2008年, 第15卷, 第1期　刊出日期：2008-02-15

  

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Metallurgy and Metal Working
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  Temperature Rise Characteristics of CarbonContaining Chromite Ore Fines in Microwave Field

  LI Ning;CHEN Jin;YAN Hong;FENG Xiumei;CUI Huijun;LIU Jinying

  中国钢铁期刊网. 2008, 15(1): 1-0.

  摘要 ( )   可视化   收藏

  To avoid the nonuniform phenomena of heat and mass transfer of metallurgical powdery materials caused by conventional heating method, the temperature rise characteristics of carboncontaining chromite ore fines in the microwave field were investigated using microwave heating in a microwave metallurgical furnace. The experimental results show that the carboncontaining chromite ore fines have better temperature rise characteristics in the microwave field at a frequency of 245 GHz. After heated in the microwave field of 10 kW, the temperature of 1 kg carboncontaining chromite ore fines rose up to 1 100 ℃ in 7 min, at a temperature rise rate of 1571 (℃·min-1·kg-1), whereas the temperature of 1 kg carboncontaining magnetite ore fines rose only up to 1 000 ℃ in 10 min, at a temperature rise rate of 100 (℃·min-1·kg-1). With increasing carbonfitting ratios and by adding calcic lime, their heating effects changed regularly.
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  Combustion Characteristics of Polyethylene and Coal Powder at High Temperature

  LONG Shigang;CAO Feng;WANG Siwei;SUN Liuheng;PANG Jianming;SUN Yuping

  中国钢铁期刊网. 2008, 15(1): 6-0.

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  To study the combustion characteristics of the polyethylene (PE) particle and coal powder at blast temperature of the blast furnace, the contents of CO and CO2 of offgas during the combustion of PE particle and coal powder at the 1 200 ℃ and 1 250 ℃ were measured using carbon monoxide and carbon dioxide infrared analyzer, and then the corresponding combustion ratio was calculated. The results showed that when the temperature is high, the combustion speed of PE and coal powder is high and the corresponding combustion ratio is high. Whereas, the combustion speed and ratio of PE are much higher than those of coal powder.
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  FeMoB Enhanced Sintering of P/M 316L Stainless Steel

  YANG Xia;GUO Shiju

  中国钢铁期刊网. 2008, 15(1): 10-0.

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  Liquidphase enhanced sintering of powder metallurgy (P/M) 316L stainless steel by addition of sintering aids was studied. 2%-8% of prealloyed FeMoB powder with two different particle sizes was added as sintering aids, and the specimens were sintered in vacuum at 1 200-1 350 ℃. The results show that the fine FeMoB powder (5-10 μm) has stronger activated effect. The sintered density increases with the increase in sintering aid content or sintering temperature. Warm compaction has a better effect on the control of dimensional precision of compacts. The prealloyed FeMoB powder deviated from Mo2FeB2 component can also be sintering aid of P/M 316L stainless steel.
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  Physical Simulation of New Desulphurization Technology Using Pulsed and Rotary StirringInjection

  WU Wei;WU Wei;HU Yanbin;LIU Liu;DING Yongliang

  中国钢铁期刊网. 2008, 15(1): 15-0.

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  The contrast experiment of different stirring modes, which includes a new type of stirringinjection with the method of pulse and rotation, and the initial oneway stirring method, is done through physical simulation in the laboratory. The stirring methods of pulse and rotation are of two kinds. One is pulsed and rotary stirrer with positive and opposite directions. The other is pulsed and rotary stirrer with rotationstoprotation. The results show that the stirring mode of pulse and rotation has better effects than the oneway stirring method. The specific effects are that the mixing time of the melting bath is apparently shortened, the number of grains involved in the liquid surface is increased, and the residence time of air bubble in water is doubled.
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  Effect of Structure Parameters on Power and Magnetic Field in Electromagnetic SoftContact Continuous Casting System

  DENG Anyuan;WANG Engang;HE Jicheng

  中国钢铁期刊网. 2008, 15(1): 19-0.

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  To design a power source system and mold for electromagnetic softcontact continuous casting process and to theoretically estimate the heat losses from the charges and the system power, the effect of structure parameters on system power and magnetic flux density distribution was calculated using finite element method. The results show that as for electromagnetic softcontact continuous casting system with partialsegment type mold, the power consumption is much more than that with a fullsegment type mold; about 62% of electric power is dissipated in the mold, and the effective acting range of magnetic field is relatively narrow. Optimizing mold structure is a crucial measure of remarkably reducing mold power consumption and saving electric energy. Increasing slit number, width, and length can remarkably increase the magnetic flux density in the mold and can reduce the electric energy consumption. Among structure parameters, slit number and slit width are relatively more effective to reduce energy consumption. For a round billet electromagnetic continuous casting system with diameter of 178 mm, the reasonable slit number, width, and length are about 24-32, 05-10 mm, and 160 mm, respectively.
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  Real Heat Flux Analysis of Continuously Casting Round Billet

  ZHAN Huiying;WANG Xudong;GUO Liangliang;YAO Man

  中国钢铁期刊网. 2008, 15(1): 25-0.

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  The distributions of heat flux along the height and the circumferential direction of round billet mould were measured continuously. The influence of casting speed, carbon content, powder, and pouring temperature on the average longitudinal and circumferential heat flux in the “high heat flux region” was discussed. The experimental and analytical results provide a basis for an intelligent mould with online detection of defects, adjustment of operational parameters, optimization of the monitoring system, and even prediction of abnormal heat transfer.
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  Analysis of Roll Gap Pressure in Sendzimir Mill by FEM

  YU Hailiang;LIU Xianghua;WANG Chao;Park Haedoo

  中国钢铁期刊网. 2008, 15(1): 30-0.

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  The acting force on the roll system of Sendzimir mill was analyzed using 3D FEM. The roll gap pressure distribution and the acting force between rolls S and O, rolls O and I, rolls O and J, rolls I and A, rolls I and B, as well as rolls J and B were analyzed. The results showed that the roll gap pressure mainly affected the roll surface layer, 50 mm for backup roll; the roll gap pressure distribution is of double peaks among the work roll, the 1st intermediate roll (IMR), and the 2nd IMR; the maximum value of the roll gap pressure between the backup roll and the second IMR appears on the edge of the barrel of rolls; the component force presents the inparacurve distribution. These are important for reducing the wear of rolls and the break of the backup roll and guiding for production.
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  Simulation of Strip Rolling Using Elastoplastic Contact BEM With Friction

  LI Yugui;HUANG Qingxue;SHEN Guangxian;XIAO Hong;PANG Siqin;WANG Jianmei

  中国钢铁期刊网. 2008, 15(1): 34-0.

  摘要 ( )   可视化   收藏

  With rollers as elastic bodies and workpieces as elastoplastic bodies, the rolling problem can be viewed as a friction elasticplastic contact problem. With fewer assumptions in the simulation of striprolling process, a boundary element method (BEM) for twodimensional elastoplastic finite strain and finite deformation analysis of contact problems with friction was presented. All the equations for contact problems, which include multinonlinearities, were obtained. Incremental and iterative procedures were used to find contact pressure and friction stress. Moreover, initial strain rate algorithm and workhardening material behavior can be assumed in the plastic analysis. Several examples were presented, and the results of contact pressure and friction stress were in excellent agreement with those of analysis.
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  Recrystallization Behavior Design for Controlling Grain Size in Strip Rolling Process

  ZHU Guohui;S V Subramanian

  中国钢铁期刊网. 2008, 15(1): 39-0.

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  To promote effectively dynamic recrystallization and obtain a homogeneous distribution of ultrafine grain size in strip finish rolling process, the behavior of static and dynamic recrystallization must be appropriately designed to provide an ultrafine austenite microstructure without mixed grain size. The design of rolling schedule was analyzed based on the control of the recrystallization behavior to achieve ultrafine grain size in the strip rolling process of niobium microalloyed steel. The experimental simulations were presented to validate the twice dynamic recrystallization design to achieve ultrafine grain size control.
Material
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  Separation of Iron Droplets From Titania Bearing Slag

  WANG Mingyu;LOU Taiping;ZHANG Li;SUI Zhitong

  中国钢铁期刊网. 2008, 15(1): 45-0.

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  Owing to smelting vanadiumtitanium magnetite ore, the amount of iron entrainment in slag as droplets is far higher than that in conventional BF slag. However, the iron droplets can be easily settled by blowing air into the molten slag. The results show that more than 80% of iron droplets in titania bearing slag can be settled and separated after treatment. The temperature rise of molten slag during the oxidizing process and the decreased viscosity caused by the component change of slag as well as air stirring in slag both accelerate the iron droplets settling. The vanadium content in the settled iron droplets and the original iron droplets was obtained by chemical analysis. The possible reason for the increased vanadium in the settled iron droplets was discussed by thermodynamic principles.
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  Inhibition Performance of EnhancedMo Inhibitor for Carbon Steel in 55% LiBr Solution

  LIANG Chenghao;HU Xianqi

  中国钢铁期刊网. 2008, 15(1): 49-0.

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  The inhibition performance of enhancedMo inhibitor for carbon steel in 55% LiBr solution was measured by means of chemical immersion, electrochemical measurements, and physical detection technologies. Results indicated that enhancedMo inhibitor showed excellent inhibition performance of carbon steel in 55% LiBr solution, especially at high temperature. With increasing the temperature of solution from 160 ℃ to 240 ℃, the corrosion rates of carbon steel increased from 1767 μm/a to 3307 μm/a. EnhancedMo inhibitor might improve the anodic polarization performance of carbon steel and widen the passive potential region of carbon steel in 55% LiBr solution. EnhancedMo inhibitor belongs to anodic inhibitor. In 55% LiBr solution, the relationship between corrosion current density icorr and corrosion potential Ecorr of carbon steel accorded with the equation lgicorr=-266-354Ecorr, and the value of cathodic Tafel constant βc for the H2 reaction was 282 mVSCE. When 55% LiBr solution contained enhancedMo inhibitor, a passive film comprising Fe3O4 and MoO2 was formed on the carbon steel surface by electrochemical reactions. The corrosion of carbon steel might be retarded by this protective film, and the anticorrosion performance of carbon steel in 55% LiBr solution might be improved by enhancedMo inhibitor.
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  Effect of Thermomechanical Processing on Mechanical Properties of Hot Rolled Multiphase Steel

  LI Zhuang;WU Di;L Huisheng

  中国钢铁期刊网. 2008, 15(1): 55-0.

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  The effect of thermomechanical processing (TMP) on the mechanical properties of hot rolled multiphase steel was investigated. TMP was conducted using a laboratory hot rolling mill, in which three different kinds of finish rolling deformation degrees and temperatures were applied. The results indicate that polygonal ferrite, granular bainite, and a considerable amount of stabilized retained austenite can be obtained by TMP. The stability of the retained austenite increases with decreasing finish rolling temperature and increasing finish rolling deformation degrees. Ultimate tensile strength (σb), total elongation (δ), and the product of ultimate tensile strength by total elongation (σb·δ) for 50% reduction at finish rolling temperature of 700 ℃ reach maximum values [791 MPa, 36% and 28 476 (MPa·%), respectively].
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  Thermal Stability of Retained Austenite in TRIP Steel After Different Treatments

  SHI Wen;LI Lin;Bruno C De Cooman;Patrick Wollants;YANG Chunxia

  中国钢铁期刊网. 2008, 15(1): 61-0.

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  Thermal decomposition of retained austenite in TRIP steel was investigated by means of differential scanning calorimetry (DSC). The decomposition curve was abnormal, and the decomposition temperature and the activation energy were measured by the Kissinger method, which were all higher than those in quenched steel. The thermal decomposition data of samples soaked in liquid nitrogen after TRIP treatment were all similar to those without additional low temperature treatment. It indicated that there is a high thermal stability in retained austenite of the TRIP steel at low temperature, which was also proved by XRD analysis.
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  Structure and Mechanical Properties of NiPNano Al2O3 Composite Coatings Synthesized by Electroless Plating

  ZHOU Guanghong;DING Hongyan;ZHOU Fei;ZHANG Yue

  中国钢铁期刊网. 2008, 15(1): 65-0.

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  NiPnano Al2O3 composite coatings were deposited by electroless plating, and their microstructures were observed by SEM (scanning electron microscope). The microhardness and the wear resistance of the NiPnano Al2O3 composite coatings were measured using microhardness tester and blockonring tribometer, respectively, and the comparison with those of NiP coatings or NiPmicro Al2O3 coating was given. The influences of aging temperature on their hardness and wear resistance were analyzed. The results showed that the nano Al2O3 particles were distributed uniformly in the NiPAl2O3 coatings. Among three kinds of NiP based coatings, the hardness and wear resistance of NiPnano Al2O3 coatings were largest, and the maximum values could be obtained at 400 ℃. This indicated that the precipitation of nano Al2O3 particles would improve the hardness and wear resistance of the NiP coatings.
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  NonMetallic Inclusion Distribution in Surface Layer of IF Steel Slabs

  ZHANG Qiaoying;WANG Litao;WANG Xinhua;LI Hong;WANG Wanjun

  中国钢铁期刊网. 2008, 15(1): 70-0.

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  Nonmetallic inclusion distribution in the surface layer of IF steel slabs during unsteady casting was investigated using the original position statistic distribution analysis (OPA) method. It was found that most nonmetallic inclusions larger than 10 μm existed in the subsurface layers of 05-35 mm from the slab surfaces and very few large nonmetallic inclusions were found in the inner regions (≥45 mm from slab surfaces). In addition, it was found that at high casting speed level (14 m/min), even a slight change of casting speed could result in a remarkable increase of the nonmetallic inclusions. Thus, at high casting speed, changing the casting speed should be avoided or considerably lower speed changing rate must be used.
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  Effect of Solid Solution Treatment on Microstructure of FeNi Based High Strength Low Thermal Expansion Alloy

  ZHANG Jianfu;TU Yifan;XU Jin;ZHANG Jiansheng;ZHANG Jinglin

  中国钢铁期刊网. 2008, 15(1): 75-0.

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  The influence of solid solution treatments on the dissolution of carbides precipitates, the grain size, and the hardness of high strength low expansion alloy were investigated through XRD analysis, microstructure observations, and theoretical computation. It was seen that most primary Mo2C type carbide band dissolved in a temperature range of 1 100-1 150 ℃. When the temperature was over 1 200 ℃, the grain size increased remarkably, which led to the reduction of hardness.
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  Influence of Lanthanum IonImplantation on Adhesive Property of Oxide Film Formed on Co40Cr Alloy

  JIN Huiming;ZHANG Linnan;LIU Xiaojun

  中国钢铁期刊网. 2008, 15(1): 79-0.

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  The isothermal and cyclic oxidizing kinetics of Co40Cr alloy and its lanthanum ionimplanted samples were studied at 1 000 ℃ in air by thermal gravimetric analysis (TGA). Scanning electron microscopy (SEM) was used to examine the Cr2O3 oxide film′s morphology after oxidation. Secondary ion mass spectrum (SIMS) method was used to examine the binding energy change of chromium caused by Ladoping and its influence on the formation of Cr2O3 film. Acoustic emission (AE) method was used in situ to monitor the cracking and spalling of oxide films during oxidizing and subsequent aircooling stages. Laser Raman spectrum was used to examine the stress changes within oxide films. A theoretical model was proposed relating to the film fracture process and was used to analyze the AE spectrum both on time domain and AEevent number domain. It was found that lanthanum implantation remarkably reduced the isothermal oxidizing rate of Co40Cr and improved the anticracking and antispalling properties of Cr2O3 oxide film. The reasons for the improvement were mainly that the implanted lanthanum reduced the grain size and internal stress of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr2O3/Co40Cr interfacial defects.
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  Kinetics of Nitrogen Diffusion in Granular Manganese

  ZHANG Jinzhu;XU Chushao;ZHAO Yueping

  中国钢铁期刊网. 2008, 15(1): 85-0.

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  The kinetics and the influence of time on granular manganese nitriding were studied by means of a vacuum resistance furnace, Xray diffraction technique, and LECO TC436 oxygen/nitrogen determinator. The longer the nitriding time, the more the nitrogen pickup. Except for a trace of oxide MnO that developed, the metal manganese could thoroughly be nitrided to form Mn4N and a little ζphase (the stoichiometric components as Mn2N) with the nitriding time lasting. A kinetic model is developed to reveal the nitriding situation and agrees well with the experimental results.
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  Magnetic Properties and Kinetics Parameters of Electroless Magnetic Loss CoFeB Films

  LIU Changhui;HE Huahui;SHEN Xiang;LI Haihua

  中国钢铁期刊网. 2008, 15(1): 89-0.

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  Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent. The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate, pH of the plating bath, plating temperature and the metallic ratio. The estimated regression coefficient b0-b3 confidence interval, residual error r and confidence interval rint were confirmed by a computer program. The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range. At 2 GHz, the μ′, μ″ of the electroless CoFeB films were 304 and 766, respectively, as the concentration of reducer is 1 g/L. Magnetic hysteresis loop of the deposited CoFeB films show a remanence close to the saturation magnetization and coercivity of about 557-1274 A/m. The loops along the hard axis display low anisotropic field Hk of 2 388-3 582 A/m.