2010年, 第17卷, 第2期　刊出日期：2010-02-15

  

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工艺
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  High Efficient Blowing Technique for Large and Medium Converters

  JIANG Xiao-fang;Yang Wen-yuan

  中国钢铁期刊网. 2010, 17(2): 1-1.

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  The high efficient blowing technique includes increasing oxygen supply intensity and optimizing slag forming. The oxygen supply intensity on 300t converters of No1 steelmaking shop at Bao Steel reaches 3.83 Nm3/t.min, and at Taiyuan Steel, Lianyuan Steel, Pinxiang Steel and other steel plants, the oxygen supply intensity on medium converters is in the range of 4.0-4.4 Nm3/t.min. The productivity of converter can be increased by 8-15% with adoption this technique. The whole technique, including design and manufacture of lance nozzle with reasonable pacnolontenue of outlets, technique of oxygen supply and slag forming, has been developed by CISRI to meet the need of technique transfer.
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  Principle and Practice on High Nitrogen Steel Melting by Blowing Ammonia Gas

  MA Shao-hua

  中国钢铁期刊网. 2010, 17(2): 6-6.

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  Abstract: During the HNS melting process, the absorption reaction of Nitrogen in the liquid steel by blowing NH3 and N2 was investigated respectively. In order to obtain higher content of nitrogen in steel, the liquid steel should be deoxidized and desulfurized because the [O] and [S] as surface activity element is not favorable to absorb nitrogen in melting process. Based on the metallurgical thermodynamics, the coupling reaction of NH3 with [O] can improve the generation of activity nitrogen atom in liquid steel. Nitrogen atom is easier to be absorbed than nitrogen molecule. At the same time, blowing ammonia gas can remove the oxygen from liquid steel and decreased the inclusion in the steel. Experiments of HNS melting in ten-kilogram inductive furnace indicated that, for liquid steel with same content of alloys and blowing the same mole of nitrogen , the absorption effect of nitrogen by blowing NH3 increase 18~75% than that of blowing N2.The technical process of melting HNS by blowing NH3 under normal pressure is feasible in industry production.h
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  Thermodynamic Calculation and MnS Solubility of Mn-Ti Oxide Formation in Si-Mn-Ti Deoxided Steel

  Zhuo Xiao－Jun

  中国钢铁期刊网. 2010, 17(2): 10-16.

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  Mn-Ti oxides in Si-Mn-Ti deoxidized steels after cooling in the furnace were investigated. The composition and morphology of inclusions were analyzed by using FE-SEM with EDS. Mn-Ti oxides were found to be effective sites to induce intragranular ferrite formation. The thermodynamic calculation was employed to interpret the critical condition for Mn-Ti oxide formation. Mn-Ti oxide formation is controlled not only by [Mn], [Ti] content, but also by total oxygen in steel. When [Mn] and [Ti] were around 1.5 wt% and 0.005~0.01 wt% respectively, Mn-Ti oxide could form as total oxygen was 0.001~0.002 wt%. The experimental results are in good agreement with thermodynamic calculation results. Also MnS solubility was examined in Mn-Ti oxide inclusion system. With MnO content in Mn-Ti oxide increasing, MnS solubility in these oxides increased. High MnO content had an benefit on MnS precipitation in Mn-Ti oxide.
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  Analysis of Strip Temperature in Hot Rolling Process by Finite Element Method

  MEI Rui-bin;LI Chang-sheng

  中国钢铁期刊网. 2010, 17(2): 17-17.

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  The program was developed by finite element method to calculate the temperature distribution in hot strip rolling. The heat transfer coefficient of air cooling, water cooling and thermal resistance between work roll and strip were analyzed. A new heat generate rate model was proposed according to the influence of source current density, work frequency, air gap and distance to edge on induction heating by finite element method (FEM). The heat generate rate was considered into the thermal analysis to predict the temperature distribution in the induction heating. The influence of induction heating on the strip temperature was investigated with different strip thicknesses. The temperature difference became more and more obvious with the increase of thickness. The strip could be heated quickly by the induction heating both in surface and center because of the thermal conductivity and skin effect. The heat loss of radiation has important influence on the surface temperature. The surface temperature could be heated quickly with high frequency when the strip is thicker.
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  Smith Prediction Monitor AGC System Based on Fuzzy Self-tuning PID Control

  SUN Jie;ZHANG Dian-hua

  中国钢铁期刊网. 2010, 17(2): 22-22.

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  In accordance with the feature of pure delay in monitor AGC system for cold rolling mill, a new fuzzy self-tuning PID Smith prediction controller is developed. The position control model is deduced based on a single stand cold rolling mill, and the fuzzy controller for monitor AGC system is designed. The analysis in dynamic performance between traditional PID Smith prediction controller and fuzzy self-tuning PID Smith prediction controller is done by MATLAB toolbox. The simulation results show that fuzzy self-tuning PID Smith controller has stronger robustness, faster response and higher static accuracy than traditional PID Smith controller.
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  Effect of Compressive stresses on Microstructure of Scales Formed on Pure Iron Under Continuous Air Cooling

  ZHOU Chang-hai Hai-tao MA Lai WANG

  中国钢铁期刊网. 2010, 17(2): 27-27.

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  The microstructure development of oxide scale on pure iron under the mutual effect of compressive stress and cooling conditions was investigated. Oxide-scale structure was examined by optical microscopy (OM) and scanning electron microscopy (SEM). It was found that oxide scale formed under normal cooling conditions had a structure mainly consisted of an outer magnetite and an inner wüstite layer. When a compressive stress was applied, numerous magnetite precipitates formed within wüstite layer homogeneously at starting cooling temperature of 900℃, and the wüstite layer in the scale transformed into a mixture of mostly magnetite/iron eutectoid and magnetite layer at starting cooling temperature of 700℃. The wüstite decomposition and precipitation of magnetite in wüstite under compressive stress was discussed.
材料
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  Fracture Characteristics of Austempered Spheroidal Graphite Aluminum Cast Irons

  Masoud Zandira

  中国钢铁期刊网. 2010, 17(2): 31-35.

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  The fracture characteristics of austempered spheroidal graphite aluminum cast iron had been investigated. The alloy contained 3.2% C, 2.2% Al, 0.8% Ni and 0.05% Mg. Impact test samples were produced from keel blocks cast in Co2 molding process. The oversized impact samples were austenitized at 850 and 950?C for two hours followed by austempering at 300 and 400?C for 30, 60, 120 and 180 minutes. The austempred samples were machined and tested at room temperature. The impact strength values in those austempered at 400?C varied between 90 and 110 joules. Lower bainitic structures showed impact strength values of 22 to 50 joules. The fractures of the samples were examined using SEM. The results showed that the upper bainitic fracture reveaed a honey Comb- like topography, which confirmed the ductile fracture behavior. The lower bainitic fractures of those austempered for short times revealed brittle fracture.
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  A Model for Precipitation Kinetics in Vanadium Microalloyed Steel

  Fang Fang Qilong Yong Caifu Yang Hang Su

  中国钢铁期刊网. 2010, 17(2): 36-42.

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  Small dispersoid particles inhibit recrystallisation and are thus critical in controlling the grain structure of many high strength low alloy steels. A general, kinetic model has been developed to predict precipitation of V(C,N) in vanadium microalloyed steels with a sery of carbon and nitrogen contents. The solubility product and driving force of carbonitrides precipitated in austenite as well as the interfacial energy and other parameters can be evaluated to predict Nucleate Rates-Temperature (NrT) and Precipitation-Time-Temperature (PTT) diagram. By using stress relaxation tests and fitting with Avrami equation, it is possible to draw PTT diagrams. When comparing the predictions of the model with results of experimental investigation on V(C,N) precipitating in austenite, they have good coincidence. The nose temperature is around 850℃obtained by experiment which is 30℃ difference with the model, and nitrogen has more effect on the shape of “C” curve of PTT diagram then carbon that made “C” curve leftward significantly.
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  Influence of Deformation on Transformation of Low Carbon and High Nb-containing Steel during Continuous Cooling

  YIN Shu-Biao Zhi-Bo ZHANG

  中国钢铁期刊网. 2010, 17(2): 43-0.

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  The effect of deformation in the nonrecrystallized region on the phase transformation for a low carbon and high Nb-containing steel with coarse austenite grain size was investigated by means of dilatometry measurement and microstructure observation. The results show that with the cooling rate increased, both the transformation start and finish temperatures measured by dilatometer are decreased, and the corresponding microstructure is changed from ferrite and pearlite to full granular bainite gradually. The dynamic CCT diagram is plotted according to the dilatometry measurements and microstructure observations. Dilatometry measurements also show that the transformation start and finish temperatures of the tested steel are raised with increasing strain, strain rate and deformation temperature, and the reasons for this are discussed.
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  Microstructure transformation behaviour of 610MPa HSLA Steel Plate for 150,000 m3 Oil Storage Tank Construction

  SUN Wei-hua;WANG Guo-dong

  中国钢铁期刊网. 2010, 17(2): 48-52.

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  Static and dynamic continuous cooling transformation (CCT) on 610MPa HSLA Steel Plate for 150,000 m3 Oil Storage Tank Construction were carried out on a MMS200 thermo-mechanical simulation system. It has found that with cooling rate increases pre-eutectoid ferrite, pearlite, granular bainite and lathing bainite will appear in the transformed microstructure. In comparison with static CCT, the transforming points of acicular ferrite, granular bainite and lathing bainite in the dynamic CCT curve shift to the left proving an increased acicular ferrite and bainite transformation area.
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  Effects of Austempering and Martempering Processes on Amount of Retained Austenite in Cr-Mo Steels (FMU-226) Used in Mill Liner

  M.H. Shaeri

  中国钢铁期刊网. 2010, 17(2): 53-53.

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  The presence of retained austenite gives rise to deterioration of the wear resistance and fracture strength of Cr-Mo steels in many cases. In this research, the effects of different heat treatments including direct quenching, martempering and austempering on the retained austenite present in the microstructure of these steels have been investigated. Samples were austenized at 950 oC followed by direct quenching using compressed and still air. The samples were also isothermally quenched in the salt bath at 200 and 300 oC for 2, 8, 30, and 120 minutes. Microstructures of the specimens were studied using optical microscope (traditional black and white etching as well as color etching), scanning electron microscope (SEM), microhardness tester, and X- ray diffraction (XRD). Results showed that the lowest amount of retained austenite in the microstructure was obtained in the specimens quenched isothermally at 300oC for 120 minutes.
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  Influence of Boron Content in Iron Oxide on Performance of Mn-Zn Ferrites

  YU Cheng-feng;LI Yu-guang

  中国钢铁期刊网. 2010, 17(2): 59-62.

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  The ferrites of PC30 (Mn-Zn ferrites) were prepared by using a dry processing route. The effect of Mn-Zn ferrites doped with H3BO3 has been investigated on the basis of microstructure analysis. The results on the samples doped with H3BO3 which is less than 50ppm show that the doping does not have significant effect on Pc, μi, microstructure and density of Mn-Zn ferrites. With further increases in H3BO3 doping(>100ppm), the microstructure of Mn-Zn ferrites is at the critical state between fine grain and ”sandwich”,, the μi and density of Mn-Zn ferrites begin falling quickly, and the increased H3BO3 doping also results in deteriorated Pc properties. Thus controlling the B content in iron oxide is of utmost importance for the quality of Mn-Zn ferrites in producing process.
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  960MPa Grade High Performance Weldable Structure Steel Plate Processed by using TMCP

  Nie Yi

  中国钢铁期刊网. 2010, 17(2): 63-66.

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  For the purpose of getting high strength with good toughness and welding ability, we designed a composition for 960MPa welding structure steel. This composition has very low carbon contents and was microalloyed. The TMCP and RPC were employed to ensure fine lath-like bainitie achievement. This kind of microstructure could induce higher strength and better toughness. This way, steels could be strengthened to reach or even exceed 960MPa.
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  Aging Precipitates and Strengthening Mechanism of T122 Boiler Steel

  Han-Sheng BAO Shi-chang CHENG Zheng-dong LIU Shu-ping TAN

  中国钢铁期刊网. 2010, 17(2): 67-73.

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  T122 steel has been used to produce superheater or reheater of ultra supercritical boilers. With the help of chemical phase extraction and microstructure characterization, the authors of the paper investigated the performance of aging precipitates of T122 steel, such as M23C6 carbide, Laves phase, MX phase and cu-rich phase, discussed the strengthening mechanism of the steel, and calculated athermal yield stress of lath substructure, dislocations and precipitates of the steel. It was found that lath substructure and dislocations dominate the strengthening attribution and precipitation hardening goes second to the strengthening attribution.
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  Formation of In-Situ Dispersion Strengthening Particles in Cast FeCrAl Alloy

  He-Li Luo Chang-hai Li

  中国钢铁期刊网. 2010, 17(2): 74-78.

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  In order to fabricate dispersion strengthened alloys that strengthened by submicron-sized or nano-sized stable particles through casting routes, understanding of the formation process of dispersion strengthening particles at metal melt is of significance. In present study, Nano NiO and TiO2 particles were selected as reactant to form in-situ dispersion strengthening oxide particles in Fe20Cr5Al alloy. Nano NiO and TiO2 particles powder was separately dispersed into nano Ni powder first. The mixed nano powder was added into Fe20Cr5Al alloy melt when pouring the melt into mold. The study shows that nano NiO particles were not as effective as nano TiO2 particles in forming dispersion strengthening Al2O3 particles. The final diameters of dispersion strengthening oxides particles arose from nano TiO2 particles were in the range of submicron. The Brownian collision of particles had caused this coarsening.