| 摘要 |
<p>In the production of threaded graphite nipples for joining electrode sections, comminuted needle-like coke and a pitch binder are extruded, baked and graphitized, and the extruded shape is allowed or caused to expand transversely to increase the transverse dimensions such that after graphitizing the ratio of transverse to longitudinal coefficients of thermal expansion is within the range 1.2-1.5. The plastic mixture of pitch and coke is extruded preferably through a cylindrical die having a diameter between 20-30 cm., and an internal contour resembling the Schiele anti-friction curve. The extrusion die may also be rifled and have an enlarged section of substantially uniform diameter at the end of the straightway section of the die such that, when the extrusion is started, the open end of the enlarged section is plugged and the mixture extruded until the enlarged section is completely filled, after which the plug is removed and the extrusion continued. The extruded product in the plastic state may be axially aligned in a container or mould, which tapers towards its ends and has such dimensions as to allow compression in the longitudinal direction. After baking the nipple may be re-impregnated and baked one or more times. Specification 829,196 is referred to.</p> |
