Hot-rolled steel sheet excellent in fatigue properties and stretch-flange formability and method for manufacturing the same
US8657970B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 12, 2008 |
| Grant date | Feb 25, 2014 |
| Priority date | — |
| Expiry date | Jun 13, 2029 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D2211/005
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
This hot-rolled steel sheet contains, in terms of mass %, C: 0.015% or more to less than 0.040%; Si: less than 0.05%; Mn: 0.9% or more to 1.8% or less; P: less than 0.02%; S: less than 0.01%; Al: less than 0.1%; N: less than 0.006%; and Ti: 0.05% or more to less than 0.11%, with the remainder being Fe and inevitable impurities, wherein Ti/C is in a range of 2.5 or more to less than 3.5, Nb, Zr, V, Cr, Mo, B and W are not included, a microstructure includes a mixed microstructure of polygonal ferrite and quasi-polygonal ferrite in a proportion of greater than 96%, a maximum tensile strength is 520 MPa or more and less than 720 MPa, an aging index AI is more than 15 MPa, a product of a hole expansion ratio (λ) % and a total elongation (El) % is 2350 or more, and a fatigue limit is 200 MPa or more.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.