Nippon Steel Corporation

Shinya Kitamura

Kenichiro Miyamoto

Katsuhiko Kato

Kenichiro Naito

Hiroshi Sugano

Keiichi Katahira

Ryuzou Hayakawa

Hiroyuki Ishimatsu

Takayuki Kaneyasu

Shinji Sasakawa

Akio Shinkai

Kimitoshi Yonezawa

Toshiya Harada

Hiroyuki Katayama

Ken-ichiro Naito

Takeo Inomoto

Akio Kasama

Yuji Ogawa

Yasushi Okumura

Michitaka Matsuo

Shin Kikuchi

Kunihiko Fujiwara

Yoji Demoto

Kenro Sato

Hikofumi Taniishi

In a straight barrel type vacuum refining apparatus, use is made of a combination of: a decarburization method wherein the flow rate of oxygen fed into a vacuum tank and the flow rate of an inert gas fed into the vacuum tank are regulated and, at the same time, the flow rate of oxygen gas blown is reduced at a rate of 0.5 to 12.5 Nm /h/t/min in a low carbon concentration region having a carbon concentration of not more than the critical carbon concentration; and a vacuum refining apparatus provided with dust accumulation preventing means.

Method and apparatus for vacuum decarburization refining of molten steel

The present invention provides a simplified ladle refining process capable of efficiently heating a molten steel in a short period of time while scattering and adhesion of splashes and erosion of refractories are suppressed. A simplified ladle refining process for refining a molten steel in a ladle comprising inserting an immersion snorkel into a ladle and blowing an oxidizing gas onto the surface of a molten steel within the immersion snorkel through a lance while the molten steel is being stirred by blowing an inert gas through the bottom of the ladle, wherein the lance has a ratio (d,/d,) of a nozzle outlet diameter d,(mm) to a nozzle throat diameter d,(mm) of from 1.2&agr; to 2.5&agr; wherein &agr; is defined as a function of a back pressure.

Simple ladle refining method

The invention intends to provide a converter refining method capable of blowing molten steel having a low degree of superoxidation with high productivity and high yield. A first aspect resides in a pressurized converter steelmaking method for use in a top-and-bottom blowing converter, wherein a converter internal pressure P is set to a higher level than the atmospheric pressure, and a top-blown oxygen flow rate F and a bottom-blown gas flow rate Q are adjusted depending on changes of the converter internal pressure P. A second aspect resides in a pressurized converter steelmaking method for use in a top-and-bottom blowing converter, wherein a converter internal pressure P is set to a higher level than the atmospheric pressure during the whole or a part of a blowing period, and a top-blown oxygen flow rate F, a bottom-blown gas flow rate Q and the converter internal pressure P are changed depending on a steel bath carbon concentration C.

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Futtsu, Japan

Shinya Kitamura