热处理工艺对挖掘机铲斗用钢组织和力学性能的影响

Influence of heat treatment process on microstructure and mechanical properties of excavator shovel steel

利用热膨胀仪、拉伸试验机、金相显微镜以及扫描电镜对挖掘机铲斗用钢的相变点、力学性能和微观组织进行了研究，分析了热处理工艺对力学性能的影响。结果表明，挖掘机铲斗用钢在10℃/s的加热速度下，其Ac1和Ac3分别为776℃和832℃；屈服强度在700 MPa以上，抗拉强度在900 MPa以上，伸长率在13%以上；微观组织为回火索氏体，细小弥散的碳化物分布其上。热处理第一次正火温度在820-860℃之间，第二次正火温度在850℃附近为宜，在450~550℃区间回火都有比较好的力学性能，回火时间不宜小于6h。

The phase transformation point, mechanical properties and microstructure of the steel for excavator shovel were studied by using dilatometry, tensile test, optical microscopy and scanning electron microscopy （SEM）, and the influence of the heat treatment process on mechanical properties was investigated. The results show that under the 10 ℃/s heating rate,Ac1 and Ac3 points are 776 ℃ and 832 ℃respectively; yield strength and tensile strength is more than 700 MPa and 900 MPa respectively, and the elongation more than 13%. Microstructure of the steel is tempered sorbite with finely distributed carbide. It shows that the suitable temperature is in the range of 820-860 ℃ for the first normalizing and around 850 ℃ for the second; and there are a better mechanical properties when the tempering temperature is from 450 ℃ to 550 ℃, while the holding time is not less than 6 h.