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采用850℃至1200℃的淬火温度,探索了奥氏体晶粒尺寸对52CrMoV4弹簧钢强韧性的影响。通过光学金相和扫描电镜观察了显微组织和断口形貌及断裂路径。结果表明,随着晶粒的粗化,强度变化很小,拉伸塑性呈线性降低,断裂韧度和冲击韧度呈现先降后增的反常趋势。晶粒尺寸和马氏体束尺寸是影响拉伸塑性的重要因素,而断裂韧度和冲击韧度与晶界状况和马氏体条的宽长比有关。
The effect of austenite grain size on the toughness of 52CrMoV4 spring steel was explored with the quenching temperature of 850 ℃ to 1200 ℃. Microstructure and fracture morphology and fracture path were observed by optical metallography and scanning electron microscopy. The results show that with the coarsening of the grains, the strength changes little, the tensile plasticity decreases linearly, and the fracture toughness and impact toughness decrease first and then increase. Grain size and martensite beam size are important factors affecting the ductility of the ductile fracture. The fracture toughness and impact toughness are related to the grain boundary conditions and the martensite length-width ratio.