Preparation of lightweight insulation materials from forsterite and fly ash cenesphere

Xie Zhe, Deng Chengji, Dong Bo, Ding Jun, Zhu Hongxi, Zhou Nian, Yu Chao

2022, (5): 369-373. doi：10.3969/j.issn.1001-1935.2022.05.001

In order to reduce the raw material cost and the sintering temperature,lightweight insulation materials were fabricated using forsterite and fly ash cenesphere as main raw materials,and borax as the texturizer,heat treating at 800 ℃ for 1 h.The influence of the borax addition (5%,10%,20% and 30%,by mass) on the phase composition,the microstructure,and the properties of the materials was studied.The results show that:(1)the main phases of the prepared lightweight insulation materials are forsterite,aluminum borate,mullite,and quartz;(2)when the borax addition is 20%,magnesium borate forms and the sample has good comprehensive properties,the true porosity of 58.6%,the bulk density of 1.08 g·cm^-3,the thermal conductivity of 0.150 W·m^-1·K^-1,and the cold compressive strength of 7.62 MPa.

Effect of pulsed electric field on corrosion of slag line refractories for submerged entry nozzles

Li Yan, Yuan Lei, Tian Chen, Liu Guoqi, Yu Jingkun, Li Hongxia

2022, (5): 374-379. doi：10.3969/j.issn.1001-1935.2022.05.002

Abstract ( ) PDF (3349KB)( )

To relieve the serious corrosion of slag line refractories for submerged entry nozzles,the effect of electric fields (non-pulsed,positive pulsed,and negative pulsed) on the corrosion of slag line refractories for submerged entry nozzles was studied.Meanwhile the corrosion resisting mechanism was also discussed.The results show that an adhesive protective layer forms on the surface of the slag line refractories when a negative pulsed electric field is applied.The layer can effectively inhibit the decarburization and prevent the further contact between refractories and protective slag,which effectively hinders the corrosion of protective slag to the slag line refractories.

Effect of Al powder and Si powder addition on structure and properties of unburned magnesium aluminate spinel refractories

Zhou Lianzhuo, Wang Zhoufu, Wang Xitang, Liu Hao, Ma Yan, Quan Zhenghuang

2022, (5): 380-385. doi：10.3969/j.issn.1001-1935.2022.05.003

Abstract ( ) PDF (2246KB)( )

Unburned magnesium aluminate spinel refractories were prepared using sintered magnesium aluminate spinel as the main raw material,phenolic resin as the binder,aluminum powder (2%,4%,and 6%,by mass) and silicon powder (when Al powder addition is 4%,Si powder addition varies:1% and 2%,by mass) as additives.The effects of the aluminum powder and silicon powder addition on the properties and the microstructure of the refractories heat treated at different temperatures (1 000,1 400,and 1 600 ℃ for 3 h) were studied.The results show that the Al powder addition can greatly enhance the cold modulus of rupture of the samples fired at 1 000 or 1 400 ℃,and meanwhile AlN reinforcement phase forms in the matrix,which greatly improves the hot modulus of rupture of the samples at 1 400 ℃;however,the heat treatment at 1 600 ℃ has little influence on the strength;the addition of aluminum powder and silicon powder result in the formation of low melting point phases,greatly reducing the hot modulus of rupture.However,the low melting point phases promote sintering,which enhances the density and the cold modulus of rupture,and decreases the volume change during heating.The specimens added with aluminum and silicon all have higher cold modulus of rupture than those added with Al powder only.

Effects of preparation processes on thermal shock resistance of Si₃N₄-SiC refractories

Zhao Shuang, Li Sichao, Yang Zichun

2022, (5): 386-390. doi：10.3969/j.issn.1001-1935.2022.05.004

Abstract ( ) PDF (2475KB)( )

This work aims at improving the thermal shock resistance of Si₃N₄-SiC refractories.Si₃N₄-SiC specimens were prepared through two means:vacuum vibration casting and machine pressing,using industrial SiC particles and Si powder as raw materials and nitridation-firing at 1 400 ℃ for 8 h.The properties and density distribution of the specimens were characterized,and a water quenching method combined with a residual fracture toughness test program was designed to evaluate the thermal shock resistance of the Si₃N₄-SiC refractories.The comparison results indicate that the vacuum vibration cast specimens have better general properties and higher fracture toughness retention ratio,more uniform density distribution and less crack sources than the traditional pressed specimens,hence the vacuum vibration cast specimens have better thermal shock resistance than the traditional pressed ones.

Preparation of lightweight alumina-silica castables by replacing closed-cell perlite aggregates with coal gangue ceramsites

Zan Wenyu, Ma Beiyue, Wang Yuqing, Jiang Zhifeng

2022, (5): 391-395. doi：10.3969/j.issn.1001-1935.2022.05.005

Abstract ( ) PDF (1867KB)( )

Lightweight alumina-silica castables were prepared using closed-cell perlite (2-4 mm),open-cell perlite (4-6 mm) and coal gangue ceramsites (≤5 mm) as aggregates,floating beads (0.3-0.5 mm),sinking beads (0.6-0.8 mm),silica micropowder,α-Al₂O₃ micropowder,zirconia and zircon micropowder as fines,and Secar 71 (calcium aluminate cement) cement as the binder.The effects of the coal gangue ceramsites addition (0,6%,12%,18% and 24%,by mass) on the properties of the as-prepared lightweight alumina-silica castables were investigated.The results show that:(1)the addition of coal gangue ceramsites can reduce the sintering shrinkage of the specimens and help to improve the strength and thermal shock resistance;(2)the specimens with the addition of coal gangue ceramsites can produce pores in the matrix of the sintered specimens,which provides enough space for the growth of CA₆ complex solid solution and expands the irregular lamellar structure;(3)with the addition of coal gangue ceramsites increasing,the linear shrinkage of the specimens sintered at 1 000 or 1 200 ℃ firstly reduces and then increases,the bulk density increases and the apparent porosity decreases;the cold compression strength and the thermal shock resistance of the specimens sintered at 1 200 ℃ firstly increase and then decrease.Thus,the optimal addition of coal gangue ceramsites is 18%.

Effect of Al₂O₃/SiO₂ mass ratio on electrical insulation performance of Al₂O₃-SiO₂-MgO composite powder

Cao Jiyuan, Ma Beiyue, Wang Lulu, Li Guangming, Liu Yongli, Song Na, Tian Jian

2022, (5): 396-399. doi：10.3969/j.issn.1001-1935.2022.05.006

Abstract ( ) PDF (1536KB)( )

In order to improve the insulation performance of MgO materials for electric heating tubes,modified Al₂O₃-SiO₂ composite powders with different mass ratios of Al₂O₃/SiO₂ were prepared by KH-550 organic modifier,and then the modified composite powder and MgO powder were mixed evenly according to the mass ratio of 1∶10 to obtain Al₂O₃-SiO₂-MgO composite powder.The properties of the Al₂O₃-SiO₂ composite powder and the electrical insulation properties of the Al₂O₃-SiO₂-MgO composite powder were studied.The results show that:the surface of organically modified SiO₂ and Al₂O₃ powders is grafted with coupling agent,and the agglomeration between particles is improved;when m(Al₂O₃)∶m(SiO₂)=1∶4,the tap density of the Al₂O₃-SiO₂ composite powder is 0.90 g·cm^-3,the activation index is 40.9%,and the dispersion and fluidity are the best;the leakage current of the Al₂O₃-SiO₂-MgO powder is 0.33 mA,and the electrical insulation performance is the best.

Effect of calcination schedule on properties of high density sintered magnesia prepared from microcrystalline magnesite

Tian Xiaoli, Li Zhixun, Feng Runtang, Zhang Jie, Zheng Quanfu, Shi Xuwu, Du Yongbin

2022, (5): 400-406. doi：10.3969/j.issn.1001-1935.2022.05.007

Abstract ( ) PDF (2221KB)( )

Microcrystalline magnesite (60-90 mm) was used as the raw material,primarily calcined at 600-1 200 ℃ for 3 h,and then held at the temperature of complete decomposition of magnesite for 1-3 h.Then,the prepared high-activity light burned MgO was broken and ground to ≤0.045 mm,pressed and formed,then baked at 110 ℃ for 12 h,and secondarily calcined at 1 700-1 900 ℃ for 1-3 h to obtain sintered magnesia.The results show that the decomposition rate of microcrystalline magnesite increases significantly with the calcination temperature rising.The activity of the prepared light burned MgO increases first and then decreases slightly with the primary calcination temperature rising,but that decreases with the prolongation of the holding time.The appropriate primary calcination schedule is 900 ℃ for 1 h.In order to prepare high density sintered magnesia,the secondary calcination temperature is ≥1 850 ℃ with holding time ≥2 h.With the sintering temperature rising (1 700-1 900 ℃),sintering mechanism gradually changes from volume diffusion control to grain boundary diffusion control.The activation energy is lower when grain boundary diffusion is dominant,the pores are easier to migrate along grain boundaries and gradually expel,achieving better densification.

Effect of SiO₂ fume addition on thermal shock resistance of corundum castables

Li Yuchuan, Zhang Sanhua, Qin Hongbin, Chen Lu

2022, (5): 407-411. doi：10.3969/j.issn.1001-1935.2022.05.008

Abstract ( ) PDF (2861KB)( )

In order to improve the thermal shock resistance of corundum castables for snorkels of RH furnaces,SiO₂ fume was added with different additions (0,0.1%,0.2%,0.3%,and 0.4%,by mass).The actual working condition was simulated,thermal shock was conducted by preheating and then dipping into steel melt,and the influence of the SiO₂ fume addition on the thermal shock resistance of the castables was investigated by XRD,SEM,and FactSage 8.0.The results show that:(1)the SiO₂ fume addition can improve the thermal shock resistance of the corundum castables for RH snorkels;with the SiO₂ fume addition increasing,the modulus of rupture retention ratio of the specimen under steel dipping thermal shock increases first and then decreases,reaching the maximum (60%) with 0.2% SiO₂ fume addition;(2)the mechanism that SiO₂ fume improves the thermal shock resistance of corundum castables for RH snorkels is as follows:after adding SiO₂ fume,the high temperature liquid phases such as nepheline and melilite formed in the matrix can buffer the thermal stress of the specimens caused by thermal shock under the steel dipping condition.

K₂CO₃ corrosion resistance of CA₆,MA or β-Al₂O₃ castables

Xu Yuanchao, Zhang Sanhua, Qin Hongbin, Xu Yingshun, Huang Zhilin

2022, (5): 412-415. doi：10.3969/j.issn.1001-1935.2022.05.009

Abstract ( ) PDF (1486KB)( )

Three castables (CA₆,MA and β-Al₂O₃) were heat treated at different temperatures (800,1 000,1 200 and 1 350 ℃) and tested in terms of the K₂CO₃ corrosion test at the corresponding temperatures (800,1 000,1 200 and 1 350 ℃),and then the change rates of the apparent porosity,the bulk density,and the CCS of the samples after K₂CO₃ corrosion resistance test were determined,and the phase composition was analyzed.The results show that:(1)all the three castables present good alkali corrosion resistance at 800 ℃;(2)at 1 200 ℃,CA₆ castable reacts with K₂CO₃ to produce a large amount of β-Al₂O₃,which has poor corrosion resistance to K₂CO₃;spinel castable reacts with K₂CO₃ to produce less β-Al₂O₃ and has good corrosion resistance to K₂CO₃;β-Al₂O₃ castable has the weakest reaction with K₂CO₃ and the best K₂CO₃ corrosion resistance.

Effect of carbon black addition on sintering of pressureless sintered boron carbide ceramics

Shi Yanmin, Xu Zhengping, Long Chengyong, Cao Jianwu, Zhang Yongliang, Dong Binbin

2022, (5): 416-419. doi：10.3969/j.issn.1001-1935.2022.05.010

Abstract ( ) PDF (1553KB)( )

Boron carbide ceramics were prepared using boron carbide micropowder and silicon carbide micropowder as main raw materials,adding carbon black with different additions (1%,1.5%,2%,2.5%,and 3%,by mass),hydraulically molding,firing at 9 different positions in a large vacuum sintering furnace at 2 210 ℃ (set temperature) for 60 min.Then,the bulk density,the relative density,the modulus of rupture,and the Vicker hardness of the samples were detected,and the standard deviation of the bulk density was calculated.The results show that:(1)with the carbon black addition increasing,the relative density,the modulus of rupture,and the Vicker hardness of the samples first increase and then decrease,the standard deviation of the bulk density basically decreases first and then increases,the inflection is 2.5% of the carbon black addition,with the relative density,the modulus of rupture,and the Vicker hardness of 98%,417.8 MPa,and 28.9 GPa;(2)the boron carbide ceramics prepared according to the optimal formulation have the bulk density,the relative density,the modulus of rupture,and the Vicker hardness of 2.59-2.61 g·cm^-3,≥97.5%,≥400 MPa,and ≥28 GPa,respectively.The human bulletproof insert board combined with hot pressure tank composite process was tested according to NIJ 0101.06 IV level protection standard,the maximum backside depression depth is 42.4 mm,satisfying the protection standard requirements.

Campaign life prolongation of a 200 t ladle in Shougang Jingtang

Zhang Jian, Wei Jidong

2022, (5): 420-422. doi：10.3969/j.issn.1001-1935.2022.05.011

Abstract ( ) PDF (917KB)( )

The various adverse factors affecting the campaign life of a 200 t ladle in Jingtang Company were analyzed.The life of the ladle was increased from 240 heats to 260 heats by stabilizing the turnover,specifying return steel operation,controlling KR desulfurizer composition and desulfurization slag iron moisture,etc.After 260 heats,the ladle was removed,the residual thickness of refractories in the working area was still higher than the removal standard.The practical application results show that:only by reducing the influence of external adverse factors and the probability of abnormal corrosion to refractories can extend the campaign life.

Influence of characteristics of reactive alumina micropowder on properties of alumina based castables

Tang Hai, Shi Yingheng, Yuan Wenjie

2022, (5): 423-426. doi：10.3969/j.issn.1001-1935.2022.05.012

Abstract ( ) PDF (1882KB)( )

Effect of three commercial reactive alumina micropowders on the properties of alumina based castables was researched using tabular alumina,reactive alumina micropowder and calcium aluminate cement as raw materials.The results indicate that:(1)the CA₆ formation is influenced by the impurities content,the particle size and the specific surface area of alumina micropowder;(2)smaller alumina powders with narrow particle size distribution present better filling effect in the castables;therefore,samples incorporated with this kind of reactive alumina micropowder present dense microstructure and excellent mechanical properties;(3)the strength of fired castables is also correlated with the sinterability of reactive alumina micropowder;samples added reactive alumina micropowders with similar particle size but larger specific surface area present higher strength.

Effect of particle distribution on properties of corundum based dispersive purging plugs

Su Yuqing, Zhu Yening, Yu Baisong, Xi Zijian, Wei Juncong, Tu Junbo, Zhang Houxing, Wang Yilong

2022, (5): 427-430. doi：10.3969/j.issn.1001-1935.2022.05.013

Abstract ( ) PDF (1648KB)( )

To improve their air permeability,corundum based dispersive purging plugs were prepared with tabular corundum (1-0.15 and ≤0.15 mm) as aggregates,tabular corundum fines (≤0.044 mm) and α-Al₂O₃ micropowder (d₅₀=3 μm) as the matrix,R1 as the water reducer,and cement Secar 71 as the binder,cast molding and heat-treating at 1 600 ℃ for 4 h.Based on the Andreasen distribution equation,the effect of the particle distribution on the properties of the materials was studied by changing the distribution index q.The results show that:(1)with the q value increasing from 0.21 to 0.33,the apparent porosity of the fired samples decreases,the bulk density,the cold modulus of rupture,the cold compressive strength and the hot modulus of rupture increase,and the air permeability is ≤0.6 Nm³·h^-1;(2)with the q value increasing from 0.33 to 0.53,the apparent porosity of the fired samples increases,the bulk density,the cold modulus of rupture,the cold compressive strength and the hot modulus of rupture decrease,while the air permeability increases;(3)when the q value is 0.49,the sample has good comprehensive performance:the apparent porosity of 25.6%,the cold compressive strength of 67.1 MPa,the cold modulus of rupture of 20.9 MPa,the hot modulus of rupture of 9.4 MPa,and the air permeability of 2.8 Nm³·h^-1.

Influence of andalusite fine powder addition on properties of corundum-mullite materials

Zhang Junjie, Qian Jing

2022, (5): 431-434. doi：10.3969/j.issn.1001-1935.2022.05.014

Abstract ( ) PDF (1779KB)( )

Corundum-mullite materials were prepared with homogeneous bauxite chamotte,andalusite fine powder,Guangxi white clay as raw materials firing at 1 400 ℃ for 4 h.The effect of the andalusite fine powder addition (0,5%,10%,and 15%,by mass) on their properties such as the density,the strength,the refractoriness under load,the thermal shock resistance,the hot creep resistance was studied.The results show that:(1)with the increase of the andalusite fine powder addition,the bulk density of the samples gradually decreases,the thermal shock resistance and the hot creep resistance gradually enhance,the refractoriness under load gradually rises,and the cold crushing strength basically remains unchanged;the sample added with 15% of andalusite has the best comprehensive performance;(2)after firing at 1 400 ℃ for 4 h,the surface layer of andalusite fine powder particles shows complete mullitization,and the mullitization degree gradually decreases from the surface to the inside,which enables further mullitization during subsequent high-temperature heating,thus playing a positive role to the thermal shock resistance,the hot creep resistance and the refractoriness under load of the materials.

Development status and prospects of China’s refractory industry

Li Yongquan, Peng Ting

2022, (5): 435-439. doi：10.3969/j.issn.1001-1935.2022.05.015

Abstract ( ) PDF (1330KB)( )

The development achievements of refractory industry in the past were reviewed,especially those during the 13^th Five-Year Plan period.The assistance of refractories as the basic materials to the development of iron and steel industry was introduced,the existing problems and challenges were analyzed,and the direction and the way of the high-quality development of the refractory industry in the future were discussed.

Research status on nano materials modified low carbon alumina-carbon refractories

Wu Shuaibing, Liang Feng, Li Yage, Zhang Xin, Cai Weijie, Zhang Haijun, Zhang Shaowei

2022, (5): 440-446. doi：10.3969/j.issn.1001-1935.2022.05.016

Abstract ( ) PDF (970KB)( )

The conventional alumina-carbon (Al₂O₃-C) refractories are widely used in the iron and steel production because of their excellent spalling resistance,slag resistance,and thermal shock resistance.However,with the development of clean steel smelting processes,they can’t satisfy the production standard of clean steel due to their high carbon content.Nevertheless,the thermal shock resistance and the corrosion resistance of Al₂O₃-C refractories will be reduced by lowering the carbon content.To solve these problems,researchers attempted to directly add or in situ synthesize nano materials in refractory matrix to improve the high temperature service performance of Al₂O₃-C refractories.The research status of matrix modification of low-carbon Al₂O₃-C refractories by nano carbon materials and nano ceramic phases in recent years was reviewed,and the research direction in this field was prospected.

Research progress on surface modification of flake graphite

Cai Weijie, Li Yage, Zhang Xin, Guo Junyan, Duan Hongjuan, Zhan Haijun

2022, (5): 447-451. doi：10.3969/j.issn.1001-1935.2022.05.017

Abstract ( ) PDF (990KB)( )

Natural flake graphite has wide application in carbon containing refractories owing to its low density,high thermal conductivity,low thermal expansion coefficient,and good thermal shock resistance and slag corrosion resistance.However,graphite has some disadvantages such as poor hydrophilicity and easy oxidation at high temperatures,which limits its application in refractories.Surface coating of graphite is an effective method to overcome the disadvantages.The research progress of graphite surface modification methods in recent years was reviewed,their advantages and disadvantages were analyzed,and the development direction was prospected.

Sintering densification of boron carbide materials and their application research progress

Zou Xin, Chen Ping’an, Xu Guangping, Li Xiangcheng, Zhu Yingli, Zhu Boquan

2022, (5): 452-457. doi：10.3969/j.issn.1001-1935.2022.05.018

Abstract ( ) PDF (957KB)( )

Boron carbide (B₄C) has excellent high-temperature oxidation resistance,high hardness,low density,high melting point and excellent abrasive resistance,which is widely used in fields such as refractories,wear-resistant materials and lightweight protective materials.The research progress and the application of B₄C materials in China and at abroad in recent years were summarized.The influences of sintering processes (pressureless sintering,hot pressing sintering,hot isostatic pressing sintering,spark plasma sintering and microwave sintering) and sintering additives (simple substances,oxides and carbides) on the B₄C densification were analyzed.The development of B₄C materials was prospected.

Quantitative non-destructive testing method of ceramic tiles for gas turbine combustors

Feng Zhiyuan, Wang Han, Song Yanyan, Fan Muxu, Zhang Tao, Wu Gang

2022, (5): 458-460. doi：10.3969/j.issn.1001-1935.2022.05.019

Abstract ( ) PDF (1201KB)( )

The percussion position and the vibration receiving position of whole ceramic tiles for the elastic modulus testing were determined,and the elastic modulus E’ at the corresponding positions was measured by the pulse excitation method.Samples were prepared according to GB/T 30758,while the elastic modulus E of the samples was measured.E’ and E were numerically fitted,and a mathematical model was established.The result shows that the linear correlation coefficient R² of the two is 0.992.Therefore,the elastic modulus of ceramic tiles can be quantitatively evaluated without damaging their structure through measuring the elastic modulus of the tiles by the excitation method and then calculating the actual elastic modulus according to the fitting formula.

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