| 摘要 |
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 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. |
