Koyo Seiko Company, Ltd.

Jfe Steel Corporation

Nippondenso Co., Ltd.

Jtekt Corporation

Daido Tokushuko Kabushiki Kaisha

Daido Steel Co., Ltd.

Aichi Steel Works, Ltd.

Koyo Seiko K.k.

Masao Goto

Takashi Iwamoto

Katsuhiko Kizawa

Akihiro Matsuzaki

Hisashi Harada

Shinji Yasuhara

Atsuhiko Ohta

Teruo Hoshino

Yoshihiro Ono

Hisato Nishisaka

Takaaki Toyooka

Kazutoshi Toda

Yoshio Yamazaki

Akihiro Mizutani

Kunikazu Tomita

Sadayuki Nakamura

Hajime Tazumi

Toshihiro Kawaguchi

Hideto Kimura

Kazuo Rokkaku

Yutaka Kurebayashi

Masayuki Kitamura

Shoji Eguchi

Yasuo Asai

Takao Tamagawa

Yoshitaka Natsume

Yasuharu Misada

Takao Ooki

Yatsuka Takata

Kiichiro Yamashita

Yoshihiro Wakikado

Satoshi Soga

Jonathan Newall

Adrian P Lee

Kazuhiko Ohno

Hazime Tazumi

Akira Muroga

A steel part having a long rolling contact fatigue life and capable of further increasing the life of a bearing under severer using condition than usual conditions. The steel part includes steel having a composition containing 0.7% by mass to 1.1% by mass of C, 0.5% by mass to 2.0% by mass of Si, 0.4% by mass to 2.5% by mass of Mn, 1.6% by mass to 5.0% by mass of Cr, 0.1% by mass to less than 0.5% by mass of Mo, 0.010% by mass to 0.050% by mass of Al, less than 0.0015% by mass of Sb as an impurity, and the balance composed of Fe and inevitable impurities, the steel being hardened and tempered. In the steel structure of a portion from the surface to a depth of 5 mm, residual cementite has a grain diameter of 0.05 to 1.5 &#x3bc;m, prior austenite has a grain diameter of 30 &#x3bc;m or less, and the ratio by volume of the residual austenite is less than 25%.

Method for producing steel part having long rolling contact fatigue life

Provided are a steel having excellent rolling contact fatigue life and the manufacturing method thereof. The steel consists essentially of 0.7 to 1.1% C, 0.2 to 2.0% Si, 0.4 to 2.5% Mn, 1.6 to 4.0% Cr, 0.1% or more and less than 0.5% Mo, 0.010 to 0.050% Al, bymass, and balance of Fe and inevitable impurities, is treated by quenching and tempering, has residual cementite grain sizes ranging from 0.05 to 1.5 &#x3bc;m, and has prior-austenite grain sizes of 30 &#x3bc;m or smaller. When the steel is used to bearing steel, the bearing life extends even under service in more severe environments.

Steel material with excellent rolling fatigue life and method of producing the same

A case hardening bearing steel having an excellent rolling contact fatigue life in intermediate temperature, in addition, excellent toughness at room temperature is provided. Specific means for solving the problems are as follows. The composition contains, by mass percent, C of 0.15 to 0.30 mass percent, Si of 0.5 to 2.0 mass percent, Mn of 0.3 to 2.0 mass percent, Cr of 1.3 to 2.5 mass percent, Mo of 0.3 to 1.0 mass percent, and O of not more than 0.0012 mass percent in a range where (Si+Mo)&#x2267;1.0 mass percent is satisfied, and contains iron and inevitable impurities as remnant; the maximum size of oxide nonmetallic inclusion is not more than 12.5 &#x3bc;m when examined area is 320 mm; number of the oxide nonmetallic inclusion having a diameter of equivalent circle of 3 &#x3bc;m or more is not more than 250 when the examined area is 320 mm; in addition, C density of an outer layer is adjusted to be in a range from 0.7 to 1.2 mass percent by carburization.

Case hardening bearing steel having excellent toughness and rolling contact fatigue life in intermediate temperature

A roller member comprising high carbon chromium bearing steel having a carburization treatment. The bearing steel comprising a surface portion defined as a range between a surface of a rolling face of the roller member to a depth where a maximum shearing stress acts thereon, the surface portion containing carbon in a total amount comprising a range of 1.0 to 1.6 wt % and an amount of residual austenite comprising a range of 20 vol % to 35 vol % wherein a compression residual stress of the surface portion comprises a range of 150 to 1000 MPa, wherein a surface hardness of the surface portion comprises a range of 64 or higher in Rockwell C hardness, wherein an amount of carbide precipitate on the surface portion comprises a range of 10% to 25% in an area rate and each carbide particle size comprises a range of 3 &#x3bc;m or less.

Carburized roller member made of high carbon chromium steel

In a heat treatment wherein a blank (intermediate material) formed with a lubrication hole is heated and quenched, the quenching of the blank is terminated at the point of time that a temperature at a portion corresponding to a depth from a raceway surface (surface of a bearing part) of an outer ring (the bearing part), to which depth the maximum shear stress affects, is lowered to an MS point.

Bearing part and fabrication method therefor

A long-life bearing steel for general purpose use is provided at low cost with no use of specific secondary refining process. Specifically, a bearing material having a component composition in which C: 0.95 to 1.10 mass %, Si: 0.15 to 0.70 mass %, Mn: 1.15 mass % or less, Cr: 0.90 to 1.60 mass %, and P: 0.025 mass % or less are contained, S and O, that are elements forming nonmetallic inclusions, are contained at S: 0.025 mass % or less and O: 0.0012 mass % or less, and the rest is composed of Fe and incidental impurities, wherein the maximum diameter of the oxide-based nonmetallic inclusion is more than 10 &#x3bc;m, but 15 &#x3bc;m or less in an inspection area: 320 mm, the number of oxide-based nonmetallic inclusions having an equivalent circle diameter of 3 &#x3bc;m or more is 250 or less in the inspection area: 320 mm, while in the material, AlN is contained at 0.020 mass % or less, and or the number of sulfide-based nonmetallic inclusions having a thickness of 1 &#x3bc;m or more is 1,200 or less in the inspection area: 320 mm.

Bearing material

An antifriction bearing comprises an inner race, an outer race having an outer peripheral surface to be brought into contact with other member for use as a roll, and a plurality of rolling elements arranged between the inner and outer races. The portion of the outer race from an outer peripheral surface thereof to a depth of 3 mm has a hardness of 58 to 62 in Rockwell C hardness (hereinafter referred to as 'HRC') and a hardness gradient of up to 1 HRC/1 mm from the outer peripheral surface inward, and contains 5 to 18 vol. % of retained austenite. The portion of the outer race from an inner peripheral surface thereof to a depth of 1 mm has a hardness of 61 to 64 in HRC and contains 5 to 15 vol. % of retained austenite. The center portion of the thickness of the outer race between the inner and outer peripheral surfaces thereof has a hardness of 35 to 42 in HRC. The outer race can be prevented from cracking or breaking and from undergoing plastic deformation due to use for a short period of time.

Antifriction bearing and process for producing outer race for use in antifriction bearing

A rolling bearing including a rolling element made of steel is provided. The rolling element has a hardness of 620 to 750 HV in its interior. The rolling element is so constructed that the hardest point may exist within a depth of 10% of its diameter from a rolling contact surface of the rolling element, and that the hardness at this point is made higher by 20 to 150 HV than the hardness in the interior.

Rolling bearing

For extension of service lives of rollers and discs of a toroidal continuously variable transmission, input discs, output discs and rollers are formed of a heat-resisting bearing steel. At least a roller has its peripheral surface subjected to a shot peening for achieving a compressive residual stress of 0.6 to 1.2 GPa and a hardness of HRC 63 to 66 at the outermost surface.

Toroidal continuously variable transmission

A blank for disc is heat treated for adjusting a surface hardness thereof to not less than Hv700. The blank has a spline hole thereof heated by high frequency heating while cooling a race thereof. Subsequently, the spline hole is subjected to slow cooling. Thus is obtained a disc having a surface hardness of not less than Hv700 at the race, and a surface hardness of not more than Hv600 at the spline hole, the disc wherein at least a thin portion is varied in hardness between a hardened layer of a bottom of the spline hole and a hardened layer of the race by an amount of not less than Hv20 per 1-mm depth.

Variator disc and a method of fabricating the same

In a material for bearing parts constructed from a steel hardened by a heat treatment, its surface layer is adjusted, before a shot peening treatment, for a mean particle size of carbide to less than 1 &mgr;m, an area percentage of carbide to 10-15%, an amount of residual austenite to 7-14% and a hardness thereof to HRC&equals;61-65; and subsequently, the shot peening treatment is conducted. Thus is produced a material for bearing parts which can satisfy the life requirements for bearings without an excessive increase in a shot time during the shot peening treatment.

Material for bearing parts

An antifriction bearing comprises bearing rings and rolling members which are made from a steel material containing 0.15 to 0.3 wt. % of carbon by being subjected to heat treatments including carburizing. The surface layer of raceway surface of each of the bearing rings and the surface layer of rolling surface of each of the rolling members are 1.0 to 1.5 wt. % in carbon content, 64 to 66 in Rockwell hardness C, 150 to 2000 MPa in compressive residual stress, up to 3 &mgr;m in maximum carbide particle size and 10 to 25% in carbide area ratio, at a depth of 0 to 50 &mgr;m as measured from the outermost surface of the surface layer. The surface layers are 0.75 to 1.3 wt. % in carbon content, 150 to 1000 MPa in compressive residual stress, 25 to 45% in residual austenite content, up to 1 &mgr;m in maximum carbide particle size and up to 15% in carbide area ratio, at a depth of 50 to 200 &mgr;m as similarly measured from the outermost surface. The bearing is given a prolonged life for use in clean oils and also in oils contaminated with extraneous matter.

Antifriction bearing

A continuously variable transmission including discs made of heat-resisting bearing steel, and rollers made of ceramics. The heat-resisting bearing steel contains 0.8-1.5 wt % of C, 0.5-2.0 wt % of Si, 0.3-2.0 wt % of Mn, 1.3-1.98 wt % of Cr, and 0.3-1.0 wt % of Mo, (Si&plus;Mo) being 1.0 wt % or more. Because the rollers are made of ceramics superior in heat resistance, the toroidal type continuously variable transmission, even if used under high load and high rotational speed, is free from occurrence of sticking between discs and rollers and damage of the raceway surfaces.

Toroidal type continuously variable transmission

Bearing component

Bearing steel materials that are superior in cold workability, machinability, hardenability and rolling contact fatigue life are provided. During the processing of steel materials, the generation of large carbides, that detrimentally affect the rolling contact fatigue life of the steel, is inhibited, thereby obviating the necessity of a heat treatment for dissolving the carbides. The present steel material contains the following alloy elements in percentage by mass: 0.55% to 0.82% of carbon; 0.05% to 0.20% of silicon; 0.50% or less of manganese; 0.90% to 1.30% of chromium; 0.05% to 0.30% of molybdenum; and the remaining percentage substantially of iron. After the spheroidizing annealing of the steel material, the total cross-sectional area rate of carbide is 25% or less.

Steel composition for bearings and method of producing the same

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Osaka, Japan

Masao Goto