Effects of Coil Configuration on Residual Stress and Hardened Layer of Shafts Due to Induction Hardening.

Abstract

This paper presents a study on effects of coil configuration on residual stresses and hardened layers of shafts due to the stationary induction hardening. Amounts of heat due to the eddy current induced in the shaft were calculated for various coil configurations by the FEM electromagnetic field analysis method, and the effects of the heating condition (electric power and frequency) and the coil configuration on the amount of heat were examined. An electromagnetic field analysis, a heat conduction analysis, and an elastic-plastic stress analysis during the induction hardening process of the shaft were carried out for various heating conditions and coil configurations by the FEM, considering changes of the magnetic permeability, the resistivity, the thermal expansion coefficient and the yield stress with the temperature. The effects of the heating condition and the coil configuration on the temperature and the stress changes during the induction hardening process, the residual stress and the hardness distribution were determined. On the basis of these calculated results, a selecting method of optimum heating condition and coil length for the residual stress and the hardened layer was indicated.