The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 21, 1997
Filed:
Jan. 22, 1996
Hisao Maeda, Kobe, JP;
Yoshitake Matsushima, Kobe, JP;
Morifumi Nakamura, Kobe, JP;
Akito Shiina, Kobe, JP;
Mikio Hirahara, Hiroshima, JP;
Yukio Arimi, Hiroshima, JP;
Yoshihiko Kojima, Hiroshima, JP;
Kabushiki Kaisha Kobe Seiko Sho, Kobe, JP;
Mazda Motor Corporation, Hiroshima, JP;
Abstract
A manufacturing method of case-hardened parts whose chemical components comprising especially Fe, C, Si, Mn, S, Ni, Mo, Al, V and N including a step of the heat treatment 1 in which, after carburizing, carbonitriding or carburizing followed by carbonitriding steel is cooled gradually at a temperature less than 100.degree. C./minute, by another step of the heat treatment 2, in which steel is heated to a temperature higher than the Ac.sub.3 transformation point and less than 850.degree. C. and kept at the above temperature before quenching, or after keeping at the temperature, is cooled down to a level not below 600.degree. C. before quenching, or quenching is done after cooling down to and keeping the temperature not below 600.degree. C. is disclosed. This method makes the surface layer a mixture of martensite and retained austenite. Thus the case hardened steel products of high precision and high strength are obtainable.