GB1335818A - Extrusion of metals - Google Patents

Abstract

1335818 Extruding FORMALLOY Ltd 23 Nov 1970 [27 Nov 1969] 57972/69 Heading B3P A metal extrusion press for extruding tubes comprises a plunger 27 with a mandrel 28 which co-operates with the extrusion die 23 at the end of the extrusion stroke to produce a reduced thickness region 25 between the extruded tube 18 and the discard 24 which can be separated by an axial pull on the tube. The pull can be applied continuously during extrusion and increased to effect the separation. A gripper jaw set 56, Fig. 10, is pneumatically operated to grip the end of the tube 18. The extruded tube displaces a crosshead 55 on which the jaws are pivoted and a rack 57 actuates a limit switch 58 to operate a piston-cylinder unit 59, 60 for the jaws. A carriage 67 is driven by a rack and pinion 68 to pull the crosshead 55 by engagement of the racks 57 and fixed pinions 79. A constant tension is applied to the tube by a pneumatic pistoncylinder unit 74. At the end of the extrusion a second pneumatic piston-cylinder unit 75 is actuated to rotate the pinions 76 by a pawl 76 and ratchet wheel 77. This causes the additional pull of the tube to separate it from the discard. In an alternative embodiment collet jaws 82 are used and operated by an outer sleeve 84 moved axially by an hydraulic piston-cylinder unit 85, 86. The jaws are moved to pull the tube for separation by an outer hydraulic piston-cylinder unit 87, 88. The mandrel 28, Figs. 2 and 6, is connected to the plunger 27 by a tie bolt 35 with internal cooling air passages. The extruded tube may also be cooled by a water jacket 36. The discard is engaged in a dovetail slot in the plunger so that it can be removed from the die and is stripped from the plunger by a ring of segments 43. The extrusion is preferably cold but the billet may be initially heated to about 200‹ C. or cooled so that during extrusion its temperature does not exceed the recrystallization temperature of the metal, e.g. aluminium or aluminium alloy. Thus the metal is work-hardened during extrusion. The plunger speed may be 10-90 inches per minute with an extrusion ratio between 25 : 1 and 60 : 1. The exit speed from the die will be 250-5400 inches per minute. The formed tube will be 20-100 feet long.