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Applications of Thermo-Calc in Research of High Nitrogen Austenitic Stainless Steels |
LANG Yu-ping1, CHEN Hai-tao1, WENG Yu-qing2, QU Hua-peng1 |
1. Institute for Special Steels, Central Iron and Steel Research Institute, Beijing 100081, China;
2. The Chinese Society for Metals, Beijing 100711, China |
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Abstract The Thermo-Calc software was used to calculate the influence of pressure factor and elements including C, Cr, Mn and Ni on the solubility of nitrogen, the phase transformation during solidification in high nitrogen austenitic stainless steel with 22%(mass fraction) Cr. The microstructures and precipitates of new designed high austenitic stainless steel were studied also. The results show that Cr increases mainly the solubility of nitrogen in liquid steel. With about 0.1%C the minimum solubility of nitrogen during higher solidification temperature is enhanced remarkably. Mn increases not only the solubility of nitrogen in liquid steel but also the minimum solubility of nitrogen during earlier solidification. With proper Mn the phase area of austenite is extended and more stably, also the "ferrite trap" can be avoided. With a little nickel less than 2% the minimum solubility of nitrogen during higher solidification temperature is enhanced and the temperature extension of δ phase presence is reduced, also to make sure full austenite in steel at room temperature. Melting under pressure is efficiently to increase the solubility of nitrogen. The main precipitates of new high austenitic stainless steel are Cr23C6 and Cr2N. To use thermodynamic calculation tools can be beneficial to research the melting, structure, heat treatment and hot working of high nitrogen austenitic stainless steels.
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Received: 26 March 2012
Published: 20 May 2013
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