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:
Jul. 16, 2002
Filed:
Oct. 15, 1999
Nippon Steel Corporation, Tokyo, JP;
Abstract
This invention provides a steel for cold forging, excellent in surface layer hardness and softening properties by annealing, which contains, in terms of wt %, C: 0.1 to 1.0%, Si: 0.1 to 2.0%, Mn: 0.01 to 1.50%, P: not greater than 0.100%, S: not greater than 0.500%, sol. N: not greater than 0.005% and the balance consisting of Fe and unavoidable impurities, wherein a pearlite ratio in the steel structure is not greater than 120×(C %) % and the outermost surface layer hardness is at least 450×(C %)+90 in terms of the Vickers hardness HV, and a production method thereof. The invention provides also a steel for cold forging, which has a structure wherein a ratio of graphite amount to the carbon content in the steel exceeds 20%, a mean grain diameter of graphite is not greater than 10×(C %) &mgr;m and a maximum grain diameter is not greater than 20 &mgr;m.