Dependence of the properties of castable samples from low­cement silicon carbide castable before and after heat treatment on the action of alkalis at 1300 °C

Abstract

The main properties and alkali resistance of silicon carbide castable samples heat­treated at temperatures of 110 and 1000 °C were investigated in comparison with the chamotte product, which is used for the same purposes in lining thermal units in contact with an aggressive environment.
 Samples of carbide­silicon castable after heat treatment at temperatures of 110 and 1000 °C were characterized by the following physical and chemical properties, respectively: wt. %: SiC — 84.60 and 79.70, Al2O3 — 13.65 and 13.60, CaO — 1.35 and 1.33; cold crushing strength — 42.2 and 67.5 N/mm2.
 The thermal conductivity of a silicon carbide castable sample heat­treated at a temperature of 1000 °C was determined to be 8.20 W/(m·K) and its thermal shock resistance (950 °C — water) was determined to be > 20 heat cycles.
 The studies of alkali resistance (to a mixture of alkalis Na2CO3 and K2CO3 in a ratio of 25:75) at a temperature of 1300 of carbide­silicon castable samples heat­treated at temperatures of 110 and 1000 °C in comparison with a sample of chamotte refractory, it was found that castable samples heat­treated at temperatures of 110 and 1000 °C are characterized by quite close alkali resistance (weight increase of 1.42 % and 1.5 %, respectively) and significantly higher (by ~ 4.3—4.5 times) alkali resistance than chamotte samples (weight increase of 6.5 %).
 It was established that castable samples after heat treatment at a temperature of 1000 °C after interaction with alkalis were characterized by a 1.6 times higher cold crushing strength compared to a castable sample heat­treated at a temperature of 110 °C.
 The study’s results made it possible to evaluate the performance of the silicon carbide castable in comparison with chamotte refractory during its operation in thermal units at consumers.