Method and installation to produce dual phase steels out of hot-rolled strip, with cooling rate at first cooling stage set sufficiently low to obtain temperature which is sufficiently high for rapid transformation of austenite into ferrite

摘要

The cooling rate of steel at the first cooling stage is chosen as low as 20 to 30 K/s, so cooling curve runs into the ferrite domain with a temperature which is sufficiently high for rapid ferrite formation and at least 70 % of the austenite has been transformed into ferrite before the start of the second cooling stage. The apparatus comprises a cooling section (6) which is located after the last finish roll stand (1) and has several cooling stages (7) arranged with gaps after one another or, alternatively, has cooling systems with steplessly variable water rate.