Effect of Si₃N₄/Si₂N₂O multiphase powder on properties of Al₂O₃-SiC-C castables

Li Youqi, He Jian, Chen Junfeng, Zhang Jialiang, Li Zhengkun

2025, (1): 1-7. doi：10.3969/j.issn.1001-1935.2025.01.001

In order to improve the comprehensive service performance of Al₂O₃-SiC-C castables,microcrystalline Si₃N₄/Si₂N₂O multiphase powder synthesized by chemical combustion was used as an additive to prepare Al₂O₃-SiC-C castables,using brown corundum,tabular corundum,silicon carbide,active α-Al₂O₃ micropowder,SiO₂ micropowder,pure calcium aluminate cement,Si powder,and ball asphalt as raw materials.The effect of the multiphase powder extra-addition (0,1%,2%,3%,and 5%,by mass) on properties of the castables was studied;and the mechanism of Si₃N₄/Si₂N₂O to enhance the comprehensive properties of the samples was explored.The results show that:(1)Si₃N₄/Si₂N₂O multiphase powder can significantly improve the mechanical properties,oxidation resistance,and thermal shock resistance of the Al₂O₃-SiC-C castables;(2)the Si₃N₄/Si₂N₂O multiphase powder optimizes the microstructure of the castable and improves its overall performance by filling pores,promoting sintering reactions,and generating whisker like substances;(3)when the Si₃N₄/Si₂N₂O multiphase powder extra-addition is 3%,the castable has the optimal performance.

High-temperature water vapor corrosion resistance of Y₂Si₂O₇ reinforced SiC based refractories

Xue Haitao, Liu Xingyu, Chen Ding, Gu Huazhi, Li Shaofei, Huang Ao, Fu Lyuping, Wu Shujun

2025, (1): 8-12. doi：10.3969/j.issn.1001-1935.2025.01.002

Abstract ( ) PDF (1640KB)( )

To solve the serious high-temperature water vapor corrosion of SiC based refractories used in waste incinerators,SiC particles and powders were adopted as main raw materials,silica sol as the binder,and Y₂O₃ as the additive to prepare strip samples of 140 mm×25 mm×25 mm under the pressure of 150 MPa.The strip samples were fired at 1 400 ℃ for 3 h to fabricate Y₂Si₂O₇ reinforced SiC based refractories,and then the SiC based refractories were corroded under a water vapor atmosphere at 1 000 ℃ for 100 h.The effect of the Y₂O₃ addition (0,1.5%,3.0%,4.5%,by mass) on properties,phase composition,microstructure of the fired and water vapor corroded samples were investigated.The results show that:the addition of Y₂O₃ increases the apparent porosity of SiC based refractories and decreases the cold modulus of rupture;however,with the increase of the Y₂O₃ addition,the bulk density and cold modulus of rupture of the samples after water vapor corrosion at 1 000 ℃ for 100 h increase,and the cold modulus of rupture increases after 5 water-cooled thermal shock cycles.This is because of the enhanced phase Y₂Si₂O₇ formed by the in-situ reaction between Y₂O₃ and SiO₂ during firing at 1 400 ℃.It tightly bonds with SiC matrix,performs good stability in high-temperature water vapor,and has an approximate thermal expansion coefficient to SiC,which can improve the high-temperature water vapor corrosion resistance of the SiC based refractories.

Effect of h-BN on properties of low carbon Al₂O₃-C refractories

Luo Yixin, Wang Xing, Liu Zhenglong, Yu Chao, Deng Chengji, Ding Jun

2025, (1): 13-18. doi：10.3969/j.issn.1001-1935.2025.01.003

Abstract ( ) PDF (2821KB)( )

This work aims at the decline in the oxidation resistance and corrosion resistance of low carbon Al₂O₃-C refractories caused by the reduced carbon content,which becomes challenging to adapt to development in smelting technology.To address this issue,low carbon Al₂O₃-C refractories were prepared using white fused corundum,α-Al₂O₃ micropowder,Al powder,Si powder and flake graphite as the main raw materials,and h-BN as the additive.The effects of the h-BN addition (0,1%,3% and 5%,by mass) on the phase composition,oxidation resistance and corrosion resistance of the low carbon Al₂O₃-C refractories were studied.The mechanism of h-BN on the corrosion resistance of the Al₂O₃-C refractories was revealed by the thermodynamic simulation analysis.The results show that the ceramic phase content in the samples increases with the increase of the h-BN addition after heat treatment at 1 600 ℃;under high temperature oxidation environment,h-BN promotes the formation of Al₁₈B₄O₃₃ and Al₆Si₂O₁₃ in the decarburized layer of the sample,thus improving the oxidation resistance of the refractories;h-BN enhances the corrosion resistance of the sample by improving the slag viscosity and generating high melting point phases.

Effects of BaO on structure and slag resistance of magnesia-calcia refractories

Quan Yiyuan, Liu Hao, Wang Zhoufu, Ma Yan, Zhu Yuxuan, Deng Chengji, Wang Xitang

2025, (1): 19-24. doi：10.3969/j.issn.1001-1935.2025.01.004

Abstract ( ) PDF (3290KB)( )

In order to solve the problems of difficult sintering and poor resistance to slag penetration of magnesia-calcia refractories,magnesia-calcia specimens were prepared by magnesia-calcia sand as the main raw materials and barium acetate as the additive.The effects of the barium acetate addition (0,3.5%,7%,and 10%,by mass) on the phase composition,microstructure,main physical properties and slag penetration resistance of the magnesia-calcia refractories were studied.The results show that:(1)BaO decomposed from barium acetate promotes the growth of MgO and CaO grains,and reacts with CaO and SiO₂ impurities in magnesia-calcium sand to generate Ba_1.55Ca_0.45SiO₄ at the same time,which fills pores,promotes sintering,and enhances the densification and mechanical properties of the materials;(2)in the process of interaction with slag,Ba_1.55Ca_0.45SiO₄ between particles solubilizes Ca²⁺ in the slag to form Ba_0.48Ca_1.52SiO₄,which improves the slag viscosity near the penetration layer,inhibits the penetration of slag into the material,and strengthens the slag penetration resistance of the magnesia-calcia refractories;(3)the material with 7% barium acetate exhibits the optimal comprehensive performance.

Properties of MgO-ZrO₂-MgAl₂O₄ refractories

Liu Zhongfei, Wu Feng, Liang Xiaocheng, Sun Jiaqu, Pei Yuhang, Luo Xudong, Yuan Qichen

2025, (1): 25-30. doi：10.3969/j.issn.1001-1935.2025.01.005

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To overcome the harsh operating environment of refractories used in RH refining furnaces,magnesia-zirconia spinel was pre-synthesized using high-grade magnesite,desilicated zirconia,and MgAl₂O₄ as raw materials.Then MgO-ZrO₂-MgAl₂O₄ refractories were prepared by mixing the pre-synthesized spinel with fused magnesia of different particle sizes,molding,drying,and calcining.The effect of the pre-synthesized magnesia-zirconia spinel addition (10%,20%,and 30%,by mass) on the properties of the MgO-ZrO₂-MgAl₂O₄ refractories was studied.The results show that:(1)with the increase of the pre-synthesized magnesia-zirconia spinel addition,the bulk density of MgO-ZrO₂-MgAl₂O₄ refractories gradually increases,the apparent porosity,the linear shrinkage rate,and the cold modulus of rupture decrease gradually,the permeation resistance is improved gradually,and the corrosion resistance slightly decreases;(2)when the pre-synthesized magnesia-zirconia spinel addition is 20%,MgO-ZrO₂-MgAl₂O₄ refractories have a lower linear expansion coefficient and exhibit optimal fracture toughness and thermal shock resistance.Overall,the optimal addition of the pre-synthesized magnesia-zirconia spinel is 20%.

Corrosion of high level radioactivity waste borosilicate liquid glass on chrome corundum refractories

Qu Xiaorui, Chen Liugang, Liu Ping, Gao Guangze, Fu Qiqi, Zhang Lixin

2025, (1): 31-37. doi：10.3969/j.issn.1001-1935.2025.01.006

Abstract ( ) PDF (2180KB)( )

In order to study the corrosion mechanism and behavior of high level radioactivity waste borosilicate liquid glass on chrome corundum refractories,the corrosion mechanism of simulated high level radioactivity borosilicate liquid glass on fused cast and sintered chrome corundum refractories at 1 200 ℃ was analyzed and compared by dynamic cylindrical corrosion test combined with thermodynamic calculation.The microstructures and the chemical composition of the two refractories before and after corrosion testing were analyzed with the electron probe X-ray microanalyzer coupled with wavelength dispersive spectroscopy (EPMA-WDS).The corrosion mechanism was discussed.The results show that:(1)(Cr,Al)₂O₃,Al₂O₃,ZrO₂ and SiO₂-rich phases in the both refractories can dissolve into the liquid glass,Al₂O₃ in the (Cr,Al)₂O₃ solid solution dissolves into the glass whereas Cr₂O₃ does not dissolve;(2)liquid glass infiltrates into the fused chrome corundum mainly via the SiO₂-rich phases,but into the sintered chrome corundum through the open pore network,so the corrosion to the fused cast chrome corundum refractories is uniform,while that to the sintered one is uneven;(3)the corrosion resistance of fused cast chrome corundum refractories can be improved by lowering the content of SiO₂-rich phases,that of the sintered one by increasing the (Cr,Al)₂O₃ solid solution content.

Effect of hollow aggregate on mechanical properties of lightweight MgO-MgAl₂O₄-C refractories

Huang Ke, Yin Chaofan, Wang Li, Yu Renhong, Dong Binbin, Zang Yunfei, Liang Yanchen, Li Mancang, Qin Feng

2025, (1): 38-44. doi：10.3969/j.issn.1001-1935.2025.01.007

Abstract ( ) PDF (2238KB)( )

In order to effectively reduce the heat loss of lining materials and maintain a stable molten steel temperature,MgO-MgAl₂O₄-C refractories were prepared using high purity fused magnesia,self-made magnesium-aluminate spinel hollow aggregates,α-Al₂O₃ micropowder,magnesium-aluminate spinel powder,Si powder,Al powder and graphite as main raw materials,and thermosetting phenolic resin as the binder,heat-treating at 1 200 or 1 400 ℃ in the carbon embedded condition.The effect of the self-made magnesium-aluminate spinel hollow aggregates addition (0,3%,6%,and 9%,by mass) on the mechanical properties of lightweight MgO-MgAl₂O₄-C refractories was investigated.The results show that SiC and AlN are formed in the sample heat-treated at 1 200 ℃.Up to 1 400℃,plate-like MgAlON is found.With the increase of the magnesium-aluminate spinel hollow aggregates addition,the apparent porosity of the sample increases and the bulk density decreases.When the heat-treating temperature is 1 400 ℃,the sample with 6% magnesium-aluminate spinel hollow aggregates has the highest cold modulus of rupture and the cold crushing strength of 14.8 MPa and 121 MPa,respectively,and the modulus or rupture retention radio reaches 80%.The introduction of hollow aggregates changes the stress distribution direction and forms different dissipative mechanisms to strengthen and toughen the materials.

Influence of nano TiO₂ addition on properties of magnesia-calcia clinkers

Zang Weinan, Luan Jian, Wang Chun-yan, Li Jia, Han Haopeng

2025, (1): 45-49. doi：10.3969/j.issn.1001-1935.2025.01.008

Abstract ( ) PDF (1898KB)( )

In order to improve the hydration resistance of magnesia-calcia materials and further enhance other properties,magnesia-calcia clinker samples were prepared using dolomite powder and light-burned magnesia powder as the main raw materials,phenolic resin as the binder,extra adding nano TiO₂,molding at 100 MPa,and calcining at 1 650 ℃ for 3 h.Effect of TiO₂ additions (0,2%,4%,6%,and 8%,by mass) on the properties of the samples was investigated.The results show that the introduction of nano TiO₂ can generate solid solution in the materials and promote grains growth,while new phases CaTiO₃ and Ca₄Ti₃O₁₀ are generated to improve the bonding degree of particles;but the excessive generation of the new phases will hinder the gas discharge in the materials and affect the sintering process.With the increase of the nano TiO₂ addition,the content of CaTiO₃ and Ca₄Ti₃O₁₀ in the samples increases,the bulk density decreases gradually,the apparent porosity increases,and the cold modulus of rupture,the cold crushing strength and the hydration resistance,as well as the cold modulus of rupture after thermal shock firstly increase and then decrease.The strength,the thermal shock resistance and the hydration resistance of the samples are the highest when the nano TiO₂ addition is 2%.

Effect of magnesia particle addition on properties of MgO-Al₂O₃-SiO₂ thermal storage materials

Du Penghui, Zhao Yuge, Wang Gang, Sun Honggang, Wang Laiwen

2025, (1): 50-53. doi：10.3969/j.issn.1001-1935.2025.01.009

Abstract ( ) PDF (2054KB)( )

To prepare high-performance thermal storage materials for solid electric heating energy storage boilers,MgO-Al₂O₃-SiO₂ thermal storage materials were prepared using bauxite and fused magnesia as the raw materials,and sulfite pulp waste liquid as the binder,pressing at 100 MPa into samples with the dimentions of 50 mm×50 mm and heat treating at 1 360 ℃ for 4 h.The effects of the magnesia addition (0,10%,30% and 50%,by mass) on the phase composition,microstructure,physical properties and thermal storage performance of the materials were studied.The results show that:(1)with the introduction of magnesia,the phase composition and structural morphology of the thermal storage materials are significantly changed,and the materials present a gradient structure of magnesia particles-annular pores-spinel/cordierite reaction layers-mullite;(2)as the magnesia addition increases,the bulk density,specific heat capacity,thermal storage density and thermal conductivity of the samples increase,indicating an improvement in the thermal storage capacity and heat efficiency of the materials;the cold compressive strength first increases and then decreases,while the thermal expansion coefficient first decreases and then increases; excessive magnesia will produce excessive liquid,forming defects in the materials,thus decreasing the strength;(3)the sample with 30% magnesia has the optimal comprehensive performance.

Preparation of mullite materials with iron tailings

Sun Jiaqu, Liu Xin, Ding Xuan, Wu Feng, Luo Xudong

2025, (1): 54-58. doi：10.3969/j.issn.1001-1935.2025.01.010

Abstract ( ) PDF (1694KB)( )

To enhance the comprehensive utilization of iron tailings,mullite materials were prepared by the solid state reaction sintering method using iron tailings as the silicon source and Al(OH)₃ as the aluminium source.The effects of heat treatment temperatures (1 250,1 300,1 350 and 1 400 ℃ for 3 h) on the microscopic morphology and sintering properties of the mullite materials were investigated.The results show that:(1)Fe³⁺ in the iron tailings can partially replace Al³⁺ in mullite to form an iron-containing mullite solid solution during the solid state reaction,which leads to an increase in the lattice constant and a shift of mullite diffraction peaks to small angles;(2)increasing the heat treatment temperature produces more liquid phases in the system,and mullite grows gradually from granular to columnar;(3)after the heat treatment at 1 350 ℃ for 3 h,a mullite material with excellent comprehensive properties can be obtained with the apparent porosity of 18.2%,bulk density of 2.53 g·cm^-3 and cold modulus of rupture of 58.8 MPa.

Influence of surface modifiers on properties of anti-corrosion coatings for cement kilns

Li Rui, Song Bo, Ma Shulong, Gao Changhe, Tian Lin, Li Guohua, Zhang Furong

2025, (1): 59-64. doi：10.3969/j.issn.1001-1935.2025.01.011

Abstract ( ) PDF (2826KB)( )

To improve the corrosion resistance of silicon carbide-mullite refractories for cement kilns,anti-corrosion coatings were prepared by the slurry method using silica-mullite bricks as the substrate,calcined alumina powder as the filler,alumina sol as the binder,as well as dodecyl trimethyl ammonium bromide (DTAB),polyethylene glycol 4000 (PEG 4000),dodecyl dimethyl betaine (BS-12) and aluminum zirconium coupling agent (DH-550) as the surface modifiers,respectively,insulating at 1 450 ℃ for 3 h.The effects of the surface modifiers on the Zeta potential of the coatings,the bonding ability between the coating and the substrate as well as the corrosion resistance of the coatings were studied.The results show that:(1)the modifiers increase the Zeta potential of the coating slurry,reduce the surface tension,and improve the stability;(2)for ionic modifiers DTAB and BS-12,anions can be generated by dissociation,so the Zeta potential of the slurry is increased and the stability is improved by electrostatic interaction;for non-ionic modifiers PEG 4000 and DH-550,an organic hydrophilic protective film is formed on the surface of the slurry filler by chemical bonding,thereby increasing the Zeta potential and improving the stability of the slurry through steric hindrance;(3)the coating can improve the corrosion resistance of the silicon carbide-mullite brick,and the best modifier is DH-550.For the sample with DH-550 after heat treatment at 1 450 ℃,the coating and the substrate are tightly bonded,and there are no pores and cracks in the coating,showing excellent corrosion resistance.

Effect of process parameters on oxidation resistance and hydration resistance of Al₂O₃-C refractories

Zhang Rui, Sun Xudong, Wei Han, Yuan Biao, Wang Juntao, Yuan Lin, Liu Shifan, Chen Songlin

2025, (1): 65-69. doi：10.3969/j.issn.1001-1935.2025.01.012

Abstract ( ) PDF (1449KB)( )

To optimize the preparation process of Al₂O₃-C refractories,the influence of various factors on the oxidation resistance and hydration resistance of the refractories was studied.Cylindrical samples of 50 mm×50 mm were prepared using tabular corundum,Al powder,fused zirconia corundum,activated alumina powder and graphite as the main raw materials and thermosetting phenolic resin as the binder,hydro-forming and heat treating in a carbon embedded atmosphere.The Al powder addition (6%,9% and 12%,by mass),graphite addition (5%,15% and 25%,by mass),heat treatment temperature (680,950 and 1 500 ℃) and thermal insulating time (3,6 and 9 h) were selected as the research factors,and three levels of each factor were selected for orthogonal design.The results show that:(1)the additions of Al powder and graphite are the main factors affecting the oxidation resistance,while the heat treatment temperature and thermal insulating time are the secondary factors;(2)the Al powder addition and heat treatment temperature are the main factors affecting the hydration resistance,while the graphite addition and thermal insulating time are the secondary factors;(3)comprehensively considering,the optimal process is 9% Al powder,5% graphite,heat treatment temperature of 1 500 ℃ and thermal insulating time of 6 h,and the prepared sample contains columnar Al₄O₄C,which can significantly improve the oxidation resistance and hydration resistance of the materials.

Effect of reactive MgO addition on properties of corundum-spinel castables

He Xuhui, Zhao Zongqiang, Gao Guangze, Zhang Hongrui, Chen Liugang, Li Jianwei

2025, (1): 70-75. doi：10.3969/j.issn.1001-1935.2025.01.013

Abstract ( ) PDF (1448KB)( )

In order to improve the properties of corundum-spinel castables,corundum-spinel castables were prepared using reactive MgO as a binder and tabular corundum,reactive alumina micropowder,and aluminum lactate as the main raw materials.The effects of the reactive MgO addition (1%,3%,5%,and 7%,by mass,respectively) on the physical properties and slag resistance of the corundum-spinel castables were studied.Combined with the changes in the microstructure and phase composition,the influence mechanism of the reactive MgO addition on the properties was analyzed.The results show that:(1)the strength of the castables after curing and drying increases with the increase of the reactive MgO addition,while the apparent porosity shows a downward trend,(2)after the heat treatment at 1 600 ℃,the strength of the castables decreases with the increase of the reactive MgO addition,the permanent linear change on heating gradually increases,the slag corrosion resistance of the castables weakens,and the slag penetration resistance first enhances and then weakens,(3)when the reactive MgO addition is 3%,the reactive MgO-bonded corundum-spinel castables exhibit the best overall performance.

Effects of high titanium slag addition on properties of Al₂O₃-SiC-C castables

Zou Zehui, Tong Shengli, Zhu Ziyun

2025, (1): 76-81. doi：10.3969/j.issn.1001-1935.2025.01.014

Abstract ( ) PDF (2070KB)( )

In order to further improve the properties of Al₂O₃-SiC-C castables used for blast furnace troughs,Al₂O₃-SiC-C castables were prepared with brown corundum,silicon carbide,spherical pitch,etc.as the main raw materials and high titanium slag as an additive.The effects of the high titanium slag addition (0,1%,2%,3% and 4%,by mass,respectively) and heat treatment temperatures (holding for 3 h at 1 200 ℃ and 1 500 ℃) on the properties of the castables were studied.The results show that:(1)compared with the specimen treated at 1 200 ℃,in the specimen heat treated at 1 500 ℃ for 3 h,TiC is generated,and the sintering state is improved,thus enhancing the specimen properties;(2)the introduction of high titanium slag promotes the sintering of the specimens,with the increase of the high titanium slag addition,the bulk density,cold modulus of rupture,cold compressive strength,oxidation resistance and slag corrosion resistance of the specimens first increase and then decrease;(3)when the high titanium slag addition is 3%,the specimens heat treated at 1 500 ℃ for 3 h exhibit the best overall performance,their bulk density,apparent porosity,cold modulus of rupture and cold compressive strength are 2.97 g·cm^-3,17.6%,7.4 MPa and 45.7 MPa,respectively,and they have good oxidation resistance and slag corrosion resistance.

Development and characteristics of refractories for side dam plates in strip casting

Peng Tao, Chen Ping’an, Li Xiangcheng, Zhu Yingli, Chen Fu

2025, (1): 82-86. doi：10.3969/j.issn.1001-1935.2025.01.015

Abstract ( ) PDF (892KB)( )

Strip casting is a near-net-shape continuous steel casting technology,which features with a short process flow,simple equipment,low energy consumption,high yield,and low production costs.Among them,side dam plates,as the key materials in strip casting technology,directly affect the quality of strips and the production efficiency.This article reviews the strip casting technology process as well as the types,characteristics,and preparation processes of refractories for side dam plates,and particularly focuses on the application of boron nitride (BN)-based ceramic composite materials in strip casting in recent years.

Research progress of refractories for cement rotary kilns

Qu Chao, Li Hang, Huang Xiaoyang, Zhang Haijun, Zhang Shaowei

2025, (1): 87-92. doi：10.3969/j.issn.1001-1935.2025.01.016

Abstract ( ) PDF (866KB)( )

Cement rotary kilns are the main equipment for cement production at present.Refractories are crucial fundamental materials that ensure the safe operation,energy conservation,emission reduction,and technological progress during the high-temperature production process.Cement rotary kilns have a high calcination temperature.They can not only be used for cement production but also for handling solid waste and domestic garbage,which saves energy while disposing of waste.However,this also places higher demands on the refractories used in cement kilns.This paper reviews the current research status and existing problems of magnesia-alumina,magnesia-ferro-alumina,and magnesia-calcia refractories for cement rotary kilns,and also looks ahead to the future research directions and key points of refractories for cement rotary kilns.

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