Alcoa Automotive Castings has been chosen by General Motors to produce the front and rear subframes for the 2006 Corvette and Cadillac XLR, as well as steering knuckles for two 2005 GM vehicle programs. The one-piece, cast-aluminum subframes will be produced at Alcoa's Kentucky Casting Center and the knuckles will be produced at the Michigan Casting Center.
Alcoa's steering knuckles are cast from A356, an alloy developed for machinability, ductility, and recyclability. The cast structures are machined and integrated into the vehicles front suspension systems. Each knuckle produced at the Michigan Casting Center is subjected to X-ray and fluorescent die-penetrant inspection.
Both the subframes and knuckles are produced using the vacuum riserless/pressure riserless casting. According to Allen Zwierzchowski, president of Alcoa Automotive Castings, "This is a proven, high-volume method for producing a wide-range of structural castings distinguished by their superior microstructural and mechanical properties."
Zwierzchowski said the subframes are critical to the handling and crash-management performance of the Corvette and XLR, and that GM will achieve "significant part-consolidation advantages" thanks to the selection.
"Steering knuckles are an important element of a vehicles' suspension system. They are the component that connects the wheel to the vehicle. They are clearly safety critical. And they are playing an increasingly important role in better handling by helping car makers improve the weight balance of their vehicles," Zwierzchowski added.