2009年, 第16卷, 第2期　刊出日期：2009-04-15

  

• 全选
  |

Metallurgy and Metal Working
• Select
  Shift From Coke to Coal Using Direct Reduction Method and Challenges

  Okonkwo Paul Chukwuleke;CAI Jiuju;Sam Chukwujekwu;XIAO Song

  中国钢铁期刊网. 2009, 16(2): 1-0.

  摘要 ( )   可视化   收藏

  Ironmaking involves the separation of iron ores. It not only represents the first step in steelmaking but also is the most capitalintensive and energyintensive process in the production of steel. The main route for producing iron for steelmaking is to use the blast furnace, which uses metallurgical coke as the reductant. Concerns over the limited resources, the high cost of coking coals, and the environmental impacts of coking and sinter plants have driven steelmakers to develop alternative ironmaking processes that can use noncoking coals to reduce iron ores directly. Since the efficiency and productivity of modern large capacity blast furnaces will be difficult to surpass, blast furnaces will continue to retain their predominant position as the foremost ironmaking process for some time to come. The alternative ironmaking processes are therefore expected to play an increasingly significant role in the iron and steel industry, especially in meeting the needs of smallsized local and regional markets. It is likely that the importance of direct reduced iron (DRI) and hot metal as sources of virgin iron will continue to increase, especially in the developing countries where steelmaking is, and will be, primarily based on electric arc furnace (EAF) minimills. Consequently, the challenges that are faced by the new technology have to be embraced.
• Select
  Numerical Simulation of Combustion Characteristics in High Temperature Air Combustion Furnace

  WANG Aihua;CAI Jiuju;XIE Guowei

  中国钢铁期刊网. 2009, 16(2): 6-0.

  摘要 ( )   可视化   收藏

  The influences of air preheating temperature, oxygen concentration, and fuel inlet temperature on flame properties, and NOx formation and emission in the furnace were studied with numerical simulation. The turbulence behavior was modeled using the standard kε model with wall function, and radiation was handled using discrete ordinate radiation model. The PDF (probability density function)/mixture fraction combustion model was used to simulate the propane combustion. Additionally, computations of NOx formation rates and NOx concentration were carried out using a postprocessor on the basis of previously calculated velocities, turbulence, temperature, and chemical composition fields. The results showed that high temperature air combustion (HiTAC) is spread over a much larger volume than traditional combustion, flame volume increases with a reduction of oxygen concentration, and this trend is clearer if oxygen concentration in the preheated air is below 10%. The temperature profile becomes more uniform when oxygen concentration in preheated air decreases, especially at low oxygen levels. Increase in fuel inlet temperature lessens the mixing of the fuel and air in primary combustion zone, creates more uniform distribution of reactants inside the flame, decreases the maximum temperature in furnace, and reduces NOx emission greatly.
• Select
  Relationship Between Activity Interaction Parameters in FeC System and Temperature

  CHEN Erbao;LIU Maoliu;WANG Shijun

  中国钢铁期刊网. 2009, 16(2): 11-0.

  摘要 ( )   可视化   收藏

  Carbon solubility in FeMn melts (xFe=0102 3-0789 9, xMn=0055 1-0638 0) was measured experimentally at various temperatures. Using GibbsDuhem equation, in combination with the experimental results in this work, quoting experimental data reported in references, and by strict thermodynamic derivation and calculation, the relation equations between the activity interaction parameters in FeC system and temperature were obtained. The calculation equation of lnγFe in FeC system was also obtained. The calculated results show that these relation equations can be used to calculate the activity coefficients of carbon and iron in FeC system and can satisfy the necessary condition to satisfy GibbsDuhem equation and the necessary condition to satisfy the stability condition of system at high carbon content. The calculation formula for lnγC in FeMnC system was also obtained.
• Select
  Slag for Decopperization and Sulphur Control in Molten Steel

  WANG Jianjun;GUO Shangxing;ZHOU Li;LI Qiang

  中国钢铁期刊网. 2009, 16(2): 17-0.

  摘要 ( )   可视化   收藏

  Decopperization in molten steel with FeSNa2S slag was investigated in the laboratory. It was found that with an increase in FeS content of the FeSNa2S slag, the decopperization ratio increased. The decopperization ratio could reach the maximum of 716% in hot metal. The decopperization ratio was closely related to the carbon content, and the higher the carbon content, the higher was the decopperization ratio. Sulphur addition was found in the process of decopperization, and the increase in sulphur content of molten steel was about 02%-042%. However, by adding 30%-50% of BaO to the FeSNa2S slag, the addition of sulfur content in molten steel could be reduced by about 50%. The finer slag system composition was FeS∶Na2S∶BaO=40∶20∶40.
• Select
  Numerical Investigation of the Fluid Flow in Continuous Casting Tundish Using Analysis of RTD Curves

  Moumtez Bensouici;Ahmed Bellaouar;Kamel Talbi

  中国钢铁期刊网. 2009, 16(2): 22-0.

  摘要 ( )   可视化   收藏

  A detailed mathematical procedure of the optimization of the fluid flow in a tundish water model with and without flow control devices (weir and dam) was carried out using the commercial CFD code FLUENT 60. The (kε) twoequation model was used to model turbulence. The residence time distribution (RTD) curves were used to analyze the behavior of the flow in tundish. The location of flow control devices in the tundish was studied. The results show that the flow modifiers play an important role in promoting the floatation of nonmetallic inclusions in steel. Comparing the three geometric configurations that are considered (bare tundish, weir, weir+dam), the tundish equipped with the arrangement (weir+dam) is a best and optimal geometric configuration of tundish.
• Select
  Generalized Shape and Gauge Decoupling Load Distribution Optimization Based on IGA for Tandem Cold Mill

  PENG Peng;YANG Quan

  中国钢铁期刊网. 2009, 16(2): 30-0.

  摘要 ( )   可视化   收藏

  Load distribution is the foundation of shape control and gauge control, in which it is necessary to take into account the shape control ability of TCM (tandem cold mill) for strip shape and gauge quality. First, the objective function of generalized shape and gauge decoupling load distribution optimization was established, which considered the rolling force characteristics of the first and last stands in TCM, the relative power, and the TCM shape control ability. Then, IGA (immune genetic algorithm) was used to accomplish this multiobjective load distribution optimization for TCM. After simulation and comparison with the practical load distribution strategy in one tandem cold mill, generalized shape and gauge decoupling load distribution optimization on the basis of IGA approved good ability of optimizing shape control and gauge control simultaneously.
• Select
  Roll Eccentricity Compensation Based on AntiAliasing Wavelet Analysis Method

  CHEN Zhiming;LUO Fei;XU Yuge;YU Wei

  中国钢铁期刊网. 2009, 16(2): 35-0.

  摘要 ( )   可视化   收藏

  Roll eccentricity is an important factor causing thickness variations during hot strip rolling and might define the limit of strip thickness control accuracy. An improved multiresolution wavelet transform algorithm was proposed to compensate for the roll eccentricity. The wavelet transform method had good localization characteristics in both the time and frequency domains for signal analysis; however, the wavelet method had a frequencyaliasing problem owing to the less than ideal cutoff frequency characteristics of wavelets. This made its component reconstruction of an inaccurate signal. To eliminate inherent frequency aliases in the wavelet transform, fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) were combined with the Mallat algorithm. This synthesis was described in detail. Then, the roll eccentricity component was extracted from rolling force signal. An automatic gauge control (AGC) system added with a multiresolution wavelet analyzer was designed. Experimental results showed that the antialiasing method could greatly restrain the inverse effect of eccentricity and the thickness control accuracy was improved from ±40 μm to ±15 μm.
• Select
  Modeling and Optimization for Piercing Energy Consumption

  XIAO Dong;PAN Xiaoli;YUAN Yong;MAO Zhizhong;WANG Fuli

  中国钢铁期刊网. 2009, 16(2): 40-0.

  摘要 ( )   可视化   收藏

  Energy consumption is an important quality index in the production of seamless tubes. The complex factors affecting energy consumption make it difficult to build its mechanism model, and optimization is also very difficult, if not impossible. The piercing process was divided into three parts based on the production process, and an energy consumption prediction model was proposed based on the step mean value staged multiway partial least square method. On the basis of the batch process prediction model, a genetic algorithm was adopted to calculate the optimum mean value of each process parameter and the minimum piercing energy consumption. Simulation proves that the optimization method based on the energy consumption prediction model can obtain the optimum process parameters effectively and also provide reliable evidences for practical production.
• Select
  Friction Coefficient Between Rolling Tube and Mandrel of Full Floating Mandrel Mill

  ZHAO Zhiyi;XIE Jianxin;HE Xiaoming;DONG Kai;YU Yong;PAN Feng

  中国钢铁期刊网. 2009, 16(2): 45-0.

  摘要 ( )   可视化   收藏

  In the process of steel tube production, continuous tube rolling is the foremost forming procedure and the critical step that decides the dimension precision and the surface quality. In the actual production of the 140 mm full floating mandrel mill in Steel Tube Branch in Baosteel, steel T91 was chosen to be the typical sample, selfmade rolling force transducer and mandrel velocity testing equipment were used, and a series of comprehensive tests on rolling parameters including the rolling force and mandrel velocity were carried out. After the experiment, the friction state between rolling tube and mandrel was analyzed. The friction coefficient was calculated and the values of 0033-0074 in each mill were obtained. The friction coefficient increases obviously along the rolling direction.
Material
• Select
  Successive Boronizing and Austempering for GGG40 Grade Ductile Iron

  Murat Baydogan;Seckin Izzet Akray

  中国钢铁期刊网. 2009, 16(2): 50-0.

  摘要 ( )   可视化   收藏

  Boronizing and austempering were successively applied to a GGG40 grade ductile iron in order to combine the advantages of both process in a single treatment. This new procedure formed a 30 μm thick boride layer on the surface with subsurface matrix structure consisted of acicular ferrite and retained austenite. Reciprocating wear tests showed that successive boronizing and austempering exhibited considerably higher wear resistance than conventional boronizing having a subsurface matrix structure consisting of ferrite and pearlite.
• Select
  Transformation Behavior of Low Carbon Steels Containing Two Different Si Contents

  CAI Minghui;DING Hua;ZHANG Jiansu;LI Long;LI Xiaobin;DU Linxiu

  中国钢铁期刊网. 2009, 16(2): 55-0.

  摘要 ( )   可视化   收藏

  Continuous cooling transformation behaviors of low carbon steels with two Si contents (050% and 135%) were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling rates on γ transformation start temperature (Ar3), phase microstructures, and hardness were studied. The results show that, in the case of the deformation with the true strain of 04, the length of bainitic ferrite laths is significantly decreased in low Si steel, whereas, the M/A constituent becomes more uniform in high Si steel. An increase in cooling rates lowers the Ar3 greatly. The steel with higher level of Si exhibits higher Ar3, and higher hardness both under undeformed and deformed conditions compared with the steel with a lower Si content. Especially, the influence of Si on Ar3 is dependent on deformation. Such effects are more significant under the undeformed condition. The hardness of both steels increases with the increase of cooling rates, whereas, the deformation involved in both steels reduces the hardness.
• Select
  Development of NonQuenched Prehardened Steel for Large Section Plastic Mould

  LUO Yi;WU Xiaochun;MIN Yongan;ZHU Zhu;WANG Hongbin

  中国钢铁期刊网. 2009, 16(2): 61-0.

  摘要 ( )   可视化   收藏

  In order to meet the demand of prehardened steel for large section plastic mould and save energy, a nonquenched prehardened (NQP) steel is developed. The temperature field of a large block is researched by finite element method simulation and 9 test steels are designed in the laboratory. Their microstructures and hardness are investigated when they are air cooled and control cooled at cooling rate similar to the simulation. The result shows that the hardness uniformity through section is closely correlated to bainitic hardenability for the NQP steel, and the hardness of one test steel (027C195Mn104Cr045Mo01V) fluctuates between HRC 40 and 43 under both cooling conditions. The test steel has better machinability compared with C45 steel, and the NQP steel is produced successfully in the factory based on the laboratory results. Its microstructure is bainite, and it is distributed uniformly through the size of 460 mm×800 mm×3 200 mm.
• Select
  Effect of Surface Mechanical Attrition Treatment on Corrosion Behavior of 316 Stainless Steel

  HAO Yunwei;DENG Bo;ZHONG Cheng;JIANG Yiming;LI Jin

  中国钢铁期刊网. 2009, 16(2): 68-0.

  摘要 ( )   可视化   收藏

  The nanocrystalline microstructure of the surface of 316 stainless steel (316SS) induced by surface mechanical attrition treatment (SMAT) was determined by Xray diffraction (XRD) and scanning electron microscopy (SEM). The technique of hydrogen embrittlement was first used to obtain the information of the brittleness cleavage plane. The effects of SMAT and the following annealing process on the corrosion behavior of 316SS were investigated by potentiodynamic polarization curves and potentiostatic critical pitting temperature measurements. The results demonstrated that the nanocrystalline layer with an average grain size of 19 nm was produced. However, there were lots of cracks on the surface, which led to the degradation in the corrosion resistance of 316SS after SMAT. Nevertheless, after annealing treatment, the corrosion resistance of the nanocrystalline surface had been improved greatly. The higher the annealing temperature, the better was the corrosion resistance.
• Select
  Investigation on Metallurgical Factors Controlling Charpy Impact Toughness in 1Cr21Ni5Ti Duplex Stainless Steel

  YANG Zhuoyue;SU Jie;WANG Yaming

  中国钢铁期刊网. 2009, 16(2): 73-0.

  摘要 ( )   可视化   收藏

  Based on the fact that toughness degradation occurred in 1Cr21Ni5Ti duplex stainless steel during slow cooling in a temperature interval of 400-600 ℃ following brazed welding, a simulated embrittlement treatment was utilized to evaluate its embrittlement tendency. Accumulated experiences have shown that high Ti and Al contents led frequently to severe toughness deterioration. To elucidate this phenomenon, four heats with various Ti and Al contents were prepared in laboratoryscale melts, which were used to investigate the inherent embrittlement nature. The results have shown that 550 ℃ aging led only to a modest toughness reduction, whereas, aging around 475 ℃ resulted in ferrite embrittlement, regardless of Ti, Al levels. However, high Ti, Al levels reduced the austenite phase, which, in the case of its inferior shape and distribution due to insufficient hot deformation, failed to resist cleavagetype cracks initiated in the ferrite phase. Increasing hotforged areas reduction could modify the shape and distribution of austenite, resulting in the enhanced resistance of the austenite to the cleavagetype cracks, which have been confirmed to be beneficial for brittlement suppression of 1Cr21Ni5Ti duplex stainless steel.
• Select
  Artificial Neural Network Modeling of Microstructure During CMn and HSLA Plate Rolling

  TAN Wen;LIU Zhenyu;WU Di;WANG Guodong

  中国钢铁期刊网. 2009, 16(2): 80-0.

  摘要 ( )   可视化   收藏

  An artificial neural network (ANN) model for predicting transformed microstructure in conventional rolling process and thermomechanical controlled process (TMCP) is proposed. The model uses austenite grain size and retained strain, which can be calculated by using microstructure evolution models, together with a measured cooling rate and chemical compositions as inputs and the ferrite grain size and ferrite fraction as outputs. The predicted results show that the model can predict the transformed microstructure which is in good agreement with the measured one, and it is better than the empirical equations. Also, the effect of the alloying elements on transformed products has been analyzed by using the model. The tendency is the same as that in the reported articles. The model can be used further for the optimization of processing parameters, microstructure and properties in TMCP.
• Select
  Improved Electrical Insulation of Rare Earth Permanent Magnetic Materials With High Magnetic Properties

  CHANG Ying;WANG Dapeng;LI Wei;PAN Wei;YU Xiaojun;QI Min

  中国钢铁期刊网. 2009, 16(2): 84-0.

  摘要 ( )   可视化   收藏

  Rare earth permanent magnetic materials are typical electrical conductor, and their magnetic properties will decrease because of the eddy current effect, so it is difficult to keep them stable for a long enough time under a high frequency AC field. In the present study, as far as rare earth permanent magnets are concerned, for the first time, rare earth permanent magnets with strong electrical insulation and high magnetic performance have been obtained through experiments, and their properties are as follows: (1) Sm2TM17: Br=062 T, jHc=8037 kA/m, (BH)m=5897 kJ/m3, ρ=7 Ω·m; (2) NdFeB: Br=0485 T, jHc=76633 kA/m, (BH)m=3796 kJ/m3, ρ=9 Ω·m. The magnetic properties of Sm2TM17 and NdFeB are obviously higher than those of ferrite permanent magnet, and the electric insulating characteristics of Sm2TM17 and NdFeB applied have in fact been approximately the same as those of ferrite. Therefore, Sm2TM17 and NdFeB will possess the ability to take the place of ferrite under a certain high frequency AC electric field.
• Select
  In Situ Synthesis of Heat Resistant Gradient Composite on Steel Surface

  CUI Xianghong;WANG Feng;WANG Shuqi;YANG Zirun;GAO Mingjuan;WEI Minxian

  中国钢铁期刊网. 2009, 16(2): 89-0.

  摘要 ( )   可视化   收藏

  A heat resistant gradient composite was synthesized in situ on steel with the selfpropagating high temperature synthesis (SHS) reaction of 3NiAlTiC system during casting. The phases, microstructure, and composition of the composite were analyzed by using an Xray diffractometer (XRD), and a scanning electron microscope (SEM) coupled with an energydispersive Xray spectroscope (EDS). The formation mechanism of the composite is also discussed. TiC/Ni3Al/steel gradient composite is achieved by forming the gradient distributions of Fe, Ni, and Al, accompanied with the gradient variation of the microstructure from TiC/Ni3Al, to TiC/Ni3Al/steel, and to steel. The composite is in situ synthesized through whole reaction of 3NiAlTiC system in liquid steel and densification procedure, and the liquid steel infiltrates into pores in the SHS product and forces liquid Ni3Al to form selfcompaction further.