Nsk Corporation

Hideyuki Hidaka

Masahide Natori

Kazuki Tamura

Daisuke Watanuki

Hirofumi Ito

Yuji Miyamoto

Hiroyuki Uchida

Hiroki Komata

Hayato Ishigami

Takahito Shimada

Sho Hashimoto

Riichiro Matoba

Tomoki Doshida

There is provided a method for evaluating the cleanliness of a steel material by an ultrasonic flaw detection method enabling rapid acquisition of highly reliable data. Ultrasonic flaw detection is performed to detect a flaw in at least one part in the range of 90% or more and 100% or less of a steel material (for example, round bar) at a radial position where the center of the steel material is set as 0% and the surface is set as 100%, and then the cleanliness is evaluated based on the dimension and the number of inclusions in the steel material obtained by the ultrasonic flaw detection.

Method for evaluating cleanliness of steel material

A method for measuring indentation resistance includes: obtaining a first curve indicating a yield shear stress in a depth direction of a raceway surface of a material forming a rolling bearing in a state before the raceway surface is subjected to machining, a second curve indicating a static shear stress in the depth direction of the raceway surface in a state in which the raceway surface is subjected to the machining, and a third curve indicating a static shear stress in the depth direction of the raceway surface in a state in which rolling elements are in contact with the raceway surface and a static load is applied to the raceway surface; and obtaining a correlation between an area and an indentation depth of the raceway ring by defining a region surrounded by exceeding the first curve and the second curve and falling below the third curve as the area.

Indentation resistance measurement method, indentation resistance prediction method for rolling bearings, machining condition selection method, bearing material quality selection method, burnishing condition selection method, and bearing manufacturing method

In a raceway surface of at least one of an inner ring and an outer ring, a region not affected by machining is set as a first region, and a region, which has (a) a machining amount of 0.03 or more, (b) an amount of residual austenite being 70% or more of an amount of retained austenite in the first region, and (c) a compressive residual stress being higher by 500 MPa or more than a compressive residual stress in the first region, is set as a second region.

Rolling bearing and method for producing same

A method for manufacturing a bearing ring of a rolling bearing includes a series of steps of cutting out an annular member from a material, forming a surface-hardened layer on the annular member, quenching and tempering the annular member, and polishing inner and outer diameter surfaces of the annular member. The method includes, after the quenching, rapidly cooling the ring member such that the ring member has a surface temperature of 50&#xb0; C. or lower to form a bearing ring intermediate member, and after the tempering, polishing inner and outer diameter surfaces of the bearing ring intermediate member.

Intermediary race member of rolling bearing, race, rolling bearing and production method therefor

A rolling bearing in which at least one of the bearing rings is obtained by applying a induction heat treatment to a spheroidizing annealed steel material having a DI value of 1.0 or more to form a hardened layer having a hardness of 550 HV or more on at least a raceway surface and a fitting surface. In the induction heat-treated bearing ring, (A) an average retained austenite amount is 12 vol % or less, (B) the raceway surface has a retained austenite amount of 12 vol % or more and a residual compressive stress of &#x2212;100 MPa or less, and (C) a difference between a hardness of the raceway surface and a minimum hardness of a region having a hardness of less than 550 HV is 150 HV or more.

Rolling bearing

In the rolling bearing of the present invention, at least one of the bearing rings is obtained by applying a induction heat treatment to a spheroidizing annealed steel material having a DI value of 1.0 or more to form a hardened layer having a hardness of 550 HV or more on at least a raceway surface and a fitting surface, and in the induction heat-treated bearing ring, (A) an average retained austenite amount is 12 vol % or less, (B) the raceway surface has a retained austenite amount of 12 vol % or more and a residual compressive stress of &#x2212;100 MPa or less, and (C) a difference between a hardness of the raceway surface and a minimum hardness of a region having a hardness of less than 550 HV is 150 HV or more.

Growing community of inventors

Fujisawa, Japan

Hideyuki Hidaka