Filière d'extrudage

966,775. Extrusion dies. E. I. DU PONT DE NEMOURS & CO. Ltd. Dec. 21, 1961 [Dec. 23, 1960], No. 45794/61. Heading B3P. A die for hot metal extrusion comprises a rib 21 of refractory material tightly encased in a housing 22 of elastic metal which imposes a radially inward pressure on the rib thereby reducing its tendency to tensile fracture. The rib is made of sintered metal silicides as described in Specification 966,774 and the housing 22 of steel. An intermediate ring 23 of stainless steel may be provided to protect the rib from excessive compression imposed by the housing. Ring 23 has an expansion coefficient greater than the rib and housing which ensures that the rib remains tightly encased at elevated temperatures. The housing may be in two parts, Figs. 6, 6a (not shown). Ring 23 may be omitted, Figs. 3, 7 (not shown), and in this case the rib 21 is slightly tapered in three steps on its external surface and is pressed into the tapered bore of the housing, Fig. 2 (not shown). The die may have an orifice of fluted shape, Fig. 8 (not shown). During extrusion a lubricant consisting of colloidal graphite suspended in light oil is used. Many examples are given for the extrusion of brass, copper, nickel-chrome alloy, nickel-chromium-thoria alloy, niobium and various steels.