Heat-treated steel wire for high strength spring

Details Heat-treated steel wire for high strength spring Heat-treated steel wire for high strength spring

2002-02-07

2009-08-18

King, Roy (Department: 1793)

Metal treatment

Stock

Ferrous

C420S114000

Reexamination Certificate

active

07575646

ABSTRACT:
The present invention provides a steel wire, for springs excellent in coiling property while having a high strength, as a heat treated steel wire for high strength springs, characterized by: comprising, in mass, C: 0.75 to 0.85%, Si: 1.5 to 2.5%, Mn: 0.5 to 1.0%, Cr: 0.3 to 1.0%, P: not more than 0.015%, S: not more than 0.015%, N: 0.001 to 0.007%, W: 0.05 to 0.3%, and the balance consisting of Fe and unavoidable impurities; having a tensile strength of not less than 2,000 MPa; spheroidal carbides, composed of mainly cementite, observed in a microscopic visual field satisfying the area percentage of the spheroidal carbides not less than 0.2 μm in circle equivalent diameter being not more than 7%, the density of the spheroidal carbides 0.2 to 3 μm in circle equivalent diameter being not more than 1 piece/μm2, and the density of the spheroidal carbides over 3 μm in circle equivalent diameter being not more than 0.001 piece/μm2; the prior austenite grain size number being #10 or larger; the content of the retained austenite being not more than 12 mass %; the maximum diameter of carbides being not more than 15 μm; and the maximum diameter of oxides being not more than 15 μm.

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English Translation of Murai (JP 05-331597).
English Translation of Yamao et al. (JP 11-006033).
English Translation of Hirai et al. (JP 06-240408).
English Translation of Nishida et al. (JP 2000-219938).

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