A NEW FURNACE LINING.

New Zealand Times, Volume XXVII, Issue 5737, 4 November 1905, Page 11

A NEW FURNACE LINING.

For several years the material known as carborundum has been known as one ■if the best abrasives used in industrial processes. It possesses hardness in excess of native emery, and relatively higher lasting properties. It is a cantide of silicon, and its manufacture is possible only under iho enormous heat of cue electric furnace. One of the few seats of manufacture is at Niagara Falls, and the temperature of SoOOdeg centigrade is developed in tho process. A material which will fuse only at oi near such a degree of heat is, of course, eminently suitable for the lining of fun-ace walls, and only its high cost has hitherto prevented its adoption for this purpose. To France belongs the credit of applying carborundum to this purpose without incurring tho prohibitive expense formerly deemed essential to any attempt to this end. Ordinary refractory bricks have been given a thin coating of carborundum upon tho sides which are to be exposed to the furnace heat. This method is'the most desirable when a new furnace is to be erected, but it is stated that where it is not expedient to rebuild the whole el ember a preparation of carborundum, known ns carborundum cement, may be applied to the walls of existing furnaces, and impart to a great extent the extra refractory properties of the material. Immunity from tho m-retsity for frequent repair is the immediate result. In addition to a fusing point far above that ever developed in a coal, coke, or gas furnace, carborundum resists tho action of the most potent chemical agents. Chlorine, bromine, sulphur, and oxygen have no effect upon it. even at a temperature of 1200 degrees centigrade. Thus there are a variety of industrial processes in which the lining of furnace walls with carhot undura may bo profitably introduced. Tho usual way of preparing this carborundum cement is by mixing three parts of carborundum with one part of water-glass, i. 0., silicate of soda. Before application the brickwork must be tbcroughly brushed to remove all oust and extraneous matter, and the cement applied like a paint. It is found that furnaces that have been already fired require a good deal more brushing down than newly-set furnace walls to secure proper adhesion of the carl orundura cement. Twenty-four hours is sufficient time to allow tho composition to become comparatively hard, and aHer this lapse of time the fire should be started. Tho furnace will be found to have an interior lining of refractory carborundum with all the resulting advantages.