可动心轨辙叉长心轨跟端掉块原因分析及预防措施

Causes Analysis and Preventive Measures of Falling Block at the Heel of the Long Point of the Movable Point Frog

为了查明可动心轨辙叉长心轨跟端掉块的原因,分析掉块位置的宏观形貌、金相组织、扫描电镜观形貌和能谱。结果表明:在中频感应加热过程中,由于温度过高,长心轨跟端轨肢与轨腰圆弧处过热,形成较深的脱碳层;在高温下,粗大的奥氏体晶粒区域形成硫化物组织,使晶界脆化,钢轨的塑性和冲击韧性明显降低。在锻压过程中,钢轨出现裂纹。在正火过程中,未能有效消除高温形成的硫化物。在后续加工过程中,由于外力的作用,裂纹向轨底和轨底角分别呈一定角度扩展,直至掉块脱落。据此提出相应预防措施。

In order to identify the cause of the falling block at the heel of the long point of the movable point switch,the macroscopic morphology,metallographic structure,scanning electron microscopy observation,and energy spec⁃trum of the fracture surface of the position of falling block were analyzed.The results show that during the intermediate frequency induction heating process,overheating occurs at the arc between the rail limb and the rail waist of the heel of the long point due to the high temperature,and a deeper decarburization layer is formed.Under high temperature,sul⁃fide structures are formed at the coarse austenite grain area,which causes grain boundary embrittlement,and signifi⁃cantly reduces the plasticity and impact toughness of the rail.During the forging process,cracks appear on the rails.Sulfides formed at high temperatures were not effectively eliminated during the normalization process.In the subse⁃quent processing,due to the action of external forces,cracks extend at certain angles to the bottom of the rail and the corner of the rail bottom,until the blocks fall off.Based on this,corresponding preventive measures are proposed.