Improved microstructure and performance of thick-walled 316L stainless steel joint by NG-GTAW with auxiliary magnetic field

Thick-walled 316L stainless steel (SS) was successfully welded by magnetic field assisted arc oscillation narrow gap GTAW (gas tungsten arc welding). The microstructure and weld performance of thick-walled 316 SS joints with and without arc oscillation were reported. The results indicated that the solute segregation of 316L SS welded joints was improved, ferrite content was significantly reduced, and the overall grain size was also refined under the action of arc oscillation, which may be mainly attributed to the uniform temperature and the reduced cooling rate resulting from the application of magnetic field. Furthermore, the growth direction of the columnar grain in the weld was changed and the texture characteristic of the grain was weakened with arc oscillation. Consequently, the strength and plasticity of the weld were improved synergistically. Based on the SEM and EBSD analysis, the enhanced corrosion resistance of selected position in the joint also was evaluated by weighing the solute segregation, phase proportion and grain boundary characteristic.