2010年, 第17卷, 第7期　刊出日期：2010-07-15

  

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工艺
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  Behavior of MgO.Al2O3 Based Inclusions in Alloy Steel During Refining Process

  YANG Shu-Feng LI Jing-feng;ZHANG Li-feng;et al

  中国钢铁期刊网. 2010, 17(7): 1-1.

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  The transformation of MgO•Al2O3 based inclusions in alloy steel during refining has been studied by industrial trials. Besides Factsage software is applied to study the formation and modification of spinel inclusions in alloy steel using calcium treatment during refining process. The results show the transformation sequence of inclusions is: MgO•Al2O3 → CaO–Al2O3–MgO complex inclusions → MgO•Al2O3; In order to avoid forming MgOAl2O3 inclusions, the content of dissolved Ca in the molten steel has to reach 1ppm.
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  Flow Control in Six-Straud Billet Continuous Casting Tundish With Different Configurations

  ZHONG Liang-cai;WANG Ming-an;CHEN Bo-yu;et al

  中国钢铁期刊网. 2010, 17(7): 7-7.

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  A 1:2.5 scale tundish model was set up in laboratory for a six-strand billet continuous casting tundish with different configurations to investigate fluid flowing characteristics under different operational conditions by measuring residence time distribution curves. It was known from the investigation that minimum residence time, maximum concentration time and average residence time of the three strands in the same side of the tundish with the former configuration under normal operation, that is, 6 strands were open, were small and non-uniform and the tundish had large dead volume fraction. Vortexes easily formed on the liquid surface in the pouring zone of the tundish. The fluid flow characteristics in the tundish with the optimal turbulence inhibitor and baffles were improved and became less non-uniform among the strands. Vortexes were not found on the pouring zone surface in the optimal tundish. Under un-normal operation, that is, one strand was close, it was important to choose which strand should be closed for flowing characteristics of the rest two strands. It was found from this investigation that fluid flowing characteristics in the optimal configuration tundish with closing strand 2 were better than those with closing strand 3 at the same side.
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  Effect of Induction Heat on Initial Solidification During Electromagnetic Continuous Casting of Steel

  WAGNG Hong-Ming;LI Gui-rong

  中国钢铁期刊网. 2010, 17(7): 13-18.

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  Aiming at the process of electromagnetic continuous casting (EMCC), a three dimensional finite element model on electromagnetic field and temperature field was developed through the commercial software ANSYS to investigate the effects of induction heat of high frequency electromagnetic field on the early solidification process of molten steel in soft contact mold under various conditions of exciting current parameters. The results show that the induction heat has significant effects on the early solidification process, which appear as increasing the billet surface temperature, thinning the initial solidified shell and lowering the starting point of the initial solidification. The increases of exciting current frequency and density make the effects of induction heat on solidification process increased remarkably. Especially, with the increase of exciting current frequency, the early solidification process and shell growth become non-uniform in billet circumferential direction. Morever, if the exciting current density exceeds a certain value, there occurs a high temperature region in the top of molten steel column, and then the initial solidification rate is decreased greatly.
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  Friction Model for Strip Rolling

  DU Feng-shan;WANG Gui-guo;et al

  中国钢铁期刊网. 2010, 17(7): 19-23.

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  To improve the accuracy and speed of finite element calculation, a new friction model is proposed with a layer of thin friction element being introduced between the roller and workpiece to consider the contact friction. This model is used in the three-dimensional elastic-plastic finite element model of strip rolling process. With the consideration of the geometry size and physical characteristics of intermediate medium between roller and workpiece, this stiffness of the friction element is corrected by two factors (the thickness of friction element and β factor). Without any assumption about the value and direction of friction force and neutral point position, the rolling processes is simulated using this model. The results obtained by this model have been compared with experimental results to verify the feasibility of the model. The model is of great important to the research of the friction model in the strip rolling process, and can be extended to all press-working process.
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  Flow Uniformity of Roller-Type Quenching Machine

  ZHU Dong-mei;LIU Guo-yong;et al

  中国钢铁期刊网. 2010, 17(7): 24-24.

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  Abstract: Three dimensional finite element flow field model of spraying pipe of roller-type quenching machine is built. The flow field under different structural parameters is computed. After grouping the nozzles, the spraying uniformity is analyzed under different water inlet pipe diameter, different water inlet pipe distance, nozzle diameter, nozzle distance. And the spraying intensity absolute deviation and relative deviation are computed under different conditions. The effect rule of different structural parameters to cooling uniformity is obtained. The results provide theoretical support for improving production quality and optimizing cooling device design.
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  Quality Prediction of Strip Steel Based on Windows-Mean MPLS

  CHANG Yu-Qing;WANG Jin-fen;et al

  中国钢铁期刊网. 2010, 17(7): 28-33.

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  A windows-mean Multi-way partial-least squares (MPLS) method was proposed to build the strip steel quality prediction model for continuous annealing process. The proposed method can deal with the problem of large time lag in hardness measurement of the strip steel and the difficulties in building mechanism model. Based on the average trajectories of the process variable information, the proposed method was used to realize the strip steel quality prediction. Comparing with the traditional MPLS, the proposed method can eliminate the abundant and redundant process information as well as reduce the number of the model input variables. Moreover, it can avoid the uneven-length modeling data problem of the traditional MPLS method. The simulation result demonstrates the performance and advantages of the proposed method for predicting the strip steel hardness.
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  MILP Model for Plant-Wide Optimal By-Product Gas Scheduling in Iron and Steel Industry

  KONG Hai-ning;QI Er-shi;et al

  中国钢铁期刊网. 2010, 17(7): 34-34.

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  The scheduling of byproduct gases in byproduct gas system, cogeneration system and production system is studied. All gas-consuming users are divided into three kinds according to their different characters and then a distribution model is established. A dynamic mixed integer linear programming (MILP) model for multiperiod optimization of byproduct gas is performed to optimize byproduct gas distribution to achieve total cost reduction. Case study shows that 6.2% operation cost is reduced using the proposed model.
材料
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  Isothermal Grain Growth of Austenite in Hypoeutectoid and Hypereutectoid Plain Carbon Steels

  Joydeep Maity;Dipak Kumar Mondal

  中国钢铁期刊网. 2010, 17(7): 38-43.

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  Grain growth kinetics of austenite in a hypoeutectoid steel (containing 0.35 wt% carbon) at 920°C and in a hypereutectoid steel (containing 1 wt% carbon) at 980°C has been investigated with holding time ranging from 1 h to 6 h. The hypoeutectoid steel exhibited normal grain growth without solute drag hindrance with a time exponent (0.51) close to the theoretical value (0.5). However, grain growth of austenite in hypereutectoid steel was extremely slow up to 3 h of holding characterized by a low value of time exponent (0.06). Thereafter, a breakaway occurred and the grain growth in hypereutectoid steel from 3 h to 6 h of holding progressed normally with a time exponent (0.55) close to the theoretical value (0.5).
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  Effect of Thermomechanical Control Processing on Microstructure and Mechanical Properties of Fe-0.2C-1.44Si-1.32Mn Hot-rolled TRIP Steel

  ZHANG Zi-Cheng;ZHU Fu-xian LI Yan-mei

  中国钢铁期刊网. 2010, 17(7): 44-44.

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  The effect of thermomechanical control processing (TMCP) on microstructure and mechanical properties of Fe-0.2C-1.44Si-1.32Mn hot-rolled TRIP steel was investigated by experiment. Strain-induced transformation and transformation-induced plasticity behavior of retained austenite was discussed. The results show that using multi-pass deformation, reduction per pass of more than critical deformation in austenite recrystallization region, total reduction of more than 58 pct in non-recrystallization region and in high temperature section of two-phase region can result in austenite being refined before γ → α transformation. It is beneficial to get refined ferrite grain in final microstructure. To obtain fine and uniform microstructure and excellent strength-ductility balance, a three-step cooling process (Laminar Cooling－Air Cooling－Ultra-Fast Cooling) after hot rolling was conducted. The ultimate tensile strength and elongation of the testing steel can reach 663 MPa and 41 pct respectively.
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  Predicting the critical conditions and stress-strain curves for dynamic recrystallization in SPHC steel

  WU Lai-zhi;LI Xue-song;CHEN Jun;et al

  中国钢铁期刊网. 2010, 17(7): 51-57.

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  The hot compression tests were carried out on a SPHC steel at the temperature range of 900～1150℃ and strain rate range of 0.1～10s-1, which the maximum true strain is 0.8. The activation energy of tested steel was calculated, which was 299.4 KJ /mol. The critical stresses and strains for initiation of dynamic recrystallization were determined based on changes in the work hardening rate ( ) as functions of the flow stress ( ) or strain ( ), respectively. The dependence of the peak strain ( ), the peak stress ( ), and the steady state stress ( ) were determined based on the Zener-Hollomen parameter. The mathematical models of the flow stress evolution were established in the hardening and dynamic recovery region and dynamic recrystallization region, respectively. The average error between experimental and predicted curves was around 3.26%.
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  Effect of Hot Band Annealing Processes on Microstructure, Texture and r-Value of Ferritic Stainless Steel

  DU Wei;JIANG Lai-zhu;SUN Quan-she;et al

  中国钢铁期刊网. 2010, 17(7): 58-62.

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  The effect of hot band annealing processes, namely simulated batch annealing and continuous annealing, on microstructure, texture, grain boundary character and r-value of ferritic stainless steel was investigated. The hot band displayed a highly elongated ribbon-like structure and a pronounced deformation texture. The fully recrystallized grains were observed after continuous annealing while the “typical” hot-rolled structure was remained after batch annealing. Also, the α-fibre texture formed during hot rolling almost disappeared after continuous annealing and a weak γ-&#64257;bre texture was obtained. By contract, the α-fibre texture remained very stable after batch annealing. After cold rolling and recrystallization annealing, the favorable γ-&#64257;bre texture was achieved in the continuous annealed steel. Instead of forming the γ-&#64257;bre texture, the recrystallization texture was notably shifted toward {223}<582> in the batch annealed steel. Finally, the improvement in drawability with high r-value and low △r-value were also displayed in sheet through the initial continuous annealing process.
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  Ti-Deoxidized Products and Formation Mechanism of Intragranular Ferrite in High Grade Pipeline Steels

  QI Jiang-Hua;XUE Zheng-liang;et al

  中国钢铁期刊网. 2010, 17(7): 63-63.

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  High grade pipeline steels were prepared using vacuum carbon deoxidization process combined with a final Ti-deoxidation process. The microstructure of the as-cast steels was investigated by using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). SEM observation shows the formation of Intragranular ferrite (IGF) structure was induced by fine inclusions. TEM selected area diffraction patterns (SAD) and elemental distribution analysis indicated that these inclusions are mainly Ti2O3 and MnS. It was also found that Ti2O3 may act as nucleus in the formation of MnS during solidification process. Raman spectroscopic analysis demonstrated the presence of another phase, MnTiO3, which could be formed through entrapment of Mn element by Ti2O3. It is believed that the formation of Mn-depleted region in the inclusions and thus the formation of MnTiO3 phase will lead to increased Mn pickup from matrix and promoted the formation of IGF during solidification of molten steel.
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  Effect of Baking Process on Microstructures and Mechanical Properties of Low Silicon TRIP Steel Sheet with Niobium

  ZTANG heng-you; DING Hua; et al

  中国钢铁期刊网. 2010, 17(7): 68-74.

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  After 2% pre-deformation, the baking treatment with different schedule was carried out in low silicon TRIP steel sheet with niobium. The effects of baking temperature and time on microstructures and mechanical properties were investigated. The results show that, with increasing of baking temperature and time, the volume fraction of retained austenite decreases, and tempered martensite increases; As baking temperature ranging from 80 to 170℃, the bake-hardening(BH) value increases obviously, while from 170℃ to 230℃, the variation of BH value is very slight; As baking time ranging from 2 to 20 min, the BH value increases significantly, while the BH value decreases when it exceeds 20 min. So that when the baking temperature is 170℃ and the baking time is 20 min, the low silicon TRIP steel sheet exhibits good bake-hardening behavior, the highest BH value being above 70MPa.
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  Kinematics and Dynamics Model of GH4169 Alloy for Thermal Deformation

  Wang Zhong-tang;ZHANH shi-hong;et al

  中国钢铁期刊网. 2010, 17(7): 75-78.

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  Abstract：It had been studied that the effect of deformation temperature and strain-rate and strain and original grain size on stress-strain law by with thermal simulation experiment. It was analyzed that the effect of factors on crystal grain size of dynamic recrystalization (DRC). It was established that the kinematics model of super-alloy GH4169, which was relationship between the grain size of dynamic recrystallization(DRC) and function Z and technology parameters. It was established that the dynamics model of super-alloy GH4169, which was relationship between the quantity of dynamic recrystalization and function Z and technology parameters. The results presented that the grain size of dynamic recrystalization increased with increasing of temperature, and increased with the reducing of strain-rate. And it having no relationship with original grain size. The quantity of dynamic recrystalization reduced with increasing of original grain size.