回火时间对高温轴承钢组织和性能的影响

Effect of tempering time on microstructure and properties of high temperature bearing steel

研究了500℃高温回火处理时不同回火时间对高温轴承钢组织和性能的影响规律。结果表明,随回火时间的延长,高温轴承钢的强度和硬度逐渐增加,而钢的塑性和冲击性能逐渐降低。回火时间的延长促进了试验钢中第二相的析出和长大,由于第二相的析出强化,使得钢的强度和硬度提高。冲击断口韧窝中析出相的数量随回火时间的延长逐渐增加,且尺寸有所增大,冲击断口中典型韧窝形貌逐渐减少,断裂机制逐步由韧性撕裂向准解理断裂转变。试验钢经500℃×100 h长时间回火后有少量μ相析出,μ相的析出使钢的塑性降低。

Microstructure and mechanical properties of a high temperature bearing steel which tempered at 500 ℃ with different tempering time after oil quenching were investigated.The results show that with the increasing of tempering time, tensile and yield strength of the tested steel rise up gradually, but toughness and ductility decrease.Long time tempering can promote second phase precipitation and growth, so as to higher strength and hardness would be caused by precipitation strengthening.Moreover, the amount and size of precipitates located in dimples increase, however, typical dimple pattern in impact fractures reduces gradually with extended tempering time.Thus, fracture mechanism for tested steel changes from ductile tearing to quasi-cleavage rupture.In addition, there are a few μ-phase precipitates determined in the tested steel tempered at 500 ℃for 100 h, which lead to reduction of plasticity.