Power limits and carburization behavior of induction crucible furnaces

E. Baake - A. Muhlbauer

Abstract
The limit of maximum installed furnace power as a function of frequency, furnace employed, as well as of the filling ratio for the medium frequency (MF) induction crucible furnaces is still largely unknown. The MF crucible furnaces exhibit also problems during carbonization in a predeterminated superheating time interval as a result of a lower bath circulation in practical operation when compared with the line-frequency induction crucible furnaces. To establish a guideline for the dimensioning of the furnace power at the transition from the line frequency to the medium ones and to improve the carbonization behaviour, this article deals with numerical calculations of the flow velocity field in the melt and the mean kinetic energy that can be derived from it using industrial and model furnaces. The experimental studies accompanying these calculations serve to check and substantiate the numerical model. A new rule has been derived for the power increase at the transition from the line-frequency to the medium ones with the bath circulation kept constant. In order to assess the carbonization behaviour, the distribution of turbulent kinetic energy is determined experimentally as a function of frequency and the furnace level. It can be demonstrated that between the upper and lower flow velocity toroids, i. e. in the region with small average velocities, the turbulent kinetic energy is very large, so that the mass transfer there is primarily caused by the turbulent diffusion. Fig. 9, ref. 19.