The invention relates to a weldless aluminum
alloy lining neck-
spinning method for a large-
diameter composite air cylinder. Three sets of multi-pass direct
spinning composite tracks of
oblique line tapering, arc bottom sealing and
ellipsoid necking are designed according to the structural features of a large-
diameter elliptical end socket and a small-
diameter pipe nozzle and the requirement that no obvious fold or other defects exist on the inner surface of the end socket, and the
spinning speed and temperature are determined, so that the
pipe nozzle is thickened obviously; and the end socket and the
pipe nozzle meet
machining requirements, the shoulder of the end socket is in smooth transition with a
barrel, and no obvious fold exists on the inner surface of the end socket. In addition, a compensation design is adopted in the third set of curve, the corner R of the lining pipe nozzle is obviously thickened, and the reliability of the
water pressure self-tightening test and fatigue and
bursting performance of the composite air cylinder is increased. Meanwhile, a pipe blank is annealed before spinning, and the inner surface near the corner R of the lining pipe nozzle is polished with a specially-made tool after spinning, so that the risks that folds, cracks and other defects happen to the inner surface near the corner R of the lining pipe nozzle are controlled.