Optimization of the microstructure and mechanical properties of the high nitrogen stainless steel weld by adding nitrides to the molten pool

Abstract

The nitrides were added to the molten pool to optimize the microstructure and mechanical properties of high nitrogen stainless steel weld. The nitrides of the alloy element that promote the nitrogen dissolution were selected. The alloy element and nitrogen element were thereby simultaneously added to the weld. MnN was selected from TiN, VN, CrN and MnN because the nitrogen content of the autogenous tungsten inert gas weld that brushed the MnN powder was the highest and manganese is an austenite forming element. And then MnN was filled into the gas metal arc welding molten pool as the way of bypass MnN-cored wire. The proportion of ferrite of the weld reduced by 51.4 %, the tensile strength of the joint increased by 7.4 % and the impact toughness of the weld increased by 28.1 %. The action mechanism of MnN during the welding was discussed. MnN was decomposed under the high temperature of the arc and the nitrogen and manganese entered the molten pool respectively. Nitrogen escape occurred along with the mass transfer process.