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Detailed Investigation of the Effects of Processes Parameters on the Joint Properties of Laser Welded Ferritic Stainless Steel
F-D. Liu, X-N. Ji, J-M. Liu, R. Zhao, G-Z. Huang and H. Zhang
In this study 1.2 mm thick 441 ferritic stainless steel sheets were subjected to Nd:YAG laser welding to investigate the impacts of the laser power, ๐, welding speed, ๐ฃ, and defocusing amount, ฮ๐, on the performance of the welded joints. The results revealed that ๐=2.0 kW, ๐ฃ=1.8 m/ min and ฮ๐=+2 mm were the optimal welding parameters. The weld seam featured a ferrite organization, with trace Fe-Ti compounds and fine isometric crystals at the center of the weld bead. The laser welded joint featured a uniform grain size, which contributed toward the tensile strength and elongation of the joint. Notably, specimen fracture, namely a typical ductile fracture, occurred at the parent metal when subjected to tension. The Ti-C compounds and Fe-Ti compounds in the weld were found to inhibit dislocation movements and grain growth behaviours, which, in turn, improved the hardness of the welded joint.
Keywords: Nd:YAG laser, 441 ferritic stainless steel, laser welding, welding parameters, mechanical properties, microstructure