Improvements in or relating to methods of producing joints between carbon electrodes and joints produced by such methods

摘要

A cement for use in joining carbon electrodes (see Division H5) contains pitch, a synthetic plastic material, which hardens prior to the carbonization of the pitch, granular solid material e.g. coke, graphite powder or silicides of titanium or iron and a swelling agent e.g. ammonium phosphate or hydrazide of benzene sulphonic acid. The surfaces to be joined are preferably impregnated with a catalyst e.g. chloranil or phosphoric acid which attacks the enveloping containing the cement and also promotes hardening. When first heated the cement swells and hardens. On further heating carbonization takes place. In examples the compositions used comprise (1) coke, coal tar pitch, a furfuracrolein-indene condensate according to German Specification 1,048,413 and the hydrazide of benzene sulphonic acid; (2) powdered graphite, soft coal tar pitch, a phenol-formaldehyde resol, ammonium phosphate, ammonium carbonate and a suspension of chloranil in aqueous methylcellulose; (3) powdered silicides of titanium or iron, powdered graphite, hard coal tar pitch, furfuryl alcohol, graphite oxide (swelling agent) and aqueous phosphoric acid.