Nippon Steel Corporation

Honda Motor Co., Ltd.

Z. I. Nekrasov Iron & Steel Institute of the National Academy of Sciences of Ukraine

Kenichiro Naito

Hiroshi Hagiwara

Koji Morita

Masayuki Hashimura

Shinya Kitamura

Kohichi Isobe

Makoto Okonogi

Takehiko Toh

Atsushi Mizuno

Hiroshi Hirata

Hideki Matsuda

Takeo Inomoto

Shinji Sasakawa

Kimitoshi Yonezawa

Yuji Ogawa

Naoto Sasaki

Michitaka Matsuo

Masamitsu Wakoh

Shin Kikuchi

Kohki Mizuno

Seiji Kobayashi

Kazuo Onuki

Sohichi Niino

S I Semykin

Kiyokazu Tateishi

Semykin S I

The present invention provides steel superior in machinability comprised of, by wt %, C: 0.005 to 0.2%, Si: 0.001 to 0.5%, Mn: 0.2 to 3.0%, P: 0.001 to 0.2%, S: 0.03 to 1.0%, T.N: 0.002 to 0.02%, T.O: 0.0005 to 0.035%, and the balance of Fe and unavoidable impurities, said steel satisfying one or both of Mn/S in the steel being 1.2 to 2.8 or an area ratio of pearlite over a grain size of 1 &#x3bc;m in a microstructure of the steel being not more than 5%.

Method of production of steel superior in machinability

The present invention provides a method of production of a steel soft nitrided machine part comprising: preparing a steel material containing, by mass %, C: 0.15-0.30%, Si: 0.03-1.00%, Mn: 0.20-1.5%, S: 0.04-0.06%, Cr: 0.01-0.5%, Mo: 0.40-1.5%, Nb: 0.005-0.05%, Ti: 0.005-0.03%, V: 0.2-0.4%, Ni: 0.05-1.5%, N: 0.002-0.0048%, a balance of Fe and unavoidable impurities, limiting P to 0.02% or less, limiting Ceq. (equation (1)) to 0.65-0.85, controlling DI (equation (2)) to 80-155, log Kp (equation (3)) to 2.5-8, and Si and Mn contents according to equation (4), heating the steel material to 1150-1280&#xb0; C., hot forging the steel material to the shape of the part, cooling the steel material at a 0.5-1.5&#xb0; C/sec cooling rate to obtain a hot forged part having a micrometallic structure with more than 50% of bainite, machining the hot forged part, and soft nitriding the machined hot forged part at 550-650&#xb0; C. for 30 minutes or more.

Method of production of steel soft nitrided machine part

Superior in machinability and method of production of same

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.

Pressure converter steelmaking method

Top-blown refining method in converter featuring excellent

Growing community of inventors

Tokyo, Japan

Kenichiro Naito