Refractories

Interfacial reaction between rare earth oxide refractories and main inclusions in molten rare earth steel

Ma Feixiang, Li Hongxia, Liu Guoqi, Gu Qiang

2025, (2): 93-98. doi：10.3969/j.issn.1001-1935.2025.02.001

The development of refractories with weak reaction to rare earth inclusions is an important direction to solve the problem of the nozzle clogging of rare earth steel.La₂Ce₂O₇,La₂Zr₂O₇,and LaAlO₃ powders were synthesized using the high-temperature solid state method with La₂O₃,CeO₂,ZrO₂,La₂S₃,and Al₂O₃(particle sizes of 5-10 μm) as raw materials,firing at 1 400 ℃ for 2 h.Subsequently,La₂Ce₂O₇,La₂Zr₂O₇,and Y₂O₃ powders were pressed into 30 mm×7 mm substrate samples with PVA as a binder,and equal amounts of La₂O₃,La₂S₃,and LaAlO₃ powders were placed on their surfaces.The samples were then fired at 1 550 ℃ for 3 h with carbon embedded.The interfacial reaction of the three rare earth oxide refractories (La₂Ce₂O₇,La₂Zr₂O₇,and Y₂O₃) with the main rare earth inclusions (La₂O₃,La₂S₃,and LaAlO₃) in molten rare earth steel was studied.The results show that the La₂Ce₂O₇ sample has poor structural stability and readily reacts with La₂S₃,thus leading to cracking.The La₂Zr₂O₇ sample reacts with La₂O₃ and LaAlO₃ weakly,but performs poor La₂S₃ corrosion resistance.The Y₂O₃ sample demonstrates the weakest interaction with the three rare earth inclusions as well as the most stable structure,indicating significant potential as a specialized anti-clogging lining material for rare earth steel.

Interfacial reaction behavior between IN6203DS Ni-base superalloy and Y₂O₃ ceramic shells

Dong Longpei, Xu Hui, Zhao Yunsong, Wang Zhentao, Gan Youlu, Wang Enhui, Hou Xinmei

2025, (2): 99-104. doi：10.3969/j.issn.1001-1935.2025.02.002

Abstract ( ) PDF (2869KB)( )

To explore the possibility of applying Y₂O₃ ceramic shells in the preparation of IN6203DS directionally solidified Ni-base superalloy (hereinafter referred to as IN6203DS alloy) low-pressure working blades for a certain type of gas turbines,Y₂O₃ ceramic shells were prepared using Y₂O₃ powder as the surface layer material.The interfacial reaction behavior between IN6203DS alloy and Y₂O₃ ceramic shells was investigated through industrial scale precision casting experiments.The interaction mechanism between the alloy melt and the ceramic shells was clarified.The results show that the interfacial reaction between IN6203DS alloy and Y₂O₃ ceramic shells is attributed to the synergistic effect of physical penetration and chemical reaction.After reaction,the IN6203DS alloy exhibits slight sand adhesion on the surface,with the interfacial reaction layer thickness of approximately 4-8 μm.The layer includes an outer layer of alloy oxides diffused from the shells into the interface and an inner Hf oxide-rich laye.The shell surface layer shows peeling,with the thickness of the interfacial reaction layer of approximately 10-20 μm.Therefore,the Y₂O₃ ceramic shells can satisfy the development requirements of IN6203DS alloy for a certain type of gas turbines.

Properties of Al₂O₃-C refractories enhanced with expanded graphite/carbon nanotube composites

Guo Yuqi, Liao Ning, Li Yawei, Wang Qinghu, Zhu Tianbin

2025, (2): 105-110. doi：10.3969/j.issn.1001-1935.2025.02.003

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To fully utilize the synergistic strengthening-toughening effects of low-dimensional nano/micrometer materials,tabular corundum,activated alumina micropowder,silicon and nano carbon black were adopted as raw materials,with thermosetting phenolic resin as a binder.Three types of expanded graphite were introduced: expanded graphite (EG),pre-synthesized carbon nanotube-modified expanded graphite (EG-CNTs),and Ni-base catalyst-loaded expanded graphite (EG-Ni).After mixing,shaping,curing,and heat treatment at 800,1 000,1 200 and 1 400 °C for 3 h,low carbon Al₂O₃-C refractories were prepared.The impact of the different types of expanded graphite (EG,EG-CNTs and EG-Ni) on the structural evolution and performance of the refractories was investigated.The results demonstrate that the cold modulus of rupture of the samples with EG-CNTs or EG-Ni is much higher than that of the samples with EG,as EG-CNTs and EG-Ni both promote the formation of SiC whiskers in the samples,thereby playing a good role in strengthening.The sample with EG-Ni performs the best thermal shock resistance,because EG-Ni can generate carbon nanotubes in situ,accompanied by the synergistic toughening effect of carbon nanotubes/SiC whiskers,which significantly improves the thermal shock resistance of the material.

Effect of La₂O₃ on mechanical properties and slag corrosion resistance of MgO-Mg₂SiO₄ refractories

Wei Jintao, Luo Yixin, Yang Bolin, Liu Zhenglong, Deng Luopeng, Yu Chao, Deng Chengji, Wang Zhoufu, Ding Jun

2025, (2): 111-117. doi：10.3969/j.issn.1001-1935.2025.02.004

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The formation of low melting point phases from impurities in natural Mg₂SiO₄ reduces the slag resistance of MgO-Mg₂SiO₄ materials.To solve the problem,MgO-Mg₂SiO₄ refractories were prepared using Mg₂SiO₄ and fused magnesia as main raw materials,and La₂O₃ as an additive.The effects of the La₂O₃ addition (0,1%,2% and 3%,by mass) on the phase composition,microstructure,mechanical properties and slag corrosion resistance (e.g.,against NaF and Na₂SO₄) of the refractories were studied.The phase transformation law of the materials during corrosion was revealed combined with thermodynamic calculations.The results show that an appropriate addition of La₂O₃ can promote sintering and improve the density of the MgO-Mg₂SiO₄ materials.The sample with 2% La₂O₃ has the lowest apparent porosity and the highest cold compressive strength as well as significantly improved resistance against NaF and Na₂SO₄ corrosion.

Effect of stress release phases on properties of low carbon spinel-carbon refractories

Li Xinzhe, Liu Guoqi, Li Hongxia, Gu Qiang, Chen Yongqiang, Guo Hairong

2025, (2): 118-122. doi：10.3969/j.issn.1001-1935.2025.02.005

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To improve their thermal shock resistance,low carbon spinel-carbon refractories were prepared with MgAl₂O₄ and graphite as the main raw materials,and environmentally friendly asphalt Carbores P (CP),sodium tripolyphosphate and boron glass powder as the additives,insulating at 900 ℃ for 3 h in a carbon embedded atmosphere.The influence of additive types on the properties of the refractories was studied.The results show that:(1) the additives have little effect on the apparent porosity and bulk density of the samples;(2) compared to sodium tripolyphosphate,the addition of CP or boron glass powder significantly improves the cold modulus of rupture of the samples;while the addition of CP increases the hot modulus of rupture of the samples;(3) the introduction of sodium tripolyphosphate significantly reduces the thermal expansion coefficient and effectively improves the thermal shock resistance of the samples;(4) low carbon spinel-carbon refractories with high strength and good thermal shock resistance can be prepared by adding sodium tripolyphosphate.

Study on infrared radiation coatings based on Si-Fe tailings slag and their performance

Zhou Tao, Fu Lyu-ping, Yang Shuang, Chen Ding, Zhang Meijie, Huang Ao, Gu Huazhi

2025, (2): 123-127. doi：10.3969/j.issn.1001-1935.2025.02.006

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To enhance the infrared radiation performance and reduce production costs,two infrared radiation coatings were prepared using Si-Fe tailings as the main raw material.The coatings were sprayed onto silica brick surfaces and heat-treated at 1 300 ℃ for 2 h to form high-temperature infrared radiation coatings.The effects of rheological additive types (ethylcellulose and acrylic resin) and solid phase mass fractions (40%,50%,60%,and 70%) on the rheological properties of the coatings were investigated,and the phase composition and infrared radiation performance of the coatings were characterized.The results show that:(1)at low shear rates (≤0.1 s^-1),the viscosity of coatings with acrylic resin as the rheological additive increases sharply with the solid phase mass fraction increasing,and decreases rapidly with the increasing shear rate,exhibiting typical shear-thinning behavior;when the solid phase mass fraction is 50%,the coatings have a wider linear viscoelastic region and a higher storage modulus than loss modulus,indicating excellent structural stability;(2)at high shear rates (≥100 s^-1),the viscosity of coatings with ethylcellulose as the rheological additive increases significantly with the solid phase mass fraction increasing,and is higher than that of the acrylic resin system;(3)the acrylic resin-based coatings demonstrate superior infrared radiation performance,with average near-infrared and mid-infrared emissivities of 0.89 and 0.90,respectively;in the infrared band (1-8 μm),the average emissivity reaches 0.94,showing promising applications in industrial furnaces.

Effect of Al₂O₃ extra-addition on Al₂O₃-SiO₂-ZnO-B₂O₃-Na₂O glass-ceramics coatings

Cong Hedi, Sun Xiao-fei, Ma Zhaorui

2025, (2): 128-132. doi：10.3969/j.issn.1001-1935.2025.02.007

Abstract ( ) PDF (1803KB)( )

To meet the requirements of some specialized high-pressure large-scale equipment and improve the crack resistance and hygroscopicity of lightweight refractories,low-temperature fired Al₂O₃-SiO₂-ZnO-B₂O₃-Na₂O (ASZBN) glass-ceramics were developed for the surface coatings of lightweight refractories using SiO₂,ZnO,Al₂O₃,B₂O₃,and sodium tetraborate as the raw materials.The effects of Al₂O₃ extra-addition (0,4%,8%,and 12%,by mass) on the TG-DSC behavior,microstructure,and elastic modulus of the glass-ceramics coatings were investigated using FactSage 8.2 thermodynamic calculations.The results show that:with Al₂O₃ extra-addition increasing,the glass transition temperature of the ASZBN glass system decreases;after heat treatment at 730 ℃,cracks on the glass surface first increase and then decrease,and the elastic modulus of the ASZBN glass-ceramics first decreases and then increases.The viscosity of the ASZBN glass-ceramic system is higher when the temperature is lower than 700 ℃.When the temperature is higher than 700 ℃,the viscosity drops sharply with temperature rising and increases with the increase of Al₂O₃ extra-addition.When the Al₂O₃ extra-addition is 12%,after heat treatment at 730 ℃,the glass coating exhibits a smooth surface with negligible cracks and a high elastic modulus .

Preparation and high-temperature resistance of Fe₂O₃-SiO₂ composite aerogel materials

Hou Jianye, Zhang Zhonglun, Fu Xiaoqing, Wang Mingming, Liu Zhensen

2025, (2): 133-137. doi：10.3969/j.issn.1001-1935.2025.02.008

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To improve the thermal insulation performance of SiO₂ aerogels at high temperatures,SiO₂ precursor solutions were prepared via a sol-gel two-step method.Fe₂O₃ powder was extra-added as an opacifier to the SiO₂ precursor solutions with mass fractions of 0,0.2%,0.5%,1.0%,and 3.0%,and Fe₂O₃-SiO₂ composite aerogels were fabricated using CO₂ supercritical drying technology.The effects of Fe₂O₃ extra-addition on the aerogels were investigated.The results show that:(1)Fe₂O₃ doping does not alter the aerogel morphology;Fe₂O₃ suppresses the mass loss caused by high temperatures and enhances the high-temperature stability of the composites;(2)below 800 ℃,the aerogel with 0.5% Fe₂O₃ exhibits the lowest thermal conductivity and the best insulation performance;between 800-1 000 ℃,the aerogel with 1% Fe₂O₃ performs the lowest thermal conductivity and a good nanoporous structure;(3)by adjusting the Fe₂O₃ extra-addition,composite aerogels suitable for different temperature ranges can be tailored.

Preparation and properties of novel yttria-silica enhanced zirconia composite aerogels

Li Zhanfeng, Sui Xue-ye, Tang Wenzhe, Liu Ruixiang, Wang Mengmeng

2025, (2): 138-143. doi：10.3969/j.issn.1001-1935.2025.02.009

Abstract ( ) PDF (1950KB)( )

The phase transition of ZrO₂ at high temperatures causes structural collapse of ZrO₂ aerogels.To improve the high-temperature stability of ZrO₂ aerogels,Y₂O₃-SiO₂ enhanced ZrO₂ composite aerogels were prepared via the sol-gel method using low-cost and non-toxic mercaptosuccinic acid as a gel accelerator,and zirconium oxychloride octahydrate,yttrium nitrate hexahydrate,and tetraethyl orthosilicate as the precursors.Mullite fiber-Y₂O₃-SiO₂-reinforced ZrO₂ composites were also fabricated by adding mullite fibers.The effects of the molar ratios of Y₂O₃ to ZrO₂ (1∶40,1∶20,1∶10,and 1∶5),SiO₂ to ZrO₂ (1∶10,1∶5,3∶10,and 2∶5) on the gel time,pore structure,and high-temperature properties were investigated.The results show that:Y₂O₃ and SiO₂ can effectively shorten the gel time;SiO₂ doping leads to a more uniform nanoporous structure;Y₂O₃ doping causes coarser skeletons and disordered nanopores;Y₂O₃ and SiO₂ hinder the phase transition and reduce the shrinkage of ZrO₂ at high temperatures.The optimal ratio of Y₂O₃-SiO₂ enhanced ZrO₂ composite aerogels was n(Y₂O₃)∶n(SiO₂)∶n(ZrO₂)=1∶3∶10.

Preparation and oxidation resistance of ZrB₂ ceramic coatings on surface of SiC aerogel

Ma Zhaorui, Sun Xiaofei, Liu Guanghua, Zhao Shixian, Cong Hedi, Wang Gang

2025, (2): 144-148. doi：10.3969/j.issn.1001-1935.2025.02.010

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In order to improve the high-temperature oxidation resistance of SiC aerogel materials,a ceramic slurry was prepared by mixing ZrB₂ powder and silica sol at a mass ratio of 7∶3.The slurry was then coated on the surface of the SiC aerogel using the dip-coating method.After heat treatment at 400 ℃ for 2 h,an anti-oxidation ZrB₂ ceramic coating was obtained.The prepared coating materials were heat-treated at 600,800,1 000 and 1 200 ℃ for 2 h,respectively,and the compressive strength and oxidation resistance were investigated.The results show that the ZrB₂ coating can provide effective anti-oxidation protection for the SiC aerogel.In the initial stage of oxidation,a continuous and dense B₂O₃ glassy liquid phase layer is formed.With the temperature rising,ZrSiO₄,which is generated by the reaction between the two oxidation products SiO₂ and ZrO₂,can fill the pores formed by the volatilization of B₂O₃ in the coating,effectively improving the oxidation resistance of the material.The compressive strength of the ZrB₂/SiC aerogel composite increases with the temperature rising,reaching a maximum of 0.82 MPa at 1 200 ℃ and performing the best oxidation resistance.

Research progress on sol-gel method for preparing Al₂O₃-SiO₂ aerogels and composites

Zhang Huangshuai, Zhu Zhenting, Yang Zihao, Chen Zhe, Ma Yu, Zhang Hang

2025, (2): 149-154. doi：10.3969/j.issn.1001-1935.2025.02.011

Abstract ( ) PDF (927KB)( )

The research progress on various sol-gel processes for preparing Al₂O₃-SiO₂ aerogels in recent years was reviewed.The influence of drying methods and Al/Si molar ratios on the thermal stability of the aerogels under extremely high temperatures,as well as the doping strategy of the reinforcing phase in composite materials were deeply analyzed.The future development directions were prospected.

Influence of spinel addition on microstructure and properties of corundum-spinel castables

Xue Junzhu, Liu Guangping, Chen Junfeng, Wei Guoping, Cheng Yaping, Yan Wen, Li Nan

2025, (2): 155-161. doi：10.3969/j.issn.1001-1935.2025.02.012

Abstract ( ) PDF (2266KB)( )

Composite phase sintered alumina aggregates,corundum fine powder,activated alumina micropowder,90# alumina-rich spinel powder,70# spinel micropowder and calcium aluminate cement were used as main raw materials to prepare corundum-spinel castables.The influence of the spinel micropowder addition (0,5%,10%,and 16%,by mass) on the microstructure,mechanical properties and corrosion resistance of the castables was systematically studied.The results show that:with the spinel micropowder addition increasing,the linear shrinkage,elastic modulus,and cold modulus of rupture of the samples after heat treatment at 1 600 ℃,and the hot modulus of rupture (1 400 ℃) of the sample after drying at 110 ℃ all show an upward trend,indicating that the addition of spinel promotes sintering.Simultaneously,the addition of spinel micropowder enhances the thermal shock resistance of the samples.When the addition of spinel micropowder increases from 5% to 16%,the solid-solution effect of spinel on MnO and FeO in the slag is dominant,the corrosion resistance of the samples gradually improves.

Preparation of high performance sintered magnesia by utilizing salt lake brine

Zhou Yujun, Tang Dacai, Wen Tianpeng, Yu Jingkun

2025, (2): 162-166. doi：10.3969/j.issn.1001-1935.2025.02.013

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To achieve high efficient and high-value comprehensive utilization of magnesium resources in Qinghai Salt Lake,high purity bischofite (MgCl₂·6H₂O) was extracted from Qinghai salt lake brine by the dissolution-precipitation method,and highly active light burned magnesia was prepared by direct decomposition,followed by ball milling,drying,and molding,The and firing at 1 600 ℃ for 1,2,and 3 h to obtain sintered magnesia.The effects of particle size of light burned magnesia powder and holding time on the bulk density and microstructure of the sintered magnesia were studied.The results show that after grinding the obtained light burned magnesia powder to 1.303 μm and firing at 1 600 ℃ for 2 h,the sintered magnesia has the bulk density of 3.43 g·cm^-3,and the apparent porosity of 3.3%.It can be applied to high-temperature industries such as iron steel,and non-ferrous metallurgy.

Analysis and improvement of typical problems in RH furnace immersion tubes and circulation tubes

Wen Weixin, Liu Jianwei, Wu Jiyu, Ji Weiye, Li Shiliang

2025, (2): 167-169. doi：10.3969/j.issn.1001-1935.2025.02.014

Abstract ( ) PDF (1435KB)( )

To effectively improve the online service life of vacuum tanks,the typical problems during service of the immersion tubes and circulation tubes in RH furnaces of Shandong Iron and Steel Group Rizhao Co.,Ltd.were analyzed.Corresponding improvement measures were implemented for the problems such as abnormal corrosion at the lower part of the immersion tubes,deep ring trench between the immersion tubes and circulation tubes,and broken bricks between the circulation tubes and lower vessels,so as to reduce the abnormal downline of the vacuum tanks.The average life of vacuum tanks is increased from 115.6 heats to 133.7 heats.

Research progress on synthesis of transition metal diborides by boro/carbothermal reduction method

Peng Jie, Liu Jianghao, Zhang Haijun

2025, (2): 170-176. doi：10.3969/j.issn.1001-1935.2025.02.015

Abstract ( ) PDF (993KB)( )

The preparation of transition metal diborides by the boro/carbothermal reduction method has the advantages of low cost,high efficiency and the ability to synthesize target products with high purity.Based on the principle of the boro/carbothermal reduction method,the current research status of the preparation of transition metal diborides such as ZrB₂,HfB₂,WB₂ and high-entropy diborides by the boro/carbothermal reduction method was reviewed.The research progress and existing problems of transition metal diboride structural ceramics were summarized.The development of transition metal diboride powders via the boro/carbothermal reduction method and diboride structural ceramics was looked ahead.

Research progress on preparation of sheet-like silicon nitride ceramics by tape-casting technology

Zhao Chenxiao, Li Shipeng, Wang Gang, Zhou Yudong, Yuan Bo

2025, (2): 177-184. doi：10.3969/j.issn.1001-1935.2025.02.016

Abstract ( ) PDF (986KB)( )

The principles and processes of preparing silicon nitride ceramics by tape-casting technology in China and aboard were reviewed.The characteristics of various additives in both organic and water-based tape-casting slurry systems as well as the influence of process parameters on the tape-casting effect were elaborated.The research progress and existing problems in the preparation of sheet-like silicon nitride ceramics by tape-casting technology were summarized.The future development direction of this technology was discussed.