Dissolution of Al2O3–C bricks in 45 wt% CaO-45 wt% SiO2-x wt% CaF2-(10-x) wt% Na2O slag

Abstract

The dissolution of Al2O3–C refractories in 45 wt% CaO-45 wt% SiO2-x wt% CaF2-(10-x) wt% Na2O slag was explored by the static test and thermodynamic calculation. The results show that the severe slag penetration into refractories occurs after corrosion test. With the gradual replacement of CaF2 in slag by Na2O, lots of pores are found in the slag phase near the refractory/slag interface due to the formation of gaseous phase from the reaction between Na2O in slag and C in refractories. Compared with the slag without Na2O, the slag bearing 5 wt% Na2O does not accelerate the dissolution of refractory into slag. The possible reason is that the reaction between CaF2 in slag and Al2O3 in bricks is inhibited due to the replacement of CaF2 in slag by Na2O. The dissolution of Al2O3–C refractories is faster in the slag bearing 10 wt% Na2O than that in the slag bearing 5 wt% Na2O, due to the severer Na2O volatilization from the reduction of Na2O in slag by C in refractories, which accelerates the renewal rate of boundary layer between refractories and slag phase. The results indicate that replacing part of CaF2 in mold slag with moderate amount of Na2O does not aggravate the corrosion of submerged entry nozzle consisting of Al2O3–C based refractories.