Effect of pitch powder addition on the microstructure and properties of carbon blocks for blast furnace

Abstract

The phase composition and microstructural evolution of pitch-containing matrix sample with additive of silicon had been compared with pitch-free or resin-containing matrix sample to illustrate the strengthening effect of pitch. Two different pitch powders (CARBORES@P and High temperature pitch) were then incorporated into carbon blocks, respectively and the effect of pitch powder addition on microstructure and properties of carbon blocks fired at 1000 °C and 1400 °C in a coke bed was evaluated systematically. The results showed that compared with amorphous carbonized resin, carbonized pitch was a kind of highly graphitized carbon and could react with silicon and form SiC whiskers at 1400 °C. In carbon blocks, pitch powder accelerated the formation of AlN at 1000 °C and growth of β-SiC whiskers at 1400 °C, respectively, which enhanced the cold compressive strength, thermal conductivity and hot metal erosion resistance of carbon blocks. Moreover, carbon blocks containing CARBORES@P pitch with higher carbon yield exhibited better properties because of formation of more ceramic whiskers. The strengthening mechanism of pitch powder for carbon blocks was attributed to the pore-blocking effect of pitch carbonization and more in-situ formed whiskers derived from the reaction between carbonized pitch with silicon at 1400 °C.