GB337605A - Improved manufacture of refractory materials from natural magnesium silicates - Google Patents

Abstract

337,605. Metallges. Akt.-Ges. Nov. 7, 1929. Refractory substances.-Relates to processes for making refractory substances from magnesium silicates, e.g. olivine, serpentine, talc, &c., containing substantial quantities of iron by heating the silicates, without fusion, with substances rich in magnesium, e.g. magnesium oxide and magnesite, in an oxidizing atmosphere. According to the invention the substances rich in magnesium are present in quantities which are sufficient for the conversion of the whole of the iron into magnesium ferrite and of the free silica into magnesium orthosilicate. The treatment may also be applied to silicates containing, instead of or in addition to iron, other metals such as nickel, manganese, chromium and aluminium. When silicates which are poorer in magnesium than magnesium orthosilicate are present, the proportion of magnesium oxide or the like is calculated so that the silicates are converted into magnesium orthosilicate. In some cases the amount of magnesium oxide, &c. is calculated to give an excess of magnesium oxide in the final product. The temperature of heating is below the melting point of the product, generally from 700 to 1,500‹ C. Other substances may be incorporated with the raw materials or with the products, for instance iron oxide or ores such as magnetite, aluminium compounds such as clay, kaolin and bauxite and chromium compounds such as chromites. In the manufacture of moulded articles, temporary binding agents, e.g. sulphite cellulose waste lyes may be used, and the moulding may be effected under high pressure, e.g. 500-1,000 kg. or more per sq. cm. Materials which on being treated increase in volume, e.g. certain olevines, may be mixed with substances which decrease in volume, e.g. serpentine, to form compositions having the desired change of volume characteristics. In an example. 1,000 kg. of a rock containing 800 kg. of an iron-containing olevine and 200 kg. of ironcontaining bronzite, with an average content of 10 per cent of FeO are mixed with sufficient magnesium oxide to convert the iron into MgFe2O4 and the silica into magnesia orthosilicate. The materials are ground to a fineness not exceeding 2 m.m. Moulding is effected with if desired binding agents and high pressure, and the moulded article is heated in an oxidizing atmosphere at 1,450‹ C. for 6 hours. Other examples are given in the Specification. Specification 301,547 is referred to.