Abstract
(1) Direct deoxidation of molten steel by manganese was experimented, obtaining the following formula for the solubility of MnO, in which the sample had been skimmed from the molten steel with a specially designed quartz apparatus and quenched immediately in mercury, and the MnO and FeO in the steel had been analysed by the alcoholic iodine method:-
Solubility of MnO (%)=1·5×10-4t°-0·198. For instance about 0·05% MnO dissoives at 1650°C and the following deoxidation equilibr%ium:
[FeO] in steel+[Mn] [Fe]+[MnO] in steel.
(2) In case where silicon was added to the molten steel, an acidic SiO2 cvolves, absorbs MnO and floats off. Therefore the abovementioned equillbrium disjoins, causing the reaction to the right alone. In other words, in case of the coexistence of silicon even the small quantity of the manganese content participates in deoxidation, being effective to the elimination of SiO2. In practice, a sample was taken with a vacuum sampling vessel from the mollen steel at the deoxidation period in the acid open hparth refining, the analysis of which yield an extremely slight quantity of SiO2 as the deoxidation product.
(3) A considerable amount of Fe-Si or Si-Mn was added to about 2kg of the molten steel with 0·2% Mn and solidified within some minutes. From the results of a number of such experiments, it was found that steels with above 0·35% Si contain below half amount of the silicate inclusion when compared with those with about 0·20% Si. Similar results were obtained in the melting teat on a larger scale.
(4) It is presnmed therefore that, the deoxidation degree of the molten steel may be improved and the silicate inclusion of ingots may be lessened by suitably utilizing the method of adding considerable amount of silicon to the molten steel with above 0·2% Mn.
