热处理工艺参数对Cr8冷作模具钢组织和性能的影响

针对Cr8冷作模具钢的二次硬化问题,采用金相显微镜、SEM、EDS和洛氏硬度计,研究了低温回火和高温回火对Cr8冷作模具钢材料组织和性能的影响。结果表明,原材料组织为珠光体和少量长为9~41μm、宽为2~11μm大颗粒共晶碳化物;不同回火温度下,材料的组织为马氏体和少量长为4~25μm、宽为1~8μm的大颗粒共晶碳化物及细小二次析出碳化物;经1030℃淬火、高温520℃回火之后材料出现二次硬化现象,硬度为58. 4 HRC,比低温200℃回火下的硬度高出1. 4 HRC。Cr8钢的二次硬化是由于高温520℃回火之后,二次纳米级小颗粒碳化物析出较多,且颗粒均匀弥散分布于基体中造成的。

Influence of heat treatment parameters on microstructure and property of Cr8 cold working die steel

For the secondary hardening problem of Cr8 cold working die steel,the influences of low temperature tempering and high temperature tempering on microstructure and property of Cr8 cold working die steel were studied by metallographic microscope,SEM,EDS and Rockwell hardness tester. The result shows that the structure of raw material are pearlite and a small amount of eutectic carbides with the length of 9-41 μm and the width of 2-11 μm,and after tempering at different temperatures,the structures of material are martensite and a small amount of large particle eutectic carbides with the length of 4-25 μm and the width of 1-8 μm as well as small secondary precipitation carbides. When the material is quenched at 1030 ℃ and tempered at 520 ℃,the material shows secondary hardening phenomenon with the hardness of 58. 4 HRC,which is 1. 4 HRC higher than that at a low temperature of 200 ℃. Furthermore,the secondary hardening of Cr8 steel is caused by the substantial precipitation of secondary nano-sized small particle carbides after tempering at a high temperature of 520 ℃,and the particles are evenly distributed in the matrix.