Microstructure, tensile property and corrosion performance of GTAW 316 L/Q345 under compound-magnetic field

Abstract

In order to investigate the regulation law of compound-magnetic field on the weld quality of dissimilar steels with significant material property differences. This study applied compound-magnetic field to gas tungsten arc welding (GTAW) 316 L/Q345 dissimilar steel welding. The compound-magnetic field is generated by longitudinal excitation current (I_L) and cusp excitation current (I_C) in the excitation coil. The forming, microstructural evolution, tensile property and corrosion performance of weld metal (WM) under different excitation parameters were studied by Leica microscope, electron backscatter diffraction (EBSD), electronic general test equipment, electrochemical measurement, scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). Study results show that:compared with No external magnetic field (EMF), under the influence of compound-magnetic field, the weld formation was significantly improved. The base metals fusion ratio were similar and the penetration was maximum when I_L = 0.5 A & I_C = 5 A; The microstructure changed from martensite to martensite + residual austenite, and the grains are significantly refined; The tensile fracture mode changed from brittle fracture to mixed fracture; The best tensile properties were obtained at I_L = 0.5 A & I_C = 3 A, with the ultimate tensile strength (UTS) and elongation (EL) being 1073.27 MPa and 6.86 %, respectively, which were 39.9 % and 68.6 % higher than those of No EMF; The residual austenite, high content of Cr and Ni elements and grain refinement in WM significantly improved the density of rust layer. WM had the best corrosion resistance when I_L = 0.5 A & I_C = 3 A.