氮含量对高氮钢PMIG焊接头组织和性能的影响

o meet high quality welding requirements of high nitrogen austenitic stainless steel components, the steel is welded by PMIG welding with 307Mo weld wire. By adjusting the shielding gas composition, the joints with different N-content are obtained, and the influence of N-content on microstructure and mechanical properties of joints is investigated. The experimental results indicate that if the N-content of the weld metal is lower than 0.24%, the solidification mode is FA and the microstructure is austenite and skeletal ferrite. The higher N-content in the weld metal, the less ferrite in it and a lower microhardness will be got; when the N-content of the weld metal is higher than 0.30%, the solidification mode is A and the microstructure is single austenite. The austenite dendrites become progressive coarse and the microhardness become higher while there is a higher nitrogen level. No nitrides can be found in the weld joints. The nitrogen pore will increase when the N-content of the weld metal is higher. The higher N-content in the weld also can benefit the toughness, but if the N-content is too high, nitrogen pores can damage the toughness of the weld.