Hydration mechanism of tabular alumina carbon composites reinforced by Al4C3 in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 ℃ to 85 ℃. It is shown...Hydration mechanism of tabular alumina carbon composites reinforced by Al4C3 in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 ℃ to 85 ℃. It is shown that hydration mechanism of the composites is chemical reaction control at 44.3 ℃-84 ℃ in H2O（g）. The hydration was controlled by diffusion from 24.7 ℃ to 33 ℃. The ratio of added Mg/Al influences the HMOR of the composites.The mechanism of HMOR of the composites with different ratios of Mg/Al can be discovered by means of SEM analysis. The active Mg/Al powder and flake graphite inside give the composites outstanding hot strength resulting from the interlocking structure of Al4C3 crystals at high temperature. Besides, the matrix changes into the Al4C3 with high refractoriness. The method of preventing the hydration of tabular alumina carbon composites reinforced by Al4C3 in situ reaction was immersed in the wax at suitable temperature or storing them below 33 ℃ in a dry place or storing them with paraffin-coating.展开更多
Three different kinds of corundum aggregates-tabular sintered alumina, dense sintered alumina, and fused dense corundum-were introduced into the silica fume .free or silica fume containing Al2O3 -SiC - C iron runner c...Three different kinds of corundum aggregates-tabular sintered alumina, dense sintered alumina, and fused dense corundum-were introduced into the silica fume .free or silica fume containing Al2O3 -SiC - C iron runner castables to investigate their influences on the flow ability, linear change on heating, bulk density, apparent porosity, cold strength, hot modulus of rupture, therm, al shock resistance, slag resistance, oxidation resistance as well as wear resistance of Al2O3 - SiC - C iron runner castables. The results show that （ 1 ） compared with the specimens with fused dense corundum, the specimens with dense sintered alumina have equivalent installation property, slag resistance and oxidation resistance, equivalent or even higher cold modulus of rupture, cold crushing strength and hot modulus of rupture, exhibiting better thermal shock resistance and cold wear resistance ; （2） adopting bimodal alumina micropowder LISAL22RABL as well as water reducers ZX2 and ZD2 can well reduce the water requirement of silica fume free castables, solving the problem of deteriorated flow ability resulted from the lack of silica fume; since the lack of silica fume avoids the formation of low melting point liquid, the hot modulus of rupture and the thermal shock resistance of the silica fume free castables are both better than those of the silica fume containing castables ; （3） the density of the castable specimens with dense sintered alumina is 4% -6% lower than that of the castable specimens with Jhsed dense corundum so the refractories consumption of one iron runner reduces by 5% by using the tastable with dense sintered alumina, which obviously reduces the cost of refractories.展开更多
Research on the effects of the amount of fillers in the form of fused alumina,mullite,and tabular alumina,zirconium-containing and silica-containing components of the batches in the form of zircon and silica sand on t...Research on the effects of the amount of fillers in the form of fused alumina,mullite,and tabular alumina,zirconium-containing and silica-containing components of the batches in the form of zircon and silica sand on the properties of alumina-zirconia-silicate(AZS)refractories was conducted.It was found that the introduction of 16%zircon into the composition of samples with fillers such as fused alumina and mullite,as well as tabular alumina,results in an increase in their density,strength,and thermal shock resistance.Petrographic studies have revealed the formation of a multiphase,microcracked structure in these samples,which accounts for the improvement in their properties.The optimal composition of a batch containing a filler of tabular alumina,a finely dispersed matrix ofα-alumina,16%zircon,and 7%silica sand has been determined,which ensures the production of AZS refractories with high bulk density,cold crushing strength,and thermal shock resistance.Research on the plastic strength of the structure of optimal composition AZS mass,depending on its storage time,was conducted.It was found that up to 24 h of storage,the mass is characterized by low plastic strength.It indicates its suitability for use in the vibration casting technology of products.Storage of the mass for more than 24 h leads to an increase in the plastic strength of its structure,which reaches a maximum after 56 h of storage.The developed composition of the batch is recommended for the manufacture of AZS crucibles for induction melting of heat-resistant alloys.展开更多
基金Funded by the National Torch Plan of China(No.2005EB031110)the Key Scientific and Technical Innovation Project of Xi’an University of Architecture and Technology(No.zx 0402)
文摘Hydration mechanism of tabular alumina carbon composites reinforced by Al4C3 in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 ℃ to 85 ℃. It is shown that hydration mechanism of the composites is chemical reaction control at 44.3 ℃-84 ℃ in H2O（g）. The hydration was controlled by diffusion from 24.7 ℃ to 33 ℃. The ratio of added Mg/Al influences the HMOR of the composites.The mechanism of HMOR of the composites with different ratios of Mg/Al can be discovered by means of SEM analysis. The active Mg/Al powder and flake graphite inside give the composites outstanding hot strength resulting from the interlocking structure of Al4C3 crystals at high temperature. Besides, the matrix changes into the Al4C3 with high refractoriness. The method of preventing the hydration of tabular alumina carbon composites reinforced by Al4C3 in situ reaction was immersed in the wax at suitable temperature or storing them below 33 ℃ in a dry place or storing them with paraffin-coating.
文摘Three different kinds of corundum aggregates-tabular sintered alumina, dense sintered alumina, and fused dense corundum-were introduced into the silica fume .free or silica fume containing Al2O3 -SiC - C iron runner castables to investigate their influences on the flow ability, linear change on heating, bulk density, apparent porosity, cold strength, hot modulus of rupture, therm, al shock resistance, slag resistance, oxidation resistance as well as wear resistance of Al2O3 - SiC - C iron runner castables. The results show that （ 1 ） compared with the specimens with fused dense corundum, the specimens with dense sintered alumina have equivalent installation property, slag resistance and oxidation resistance, equivalent or even higher cold modulus of rupture, cold crushing strength and hot modulus of rupture, exhibiting better thermal shock resistance and cold wear resistance ; （2） adopting bimodal alumina micropowder LISAL22RABL as well as water reducers ZX2 and ZD2 can well reduce the water requirement of silica fume free castables, solving the problem of deteriorated flow ability resulted from the lack of silica fume; since the lack of silica fume avoids the formation of low melting point liquid, the hot modulus of rupture and the thermal shock resistance of the silica fume free castables are both better than those of the silica fume containing castables ; （3） the density of the castable specimens with dense sintered alumina is 4% -6% lower than that of the castable specimens with Jhsed dense corundum so the refractories consumption of one iron runner reduces by 5% by using the tastable with dense sintered alumina, which obviously reduces the cost of refractories.
文摘Research on the effects of the amount of fillers in the form of fused alumina,mullite,and tabular alumina,zirconium-containing and silica-containing components of the batches in the form of zircon and silica sand on the properties of alumina-zirconia-silicate(AZS)refractories was conducted.It was found that the introduction of 16%zircon into the composition of samples with fillers such as fused alumina and mullite,as well as tabular alumina,results in an increase in their density,strength,and thermal shock resistance.Petrographic studies have revealed the formation of a multiphase,microcracked structure in these samples,which accounts for the improvement in their properties.The optimal composition of a batch containing a filler of tabular alumina,a finely dispersed matrix ofα-alumina,16%zircon,and 7%silica sand has been determined,which ensures the production of AZS refractories with high bulk density,cold crushing strength,and thermal shock resistance.Research on the plastic strength of the structure of optimal composition AZS mass,depending on its storage time,was conducted.It was found that up to 24 h of storage,the mass is characterized by low plastic strength.It indicates its suitability for use in the vibration casting technology of products.Storage of the mass for more than 24 h leads to an increase in the plastic strength of its structure,which reaches a maximum after 56 h of storage.The developed composition of the batch is recommended for the manufacture of AZS crucibles for induction melting of heat-resistant alloys.
