Abstract: A process for making silica bricks with increased bulk density from a starting mix containing graded granular quartzite (silica) and elemental silicon, wherein the starting mix contains 0.5 to 10 weight percent of the elemental silicon and also contains 1.5 to 8 weight percent of pyrogenic silicon dioxide based on the weight of the quartzite, elemental silicon and pyrogenic silicon dioxide in the starting mix.

Abstract: A sliding closure unit includes a pair of spaced guide members and a discharge control member movable between the guide members. The control member has therethrough at least one discharge opening to be moved into or out of alignment with discharge openings through the guide members. The control member is formed of a ceramic fiber material.

Abstract: An electrically heated valve element for sliding type valve joints in the outlet of a molten metal vessel has an electrical heating conductor disposed predominately in the outlet closing surface section of the valve element so that when moved to the casting position where the molten metal flow passage aligns with the flow passage from the vessel, the outlet closing surface of the element is maintained at a uniformly high temperature so that any cooling down of the outlet closing surface is avoided. The valve element is made by embedding the heating conductor which is air annealed nichrome wire in spiral form, into the refractory material of the valve element by vibration, the embedding mass being free of organic substances, carbon, sulfur, metallic iron, alkalies and/or electrically conductive substances.

Abstract: Parts subject to wear, which come into contact with metal melts, are formed with a hydraulically setting high-alumina refractory concrete having a compression strength when cold, measured on dried crude product, of at least 400 kp/cm.sup.2. The compression strength is at least 700 kp/cm.sup.2 after firing at 1400.degree. C. The refractory concrete has a dimensional stability at 1400.degree. C. of at least plus or minus 0.2%. The refractory concrete contains corundum and active alumina as aggregates, an alumina concrete containing less than 22% lime and, as required, a thinning agent. Up to 5% of the aggregates can be replaced by a spinel-forming substance preferably MgO or MgO-yielding compounds; or up to 5% of the aggregates can be replaced by carbon black, pitch or graphite; or up to 7% of the aggregates can be replaced by chromium oxide. Aggregates under 0.5 mm can be present in the refractory concrete as round grains.

Abstract: Parts subject to wear, which come into contact with metal melts, are formed with a hydraulically setting high-alumina refractory concrete having a compression strength when cold, measured on dried crude product, of at least 400 kp/cm.sup.2. The compression strength is at least 700 kp/cm.sup.2 after firing at 1400.degree. C. The refractory concrete has a dimensional stability at 1400.degree. C. of at least plus or minus 0.2%. The refractory concrete contains corundum and active alumina as aggregates, an alumina .[.concrete.]. .Iadd.cement .Iaddend.containing less than 22% lime and, as required, a thinning agent. Up to 5% of the aggregates can be replaced by a spinel-forming substance preferably MgO or MgO-yielding compounds; or up to 5% of the aggregates can be replaced by carbon black, pitch or graphite; or up to 7% of the aggregates can be replaced by chromium oxide. Aggregates under 0.5 mm can be present in the refractory concrete as round grains.