Inductor for Uniform Bulk Heat Treatment of Welded Butt Joints of Railway Rails

Abstract

To improve the structure of metal in welded butt joints of railway rails produced by flash-butt welding and increase the reliability of butt joints, it is advisable to carry out their induction heat treatment using high-frequency currents. Solving the problem of a uniform bulk heating of weld metal of railway rails in a narrow area during its heat treatment remains an urgent task. The work describes the principle of designing an inductor without magnetic cores for carrying out a uniform bulk heat treatment of welded butt joints of railway rails for realization of favorable phase transformations of metal and normalization of its structure. The principle is based on the physical laws of propagation of electromagnetic fields and electric currents in the inductor and a rail. Based on the carried out investigations, an inductor was designed that has a variable shape along the perimeter of a rail and a variable distance from it, as well as a partial splitting of the inductor busbar for current parallelization, which provides a uniform bulk heating of a rail butt joint. Splitting of the inductor busbar allowed adjusting the propagation of currents in the inductor and a rail in such a way as to avoid overheating of a rail in its particular areas without a significant increase in the distance between the inductor and a rail, and respectively without a significant increase in the reactive power of the “inductor-product” system. The carried out experiments on heating the welded butt joint of a rail by the designed inductor showed the indices of uniformity and rate of its bulk heating, which are acceptable for heat treatment of rails both on the surface as well as in the depth of a rail in a narrow heating zone with providing the required temperature levels.