MOLTEN STEEL SECONDARY REFINING METHOD AND STEEL PRODUCTION METHOD

A method for secondarily refining molten steel s by which a low nitrogen concentration range can be stably reached at high speed without causing operational problems, and a method of producing steel are proposed. In the method for secondarily refining molten steel, CaO-and-Al2O3-containing slag is formed by a combination of an Al addition step of adding a metal-Al-containing substance to molten steel to turn the molten steel into Al-containing molten steel and a CaO addition step of adding a CaO-containing substance to the molten steel, and then an oxygen blowing process including a denitrification process is performed by blowing oxygen-containing gas so as to pierce the slag to reach the Al-containing molten steel, in which an Al concentration [Al]i (mass%) in the molten steel immediately before the oxygen blowing process is equal to or higher than a value [Al]e calculated by Formula (A) based on a stirring power density ε (W/t) during formation of the slag, and an Al concentration [Al]f upon completion of the oxygen blowing process is 0.03 mass% or higher. In the method of producing steel, the obtained molten steel is cast after adjusting the composition. Ale=−0.072×lnε+0.5822