Abstract: There is prepared a formed body constituted of steel and having an outer circumferential surface having an annular groove having a bottom surface to serve as a raceway surface of the bearing ring. In the step of forming a heated region, the formed body is induction heated to form a heated region including the bottom surface of the groove and heated to a temperature of at least an A1 point. In the cooling step, the whole of the heated region is simultaneously cooled to a temperature of not more than an Ms point. The step of retaining the formed body in a state in which heating is stopped is performed after the step of forming a heated region before the step of cooling. In the step of retaining, dispersion in temperature in the heated region in the circumferential direction is suppressed to not more than 20° C.

Abstract: Provided is a high strength steel machine part. A method for manufacturing a machine part comprises the steps of: preparing a workpiece of steel to be a machine part; and subjecting the workpiece to a quenching process by heating a surface portion of the workpiece, with shear strain applied to the surface portion, to a heating temperature of an A3 transformation point temperature or higher, and subsequently cooling the surface portion. The workpiece has a carbon content of 0.2 mass % or more. In the step of subjecting the workpiece to a quenching process, the heating temperature is 800° C. or higher, and in the quenching process the workpiece has the surface portion cooled at a rate of 35° C./second or faster for a temperature range of 850° C. to 300° C.

Abstract: A method for producing a bearing ring of a double row tapered roller bearing includes the steps of: preparing a formed body; forming a heated region; cooing; and removing. In the step of forming a heated region, an induction heating coil arranged to face part of the groove and induction-heating the fixated body is relatively rotated along the circumferential direction of the groove to form a heated region including the bottom surface of the groove and heated to a temperature of at least an Al point. In the cooling step, the whole of the heated region is simultaneously cooled to a temperature of not more than an Ms point. After the step of forming a heated region before the step of cooling, the method further includes the step of retaining the formed body in a state where heating is stopped.

Abstract: A bearing component composed of steel which contains carbon not less than 0.95 mass % and not more than 1.1 mass %, silicon less than 0.3 mass %, manganese less than 0.5 mass %, sulfur less than 0.008 mass %, and chromium not less than 1.4 mass % and less than 1.6 mass % and is composed of remainder iron and an impurity and having a carbonitrided layer formed at a surface portion including a contact surface is provided. An average concentration of nitrogen in the surface portion is not lower than 0.3 mass % and not higher than 0.6 mass % and variation in nitrogen concentration in the surface portion is not higher than 0.1 mass %. An area ratio of a precipitate in a region where no carbonitrided layer is formed is not higher than 7%.

Abstract: A bearing component composed of steel which contains carbon not less than 0.95 mass % and not more than 1.1 mass %, silicon less than 0.3 mass %, manganese less than 0.5 mass %, sulfur less than 0.008 mass %, and chromium not less than 1.4 mass % and less than 1.6 mass % and is composed of remainder iron and an impurity and having a carbonitrided layer formed at a surface portion is provided. An average concentration of nitrogen in the surface portion is not lower than 0.3 mass % and not higher than 0.6 mass % and variation in nitrogen concentration is not higher than 0.1 mass %. An amount of retained austenite is not greater than 8 volume %. An area ratio of a precipitate in the inside where no carbonitrided layer is formed is not lower than 11%.

Abstract: A bearing component composed of steel which contains carbon not less than 0.95 mass % and not more than 1.1 mass %, silicon less than 0.3 mass %, manganese less than 0.5 mass %, sulfur less than 0.008 mass %, and chromium not less than 1.4 mass % and less than 1.6 mass % and is composed of remainder iron and an impurity and having a carbonitrided layer formed at a surface portion including a contact surface which is a surface in contact with other components is provided. An average concentration of nitrogen in the surface portion is not lower than 0.3 mass % and not higher than 0.6 mass % and variation in nitrogen concentration in the surface portion is not higher than 0.1 mass %.

Abstract: A first step of setting a steel material heated to a temperature not lower than an A1 transformation point on a forming table and a second step of punching a ring-form member from the steel material and thereafter forming and quenching the ring-form member on the forming table are included. A press die is constructed to be dividable into an inner cylinder and an outer cylinder. In the second step, the ring-form member is punched from a coil material by pressing a tip end portion of the inner cylinder and a tip end portion of the outer cylinder against the coil material. The punched ring-form member is formed and quenched by further pressing a tip end of the inner cylinder against the ring-form member while the ring-form member is held between the outer cylinder and a forming die. A method of manufacturing a rolling bearing ring which achieves a shortened manufacturing process while accuracy in forming of the rolling bearing ring is satisfactorily maintained is thus provided.

Abstract: Provided is a gas nitrocarburizing method forming a nitride layer in a surface layer portion of a workpiece made of steel by heating the workpiece within a heat treatment furnace into which a heat treatment gas is introduced, the heat treatment gas containing ammonia gas and at least one of carbon dioxide gas and hydrogen gas, and having a remainder formed of an impurity.

Abstract: There is provided a high-strength steel mechanical component. A mechanical component is a mechanical component composed of a steel having a carbon content of more than or equal to 0.2 mass % and less than or equal to 0.8 mass %, and includes a quench-hardened layer formed in a surface layer of the mechanical component. In the quench-hardened layer, a grain size number of prior austenite crystal grains is No. 11 or higher. Moreover, the quench-hardened layer may have a Vickers hardness of more than or equal to 500 HV. In this case, prior austenite crystal grains in the quench-hardened layer become fine, thereby providing the mechanical component with high strength.

Abstract: An outer ring, an inner ring, and a ball each serving as a bearing part is made of a steel containing 0.95 mass % or more and 1.10 mass % or less of carbon, 0.05 mass % or more and less than 0.3 mass % of silicon, 0.10 mass % or more and 0.50 mass % or less of manganese, and 1.30 mass % or more and 2.00 mass % or less of chromium, with the rest made up of iron and an impurity. A surface layer region defined as a region extending to a depth of not more than 20 ?m from an outer ring raceway surface, an inner ring raceway surface, and a ball rolling surface, which are each a surface where the bearing part is in rolling contact with another part, has an average nitrogen concentration of 0.2 mass % or more and 0.7 mass % or less. Five or more carbides with a diameter of 0.5 ?m or less are present per 100 ?m2 in the surface layer region.

Abstract: Each of an outer race (10), an inner race (11) and a ball (12) as a bearing part is a bearing part made of JIS standard SUJ2 and having a carbonitrided layer formed in a surface thereof, wherein, after heat treatment at a heating temperature of 500° C. for a retention time of one hour is performed, a Vickers hardness at a position with a depth of 0.02×T+0.175 (mm) from the surface is higher than a Vickers hardness at a core portion, which is a region where the carbonitrided layer is not formed in a thickness direction of the bearing part, by not less than 80 HV, where T represents the time of carbonitriding treatment for forming the carbonitrided layer.

Abstract: A joint unit includes a first metal pipe, a second metal pipe, and a joint portion (a region including a joint interface at which the end faces of the first and second metal pipes are joined to each other. At the joint portion, an outer circumferential bead portion protruding toward the outer circumference side and an inner circumferential bead portion protruding toward the inner circumference side are formed. The difference between the width of the outer circumferential bead portion (the width L1 of a grinding portion and the width L2 of the inner circumferential bead portion in a direction from the first metal pipe toward the second metal pipe is equal to or smaller than 40% with respect to the average value of the width L1 of the outer circumferential bead portion and the width L2 of the inner circumferential bead portion.

Abstract: A method of manufacturing a rolling bearing ring includes preparing a coil material and a press machine for obtaining a rolling bearing ring from the coil material, setting the coil material on the press machine, and obtaining the rolling bearing ring by heating the coil material on the press machine to a temperature not lower than an A1 transformation point, thereafter punching a part of the coil material into a ring form, and thereafter quenching a formed object on the press machine.

Abstract: A method for producing a bearing ring of a rolling bearing includes the steps of: preparing a formed body constituted of hypereutectoid steel; forming an annular heated region heated to a temperature of at least an A1 point on the formed body by relatively rotating an induction heating member arranged to face part of an annular region for becoming a rolling contact surface of the bearing ring in the formed body to induction-heat the formed body along the circumferential direction of the annular region; and simultaneously cooling the whole of the heated region to a temperature of not more than an Ms point.

Abstract: An outer ring, an inner ring, and a ball each serving as a bearing part is made of a steel containing 0.95 mass % or more and 1.10 mass % or less of carbon, 0.05 mass % or more and less than 0.3 mass % of silicon, 0.10 mass % or more and 0.50 mass % or less of manganese, and 1.30 mass % or more and 2.00 mass % or less of chromium, with the rest made up of iron and an impurity. A surface layer region defined as a region extending to a depth of not more than 20 ?m from an outer ring raceway surface, an inner ring raceway surface, and a ball rolling surface, which are each a surface where the bearing part is in rolling contact with another part, has an average nitrogen concentration of 0.2 mass % or more and 0.7 mass % or less. Five or more carbides with a diameter of 0.5 ?m or less are present per 100 ?m2 in the surface layer region.

Abstract: Disclosed is a method for heat-treating a ring-shaped member, which makes it possible to form a quench-hardened region having a uniform annular shape in the circumferential direction, while the production costs in terms of the quenching apparatus are kept down. The method includes the following steps: a step in which a coil which is disposed in such a way as to face a rolling contact surface of a ring-shaped formed body made of steel and which performs induction heating of the formed body is rotated relative to the formed body in the circumferential direction thereof, whereby an annular heating region which is heated to a temperature at or above an A1 point is formed on the formed body; and a step in which the whole of the heating region is simultaneously cooled to a temperature at or below an MS point.

Abstract: A bearing component composed of steel which contains carbon not less than 0.95 mass % and not more than 1.1 mass %, silicon less than 0.3 mass %, manganese less than 0.5 mass %, sulfur less than 0.008 mass %, and chromium not less than 1.4 mass % and less than 1.6 mass % and is composed of remainder iron and an impurity and having a carbonitrided layer formed at a surface portion including a contact surface which is a surface in contact with other components is provided. An average concentration of nitrogen in the surface portion is not lower than 0.3 mass % and not higher than 0.6 mass % and variation in nitrogen concentration in the surface portion is not higher than 0.1 mass %. An amount of retained austenite in the surface portion is not greater than 8 volume %.

Abstract: A bearing component composed of steel which contains carbon not less than 0.95 mass % and not more than 1.1 mass %, silicon less than 0.3 mass %, manganese less than 0.5 mass %, sulfur less than 0.008 mass %, and chromium not less than 1.4 mass % and less than 1.6 mass % and is composed of remainder iron and an impurity and having a carbonitrided layer formed at a surface portion including a contact surface is provided. An average concentration of nitrogen in the surface portion is not lower than 0.3 mass % and not higher than 0.6 mass % and variation in nitrogen concentration in the surface portion is not higher than 0.1 mass %. An area ratio of a precipitate in a region where no carbonitrided layer is formed is not higher than 7%.

Abstract: A bearing component composed of steel which contains carbon not less than 0.95 mass % and not more than 1.1 mass %, silicon less than 0.3 mass %, manganese less than 0.5 mass %, sulfur less than 0.008 mass %, and chromium not less than 1.4 mass % and less than 1.6 mass % and is composed of remainder iron and an impurity and having a carbonitrided layer formed at a surface portion including a contact surface which is a surface in contact with other components is provided. An average concentration of nitrogen in the surface portion is not lower than 0.3 mass % and not higher than 0.6 mass % and variation in nitrogen concentration in the surface portion is not higher than 0.1 mass %.

Abstract: A bearing component composed of steel which contains carbon not less than 0.95 mass % and not more than 1.1 mass %, silicon less than 0.3 mass %, manganese less than 0.5 mass %, sulfur less than 0.008 mass %, and chromium not less than 1.4 mass % and less than 1.6 mass % and is composed of remainder iron and an impurity and having a carbonitrided layer formed at a surface portion is provided. An average concentration of nitrogen in the surface portion is not lower than 0.3 mass % and not higher than 0.6 mass % and variation in nitrogen concentration is not higher than 0.1 mass %. An amount of retained austenite is not greater than 8 volume %. An area ratio of a precipitate in the inside where no carbonitrided layer is formed is not lower than 11%.