4. Metallurgical developments

4.1 Ferritic phase rolling

Rolling ultra-low-carbon steel in the austenitic phase presents a number of difficulties. Despite a relatively high defurnishing temperature, it is difficult to obtain a rolling temperature above the AR3 point in the last rolling stands, even for medium thicknesses. By rolling in a two-phase domain, deformation stresses are no longer the same, and the rolling process becomes delicate, with the risk of thickness defects or mishaps.

To avoid this difficulty, fully ferritic phase rolling was...