Patent ID: 11952668
Assignee: NIPPON STEEL CORPORATION
Field: Materials, metallurgy (Chemistry)
Classification: CPC C | IPC C

Claim 2:
3. A method of manufacture for manufacturing the carburized part of claim 1 comprising the steps of:
shaping into the shape of a machine part a steel material having a chemical composition in a region of a depth of 1.5 mm or more from the surface as described in claim 1,
vacuum carburizing the shaped steel material,
cooling the vacuum carburized steel material by a cooling rate of 10° C./s or more from a temperature region of 850° C. or more until reaching 200° C., and
tempering the cooled steel material at 130 to 200° C.;
the process of vacuum carburizing comprising
a carburizing period of holding the steel material at 850 to 1100° C. for 10 to 200 minutes and causing carbon to penetrate it in a carburizing gas atmosphere and
a diffusion period of stopping the supply of carburizing gas and holding the steel material at
(a) 850 to 970° C. for 50 to 300 minutes or
(b) over 970 to 1100° C. for 15 to 300 minutes.