Method of manufacturing cold rolled steel sheet excellent in resistance of natural aging and panel properties
US6273971A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 10, 2000 |
| Grant date | Aug 14, 2001 |
| Priority date | — |
| Expiry date | Apr 10, 2020 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D8/0478
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The present invention provides a method of manufacturing a cold rolled steel sheet and a hot-dip zinc-coated steel sheet having excellent surface properties, an excellent resistance to natural aging and an excellent dent resistance of panel and, thus, adapted to the manufacture of steel sheet for outer panels of vehicles. The method comprises the steps of preparing steel consisting of 0.005 to 0.012% by weight of C, 0.01 to 0.4% by weight of Si, 0.15 to 1.0% by weight of Mn, 0.01 to 0.08% by weight of P, at most 0.02% by weight of S, 0.01 to 0.1% by weight of sol. Al, at most 0.004% by weight of N, and at least one element selected from the group consisting of 0.01 to 0.2% by weight of Nb and 0.04 to 0.1% by weight of Ti, and satisfying the condition 1.2.ltoreq.(12/93) (Nb%/C%)+(12/48) (Ti*%/C%).ltoreq.2.5, applying a hot rolling and a cold rolling to the steel, soaking the cold rolled steel sheet at T(.degree. C.) meeting a formula Ac3.gtoreq.T(.degree. C.).gtoreq.157log(X)+737, and cooling the steel sheet after the soaking step at a cooling rate meeting a formula R(.degree. C./sec).ltoreq.-35+162/X. Ti*% (noted above)=Ti%-(48/14)N%-(48/32)S%. When Ti* in the above equation is not…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.