In-situ formed ceramic bonded Ti(C,N) composites and their properties

Zou Qiliang, Deng Chengji, Dong Bo, Ding Jun, Zhu Wanzheng, Wang Zhoufu, Zhu Hongxi, Wang Lin, Yu Chao

2023, (2): 93-98. doi：10.3969/j.issn.1001-1935.2023.02.001

Ceramic bonded Ti(C,N) composites were prepared by carbothermal reduction nitridation at 1 450 ℃ for 2 h using TiO₂ powder,flake graphite and Si powder as raw materials.The effects of the Si powder addition (0%,5%,15%,and 25%,by mass) on the phase composition,the microstructure,the physical properties,and the oxidation resistance of the material were investigated.The results show that the appropriate addition of Si powder refines the Ti(C,N) grains and improves the cold mechanical properties and the oxidation resistance of Ti(C,N) composites.The in-situ formed ceramic bonded Ti(C,N) composite with 5% Si powder has the optimal comprehensive properties,with the apparent porosity of (38.8±1.6)%,the cold modulus of rupture of (62.5±2.4) MPa,and the cold elastic modulus of (59.6±2.2) GPa.When the Si powder addition increases to 15 % or 25 %,the bulk density and the mechanical properties of the composite decrease.

Preparation of periclase-forsterite lightweight insulating refractories by molten salt method

Wang Shaoyang, Qi Xin, Hou Qingdong, Luo Xudong, You Jiegang, Zhang Ling

2023, (2): 99-103. doi：10.3969/j.issn.1001-1935.2023.02.002

Abstract ( ) PDF (2816KB)( )

Low grade magnesite is one of the main research directions in the future as the raw material for the preparation of magnesia based insulating refractories.Periclase-forsterite (MgO-Mg₂SiO₄) lightweight insulating refractories were prepared by the molten salt method with high silicon magnesite and cut-off grade talc ore as raw materials by pretreating them to get light burnt magnesia and talc,and NaCl molten salt as the reaction medium.The effects of the NaCl addition,the sintering temperature,the holding time and the raw material ratio on the specimen preparation were studied.The results show that when the NaCl addition is 20% of the mass of light burnt magnesia and talc mixture,the sintering temperature is 1 200 ℃,the holding time is 6 h,and m(light burnt magnesia)∶m(talc)=5∶5,the specimen has the optimal comprehensive properties:the bulk density of 1.46 g·cm^-3 and the apparent porosity of 55.0%.In addition,it is found that self-decomposition of talc and the formation of forsterite can form pores inside the specimen.

Effect of calcination temperature on properties of MgO-MgAl₂O₄-Mg₂SiO₄ complex porous materials prepared from magnesite tailings

Zhou Ping, Ma Beiyue, Ren Xinming

2023, (2): 104-106. doi：10.3969/j.issn.1001-1935.2023.02.003

Abstract ( ) PDF (1481KB)( )

MgO-MgAl₂O₄-Mg₂SiO₄ specimens were prepared by mixing raw materials according to m(magnesite tailings)∶m(secondary aluminum ash)=7∶3,shaping,and calcining at 1 200,1 300,1 400 and 1 500 ℃,respectively.The effect of the calcination temperature on the properties of the prepared specimens was studied.The results show that with the increase of the calcination temperature,the bulk density and the linear shrinkage of the specimens increase,the cold compressive strength basically increases,while the apparent porosity decreases accordingly;when the calcination temperature increases from 1 300 ℃ to 1 400 ℃,the apparent porosity of the specimens changes significantly.This is related to the formation of magnesium aluminate spinel.Under the condition of the apparent porosity exceeding 40%,the specimens calcined at 1 300 ℃ has a higher cold compressive strength.Therefore,the optimum calcination temperature is 1 300 ℃.

Effect of CaO impurity on mullite formation from SiO₂ gel and Al₂O₃ powders

Geng Qiankun, Yang Zhuoran, Hu Qianying, Tian Xuekun, Wang Hongsen, Shen Jiaxin, Ouyang Deze, Liu Xinhong

2023, (2): 107-112. doi：10.3969/j.issn.1001-1935.2023.02.004

Abstract ( ) PDF (3384KB)( )

To broaden the application of SiO₂ sol-bonded castables,using micro- or nano-Al₂O₃ powder and SiO₂ gel powder as the main raw materials,the effects of CaO impurity on the formation of mullite from the reaction of Al₂O₃ and SiO₂ at different temperatures (1 350,1 400,1 500,and 1 600 ℃) and in different atmospheres (oxidation atmosphere and reduction atmosphere) were studied.The results show that:(1)in oxidizing atmosphere,the introduction of CaO can promote the formation of mullite;when the temperature increases from 1 350 ℃ to 1 600 ℃,the formation of mullite gradually increases;(2)in reducing atmosphere,the introduction of CaO is not conducive to the formation of mullite,and the mullite formation decreases with the increasing temperature;(3)the smaller the particle size of Al₂O₃,the more easily it reacts with SiO₂ gel powder to generate mullite.

Analysis of corrosion mechanism of slag-line refractories of ZrO₂-C submerged entry nozzles

Tian Chen, Zhi Jianjun, Gan Feifang, Fan Zhengjie, Gao Hua, Yuan Lei, Liu Guoqi, Yu Jingkun, Li Hongxia

2023, (2): 113-116. doi：10.3969/j.issn.1001-1935.2023.02.005

Abstract ( ) PDF (1993KB)( )

In view of the service failure and low continuous casting production efficiency due to the corrosion of refractories at slag-line in the submerged entry nozzles,a submerged entry nozzle for the low-carbon aluminum killed steel continuous casting in one steel plant was sampled and taken as the research object to analyze the causes and the mechanism of refractory corrosion at the slag-line.The results show that the core issue of the corrosion and necking of the slag-line materials is that the slag-line material are eroded,dissolved,and reacted by the mold flux gradually.Therefore,it is important to suppress or avoid the contact and reaction between the mold flux and slag-line materials.

Modification of flake graphite with magnesium hydroxide by hydrothermal method

Zhou Ruiqi, Fan Huilin, Wang Zhiming, Cai Weijie, Duan Hongjuan, Zhang Haijun

2023, (2): 117-120. doi：10.3969/j.issn.1001-1935.2023.02.006

Abstract ( ) PDF (2166KB)( )

In order to improve the water wettability of flake graphite,a magnesium hydroxide modified layer was coated on the surface of flake graphite by the hydrothermal method with anhydrous magnesium sulfate and ammonia as the main raw materials.The effects of the surfactant types (sodium dodecyl benzene sulfonate and sodium polyacrylate),the hydrothermal temperature (180,190,and 200 ℃) and the mass ratio of C to Mg²⁺ (1∶10,2∶10,and 3∶10) on the water wettability and the oxidation resistance of modified flake graphite were mainly studied.The results show that:(1)magnesium hydroxide is coated on the surface of the modified flake graphite,improving its water wettability and oxidation resistance;(2)the modified flake graphite prepared with sodium polyacrylate as the surfactant,the C/Mg²⁺ mass ratio of 3∶10,and the hydrothermal treatment at 190 ℃ for 12 h has the best water wettability and oxidation resistance.

Influence of silica fume addition on properties of β-SiAlON-SiC material

Cao Huiyan, Zheng Han, Qian Fan, Wu Jiguang, Wan Longgang, Ma Zhaoyang

2023, (2): 121-124. doi：10.3969/j.issn.1001-1935.2023.02.007

Abstract ( ) PDF (1905KB)( )

Under the premise of keeping good alkali resistance of β-SiAlON-SiC material used as saggers for firing ternary cathode materials of lithium batteries,β-SiAlON-SiC materials were prepared with SiC particles and fine powder,Si powder,Al powder and α-Al₂O₃ micropowder as starting materials by the high temperature nitridation method.The influences of the silica fume addition (0,1%,2%,and 3%,extra adding,by mass) on the apparent porosity,the bulk density,the cold modulus of rupture,the hot modulus of rupture,the phase composition and the alkali resistance were researched.The results show that:(1)the silica fume addition reduces the apparent porosity,and increases the cold modulus of rupture and the hot modulus of rupture greatly;(2)the silica fume addition does not affect the nitridation of Si powder and Al powder,while impedes the solid solubility of Al₂O₃ in Si₃N₄ and the formation of β-SiAlON;(3)the optimal silica fume addition is 1% and the obtained sample has much better alkali resistance than that without silica fume.

Lithium hydroxide corrosion resistance of three sagger materials

Zheng Han, Ma Zhaoyang, Cao Huiyan, Wan Longgang, Xiang Yubo, Qian Fan, Wu Jiguang

2023, (2): 125-130. doi：10.3969/j.issn.1001-1935.2023.02.008

Abstract ( ) PDF (4411KB)( )

In order to get sagger material with high alkali resistance and suitable for ternary cathode material,LiOH·6H₂O was placed on the surface of recrystallized SiC sagger material and β-SiC bonded SiC sagger material,respectively,to investigate their corrosion at 780 ℃ for 20 h in oxygen atmosphere.The two sagger materials were compared with the commercial cordierite-mullite saggar material.The microstructure and the phase composition of the three materials were analyzed by SEM and XRD.The results show that:(1)a reaction layer with a thickness of 4.2 mm is formed on the surface of β-SiC bonded SiC material after corrosion; there is no obvious reaction layer on the surface of the recrystallized SiC material; the surface of cordierite-mullite material becomes uneven,and a reaction layer with a depth of about 1.8 mm is formed below the surface;(2)the density of sagger materials can significantly affect the penetration depth of Li₂O;the β-SiC bonded SiC material is denser and the penetration of Li₂O is shallower;the volume expansion caused by the reaction seriously damages the surface structure of the material;(3)the apparent porosity and the pore size of the recrystallized SiC material are larger than those of the β-SiC bonded SiC material,Li₂O can penetrate into the recrystallized SiC more easily and form Li₂SiO₃ in the internal pores,but the overall structure of the material is not affected obviously.

Alkali corrosion resistance of different alumina-silica refractory bricks for cement kilns

Ma Shulong, Kang Jian, Yang Chen, Meng Linghan, Xi Hanbo, Su Yuzhu, Ma Fei, Li Yanjing, Luo Huaming

2023, (2): 131-134. doi：10.3969/j.issn.1001-1935.2023.02.009

Abstract ( ) PDF (2954KB)( )

The alkali corrosion resistance of commercial SiC-mullite brick 1 680,SiC-mullite brick 1 550,spalling resistant high alumina brick JA,and low alumina mullite brick M55 was tested by the crucible method.The phase composition and the microstructure of the bricks after corrosion and the alkali corrosion behavior were discussed.The results show that:(1)the alkali corrosion resistance of the SiC-mullite bricks and low alumina mullite bricks is better,while that of the spalling resistant high alumina brick is worse;(2)the silicon carbide in the SiC-mullite bricks oxidizes at high temperatures,forming a dense layer on the surface of the bricks,which can effectively inhibit the infiltration of K element,so the material has excellent alkali corrosion resistance;the spalling resistant high alumina brick,due to the low grade raw materials,has high porosity and the deepest alkali penetration depth;a large amount of kaliophylite forms,leading to big cracks,so the material has poor alkali resistance;(3)the low alumina mullite brick has low porosity,whose raw materials are mullite homogenous materials and andalusite with a dense structure;a certain amount of high silicon amorphous phase can react with K element producing high viscosity glass phases to block pores,so the brick has better alkali corrosion resistance.

Effect of modified multilayer graphene addition on properties of Al₂O₃-SiC-C castables

Zhu Yening, Xi Zijian, Yu Baisong, Su Yuqing, Tu Junbo, Wei Juncong, Huang Jiankun, Wang Yilong

2023, (2): 135-138. doi：10.3969/j.issn.1001-1935.2023.02.010

Abstract ( ) PDF (943KB)( )

In order to make better use of multilayer graphene with poor hydrophilicity in Al₂O₃-SiC-C iron trough castables,multilayer graphene was modified using silica sol,and then added to Al₂O₃-SiC-C castables for iron trough.Effects of the silica sol modified multilayer graphene addition (extra addition,0,0.05%,0.1%,0.15%,0.2%,by mass) on the fluidity,the linear change on heating,the apparent porosity,the cold strength and the hot strength were researched.The results show that:(1)with the same water addition,the flow value of the castables decreases linearly with the modified multilayer graphene addition increasing;(2)with the modified multilayer graphene addition increasing,the density,the cold strength,and the hot strength of the castables after drying or heat treatment at different temperatures increase first and then decrease,and reach the maximum with 0.1% of modified multilayer graphene.

Preparation and properties of SiC assembled large block for blast furnace tuyere

Lyu Chunjiang, Chang Cheng, Huang Yifei, Cao Huiyan, Li Jie, Zhu Chong

2023, (2): 139-144. doi：10.3969/j.issn.1001-1935.2023.02.011

Abstract ( ) PDF (3564KB)( )

SiC assembled large blocks for blast furnace tuyere 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,and ρ-Al₂O₃,etc.as raw materials.The new blocks were compared with silicon nitride bonded silicon carbide brick,self-bonded silicon carbide brick and imported self-bonded silicon carbide brick to analyze and evaluate their service performance.The results show that:(1)in the 0-100 mm zone,the new SiC large block manly consists of composites of β-SiC and one or more nitrides such as O’-SiAlON,β-SiAlON,α-Si₃N₄,and Si₂N₂O,the bulk density is 2.68-2.70 g·cm^-3,the apparent porosity is 14%-15%,and the material structure is uniform;(2)in the 0-100 mm zone,β-SiC nano-whiskers intercalate with nitrides;with the depth increasing,the flocculent β-SiC nano-whiskers increase,while the nitrides decrease;when the depth reaches 150 mm or more,the main bonding phases are β-SiC and mullite;(3)compared with the reference products,the new SiC block has a good basic performance,and after alkali corrosion,the mass change rate is -0.1%,which is obviously superior to the imported self-bonded silicon carbide and the homemade silicon nitride bonded silicon carbide materials.

Effect of Sc₂O₃ on properties of magnesia prepared from magnesite

Chen Lu, Zhang Ling, Meng Xin, Yang Yuxuan, Wan Jianqiang, Luo Xudong, You Jiegang

2023, (2): 145-148. doi：10.3969/j.issn.1001-1935.2023.02.012

Abstract ( ) PDF (2944KB)( )

In order to improve the properties of sintered magnesia,the light burned magnesia powder prepared by calcining magnesite at 900 ℃ was used as the main raw material and Sc₂O₃ was introduced as an additive.Sintered magnesia samples were obtained by calcining them at 1 600 ℃ for 3 h.Effects of the Sc₂O₃ addition (0,1%,2%,3% and 4%,by mass) on the density,the phase composition and the microstructure of the samples were studied.The results show that Sc₂O₃ can dissolve into MgO grains and cause lattice distortion of MgO,activating the lattice and promoting the sintering.At the same time,Sc₂O₃ reacts with the impurity CaO in magnesia to generate high-melting point phase CaSc₂O₄ among magnesite crystals.Therefore,adding Sc₂O₃ increases the density of the samples,and with 3% Sc₂O₃,the densification is the best.

Effect of different particle sizes zinc alumina spinel addition on properties of periclase-zinc alumina spinel

Xie Yonghuan, Tian Lin, Mao Shuo, Ma Shulong, Wu Shigang, Li Guohua

2023, (2): 149-152. doi：10.3969/j.issn.1001-1935.2023.02.013

Abstract ( ) PDF (2308KB)( )

Periclase-zinc alumina spinel specimens were prepared using high-purity magnesia (5-0.074 and ≤0.074 mm) as the main raw material,replacing the high-purity magnesia with zinc alumina spinel particles (5-0.074 mm) and the fine powders (≤0.074 mm) synthesized by the sintering method.Effects of the zinc alumina spinel particles addition (10%,15% and 20%,by mass) or fine powder addition (5%,10% and 15%,by mass) on the properties of the specimens were studied.Their properties were compared with those of commercial hercynite bricks,respectively.The results show that:(1)with the increase of the zinc alumina spinel particles addition,the apparent porosity of the specimens increases,the bulk density and the cold crushing strength decrease,and the thermal shock resistance slightly improves;(2)with the increase of the zinc alumina spinel fine powder addition,the cold physical properties and the thermal shock resistance of the specimens increase;(3)when zinc alumina spinel is introduced as 10% particles or 5%-10% fine powder,the corrosion resistance of the specimens is better than that of the hercynite brick used in cement kiln at present.In summary,the specimens with 5% zinc alumina spinel fine powder have the best performance.

Effect of Al/Si composite powder coating modified corundum particles on properties of Al₂O₃-C materials

Liu Yang, Liu Baoliang, Shi Kai, Ma Shihang, Shang Jianzhao, Xia Yi

2023, (2): 153-156. doi：10.3969/j.issn.1001-1935.2023.02.014

Abstract ( ) PDF (1392KB)( )

First,Al/Si composite powder coating modified corundum particles were prepared using tabular corundum particles (1-3 mm),Al/Si composite powder (mass ratio of Al powder to Si powder=4∶0,3∶1 or 2∶2),and phenolic resin-ethylene glycol mixed solution as raw materials,stirring,baking at 180 ℃ and disintegrating.Then,Al₂O₃-C samples were prepared according to the conventional process.The cold and hot properties of the samples were tested.The phase composition and the microstructure were analyzed.The results show that:(1)adding Al/Si composite powder coating modified corundum particles into Al₂O₃-C samples can improve their density,cold and hot strengths,thermal shock resistance and oxidation resistance;the Al/Si composite powder with the mass ratio of Al powder to Si powder of 3∶1 is the optimum;(2)the Al powder and the Si powder fill in the depressions on the surface of the modified tabular corundum particles,which improves the forming density of the samples as well as the density,the strength and the oxidation resistance of the samples after baking and carbon embedded heat treatment;after high temperature carbon embedded heat treatment,the Al powder and the Si powder react to form non-oxides such as AlN,Al₄C₃ and SiC,which enhance the bonding of the modified corundum particles and the matrix,thus improving the thermal shock resistance and the strength of the samples.

Performance improvement and application of zirconia plates for slag skimming slide plates

Fang Binxiang, Mou Jining, Shi Yueming, Luo Ming, Xu Zhijiang, Yin Mingqiang

2023, (2): 157-160. doi：10.3969/j.issn.1001-1935.2023.02.015

Abstract ( ) PDF (2186KB)( )

The application status of the zirconia plate inlaid slag skimming slide plates in a 300 t converter in a steel plant was introduced,and the reasons for the spalling of the zirconia plate and the zirconia tube of the inner slide plate were analyzed.Through granulation and stability control,the performance of the zirconia plate and the zirconia tube was improved,achieving good mechanical properties and thermal shock resistance.The structure of the slag skimming slide plate was improved by integrating the zirconia plate with the zirconia tube to improve its resistance to mechanical damage.The improved slag skimming slide plate solved the spalling problem of the original zirconia plate and zirconia tube,and the service life was expected to reach 25 heats.

Preparation of SiC from organosilicon slurry solid waste

Wu Bowen, Wang Shuai, Guo Xiaolin, Xing Pengfei, Song Ailin, Zhuang Yanxin

2023, (2): 161-165. doi：10.3969/j.issn.1001-1935.2023.02.016

Abstract ( ) PDF (2259KB)( )

The organosilicon slurry solid waste was firstly pyrolyzed at high temperatures,pelletized with excess petroleum coke,and then prepared into SiC powder was by the carbothermal reduction method.The effect of the pyrolysis temperature (1 000,1 200,1 400 and 1 500 ℃) on the organosilicon slurry solid waste was studied.On this basis,the effects of the heat treatment temperature (1 550,1 650,1 750 and 1 850 ℃) and the holding time (15,30,45,60 and 75 min) on the preparation of SiC were investigated.The results show that when the pyrolysis temperature is 1 500 ℃,the organosilicon slurry solid waste can be pyrolyzed to a large extent,and the products are mainly SiC and cristobalite,which indicates that SiC can be prepared with the raw material by the metallurgical method.The optimum heat treatment temperature for excess carbon smelting is 1 750 ℃,obtaining the highest SiC content.The SiC grain size increases with the temperature further increasing.Prolonging the holding time at 1 750 ℃ is helpful to the reaction.The optimal holding time is 60 min,achieving the highest SiC content.However,when further prolonging the holding time,the granular SiC aggregates and grows to form massive SiC.

Effect of firing temperature on properties of titanium-based aluminate cement

Zhang Kangkang, Ma Shulong, Su Yuzhu, Yang Chen, Liu Lei, Li Yanjing, Luo Huaming

2023, (2): 166-168. doi：10.3969/j.issn.1001-1935.2023.02.017

Abstract ( ) PDF (1875KB)( )

Using ferrotitanium slag and calcia as raw materials,in the CaAl₂O₄-CaAl₄O₇-CaTiO₃ triangle of the Al₂O₃-CaO-TiO₂ phase diagram,the composition of 58% Al₂O₃,34% CaO and 8% TiO₂,by mass,was adopted as the batching formulation,whose aluminate alkalinity was 0.9.Cement clinker samples were prepared after batching,mixing,molding,firing at 1 300,1 400 and 1 450 ℃ for 30 min,respectively,taking out when the furnace interior is cooled to nearly 1 200 ℃,quenching in air,and then grinding (residue≤10% after sieving with a square hole mesh of 0.088 mm).The phase composition and the microstructure of the samples were analyzed.The setting time and the strength were tested.The results show that with the increase of the firing temperature,the amount of CA₂ in the cement clinkers increases and the amount of C₁₂A₇ decreases gradually.The cement clinker fired at 1 400 ℃ has the most CA,the shortest setting time and the highest early strength.

Research progress on boron-based antioxidants for carbon-containing refractories

Li Tao, Li Yage, Wu Shuai-bing, Li Hang, Lyu Junyi, Zhang Haijun

2023, (2): 169-174. doi：10.3969/j.issn.1001-1935.2023.02.018

Abstract ( ) PDF (996KB)( )

Carbon-containing refractories are widely used in key parts of steelmaking systems because of their excellent thermal shock resistance and slag resistance.However,the excessive carbon content in the refractories will lead to the carburization of molten steel and the increase of energy consumption.To satisfy the requirements of their low-carbon development,the research on high-efficiency antioxidants is of vital importance.Therefore,the action mechanism of antioxidants for carbon-containing refractories and the research progress of boron-based antioxidants were reviewed,emphasizing on the research and development of single-phase and composite boron-based antioxidants as well as their effects on the properties of carbon-containing refractories.Their development was also prospected.

Research status of rare earth salt thermal barrier/environmental barrier coatings

Liu Tao, Ma Beiyue, Zan Wenyu

2023, (2): 175-179. doi：10.3969/j.issn.1001-1935.2023.02.019

Abstract ( ) PDF (924KB)( )

With the increasingly harsh service environment of thermal barrier/environmental barrier coatings on the surface of hot end components in aerospace and other fields,the performance requirements of the coatings increase obviously.As a widely used material at present,Y₂O₃ partially stabilized ZrO₂ (YSZ) cannot fully meet the application requirements.Therefore,it is increasingly important to develop new coating materials with excellent performance for high temperature environment.As a new type of thermal barrier/environmental barrier coating materials,rare earth salts have been widely concerned and studied in China and at abroad because of their complex structure,low thermal conductivity and high thermal expansion coefficient.Therefore,the crystal structure,the mechanical properties and the thermal properties of several rare earth salt coating materials were reviewed,and their development was prospected.

Application progress on binders for magnesia refractories

Yang Zhongde, Lin Xin, Wang Shaoyang, Qi Xin, Luo Xudong

2023, (2): 180-184. doi：10.3969/j.issn.1001-1935.2023.02.020

Abstract ( ) PDF (970KB)( )

Magnesia refractories are widely used in iron and steel,metallurgy and other fields,whose binder type not only affects their quality,but also affects their microstructure and performance at high temperatures.The basic classification of the binders for magnesia refractories and their application in magnesia monolithic refractories and magnesia refractory products were summarized,and some suggestions on the application of the binders were put forward.

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