Aluminium Cast House Technology XI

Volume 630

doi: 10.4028/www.scientific.net/MSF.630

Paper Title Page

Authors: Peter Whiteley
Abstract: Over the past thirty (30) years or so aluminium casthouse technology has been driven by a number of factors which have variously included: • Competition from alternative materials • Lightweighting • Market requirements for enhanced properties affecting gas levels, impurities, inclusions, physical and chemical properties, ease of downstream processing, reduced cost and improved delivery • Reduction in conversion cost by various means including capacity creep, maximising asset utilization, minimizing scrap, reducing melt loss, labour, and energy costs • The ever present need for improved safety performance. This paper will explore how these, and related considerations have provided the stimulus for improved casthouse technology which has included developments in hardware, software and culture.
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Authors: Trond Furu, Idar Kjetil Steen
Abstract: Since October 2006 the Hydro Casthouse Reference Centre has been operating. The centre is a full scale state of the art pilot casting centre for extrusion ingot, sheet ingot and foundry alloys, consisting of a 17Mtons furnace with a metal loop, a launder system including modular in-line melt treatment units such as ceramic foam filters (CFF) and inline melt refining units (Hycast SIR) and a casting pit with the possibility to cast full size geometries and a casting length of 5.5m. A two strand horizontal casting machine further adds the possibility of continuous casting of extrusion ingot and foundry alloy ingot. The centre has a state of the art superior control system (SCS) and a lay-out, including control room facilities, well suited for training and demonstration purposes. In addition the centre has access to state of the art software codes for simulating the casting process (Alsim) and the as cast microstructure (Alstruc). The present paper gives some examples on how the centre is operating and the support that is offered to casthouses in Hydro. This includes (i) simulation of the casting processes (hot tearing and as cast structures) applying the Alsim and Alstruc codes, (ii) pilot scale testing of casting and melt treatment equipment, (iii) testing of new parameters and procedures for melt treatment and casting (iv) production of trial orders of new alloys and (v) practical training of casthouse operators (basic for molten metal handling, emergency situations and response, casting principles and trouble shooting, etc.).
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Authors: Michael Lee
Abstract: Abstract With the recent release of the Victorian WorkSafe Authority Foundries Compliance Code [1] it is appropriate that Australian Aluminium cast houses, die casting shops and foundries review the status of their personal protective clothing/ equipment (PPE) and practices. Since the issuing of the Foundry Code of Practice [2] in 1986 and the issuing of the new Compliance Code in September 2008 there has been a significant change in the range of PPE utilised in cast houses. This change has been brought about as a result of the advancement in the design and development of the materials used, extensive industry experience and collaboration. The choice of appropriate PPE is also guided by the range and impact of injuries sustained in cast houses. This paper aims to highlight the number of PPE advancements and range of experiences gained between the writing of the Foundry Code of Practice and Foundry Compliance Code as well as to serve as a reference for future improvements for the protection of cast house personnel.
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Authors: Paul Koltun, Ambavalavanar Tharumarajah, John F. Grandfield
Abstract: The aluminium industry is reducing its carbon dioxide emissions and environmental footprint. In order to identify and prioritise areas in the cast house where greenhouse gas emissions can be reduced it is necessary to quantify CO2e (CO2 equivalent tonnes) emissions for the various cast house operations. In this study two typical cast house layouts are examined. In one case, 22kg 99.85% aluminium remelt ingots are produced using chain conveyor ingot casting machines. In the second case, wrought alloy extrusion and rolling slab direct chill cast products are made. Both plants are sized at 500ktpa. The various process inputs in terms of energy and materials were identified and typical usage rates assigned. The results show that general electricity consumption, dross generation and furnace energy consumption are the three biggest areas of CO2e and should be targeted for improvement. Magnesium consumption also has a large effect in the case of the
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Authors: John A. Taylor, M. Prakash, G.G. Pereira, P. Rohan, Michael Lee, Barbara Rinderer
Abstract: Aluminium melt transfer operations can lead to significant amounts of dross formation as a result of chemical oxidation and physical entrapment processes. It has been suggested that these activities may contribute up to 50% of the total metal loss of ~1% in a typical primary aluminium smelter (i.e. 2,500 tonne/annum (tpa) in a smelter of 500,000tpa output). This is a large financial loss to any company, and also, in the new CO2-conscious era, it also represents a significant carbon footprint to ameliorate. A significant proportion of this metal loss may be prevented by adopting more efficient melt transfer strategies that reduce splashing and turbulence thereby resulting in reduced oxide and therefore dross formation. Optimisation of such systems is normally achieved by trial-and-error approaches, however a clear opportunity exists for rapid optimisation by employing computational modelling to explore the effects of changed equipment design and process conditions, such as tilt speed, spout height, spout geometry, etc. In the present paper, the Smoothed Particle Hydrodynamics (SPH) modeling method is used to predict the amount of oxide generated during molten metal transfers from a 500kg capacity tilting crucible furnace into a heated sow mould. Various conditions were tested. An oxidation model based on skimming trials performed in a laboratory-scale (8kg) oxidation rig is employed in the simulation. The predicted oxide from the simulations is compared against those of the experimental pours. It is anticipated that the validated model will be used for modifying the design and optimizing the operation of various melt transfer operations occurring in the aluminium industry.
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Authors: Alan Peel, James Herbert, David Roth, Martin J. Collins
Abstract: While it is generally acknowledged that dross generation should be kept to a minimum, too often, the importance of maximising the aluminium content of the dross is overlooked. Some mistakenly believe that a low metal content is a good thing and that the aluminium is being kept in the furnace. In reality, this metal is most likely being lost due to insufficient cooling and thermiting. Much can be gleaned from looking at the dross that is generated in a casthouse; in fact, the quality of dross can provide a good indication of the overall efficiency of the operation. Even with the very low aluminium prices of today, of circa. US$1400 per tonne, a reduction in dross generation within the furnace can provide huge savings per year. Effective dross management also results in better metal quality, improved fuel efficiency, prolonged refractory life and improved yield in the entire facility. This paper will look at how dross is generated within the furnace in the first place, followed by ways to minimize the dross generation within the furnace using continuous and sub-surface circulation which can also provide significant energy and CO2 reductions. A separate paper will discuss dross processing options and possibilities. In summary, by careful attention to the equipment and process techniques around the furnace and the follow-on dross management significant cost savings and environmental benefits can be realized by cast house operations.
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Authors: Alan Peel, James Herbert, David Roth, Martin J. Collins
Abstract: While it is generally acknowledged that dross generation should be kept to a minimum, too often the importance of maximizing the aluminium content of the dross is overlooked. Some mistakenly believe that a low metal content is a good thing and that the aluminium is being kept in the furnace. In reality, this metal is most likely being lost due to insufficient cooling and thermiting. Much can be gleaned from looking at the dross that is generated in a casthouse; in fact, the quality of dross can provide a good indication of the overall efficiency of the operation. Even with the very low aluminium prices of today of about US$1400 per tonne, a recovery improvement of just 3% for a facility producing 500t of dross per month can provide savings in excess of $250.000 per year. Effective dross management also results in better metal quality, improved fuel efficiency, prolonged refractory life and improved profitability in the entire facility. Over the years, as facilities have focused on better dross cooling and handling techniques, dross recoveries have improved. Today, dross recoveries should be in the range of 60 – 70%. These numbers will raise debate but 30 years of experience give us deep insight into these results. The paper looks at the different techniques of handling the dross that is produced within the melting/casting operation with the objective of maximizing aluminium recovery. This paper will consider both the initial dross handling within the cast house but then also how secondary processors should be evaluated to maximize the value of the dross being processed. A company can lose as much dross recovery opportunity here as in their own facility. . In summary, by careful attention to the equipment and process techniques around the furnace and the follow-on dross management, significant cost savings and environmental benefits can be realized by cast house operations.
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