采用金相显微镜研究了正火冷却工艺对18CrNiMo7-6齿轮钢带状组织的影响.采用显微硬度计、SEM、拉伸试验机、冲击试验机以及金相显微镜研究了不同程度带状组织对淬回火后试验钢显微硬度的均匀性、成分偏析程度和力学性能的影响.试验结果表明：在930℃奥氏体化保温后,采用强风冷却方式快速冷却到610℃,再炉冷到400℃,最后空冷至室温,可以将带状组织降低到1.5级.但若采用连续快速冷却的方式,则会导致大量贝氏体组织的生成；不同带状组织试验钢经850℃淬火、180℃回火热处理后,显微硬度极差值在30~35 HB 之间,硬度分布均匀性及力学性能各向异性程度相当.
Effect of normalized cooling treatment on banded structure of gear steel 18CrNiMo7-6 was analyzed by metallographic microscope.Effects of banded structures with different degree on micro hardness uniformity,com-position segregation,mechanical properties of test steels after quenching and tempering were analyzed by micro-hardness tester,scanning electron microscope,tensile testing machine,impact testing machine and metallographic microscope.The results show that banded structure can be reduced to 1.5 degree after austenizing heat preserva-tion at 930℃,strong wind cooling to 610℃,furnace cooling to 400℃ and then air cooling.But continuous rapid cooling can result to a large amount of bainite formation;Micro hardness range of test steels with different banded structure degree is between 30-35 HB after quenching at 850 ℃ and tempering at 180 ℃.Hardness uniformity and anisotropy of mechanical properties are comparable.
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