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Nb、Ti、V微合金钢常常因轧制工艺的不同而导致其力学性能截然不同。对在工业生产中力学性能出现显著差异的700 MPa级微合金钢的微观结构,采用光学金相、扫描电镜、透射电镜和物理化学相分析进行研究。结果表明:因轧后冷却速率的不同而形成的铁素体+少量珠光体、准多边形铁素体、准多边形铁素体+部分贝氏体三类组织,其力学性能特征分别表现为:屈服强度低、抗拉强度低、冲击功高、断后伸长率高;屈服强度高、抗拉强度高、冲击功适中、断后伸长率适中;屈服强度低、抗拉强度高、冲击功低、断后伸长率低。第二相粒子(Ti,Nb,V)C的析出量及其尺寸分布的不同,以及铁素体晶粒尺寸差异是产生强度差异显著的主要原因,而较多大尺寸不规则状M/A岛的形成是该钢种冲击功明显下降的关键因素。
The mechanical properties of Nb, Ti, V microalloyed steels are often different due to different rolling processes. The microstructure of 700 MPa microalloyed steels with significant difference in mechanical properties in industrial production was studied by optical metallography, scanning electron microscopy, transmission electron microscopy and physicochemical phase analysis. The results show that the mechanical properties of ferrite + a small amount of pearlite, quasi-polygonal ferrite, quasi-polygonal ferrite + bainite formed by the different post-rolling cooling rates are as follows: yield Low strength, low tensile strength, high impact energy, high elongation at break; high yield strength, high tensile strength, impact energy moderate elongation after moderate; low yield strength, high tensile strength, low impact energy, Elongation at break is low. The amount of precipitated second phase particles (Ti, Nb, V) C and its size distribution, as well as ferrite grain size difference is the main reason for the significant difference in the intensity of production, and more large size irregular M / A Island The formation of the steel is a significant factor in reducing the impact energy.