Large aluminum alloy forged ring blank step-by-step punching device and punching method

The large aluminum alloy forged ring blank step-by-step punching device comprises centering mechanisms, a swing arm mechanism and a punching die which are arranged on a hydraulic machine, the number of the centering mechanisms is left and right, the left centering mechanism and the right centering mechanism are installed between a front stand column and a rear stand column on the left side and the right side of the hydraulic machine respectively, and V-shaped chucks are installed on the centering mechanisms. The right side swing arm mechanism and the left side swing arm mechanism are installed on the right side and the left side of a movable cross beam of the hydraulic machine respectively, the free ends of the right side swing arm mechanism and the left side swing arm mechanism can swing to the center of the hydraulic machine, and the bottom face of an upper anvil of the hydraulic machine is in contact connection with a punching rod. The bottom end of the punching rod connected to the right swing arm mechani