Abstract: A hearth for use in a furnace, which comprises an upper layer of magnesia containing chromic oxide, a lower layer containing graphite and an organic bonding agent, and an intermediate layer of a mixture of the materials forming the upper and lower layers. The hearth is particularly useful in DC arc funaces, in which steel rods embedded in the bottom act as the anode. The hearth has improved service durability.

Abstract: An electrode for an electric arc furnace includes a cooled metal sheath covered with a refractory protective jacket. A plurality of refractory anchors are fixed to the exterior of the sheath, and the anchors are spaced from each other. The protective jacket includes an undercoat on the exterior of the sheath and a protective layer over the undercoat and extending between the anchors. The protective layer is formed of a refractory material such that, at the operating temperature of the electrode, the protective layer has an inner zone which is thermoplastic and an outer zone which is rigid or which is a high-viscosity melting phase.

Abstract: A blast heating apparatus includes an inner metal shell having therein a refractory lining. An outer metal shell surrounds at least a portion of the inner metal shell and defines therewith a double shell structure. Spacers are positioned between the outer and inner metal shells to define therebetween a gap. At least a portion of such gap is filled with a pourable dry material having a grain size of up to 8 mm and a heat conductivity of at least approximately 1.5 W/Km.

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: A refractory plate for use in slide closures for metallurgical vessels includes a basic plate element adapted to face a liquid metal melt. The basic plate element is formed of a moldable refractory concrete material including 70 to 95% by weight of alumina and 5 to 30% by weight of a cement containing approximately 80% by weight alumina. Alternatively, the 70 to 95% by weight of alumina may be replaced by an alumina-containing raw material containing more than 70% by weight of alumina, for example at least one raw material selected from the group consisting of sintered bauxite, synthetic mullite, corundum, and grinding disk fragments. The basic plate element has embedded therein a ceramic oxide insert having a cold bending strength higher than 300 kp/cm.sup.2, a hot bending strength at 1500.degree. C. higher than 40 kp/cm.sup.2, a cold compressive strength higher than 2000 kp/cm.sup.2, and a permeability to gas lower than 1.0 nanoperm.

Abstract: Improved refractory compositions for the production of blast furnace pouring ducts are realized by the inclusion of Cr.sub.2 O.sub.3 in said compositions.

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.