Cr18Mn6Ni4N奥氏体不锈钢连铸坯热塑性及其影响机制

Thermoplasticity and influence mechanism of continuous casting billet of Cr18Mn6Ni4N austenitic stainless steel

针对Cr18Mn6Ni4N奥氏体不锈钢在实际连铸生产中容易出现表面裂纹问题,对连铸坯样皮下20 mm进行取样,用Gleeble3500测定不同温度下的断面收缩率,并通过Thermo-Calc软件计算与电镜观察相结合的方法得出热塑性变化机制。研究结果表明:当在900～1 250℃温度范围,断面收缩率较高,都在50%以上。当温度低于900℃时,断面收缩率显著下降;采用Thermo-Calc软件计算Cr18Mn6Ni4N在不同温度下的平衡相,并结合电镜观察结果得出,在低于900℃时,平衡相M_(23)C_6与Cr_2(C,N)大量析出,降低了Cr18Mn6Ni4N的热塑性。该研究对了解该钢种的高温特性和制定合理的连铸工艺具有重要意义。

For the Cr18Mn6Ni4N austenitic stainless steel,the surface crack problem is prone to occur in the continuous casting production. In this study,the 20 mm of the continuous casting billet was sampled,and the reduction of the area at different temperatures was measured by Gleeble 3500. The mechanism of thermoplastic change was obtained by the combination of Thermo-Calc software and electron microscopy. The results show that when the temperature range is 900-1 250 ℃,the area shrinkage is higher,which is above 50%. When the temperature is lower than 900 ℃,the reduction in area is remarkably lowered. The equilibrium phase of Cr18Mn6Ni4N at different temperatures was calculated by Thermo-Calc software and the results of electron microscopy showed that the equilibrium phase M23C6 and Cr2(C,N)precipitated a lot when the temperature was lower than 900 ℃,which reduced the thermoplasticity of Cr18Mn6Ni4N.This study is of great significance for understanding the high temperature characteristics of this steel grade and for developing a reasonable continuous casting process.