Welding of high-nitrogen austenitic steels (Review)

Alloying with nitrogen allows one to substantially increase the strength of steels, especially of the austenitic steels, in which the equilibrium nitrogen content can reach 0.4 – 0.7 wt % depending on their chemical composition. Nitrogen stabilizes austenite and enhances its corrosion and wear resistance. For this reason, nitrogen-containing austenitic steels are advantageous structural materials, in particular, for heavy loaded welded structures. However, wrong choice of the welding method, regime, or filler for high-nitrogen steels can cause critical defects such as pores and cracks in the welded joints and substantially decrease their mechanical properties and corrosion resistance compared to those of the base metal. More than hundred literature sources have been considered for the analysis of welding types and methods for austenitic steels containing ≥ 0.4 wt. % nitrogen, the criteria for their weldability, and the causes for potential negative phenomena occurring upon their welding. For such steels, information is provided on the welding filler materials as well as on the modes and parameters of the welding process (supplied heat, presence/absence of a protective atmosphere, its composition, etc.). The structure, phase composition, and properties of the resulting welded joints are considered. The examples are given on the effect of the subsequent processing of welded joints (heat treatment and thermal deformation processing for the elimination of the resulting distortion) on their basic properties.