Abstract
Stainless steel features high corrosion resistance but may undergo intergranular corrosion in some specific environments especially in seawater. To cope with this problem, it can be considered to a useful technique to apply titanium material selectively to the part exposed to such specific environments. However, if austenitic stainless steel and titanium are fused together, Fe and Ti create brittle intermetallic compounds, which makes it difficult to configure suitable welding parameters. The authors have studied the laser brazing process to minimize the fusing of the base metal to join the lap joint of stainless steel and titanium.
As the results of examining the base metal arrangement for a lap joint in the use of Cu-Si filler metal, the lap joint with a top plate of stainless steel and a bottom plate of titanium was clarified to be suitable to obtain a crack-free weld joint. The optimum combination of laser brazing parameters with a Cu-Si filler metal was clarified as follows for the present study: 2 kW laser power, 70 degree beam angle, 0.2 mm beam shift, 0.70 m/min brazing speed, and 1.1 m/min filler-metal feed speed by using a semiconductor laser. The examination of several kinds of filler metals verified that the Ni-Cu type and Ni type filler metals increased the formation ratio of Ni-Ti intermetallic compound, thereby causing the occurrence of cracking. In contrast with the filler metals of Cu-Si type, Cu type, and Cu-Ni type, the rupture load fulfilled the JIS standard for titanium clad steel with no cracking in the optimized brazing condition.
