PURPOSE: To protect erosion of furnace inner wall by specifying TiO2 and MgO contents in molten slag and basicity of the slag at the time of refining molten iron in the metal refining furnace of the type stirring the molten metal and the molten slag in the furnace by gas blowing.

CONSTITUTION: In the case of promoting reduction refining reaction while stirring the molten metal 19 and the molten slag 20 on this by blowing inert gas, etc., into the molten metal 19 of the molten iron, etc., from furnace bottom tuyere 6, the furnace inner wall refractory 32 has fear of erosion by vigorous flow of the molten metal 19 and the molten slag 20. In this case, by using iron sand containing much TiO2 content together with raw material iron ore 7, the produced molten slat 20 is made to 7W15wt.% TiO2 content, 10W18wt.% MgO content and ≥1.0 value of the basicity (CaO/SiO2). The reduction of TiO2 in the molten slag 20 is promoted to come to Ti, and C and N in the molten pig 19 are reacted to come to TiC and TiN and they are stuck to the furnace inner wall to protect it, and service life of the refining furnace 4 is extended.