Improvement of inhomogeneity of microstructure and mechanical properties for 316 stainless steel laser-MIG hybrid welded joint assisted by alternating magnetic field

Abstract

An alternating magnetic field was employed to improve inhomogeneity of microstructure and mechanical properties of laser-MIG hybrid welded 316 stainless steel joints. More uniform distribution of elements and ferrite phase, and austenite crystallographic characteristics in upper arc zone and lower laser zone of weld were obtained by alternating magnetic field, due to mixing of molten metal in whole weld. Longer solidification time of molten pool and more nucleation sites of austenite grain were obtained by stirring effect of magnetic field, leading to reduction of ferrite content and refinement of austenite grain. The hardness in vertical weld was more homogeneous and difference of tensile strength in both zones was reduced from 74 MPa to 10 MPa by magnetic field, due to microstructural homogeneity.