| | SpeakersOrganisation: Swinburne University of Technology Control and removal of impurities from Al melts: A review
Control of impurity elements in Al-based alloys is of increasing technological importance, both in primary and secondary alloy production. In primary alloy production, Ni and V concentrations in the coke are rising and this is increasing the level of impurities in the final products to the extent that they are out of specification. Impurity control is also of concern in recycling due to the pickup of elements such as Fe from contaminants in the scrap, which can detrimentally affect the alloy properties. Dissolved elemental impurities can be removed by a number of different processes including boron treatment for some of the transition metals. Other processes in the cast shop for removing impurities and inclusions from Al melts include fluxing, floatation, and filtration. Gas purging, vacuum treatment, filtration, the use of salts, and combinations of these presently find commercial applications. Ultra purity Al and its alloys can be obtained using zone refining and three-layer electrolysis methods. The demand for higher purity Al has been largely met by additional electrolytic refining processes. This paper reviews the tools that are currently available to the casthouse for removing impurities and inclusions from Al melts and suggests approaches that may be useful to meet future challenges.
Organisation: Altek Preserving metal units utilizing the latest generation of aluminium dross press
The handling of dross is an unfortunate but necessary activity in any aluminum cast house. One technology designed to cool dross and maximise metal recoveries is the dross press. Since its introduction to the industry in the mid 1990’s this technology has evolved to meet the demands of the modern cast house and ever more stringent environmental legislation. This paper describes developments that address the weaknesses and limitations of early systems and enhancements that have enabled the cooling of a wide variety of dross types including salt slag from rotary furnaces. The paper will discuss data and results from the first fully commercialized installation of a specially designed press for cooling salt slag from Tilt Type Rotary Furnaces. Finally the paper will look at some of the economical benefits of using a press through various economic models showing the positive effect small improvements in dross recoveries can have on plant profitability.
Organisation: Wisechem Can the aluminium industry learn from another industry's catastrophe?
On April 20, 2010, an explosion rocked the Deepwater Horizon in the Gulf of Mexico resulting in the deaths of 11 workers. Tens of thousands of documents were released during the investigation for the root cause of the explosion."What emerges is stark and singular fact: crew members died and suffered terrible injuries because every one of the Horizon's defenses failed on April 20. Some were deployed but did not work. Some were activated too late, after they had almost certainly been damaged by fire or explosions. Some were never deployed at all.(Barstow et al. 2011)". Parallels with the aluminium industry standout when comparing the Deepwater Horizon disaster (e.g. violent explosions, damaged equipment, worker deaths and worker injuries). The list of aluminium industry catastrophes is not short: Binzhou Weiqiao Aluminum, Reynolds Alabama, Alcan France, etc. Aluminium plants, just as deepwater oil rigs, value training and safety measures to prevent accidents from occurring. But, on April 20, 2010 every safety measure employed failed, could the safety measures employed in a casthouse to prevent a molten metal steam explosion fail too?
Organisation: Morgan Crucibles Improved monolithic materials for lining aluminium holding and melting furnaces - roof, upper walls and flue
Monolithic refractories are now well established as linings for a range of holding and melting applications for the processing of aluminium. The refractory lining in an aluminium furnace has to withstand a wide variety of physical and chemical environments. Each of the different furnace zones presents a different set of operating conditions, in terms of peak temperature, temperature fluctuation, metal contact, flux contact, impact from ingot loading, etc. Therefore, in order for a monolithic material to successfully perform in a particular area of the furnace, it needs to be able to cope with the specific environmental conditions in that region of the furnace. Aluminium producers continue to increase productivity through their Melt-Hold furnaces to maintain competitiveness. The use of more powerful burners to increase heat input to the furnace is therefore becoming increasingly common practice. But faster melting leads to increased metal losses from surface oxidation and to segregation from large heat gradients. These effects are countered by increased use of fluxes and increased stirring. Given the increasingly challenging environment within which the refractory lining has to work, traditional lining solutions can no longer be relied upon to provide the service lives that were previously achieved. Therefore, a new generation of furnace lining materials is required to cope with today’s aluminium furnace. This paper describes one such newly developed monolithic material, designed specifically to improve performance in the superstructure zone of Aluminium furnaces. The non-metal contact, superstructure regions of aluminium furnaces present their own unique set of challenges for the refractory lining. Refractories in these regions - roof, upper walls and flue - have to cope with excessively high levels of alkali vapour and thermal shock. This paper reviews the operating conditions found in the superstructure areas of a typical melting and holding furnace and the implications these have on monolithic lining material design and performance. The improved behaviour of the newly developed monolithic material against the critical performance criteria in these furnace regions is demonstrated in the laboratory, compared to existing industry leading materials, using industry standard test methods.
Organisation: Sintef Oxidation of rolled and flash anodized 3000 aluminum in air, nitrogen, oxygen, and carbon dioxide atmospheres
Thermal oxidation of a 3000 Al sheet rolled alloy was carried out in various atmospheres with a thermogravimetric analyzer (TGA). The effect of a flash anodized surface versus an untreated rolled surface is investigated. All samples were oxidized for 4 hours at 800°C. Samples oxidized in air, 100% CO2 and 50% CO2-50% air, showed no difference in total oxidation. The flash anodized samples oxidized in 10% CO2-90% air had approximately half of the mass gain of the rolled samples. Oxidation of anodized samples in pure oxygen and nitrogen showed a drastic decrease in the amount of mass gained compared to the other atmospheres. Flash anodized samples gave consistent results, and the oxidation behavior tended to be linear or S-shaped for the 4 hours investigated. Rolled samples gave less consistent data and tended to be decelerating curves. Transmission electron microscope (TEM) analysis of the oxide layer before and after showed magnesium diffusion toward the surface of the sample, with a steep gradient over a distance of 400 µm. The flash anodized oxide layer was often difficult to find, having been removed during of the TEM sample preparation, but was found to double in size from 200 to 400 µm when located.
Organisation: Consulting in Partnership The metallurgy of homogenisation
Homogenisation of aluminium alloys is the high temperature heat treatment (450-600 °C) performed after casting and consists of three distinct steps; heat-up, soak and cooldown. This review considers the metallurgical importance of homogenisation and how it impacts on the further processing and final properties of some aluminium alloys, with emphasis on homogenisation of extrusion billet. The introduction of continuous homogenisation has significantly improved the temperature uniformity of homogenisation allowing the soak time to be minimised. Batch homogenisation, however, provides flexibility in practices tailored for different aluminium alloys. Soft 6060 and 6063 alloys are best homogenised at a higher soak temperature than harder alloys such as 6061 and 6082. The homogenisation cooling rate can also impact on the behaviour of the billet during extrusion processing as well as affecting the final mechanical properties. An understanding of the microstructural changes occurring as a result of homogenisation allows the cast house to ensure that the billet processing meets the customer requirements.
Organisation: Consulting in Partnership Barbara Rinderer is a Materials Engineering graduate from Monash University. She has 20 years experience in aluminium research formerly with Comalco, now Rio Tinto Alcan. Barbara spent a year as a visiting scientist at the Swedish Institute for Metals Research in Stockholm, Sweden as well as several secondments to operating sites in Australia and the USA to complete process improvement projects. Barbara is also a certified black belt in Lean Six Sigma, a method of systematic problem solving. Barbara’s expertise includes aluminium metallurgy, metal quality, as well as failure analysis of extruded and rolled products. Industrial projects include development and implementation of homogenisation practices for extrusion billet alloys, establishment of billet and slab quality monitoring programs and other projects evaluating process improvement changes. There are numerous conference and journal publications on these topics, in addition to the involvement in new alloy development. Barbara’s current role is Principal Consultant with Consulting in Partnership Pty Ltd providing independent technical analysis, and delivery of education and training programs. Barbara is a regular presenter at the Aluminium Cast House Technology conference, and is a member of the organising committee.
Organisation: CAST CRC Improving casthouse throughput using discrete-event modelling
The scheduling of metal to different casters in a casthouse is a complicated problem, attempting to find the balance between pot-line, crucible carrier, furnace and casting machine capacity. In this paper, a description will be given of a casthouse modelling system designed to test different scenarios for casthouse design and operation. Using discrete-event simulation, the casthouse model incorporates variable arrival times of metal carriers, crucible movements, caster operation and furnace conditions. Each part of the system is individually modelled and synchronised using a series of signals or semaphores. In addition, an easy to operate user interface allows for the modification of key parameters, and analysis of model output. Results from the model will be presented for a case study, which highlights the effect different parameters have on overall casthouse performance. The case study uses past production data from a casthouse to validate the model outputs, with the aim to perform a sensitivity analysis on the overall system. Along with metal preparation times and caster strip-down/setup, the temperature evolution within the furnaces is one key parameter in determining casthouse performance.
Organisation: Mechatherm Tilting rotary furnaces
The presentation will review the role of the rotary furnace in the processing of drosses which arrive to the furnace in various forms, loose or pressed, hot or cold. Furnace design features necessary, ancillary equipment required and an overview of why and where the furnaces are installed will be discussed. Organisation: Wagstaff Inc Aluminum ingot thermal stress development modeling of the Wagstaff Epsilon Rolling Ingot DC casting system during the start-up phase
Based on sequentially coupled CFD and FEM models, aluminum alloy rolling ingot thermal stress simulations have been conducted in order to understand start-up phase cold cracking phenomena and optimize tooling designs for 520×2120 mm rolling ingot casting on Wagstaff® Epsilon? Ingot Tooling. In the CFD model, ingot surface temperature dependant and water flow rate dependant water boiling curves are applied. Thermal boundary conditions for the complex water intrusion phenomena under the ingot butt have been attempted. Temperature dependant elastic-plastic materials constitutive relationship has been employed in the transient thermal stress FEM model. Results of thermal stress development at ingot surface and inside the ingot are presented; Connection of cold cracking (ingot butt quarter and center cracks) with near surface stress development at the ingot butt is shown and the effect of water intrusion under the ingot butt on the butt stress development is also discussed. The predicted temperatures are validated against temperatures measured from cast-in thermocouples at strategic locations in field ingots in order to obtain realistic thermal boundary conditions. The predicted butt curl is also verified through field observation and measurement.
Organisation: IFE The development of Alsim - a modelling tool for direct chill casting, twin roll casting, wheel and belt casting and chain conveyor casting
A coupled heat and fluid flow, stresses and deformation modelling tool including macrosegregation and inter-dendritic flows have been developed for various semi-continuous or batch casting processes in use by the light metal industries. Results from the mechanical calculation are back-coupled to the thermal boundary conditions regarding size of contact zones and air-gaps and thereby enabling automatic calculation of gap dependent heat transfer coefficients, which is very useful for the industrial use of the tool. Examples from the application of the model on direct chill castings are made, as well as on twin roll, wheel and belt and chain conveyor casting. Comparison with measurements and other process data are done. The finite element method is used for the modelling tool including dynamic treatment of elements in moving parts of the calculation domains. In continuous casting there are frequently interfaces where the metal slides against the equipment, and although the grid across such surfaces does not match they are still coupled implicitly in Alsim. This adds an ability to model complex processes involving stresses and deformations in mechanical coupled moving parts and it alleviates the time consuming process of producing the initial finite element grids for the geometries. In order to handle solidification phenomena like hot-tearing, macrosegregation and exudation local adaptive grid refinement is necessary, as well as parallelization of the code, to achieve acceptable accuracies. How these numerical challenges are handled in the model is described.
Organisation: GPS Global Solutions The approach to zero waste from smelter and secondary dross processing
The advantages to the primary and secondary aluminium industry for mechanical dross processing in the TUMBLER are laid out. There are additional opportunities for improving environmental impact through better dross processing and management, old dross dumps and landfills, and one piece of equipment can process all materials. The equipment is simple to run, low in maintenance and batch operated to keep unlike materials and alloys separate. In the evaluation for the capital expenditure for this type of system all these factors must be added together to determine the capital and environmental return on investment. The coarse and fine aluminium concentrates can be recycled at most operations although the markets for the aluminium, oxide and flux rich fines fractions are regional.
Organisation: Novelis The effect of calcium on the rolling behaviour and hot tensile properties of AA5182.
The impact of sodium on the edge cracking behaviour of high magnesium alloys such as 5182 has been the subject of many studies. Relatively less information is available on the role of calcium and much of this is contradictory, some authors reporting that relatively modest levels of Ca reduce hot ductility (and by inference promote edge cracking) whereas other reports recommend the intentional addition of calcium to these alloys in order to control oxidative casting defects such as vertical folds. This paper will describe and discuss a series of experiments in which AA5182 ingots containing sodium and calcium alone, and also in combination, were cast, hot-rolled and subsequently hot tensile tested. As expected, sodium alone led to a large drop in the hot tensile elongation and promoted edge cracking. However, no such effects were observed in materials containing only calcium. Calcium had a slight mitigating influence on the impact of sodium when both elements were present.
Organisation: Rio Tinto Alcan Organisation: Rio Tinto Alcan Increasing cast house throughput through “In-spec first time”
Achieving in-specification melt analysis first time has been the Holy Grail of many cast houses for a number of years and for a good reason. For many producers, the furnaces are the bottleneck of the value added casting process and removing that hurdle means big dollars. A six sigma project was carried out at the Bell Bay smelter aimed at reducing the time it takes to bring a furnace within chemical specification and highlighted that “in-spec first time” is more achievable than many think. This paper covers the steps having an impact on alloy recovery and suggests a “best practice” to be followed in each area. As is shown, consistently following these guidelines through robust controls can generate a significant increase in throughput of value add facilities in your cast house
Organisation: Pyrotek Inc Cost savings in the cast house through optimizing furnace operation, staff training and associated variables
While it is generally acknowledged in our industry that people are the most important asset, the importance of technical training for furnace operators is often overlooked. The primary focus for training is often on the down stream process where the final product is either being cast or fabricated. The furnace operators have a key role since they have direct influence on factors that dramatically govern a range of costs factors which include: productivity; melt loss; metal content in the dross; energy usage, and metal cleanliness.
Organisation: Thermbond Phosphate bonded monolithic refractory materials with improved hot strengths as a potential replacement for phosphate bonded bricks
The phosphate bond generally provides a lower modulus of elasticity compared to more brittle conventional cement and ceramic bonded materials. The flexible bonding mechanism results in higher impact resistance. Moreover, phosphate bonded materials show excellent resistance to aluminium metal penetration and corundum growth. In addition, phosphate bonded bricks with low alkali content possess high hot strengths at elevated temperatures which can significantly increase their performance against mechanical abuse. Based on this information a project was started to develop phosphate bonded monolithic materials with similar or better physical and chemical properties than phosphate bonded bricks but with the advantage of installation characteristics of conventional cement bonded materials. Additional goals were to use a water based system and minimize restrictions on installations techniques. Flow and working time should be similar to conventional monolithic materials, making this material as versatile as possible. In order to achieve these goals extensive tests were carried out in collaboration with independent research laboratories and as a secondary step, some of the new formulations were installed in severe environment applications with high mechanical abuse and chemical attack. The development process and the physical and chemical properties of a new phosphate bonded monolithic material will be shown in context with available literature and in comparison with test data of phosphate bonded bricks and conventional cement bonded materials. The results of field tests and potential new applications will also be presented.
Organisation: MQP Development of a fused magnesium chloride containing refining flux based on a ternary system
The costs of salt flux treatment have received a strong industry focus as solid flux addition has replaced the usage of Chlorine for alkali and inclusion reduction. The magnesium chloride component has historically had the higher cost incidence but since 2008 the potassium chloride component because of its role as feedstock of fertilizer production has been subject to large commodity price driven fluctuations and rose 350% in 200 - 2009. As demand for world food production and bio fuels increases as the global economy recovers further price rises can be anticipated. A programme of work and field results are presented on the development of an alternative flux system based on a ternary composition.
Recent results with new filter technologies based on the principle of multi stage filtration with grain refiner added in the intermediate stage
Filtration technology based on a three stage process where a ceramic foam filter is operated in cake mode in the first stage; grain refiner added in a second chamber and a further filtration means is used in the third stage to remove oxide inclusions or agglomerates originating from the grain refiner addition has been developed along two directions. In one case, the XC Filter uses a small deep bed filter (DBF) in the third chamber, whereas in the second case a cyclone is employed. The most recent results with both are reported.
Organisation: Grandfield Technology 3D thermo-mechanical modelling of wheel and belt continuous casting
Wire rod is produced by hot-rolling a bar of metal coming from a wheel/belt continuous casting process. This kind of process, e.g. Properzi, is an elaborate process in which the molten metal is poured in a cooled rotating mould formed by the groove of a wheel and closed by a belt. In order to better understand the heat transfer phenomenon and solidified bar characteristics, depending on process parameters a three dimensional thermo-mechanical model has been developed. The model, based on the finite-element method, calculates the heat transfer coefficient of the air gap at the metal-mould interface as a function of the size of the gap determined by the bar contraction and wheel and belt thermal deformations. The air gap formation due to metal shrinkage and mould deformation is the main factor which determines the heat extraction. Wheel temperature measurements with thermocouple and belt temperature measurements with an infrared system were carried out to verify model results. Attempts were also made to measure a liquid pool profile using doping with copper rich alloy. The model shows the effect of the casting temperature and the rotation speed on the air gap formation and resulting temperature and stress fields. The model can be applied to issues such as maximising wheel and belt life and minimising solidification defects.
Organisation: Grandfield Technology Dr. John Grandfield is director of Grandfield Technology Pty Ltd and Adjunct Professor at the Swinburne University of Technology, Faculty of Engineering and Industrial Science
Dr. Grandfield has a Bachelor of Applied Science in Metallurgy (RMIT), a MSC in Mathematical Modelling (Monash) and a PhD in Materials Science (University of Queensland).
John has 25 years experience in metal production and processing research in industry and government laboratories (Rio Tinto Alcan, CASTcrc and CSIRO). He has experience with aluminium, and magnesium smelting, continuous casting and metal refining. He has conducted technology reviews, optimised existing technology, managed technology transfer and developed and commercialised new technology. Dr Grandfield is particularly experienced in direct chill (DC) casting including optimising casting conditions for a variety of cast alloys including magnesium alloys. Dr Grandfield’s PhD thesis was on the hot tearing of magnesium alloys during horizontal direct chill casting. He is the co-inventor of AirCAST, a new patented gas pressurised hot top DC mould for aluminium and magnesium.
Dr Grandfield uses process measurement methods and mathematical modelling techniques to solve casting problems. He has published extensively on DC casting with particularly reference to cracking and water cooling control. He lead a successful program of work on open mould ingot casting to develop two new patented technologies which are being adopted by industry. His aluminium and magnesium work has been awarded internationally and within CSIRO and the CAST cooperative research centre and he is regularly invited to give training courses, participate in in-house innovation workshops and conduct R&D program reviews.
John has four patents and has published more than 50 conference and journal papers. He is chair of the Australasian Aluminium Casthouse Technology conference and a member of the TMS Aluminum committee.
Organisation: Aluar Mold and casting table maintenance management system at Aluar: a key to quality billets and saving costs
It is well known that mould and casting table maintenance has a direct impact on the internal quality and surface quality of billets. In this paper, the evolution of the main key performance indicators (KPIs) associated with the main consumables of the Wagstaff Air slip billet casting technology is shown, such as moulds, casting rings, transition plates and thimbles. The strategies taken to preserve a high standard of quality whilst monitoring the associated costs are discussed. An automated Mould and Casting Table Maintenance Management system has been developed in house to make available the relevant information from the casting table servicing at the casting pit and at the mould room. A case study is described where this tool allowed us to reduce costs, keeping a high quality standard of the casting table maintenance, ensuring the internal quality of the final product.
Organisation: Chalco Effect of homogenisation parameters on dissolution and precipitation in aluminium alloy AA7150
The thermal stability of constituent particles in both as-cast and homogenised alloy AA7150 has been investigated by means of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results indicate that the as-cast eutectic starts to melt at 474°C and that the melting onset temperatures of the ?- and S-phase particles after homogenisation are 474°C and 484°C, respectively. Two types of homogenisation treatments were used to dissolve eutectic particles: a two-step homogenisation treatment (40 h at 465°C + 4 h at 480°C) can completely dissolve the ?- and S-based constituents, whereas a significant amount of S-phase still exists after a single-step homogenisation treatment of 40 h at 465°C. After utilising the two-step homogenisation treatment to dissolve all the ?- and S-based constituents without overheating, samples were cooled at different controlled cooling rates and analysed by SEM and DSC to understand the effect of cooling rate on the type, size, distribution and density of precipitates formed during the cooling process. Slow cooling was found to result in the precipitation of coarse ?-phase particles, with both the amounts and sizes of these ?-phase particles increasing with decreasing cooling rate.
Organisation: CAST CRC Hot tearing in Al-Mg-Si alloys with minor additions of Cu or Mn
A study of the influence of minor additions of copper or manganese on hot tear susceptibility in Al-Mg-Si alloys has been conducted. Testing was carried out using a laboratory scale hot tearing rig and the results were validated using an analysis of cast house cracking scrap data for 6060 and 6063 extrusion billet alloys. Mn content was found to have a strong influence on hot tearing rates.
Organisation: CAST CRC SPH modeling of the effect of crucible tipping rate on oxide formation
When hot molten aluminium is poured into a furnace from crucibles, oxide is generated due to the interaction of the liquid metal with the surrounding air. The amount of oxide produced is a function of several factors including the rate at which the crucible is tilted, the height of the crucible in relation to the furnace position and the location of the pivot of rotation. In this paper we evaluate the effect of crucible tilting rate on oxide formation for an industrial scale crucible and furnace setup. The mesh free Smoothed Particle Hydrodynamics (SPH) method is used for modelling the metal flow and oxide prediction. The model predicts rapid oxidation rates during periods of energetic fluid motion on freshly exposed metal surface and lower oxidation rates as oxide thickness increases. Four crucible rotation rates typical of normal operating conditions in a smelter are evaluated. The simulations showed that oxide generated due to fresh free surface created from a falling stream makes only a limited contribution to the overall oxide generated for the time scales of interest in this study. The secondary flows observed in the furnace make a significant contribution to the overall oxide generated. The rate of oxidation decreases and eventually ceases at a sufficiently long time when there is no disruption to the protective oxide skin. There is a 75% increase in oxide generated for the highest tilt rate (crucible emptied in 40 s) compared with the lowest tilt rate (emptied in 2.0 min).
Organisation: ARC Centre of Excellence for Design in Light Metals 6xxx Series Alloy Design Considerations Relating to Recycling
This paper considers 6xxx alloy design from two perspectives: (i) the consequences for processing, quality, composition and performance of alloys that are made with a significant proportion of recycled metal or scrap, and (ii) a suitable choice of alloy which takes into consideration the recyclability in the end-use application. Based on a review of available literature, an attempt will be made to highlight technology gaps and future development opportunities.
Organisation: Australian Aluminium Council Aluminium industry overview Organisation: Solios The challenges to supply new casthouse furnaces in a modern aluminium smelter project
In this paper Solios Thermal will share its recent experiences in designing and integrating 11 melting and holding furnaces and 2 cooling water plants in Qatar for the new aluminium smelter, planning to produce 585,000 t/yr. This paper will discuss the alternative furnace design specific for this contract and will focus on the key design differences referenced to the traditional furnace type.
Organisation: Pyrotek Inc Thermocouple protection tube options for aluminium casthouses
Thermocouple Protection Tubes (TCPTs) are utilised to allow continuous temperature monitoring in harsh and demanding environments for remote monitoring and process control. Choice of optimum TCPT for an application is dependent on a thorough understanding of the operating environment, characteristics of the TCPTs available and an assessment of the Total Cost of Ownership (TCO) of the different options, including the cost of the particular thermocouple being protected.
Organisation: Munimula Technology A historical perspective of aluminium casthouse furnace developments
This paper provides an historical perspective of aluminium casthouse furnace evolution over the past 30 years or so with a view towards explaining the reasons for those innovations, and the success or otherwise of some of the changes which were tried. The paper covers electrically energized furnaces such as channel and coreless induction furnaces as well as “glo-bar” heated furnaces. It goes on to discuss fuel fired furnaces including melters of many varieties including side charged, top charged, sidewell, and multichamber designs. Additionally it includes melter/holders and conventional holding (casting furnaces). The drivers for change have been many and varied, and have included the need to cope with capacity creep, reduced specific energy consumption, improved asset utilization, greatly enhanced process intensity, reduced melt loss, improved furnace reliability, acceptance of the benefits of automation, and always the concern for improved safety in all aspects of furnace operation. Accordingly the paper covers related matters such as major changes in burner choices; furnace charging and tending; refractory type and design; furnace enlargement; forced convection stirring; dealing with difficult scraps; the demise of stationary casting furnaces, recognition of the need for improved metal cleanliness; and the challenge to deal with a wider range of difficult alloys. Additionally there has been a much greater understanding of furnace functionality by computer modelling of heat transfer as well as modelling of furnace stress design by FEA as well as some physical modelling and full scale tests to validate computer model assumptions. One of the most significant aspects of improved science has been the manner in which furnaces are operated to maximize productivity, reduce energy cost and melt loss, and by the adoption of purpose built tending vehicles. Finally the paper discusses prospects for future technological development and other aspects of improved productivity through achieving target composition first time as well as by better production planning, together with the aid of dynamic simulation for optimisation of activities.
Organisation: Aleris A historical perspective on dross processing
As long as aluminum has been manufactured and melted, various by-products with a mixture of aluminum and aluminum oxide have existed. The general name for this class of materials has historically been called “dross”. Within the larger family of drosses, there are a number of subclasses which we will explore. Unfortunately, the presence of even minor amounts of oxide in aluminum metal, render it useless for most structural applications. To be of value the aluminum metal must be free of oxides. Additionally, the inherently high value of the metal has driven innovation in methods to effectively and economically separate the metallic values from this mixture. This paper will present background information on the formation of drosses and the historical methods used to process the drosses.
Organisation: CSIRO Aluminium, Past, Present and Future Prospects
A brief examination of the history and growth of the global aluminium industry up to the present day is provided, including an overview of some of the most significant achievements, breakthroughs and challenges which have occurred within this important industry. Future avenues of growth and global trends for the period between now and the year 2030 will be discussed. Primary production forecasts and per-capita consumption data by region will be examined, with reference to important global consumer growth markets. In light of this data, it may be surmised that demand for primary aluminium may begin to exceed supply by this date. Growth of secondary aluminium markets will largely parallel that of the primary material. Particular focus will be drawn to the increased influence of the transport sector in driving aluminium market growth, which is expected to more than double over the next 20 years. Design of secondary alloy compositions for high performance aluminium pressure diecastings
High pressure die-casting (HPDC) is a widely used production technique for metal components that are required to have close dimensional tolerances and smooth surface finishes. Approximately 50% of the aluminium castings produced globally are manufactured by HPDC from secondary alloy and these are dominant in the automotive sector where they account for the majority of aluminium components present in each vehicle manufactured. Recently, it has been shown that industrially produced aluminium alloy high pressure diecastings (HPDC’s) can be successfully heat treated without encountering problems with surface blistering or dimensional instability. These processes may significantly improve the properties which develop from the alloys, thereby significantly increasing the scope of applications that may be realized. HPDC alloys however have not been developed specifically for heat treatment or the optimization of specific properties. In particular, recent work in Al-Si-Cu HPDC alloys has identified composition ranges of alloys for a) achieving yield strengths exceeding 400 MPa, b), rapid heat treatment that minimizes cost / cycle times, and c) high strength combined with elevated ductility levels. The role of alloying elements, composition limits and effects on mechanical property development are discussed.
Organisation: Worley Parsons Cast house layouts
The increasing size of aluminium smelter projects and expansions has meant that huge amounts of metal are being produced from new facilities after a short start-up phase. To minimise exposure to product premium variations, and to permit entry into higher margin product areas, increasingly the product mix from new facilities are diverse and complex. This creates challenges for the engineer and the operator. Issues of casthouse design, product mix considerations, economies of scale, project schedule impacts and increasing complexity of the project, start-up and operations organisation are discussed.
Organisation: Hydro Aluminium Crucible fluxing with Hycast? RAM- effect on metal quality and operational cost.
Hycast? RAM, hereafter called RAM, is a crucible fluxing technology for removal of alkaline elements (Na, Ca, and Li), as well as carbides, oxides and cryolite, from aluminium pot-room metal without the use of chlorine. AlF3 powder is injected into the liquid metal (below the metal surface) by the use of a specially designed rotor system and argon as a carrier gas. The fluxing system can be adapted to different crucible transport/tapping system, and is proven for crucible sizes from 2 to 9 tons. Since surface active elements like Sodium are removed before the metal enters into the furnace, the metal oxidation during pouring and furnace treatment is significantly reduced. Pretreatment will also reduce the carbide level in the metal, and by this improve the overall metal quality, and prevent clogging/deposits in furnaces, degassers, ceramic foam filters etc. This paper describes the principles of the RAM technology, effect on metal quality and documented operational benefits in a primary casthouse. Also environmental issues are discussed.
Organisation: Precimeter Automatic control of molten metal flow for improving casting performance
The ways to gain better quality and higher casting performance is an urgent topic among aluminium producers today. This issue is also often on the agenda at conferences like this and the subjects and technologies to achieve this varies. Controlling the molten metal flow by maintaining predefined levels or level patterns is one of many powerful tools to reach this goal. Precimeter Control specializes in applications for non-ferrous molten metal level measurement and molten metal flow control. By integration, or retrofitting, any new or existing casting line can easily be automatically controlled and gain improved casting performance in a cost efficient way. This paper will focus on the main benefits from automatic level control and how some plants have achieved improvements in their casting process of DC (Direct Chill) slab (or rolling ingot) casting after implementing such technology.
Organisation: MBD Algal sequestration: opportunities for the aluminium industry
Algal sequestration of carbon dioxide is a possible method for the aluminium industry to reduce its green house gas emissions. The technology is being tested on a pilot scale for coal fired power stations to capture flue gases. The algae provide a saleable by product as oil which can be converted to bio-diesel and as animal feedstock. The status of the technology and how it might be applied to aluminium smelters will be described.
Organisation: CAST CRC Implementation of CASTfill low dross pouring system for ingot casting
Producing low-dross ingots has been a long-term goal in aluminium cast houses. The patented CASTfill technology [1] is a low-dross and high-productivity pouring system developed to fulfil this demand. This paper describes the research methods used during the development of CASTfill; now in service at Boyne Smelters Limited (BSL) since August 2009. The importance of combining scientific modelling and testing procedures with process operability, maintainability and durability to ensure the success of new technology in a production facility is also highlighted. Ingot assessments showed that the latest CASTfill design greatly reduced dross generated during mould filling. Improved ingot packaging and reduced variation of ingot weights were also observed as the results of a more tranquil flow of molten aluminium through CASTfill and its uniquely modular design.
Organisation: CRU An overview of the global market for primary aluminium smelter casthouse shapes
Many primary aluminium smelters rely upon the production of value-added casthouse shapes in order to boost margins and gain a competitive advantage. The global structure and market for various casthouse products will be reviewed, including remelt ingot, billet, slab, rod and foundry alloy. An analysis of the size of the markets for the different products will be discussed, as will the relative costs of producing such products. Premiums for these products remain regional and varied, affecting profitability. CRU’s value based costing (VBC)? methodology will be used to help identify how the different casthouse shapes can affect the competitive positions of individual production facilities.
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