220 – Induction Hardening Analysis Including the Cooling Process for Gears

Application Note / Model Data

Overview

Gears are created in such a way that the surfaces of their teeth are hard in order to resist the wear and tear that occurs when they come into contact with the teeth of other gears. However, this has to be accomplished while maintaining the gear’s overall toughness. In induction hardening, which is one of the surface hardening methods, it is possible to locally rapidly heat and harden only the tooth surface.
In the induction hardening heating process, it is necessary to uniformly heat the surface of the gear. It is also necessary to reduce time in order to suppress oxidation, decarbonization, and deformation in the cooling process at the same time. For this reason, the cooling rate is an important factor affecting the mechanical properties of the heated object.
In order to accurately obtain the temperature change of the heated object using induction heating analysis, not only does heat generated in the workpiece by electromagnetic induction need to be accurately expressed, temperature must be calculated with consideration of changes in temperature and physical properties due to heat generation. For this purpose, a two-way coupled analysis of electromagnetic field analysis and thermal analysis is required.
In this example, inductive heating calculation including the cooling process are handled. The cooling process is simulated using the time dependencies of the heat transfer boundary and the reference temperature, and we introduce examples where the cooling speed of the gear differs between water cooling and air cooling.

Gear Temperature Distribution and Timing of Temperature Changes

Fig. 1 shows the temperature distribution of the gear, and Fig. 2 shows the timing of the temperature change of the teeth tips. From the displayed temperature distribution, it is apparent that the eddy currents generate heat in the teeth tips. Fig. 2 shows the change in temperature at the center of a tooth’s width (point of measurement) shown in Fig. 1. It can be verified that water cooling is faster than the air cooling, and that its cooling is more effective.

Gear Temperature Distribution and Timing of Temperature Changes

Fig. 1 shows the temperature distribution of the gear, and Fig. 2 shows the timing of the temperature change of the teeth tips. From the displayed temperature distribution, it is apparent that the eddy currents generate heat in the teeth tips. Fig. 2 shows the change in temperature at the center of a tooth’s width (point of measurement) shown in Fig. 1. It can be verified that water cooling is faster than the air cooling, and that its cooling is more effective.

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