high quality tunnel bolt is a key component of railway track. Proper heat treatment process is a necessary condition for the production of high quality tunnel bolt. high quality tunnel bolt is a malleable part that is connected with bolts. The partition board is constituted together, collectively referred to as the scaffold fastener. The high quality tunnel bolt fastener is the key component of the rail, and the rail and cement sleeper are connected together according to the elastic fastener. The raw material of high quality tunnel bolt is 60Si2MnA hot-tie tool steel used for the production of high quality tunnel bolt, and its composition and surface carburizing layer do not exceed 1% of the diameter. Grain size ≥7 grade. High purity graphite carbon composition ≤1.5 agent. The key steps of high quality tunnel bolt production are feeding → high frequency non-contact heating → stamping die forming → oil cold fire → medium temperature quenching → shot peening → anti-corrosion solution. The characteristics and mechanism of high quality tunnel bolt stipulate that the strength after exposure to fire should be HRC60. The strength after quenching should be HRC44-48, and the high quality tunnel bolt is unbreakable after 300-5m fatigue tests, and the residual deformation should not exceed 1.b250m. Heat treatment process, the workpiece is put into the induction switch (electromagnetic coil), when the induction switch reaches a certain frequency of alternating current, the surrounding electromagnetic field is caused by alternating changes. The magnetic effect of alternating changing electromagnetic field currents causes a closed induced electromotive force - vortex in the workpiece. The induced electromotive force is very uneven across the cross section of the workpiece, the surface current intensity of the workpiece is very high, and it is slowly reduced inward, which is called the skin effect. The electromagnetic energy of the high-density electric flux on the surface of the workpiece changes into energy, so that the temperature of the surface rises, that is, the surface heating is completed. The higher the frequency of current flow, the greater the difference of current intensity between the surface and the inside of the workpiece, and the thinner the heating layer. After the temperature of the heating layer exceeds the zero boundary point temperature of the steel, the surface fire and heat treatment process can be completed. It is expected that according to this information content, we can improve the heating treatment process of the railway bullet, and master what is the railway bullet and its key role.
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