Such plasticizing agents are not compatible with basic refractory substances. Starch is an organic material comprising carbon, hydrogen and oxygen, and when heated it burns or decomposes, causing a reducing condition which may be deleterious to the refractory substance.Also it leaves the individual grains of the refractory substance in poor contact with each other, thereby weakening the structure. gold milling machine Clays and bentonites are aluminum silicates, having compositions which are typical or inclusive as follows: Ball clay Plastic fire Bentonite Clays and bentonites thus have the serious disadvantage of imparting to a basic refractory sufficient alumina and silica to lower the refractoriness to an undesirable extent. For satisfactory results, alumina in commercial periclase refractories used at high temperatures should not be more than 2 per cent. The usual impurities of the raw material ordinarily impart this amount, hence addition of clay or bentonite in effective amount is precluded. Basic refractory substances such as chrome ore, are somewhat less sensitive, but alumina is deleterious.
In accordance with the present invention, plasio ticity, cohesion and desirable working properties which are normally absent, may be imparted to basic refractories, and the chemical composition involved is such that the high temperature refractoriness of basic materials is not appreciably affected. This new bond is unique in that it introduces neither organic matter nor alumina.To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described, iron ore crusher and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative however, of but a few of the various ways in which the principle of the invention may be employed.
The refractory material which is to be made up into refractory products is burned at suitable temperature, magnesite, dolomite, chromite, etc. being common raw materials. In general, it is 3u necessary to properly stabilize basic substances against physical or chemical changes. The principal physical change prone to occur in basic refractories is inversion of dicalcium silicate.This may be prevented however by burning -:i clinker which will contain dicalcium silicate, with small additions of a stabilizer such as boric oxide, iron ore mines chrome ore, or phosphate, as in U. S. Patent No. 2,229,297. The principal chemical change prone to occur in basic substances is hydration, .i) with consequent disruption of bond, and even under some circumstances the heaving of a hearth or bursting of a furnace shell. Hydration of magnesia clinkers may be inhibited by suitably hard burning of the clinker and by inclusion of 3 to 4 per cent of mill scale, iron oxide or chrome ore as a burning agent.