Optimization of ND:YAG laser weld joints of thin wall stainless steel enclosures

Stainless steel enclosures called as 'fume hood' are constructed out of 1.6/2.0mm thick sheet type 304l AISI material. The surface and interior of shell after fabrication must be smooth, free from sharp edges, corners, excess weld reinforcement, concavity, etc, for easy cleaning and decontamination. The surfaces shall meet the geometrical tolerances in terms of flatness, straightness etc. after fabrication. Fabrication and welding of 2.0 mm thick sheet poses challenge in terms of buckling distortion and stringent acceptance criteria. The Nd:YAG laser was chosen for the welding of thin SS304L panels because its pulsing capabilities can deliver the power to the work piece with minimal heat input and distortion. It can weld reflective materials and tolerate poor sheet metal fit-up. The stainless steel enclosures were placed on a fixture in the laser workstation 'TruLaser500' (TRUMF) for carrying out long seam welding of side panels. Each side of the enclosure was welded during a cycle and rotated to weld the adjacent surface (left, right and rear). This paper aims to investigate the influence of laser process parameters on geometrical tolerance, strength, microstructure and chemical composition of weld joints