Effect of Melt Holding in Mushy Zone on the Nitrogen Content of 201 Austenitic Stainless Steel

Abstract

The melting of a 201 austenitic stainless steel was conducted in mushy zone for 0, 5, 10, 15 min under nitrogen atmosphere. The effect of the holding time on nitrogen content was investigated. The results showed that with the increase of holding time, the nitrogen content was significantly increased. It was found that the holding in mushy zone could avoid ferrite region during solidification, and facilitate the diffusion of nitrogen from liquid into austenite. Thermodynamic analysis demonstrates that the difference between the chemical potential of nitrogen in liquid and austenite provides the driving force for the nitrogen diffusion. It is concluded that melt holding in mushy zone is an effective way for increasing the nitrogen content in stainless steel, and thus provides a new method for the production of high nitrogen stainless steel.