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模拟钢轨焊接及焊后热处理工况,采用热膨胀方法分别测定UIC900A及U75V钢轨钢的连续冷转变曲线(CCT曲线)。通过对UIC900A及U75V钢轨钢连续冷却特性的分析和比较,结果表明:当模拟焊接的奥氏体化温度为1 300℃和冷却速度小于1.5℃.s-1时,这2种钢轨钢的组织均为珠光体,并且在正常情况下焊接后直接空冷也都不会出现马氏体组织,这时UIC900A和U75V钢轨钢的硬度分别达到329 HV和354 HV;当模拟焊后热处理的奥氏体化温度为900℃和冷却速度为0.5℃.s-1时,这2种钢轨钢的硬度均为300 HV左右。UIC900A钢轨钢可直接空冷,U75V钢轨钢则需用冷却速度为1~2℃.s-1的喷风软淬火,以使其硬度达到320~350 HV左右。
Simulated rail welding and post-weld heat treatment conditions, the thermal expansion method were used to determine the continuous cold transformation curve (CCT curve) of UIC900A and U75V rail steel. By analyzing and comparing the continuous cooling characteristics of UIC900A and U75V rail steel, the results show that when the austenitizing temperature of simulated welding is 1 300 ℃ and the cooling rate is less than 1.5 ℃ .s-1, the structure of these two kinds of rail steel Are pearlite, and under normal circumstances, the direct air cooling after welding will not appear martensite, then UIC900A and U75V rail hardness of 329 HV and 354 HV, respectively; when simulated after heat treatment of austenite The hardness of these two kinds of rail steels is about 300 HV when the temperature is 900 ° C. and the cooling rate is 0.5 ° C.s-1. UIC900A rail steel can be directly air-cooled, U75V rail steel is required cooling rate of 1 ~ 2 ℃ .s-1 jet soft-quenching, so that the hardness reaches about 320 ~ 350 HV.