Welding of stainless steel using defocused laser beam

Type 321 stainless steel has a wide range of applications, including welded constructions. Common arc welding has disadvantages because of low speed and higher heat input that result in significant residual stresses and strains. The alternative to arc welding is laser welding that allows elimination of these negative effects. The results of research on welding of stainless steel with a defocused laser beam are presented and discussed in this paper. It was assumed that the use of defocused laser beam would increase volume of the weld pool that in turn would reduce requirements for preparation of edges and the gap between workpieces. Attention was mainly paid to metallurgical processes of the weld pool formation, depending on the welding conditions. Microhardness of the selected sample was measured, 2D-imaging, metallographic studies, quantitative evaluation of phase components of various zones of the weld pool were conducted. The obtained results prove that the use of the defocused beam allows obtaining quality welded joints, and this technique has also positive influence on the stability of the keyhole, and on the phase composition of the weld metal.