2011年, 第18卷, 第5期　刊出日期：2011-05-15

  

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工艺
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  Removal of Phosphorus From High Phosphorus Iron Ores by Selective HCl Leaching Method

  XIA Wentang,REN Zhengde,GAO Yifeng

  中国钢铁期刊网. 2011, 18(5): 1-4.

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  The selective HCl leaching method was used to remove phosphorus from high phosphorus iron ores. The hydroxyapatite in high phosphorus iron ores was converted into soluble phosphate during the process of HCl leaching. The effects of reaction time, particle size, hydrochloric acid concentration, reaction temperature, liquidsolid ratio and stirring strength on the dephosphorization ratio were studied. The results showed that the dephosphorization ratio can exceed 98% under the conditions of reaction time 30-45 min, particle size ＜0147 mm, hydrochloric acid concentration 25 mol/L, reaction temperature 25 ℃, liquidsolid ratio 5∶1 and stirring strength 502-1276 s-1. After dephosphorization reaction, the content of phosphorus in iron ore complied completely with the requirements of steel production.
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  Influence of Iron Ore Characteristics on FeO Formation During Sintering

  WU Shengli,WANG Qingfeng,BIAN Miaolian,ZHU Juan,LONG Fangyi

  中国钢铁期刊网. 2011, 18(5): 5-10.

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  The influence of iron ore characteristics on FeO formation during sintering was examined mainly in terms of chemical composition and the melting characteristics of iron ores. Statistical regression and Xray diffraction were used to further explain the specific effect of iron ore characteristics on FeO formation. The results indicate that LOI (loss on ignition) in iron ores have a positive influence on FeO formation by promoting the sintering process of Fe2O3 decomposing and reducing. Silica contents in iron ores play a determining role in final content of FeO in sinter. The melting characteristics of iron ores significantly affect FeO formation during sintering.
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  Melting Characteristics of Iron Ore Fine During Sintering Process

  LI Hongge,,ZHANG Jianliang,PEI Yuandong,ZHAO Zhixing,MA Zejun

  中国钢铁期刊网. 2011, 18(5): 11-15.

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  The whole melting curve of iron ore during sintering process was obtained, and the melting characteristics of iron ore were defined and explained. The whole melting process of mixture, mixed by iron ore and CaO reagent at basicity of 20 and 40, respectively, was observed using a SiC heating furnace with camcorder unit, and the melting curves of mixture that were relative height vs temperature curves were obtained. Besides, the melting characteristics of iron ore during sintering were introduced through defining some points in the melting curves, such as liquid forming temperature, inflexion temperature and flowing temperature, and the meaning of different shapes of the melting curves was clarified.
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  Fractal Study on Raceway Boundary

  DI Zhanxia,LUO Zhiguo,HAN Yanzhi,ZOU Zongshu,LI Jiaxin

  中国钢铁期刊网. 2011, 18(5): 16-19.

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  The raceway has been studied extensively both theoretically and experimentally. The raceway boundary is coarse and fragmentary, but all of previous studies are based on Euclidean geometry, which regards the dimension of raceway as an integer. The fractal method of calculating raceway size, which describes boundary with extremely irregular or fragmentary characteristic, is brought forward in physical model. The fractal theory is used to calculate the fractal dimension of raceway boundary and the precise surface area of ellipsoidal raceway boundary. The result shows that the surface area based on fractal is larger than that based on Euclidean. And the surface area increases with the rise of blowing rate.
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  Mathematical Model Development of Raceway Parameters and Their Effects on Corex Process

  S C Barman,K P Mrunmaya,M Ranjan

  中国钢铁期刊网. 2011, 18(5): 20-24.

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  Corex is an alternative ironmaking process and raceway is one of the important areas to maintain the stability of the furnace. The raceway parameters are well established for blast furnace operation. But for Corex process, it has not yet been established and optimized. Thus, a mathematical model was developed to determine various raceway parameters such as RAFT (raceway adiabatic flame temperature), tuyere gas velocity and kinetic energy. The model provides an idea about the raceway geometry, zone temperature and kinetic energy accumulated in tuyere gas. Besides, all the raceway parameters have been analyzed to find out their effects on the Corex process. It is found that RAFT influences the gasification reaction kinetics and higher RAFT generates more CO in reduction gas, which improves the metallisation degree of the DRI in shaft. It is also found that increased gas velocity and kinetic energy generate more fines and demand more coke to maintain char bed permeability. High coke rate increases the production cost and lowers the production of hot metal.
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  Oscillation Characteristics of Molten Metal Free Surface Under Compound Magnetic Field

  DENG Anyuan,WANG Engang,XU Yongyi,ZHANG Xingwu,HE Jicheng

  中国钢铁期刊网. 2011, 18(5): 25-30.

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  The free surface waves of a molten lowmelting point Sn32%Pb52%Bi alloy under the imposition of an AC and a static magnetic field were visualized and recorded by use of a laser displacement sensor and a high speed video camera. The Fourier analysis method was used to analyze the oscillation characteristics. The results show that at the center of the free surface, the azimuthal and radial oscillation mode can be found simultaneously owing to AC magnetic field. With increasing coil current intensity, the amplitude and the main frequencies of the oscillations increase, and the azimuthal fluctuation at the center of the free surface is also enhanced. The fluctuation characteristics are closely related to the turbulent flow induced by the alternating electromagnetic force. A series of regular traveling waves can be observed on free surface, and the main frequencies of oscillations at threephase points decrease owing to superposing AC and static magnetic field. The static magnetic field can remarkably control the unstable swinging behavior of free surface. With increasing static magnetic flux density, the amplitude of oscillations at the center of free surface decreases firstly, and then increases, but the fluctuation amplitude at the triplephase point always reduces and keeps within 1 mm, and the azimuthal waves at the center of free surface are weakened. Especially at 144 T, the radial waves are dominant. The static magnetic flux density should be controlled in an appropriate range to obtain more stable free surface. With compound magnetic field, even if the static magnetic flux density is above 10 T, the free surface still vibrates with lower amplitude and dominant frequency.
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  Crystallization Behavior in FluorideFree Mold Fluxes Containing TiO2/ZrO2

  ZHANG Zuotai,LI Jing,LIU Peng

  中国钢铁期刊网. 2011, 18(5): 31-37.

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  The timetemperaturetransformation (TTT) diagrams of fluoridefree mold fluxes containing TiO2/ZrO2 were constructed through the confocal scanning laser microscope (CSLM) technique. It was found that the crystallization temperature of Ffree mold fluxes containing TiO2 or ZrO2 increases, while incubation time decreases with increasing basicity. The crystallization tendency increases with the zirconia addition in slag melt, as it may be thought that the addition solubility is limited in molten slag and the solid particles act as heterogeneous nucleation sites. Three types of crystal morphologies were observed, corresponding to different crystallization mechanisms. CaSiO3 and Ca3Si2O7 precipitate in the slag with low basicity, and Ca2SiO4 was formed with increasing basicity. The addition of TiO2 promotes the precipitation of CaTiO3. The logarithm of crystal growth rate increased with increasing isothermal temperature, suggesting that the crystal/melt interface reaction is the controlling step in the present experiment.
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  Calculation Method of Optimal Speed Profile for Hot Plate During Controlled Cooling Process

  WANG Bingxing,CHEN Xiaolin,TIAN Yong,WANG Zhaodong,WANG Jun,ZHANG Dianhua

  中国钢铁期刊网. 2011, 18(5): 38-41.

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  The healthy and rapid development of the controlled cooling technology was hampered by the uneven cooling phenomenon. During the process of hot plate production, the homogeneous cooling along the length direction of plate was constrained by lots of factors. And because the speed was a flexible control parameter, the calculation method of optimal speed profile was developed based on the measured start cooling temperature and its matrix equation was solved by the Cholesky decomposition method. The optimal speed profile was used in online control system. As a result, the temperature distribution along the plate length direction was relatively uniform, and 95% of measured final cooling temperature difference from the target temperature 700 ℃ was controlled within ±20 ℃.
材料
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  Effects of Finish Rolling Temperature on Microstructure and Mechanical Properties of FerriticRolled PAdded High Strength InterstitialFree Steel Sheets

  GUO Weimin,,WANG Zuocheng,,LIU Sheng,,WANG Xiebin,

  中国钢铁期刊网. 2011, 18(5): 42-46.

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  The steels were rolled at 3 different finishing temperatures. The mechanical properties were tested by tensile tests. The results show that as finish rolling temperature decreases from 620 to 560 ℃ in ferrite region, the deep drawability of ferriticrolled Padded high strength IF steels is improved, and r value rises from 114 to 137. Finish rolling temperature (FT) has less influence on other mechanical properties, such as yield strength, tensile strength and elongation. Microstructures of hot rolled and annealed steel sheets and precipitates of annealed steel sheets were also analyzed.
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  Effect of Tempering Temperature on Microstructure and Mechanical Properties of Steel Containing Ni of 9%

  ZHAO Xiqing,PAN Tao,WANG Qingfeng,SU Hang,YANG Caifu,YANG Qingxiang

  中国钢铁期刊网. 2011, 18(5): 47-51.

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  Mechanical properties of quenching, intercritical quenching and tempering (QLT) treated steel containing Ni of 9% were evaluated from specimens subject to various tempering temperatures. The detailed microstructures of steel containing Ni of 9% at different tempering temperatures were observed by optical microscope (OM) and transmission electron microscope (TEM). The volume fraction of austenite was estimated by XRD. The results show that high strength and cryogenic toughness of steel containing Ni of 9% are obtained when the tempering temperature are between 540 and 580 ℃. The microstructure keeps the dual phase lamellar structure after the intercritical quenching and there is cementite created in the Nirich constituents when tempering temperature is 540 ℃. When tempering temperatures are between 560 and 580 ℃, the reversed austenites (γ′) grow up and the dual phase lamellar structure is not clear. The γ′ becomes instable at 600 ℃. When tempered at temperature ranging from 500 to 520 ℃, the increase of dislocation density in the lamellar matrix makes both tensile strength and yield strength decrease. When tempered at 540 ℃ and higher temperature, the yield strength decreases continuously because the C and alloying elements in the matrix are absorbed by the cementite and the γ′, so the yield ratio is decreased by the γ′. There are two toughness mechanisms at different tempering temperatures. One is that the precipitation of cementite absorbs the carbon in the steel which plays a major role in improving cryogenic toughness at lower temperature. Another is that the γ′ and the purified matrix become major role at higher tempering temperature. When the tempering temperature is 600 ℃, the stability of γ′ is decreased quickly, even the transformation takes place at room temperature, which results in a sharp decrease of CharpyV impact energy at 77 K. The tempering temperature range is enlarged by the special distribution of cementite and the lamellar structure.
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  Microstructure and Properties of Mo Microalloyed Cold Rolled DP1000 Steels

  HAN Qihang,KANG Yonglin,ZHAO Xianmeng,L Chao,GAO Lufeng

  中国钢铁期刊网. 2011, 18(5): 52-58.

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  Two kinds of ultrahigh strength cold rolled dual phase steels have been developed by designing CSiMnCr and CSiMnCrMo alloy systems. Tensile strength and elongation of both steels exceed 1100 MPa and 10%, respectively. The microstructures of both steels consist of massive martensite and ferrite. And the massive martensite of Mofree steel disperses in the ferrite with volume fraction of 64%. However, the massive martensite of Mocontaining steel is connected or closed by small martensite islands each other, and martensite volume fraction is 69%. As to Mofree steel, the yield strength, yield ratio, and work hardening exponent n are 548 MPa, 049, and 026, respectively. As for Mocontaining one, the yield strength, yield ratio, and n value are 746 MPa, 066, and 033, respectively. Besides, the ferrite of Mofree steel is deformed at the initial stage of plastic deformation. However, for Mocontaining one, Mo solution strengthened ferrite and small overaged martensite islands are deformed preferentially at small strain, which causes the yield strength to reach approximately 200 MPa higher than that of Mofree steel.
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  Influence of Hot Press Forming Techniques on Properties ofVehicle High Strength Steels

  CHANG Ying,MENG Zhaohuan,YING Liang,LI Xiaodong,MA Ning,HU Ping

  中国钢铁期刊网. 2011, 18(5): 59-63.

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  Based on the combination of materials science and mechanical engineering, hot press forming process of the vehicle high strength steels was analyzed. The hot forming process included: heating alloys rapidly to austenite microstructures, stamping and cooling timely, maintaining pressure and quenching. The results showed that most of austenite microstructure was changed into uniform martensite by the hot press forming while the samples were heated at 900 ℃ and quenched. The optimal tensile strength and yield strength were up to 1530 MPa and 1000 MPa, respectively, and the shape deformation reached about 23%. And springback defect did not happen in the samples.
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  Fatigue Behaviour of Naval Steel Under Seawater Environmental and Variable Loading Conditions

  C Gheorghies,L Palaghian,S Baicean,M Buciumeanu,S Ciortan

  中国钢铁期刊网. 2011, 18(5): 64-69.

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  The way to characterize the behaviour of a naval steel grade E36 subjected to the corrosive fatigue process is investigated. The tests were carried out by bending fatigue of plate specimens with thickness of 10 mm in the corrosive environment consisting of an aqueous solution of 35% of NaCl which is similar to seawater. Experimental results show that the principal mechanism of degradation of the superficial layer is based on the pit evolution, evidenced by electrochemical, micro and macro structural timely changes such as evolution of electrode potential, evolution of current density, polarization resistance, anodic and cathodic parameters, and dislocation density evolution.
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  Development of Data Sheets for Statistical Evaluation of Fatigue Data

  YU Jia,Gary Marquis,Timo Bjrk

  中国钢铁期刊网. 2011, 18(5): 70-78.

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  Instructions were developed for statistical analysis of the laboratory fatigue data stepbystep. Practical cases for solving several questions raised in the treatment of test data, which involved estimation of necessary sample size, verification of the statistical equivalence of the collated sets of data, and determination of characteristic curves in different cases, were given by using the methods and formulae in the document IIWXIII213806 (best practice guide on the statistical analysis of fatigue data) as a demonstration of various statistical methods of developing a sound procedure for creating reliable calculation rules for the fatigue analysis.