JPS56168902A - Manufacture of pipe having nonuniform wall thickness along longitudinal direction - Google Patents

Abstract

PURPOSE: To form a thin-walled part and thick-walled part at required places along the longitudinal direction of a pipe with a simple operation, in case of roll-forming a steel pipe by the pilger mill rolling process, by operating suitably combined mandrel rolling pass and a nonmandrel rolling pass.

CONSTITUTION: In a pilger mill rolling process wherein a rolling roll 3 provided with a tapered groove 301 is reciprocated in the outside of a steel pipe 1 into which a tapered mandrel 2 is inserted, a mandrel rolling pass with the mandrel 2 is applied to a range S between a point (a) and a point (b), and the mandrel 2 is withdrawn from a halfway, and then, a nonmandrel rolling pass is applied. In the part of the steel pipe 1 on the way of the mandrel rolling pass, a tapered introducing zone 102 ranging from a thin-walled part 101 to a thick-walled part 103 is formed, and a stepless thin-walled part 101 and a stepless thick-walled part 103 are obtained. The mandrel 2 is then inserted into the rolling zone S to be rolled by the roll 3 so as to apply a mandrel rolling pass for thinning the wall thickness; at the same time, a part of the pipe 1 on the way of the nonmandrel rolling pass is formed into a tapered introducing zone ranging from the thick-walled part 103 to the thin-walled part 101; hereby, a steel pipe having the thick-walled part 103 and the thin-walled part 101 is simply formed.

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