Improvement of Steel Cleanliness by Deoxidation With Mg Vapor

摘要

The purpose of present work is to study the distributions and characteristics of the inclusions after deoxidation process of molten steel with magnesium vapor produced in situ by aluminothermic reduction of magnesium oxide. A high frequency induction furnace was used to melt electrolytic iron of 360 g in the magnesia crucible of 40 mm i.d. and 100 mm in height. The crucible contained 98% MgO and 1% CaO. The pellets containing MgO and Al were charged into an immersion tube. The Mg vapor produced in situ by aluminothermic reduction of magnesium oxide was directly injected into the melt with argon gas for deoxidation. It was found that most of the inclusions were floated up to the melt surface after deoxidation. The thickness of inclusion layer on the melt surface was increased with the progress of deoxidation and it mainly contained MgO. Some inclusions were also found near the surface layer, the side and the bottom wall of the crucible. This indicates that the inclusions could be also removed from the melt by adsorption onto the crucible wall. The inclusion number per unit area inside the ingot was rather uniform in the vertical direction. It increased at the initial stage of deoxidation due to the fast rate of aluminothermic reduction of magnesium oxide, and decreased at the later stage because most of the produced inclusions were removed from the melt by floating up with the rising argon bubbles. In the present deoxidation process, the harmful impact of the large deoxidation products on the mechanical properties of steel such is minimized.