High-strength and high-ductility steel for spring, method for producing same, and spring
AssigneeNHK Spring Co., Ltd.
InventorsTakeshi Suzuki, Yoshiki Ono
Life of this patent
Estimating the term…
Abstract
A steel for spring includes C: 0.5 to 0.6%, Si: 1.0 to 1.8%, Mn: 0.1 to 1.0%, Cr: 0.1 to 1.0%, P: 0.035% or less, S: 0.035% or less, by mass %, and a balance of iron and inevitable impurities, as the overall composition, wherein an area ratio of an internal structure on an optional cross section comprises bainite: 65% or more, retained austenite: 6 to 13%, and a balance of martensite, and average C content in the retained austenite is 0.65 to 1.7%. The steel for spring can have high strength in which tensile strength is 1800 MPa or more and have high ductility.
Claims4
A steel for a spring, consisting of, by mass % as an overall composition:
- C:
- 0.5 to 0.6%,
- Si:
- 1.0 to 1.8%,
- Mn:
- 0.1 to 1.0%,
- Cr:
- 0.1 to 1.0%,
- P:
- 0.035% or less,
- S:
- 0.035% or less, and
- a balance of iron and inevitable impurities,
- wherein
- an area ratio of an internal structure on a cross section comprises
- bainite:
- 65% or more,
- retained austenite:
- 6 to 13%, and
- a balance of martensite, and
- an average C content in the retained austenite is 0.65 to 1.7%.
Dependencies are inferred from the claim text.