Consideration on the Deoxidation Mechanism of Steel by Metallic Aluminium

Abstract

Although it is important to know the deoxidation process of aluminium as strong deoxidizer and studies about deoxidation products have been done by many people, we could not clarify the process. L. S. SLOMAN and E. L. EVANS found some unknown substances formed beside aluminium deoxidation.They identified them as silica from the chemical analysis result of total isolated residues. C. E. Sims, H. A. SALLER and F. W. BOULGER reported about the deoxidation products with aluminium via the substance like AlO, but the process has remained unknown.
In ceramic division, the dehydration mechanism of aluminium hydrates has been established. But, there are many questions about their crystal structures and about the existence of many modifiers of aluminium oxide.
It is very important to know the formation mechanism of aluminium oxide in the molten iron from the viewpoint of metallurgical research and practical basis.
In this paper, the authors discussed how the variation of solidifying and cooling velocities influences the structures of deoxidation products.
The results obtained are summarized as follows:
1) Under rapid solidification, we could determine the formation of various low temperature stable modifiers besides corundum.They are chiefly θ type alumina, and supposed to be σ and κ types.
2) From their formation, we could suppose the formation of aluminium hydroxide in a moment after addition of deoxidizing agent.We must appreciate the role of hydrogen in molten steel.
3) For comparison, we used a platelet and a small lump of metallic aluminium.There was difference between their alumina modifications.Especially, in the case of small lump, they exhibited an appearance of γ type.
4) Although there are two dehydration paths in alumina modification, we could estimate from this experiment that alumina formed in steels takes both processes.