PROCESS FOR MANUFACTURING COLD ROLLED SHEATHES WITH HIGH RESISTANCE OF MICRO-ALLOY DUAL PHASE STEELS

摘要

The invention relates to a method for manufacturing cold rolled dual phase steel sheet having a strength greater than 600 MPa, the composition of which comprises (contents expressed in% by weight): 0.05% ≤ C ≤ 0.5% , 1% ≤ Mn ≤ 2, 5%, 0.05% ≤ If ≤ 5%, 0.01% ≤ Al ≤ 1.5%, Cr ≤ 0.75%, S ≤ 0.01%, P ≤ 0 , 1%, N 0.01% and having as titanium alloy element (0.01% ≤ Ti -3, 4N ≤ 0.20%) or zirconium (0.01% Zr - 6.5N) 0, 15%) or niobium (0.01% ≤ Nb - 6.5N ≤ 0.15%) or vanadium (0.01% ≤ V - 3.6 N ≤ 0.2%), or combination of titanium with these last two elements. A steel slab of the above composition is heated to a temperature of between 1000 and 1250 ° C, rolled to a temperature greater than or equal to Ar3, and then the sheet is cooled to a speed v R ≥ 10 ° C / s, coiled at a temperature between 400 and 700 ° C. After cold rolling, an annealing is carried out at a temperature of between Ac 1 and 810 °, followed by a cooling whose speed is greater than 2 ° C./s.