Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Kabushiki Kaisha Kobe Seiko Sho (kobe Steel, Ltd.)

Yosuke Shindo

Masaki Kaizuka

Shunichi Hashimoto

Shushi Ikeda

Hiroshi Yaguchi

Takehiro Tsuchida

Koichi Makii

Takahiro Kashima

Masato Kaiso

Sei Kimura

Masami Somekawa

Koichi Sakamoto

Tomoko Sugimura

Hiroshi Akamizu

Masaki Shimamoto

Tetsushi Deura

Masahiro Nomura

Nariaki Okamoto

Sayaka Nagamatsu

Akihiro Owaki

Manabu Fujita

Ikuo Hoshikawa

Takahiro Kudou

A bearing component having increased rolling-contact fatigue life, the bearing component being made of a bearing steel that satisfies a predetermined chemical composition, and Si (boundary Si), Mn (boundary Mn), Cr (boundary Cr), Cu (boundary Cu), Ni (boundary Ni), and Mo (boundary Mo) included in a matrix phase region (boundary surface region) from the surface of spheroidized cementite to 20 nm away satisfy the formula:9.0&#x2266;1.4&#xd7;boundary Si+1.8&#xd7;boundary Mn+5.5&#xd7;boundary Cu+4.2&#xd7;boundary Ni+4.8&#xd7;boundary Cr+5.5&#xd7;boundary Mo.

Bearing steel excellent in rolling-contact fatigue properties and method for producing same

This gear has a predetermined chemical composition and has, in a surface-layer part, a texture of tempered martensite and/or tempered bainite and a steel material texture in which retained austenite exists in 1-10% by area percentage and in which a carbide is deposited in at least 5% by area percentage, and the nitrogen content at a depth of 20 &#x3bc;m below the surface is 2.0-6.0%. Thus, a gear that achieves even better seizing resistance in a power transmission part subjected to high rotation and high slippage and using a low-kinematic-viscosity lubricating oil is provided.

Gear having excellent seizing resistance

A bearing steel material which contains 0.8-1.1 mass % C, 0.15-0.8 mass % Si, 0.1-1.0 mass % Mn, 1.3-1.8 mass % Cr, up to 0.05 mass % P (0 mass % is excluded), up to 0.015 mass % S (0 mass % excluded), 0.0002-0.005 mass % Al, 0.0002-0.0020 mass % Ca, 0.0005-0.010 mass % Ti, up to 0.0080 mass % N (0 mass % is excluded), and up to 0.0025 mass % O (0 mass % is excluded). The steel material contains oxide inclusions which have an average composition that comprises, in terms of mass %, 20-50% CaO, 20-50% AlO, 20-70% SiO, and 3-10% TiO.

Bearing steel material with excellent rolling fatigue property and bearing part

A case hardening steel, which has excellent cold forgeability and excellent crystal grain coarsening prevention characteristics after carburization, contains, in mass %, 0.05-0.20% of C, 0.01-0.1% of Si, 0.3-0.6% of Mn, 0.03% or less of P (excluding 0%), 0.001-0.02% of S, 1.2-2.0% of Cr, 0.01-0.1% of Al, 0.010-0.10% of Ti, 0.010% or less of N (excluding 0%), and 0.0005-0.005% of B, with the balance consisting of iron and unavoidable impurities. The density of Ti-based precipitates having circle-equivalent diameters less than 20 nm in the case hardening steel is 10-100 pieces/&#x3bc;m; the density of Ti-based precipitates having diameters of 20 nm or more in the case hardening steel is 1.5-10 pieces/&#x3bc;m; and the case hardening steel has a Vickers hardness of 130 HV or less.

Case hardening steel, method for producing same, and mechanical structural part using case hardening steel

This bearing steel material satisfies a predetermined elemental composition, and is characterized by having, in the region (boundary region) from the boundary surface of spheroidal cementite to a position at 20 nm away in a base material, no greater than 0.6% (excluding 0%) of Si (boundary Si), no greater than 0.10% (excluding 0%) of Ni (boundary Ni), no greater than 0.10% (excluding 0%) of Cu (boundary Cu), no greater than 0.03% (including 0%) of Mo (boundary Mo), no greater than 0.10% (excluding 0%) of Mn (boundary Mn), and no greater than 0.9% (excluding 0%) of Cr (boundary Cr), and the circularity coefficient of the spheroidized cementite being at least 0.80. The bearing steel material exhibits favorable cold-workability during the production of a bearing component by means of cold working.

Bearing steel excellent in cold workability and manufacturing method thereof

A machine structure steel superior in chip disposability and mechanical properties which contains sulfide-type inclusions such that those particles of sulfide-type inclusions with major axes not shorter than 5 &mgr;m have an average aspect ratio not larger than 5.2 and which also contains coarse particles of sulfide-type inclusions such that the relation a/b&lE;0.25 is satisfied, where a denotes the number of particles of sulfide-type inclusions with major axes not shorter than 20 &mgr;m, and b denotes the number of particles of sulfide-type inclusions with major axes not shorter than 5 &mgr;m. The machine structure steel exhibits good chip disposability and mechanical properties despite its freedom from lead.

Machine structure steel superior in chip disposability and mechanical properties and its method of making

Free machining steel for use in machine structure of excellent mechanical characteristics

A P- and Ti-added galvannealed steel sheet superior in ductility, and a process for production thereof. It is made of a cold-rolled steel sheet and has alloyed hot-dip galvanizing on the surface thereof, said cold-rolled steel sheet having the chemical composition (in terms of wt %) of C: less than 0.010%, Si: no more than 0.5%, Mn: 1.0&tilde;3.0%, P: no more than 0.20%, S: no more than 0.01%, Al: 0.005&tilde;0.10%, N: no more than 0.0050%, Ti/48&minus;(C/12&plus;N/14&plus;S/32): 0.0003&tilde;0.0018 with the remainder being chiefly Fe, and said cold-rolled steel sheet being characterized by &rgr;1&lE;10,and &rgr;2&lE;5&times;10,, where &rgr;1 is the number of precipitates whose particle diameter (D) is in the range of 10 nm&lE;D<100 nm and &rgr;2 is the number of precipitates whose particle diameter (D) is in the range of 100 nm&lE;D.

Galvanized steel sheet superior in ductility and process for production thereof

A hot-dip galvanized steel sheet which is produced from a cold-rolled steel sheet, as a base steel sheet, consisting essentially of C: 0.010-0.06 wt %, Si: no more than 0.5 wt %, Mn: no less than 0.5 wt % and less than 2.0 wt %, P: no more than 0.20 wt %, S: no more than 0.01 wt %, Al: 0.005-0.10 wt %, N: no more than 0.005 wt %, Cr: no more than 1.0 wt %, Mn&plus;1.3Cr: 1.9-2.3 wt %, Fe: remainder, and having a structure composed of ferrite and a second phase containing martensite, said second phase in the structure accounting for no more than 20% in terms of area and martensite in the second phase accounting for no less than 50%, and which has a zinc-plated layer formed on the surface thereof by hot-dip galvanizing or hot-dip galvannealing. A process for production of said hot-dip galvanized steel sheet. This steel sheet has a composite structure containing martensite and yet it has a low strength (no higher than 500 MPa) and also has good strength-ductility balance.

Hot-dip galvanized steel sheet and process for production thereof

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Kobe, Japan

Yosuke Shindo