GB1347391A - Composite moulded carbonaceous bodies - Google Patents

Abstract

1347391 Carbon electrode CARBORUNDUM CO 19 April 1971 [26 March 1970] 24133/71 Heading C1A A moulded carbon body comprises (1) a particulate powdered carbon filler, each 100 parts by weight of filler comprising (a) 60-90 parts by weight of graphite powder and (b) 10 to 40 parts of a petroleum coke powder, and (2) 5 to 25 parts by weight per 100 parts of carbon filler, of a carbonized cured novolac resin matrix binding together the particulate carbon filler. In the Specification the word "powder" is used to mean a particulate material, the particle size of which is smaller than 297 microns (50 mesh U.S. Standard Sieve). The petroleum coke may be calcined and is preferably calcined. At least 98% of the carbon filler may have a particle size of less than 74 microns. The body may have a density of 1-6 to 1À8 g/c.c. and may be used as an electrical discharge machining electrode. The body may be formed by forming a dry mixture of the powdered carbon filler, coating the filler with the appropriate amount, viz. 10-35 parts/100 parts dry powder, of a novolac resin containing a suitable curing agent, moulding the coated powder into a composite body at a temperature of 150‹ to 600‹ C. and at a mechanical pressure of 20-600 kg/cm.<SP>2</SP> for a period of 2 mins. to 5 hrs. and finally baking the resin bonded composite in a non- oxidizing atmosphere at a temperature of at least 1250‹ C. for at least 30 mins. so as to cure and carbonize the resin and produce the desired carbon matrix. The body may be moulded in a mould having vents covered with carbon or graphite cloth placed between the contents of the mould and the body of the mould, whereby volatile materials are allowed to escape from the mould whilst pressure can still be applied to produce the desired shape.