调质处理22MnCrNiMo钢的显微组织及力学性能

Microstructure and mechanical properties of quenched and tempered 22MnCrNiMo steel

对22MnCrNiMo钢进行调质热处理,采用扫描电镜和透射电镜观察了不同淬火温度下原奥氏体晶粒和板条马氏体组织形貌.研究了不同回火温度下基体组织特征和碳化物析出行为.对比分析了实验钢经不同调质热处理后的室温拉伸性能和低温冲击韧性.研究结果表明:当淬火温度超过920℃时,实验钢基体组织发生明显的粗化;淬火后的回火过程中,随着回火温度的升高,α-Fe板条变宽,位错密度下降,析出的碳化物发生粗化,使得亚晶界强化、位错强化和析出强化作用逐渐减弱.同时,实验钢的韧性增加趋势也随着碳化物的粗化而减缓.实验钢在920℃×1h+600℃×1.5h热处理工艺下可获得最佳综合力学性能,抗拉强度和低温冲击功分别达到1162MPa和138J.

The microstructures of quenched and tempered(Q&T)22MnCrNiMo steel were observed by SEM and TEM.Changes of the size of prior austenite grain and morphologies of lath martensite at different quenching temperatures,as well as microstructural characteristics of the matrix and precipitation behaviors of carbides at different tempering temperatures,were studied.Additionally,tensile properties and low-temperature impact toughness of the tested steel with different Q&T treatments were analyzed.The results show that the microstructure of matrix obviously coarsened as the quenching temperature was above 920℃.During the tempering process,contributions to strength resulted from sub-grain boundary,dislocation and precipitation strengthening mechanisms gradually decreased,owing to widening of lathα-Fe,reduction of dislocation density and coarsening of carbides.Meanwhile,the increment of impact toughness reduced for coarse carbides.As a result,the tested steel quenched at 920℃for 1 h and then tempered at 600℃for 1.5 h would obtain an excellent comprehensive mechanical properties,with tensile strength of 1162 MPa and low temperature impact value of 138 J.