ISIJ International
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ONLINE ISSN: 1347-5460
PRINT ISSN: 0915-1559

ISIJ International Vol. 33 (1993), No. 4

  • Production and Technology of Iron and Steel in Japan during 1992

    pp. 427-445

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    DOI:10.2355/isijinternational.33.427

  • Effect of Firing Condition and Ingredients on the Swelling Behaviour of Iron Ore Pellets

    pp. 446-453

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    DOI:10.2355/isijinternational.33.446

    In the present investigation an attempt has been made to determine the effect of firing temperture, firing time and ingredients/additives (CaO, MgO, SiO2, Al2O3) on the swelling behaviour of iron ore pellets. For this purpose two Indian iron ore fines from Bailadila and Noamundi deposits and chemically pure iron oxide were used.
    From the results obtained, it is observed that the swelling of iron ore pellet is controlled by the firing temperature, firing time and additives/ingredients present in the pellet. The growth of iron whisker is controlled by these ingredients. The presence of free lime promotes the swelling index of the pellet.
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    1. Effect of Reducing Gas on the Volume Change during Reduction of Iron Oxide Compacts ISIJ International Vol.36(1996), No.6
    2. Swelling of Iron Ore Pellets by Statistical Design of Experiment ISIJ International Vol.32(1992), No.12
    3. Factors Affecting the Sticking of Fine Iron Ores during Fluidized Bed Reduction ISIJ International Vol.32(1992), No.9
  • Commercial Production of Iron Ore Agglomerates Using Sinter Feeds Containing a Large Amount of Fine Ores

    pp. 454-461

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    DOI:10.2355/isijinternational.33.454

    In order to improve present iron ore agglomeration processes drastically and meet the demands of future trends in iron ore resources suitably, a new agglomeration process named the Hybrid Pelletized Sinter process was studied. On the basis of a prior experimental study and the semi-commercial plant trial, a commercial plant of the HPS process with annual capacity of 6 million tons was constructed by remodeling the No. 5 Sinter Plant at NKK Fukuyama Steel Works. Through long term operation using a large amount of high grade fine ores, the superiority of this process was confirmed in terms of both productivity and fuel consumption.
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    1. Production and Technology of Iron and Steel in Japan during 1991 ISIJ International Vol.32(1992), No.4
    2. Prediction of the Blast Furnace Process by a Mathematical Model ISIJ International Vol.32(1992), No.4
    3. Production and Technology of Iron and Steel in Japan during 1994 ISIJ International Vol.35(1995), No.4
  • Effect of Raw Material Composition on the Mineral Phases in Lime-fluxed Iron Ore Sinter

    pp. 462-473

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    DOI:10.2355/isijinternational.33.462

    In this study small tablet specimens of powdered commercial iron ores mixed with fluxes and kaolin were heated in a reducing atmosphere and then cooled slowly in air to simulate industrial sintering. The effect of different ore and flux compositions on the phases found in the sinter bond was studied.
    An increase in basicity (CaO/SiO2) favoured the formation of calcium ferrite and densification of the bond at a low sintering temperature. The amount of calcium ferite decreased as the Al2O3 content decreased and the amount of reoxidized hematite produced on cooling decreased. A decrease in Al2O3 content promoted a densification of the bond.
    An increase in MgO content, introduced by addition of dolomite, decreased the amount of calcium ferrite slightly. When MgO was added in the form of serpentine the calcium ferrite content increased considerably. Increase in MgO markedly reduced the amount of reoxidized hematite but produced a less dense bond.
    Generally the same composition and sintering temperature produced similar mineral compositions in the bond independent of the iron ore used. The only exception was when an ore with coarse dense hematite was used, in which case the bond contained some unreacted hematite. The porosity of the bond did vary with the type of ore used. Limonitic ore produced a bond with closed pores and less reoxidized hematite at lower temperature and basicity than did hematite ores.
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    Readers Who Read This Article Also Read

    1. Production and Technology of Iron and Steel in Japan during 1991 ISIJ International Vol.32(1992), No.4
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    3. Production and Technology of Iron and Steel in Japan during 1994 ISIJ International Vol.35(1995), No.4
  • A Comparison of Experimentally Measured and Theoretically Calculated Velocity Fields in a Water Model of an Argon Stirred Ladle

    pp. 474-478

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    DOI:10.2355/isijinternational.33.474

    A model is developed to calculate the multi-phase flow produced by the bubbling of air into water. Two turbulence models are employed to represent the turbulence field namely, the k-ε model and an anisotropic eddy viscocity (algebraic stress) model. The predicted mean flow and turbulence parameters compare well with the experimental data.
  • Kinetics of Phosphorus Transfer between Iron Oxide Containing Slag and Molten Iron of High Carbon Concentration under Ar-O2 Atmosphere

    pp. 479-487

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    DOI:10.2355/isijinternational.33.479

    In the present report, the results are described of kinetic experiments of phosphorus reaction in a molten CaO-Li2O-SiO2-FeO-Fe2O3 slag/Fe-4.4%C molten metal/Ar-O2 gas (PO2=0-0.2 atm) system. The experimental temperature is 1300°C and the slag-metal bath is stirred by an eccentric alumina stirrer (rotation speed, R=30-300 rpm). From the experimental results, it is found that dephosphorization rate increases with increasing the oxygen partial pressure of the Ar-O2 gas atmosphere. The change in the stirrer's rotating speed does not affect the dephosphorization rate obviously, while rephosphorization rate increases with increasing the stirring speed. It is also shown that maximum phosphorus concentration ratio, ((%P)/[%P])max, obtained at the time point when the phosphorus reaction changes from dephosphorization to rephosphorization, increases with the increase in the ratio of ferric iron to total iron of the slag. The ((%P)/[%P])max ratio decreases with increasing the stirring speed in the range of R>50 rpm. The relation between the experimental conditions and the rate of the phosphorus reaction accompanied by simultaneous slag-metal-gas reactions are interpreted qualitatively in terms of the change in a hypothetical slag-metal interfacial oxygen potential. The experimental results are explained quantitatively by means of a mathematical kinetic model calculations. The model calculation fits the experimental results resonably well.
  • Simulated Rod Rolling of Interstitial Free Steels

    pp. 488-497

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    DOI:10.2355/isijinternational.33.488

    Simulations of the rod rolling of a Ti-Nb interstitial free (IF) steel were carried out in the ferrite (840, 770, 700, 600, 500°C) and austenite (950°C) ranges. Typical industrial pass strains and temperatures were employed, but the strain rates were much lower because of the limitations of the experimental apparatus. To allow for this difference, "strain rates corrected" interpass times were used. The mean flow stresses for ferrite rolling at 700°C were observed to be similar to those developed in the austenite at 950°C. Industrial schedules at 950°C, as well as strain rate corrected ones at this temperature and at 840°C, led to mean flow stress envelopes which displayed peaks and valleys. This is shown to result from the periodic triggering of dynamic recrystallization during deformation, with the subsequent occurrence of rapid metadynamic softening during the interpass intervals. Microstructural examination of the material indicated that dynamic recrystallization took place in the ferrite at 840°C, whereas dynamic recovery was operative at the lower deformation temperatures. The final mechanical properties of the material were evaluated after the simulations, by means of tensile tests on hollowed out torsion specimens. These showed that yield strengths of up to 420 MPa can be reached by the warm working of IF steels. Thus the low temperature rod rolling of IF steels has distinct promise for the production of highly ductile materials, with controlled levels of yield strength ranging from 180 to 420 MPa. In this way, the high price of IF steels can be offset by the economies resulting from low temperature reheating which include lower scale losses, and by the possible elimination of subsequent cold drawing/heat treatment/pickling processes.
  • Experimental Study on Dissolution of α Phase in γ/α/γ Diffusion Couples of the Fe-Cr-Ni System

    pp. 498-507

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    DOI:10.2355/isijinternational.33.498

    The dissolution kinetics of body-centered-cubic (bcc) α-ferrite in face-centered-cubic (fcc) γ-austenite matrix was experimentally studied using four sets of γ/α/γ diffusion couples of the ternary Fe-Cr-Ni system in order to understand the general characteristics of the dissolution reaction of a solid-solution phase in multicomponent systems. The γ/α/γ diffusion couples consisting of an α-phase sheet with thicknesses of 0.07 to 0.19 mm and γ-phase plates with a thickness of 2 mm were annealed at 1373 K for various times between 3.6×103 and 3.6×106 s. Although the α phase should completely dissolve in the γ phase after sufficiently long annealing, the thickness of the α phase transiently increased with increasing annealing time at an early stage of the reaction. After reaching a maximum value, the thickness of the α phase decreased with increasing annealing time. The composition of the moving α/γ interface changed with annealing time after overlap of diffusion zones took place in the α phase. The change in the interface composition and the transient thickening of the α phase were qualitatively explained using approximate solutions of the diffusion equations for the semi-infinite α/γ diffusion couples.
  • Elastic Moduli and Internal Friction of Low Carbon and Stainless Steels as a Function of Temperature

    pp. 508-512

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    DOI:10.2355/isijinternational.33.508

    Elastic (Young, shear and bulk moduli, Poisson's ratio and Lamé parameter), longitudinal and transverse internal friction values for low carbon steel and stainless steel were simultaneously measured over a temperature range 300-1500 K, by an ultrasonic pulse sing-around method. These elastic moduli decrease and Poisson's ratio increases with increasing temperature, suggesting activation of shear mode in a high temperature region. Longitudinal and transverse internal frictions are sensitive to recrystalization, and to α(ferritic)/γ(austenitic) phase transition and solution of precipitated carbide phases into the austenitic matrix, respectively. A relaxation peak with an apparent activation energy of 0.97 eV was observed at around 610 K for the carbon steel.
  • Considerations Concerning the Numerical Computation of Mixing Times in Steelmaking Ladles

    pp. 513-516

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    DOI:10.2355/isijinternational.33.513

    x

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  • Rebuttal by Turkoglu and Farouk on the Note Titled "Considerations Concerning the Numerical Computation of Mixing Times in Steelmaking Ladle" by Mazumdar and Guthrie

    pp. 517-518

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    DOI:10.2355/isijinternational.33.517

  • Thermal Stratification Phenomena in a 4-strand CC Tundish during Teeming of Steel-Water Model Study

    pp. 519-521

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    DOI:10.2355/isijinternational.33.519

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