Boron carbide is a refractory compound with rigid, high-strength covalent bonds.Industrial boron carbide powders do not sinter before the fusing temperatures, and using powders with an average grain size of less than 1 ~m leads to densification and to a pore-free state only when additives are incorporated in the temperature range 2150-2250~[i].Reaction sintering of boron carbide with additions of boron in a gaseous atmosphere (CO, C02, 02, SiO) formed in a filling of coke and quartz sand occurs at lower temperatures (1600-1700~ and upon completion, yields specimens having a substantial porosity [2].When boron carbide reacts with molten silicon and also with gaseous silicon, the following reaction occurs [3, 4]:Reaction sintering of boron carbide during impregnation of molten silicon leads to the products having a porosity close to zero [5]. With the addition to the batch of carbon (petroleum coke) there is a parallel reaction: and the volume effect of reaction (2) is ( V' )2__ Vsic__ 12A--2,33.The construction of a model of the reaction sintering of boron carbide and carbon with impregnation by silicon melt is prevented by the lack of data on the kinetics of the solution of boron carbide and silicon.It was shown experimentally that at 1850~ grains of boron carbide of less than 20-~m diameter are dissolved in i0 min completely.The grains measuring more than 20 ~m are dissolved incompletely (the solution depth can be taken to be i0 ~m, i.e., half of the grain diameter).Coke reacts with the molten silicon much more rapidly than boron carbide. When boron carbide and coke come into contact with molten silicon at 1850~ in 1 min, the grains of boron carbide remain practically unaltered, while the coke is dissolved completely. These facts formed the basis of two extreme variations of the model for reaction sintering.The first variant starts from the assumption that boron carbide does not react with silicon, and is inert.The second variant starts from the assumption that the grains of boron carbide, upon contact with silicon for i0 min at 1850~ are dissolved to a depth of i0 ~m.From the batch containing y (in unit parts) of carbon and (i -y) boron carbide, blanks are formed which have a porosity ~ (since the true density values of coke and boron carbide are close, the volume and mass proportions in percentages with an accuracy up to the second sign are equal).The blank has an apparent density O----QB,C (l--Y) (t--H) --+-Qcy ( 1 --H).

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