Welding/Joining of High Nitrogen Stainless Steels

Abstract

Nitrogen in steel increases the yield and tensile strength, but decreases the ductility. Therefore, nitrogen has long been considered as an impurity element especially in low carbon steel. Recently, nitrogen has received an increasing attention as an alloying element to steel, as the high nitrogen steel which has been developed with the improvement of steel-making technology, reveals several beneficial effects on properties. The advantages provided by high nitrogen steels are the high yield and tensile strength without sacrificing the toughness and ductility, and the excellent pitting corrosion resistance. The high nitrogen steels have been expected as advanced materials because of their combination of superior strength, toughness and corrosion resistance. Nitrogen in steel also has an effect of stabilizing austenite, and expected as a nickel replacement element for austenitic steels in connection with the nickel shortage and nickel allergy for human body. However, it has some problems, because the high nitrogen steel is a newly developed material. The welding / joining of this material is also one of the problems, since the material is susceptible to decrease of nitrogen content, nitride precipitation and / or pores formation during thermal cycle of the welding. This review tries to make clear the problems for welding / joining of high nitrogen stainless steel, and describes the possibility of welding / joining technology of the material.