| 摘要 |
<p><PICT:1115917/C6-C7/1> In the extrusion of metallic carbides the starting workpiece may be a preliminary molten product or made by compressing a powder mixture of uranium oxide and graphite, preferably into porous pellets. The extrusion temperature ranges from 2200-2400 DEG C., preferably 2250-2350 DEG C., the extrusion pressure 200-800 kg/cm2 and the extrusion ratio from 2.8 to 10. To prevent surface cracking, a layer of uranium dicarbide may be applied to the starting workpiece in suspension in collodium solution or in another organic liquid. In a direct extrusion process, Fig. 1, the graphite die 2 is mounted on graphite supports 3, 4 on the hearth 5 of a vacuum furnace 1. Pressure is applied by a graphite ram 6 acting through a graphite block 7. A heating element 10 surrounds the die which may have a conical orifice portion (12), Fig. 2 (not shown) or a hyperbolic portion (14), Fig. 3 (not shown). In another embodiment, Fig. 4 (not shown), the die (2) is placed in the bore of a graphite container (15) having a liner (16) of low strength graphite; a graphite ram (8) is used. In a further embodiment, Fig. 5 (not shown), the workpiece is extruded backwardly through a die (2) mounted on the end of a graphite ram (8). Reference is made to the extrusion of uranium monocarbide, dicarbides of uranium thorium, plutonium, tungsten or a mixture of thorium and uranium carbides.</p> |
