Nippon Steel Corporation

Hiroshi Hirata

Masayuki Hashimura

Kohichi Isobe

Hiroshi Hagiwara

Atsushi Mizuno

Kenichiro Naito

Ken-ichiro Naito

Yuji Ogawa

Hirobumi Maede, Deceased

Masayuki Arai

Noriyuki Masumitsu

Fumio Koizumi

Masataka Yano

By Keiko Ikemizu

By Noriko Kawai

Yoshiaki Kusano

Kenji Fukuyasu

Hideaki Sasaki

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

Superior in machinability and method of production of same

The present invention is a steel, excellent in machinability, wherein forging workability is improved by suppressing the deterioration of mechanical properties in the direction in which the mechanical properties are the lowest, and more specifically, is a steel excellent in forgeability and machinability, characterized in that: the steel contains, in mass, C: 0.1 to 0.85%, Si: 0.01 to 1.5%, Mn: 0.05 to 2.0%, P: 0.003 to 0.2%, S: 0.003 to 0.5%, and Zr: 0.0003 to 0.01%; the following steel components are controlled in the following ranges respectively, in mass, Al: 0.01% or less, total O: 0.02% or less, and total N: 0.02% or less; the average aspect ratio of MnS grains is 10 or less and the maximum aspect ratio of those is 30 or less; and the balance of the steel components consists of Fe and unavoidable impurities.

Steel excellent in forgeability and machinability

Process for producing steel by converter

Growing community of inventors

Muroran, Japan

Hiroshi Hirata