrical contact degradationDegradation is still considered as one of the main cause for the CVDCVD increase over the lifetime of the electrolysis cell. A thermoelectric finite element model was developed to evaluate the effect of the carbon-cast iron electrical contact degradation and the cathodeCathodeerosionErosion on the CVD and the current distribution inside the cathodic assembly. Chemical degradation data from laboratory and industrial samples were used to calibrate the cast iron and the contact resistivities. Results demonstrate that the carbonCarbon block erosion and the contact degradation at the cast iron interface have a direct impact on the current distribution at the carbonCarbon block surface. Both factors increase the CVD when taken separately but the contact degradationDegradation outperforms the carbon block wear when taken together.

In the aluminium industry, the anode quality is an important factor that influences the Hall-Héroult processHall-Héroult process efficiency. For this purpose, many efforts have been done in order to optimize the anode design such as the use of slotsSlots, which allow gases, generated through the reduction operation, to escape. The aim of this work is to investigate the effect of the slots size on the thermo-electricalThermo-electrical model behaviour of the anode. To this end, a 3D thermoelectric model taking into account the anode, the bath and the anode connector has been developed using ANSYSAnsys software. Material parameters such as electrical resistivity, thermal conductivity and electrical contact resistance are temperature dependent. Numerical simulations were performed for several slots thicknesses. Furthermore, a new design based on a variable slots thickness is simulated.

Carbon anodes in Hall-Héroult electrolytic cell are the main source of carbon to reduce alumina into aluminium. Carbon dioxide resulting from the reduction reaction is evacuated through the lateral sides of the anode and through the slots. The shape and size of the slots is an important parameter for the anodes design. During manufacture, slots are formed in the anodes before or after baking. However, to avoid the stresses due to the introduction of slots in green anodes during molding, the solution is to saw the anodes after baking. The challenge here is to remove minimum carbon from the anodes while having high energy efficiencyEnergy efficiency during electrolysis process. This study is conducted to test numerically different sawn slotsSawn slots configurations in the anode using a 3D mathematical model of the electrolytic cell. The model takes into account the main thermoelectric phenomena and flow dynamics that govern the operation of the electrolysis cell.

One of the major downsides of the current aluminium production process is the high CO₂ emission. One alternative is to replace the consumable carbon anodes with inert anodes so that oxygen evolves instead of CO₂. Also PFC emissions will be eliminated by using inert anodes. However, so far a sufficiently inert anode has not been found. Another option is to utilize natural gas through porous anodesPorous anodes in order to change the anode process. This will decrease CO₂ emission remarkably and also eliminate PFC emissions and anode effect. The porous anode could be made of carbon or it can be inert. However, the as-mentioned problem still exists regarding porous inert anodes. Therefore, at the moment porous carbon anodes seem to be the best practical option. In this study, porous anodes made of different grades of graphite were used for electrolysis experiments in a laboratory cell. Also, off-gas analysis was performed to get an insight of the ongoing reactions. Our results show that for some types of graphite anodes, methaneMethane participates effectively in the anodic reaction.

The solidification shrinkage of cast ironCast iron causes low contact pressure and high contact resistanceContact resistance in the stub to carbonStub to carbon connection. The use of steel anode nails to bridge the shrinkage gap has previously been demonstrated to reduce contact resistance with full diameter stubs. New laboratory testing with reduced diameter stubs to simulate stub corrosionCorrosion, and with anode nails, demonstrates the higher electrical resistances that result from the wider iron shrinkage gap, and how the anode nails can consistently provide a lower contact resistance over the full anode cycle. This lower and more consistent resistance between hot vs. cold stubs, and new vs. worn stubs can be used to predict a reduced variation in current distribution between anodes in a reduction cell.

Amperage creeping projects are key milestones to improve productivity of aluminium smelters. They are also opportunities to upgrade vibrocompactors to the state of the art. In 2014, two smelters in the Gulf awarded to Fives contracts to upgrade their vibrocompactors to the most advanced eco-design standard. This paper details the return on experience (ROE) of these challenging and successful projects in term of overall equipment effectiveness (OEE) and Environmental performancePerformances including:AvailabilityAvailability of the complete paste plant increased thanks to the reliabilityReliability and space out maintenance requirements.Best QualityQualityAnodesAnode produced with the incorporated features: Dynpac, Accurate Dosing system and integrated vacuum solution allowing high density and low standard deviation.Shortest proven cycle time per former, demonstrating once more Fives unique capacity of high throughput equipment.Advanced eco-design solutions meeting also expectations in terms of noise and fume captures.

The NiFe₂O₄nanocermetNanocermet developed in this paper was prepared by homogeneous precipitation, mould pressing and sintering process. And the nanocermet was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The experiments and tests on corrosion and electrical conductivityConductivity show that the nanocermet can be used for inert anodeInert anode of aluminum electrolysis. The mechanical properties and processability of cermet for inert anode of aluminum electrolysis can be improved.

The solidification shrinkage of cast iron between the collector bar and carbon slot surfaces of a cathode assembly introduces low contact pressure and high electrical contact resistance, particularly at the top of the cathode slot. The use of steel nails to bridge the cast iron shrinkage gap lowers the contact resistance significantly. Recent laboratory testing of varying densities and diameters of nails in the cathode assembly demonstrates the reduction of resistance that is possible through the top of the cathode slot, and the corresponding reduction of resistance through the cathode. The selective use of cathode nails towards the center of the collector bar is modeled to demonstrate the potential of improved current distribution with reduced peak current density.

In order to meet an ambitious Strategic Growth plan, Aluminerie Alouette inc. (AAI) decided to upgrade its smelting technology from AP30 to AP40LE. A portion of this upgrade was dedicated to the modification of the pots, while another portion was dedicated to reducing the electrical resistivity in the anodic assembly. The hexapod replacement was the most complicated portion of the anodic assembly upgrade. It required extensive testing in order to meet the AP40 technology requirements. The new hexapod design also had to satisfy the need for a robust, long lasting product to minimize future operating costs. Once testing was completed, a logistical plan needed to be put into place to permit a seamless transition into the new technology without negatively impacting day-to-day operations. A hexapod fabrication process needed to be developed to ensure a constant supply of finished product to the plant without putting operations at risk.

The Alcoa Deschambault smelter is investigating increasing anode sizeAnode size change as part of a drive to continuously increase pot amperage (amperage creepAmperage creep). The new larger anodesAnodes will be both taller and longer and will impact the number of green and baked anodes, as well as the number of pallets, that can be stored within the smelter. Each of these storage areas have multiple functions: to link the operations of upstream and downstream plant areas, required due to differences in production rates, maintenance schedules, and working schedules; as a buffer for unplanned downtime; and to allow for anode or butt cooling before subsequent operations. The present article reviews the methodology used to evaluate the impact that a change in anode dimensions and amperage creep can have on storage areas and their ability to maintain their functions. The methodology includes layout reviews, mass and anode balance, functional analysis, and schedule optimization.

Christian Simensen and Thorvald Abel Engh have made a sustained and significant contribution to the general field of melt refining in aluminiumAluminium but also to other materials including steel, magnesiumMagnesium and silicon. Both have been ambassadors for Norway spending extended periods in England, Australia, USA, Sweden and Japan. They have supervised many PhD students and collaborated extensively with industry and other researchers. Topics covered include: modelling, degassingDegassing, filtrationFiltration, dissolved impurity removal including hydrogen sodium and iron in aluminium, analytical techniques for characterizingCharacterization microstructures and inclusions, inclusion detection, melt oxidation and alloying.

Gases are now widely used for stirring purposes in liquid metalsLiquid metals, given the inventions of the porous plug, as well as other submerged gas injectionGas injection methods, such as through nozzles, or tuyeres. Nonetheless, we know that any small bubbles forming at the exit pores of porous plugs, will normally rapidly coalesce into much larger bubbles. So, the question of how to form, and maintain, microbubblesMicrobubbles in liquid metal systems still remains something of a question. It is nevertheless possible, but only under well-defined conditions. Given that such micro-bubbles can be very helpful in promoting mass transfer reactions (e.g. hydrogen degassing of liquid aluminum), and efficiently removing micro-inclusions (e.g. from liquid steel or aluminium), this is an important topic that needs to be properly addressed. We demonstrate the necessary conditions for the formation of microbubbles, and for their continued existence, by way of a typical ladle-tundish metallurgy example.

Metal cleanlinessMetal cleanliness is an important aspect of ingot quality, with requirements that vary according to the final product. Too often, filters are treated as the only option to improve metal cleanliness. All of the molten aluminum filters used in industry today act by removing a percentage of the incoming inclusions. The cleanliness of the metal coming into the filter is thus critical to the final ingot quality. This means that final ingot quality is impacted by charge makeup, melting practices, furnace treatment, and in-line degassing as well as filter performance. Each of these individual steps must be considered to provide the metal cleanliness required for a particular product at the lowest cost. This paper will provide an overview of how various steps in the casting process affect metal cleanliness and will examine several examples of how they might be combined into a holistic economical process.

The development of a multi stage filter comprising a ceramic foam filter applied in a first chamber operating in cake mode; grain refiner added in a second chamber and a cycloneCyclone deployed in a final chamber to ensure removal of oxides and agglomerates arising from grain refiner addition was presented in TMS 2008. The first industrial prototype, installed at Trimet Aluminium at Essen in Germany, demonstrated that liquid metal could pass through the cyclone successfully without excessive turbulence or splashing. Initial difficulties in achieving the desired flow rate through the cyclone were overcome by increasing the head height difference to 150 mm and a flow rate of >20 t/h was achieved in testing on a sow casting station and reported at TMS 2011. In 2016 the program has been restarted and two further trials carried out on the Research Casting pit at Trimet. Podfa measurements of metal cleanliness before and after passing through the filter have been made together with analysis of the spent filter section. The results are reported in this paper.

This paper reviews the past, present and possible future of molten aluminium inclusion removal technology. FiltrationFiltration technology is far from a stagnant field. Methods used to remove inclusionsInclusions from the melt are selected on the basis of the product requirements, operating and capital costs of the method, ease of use, efficiency and reliability of the method. The basic principles of inclusion removal for settlingSettling, floatationFloatation and filtration are reviewed along with an overview of current typical practice. New developments such as cyclones, MHD priming, vacuum assisted filtration and combined filters are described. Some ideas that have yet to result in commercial systems like “sticky” filters and use of centrifugal and Lorentz forcesLorentz forces to increase filter efficiency are listed. The potential for new filter structures utilizing 3D printing methods to achieve high efficiency at low head loss is highlighted.

Ultrasonic degassingDegassing attracts industrial attention as an alternative to Ar-rotary and Ar-lancing degassing, offering environmentally friendly, economical and efficient technology. This paper gives a brief historical overview of ultrasonic degassing development in the 1960s–2010s, discusses basic principles of cavitation-induced degassing and demonstrates various technological implementations of ultrasonic degassing technology in foundry and cast house. Batch versus continuous, gas- or vacuum-assisted versus purely ultrasonic variant of the technology are considered. Main advantages of ultrasonic degassing include rapid degassing without the use of a carrier gas, significantly reduced dross formation, absence of rotating brittle parts. There are also some technological issues associated with the ultrasonic degassing such as material selection of a sonotrode, requirement to process larger melt volumes with less ultrasonic sources, rapid re-gassing of hydrogen-depleted melt. The paper is illustrated mainly with own results.

Rotary degassing is one of the most commonly used methods for removing dissolved hydrogen and solid particles from molten aluminiumAluminium. In order to improve the removal efficiency of both hydrogen and inclusions removal, together with possibly lower investment and operating cost for the degassing equipment, modellingModelling can be used to study the process in detail. The removal efficiency depends on bubble sizeBubble size distribution, level of turbulence, residence time of bubbles in the melt etc. A modelling approach is presented including multiphase flow and mass transfer of impurities between the phases dependent on the solubility of the impurities in the different phases. A finite element model is used to solve the conservation equations and the impurity transport. A detailed 3D model for the in-line Hycast I-60 SIR melt refiner unit is used and the model is compared with experimental results.

This paper present oxide skin strengthOxide skin strength measurements of AA5XXX alloy with and without 2 ppm by weight berylliumBeryllium. The Pilling-Bedworth ratioPilling-Bedworth ratio of oxide compounds is used to discuss alternatives for beryllium addition.

Organic contaminated aluminum scraps have to be recycled in an economical, effective and ecological way. It is state of the art to remove organic coatings by thermal pre-treatment under reduced oxygen atmosphere, which can be achieved in multi chamber furnaces. If the organic coating is not removed completely during pre-treatment, gasification can continue while the scrap is submerged into the melt. Subsequently, undesirable gas-melt reactions cause an increase of dross formationDross formation and a decrease of metal recovery. This work aims to improve the understanding of interactions between pyrolysis gasesPyrolysis gases and liquid aluminum as a scientific basis to reduce oxidation losses. Experiments were performed in a lab-scale furnace with injection of synthetic pyrolysis gases (CO₂, CO, C_xH_y) into molten aluminum. Thermochemical calculations, off-gas and dross structure analysis were performed to support the evaluation of the experimental findings. The paper presents qualitative and quantitative results about the impact of reactive gases on oxidation of aluminum melts and finally derives a mechanism model.

The oxidationOxidation of molten aluminumAluminum has been thoroughly studied, and it is established empirically that berylliumBeryllium has an inhibiting effect on the oxidation behavior. The aim of this work was to increase the fundamental understanding of this inhibiting effect. Two 5XXX aluminum alloys (4.7% Mg), one with 2 ppm of beryllium and one without beryllium, were oxidized in a tube furnace under a dry air atmosphere. Samples were oxidized at temperatures from 500 to 750 °C for 10, 30 and 120 min. The composition and morphology of the oxide layers were examined with FIB and EDS, revealing the differences between the samples. The results showed up to a tenfold reduction in mass gain in samples containing beryllium. Significant differences in the oxide layer morphology were found for the two alloys at all times, including from 10 min. Thus, beryllium plays a significant role from the onset of high temperature oxidation.

The use of argonArgon to degas molten aluminium is a widespread practice in aluminium casthouses, and the removal of the hydrogen contained in the metal by using this noble gas is a proven method with no downside effect on the metallurgical quality of the resulting metal. On the other hand, an increasing number of producers are looking for cost reduction opportunities, and nitrogenNitrogen often comes as an alternative to replace argonArgon to degas molten aluminium. However, some are questioning the degassingDegassing efficiency of this gas or the risk to deteriorate metal cleanliness. STAS Inc. has carried out a series of comparative tests, using argon and nitrogen in an ACDACD. Metallurgical measures for degassing and metal cleanliness have been taken to compare both gases. This paper presents the results obtained during this test campaign carried out in North America.