GB573410A - An improved manufacture of refractories - Google Patents

Abstract

Fluorspar, in amount equal to 1-10 per cent, is added to refractory ramming or trowelling mixtures containing over 65 per cent of magnesia and bonded with sodium silicate in order to correct the effect of the silica in lowering the melting-point, the fluorspar being easily dispersed through the mass at firing temperature, the fluorine being finally eliminated, and the calcium uniting with the silica to produce a refractory silicate. The amount of fluorspar to be added is calculated from the formula 78(2x - y) where x and y are the molecular equivalents of silica and calcium oxide in the final product. When magnesia clinkers are used in the preparation of the refractory, they are stabilized against hydration by the addition of small amounts of iron oxide or chrome ore and burning at high temperatures (3000 DEG F. or over), and against inversion of the dicalcium silicate therein by incorporation of chromates, borates, or phosphates, preferably a borate, sufficient to provide a content of 0.06 per cent boron trioxide in the finished clinker, added in the form of ragonite, ulexite, colemanite or boric acid. The mixture is prepared for use by mixing with 10-11 per cent of water and is stabilized during drying by the addition of 1-2 per cent of sodium carbonate. According to examples: (a) a ramming-mixture is formed from magnesium clinker, sodium silicate, sodium carbonate, and fluorspar, with or without a small amount of colemanite; (b) a plastic mixture for tap-holes and lining spouts and runners is prepared from magnesium clinker, sodium silicate, sodium carbonate, trisodium phosphate, ball clay, and fluorspar.