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Enhanced slag resistance and mechanical properties of magnesia castables with strontium carbonate addition

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Journal of Iron and Steel Research(International) 2023年第10期30卷 2021-2030页

作者： Hao Liu Yu-xuan Zhu Zhou-fu Wang Yan Ma Xi-tang Wang The state key laboratory of refractories and metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina

Magnesia castables have been widely used in metallurgical industries with the advantages of high refractoriness,non-polluting steel,and resistance to alkaline slag.Magnesia castables were prepared using strontium carbonate(SrCO_(3))as additive to enhance slag resistance and mechanical properties,and the influence of SrCO_(3) on the evolution of phases,microstructure and properties of magnesia castables sintered at different temperatures was clarified.The results show that,with the introduction of SrCO_(3)(lower than 3 wt.%),elastic modulus,mechanical strength,thermal shock resistance and densification of magnesia castables were significantly enhanced owing to the formation of needle-like Ca_(0.9)Sr_(0.1)MgSi_(2)O_(6) phase and liquid phase when sintering at high temperatures,and the introduced SrCO_(3) presented minor effects on the mechanical properties of castables for its highly structural stability below 1100℃.During the slag corrosion process,SrCO_(3) and SiO_(2) in castables reacted with Al^(3+)in molten slag to form SrAl_(2)SiO_(8) phase,resulting in the increased slag viscosity and suppressed continuing penetration.

关键词： Magnesia castable SrCO_(3) Microstructure Slag resistance Mechanical property

Application of calcium alumino-titanate to taphole clay

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Journal of Iron and Steel Research(International) 2022年第7期29卷 1089-1100页

作者： Mao-qi Ju Man-fei Cai Yong-he Liang Jian-hua Nie Meng-zhen Guo The state key laboratory of refractories and metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina

Calcium alumino-titanate(CAT)can be used as a raw material owing to its excellent refractoriness and thermal expansion.CAT-containing taphole clay(THC)with different particle sizes was prepared and characterized.The results indicated that THC with CAT aggregate has better thermo-mechanical performance than that with a fine CAT powder because of different sintering processes.The CAT aggregate and SiO_(2)reacted and formed liquid phase covering their surface,enhancing the bonding of the particle–matrix and promoting the internal transformation of the substance.Further,the mullite was formed in aggregate with the interwoven network structure.Fine CAT powder has a higher specific surface area,and its surface energy decreases with the particle size.This could cause a reaction between CAT and SiO_(2)at relatively low temperature,making it unable to form a core–shell structure similar to that of the aggregate,with the excessive liquid phase affecting the performance of the samples.Meanwhile,the liquid phase was formed to close the pores and cover the SiC surface,and this was found to enhance the oxidation resistance.A corrosion test confirmed that the THC refractories with CAT aggregates showed better corrosion resistance than other samples.Scanning electron microscopy and energy-dispersive spectrometry results indicated that Ti(C,N)transformed by TiO_(2)in CAT was deposited at the interface between the molten slag and the refractory,and it efficiently prevented the penetration and reaction owing to its high melting point and small wetting angle with the slag.

关键词： Taphole clay Calcium alumino-titanate Microstructure Corrosion resistance

Rheological and mechanical properties of aluminosilicious cementitious materials as refractory castable binders

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Journal of Iron and Steel Research(International) 2022年第7期29卷 1145-1151页

作者： Zhong-feng Xia Chang-hao Chen Wen-hao Chi Zhou-fu Wang Hao Liu Yan Ma Xi-tang Wang The state key laboratory of refractories and metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina

Metakaolin(MK)is an important refractory raw material,which has been used as a cementitious material.In order to improve the bonding strength of MK,the composite cementitious materials were prepared by MK mixed with hydrat-able alumina(HA)and microsilica(MS),respectively.The silane coupling agent(SCA)was introduced as a modifying agent.The rheological properties of MK-based composite cementitious slurries were investigated.The mechanical properties of corundum castables bonded with the composite cementitious materials and calcium aluminate cement(CAC)were comparatively studied.The results show that SCA improves the rheological properties of MK-based composite cementitious materials.The slurry of MK–MS mixture flows in a plastic manner,while the slurry of MK–HA mixture presents pseudoplastic flow.The addition of SCA reduces the yield stress value of the MK–HA slurry.The bonding strength of castables bonded with MK-based composite cementitious materials is lower than that of CAC bonding castables.The room temperature strength of MK–MS composite bonding castable remains the highest after being treated either at 1100 or 1550°C,and its high temperature modulus of rupture is higher than that of CAC bonding castables with microsilica added.

关键词： Metakaolin Hydratable alumina Microsilica Silane coupling agent Corundum castable Calcium aluminate cement

TiO_2 hierarchical pores/nanorod arrays composite film as photoanode for quantum dot-sensitized solar cells

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Journal of Energy Chemistry 2019年第3期28卷 1-7页

作者： Xing Du Lei Zhao Xuan He Hui Chen Weixin Li Wei Fang The state key laboratory of refractories and metallurgy Wuhan University of Science and Technology

Power conversion efficiency(PCE) of quantum dot-sensitized solar cells(QDSSCs) was boosted in a TiO_2 composite film(TCSF) with delicate design in structure where TiO_2 hierarchical porous film(THPF) situated on the top of TiO_2 nanorod arrays film(TNAF). In this case, TNAF could supply efficient scattering centers for high light harvesting and direct electrical pathways for fast electron transfer while the THPF could offer porous channels for loading high quantity of previously synthetized quantum dots(QDs) and facilitate the penetration of electrolyte. Meanwhile, in this specific configuration, the presence of anatase–rutile heterojunction at the interface could help the rutile TNAF layer to efficiently collect photo-injected electrons from the anatase THPF layer thus suppressing the recombination of electrons and holes in electrolyte. The results showed that the PCE of QDSSC based on the TNAF photoanode was about 1.4-fold higher(η = 3.05%, J_(sc)= 15.86 m A cm^(-2), V_(oc)= 0.602 V, FF = 0.319) than that of device based on pure THPF(η = 2.20%, J_(sc)= 13.82 m A cm^(-2), V_(oc)= 0.572 V, FF = 0.278).

关键词： Hierarchical pores Nanorod arrays Composite photoanode Quantum dot-sensitized solar cells

Precipitation and Solid Solution of Titanium Carbonitride Inclusions in Hypereutectoid Tire Cord Steel

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Journal of Iron and Steel Research(International) 2016年第4期23卷 338-343页

作者： Chen-fan YU Zheng-liang XUE Wu-tao JIN The state key laboratory of refractories and metallurgy Wuhan University of Science and Technology

The properties of titanium carbonitride Ti（CxN1-x） inclusions precipitated during solidification of tire cord steels and the thermodynamic conditions for their decomposition and solid solution during billet heating were investigated using a thermodynamics method. The solid solution of Ti（CxN1-x） inclusions during high-temperature heating was also studied experimentally. The results revealed that：（1） the higher the content of carbon in the tire cord steel is, the greater the value of .r in the Ti（CxN1-x） inclusions is; （2） the higher the content of carbon in the tire cord steel is, the earlier the Ti（CxN1-x） inclusions precipitated during the solidification process and the lower the solidification front temperature is during precipitation; （3） when an 82A steel sample was heated to 1087℃, the Ti（CxN1-x） inclusions possess the thermodynamic conditions of decomposition and solid solution; and （4） when 82A samples were heated to 1150 and 1 250℃, the total number of Ti（CxN1-x） inclusions larger than 5μm in diameter decreased by 55.0% and 70.3%, respectively. In addition, although smaller inclusions with diameter less than 2 μm continued to decompose when the sample was heated at 1 250℃ for 2 h and then cooled to 1000℃ in the furnace, the number of inclusions larger than 5 μm in diameter increased.

关键词： hypereutectoid tire cord steel titanium carbonitride inclusion precipitation solidification solid solution billet heating

Effect of Al Powder and Si Powder Additions on Structure and Properties of Unburned Magnesium Aluminate Spinel refractories

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China's refractories 2023年第3期32卷 14-19页

作者： ZHOU Lianzhuo WANG Zhoufu WANG Xitang LIU Hao MA Yan QUAN Zhenghuang The state key laboratory of refractories and metallurgy Wuhan University of Science and TechnologyWuhan 430081China

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 Al powder and Si powder additions on the properties and microstructure of the refractories heat treated at different temperatures(1000,1400,and 1600℃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 1000 or 1400℃,and meanwhile AlN reinforcement phase forms in the matrix,which greatly improves the hot modulus of rupture of the samples at 1400℃;however,the heat treatment at 1600℃has little influence on the strength;the addition of Al powder and Si powder results 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 samples added with Al and Si all have higher cold modulus of rupture than those added with Al powder only.

关键词： aluminum powder silicon powder magnesium aluminate spinel unburned refractories strength

Enhancing mechanical properties and air permeability of corundum porous materials by in situ formation of LaAl11O18 in bonding phase

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Journal of Rare Earths 2020年第2期38卷 195-202页

作者： Xin Xiong Zhoufu Wang Xitang Wang Hao Liu Yan Ma The state key laboratory of refractories and metallurgy Wuhan University of Science and TechnologyWuhan 430081China

Corundum porous materials of particle-packing type with different contents of in situ formed LaAl11O18were prepared using tabular corundum,reactive alumina and La2O3 powder as raw materials.The effects of the introduction of LaAl11O18 on the microstructure.phase composition and properties of the porous materials were investigated.The specimens were characterized by scanning electron microscopy.X-ray diffraction and mercury porosimetry.Results show that platelet-like LaAl11O18 is formed in situ by the reactions of La2O3 and Al2O3.With a certain amount of La2O3 added.the cold crushing strength,cold modulus of rupture and hot modulus of rupture(1400 x 0.5 h) of the specimens are increased,and the air permeability is improved simultaneously.However.upon further increasing the amount of La2O3 added,the mechanical properties and air permeability of the porous materials then decrease gradually owing to the increased numbers of pores and cracks in the bonding phase.The enhanced mechanical properties of the specimens with La2O3 added are attributed to the strengthening effects of plate-like LaAl11O18 in the bonding phase and to the activated sintering of both Al2O3 powder and corundum coarse aggregate for the diffusion of La3+in Al2O3 lattice.In addition,the improved air permeability of the specimens should be related to the decreased content of pores in the bonding phase and the reduced number of interfacial cracks.

关键词： Porous materials of particle-packing type Lanthanum hexaluminate Mechanical strength Strengthening mechanism Air permeability Rare earths

Effect of 0.5 mass% Cu Addition on Ductility and Magnetic Properties of Fe-6.5Si Alloy

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Journal of Iron and Steel Research(International) 2016年第7期23卷 717-721页

作者： Zhao-yang CHENG Jing LIU Wen-si CHEN Jia-chen ZHU Xi-feng LIN Zhi-dong XIANG The state key laboratory of refractories and metallurgy Wuhan University of Science and Technology

The effect of adding 0.5mass% Cu on ductility and magnetic properties of Fe-6.5Si（mass%）alloy was investigated.The alloys with and without 0.5mass% Cu addition were warm rolled into thin sheets of thickness no more than 0.3mm at temperature below 600 ℃.It was found that the alloy with 0.5mass% Cu addition was more easily warm rolled than Cu-free alloy.Tensile tests were carried out to further investigate this phenomenon,which confirmed that the ductility of the alloy with 0.5mass% Cu addition was significantly higher than that of Cu-free alloy at 550 ℃.Based on the results of transmission electron microscopy analysis,the ductility increase of the alloy with 0.5mass% Cu addition was attributed to the effect of Cu on the promotion of dynamic recovery and suppression of long-range order in the alloy during warm rolling process.It was also observed that the iron loss was lower and inductance was higher for the alloy with 0.5 mass% Cu addition.Thus,it can be concluded that adding a suitably small amount of Cu would not only increase the ductility of Fe-6.5Si alloy at warm rolling temperatures but also improve its magnetic properties.

关键词： Fe-6.5Si alloy alloying ductility magnetic property microstructure long-range order

Enhanced oxidation resistance of low-carbon MgO-C refractories with ternary carbides:a review

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Journal of Iron and Steel Research(International) 2022年第7期29卷 1052-1062页

作者： Chao Yu Bo Dong Yu-feng Chen Bei-yue Ma Jun Ding Cheng-ji Deng Hong-xi Zhu Jing-hui Di The state key laboratory of refractories and metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina School of metallurgy Northeastern UniversityShenyang 110819LiaoningChina

The demand for low-carbon MgO–C refractories is ever growing to meet the development of advanced steelmaking technologies and efficient energy conservation.Meanwhile,to improve the oxidation resistance and inhibit the weakness of low-carbon MgO–C refractories,antioxidants are necessary.The application of ternary carbides that focused on improving the oxidation performance of MgO–C refractories has been explored,and the ternary carbides including Al_(4)O_(4)C,Al8B_(4)C_(7),Al_(4)SiC_(4),Ti_(2)AlC,Ti_(3)AlC_(2),and Ti_(3)SiC_(2)have been proved effective.The crystal structure,physical properties,oxidation behavior,and synthesis of these ternary carbides were summarized,and their oxidation mechanism in assisting antioxidation of MgO–C refractories was discussed.In addition,the potential aspects related to the usage and development of ternary carbides in low-carbon MgO–C refractories were proposed.

关键词： Low-carbon MgO–C refractory Ternary carbide MAX phase Oxidation mechanism Oxidation resistance