Preparation method for improving surface quality of 6xxx series aluminum alloy plate for automobile

The invention provides a preparation method for improving the surface quality of a 6xxx series aluminum alloy plate for an automobile. The preparation method comprises the steps of fusion casting, homogenization, hot rolling, primary cold rolling, intermediate annealing, secondary cold rolling, solid solution and pre-aging. Primary cold rolling is conducted, and the machining rate is 30-60%; intermediate annealing is conducted, the temperature is 380-420 DEG C, and the heat preservation time is 1-2 h; carrying out secondary cold rolling, wherein the processing rate is 50-70%; the rolling coiling temperature of a cold-rolled finished product is not more than 90 DEG C; solid solution: the heating rate is divided into two steps: the temperature interval is 0-300 DEG C, and the heating rate is 20-30 DEG C/s; the temperature is 300-target solid solution temperature interval, and the heating rate is 7-10 DEG C/s. According to the method, by controlling the intermediate annealing temperature, the heat preservation t