U20Mn和U78CrVH高强钢轨氢脆敏感性试验研究  

Research on Hydrogen Embrittlement Susceptibility of U20Mn and U78CrVH High Strength Rails

作　　者：张倩 吕晶 胡杰 吴广 张永健[2] 惠卫军[2] ZHANG Qian;LYU Jing;HU Jie;WU Guang;ZHANG Yongjian;HUI Weijun(Metals and Chemistry Research Institute,China Academy of Railway Sciences Corporation Limited,Beijing 100081,China;School of Mechanical Electronic and Control Engineering,Beijing Jiaotong University,Beijing 100044,China)

机构地区：[1]中国铁道科学研究院集团有限公司金属及化学研究所,北京100081 [2]北京交通大学机械与电子控制工程学院,北京100044

出　　处：《高速铁路新材料》2022年第6期8-15,共8页Advanced Materials of High Speed Railway

基　　金：中国铁道科学研究院集团有限公司基金项目(2020YJ084)。

摘　　要：利用氢热分析(TDS)试验研究了贝氏体钢轨U20Mn(轧制后250~280℃回火10 h以上)和在线热处理钢轨U78CrVH试样的氢吸附特征。同时,采用电化学预充氢及慢应变速率拉伸试验(SSRT)研究了光滑拉伸试样的氢脆敏感性,并利用扫描电子显微镜(SEM)观察了试样的断口形貌。结果表明:以相对断面收缩率损失率表征的氢脆敏感性指数,U78CrVH为63%,U20Mn为31%;U78CrVH断口形貌由解理+韧窝演变为穿晶+解理断裂,U20Mn钢断口形貌特征则变化不明显,为准解理+韧窝形貌。分析认为电化学充氢后U78CrVH钢中的氢基本被可逆氢陷阱所捕获,而U20Mn钢除大部分被可逆氢陷阱吸附外,仍有少部分氢被残余奥氏体等不可逆氢陷阱所吸附,这种氢吸附特征是在相同氢含量下,U20Mn钢较U78CrVH钢具有较低氢致塑性损失的主要原因之一,但在相同充氢条件下,U20Mn钢吸附的氢含量明显地高于U78CrVH钢,这种氢吸附特征对钢轨实际服役行为的影响有待深入分析。同时,对于U20Mn贝氏体钢轨而言,发生氢脆的过程更加复杂,尤其应重视钢中氢含量的控制和钢中亚稳态残余奥氏体对氢脆敏感性的影响。The hydrogen adsorption characteristics of U20Mn rails(tempered at 250~280 ℃ for more than10 h after rolling) and U78CrVH rails have been investigated by means of thermal desorption spectroscopy(TDS). Meanwhile, the hydrogen embrittlement susceptibility of smooth specimens were evaluated by electrochemical hydrogen charging and slow strain rate tests(SSRT), and the fracture morphology was also observed by scanning electron microscopy(SEM). The results showed that the hydrogen embrittlement susceptibility index of U78CrVH steel characterized by the loss rate of reduction of area is 63%,as well as U20Mn steel is 31%. The fracture morphology changes from cleavage+ dimple to transgranular+ cleavage,while the fracture morphology of U20Mn steel has no obvious change, which is quasi cleavage+ dimple morphology. After electrochemical hydrogen charging, all hydrogen in U78CrVH steel is captured by reversible hydrogen traps. In addition to most of the hydrogen in U20Mn steel is adsorbed by reversible hydrogen traps, minute quantities of hydrogen is still adsorbed by irreversible hydrogen traps such as retained austenite. This hydrogen adsorption feature is one of the main reasons why U20Mn steel has lower hydrogen induced plasticity loss than U78CrVH steel at the same hydrogen content, but the hydrogen content adsorbed by U20Mn steel under the same hydrogen charging conditions is significantly higher than that of U78CrVH steel. The influence of hydrogen adsorption characteristics on the actual service behavior of rails needs to be further analyzed. At the same time, the process of hydrogen embrittlement is more complex for U20Mn bainite rail, and more attention should be paid to the control of hydrogen content in steel and the influence of metastable retained austenite in steel on hydrogen embrittlement susceptibility.

关 键 词：高强钢轨 U20Mn U78CrVH 氢脆敏感性 氢吸附特征 

分 类 号：U231.41[交通运输工程—道路与铁道工程]