U71Mn钢分段式冷却强化工艺试验研究

Experimental Study on Sectional Type Cooling Strengthening Technology of U71Mn Steel

通过测定U71Mn钢的过冷奥氏体转变动力学曲线,分析其相变规律。基于现场钢轨热处理工艺进行分段式冷却强化热模拟试验,研究冷速和终冷温度对组织及硬度的影响。结果表明,U71Mn钢的珠光体转变临界冷速为7℃/s,允许珠光体转变的温度范围为500~600℃。其分段式冷却合理工艺参数为开始冷却温度为850℃,冷速为6~12℃/s,终冷温度为570℃,此工艺参数下可获得珠光体组织,同时满足钢轨硬度要求。

The phase transformation law is analyzed through determining the transformation kinetics curve of supercooled austenite for U71Mn steel.The effects of cooling rate and finish cooling temperature on microstructure and hardness are studied with the thermal simulation tests of sectional type cooling strengthening based on the heat treatment process of rails on site.The results showed that the critical cooling rate of perlitic transformation for U71Mn steel was 7℃/s and temperature range allowing perlitic transformation was 500~600℃.The reasonable process parameters of sectional type cooling for U71Mn steel were that the starting cooling temperature was 850℃,cooling rates was 6~12℃/s and finish cooling temperature was 570℃.The perlite structrure could be obtained with this process parameter and it could meet the hardness requirements of rails.