【摘要】 07MnNiMoDR中厚钢板厚度方向上硬度不均匀的问题限制了该钢板的应用，回火工艺作为一种调控力学性能的重要方法，可起到改善的作用。为拓展该钢种的应用场景，生产出在厚度方向具有高硬度均匀性的07MnNiMoDR中厚钢板，使用了热模拟试验机、光学显微镜、扫描电子显微镜、布氏硬度计、拉伸和冲击试验机，分析了厚度50 mm的07MnNiMoDR钢板在厚度方向性能差异大的原因和回火工艺对钢板厚度方向组织及硬度均匀性的影响。结果表明，淬火时中厚钢板厚度方向上的冷速差异是造成组织及力学性能差异的主要原因，钢板较厚位置的贝氏体组织较钢板近表面的淬火马氏体组织回火稳定性更好。厚度方向硬度均匀性最佳的回火温度为660℃,保温时间为30～60 min,可使表面与心部的硬度差异最小为HBW37.44,与原工艺相比，厚度方向硬度均匀性提高了约52.7%。更多还原

【Abstract】 The uneven hardness in the thickness direction of the 07MnNiMoDR medium-thick steel plate restricts its further application.As a crucial role in regulating mechanical properties of steels, the tempering process can improve this problem efficiently.In order to expand the application scenarios of this steel, a medium-thick steel plate of 07MnNiMoDR with highly uniform hardness in the thickness direction was produced.In this study, the thermal simulation test machine, optical microscope, scanning electron microscope, Brinell hardness tester, tensile and impact testing machine were used.The causes for significant performance differences and the impact of tempering process on the microstructure and hardness uniformity in the thickness direction of the 50 mm thick 07MnNiMoDR steel plate were analyzed.The results show that the cooling rate difference in the thickness direction during quenching is the main cause of the microstructural and mechanical performance differences.The bainite structure at thicker positions of the steel plate exhibits better tempering stability compared to the quenched martensite structure near the surface of the plate.The optimal tempering temperature for the best hardness uniformity in the thickness direction is 660℃,and the holding time is 30 to 60 minutes.This treatment minimizes the hardness difference between the surface and the core to HBW37.44,representing an improvement of approximately 52.7% compared to the original process.更多还原