| 摘要 |
PURPOSE:To effectively execute denitrogenization by CO bubble, by blowing oxygen gas in molten steel under reduced pressure, maintaining oxygen concn. in the molten steel at less than the specific value and maintaining C content in the molten steel at more than the specific value. CONSTITUTION:The oxygen gas is blown into the molten steel under reduced pressure. The oxygen gas is reacted with C in the steel to generate the CO bubble and denitrogenized reaction is promoted. Then, by blowing intermittently the oxygen gas or by blowing continuously a little quantity of the oxygen gas, the denitrogenization is effectively executed under maintaining O concn. in the molten steel to <=140ppm till N concn. in the molten steel is become to <=35ppm. Further, if necessary, carburizing agent is added into the molten steel to maintain C content in the steel to >=0.05%, and the denitrogenization is further effectively executed.
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