Design and evaluation of nitrogen-rich welding wires for high nitrogen stainless steel

Abstract

Three nitrogen-rich welding wires with nitrogen content of 0.15 %, 0.6 % and 0.9 % for high nitrogen stainless steel welding were developed by a modified Schaeffler diagram and equilibrium phase diagram calculation. The effect of the chemical compositions especially the nitrogen on the weld defects, element distribution, microstructure, mechanical properties and droplet transfer were studied to evaluate the performance of the welding wires. Nitrogen element in the droplets of nitrogen-rich welding wires was partially lost due to the escape of nitrogen during the welding process, so nitrogen in the welding materials was not completely transported to the weld as designed, resulting in a deviation of actual weld from the design. The joint of the welding wire with 0.6 % nitrogen content had the highest mechanical properties, the tensile strength reached 912.5 MPa, and the impact energy of the weld reached 138.17 J. Full-austenite weld was only obtained in the weld of the wire with 0.15 % nitrogen content, but the tensile strength of the joint was lowest because of the low nitrogen content in the weld. Welding wire with 0.9 % nitrogen content had the most serious nitrogen loss, a few of pores were found in the weld. Moreover, the content of skeleton ferrite in the weld with the welding wire containing 0.9 % nitrogen content was high, resulting in the decrease of the weld impact energy.