重轨轨头廓形尺寸精度控制的有限元分析

重轨轨头的廓形精度是衡量高速铁路用钢轨质量水平的重要指标之一。采用有限元方法对半万能工艺下UF轧制过程进行了模拟,通过对比实验,分析了来料宽度、水平辊压下量及腹高差值变化对轨头与轨腰间金属横向流动及轨头廓形成形精度的影响。结果表明,轨头部分来料宽度变化对轨头与轨腰间金属横向流动基本无影响;水平辊压下使轨腰金属向轨头流动,使轨头展宽量增大;腹高差值使轨头金属向轨腰流动,使轨头展宽量减小,在两者综合作用下,轨头金属最终向轨腰流动,造成轨头金属量减少,孔型设计时应考虑此偏差造成的头腰延伸率不匹配及廓形充满度问题。轨头部分来料宽度变化会直接改变轨头金属量进而影响其廓形精度,孔型过充满后,来料宽度增加引起的轨头展宽量显著增加;腹高差值过大或水平辊压下量过大均会加剧轨头与轨腰间金属横向流动,不利于降低钢轨轧后残余应力。

Finite element analysis of dimension precision control of heavy rail head profile

Dimension precision of heavy rail head profile is an important index to estimate the quality of rails for high speed railway. The finite element method was used to simulate half-universal finish pass rolling. The effects of dimensional change, rolling reduction and difference of wedge height on metal transverse flow and precision of rail head profile was analyzed though the contrast simulation experiments. The results show that the change in the width of the incoming material at the rail head has basically no effect on the metal transverse flow between the rail head and the rail web. The horizontal rolling reduction causes the rail web metal to flow to the rail head, which increases the width of the rail head.The wedge height difference causes the rail head metal flows to the rail web, which reduces the rail head spreading. Under the combined effect, the rail head metal eventually flows to the rail web, resulting in a reduction in the amount of rail head metal. The pass design should consider the profile fullness problems caused by this deviation. The change in the incoming material width of the rail head will directly change the metal amount of the rail head and affect its profile accuracy. After the groove is overfilled, the increase in the incoming material width will cause the rail head to increase significantly; the wedge height difference or the horizontal rolling reduction is too large will aggravate the metal transverse flow between the rail head and the rail web, which is not conducive to reducing the residual stress of the rail after rolling.