2013年, 第20卷, 第7期　刊出日期：2013-07-15

  

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工艺
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  Two-Stage Mathematical Programming Approach for Steelmaking Process Scheduling Under Variable Electricity Price

  TAN Yuan-yuan,,HUANG Ying-lei,LIU Shi-xin,

  中国钢铁期刊网. 2013, 20(7): 1-8.

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  The steelmaking process scheduling problem by considering variable electricity price (SMSPVEP) was investigated. A decomposition approach was proposed for the SMSPVEP. At the first stage, mathematical programming was utilized to minimize the maximum completion time for each cast without considering variable electricity price. At the second stage, based on obtained relative schedules of all casts, a mathematical model was formulated with an objective of minimizing the energy cost for all casts scheduling problem. The two-stage models were tested on randomly generated instances based on the practical process in a Chinese steelmaking plant. Computational results demonstrate the effectiveness of the proposed approach.
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  Prediction of Mechanical Properties of Hot Rolled Strip by Using Semi-Parametric Single-Index Model

  ZHAO Yong-hong,WENG Yang,PENG Ning-qi,TANG Guang-bo,LIU Zheng-dong

  中国钢铁期刊网. 2013, 20(7): 9-15.

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  A semi-parametric single-index model based approach was proposed for prediction of mechanical properties of hot rolled strip. Based on industrial production data, a semi-parametric single-index model was developed by choosing the appropriate kernel function and window width to predict the yield strength, tensile strength and elongation. When data samples are limited, compared with regression method and neural network method, the prediction results show that the semi-parametric single-index model based method is more adaptive and the prediction performance is superior to those by both regression and neural network methods.
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  Effects of CaO on Precipitation Morphology of Metallic Iron in Reduction of Iron Oxides Under CO Atmosphere

  ZHAO Zhi-long,,TANG Hui-qing,GUO Zhan-cheng

  中国钢铁期刊网. 2013, 20(7): 16-24.

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  Growth process of iron whiskers and mechanism of CaO influence on precipitation morphology of metallic iron at the gas-solid interfaces was studied. Analytical reagents of Fe(NO3)3 and Ca(NO3)2 aqueous solution were used to prepare sheet film sample of Fe2O3-CaO by thermal decomposition at high temperature. In-situ observation was conducted using a stereo optical microscope and a hot-stage. And reduction kinetics of samples was studied by thermo gravimetric (TG) method. Some samples after reduction were analyzed by using the scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and fourier transform infrared (FT-IR) spectrometer. Results indicate that during the reduction of iron oxides with CO, metallic iron is mostly precipitated as whisker and the precipitation behavior mainly depends on reduction rate. Doping CaO can significantly increase the reduction rate and effectively change the precipitation morphology of metallic iron after the reduction. When CaO doping concentration is less than 4% (mass percent), CaO can promote whisker formation of reduced iron; as it reaches 6% (mass percent), CaO inhibits iron whiskers growth; as it is more than 8% (mass percent), no whiskers could be observed. Therefore, controlling the quantity of Ca2+ is effective to control the formation and growth of iron whiskers during gaseous reduction and thus eliminating ore grain sticking caused by intertexture of iron whiskers.
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  Effects of MgO Containing Additive on Low-Temperature Metallurgical Properties of Oxidized Pellet

  GAO Qiang-jian,SHEN Feng-man,WEI Guo,JIANG Xin,ZHENG Hai-yan

  中国钢铁期刊网. 2013, 20(7): 25-28.

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  As a main charging form of BF (blast furnace), pellets play an important role in blast furnace process. However, comparing with sinters, pellets have many disadvantages, such as reduction swelling, low softening and melting temperature and so on. Therefore, the flux pellets have been applied in blast furnace widely, especially MgO containing pellets. The light burned magnesite is applied as MgO containing additive in pellet production. The characters of light burned magnesite are explored. Meanwhile, the effects of it on low-temperature metallurgical properties are investigated such as low-temperature reduction degradation index (RDI), compressive strength (CS) and the reduction swelling index (RSI). The light burned magnesite calcined at 850 ℃ manifests better grindability, larger specific surface area, and higher hydration activity. It is found that the addition of light burned magnesite can improve low-temperature metallurgical properties (RDI, RSI) of the pellets. With the increase of light burned magnesite in pellets, the RSI and RDI decrease gradually; when the proportion of light burned magnesite does not exceed 2. 0% in pellets, the CS decreases slightly, but it still surpasses 2689 N, which can still meet the demand of BF.
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  Development of New Generation Cooling Control System After Rolling in Hot Rolled Strip Based on UFC

  LI Hai-jun,LI Zhen-lei,YUAN Guo,WANG Zhao-dong,WANG Guo-dong

  中国钢铁期刊网. 2013, 20(7): 29-34.

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  Ultra-fast cooling (UFC) is an advanced technology in hot rolling field. Through this technology, great changes on the run-out table are produced in the strip cooling process. In order to adapt to these changes, a new generation of hot strip cooling control system after rolling was developed based on the UFC basic principle. The system can not only accomplish temperature of UFC delivery side, coiling temperature, cooling rate, etc, and multi-objective accuracy control, but also offer more flexibility and new attractive possibilities in terms of cooling pattern on the run-out table, which could be of prime importance for the production of some difficult steels. In addition, through the time-velocity-distance (TVD) profile prediction combined with speed feed-forward control and coiling temperature feedback control, the coiling temperature control precision can be effectively improved during accelerative rolling in the system. At present, the system has been successfully used in the conventional strip production line and CSP short process production line, and its application effect is perfect.
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  Floating Properties of Agglomerated Inclusion in Liquid Steel

  GUO Luo-fang,,WANG Yao,,LI Hong,,LING Hai-tao,

  中国钢铁期刊网. 2013, 20(7): 35-39.

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  The fractal properties and floating features of agglomerated inclusions are investigated by the analysis of fractal theory and water simulation experiment. The results show that there is an obvious quantitative relationship between the aggregate floating velocity, the number of tiny inclusion granules and fractal dimension. Namely, for the aggregates which contain the same number of micro granules, the greater the fractal dimension, the larger the floating velocity; for the aggregates which have the same fractal dimension, the more the number of tiny inclusion granules contained by an aggregate, the larger the floating velocity. The mathematical model obtained by regression analysis can better reflect the relationship between the aggregate floating velocity, the number of tiny inclusion granules and fractal dimension. So in order to increase the floating velocity of aggregated inclusion with small fractal dimension, some appropriate measures of making it reconstruct to increase its fractal dimension can be taken.
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  Behaviors of Denitrogenation in RH-MFB

  ZHOU Jian,QIN Zhe,ZHANG Bo,PENG Qi-chun,QIU Sheng-tao,GAN Yong

  中国钢铁期刊网. 2013, 20(7): 40-44.

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  According to the analysis related to kinetic mechanism of vacuum denitrogenation and combining with the actual production of RH-MFB (a combination of Ruhstahl-Hausen vacuum degassing process with a multifunctional oxygen lance) at Liansteel, the limit step and model equation of vacuum denitrogenation are determined. Meanwhile, the influencing factors of nitrogen removal from liquid steel in vacuum of RH-MFB are analyzed. The results show that the limit step of vacuum denitrogenation in RH-MFB is the mass transfer of nitrogen in liquid boundary layer and the reaction follows first order kinetics. Keeping the necessary circulation time under the working pressure (67 Pa) is helpful to nitrogen removal from steel. The oxygen content in molten steel has little influence on the removal of nitrogen after deep deoxidation, while the sulphur content in liquid steel is always relatively low and has little effect on denitrogenation. The sharp decrease of carbon content in steel drives the process of denitrogenation reaction so as to exhibit a faster denitrogenation rate. The interfacial chemical reaction and argon blowing play a major role in the nitrogen removal when the carbon content in liquid steel is stable.
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  Microstructure of a Variety of Cokes After Alkali Enrichment

  QI Cheng-lin,ZHANG Jian-liang,LIU Hong-quan,KONG De-wen,WANG Xiao-liu

  中国钢铁期刊网. 2013, 20(7): 45-49.

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  It is difficult to distinguish tamping coke and top charging coke by conventional testing methods, such as cold strength, abrasion resistance, reactivity and strength after reaction. Some of tamping coke′s properties were even better than those of top charging coke, but from practical using effects of blast furnace, tamping coke was not as good as top charging coke. The reaction conditions were featured as high temperature, high alkali condition, intense reaction atmosphere and short time. Distribution of porosity in profile, microstructure and slag forming property of ash were analyzed and following conclusions were obtained. After alkali-rich reaction, there were obvious differences between top charging coke and tamping coke in microstructure. The porosity′s unevenness of tamping coke was greater than those of top charging coke, and tamping coke was with less and big pores in out space and inner part was dense with more throughout pores. After phase diagram and microstructure analysis, it could be obtained that ash forming characteristics of top charging coke were better than those of tamping coke, and top charging coke′s pores were blocked more seriously than those of tamping coke. From analysis of tuyere samples, it could be found that calcium content of ash in coke′s pores was small and it should belong to coke′s inherent ash; kalium (wK=28%) was unusually high in coke, so the situation of high alkali was close to real blast furnace reaction condition.
材料
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  Effects of Strain Rate on Low Cycle Fatigue Behaviors of High-Strength Structural Steel

  LUO Yun-rong,,HUANG Chong-xiang,TIAN Ren-hui,WANG Qing-yuan

  中国钢铁期刊网. 2013, 20(7): 50-56.

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  The low cycle fatigue (LCF) behavior of a high-strength structural steel was investigated in the strain rate range of 4×10-5-0. 12 s-1 (0. 001-3 Hz) under constant total strain (±1%) control. The cyclic stress response at all strain rates exhibited behavior of rapid softening in the early stage of fatigue life and subsequent saturation up to failure. It was found that the stress amplitude, the plastic strain amplitude, the plastic strain energy density and the fatigue life depend mainly on the strain rate. The strain rate of 0. 012 s-1 was found as a transition point where the LCF of the steel showed different behavior from low strain rate to high strain rate. The relationship between the time to failure and strain rate was expressed well by a power law relation. The fracture surfaces of the fatigue samples were characterized by using a scanning electron microscope (SEM) and the fracture mechanisms were discussed in terms of time-dependent deformation of the steel.
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  Microstructural Characterization of Spray Formed FGH4095 Superalloy During Hot Deformation

  XU Yi,SHU Qin,GUO Biao,SUN Chuan-shui

  中国钢铁期刊网. 2013, 20(7): 57-62.

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  In order to study the hot workability and to optimize the processing parameters for spray formed FGH4095 superalloy, thermal compression tests for spray formed FGH4095 superalloy have been finished by using a Gleeble 1500 thermal simulated test machine at the strain rates of 0. 01-10. 0 s-1 and temperatures of 1050-1140 ℃. The effects of strain rate and deformation temperature on the true stress-true strain curves and microstructure evolution were investigated. The results show that the generation of dynamic recrystallization (DRX) depends sensitively on deformation temperature. When the temperature was lower than 1080 ℃, long and narrow necklace grains were shown in the microstructure. When the temperature increased to 1140 ℃, new recrystallization grains were generated. The size and shape of γ′ precipitates in the grains have a very important effect as factors of hindering sufficient migration of dislocations on plastic deformation. The result of thermal processing map is in accord with the microstructure observation, and the best material thermal processing temperature is above 1128 ℃.
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  Dipping Paint Curing Amorphous U-Core Used as Reactor

  LI Guang-min,LI De-ren,LIU Tian-cheng,LI Li-jun,LU Zhi-chao

  中国钢铁期刊网. 2013, 20(7): 63-68.

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  Non-oriented silicon steel (35W310) and amorphous ribbon (Fe78Si9B13 amorphous alloy) reactor U-cores are made by welding and dipping paint curing, respectively. Amorphous U-core used to make reactor cut sharply eddy current loss due to high electrical resistivity characteristic, thickness of thin ribbon and insulation of dipping paint. The amorphous alloy has high and constant magnetic permeability, and is more suitable for reactor design power to filter high order harmonic component. Keeping off high magnetostriction district with magnetic flux density of 50-100 mT can weaken influence on inductance of inductor due to elongation of magnetostriction. Amorphous alloy has a lower temperature rise using the software Infolytica 7. 2 simulation.
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  Kinetics of Precipitation Behavior of Second Phase Particles in Ferritic Ti-Mo Microalloyed Steel

  HU Bin-hao,CAI Qing-wu,WU Hui-bin

  中国钢铁期刊网. 2013, 20(7): 69-77.

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  Two types of stress relaxation tests were carried out to investigate the incubation time for incipient precipitation of Ti(C,N) in deformed austenite and (Ti,Mo)C in ferrite of ferritic Ti-Mo microalloyed steel. The size distribution, amount and chemical composition of precipitates were obtained by using physicochemical phase analysis, and calculated according to thermodynamics and kinetics. The experimental results demonstrated that the incubation time was reduced with increasing Ti content, and prolonged with the addition of Mo. After 30% deformation at 850 ℃, the nucleation of strain-induced Ti(C,N) was a relatively slow process. On the other hand, the temperature where the nucleation rate of (Ti,Mo)C in ferrite was the highest descended first and then ascended with increasing Ti content, and so did the temperature where the incubation time was the shortest. The key point is that the temperature of steel containing about 0. 09% Ti is the lowest. The mass fraction of MC-type particles with size smaller than 10 nm in steel containing 0. 09% Ti and 0. 2% Mo reached 73. 7%. The size distributions of precipitates in steel containing 0. 09% Ti were relatively concentrated compared with that in steel containing 0. 07% Ti.
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  Influence of Mould and Insulation Design on Soundness of Tool Steel Ingot by Numerical Simulation

  M Heidarzadeh,H Keshmiri

  中国钢铁期刊网. 2013, 20(7): 78-83.

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  The solidification of 4. 4 t cold work tool steel ingot type X210Cr12 was simulated by Magma software. By the reduction of ingot height, solidification modeling and pouring of a new 3 t ingot were performed and decreasing the porosity formation potential in 3 t ingot in comparison with 4. 4 t ingot on the basis of Niyama criterion was observed which was in good accordance with experimental data. In order to produce sound ingot, a new 2. 8 t ingot mould was designed which includes some parameteric changes in mould such as mould slope, slenderness ratio, mould concavity radius, fillet radius of mould internal corners and feeding diameter to ingot upper diameter ratio. Furthermore, the effects of insulating between kokil and feeding ring and also insulating the outer surface of feeding ring as well as insulating the outer surface of one third of kokil upper part on centerline porosity formation were investigated in both 2. 8 and 4. 4 t ingots. The results show that the ingot which was produced in new designed 2. 8 t mould has a better Niyama pattern and the centerline porosities were eliminated.
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  Effect of Additive Cu-10Sn on Sintering Behavior and Wear Resistance of 316L Stainless Steel

  YANG Xia,BAI Ying-long,XU Meng,GUO Shi-ju

  中国钢铁期刊网. 2013, 20(7): 84-88.

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  Austenitic 316L stainless steel has good corrosion resistance; however, the relative softness often limits its application. Severe adhesive wear often occurs between the 316L stainless steel and the metal counterpart. Cu-10Sn alloy is often used to improve the wear resistance of powder metallurgy 316L stainless steel. The influence of Cu-10Sn on sintering behavior and wear resistance of powder metallurgy 316L stainless steel was investigated. The parameters investigated included sintering temperature and volume percent of Cu-10Sn. A maximum relative density of 97% was achieved with 25% (in volume percent) Cu-10Sn content at a sintering temperature of 1300 ℃ for 60 min. The irregular and sharp angles of 316L stainless steel particles become round, and the pores are removed completely as a result of large amount of liquid phase formed during sintering. The minimum friction mass loss was achieved with 25% Cu-10Sn content.
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  Ferrite Evolution During Isothermal Process in a High Deformability Pipeline Steel

  TAN Feng-liang,,LIU Qing-you,LEI Ting,JIA Shu-jun,DUAN Lin-na,

  中国钢铁期刊网. 2013, 20(7): 89-94.

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  In order to ensure the safety of long-distance oil and natural gas transmission pipeline installed in seismic and/or permafrost region, high strength pipeline steel with excellent deformability has been developed. The ferrite and bainite dual phase pipeline steel is a very important kind of high deformability pipeline steel. Polygonal ferrite is a key microstructure in ferrite and bainite dual phase deformability pipeline steel. Ferrite evolution during isothermal process at 700 ℃ after 50% deformation at 800 ℃ was conducted by using a Gleeble-3800 thermal simulator, and microstructure was characterized by using an optical microscope, a scanning electron microscope and a transmission electron microscope. There are two types of ferrite, ferrite with high density dislocation and ferrite with a little dislocation. There is about 7% (volume percent) deformation induced ferrite (DIF) for compression of 50% at 800 ℃ and strain rate of 1 s-1. During the isothermal process at 700 ℃, with the holding time increasing, ferrite volume percent, ferrite grain number and average ferrite grain size increase. As the holding time is prolonged, dislocation recovery occurs in DIF. There are secondary phases in ferrite when the holding time is too long, and secondary phases and dislocation formation in dislocation pinning.