Ultra low carbon, cold rolled steel sheet and galvanized steel sheet having improved fatigue properties and processes for producing the same
US5855696A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 19, 1997 |
| Grant date | Jan 5, 1999 |
| Priority date | — |
| Expiry date | Mar 19, 2017 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D8/0478
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The cold rolled steel sheet or galvanized steel sheet comprises by weight C: 0.0001 to 0.0026%, Si: not more than 1.2%, Mn: 0.03 to 3.0%, P: 0.015 to 0.15%, S: 0.0010 to 0.020%, Al: 0.005 to 0.1%, N: 0.0005 to 0.0080% and B: 0.0003 to 0.0030% with the balance consisting of Fe and unavoidable impurities. A process for producing the above steel sheet is also provided which comprises the steps of: performing hot roll finishing of a slab having the above chemical composition at the Ar.sub.3 transformation point or above; preferably, then cooling the hot rolled strip, within 1.5 sec after the completion of the hot rolling, to 750.degree. C. at a rate of not less than 50.degree. C./sec; coiling the strip in the temperature range of from room temperature to 750.degree. C.; cold rolling the coiled strip a reduction ratio of not less than 70%; subjecting the cold rolled strip to continuous annealing at 600.degree. to 900.degree. C. or to continuous galvanizing by the sendzimer method; and performing temper rolling with a reduction ratio of not less than 1.5.times.(1-400.times.C) % and not less than 2080.times.(C - 0.0015) wherein C represents the carbon content in % by weight.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.