Abstract: Effect of quenched and tempered treatment, normalizing & quenched and tempered treatment on micro¬structure and properties of 42CrMo forging crankshaft steel is studied by means of metallographic microscope observation and mechanical performance analysis. The results show that after the quenching and tempering treatment ( 860 ℃ quenched + 580℃ tempered) , the base structure for the forging crankshaft billet is temped sorbite and much amount of white ferrite with coarse grain non-homogeneously distributed at the central area of crankshaft. Its mechanical properties are TS 997 ~ 1211 MPa, YS 990 〜1204 MPa, el. 11% ~ 13% , RA 40% -48% , and impact energy 72 ~92 J. On the contrary,with a normalizing pretreatment(880℃ air cooling) before the quenching and tempering treatment process, the microstructure for the 42CrMo forging crankshaft steel become more uniform, its mechanical properties are TS 1100 〜1220 MPa, YS 1107 ~ 1188 MPa, el. 13% ~ 15% , RA 50% ~56% and impact energy 83 ~91 J. Therefore, the normalizing pretreatment at 880 °C air quenching at 860 °C and high temperature tempering treatment at 580 T is the optimized heat treatment process for the 42CrMo forging crankshaft steel.

摘要： 利用金相显微观察及力学性能分析,研究调质处理、正火+调质热处理对42CrMo曲轴钢组织与性能的影响。结果表明,经过860℃淬火+580℃回火处理后,曲轴钢基体组织为回火索氏体,但轴颈心部区域白色铁素体数量较多且晶粒粗大、分布不均。其力学性能为抗拉强度997～1211 MPa,屈服强度990～1204 MPa,伸长率11%～13%,断面收缩率40%～48%,冲击功72～90 J。而在调质热处理前增加一次(880℃空冷)正火预处理后,42CrMo曲轴钢的显微组织更趋均匀化,其力学性能为抗拉强度1100～1220 MPa,屈服强度1107～1188 MPa,伸长率13%～15%,断面收缩率50%～56%,冲击功83-91 J。因此,880℃空冷正火预处理+860℃淬火与580℃高温回火是42CrMo曲轴钢优化的热处理工艺。

关键词: 42CrM钢, 锻造曲轴, 调质处理, 正火预处理组, 织性能