Effects of a Combined Silica-containing Additive on Structural and Rheological Properties of a Low-cement Silicon Carbide Castable

The use of a combined additive consisting of silica-containing additives“F”(thinning)and“S”(accelerating castable hardening)instead of the previously used silica-containing additive“A”and a mixture of dispersing additives based on polyethylene glycol in low-cement silicon carbide castable allows to improve the castable workability by increasing(in 5.4 times)the flowability of a freshly prepared castable,and increase by 1.2 and 1.1 times the cold crushing strength of heat-treated at temperatures of 110 and 1580°C,respectively,castable samples from low-cement silicon carbide castable with practically equal values of open porosity(15.8%and 16.0%).The petrographic studies of the castable sample microstructure after firing at a temperature of 1580°C showed that the investigated silica-containing additives“F”and“S”contribute to the denser and more uniform structure formation.As a result of the carried out research,the manufacturing technology of a low-cement silicon carbide castable was improved,of which the production was mastered at JSC“URIR named after A.S.Berezhnoy”.

Effect of Treated Graphite on Properties of Al_2O_3-SiC-C Castables

Al2O3 - SiC - C castables with 2% pitch or 2%, 4% and 6% treated graphite, respectively, were prepared based on the basic formulation of traditional Al2O3 - SiC - C castables. The flowability of castables, and bulk density, volume stability, strength, oxidation resistance and slag resistance of specimens fired at 110 ℃, 1 100 ℃, and 1 500 9Z respectively were comparatively studied. The results showed that： （1） With carbon source changing from pitch to treated graphite and the increase of treated graphite addition, water addition of castables increased, bulk density of specimens fired at different temperatures increased firstly and then decreased, strength after drying decreased obviously, strength after firing and oxidation resistance changed slightly, hot modulus of rupture increased obviously; （2） Slag resistance of specimen with treated graphite was worse than that of specimen with the same amount of pitch, but the former was obviously improved with the increase of treated graphite addition.

Application Research of Dense Sintered Alumina in Iron Runner Castables

Three different kinds of corundum aggregates-tabular sintered alumina, dense sintered alumina, and fused dense corundum-were introduced into the silica fume .free or silica fume containing Al2O3 -SiC - C iron runner castables to investigate their influences on the flow ability, linear change on heating, bulk density, apparent porosity, cold strength, hot modulus of rupture, therm, al shock resistance, slag resistance, oxidation resistance as well as wear resistance of Al2O3 - SiC - C iron runner castables. The results show that （ 1 ） compared with the specimens with fused dense corundum, the specimens with dense sintered alumina have equivalent installation property, slag resistance and oxidation resistance, equivalent or even higher cold modulus of rupture, cold crushing strength and hot modulus of rupture, exhibiting better thermal shock resistance and cold wear resistance ; （2） adopting bimodal alumina micropowder LISAL22RABL as well as water reducers ZX2 and ZD2 can well reduce the water requirement of silica fume free castables, solving the problem of deteriorated flow ability resulted from the lack of silica fume; since the lack of silica fume avoids the formation of low melting point liquid, the hot modulus of rupture and the thermal shock resistance of the silica fume free castables are both better than those of the silica fume containing castables ; （3） the density of the castable specimens with dense sintered alumina is 4% -6% lower than that of the castable specimens with Jhsed dense corundum so the refractories consumption of one iron runner reduces by 5% by using the tastable with dense sintered alumina, which obviously reduces the cost of refractories.