This paper discusses results from several main areas of investigation in a research and development project on low-pressure diecasting (LPDC) with six major Australian diecasting companies. A study of the die coats used in these LPDC companies was conducted to provide heat transfer data for comparative purposes. The average heat transfer coefficient shows strong dependence on thickness, and a correlation was proposed for general use with these water-based ceramic die coats.Extensive water analog experiments and computer simulation using thermal modeling software were undertaken to study the mold filling in a cylinder head casting. For typically low-and medium-pressure ramps, the flow in the cavity is fairly uniform in thevertical direction. However, higher-pressure ramps increased turbulence and surface eddies. Thus, a slow fill resulting from a small pressure ramp appeared best for minimizing these turbulent effects.The solidification models generally gave a thermal pattern that was similar to that measured by thermocouples in casting trials, as well as that calculated from metallographic studies of a number of cylinder heads. The local solidification pattern wascomplicated, due to the presence of intricate sand cores, but the general trend clearly showed the slow rate of solidification of the area around the sprues.Solidification models were used to optimize a patented die cooling system, which was designed to promote directional solidification and to reduce the casting cycle time. This was achieved by targeting the cooling of specific thick sections in the top ofthe casting, and particularly around the sprues in the bottom part of the mold. This resulted in good-quality castings made with a cycle time reduced by at least 25% compared to normal production. The cooling design was considered to be sufficientlygeneric for application to other automotive components, such as wheels and engine blocks.
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