SLAG DETECTING METHOD OF MOLTEN METAL VESSEL

PURPOSE:To effectively prevent a slag from being mixed into an outflow molten metal flow, by applying in advance a high-frequency current to a molten metal, and discriminating the molten metal and the slag by a variation of electric current. CONSTITUTION:When depth of molten steel in a converter A has become a prescribed value, a conductive slag stopper 5 is inserted into the converter A, and a steel outflow port 2 is stopped by the lower end of the stopper. Subsequnently, after a prescribed interval of time has passed, the stopper is raised by a set extent, and outflow of steel is started again. At the initial period of steel outflow, the stopper 5 and a shell 4 are in conduction of a high frequency current by molten steel 2, therefore, voltmeters 10, 11 provided on a conduction line 7 are deflected by a set value. As a contact substance of the tip of the stopper is changed to a slag 1, however, a phase shift is generated between the voltmeters 10, 11, and it is brought to a comparator 14 through a phase comparator 12 and an integration circuit 13. When the phase shift exceeds a set value, the comparator 14 sends a prescribed control signal to a driving mechanism of the stopper 5, the stopper is lowered again, and an outflow molten metal flow is controlled or stopped.