Tetsu-to-Hagané
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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 79 (1993), No. 11

  • Subjects on the Evaluation of the Process and Products in the Sintering of Iron Ores

    pp. 1217-1223

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    Readers Who Read This Article Also Read

    1. Development of "In-situ" Observation System for Oxide Films Formed during Thermal Oxidation Using Raman Spectroscopy Tetsu-to-Hagané Vol.81(1995), No.6
    2. Sintering Process Usiug Pisolite Lumpy Ore as Hearth Layer Tetsu-to-Hagané Vol.80(1994), No.4
    3. Rist Operating Diagram(I) Tetsu-to-Hagané Vol.79(1993), No.9
  • X-ray Fluorescence Spectrometric Analysis of Titanium Alloy

    pp. 1224-1229

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  • Low and Medium Temperature Carbonization under Loading and Pressurization

    pp. 1230-1235

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    A new cokemaking process carbonizing at low and medium temperature under loadingand pressurized conditions has been developed. The productivity and quality of coke in this process were studied by a mathematical simulation model and test ovens with loading and pressurized condition.
    Following results were obtained:
    (1) As compared with qualities of conventional coke, approximately the same qualities could be obtained by low andmedium temperature carbonization under loading and pressurized conditions.
    (2)In addition to optimum values of loading andpressurization, direction and tirning of loading and pressurization during the carbonization are also important to improve coke qualities.
    (3)Evaluation by the sirnulation model indicated that the sarne productivity of coke in comparison with conventional oven was expected by decreasing coal layer thickness and increasing bulk density of charged coal even at low and medium temperature carbonization.
    x

    Readers Who Read This Article Also Read

    1. Development of "In-situ" Observation System for Oxide Films Formed during Thermal Oxidation Using Raman Spectroscopy Tetsu-to-Hagané Vol.81(1995), No.6
    2. Sintering Process Usiug Pisolite Lumpy Ore as Hearth Layer Tetsu-to-Hagané Vol.80(1994), No.4
    3. Rist Operating Diagram(I) Tetsu-to-Hagané Vol.79(1993), No.9
  • Agglomeration of Coal Particles in Fluidized Bed Heating

    pp. 1236-1241

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    Agglomeration properties of coal in a fluidized bed was investigated to obtain a fundamental information for the design of a rapid heating unit of a newly proposed continuous coke oven.
    The agglomeration causes troubles in the bed. Agglomeration temperature was defined as the temperature at which a steep temperature change was found in the bed. Effects of properties of raw coals, e.g., softening and solidification properties and fluidity, and operational conditions, e.g., heating rate, and fluidizing gas velocity, on the agglomeration temperature were investigated.
    The following results were obtained:
    (1) Agglomeration temperature rose with decreasing maximum fluidity of coal, increasing coal size, and increasing gas velocity.
    (2) Agglomeration temperature was higher for the coal treated at high heating rate than that for coal treated at low heating rate.
    (3) Agglomeration temperature was well correlated with the temperature at which gas (CH4, or H2) production began.
    x

    Readers Who Read This Article Also Read

    1. Development of "In-situ" Observation System for Oxide Films Formed during Thermal Oxidation Using Raman Spectroscopy Tetsu-to-Hagané Vol.81(1995), No.6
    2. Sintering Process Usiug Pisolite Lumpy Ore as Hearth Layer Tetsu-to-Hagané Vol.80(1994), No.4
    3. Rist Operating Diagram(I) Tetsu-to-Hagané Vol.79(1993), No.9
  • Dephosphorization Test of Cr-containing Molten Iron by CaO-based Flux

    pp. 1242-1247

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    Dephosphorization tests of Cr-containing molten iron by CaO-based flux have been carried out by a induction furnace. The following results were obtained:
    1) When the carbon content in metal was enough high, Cr-containing molten iron was able to be dephosphorized by CaO-CaF2-FeO flux. In this case, oxygen partial pressure at slag and metal interface was calculated as about 10-12Pa.
    2) The higher ratio of CaF2/(CaO+CaF2) and of CaO/O in flux were effective for the dephosphorization without the oxidization of Cr.
    Based on these results, 200ton scale industrial tests have been carried out by the hot metal pretreatment station at Yawata Works. By the combination of the flux injection method and the oxygen top blowing method, it was clarified that the dephosphorization without Cr oxidation and the suppression of temperature drop were able to be achieved simultaneously.
  • Effect of geometry of vacuum vessel on decarburization rate and final carbon content in RH degasser

    pp. 1248-1253

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    Experimental and theoretical studies were carried out to quantitatively understand the effects of geometry such as a vacuum vessel and snorkels on the decarburization rate and final carbon content in the RH degasser.
    The inner diameter of snorkel was varied between 0.6 and 1.0m, the cross-sectional area of the vacuum vessel between 3.5 and 5.1m2 and the amount of steel melt between 240 and 300t in the experiments made at Mizushima works. The reaction rate was increased and the final carbon content was decreased with the increase in the snorkel diameter and the cross-sectional area of the vacuum vessel, and with the decrease in the amount of molten steel. The maximum decarburization rate and a minimum final carbon content to less than 10 ppm were attained with the largest vacuum vessel whose inner diameter was 1.0m and the cross-sectional area was 5.1m2. The relation between the final carbon content and the initial decarburization rate was found quantitatively in the experiment.
    The experimental results agreed well with calculated values on the basis of the theoretical analysis and proved that it is possible to determine the geometry of the RH vacuum vessel required to obtain a specified aimed carbon content.
  • Quantitative Analysis of Contamination of Liquid Steel in Tundish

    pp. 1254-1259

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    Recently, the high grade quality has been demanded for strips and surface-treatment steel plates. Especially, the cleanliness of molten steel in tundishs plays a crucial part in order to improve the quality of steel plate as well as to prevent immersion nozzle clogging. The tundish has functions of floatation and removal of inclusions, though, some contaminations to the molten steel also occur in tundishs. Therefore, it is necessary to make clear the cause of each contamination and their level for producing super clean steels.
    In this study, the contamination factors to molten steel in the tundish and their influences were analyzed by continual metal sampling during operation and of investigation of size, number and composition of inclusions. The results are as follows.
    (1) Air-oxidation to molten steel is the biggest factor of contamination in the tundish.
    (2)As the influence of air-oxidation decreases, slag contamination increases during continuous operations.
  • Wave Behavior of Melt in a Continuous Casting Mold with Imposition of Magnetic Field

    pp. 1260-1265

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    Surface quality of continuously cast metal can be improved by imposing high frequency magnetic field from the outside of a mold. In order to analyze the mechanism of surface quality improvement, the surface wave motion on meniscus and the contacting behavior between the mold and melt were measured by a laser level meter and by an electrical circuit method, respectively. These measured data were analyzed by use of the Fourier analysis method. Molten tin was continuously cast under the condition imposing magnetic field from the outside of the mold and a mathematical model describing wave motion on meniscus was developed. It was found that the motion of melt is consisted of a surface wave and a transverse swing which provides the intermittently contacting between the meniscus and the mold, and the space of ripple marks on the surface of the cast metal is related to frequency of the transverse swing caused by imposition of magnetic field. Surface quality of the cast metal can be improved by decreasing the wave amplitude of meniscus.
  • Precipitation of Fine Carbonitride and High Temperature Embrittlement of Low Carbon Steel during Cooling in Secondary Cooling Zone of Continuous Caster

    pp. 1266-1272

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    In order to reduce frequency of surface cracks in continuously cast low carbon steel slabs containing niobium, relation between morphology of carbonitride precipitates and high temperature ductility has been examined under the condition simulating thermal cycle of steel slabs passing through secondary cooling and bending zones of a vertical bending type continuous caster. Through experiments, it is found that precipitation of niobium carbonitrides is mainly affected by thermal cycle in the temperature range from 973 to 1073K, and fine precipitates at γ grain boundary make high temperature ductility worse. Number of fine precipitates containing niobium increases when a specimen stays in the temperature range longer. It is found that grain boundary embrittlement is becoming dominant in case when ductility becomes less, which means deformation takes place mainly at γ grain boundary because grain itself is strengthened by fine precipitates.
    For improvement of high temperature ductility, it is recommended to modify fine niobium carbonitrides to coarser ones containing titanium and niobium by microalloying of titanium.
  • Alloying Reactions and Coating Microstructure in Continuous Galvanizing and Galvannealing Process

    pp. 1273-1277

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    The iron-zinc alloying reactions which take place during hot dip galvanizing and galvannealing processes were investigated with special reference to the formation and growth behavior of Fe-Zn intermetallic compounds. The SEM observation and X-ray diffraction analysis of the intermetallic compounds which had formed on laboratory galvanized Ti stabilized interstitial free steel and low carbon Al killed steel sheets showed that there were two types of elementary Fe-Zn alloying reactions; one was the formation of ζ or δ1 crystals and another was so-called outburst reaction. The ζ crystals nucleated on the Fe-Al intermetallic compound which had been formed on the steel surface and grew into the melt as a single phase crystal, while the outburst structure generated as a result of direct reaction between iron and molten zinc and grew as a multi-phase structure (ζ, δ1 and Γ phases ). The ζ-phase was generated only at the is othermal galvannealing temperature of below 773K, and it was explained in terms of the Zn-Fe equilibrium phase diagram (peritectic temperature of ζ-phase). The effect of solute element in steel on the thickness of Γ-phase was explained by its suppression effect toward the outburst reaction.
  • Effects of Kinds of Monomers on Film Properties for Electron Beam Cross-linked Poly (vinyl chloride) Coated Steel Sheets

    pp. 1278-1283

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    Poly (vinyl chloride) (PVC) paints containing electron beam (EB) sensitive monomers were coated on steel sheets and baked and cross-linked by EB subsequently. Increase of film hardness for the EB cross-linked PVC coated steel sheets was investigated by the use of various monomers. As the amounts of monomer in film increased, the film hardness increased. In case of smaller equivalent of double bonds of monomer, higher film hardness value was obtained with smaller portions of monomer. Property balance between the film hardness and the bend formability depended upon kinds of monomers, and as the difference of solubility parameter for monomer from that of plasticizer decreased, the property balance improved. EB cross-linked PVC coated steel sheet containing 50phr trimethyol propane trimethacrylate (TMPTMA) had pencil hardness F and OT bend formability. From dynamic viscoelasticity of EB cross-linked PVC film, it is assumed that plasticized PVC and TMPTMA were in miscibility, and rigidity of film was obtained by the dense bridging PVC by TMPTMA.
  • Parameter Analysis for Temperature and Strain Rate Dependence of Low-Cycle Fatigue Life at High Temperatures

    pp. 1284-1287

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    A modified Larson-Miller parameter has been proposed to evaluate temperature and strain rate dependence on lowcycle fatigue life; it is written as P=T (logN25-Alogε+B), where T is temperature, N25 is fatigue life under symmetrical strain wave shapes, ε is strain rate, and A and B are constants. Material used in the analysis is SCMV 4 steel. The method is based on consideration of thermally activated processes causing temperature and strain rate dependence. It can give a threshold strain at fatigue limit, as Strohmeyer type equation is adopted to express a relationship between total strain range and fatigue life.
  • Low-Cycle Fatigue Life Analyzed by Parameter Method for Various High Temperature Materials

    pp. 1288-1292

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    Low-cycle fatigue life for various kinds of high temperature materials has been analyzed by a modified Larson-Miller parameter. written by P = T (logN25 Alogε + B) where T is temperature, N25 is fatigue life under symmetrical strain wave shapes, ε is strain rate, and A and B are constants. Test data used in the analysis are from NRIM Fatigue Data Sheets of popular engineering materials of nine kinds, ten heats including carbonsteel to Fe-base super alloy. The results have been compared between the materials and compared with statistical analysis results adopted in a design code.
  • Effect of Long Term Exposure on Mechanical Properties and Precipitation Behaviors of Hastelloy X for Gas Turbine Combustor

    pp. 1293-1298

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    Transition pieces of Hastelloy X in gas turbine combustor were suffered significant creep deflection due to material degradation during the operations. Specimens of Hastelloy X were aged up to 10000h in the temperature range of 750900°C. By using these prior-aged specimens, metallurgical observations and short term creep tests at 850°C under the stresses of 78.5 and 49 MPa were carried out to evaluate the degree of degradation, and precipitation behaviors were quantitatively analyzed by using the image analyzer. The density of precipitates, the grain boundary coverage ratio, and volume fraction of precipitates unexpectedly become larger with increasing the aging time. Increases of tensile strength, 0.2% proof stress, and hardness at room temperature were interpreted by the increase in the density of precipitates. But the precipitates, which commonly exert as strengtheners, exerted inversely to the creep resistance. This phenomenon was figured out due to the precipitation of Mo-rich, μ-phase in the grains, which reduced the Mo concentration in the matrix and reduced the solid-solution strengthening effect.
  • High Temperature Creep Resistance of High Purity Chromium in Argon

    pp. 1299-1304

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    The creep properties of a pure chromium have been investigated in argon by comparing with those in air at 1273K in the stress range of 14.7 to 58.8MPa. The minimum creep rate of the pure chromium in argon was nearly equal to that in air at higher stresses, but at lower stresses the minimum creep rate in argon was larger than that in air and the difference in the minimum creep rates between in argon and in air became larger at lower stresses. Nitrogen content of the specimen interrupted at the minimum creep rate in air increased with decreasing the stress. The minimum creep rate of the specimens pre-aged in air at 1323K for 3.6 × 101 to 3.6 × 103ks, was investigated by carrying out creep test at 1273K and 49.0MPa in argon. The minimum creep rate of the pre-aged specimens decreased with the increase in nitrogen content. The results conclusively demonstrate that the higher creep resistance of the specimens crept in air than that in argon at lower stresses is mainly attributed to the solid solution strengthening of nitrogen due to nitriding.
  • Intergranular Fracture of Iron and Effects of Trace and Alloying Elements

    pp. N754-N760

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  • State of Numerical Analysis for Sheet Metal Forming

    pp. N761-N767

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  • Physical Property of Paint Liquid and Film

    pp. N768-N773

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    [in Japanese]

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