The investigation of microgranular constituents of magnesia concretes should be made in order to obtain further improvements in the quality. Microgranular constituents from periclase powder, sintered dunite, and chromite are the most common materials for magnesia concretes. The authors therefore studied the thermomechanical properties of pressed and cast TABLE 1 Chemical Composition of Original Materials Material ~ ~madd Periclase powder fractions 3-0 mm 18~2, 42 1 !,55 [ !,44 1 -[ o,sa Sintered Solov evogorsk dunite fractionsl-0 rnm 149,02140,28 I 0,17 I 0,24 I 9,79 ] 0,48 ~Nt. inc. Kempiraiskchromiteorefractions10mm I.lOl.Ol0Oo Io7o 1,33o1 9ol ,78 *Here and subsequently mass proportions are indicated.

Components whose properties are shown in Table 1 were used to study the milling processes of periclase~ dunite, chromite powders, and their combined mixtures~ Mathematical planning of the experiment was carried out according to the D-optimal simplex-solving plan of the third order.This plan enabled us to determine the regression coefficient in the following mathematical model, consisting of a polynomial of the third degree:In the work the number of components q = 3, the order of the model was n = 3, the number of experiments N= C~+n_ I = C~+3-I = i0; and C~ was the number of combinations from the elements with respect to k~The regression coefficients in the given model were calculated on the Mir-i electronic computer.The compositions of the mixtures of the original components were established with respect to the incomplete cubic matrix for the (3,3)-lattice.The powders and mixture were milled in a ballmill for 4 h, and with a mass ratio of balls to powders of 3:1.

The slag crust consisted of 12-17% corundum, 20-23% of glassy and crystalline substances, 7-8% of spinel, 8-12% of gehlenite, 13-151 of calcium hexaaluminate, 28-30~ calcium dialuminate.The slag crust and the covering layer under it contained 2-3% metal.The new high-alumina mass was used to Gunite both high-alumina and silica--clay bucket linings.The average increment on the resistance of the lining of 180-ton steel-casting buckets as a result of using gunniting for 209 bucket campaigns was 2.88 smeltings. CONCLUSIONSThe composition for a high-alumina gunniting mass with an A1203 concentration of~65% was developed on the basis of chamotte obtained by firing the natural raw material.The production of the high-alumina gunniting mass was organized at the Semiluksk Refractory Plant.

Acceleration of metallurgical processes and an increase in unit capacity of heating equipment continuously imposes new and higher requirements for refractory materials. In addition, in recent years requirements for low energy consumption in the production and use of refractory materials have been added to the requirement for high resistance. Unformed refractories meet these requirements most fully.

Plastic aluminosilicate compounds are widely used in foreign furnace construction practice [i, 2]. According to the data of [3] 331,000 tons are prepared in the USA and 69,400 tons in Japan.The use of plastic compounds in the roofs, walls, covers, and other elements of soaking pits and heating and heat treatment furnaces makes it possible to sharply reduce the quantity of shaped parts used, to reduce the thermal conductivity of multi-layer linings of fiber, thermal insulation parts, and compounds, and to increase their life by two to four times.Eastern Refractory Institute has developed plastic compounds of different compositions [4,5]. The properties of the compounds are given in Table i. The Experimental Plant of the institute has developed a method of preparation of the compounds in loose form and in briquettes.Refractory chamotte and high-alumina fillers were used for preparation of the compounds, and refractory plastic clays from Druzhkovka and Nizhnii Uvel'sk Deposits as the binder.The role of the antishrinkage addition in the compound was filled by electrocorundum and the plasticizing addition was a formate-alcohol stabilizer [6].Chamotte compounds without orthophosphoric acid are intended for use at service temperatures of 800-1450~To increase the strength of the compound below 1000~ 2.5-3% orthophosphoric acid (in excess of 100%) was added to it.To obtain the compound in loose form the original materials were weighed, placed in a forced action mixer, moistened with a solution of the plasticizing addition (6.0-8.5%), and mixed for 5-7 min.The compound was packed in polyethylene bags or rubber cord containers and shipped to the user.In storage for 6 months in rubber cord containers the moisture content of the compound dropped to 5-7% and before use it was moistened with water or orthophosphoric acid and mixed.Briquettes of the plastic compound are necessary for convenience in laying it in the monolithic lining of furnace roofs.The briquettes were produced in a special mold (Fig. i). The loose compound was placed in the mold and compacted by pneumatic ramming in three layers.The i000 • 250 • 250 mm block of compound was cut with a special knife into 250 • 250 • 70 mm briquettes and two or three each placed in polyethylene bags and then in wooden or plywood boxes.The use of polyethylene bags larger than the briquettes and the absence of tightness of the package led in long storage to drying of them, which created major difficulties in further moistening of them before use.