Nsk Corporation

Akihiro Kiuchi

Shigeru Okita

Manabu Ohori

Yasuo Murakami

Hiromichi Takemura

Koji Ueda

Susumu Tanaka

Satoshi Kadokawa

Kenji Yamamura

Tomonobu Yoshikawa

Kiyoshi Hirakawa

Yoichi Matsumoto

Yasuo Utsumi

Kikuaki Kamamura

Akira Iida

Kazuo Hayakawa

Shizuo Mitsuhashi

Masaru Kawabe

Nancy Naoko Yokoyama

Youichi MATSUM0TO

The present invention provides a rolling bearing having high wear resistance at high temperature and with reduced manufacturing cost. At least one of an inner ring, an outer ring and rolling elements is formed of the following steel material into a predetermined shape, then applied with hardening and tempering at a temperature of 240&deg; C. or higher or 350&deg; C. or lower to make the Vickers hardness (Hv) on the raceway surface and/or rolling surface to 720 or more. The steel material contains, as the alloy ingredient, 0.8% by weight or more and 1.2% by weight or less of C, 0.5% by weight or more and 2.5% by weight or less of Si, 0.7% by weight or more and 1.5% by weight or less of Cr, 0.8% by weight or more and 2.0% by weight or less of Mo and 0.3% by weight or more and 1.2% by weight or less of Mn, with a ratio of Mo to Cr (Mo/Cr: weight ratio) of 1.1 or more.

Rolling bearing

A surface to serve as a surface under ultrasonic inspection has a roughness of 0.4 &mgr;mRa or less, and wherein all imperfections existing a controlled volume X corresponding to all cross sections of a raceway ring assume a length of 0.2 mm or less as represented by the square root of areas of the imperfections. Accordingly, it is possible to provide a rolling bearing which does not become short-lived and obviates a concern about occurrence of cracking even when used in a harsh environment.

Rolling bearing, and method of ultrasonically detecting flaws in bearing raceway ring of rolling bearing

The continuous annealing furnace has two or more treatment chambers sequentially connected with each other and respectively filled with a gas atmosphere differing in carburizing property, which includes a carburizing chamber wherein roller members to be treated are carburized at 750&deg; C. to 820&deg; C., a slow cooling chamber wherein the roller members are cooled at said temperature or less of the carburizing chamber, an intermediate chamber including atmosphere gas blocking doors that can open/close an exit of the carburizing chamber and an entrance of the slow cooling chamber independently, and transferring means, and each chambers is filled to satisfy a relationship of K &minus;K &gE;2 where K represents a partial pressure ratio between CO and CO in an atmosphere within the carburizing chamber and K represents a partial pressure ratio between CO and CO in an atmosphere within the slow cooling chamber.

Method of manufacturing inner and outer races of deep groove ball bearing in continuous annealing furnace

There is disclosed a sliding rotation member which is rotatably supported by a support shaft in a toroidal continuously variable transmission, and slides on another member, wherein a maximum shear stress depth generated at a maximum deceleration time of the toroidal continuously variable transmission is defined as Z , a size of a defect obtained in accordance with a shape of the defect detected by a nondestructive inspection method is defined as a square root length, and then a defect of 0.05 mm or more in terms of the square root length is not included in a range of a depth from the surface which is twice the depth Z .

Sliding rotation member for toroidal continuously variable transmission and evaluation method

Rolling bearing and method manufacturing the same

A rolling bearing contains no more than 0.3 wt % of nitrogen in a grinding allowance portion after carbonitriding and hardening heat treatments, contains from 0.9 wt % (inclusive) up to 1.6 wt % (inclusive) of carbon and from 0.05 wt % (inclusive) up to 0.3 wt % (inclusive) of nitrogen in the surface layer of the finished part and has a nitrogen gradient of no more than 0.5 wt %/mm in the surface layer of the finished part. The rolling bearings are improved in grinding efficiency and which have their rolling life extended significantly.

Rolling bearing and heat treatment method therefor

In view of the fact that, when backup roll bearings which have been found satisfactory in the purity thereof in the sample evaluation through observations using a microscope are checked many times for the top surface layer portions of the raceway surfaces thereof according to an ultrasonic detecting method, on quite rare occasions, there can be found a bearing which contains one or more inclusions each having a size of as large as several hundreds &mgr;m, and such inclusions give rise to occurrence of a short-life bearing as a finished product, a range expressed by 2% Da depth&times;raceway surface is used as a test piece volume and the size of a non-metallic inclusion existing in the test piece volume is restricted to a length less than 500 &mgr;m, preferably, less than 100 &mgr;m. Here, the term &ldquo;2% Da depth&rdquo; means a depth up to 2% of a rolling element mean diameter from the surface of an inner or outer race of a bearing.

Method of manufacturing rolling bearings

At least one of the components of a rolling member used in a manner in which it is rolled or slid with a mated member is made of carbon steel containing 0.8%-0.9% by weight of C, 0.1%-0.7% by weight of Si, 0.5%-1.1% by weight of Mn, and 0.1%-0.6% by weight of Cr and Fe substantially in the remaining part, wherein an ideal critical diameter DI value calculated from the compositions is 1.5-4.0, and the retained austenite amount after hardened heat treatment is 8%-22% by volume. The value DI is determined by the following equation:

Rolling member and rolling device comprising the same

In an ultrasonic detecting method for a bearing ring in which a bearing ring 2 and an ultrasonic detection probe 3 are disposed within ultrasonic transmission medium such as water, then ultrasonic wave is transmitted from the ultrasonic detection probe 3 to the bearing ring 2, and a defect of the bearing ring 2 is detected on the basis of an ultrasonic wave echo reflected from the bearing ring 2, wherein at least a defect in a range from the surface of the bearing ring 2 to a position beneath by 2 mm from the surface of the bearing ring which is deeper than a maximum shearing stress position of the bearing ring 2 is detected by an angle beam method with an incident angle in a range of 10 to 30.degree., preferably in a range of 25 to 30.degree., and a defect in a range deeper than the range detected by the angle beam method is detected by a normal beam method with an incident angle in a range of 0 to 10.degree., preferably in a range of 0 to 5.degree., thereby to detect a defect in the entire section of the bearing ring 2.

Ultrasonic detecting method for bearing ring

A rolling bearing includes a rolling element made of a steel containing 0.9 to 1.1 wt. % C, 0.1 to 0.5 wt. % Si, 0.2 to 0.8 wt. % Mn, 1.0 to 1.8 wt. % Cr, with the balance being Fe and inevitable impurities. In the rolling bearing at least the surface of the rolling element includes carbides having an area fraction of 5% to 15%; of these carbides, carbides having an averaged particle diameter of 0.5 .mu.m or more share 50% or more of the area fraction of all the carbides; and of the carbides, carbides having an averaged particle diameter of 1 .mu.m or more share 2% or less of the area fraction of all the carbides; and wherein the rolling element has at least a Vickers surface hardness HV of 750 to 900.

In a rolling bearing comprising at least one member of an inner race and a shaft, the member having an inner raceway on an outer circumference, an outer race having an outer raceway on an inner circumference, and a plurality of rolling elements interposed rollingly between the inner raceway and the outer raceway, the member having raceways or rolling elements are formed of a steel containing 5-18 wt% of Cr, 0.5-1.2 wt% of C and the balance being Fe. The steel is tempered at a temperature for secondary hardening or subjected to shot peening after low-temperature tempering, so that its hardness is increased to H.sub.2 C 57 or more. At the same time, the amount of retained austenite in the steel is reduced to 6 vol% or less. As a result, the impression resistance of the raceways is sufficiently improved to insure that there is no deterioration in acoustic characteristics due to indentation. In addition, the fatigue life and wear resistance of the bearing are improved.

Rolling bearing for supporting rotating spindles

In a method and an apparatus for correcting a hardening deformation of an annular element made out of steel, during the cooling stage of hardening, the annular element which still has an austenitic structure is subjected to working on either the outside or inside diameter, with the degree of working being 0.05-1.0% if it is on the outside diameter with the annular element being pressed into a mold, and 0.5-3.0% if the working is on the inside diameter. Thus the deformation that develops in annular steel elements due to heat treatments is effectively corrected to yield completely round, strain-free or deformation-free annular elements.

Growing community of inventors

Kanagawa, Japan

Akihiro Kiuchi