| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce particularly alumina base non-metallic inclusion by satisfying each specific condition before and after Al deoxidizing treatment of molten steel in the following process with respect to slag after reforming in a third process. SOLUTION: In the third process, after completing the tapping of molten steel, a reducing agent is added into new slag formed by consisting of the slag inevitably flowing into a ladle during tapping the molten steel and lime charged into the ladle to reform the new slag. In the following process, a vacuum decarburizing treatment and the deoxidizing treatment are applied to the molten steel in the ladle covering the upper surface with the reformed slag by using a vacuum degassing apparatus. At this time, the slag before deoxidizing treatment, is regulated to in the range of 3.0-7.0 basicity shown with CaO/SiO2 and in the range of 30-45% Al2O3 content shown by Al2O3/(Al2O3+SiO2+ CaO)}×100(%) and the slag after deoxidizing treatment, is regulated to <=5.0 wt.% T.Fe content. Wherein, each component content in the slag is shown by the wt.%.</p> |
