Influence of fiber laser cutting parameters on the subsequent laser welding of Ti6Al4V sheets

One approach to reduce the titanium alloy machining costs and extensive material usage, is to join pieces obtained by Laser Beam Cutting (LBC) process. Cutting with fiber laser sources represents a promising tool in machining titanium alloy parts with subsequent welding requirements. Fiber lasers offer a great potential in improving the productivity of cutting phase with an acceptable edge quality, in particular when thin sheets are concerned. The paper investigates, using Design of Experiment techniques, the effect of laser cutting parameters on the mechanical behaviour of laser butt welded joints whose edges were obtained by laser cutting. In the first part of the experimental activity, the laser welding process using a Nd:YAG laser, performed on cut edges generated by machining, was investigated. Once the optimal welding condition (in terms of laser power and welding speed) was determined, the mechanical characterization of titanium alloy butt joints cut using a 2 kW fiber laser, was carried out. Tensile tests revealed that the shear gas pressure is the main parameter affecting the Ultimate Tensile Strength because it is directly correlated to the quality of the cutting edge in terms of squareness, dross height and roughness.