淬火工艺对U75V重轨钢组织及力学性能的影响

采用光学显微镜、扫描电镜、硬度计、冲击试验机、万能拉伸试验机研究了U75V重轨钢轧态及淬火冷速为3 ℃/s和5 ℃/s条件下的微观组织、力学性能及断口形貌。结果表明:随着淬火冷速的增加,U75V钢的晶粒逐渐细化,珠光体片层间距减小,其中,轧态U75V钢的晶粒和片层间距最大,而5 ℃/s淬火冷速的U75V钢晶粒和片层间距最小;随着淬火冷速的增加,U75V钢的冲击吸收能量、硬度等综合力学性能增加。其中,轧态U75V钢轨的冲击吸收能量、硬度及抗拉强度最小,而5 ℃/s淬火冷速的U75V钢冲击吸收能量、硬度最优且抗拉强度较好。

Effect of quenching process on microstructure and mechanical properties of U75V heavy rail steel

Microstructure, mechanical properties and fracture morphology of U75V heavy rail steel as rolled and as quenched at 3 ℃/s and 5 ℃/s were studied by optical microscope, scanning electron microscope, hardness tester, impact testing machine and universal tensile testing machine. The results show that with the increase of quenching rate, the grain size of the steel is refined gradually, and the pearlite lamellar spacing decreases. Among them, the grain size and lamellar spacing of the steel as rolled are the largest, and that as quenched at 5 ℃/s are the smallest. Meanwhile, the comprehensive mechanical properties such as impact absorbed energy and hardness of the U75V steel are increased. Among them, the impact absorbed energy, hardness and tensile strength of the steel as rolled are the lowest, and that as quenched at 5 ℃/s are the best.