Low carbon high nitrogen stainless steel

Abstract:
Austenitic stainless steel is one of the most important stainless steels. This article aims to investigate the effect of partial and total replacement of nickel by nitrogen on both mechanical properties and phase of steel. The proposed stainless steels were produced in 10 kg induction furnace under nitrogen pressure. The produced stainless steels forged at high temperature. The investigated stainless steels heat treated at 1200 oC for 1 hour cooled in water, followed by tempering at 300 oC for1 hour. Nonmetallic inclusions such as nitrides were separated by electrolytic dissolution. Nitrogen as nitrides was determined and soluble nitrogen was calculated. XRD technique was used to investigate the types of nonmetallic inclusions. The microstructure of produced stainless steels was observed. The tensile properties were determined of tempered stainless steels after quenching process. The base stainless steel has chemical composition 14.42%Ni, 0.0387%C,1.64%Si, 1.62%Mn, 20.24%Cr, 2.39%Mo and 0.008%N. It was found that it has yield and ultimate tensile strength 352.6 MPa and 550.2 MPa respectively. The developed stainless steel has the same chemical composition of the base one with 6.54%Ni and 0.232%N. It has yield and ultimate tensile strength 494.5 MPa and 714.9 MPa respectively. In addition to the free nickel stainless steel grade with 0.342%N- has yield and ultimate tensile strength 746.2 MPa and 886.0 MPa respectively. From experimental results, either partial or total replacement of nickel by nitrogen improves tensile properties, in addition to the microstructure will be not changed.