Study on seam nitrogen behavior of high nitrogen steel hybrid welding

Abstract

The nitrogen content in welding of high nitrogen steel is an important factor affecting its performance. To solve the problem of nitrogen content reduction and nitride precipitation, a laser-arc hybrid welding experiment was carried out on high nitrogen steel with 12 mm thickness. The effects of different filler materials and heat input on nitrogen porosity, nitrogen content, nitride and joint microstructures were studied. The thermodynamic calculations of high nitrogen steel base metal, stainless steel welding wire and nitrogenous welding wire are carried out using JMatPro thermodynamic software. The precipitation mode and nitride type in welding are analyzed. The results show that there are process and precipitation pores in the welding of high nitrogen steel. The irregular shape and large size of technological pores are related to the keyhole instability. The shape of precipitated pores is oval and small; it is related to the nitrogen solubility during solidification. Additionally, longer residence time in the heat-sensitive zone will increase the precipitation of nitride. Lastly, the use of nitrogen-containing welding wire can effectively supplement the nitrogen loss in welding.