2003年, 第10卷, 第2期　刊出日期：2003-05-25

  

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  Experiment of Microwave Heating on Self-Fluxing Pellet Containing Coal

  CHEN Jin, LIU Liu, ZENG Jia-qing, LIU Jin-ying, REN Rui-gang

  钢铁研究学报（英文版）. 2003, 10(2): 1-4.

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  The self-fluxing pellets containing coal possess an independent self-reducing and self-slag-making system. A high metallization rate can be achieved without external reduction condition at high temperature, and it looks like a micro-blast-furnace by itself. The essential condition to use it is to supply heat to the pellet rapidly and uniformly and keep it at a certain temperature. Microwave heating can meet the need of rapid and uniform heating. The results show that the temperature of the pellet with a certain weight increases as the microwave power in-creases. The heating rate of the pellet is increased from 9. 17 K/min (5kW) to 71. 65 K/min (15kW).
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  Calculation Model of Mass Action Concentration for Mg-Al, Sr-Al and Ba-Al Melts and Determination of Their Thermodynamic Parameters

  ZHANG Jian

  钢铁研究学报（英文版）. 2003, 10(2): 5-9.

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  Based on the phase diagrams and the mass action law in combination with the coexistence theory of metallic melts structure, the calculation model of mass action concentration for Mg-A1, Sr-Al and Ba-Al was built, and their thermodynamic parameters were determined. The agreement between calculated and measured results shows that the model and the determined thermodynamic parameters can reflect the structural characteristics of relevant melts. Howev-er, the fact that the thermodynamic parameters from literature don t give the value agree with the measured result may be due to unconformity of these parameters to real chemical reactions in metallic melts.
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  Numerical Evaluation of Two k-ε Turbulence Model for Predicting Flow and Solidification in Continuous Casting Slab

  LIU He-ping, GAN Yong, QIU Sheng-tao

  钢铁研究学报（英文版）. 2003, 10(2): 10-16.

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  A steady three-dimensional fluid flow and solidification model was built based on CFD software by high-Reynolds-number and Lam-Bremhorst low-Reynolds-number k-ε model. During the simulation, the fixed-grid enthalpy-porosity technique was used to represent the solidification, and Darcy law was adopted to simulate the flow in mushy region. The prediction for steel flow and solidification was evaluated by the comparison of two turbulence models. It is found that both Lam-Bremhorst low-Reynolds-number and high-Reynolds-number k-ε models predict the same trend of the steel flow and temperature distribution. However, due to the effect of turbulent flow on heat transfer, the low-Reynolds-number turbulence model predicts longer penetration depth of molten steel in sub-mold region, less shell growth and higher shell surface temperature at the narrow face compared with standard k-ε model.
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  Numerical Simulation of Level Magnetic Field

  HUANG Jun-tao, WANG En-gang, HE Ji-cheng

  钢铁研究学报（英文版）. 2003, 10(2): 17-20.

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  According to Maxwell electromagnetic field theory and magnetic vector potential integral equation, a mathematical model of LMF (Level Magnetic Field) for EMBR (Electro-magnetic brake) was proposed, and the reliable software for LMF calculation was developed. The distribution of magnetic flux density given by numerical simulation shows that the magnetic flux density is greater in the magnet and magnetic leakage is observed in the gap. The magnetic flux density is uniform in horizontal plane and a peak is observed in vertical plane. Furthermore, the effects of electromagnetic and structural parameters on magnetic flux density were discussed. The relationship between magnetic flux, electromagnetic parameters and structural parameters is obtained by dimensional analysis, simulation experiment and least square method.
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  Optimum Position of Electromagnetic Brake on Slab Caster

  LEI Hong, ZHU Miao-yong, HE Ji-cheng

  钢铁研究学报（英文版）. 2003, 10(2): 21-26.

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  Three-dimensional mathematical models were developed for studying the molten steel flow and the trajectories of inclusions and bubbles in continuous casting mold with electro-magnetic brake. The results show that the effect of the electromagnetic brake on the molten steel flow and the movement of inclusions and bubbles depends on the position of electromagnetic brake. While EMBR Ruler is installed at the exit of the submerged entry nozzle, the velocity of the main jet of molten steel from the nozzle can be decreased effectively, the velocity of the molten steel streams near the free surface and the narrow face is reduced obviously; Mean-time more inclusions and bubbles could float up to the slag layer.
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  Fine Microstructure of Bainitic Ferrite in Bainitic Steel

  LI Feng-zhao, AO Qing, QIN Chao, JIANG Jiang, LIU Yu-xian, MENG Xiang-min, HE Lian-long

  钢铁研究学报（英文版）. 2003, 10(2): 27-29.

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  The fine microstructures of medium and medium-high carbon bainitic steels were observed and analyzed by high resolution electron microscope (HREM). The investigation results show that there are retained austenitic films with different appearances and sizes in bainitic fer-rite laths. The boundaries of different structure levels are separated and encircled by retained austenitic films. The fine structure units and their sizes of different structure levels in the bai-nitic ferrite were determined by retained austenitic films. The bainitic ferrite laths are com-posed of different structure level sublaths, subunits and elementary units (or so called sub-sub-units). The dimensions of most sublaths, subunits and elementary units are 25-80 nm, 25-80 nm and 5. 0-30 nm, respectively.
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  C-Curves of Tool Steels for Annealing and Their Application

  LIU Zong-chang, LI Wen-xue, SUN Jiu-hong

  钢铁研究学报（英文版）. 2003, 10(2): 30-32.

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  TTT diagrams, CCT diagrams and critical points of steels H13, S7, S5 for annealing were measured and investigated by means of Formastor-Digital full-automatic phase trans-formation dilatometer in order to make their annealing technology reasonable and scientific. The basis is provided for making a new annealing technology scientifically. The new technology improves the quality of annealed materials, saves energy and increases productivity.
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  Simplified Thermodynamic Model for Pro-Eutectoid FerriteFormation in Multicomponent Structural Steel

  ZHU Hong-tao, CHANG Hong-bing, XU Zu-yao

  钢铁研究学报（英文版）. 2003, 10(2): 33-37.

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  By introducing a parameter of difference in ferrite formation temperature between bi-nary Fe-C and multicomponent system, and referring to the thermodynamic model for Fe-C bi-nary system, a simplified thermodynamic model for pro-eutectoid ferrite formation in Fe-∑X_i-C multicomponent structural steels (X_i, =Mn, Si, Mo, Cr, Ni or Ti, etc) was suggested. The comparison of the calculated A_e3 temperatures with the measured data of steels 42 shows that the relative standard deviation and root-mean-square (RMS)error between them are only 0.71% and 8. 92 K, respectively. However, the deviations between the same measured data and the values calculated from the super element model are as high as 1.86% and 23. 83 K, respectively. It can be concluded that the simplified thermodynamic model for pro-eutectoid ferrite formation in multicomponent structural steels is acceptable and the calculated A_e3 temperatures are in good agreement with the experimental data.
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  Theory and Practice of Oxide Inclusion Composition and Morphology Control in Spring Steel Production

  XUE Zheng-liang, LI Zheng-bang, ZHANG Jia-wen, YANG Wu, GAN Chao-fu, WANG Yu

  钢铁研究学报（英文版）. 2003, 10(2): 38-44.

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  In order to control the composition, morphology and size distribution of oxide inclusions in spring steel, the relationship between the content or activity of aluminum and calciumin molten steel and compositions of oxide inclusion precipitated at different temperatures was determined based on thermodynamic equilibrium for spring steel 60Si2MnA, and has been verified by practice. The size distribution of non-metallic inclusions electrolytically extracted from specimens of hot rolled spring steel was determined by image analyzer. The results show that there are a great deal of large inclusions in spring steel produced by the conventional process, and the quantity and the size of large inclusions in spring steel produced by new process are largely reduced. As a result, the fatigue properties of the spring steel produced by new process are highly improved, and the ratio of σ-1/σb is raised from 0. 451 to 0. 468.
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  Effect of Adding Nitrogen on Microstructure and Property of Vanadium Microalloyed Reinforcing Bar Steel

  LIU Shu-ping, YANG Cai-fu, ZHANG Yong-quan

  钢铁研究学报（英文版）. 2003, 10(2): 45-50.

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  The mechanical properties of reinforcing bar steel microalloyed with vanadium and nitro-gen (known as V-N steel) and its microstructures were studied. The results indicate that by adding nitrogen to the steel, the tensile strength of the steel is increased by 135 MPa and the yield strength is increased by 120 MPa for the same vanadium content of vanadium steel. The saving ratio in vanadium content is higher than 33. 3% for identical or similar yield strength. Nitrogen added to the steels promotes the precipitation of V(C, N), because the ratio of vanadium content to nitrogen content is near to stoichiometric ratio. The amount of V(C, N) is doubled and fine particles of1-10 nm are increased by 53 %. At the same time, adding nitrogen to the steel refines ferrite grain size effectively. The practical ferrite average grain size of V-N steel bar is 5. 8μm. So nitrogen in the steel promotes effectively the role of vanadium precipitation strengthening and grain refinement, reaching the target of full utilization of vanadium.
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  Research on Stress-Induced Nucleation of ε-Martensite inFe-17Mn-10Cr-5Si-4Ni Polycrystalline Alloy

  LIU Qing-suo, GU Nan-ju, LIN Cheng-xin

  钢铁研究学报（英文版）. 2003, 10(2): 51-54.

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  The relation between stacking fault overlap and martensitic nucleation in Fe-17Mn-10Cr-5Si-4Ni alloy was studied. The arrayed structure of dislocations and characteristics of ε-martensite formation under stress were in-situ observed by TEM. The results reveal that ε-martensite nucleates at the top of stacking faults overlapped band, where the ordered arrayed structure of Shockley partial dislocations exists. External stress promotes e-martensitic nucleation ability because of accelerated ordering of Shockley partial dislocations in stacking faults overlapped band.
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  Giant Magnetoimpedance Effect of As-Spun Nanocrystalline Ribbon of FeZrBCu Alloy

  LI Bo, HU Ji-fan, QIN Hong-wei, MA Nuo, AN Kang, WANG Xin-lin

  钢铁研究学报（英文版）. 2003, 10(2): 55-57.

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  The melt-spun nanocrystalline ribbons of Fe₈65Zr₇B₄Cu25 alloy were prepared by single wheel technique with wheel surface velocity of 37 m/s. It is found that there appears a lot of α-Fe nanoparticles with sizes of 5-10 nm in as-spun nanocystalline ribbons which exhibit giant magneto-impedance (GMI) effect. The GMI ratio up to 33.69% at frequency f=1 MHz under a DC field of 5172 A/m can be obtained.
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  Simple Predicting Method for Fatigue Crack Growth Rate Based on Tensile Strength of Carbon Steel

  WANG Xi-shu, KAWAGOISHI Norio

  钢铁研究学报（英文版）. 2003, 10(2): 58-62.

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  Three types of fatigue tests for an annealed carbon steel containing carbon of 0. 42% were carried out on smooth specimens and specimens with a small blind hole in order to investigate the fatigue crack growth law. A simple predicting method for crack growth rates has been proposed involving strength σ_b and the relation between cyclic stress and strain. The validity of proposed method has been confirmed by experiments on several carbon steels with different loadings.