A computer aided finite element/experimental analysis of induction heating process of steel

Abstract

The characteristics of steels during electroplating or induction heating are very complex. Induction heat-treating of steel has become increasingly important as a means of reducing cost and improving the quality of carbon steel components. The use of high frequency (40 to 200kHz) offers many advantages, but tooling and cycle optimization is complex and time consuming. Approximate analytical methods suitable for low-frequency approximations are not sufficient for the low-frequency domain and the fact that important material properties change drastically with temperature makes more exact analysis methods very difficult to implement. Therefore, a powerful computer aided numerical tool (i.e., finite element analysis) is selected to numerically model an induction heating process. A general-purpose finite element program was employed to simulate and analyze the above problem. The combination of magnetic and thermal routines, within the package, enabled us to complete the task. A coupling method between the two magnetic and thermal routines was also developed and implemented. This was done to incorporate the change in the material properties due to the change in temperature. For the sake of comparison and verification, a high-frequency induction heating experiment was set up and a series of tests was performed. The finite element results were evaluated and compared with the experimental results. The effect of the time duration size (time step) for coupling between the magnetic and thermal analyses was also studied. Particular attention was given to the coupling procedure after the Curie temperature was reached. The skin effect was studied and demonstrated in the numerical model. A discussion of induced power density profile and transient temperature distribution is also presented. The accuracy and efficiency of the numerical models are demonstrated and appreciated. This tool is therefore proposed to be a powerful alternative prior to the actual induction heating process.