【摘要】 研究了7Cr7Mo2V2Si钢回火时相及组织和力学性能的变化规律,着重观察了二次硬化峰值附近碳化物的结构和形貌.结果表明,该钢的二次硬化主要是具有fcc结构的V₄C₃及Mo₂C呈圆盘状沉淀所致.550℃回火时,fcc结构的Mo₂C转变为hcp结构并呈针状析出,此时硬度略有下降.高于600℃回火,在原奥氏体晶界处析出粗大的M₇C₃型碳化物,并形成一定宽度的无沉淀区,硬度明显下降.更多还原

【Abstract】 The changes of the phase, structure and mechanical property during tempering have been studied on steel 7Cr7Mo2V2Si. The structure and morphology of carbides near the peak of secondary hardening were observed emphatically. The results showed that the cause of secondary hardening of the steel is the precipitation of V4C3 and Mo2C having the fcc structure in the shape of disc. When tempering at 550℃, the Mo2C having the fcc structure transforms into the eguilibrium (hcp) structure in situ, the particles of which are needlelike. Meanwhile, the hardness of the steel slightly drops. While the tempering temperature is raised to more than 600℃, the coarse carbide of M7C3-type precipitate at the austenite grain boundaries and a certain width of zone without precipitation form and the hardness of the steel evidently drops.更多还原