Process for manufacturing a 6xxx alloy sheet having an excellent surface quality

A method for manufacturing a metal sheet, comprising:

• a. Producing a 6xxx series aluminum alloy comprising, as % by weight:
• i. Fe from 0.10% to 0.40%,
• ii. Mn from 0.05% to 0.20%,
• iii. Cr from 0.01% to 0.04%,
• b. Casting of the aluminum alloy in a plate, optionally by semicontinuous vertical casting,
• c. homogenization of the plate at a homogenization temperature, between 540° C. and 580° C., optionally above 550° C., followed by cooling, optionally forced, either to a hot-rolling start temperature of 400 to 520° C. or to a temperature below hot-rolling start temperature,
• d. First hot rolling from the hot-rolling start temperature to a temperature of end of the first hot rolling of 370 to 450° C.,
• e. Second hot rolling from the end temperature of first hot rolling to the end of rolling temperature of 250 to 380° C. into a strip under conditions such that the microstructure of the strip is recrystallized or non-recrystallized after the second hot rolling,
• f. Cold rolling of the strip, with optionally with annealing on a continuous furnace, and without static annealing,
• g. Solution heat treatment, optionally in air, of the strip into a sheet,
• h. optionally, pre-aging at a pre-aging temperature of 50 to 120° C. for a period of 2 to 16 hours, optionally obtained by coiling and then cooling to ambient temperature,
• i. Natural aging from 72 hours to 6 months,
• wherein at least an intermediate recrystallization occurs in e and/or f followed by a reduction by cold rolling of at least 60%.