Obtaining fused quartz in a semicontinuous electric furnace

Abstract

Owing to its low coefficient of thermal expansion, high resistance to molten steels, slags, and certain types of glass, fused quartz is widely used for making immersion nozzles for continuous steel-castingmachines, precision casting molds, coatings, glass blocks for tank furnaces, and also for the production of ramming compounds [1][2][3][4].Transparent fused quartz, and also opaque, is distinguished by a high content of fine air inclusions, and it is produced mainly by electric melting in periodic furnaces.One of the production units for obtaining opaque fused quartz (quartz glass) is an electric resistance furnace of the semicontinuons type, the design of which was developed by the Institute of Fused Quartz [5]. This paper descries the results of determining the working characteristics of the PS-75 furnaces introduced at the Pedolsk Factory and a study of fused quartz obtained in them.The method of free melting in single-phase PS-75 furnaces is suitable for melting blocks weighing several tons.The design of the PS-75 furnace is shown in Fig. 1. The quartz sand (startiug material) enters the melter through the telescopic Charging devices. After the melting-in process is complete the melting chamber together with the telescopic hearth is raised, and the block of fused quartz remains, as it is being melted, on the hearth in a filling of quartz sand.After completion of the melting, the melting chamber is separated from the hearth, which is installed on the roll-cut platform. The block after cooling is extracted, and the sand remaining in the hearth is poured in for further use.The rate at which the melter is raised is determined by the viscous flow of the melt and the specific surface capacity of the heaters. The rise rate of the chamber without the coolers is 9, and with the coolers 8 cm/h. The coolers are designed to stabilize the shape of the blocks and reduce the duration of action on the fused quartz of temperatures at which it may crystallize (1200-1500~The fused block is covered with a ~s ~8 Fig. 1. Circuit for PS-75 electric furnace: 1) Electrodes; 2) graphite heaters; 3) barties; 4) frame of melting chamber; 5) block of fused quartz; 6) cooler.Soyuzogneupor. All-Union Institute of Refractories. Podolsk Refractories Factory. State Scientific-Research Institute of Fused Quartz.