Behavior of Inclusions in Deoxidation Process of Molten Steel with <i>in Situ</i> Produced Mg Vapor

Abstract

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 SiO 2 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 Al 2 O 3 immersion tube. The formed inclusion number per unit area has a larger value than that with the dense Al 2 O 3 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.KEY WORDS: deoxidation; magnesium vapor; pellet; magnesia; aluminothermic reduction; inclusion; clean steel; grain refinement. ISIJ International, Vol. 47 (2007), No. 5, © 2007 ISIJ crostructural control of steel in recent years. On the basis of in-situ observation of inclusions on the molten steel surface with a confocal scanning laser microscope, the attractive force between a pair of MgO inclusions was found to be one-tenth of that between a pair of alumina inclusions so that MgO inclusions had a much weaker tendency to aggregate or to form clusters. 17) The grain growth of Fe-10mass%Ni alloy was strongly inhibited by the primary inclusions of MgO particles, which were evenly distributed in the alloy after Mg deoxidation. 18) With using Fe-10mass%Ni alloy, Suito et al. systematically examined the dispersion of fine primary MgO inclusions, 19) studied the characteristics of size distribution of MgO particles 20) and the dispersion behavior of deoxidation particles of MgO during solidification, 21) furthermore, clarified the effect of primary deoxidation products of MgO on precipitation of TiN 22) and MnS 23) in the alloy. The effect of size distribution of MgO particles on austenite grain growth in Fe-0.05mass%C alloy was also investigated. 24) The purpose of present work is to study the behavior of the primary inclusions in deoxidation process of molten steel with magnesium vapor produced in situ by aluminothermic reduction of magnesium oxide. The produced magnesium vapor was i...

Simultaneous Desulfurization and Deoxidation of Molten Steel with in Situ Produced Magnesium Vapor

“…The difference of [ppmO] between the experimental results and the equilibrium ones is mainly caused by the inclusions of MgO, SiO 2 and Al 2 O 3 . The formation of SiO 2 and Al 2 O 3 inclusions was confirmed in our other article, 37) and it resulted from the quartz sample tube and the impurities in the crucible.…”

“…The first reason is that the measured oxygen concentration is the total oxygen concentration including oxide inclusions. The produced MgO inclusions usually have a average diameter of about 1 mm, 34) which is so small that it takes quite a long time to float up to the melt surface. The second reason is that the oxygen concentration in the melt is not only affected by the equilibrium with magnesium concentration in the melt, but also increased with dissolution of the MgO crucible.…”

Magnesium Non-metallic Inclusions in Non-oriented Electrical Steel Sheets

“…26) It was reported [27][28][29] that the aluminothermic reduction of magnesium oxide can be roughly classified into two stages. During the first stage, spinel is formed, as evident from Eq.…”

Characteristics of Inclusions Generated during Al–Mg Complex Deoxidation of Molten Steel

“…In our previous article, 23) behavior of inclusions during deoxidation of molten steel with magnesium vapor in situ produced by aluminothermic reduction of magnesium oxide was studied. The formed inclusions were mostly small in size and of spherical shape.…”