Magnesia-calcium materials have stable hot performance,good resistance to the erosion and corrosion of liquid steel and steel slag,and a special role in purifying liquid steel,so they are widely used in iron and steel...Magnesia-calcium materials have stable hot performance,good resistance to the erosion and corrosion of liquid steel and steel slag,and a special role in purifying liquid steel,so they are widely used in iron and steel industry.However,hydration of magnesia-calcium materials seriously restricts their use,so researches have been done to improve their hydration resistance,obtaining a series of achievements.In this paper,the improvements on the hydration resistance of magnesia-calcium materials by additives in recent 20 years were presented,and their mechanisms were summarized.展开更多
The application of CaO refractories was limited due to its poor hydration resistance.Introducing appropriate additive is an effective way to improve its hydration resistance.Additive WO3 was introduced in the preparat...The application of CaO refractories was limited due to its poor hydration resistance.Introducing appropriate additive is an effective way to improve its hydration resistance.Additive WO3 was introduced in the preparation of CaO aggregates using calcination method in this study.The introduction of WO3 decreased the apparent porosity of CaO aggregates and promoted the grain growth of CaO by the formation of liquid at high temperatures.The average grain size of the specimens with 0.4 mass%WO3 and treated at 1550℃was increased to 51.6μm comparing to 33.5μm that without WO3 additive.As a result,the hydration resistance of CaO aggregate was significantly improved.Besides,WO3 sublimate easily,therefore,less WO3 was remained after the heat treatment.The further increase of WO3 addition had little effect on the hydration resistance of CaO specimens.展开更多
Active lime was used to produce Ca（OH）2fine powder.And then Ca（OH）2fine powder with analytically pure CeO2fine powder（0,0.2%,0.4%,0.6%,0.8%and1.0%by mass,respectively）were mixed via wet mixing.After drying and b...Active lime was used to produce Ca（OH）2fine powder.And then Ca（OH）2fine powder with analytically pure CeO2fine powder（0,0.2%,0.4%,0.6%,0.8%and1.0%by mass,respectively）were mixed via wet mixing.After drying and ball milling,the specimens were pressed and fired at 1 450℃,1 500℃,1 550℃,1 600℃and1 650℃,respectively.The hydration resistance of the specimens was evaluated by measuring the mass gain after soaking the specimens in a chamber kept at 20℃and90%relative humidity.The influences of CeO2and calcination temperature on the hydration resistance of CaO aggregates were investigated by determination of bulk density,apparent porosity,and XRD,SEM and EDS analysis.The results show that：（1）the sintering of CaO aggregates is promoted by CeO2addition and the hydration resistance of CaO aggregates is improved;（2）CeO2mainly locates in CaO grain boundary,some CeO2is solved in the CaO grains which improves CaO sintering;（3）the appropriate calcination temperature is 1 550℃.When the calcination temperature is below 1 550℃,the specimens are sintered inadequately.The density and hydration resistance of CaO aggregates are nearly stable when the calcination temperature is above 1 550℃.展开更多
Considering the high melting point and high stability of SrO,it has potential applications in the field of the preparation of titanium alloys.To improve the hydration resistance,SrO samples with different ZrO_(2)addit...Considering the high melting point and high stability of SrO,it has potential applications in the field of the preparation of titanium alloys.To improve the hydration resistance,SrO samples with different ZrO_(2)additions were fabricated after firing at 1750℃for 6 h.The phase,the microstructure,and the hydration resistance of the samples were researched.The results show that the sample with 33 mol%ZrO_(2)addition possesses good hydration resistance with the mass gain after hydration for 13 days of less than 0.42 mass%.The SrO crucible with 33 mol%ZrO_(2)addition does not react with TiNi alloy melt during melting,which provides a support for searching new refractories with good hydration resistance for induction melting titanium alloys.展开更多
According to the dual needs of heat transfer and thermal insulation in incinerators,different parts of the incinerators are designed with refractories of different SiC contents.Water vapor is mainly concentrated in th...According to the dual needs of heat transfer and thermal insulation in incinerators,different parts of the incinerators are designed with refractories of different SiC contents.Water vapor is mainly concentrated in the zones of feeding,drying and combustion,and the main damage factors of SiC refractories include high temperature and hydration.The results of hydration resistance of typical SiC-containing refractories show that the higher the SiC content,the worse the hydration resistance.Si_(3)N_(4)-SiC refractories after oxidation treatment have good hydration corrosion resistance,which are appropriate for water-cooled wall of waste incinerators.展开更多
The complex coating on the MgO CaO clinker was prepared by dipping method and adding the second mineral to restrain the formation and expansion of the cracks. Meanwhile, the microstructure and the morphology of the c...The complex coating on the MgO CaO clinker was prepared by dipping method and adding the second mineral to restrain the formation and expansion of the cracks. Meanwhile, the microstructure and the morphology of the coating and hydration resistance of the MgO CaO clinker were also investigated. The result shows that the coating consists mainly of Ca 2P 2O 7, MgO and CaCO 3, its thickness ranges from 5μm to 20μm, and the coating is dense and even, no micro cracks are observed. Also, the coating adheres closely to the matrix. The hydration resistance of the MgO CaO clinker after treatment is improved greatly, and the castables prepared with the treated MgO CaO clinker have better physical properties than MgO castable.展开更多
To obtain CaO clinker with high density, low po- rosity, and good hydration resistance, the effect of the La2 03 content on physical properties, such as sintering property and hydration resistance of CaO clinker was r...To obtain CaO clinker with high density, low po- rosity, and good hydration resistance, the effect of the La2 03 content on physical properties, such as sintering property and hydration resistance of CaO clinker was re- searched in this paper. Apparent porosity and bulk density were measured by Archimedes principle with kerosene as the medium. Two methods were used to test hydration resistance of CaO clinker. One was carried out in a hu- midity cabinet at 20℃ with 90% of relative humidity. Another was the boiling method. SEM and EDS charac- terization analyses of CaO clinker were pe.rformed to observe the microstructural information and the hydration mechanism was put forward. The results show that： （1） the specimen with 0.79 mass% of La2O3 addition has lower apparent porosity, and higher bulk density; （2） the hydration mass gain of CaO clinker with 0.79 mass% La2O3 addition is lower, which is less than 1% after 20 days ; （3） La2O3 mainly distributes in the grain boundary, attd a small amount of La203 dissolves in grains. The average grain size of CaO specimens with 0.79 mass% La2O3 addition sintered at 1 450℃, 1 550℃, and 1 650℃, is 44. 5 μm, 48. 6 μm, and 63. 5 μm , respectively; （4） solid solution is formed due to the similar ionic radius of La^3＋ and Ca^2＋, which promotes the sintering of CaO clinker and improves the hy- dration resistance simultaneously.展开更多
The Al-AlN bonded corundum based refractories was synthesized with the starting materials of fused alumina and metallic aluminium in nitrogen atmosphere through in-situ reaction. The study indicated that with the addi...The Al-AlN bonded corundum based refractories was synthesized with the starting materials of fused alumina and metallic aluminium in nitrogen atmosphere through in-situ reaction. The study indicated that with the addition of 14% metallic aluminium （13% of Al powder and 1% of Al fiber） , the material nitridized at 1100℃ for 3h has excellent physical properties. It is found that a massive quantity of alN in the forms of both whiskers and hexagon pellet particles is formed, and a large quantity of Al remained in the matrix. This multiple bonding system resulted in the excellent mechanical properties of the material. It is also found that the hydration tendency of the prepared material is inhibited, and the material exhibited excellent thermal shock resistance. The nature of protective oxidation of the bonding system is characterized. Thus, this material may become a new candidate of carbon-free sliding plate material for continuous casting.展开更多
The mullitization of andalusite from Xinjiang, Chi- na and influence of aggregates on properties of alumino- silicate refractories were studied by XRD, SEM, EDS, DSC. It was found that mullitization was obvious at 1 4...The mullitization of andalusite from Xinjiang, Chi- na and influence of aggregates on properties of alumino- silicate refractories were studied by XRD, SEM, EDS, DSC. It was found that mullitization was obvious at 1 400 ℃, but considerable at 1 500 ℃. The refractories with corundum aggregates had the highest RUL and the lowest creep rate, but refractories with bauxite aggregates had the lowest RUL and the highest creep rate.展开更多
The irfluences of C/S mass ratio and kieserite im-pregnation on performance of 95-grade magnesia bricks prepared using sintered magnesia DBM95 as main start-ing material, silica fi, me and limestone as additives were ...The irfluences of C/S mass ratio and kieserite im-pregnation on performance of 95-grade magnesia bricks prepared using sintered magnesia DBM95 as main start-ing material, silica fi, me and limestone as additives were researched. The cold and hot physical properties were tested according to Chinese standards on refractories. The hydration resistance was determined in a high pres-sure autoclave with 0. 55 MPa of water vapor pressure for different holding times of 0. 5 h, 3 h, and 5 h. The tri-al results show （ 1 ） adding silica fume to decrease C/S ratio from 0. 84 to 0. 33 improves sintering property; addin,g limestone to increase C/S ratio J？om 0. 84 to 1.95 causes more pores and negatively influences physi-cal properties： BD decreases, AP increases, MOR and CCS decrease generally, but HMOR increases obviously; （2） for non-impregnated specimens, adjusting C/S mass ratio can not improve hydration resistance; （3） the impregnation with kieserite solution can improve hydra-tion resistance of magnesia bricks significantly.展开更多
文摘Magnesia-calcium materials have stable hot performance,good resistance to the erosion and corrosion of liquid steel and steel slag,and a special role in purifying liquid steel,so they are widely used in iron and steel industry.However,hydration of magnesia-calcium materials seriously restricts their use,so researches have been done to improve their hydration resistance,obtaining a series of achievements.In this paper,the improvements on the hydration resistance of magnesia-calcium materials by additives in recent 20 years were presented,and their mechanisms were summarized.
文摘The application of CaO refractories was limited due to its poor hydration resistance.Introducing appropriate additive is an effective way to improve its hydration resistance.Additive WO3 was introduced in the preparation of CaO aggregates using calcination method in this study.The introduction of WO3 decreased the apparent porosity of CaO aggregates and promoted the grain growth of CaO by the formation of liquid at high temperatures.The average grain size of the specimens with 0.4 mass%WO3 and treated at 1550℃was increased to 51.6μm comparing to 33.5μm that without WO3 additive.As a result,the hydration resistance of CaO aggregate was significantly improved.Besides,WO3 sublimate easily,therefore,less WO3 was remained after the heat treatment.The further increase of WO3 addition had little effect on the hydration resistance of CaO specimens.
文摘Active lime was used to produce Ca（OH）2fine powder.And then Ca（OH）2fine powder with analytically pure CeO2fine powder（0,0.2%,0.4%,0.6%,0.8%and1.0%by mass,respectively）were mixed via wet mixing.After drying and ball milling,the specimens were pressed and fired at 1 450℃,1 500℃,1 550℃,1 600℃and1 650℃,respectively.The hydration resistance of the specimens was evaluated by measuring the mass gain after soaking the specimens in a chamber kept at 20℃and90%relative humidity.The influences of CeO2and calcination temperature on the hydration resistance of CaO aggregates were investigated by determination of bulk density,apparent porosity,and XRD,SEM and EDS analysis.The results show that：（1）the sintering of CaO aggregates is promoted by CeO2addition and the hydration resistance of CaO aggregates is improved;（2）CeO2mainly locates in CaO grain boundary,some CeO2is solved in the CaO grains which improves CaO sintering;（3）the appropriate calcination temperature is 1 550℃.When the calcination temperature is below 1 550℃,the specimens are sintered inadequately.The density and hydration resistance of CaO aggregates are nearly stable when the calcination temperature is above 1 550℃.
基金supported by the Independent Research and Development Project of the State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS 2021-03)National Science Fund for Distinguished Young Scholars(No.52025041)National Natural Science Foundation of China(Grant No.52104305)
文摘Considering the high melting point and high stability of SrO,it has potential applications in the field of the preparation of titanium alloys.To improve the hydration resistance,SrO samples with different ZrO_(2)additions were fabricated after firing at 1750℃for 6 h.The phase,the microstructure,and the hydration resistance of the samples were researched.The results show that the sample with 33 mol%ZrO_(2)addition possesses good hydration resistance with the mass gain after hydration for 13 days of less than 0.42 mass%.The SrO crucible with 33 mol%ZrO_(2)addition does not react with TiNi alloy melt during melting,which provides a support for searching new refractories with good hydration resistance for induction melting titanium alloys.
文摘According to the dual needs of heat transfer and thermal insulation in incinerators,different parts of the incinerators are designed with refractories of different SiC contents.Water vapor is mainly concentrated in the zones of feeding,drying and combustion,and the main damage factors of SiC refractories include high temperature and hydration.The results of hydration resistance of typical SiC-containing refractories show that the higher the SiC content,the worse the hydration resistance.Si_(3)N_(4)-SiC refractories after oxidation treatment have good hydration corrosion resistance,which are appropriate for water-cooled wall of waste incinerators.
文摘The complex coating on the MgO CaO clinker was prepared by dipping method and adding the second mineral to restrain the formation and expansion of the cracks. Meanwhile, the microstructure and the morphology of the coating and hydration resistance of the MgO CaO clinker were also investigated. The result shows that the coating consists mainly of Ca 2P 2O 7, MgO and CaCO 3, its thickness ranges from 5μm to 20μm, and the coating is dense and even, no micro cracks are observed. Also, the coating adheres closely to the matrix. The hydration resistance of the MgO CaO clinker after treatment is improved greatly, and the castables prepared with the treated MgO CaO clinker have better physical properties than MgO castable.
文摘To obtain CaO clinker with high density, low po- rosity, and good hydration resistance, the effect of the La2 03 content on physical properties, such as sintering property and hydration resistance of CaO clinker was re- searched in this paper. Apparent porosity and bulk density were measured by Archimedes principle with kerosene as the medium. Two methods were used to test hydration resistance of CaO clinker. One was carried out in a hu- midity cabinet at 20℃ with 90% of relative humidity. Another was the boiling method. SEM and EDS charac- terization analyses of CaO clinker were pe.rformed to observe the microstructural information and the hydration mechanism was put forward. The results show that： （1） the specimen with 0.79 mass% of La2O3 addition has lower apparent porosity, and higher bulk density; （2） the hydration mass gain of CaO clinker with 0.79 mass% La2O3 addition is lower, which is less than 1% after 20 days ; （3） La2O3 mainly distributes in the grain boundary, attd a small amount of La203 dissolves in grains. The average grain size of CaO specimens with 0.79 mass% La2O3 addition sintered at 1 450℃, 1 550℃, and 1 650℃, is 44. 5 μm, 48. 6 μm, and 63. 5 μm , respectively; （4） solid solution is formed due to the similar ionic radius of La^3＋ and Ca^2＋, which promotes the sintering of CaO clinker and improves the hy- dration resistance simultaneously.
文摘The Al-AlN bonded corundum based refractories was synthesized with the starting materials of fused alumina and metallic aluminium in nitrogen atmosphere through in-situ reaction. The study indicated that with the addition of 14% metallic aluminium （13% of Al powder and 1% of Al fiber） , the material nitridized at 1100℃ for 3h has excellent physical properties. It is found that a massive quantity of alN in the forms of both whiskers and hexagon pellet particles is formed, and a large quantity of Al remained in the matrix. This multiple bonding system resulted in the excellent mechanical properties of the material. It is also found that the hydration tendency of the prepared material is inhibited, and the material exhibited excellent thermal shock resistance. The nature of protective oxidation of the bonding system is characterized. Thus, this material may become a new candidate of carbon-free sliding plate material for continuous casting.
文摘The mullitization of andalusite from Xinjiang, Chi- na and influence of aggregates on properties of alumino- silicate refractories were studied by XRD, SEM, EDS, DSC. It was found that mullitization was obvious at 1 400 ℃, but considerable at 1 500 ℃. The refractories with corundum aggregates had the highest RUL and the lowest creep rate, but refractories with bauxite aggregates had the lowest RUL and the highest creep rate.
文摘The irfluences of C/S mass ratio and kieserite im-pregnation on performance of 95-grade magnesia bricks prepared using sintered magnesia DBM95 as main start-ing material, silica fi, me and limestone as additives were researched. The cold and hot physical properties were tested according to Chinese standards on refractories. The hydration resistance was determined in a high pres-sure autoclave with 0. 55 MPa of water vapor pressure for different holding times of 0. 5 h, 3 h, and 5 h. The tri-al results show （ 1 ） adding silica fume to decrease C/S ratio from 0. 84 to 0. 33 improves sintering property; addin,g limestone to increase C/S ratio J？om 0. 84 to 1.95 causes more pores and negatively influences physi-cal properties： BD decreases, AP increases, MOR and CCS decrease generally, but HMOR increases obviously; （2） for non-impregnated specimens, adjusting C/S mass ratio can not improve hydration resistance; （3） the impregnation with kieserite solution can improve hydra-tion resistance of magnesia bricks significantly.
