Cold-rolled steel sheet and hot-dip galvanized cold-rolled steel sheet having excellent bake hardenability, non-aging properties at room temperature and good formability and process for producing the same
US5690755A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 11, 1996 |
| Grant date | Nov 25, 1997 |
| Priority date | — |
| Expiry date | Sep 11, 2016 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/12799
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The present invention provides a cold-rolled steel sheet and a hot-dip galvanized steel sheet having good bake hardenability, non-aging properties at room temperature and good formability and a process for producing the same. An extra low carbon steel or an extra low carbon steel containing at least one element selected from Ti and Nb is annealed at a temperature of not lower than the AC.sub.3 transformation point to bring the structure after annealing to a structure of low-temperature transformation products. This makes it possible to provide a steel sheet that has a combination of high paint-bake hardenability and non-aging properties at room temperature and is excellent also in formability in respect of average r value (deep drawability) and elongation (punch stretchability). In particular, with respect to paint-bake hardenability, a BH property on a high level up to about 10 kgf/mm.sup.2 can be imparted according to need, and it is possible to provide a cold-rolled steel sheet and a hot-dip galvanized cold-rolled steel sheet that also have a non-aging property at room temperature.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.