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用膨胀法结合显微组织观察及硬度测量方法,得到了U75V钢轨钢动态CCT曲线。结果表明:当冷却速度为0.05~3℃/s时的U75V钢轨钢的显微组织为珠光体组织,而且随着冷却速度的加快珠光体片层间距逐渐减小;冷却速度为5℃/s时主要的显微组织为珠光体组织,但出现少量马氏体组织;当冷却速度为15~50℃/s时的显微组织为马氏体和残余奥氏体组织。随着冷却速度的增大,硬度呈增加趋势。高铁用U75V钢轨钢奥氏体向珠光体开始转变温度不超过700℃,相变结束温度不低于500℃,当冷却速度为2~3℃/s时珠光体片层间距最为细小。
The dynamic CCT curve of U75V rail steel was obtained by means of expansion method combined with microstructure observation and hardness measurement. The results show that the microstructure of U75V rail steel is pearlite when the cooling rate is 0.05-3 ℃ / s, and the spacing of pearlite layer decreases with the cooling rate increasing. The cooling rate is 5 ℃ / s When the cooling rate is 15 ~ 50 ℃ / s, the microstructure is martensite and retained austenite. The main microstructure is pearlite, but a small amount of martensite appears. With the cooling rate increases, the hardness tends to increase. The transition temperature of austenite to pearlite in U75V rail steel for high-speed rail does not exceed 700 ℃ and the end temperature of phase transition is not less than 500 ℃. When the cooling rate is 2 ~ 3 ℃ / s, the spacing of pearlite is the smallest.