Importance

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Abstract

The present invention belongs to a technical field in the oxygen steel making, more particularly in the steel making by blowing oxygen into a converter from its top and bottom. The total amount of oxygen to be blown into a top and bottom blowing converter is substantially the same as that of oxygen to be blown into a bottom blowing converter, but a part of the total amount of the oxygen is blown into the converter from its top. Therefore, the injection capacity for lime powder is necessarily decreased corresponding to the decrease of the blow rate of the bottom blown oxygen, and the decrease of the injection capacity causes the initial stage blowing up, being generated often in the case where blowing of lime powder is not carried out in the bottom blowing. The present invention aims to solve the above described drawback of the initial stage blowing up in the conventional top and bottom blowing technic and at the same time to improve the dephosphorization effect at the final stage of the blowing by blowing lime powder into a top and bottom blowing converter according to such a blowing pattern that the lime powder is blown in an amount satisfying a condition of (CaO/SiO.sub.2).sup.-1 .times.SiO.sub.2 (kg/t).ltoreq.13 (kg/t) at the initial stage of the blowing and further is blown in an amount of 3 kg/t at the final stage of the blowing. The use is a production of steel mainly from molten pig iron.

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First Claim