材料热处理学报

设计了一种低碳Fe-Mn-Nb-Cu-B系屈服强度690 MPa级工程机械结构用钢,利用扫描电镜(SEM)和透射电镜(TEM)等仪器研究了不同回火温度对实验钢的组织和性能的影响。结果表明:回火温度对屈服强度和抗拉强度均有较大影响,都呈现出先降低再升高再降低的规律。600℃回火时的综合力学性能较好,屈服强度比未回火时增加了145 MPa;并且屈强比和硬度随回火温度的变化趋势同抗拉强度和屈服强度的变化规律是相同的。分析认为:回火前后力学性能的变化的主要原因是与回火后有更多弥散的尺寸在20 nm以下的新的细小(Nb,Ti)(N,C)粒子析出以及发生位错的回复和M-A岛的分解有关。

A low-carbon Fe-Mn-Mo-Nb-Cu-B 690 MPa grade structural steel for construction machinery was designed and the effects of tempering temperature on microstructure and mechanical properties of the steel were investigated by means of scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The results show that tempering temperature has considerable influence on both the yield strength and the tensile strength.The yield strength and the tensile strength decrease first,and increases to the maximum value of 840 MPa,and then decline with the increasing tempering temperature.In comparison with the as-received steel,the yield strength of the steel tempered at 600 ℃ increases by 145 MPa.The changing trend of the yield/tensile ratio and hardness with the tempering temperature is the same with the variation of tensile and yield strength.The change of mechanical properties after tempering is relative to the dispersive precipitates with the size of less than 20 nm,the recovery of dislocations and the decomposition of large M-A islands.