Kawasaki Steel Corporation

Arata Ueda

Toshio Fujimura

Tetsuya Fujii

Yukio Oguchi

Toshihiko Emi

Norio Sumida

Osamu Furukimi

Saiji Matsuoka

Masahiko Morita

Takemi Yamamoto

Takashi Sekita

Kenichi Orito

Toyohito Nakahara

Taro Yahiro

Katsutoshi Yamashita

The state of slag foaming generated in an electric furnace steel manufacture is judged by measuring the NO amount in exhaust gas. The foaming state is adjusted to completely interrupt the contact of melted steel with air so that low nitrogen of the steel is always achieved or reduction of electric power consumption rate is achieved. Thus, in the manufacture of steel by subjecting iron scrap to dissolving, refining and heating stages successively in an electric arc furnace, the NO amount in the exhaust gas is measured at the refining and heating stages of the melted steel and then the state of the slag foaming is judged depending upon the measured data.

Method of judging slag forming state in electric furnace steel production and method of operating electric furnace

Steel having excellent workability and deep drawability is produced by an electric furnace-vacuum degassing process. The steel has a composition which comprises about:

Steel, steel sheet having excellent workability and method of producing

A method of stirring molten metal by repeatedly sucking and rapidly discharging part of the molten metal into and out of a refractory cylinder having a lower opening end immersed in the molten metal in a ladle, comprises operating the stirring under a condition that an inner diameter (d) of the refractory cylinder is less than 1,000 mm, a relation between the inner diameter (d, mm) of the refractory cylinder and weight (W, ton) of the molten metal in the ladle is d/W.sup.0.5 &gt;30, and an immersed depth of the refractory cylinder is within 200-700 mm. A pressurized gas for discharging the sucked molten metal out of the cylinder is introduced thereinto in an inclined direction relative to a vertical line against a point on an opposite inner wall of the cylinder at least 500 mm above the maximum suction level of the molten metal in the cylinder. A refractory cylinder operated in the above manner according to the invention comprises a flange connection between an uppermost and an intermediate cylinder parts of the cylinder at a location higher than the maximum suction height of the molten metal and a further flange connection between the intermediate cylinder part and a lowermost cylinder part. The refractory cylinder comprises at its immersed end a flow restricting opening to obtain more strong stirring the molten metal.

Method of stirring molten metal and refractory cylinder for the purpose

A method of refining molten metal with stirring in a refining vessel by repeated operation of suction and discharge is disclosed, wherein a lower end of a refractory cylinder is immersed into a molten metal bath in the vessel and an inside of the cylinder opposite to the immersed end is alternately subjected to evacuation and pressurization. In this method, maximum and average values of pressure reduction velocity to be applied to the inside of the cylinder are limited to not more than 1,000 mmHg/sec and not more than 500 mmHg/sec, respectively, and an evacuation time is extended over at least 1.5 times intrinsic oscillation period of up and down movement of molten metal column inside the cylinder.

Method of refining molten metal with stirring by repeated operation of

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Okayama, Japan

Arata Ueda