A method of making a cement joint between an externally screw threaded carbon member and an internally screw threaded carbon electrode

摘要

PICT:0968089/C1/1 PICT:0968089/C1/2 A cement joint is made between an externally screw-threaded carbon member and an internally screw-threaded carbon electrode by applying, before the member is screwed to the electrode, a quantity of cement which is plastic on application to an area of the screw-thread of the member and/or electrode which is equal in length in the axial direction to a few, e.g. 4, screw-threaded turns and is transversely of the same or smaller width as the length. The cement may be expressed from a bag or tube, e.g. of polythene, of which the contents are sufficient for the quantity to be applied. The cement may be introduced, e.g. in the bag, into recesses, e.g. round, square, or elongated-rectangle, in the threads and which may extend 2-4 threads of the member and/or electrode. The screw-thread turn adjacent the butt end may remain free from cement. The depth of the recesses may be not greater than the depth of the threads. The first 4 or more turns of the threads of the member and electrode may be profiled or corrugated starting from the base of the thread socket. The cement may consist of 40-60 parts of a polyformaldehyde resin, 30-50 parts pitch powder of softening point above 150 DEG C. and 10-20 parts coke powder of mean grain size less than 100m and which may harden at 100 DEG C., and/or with a curing catalyst in the form of a capsule or tablet, which may be introduced into the recess in the threads.