工程科学学报.第42卷，第6期：747-754.2020年6月 Chinese Journal of Engineering,Vol.42,No.6:747-754,June 2020 https://doi.org/10.13374/j.issn2095-9389.2019.06.27.002;http://cje.ustb.edu.cn 含有上贝氏体的ER8车轮钢的裂纹扩展行为 李迁，赵爱民四，郭军，裴伟，刘素鹏 北京科技大学钢铁共性技术协同创新中心，北京100083 ☒通信作者，E-mail:zhaoaimin@ustb.edu.cn 摘要研究不同含量的上贝氏体对ER8车轮钢裂纹扩展行为的影响.利用激光共聚焦显微镜(LSCM)和扫描电镜(SEM) 对ER8车轮钢的显微组织和裂纹扩展路径进行了研究.实验结果表明：ER8车轮钢中的组织除了有铁素体和珠光体，还存在 上贝氏体；裂纹穿过上贝氏体和珠光体扩展，最终停止在珠光体区域：与珠光体组织相比，裂纹在上贝氏体中的扩展路径更曲 折.利用扫描电镜(SEM)对ER8车轮钢的裂纹扩展变形进行原位观察.实验结果表明：含有80%上贝氏体的ER8车轮钢拉 伸时，组织变形过程主要以铁素体和上贝氏体为主，裂纹在上贝氏体和珠光体中连续扩展，伴随着珠光体的变形：而含有 50%上贝氏体的ER8车轮钢拉伸时，组织变形过程主要以铁素体和珠光体为主，并且上贝氏体对铁素体和珠光体的变形起 到阻碍作用.上贝氏体能够有效地阻止裂纹扩展，在偏转裂纹路径和延缓裂纹扩展方面起着重要作用：并且对铁素体和珠光 体的变形起到阻碍作用. 关键词ER8车轮钢：上贝氏体：裂纹；原位拉伸：塑性变形 分类号TG142.1 Crack propagation behavior of ER&wheel steel containing upper bainite LI Qian,ZHAO Ai-min,GUO Jun,PEI Wei,LIU Su-peng Collaborative Innovation Center of Steel Technology,University of Science and Technology Beijing,Beijing 100083,China Corresponding author,E-mail:zhaoaimin@ustb.edu.cn ABSTRACT In recently years,high-speed and heavy-haul railway technology has been rapidly developed and widely used in China Pearlite steel is usually used in railway wheels,and its structure is composed of pearlite and ferrite.Pearlite has properties,including mechanical properties,that combine those of ferrite and cementite,and it also has acceptable strength and toughness.The comprehensive mechanical properties of pearlite are better than those of ferrite or cementite alone.When upper bainite is produced after the heat- treatment of ER8 wheel steel,the upper bainite may become the channel of crack development because of the large carbide particles and the weak strengthening effect and especially because of the presence of flake ferrites.In this study,the influence of different contents of upper bainite on the crack propagation behavior of ER8 wheel steel was investigated.The microstructure and crack growth path of ER8 wheel steel were studied by laser scanning confocal microscopy (LSCM)and scanning electron microscopy (SEM).The experimental results show that ER wheel steels not only have ferrite and pearlite but also upper bainite.The crack propagates through the upper bainite and pearlite and finally stops in the pearlite region.Compared with the pearlite microstructure,the crack propagation path in the upper bainite is more tortuous.The crack propagation and deformation of ER8 wheel steels were observed in situ by scanning electron microscopy.The experimental results show that when ER8 iron wheel steel containing 80%upper bainite is stretched,the microstructure deformation process is mainly ferrite and upper bainite.The crack in the upper bainite and the pearlite continues to expand with the pearlite deformation.However,when ER8 iron wheel steel containing 50%upper bainite is stretched,the deformation process mainly involves ferrite and pearlite,and the upper bainite retards the ferrite and pearlite deformation.The upper bainite can effectively prevent 收稿日期：2019-06-27含有上贝氏体的 ER8 车轮钢的裂纹扩展行为 李    迁，赵爱民苣，郭    军，裴    伟，刘素鹏 北京科技大学钢铁共性技术协同创新中心，北京 100083 苣通信作者，E-mail：zhaoaimin@ustb.edu.cn 摘    要    研究不同含量的上贝氏体对 ER8 车轮钢裂纹扩展行为的影响. 利用激光共聚焦显微镜（LSCM）和扫描电镜（SEM） 对 ER8 车轮钢的显微组织和裂纹扩展路径进行了研究. 实验结果表明：ER8 车轮钢中的组织除了有铁素体和珠光体，还存在 上贝氏体；裂纹穿过上贝氏体和珠光体扩展，最终停止在珠光体区域；与珠光体组织相比，裂纹在上贝氏体中的扩展路径更曲 折. 利用扫描电镜（SEM）对 ER8 车轮钢的裂纹扩展变形进行原位观察. 实验结果表明：含有 80% 上贝氏体的 ER8 车轮钢拉 伸时，组织变形过程主要以铁素体和上贝氏体为主，裂纹在上贝氏体和珠光体中连续扩展，伴随着珠光体的变形；而含有 50% 上贝氏体的 ER8 车轮钢拉伸时，组织变形过程主要以铁素体和珠光体为主，并且上贝氏体对铁素体和珠光体的变形起 到阻碍作用. 上贝氏体能够有效地阻止裂纹扩展，在偏转裂纹路径和延缓裂纹扩展方面起着重要作用；并且对铁素体和珠光 体的变形起到阻碍作用. 关键词    ER8 车轮钢；上贝氏体；裂纹；原位拉伸；塑性变形 分类号    TG142.1 Crack propagation behavior of ER8 wheel steel containing upper bainite LI Qian，ZHAO Ai-min苣 ，GUO Jun，PEI Wei，LIU Su-peng Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China 苣 Corresponding author, E-mail: zhaoaimin@ustb.edu.cn ABSTRACT    In recently years, high-speed and heavy-haul railway technology has been rapidly developed and widely used in China. Pearlite steel is usually used in railway wheels, and its structure is composed of pearlite and ferrite. Pearlite has properties, including mechanical properties, that combine those of ferrite and cementite, and it also has acceptable strength and toughness. The comprehensive mechanical  properties  of  pearlite  are  better  than  those  of  ferrite  or  cementite  alone.  When  upper  bainite  is  produced  after  the  heat￾treatment of ER8 wheel steel, the upper bainite may become the channel of crack development because of the large carbide particles and the weak strengthening effect and especially because of the presence of flake ferrites. In this study, the influence of different contents of upper bainite on the crack propagation behavior of ER8 wheel steel was investigated. The microstructure and crack growth path of ER8 wheel steel were studied by laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM). The experimental results show that ER8 wheel steels not only have ferrite and pearlite but also upper bainite. The crack propagates through the upper bainite and pearlite and finally stops in the pearlite region. Compared with the pearlite microstructure, the crack propagation path in the upper bainite is more tortuous. The crack propagation and deformation of ER8 wheel steels were observed in situ by scanning electron microscopy. The experimental results show that when ER8 iron wheel steel containing 80% upper bainite is stretched, the microstructure deformation process is mainly ferrite and upper bainite. The crack in the upper bainite and the pearlite continues to expand with the pearlite deformation. However, when ER8 iron wheel steel containing 50% upper bainite is stretched, the deformation process mainly involves ferrite and pearlite, and the upper bainite retards the ferrite and pearlite deformation. The upper bainite can effectively prevent 收稿日期: 2019−06−27 工程科学学报，第 42 卷，第 6 期：747−754，2020 年 6 月 Chinese Journal of Engineering, Vol. 42, No. 6: 747−754, June 2020 https://doi.org/10.13374/j.issn2095-9389.2019.06.27.002; http://cje.ustb.edu.cn