Dissimilar Metal Joining Technologies for Steel Sheet and Aluminum Alloy Sheet in Auto Body

Multi-material structure of auto body partially employing aluminum alloy sheets may be adopted in order to satisfy requests at the same time improving crash safety and lightweight. This paper described the dissimilar metal joining technologies required to achieve multimaterial structure. In resistance spot welding, high current & short time welding condition is conducted to avoid formation of brittle Fe-Al intermetallic compound layer at joint interface and joint strength is investigated. In mechanical joining, current application situation of SPR, Tog-L-Loc ® , TOX ® and FDS ® methods are outlined and application examples of Blind rivet in automobile body are introduced. In addition to that, joint strengths in shear direction of SPR joints for cold rolled steel sheets and 6000 series aluminum alloy sheets are described. In adhesion bonding, it was shown that joint strength of TSS over 20 MPa is obtained by using of recent adhesive for automobile in sheet combinations of cold rolled mild steel sheets and 6000 series aluminum alloy sheets. In FSSW, effects of holding time, rotating speed and coating layer on joint strength were clarified in sheet combinations of Super Dyma ® steel sheets and 6000 series aluminum alloy sheets. Also, in laser brazing, it was shown that joining of cold rolled or GA mild steel sheets and 6000 series aluminum alloy sheets are possible by using 4000 series aluminum alloy filler (A4043) with fluoride type NOCOLOK ® flux. Finally, direction of development needed in the future in the field of dissimilar metal joining technologies of steel and aluminum alloy was described based on past development history.