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:
Mar. 02, 1999
Filed:
Apr. 28, 1997
Hideaki Nagayoshi, Fukuoka-ken, JP;
Seishin Ueda, Fukuoka-ken, JP;
Kouhei Imanishi, Fukuoka-ken, JP;
Hitachi Metals, Ltd., Tokyo, JP;
Abstract
A method of producing a spheroidal graphite cast iron article containing at least one pearlite stabilizing element selected from the group consisting of Mn, Cu, Sn, Sb and Pb and having a double layer structure which comprises a surface layer portion and an inner portion. The surface layer portion has a matrix 60% or more of which is ferrite phase and a thickness of at least 0.5 mm. The inner portion has a matrix substantially comprising pearlite phase. The method comprises: (1) heat-treating a starting spheroidal graphite cast iron at a temperature which transforms a whole part of a matrix of the starting spheroidal graphite cast iron substantially to austenite phase; (2) slowly cooling the austenitized spheroidal graphite cast iron at a cooling rate (5.degree. to 20.degree. C./min) which allows in a subsequent step the surface layer portion to be ferritized before the inner portion starts to be pearlitized; (3) holding the cooled spheroidal graphite cast iron at a temperature (710.degree. to 770.degree. C.) which allows the surface layer portion to be first ferritized and subsequently allows the inner portion to be pearlitized while preventing the ferrite phase of the surface layer portion from being transformed to another; and (4) cooling the spheroidal graphite cast iron thus transformed immediately after completion of the pearlitization of the inner portion.