Abstract
Over the last 4 decades, remarkable progress has been made in the modelling of casting processes. The development of casting models is well reflected in the proceedings of the 15 Modelling of Casting, Welding and Advanced Solidification Processes (MCWASP) conferences that have been held since 1980.Computer simulations have enabled a better understanding of the physical phenomena involved during solidification. Modelling gives the opportunity to uncouple the physical processes. Furthermore, quantities that are difficult or impossible to measure experimentally can be calculated using computer simulations e.g. flow patterns and recalescence. However, when it comes to accurately predicting casting performance and in particular, the occurrence of defects like cracks, segregation and porosity there is certainly some way to go.In this paper, the current understanding of the main mechanisms of defect formation during shape and DC casting processes will be reviewed and requirements will be discussed to give a direction to making casting models more predictive and quantitative.
Highlights
Casting is a prehistoric process, but it is thought to be predated by wrought metals, because the temperatures required to achieve the molten metal are far higher than those needed for wrought processes
These come in various guises and combinations of solutions, and include finite difference method (FDM) and finite volume method (FVM); finite element methods (FEMs); cellular automaton (CA) methods and lately, phase field theory [118]
Finite difference (FD)/finite volume (FV)/finite element (FE) methods These names are given to a mathematical technique whereby the answer to a complex problem is obtained by dividing up the complete region of the problem into small pieces, and applying the equations to each of these pieces in turn
Summary
Casting is a prehistoric process, but it is thought to be predated by wrought metals, because the temperatures required to achieve the molten metal are far higher than those needed for wrought processes. Shape casting is essentially a batch process, even though modern engineering techniques have been applied to many processes to automate them This is in direct contrast to continuous casting of steel or the so-called continuous casting of aluminium and its alloys developed in the 20th century. The largest ingots produced to date are “Jumbo” slabs 2700 mm by 610 mm [1] and round billets 1050 mm (42”) diameter × 7 m weighing 20 tonnes [2]. In both of the continuous processes, the final product is usually the feedstock for some other forming process, such as rolling, forging, machining or extrusion. Al > 99.5% Cu 2–6% total additions < 7% Mn < 1.5% total additions < 2.2% Si < 6% (usually) Mg < 5% (Mn < 1%) total additions < 6% Si < 1.4% Mg < 1.1% total additions < 4.3% Zn < 11% Mg < 3.3% (Cu < 2.3%) total additions < 15% Fe < 8.6% (Li < 3%) total additions < 12.5% Unused a Alloy additions can be as high as 30 wt% for example A39x (high silicon alloys) in which case the freezing range is over 220 ◦C
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