Provided is a cage (5, 65, 95) for a constant velocity universal joint, which is formed into a ring shape with a substantially uniform thickness, including a plurality of pockets (20, 80, 110) formed in a circumferential direction of the cage (5, 65, 95), for receiving torque transmitting balls, respectively, the cage (5, 65, 95) being formed of carbon steel including 0.41 to 0.51 mass % of C, 0.10 to 0.35 mass % of Si, 0.60 to 0.90 mass % of Mn, 0.005 to 0.030 mass % of P, and 0.002 to 0.035 mass % of S, with the balance being Fe and an element inevitably remaining at the time of steelmaking and refining, the cage (5, 65, 95) being subjected to carburizing, quenching, and tempering as heat treatment, each of the plurality of pockets (20, 80, 110) having a side surface (23, 83, 113) finished after the heat treatment.

Provided is a cage (5, 65, 95) for a constant velocity universal joint, which is formed into a ring shape with a substantially uniform thickness, including a plurality of pockets (20, 80, 110) formed in a circumferential direction of the cage (5, 65, 95), for receiving torque transmitting balls, respectively, the cage (5, 65, 95) being formed of carbon steel including 0.41 to 0.51 mass % of C, 0.10 to 0.35 mass % of Si, 0.60 to 0.90 mass % of Mn, 0.005 to 0.030 mass % of P, and 0.002 to 0.035 mass % of S, with the balance being Fe and an element inevitably remaining at the time of steelmaking and refining, the cage (5, 65, 95) being subjected to carburizing, quenching, and tempering as heat treatment, each of the plurality of pockets (20, 80, 110) having a side surface (23, 83, 113) finished after the heat treatment.

A bearing steel composition contains 0.1 to 0.2 wt % C, 3.25 to 4.25 wt % Cr, 9.5 to 11.5 wt % Mo, 5.75 to 6.75 wt % W, 1.5 to 2.5 wt % V, and 2.5 to 3.5 wt % Ni. A bearing component, such as a rolling element, an inner race or outer race, is formed from the bearing steel composition, for example, by a powder metallurgical technique and then is subjected to a case hardening treatment. The bearing component may have a microstructure composed of martensite, retained austenite and at least one of carbides and/or carbonitrides. The carbon level at the surface of the bearing component may be 0.5 to 1.1 wt %.

A bearing steel composition contains 0.1 to 0.2 wt % C, 3.25 to 4.25 wt % Cr, 9.5 to 11.5 wt % Mo, 5.75 to 6.75 wt % W, 1.5 to 2.5 wt % V, and 2.5 to 3.5 wt % Ni. A bearing component, such as a rolling element, an inner race or outer race, is formed from the bearing steel composition, for example, by a powder metallurgical technique and then is subjected to a case hardening treatment. The bearing component may have a microstructure composed of martensite, retained austenite and at least one of carbides and/or carbonitrides. The carbon level at the surface of the bearing component may be 0.5 to 1.1 wt %.

The present invention provides a method for obtaining a carburized part using steel high in content of Cr and realizing bending fatigue strength at an extremely high level by vacuum carburizing. The carburized part is obtained by treating a steel material having a predetermined chemical composition by vacuum carburizing provided with a carburizing period of 10 to 200 minutes at 850 to 1100° C. and a diffusion period of 15 to 300 minutes at 850 to 1100° C., then quenching and tempering it.

The present invention provides a method for obtaining a carburized part using steel high in content of Cr and realizing bending fatigue strength at an extremely high level by vacuum carburizing. The carburized part is obtained by treating a steel material having a predetermined chemical composition by vacuum carburizing provided with a carburizing period of 10 to 200 minutes at 850 to 1100° C. and a diffusion period of 15 to 300 minutes at 850 to 1100° C., then quenching and tempering it.

A soft magnetic material that is sheet-shaped or foil-shaped and has a high saturation magnetic flux density, contains iron, carbon, and nitrogen, and includes a martensite containing carbon and nitrogen, and γ-Fe, wherein the γ-Fe includes a nitrogen-containing phase. The soft magnetic material is produced by steps of heating an iron-based material that is sheet-shaped or foil-shaped, carburizing the iron-based material with a carburizing gas, dispersing a granular carbide in α-Fe in the iron-based material at a temperature equal to or lower than a eutectoid temperature, transforming the α-Fe into γ-Fe at a temperature higher than the eutectoid temperature, diffusing nitrogen into the γ-Fe using a nitrogen supply gas to form γ-Fe—N—C, and rapidly heating and then rapidly cooling the γ-Fe—N—C to transform the γ-Fe—N—C into a martensite. The result is a thermally stable soft magnetic material having a saturation magnetic flux density higher than that of pure iron.

A soft magnetic material that is sheet-shaped or foil-shaped and has a high saturation magnetic flux density, contains iron, carbon, and nitrogen, and includes a martensite containing carbon and nitrogen, and γ-Fe, wherein the γ-Fe includes a nitrogen-containing phase. The soft magnetic material is produced by steps of heating an iron-based material that is sheet-shaped or foil-shaped, carburizing the iron-based material with a carburizing gas, dispersing a granular carbide in α-Fe in the iron-based material at a temperature equal to or lower than a eutectoid temperature, transforming the α-Fe into γ-Fe at a temperature higher than the eutectoid temperature, diffusing nitrogen into the γ-Fe using a nitrogen supply gas to form γ-Fe—N—C, and rapidly heating and then rapidly cooling the γ-Fe—N—C to transform the γ-Fe—N—C into a martensite. The result is a thermally stable soft magnetic material having a saturation magnetic flux density higher than that of pure iron.

An object of the present disclosure is to make it possible to allow an operator or the like to grasp a carbon potential value of an atmosphere in a heat treatment furnace more simply. A heat treatment furnace (10) according to one aspect of the present disclosure includes a carbon potential value deriving section configured to derive a carbon potential value of an atmosphere in a heat treatment chamber on a basis of output of a gas sensor, and output of a temperature sensor, and a first display section configured to display the derived carbon potential value (P1) on a graph D that is displayed in a first display area (41A), and has a first axis representing carbon potential values, and a second axis representing temperatures and crossing the first axis.

An object of the present disclosure is to make it possible to allow an operator or the like to grasp a carbon potential value of an atmosphere in a heat treatment furnace more simply. A heat treatment furnace (10) according to one aspect of the present disclosure includes a carbon potential value deriving section configured to derive a carbon potential value of an atmosphere in a heat treatment chamber on a basis of output of a gas sensor, and output of a temperature sensor, and a first display section configured to display the derived carbon potential value (P1) on a graph D that is displayed in a first display area (41A), and has a first axis representing carbon potential values, and a second axis representing temperatures and crossing the first axis.