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采用扫描电子显微镜、透射电子显微镜和冲击性能测试等方法,研究了正火冷却速度和回火温度对45Cr MOV钢的组织和冲击韧性及其断口形貌的影响规律。结果表明,由于组织中有先共析铁素体的存在,以及贝氏体板条较宽,因而45Cr MOV钢正火后的冲击韧性值较低。随正火冷却速度的升高,贝氏体中M-A岛由多边形及近球状逐渐变为片状、细长状及尖角状,但冲击值稍有增加;在600℃以下温度进行回火时,冲击韧性变化不大,当回火温度超过600℃,由于发生了再结晶,冲击韧性明显增加。冲击断口纤维区和剪切唇所占比例随回火温度的升高而逐渐增加,回火温度低于650℃的冲击断口放射区的微观形貌均呈现准解理断裂特征。
The effects of normalizing cooling rate and tempering temperature on the microstructure, impact toughness and fracture morphology of 45Cr MOV steel were studied by scanning electron microscopy, transmission electron microscopy and impact properties testing. The results show that due to the presence of pro-eutectoid ferrite in the structure and the wide bainite lath, the impact toughness of 45Cr MOV steel after normalizing is low. With the increase of normalizing cooling rate, the island of MA in bainite gradually changed from polygons and nearly globular to flaky, slender and sharp, but the impact value increased slightly. When the temperature was below 600 ℃, , Little change in impact toughness, when the tempering temperature exceeds 600 ℃, due to recrystallization, impact toughness increased significantly. The proportion of impact fracture fiber region and shear lip increased gradually with the increase of tempering temperature. The microstructure of the impact fracture zone with the tempering temperature less than 650 ℃ exhibited quasi-cleavage fracture characteristics.