| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat-up method by blowing oxygen into a medium or high carbon steel, with which to the medium or high carbon steel having >=0.3 mass% target carbon content as the object, while restraining decarburizing reaction for bringing about troubles to the adjustment of the target carbon content, the surrounding equipment of a ladle refining or casting operation, etc,. the medium or high carbon steel can be heated up with a high efficiency. SOLUTION: In the heat-up method of the molten steel in the ladle by dipping an immersion tube into the molten steel in the ladle to blow gaseous oxygen through a top-blown lance onto the molten steel surface in the immersion tube, while stirring the molten steel having >=0.3 mass% C content in the ladle by blowing inert gas from the bottom part in the ladle, after beforehand charging oxidizing agent into the molten steel, a distance L between the tip part of the top-blown lance and the molten steel static surface in the immersion tube is regulated to the distance satisfying the value having >=0.006εin the following equation (1).ε=0.06/[C].(Fo22/3.exp(-63L/(Fo2/d)2/3)0.5.[1+Fo22/3.exp(-63L /(Fo2/d)2/3)/L)]...(1). Wherein, [C]: the target carbon content (mass%), Fo2: oxygen flow rate [m3/(h.t)] and d: diameter (m) of the top-blown lance hole.
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