Kawasaki Steel Corporation

Ryuichi Asaho

Nagayasu Bessho

Hiroshi Nishikawa

Kyoji Nakanishi

Takuo Imai

Masaaki Tsukamoto

Kyoichi Kameyama

Tatsukichi Chino

A process of degassing and decarbonizing is directed to a process for performing vacuum degassing non-deoxidized or slightly deoxidized molten steel utilizing RH process or DH process. The process includes blowing of oxygen or oxygen containing gas toward the surface of the molten steel in a vacuum chamber for promoting decarbonizing reaction. The process further includes a step of combustioning of CO gas in the vicinity of the surface of the molten metal at a timing, in which concentration of (CO+CO.sub.2) in an exhaust gas is higher than or equal to 5% and a ratio of CO.sub.2 versus (CO+CO.sub.2) in the exhaust gas is approximately 30%. Heat generated by combustioning of CO gas is utilized for compensating temperature drop of the molten steel.

Process for vacuum degassing and decarbonization with temperature drop

A tuyere for blowing an agitating gas into molten steel is arranged in the bottom of an oxygen top-blown converter in order to improve the refining effect of molten steel and has a ratio of blow sectional area S (cm.sup.2) to inner peripheral length L (cm) of not more than 0.17, preferably not more than 0.125.

Bottom tuyeres in an oxygen top-blown converter

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Chiba, Japan

Ryuichi Asaho