Analysis of temperature distribution in a billet by induction heating.

In order to understand the temperature distribution in a billet at the induction heating stage of extrusion process, a computer analysis program is developed and some results of its application are presented in this work.Three coils were linearly arranged, and two billets were inserted into the coils one after another, and then were heated up to the pre-determined temperature in two steps, that is, pre-heating step and main heating step.Repeated numerical calculation were carried out, considering Joule heat due to induced current, heat conduction and radiation from surface of the billet.The temperature distribution in the billet at pre-heating step, main heating step and just before insertion into the container were given on an isothermal map.The computer analysis on 155, 204, 254 and 307mm diameter billets showed that the thicker billet had the more uneven radially temperature distribution, and that at the warming-up stage of induction heater for the thicker billet each main heating time was unstabler, and the poorer temperature distribution was obtained.