Provided is a tripod type constant velocity universal joint (1), including: an outer joint member (2) having track grooves (6) formed at trisected positions in a circumferential direction to extend in an axial direction; a tripod member (3) including leg shafts (9) radially projecting from trisected positions in the circumferential direction; and rollers (4) fitted in a freely rotatable manner about the leg shafts (9), respectively, and received in the track grooves (6), respectively, in which a radially outer surface (4a) of each of the rollers (4) is formed of a surface unsubjected to grinding or cutting work after heat treatment.

A method for cost effectively case hardening a component formed from a martensitic stainless steel material with a desired metallurgical condition for high temperature, high rolling contact fatigue, corrosion and spall initiation and propagation resistance bearing performance. The method describes a method to significantly reduce the carburization or carbo-nitriding process times for appreciable reduction in manufacturing cost. The Method includes the steps of: forming the component from a martensitic stainless steel material having an ASTM grain size of 9 or finer; and subjecting the component to one of a carburization and a carbo-nitriding treatment with significantly lower case hardening times for manufacturing cost-effectiveness.

A method for cost effectively case hardening a component formed from a martensitic stainless steel material with a desired metallurgical condition for high temperature, high rolling contact fatigue, corrosion and spall initiation and propagation resistance bearing performance. The method describes a method to significantly reduce the carburization or carbo-nitriding process times for appreciable reduction in manufacturing cost. The Method includes the steps of: forming the component from a martensitic stainless steel material having an ASTM grain size of 9 or finer; and subjecting the component to one of a carburization and a carbo-nitriding treatment with significantly lower case hardening times for manufacturing cost-effectiveness.

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%.

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%.

A method of manufacturing a component of a rolling-element bearing includes: providing a steel body having a carbon content of less than 0.3 weight-%, a chromium content of greater than 8.0 weight-%, and a nitrogen content of less than 0.1 weight-%; high-temperature solution nitriding the steel body; after the high-temperature solution nitriding, performing an intermediate tempering process to reduce a size of austenite grains in the steel body; and after the intermediate tempering process, performing a reaustenitizing annealing. Also the component made by the method.

A composite casting special-shaped roll is compounded of two parts: an inner layer and an outer layer. The shape of body of the roll is curved surface, and a center hole is arranged for mount the shaft in that central axis of roll. The casting mold is designed into two parts, namely inner cast mold and outer cast mold through the curved surface design and mold design of the roll body. The composite casting special-shaped roll with the wear-proof working layer of the roll body that is resistant to impact, rapid cooling and heating resistance and the high-strength and high-toughness core is prepared by separate casting. It meets the requirements of the service conditions of rolls used by the steel pipe and cold forming sectional steel rolling mill and other equipment, improves the service life of the roll, saves the alloy material and reduces the manufacturing cost.

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.

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.

There is provided a roll surface layer material including a roll surface layer with excellent fatigue resistance. The roll surface layer material has a composition including, on a mass % basis, C: 2.3% to 2.9%, Si: 0.2% to 0.8%, Mn: 0.2% to 1.0%, Cr: 5.0% to 7.5%, Mo: 4.4% to 6.5%, V: 5.3% to 7.0%, Nb: 0.6% to 1.5%, and Co: 0.1% to 4.0% so as to satisfy 14.0(Mo+1.7V)17.0 (where Mo represents a content (mass %) of Mo and V represents a content (mass %) of V) and further including Al: 0.001% to 0.03% and/or REM: 0.001% to 0.03%, wherein a carbide is contained at an area fraction of 13% to 40%. A composite roll obtained by integrally welding a shaft member to the roll surface layer member is treated as a centrifugal cast roll that includes a surface layer with excellent fatigue resistance.