Daido Tokushuko Kabushiki Kaisha

Masahide Tsuno

Yoshio Inagaki

Motoshi Shinkai

Akihiro Nagatani

In the production of stainless steel it is aimed at to depress the highest temperature reaching during refining the molten steel with keeping the necessary tapping temperature so as to prolong the life of refractory materials of the refining furnace. After carrying out decarburization treatment under atmospheric pressure in a refining furnace by blowing an oxygen-containing gas into molten steel, further decarburization of the molten steel and reduction of chromium oxides is carried out under stirring by blowing a non-oxidizing gas under a reduced pressure, and then, reducing agent is charged into the furnace to reduce chromium oxides under keeping the reduced pressure. At the above atmospheric pressure operation total quantity of the oxygen gas blown is smaller than in a conventional process, while at the final stage of the reduced pressure operation an oxygen-containing gas is blown again in the quantity which is equivalent to the balance of the quantity of oxygen gas usually blown in the conventional process and the quantity of oxygen gas blown at the above atmospheric pressure operation so as to cause heat generation by oxidation reaction of chromium thereby increasing molten steel temperature to a necessary temperature with anticipation of subsequent temperature decrease.

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Tokai, Japan

Masahide Tsuno