Abstract: High nitrogen nickel-free austenitic stainless steel with 0.54%N was prepared by vacuum induction furnace+electroslag remelting furnace under 0.08 MPa. After hot rolling, the tested steel was solution treated at 800, 900, 1000, 1100 and 1200 ℃ for different time, respectively. The microstructure and corrosion resistance of the tested steel were studied with different solution treatment processes, in which the corrosion resistance was studied in 3.5% NaCl solution by potentiodynamic polarization curve, and the mass loss ratio and corrosion rate were calculated after soaking in 6% FeCl₃ solution for 8 days. The results show that solution treatment has a great influence on microstructure and corrosion resistance of the high nitrogen stainless steel. The tested steel after solution treatment at 1000 ℃ and 1100 ℃ has a single austenite structure. The precipitation phase Cr₂N exists in the microstructure of the tested steel without heat treatment and in that solution treated at 800 ℃ and 900 ℃. In the tested steel solution treated at 1200 ℃, the ferrite structure is precipitated from the austenite. The tested steel heated at 1100 ℃ for 1 h has the best corrosion resistance, and the corrosion rate is only 1.35×10^-5 g·cm^-2·h^-1. While the corrosion resistance of the tested steel heated at 800 ℃ for 3 h is the worst, the corrosion rate is as high as 8.18×10^-4 g·cm^-2·h^-1. The corrosion resistance of 316L stainless steel is somewhere in between, and the corrosion rate is 1.24×10^-4 g·cm^-2·h^-1.

Key words: high nitrogen austenitic stainless steel, heat treatment, polarization curve, corrosion rate