PROCESS-CONTROL FOR THE VACUUM REFINING OF HIGH-CHROME STEELS

A computer-aided process control system has been developed in a cooperative project of the Betriebsforschungsinstitut and Krupp Stahl AG for the vacuum refining plant in Siegen-Geisweid. The decarburization rate, the carbon content, the melting loss rate of chromium and the bath temperature are calculated in cyclic balances. In the end phase of refining, a linear relationship exists between the decreasing decarburization rate and the carbon content, as indicated also by a dynamic process model. This allows a correction of the balanced carbon content, and makes it thus possible to calculate same with an increasing accuracy at the end of refining. The oxygen supply is controlled according to the demand of the decreasing decarburization rate in order to minimize the chromium melting loss.