High Nitrogen Austenitic Stainless Steels Manufactured by Nitrogen Gas Alloying and Adding Nitrided Ferroalloys

• Published in: Journal of iron and steel research, international Vol. 14; no. 3; pp. 63 - 68
• Main Authors: LI, Hua-bing, JIANG, Zhou-hua, SHEN, Ming-hui, YOU, Xiang-mi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2007; School of Materials and Metallurgy, Northeastern University, Shenyang 110004, Liaoning, China
• Subjects: electroslag remelting; high nitrogen austenitic stainless steel; nitrided ferroalloy; nitrogen gas alloying; vacuum induction melting; 氮气合金化; 渗氮铁合金; 高氮奥氏体不锈钢; nitrided ferroalloy; vacuum induction melting; high nitrogen austenitic stainless steel; nitrogen gas alloying; electroslag remelting
• ISSN: 1006-706X; 2210-3988
• DOI: 10.1016/s1006-706x(07)60045-4

A simple and feasible method for the production of high nitrogen austenitic stainless steels involves nitrogen gas alloying and adding nitrided ferroalloys under normal atmospheric conditions. Alloying by nitrogen gas bubbling in Fe-Cr-Mn-Mo series alloys was carried out in MoSi2 resistance furnace and air induction furnace under normal atmospheric conditions. The results showed that nitrogen alloying could be accelerated by increasing nitrogen gas flow rate, prolonging residence time of bubbles, increasing gas/molten steel interfaces, and decreasing the sulphur and oxygen contents in molten steel. Nitrogen content of 0.69% in 18Crl8Mn was obtained using air induction furnace by bubbling of nitrogen gas from porous plug. In addition, the nickel-free, high nitrogen austenitic stainless steels with sound and compact macrostructure had been produced in the laboratory using vacuum induction furnace and electroslag remelting furnace under nitrogen atmosphere by the addition of nitrided alloy with the maximum nitrogen content of 0.81%. Pores were observed in the ingots obtained by melting and casting in vacuum induction furnace with the addition of nitrided ferroalloys and under nitrogen atmosphere. After electroslag remelting of the cast ingots, they were all sound and were free of pores. The yield of nitrogen increased with the decrease of melting rate in the ESR process. Due to electroslag remelting under nitrogen atmosphere and the consequential addition of aluminum as deoxidizer to the slag, the loss of manganese decreased obviously. There existed mainly irregular Al2O3 inclusions and MnS inclusions in ESR ingots, and the size of most of the inclusions was less than 5 um. After homogenization of the hot rolled plate at 1 150℃ × 1 h followed by water quenching, the microstructure consisted of homogeneous austenite.