Hydrostatic extrusion of round and shaped tubes

Abstract

The manufacture of tubes of round and of complicated shape by cold or hot hydrostatic extrusion is investigated with regard to the extrusion pressure, the tool arrangements and the productivity attainable with hydrostatic extrusion. The pressures required to extrude round tubes are 3 to 20% higher than those required for rods of aluminium, aluminium alloy, copper, carbon steel, zircaloy and stainless steel. For shaped tubes having complicated profiles, the extrusion pressures are 10 to 40% higher than those for rods. Three kinds of tool arrangement for tube extrusion are proposed for increasing the production rate and reducing manufacturing costs. They use, respectively, a mandrel fixed to the connecting cylinder, a travelling mandrel not supported by the billet end and a floating-tipped mandrel in which the floating tip behaves similarly to the floating plug in tube drawing. By employing these tool arrangements, disadvantages of the conventional fixed and travelling mandrels can be eliminated. The assessment of the production rate copper tube that could possibly be attained by using hot hydrostatic extrusion is also compared with that for the conventional tube manufacturing process. The opinion is advanced that a large number of drawing and tube reducing passes could be eliminated by applying hot hydrostatic extrusion. Eccentricities of tubes as extruded range from 2 to 3%.