Hydraulically hardening ranching compounds with a 90-94% A1203 content based on fused corundum and high-alumina cement are more resistant in vacuum than compounds with an aluminophosphate binder.This makes it possible to use them in place of complex-shaped parts for lining the inlet and outlet extensions, the extensions for adding deoxidizers, and the cover of vacuum chambers [i].For the production of hydraulically hardeningcompounds the Experimental Technology Section of the All-Union Institute of Refractories developed a method and produced an experimental production lot of high-alumina cement.Finely ground chalk with a coarser than 0.063 mm fraction content from 9.6 to 24% and technical grade alumina previously ground in a tub mill to a coarser than 0.063 mm fraction content of not more than 10% were used as the original components for production of the high-alumina cement [2][3][4].The chemical composition of the original components, shown in Table i, shows the low impurity (oxides of silicon, sodium, etc.) content in them.For the production of the mixture the components were dispensed from bins located above the mixing mills by weight dispensers in ratios of 30-35% chalk and 65-70% alumina.The mixture was mixed with a single moistening with sulfite-yeast mash with a density of I.i g/cm 3 in a quantity of 24-26% over 100% of dry components.Then the compound was mixed in mills for 15 min and discharged into a bin. With the accumulation of about 2000 kg of compound the bins were placed above the receiving bunker of the PK-630 press. The 230 • 114 • 60-65 mm briquettes were pressed with six strikes per minute. The apparent density of the raw part was 1.9-2.14 g/cm 3. T~e briquettes were removed from the press manually and placed on a pallet.Then without preliminary drying the briquettes were placed on furnace cars (height of the charge about 400 mm) and fired in a tunnel kiln with a 4-h hold at the maximum temperature of 1450~The total firing and cooling time was 76 h.The fired briquettes (clinker) were pulverized in a jaw crusher and then in a ball mill with subsequent grinding in a tube mill to a material with a coarser than 0.088 mm fraction content of not more than 5%.Microscopic investigations in reflected and transmitted light established that the highalumina cement is composed primarily of CaO-2AI203 and CaO.AI203.Rare grains of 5CaO,3AI203 and an insignificant quantity of glassy phase are also present [5, 6].N' Monocalciumdialuminate CaO-2AI203 ( g -1.654, high~ouble refraction) is represented by coarser (0.01-0.05 mm) prismati~ crystals than monocalcium aluminate CaO.AI203 (N~ ~ 1.662, medium double refraction) with fine (0.005-0.02 mm) crystals often filling the intervals between the CaO.2AI203 crystals with the formation of a structure of mutual intergrowth.The pentacalcium trialuminate 5CaO-3AI203 (N ~ 1.610, isotropic) is represented by rare grains (0,03-0.07 mm).For the microstructure of the high-alumina cement the presence of aggregate grains of rounded form (0.03-0.2 mm) consisting basically of C...

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