2007年, 第14卷, 第5期　刊出日期：2007-10-15

  

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Metallurgy and Metal Working
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  Mass Balance Modeling for Electric Arc Furnace and Ladle Furnace System in Steelmaking Facility in Turkey

  smail Ekmeki;Ya?瘙
  塂ar Yetisken;nal amdali

  中国钢铁期刊网. 2007, 14(5): 1-0.

  摘要 ( )   可视化   收藏

  In the electric arc furnace (EAF) steel production processes, scrap steel is principally used as a raw material instead of iron ore. In the steelmaking process with EAF, scrap is first melted in the furnace and then the desired chemical composition of the steel can be obtained in a special furnace such as ladle furnace (LF). This kind of furnace process is used for the secondary refining of alloy steel. LF furnace offers strong heating fluxes and enables precise temperature control, thereby allowing for the addition of desired amounts of various alloying elements. It also provides outstanding desulfurization at hightemperature treatment by reducing molten steel fluxes and removing deoxidation products. Elemental analysis with mass balance modeling is important to know the precise amount of required alloys for the LF input with respect to scrap composition. In present study, chemical reactions with mass conservation law in EAF and LF were modeled altogether as a whole system and chemical compositions of the final steel alloy output can be obtained precisely according to different scrap compositions, alloying elements ratios, and other input amounts. Besides, it was found that the mass efficiency for iron element in the system is 9593%. These efficiencies are calculated for all input elements as 845% for C, 3031% for Si, 4636% for Mn, 3064% for P, 4196% for S, and 6979% for Cr, etc. These efficiencies provide valuable ideas about the amount of the input materials that are vanished or combusted for 100 kg of each of the input materials in the EAF and LF system.
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  Mathematical Model for Electroslag Remelting Process

  DONG Yanwu;JIANG Zhouhua;LI Zhengbang

  中国钢铁期刊网. 2007, 14(5): 7-0.

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  A mathematical model, including electromagnetic field equation, fluid flow equation, and temperature field equation, was established for the simulation of the electroslag remelting process. The distribution of temperature field was obtained by solving this model. The relationship between the local solidification time and the interdendritic spacing during the ingot solidification process was established, which has been regarded as a criterion for the evaluation of the quality of crystallization. For a crucible of 950 mm in diameter, the local solidification time is more than 1 h at the center of the ingot with the longest interdendritic spacing, whereas it is the shortest at the edge of the ingot according to the calculated results. The model can be used to understand the ESR process and to predict the ingot quality.
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  Dynamic Soft Reduction for Continuously Cast Rail Bloom

  CHEN Yong;LI Guijun;YANG Subo;ZHU Miaoyong

  中国钢铁期刊网. 2007, 14(5): 13-0.

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  Center porosity and centerline segregation in continuously cast bloom can be minimized by the wellknown method of dynamic soft reduction. Metallurgical results of soft reduction previously employed in continuous bloom casting for heavy rail steel in Panzhihua Iron and Steel Group were not fully achieved because of the improper soft reduction process. Therefore, experiments for optimizing the process parameters of soft reduction for bloom were carried out. The results show that the proportion of the center porosity, which is less than 10, increases from 2841% to 9981%, while the proportion of the centerline segregation class increases from 4091% to 100%, and the proportion of the central cavity increases from 9205% to 100%, whereas the center carbon segregation index decreases from 117 to 105. The internal quality and the mechanical performance of the rails produced from continuously cast blooms meet the requirement of highspeed tracks of 350 km/h.
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  Numerical Simulation of Temperature Field and Thermal Stress Field of Work Roll During Hot Strip Rolling

  LI Changsheng;YU Hailiang;DENG Guanyu;LIU Xianghua;WANG Guodong

  中国钢铁期刊网. 2007, 14(5): 18-0.

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  Based on the thermal conduction equations, the threedimensional (3D) temperature field of a work roll was investigated using finite element method (FEM). The variations in the surface temperature of the work roll during hot strip rolling were described, and the thermal stress field of the work roll was also analyzed. The results showed that the highest roll surface temperature is 593 ℃, and the difference between the minimum and maximum values of thermal stress of the work roll surface is 1457 MPa. Furthermore, the results of this analysis indicate that temperature and thermal stress are useful parameters for the investigation of roll thermal fatigue and also for improving the quality of strip during rolling.
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  FEM Analysis of Rolling Pressure Along Strip Width in Cold Rolling Process

  LIU Xianghua;SHI Xu;LI Shanqing;XU Jianyong;WANG Guodong

  中国钢铁期刊网. 2007, 14(5): 22-0.

  摘要 ( )   可视化   收藏

  Using 3D elasticplastic FEM, the cold strip rolling process in a 4high mill was simulated. The elastic deformation of rolls, the plastic deformation of the strip, and the pressure between the work roll and the backup roll were taken into account. The distribution of rolling pressure along the strip width was obtained. Based on the simulation results, the peak value of rolling pressure and the location of the peak were analyzed under different rolling conditions. The effects of the roll bending force and the strip width on the distribution of rolling pressure along the width direction were determined.
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  Shape Setup System for 1700 Hot Strip Mill

  GUO Zhongfeng;XU Jianzhong;LI Changsheng;LIU Xianghua

  中国钢铁期刊网. 2007, 14(5): 27-0.

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  Shape setup (SSU) system is the core technology for hot strip mill (HSM). A precise SSU system was used to improve the strip quality for HSM. The function of SSU, setup, and feedback was introduced. The main mathematical models of roll gap profile and longitudinal strain difference are set up. Strip profile allocation strategy was researched according to the SSU system of a domestic 1 700 mm HSM. The SSU system was put into practical use and the measurement results showed that strip flatness variation and strip profile variation could be controlled in target scope.
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  Mechanical Properties of New Type Negative Offset Structure During Shearing Process of Heavy Steel Plate

  MA Lifeng;HUANG Qingxue;WANG Jianmei;YANG Jianwei;LI Ying;LI Jinbao

  中国钢铁期刊网. 2007, 14(5): 31-0.

  摘要 ( )   可视化   收藏

  According to the revised Cailikefu′s rolling shear force formula, motion path equation of spatial sevenbar path was built, and a mechanical model, with the new structural feature of negative offset, was thus successfully established for 2 800 mm heavy shear of some iron and steel company. Shear and bar forces of steel plate, before and after the adoption of negative offset structure, were analyzed, as well as horizontal force component of mechanism that influences pure rolling shear and backwall push force that keeps blade clearance. It was found that the backwall push force keeps large even at the time that the maximum rolling shear was obtained; meanwhile, backwall push force is the most approximate to side forces when 60-100 mm of offset was adopted. Both theoretical results and onsite shear quality show that the negative offset plays an important role in ensuring the stability of pure rolling shear and keeping blade clearance constant.
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  umerical Study on Welding Line Behavior of Deep Drawing TWB Process

  WANG Lijuan;WANG Guodong;LIU Xianghua;WU Mingtang

  中国钢铁期刊网. 2007, 14(5): 36-0.

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  The FEM technology is used to analyze the welding line movement behavior of deep drawing TWB sheet with different thickness. It is found that high stress fields are concentrated around the welding line and large residual stresses are left. The effect of the welding line movement is like a rigid string and the selected nodes of the thin part near the welding line show the related larger strain.
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  Oxide Inclusions at Different Steps of Steel Production

  Yousef Payandeh;Mansour Soltanieh

  中国钢铁期刊网. 2007, 14(5): 39-0.

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  The formation of oxide inclusions in one of the carbon steel productions of Mobarakeh Steel Complex of Isfahan has been evaluated. Several samples from different steps of steel production were taken, from arc furnace, ladle furnace, tundish, and continuous casting mold. Moreover, samples of slab and hot rolling products were prepared. The samples were investigated by optical and scanning electron microscopes equipped with the EDS system. According to the results, the number, composition, and kind of inclusions were directly influenced by the production variables. It was found that when the amount of dissolved oxygen was high (say more than 0002 5%), the dissolved aluminum was able to reduce silicon oxide and react with the dissolved oxygen simultaneously, whilst, the dissolved aluminum could reduce the magnesium oxide only when the oxygen content was below 0000 5%. Based on this research, a mechanism for forming the complex inclusions was suggested. It was also found that if the aluminum is added to the melt as late as possible, a cleaner melt with fewer inclusions is prepared; this method will be more effective, especially in the case of complex inclusions.
Material
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  Properties of CrossRolled Low Alloy White Cast Iron Grinding Ball

  CHANG Limin;LIU Lin;LIU Jianhua

  中国钢铁期刊网. 2007, 14(5): 47-0.

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  The lowenergy, multiimpact fracture resistance and the abrasiveness of the crossrolled low alloy white cast iron grinding balls were studied after heat treatments at residual rolling temperature. Moreover, the means by which they are damaged and characters of the wear surface were analyzed. The results show that high resistance to impact fracture and high abrasiveness can be achieved after appropriate heat treatment at residual rolling temperature. This kind of heat treatment technology has several advantages under low impact and hard abrasive. These results are very useful for determining the optimized heat treatment technology at residual rolling temperatures.
论文
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  Gray Cast Iron With Directional Graphite Flakes Produced by Cylinder Covered Compression Process

  ZHAO Xin;WANG Jinfeng;JING Tianfu

  中国钢铁期刊网. 2007, 14(5): 52-0.

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  A new plastic deformation process for gray cast iron named cylinder covered compression (CCC) was developed. By CCC process, gray cast iron (GCI) specimens, which are embedded in steel cylinders, were hot compressed up to 80% reduction in height without the cracking problem. It was clearly observed that the uniform distribution of directional graphite flakes appeared after more than 45% reduction hot compression. The strength, ductility, and microhardness of GCI after 80% reduction deformation were significantly enhanced: the tensile strength varied from 117 MPa to 249 MPa, while the total elongation varied from 0 to 52%, and the microhardness varied from 153 HV to 217 HV. It was shown that the tensile fracture surface presented ductility characters after more than 45% reduction hot deformation.
Material
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  Adiabatic Shear Localization for Steels Based on JohnsonCook Model and Second and FourthOrder Gradient Plasticity Models

  WANG Xuebin

  中国钢铁期刊网. 2007, 14(5): 56-0.

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  To consider the effects of the interactions and interplay among microstructures, gradientdependent models of second and fourthorder are included in the widely used phenomenological JohnsonCook model where the effects of strainhardening, strain rate sensitivity, and thermalsoftening are successfully described. The various parameters for 1006 steel, 4340 steel and S7 tool steel are assigned. The distributions and evolutions of the local plastic shear strain and deformation in adiabatic shear band (ASB) are predicted. The calculated results of the second and fourthorder gradient plasticity models are compared. S7 tool steel possesses the steepest profile of local plastic shear strain in ASB, whereas 1006 steel has the least profile. The peak local plastic shear strain in ASB for S7 tool steel is slightly higher than that for 4340 steel and is higher than that for 1006 steel. The extent of the nonlinear distribution of the local plastic shear deformation in ASB is more apparent for the S7 tool steel, whereas it is the least apparent for 1006 steel. In fourthorder gradient plasticity model, the profile of the local plastic shear strain in the middle of ASB has a pronounced plateau whose width decreases with increasing average plastic shear strain, leading to a shrink of the portion of linear distribution of the profile of the local plastic shear deformation. When compared with the secondorder gradient plasticity model, the fourthorder gradient plasticity model shows a lower peak local plastic shear strain in ASB and a higher magnitude of plastic shear deformation at the top or base of ASB, which is due to wider ASB. The present numerical results of the second and fourthorder gradient plasticity models are consistent with the previous numerical and experimental results at least qualitatively.
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  Influence of Holding Time After Deformation on Bainite Transformation in Niobium Microalloyed Steel

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

  中国钢铁期刊网. 2007, 14(5): 62-0.

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  Using Gleeble1500 system, the influence of holding time on bainite transformation in deformed niobium microalloyed steel during continuous cooling was analyzed, and the carbides in upper bainite were also systematically researched. The results show that the occurrence of the static recrystallization decreases the amount of bainite with an increase in the holding time and the emergence of retained austenite (RA) with the longer holding time. Two types of carbides were observed in upper bainite with regard to their precipitation sites. They either existed between the bainite ferrite laths or coexisted with RA. The formation mechanism of two kinds of carbides was analyzed by combining TEM micrographs with the model.
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  Hot Compression Behavior of AsCast Precipitation Hardening Stainless Steel

  A Momeni;S M Abbasi;A Shokuhfar

  中国钢铁期刊网. 2007, 14(5): 66-0.

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  High temperature deformation characteristics of a semiaustenitic grade of precipitationhardening stainless steels were investigated by conducting hot compression tests at temperatures of 900-1 100 ℃ and strain rates of 0001-1 s-1. Flow behavior of this alloy was investigated and it was realized that dynamic recrystallization (DRX) was responsible for flow softening. The correlation between critical strain for initiation of DRX and deformation parameters including temperature and strain rate, and therefore, ZenerHollomon parameter (Z) was studied. Metallographic observation was performed to determine the asdeformed microstructure. Microstructural observation shows that recrystallized grain size increases with increasing the temperature and decreasing the strain rate. The activation energy required for DRX of the investigated steel was determined using correlations of flow stress versus temperature and strain rate. The calculated value of activation energy, 460 kJ/mol, is in accordance with other studies on stainless steels. The relationship between peak strain and Z parameter is proposed.
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  Reactive Plasma Sprayed TiN Coating and Its Thermal Stability

  ZOU Dongli;YAN Dianran;HE Jining;LI Xiangzhi;DONG Yanchun;ZHANG Jianxin

  中国钢铁期刊网. 2007, 14(5): 71-0.

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  TiN coating was prepared by reactive plasma spraying in the Ar and N2 containing plasma jet. The results of XRD show that the TiN coating consists of TiN and Ti3O, neither Ti2N nor TiO2 phases. The toughening mechanism was characterized by analyzing the SEM morphologies of the TiN coating′s indentation of microhardness and fracture surfaces. The results indicate that the coating possesses a high toughness. The adhesion strength among the TiN layers is 2588 MPa, which is slightly lower than that of the Ni/Al bonding coating. The oxidation process of the RPS TiN coating is TiN→Ti3O→TiO2.
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  Heredity of Aluminum Melt by Electric Pulse Modification (Ⅱ)

  QI Jingang;WANG Jianzhong;DU Huiling;CAO Liyun

  中国钢铁期刊网. 2007, 14(5): 76-0.

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  Heredity of high pure aluminum melts under different pulse electric field was investigated by means of repetitious remelt experiment. The results indicate that the genetic coefficient by measurement of grain size of cast structure has a close relation with pulse voltage. Moreover, the hereditary law accords with the function of In=1+e-αn+β. The stability of genetic carrier (cluster) comprises in the competition between repetitious cooling and heating impulse and the effect of electric pulse modification.