Nippon Steel Corporation

Seiji Aso

Hideyuki Takahama

Yasuo Obana

Hideo Yaoi

Koichi Endoh

Toshiyuki Kaneko

A treating agent of molten steel according to the present invention is used for desulfurization molten steel for desulfurizing it in a reaction vessel which is lined with a basic refractory containing MgO, and consists of CaO, CaF.sub.2 and MgO and unavoidable impurities contains from 10 to 60% by weight of MgO, and has a weight ratio of {(% CaF.sub.2)/((% CaO)+(% CaF.sub.2))}.times.100(%) of from 20 to 80%. Said agent is injected with the aid of inert carrier gas into the molten steel and floats toward a portion of the molten steel bath essentially free of slag. Another treating agent essentially consisting of CaO and CaF.sub.2 may be also injected prior and/or subsequent to injection of said agent, so as to decrease inclusions. The inert gas may also be injected after injection of said agent(s).

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Oita, Japan

Seiji Aso