Multi-pass spinning forming clamping structure and spinning method for variable cross-section conduit of oil tank

The invention relates to a multi-pass spinning forming clamping structure and a spinning method for a variable cross-section conduit of an oil tank. The structure comprises cylindrical core shafts with different diameters, a three-jaw chuck, a positioning block, a rotating wheel frame, a rotating wheel and a motor, wherein the three-jaw chuck is fixed on a main shaft of a spinning machine, the positioning block is fixed in a central hole of the three-jaw chuck, and the core shafts are fixed by the positioning block and the three-jaw chuck; the rotating wheel is connected with the rotating wheel frame through the rotating wheel rotating shaft, and the rotating wheel frame is fixed on a cutter frame of the spinning machine. The method comprises the following specific steps of: 1, sleeving the core shafts into an equal-section pipe blank to be processed in advance; 2, fixing the axial and radial positions of the pipe blank and the core shafts through the three-jaw chuck and the positioning block; 3, deducing the