the industry that casts melts of such rocks as basalts and diabases and such industrial wastes as slag and ashes into glass-ceramic materials and articles.
The rock-casting industry arose in the USSR, Germany, and France in the 1920’s. It provided a nonmechanical method of obtaining items that are made from rocks and wastes with good mechanical, chemical, and thermal properties. A nonmechanical method is more advantageous than a mechanical one, since the latter is very complicated and expensive. A technology was developed for handling the physicochemical properties of multi-component silicate melts, which are more viscous than metallic melts. Furthermore, crystallization of silicate melts is achieved under conditions that differ considerably from equilibrium conditions.
The material from which rock castings are made consists of an amorphous glass phase and crystal formations that range in size from 5 to 800 microns. To a considerable extent, the predominant mineral in the initial material determines the properties of the finished product, and thus the finished products are classified as pyroxene, olivine, wollastonite, or mullite glass ceramics.
The major steps in rock casting are production of the melt in a fired or electrical furnace; cooling and preparation of the melt, which is called the precrystallization stage; casting of articles from the melt; and crystallization and annealing of the articles in heat-treating furnaces.
Different desirable properties can be obtained by changing the composition of the melt as well as by varying the temperature and duration of the various stages of the casting process. For example, in the most common pyroxene cast material from basalt, the compression strength can be varied from 250 to 500 meganewtons per square meter (MN/m2, or 25–50 kgf/mm2), and bending strength can be varied from 40 to 80 MN/m2. The chemical stability of this material in hydrochloric acid is 97.5–99.7 percent, and in sulfuric acid, 99.4–99.9 percent; the abrasion losses vary from 0.04 to 0.05 g/cm2. The coefficient of thermal expansion varies from 6 × 10–6 to 7 × 10–6 per °C between 25° and 100°C. Some glass ceramic articles are reinforced, for example, by steel wire, to increase strength and durability.
The rock-casting industry makes tubes, plates, and trays for protecting the working surfaces of hoppers, gutters, mineral-enrichment units, and metallurgical and power equipment. It also produces acid-resistant plates and shaped articles for the chemical industry, as well as linings for ball mills and linings and other items that operate in contact with acids, bases, or finegrained abrasive noncohesive materials and pulps.
REFERENCESPelikan, A. Plavlennye kamni: Proizvodstvo i ispol’zovanie ν promyshlennosli. Moscow, 1959. (Translated from Czech.)
Problemy kamennogo lit’ia. Kiev, 1963.
Lipovskii, S. E., and V. A. Dorofeev. Kamneliteinoe proizvodstvo. [Moscow] 1965.
G. A. RASHIN and A. P. SHAPOSHNIKOV