In order to improve the performance of Al_(2)O_(3)-SiC-C castables for iron trough,samples were prepared using brown corundum,dense corundum,activated alumina micropowder,ball pitch,and silicon as main raw materials,c...In order to improve the performance of Al_(2)O_(3)-SiC-C castables for iron trough,samples were prepared using brown corundum,dense corundum,activated alumina micropowder,ball pitch,and silicon as main raw materials,calcium aluminate cement as the binder.Several kinds of silica fumes(93SiO_(2),96SiO_(2),and 99SiO_(2))with different particle size distributions and chemical composition were added to research the effects on the properties of castables.The results show that the sample with 99SiO_(2) fume has high water requirement for molding,but the bulk density is the lowest,the apparent porosity is the highest,the oxidation resistance is the worst,and the permanent linear change on heating is low after firing at 1 450 ℃ for 3 h.The bulk density and the apparent porosity of the sample with 93SiO_(2) fume or 96SiO_(2) fume are equivalent,the hot modulus of rupture of the sample with 93SiO_(2) fume is the lowest,and the slag resistance of the sample with 96SiO_(2) fume is the best.The comprehensive performance of the sample with 96SiO_(2) fume is the best.展开更多
Al_(2)O_(3)-SiC-C castables were prepared using C@SiC composite powder modified by molten salts to replace ball pitch gradually.The effects of the C@SiC composite powder addition(0,1%,1.5%,and 2%,by mass)on the water ...Al_(2)O_(3)-SiC-C castables were prepared using C@SiC composite powder modified by molten salts to replace ball pitch gradually.The effects of the C@SiC composite powder addition(0,1%,1.5%,and 2%,by mass)on the water requirement,the flow value,the physical properties,the thermal shock resistance,the oxidation resistance,and the corrosion resistance of castables were studied.The results show that with the C@SiC addition increasing,the amount of water added to the castable increases,but the apparent porosity of the samples after heat treatment first increases and then decreases,and the cold modulus of rupture increases significantly.After completely replacing the ball pitch,the cold modulus of rupture of the sample increases by 51.2%,and the residual strength ratio increases by 28.7%.In addition,the sample with 2%C@SiC has the best oxidation resistance,and the sample with 1.5%C@SiC composite powder has the smallest corrosion depth.展开更多
The properties and microstructure of sol self-clean bonded Al2O3-SiC-C castable in iron runner were studied, and the relation between the amount of sol self- clean binder and the properties of castable were discussed....The properties and microstructure of sol self-clean bonded Al2O3-SiC-C castable in iron runner were studied, and the relation between the amount of sol self- clean binder and the properties of castable were discussed. It is believed that the addition of sol self-clean binder can improve the compressive strength, but has little effect on the bulk density and the apparent porosity, which enable the castable to be applicable in different conditions.展开更多
This work investigates the effect of the pre-firing temperature of andalusite aggregate(5-3 mm)on the conversion of andalusite,the volume stability,the thermal shock resistance and the slag resistance of Al2O3-SiC-C c...This work investigates the effect of the pre-firing temperature of andalusite aggregate(5-3 mm)on the conversion of andalusite,the volume stability,the thermal shock resistance and the slag resistance of Al2O3-SiC-C castables.The results show that the volume stability and the thermal shock resistance of the castables could be adjusted at different pre-firing temperatures of andalusite aggregates.There was no noticeable difference in the slag resistance between the specimens without andalusite and those with andalusite aggregate pre-fired at different temperatures.展开更多
Effects of B4C additions （0,0.2%,0.4%,and 0.6%） on cold physical properties and hot modulus of rupture of Al2O3-SiC-Si3N4 castables for iron trough were investigated. The phase composition and microstructure were an...Effects of B4C additions （0,0.2%,0.4%,and 0.6%） on cold physical properties and hot modulus of rupture of Al2O3-SiC-Si3N4 castables for iron trough were investigated. The phase composition and microstructure were analyzed by XRD and SEM. The results show that bulk density,cold strength,and hot modulus of rupture of the castables first increase and then decrease while apparent porosity first drops and then increases with B4C addition increasing. The optimum addition of B4C is 0.4%. B4C mainly contributes to sintering and antioxidation. Compared with the specimens without B4C,the specimens with B4C have more fibrous O＇-SiAlON with larger length-diameter ratio. The growth mechanism of O＇-SiAlON crystals is deduced to gas-solid mechanism.展开更多
Al_(2)O_(3)-SiC castables,for the relining of BF hearths in mid-campaign repair,were sampled and investigated after two years’service.The chemical and mineralogical characteristics of the residual castables were anal...Al_(2)O_(3)-SiC castables,for the relining of BF hearths in mid-campaign repair,were sampled and investigated after two years’service.The chemical and mineralogical characteristics of the residual castables were analyzed by X-ray diffraction,scanning electron microscopy,and energy dispersive X-ray spectrometry to study the erosion mechanism.The results show that as gaseous K diffuses in the castables,leucite(KAlSi_(2)O_(8))and multiple cracks are formed.Molten iron and slag penetrate through the cracks to form anorthite([Ca,Na][Al,Si]_(4)O_(8))and iron,which will not form an embrittlement layer similar to carbon bricks.The entire repair of the hearth with Al_(2)O_(3)-SiC castables combined with the design of thin-wall lining hearth eliminates“elephant foot shaped”erosion,greatly prolonging the service life of the hearth lining.展开更多
The abnormal corrosion of hot iron ladles was investigated.The performance,the composition and the structure of bricks for hot iron ladles were analyzed.The results show that(1)compared with the alumina-silicon carbid...The abnormal corrosion of hot iron ladles was investigated.The performance,the composition and the structure of bricks for hot iron ladles were analyzed.The results show that(1)compared with the alumina-silicon carbide-carbon bricks for the ladle bottom,those for the ladle wall have more pyrophyllite and the Al2O3 content of 36.32 mass%;their bulk density,apparent porosity and cold compressive strength are lower than the requirement of industry standard;they have poor anti-oxidation performance and are oxidized to form a porous layer during service,which loosens the brick lining structure thus leading to fracture,local wear and structural damage of bricks;(2)without preheating,steel scraps are not completely melted,resulting in slag or steel attachment at the mouth or the bottom of ladles thus increasing damage of ladles;(3)and the residual bricks react with the attached slag to form low melting point phases affecting their hot properties.The refractories for the lining of hot iron ladles must be improved in combination with process changes,not entirely by raw materials replacement to reduce costs.展开更多
Silicon oxynitride was added in shaped Al_2O_3-SiC-C refractory material to improve the slag resistance in this paper.Optimum adding quantity of silicon oxynitride powder was also studied. The results show that the sl...Silicon oxynitride was added in shaped Al_2O_3-SiC-C refractory material to improve the slag resistance in this paper.Optimum adding quantity of silicon oxynitride powder was also studied. The results show that the slag resistance of Al_2O_3-SiC-C shaped refractory is improved when 2% or 3% Si_2N_2O is added. A reasonable amount of Si_2N_2O added into Al_2O_3-Si C-C shaped refractory can produce silicon oxide into the slag, which can improve the viscosity of slag and prevent the slag erosion and penetration.展开更多
Al2O3-SiC-C specimens were prepared using white fused corundum （3-1,≤1 and ≤0.044 mm）,Al2O3-SiC composite powders （d50 ≤ 5 μm）,α-Al2O3 micropowder （d50 =1.2 μm）,SiC powder （≤ 0.044 mm）,flake graphite （...Al2O3-SiC-C specimens were prepared using white fused corundum （3-1,≤1 and ≤0.044 mm）,Al2O3-SiC composite powders （d50 ≤ 5 μm）,α-Al2O3 micropowder （d50 =1.2 μm）,SiC powder （≤ 0.044 mm）,flake graphite （≤ 0.088 mm）,Si powder （d50 =42.8 μm） and B4C powder （d50 ≤10 μm） as main starting materials,and thermosetting phenolic resin as binder.4%,8%,12% and 16% （in mass,the same hereinafter） of Al2O3-SiC composite powders substituted the same quantity of α-Al2O3 micropowder ＋ SiC powder.Effects of composite powder additions on apparent porosity,bulk density,cold modulus of rupture,cold crushing strength,hot modulus of rupture （1 400 ℃）,thermal shock resistance （1 100 ℃,water quenching） and oxidation resistance （1 000 and 1 500 ℃） of Al2O3-SiC -C specimens after 180 ℃ curing,1 000 ℃ 3 h carbon-embedded firing and 1 500 ℃ 3 h carbon-embedded firing,respectively,were researched.The results indicate that：（1） with the increase of Al2O3-SiC composite powder,cold strengths of the cured specimens decline,those of the specimens fired at 1 000 ℃ change a little,and those of the specimens fired at 1 500 ℃ change a little except for an obvious improvement of cold crushing strength ; （2） with the increase of Al2O3-SiC composite powder,hot modulus of rupture at 1 400 ℃ decreases and thermal shock resistance enhances significantly; （3） when Al2O3-SiC composite powder addition is 4%,the oxidation resistance at 1 500 ℃ is the best,and the reason may be the composite powder is finer and more active,which is beneficial to form dense mullite protective layer to retard the O2 diffusion into the specimens.展开更多
Hot metal transfer ladles were historically lined with high alumina refractories because of compatibility of high alumina refractories with the highly acidic slag, which is transferred .from the iron making plant alon...Hot metal transfer ladles were historically lined with high alumina refractories because of compatibility of high alumina refractories with the highly acidic slag, which is transferred .from the iron making plant along with hot metal. With the introduction of higher capacity ladles, technological advancement in the process and increased productivity, calls for a higher campaign life of hot metal ladles, which could not be performed by ordinary high alumina refractories. Resin bonded Al2O3- SiC-C （hereinafter ASC ） bricks gradually developed which at present taking place replacing the conventional refractories. Considerable work has been carried out in developing the ASC refractory to reach the present state. However, for higher capacity ladles still there is a lot of scope for improvement. The present paper deals with the newly developed ASC bricks, which was used in 165 ton capacity hot metal ladles in one European plant and has given a substantial increase in performance. But, the customer was not fuUy satisfied since the brick was reported to produce smokes during preheating of the ladle. In the subsequent supply the smoke generation problem was taken care by adjusting the binders and additives and eco-friendly bricks were re-engineered and supplied to the same plant, which also performed splendidly and created all time record in their plant history.展开更多
文摘In order to improve the performance of Al_(2)O_(3)-SiC-C castables for iron trough,samples were prepared using brown corundum,dense corundum,activated alumina micropowder,ball pitch,and silicon as main raw materials,calcium aluminate cement as the binder.Several kinds of silica fumes(93SiO_(2),96SiO_(2),and 99SiO_(2))with different particle size distributions and chemical composition were added to research the effects on the properties of castables.The results show that the sample with 99SiO_(2) fume has high water requirement for molding,but the bulk density is the lowest,the apparent porosity is the highest,the oxidation resistance is the worst,and the permanent linear change on heating is low after firing at 1 450 ℃ for 3 h.The bulk density and the apparent porosity of the sample with 93SiO_(2) fume or 96SiO_(2) fume are equivalent,the hot modulus of rupture of the sample with 93SiO_(2) fume is the lowest,and the slag resistance of the sample with 96SiO_(2) fume is the best.The comprehensive performance of the sample with 96SiO_(2) fume is the best.
基金supported financially by the Natural Science Foundation of Hubei Province(Grant No.2021BAD002)the National Natural Science Foundation of China(Grant No.U20A20239)
文摘Al_(2)O_(3)-SiC-C castables were prepared using C@SiC composite powder modified by molten salts to replace ball pitch gradually.The effects of the C@SiC composite powder addition(0,1%,1.5%,and 2%,by mass)on the water requirement,the flow value,the physical properties,the thermal shock resistance,the oxidation resistance,and the corrosion resistance of castables were studied.The results show that with the C@SiC addition increasing,the amount of water added to the castable increases,but the apparent porosity of the samples after heat treatment first increases and then decreases,and the cold modulus of rupture increases significantly.After completely replacing the ball pitch,the cold modulus of rupture of the sample increases by 51.2%,and the residual strength ratio increases by 28.7%.In addition,the sample with 2%C@SiC has the best oxidation resistance,and the sample with 1.5%C@SiC composite powder has the smallest corrosion depth.
文摘The properties and microstructure of sol self-clean bonded Al2O3-SiC-C castable in iron runner were studied, and the relation between the amount of sol self- clean binder and the properties of castable were discussed. It is believed that the addition of sol self-clean binder can improve the compressive strength, but has little effect on the bulk density and the apparent porosity, which enable the castable to be applicable in different conditions.
基金the National Natural Science Foundation of China (51572244 and U1604252, 51672255) for the financial supportpartly co-financed by Imerys Aluminates
文摘This work investigates the effect of the pre-firing temperature of andalusite aggregate(5-3 mm)on the conversion of andalusite,the volume stability,the thermal shock resistance and the slag resistance of Al2O3-SiC-C castables.The results show that the volume stability and the thermal shock resistance of the castables could be adjusted at different pre-firing temperatures of andalusite aggregates.There was no noticeable difference in the slag resistance between the specimens without andalusite and those with andalusite aggregate pre-fired at different temperatures.
基金supported by the Natural Science Foundation of Hebei Province(No:E2009000784)Educational Department of Hebei Province (2008453)
文摘Effects of B4C additions （0,0.2%,0.4%,and 0.6%） on cold physical properties and hot modulus of rupture of Al2O3-SiC-Si3N4 castables for iron trough were investigated. The phase composition and microstructure were analyzed by XRD and SEM. The results show that bulk density,cold strength,and hot modulus of rupture of the castables first increase and then decrease while apparent porosity first drops and then increases with B4C addition increasing. The optimum addition of B4C is 0.4%. B4C mainly contributes to sintering and antioxidation. Compared with the specimens without B4C,the specimens with B4C have more fibrous O＇-SiAlON with larger length-diameter ratio. The growth mechanism of O＇-SiAlON crystals is deduced to gas-solid mechanism.
文摘Al_(2)O_(3)-SiC castables,for the relining of BF hearths in mid-campaign repair,were sampled and investigated after two years’service.The chemical and mineralogical characteristics of the residual castables were analyzed by X-ray diffraction,scanning electron microscopy,and energy dispersive X-ray spectrometry to study the erosion mechanism.The results show that as gaseous K diffuses in the castables,leucite(KAlSi_(2)O_(8))and multiple cracks are formed.Molten iron and slag penetrate through the cracks to form anorthite([Ca,Na][Al,Si]_(4)O_(8))and iron,which will not form an embrittlement layer similar to carbon bricks.The entire repair of the hearth with Al_(2)O_(3)-SiC castables combined with the design of thin-wall lining hearth eliminates“elephant foot shaped”erosion,greatly prolonging the service life of the hearth lining.
文摘The abnormal corrosion of hot iron ladles was investigated.The performance,the composition and the structure of bricks for hot iron ladles were analyzed.The results show that(1)compared with the alumina-silicon carbide-carbon bricks for the ladle bottom,those for the ladle wall have more pyrophyllite and the Al2O3 content of 36.32 mass%;their bulk density,apparent porosity and cold compressive strength are lower than the requirement of industry standard;they have poor anti-oxidation performance and are oxidized to form a porous layer during service,which loosens the brick lining structure thus leading to fracture,local wear and structural damage of bricks;(2)without preheating,steel scraps are not completely melted,resulting in slag or steel attachment at the mouth or the bottom of ladles thus increasing damage of ladles;(3)and the residual bricks react with the attached slag to form low melting point phases affecting their hot properties.The refractories for the lining of hot iron ladles must be improved in combination with process changes,not entirely by raw materials replacement to reduce costs.
文摘Silicon oxynitride was added in shaped Al_2O_3-SiC-C refractory material to improve the slag resistance in this paper.Optimum adding quantity of silicon oxynitride powder was also studied. The results show that the slag resistance of Al_2O_3-SiC-C shaped refractory is improved when 2% or 3% Si_2N_2O is added. A reasonable amount of Si_2N_2O added into Al_2O_3-Si C-C shaped refractory can produce silicon oxide into the slag, which can improve the viscosity of slag and prevent the slag erosion and penetration.
文摘Al2O3-SiC-C specimens were prepared using white fused corundum （3-1,≤1 and ≤0.044 mm）,Al2O3-SiC composite powders （d50 ≤ 5 μm）,α-Al2O3 micropowder （d50 =1.2 μm）,SiC powder （≤ 0.044 mm）,flake graphite （≤ 0.088 mm）,Si powder （d50 =42.8 μm） and B4C powder （d50 ≤10 μm） as main starting materials,and thermosetting phenolic resin as binder.4%,8%,12% and 16% （in mass,the same hereinafter） of Al2O3-SiC composite powders substituted the same quantity of α-Al2O3 micropowder ＋ SiC powder.Effects of composite powder additions on apparent porosity,bulk density,cold modulus of rupture,cold crushing strength,hot modulus of rupture （1 400 ℃）,thermal shock resistance （1 100 ℃,water quenching） and oxidation resistance （1 000 and 1 500 ℃） of Al2O3-SiC -C specimens after 180 ℃ curing,1 000 ℃ 3 h carbon-embedded firing and 1 500 ℃ 3 h carbon-embedded firing,respectively,were researched.The results indicate that：（1） with the increase of Al2O3-SiC composite powder,cold strengths of the cured specimens decline,those of the specimens fired at 1 000 ℃ change a little,and those of the specimens fired at 1 500 ℃ change a little except for an obvious improvement of cold crushing strength ; （2） with the increase of Al2O3-SiC composite powder,hot modulus of rupture at 1 400 ℃ decreases and thermal shock resistance enhances significantly; （3） when Al2O3-SiC composite powder addition is 4%,the oxidation resistance at 1 500 ℃ is the best,and the reason may be the composite powder is finer and more active,which is beneficial to form dense mullite protective layer to retard the O2 diffusion into the specimens.
文摘Hot metal transfer ladles were historically lined with high alumina refractories because of compatibility of high alumina refractories with the highly acidic slag, which is transferred .from the iron making plant along with hot metal. With the introduction of higher capacity ladles, technological advancement in the process and increased productivity, calls for a higher campaign life of hot metal ladles, which could not be performed by ordinary high alumina refractories. Resin bonded Al2O3- SiC-C （hereinafter ASC ） bricks gradually developed which at present taking place replacing the conventional refractories. Considerable work has been carried out in developing the ASC refractory to reach the present state. However, for higher capacity ladles still there is a lot of scope for improvement. The present paper deals with the newly developed ASC bricks, which was used in 165 ton capacity hot metal ladles in one European plant and has given a substantial increase in performance. But, the customer was not fuUy satisfied since the brick was reported to produce smokes during preheating of the ladle. In the subsequent supply the smoke generation problem was taken care by adjusting the binders and additives and eco-friendly bricks were re-engineered and supplied to the same plant, which also performed splendidly and created all time record in their plant history.
