| 摘要 |
PROBLEM TO BE SOLVED: To make fine oxide size existing in molten steel at a low cost by adding specified ratios of MgO and metallic Al into the molten steel. SOLUTION: The MgO and the metallic Al of >=0.2 kg/kg of MgO, are added and mixed into the molten steel. In order to improve the reaction efficiency, it is desirable that the sizes of MgO and metallic Al are <=10μm. C in the molten steel before adding Mg alloy is regulated to <=1.2 wt.% to prevent the formation of MgC. The pre-deoxidation is executed by beforehand containing Si and Mn in the molten steel to reduce the Mg quantity consumed to the deoxidation. When the MgO and the metallic Al are charged into the molten steel, the metallic Al reduces MgO to generate Mg gas. The Mg gas is reacted with oxygen in the molten steel and MgO is produced and Al2O3 easily coagulated and coarsened, is reformed and the composition is made to Al2O3.MgO or MgO and the oxide is made to fine. The inexpensive MgO and metallic Al are used and the oxide is made to fine in the same degree as the using time of an expensive metallic Mg.
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