TUBES WITH SHAPED END PORTIONS MAKING METHOD Russian patent published in 2008 - IPC B21D51/16 B21D41/00 

FIELD: plastic working of metals, possibly forming in end portions of heat exchange tubes shaped ends having at least two outer and one inner annular protrusions due to using effect of localized directional yielding of tube material.

SUBSTANCE: each outer annular protrusion is formed by preliminary and finally shaping initial tube. Preliminary shaping is realized at squeezing tube and simultaneously fixing it against axial movements in detachable die having segments with annular groove. Final shaping is realized by drifting inner surface of tube along part of its length at filling free space of annular groove of die with tube material. In order to form each outer and inner annular protrusion, tube is released from die segments and it is moved in axial direction by predetermined pitch. At such operation inner edge of formed inner protrusion is arranged flush with die end. Then next operations of squeezing and drifting are realized.

EFFECT: improved quality of articles.

6 dwg