2008年, 第15卷, 第2期　刊出日期：2008-04-15

  

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Metallurgy and Metal Working
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  Thermodynamic Properties of MnC Melts

  CHEN Erbao;WANG Shijun

  中国钢铁期刊网. 2008, 15(2): 1-0.

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  Carbon solubility in MnFe melts (xMn=0161-0706, xFe=0034-0633) was measured experimentally at various temperatures. By thermodynamic derivation and calculation, the relationship between activity coefficient of carbon in infinite dilute solution of manganese in MnC system and temperature was obtained. Using GibbsDuhem relationship, the experimental results of this study, and experimental data reported in references, the relationship between other thermodynamic properties in MnC system and temperature were obtained by thermodynamic derivation and calculation.
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  Fluid Flow and Mixing in NonIsothermal Water Model of Continuous Casting Tundish

  Mehdi ALIZADEH;Hossein EDRIS;Ali SHAFYEI

  中国钢铁期刊网. 2008, 15(2): 7-0.

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  Fluid flow and mixing of molten steel in a twinslabstrand continuous casting tundish were investigated using a mixing model under nonisothermal conditions. This model led to a set of ordinary differential equations that were solved with a RungeKutta algorithm. Steady state water modeling was carried out under nonisothermal conditions. Experimental data obtained from the water model were used to calibrate the mixing model. Owing to the presence of a mixed convection in the nonisothermal conditions, a channelizing flow would be created in the fluid inside the tundish. A mixing model was designed that was capable of predicting RTD (residence time distribution) curves for different cases in nonisothermal conditions. The relationship between RTD parameters and the Tu (tundish Richardson number) was obtained for various cases under nonisothermal conditions. The results show that the RTD parameters were completely different under isothermal and nonisothermal conditions. The comparison of the RTD curves between the isothermal and nonisothermal conditions presents that the extent of mixing in the tundish in nonisothermal conditions is lower than the mixing extent in isothermal conditions.
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  Dynamic Water Modeling and Application of Billet Continuous Casting

  LIU Wenhong;XIE Zhi;JI Zhenping;WANG Biao;LAI Zhaoyi;JIA Guanglin

  中国钢铁期刊网. 2008, 15(2): 14-0.

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  The continuous casting process is used for solidifying molten steel into semifinished steel. The technology of secondary cooling is extremely important for output of the casting machine and billet quality. A dynamic water model was introduced, including solidification model in the secondary cooling, feedforward control strategy based on continuous temperature measurement in tundish, and feedback control strategy based on surface temperature measurement. The mathematical model of solidification process was developed according to the principle of solidification, and the solidification model was validated by measuring billet shell thickness through shooting nail and sulfur print. Primary water distribution was calculated by the solidification model according to procedure parameters, and it was adjusted by the other two control strategies online. The model was applied on some caster and billet quality was obviously improved, indicating that the dynamic water model is better than conventional ones.
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  Genetic AlgorithmBased Optimization Used in Rolling Schedule

  YANG Jingming;CHE Haijun;DOU Fuping;ZHOU Tao

  中国钢铁期刊网. 2008, 15(2): 18-0.

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  A genetic algorithmbased optimization was used for 1 370 mm tandem cold rolling schedule, in which the press rates were coded and operated. The superiority individual is reserved in every generation. Analysis and comparison of optimized schedule with the existing schedule were offered. It is seen that the performance of the optimal rolling schedule is satisfactory and promising.
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  High Precision Prediction of Rolling Force Based on Fuzzy and Nerve Method for Cold Tandem Mill

  JIA Chunyu;SHAN Xiuying;NIU Zhaoping

  中国钢铁期刊网. 2008, 15(2): 23-0.

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  The rolling force model for cold tandem mill was put forward by using the Elman dynamic recursive network method, based on the actual measured data. Furthermore, a good assumption is put forward, which brings a full universe of discourse selfadjusting factor fuzzy control, closedloop adjusting, based on error feedback and expertise into a rolling force prediction model, to modify prediction outputs and improve prediction precision and robustness. The simulated results indicate that the method is highly effective and the prediction precision is better than that of the traditional method. Predicted relative error is less than ±4%, so the prediction is high precise for the cold tandem mill.
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  Dynamic Decoupling for Combined Shape and Gauge Control System in Wide Strip Rolling Process

  LINGHU Kezhi;HE Anrui;YANG Quan;ZHAO Lin;GUO Xiaobo

  中国钢铁期刊网. 2008, 15(2): 28-0.

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  The precision of profile and thickness is the most important target for wide strip rolling, but the coupling of profile control and thickness control is ignored in rolling schedule, which holds down the simultaneous quality improvement of profile and thickness. A crosscoupled process control model for combined shape and gauge control was developed on the basis of the fact that both controls for profile and thickness are realized by controlling the rolling gap. A dynamic decoupling controller was then proposed to decouple the model. Both the simulation results and the online production data are valid and ensure the quality of the decoupling controller.
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  Determination of Forward Slip Coefficient During Heavy Rail Rolling Using Universal Mill

  DONG Yonggang;ZHANG Wenzhi;CAO Hui

  中国钢铁期刊网. 2008, 15(2): 32-0.

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  The forward slip coefficient is one of the most important parameters for heavy rail rolling using universal mill. For simplifying the theoretical model, the vertical roll with box pass was simplified as an equivalent flat roll first. Second, the neutral angle of horizontal roll and vertical roll was represented. Then, the equation of neutral line on the flank of horizontal roll was determined and the forward slip coefficient of the web was derived according to different positions of neutral line. Finally, the forward slip coefficient of the top and base of heavy rail was obtained. The theoretical results were basically in agreement with the experimental data.
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  Dynamic Optimization of Feedforward Automatic Gauge Control Based on Extended Kalman Filter

  YANG Binhu;YANG Weidong;CHEN Liangui;QU Lei

  中国钢铁期刊网. 2008, 15(2): 39-0.

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  Automatic gauge control is an essentially nonlinear process varying with time delay, and stochastically varying input and process noise always influence the target gauge control accuracy. To improve the control capability of feedforward automatic gauge control, Kalman filter was employed to filter the noise signal transferred from one stand to another. The linearized matrix that the Kalman filter algorithm needed was concluded; thus, the feedforward automatic gauge control architecture was dynamically optimized. The theoretical analyses and simulation show that the proposed algorithm is reasonable and effective.
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  Transient Temperature Analysis of Slab in Erdemir

  nal amdali;Murat Tun;Sedat ?瘙
  塁i?瘙
  塂bot

  中国钢铁期刊网. 2008, 15(2): 43-0.

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  A transient thermal model was developed for slab furnaces in Ereli Iron and Steel Works (Erdemir) in Turkey and the model was solved using the FlexPDE computer program. This program uses the finite element method. Program codes were written to solve the temperature distribution of slabs that are put into furnace at 25 ℃ and removed at about 1 250 ℃. To obtain the optimum slab exit temperature variation, the necessary air temperature inside the furnace was calculated to be 1 390 ℃. The slab temperature versus time and the temperature variation inside the slab were depicted.
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  Metal Spray Forming Process Examined Using Mathematical Model

  ZHANG Yin;HE Youduo;FAN Junfei;REN Sanbin

  中国钢铁期刊网. 2008, 15(2): 46-0.

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  The metal spray forming process was examined using the mathematical model simulation by Baosteel′s test and developed facilities. The mathematical model comprised of the probability and statistical analysis of the droplet mass behavior and predicted the shape and temperature distribution of the billet during the spray forming process.
Material
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  Influence of Mn Content and Hot Deformation on Transformation Behavior of CMn Steels

  LI Long;DING Hua;DU Linxiu;WEN Jinglin;SONG Hongmei;ZHANG Pijun

  中国钢铁期刊网. 2008, 15(2): 51-0.

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  The hot deformation behaviors and the microstructural evolution of plain CMn steels with similar contents of C and Si but different contents of Mn have been investigated by compressive processing using Gleeble1500 mechanical simulator. Influence of Mn and hot deformation on continuous cooling transformation of steels has been studied. The experimental results showed that deformation in austenite region accelerated transformation process, and the extent is dependent on the hot deformation and cooling conditions. The hot deformation would promote transformation process, but the increase of transformation temperature is dependent on Mn contents. The results have also shown that the effect of deformation on ferrite transformation becomes more obvious with the increase of Mn content at relatively low cooling rate.
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  Computer Simulation of Microstructure Evolution of 82B Rod at Different Cooling Rates

  XU Jinqiao;LIU Yazheng;ZHOU Shumei

  中国钢铁期刊网. 2008, 15(2): 56-0.

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  According to thermodynamics and kinetics of phase transformation, a mathematical model of phase transformation was proposed, and the microstructure evolution of an 82B rod at different cooling rates was simulated by using the FEM software Marc/Mentat, based on the measurement of timetemperature transformation (TTT) curves of the 82B rod. The simulated results were in good agreement with the actual measurements. From the results of computer simulation it was found that the cooling rate of the 82B rod, after laying, should be controlled within 5-8 ℃/s. In the microstructure of rod there were over 95% of pearlite volume fraction and a small quantity of dispersive martensite (less than 5%).
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  Dynamic CCT Diagram of Automobile Beam Steel With High Strength Produced by FTSR Technology

  WANG Xin;KANG Yonglin;YU Hao;CHEN Libin;KONG Qingfu

  中国钢铁期刊网. 2008, 15(2): 60-0.

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  The dynamic continuous cooling transformation (CCT) diagram and phase transformation rules of 510 MPa automobile beam steel, which is produced by a continuous casting of thin slab of FTSR technology in Tangshan Iron and Steel Co Ltd, are researched by thermal simulation experiment. The microstructure characteristics of the beam steel under different test conditions are studied by means of optical microscope and scanning electron microscope. The test results show that the critical temperatures of phase transformation Ar3 and Ar1 will all decrease with the increase of the cooling rate. When the cooling rate is lower than 20 ℃·s-1, the ferrite and pearlite phase transformations are the main parts; when the cooling rate is higher than 20 ℃·s-1, the bainite phase appears. Moreover, the microstructures of 510 MPa automobile beam steel produced by FTSR technology are also studied, and the results are basically in accordance with the CCT diagram gained from the test.
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  Effect of Controlled Cooling After Hot Rolling on Mechanical Properties of Hot Rolled TRIP Steel

  WU Di;LI Zhuang;L Huisheng

  中国钢铁期刊网. 2008, 15(2): 65-0.

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  A threestep cooling pattern on the runout table (ROT) was conducted for the hot rolled TRIP steel. Microstructural evolution during thermomechanical controlled processing (TMCP) was investigated. Processing condition of controlled cooling on a ROT in the laboratory rolling mill was discussed. The results indicated that the microstructure containing polygonal ferrite, granular bainite and a significant amount of the stable retained austenite can be obtained through threestep cooling on the ROT after hot rolling. TMCP led to ferrite grain refinement. Controlled cooling after hot rolling resulted in the stability of the remaining austenite and a satisfactory TRIP effect. Excellent mechanical properties were obtained through TMCP for the hot rolled TRIP steel.
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  Microstructures and Properties of X60 Grade Pipeline Strip Steel in CSP Plant

  DONG Ruifeng;SUN Ligang;LIU Zhe;WANG Xuelian;LIU Qingyou

  中国钢铁期刊网. 2008, 15(2): 71-0.

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  The microstructures and properties of X60 grade pipeline strip steel were researched. With Nb microalloying and TMCP, the X60 grade pipeline strip steel was developed in the Baotou CSP Plant. The mechanical properties meet the demands on machining and using of pipeline manufacture. The X60 strip steels had been used extensively, which had fine and uniform structures, good performance and excellent toughness.
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  Strengthening Mechanism of a New 700 MPa Hot Rolled High Strength Steel

  YI Hailong;DU Linxiu;WANG Guodong;LIU Xianghua

  中国钢铁期刊网. 2008, 15(2): 76-0.

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  The microstructural evolution in a 700 MPa hot rolled high strength steel was analyzed in terms of strengthening mechanisms. The results show that the hot rolled sheet steel has yield strength of 710 MPa with good elongation and toughness. The strength of the developed 700 MPa hot rolled high strength steel is derived from the cumulative contribution of fine grain size, dislocation hardening and precipitation hardening. The fine grain strengthening and precipitation hardening are the dominant factors responsible for such high strength, and the amount of precipitation hardening is two or four times higher than that of conventional microalloyed hot rolled sheet steels reported in the past. Good toughness is due to refinement of ferrite grain size.
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  Research, Development, and Production of VN Microalloyed High Strength Rebars for Building in China

  YANG Caifu;WANG Quanli

  中国钢铁期刊网. 2008, 15(2): 81-0.

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  The research, production, and application of VN microalloyed high strength rebars in China were reviewed. Enhanced nitrogen in vanadiumcontaining rebars promotes the precipitation of fine V(C, N) particles, and markedly improves the precipitation strengthening effectiveness of vanadium. Therefore, vanadium added to VN microalloyed rebars can be reduced by 40% compared to the same strength level of vanadiumcontaining rebars.
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  RBFType Artificial Neural Network Model Applied in Alloy Design of Steels

  YOU Wei;LIU Yaxiu;BAI Bingzhe;FANG Hongsheng

  中国钢铁期刊网. 2008, 15(2): 87-0.

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  RBF model, a new type of artificial neural network model was developed to design the content of carbon in lowalloy engineering steels. The errors of the ANN model are: MSE 0052 1, MSRE 1785%, and VOF 1932 9. The results obtained are satisfactory. The method is a powerful aid for designing new steels.
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  Influence of Frequency and Bias Current on Asymmetrical GMI Effect in Co718Fe49Nb08Si75B15 Amorphous GlassCovered Wires

  CHEN Zheng;LI Deren;LU Zhichao;ZHOU Shaoxiong;

  中国钢铁期刊网. 2008, 15(2): 91-0.

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  The Co718Fe49Nb08Si75B15 amorphous glasscovered wires (AGCW) are prepared by the TaylorUlitovsky technique. The frequency dependence of asymmetrical giant magnetoimpedance (AGMI) effect in amorphous glasscovered wires annealed by 70 mA DC current is here presented. The resistance R and the reactance X have been measured, respectively. The real part R and the imaginary part X of impedance play an important role at high frequency and low frequency, respectively. The influence of DC bias current from Ib=0 mA to Ib=5 mA at 30 MHz on the GMI effect in the glasscovered wires annealed by 70 mA DC current is investigated. The asymmetry becomes the largest around Ib=1 mA, and finally decreases for the larger bias current Ib=5 mA. The maximum ΔZ/Z ratio of 310% is observed at 58 MHz under 1 mA bias current.