GB441516A - Improved process for the manufacture of refractory products from raw materials rich in magnesium orthosilicate, particularly olivine rocks - Google Patents

Abstract

Refractory articles of substantially constant volume are made by heating without melting a mixture of powder and granules and/or lumps of impure olivine complying with the following conditions. They contain at least 70 per cent by weight of olivine (corresponding to about 60 per cent of magnesium orthosilicate), from 10 to 30 per cent of other minerals, not more than 10 per cent of iron calculated as Fe O, not more than 10 per cent of magnesium hydrosilicates, not more than 20 per cent of rhombic pyroxene, not more than 10 per cent, preferably not more than 5 per cent of monoclinic pyroxene and not more than 10 per cent, preferably not more than 2 per cent of felspar. Chromium compounds may be added to the mixture either as fine powder or in solution. The chromium compounds are preferably such as after being heated to 1000 DEG C., contain not less than 50 per cent by weight of Cr2O3, e.g. chromite. The amount of chromium compounds added is such as to give in the finished product from ,3 to 10 per cent of Cr2O3. Small quantities, e.g. from ,3 to 2 per cent, of very hard substances such as corundum, spinel, or titanium carbide may also be added. Examples are given. Specifications 340,437, [Group IV], 352,881, and 373,846 are referred to.