2012年, 第19卷, 第6期　刊出日期：2012-06-15

  

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工艺
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  Sintering Properties and Optimal Blending Schemes of Iron Ores

  Dauter Oliveira,,WU Sheng-li,DAI Yu-ming,XU Jian,CHEN Hong

  中国钢铁期刊网. 2012, 19(6): 1-5.

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  In order to obtain good sintering performance, it is important to understand sintering properties of iron ores. Sintering properties including chemical composition, granulation and high-temperature behaviors of ores from China, Brazil and Australia. Furthermore, several indices were defined to evaluate sintering properties of iron ores. The results show that: for chemical composition, Brazilian ores present high TFe, low SiO2, and low Al2O3 content. For granulation, particle diameter ratio of Brazilian ores are high; particle intermediate fraction of Chinese concentrates are low; and average particle size and clay type index of Australian ores are high. For high-temperature properties, ores from China, Brazil and Australia present different characteristics. Ores from different origins should be mixed together to obtain good high-temperature properties. According to the analysis of each ore′s sintering properties, an ore blending scheme (Chinese concentrates 20%+Brazilian ores 40%+Australian ores 40%) was suggested. Moreover, sinter pot test using blending mix was performed, and the results indicated that the ore blending scheme led to good sintering performance and sinter quality.
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  Kinetics of Reduction Reaction in Micro-Fluidized Bed

  LIN Yin-he,GUO Zhan-cheng,TANG Hui-qing,REN Shan,LI Jing-wei

  中国钢铁期刊网. 2012, 19(6): 6-8.

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  Micro-fluidized bed reactor is a new research method for the reduction of iron ore fines. The reactor is operated as a differential reactor to ensure a constant gas concentration and temperature within the reactor volume. In order to understand the dynamic process of the reduction reaction in micro-fluidized bed, a series of kinetic experiments were designed. In the micro-fluidized bed, the use of shrinking core model describes the dynamic behavior of reduction of iron ore. And the apparent activation energy is calculated in the range of 700-850 ℃ while the initial atmosphere is 100% content of CO.
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  Comprehensive Utilization of Paigeite Ore Using Iron Nugget Making Process

  DING Yin-gui,WANG Jing-song,WANG Guang,MA Sai,XUE Qing-guo

  中国钢铁期刊网. 2012, 19(6): 9-13.

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  The feasibility of paigeite ore treatment with iron nugget making process is proved. The isothermal reduction experiments at laboratory scale were carried out, using carbon bearing pellets which were made of boron containing iron concentrate and pulverized coal mainly, from 1623 to 1723 K with different heating time. The results indicated that iron nugget making process depends mainly on heating time and temperature. And the iron nugget and slag can separate in a clean manner at 1673 K for 15 min. For the iron nugget, the C content is 357% (mass percent) and B is 0065% (mass percent). The B2O3 content of slag is 2001%, and the boron was concentrated into one phase which is identified as suanite (Mg2B3O5) during the solidification. With an extraction ratio of 80% under the atmospheric conditions, the activity of boron in slag is good. The boron-rich slag can be used to extract boric or boric acid and alleviate the shortage of boron resource. Through series of calculation and analysis related, it can be concluded that the recovery ratio of Fe and boron are about 98% and 97% respectively. The results show that this method is feasible and effective on the utilization of paigeite ore.
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  Prediction of Activities in Fe-Based Ternary Liquid Alloys by Hoch-Arpshofen Model

  YANG Hong-wei, ,LIAN Chao,TAO Dong-ping

  中国钢铁期刊网. 2012, 19(6): 14-18.

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  Thermodynamic properties for an alloy system play an important role in the materials science and engineering. Therefore, theoretical calculations having the flexibility to deal with complexity are very useful and have scientific meaning. The Hoch-Arpshofen model was deduced from physical principles and is applicable to binary, ternary and larger system using its binary interaction parameters only. Calculations of the activities of Fe-based liquid alloys are calculated using Hoch-Arpshofen model from data on the binary subsystems. Results for the activities for Fe-Au-Ni, Fe-Cr-Ni, Fe-Co-Cr and Fe-Co-Ni systems at required temperature are presented by Hoch-Arpshofen model. The average relative errors of prediction are 78%, 45%, 49% and 27%, respectively. It shows that the calculated results are in good agreement with the experimental data except Fe-Au-Ni system, which exhibits strong interaction between unlike atoms. The model provides a simple, reliable and general method for calculating the activities for Fe-based liquid alloys.
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  Entry and Exit Stress Variation of Cold Rolling Strip

  WANG Dong-cheng

  中国钢铁期刊网. 2012, 19(6): 19-24.

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  The shortcomings of an exit stress variation formula which has been well accepted are analyzed; it is found that the exit stress variation formula violates the premise of the law of volume constancy. The shortcomings of an entry stress variation formula are analyzed too, and the basic assumption of the formula is uniform exit velocity. However, for a rigid-plastic material uniform exit velocity implies that the lateral distribution of elongation is uniform, so the exit stress must be uniform and any type of flatness defect is impossible, which is contrary to the practice. In fact, entry and exit velocity variation influence entry and exit stress variation, and entry and exit stress variation influence entry and exit velocity variation too, so a precise explicit stress variation formula cannot be got easily. Considering the relationship between stress variation and velocity variation, an iteration method is presented to calculate entry and exit stress variation of cold rolling strip. To avoid divergent phenomenon of the iteration course, a relaxation factor method is adopted. The calculation results are compared with the entry and exit stress variation formula commonly used by many researchers. The difference is remarkable, while the result calculated agree more well with measured result if the exit elastic recovery zone is considered. Specially, the incoming flatness′ propagate efficiency calculated gives a more realistic result.
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  Establishment of Neural Network Prediction Model for Terminative Temperature Based on Grey Theory in Hot Metal Pretreatment

  ZHANG Hui-ning,,XU An-jun,,CUI Jian,HE Dong-feng,,TIAN Nai-yuan,

  中国钢铁期刊网. 2012, 19(6): 25-29.

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  In order to improve the accuracy of model for terminative temperature in steelmaking, it is necessary to predict and control before decarburization. Thus, an optimization neural network model of terminative temperature in the process of dephosphorization by laying correlative degree weights to all input factors related was used. Then simulation experiment of model newly established is conducted utilizing 210 data from a domestic steel plant. The results show that hit rate arrives at 5645% when error is within plus or minus 5%, and the value is 100% when within ±10%. Comparing to the traditional neural network prediction model, the accuracy almost increases by 6839%.Thus, the simulation prediction fits the real perfectly, which accounts for that neural network model for terminative temperature based on grey theory can reflect accurately the practice in dephosphorization. Naturally, this method is effective and practicable.
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  Optimization of Low-Temperature Exhaust Gas Waste Heat Fueled Organic Rankine Cycle

  WANG Hui-tao,WANG Hua,ZHANG Zhu-ming

  中国钢铁期刊网. 2012, 19(6): 30-36.

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  Low temperature exhaust gases carrying large amount of waste heat are released by steel-making process and many other industries, Organic Rankine Cycles (ORCs) are proven to be the most promising technology to recover the low-temperature waste heat, thereby to get more financial benefits for these industries. The exergy analysis of ORC units driven by low-temperature exhaust gas waste heat and charged with dry and isentropic fluid was performed, and an intuitive approach with simple impressions was developed to calculate the performances of the ORC unit. Parameter optimization was conducted with turbine inlet temperature simplified as the variable and exergy efficiency or power output as the objective function by means of Penalty Function and Golden Section Searching algorithm based on the formulation of the optimization problem. The power generated by the optimized ORC unit can be nearly as twice as that generated by a non-optimized ORC unit. In addition, cycle parametric analysis was performed to examine the effects of thermodynamic parameters on the cycle performances such as thermal efficiency and exergy efficiency. It is proven that performance of ORC unit is mainly affected by the thermodynamic property of working fluid, the waste heat temperature, the pinch point temperature of the evaporator, the specific heat capacity of the heat carrier and the turbine inlet temperature under a given environment temperature.
材料
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  Effects of TMCP Parameters on Microstructure and Mechanical Properties of Hot Rolled Economical Dual Phase Steel in CSP

  TAN Wen,HAN Bin,WANG Shui-ze,YANG Yi, ZHANG Chao,ZHANG Yong-kun

  中国钢铁期刊网. 2012, 19(6): 37-41.

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  Effects of chemical compositions, finish rolling temperature, isothermal temperature on runout table and coiling temperature on microstructure and mechanical properties of economical dual phase steel produced on CSP line were investigated. Experimental results showed that martensite volume fraction could be enhanced and banding microstructure could be reduced by controlling Mn, Si contents and applying proper finish rolling temperature. Optimized processing-parameters were obtained for DP580 production on CSP line of Wuhan Iron and Steel (group) Co (WISCO) in China. Optimal microstructure and mechanical properties could be achieved when the strip was finished rolling at the range of 790 to 830 ℃, isothermally holding at 680 to 740 ℃ and coiling below 250 ℃.
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  Magnetic State of Deformed Austenite Before and After Martensite Nucleation in Austenitic Stainless Steels

  Gennadii V Snizhnoi,Mariya S Rasshchupkyna,

  中国钢铁期刊网. 2012, 19(6): 42-46.

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  The effect of the increase in the paramagnetic susceptibility of austenite up to the true value of the deformation-induced martensite transition point εs has been experimentally established in steels X6CrNiTi18-10 (corresponding to AISI 321 steels). At this point nucleation and accumulation of martensite with the increase in the extent of deformation but at a constant magnetic state of austenite takes place.
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  Effects of Warm Deformation on Mechanical Properties of TRIP Aided Fe-C-Mn-Si Multiphase Steel

  TIAN Yong,LI Zhuang

  中国钢铁期刊网. 2012, 19(6): 47-52.

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  Warm deformation tests were performed using a kind of tubby heater. The microstructures and mechanical properties of an Fe-C-Mn-Si multiphase steel resulting from different warm deformation temperatures were investigated by using LOM (light optical microscopy), SEM and XRD. The results indicated that the microstructure containing polygonal ferrite, granular bainite and a significant amount of the stable retained austenite can be obtained through hot deformation and subsequent austempering. Warm deformation temperature affects the mechanical properties of the hot rolled TRIP steels. Ultimate tensile strength balance reached maximum (881 MPa) when the specimen was deformed at 250 ℃, and the total elongation and strength-ductility reached maximum (38% and 28614 MPa·%, respectively) at deforming temperature of 100 ℃. Martensite could nucleate when austenite was deformed above Ms, because mechanical driving force compensates the decrease of chemical driving force. The TRIP effect occurs in the Fe-C-Mn-Si multiphase steel at deforming temperature ranging from 15 to 350 ℃. The results of the effects of warm deformation on the mechanical properties of the Fe-C-Mn-Si multiphase steel can provide theoretical basis for the applications and the warm working of the hot rolled TRIP sheet steels in industrial manufacturing.
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  Constitutive Equation Models of Hot-Compressed T122 Heat Resistant Steel

  CAO Jin-rong,LIU Zheng-dong,CHENG Shi-chang,YANG Gang,XIE Jian-xin

  中国钢铁期刊网. 2012, 19(6): 53-58.

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  Based on dislocation reaction theory and Avrami equation, a constitutive equation model was developed to describe dynamic recovery and dynamic recrystallization during hot deformation of T122 heat resistant steel, which have taken the effect of dynamic strain aging into account. Uniaxial hot compression test had been carried out over a wide range of strain rate (001 to 10 s-1) and temperature (900 to 1200 ℃) with the help of Gleeble 3500. Obtained experimental data was applied to determine the material parameters in proposed constitutive equations of T122 steel, by using the non-linear least square regress optimization method. The calculated constitutive equations are quantitatively in good agreement with experimentally measured curves and microstructure observation. It shows that propose constitutive equation T122 steel is able to be used to predict flow stress of T122 steel during hot deformation in austenite temperature scope.
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  Corrosion Resistance of High Performance Weathering Steel for Bridge Building Applications

  CHEN Ai-hua,XU Jian-qiu,LI Ran,LI Hua-long

  中国钢铁期刊网. 2012, 19(6): 59-63.

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  The mechanical properties, corrosion resistance and microstructures of high performance steel (HPS) was investigated by tensile testing machine, Charpy V-Notch (CVN) testing machine, cyclic immersion corrosion tester, XRD, optical microscopy (OM), scanning electron microscopy (SEM), and electron probe micro-analyzer (EPMA). The results showed that significant differences existed in the tensile strength, yield strength and impact toughness between HPS and PCS. After 72 h cyclic immersion accelerated corrosion test, the inner rust layer on HPS was composed of α-FeOOH phase and denser than that on PCS that was a mixture of α-FeOOH and Fe3O4. The rust formed on HPS provides better protection and HPS has lower corrosion rates than PCS. Copper and chromium in HPS enrich in the rust layer and enhance the compactness of the rust layer. Based on the results of the accelerated corrosion tests and rust layer analysis, the roles of Cu and Cr against corrosion are discussed, providing HPS with chemical specification which has been industrially successful to produce weathering steel for bridge structure.
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  Weldability of 780 MPa Super-High Strength Heavy-Duty Truck Crossbeam Steel

  WANG Xiao-nan,DI Hong-shuang,ZHANG Chi,DU Lin-xiu,DONG Xue-xin

  中国钢铁期刊网. 2012, 19(6): 64-69.

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  CO2-shielded welding experiments of newly developed, 780 MPa super-high strength heavy-duty truck crossbeam steel were conducted, and the microstructure, microhardness, mechanical properties, and impact toughness of the welded joint were studied. The evolution of the microstructure of the welded joint occurred as follows: welding seam (acicular ferrite+proeutectoid ferrite)→fusion zone (granular bainite-long strip M/A island)→coarse grain zone (granular bainite-long strip or short bar M/A island)→fine grain zone (ferrite+pearlite+blocky M/A island)→mixed grained zone (ferrite+granular bainite+blocky M/A island)→base metal (proeutectoid ferrite+granular bainite-blocky or granular M/A island). Increasing the density of the grain boundaries can effectively improve the impact toughness, and the blocky M/A island hindered crack propagation more effectively than the long strip M/A island. The new hot-rolled 780 MPa super-high strength steel had excellent weldability. The welding technology was applied under the following conditions: welding voltage was 20 to 21 V, welding current was 200 to 210 A, and the gas flow rate was 25 L/min.
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  Influence of Air-Knife Wiping on Coating Thickness in Hot-Dip Galvanizing

  ZHANG Yan,,CUI Qi-peng,SHAO Fu-qun,WANG Jun-sheng,ZHAO Hong-yang

  中国钢铁期刊网. 2012, 19(6): 70-78.

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  In hot-dip galvanizing process, air jet wiping control is so crucial to decide the coating thickness and uniformity of the zinc layer on the steel strip. The mathematical models developed predict the zinc coating thickness as a function of pressure and shear stress. The required pressure and shear stress profile on the strip surface were calculated using regression analysis, and carried out using numerical simulation as FLUENT, a finite element analysis software. The influences of the outlet pressure, the nozzle to strip distance, the slot opening, the edge baffle plate, as well as the tilting angle of air knife were discussed. Combining with these results and regression analysis on the practical data, four first-order polynomial multi-parameter models were established for different targeted coating thicknesses with better regression coefficients. The validated model was used to carry out sensitivity analysis to determine the favorable controlling regime for the air jet wiping process.