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The use of aluminum to produce lightweight automotive castings has gained wide acceptance despite significant cost penalties. Lightweight iron and steel casting designs have been largely ignored despite their obvious cost and property advantages. This paper reviews and discusses the following: 1) various processes for producing lightweight iron and steel castings, 2) examples of lightweight components in high-volume production, 3) examples of conversions from aluminum to iron, 4) material properties of interest to designers, 5) examples of concept components and 6) efforts to improve the design and manufacturing processes for lightweight iron and steel castings. In summary, the potential for low-cost, lightweight iron and steel castings to aid the automotive industry in achieving both cost and weight objectives has been demonstrated and continues to expand. In general, however, automotive designers and engineers have not yet fully taken advantage of these technologies.

Austempered ductile iron (ADI) castings provide a unique combination of high strength and toughness coupled with excellent design flexibility for chassis applications. This paper describes the development of the upper control arm for the 1999 Ford Mustang Cobra as an austempered ductile iron casting. The full service development process used is described from initial design through finite element analysis (FEA), design verification, casting production, heat treatment, nondestructive evaluation and machining. To achieve significant weight savings, an austempered ductile iron casting was chosen for this application instead of an as-cast SAE J4341, Grade D4512 ductile iron casting or a steel forging. This is believed to be the first application of an austempered ductile iron casting for a safety critical, automotive chassis application.