Production of corundum refractories and their service in gate valves

Abstract

Owing to the widespread use of gate valves for steel casting, metallurgical factories are increasing their demands for highly resistant refractories. To satisfy these needs the Krasnogorovsk Factory, using experience of the Semiluksk Refractories Factory, has developed the production of corundum plates. The basis of the method is the use of corundum chamotte obtained by firing a mixture af alumina and kaolin at 1620-1640~The mixture af alumina and kaolin is milled in a tubemill to a content of nat more than 1% fractions plus 0.06 ram, and moistened with a water solution of sulfite lye to a water content of 15-18%. The briquet, about 50 mm thick, is prepared on a 4_KF-200 friction press using a rectangular mold. The apparent density of the briquet is at least 2.25 g/cm 3.To obtain stable properties and ensure an increase in the output of corundum goads, the plant has built and put into use a tunnel kiln especially for firing the briquet.The chamotte is crushed and milled sequentially in jaw crushers and in roller crushers, and then is subjected to magnetic separation and screened into fractions 2-0.5 and finer than 0.5mm. The finely milled constituent of the batch is prepared by grinding the chamotte fractions minus 0.5 mm, or alumina grade GK in a M-400 vibramill to a fraction content of not more than 1% plus 0.06 ram.Using alumina substantially reduces the demand for scarce chamotte fractions (--0.5 ram), and awing to the better grindabiHty of GK alumina there is an increase of about three times in the productivity of the vibromill.Originally the body was prepared in the I-A-H mixer runnermills by blending and moistening with a solution af sulfite lye to a water content of 3.5-4.4% corundum chamotte fractions 2-0.5 and --0.5 mm together with the finely milled constituent. However, pressing the goods showed that compounds prepared in these