Title:
STEEL FOR HIGH-STRENGTH SPRING AND HEAT-TREATED STEEL WIRE FOR HIGH-STRENGTH SPRING
Document Type and Number:
WIPO Patent Application WO/2008/056428
Kind Code:
A1
Abstract:
A heat-treated steel wire for springs which is coiled by cold working, can combine
sufficient atmospheric strength with suitability for coiling, and has a tensile
strength of 2,000 MPa or higher; and a spring-use steel for use in producing the
steel wire therefrom. The heat-treated steel wire for high-strength springs
is characterized by containing, in terms of mass%, 0.5-0.9% C, 1.0-3.0% Si, 0.1-1.5%
Mn, 1.0-2.5% Cr, 0.15-1.0%, excluding 0.15%, V, and up to 0.005% Al, having a nitrogen
content reduced to 0.007% or lower, further containing one or both of 0.001-0.01%,
excluding 0.01%, Nb and 0.001-0.005%, excluding 0.005%, Ti, and having a tensile
strength of 2,000 MPa or higher. It is further characterized in that in a microscopic
examination concerning cementite carbide spheres and alloy carbide spheres,
the proportion of that area in the surface being examined which is occupied by
these spheres having a diameter of 0.2 µm or larger in terms of equivalent-circle
diameter is 7% or lower and the population of the spheres having a diameter of 0.2
µm or larger in terms of equivalent-circle diameter is 1 or less per µm2,
and that the former austenite grain size number is not smaller than 10 and the residual
austenite content is 15 mass% or lower.
Inventors:
HASHIMURA MASAYUKI (JP)
HAGIWARA HIROSHI (JP)
KISU TAKAYUKI (JP)
YAMAZAKI KOUICHI (JP)
OCHI TATSUROU (JP)
FUJITA TAKASHI (JP)
HAGIWARA HIROSHI (JP)
KISU TAKAYUKI (JP)
YAMAZAKI KOUICHI (JP)
OCHI TATSUROU (JP)
FUJITA TAKASHI (JP)
Application Number:
PCT/JP2006/322784
Publication Date:
May 15, 2008
Filing Date:
November 09, 2006
Export Citation:
Assignee:
NIPPON STEEL CORP (JP)
HASHIMURA MASAYUKI (JP)
HAGIWARA HIROSHI (JP)
KISU TAKAYUKI (JP)
YAMAZAKI KOUICHI (JP)
OCHI TATSUROU (JP)
FUJITA TAKASHI (JP)
HASHIMURA MASAYUKI (JP)
HAGIWARA HIROSHI (JP)
KISU TAKAYUKI (JP)
YAMAZAKI KOUICHI (JP)
OCHI TATSUROU (JP)
FUJITA TAKASHI (JP)
International Classes:
C22C38/58; C22C38/00
Domestic Patent References:
| WO2006059784A1 | 2006-06-08 |
Foreign References:
| JP2006342400A | 2006-12-21 |
Other References:
See also references of EP 2058411A4
None
None
Attorney, Agent or Firm:
AOKI, Atsushi et al. (Toranomon 37 Mori Bldg.5-1, Toranomon 3-chom, Minato-ku Tokyo, JP)
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