Method of manufacturing constituent member of constant-velocity joint

1. A method of manufacturing a constituent member of a constant-velocity joint, comprising:

heating a temperature of a material of the constituent member to a plastic working start temperature;

performing plastic working on the material of the constituent member while the temperature of the constituent member decreases such that the temperature of the constituent member is at a hardening cooling start temperature immediately after the plastic working is completed; and

performing hardening of the material by cooling the material from the hardening cooling start temperature after performing the plastic working,

wherein the plastic working start temperature is between 900° C. and 1050° C., and

wherein the hardening cooling start temperature is greater than or equal to a transformation point of the material of the constituent member.

2. The method of manufacturing a constituent member of a constant-velocity joint according to claim 1 , further comprising:

applying a paint to the material after performing the hardening;

drying the paint on the material in a predetermined drying temperature range after applying the paint; and

performing tempering of the material by utilizing heat applied for heating to the drying temperature range in the drying as heat for the tempering of the material and by cooling the material.

3. The method of manufacturing a constituent member of a constant-velocity joint according to claim 2 , further comprising

performing turning of the material after performing the hardening and before applying the paint.

4. The method of manufacturing a constituent member of a constant-velocity joint according to claim 1 , further comprising:

performing tempering of the material after performing the hardening; and

performing turning of the material after performing the tempering.

5. The method of manufacturing a constituent member of a constant-velocity joint according to claim 1 , wherein the heating the temperature of the constituent member to the plastic working start temperature is performed in an inert gas atmosphere.

6. The method of manufacturing a constituent member of a constant-velocity joint according to claim 1 , further comprising

removing scales of the material immediately after performing the hardening.

7. The method of manufacturing a constituent member of a constant-velocity joint according to claim 1 , wherein the hardening is performed with the material restrained so as to suppress deformation and distortion of the material due to the hardening.

8. The method of manufacturing a constituent member of a constant-velocity joint according to claim 1 , further comprising

correcting the material after performing the hardening so as to remove deformation and distortion of the material due to the hardening.

9. The method of manufacturing a constituent member of a constant-velocity joint according to claim 1 , wherein the performing plastic working on the material of the constituent member includes rough processing of an outer periphery of a cup portion and an outer periphery of a coupling shaft portion through warm forging, and finishing of an inner peripheral surface of the cup portion and a spline portion of the coupling shaft portion and rough processing of an outside ball groove portion and an inside spherical surface portion through warm ironing.

10. A method of manufacturing a constituent member of a constant-velocity joint, comprising:

heating a temperature of a material of the constituent member to a plastic working start temperature;

performing plastic working on the material of the constituent member while the temperature of the constituent member decreases from the plastic working start temperature such that the temperature of the constituent member is greater than or equal to a transformation point of the material of the constituent member immediately after the plastic working is completed;

cooling the material of the constituent member to room temperature after the plastic working is completed;

performing hardening of the material of the constituent member by heating the material of the constituent member to a hardening start temperature and then cooling the material of the constituent member to room temperature;

applying a paint to the material after performing the hardening;

heating the material to a predetermined drying temperature after applying the paint to dry the paint; and

performing tempering of the material by keeping the material at the drying temperature for a predetermined tempering time and then cooling the material,

wherein the hardening cooling start temperature is greater than or equal to the transformation point of the material of the constituent member.

11. The method of manufacturing a constituent member of a constant-velocity joint according to claim 10 , further comprising

removing scales of the material immediately after performing the hardening.

12. The method of manufacturing a constituent member of a constant-velocity joint according to claim 11 , further comprising

correcting the material after performing the hardening so as to remove deformation and distortion of the material due to the hardening.

13. The method of manufacturing a constituent member of a constant-velocity joint according to claim 10 , wherein the hardening is performed with the material restrained so as to suppress deformation and distortion of the material due to the hardening.

14. The method of manufacturing a constituent member of a constant-velocity joint according to claim 10 , wherein the predetermined drying temperature is between 150° C. and 200° C.