Effect of graphite type on properties of Al2O3-MgO castables
To develop high-performance carbon-containing castables,SiC-coated graphite was prepared using Si powder and flake graphite as raw materials by a molten salt isolation method firing at 1 350 ℃ for 3 h.Then,flake graphite and SiC-coated graphite were introduced into tabular corundum particles,white corundum powder,fused magnesia powder,alumina micropowder,Secar 71 cement,and silica micropow-der to prepare Al2O3-MgO castable blank samples and Al2O3-MgO-C castable samples by carbon em-bedded heat treatment at 1 100 and 1 600 ℃.The effect of different graphite types on the properties of the castables was studied.The results show that:(1)compared with the Al2O3-MgO castable sample without graphite,the castable sample with flake graphite has significantly increased water demand for molding,sig-nificantly reduced cold modulus of rupture,significantly increased apparent porosity but improved thermal shock resistance and slag resistance;the castable sample with SiC-coated graphite has slightly increased water demand,decreased cold modulus of rupture,slightly increased apparent porosity,and improved hot strength,thermal shock resistance,and slag resistance;(2)with the increase of the heat treatment temper-ature,the cold strength and permanent linear change rate on heating of the samples increase significantly;(3)when 5 mass％SiC-coated graphite is added and the heat treatment temperature is 1 600 ℃,the com-prehensive properties of the sample are the best:the cold modulus of rupture is 16.9 MPa,the apparent porosity is 16.0％;the hot modulus of rupture is 2.0 MPa;and the thermal shock resistance and corrosion resistance are good.
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