热力学计算在高氮奥氏体不锈钢研究中的应用

摘要

采用Thermo-Calc软件,计算了碳、铬、锰、镍元素和压力因素对22Cr高氮奥氏体不锈钢氮溶解度、凝固过程中相转变以及析出相的影响,并对设计的新型高氮奥氏体不锈钢组织及析出相进行了研究.结果表明:铬元素主要增加液态钢的氮溶解度,增加0.1％(质量分数)的碳即能显著增大奥氏体不锈钢在高温凝固时的最小氮溶解度.锰元素既增加液态钢中的饱和氮溶解度,又增加凝固初期的最小氮溶解度.适当的锰含量能扩大并稳定奥氏体相区,避免“铁素体阱”的出现.少量的镍含量既增加奥氏体不锈钢高温凝固时的最小氮溶解度,缩小高温δ铁素体存在的温度区间,也能使钢在室温下有完全的奥氏体组织.加压冶炼能有效促进氮溶解度.新型高氮奥氏体不锈钢的析出相主要为Cr23C6,Cr2N.采用热力学计算工具可以对高氮奥氏体不锈钢的冶炼、组织控制、热处理和热加工提供科学的指导.%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.