Thermal behavior and physical properties of castables during curing and drying-out are associated with their binding system. In this work, five alumina based （ Al2O3 〉 87% ） castables with different combinations of...Thermal behavior and physical properties of castables during curing and drying-out are associated with their binding system. In this work, five alumina based （ Al2O3 〉 87% ） castables with different combinations of binding materials, i. e. , （ 1 ） CA cement （CA） ＋ Reactive alumina （ RA ） ＋ H2O ; （ 2 ） high level addi- tion of CA ＋ Microsilica （MS） ＋ H2O ; （ 3 ） low level addition of CA ＋ MS ＋ H2O ; （4） MS ＋ Hydratable alumina ＋ H20 and （ 5 ） MS ＋ Magnesia ＋ H2O, respectively, have been investigated on the flowability and thermal behavior during curing at room temperature, drying at 110% and heating from 200℃ to 1000℃ at an interval of 100℃ , in terms of water addition, vibration flow value, porosity, dehydration, explosion resistance, cold and hot bending strengths. Differences in dehydrating behavior and the mentioned properties have been revealed and correlated to the binding system.展开更多
Compared with traditional aggregates,spherical aggregates with high flowability,easy control of particle size distribution and favor of dense packing and so on,are expected to replace traditional aggregates as importa...Compared with traditional aggregates,spherical aggregates with high flowability,easy control of particle size distribution and favor of dense packing and so on,are expected to replace traditional aggregates as important raw materials for future high performance refractories. Therefore,investigation of effects of spherical aggregates addition on properties of refractories becomes very meaningful. Using A70 mullite traditional aggregates and A70 mullite spherical aggregates, bauxite homogenization powder,microsilica,and calcium aluminate cement as raw materials,different AlO-SiOsystem low cement castables were prepared by replacing conventional aggregates with spherical aggregates. The effect of spherical aggregates addition on workability and mechanical properties of castables after heated at different temperatures was researched,and microstructure of the specimen was analyzed by SEM. Compared with traditional irregularly shaped aggregates,spherical aggregates endow castables with better flowability and easy pump ability. By introduction of spherical aggregates into the castables,flowability and pumpability are significantly improved,and water addition and ball completely sunk time are reduced. The introduction of spherical aggregates is favorable to density and cold crushing strength of castables,but unfavorable to CMOR. The effect of spherical aggregates addition on HMOR at1 400 ℃ can be negligible. Microstructure analysis showsthat the boundary bonding between spherical aggregates and matrix is strong,similar to the traditional aggregates.展开更多
MgO -ZrO2 unfired bricks with ZrO2 content up to 8% at the interval of 2% were prepared, using fused magnesia （ MgO ： 97% ） and fused MgO - ZrO2 clinker （ ZrO2 ： 14. 33% ） as starting materials and phenolic resi...MgO -ZrO2 unfired bricks with ZrO2 content up to 8% at the interval of 2% were prepared, using fused magnesia （ MgO ： 97% ） and fused MgO - ZrO2 clinker （ ZrO2 ： 14. 33% ） as starting materials and phenolic resin as binder. The effects of ZrO2 content on thermal shock resistance （TSR） and other properties such as cold and hot modulus of rupture have been investigated. Re- sidual cold modulus of rupture ratio after heating at 1 000 ℃ and quenching by air blowing was adopted to characterize TSR. Addition of the MgO -ZrO2 clinker improves TSR, attributing to the microcrack toughening effect by thermal expansion mismatch between different phases. When ZrO2 content goes above 4%. the impro- ving effect tends to be moderate. The introduction of MgO- ZrO2 clinker can also improve the HMOR at 1 500 ℃, while the increased ZrO2 content reduces CMOR of the bricks prefired at 1 600 ℃, due to the thermal expansion mismatch effect. Compromising the overall properties, the optimal ZrO2 content for such magnesia based unfired brick is suggested to be 4%.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
Magnesite fine powder, natural silica powder,light-burned magnesia fine powder, silica fume and middle grade magnesia fine powder were used as the starting materials,and silica sol as binder to get high purity lightwe...Magnesite fine powder, natural silica powder,light-burned magnesia fine powder, silica fume and middle grade magnesia fine powder were used as the starting materials,and silica sol as binder to get high purity lightweight spherical forsterite aggregates. The mixture was granulated on a disc pelletizer and then calcined at 1 400 ℃ for 3h. The synthesized spherical forsterite aggregates were added in Mg O based castables with MgO-SiO2-H2O binding system to replace equaldensity high purity common forsterite aggregates. Effect of spherical forsterite aggregates addition on properties of MgO based castables was investigated. The results show that: compared with common aggregates,lightweight spherical forsterite aggregates can improve castables ’flow ability and decrease water addition; addition of spherical aggregates has little effect on cold strength of castables; with the increase of spherical aggregate addition,shrinkage of specimens after drying and heating at intermediate temperatures decreases,but the expansion of specimens after heating at high temperatures increases,bulk density decreases and apparent porosity increases,and thermal conductivity declines.展开更多
The paper describes the ries with high thermal shock development of brick seresistance and low creep rate for hot blast stove, including research target and research plan on the basis of analysis on how to enhance the...The paper describes the ries with high thermal shock development of brick seresistance and low creep rate for hot blast stove, including research target and research plan on the basis of analysis on how to enhance the thermal shock resistance and to lower creep rate of the bricks. Efforts have been made on the selection of starting materials such as corundum, mullite, andalusite and sillimanite etc., together with some measures taken on multi-grade formulation, homogenizing of the matrix of bricks and addition of some special additives. The results indicated that the bricks were with characteristics such as higher thermal shock resistance of 〉 30 cycles under quenching in water from 1000℃, and creep rate of 0. 2 under 1400℃ for 20 -50hrs with load of 0.2 MPa. Now a series of products of this kind have been developed and produced. The application of the products in Wuhan Iron and Steel Co. showed very prospective results. Now most of domestic large sized blast furnaces say ≥- 1000m^3, including those of Baoshan Iron and Steel Co. , have selected the series products made by Gongyi No. 5 Refractories Head Factory（GYWN） for their hot blast stoves.展开更多
Using tabular alumina as aggregate,tabular alumina fines,reactive alumina ultra-fines,aluminum powders,silicon powders,carbon black,flake graphite,B4 C and zircon fines as matrix,low carbon Al2O3-C refractories were p...Using tabular alumina as aggregate,tabular alumina fines,reactive alumina ultra-fines,aluminum powders,silicon powders,carbon black,flake graphite,B4 C and zircon fines as matrix,low carbon Al2O3-C refractories were prepared.Influences of zircon powders additions （0,3%,5% and 7%,in mass,the same hereinafter） on properties,phase composition and microstructure were investigated.The results show that the ZrO2-nitride can be in-situ formed through carbothermal reduction and nitridation in Al2O3-C refractories.With the increase of zircon powder,the oxidation resistance of the Al2O3-C refractories improves obviously,the oxidized layer thickness decreases from 7.94 mm without zircon to 2.71 mm with 5% zircon.HMOR at 1 400 ℃ of the Al2O3-C refractories reaches the maximum 14.9 MPa when zircon addition is 5%.With the increase of zircon powder,the apparent porosity and bulk density change a little,CMOR and CCS increase.展开更多
In order to enhance performance of pre-cast shapes of alumina based castables, the present work explored the approach of forming in-situ bonding phases by incorporating Si powders and then heating in carbon, embedded ...In order to enhance performance of pre-cast shapes of alumina based castables, the present work explored the approach of forming in-situ bonding phases by incorporating Si powders and then heating in carbon, embedded atmosphere. Using tabular alumina as aggregates, tabular alumina, SiC powders, Si powders, calcium aluminate cenwnt, microsilica and ultrafine α-A12 03 powders as matrix, alumina based ultra low cement （ULC） castables were prepared. Influences of Si powder addition at O, 4% , 6% , 8% alul 10% （in nutss ） on regular properties, cold modulus of rupture （CMOR）, hot modulus of rupture （HMOR）, thermal shock resistance （TSR） and microstructure of the castables after carbonization were investigated. After incorporation of Si powders and carbon embedded heating, the in-situ mullite and nonoxide phases such as SiAION and SiC can be fornwd by oxidation, nitridation or carbomlzation reaction. HMOR and TSR of the castables with in-situ nonoxides bonding are obviously improted. After carbon embedded heating, the HMOR at 1 400 ℃ increases from 1.6 MPa to 8. 3 MPa, and the residual CMOR ratio after thermal shock increases from 64. 9% to 137. 9% when Si addition increases from 0 to 10%.展开更多
Globalization is a reality resulting in many changes in the refractory industry. In this paper some of the threats and opportunities, which are influencing the future prosperity of the refractory industry on a worldwi...Globalization is a reality resulting in many changes in the refractory industry. In this paper some of the threats and opportunities, which are influencing the future prosperity of the refractory industry on a worldwide basis, are being evoked. Some key technical and management issues are underlined, in terms of adjusting the productivity-quality-cost to the customers requirements ; producing unshapes versus shapes; innovations supported by research; international profile for the import-export game; training and education. Consequences for China, who does play a dominant role due to the size of its internal market （ customers demand） and the magnitude of its production capability （including raw materials availability）, are being drawn.展开更多
High purity forsterite with a mass ratio 60：40 of MgO over SiO2 was synthesized using magnesite, caustic magnesia and natural silica as starting materials. The synthesized forsterite aggregates were added in magnesia...High purity forsterite with a mass ratio 60：40 of MgO over SiO2 was synthesized using magnesite, caustic magnesia and natural silica as starting materials. The synthesized forsterite aggregates were added in magnesia based custable with MgO -SiO2 -H2 0 binding system to replace dead burned magnesia up to 60 mass% at an in- terval of 15 mass%. Effect of the forsterite addition on properties ~f MgO based castables was investigated. Micro- structure analysis of related specimens was carried out by means of SEM. Special grade bauxite powders were also in- corporated to form spinel by reaction with magnesia, ac- companying volumetric expansion to compensate high tem- perature shrinkage. Bulk density of the castable decreases with increased forsterite addition. Properties in terms of cold crushing strength and cold modulus of rupture, hot modulus of rupture at 1 400 ℃ and thermal shock resist- ance can be improved by adding an appropriate amount of the forsterite aggregate, preferably around 30 mass%.展开更多
Microstructure analysis shows quartz remains more or less in used silica brick for coking chamber of coke oven, and quartz gradually becomes metastable cristobalite and then translates into tridymite in used brick for...Microstructure analysis shows quartz remains more or less in used silica brick for coking chamber of coke oven, and quartz gradually becomes metastable cristobalite and then translates into tridymite in used brick for high temperature combustion chamber. Phase change of silica brick only limits to transformation of quartz and metastahie cristobalite. When finished, structure of silica brick tends to stable. Carbon sedimentates and graphitize. helping to protect the silica brick and improve heat conductivity of silica brick for coking chamber.展开更多
Micro-pored CA6 -MA lightweight material with CAM： MA mass ratio of 7：3 was prepared using Al（OH） 3, MgCO3 and CaCO3 as starting materials, and anthracite. sweet potato starch and anthracite ＋ sweet potato starch...Micro-pored CA6 -MA lightweight material with CAM： MA mass ratio of 7：3 was prepared using Al（OH） 3, MgCO3 and CaCO3 as starting materials, and anthracite. sweet potato starch and anthracite ＋ sweet potato starch as pore forming agent （PFA） with an addition of 10 mass%, 20 mass% and 30 mass%, respectively. The starting materials were dry mixed, wet co-milled in a ball mill for 1 h. slip cast into cylindrical specimens with a diameter of 60 ram. and then calcined at 1 450 ℃ for 3 h. With the increase of PFA addition,, apparent porosity increases, and bulk density decreases. The influence of different PFAs on properties of the micro-pored LW CAM -MA aggregate was investigated. The achieved CAM - MA, by adding 30% sweet potato starch, has a porosity of 76. 8%, bulk density of 0. 78 g · cm^ - 3 and median pore size of 1.90 μm.展开更多
文摘Thermal behavior and physical properties of castables during curing and drying-out are associated with their binding system. In this work, five alumina based （ Al2O3 〉 87% ） castables with different combinations of binding materials, i. e. , （ 1 ） CA cement （CA） ＋ Reactive alumina （ RA ） ＋ H2O ; （ 2 ） high level addi- tion of CA ＋ Microsilica （MS） ＋ H2O ; （ 3 ） low level addition of CA ＋ MS ＋ H2O ; （4） MS ＋ Hydratable alumina ＋ H20 and （ 5 ） MS ＋ Magnesia ＋ H2O, respectively, have been investigated on the flowability and thermal behavior during curing at room temperature, drying at 110% and heating from 200℃ to 1000℃ at an interval of 100℃ , in terms of water addition, vibration flow value, porosity, dehydration, explosion resistance, cold and hot bending strengths. Differences in dehydrating behavior and the mentioned properties have been revealed and correlated to the binding system.
基金financial support from the National Natural Science Foundation of China ( Grant No.51402089)the Plan of Young-backbone Teachers of Colleges and Universities in Henan Province ( Project No.2015GGJS-045)
文摘Compared with traditional aggregates,spherical aggregates with high flowability,easy control of particle size distribution and favor of dense packing and so on,are expected to replace traditional aggregates as important raw materials for future high performance refractories. Therefore,investigation of effects of spherical aggregates addition on properties of refractories becomes very meaningful. Using A70 mullite traditional aggregates and A70 mullite spherical aggregates, bauxite homogenization powder,microsilica,and calcium aluminate cement as raw materials,different AlO-SiOsystem low cement castables were prepared by replacing conventional aggregates with spherical aggregates. The effect of spherical aggregates addition on workability and mechanical properties of castables after heated at different temperatures was researched,and microstructure of the specimen was analyzed by SEM. Compared with traditional irregularly shaped aggregates,spherical aggregates endow castables with better flowability and easy pump ability. By introduction of spherical aggregates into the castables,flowability and pumpability are significantly improved,and water addition and ball completely sunk time are reduced. The introduction of spherical aggregates is favorable to density and cold crushing strength of castables,but unfavorable to CMOR. The effect of spherical aggregates addition on HMOR at1 400 ℃ can be negligible. Microstructure analysis showsthat the boundary bonding between spherical aggregates and matrix is strong,similar to the traditional aggregates.
文摘MgO -ZrO2 unfired bricks with ZrO2 content up to 8% at the interval of 2% were prepared, using fused magnesia （ MgO ： 97% ） and fused MgO - ZrO2 clinker （ ZrO2 ： 14. 33% ） as starting materials and phenolic resin as binder. The effects of ZrO2 content on thermal shock resistance （TSR） and other properties such as cold and hot modulus of rupture have been investigated. Re- sidual cold modulus of rupture ratio after heating at 1 000 ℃ and quenching by air blowing was adopted to characterize TSR. Addition of the MgO -ZrO2 clinker improves TSR, attributing to the microcrack toughening effect by thermal expansion mismatch between different phases. When ZrO2 content goes above 4%. the impro- ving effect tends to be moderate. The introduction of MgO- ZrO2 clinker can also improve the HMOR at 1 500 ℃, while the increased ZrO2 content reduces CMOR of the bricks prefired at 1 600 ℃, due to the thermal expansion mismatch effect. Compromising the overall properties, the optimal ZrO2 content for such magnesia based unfired brick is suggested to be 4%.
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Magnesite fine powder, natural silica powder,light-burned magnesia fine powder, silica fume and middle grade magnesia fine powder were used as the starting materials,and silica sol as binder to get high purity lightweight spherical forsterite aggregates. The mixture was granulated on a disc pelletizer and then calcined at 1 400 ℃ for 3h. The synthesized spherical forsterite aggregates were added in Mg O based castables with MgO-SiO2-H2O binding system to replace equaldensity high purity common forsterite aggregates. Effect of spherical forsterite aggregates addition on properties of MgO based castables was investigated. The results show that: compared with common aggregates,lightweight spherical forsterite aggregates can improve castables ’flow ability and decrease water addition; addition of spherical aggregates has little effect on cold strength of castables; with the increase of spherical aggregate addition,shrinkage of specimens after drying and heating at intermediate temperatures decreases,but the expansion of specimens after heating at high temperatures increases,bulk density decreases and apparent porosity increases,and thermal conductivity declines.
基金The paper was presented at the Unitecr’05,which was held in Orlando. USA on Nov.8~11,2005
文摘The paper describes the ries with high thermal shock development of brick seresistance and low creep rate for hot blast stove, including research target and research plan on the basis of analysis on how to enhance the thermal shock resistance and to lower creep rate of the bricks. Efforts have been made on the selection of starting materials such as corundum, mullite, andalusite and sillimanite etc., together with some measures taken on multi-grade formulation, homogenizing of the matrix of bricks and addition of some special additives. The results indicated that the bricks were with characteristics such as higher thermal shock resistance of 〉 30 cycles under quenching in water from 1000℃, and creep rate of 0. 2 under 1400℃ for 20 -50hrs with load of 0.2 MPa. Now a series of products of this kind have been developed and produced. The application of the products in Wuhan Iron and Steel Co. showed very prospective results. Now most of domestic large sized blast furnaces say ≥- 1000m^3, including those of Baoshan Iron and Steel Co. , have selected the series products made by Gongyi No. 5 Refractories Head Factory（GYWN） for their hot blast stoves.
基金the Natural Science Foundation of Henan Educational Committee ( N0. 2011B430011 and N0. 13B430991)
文摘Using tabular alumina as aggregate,tabular alumina fines,reactive alumina ultra-fines,aluminum powders,silicon powders,carbon black,flake graphite,B4 C and zircon fines as matrix,low carbon Al2O3-C refractories were prepared.Influences of zircon powders additions （0,3%,5% and 7%,in mass,the same hereinafter） on properties,phase composition and microstructure were investigated.The results show that the ZrO2-nitride can be in-situ formed through carbothermal reduction and nitridation in Al2O3-C refractories.With the increase of zircon powder,the oxidation resistance of the Al2O3-C refractories improves obviously,the oxidized layer thickness decreases from 7.94 mm without zircon to 2.71 mm with 5% zircon.HMOR at 1 400 ℃ of the Al2O3-C refractories reaches the maximum 14.9 MPa when zircon addition is 5%.With the increase of zircon powder,the apparent porosity and bulk density change a little,CMOR and CCS increase.
文摘In order to enhance performance of pre-cast shapes of alumina based castables, the present work explored the approach of forming in-situ bonding phases by incorporating Si powders and then heating in carbon, embedded atmosphere. Using tabular alumina as aggregates, tabular alumina, SiC powders, Si powders, calcium aluminate cenwnt, microsilica and ultrafine α-A12 03 powders as matrix, alumina based ultra low cement （ULC） castables were prepared. Influences of Si powder addition at O, 4% , 6% , 8% alul 10% （in nutss ） on regular properties, cold modulus of rupture （CMOR）, hot modulus of rupture （HMOR）, thermal shock resistance （TSR） and microstructure of the castables after carbonization were investigated. After incorporation of Si powders and carbon embedded heating, the in-situ mullite and nonoxide phases such as SiAION and SiC can be fornwd by oxidation, nitridation or carbomlzation reaction. HMOR and TSR of the castables with in-situ nonoxides bonding are obviously improted. After carbon embedded heating, the HMOR at 1 400 ℃ increases from 1.6 MPa to 8. 3 MPa, and the residual CMOR ratio after thermal shock increases from 64. 9% to 137. 9% when Si addition increases from 0 to 10%.
文摘Globalization is a reality resulting in many changes in the refractory industry. In this paper some of the threats and opportunities, which are influencing the future prosperity of the refractory industry on a worldwide basis, are being evoked. Some key technical and management issues are underlined, in terms of adjusting the productivity-quality-cost to the customers requirements ; producing unshapes versus shapes; innovations supported by research; international profile for the import-export game; training and education. Consequences for China, who does play a dominant role due to the size of its internal market （ customers demand） and the magnitude of its production capability （including raw materials availability）, are being drawn.
文摘High purity forsterite with a mass ratio 60：40 of MgO over SiO2 was synthesized using magnesite, caustic magnesia and natural silica as starting materials. The synthesized forsterite aggregates were added in magnesia based custable with MgO -SiO2 -H2 0 binding system to replace dead burned magnesia up to 60 mass% at an in- terval of 15 mass%. Effect of the forsterite addition on properties ~f MgO based castables was investigated. Micro- structure analysis of related specimens was carried out by means of SEM. Special grade bauxite powders were also in- corporated to form spinel by reaction with magnesia, ac- companying volumetric expansion to compensate high tem- perature shrinkage. Bulk density of the castable decreases with increased forsterite addition. Properties in terms of cold crushing strength and cold modulus of rupture, hot modulus of rupture at 1 400 ℃ and thermal shock resist- ance can be improved by adding an appropriate amount of the forsterite aggregate, preferably around 30 mass%.
文摘Microstructure analysis shows quartz remains more or less in used silica brick for coking chamber of coke oven, and quartz gradually becomes metastable cristobalite and then translates into tridymite in used brick for high temperature combustion chamber. Phase change of silica brick only limits to transformation of quartz and metastahie cristobalite. When finished, structure of silica brick tends to stable. Carbon sedimentates and graphitize. helping to protect the silica brick and improve heat conductivity of silica brick for coking chamber.
文摘Micro-pored CA6 -MA lightweight material with CAM： MA mass ratio of 7：3 was prepared using Al（OH） 3, MgCO3 and CaCO3 as starting materials, and anthracite. sweet potato starch and anthracite ＋ sweet potato starch as pore forming agent （PFA） with an addition of 10 mass%, 20 mass% and 30 mass%, respectively. The starting materials were dry mixed, wet co-milled in a ball mill for 1 h. slip cast into cylindrical specimens with a diameter of 60 ram. and then calcined at 1 450 ℃ for 3 h. With the increase of PFA addition,, apparent porosity increases, and bulk density decreases. The influence of different PFAs on properties of the micro-pored LW CAM -MA aggregate was investigated. The achieved CAM - MA, by adding 30% sweet potato starch, has a porosity of 76. 8%, bulk density of 0. 78 g · cm^ - 3 and median pore size of 1.90 μm.
