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Technical Paper

Statistical Analysis of the Mechanical Properties of Thin Walled Ductile Iron Castings

Ductile iron castings have long been used in the automotive market. Ductile iron is inexpensive to produce and has desirable fracture resistance and mechanical properties. However, the weight of ductile iron is driving an effort to reduce wall thickness in order to increase fuel economy. Traditionally, cast iron has been cast into thick, bulky shapes. Reducing the section size of cast iron can be done, but pushes foundry practice into new areas. A consortium of foundries, foundry suppliers, and automotive manufacturers has been pursuing the use of thin walled ductile cast iron. This paper investigates the mechanical behavior of three experimental heats of thin-wall castings in order to evaluate property trends and limits. Castings as thin as 1.7 mm (0.07 in) have been successfully cast.
Technical Paper

Induction Hardened Ductile Iron Camshafts

The General Motors L850 world engine uses an induction hardened, ductile iron, camshaft. Unlike most induction hardened camshafts that are machined first and then hardened, this camshaft is deep hardened first and then machined. Using this process, the beneficial compressive surface residual stresses are extremely high. During the development of the L850 camshaft, the casting process was optimized to produce material of sufficient quality to resist quench cracking during the hardening process and to resist mechanical cracking during the machining process. Retained austenite content, residual stress profiles, hardness, microstructure and chemical composition were all characterized and optimized. This paper reviews the material and process development for this unique automotive application.
Technical Paper

Evaluation of High Temperature, Cast Magnesium Alloy, Front Engine Covers

A variety of new magnesium casting alloys specifically designed for high temperature applications are currently available. However, there is little published data from component tests or from test specimens sectioned from component castings. In this study, the mechanical properties (tensile, bracket thread integrity, bracket distortion and fastener/attachment point acceptability) of front engine covers made from three magnesium alloys (AZ91D, AJ62x and MRI-153M) and from aluminum alloy 380 are presented.