Figure 1. The hinge of an instrument panel beam features an AM50 magnesium com- plex shape, pressure diecast over a 15mm OD mild steel hollow cylinder.
A
s vehicle weight reduction continues to be a driver in part de-
sign and development, various new strategies are being developed to provide strength at reduced weight. One strategy is the process of cast- ing a light metal such as aluminum or magnesium onto a heavier metal substrate. Overcasting steel or cop- per with aluminum or magnesium allows one to take advantage of the strength of steel and the corrosion resistance and heat transfer capabil- ity of copper without compromising the light weight sought in many applications. Following the sub- stitution of aluminum for ferrous castings in the automotive industry, further innovations involve adopt- ing hybrid solutions where a mix of widely different materials are combined. For instance, the high mechani-
cal resistance of steel may be allied to the lightness of magnesium, as in the example shown in Fig. 1. Another spectacular example of a hybrid assembly is the BMW inline six-cylinder engine. In this instance, weight reduction was achieved by casting magnesium over aluminum which, unlike magnesium, resists the corrosive aggression of the cooling fluid. Overcasting can be advanta- geous in reducing machining cost or enhancing heat transfer, such as by embedding copper pipes in
Mar/Apr 2014 | METAL CASTING DESIGN & PURCHASING | 35
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