Method of making 6xxx aluminium sheets with high surface quality

A solution heat-treated and quenched 6xxx series aluminum sheet, obtainable by:

• homogenizing an ingot made from a 6XXX series aluminum alloy optionally comprising 0.3-1.5 wt. % of Si, 0.1-1.2 wt. % of Mg and 0.5 wt. % or less of Cu, Mn 0.03-0.5 wt. and/or Cr 0.01-0.4 wt. %, Fe 0.03 to 0.4 wt. %, Zn up to 0.5 wt. %, V up to 0.2 wt. %, Zr up to 0.2 wt. %, Ti up to 0.1 wt %, rest aluminum and unavoidable impurities up to 0.05 wt. % each and 0.15 wt. % total,
• 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,
• 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 is comprised 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, and
• cold rolling to obtain a cold rolled sheet,
• wherein the cold rolled sheet is further solution heat treated and quenched in a continuous annealing line,
• wherein the 6xxx series aluminum sheet has a surface quality quotation according to VDA Recommendation 239-400 of less than 4.8, optionally less than 4.5.