Cold-rolled steel sheet having excellent strain aging hardening properties and method for producing the same
US6695932B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 23, 2002 |
| Grant date | Feb 24, 2004 |
| Priority date | — |
| Expiry date | Jan 23, 2022 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02P10/20
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The present invention provides a cold-rolled sheet exhibiting superior strain-aging hardenability which is suitable for use in automobile bodies, and a method for manufacturing the same. In particular, a slab including, by mass, not more than 0.15% carbon, not more than 0.02% Al, and 0.0050% to 0.0250% nitrogen in which Si+Mn/5+10P is adjusted to less than 0.44 and the ratio N/Al is adjusted to not less than 0.3 is hot-rolled at a finish-rolling delivery temperature FDT of not less than 800° C., and then coiled at a temperature of not more than 650° C. Next, after cold-rolling, continuous-annealing at a temperature between the recrystallization temperature and 950° C., primary cooling for cooling to a temperature zone of not more than 500° C., and overaging in the temperature zone of 350° C. to 450° C. for a retention time of not more than 30 seconds are performed to prepare a steel sheet containing not less than 0.0010% of solute nitrogen and having a structure in which the ferrite phase with the grain size of not more than 15 &mgr;m is included at a ratio of not less than 90%, the remainder of the structure being the pearlite phase. The resulting steel she…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.