Jfe Steel Corporation

Kawasaki Steel Corporation

Panasonic Electric Works Co., Ltd.

Fuji Ceramics Corporation

Seiji Nabeshima

Kenichi Sorimachi

Hiroki Ota

Masao Yuga

Yasuhide Ishiguro

Mitsuhiro Okatsu

Shuji Takeuchi

Hakaru Nakato

Yoshihiko Oda

Hiroaki Nakajima

Tomoyuki Okubo

Masanori Uesaka

Yuji Miki

Tadashi Nakanishi

Tomoyuki Yokota

Norichika Aramaki

Yoshiei Kato

Kimihiro Nishimura

Yasuo Kishimoto

Itaru Saida

Shinji Mitao

Hirokazu Tozawa

Mahito Nunomura

Kohei Furumai

Kazuhiro Iga

Yuki Nabeshima

Naomichi Iwata

Akihiro Tsujita

Hisashi Ogawa

Yasuyuki Masumoto

Yoichi Ito

Koji Ito

A steel containing C: not more than 0.0050%, Si: 0.1-5.0%, Mn: 0.02-3.0%, sol. Al: not more than 0.0050%, P: not more than 0.2%, S: not more than 0.0050%, N: not more than 0.0040%, T. Ca: 0.0010-0.0080%, T. O: not more than 0.0100% and having (T. Ca/T. O) of not less than 0.50 but not more than 2.0 by decarburizing to a C content of not more than 0.0050%, adding Si, decreasing Al as much as possible, and adding Ca is melted to form a slab. The slab is subjected to a hot rolling at a coiling temperature of not lower than 550&#xb0; C., a cold rolling and a finish annealing, or the slab is subjected to a hot rolling, a hot band annealing at a temperature of 900-1150&#xb0; C., a cold rolling and a finish annealing to thereby produce a non-oriented electrical steel sheet.

Non-oriented electrical steel sheet and production method thereof

A seamless steel pipe having a specific chemical composition. A ratio of Ti to N is in a range of 2.0 to 5.0. The steel pipe has a microstructure including tempered martensite having a volume ratio of 95% or more, and prior austenite grains having a grain size number of 8.5 or more. In a cross-section perpendicular to a rolling direction of the steel pipe a number of nitride-based inclusions having a particle size of 4 &#x3bc;m or more is 100 or less per 100 mm, a number of nitride-based inclusions having a particle size of less than 4 &#x3bc;m is 1000 or less per 100 mm, a number of oxide-based inclusions having a particle size of 4 &#x3bc;m or more is 40 or less per 100 mm, and a number of oxide-based inclusions having a particle size of less than 4 &#x3bc;m is 400 or less per 100 mm.

High-strength seamless steel pipe for oil country tubular goods and method of producing the same

A high-strength seamless steel pipe for oil country tubular goods comprising, by mass %, C: 0.20% to 0.50%, Si: 0.05% to 0.40%, Mn: 0.3% to 0.9%, P: 0.015% or less, S: 0.005% or less, Al: 0.005% to 0.1%, N: 0.006% or less, Mo: more than 1.0% to 3.0% or less, V: 0.01% to less than 0.05%, Nb: 0.001% to less than 0.01%, B: 0.0003% to 0.0030%, O: 0.0030% or less, and Ti: 0.003% to 0.025%, and wherein Ti/N: 2.0 to 5.0 is satisfied, a volume fraction of a tempered martensitic is 95% or more, prior austenite grains have a grain size number of 8.5 or more, and in a cross-section perpendicular to a rolling direction, the number of nitride-based inclusions having a grain size of 4 &#x3bc;m or more is 100 or less per 100 mm, the number of nitride-based inclusions having a grain size of less than 4 &#x3bc;m is 1000 or less per 100 mm, the number of oxide-based inclusions having a grain size of 4 &#x3bc;m or more is 40 or less per 100 mm, and the number of oxide-based inclusions having a grain size of less than 4 &#x3bc;m is 400 or less per 100 mm.

A high-strength seamless steel pipe for oil country tubular goods comprising, by mass %, C: 0.20% to 0.50%, Si: 0.05% to 0.40%, Mn: more than 0.6% to 1.5% or less, P: 0.015% or less, S: 0.005% or less, Al: 0.005% to 0.1%, N: 0.006% or less, Mo: more than 1.0% to 3.0% or less, V: 0.05% to 0.3%, Nb: 0.001% to 0.020%, B: 0.0003% to 0.0030%, O: 0.0030% or less, and Ti: 0.003% to 0.025%, and wherein Ti/N: 2.0 to 5.0 is satisfied, a volume fraction of a tempered martensitic is 95% or more, prior austenite grains have a grain size number of 8.5 or more, and in a cross-section perpendicular to a rolling direction, the number of nitride-based inclusions having a grain size of 4 m or more is 100 or less per 100 mm, the number of nitride-based inclusions having a grain size of less than 4 &#x3bc;m is 1000 or less per 100 mm, the number of oxide-based inclusions having a grain size of 4 &#x3bc;m or more is 40 or less per 100 mm, and the number of oxide-based inclusions having a grain size of less than 4 &#x3bc;m is 400 or less per 100 mm, and methods of producing the same.

The composition of inclusions and the S concentration in steel are controlled in a manner such that, among the CaO-containing oxide inclusions present in a Ca-containing steel, an equilibrium S soluble amount (% S inc.) of at least 80% of the oxide inclusion particles having a particle diameter of 2 &#x3bc;m or more are about 0.03 wt % or less, thereby inhibiting rust formation due to the inclusions, thus solving a problem which has long been of concern in Ca-containing steels.

Rust-resistant calcium steel

Process for producing high-nitrogen ultralow-carbon steel

Method of producing cluster-free Al-killed steel

Titanium killed steel sheets which are not troubled by nozzle clogging while they are produced in a continuous casting process, have few surface defects caused by cluster-type inclusions, and are highly rust resistant, and are formed from a melt of titanium killed steel that contains any one or two of Ca and metals REM in an amount of not smaller than 0.0005% by weight, and wherein the steel contains major oxide inclusions of any one or two of CaO and REM oxides in an amount of from about 5 to 50% by weight, Ti oxides in an amount of not larger than about 90% by weight, and Al.sub.2 O.sub.3 in an amount of not larger than about 70% by weight.

Titanium killed steel sheet and method

Adding aluminum and/or silica to molten steel after decarburization containing about 0.005 percent by weight or less of carbon and about 1.0 percent by weight or less of manganese to form a mildly deoxidized molten steel; adding titanium to the mildly deoxidized molten steel to continue deoxidation so that the molten steel contains about 0.005 percent by weight or less of aluminum, about 0.20 percent by weight or less of silicon and about 0.01 to 0.10 percent by weight of titanium, to form inclusions in the molten steel which essentially consist of a complex oxide of titanium and aluminum, a complex oxide of titanium and silicon, and/or a complex oxide of titanium, aluminum and silicon.

Method of making ultra low-carbon steel

In a method of producing a molten aluminum-killed steel for forming a thin steel sheet, molten steel tapped from a converter is decarburized to a predetermined carbon concentration by using a vacuum degasser, and Al is added to the molten steel in the vacuum degasser to deoxidize the molten steel. A material containing metallic Ca is then added to the molten steel to produce a Ca content of about 0.0005 to 0.005 wt %, and to satisfy [%Ca].times.[%S].ltoreq. about 2.times.1 0.sup.-5. Thereafter, degassing is performed on the molten steel.

Method of producing molten aluminum-killed steel for thin steel sheet

Growing community of inventors

Kurashiki, Japan

Seiji Nabeshima