2007 Volume 47 Issue 5 Pages 699-708
In the deoxidation process of molten steel with magnesium vapor produced in situ by aluminothermic reduction of magnesium oxide, the formed inclusions are usually small in size and of spherical shape. They tend not to aggregate and form cluster. The MgO content in the inclusions decreases, while the SiO2 content increases with the progress of experiment. Larger inclusions are removed by floating up with the rising bubbles more easily and the fine inclusions tend to remain in the melt. The oxygen concentrations originated from the inclusions can be reasonably explained from the experimental analysis ones.
By use of the MgO porous immersion tube, deoxidation proceeds slowly at the initial stage, but it continues until the later stage of experiment, in contrast to that using the dense Al2O3 immersion tube. The formed inclusion number per unit area has a larger value than that with the dense Al2O3 tube. The number of inclusions also increases with increasing the initial oxygen concentration and dividing pellets charging into several portions. When the carrier gas flow rate is large, the number of inclusions tends to increase at the later stage of experiment due to the strong involvement of inclusions from the melt surface into the melt.
In the present deoxidation process, it is considered that the rapid removal of larger inclusions by rising bubbles is beneficial to produce high cleanness steel, while the remaining fine inclusions is helpful for the grain refinement of steel during the solidification and phase transformation process.