一步等温和两步等温处理对30CrMnSiA钢力学性能的影响

Effect of one step isothermal treatment and two step isothermal treatment on mechanical properties of 30CrMnSiA steel

设计了一步等温和两步等温Q&P处理,通过改变淬火温度和等温温度使30CrMnSiA钢获得了不同含量一次马氏体(PM)、残留奥氏体(RA)、二次马氏体(FM)及贝氏体(BF)的多相微观组织。采用X射线衍射(XRD)、电子背散射衍射(EBSD)技术和透射电镜(TEM)等分析了Q&P处理对试验钢组织和力学性能的影响,并分析了热处理工艺影响RA含量、形态和C浓度的微观机制。结果表明:Q&P工艺中的淬火温度和等温温度决定了各相的含量和特性,高的等温温度有利于提升试验钢的拉伸塑性,而残留奥氏体的含量和碳浓度能够显著影响试验钢的伸长率、强塑积和屈服强度;330℃是一步等温和两步等温处理的最佳淬火温度,该温度下高的RA的含量及C浓度能够显著提升30CrMnSiA钢的伸长率、强塑积和屈服强度。与一步等温Q&P处理比较,两步等温Q&P处理可以提高组织中的RA含量,并能显著降低FM含量,这有助于提升30CrMnSiA钢的力学性能。

A one-step isothermal and two-step isothermal Q&P treatment was designed,and the multiphase microstructure of 30CrMnSiA steel with different contents of primary martensite(PM),retained austenite(RA),secondary martensite(FM)and bainite(BF)was obtained by changing the quenching temperature and isothermal temperature.The effects of Q&P treatment on microstructure and mechanical properties of the experimental steel were analyzed by means of X-ray diffraction(XRD),electron backscatter diffraction(EBSD)technique and transmission electron microscopy(TEM).The micro mechanisms by which the heat treatment process affects the RA content,morphology and C concentration were also analyzed.The results show that the quenching temperature and isothermal temperature in the Q&P process determine the content and characteristics of each phase.A high isothermal temperature is beneficial for improving the tensile plasticity of the experimental steel,while the content of retained austenite and carbon concentration can significantly affect the elongation,product of strength and elongation,and yield strength of the experimental steel.330℃is the optimal quenching temperature for one-step and two-step isothermal treatment.At this temperature,high RA content and C concentration can significantly improve the elongation,product of strength and elongation,and yield strength of the 30CrMnSiA steel.Compared with one-step isothermal Q&P treatment,two-step isothermal Q&P treatment can increase the RA content in the microstructure and significantly reduce the FM content,which helps to improve the mechanical properties of the 30CrMnSiA steel.