High strength spring steel and steel wire
US10131973B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 30, 2005 |
| Grant date | Nov 20, 2018 |
| Priority date | — |
| Expiry date | Aug 13, 2028 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC22C38/28
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The present invention provides spring steel used for spring steel wire achieving both high strength and cold coilability and spring steel wire, that is, spring steel containing, by mass %, C: 0.45 to 0.70%, Si: 1.0 to 3.0%, Mn: 0.05 to 2.0%, P: 0.015% or less, S: 0.015% or less, N: 0.0015 to 0.0200%, and t-O: 0.0002 to 0.01 and further limiting Al≤0.01% and Ti≤0.003%. Further, it is characterized by satisfying the following regarding the cementite-based spherical carbides present at an observed plane, an occupied area ratio of grains with a circle equivalent diameter of 0.2 μm or more of 7% or less, a density of presence of grains with a circle equivalent diameter of 0.2 to 3 μm of 1/μm2 or less, and a density of presence of grains with a circle equivalent diameter 3 μm or more of 0.001/μm2 or less, having an prior austenite grain size number of #10 or higher and a residual austenite of 15 mass % or less, and having an area ratio of poor regions with a small density of presence of cementite-based carbides of a circle equivalent diameter of 2 μm or more of 3% or less.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.