Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Kenichiro Miyamoto

Hiroshi Sugano

Shinya Kitamura

Masayuki Abe

Masaharu Oka

Katsuhiko Kato

Masafumi Zeze

Yuji Koyama

Keiichi Katahira

Akio Shinkai

Ryuzou Hayakawa

Hiroyuki Ishimatsu

Ryusuke Miura

Shintaro Kusunoki

Masafumi Miyazaki

Masayuki Hashimura

Kei Miyanishi

Takashi Morohoshi

Yasuhiro Kinari

Takayuki Kaneyasu

Kazumi Mizukami

Atsushi Mizuno

Naotsugu Yoshida

Michimasa Aono

Shinji Sasakawa

Junya Yamamoto

Kimitoshi Yonezawa

Masanobu Suzuki

Seiji Ito

Jun Aoki

Kunihiko Fujiwara

Low-oxygen clean steel is provided containing C, Si, Mn, P, and S as chemical components, and further containing, by mass %, 0.005% to 0.20% of Al, greater than 0% to 0.0005% of Ca, 0.00005% to 0.0004% of REM, and greater than 0% to 0.003% of T.O, wherein the REM content, the Ca content, and the T.O content satisfy 0.15&#x2264;REM/Ca&#x2264;4.00 and Ca/T.O&#x2264;0.50, nonmetallic inclusions which have a maximum predicted diameter of 1 &#x3bc;m to 30 &#x3bc;m measured using an extreme value statistical method under the condition in which a prediction area is 30,000 mm, and contain AlOand REM oxide are dispersed in the steel, an average proportion of the AlOin the nonmetallic inclusions is greater than 50%, the REM is one or two or more of rare-earth elements La, Ce, Pr, and Nd, and the steel is Al-deoxidized steel or Al&#x2014;Si-deoxidized steel.

Low-oxygen clean steel and low-oxygen clean steel product

A spring steel according to the present embodiment has a chemical composition consisting of, in mass %, C: 0.4 to 0.7%, Si: 1.1 to 3.0%, Mn: 0.3 to 1.5%, P: 0.03% or less, S: 0.05% or less, Al: 0.01 to 0.05%, rare earth metal: 0.0001 to 0.002%, N: 0.015%, O or less: 0.0030% or less, Ti: 0.02 to 0.1%, with the balance being Fe and impurities. In the spring steel, the number of oxide inclusions having an equivalent circular diameter of equal to or greater than 5 &#x3bc;m is equal to or less than 0.2/mm, the oxide inclusions each being one of an Al-based oxide, a complex oxide containing REM, O and Al, and a complex oxysulfide containing REM, O, S, and Al. Further, a maximum value among equivalent circular diameters of the oxide inclusions is equal to or less than 40 &#x3bc;m.

Spring steel and method for producing the same

A cast steel with excellent workability, characterized in that not less than 60% of the total cross section thereof is occupied by equiaxed crystals, the diameters (mm) of which satisfy the following formula:&#x3c;1.2+0.75,wherein D designates each diameter (mm) of equiaxed crystals in terms of internal structure in which the crystal orientations are identical, and X the distance (mm) from the surface of the cast steel. The cast steel and the steel material obtained by processing the cast steel have very few surface flaws and internal defects.

Cast steel and steel material with excellent workability, method for processing molten steel therefor and method for manufacturing the cast steel and steel material

Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof

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

Method of vacuum decarburization/refining of molten steel

Vacuum refining method for molten steel

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Kitakyushu, Japan

Kenichiro Miyamoto