Some Consideration on the Mechanism of Deoxidation Reaction of Molten Steel

Abstract

The behaviour of oxygen in melt, when deoxidizer was added into molten steel, was studied. Both macroscopic and microscopic oxide inclusions in solid steel, which was enriched with oxygen and contained silicon or aluminum, were disposed iniide interdendritic spaces. The result shows that all of inclusions found in solid steel are precipitated from melt during solidification of the steel, and that there are no suspended deoxidation products in melt. It was observed that deoxidation products were precipitated on the inner surface of crucible during holding in melt. In some cases, the deoxidation products were dendritic. From above experimental results, the following conclusions were introduced.
(1) When deoxidant was added in molten steel enriched with oxygen, dissolved oxygen and deoxidant react rapidly to produce an oxide dissolved in monomolecule state, but not to be grown to oxide particles.
(2) Dissolved monomolecular oxides in steel diffuse through diffusion layer on the boundary between melt and crucible, and form oxide phase only on the inner surface of crucible. Consequently oxygen content in steel is decreased slowly.
Rate of oxygen drop after addition of silicon in iron melt enriched with oxygen was measured.
The experimental results were consistent with theoretical result introduced by the above model of deoxidation reaction.
When a deoxidant is added into the melt containing a great amount of oxygen, then deoxidation occurs according to different reaction mechanism from the above mentionedi The reaction comes rapidly to an end. It is observed that some calcium can dissolve in molten steel.