Patent GB-893116-A (GB)
Title: Improvements in or relating to graphite bodies
IPC: C21B7/06
Filed: 1958-08-20
Abstract: In the production of dense refractory bodies consisting of discrete graphitic masses embedded in a continuous matrix of carbide, a mixture comprising particulate pure graphite or graphitic carbon, e.g. anthracite, a carbonizable adjuvant, e.g. a thermosetting resin (phenolpformaldehyde), cornstarch, dextrin, polyethylene glycol, methyl cellulose, waxes, polyvinyl alcohol, lignone or gum tragacanth and sufficient volatile or carbonizable solvent, e.g. water or pine oil to dissolve the adjuvant and wet the graphitic particles, is formed into shape, e.g. by pressing at 1800 p.s.i., and dried and baked, e.g. at 150 DEG  C. for four hours and 300 DEG  C. for a further four hours, to cure the resin.  The shape is then fired in a neutral or reducing atmosphere, e.g. in argon, in the presence of one or more carbide-forming elements, e.g. silicon, boron, zirconium, hafnium, vanadium, niobium, titanium, tantalum, chromium, molybdenum, tungsten, thorium and uranium, preferably in vapour form, at a sufficiently high temperature, e.g. 2150 DEG  - 2250 DEG  C. for half to 1 hour, so that the carbide former penetrates into the network of interconnecting pores within the shape and reacts with fine carbon and graphite particles and carbonized resin to form carbide in situ in hexagonal crystalline form, the final bodies having densities of 1,8 to 2,0 gm./cc.  At least 20% of the particulate graphite in the initial mix is about 74 microns or less, the remainder being preferably in the range 200 microns to 2,4 mm., and preferably about 20% by weight, of resin is added the mixtures being tumbled before the addition of approximately 20% by weight, of the solvent.  After screening, e.g. through a No. 6 screen, the mixture is shaped and baked and the firing in the presence of the carbide former effected, e.g. by placing the shape in a closed environment on a porous graphite wick through which vapour of the carbide former must pass to reach it.ALSO:In the production of dense refractory bodies consisting of descrete graphitic masses embedded in a continuous matrix of carbide, a mixture comprising particulate pure graphite or graphitic carbon, e.g. anthracite, a carbonizable adjuvant, e.g. a p thermosetting resin (such as phenolformaldehyde), corn startch, dextrin, polyethylene glycol, methyl cellulose, waxes polyvinyl alcohol, lignone, or gum tragacanth, and sufficient volatile or carbonizable solvent, e.g. water or pine oil, to dissolve the adjuvant and wet the graphitic particles, is formed into a shape, e.g. by pressing at 1800 psi, and dried and baked, e.g. at 150 DEG C. for 4 hours and 300 DEG C. for a further 4 hours, to cure the resin. The shape is then fired in a neutral or reducing atmosphere, e.g. in argon, in the presence of an excess of one or more carbide-forming elements, e.g. Silicon, boron, zirconium, hafnium, vanadium, niobium, titanium, tantalum, chromium, molybdenum, tungsten, thorium and uranium, preferably in vapour form, at a sufficiently high temperature, e.g. 2150-2250 DEG C for 1/2 to 1 hour, so that the carbide-former penetrates the network of interconnecting pores of the shape and reacts with fine carbon and graphite particles and carbonised resin to form carbide in situ in hexagonal crystalline form, the final bodies having a density of 1,8 to 2,0 g/cc.  At least 20% of the particulate graphite in the initial mix is about 74 microns or less, the remainder being preferably in the range 200 microns to 2,4 millimetres and preferably about 20% by weight of resin is added thereto, the constituents being mixed by tumbling before the addition of about 20% by weight of the solvent.  After screening, e.g. through a No. 6 screen, the mixture is shaped and baked and the firing in the presences of the carbide former preferably carried out by placing the shape in a closed environment on a porous graphite wick through which vapour of the carbide-former must pass to reach it.