Process for manufacturing a galvanized or a galvannealed steel sheet by DFF regulation
US8470102B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 11, 2008 |
| Grant date | Jun 25, 2013 |
| Priority date | — |
| Expiry date | Feb 1, 2030 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/12799
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
The invention deals with a process for manufacturing a hot-dip galvanized or galvannealed steel sheet having a TRIP microstructure, said process comprising the steps consisting in: -providing a steel sheet whose composition comprises, by weight: 0.01≦C≦0.22%, 0.50≦Mn≦2.0%, 0.2≦Si≦2.0%, 0.005≦Al≦2.0%, Mo<1.0%, Cr≦1.0%, P<0.02%, Ti≦0.20%, V≦0.40%, Ni≦1.0%, Nb≦0.20%, the balance of the composition being iron and unavoidable impurities resulting from the smelting, -oxidizing said steel sheet in a direct flame furnace where the atmosphere comprises air and fuel with an air-to-fuel ratio between 0.80 and 0.95, so that a layer of iron oxide having a thickness from 0.05 to 0.2 μm is formed on the surface of the steel sheet, and an internal oxide of Si and/or Mn and/or Al is formed, -reducing said oxidized steel sheet, at a reduction rate from 0.001 to 0.010 μm/s, in order to achieve a reduction of the layer of iron oxide, -hot-dip galvanising said reduced steel sheet to form a zinc-coated steel sheet, and -optionally, subjecting said hot-dip coated steel sheet to an alloying treatment to form a galvannealed steel sheet.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.