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用扫描电镜(SEM)对长期运行后的U71Mn钢轨踏面马氏体白层组织进行了分析。结果得出,曲线段钢轨踏面白层较直线段白层厚度深,硬度更高。随距表面距离增加,曲线段钢轨踏面白层内原奥氏体晶粒分别呈等轴状、长条状和非常细小的等轴状,原奥氏体晶粒内的马氏体形态随深度的增加,由以片状马氏体为主逐渐转变为以板条状为主的混合马氏体;而直线段钢轨踏面白层内原奥氏体晶粒均为长条状,且长轴方向平行于踏面,原奥氏体晶粒内为以板条状马氏体为主的混合马氏体。结合分析结果和可能的运行情况,作者认为,出现上述结果的主要原因是在钢轨使用过程中,由于蠕滑等原因造成表面温度急剧升高,超过了奥氏体的形成温度,使得组织中的碳化物发生不同程度的溶解,形成的奥氏体晶粒形状和大小,以及随后的快速冷却过程中得到的马氏体形态也与这种快速冷热循环有关。
The long-run U71Mn rail tread martensite white layer was analyzed by scanning electron microscopy (SEM). The result shows that the white layer of the rail tread of the curved section is deeper than the white layer of the straight section and has a higher hardness. As the distance from the surface increases, the original austenite grains in the white layer of the rail tread of the curve section are equiaxed, elongated and very fine equiaxed. The martensite morphology of the original austenite grains varies with the depth Increased mainly from lamellar martensite to lath-based mixed martensite; whereas the straight austenite grains in the white layer of the rail tread of the straight section were long strips and the long axis directions were parallel In the tread, the original austenite grain lath martensite-based mixed martensite. According to the analysis results and the possible operation conditions, the author believes that the main reason for the above results is that the surface temperature rises sharply due to creep and other reasons during the use of rails, exceeding the formation temperature of austenite, making the The carbides dissolve to varying degrees, the shape and size of the austenite grains formed, and the martensite morphology obtained during the subsequent rapid cooling are also related to this rapid cooling and heating cycle.