Residual Stress and Hardened Layer of Shouldered Shafts Due to Dual Frequency Induction Hardening.

Abstract

This paper presents a study on residual stress and hardened layer of shouldered shafts due to dual frequency induction hardening (using both high- and low-frequency heat sources). Amounts of heat due to eddy current induced in the shouldered shaft were calculated by the FEM electromagnetic field analysis method, and the effect of the frequency on the amounts of heat was examined. An electromagnetic field analysis, a heat conduction analysis, and an elastic-plastic stress analysis during the single and the dual frequency induction hardening process of the shouldered shaft were carried out 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 induction hardening method on the temperature and the stress changes during the induction hardening process, the residual stress and the hardened layer were determined. The validity of the dual frequency induction hardening method for the shouldered shaft was confirmed. Furthermore, a method of determining optimum coil configuration and hardening condition was indicated.