2008年, 第15卷, 第3期　刊出日期：2008-06-15

  

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Metallurgy and Metal Working
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  Evaluation of Scheme Design of Blast Furnace Based on Artificial Neural Network

  TANG Hong;LI Jingmin;YAO Biqiang;LIAO Hongfu;YAO Jin

  中国钢铁期刊网. 2008, 15(3): 1-0.

  摘要 ( )   可视化   收藏

  Blast furnace scheme design is very important, since it directly affects the performance, cost and configuration of the blast furnace. An evaluation approach to furnace scheme design was brought forward based on artificial neural network. Ten independent parameters which determined a scheme design were proposed. The improved threelayer BP network algorithm was used to build the evaluation model in which the 10 independent parameters were taken as input evaluation indexes and the degree to which the scheme design satisfies the requirements of the blast furnace as output. It was trained by the existing samples of the scheme design and the experts′ experience, and then tested by the other samples so as to develop the evaluation model. As an example, it is found that a good scheme design of blast furnace can be chosen by using the evaluation model proposed.
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  Thermodynamic Calculations of Melt in Melt Pool During Laser Cladding High Silicon Coatings

  DONG Danyang;LIU Changsheng;ZHANG Bin

  中国钢铁期刊网. 2008, 15(3): 5-0.

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  Based on the Miedema′s formation heat model for binary alloys and the Toop′s asymmetric model for ternary alloys, the formation heat, excess entropy, and activity coefficients of silicon ranging from 1 900 K to 4 100 K in the FeSiC melt formed during the laser cladding high silicon coatings process were calculated. The results indicated that all values of lnγ0Si, εCSi, ρSiSi and ρCSi are negative in the temperature range and these values increase as the temperature increases. And all values of εSiSi and ρSiCSi are positive and these values decrease with increasing temperature. The isoactivity lines of silicon are distributed axisymmetrically to the incident laser beam in the melt pool vertical to the laser scanning direction. And the isoactivity lines of silicon in the front of the melt pool along the laser scanning direction are more intensive than those in the back of the melt pool. The activity of silicon on the bottom of the melt pool is lower than that in the effecting center of laser beam on the top surface of the melt pool and it may be the important reason for the formation of the silicides and excellent metallurgical bonding between the laser cladding coating and the substrate.
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  Heat Transfer in Steelmaking Ladle

  André Zimmer;lvaro Niedersberg Correia Lima;Rafael Mello Trommer;Saulo Roca Bragana;Carlos Pérez Bergmann

  中国钢铁期刊网. 2008, 15(3): 11-0.

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  The heat transfer in a steelmaking ladle was studied. The evaluation of heat transfer of the steel was performed by measuring steel temperature in points including all refining steel process. In the ladle, the temperatures in the refractories and the shell were also measured. To evaluate the thermal profile between the hot and cold faces of the ladle in the slag line position, an experiment which shows the importance of thermal contact resistance was carried out. Higher heat losses in the tapping and the vacuum were verified. The temperature measurements of the ladle indicate distinct thermal profiles in each stage of steel refining. Moreover, as each stage of the process depends on the previous one, the complexity of the ladle thermal control is incremental. So a complete model of heat losses in the ladle is complex.
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  Effects of AlMnCa and AlMnFe Alloys on Deoxidization of Low Carbon and Low SiliconAluminum Killed Steels

  ZHAN Dongping;ZHANG Huishu;JIANG Zhouhua

  中国钢铁期刊网. 2008, 15(3): 15-0.

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  To confirm the effects of AlMnCa and AlMnFe alloys on the deoxidization and modification of Al2O3 inclusions, experiments of 4heat low carbon and low siliconaluminum killed steels deoxidized by AlMnCa and AlMnFe alloys were done in a MoSi2 furnace at 1 873 K. It is found that the 1# AlMnCa alloy has the best ability of deoxidization and modification of Al2O3 inclusions than 2# AlMnCa and AlMnFe alloys. Steel A deoxidized by 1# AlMnCa alloy has the lowest total oxygen content in the terminal steel, which is 37×10-6. Most of the inclusions in the steel deoxidized by 1# AlMnCa alloy are spherical CaOcontaining compound inclusions, and 891% of them are smaller than 10 μm. The diameter of the inclusion bigger than 50 μm is not found in the final steels deoxidized by AlMnCa alloys. Whereas, for the steels deoxidized by AlMnFe alloys, most inclusions in the terminal steel are Al2O3 or Al2O3MnO inclusions, and a few of them are spherical, and only 768% of them are smaller than 10 μm. Some inclusions bigger than 50 μm are found in the steel D deoxidized by AlMnFe alloy.
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  Analysis of Crack Tip Stress of Transversal Crack on Slab Corner During VerticalHorizontal Rolling Process by FEM

  YU Hailiang;LIU Xianghua;WANG Guodong

  中国钢铁期刊网. 2008, 15(3): 19-0.

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  Behavior of transversal crack notched on slab corner during verticalhorizontal rolling process was simulated by FEM. The crack tip stress in the whole rolling process was obtained. Influences of the friction coefficient, the initial crack size, the edger roll profile, and the groove fillet radii of grooved edger roll on crack tip stress were analyzed. For vertical rolling, the tension stress appears at crack tip near the slab top surface and the compression stress appears at crack tip near the slab side surface for the flat edger roll; however, the compression stress appears at crack tip near the slab top surface and the tension stress appears at crack tip near the slab side surface in the exit stage for the grooved edger roll. For horizontal rolling, the tension stress appears at crack tip just at the exit stage for the flat edger roll, and the tension stress appears in whole rolling stage; the tension stress value near the slab side surface is much larger than that near the slab top surface for the grooved edger roll.
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  Output Model of Steel Plant

  ZHANG Longqiang;TIAN Naiyuan;ZHANG Jin;XU Anjun

  中国钢铁期刊网. 2008, 15(3): 27-0.

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  Based on the requirement of compactivity, continuity, and high efficiency, and taking full advantage of cushion capability of flexible parts such as external refining in new generation steel plant, an output model of steel plant was established in terms of matching between BOF and caster. Using this model, the BOF nominal capacity is selected, the caster output and equipment amount are computed, and then the steel plant output is computed.
Material
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  Effect of Niobium and Titanium on Dynamic Recrystallization Behavior of Low Carbon Steels

  MA Liqiang;LIU Zhenyu;JIAO Sihai;YUAN Xiangqian;WU Di

  中国钢铁期刊网. 2008, 15(3): 31-0.

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  Using a Gleeble 3800 thermomechanical simulator, the effect of niobium and titanium on the dynamic recrystallization (DRX) behavior of low carbon steels was investigated. Isothermal single compression tests were performed in the temperature range of 850 to 1 150 ℃ at constant strain rates of 01 to 5 s-1. The experimental results showed that the addition of niobium and titanium to the low carbon steels significantly increased both the peak stress and steady state stress. The activation energy of deformation Qd was larger than the activation energy associated with the steady state stress Qss. Furthermore, the difference between Qd and Qss became significant because of the addition of niobium and titanium. DRX is effectively retarded because of solute dragging and dynamic precipitate pinning of niobium and titanium, resulting in higher values of the peak strain and steady state strain. Finally, the influence of niobium and titanium on the DRX kinetics and steady state grain size was determined.
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  Vertical Short Crack Initiation in Medium Carbon Bainitic Steel Under Mild Tractive Rolling Contact

  DOU Peng;SUO Shuangfu;BAI Bingzhe;YANG Zhigang;LI Youguo

  中国钢铁期刊网. 2008, 15(3): 37-0.

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  To improve the current grinding procedure of the backup roll of CVC hot rolling mills so that the backup roll service life can be extended, the crack initiation and propagation behavior of medium carbon bainitic backup roll steel was investigated, a kind of asperityscale, surface originated vertical short cracks occurred at 5×102-1×104 cycles. Theoretical analysis indicated that the maximum tensile stress occurring at the back edge of the contact of asperities keeps at above 1 34797 MPa, and ratcheting and cyclic plastic deformation take place at such sites within 1×104 cycles. The early initiation of the vertical short cracks is caused by the asperity contact. According to the crack initiation mechanism, short crack behavior and preventive grinding strategy, steel consumption can be reduced considerably by decreasing the surface roughness and removing the asperity influenced surface thin layer at about 70%-80% of the surface distress life.
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  Mechanism of Austenite Evolution During Deformation of UltraHigh Carbon Steel

  ZHANG Shulan;SUN Xinjun;DONG Han;

  中国钢铁期刊网. 2008, 15(3): 42-0.

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  The mechanism of transformation of austenite to cementite and pearlite during the deformation of ultrahigh carbon steel was discussed. The results indicate that the pearlite and cementite can be induced by deformation between Acm to Arcm. The transformation during deformation is still considered as a diffusioncontrolled process. With the increase of time and reduction, the pearlite fraction increased. At the beginning of the transformation, the pearlite was lamelliform. When the rate of reduction was increased to 70%, some of the induced lamellar pearlite was broken up under deformation.
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  Abnormal Failure Analysis of H13 Punches in Steel Squeeze Casting Process

  ZHANG Milan;XING Shuming;XIN Qiao;XIAO Liming;GOU Junnian;WU Xialing

  中国钢铁期刊网. 2008, 15(3): 47-0.

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  In steel squeeze casting process, the working condition of a punch was very rigorous. The abnormal failure models of an H13 punch, such as plastic rubbed damnification, could not be avoided easily. Based on the analysis of the flow stress and the frictionshearing stress of an H13 punch in steel squeeze casting process, the following results were obtained: if the flow stress of an H13 punch was smaller than its frictionshearing stress, these abnormal failures could not be avoided; and if there were some protection measures that enable the flow stress to have a greater value than its frictionshearing one, the abnormal failures would not occur. In the production of 45# steel valves and catenary system components, the flow stress of a lateral H13 punch without any protection measure was about 29 MPa and its frictionshearing stress was about 51 MPa, then, the abnormal failures occurred; however, when the protection measures of the punch enabled its working temperature to have a value below 682 ℃, its flow stress was greater than its frictionshearing stress, and the abnormal failures were avoided.
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  Microstructure and Property of HD Die Steel With Unsmoothed Surface With Various Laser Parameters

  CHEN Li;ZHOU Hong;ZHAO Yu;REN Luquan

  中国钢铁期刊网. 2008, 15(3): 52-0.

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  The reticulate unsmoothed surfaces on HD die steel, which imitate the surface of soilburrowing animals (such as the dung beetle, earthworm, pangolin, and ant) are produced with various laser parameters. The characteristics (including width, depth, area ratio, and volume), microstructure, and hardness of the unsmoothed units are studied. At the same time, the wear resistance of the material with an unsmoothed surface is measured. The results show that the width and volume of the unit increase, the microstructure becomes coarser, the hardness decreases, and the wear resistance improves with the increase of the current intensity and pulse duration within a certain range. However, there is little difference between the extent to which the wear resistance of the material increases and the unsmoothed surface, when the current intensity and pulse duration increase to some extent. The wear resistance of the unsmoothed material under 300 A or 20 ms is better in the experiments. The improving extent of the wear resistance lies in a combination of the characteristics, microstructure, and hardness of the unsmoothed unit. An unsmoothed material with better properties can be processed if the laser parameters are well matched.
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  Solidification Structure Refining of 430 Ferrite Stainless Steel With TiN Nucleation

  SHI Caixia;CHENG Guoguang;LI Zhanjun;ZHAO Pei

  中国钢铁期刊网. 2008, 15(3): 57-0.

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  The thermodynamics of TiN precipitation in liquid steel of 430 ferrite stainless steel has been calculated to find out the condition of TiN precipitation during the initial solidification stage. The difference in the solidification structure of 430 ferrite stainless steel has been discussed through comparative tests of vacuum induction furnace melting with different contents of Ti. It has been found that the equiaxed grain proportion can be increased from 20% to 69% as the content of Ti from 01% up to 04%. The size of the TiN particles precipitated is 1-3 μm and the number of TiN particles is about (200-300)/μm2. It is found that the effect of using TiN to refine the solidification structure has been confirmed under the strict process condition used for 430 ferrite stainless steel.
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  Effect of Direct Ageing Treatment on StressRupture Properties of GH761 Alloy

  YANG Shulin;SUN Wenru;LIU Fang;GUO Shouren;YANG Hongcai;HU Zhuangqi

  中国钢铁期刊网. 2008, 15(3): 61-0.

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  The effect of direct ageing treatment on microstructure and stressrupture properties of GH761 alloy was studied. Phosphorus was added to the tested alloy for its beneficial effect on stressrupture life. It was found that the grain size of the tested alloy became much finer after direct ageing treatment, in comparison with the commercial GH761 alloy under standard heat treatment condition. The optimum direct ageing treatment has been determined as follows: 830 ℃×4 h, air cooling+720 ℃×24 h, air cooling. After such treatment, the higher stressrupture properties of the test alloy at 650 ℃, 690 MPa were obtained. The role of phosphorus is still effective under the condition of direct ageing treatment.
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  Modeling of StrainInduced Precipitation Kinetics and Evolution of Austenite Grains in Nb Microalloyed Steels

  ZHOU Xiaoguang;LIU Zhenyu;YUAN Xiangqian;WU Di;WANG Guodong;LIU Xianghua

  中国钢铁期刊网. 2008, 15(3): 65-0.

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  Considering the effect of strain and chemical composition on precipitation behavior, new models for the start and end time of Nb(C,N) precipitation in austenite under the conditions of different temperatures and strains have been investigated for Nb microalloyed steel. The value of n in the precipitation kinetic equation has been determined by using the available experimental data in literature, which indicated that n is a constant and independent of temperature. The values of the start and end time of the predicted precipitation are compared with the experimental values. Calculated results are in good agreement with the experimental results. Also, the evolution of austenite grains before ferrite transformation is simulated by taking the effect of precipitation into consideration. The measured austenite grain size is in good agreement with predicted one prior to ferrite transformation.
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  Formation and Thermal Stability of Large Precipitates and Oxides in Titanium and Niobium Microalloyed Steel

  ZHUO Xiaojun;WOO Daehee;WANG Xinhua;LEE Haegeon

  中国钢铁期刊网. 2008, 15(3): 70-0.

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  Ascast CC slabs of microalloyed steels are prone to surface and subsurface cracking. Precipitation phenomena initiated during solidification reduce ductility at high temperature. The unidirectional solidification unit is employed to simulate the solidification process during continuous casting. Precipitation behavior and thermal stability are systematically investigated. Samples of adding titanium and niobium to steels have been examined using field emission scanning electron microscope (FESEM), electron probe Xray microanalyzer (EPMA), and transmission electron microscope (TEM). It has been found that the addition of titanium and niobium to highstrength lowalloyed (HSLA) steel resulted in undesirable large precipitation in the steels, ie, precipitation of large precipitates with various morphologies. The composition of the large precipitates has been determined. The effect of cooling rate on (Ti,Nb)(C,N) precipitate formation is investigated. With increasing the cooling rate, titaniumrich (Ti,Nb)(C,N) precipitates are transformed to niobiumrich (Ti,Nb)(C,N) precipitates. The thermal stability of these large precipitates and oxides have been assessed by carrying out various heat treatments such as holding and quenching from temperature at 800 and 1 200 ℃. It has been found that titaniumrich (Ti,Nb)(C,N) precipitate is stable at about 1 200 ℃ and niobiumrich (Ti,Nb)(C,N) precipitate is stable at about 800 ℃. After reheating at 1 200 ℃ for 1 h, (Ca,Mn)S and TiN are precipitated from CaAl oxide. However, during reheating at 800 ℃ for 1 h, CaAlTi oxide in specimens was stable. The thermodynamic calculation of simulating the thermal process is employed. The calculation results are in good agreement with the experimental results.
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  Dynamic Recrystallization Behavior of Microalloyed Forged Steel

  WANG Jin;CHEN Jun;ZHAO Zhen;RUAN Xueyu

  中国钢铁期刊网. 2008, 15(3): 78-0.

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  The dynamic recrystallization behavior of microalloyed forged steel was investigated with a compression test in the temperature range of 1 223-1 473 K and a strain rate of 001-5 s-1. Activation energy was calculated to be 3059 kJ/mol by regression analysis. Modeling equations were developed to represent the dynamic recrystallization volume fraction and grain size. Parameters of the modeling equations were determined as a function of the ZenerHollomon parameter. The developed modeling equation will be combined with finite element modeling to predict microstructural change during the hot forging processing.
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  Modeling of Cell/Dendrite Transition During Directional Solidification of TiAl Alloy Using Cellular Automaton Method

  WANG Kuangfei;LI Bangsheng;MI Guofa;GUO Jingjie;FU Hengzhi

  中国钢铁期刊网. 2008, 15(3): 82-0.

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  Solute diffusion controlled solidification model was used to simulate the initial stage cellular to dendrite transition of Ti44Al alloys during directional solidification at different velocities. The simulation results show that during this process, a mixed structure composed of cells and dendrites was observed，where secondary dendrites are absent at facing surface with parallel closely spaced dendrites, which agrees with the previous experimental observation. The dendrite spacings are larger than cellular spacings at a given rate, and the columnar grain spacing sharply increases to a maximum as solidification advance to coexistence zone. In addition, simulation also revealed that decreasing the numbers of the seed causes the trend of unstable dendrite transition to increase. Finally, the main influence factors affecting cell/dendrite transition were analyzed, which could be the change of growth rates resulting in slight fluctuations of liquid composition occurred at growth front. The simulation results are in reasonable agreement with the results of previous theoretical models and experimental observation at low cooling rates.
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  Mechanical Property Prediction of Strip Model Based on PSOBP Neural Network

  WANG Ping;HUANG Zhenyi;ZHANG Mingya;ZHAO Xuewu

  中国钢铁期刊网. 2008, 15(3): 87-0.

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  Mechanical property prediction of hot rolled strip is one of the hotspots in material processing research. To avoid the local infinitesimal defect and slow constringency in pure BP algorithm, a kind of global optimization algorithm—particle swarm optimization (PSO) is adopted. The algorithm is combined with the BP rapid training algorithm, and then, a kind of new neural network (NN) called PSOBP NN is established. With the advantages of global optimization ability and the rapid constringency of the BP rapid training algorithm, the new algorithm fully shows the ability of nonlinear approach of multilayer feedforward network, improves the performance of NN, and provides a favorable basis for further online application of a comprehensive model.
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  Silicon Pickup of InterstitialFree Steel From MgOSiC Refractories

  WEI Yaowu;LI Nan;CHEN Xiaoxia;HU Tieshan;RAO Jiangping;TAO Xiaolin

  中国钢铁期刊网. 2008, 15(3): 92-0.

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  The silicon pickup of interstitialfree steel (IF steel) from resin bonded MgOSiC refractories is studied via a medium frequency induction furnace. Samples of IF steel were heated in MgOSiC crucibles with mould flux cover at 1 600 ℃ for 180 min. The silicon contents of IF steel samples taken from the molten steel in every 30 min were examined and the refractories after heating were investigated by electron probe microanalysis (EPMA) with energy dispersive spectrometer (EDS). The silicon content of steel rapidly increased in the first 90 min of heating, and then decreased because of the formation of liquid layer on the refractory. Liquid layer separated the liquid steel from the bulk refractory and stopped the pickup of silicon. At the same time, desilication via oxygen through the liquid layer and flux started to reduce the silicon content of the liquid steel.