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Previous work has shown that mirror bright stainless steel clad to lightweight aluminum offers an optimum combination of weight, appearance, fabricability, styling, and durability against road damage and corrosion for automotive trim and bumper applications. This paper characterizes the properties of stainless steel-aluminum clad bumper materials for application on Class 8 trucks. The rule of mixtures is confirmed for an SAE 30301 stainless steel clad to 3003 aluminum, and is applied to show the tradeoffs between weight, strength, and cost that affect material selection for truck bumpers. The fabricability is demonstrated by sweeping, aerodynamic bumper designs that are readily formed, and is quantified by forming limit diagrams of 301SS / 3003Al clad and 301 stainless steel. The durability against road damage is demonstrated with Gravelometer testing, followed by ASTM standardized corrosion testing. The clad is also resistant to erosion from water impingement.

1006 steel clad aluminum has been used as a transition material to directly spot weld steel to aluminum. Advantages of the clad metal transition include the ability to spot weld with existing equipment and reduction of dissimilar metal crevice corrosion at the steel-aluminum interface. Sheet steel between 0.8mm and 2.0mm has been spot welded to aluminum between 0.8mm and 3.0mm in a variety of combinations with the transition material. This paper contains specific spot welding parameters for a variety of joints containing steel and aluminum at thicknesses normally encountered in body applications. The mechanism of weld nugget formation for aluminum-transition-steel joints is evaluated. Weld lobes established according to SAE and Aluminum Association guidelines are presented. The effect of electrode design on joint strength and heat balance are discussed.

Clad metals are metallurgical materials systems comprised of two or more metals or alloys which are metallurgically bonded to form a single material. This results in specific and unique properties of the clad metal system which are not available in a monolithic metal or alloy. Historically, they have been used for many decades by the automotive industry but the cladding process as well as the ability to design specific properties into a clad system are not well understood. This paper describes the cold roll bonding process for fabrication of clad metals. The mechanism of bond formation and limitations of the process are discussed. Rules for calculating a number of properties of clad metals are presented. Methods for designing clad metals to obtain unique properties for specific applications are described. The history of the use of clad metals on automobiles is also reviewed.