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Behavior of particles in front of metallic solid/liquid interface in electromagnetic field

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中国有色金属学会会刊：英文版 2003年第4期13卷 755-763页

作者：钟云波任忠鸣孙秋霞江志文邓康徐匡迪 Shanghai Enhanced Laboratory of Ferrous metallurgy

The first part deals with the behavior of particles theoretically, and the critical electromagnetic force needed to alter the behavior of particles was deduced under different conditions. It was proposed that applying electromagnetic force would change the distribution coefficient of the particles. By using the data from literatures, the migrating rate of SiC particle by electromagnetic force was calculated, which is far more than the critical rate of solidifying interface which will result in the engulfment of the SiC particle in the Al SiC matrix metal. Therefore the possibility of controlling the behavior of the particles in front of the solidifying interface by electromagnetic field was confirmed. In the second part, by using simulative experiments, the man made alternation of the behavior of the particles in front of the solidifying interface under electromagnetic field was observed, and the idea of changing the distribution of the particles in solidified metal by electromagnetic force was verified experimentally. It is shown that, the particle, which would be engulfed by the solidifying interface, would escape from the interface under electromagnetic buoyant force (EMBF), and the particles adherent to the interface would migrate toward it and be engulfed finally under EMBF. Further more, the particles being pushed by the interface would stay at the interface, the repulsive force exerted on the particles would be counteracted by EMBF, and then the particle would turn to be engulfed. Adjusting the direction and magnitude of EMBF could alter the distribution of the particles in the solidifying metal.

关键词：电磁连铸电磁场固液界面 EMBF 碳化硅铝合金

Effect of TiN Particles and Grain Size on the Charpy Impact Transition Temperature in Steels

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Journal of Materials Science & Technology 2012年第10期28卷 878-888页

作者： J.Du M.Strangwood C.L.Davis School of metallurgy and Materials University of Birmingham

The toughness of ferritic steels is influenced by the grain size distribution, second phase, precipitates and coarse inclusions. In this work an examination of the effect of coarse TiN particles （〉0.5 μm） and ferrite grain size on the Charpy impact transition temperature in high strength low alloyed steels has been carried out. Steels with high Ti content （up to 0.045 wt%）, have been heat-treated and furnace cooled to obtain a ferrite-pearlite microstructure with different ferrite grain sizes. Coarse TiN particle size and ferrite grain size distributions have been measured and Charpy impact testing has been carried out. Scanning electron microscopy （SEM） analysis has been used to measure the grain boundary carbide thickness and to determine if the coarse TiN particles are acting as cleavage initiation sites by fractographic analysis. The Charpy ductile-brittle transition temperatures （DBTT） have been predicted using standard literature equations, and compared to the measured values. The relationship between the ferrite grain size and coarse TiN particle size and number density in terms of whether the coarse TiN particles act as effective cleavage initiation sites is discussed in this paper.

关键词： TiN particles Grain size Charpy impact test Ductile-brittle transitiontemperatures (DBTT) Steels

Gas-solid reduction kinetic model of MgO-fluxed pellets

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International Journal of Minerals,metallurgy and Materials 2014年第1期21卷 12-17页

作者： Qiang-jian Gao Feng-man Shen Xin Jiang Guo Wei Hai-yan Zheng School of Materials and metallurgy Northeastern University

The reduction process of MgO-fluxed pellets was investigated and compared with traditional acidic pellets in this paper. Based on the piston flow concept and experimental data, a kinetic model fitting for the gas-solid phase reduction of pellets in tubular reactors （blast furnace, BF） was built up, and the equations of reduction reaction rate were given for pellets. A series of reduction experiments of pellets were carried out to verify the model. As a result, the experimental data and calculated result were fitted well. Therefore, this model can well describe the gas-solid phase reduction process and calculate the reduction reaction rate of pellets. Besides, it can give a better explanation that the reduction reaction rate （reducibility） of MgO-fluxed pellets is better than that of traditional acidic pellets in BF.

关键词： ore pellets magnesia reduction kinetics blast furnaces

Electrical conductivity of Na_3AlF_6-AlF_3-Al_2O_3-CaF_2-LiF(NaCl) system electrolyte

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中国有色金属学会会刊：英文版 2007年第1期17卷 181-186页

作者：阚洪敏王兆文班允刚石忠宁邱竹贤 School of Materials and metallurgy Northeastern University

A PGSTAT 30 and a BOOSTER 20A were used to measure cell *** conductivity was gained by the Continuously Varying Cell Constant *** conductivity of KCl was measured for *** results prove that the method is reliable and *** electrical conductivity of Na3AlF6-AlF3-Al2O3-CaF2-LiF(NaCl)system was studied by this *** energy of conductance was obtained based on the experiment *** experiments show that electrical conductivity is increased greatly with NaCl and LiF *** 1%LiF(mass fraction)results in corresponding increase of 0.0276 S/cm for superheat condition of 15℃.For NaCl,it is 0.024 S/*** conductivity is increased by 0.003 S/cm with 1℃temperature *** electrical conductivity is lower than that predicted by the WANG Model and higher than that predicted by the Choudhary Model.

关键词：电解质导电性过热性熔化工艺

Influence of Austenitizing Temperature on the Microstructure and Corrosion Resistance of 55Cr18Mo1VN High-Nitrogen Plastic Mould Steel

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Acta Metallurgica Sinica(English Letters) 2016年第12期29卷 1148-1160页

作者： Hua-Bing Li Wei-Chao Jiao Hao Feng Zhou-Hua Jiang Cui-Dong Ren School of metallurgy Northeastern University Key Laboratory for Ecological metallurgy of Multimetallic Mineral(Ministry of Education) Northeastern University

The influence of austenitizing temperature on the microstructure and corrosion resistance of 55Cr18MolVN high-nitrogen plastic mould steel was investigated. The microstructure, elemental distribution and Cr-depleted zone of different heat-treated samples were investigated by X-ray diffraction, electron probe microanalyzer analysis, and trans- mission electron microscopy. The corrosion resistance was evaluated using electrochemical measurements, and the analysis of passive film was carded out by X-ray photoelectron spectroscopy. The results indicated that the volume fraction of precipitates decreased, and the homogeneity of elements was improved with increasing austenitizing temperature. The degree of Cr-depleted zone around coarse M23C6 was severer than that around M2N, and pitting corrosion initiated preferentially around M23C6. The corrosion resistance of the samples increased with the austenitizing temperature. With the increase in austenitizing temperature, the passive film was thickened and Cr（III）cr2O3 in the inner layer of passive film was enriched, which enhanced the corrosion resistance of the steel. The higher content of nitrogen in solid solution at higher austenitizing temperature contributed to the increased intensity of CrN and NH3, leading to the increase in pH value in the pit, and promoting the repassivation of 55Cr18Mo1N steel.

关键词： High-nitrogen plastic mould steel Austenitizing temperature Microstructure Corrosion resistance Cr-depleted zone

Recovery of silica from sodium silicate solution of calcined boron mud

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Rare Metals 2016年第2期35卷 204-210页

作者： Zhi-Qiang Ning Yu-Chun Zhai Hong-Wei Xie Qiu-Shi Song Ka Yu School of Materials and metallurgy Northeastern University

The effect of several parameters on the recovery of silicon dioxide from calcined boron mud（CBM）such as stirring speed, temperature, sodium silicate concentration, and carbonation time was studied. The recovery of silicon dioxide is 88 % when the stirring speed is450 r min-1, temperature is 60 °C, sodium silicate concentration is 1 mol L-1, and the carbonation time is 6 *** effect of carbonation time on the recovery of silicon dioxide is divided into three kinetic regimes, and the carbonation process of sodium silicate solution follows a second-order reaction based on the double-film theory model. The apparent rate constant of the three kinetic regimes is 0.064, 3.178, and 1.130 L h mol-1, *** amorphous SiO_2 products obtained by carbonating the purified solution have 99.6 % purity and are spherical with diameters of about 100 nm.

关键词： Boron mud Carbonation Recovery Silicon dioxide

Cathodic electrophoretic deposition of α-Fe_2O_3 coating

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Journal of Central South University 2015年第6期22卷 2027-2035页

作者：马莉常通李小斌李志友张斗周科朝 School of metallurgy and Environment Central South University State Key Laboratory of Powder metallurgy (Central South University)

Submicro α-Fe2O3 coatings were formed using electrophoretic deposition(EPD) technique in aqueous media. The zeta potentials of different α-Fe2O3 suspensions with different additives were measured as a function of p H to identify the optimum suspension condition for deposition. Electrophoretic depositions of α-Fe2O3 coatings under different applied electric fields and deposition time were studied and the effects of applied voltages and deposition time on deposition rates and thicknesses were investigated. The particle packing densities of the deposits at various applied voltages and deposition time were also analyzed by a scanning electron microscope(SEM). The results show that crack-free α-Fe2O3 coatings with uniform microstructure and good adherence to the nickel substrates are successfully obtained. Electrophoretic deposited α-Fe2O3 coating from aqueous suspension is a feasible, low-cost and environmental friendly method.

关键词： electrophoretic deposition Fe2O3 coating aqueous solutions zeta potential

Thermodynamics and kinetics of extracting zinc from zinc oxide ore by the ammonium sulfate roasting method

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International Journal of Minerals,metallurgy and Materials 2015年第5期22卷 467-475页

作者： Yi Sun Xiao-yi Shen Yu-chun Zhai School of Materials and metallurgy Northeastern University

Thermodynamic analyses and kinetic studies were performed on zinc oxide ore treatment by （NH4）2SO4 roasting technology. The results show that it is theoretically feasible to realize a roasting reaction between the zinc oxide ore and （NH4）2SO4 in a temperature range of 573-723 K. The effects of reaction temperature and particle size on the extraction rate of zinc were also examined. It is found that a surface chemical reaction is the rate-controlling step in roasting kinetics. The calculated activation energy of this process is about 45.57 kJ/mol, and the kinetic model can be expressed as follows： 1 - （1 - α）1/3 = 30.85 exp（-45.57/RT）·t. An extraction ratio of zinc as high as 92% could be achieved under the optimum conditions.

关键词： zinc metallurgy extraction ammonium sulfate ore roasting thermodynamics kinetics

Tungsten carbide platelet-containing cemented carbide with yttrium containing dispersed phase

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中国有色金属学会会刊：英文版 2008年第1期18卷 104-108页

作者：张立陈述王元杰余贤旺熊湘君 State Key Laboratory of Powder metallurgy Central South University Changsha Mining and metallurgy Research Institute

A fine and platelet tungsten carbide patterned structure with fine yttrium containing dispersed phase was observed in liquid phase sintered WC-20%Co-1%Y2O3 cemented carbide with ultrafine tungsten carbide and nano yttrium oxide as starting *** comparing the microstructures of the alloy prepared by hot-press at the temperature below the eutectic melting temperature and by conventional liquid phase sintering,it is shown that hexagonal and truncated trigonal plate-like WC grains are formed through the mechanism of dissolution-precipitation(recrystallization)at the stage of liquid phase *** in the addition form of oxide exhibits good ability in inhibiting the discontinuous or inhomogeneous WC grain growth in the alloy at the stage of solid phase sintering.

关键词：水泥碳化物碳化颗粒烧结处理钇元素