A Study on Melting Practice of High Nitrogen Superaustenitic Stainless Steels Using Conventional Induction Melting Technique+

摘要

Superaustenitic stainless steels (SASS) are a group of austenitic stainless, which contain higher amount of Cr, Ni, Mo and N than the conventional austenitic stainless steels. Demand of these alloys for use in harsh environments has tremendously increased, especially in the last decade, due to their excellent pitting resistance and good mechanical properties. Due to the presence of high nitrogen, these steels have to be produced under the controlled atmosphere or controlled melting practice. Presently, these steels are produced by secondary melting techniques like VAR, ESR or degassing processes with high melting cost. The melting of these alloys by induction melting is scanty and is not standardised yet. In the present research, six different compositions of SASS were produced using air induction melting furnace. At each of the alloys, the loss of alloying elements was calculated by charge calculations. The effect of alloying elements on nitrogen solubility was studied experimentally and the same was also validated thermodynamically using Thermo-Calc software. The alloys containing high nitrogen showed higher strength and comparable toughness in the solution-annealed condition when compared to the alloys with low nitrogen content.