METHOD FOR DISCRIMINATING SLAG AT FIRING POINT, AND METHOD FOR DEPHOSPHORIZING MOLTEN IRON BASED ON THE METHOD

PROBLEM TO BE SOLVED: To establish a method for discriminating whether slag exists or not in a firing point formed at a collision point when oxygen-containing gas is blown toward molten iron surface or molten steel surface and also discriminating a molten state of the slag. SOLUTION: When oxygen or mixed gas containing oxygen is blown toward the molten iron surface or the molten steel surface, the temperature of the firing point formed at the collision point, is measured, and the measured temperature at the firing point is compared with a solidus temperature and a liquidus temperature of the slag floated up on the molten iron surface or the molten steel surface, and a solidus temperature and a liquidus temperature of the molten iron and the molten steel, to discriminate whether or not the slag at the firing point exists and the molten state of the slag.