Manufacturing method of steel pipe with different thickness and steel pipe with different thickness

摘要

The manufacturing method of this steel pipe from which thickness differs is a method of manufacturing a steel pipe from which a thickness differs from a hollow tubular element pipe, The said element pipe is arrange | positioned in the dice | dies, and the said element pipe is in the state which regulated the movement to the longitudinal direction of the element pipe. A locking step of press-fitting the plug from one end of the tube to enlarge the external shape of the one end and catching the die, and releasing the restriction of the pipe, while maintaining the locking of the pipe. It presses toward the other end side of the, and has the ironing process which forms the thin part by applying the ironing process which expands an internal shape, maintaining the external shape of the said small pipe.