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本文研究了3Cr3Mo3VNb钢等温淬火后贝氏体回火时的相及组织转变规律。实验结果表明,贝氏体的二次硬化机制和马氏体一样,主要是由Mo_2C,V_4C_3,NbC等细小弥散的合金碳化物析出造成的。回火时,贝氏体中粗大的渗碳体溶解较慢,减慢了合金碳化物的析出速率。贝氏体中的残余奥氏体分解和转变的行为与马氏体中的不同。贝氏体中位错密度较低,不利于合金碳化物的聚集粗化。以上诸因素的共同作用,使贝氏体具有比直接淬火所获得的马氏体更高的二次硬化效应、热强性和组织稳定性。
In this paper, the phase and microstructure transformation of 3Cr3Mo3VNb steel after isothermal quenching was studied. The experimental results show that the secondary hardening mechanism of bainite, like martensite, is mainly caused by the precipitation of finely dispersed alloy carbides such as Mo_2C, V_4C_3 and NbC. When tempering, the coarse cementite in bainite dissolves slowly, which slows down the precipitation rate of alloy carbides. Residual austenite decomposition and transformation in bainite behaves differently than in martensite. Bainite dislocation density is low, is not conducive to the aggregation of alloy carbide coarsening. The combined effect of the above factors makes the bainite have a higher secondary hardening effect, thermal strength and tissue stability than the martensite obtained by direct quenching.