To meet the needs of environmental protection and promote the application of chromium-free refractories for RH refining furnaces, research on application of new non-burned periclase-magnesia alumina spinel bricks was ...To meet the needs of environmental protection and promote the application of chromium-free refractories for RH refining furnaces, research on application of new non-burned periclase-magnesia alumina spinel bricks was carried out. Through laboratory research and field application, it is concluded that the non-burned periclase-magnesia alumina spinel brick can replace magnesia-chrome material, and its service life is equivalent to that of the magnesia-chrome material with reduced cost.展开更多
In order to improve the properties of purging plugs and to prolong their service life,this work attempted to impregnate alumina-spinel castables for purging plugs in refining ladle with saturated magnesium chloride so...In order to improve the properties of purging plugs and to prolong their service life,this work attempted to impregnate alumina-spinel castables for purging plugs in refining ladle with saturated magnesium chloride solution under vacuum.After being impregnated for the first time,the specimens were treated in two different ways:(1)dried at 110℃for 24 h;(2)heated at 600℃for 3 h.Then they were impregnated for the second time.All specimens were heated at 1550℃for 3 h,then the cold properties and the high temperature properties were tested according to corresponding standards.Test results were compared and analyzed.The results show that:after being impregnated,the specimen have both better cold properties and high temperature properties,the microstructure analysis result proves that it is attributed to in situ formed spinel.However,because MgO produced by MgCl2-6H20 decomposing above 527℃can hydrate and destroy specimen microstructure,which can make the properties of specimens impregnated in the second way get worse.By comprehensive consideration,the first scheme way is more suitable.展开更多
The effects of several commercial dispersants,including AN 2000,ammonium polyacrylate,sodium tripolyphosphate,sodium hexametaphosphate, and of solids loading and of electro fused magnesia on rheological properties o...The effects of several commercial dispersants,including AN 2000,ammonium polyacrylate,sodium tripolyphosphate,sodium hexametaphosphate, and of solids loading and of electro fused magnesia on rheological properties of aqueous alumina spinel slurries were studied. The results reveal that AN 2000 is the most effective one among the selected dispersants for alumina spinel slurries. With 0.5% weight of AN 2000, the 57vol% solids loading alumina spinel slurry with viscosity of 0.37 Pa·s was obtained at shear rate of 50s 1 .展开更多
In order to study the effect of fused spinel on the properties of phosphoricacid bonded high alumina castables, samples with different contents of fused spinel were prepared.The results show that when the contents of ...In order to study the effect of fused spinel on the properties of phosphoricacid bonded high alumina castables, samples with different contents of fused spinel were prepared.The results show that when the contents of the fused spinel are between 8% and 16% (mass fraction),the castables have good properties. The castables overcome the shortages of the phosphoric acidbonded high alumina castables with bauxite cement as a hardening promoter. The experimentsdemonstrate that most of the service properties of the castables with fused spinel are better thanthose of the normal phosphoric acid bonded castables which use bauxite cement as a hardeningpromoter. The examination of the materials indicates that free MgO inclusions in the spinel powdercan promote the hardening of the castables.展开更多
In order to clarify the effect of ultrafine spinel sources on slag resistance and microstructure of alumina -spinel castables,using tabular alumina and spinel as coarse aggregates,tabular alumina powders,spinel powder...In order to clarify the effect of ultrafine spinel sources on slag resistance and microstructure of alumina -spinel castables,using tabular alumina and spinel as coarse aggregates,tabular alumina powders,spinel powders,calcium aluminate cement,spinel containing cement,spinel micro-powder and reactive alumina ultrafines as matrix,alumina-spinel castables used for RH snorkels were prepared by changing the particle size and sources of preformed spinel.The effects of different ultrafine spinel sources (CMA72,spinel micro-powder) on the properties of alumina-spinel castables were investigated.Thermal shock resistance and slag resistance of specimens were compared by the residual strength rate (1 100 ℃,air cooling 1 cycle) and static crucible method.The microstructure and the slag corrosion resistance mechanism of the specimens were analyzed by SEM and EDS.The result shows that slag resistance of alumina-spinel castables can be improved by adding ultrafine preformed spinel,such as CMA72,and spinel micro-powder.The introduction of ultra-fine preformed spinel has little effect on HMOR of alumina-spinel castables,but has negative effect on TSR.ultra-fine and dispersive preformed spinel in the matrix and fine microstructure are the main reasons for the improvement of slag resistance of castables.展开更多
Chrame containing refractories are a kind of traditional material for the lining of alkali recovery furnaces, but the formation of hexavalent chrome compounds will give rise to detrimental effect on environment and hu...Chrame containing refractories are a kind of traditional material for the lining of alkali recovery furnaces, but the formation of hexavalent chrome compounds will give rise to detrimental effect on environment and human's health. With the gradual awakening of people's comciousness about environment protection, it is urgent to prepare environmental-friendly materials for alkali recovery jurnaces with high quality and long life. In this paper, alumina-rich MgAl2O4 spinel ( AR90 ) was used to replace chromite. The physical properties of dried (110 ℃ for 24 h) or fired (1 300 ℃ for 3 h) AR90 and chromite were studied, respectively. The alkali vapor method was used to determine the alkali resistance of the two materials. The results show that: (1) after drying at 110 ℃ for 24 h, AR90 specimens show higher apparent porosity and slightly lower bulk density than chromite specimens; after firing at 1 300 ℃ for 3 h, AR90 has significantly higher apparent porosity as well as higher bulk density; (2) after the alkali attack, the AR90 specimens sintered at 1 300 ℃ exhibit smaller strength change and much higher compressive strength than the chromite specimens; meanwhile, the permeability degree of alkali salt in chromite specimens is more serious than that in AR90 specimens, which indicates that AR90 possesses better alkali resistance.展开更多
The corrosion behavior of alumina-chromia refractory against two kinds of industrial slags (coal slag and iron smelting slag) at 1550℃ was investigated via thermodynamic simulations. In the proposed simulation mode...The corrosion behavior of alumina-chromia refractory against two kinds of industrial slags (coal slag and iron smelting slag) at 1550℃ was investigated via thermodynamic simulations. In the proposed simulation model, the initial slag first attacks the matrix and surface aggregates and subsequently attacks the inner aggregates. The simulation results indicate that the slag chemistry strongly affects the phase formation and corrosion behavior of the refractory brick. Greater amounts of alumina were dissolved and spinel solid phases formed when the brick interacted with iron smelting slag. These phenomena, as well as the calculated lower viscosity, may lead to much deeper penetration than that exhibited by coal slag and to more severe corrosion compared to that induced by coal slag. The thermodynamic calculations well match the experimental observations, demonstrating the efficiency of the proposed simulation model for evaluating the corrosion behavior of alumina-chromia refractory.展开更多
Purging plugs installed in the bottom of steel ladles are widely used for the secondary refining of high quality steel grades.The dynamic service conditions and temperature gradients caused by the cold inert gas blown...Purging plugs installed in the bottom of steel ladles are widely used for the secondary refining of high quality steel grades.The dynamic service conditions and temperature gradients caused by the cold inert gas blown through the plug during stirring create a strong thermal shock impact on the materials.This can affect its service life and restrict the safety and efficiency of steel making if the plug fails during use.In this work,the influence of the particle size distribution (PSD) and amount of reactive alumina on the sintering behavior of ultra-low cement bonded corundum-spinel based castables was investigated on lab scale.The relationship between sintering reactivity of matrix and thermal shock resistance of castables was evaluated in detail.Results show that the sintering of castables can be intensified by using finer reactive alumina.However,excessive sintering of the castable through finer reactive alumina is negative for thermal shock resistance.The microstructure characterization reveals that castables with more intense sintering show denser matrix structure,which is less effective in hampering crack propagation and therefore results in decline of their thermal shock resistance.展开更多
MgO·Al 2O 3 spinel fibers may be obtained by thermal treatment of pressed specimens composed of Mg-Al-O materials with appropriate oxide-metal ratio at high temperature under controlled atmosphere. Their phase ...MgO·Al 2O 3 spinel fibers may be obtained by thermal treatment of pressed specimens composed of Mg-Al-O materials with appropriate oxide-metal ratio at high temperature under controlled atmosphere. Their phase composition and microstructure have been examined.展开更多
Regarding the morphology of alumina,effect of the heredity of raw materials on properties of aluminamagnesia refractory castables was investigated by adding platelet alumina as the specific template.In-situ spinel pla...Regarding the morphology of alumina,effect of the heredity of raw materials on properties of aluminamagnesia refractory castables was investigated by adding platelet alumina as the specific template.In-situ spinel platelet formed derived from platelet alumina.By comparing phase evolution,apparent porosity,bulk density,permanent linear expansion and strength,it was demonstrated that the utilization of the microstructures' heredity of platelet alumina was a new alternative for controlling properties of alumina-magnesia refractory castables.展开更多
文摘To meet the needs of environmental protection and promote the application of chromium-free refractories for RH refining furnaces, research on application of new non-burned periclase-magnesia alumina spinel bricks was carried out. Through laboratory research and field application, it is concluded that the non-burned periclase-magnesia alumina spinel brick can replace magnesia-chrome material, and its service life is equivalent to that of the magnesia-chrome material with reduced cost.
文摘In order to improve the properties of purging plugs and to prolong their service life,this work attempted to impregnate alumina-spinel castables for purging plugs in refining ladle with saturated magnesium chloride solution under vacuum.After being impregnated for the first time,the specimens were treated in two different ways:(1)dried at 110℃for 24 h;(2)heated at 600℃for 3 h.Then they were impregnated for the second time.All specimens were heated at 1550℃for 3 h,then the cold properties and the high temperature properties were tested according to corresponding standards.Test results were compared and analyzed.The results show that:after being impregnated,the specimen have both better cold properties and high temperature properties,the microstructure analysis result proves that it is attributed to in situ formed spinel.However,because MgO produced by MgCl2-6H20 decomposing above 527℃can hydrate and destroy specimen microstructure,which can make the properties of specimens impregnated in the second way get worse.By comprehensive consideration,the first scheme way is more suitable.
文摘The effects of several commercial dispersants,including AN 2000,ammonium polyacrylate,sodium tripolyphosphate,sodium hexametaphosphate, and of solids loading and of electro fused magnesia on rheological properties of aqueous alumina spinel slurries were studied. The results reveal that AN 2000 is the most effective one among the selected dispersants for alumina spinel slurries. With 0.5% weight of AN 2000, the 57vol% solids loading alumina spinel slurry with viscosity of 0.37 Pa·s was obtained at shear rate of 50s 1 .
文摘In order to study the effect of fused spinel on the properties of phosphoricacid bonded high alumina castables, samples with different contents of fused spinel were prepared.The results show that when the contents of the fused spinel are between 8% and 16% (mass fraction),the castables have good properties. The castables overcome the shortages of the phosphoric acidbonded high alumina castables with bauxite cement as a hardening promoter. The experimentsdemonstrate that most of the service properties of the castables with fused spinel are better thanthose of the normal phosphoric acid bonded castables which use bauxite cement as a hardeningpromoter. The examination of the materials indicates that free MgO inclusions in the spinel powdercan promote the hardening of the castables.
基金the financial support from the National Natural Science Foundation of China(Grant no.51402089)the Science and Technology Research Planning Project of Henan Province(Project No.162102210206)the Plan of Young-backbone Teachers of Colleges and Universities in Henan Province(Project No.2015GGJS-045)
文摘In order to clarify the effect of ultrafine spinel sources on slag resistance and microstructure of alumina -spinel castables,using tabular alumina and spinel as coarse aggregates,tabular alumina powders,spinel powders,calcium aluminate cement,spinel containing cement,spinel micro-powder and reactive alumina ultrafines as matrix,alumina-spinel castables used for RH snorkels were prepared by changing the particle size and sources of preformed spinel.The effects of different ultrafine spinel sources (CMA72,spinel micro-powder) on the properties of alumina-spinel castables were investigated.Thermal shock resistance and slag resistance of specimens were compared by the residual strength rate (1 100 ℃,air cooling 1 cycle) and static crucible method.The microstructure and the slag corrosion resistance mechanism of the specimens were analyzed by SEM and EDS.The result shows that slag resistance of alumina-spinel castables can be improved by adding ultrafine preformed spinel,such as CMA72,and spinel micro-powder.The introduction of ultra-fine preformed spinel has little effect on HMOR of alumina-spinel castables,but has negative effect on TSR.ultra-fine and dispersive preformed spinel in the matrix and fine microstructure are the main reasons for the improvement of slag resistance of castables.
文摘Chrame containing refractories are a kind of traditional material for the lining of alkali recovery furnaces, but the formation of hexavalent chrome compounds will give rise to detrimental effect on environment and human's health. With the gradual awakening of people's comciousness about environment protection, it is urgent to prepare environmental-friendly materials for alkali recovery jurnaces with high quality and long life. In this paper, alumina-rich MgAl2O4 spinel ( AR90 ) was used to replace chromite. The physical properties of dried (110 ℃ for 24 h) or fired (1 300 ℃ for 3 h) AR90 and chromite were studied, respectively. The alkali vapor method was used to determine the alkali resistance of the two materials. The results show that: (1) after drying at 110 ℃ for 24 h, AR90 specimens show higher apparent porosity and slightly lower bulk density than chromite specimens; after firing at 1 300 ℃ for 3 h, AR90 has significantly higher apparent porosity as well as higher bulk density; (2) after the alkali attack, the AR90 specimens sintered at 1 300 ℃ exhibit smaller strength change and much higher compressive strength than the chromite specimens; meanwhile, the permeability degree of alkali salt in chromite specimens is more serious than that in AR90 specimens, which indicates that AR90 possesses better alkali resistance.
基金financially supported by the Preliminary Research Project for National Basic Research Program of China (No. 2012CB724607)the Research Planning Project of Basic and Advanced Technology of Henan Province, China (No.162300410043)
文摘The corrosion behavior of alumina-chromia refractory against two kinds of industrial slags (coal slag and iron smelting slag) at 1550℃ was investigated via thermodynamic simulations. In the proposed simulation model, the initial slag first attacks the matrix and surface aggregates and subsequently attacks the inner aggregates. The simulation results indicate that the slag chemistry strongly affects the phase formation and corrosion behavior of the refractory brick. Greater amounts of alumina were dissolved and spinel solid phases formed when the brick interacted with iron smelting slag. These phenomena, as well as the calculated lower viscosity, may lead to much deeper penetration than that exhibited by coal slag and to more severe corrosion compared to that induced by coal slag. The thermodynamic calculations well match the experimental observations, demonstrating the efficiency of the proposed simulation model for evaluating the corrosion behavior of alumina-chromia refractory.
基金the National Natural Science Foundation of China(51572244 and U1604252)for supporting this work
文摘Purging plugs installed in the bottom of steel ladles are widely used for the secondary refining of high quality steel grades.The dynamic service conditions and temperature gradients caused by the cold inert gas blown through the plug during stirring create a strong thermal shock impact on the materials.This can affect its service life and restrict the safety and efficiency of steel making if the plug fails during use.In this work,the influence of the particle size distribution (PSD) and amount of reactive alumina on the sintering behavior of ultra-low cement bonded corundum-spinel based castables was investigated on lab scale.The relationship between sintering reactivity of matrix and thermal shock resistance of castables was evaluated in detail.Results show that the sintering of castables can be intensified by using finer reactive alumina.However,excessive sintering of the castable through finer reactive alumina is negative for thermal shock resistance.The microstructure characterization reveals that castables with more intense sintering show denser matrix structure,which is less effective in hampering crack propagation and therefore results in decline of their thermal shock resistance.
文摘MgO·Al 2O 3 spinel fibers may be obtained by thermal treatment of pressed specimens composed of Mg-Al-O materials with appropriate oxide-metal ratio at high temperature under controlled atmosphere. Their phase composition and microstructure have been examined.
基金supported by the Natural Science Foundation of China under Grant No.51502214
文摘Regarding the morphology of alumina,effect of the heredity of raw materials on properties of aluminamagnesia refractory castables was investigated by adding platelet alumina as the specific template.In-situ spinel platelet formed derived from platelet alumina.By comparing phase evolution,apparent porosity,bulk density,permanent linear expansion and strength,it was demonstrated that the utilization of the microstructures' heredity of platelet alumina was a new alternative for controlling properties of alumina-magnesia refractory castables.