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

ISIJ International Vol. 34 (1994), No. 9

  • Experimental and Computational Investigation of Rotary Electromagnetic Stirring in a Woods Metal System

    pp. 707-714

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    DOI:10.2355/isijinternational.34.707

    An experimental and computational investigation was carried out in an electromagnetically stirred Woods metal system, and the associated free-surface deformation was studied. The free-surface velocities were measured at various strengths of the applied magnetic fields using high-speed video photography. The effect of the magnetic field strength of the electromagnetic stirrer on the free surface deformation was studied by varying the position of the melt relative to the electromagnetic stirrer. The calculated free surface deformation was compared to experimental observations made on a laboratory-scale installation.
  • Action of Pulse Magnetic Field on Molten Metal

    pp. 715-721

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    DOI:10.2355/isijinternational.34.715

    Effect of pulse magnetic field on two-phase zone of crystallizing metal has been investigated by methods of mathematical modelling in reference to vertical continuous casting machine. On the first step of the investigation electromagnetic problem for penetration of pulse magnetic field of cylindrical inductor in depth of liquid metal has been solved and distribution of electromagnetic forces in the melt has been obtained at different time moments. With a view to solve this problem combined method has been proposed. It contains boundary element method for description of field in surrounding air medium with inductor and also finite difference method for solving of the problem in molten metal. On the second step of the investigation with the help of obtained distribution of electrodynamic forces problem for acceleration of the melt has been solved. It is determined the optimal relation for pulse duration (in the case of single pulse), when melt velocity reaches its maximum value. Besides, it is shown that magnetic field may be used with the purpose of effect on crystallization zone through shell of solidified metal.
  • Application of Pinch Force to the Separation of Inclusion Particles from Liquid Steel

    pp. 722-731

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    DOI:10.2355/isijinternational.34.722

    The pinch force which is one of the most common electromagnetic forces in the metallurgical field can be generated by imposing an electrical current on a liquid metal. In this force field, electrically nonconductive particles suspended in a liquid metal experience a force in the opposite direction to the pinch force, and are squeezed out from the liquid metal.
    In this study, the above principle was applied to the separation of nonmetallic inclusion particles from liquid steel. Firstly, the separation efficiency, η, of nonmetallic inclusion particles from the liquid steel flowing in a circular pipe was calculated by the trajectory method under laminar flow conditions. The value of η was found to be a function of VR, (CIDR2/Re)Z and r1/δ, where r1 is the radius of the pipe, δ is the skin depth and VR, CI, DR, Re and Z are nondimensional parameters. The estimated value of η is a continuous casting tundish equipped with a channel-induction furnace was greater than 95% for particles with a diameter over 60 μm. Secondly, the value of η for a square pipe was computed by the concentration method. In this case, the value of η was found to be a function of V'R and (CIDR2/Re)Z at x1/δ=0, where x1 is the half width of the square pipe. However, with increasing x1/δ, secondary flows appeared in a cross section of the pipe because of the skin effect. These flows were found to increase the value of η by transporting the particles in the inner region toward the wall.
  • Application of the Two-fluid Model of Turbulence to Tundish Problems

    pp. 732-738

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    DOI:10.2355/isijinternational.34.732

    A two-fluid model of turbulence is presented and applied to flow in tundishes. The fluids are defined as turbulent and non-turbulent. Transport equations are solved for the variables of each fluid, and empirical relations, established in prior work, are used to express interchange of mass and momentum at the interface. Gradient-diffusion flux is considered an intra-fluid source of turbulence. A critical comparison is made between the results based on the application of this model and the conventional k-ε model. Such results include velocity vectors, effective viscosity and tracer dispersion. In addition, the two-fluid model predicts spatial distribution of the intermittency factor, which provides a measure of the extent of turbulence in the tundish.
  • Phase Equilibria and Activities of the Constituents in FeO·Cr2O3–MgO·Cr2O3 Spinel Solid Solution Saturated with Cr2O3

    pp. 739-745

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    DOI:10.2355/isijinternational.34.739

    en-abstract= The phase equilibria and the activities of the constituents in FeO·Cr2O3-MgO·Cr2O3 spinel solid solution saturated with Cr2O3 have been determined at temperature ranging from 1423 to 1723 K, by the equilibrium of iron dissolved in liquid silver held in spinel crucible with CO-CO2 gas mixture, to clarify the thermodynamic properties of chromium ores in chromium ore smelting reduction process being recently developed.
    The solubility of FeO·Cr2O3-MgO·Cr2O3 spinel in Cr2O3 was found to be negligible. On the other hand, very small solubility of Cr2O3 in the spinel was observed, but the nonstoichiometry of spinel solid solution was insignificant and spinel phase was reasonably approximated as stoichiometric (Fe, Mg)O·Cr2O3.
    The free energy of formation of FeO·Cr2O3 was determined as
    Fe (s)+1/2O2 (g)+Cr2O3 (s)=FeO·Cr2O3 (s),
    Δ=-307600+66.82 T (1423-1723 K) (J/mol).
    The activities of constituents in FeO·Cr2O3-MgO·Cr2O3 spinel solid solution coexisted with Cr2O3 showed negative deviation from ideality. It was observed that the spinel solid solution takes regular solution behavior, and α-function of FeO·Cr2O3-MgO·Cr2O3 system was determined as follows;
    αFeO·Cr2O3=RT ln γFeO·Cr2O3/(1-NFeO·Cr2O3)2
    MgO·Cr2O3=RT ln γMgO·Cr2O3/(1-NMgO·Cr2O3)2
    =-12800 (J).
  • Magnesium Deoxidation and Nitrogen Distribution in Liquid Nickel Equilibrated with CaO-Al2O3-MgO Slags

    pp. 746-754

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    DOI:10.2355/isijinternational.34.746

    Based on the reciprocal relationships with respect to the interaction parameters on mass percent, the first-order and second-order interaction parameters between Mg and O in liquid nickel were estimated at 1873 K in the equilibrium experiments between liquid nickel and CaO-Al2O3-MgO slags in an Al2O3, CaO or MgO crucible. The values for eOMg, rOMg, rOMg, O, eMgO, rMgO and rMgO, Mg were determined as -46, 800, 2400, -70, 1800 and 2400, respectively. Nitride capacities, C(N), defined by (mass%N)·PO23/4/PN21/2 were obtained by using the present results for nitrogen distribution ratio, LN {=(mass%N) / [mass%N]}, and the reported values for the activity of Al2O3.
  • Die Shape Design and Evaluation of Microstructure Control in the Closed-die Axisymmetric Forging by Using FORGE2 Program

    pp. 755-760

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    DOI:10.2355/isijinternational.34.755

    The microstructural equations describing processes of recrystallization and grain growth are implemented in the FORGE2* commercial program first. Then, the calculations of the grain size distribution on the cross section of the axisymmetrical forging are performed. Finally, the influence of the shape of the preform die on the microstructure of the final product is investigated.
  • A Reexamination of the Gibbs Energies of Formation of TiS and Ti4C2S2 in Austenite

    pp. 761-763

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    DOI:10.2355/isijinternational.34.761

    The Gibbs energies of formation of TiS and Ti4C2S2 in austenite at 1300°C are revaluated from the solubility data measured by Swisher in the Fe-C-S-Ti system. The reevaluation is based on the more realistic assumption that TiS and Ti4C2S2 precipitate as mutually insoluble particles. This is in contrast to the previous analysis, which was based on an ideal solution model of the sulphide and carbosulphide phases. The reevaluated values lead to better agreement with the solubility products measured recently by Yoshinaga et al.
    x

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  • Effect of Alloying Elements on the Mechanical Properties of the Stable Austenitic Stainless Steel

    pp. 764-772

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    DOI:10.2355/isijinternational.34.764

    The effects of various alloying elements on the mechanical properties of stable austenitic stainless steel have been investigated in order to soften it. Results obtained are as follows:
    (1) Experimental equations are proposed, which give the hardness (HV), 0.2% proof stress (σ0.2) and tensile strength (σB) as functions of the chemical composition.
    (2) Reduction of C, N, Si, Cr and Mo and addition of Ni, Cu and Mn are effective to decrease the hardness, 0.2% proof stress and tensile strength.
    (3) σ0.2 is increased by the addition of alloying elements which cause lattice strains, i.e., C, N and Mo. The larger the lattice strain, the larger the increase in σ0.2·0.2% proof stress is decreased by the addition of Ni, Cu and Mn, which increase the stacking fault energy (SFE), although these elements cause slight lattice strains. Addition of Si, which reduces SFE, increases σ0.2.
    (4) The dislocation structures are essentially cell-structures, except for N-added steels. The cell size is varied with alloying elements through the change in SFE.
    (5) The work hardening rate is reduced by Ni, Cu and Mn, which have been reported to increase SFE and hence are considered to activate cross-slip. On the other hand, a SFE-reducing element, Si, increases the work hardening rate. The addition of N, another SFE-reducing element, decreases work hardening rate. This effect may result from the difficulty in forming the cell-structure in the N-added steel in contrast with the Si-added steel.
  • Viscosity of the CaO-CaF2 System Containing Chromium Oxide

    pp. 773-775

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    DOI:10.2355/isijinternational.34.773

    Viscosity of the CaO-CaF2-Cr2O3 system (15%<CaO<25%, 75%<CaF2<85%, 0%<Cr2O3<10%) was measured by the vibrational resonant amplitude method. From the experimental data on slags viscosity as a function of temperature, liquidus temperatures were determined. Viscosities and liquidus temperatures were found to increase with an increase in the chromium oxide concentration in the slag.

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