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钢轨焊接接头电感应加热数值模拟及工艺

Numerical simulation and technology of electric induction heating for welded joints of rail

  • 摘要: 钢轨在经历闪光焊高温加热之后,焊缝及热影响区晶粒比较粗大,同时在此过程中,当氧化物夹杂残留在接头中时,容易萌生裂纹源,使用感应加热对钢轨焊接接头进行焊后热处理,可以细化晶粒改善组织性能,减小残余应力,有利于线路运营与维护.文中建立了钢轨开合式线圈的感应加热有限元模型,研究了感应加热过程中温度场和组织的转变过程,基于有限元仿真获得了钢轨指定路径上的温度分布,以温度均匀度作为响应值进行响应曲面试验,优化正火工艺参数.结果表明,在感应加热过程中热量呈仿形向内部非均匀传递,当单频的加热时间为120 s时,热量的最大值位于轨底角区域;当加热到45 s时轨底角区域会最先发生奥氏体转变,影响钢轨电感应加热温度均匀性的因素依次为加热功率、线圈间距、频率,同时通过响应曲面法优化试验,得到温度均匀度的加热最优解,温度均匀度能够达到97.479%,通过试验验证计算值与试验值之间最大平均相对误差在4.95%以内,验证了模型的可靠性.

     

    Abstract: After the rail is heated at high temperature by flash welding, the grains of the weld and the heat-affected zone are relatively coarse, and at the same time, when the oxide inclusions remain in the joint during the flash welding process, it is easy to germinate the crack source. The use of induction heating to perform post-weld heat treatment of rail welded joints can refine the grains to achieve the purpose of improving the microstructure and reducing the residual stress, which is conducive to the operation and maintenance of the line. In this paper, a finite element model of induction heating for open-close coil of rail was established, and the transformation process of temperature field and microstructure during induction heating was studied. Based on the finite element simulation, the temperature distribution along the specified path of rail was obtained. The response surface experiment was carried out with temperature uniformity as the response value, and the normalizing process parameters were optimized. The results show that heat transfer to the interior is non-uniform in the process of induction heating. When heating to 45s, the first austenitic transformation will occur in the bottom Angle of the rail. The order of significance of factors affecting the temperature uniformity of rail induction heating is heating power, coil spacing and frequency in descending order. The maximum average relative error between the calculated value and the experimental value is less than 4.95%, which verifies the reliability of the model established in this paper.

     

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