Drawing of Tubes Filled With Particulate Solids

Abstract

The principal parameters involved in drawing of metal tubes containing metallic, mineral, and organic powders were investigated on small copper, mild steel, and 304 stainless tubing. The type of filler controlled the change of the ratio of diameter to wall thickness which decreased at first but became constant after a certain reduction. The above decrease could be held to a minimum by employing a center rod of ductile metal separated from the tube by a powder barrier. The particulate core or barrier need not form an integral part of the product but can be used as a “deformable mandrel” being eventually removed from the reduced tube by reeling, melting, dissolving, or washing the powder out. Such a drawing procedure should prove useful in bulk reducing hard to draw (e.g., refractory) tubing. If warm drawing is called for, the operation is facilitated by the substantial heat capacity of the quasi-solid cross section. The danger of local interwelding (galling) between tube and inside tool is eliminated because of the absence of relative slippage between tube and inside tool.