PURPOSE: To restrain the initial spouting of a molten steel at the time proximate to the final period of desiliconization by a method wherein the feed rate of top-blown and/or bottom-blown oxygen is regulated in accordance with the results of detection of vibration of a lance for the top-blown oxygen or a lance for vibration measurement in a blow refining period proximate to the time of finishing the desiliconizing reaction.

CONSTITUTION: The molten steel 2 in the furnace body 1 of the converter is refined by blowing oxygen to the molten steel 2 respectively through the lance 4 for the top-blown oxygen and through a tuyere 3 for the bottom- blown oxygen. In the proximity of the time of finishing the desiliconizing reaction by the blow refining, the waveform of the vibration generated at the lance 4 is detected by an accelerometer 8, and the occurrence of the initial spouting phenomenon of the molten steel is predicted based on the vibration detected. In order to prevent the initial spouting, the feed rate of the top-blown oxygen is reduced first, and when the vibration of the lance 4 is not yet alleviated, the feed rate of the bottom-blown oxygen is also reduced. Thereafter, when the vibration of the lance is reduced, the feed rate of the bottom-blown oxygen is gradually increased in accordance with the reduction of vibration, and after confirming that the vibration does not increase, the feed rate of the top-blown oxygen is also increased to recover a predetermined feed rate of oxygen. In the figure, numeral 9 represents a waveform converter and numeral 10 represents a recording potentiometer.