Method and apparatus for fabricating a metal pipe having at least one smooth portion and at least one grooved portion

摘要

A metal pipe having at least one smooth portion and at least one grooved portion is obtained by progressive deformation of its wall in at least two consecutive phases. Each phase is carried out using a tool assembly including a grooved female die that accommodates the portion of pipe being deformed, and a grooved male punch that moves axially in order to give the pipe a cross section with an undulating profile, defining longitudinal ribs distributed around the pipe. The majority of the ribs each have a width in the circumferential direction that is less than the distance in the circumferential direction from one rib to the next. The pipe is subjected to a further deformation step in order to force the flanks of each rib into contact with each other using a tool assembly that includes radially movable sectors or a bushing that supports a plurality of radial rollers.

主权项

1. A method for forming a metal tube having at least one smooth portion and at least one fluted portion, wherein the fluted portion is obtained by the steps of:
subjecting an initially smooth portion to a progressive deformation through at least two subsequent stages, wherein each stage is carried out using a tool unit including a fluted female die adapted for receiving therein the tube portion to be formed, and a fluted male mandrel that is axially movable within said tube portion, so as to provide the tube with a cross-section having an undulated profile, defining a plurality of longitudinal ridges distributed around the tube at positions circumferentially spaced from each other, wherein a plurality of the ridges formed by said progressive deformation of said tube portion each have a width in the circumferential direction which is substantially less than the distance along the circumferential direction between each pair of adjacent ridges, and wherein after said progressive deformation of said tube portion, the tube portion is subjected to a further deforming operation in order to press two sides of at least some of the ridges in contact against each other.