原始铸态组织对Cr13Ni4Mo钢逆变奥氏体形成的影响

Effect of Original As-Cast Microstructure on Reverse Austenite Formation of Cr13Ni4Mo Steel

采用扫描电子显微镜、X射线衍射分析仪、电子背散射衍射研究了原始铸态组织对Cr13Ni4Mo马氏体不锈钢回火过程中逆变奥氏体形成的影响。浇注厚度为40mm、60mm、80mm的阶梯形铸件,以获得凝固速度不同的原始等轴晶铸态组织,经正火+二次回火处理后,随铸件厚度的减小,组织中逆变奥氏体的含量增加,Cr13Ni4Mo钢的抗拉强度和伸长率均提高。采用定向凝固方法,改变下拉速度为1μm/s、5μm/s和50μm/s,以获得原始柱状晶铸态组织,结果发现随着下拉速度的提高,定向生长的柱状晶细化,逆变奥氏体的含量增多,Cr13Ni4Mo钢的抗拉强度和强塑积增大。Cr13Ni4Mo钢综合力学性能的提高源于细晶强化和逆变奥氏体TRIP效应的双重效果。

Scanning electron microscopy(SEM),X-ray diffraction analyzer(XRD)and electron backscattering diffraction(EBSD)were used to investigate the effect of the original as-cast structure on the formation of reverse austenite during tempering of Cr13Ni4Mo martensitic stainless steel.The stepped castings with the thickness of 40 mm,60 mm and 80 mm were poured to obtain the original equiaxed crystal structure with different solidification rates.After normalizing and twice tempering treatment,the reverse austenite content in the structure increased with the decrease of the casting thickness,and the tensile strength and elongation of Cr13Ni4Mo steel increased.By the method of directional solidification,the original columnar crystal was obtained by changing the pull-down velocity to 1μm/s,5μm/s and 50μm/s.The results showed that with the increase of pull-down velocity,the columnar crystal was refined,the reverse austenite content increased,and the tensile strength and strong plastic deposition of Cr13Ni4Mo steel increased.The improvement of mechanical properties of Cr13Ni4Mo steel was due to the double effect of fine grain strengthening and reverse austenite TRIP effect.