| The mainly investigated object of this work is nonoxide (SiC, Sialon)-containing bauxite-based castables. The influences of ultra fine powders, cement etc. and nonoxide (SiC, Sialon) on rheology and thermo-mechanical properties of bauxite-based castables have been studied. The purpose of this work is to find the optimum castable composition and the optimum nonoxide (SiC,. Sialon) addition.This work can be divided into four parts: (1) The influences of ultra fine powders, cement, dispersants and SiC or Sialon fines on rheology of castable matrix have been studied using viscometer of model NXS-11 A. (2) The influences of ultra fine powders, cement, shape of aggregates, SiC or Sialon fines on castable flowability have been studied using flowing table. (3) The influences of ultra fine powders, cement and SiC or Sialon fines on room temperature properties (such as porosity, bulk density, MOR and CCS etc.) of castables after drying at 110℃ * 24h and heat treating at 1100℃*X 3h and 1400癈 X 3h have been studied. (4) The influences of microsilica/ultra fine alumina powders ratios, contents of SiC or Sialon fines on thermomechnical properties (such as HMOR, stress-strain relationship, TSR etc) of castables have been studied using conventional three point bend testing(HMOR, stress-strain relationship ) and 1200 癈 to water cycling(TSR).The results show that (1) the slurry with ultra fine powders is thixtropy and the rheological type of matrix is Bingham model; ultra fine powders and dispersants are the principal factors influencing matrix rheology, the effect of dispersants are FS-20>P3>C>P' >N>B>P6>G and the effective dispersants have an optimal addition; microsilica can improve matrix rheology noticeably; ultra fine alumina and cement have slightly negative effect on matrix rheology; when the ratio of bauxite particles (-325mesh/-200mesh) is over 2/1, the viscosity of slurries begin to increase; the influence of Alumina, magnesia and spinel fines on matrix rheology are minor.(2) The round aggregates contribute to improving castables flow-ability; when the ratio of aggregates/matrix in the castable is 60/40, the value of the flowability is the highest; microsilica can noticeably improve flowability but ultra fine alumina and cement slightly reduce flowability of castables; the appropriate amount SiC fines addition can increase flowablity, but Sialon fines addition reduce flowablity of castables.(3) when the ratio of ultra fine powders/cement is varied, with decrease of the cement content (i.e. the ultra fine powders content is increased, LCC@ULCC@ZCC), the linear change of the specimens exhibites a little swell, the apparent porosity decreases, the bulk density slightly increases, MOR and CCS increase after heat treating at 1100℃*3h and 1400℃*3h; when the contents of cement and ultra fine powders are fixed, with increase of SiC and Sialon content in the matrix, the porosity increases, the bulk density, MOR and CCS decrease after heat treating at medium and high temperatures.(4) a. when the cement content is 2% and the ratio of microsilica /ultra fine alumina is varied, with increase of microsilica content, HMOR and TSR of the specimens are increased; when uf-Al2Od3/uf-SiO2 is 25/75 and the content of SiC or Sialon is in the range of 0-8% in the matrix, with increase of SiC or Sialon content, HMOR and TSR of the specimens are increased, and the maximum value of HMOR is specimen with 4% SiC or 8%Sialon; when uf-Al2O3/uf-SiO2 is 75/25 and the content of SiC or Sialon is in the range of 0-16%, with increase of SiC or Sialon content, HMOR and TSR are increased, and the maximum value of HMOR is specimen with 16% SiC or Sialon.b. MOR-T curves of the specimens with 8% SiC or Sialon belong to type I and their Tm is 800℃or 1000℃; the critical temperature difference (ATc) of the specimens is 800℃; the stress-strain relationship shows that the range of elastic deformation is 20-600℃,the range of plastic deformation is 600-1000℃ and the range of rapid flow range is 1000-1200℃.c. According to... |
PDF Full Text Request