Abstract: A carbonitriding method that can improve the nitrogen permeating rate to render the carbonitriding process effective is directed to carbonitriding a workpiece formed of steel that contains at least 0.8 mass % of carbon by heating in an atmosphere including ammonia, carbon monoxide, carbon dioxide and hydrogen. The method includes an atmosphere control step (50), and a heating pattern control step (60). The atmosphere control step (50) includes an undecomposed NH3 partial pressure control step (51), a CO/CO2 partial pressure control step (53), and an H2 partial pressure control step (52). The undecomposed NH3 partial pressure control step (51), the CO/CO2 partial pressure control step (53) and the H2 partial pressure control step (52) are carried out such that the partial pressure of hydrogen in the heat treatment furnace is at least 0.1 atmospheric pressure and not more than 0.3 atmospheric pressure, and ? defined by the following equation (1) is at least 2.0 and not more than 6.

Abstract: A bearing part comprising steel subjected to carbonitriding at a carbonitriding temperature exceeding the A1 transformation temperature, and cooled to a temperature lower than the A1 transformation temperature. The steel is reheated to a temperature for quenching that is not lower than the A1 transformation temperature but lower than the carbonitriding temperature, and then quenched.

Abstract: A structure supporting a differential rotatably includes an inner ring arranged at the differential, an outer ring arranged at an external peripheral portion formed to surround the differential, and a tapered roller rolling between the inner ring and the outer ring. At least any one of the inner ring, the outer ring and the tapered roller has a carbo-nitrided layer and provides an austenite grain number falling within a range exceeding 10. Thus the structure can be provided with increased anti-crack strength and dimensional stability, and increased rolling contact fatigue life.

Abstract: Ball-and-roller bearing parts are alloyed with alloyed with 0.6% to 1.3% by weight of C, 0.3% to 3.0% by weight of Si, 0.2% to 1.5% by weight of Mn, 0.03% by weight or less of P, 0.03% by weight or less of S, 0.3% to 5.0% by weight of Cr, 0.1% to 3.0% by weight of Ni, 0.050% by weight or less of Al, 0.003% by weight or less of Ti, 0.0015% by weight or less of O, and 0.015% by weight or less of N with the remainder being made up of Fe and inevitable impurities. The part has a nitrogen-enriched layer. The austenite crystals of the steel have a grain size number of greater than 10.

Abstract: To provide a constant velocity universal joint having a high resistance to cracking, a high dimensional stability and an excellent rolling fatigue life, the constant velocity universal joint includes an outer coupling member (5), an inner coupling member such as a tripod member (2), and a drive transmitting member such as rollers (7) operatively interposed between the outer and inner coupling members (5 and 2). At least one of the outer coupling member (5), the tripod member (2) and the rollers (7) has a carbonitrided layer and, at the same time, an austenite grain size is greater than the grade of No. 10.

Abstract: There is provided a rolling bearing which has long life against rolling fatigue and exhibits no decrease in fracture strength and no increase in rate of dimensional change over time, even if the part size thereof is large, and which can obtain higher strength by crystal grains being further refined, if it has a size equal to or smaller than a prescribed size. The rolling bearing according to the present invention includes a race and a rolling element. At least one member of the race and the rolling element has a nitrogen-enriched layer in its surface layer, and a surface layer portion contains austenite crystal grains having a grain size number of at least 11. The member has hardenability allowing a position exhibiting HRC50 in a hardenability test method for steel to be apart from a quenched end by a distance of at least 12.7 mm ( 8/16 inch).

Abstract: A rolling bearing (10) having an outer ring (1), an inner ring (2), and a plurality of rolling elements, wherein at least one of the members, the outer ring (1), inner ring (2) and rolling elements (3), has a nitrogen rich layer and the grain size number of austenite crystal grains is in the range exceeding the number 10.

Abstract: A bearing part comprising steel subjected to carbonitriding at a carbonitriding temperature exceeding the A1 transformation temperature, and cooled to a temperature lower than the A1 transformation temperature. The steel is reheated to a temperature for quenching that is not lower than the A1 transformation temperature but lower than the carbonitriding temperature, and then quenched.

Abstract: Obtain a bearing's component, a heat treatment method thereof, and a rolling bearing having a long life against rolling contact fatigue and high anti-crack strength, and suppressed long-term dimensional variation rate. The bearing's component is carbonitrided at a carbonitriding temperature higher than an A1 transformation point of steel for the bearing's component and then cooled to a temperature lower than the A1 transformation point, and subsequently, using a heat treatment apparatus that successively moves and heats each individual bearing's component, reheated to a range of quenching temperature of no less than the A1 transformation point and less than the carbonitriding temperature to be quenched.

Abstract: To provide a constant velocity universal joint having a high resistance to cracking, a high dimensional stability and an excellent rolling fatigue life, the constant velocity universal joint includes an outer coupling member (5), an inner coupling member such as a tripod member (2), and a drive transmitting member such as rollers (7) operatively interposed between the outer and inner coupling members (5 and 2). At least one of the outer coupling member (5), the tripod member (2) and the rollers (7) has a carbonitrided layer and, at the same time, an austenite grain size is greater than the grade of No. 10.

Abstract: A compressor component incorporated into a compressor having a compressor body and a compressor pulley mechanism transmitting a driving force to the compressor body has an austenite grain with a grain size number falling within a range exceeding 10, a fracture stress value of at least 2650 MPa, or a hydrogen content of at most 0.5 ppm. This provides a compressor component and a compressor bearing with a long fatigue life, a high anti-crack strength, and a reduced secular dimensional variation.

Abstract: A structure supporting a differential rotatably includes an inner ring arranged at the differential, an outer ring arranged at an external peripheral portion formed to surround the differential, and a tapered roller rolling between the inner ring and the outer ring. At least any one of the inner ring, the outer ring and the tapered roller has a carbo-nitrided layer and provides an austenite grain number falling within a range exceeding 10. Thus the structure can be provided with increased anti-crack strength and dimensional stability, and increased rolling contact fatigue life.

Abstract: There is provided a bearing for alternators and a bearing for pulleys capable of reducing hydrogen embrittlement or cracking despite that the bearing is used in an environment under such a severe condition that hydrogen is generated from grease or the like and the bearing experiences a load of a condition facilitating hydrogen embrittlement or cracking. The bearing includes a rolling element, an inner ring and an outer ring, and at least one of the rolling element and the inner and outer rings has a nitrogen enriched layer and contains austenite crystal grains having a grain size number exceeding 10.

Abstract: A transmission component is incorporated into a transmission in which an input shaft, an output shaft, or a gear is rotatably supported by a rolling bearing. The component has a nitriding layer at a surface layer and an austenite grain with a grain size number falling within a range exceeding 10. This provides a transmission component having an increased anti-crack strength, enhanced dimensional stability, and a long fatigue life. A method of manufacturing such a transmission component and a tapered roller bearing are also provided.

Abstract: A bearing part having long life against rolling contact fatigue, excellent in anti-crack strength and restricted in an increase of aged dimensional change, a heat treatment method thereof, and a rolling bearing including the bearing part are obtained. Steel for a bearing part is subjected to carbonitriding at a carbonitriding temperature exceeding the A1 transformation temperature, and cooled to a temperature lower than the A1 transformation temperature. The steel is reheated to a temperature for quenching that is not lower than the A1 transformation temperature but lower than the carbonitriding temperature, and then quenched.