道岔贝氏体钢轨轧后冷却过程的弯曲变形及微观组织演变规律  

Bending Deformation and Microstructure Evolution of Bainite Rail during Cooling Process after Rolling

作　　者：岑耀东[1] 陈林[1] 包喜荣[1] 李晓娜[1] CEN Yaodong;CHEN Lin;BAO Xirong;LI Xiaona(School of Materials and Metallurgy,Inner Mongolia University of Science and Technology,Baotou 014010)

机构地区：[1]内蒙古科技大学材料与冶金学院,包头014010

出　　处：《机械工程学报》2024年第14期139-152,共14页Journal of Mechanical Engineering

基　　金：国家自然科学基金(51361021);内蒙古自治区重点研发和成果转化计划(2023YFHH0036);内蒙古自治区直属高校基本科研业务费(2023QNJS002,2023YXXS007)资助项目。

摘　　要：道岔钢轨由于具有非对称的横断面特征使其轧制、热处理、矫直等工艺非常复杂,生产难度极大。针对道岔贝氏体钢轨的平直度和残余应力兼顾问题,通过Gleeble-1500热模拟试验机测定了CCT曲线,采用扫描电镜(Scanningelectron microscope,SEM)观察了不同冷速下的微观组织,利用有限元软件进行了相变前与相变区间控制冷却的模拟计算。结果表明,当未变形的奥氏体以0.05~1℃/s的冷速连续冷却时,随着冷速的增快,组织由粒状贝氏体逐步转变为马氏体。当变形处理的奥氏体以0.2~2℃/s的冷速连续冷却时,随着冷速的增快,组织由粒状贝氏体逐步转变为大量马氏体+少量板条贝氏体;相变区间控制冷却采用轨头表面中心冷至500℃,再由500℃冷却到300℃(钢轨表面冷速0.4℃/s),然后空冷至室温可得到的贝氏体量为35.6%,纵向最大拉应力、最大压应力及最终Y方向和Z方向的弯曲挠度均符合要求。相变前控制冷却采用轨头表面中心冷至500℃(轨头上表面及非工作侧和轨腰冷速3℃/s,轨头工作侧3.5℃/s),再由500℃空冷至室温后可得到99.3%贝氏体组织的同时,最终残余应力值及弯曲挠度均符合要求。通过控制冷却实现了减小弯曲变形度和降低矫后残余应力的目的。Due to the asymmetric cross-sectional characteristics of turnout rail,the rolling,heat treatment and straightening processes are very complex and the production is very difficult.In view of the flatness and residual stress of turnout bainite rail,the CCT curve was measured by Gleeble-1500,the microstructure under different cooling rates was observed by SEM,and the simulation calculation of controlled cooling before and between phase transformation was carried out by finite element software.The results show that with the increase of cooling rate,when the undeformed austenite is continuously cooled at the cooling rate of 0.05-1℃/s,the microstructure gradually changes from granular bainite to martensite.When the deformed austenite is continuously cooled at the cooling rate of 0.2-2℃/s,the microstructure gradually changes from granular bainite to a large amount of martensite+a little of lath bainite;Controlled cooling in phase change section adopts cooling the center of rail head surface to 500℃,then cooling from 500℃to 300℃(cooling rate of rail surface is 0.4℃/s),and then air cooling to room temperature to obtain bainite volume of 35.6%,The final maximum tensile stress,maximum compressive stress,bending deflection in“Y”direction and“Z”direction meet the requirements.Before phase transformation,the center of rail head surface is cooled to 500℃(the cooling rate of rail head upper surface,non working side and rail waist is 3℃/s,and the working side of rail head is 3.5℃/s).After air cooling from 500℃to room temperature,99.3%bainite structure can be obtained.The final residual stress value and bending deflection meet the requirements.The purpose of reducing bending deformation and residual stress after straightening is realized by controlling cooling.

关 键 词：道岔钢轨 贝氏体 控制冷却 组织 

分 类 号：TG156[金属学及工艺—热处理]