Advanced refractories innovation boosts China’s strategy implementation

Li Hongxia

2023, (5): 369-376. doi：10.3969/j.issn.1001-1935.2023.05.001

Refractories,indispensable supporting materials for high temperature technology,are widely used in steel,nonferrous metals,environmental protection,aerospace and other fields.Based on the important fundamental raw material industry and strategic emerging industries,the requirements of China’s high-quality development,green and dual carbon target,and defense and security strategies for advanced refractories were analyzed,and the status of refractories was summarized.The opportunities and challenges of the refractories industry were discussed in the light of its own high-quality,green and low-carbon development.In the end,combined with the implementation of the China’s development strategy,the future development directions of advanced refractories were proposed:digitization and intelligence of research and development,reduction and structural functionalization,advanced refractories for green and low-carbon new technologies,and key technologies and standards for refractories green-low-carbonization and digital manufacturing.

New technology progress of refractories for iron and steel industry

Wang Zhanmin, Cao Xiying, Wu Jiguang, Qin Hongbin, Li Zhigang, Yu Tongshu, Liu Jun, Liu Guoqi, Duan Binwen, Wang Ziqiang

2023, (5): 377-385. doi：10.3969/j.issn.1001-1935.2023.05.002

Abstract ( ) PDF (2013KB)( )

Recent new technologies and progress of refractories for iron and steel industry were introduced,including composite bonded silicon carbide materials for coke dry quenching furnaces,key refractories for hydrogen-based shaft furnaces,key refractories for OY furnaces (improved COREX-C3000),silicon carbide tuyere combination bricks for iron-making blast furnaces,environmentally friendly long-life Al₂O₃-SiC-C castables for blast furnace iron trough,zirconia slide plates for slag skimming of converters,refractories for refining ladles,gradient functional refractories for continuous casting,high-efficiency thermal insulation materials for high-temperature devices,recycling of hot blast furnace slag and foam ceramic filters for casting.Through the adoption of these new technologies,the requirements of new equipment and new technology in iron and steel industry can be met,improving the service life of existing furnace lining or key refractory materials,saving energy and decreasing consumption,purifying molten steel or molten iron,and strengthening the utilization of solid waste.

Effect of solid solution reaction on structure and properties of MA-Al₂O₃ materials

Shi Gan, Fan Muxu, Liu Xinyu

2023, (5): 386-389. doi：10.3969/j.issn.1001-1935.2023.05.003

Abstract ( ) PDF (1836KB)( )

In order to investigate the effect of the solid solution reaction between corundum and magnesium aluminate spinel on the properties and microstructure of MA-Al₂O₃ materials,two groups of MA-Al₂O₃ materials were prepared using fused magnesium aluminate spinel as the main raw material,adding a small amount of sintered corundum fine powder to partially replace spinel fine powder,or using white corundum as the main raw material and adding a small amount of fused magnesium aluminate spinel fine powder to replace white corundum fine powder.The results show that:(1)the solid solution reaction occurs in both groups,increasing the alumina content in the magnesium aluminate spinel from about 76 mass% to over 80 mass%,thereby strengthening the bonding between the aggregates and matrix of the samples,reducing structural defects,and improving the hot performance of the materials;(2)for the MA-Al₂O₃ specimens with magnesium aluminate spinel as the main raw material,adding corundum increases the cold compressive strength and improves the hot creep resistance and thermal shock resistance;(3)for the MA-Al₂O₃ specimens with corundum as the main raw material,adding magnesium aluminate spinel fine powder significantly improves the cold compressive strength,hot creep resistance and hot modulus of rupture.

Effect of heat treatment temperature on properties of SiC-MgAl₂O₄-Al composites

Sun Honggang, Li Hongxia, Si Yaochen, Du Yihao, Zhao Shixian, Shang Xinlian, Xia Miao

2023, (5): 390-396. doi：10.3969/j.issn.1001-1935.2023.05.004

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In order to improve the mechanical properties of SiC-MgAl₂O₄ composites for coal gasifiers,SiC-MgAl₂O₄-Al composites were prepared by heat treatment in the nitrogen atmosphere using SiC particles (≤ 2.5 mm),MgAl₂O₄ fine powder (≤90 μm),α-Al₂O₃ micro-powder(d₅₀≈5 μm) and aluminum powder (≤74 μm) as the main raw materials.The effects of different heat treatment temperatures from 200 ℃ to 1 600 ℃ on the microstructure,phase composition and mechanical properties of the composites were analyzed.The results show that:(1)when the heat treatment temperature is higher than 1 000 ℃,Al in the composites gradually forms Al-O-C-N whiskers,which can significantly improve the mechanical properties of the composites;(2)the cold and hot modulus of rupture increases with the increasing content and size of Al-O-C-N whiskers in the composites.The phase composition,content,and morphology of the Al-O-C-N whiskers can be controlled by adjusting the heat treatment temperature,thereby achieving the control of the phase composition and microstructure,and improving the mechanical properties of the composites.

Effect of stabilizer types on properties of high purity zirconia bubble products

Zhang Tao, Tan Qinghua, Feng Zhiyuan, Wang Han, Liu Pengcheng

2023, (5): 397-401. doi：10.3969/j.issn.1001-1935.2023.05.005

Abstract ( ) PDF (1618KB)( )

In order to prepare high purity zirconia bubble products with better heat insulation performance,high purity zirconia bubble refractories with different types of stabilizers were prepared using CaO stabilized zirconia bubble particles and powder,Y₂O₃ stabilized zirconia bubble particles and powder,or CaO+Y₂O₃ stabilized zirconia bubble particles and powder as the main raw materials,respectively,industrial Y₂O₃ micropowder as the sintering aid,and water-soluble resin as the binder,vibration pressure forming,and firing at 1 800 ℃ for 6 h.The effect of the stabilizer types on the properties of high purity zirconia bubble refractories was studied.The results show that:(1)the main phase of the samples is cubic zirconia;the zirconia bubble particles and powder are well bonded;the sample with CaO stabilizer has relatively narrow and interconnected network pores,moderate mechanical properties and the best thermal shock resistance;the sample with Y₂O₃ stabilizer has uneven,dispersed and isolated pores,and the worst mechanical properties;the sample with CaO+Y₂O₃ stabilizer has smaller and more even pores,obvious densification trend,and the best mechanical properties,but the worst thermal shock resistance;(2)the linear expansion rate and thermal conductivity of the samples gradually increase with the temperature increasing;at high temperatures,the sample with CaO stabilizer has the lowest linear expansion rate and thermal conductivity;(3)overall,the sample with CaO stabilizer has the best performance.

Properties of MgO-C refractories bonded with different binders

Han Yihui, Cao Xiying, Feng Haixia, Wang Hui, Liu Jun, Pan Yuanshuai, Wang Jianbin

2023, (5): 402-406. doi：10.3969/j.issn.1001-1935.2023.05.006

Abstract ( ) PDF (2331KB)( )

In order to reduce carbon emissions,MgO-C refractories were prepared using fused magnesia,flake graphite,Al-Si composite powder and α-Al₂O₃ micropowder as raw materials,and new environmental friendly complex magnesium-aluminum cementing agent (abbreviated as W powder) and phenolic resin (abbreviated as PF) as binders,respectively.The physical properties and thermal shock resistance of the MgO-C refractories were compared.The results show that:(1)after different temperature treatment,W powder bonded samples have higher linear change rate and apparent porosity but lower bulk density and cold compressive strength than PF bonded samples;(2)W bonded samples have better thermal shock resistance than PF bonded samples,and the cold modulus of rupture of the sample bonded with W after one thermal shock is increased by 19.2%.

Effect of sintering agent on properties of calcium zirconate materials

Lu Yue, Liu Guoqi, Yang Wengang, Yan Pengfei, Ma Weikui, Li Hongxia

2023, (5): 407-411. doi：10.3969/j.issn.1001-1935.2023.05.007

Abstract ( ) PDF (1786KB)( )

Calcium zirconate material is a crucible material for high temperature alloy melting with potential application prospects.The crucibles with dimensions of 30 mm×7 mm were prepared using fused calcium zirconate (CaZrO₃) as the main raw material,adding a small amount (0.5%-2%,by mass) of TiO₂,Al₂O₃,La₂O₃,CeO₂,and Y₂O₃ powders as the sintering agents,pressing under 150 MPa,and sintering at 1 650 ℃ for 3 h.Effects of the type and addition of sintering agents on the sintering degree,phase composition and microstructure of calcium zirconate materials were studied.The results show that:(1)the sintering performance of the sample with 2% TiO₂ is the best because the sintering of the material is promoted due to the solid solution reaction;(2)the suitable addition of Al₂O₃ is 1% because the formed liquid phase promotes the sintering of the material and the average grain size in the sample after sintering is 10-30 μm;(3)the suitable addition of Y₂O₃ is 0.5% because the solid solution reaction promotes the material sintering and the average grain size in the sample after sintering is 10-50 μm.

Effect of industrial carbon black addition on properties of multiphase bonded silicon carbide refractories

Chang Cheng, Lyu Chunjiang, Gong Jianfeng, Huang Yifei, Ma Zhaoyang, Liu Zhen

2023, (5): 412-416. doi：10.3969/j.issn.1001-1935.2023.05.008

Abstract ( ) PDF (3131KB)( )

In order to study the effect of industrial carbon black on properties of multiphase bonded silicon carbide refractories,the samples were prepared using silicon carbide particles (3-1 and 1-0.088 mm) and fine powder (<0.088 mm),silicon powder (<0.088 mm),industrial carbon black (N990),microsilica (d₅₀=0.26 μm) and ρ-Al₂O₃ micropowder (d₅₀=6.0 μm) as the main raw materials,casting molding and heat treating at 1 400 ℃ in nitrogen atmosphere.The physical properties,phase composition and microstructure of samples with N990 additions of 2.5%,3.0%,and 3.5% by mass were analyzed and compared.The results show that:(1)with N990 addition increasing,the flowability of the casting mud is improved,the demoulding and drying strengths are increased;(2)with the increase of N990 addition,the apparent porosity of the nitridized material increases,the bulk density and modulus of rupture both decrease,the content of free carbon increases,and the α-Si₃N₄ content decreases;(3)with the increase of N990 addition,because the particles agglomerating probability of carbon black increases,the uniformity of the samples become worse after nitridizing.Reaction sintering occurs between Si-C and Si-N,in addition to the continuous flocculent matrix,dense island-like β-SiC or O’-SiAlON phases also appear locally.It is thought after comprehensive analysis that the sample with 3.0% carbon black addition can better meet the need of material preparation and properties.

Structure, properties and corrosion resistance of high entropy (Y_0.2Gd_0.2Dy_0.2La_0.2Sm_0.2)TaO₄ ceramic materials

Wang Ruida, Zhao Shixian, Chen Liugang, Si Yaochen, Li Lingfeng, Li Hongxia, Liu Guanghua

2023, (5): 417-422. doi：10.3969/j.issn.1001-1935.2023.05.009

Abstract ( ) PDF (2308KB)( )

In order to meet the urgent demand of new thermal barrier coating materials for a new generation of aero-engines,a high entropy rare earth tantalate (Y_0.2Gd_0.2Dy_0.2La_0.2Sm_0.2)TaO₄ material,abbreviated as (5RE_0.2)TaO₄,was developed using high-purity oxides (Y₂O₃,Gd₂O₃,Dy₂O₃,Sm₂O₃,La₂O₃,Ta₂O₅) as raw materials according to the stoichiometric ratio,and insulating at 1 200-1 750 ℃ for 5 h for a solid phase reaction. The phase composition,microstructure,thermal properties,mechanical properties,and CMAS (CaO-MgO-Al₂O₃-SiO₂) corrosion resistance of the material were studied.The results show that:(1)the (5RE_0.2)TaO₄ ceramic material has a monoclinic structure with obvious ferroelastic domain;(2)the material fired at 1 750 ℃ exhibits extremely low thermal conductivity (1.65 W·m^-1·K^-1,600 ℃) and high thermal expansion coefficient (10.2×10^-6K^-1,1 200 ℃);(3)due to the unique ferroelastic toughening effect,the fracture toughness of the (5RE_0.2)TaO₄ material fired at 1 750 ℃ reaches 2.4 MPa·m^1/2;(4)(5RE_0.2)TaO₄ reacts with CMAS melt forming a reaction layer,showing excellent corrosion resistance.

Oxidation of recrystallized SiC in 1 000 ℃ saturated steam

Cao Huiyan, Wan Longgang, Wang Jianbo, Liu Yun, Zheng Han, Zhang Xinhua, Feng Yanbin, Wu Jiguang

2023, (5): 423-426. doi：10.3969/j.issn.1001-1935.2023.05.010

Abstract ( ) PDF (3498KB)( )

Three kinds of recrystallized SiC from 3 different producers with the service lives of 30,50,and 80 heats were selected to test the oxidation in 1 000 ℃ saturated steam for 500 h.The mass change rate and volume change rate after oxidation were determined.The phase composition and microstructure before and after oxidation were analyzed and related with the service life.The results show that:(1)under the saturated steam oxidation,the sample with the best recrystallization degree has the smallest mass change rate and volume change rate after oxidation,so as to the longest service life;(2)under the premise of meeting the molding performance,SiC with appropriate critical particle size shall be introduced as much as possible,ensuring the formation of evaporation-condensation mass transfer in a large range,so as to get more recrystallized networks and achieve better oxidation resistance and longer service life.

Influence of waste incineration grate furnace lining materials on outlet flue gas temperature and their application

Wang Jiaping, Yang Wengang, Huang Zhigang, Jiang Xing, Shi Shubing, Wang Wenwu

2023, (5): 427-430. doi：10.3969/j.issn.1001-1935.2023.05.011

Abstract ( ) PDF (1196KB)( )

In order to explore the effect of lining materials on the outlet flue gas temperature of waste incineration grate furnaces,the heat conduction of two kinds of water-cooled wall linings (SiC tiles+SiC self-flow mix and SiC castables) was numerically simulated by fluid module FLUENT of finite element analysis software ANSYS.The effects of lining materials and structures on the flue gas temperature in the grate furnace first channel outlet were analyzed.The simulation results were practically applied.The results show that:(1)the flue gas temperature in the first channel outlet is higher when the furnace lining is thicker;the flue gas temperature in the first channel outlet of the SiC castable lining is significantly higher than that of the SiC tiles+SiC self-flow mix lining when the lining thickness is the same;(2)with the fixed thickness of the SiC tiles,the flue gas temperature in the first channel outlet increases with the increasing thickness of the SiC self-flow mix;with the fixed lining thickness,the flue gas temperature in the first channel outlet gets lower as the SiC tiles get thicker;with the fixed working layer thickness,the flue gas temperature in the first channel outlet decreases with the increasing thermal conductivity of the SiC self-flow mix.The onsite application shows that the SiC tiles+SiC self-flow mix lining has lower flue gas temperatures in the first channel outlet,higher boiler thermal efficiency and stronger anti-coking properties than the SiC castable lining under the same operating conditions.

Analysis and countermeasures of surface spots on ceramic dielectric filters

Zhou Huijun, Luo Tian, Wang Longguang, Niu Shicheng, Wang Jiankun, Lu Xiangyang

2023, (5): 431-433. doi：10.3969/j.issn.1001-1935.2023.05.012

Abstract ( ) PDF (2382KB)( )

To improve the firing yield of ceramic dielectric filters,the surface spots of MgTiO₃-CaTiO₃ (MCT) ceramic dielectric filters fired on corundum-mullite load bearing boards were analyzed by a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS).The results show that at 1 300 ℃,the filters react with the boards at their contact areas to generate 2MgO·SiO₂ and Al₂O₃·TiO₂,forming discoloration spots.Based on the thermodynamic analysis of the composite oxide reaction,after spraying ZrO₂ coatings on the working surface of the corundum-mullite load bearing boards,the fired filters are of uniform color without discoloration spots.

Application of laser scanning method in fully automatic thermal shock resistance tester

Zhang Jian, Zhang Yi, Song Yanyan, Dong Dianmin, Wang Bo, Hu Piao, Liu Ke

2023, (5): 434-437. doi：10.3969/j.issn.1001-1935.2023.05.013

Abstract ( ) PDF (1405KB)( )

The principle,structure and characteristics of a fully automatic thermal shock resistance tester using 3D laser scanning technology were introduced.The tester was designed according to the relevant requirements of the thermal shock resistance test through water quenching in GB/T 30873—2014.Compared with the traditional testing method,it can automatically complete the measurement and calculation of the damage of the test end face,data archiving and recording and shutdown judgement during the thermal shock resistance test.The application results show that the tester greatly improves the testing efficiency and accuracy,eliminates the human error,and provides rich data and image information for the result analysis and process analysis of the thermal shock resistance.

MgAlON whisker bond in refractories

Guo Zongqi

2023, (5): 438-441. doi：10.3969/j.issn.1001-1935.2023.05.014

Abstract ( ) PDF (1780KB)( )

Unburned periclase-spinel-Al bricks,as a chromium-free material for RH degassers,have superior mechanical characteristics and slag penetration resistance,successfully replacing traditional magnesia-chrome bricks under extremely harsh working conditions.Instead of the common ceramic bond,a whisker bond is formed in the matrix of used periclase-spinel-Al bricks,which exhibits micron-size columnar MgAlON whiskers and densely interwoven network structure.The concept of the whisker bond was suggested in refractories,by detailing its fundamental characteristics and formation mechanism and differentiating whisker reinforcement and the whisker bond in this article.

Research progress of crucibles for precision casting of high-temperature alloys

Wang Gang, Wang Laiwen, Yuan Bo, Du Penghui, Feng Haixia, Liu Jun, Wang Qu, Wu Hao, Zhang Qi

2023, (5): 442-445. doi：10.3969/j.issn.1001-1935.2023.05.015

Abstract ( ) PDF (1228KB)( )

High temperature alloys are an important guarantee for the development of aviation engines and gas turbines.Precision casting is the main technology for manufacturing high-temperature alloy castings.Due to the severe working conditions,such as high temperature,high vacuum and frequent temperature fluctuation as well as the existence of active metal elements in high-temperature alloys,high requirements to crucibles for casting are needed.There are many types of crucibles for precision casting of high-temperature alloys,showing different application problems.Crucibles made of different materials for precision casting of high-temperature alloys and their research status were summarized.The research direction of crucibles for precision casting of high-quality high-temperature alloys was prospected.

Research progress on zirconia-containing refractories

Zhang Yanli, Peng Xigao, Zhang Xiaohui, Cheng Qing-xian, Wang Xiaoli

2023, (5): 446-451. doi：10.3969/j.issn.1001-1935.2023.05.016

Abstract ( ) PDF (1043KB)( )

The research progress of high-zirconia refractories,zirconia-containing magnesia refractories,zirconia-containing calcia refractories,zirconia-containing corundum refractories and non-oxides-ZrO₂ composite refractories was reviewed.It is found that:(1)the reasonable selection of stabilizers for ZrO₂ raw materials can effectively improve the thermal shock resistance of high-zirconia refractories and prolong the service life;(2)pre-synthetic raw materials (such as magnesia zirconia sand,CaZrO₃,zirconia-mullite,granulated zirconia micropowder and Zr(OH)₄ gel) and lightweight zirconia-containing raw materials (such as zirconia hollow beads) perform good application effects in magnesia refractories,calcia refractories and corundum refractories;(3)zircon sand is suitable for preparing non-oxides-ZrO₂ composites and some monolithic refractories.Based on this,the research direction of zirconia-containing refractories in the future was put forward.

Control factors of CO disproportionation reaction and its effect on refractories

Feng Yihang, Liu Guoqi, Li Hongxia, Qin Hongbin, Yang Wengang

2023, (5): 452-456. doi：10.3969/j.issn.1001-1935.2023.05.017

Abstract ( ) PDF (969KB)( )

Much high-temperature industrial equipment operates in a reducing atmosphere,such as blast furnaces,gasifiers and coke dry quenching furnaces.CO in reducing atmospheres is prone to disproportionate under the action of catalysts,generating CO₂ and solid carbon,which are deposited in the pores and gaps of refractories,thus leading to premature spalling or damage of refractories.For this reason,the disproportionation reaction of CO was described in terms of catalysts,CO partial pressure,atmosphere composition,temperatures and other controlling factors.The methods to inhibit carbon deposition were discussed.The effect of CO disproportionation reaction on the service performance of refractories was analyzed.The direction of the future work was pointed out.

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