Method for improving flatness of aluminum alloy board

The invention provides a method for improving the flatness of an aluminum alloy board. The method is characterized in that after hot rolling, shearing and quenching are carried out on the aluminum alloy board, the aluminum alloy board is stretched and straightened step by step, the board is set to be stretched in multiple steps in cooperation with a movable board supporting frame, and the total stretch rate ranges from 0.3% to 4.0%. The first several steps for stretching the boards are carried out after the board supporting frame is lifted to jack different positions of the board, and the stretch rate is determined according to the set number of the stretch steps; the final step for stretching serves as straightening of the longitudinal flatness of the board, and the board supporting frame drops to the horizontal base line position and does not need to be lifted to jack the board. The board supporting frame is located at the portion, between a movable chuck and a stretchable chuck, of a moving way and can be independent of other machines to perform horizontal traveling movement and lifting movement. Compared with original stretching straightening, in the aspect of improving the shape of the board, the method has the advantages that the longitudinal flatness of the board can be improved, and meanwhile the transverse flatness of the board can be effectively improved.