Method of making 6XXX aluminium sheets with high surface quality

A method for producing a 6xxx series aluminum sheet comprising

• homogenizing an ingot made from a 6XXX series aluminum alloy,
• cooling the homogenized ingot with a cooling rate in a range from 150° C./h to 2000° C./h directly to a hot rolling starting temperature HRST, wherein the ingot thickness is at least 250 mm and the ingot is from 1000 to 2000 mm in width and 2000 to 8000 mm in length, the ingot has a top surface, a bottom surface, and four side surfaces, wherein the top and bottom surfaces have a larger surface area than the side surfaces,
• hot rolling the ingot to a hot rolling final thickness and coiling at the hot rolling final thickness and at a hot rolling exit temperature with such conditions that at least 90% recrystallization is obtained, wherein said HRST is between 350° C. and 450° C. and the hot rolling exit temperature is at least 300° C. and between 1.2*HRST-135° C. and 1.2*HRST-109° C. and/or is set to obtain an average grain size in L/ST section between mid-thickness and quarter thickness according to ASTM E-112 intercept method of less than 160 μm in the longitudinal direction,
• cold rolling to obtain a cold rolled sheet,
• wherein the cooling is carried out in at least two phases:
• a first spraying phase in which the ingot is cooled in a chamber comprising ramps of nozzles for spraying cooling liquid or spray under pressure, divided into upper and lower parts of said chamber, so as to spray the two large top and bottom surfaces of said ingot, and
• a second phase of thermal equalization in still air, in a tunnel with interior reflective walls, lasting from 2 to 30 minutes.