珪素およびマンガンによる強制脱酸

鋼の脱酸の速度論的研究-I

抄録

Deoxidation problems of non-metallic inclusions being formed as reaction products were dealt with from the kinetic viewpoint on the example of silicon and/or manganese deoxidation.
The experimental results are as follows: 1) Silica particles, deoxidation products of silicon addition, are very hard to separate from molten iron because of their poor ability to coalesce. 2) Manganese oxide particles in case of much manganese addition consist of two phases which suggest that liquid and solid phases get together without any difficulty. Thus they grow to rather large particles and are separated in a short time. 3) Even in complex deoxidation of silicon and manganese where solid silica particles are expected to be produced according to equilibrium theory, large and globular particles of iron and manganese silicate were observed. 4) The property of liquid silicate particle to coalesce and be separated from molten steel easrily is confirmed. 5) The motion of iron bath by induction stirring increased the growth rate of all kinds of deoxidation products and proved effective for their removal from molten iron. 6) Crucible materials influenced not on the deoxidation but on the reoxidation behavior as a result of reactions at the metal-crucible interface. 7) The experiment under oxidizing atmosphere showed that the rate of reoxidation is very large and in contradiction to the above-mentioned the addition of only silicon gave desirable results because a viscous film formed prevented the penetration of oxygen into iron bath from atmosphere or slag.
The nucleus size and nucleation rate were calculated and the lattertoroved so large that this step could not be a rate-determining one of deoxidation. The following supposed mechanisms of the growth of deoxidation products were applied to the discussions of the experimental results. These are: 1) Coalescence by Brownian movement, 2) growth by diffusion of oxygen or deoxidizer atom to the surface of particle, and 3) coalescence during floating up.
Finally the maximum particle size to be observed under experimental conditions was calculated; it was in good agreement with measured one.
These experimental results were applied to the explanation of those obtained in the industrial open hearth deoxidation.