High-speed Hot-wire laser Brazing Technology for Steel/Aluminum alloy Dissimilar Joint using Twin Beam Irradiation

The demand for steel/aluminum alloy dissimilar joints has increased for light-weighting the automobile body. However, it is well known that joining both metals by conventional welding methods, the brittle intermetallic compound (IMC) is generated at the interface, and it significantly deteriorates the joint strength. In this paper, the hot-wire laser brazing process using the twin-spot irradiation was proposed and its conditions were optimized to achieve the high brazing speed and the high joint strength on a lap-fillet joint of the steel/aluminum alloy dissimilar combination. The twin spots of a circle (ϕ5) and rectangular (5 × 11) laser beams aligned at spot ends achieved the high brazing speed up to 6 m/min, stable brazing phenomena and sound bead appearance. The joints fabricated using the optimized conditions realized the very thin IMC thickness under 2 μm and high joint strength over the yield strength of the base steel sheet.