Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Volume 80 , Issue 5
Showing 1-17 articles out of 17 articles from the selected issue
  • Fujio ISHII, Shiro BAN-YA
    1994 Volume 80 Issue 5 Pages 359-364
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    In order to investigate the equilibrium between yttrium and oxygen in liquid iron and nickel, the deoxidation of yttrium in liquid iron and nickel saturated with yttria has been measured at the temperature ranges from 1600°C to 1700°C using the sampling technique.
    The effect of temperature on the equilibrium constant of the deoxidation reaction in liquid iron was found to be:
    log KY(Fe)(=a2Y·a3O) =-36160/T + 7.33
    while the deoxidation product of iron, log K'Y(Fe) (= [%Y]2[%O]3), was expressed as follows:
    log K'Y(Fe)=log KY(Fe)-(-17350/T + 3.14) (3 [%Y] + 11.1 [%O])
    0.02< [%Y] <0.11
    by the use of the interaction parameter, eYO(Fe) =-17350/T + 3.14.
    The temperature dependence of the equilibrium constant for the deoxidation of nickel, log KY(Ni), was given by the expression:
    log KY(Ni) =-36250/T + 6.36
    Besides, the deoxidation product of nickel was represented to be:
    log K'Y(Ni) = logKY(Ni) + 6.47(3[%Y] + 11.1 [%O])
    0.01<[%Y]<0.11
    with the interaction parameter, eYO(Ni) =-6.47.
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  • Manabu IGUCHI, Hirotoshi KAWABATA, Zen-ichiro MORITA, Keiji NAKAJIMA, ...
    1994 Volume 80 Issue 5 Pages 365-370
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    A novel electro-resistivity probe was developed for measuring the bubble characteristics in a molten iron bath subject to centric bottom Ar gas injection. This probe is able to be continuously used for about two hours at a bath temperature of 1250°C. The radial and vertical distributions of gas holdup α, bubble frequency fB, bubble rising velocity uB and bubble diameter dB were measured for the Ar gas flow rate of 50 and 100cm3/s (at 1250°C). The Ar gas preheated up to 1250°C was injected from the bottom nozzle at 1250°C.
    The results were compared with empirical correlations derived from cold and hot model experiments. The values of α, fBanduB measured in the vicinity of bath surface were approximated satisfactorily by correlations proposed by the present authors, but they did not agree with the experimental results of Kawakami et al. The measured values of dB were a little smaller than those of Sano et al. and Irons ea al.
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  • Seiji FURUHASHI, Shigeo ASAI
    1994 Volume 80 Issue 5 Pages 371-376
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    In order to make use of the electromagnetic force replacing a solid side dam to confine molten metal at the side edges in a twin roll caster, the stability analysis of an electromagnetic dam, where the vertical free surface of molten metal is held without any contact with a solid wall, has been studied. The electromagnetic dam which makes use of the electromagnetic force induced by the static magnetic field and the direct electric current is expected to avoid the troubles caused by the solid side dams in conventional operations. By using the normal mode method developed in the perturbation theory, the effects of operational variables such as imposed electric current, imposed magnetic field, and the imposing direction of magnetic field to that of a wave vector on the stability of the free surface of molten metal have been studied. This stability analysis derives that the better stability are found in the conditions with the less electric current, the stronger magnetic field, and the magnetic field parallel to the direction of a wave vector.
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  • Seiji FURUHASHI, Shigeo ASAI
    1994 Volume 80 Issue 5 Pages 377-382
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    In order to make use of the electromagnetic force to confine molten metal at the side edges in a twin roll caster, the model experiment of an electromagnetic dam, where the vertical free surface of molten metal is held without any contact with a solid wall, has been conducted. The electromagnetic dam makes use of the electromagnetic force induced by a static magnetic field and a direct electric current. In order to study the effects of operating variables such as imposed electric current, imposed magnetic field, and the imposing direction of magnetic field on the stability of the free surface of molten metal, a static model experiment with no metal flow has been conducted by use of molten Gallium. The theoretical results derived in the previous paper have been confirmed by experimental ones that the better stability are found in the condition with the less electric current, the stronger magnetic field, and the magnetic field parallel to the direction of a wave vector in this paper. The feasibility study for confining molten steel in the twin roll caster has been theoretically predicted that the horizontal magnetic field is superior to the vertical one.
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  • Keiji NAKAJIMA
    1994 Volume 80 Issue 5 Pages 383-388
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    Inclusion separation at the interface is governed by the interfacial properties between phases in the molten iron-slag-inclusion system. The behavior of inclusion separation and assimilation in a slag can be related to the change in the interfacial free energies as the inclusion goes from the immersed state to the separated state.
    To understand this interfacial phenomena, a model has been developed which permits the calculation ot interfacial tensions of the inclusion (alumina)-molten iron, molten iron-slag and slag-inclusion (alumina) systems. This model, which incorporates Girifalco and Good's approach, was tested on these systems. Calculated values obtained from the model show excellent agreement with reported data.
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  • Joon-Pyou PARK, Atusi MORIHIRA, Kensuke SASSA, Shigeo ASAI
    1994 Volume 80 Issue 5 Pages 389-394
    Published: May 01, 1994
    Released: January 19, 2010
    JOURNALS FREE ACCESS
    In order to produce high quality metals, decreasing of the amount of non-metallic inclusions is indispensable. A new elimination method of non-metallic inclusions using electromagnetic force is proposed. The principle of the method is that the electromagnetic force induced in molten metal by imposing direct electric current and magnetic field, scarcely acts on the non-metallic inclusions due to the low electrical conductivity. Thus, the non-metallic inclusions move in the opposite direction to that of the electromagnetic force. In order to confirm the principle of the method, the movement of polystyrene particles suspending in a NaCl aqueous solution by electromagnetic force is visualized. Moving velocity of the polystyrene particles is compared with the theoretical one. The turbulent fluid motion caused by unevenly distributed electromagnetic force agitates the inclusions which have to be eliminated by the electromagnetic force and makes the principle of the method useless. Thus, the suppression of the turbulent motion is essential and therefore, the molten metal has to be passed through porous bricks or a bundle of thin pipes under the electromagnetic force. That is, the turbulent motion of molten metal causing in the unevenly distributed electromagnetic force is substantially surpressed so as not to influence the effect of elimination of inclusions, because the turbulent motion is bounded in small spaces such as the pore in the brick or thin pipe. The usefulness of the method is demonstrated by the experimental works using molten tin including the non-metallic inclusions of Al2O3 or intermetallic compounds.
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  • Katsuhiro SASAI, Yoshimasa MIZUKAMI
    1994 Volume 80 Issue 5 Pages 395-400
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    A kinetic study has been made on reactions between the alumina graphite refractory containing SiO2 and molten steel by measuring mass losses of the refractories heated at 1100-1600°C and Si contents of molten steel immersing the refractories in at 1600°C.
    The results are summarized as follows.
    1) Rate of reaction in the refractory, namely carbothermic reduction rate of SiO2, is controlled by the diffusion of SiO and CO gases through refractory pores.
    2) Rate of reaction between the refractory and molten steel is controlled by the diffusion of SiO and CO gases through oxide layer formed at refractory-molten steel interface.
    3) Rate of reaction between the refractory and Ti killed steel is higher than that of reaction between the refractory and Al killed steel. This is because gas permeability of oxide layer formed at refractory-Ti killed steel interface is higher than that at refractory-Al killed steel interface.
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  • Seishi TSUYAMA, Hiroyuki TSUNODA, Yoshihiro HOSOYA
    1994 Volume 80 Issue 5 Pages 401-405
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    Effects of strain rate and temperature on tensile ductility of an interstitial free ultra low carbon steel sheet, which does not show dynamic strain aging have been studied. Total elongation of this steel decreases with an increase in strain rate up to 5×10-2/s and contrarily increases in the higher strain rate region. This increase of total elongation is due to a drastic increase of post-uniform elongation, which can be explained neither by heat generation due to plastic deformation nor by equivalency of temperature to strain rate. The possible mechanism for large post-uniform elongation in the high strain rate region is an increase in diffusion of local necking area due to grain boundary sliding.
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  • Mitsuru NAKAMURA, Kousuke TAGASHIRA, Hiroshi HORIE, Eiji KAJIWARA, Hir ...
    1994 Volume 80 Issue 5 Pages 406-411
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    Influence of post-weld heat treatment (PWHT) on the mechanical properties of high strength steel for welded structure (TMCP steel), especially the relation between the microstructures of Heat-affected zone (HAZ), the stress relaxation behavior and high temperature deformability was investigated. The synthetic-weld heat treatment were carried out by Weld-heat cycle simulator and a maximum temperature of 1623K. PWHT conditions were done at heating rate 55.6K/ks. The mechanical properties during PWHT process were evaluated by means of high temperature tensile test, constant-strain rate test on heating and constant-load test on heating. Influence of PWHT on the stress relaxation behavior and the reducing ductility was discussed by each microstructures of HAZ (Bainitic or Lath-martensitic structure). The results are summarized as follows.
    1) As a result of high temperature tensile test, the value of elongation and the reduction of area of Bainitic structure specimens were lower than that of Lath-martensitic and Bainitic-ferritic structure specimens.
    2) The stress relaxation behavior of Bainitic structure specimens during PWHT process were delayed clearly over 500K than that of another structure specimens. Bainitic structure specimens appeared to the resistance of softening tendency of matrix during PWHT.
    3) High temperature deformability of Bainitic structure specimens were a remarkable reducing tendency of ductility at 850900K. The difference of these tendency of the microstructures of HAZ could be explained by the shape and site of precipitated carbides during PWHT process.
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  • Takao ENDO, Kuocheng TAI, Fujimitsu MASUYAMA
    1994 Volume 80 Issue 5 Pages 412-417
    Published: May 01, 1994
    Released: January 18, 2010
    JOURNALS FREE ACCESS
    The effect of pre-creep on the creep life has been investigated over a stress range from 78.4 to 125 MPa at 873K. It was found that the creep life was decreased with increasing pre-creep stress and strain. In the case where the time elaspsed for pre-straining is relatively short(t≤3.6 × 105s), and thereby creep damage due to aging is unimportant, pre-creep strain has a dominant effect on the creep damage. Defining the creep damage parameter, Φ as the ratio of the minimum creep rate of a damaged specimen to that of an unused specimen, the extent of the structural deterioration is expressed as a function of pre-strain, εp as follows:
    Φp= (a·εp + 1)b
    where a and b are constants of the magnitude of 0.60 and 0.74 at 873K, respectively. The Monkman-Grant rule was obeyed for the damaged specimens, and the relationship between creep life and minimum creep rate is expressed as follows:
    (tr/s)·(εm/s-1)Y=KP
    where Y and KP are constant independent of stress, and their values are 1.63 and 4.18 × 10-6, respectively.
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  • Tsunemi WADA, Sadahiro YAMAMOTO, Hiroyuki KUTSUMI, Yasuo KOBAYASHI
    1994 Volume 80 Issue 5 Pages 418-423
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    Boronated stainless steel containing up to 2 mass%B, which is used for storage and transportation of spent nuclear fuel, has been well known as a poor workable material with large volume fraction of coarsely dispersed plate-like borides.
    Rapid solidification processes were applied to boronated stainless steels for refining borides and improving ductility and toughness.
    Borides were a little refined by the casting process using a water-cooled Cu mold. It was found that boron almost existed as solute atoms in a nonequilibrium state for as-solidified powders produced by N2-gas and water atomizations. Fine spherical borides precipitated during HIP treatment.
    HIP compacts and hot rolled plates processed from gas atomized powder exhibited a microstructure with finely dispersed sperical borides below 3μm in diameter and had superior ductility and toughness. Furthermore, it was found that refined borides also improved the corrosion resistance. A phenomenon similar to crevice corrosion was considered to occur at the interface between coarse plate-like borides and matrix.
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  • Masanori HOSOMI, Takashi MAEDA, Minoru OKADA
    1994 Volume 80 Issue 5 Pages 424-429
    Published: May 01, 1994
    Released: January 18, 2010
    JOURNALS FREE ACCESS
    The effects of thermo-mechanical treatment on the tensile ductility at room temperature were investigated in the three binary γ-base titanium aluminides containing different volume fraction of α2 phase. The tensile ductility at room temperature was improved by the formation of fine and homogenious "duplex" microstructure, which was optimised by the high reduction of forging and the adequate heat treatment temperature. The effect was most remarkable on the stoichiometric composition containing less α2 content than Ti-rich composition. In the duplex microstructure, deformation was taken upon the equi-axed γ grains rather than the lamellar region. However, the fracture mode was still brittle even in the specimen showing the high elongation of 7.8%.
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  • 1994 Volume 80 Issue 5 Pages N253
    Published: 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
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  • Koki GUNJI
    1994 Volume 80 Issue 5 Pages N208-N221
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
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  • Koichi EGAWA
    1994 Volume 80 Issue 5 Pages N222-N226
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
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  • Sadao OHTA
    1994 Volume 80 Issue 5 Pages N227-N232
    Published: May 01, 1994
    Released: June 19, 2009
    JOURNALS FREE ACCESS
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  • Kunio NAMIKI
    1994 Volume 80 Issue 5 Pages N233-N239
    Published: May 01, 1994
    Released: January 19, 2010
    JOURNALS FREE ACCESS
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