Features of heating technology at induction thermal processing with external electromagnetic field

According to the data of performed calculations and modeling of the hardening process, a design of inductors with magnetic cores for hardening long flat parts has been developed. At the design stage of this type of inductors, it was necessary to find out the degree of influence of the magnetic circuit design on the distribution of the temperature field during heating. To do this, we simulated electromagnetic and temperature fields to assess the concentration of the electromagnetic field at different heights of the “legs” of the inductor. As a result, a significant effect of the length of the “legs” of the magnetic circuit on the intensity of heating and the operability of the system as a whole was established. It is noted that insufficient height of the “leg” leads to a significant decrease in the field concentration, which leads to insufficient heating temperature and uneven distribution of heat zones in the heated part. In turn, an increase in the height of the “legs” leads to a narrowing of the heat release zone in the part compared to the total width of the coil and magnetic circuit. With a significant lengthening of the “legs”, the cooling circuit of the inductor will not be able to remove heat from the magnetic circuit obtained from the part, which will lead to the destruction of the magnetic circuit. The developed design of a two-turn single-circuit inductor and the general methodology made it possible to obtain a high-quality hardened layer with a depth of up to 3 mm with the formation of a martensitic structure of the required hardness on a planar-type flat part without significant energy loss. The part was machined by fixing it on a rigid base to compensate for the effect of temperature changes in linear dimensions. To obtain a uniform gap between the part and the inductor, a special pressure roller was used. The resulting structure of the hardened layer adequately meets the stated requirements for the part. The results of the research were used to develop a flat part of the “guide” type for lifting equipment (for example, a guide for the movement of the traction chain) and were introduced into production.

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