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

Tetsu-to-Hagané Vol. 63 (1977), No. 10

  • ブラジル鉄鋼会社見学の憶い出

    pp. 1621-1622

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  • On the Permeability Resistance of Pellets Containing MgO in the Softening and Melting Zone of Blast Furnace

    pp. 1623-1632

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    An investigation has been made of the permeability resistance of iron ore pellets and sinters in the softening and melting zone, which has large influence on the productivity and the fuel ratio in the blast furnace perfbrmance. The results obtained are as follows:
    (1) The pressure drop in this zone greatly increases as the FeO-containing slag melts and flows out into the void in the packed bed of pellets of sinters.
    (2) MgO addition in the pellets is effective to decrease this pressure drop because, during reduction, MgO makes solid solution with wnstite called magnesio-wnstite with higher melting point.
    (3) By X-ray microanalysis and optical microscopy Mg has proved to be concentrated in the magnetite and Ca-ferrite in the MgO added pellets before reduction.
  • Theoretical Investigation of Mass Transfer from a Cylinder and a Sphere in Pulsating Flow

    pp. 1633-1642

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    Analytical solutions of the velocity around bodies oscillating harmonically with small amplitude in a stagnant fluid are derived from the boundary-layer theory. Steady secondary flows around a circular cylinder and a sphere are calculated and shown schematically.
    Generalized expressions for the local and overall mass transfer from these bodies in steady, oscillating, and pulsating flows are derived on the basis of the equation of mass balance by using the solutions mentioned above and those reported previously for steady flow. The integrals included in these expressions being evaluated numerically, the local mass-transfer distributions around bodies a d the overall expressions are shown for each flow. These results are compared with the analytical and experimental ones reported previously, and shown to be rather satisfactory. The approximate expressions for pulsating flow are
    Sh= [(0.615) 1.74+ (0.728z1/3) 1.74] 1/1.74 Sc1/3 Rep1/2 (circular cylinder)
    and Sh=2+ [(0.654) 1.85+ (0.648 z1/3) 1.85] 1/1.85 Sc1/3 Rep1/2 (sphere),
    where sh=2r0kf/D, z= (aω/U∞) 3/2 (a/r0) 1/2, Sc=ν/D, and Rep=2r0U∞/ν (a, amplitude; D, di ffusivity; kf, mass-transfer coefficient; ro, radius; U∞, free stream velocity; ν, kinematic viscosity; ω, angular frequency)
    These expressions become ones for steady flow as z→0, and ones for oscillating flow as z→∞.
  • Application of Calcia Electric Arc Furnace Hearth and Its Effect on Oxide Inclusions in Steel

    pp. 1643-1652

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    In order to decrease the macroscopic inclusions containing spinel (MgO·Al2O3), the main mineral phase of oxide inclusions in steel, calcia refractories were newly developed for electric are furnace hearth materials. Some properties of calcia hearth materials and the effects of using calcia hearth materials on oxide inclusions were studied.
    Main results are summarized as follows.
    By using calcia hearth materials, not only the quantity of MgO in the form of oxide inclusions, but also the quantities of Al2O3 and SiO2 were lower than those in the case of using magnesia or dolomite hearth materials. The quantity of CaO in the form of oxide inclusions did not increase. Accordingly, the total quantity of oxide inclusions decreased to less than the half for the case of using magnesia or dolomite hearth materials.
    Moreover, it was recognized that the sulfide inclusions decreased remarkably. By these results, it was confirmed that number of macroscopic inclusions in steel were decreased and cleanness of steel was improved remarkably by using calcia hearth materials.
  • Influence of Ca-Al Deoxidizer on the Morphology of Inclusions

    pp. 1653-1662

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    In order to make clear the influence of Ca-Al deoxidizer on the shape control of Al2O3 and MnS inclusions which cause the anisotropy of the Al deoxidized steel, experiments of Ca-Al deoxidation for the Al predeoxidized steel have been carried out. And a formation mechanism of the inclusions characteristic to this deoxidation are discussed. The results are summarized as follows:
    (1) Inclusions in the molten steel change to low melting ones consisted of Al2O3-CaO-CaS in which CaS distributed uniformaly.
    (2) Inclusions in the ingot change to complex type consisted of Al2O3-CaO-(CaS) in which CaS deposits peripherally. These complex inclusions are thought to he formed by precipitation of CaS due to the solubility drop during solidification process.
    (3) The anisotropy of the steel is improved by this shape coatrol of inclusions.
  • Solubility of Nitrogen and Equilibrium Of Ti-nitride Forming Reaction in Liquid Fe-Ti Alloys

    pp. 1663-1671

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    The solubility of nitrogen and the equilibrium of the Ti-nitride forming reaction in liquid Fe-Ti alloys under the presence and absence of Ti-nitride were studied hy the sampling method at 1600, 1650 and 1700°C in the concentration range of 0-0.5% Ti.
    The results are summarized as follows:
    1) Solubility of nitrogen markedly increased with increasing titanium concentration, and Ti-nitride was formed at very low concentration of titanium in the liquid Fe-Ti alloys.
    2) The intraction parameters, e (Ti) N were found to be -0.60 at 1600°C, -0.49 at 1650°Cand -0.44 at 1700°C, and e (Ti) Ti have been deduced as 0.53 (1600°C), 0.29 (1650°C), and 0.26 (1700°C).
    3) The Ti-nitride which appeared in the liquid Fe-Ti-N system was identified as cubic TiN by X-ray diffraction analysis. The standard free energy of decomposition was determined as
    TiN (s) =Ti+N
    ΔG°=90 400-35.6T
  • Effect of Alloying Elements on Primary Dendrite Arm Spacing in Iron-base Alloys

    pp. 1672-1680

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    The influence of the solidification rate R, the temperature gradient G and the kind and amount of solute on primary dendrite arm spacing are investigated in unidirectionally solidified Fe-C, Fe-P, Fe-0.5%C-P and Fe-0.5%C-S alloys.
    The effects of the kind and amount of solute on primary dendrite arm spacing are discussed on the basis of Okamoto-Kishitake's equation.
    The results are summarized as follows.
    1) Nearly linear relation is obtained between primary dendrite arm spacing and G-0.4R-0.2 in Fe-C alloy
    as well as stainless and Cr-Mo steels.
    2) Primary dendrite arm spacings in Fe-C and Fe-P alloys slightly increase as the solute content increases.
    3) Primary dendrite arm spacings in Fe-0.5%C-P and Fe-0.5%C-S alloys are not affected by phosphorus and sulfur content.
    4) The effects of the kind and amount of solute on primary dendrite arm spacing can be almost explained by Okamoto-Kishitake's equation in iron-base alloys as well as aluminium alloys.
  • Solidification Structures and Microsegragation of Fe-Ni-Cr Alloys

    pp. 1681-1690

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    The solidification phenomena in 10kg ingots of Fe-Ni-Cr alloys were investigated by observation of macroand micro-structures and determination of micro-segregation.
    1) The phase changes of Fe-Cr-Ni alloys are classified into the following four kinds.
    A) Liquid→Liquid+δ→δ (α) -α+γ (solid transformation)
    B) Liquid→Liquid+δ→Liquid+δ+γ→α+γ
    C) Liquid→Liquid+γ→Liquid+γ+δ→γ+α
    D) Liquid→Liquid+γ→γ (no solid transformation)
    Both types B and C have pseudo-columnar zone, which is composed of equiaxed structure microscopically but is macroscopically observed as columnar structure. This zone is formed with equiaxed structure, which is detached from the columnar crystals by microscopic thermal stagnation on the thernary peritecticeutectics, and is followed by γ formation which has previously begun during solidification.
    2) Micro-segregation of Fe, Cr, and Ni may be estimated from the isothermal curves in the phase diagram by JENKINS et al.
    Segregation index and effective distribution coefficient of Cr and Ni in this work agreed with those by others. Si and Mn segregate more extensively with increasing Ni content. In case of γ-primary (types C and D), Cr, Si, and Mn concentrate more extensively in the interdendritic region than in the center of dendrite, but Fe and Ni over 50% are higher at the center.
  • Strengthening and Toughening of 280kg/mm2 Grade Maraging Steel through Thermomechanical Treatment

    pp. 1691-1699

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    In order to improve the strength and toughness of 280kg/mmmm2 grade maraging steels, the effects of two types of thermomechanical treatments by multiple-pass rolling and single-pass large reduction pressing followed by annealing, on the microstructure, tensile properties and fracture toughness have been investigated. The excellent combination of stkrength, ductility and toughness can be achieved by the former treatment, particularly in low finishing temperature of the rolling, because uniform and fine grained structure is obtained. However, the latter treatment leads to the poor ductility, because mixed structure with fine and coarse grains is produced. The strength and ductility of maraging steel could be improved by grain refinement and warm working below recrystallization temperature, but the toughness is essentially unaffected by those factors.
  • Effect of Metallurgical Factors on Fatigue Properties in 5.5Ni-Cr-Mo-V Steel

    pp. 1700-1708

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    Martensitic structures or mixed structures of martensite and bainite with various prior austenitic grain sizes and volumes or sizes of precipitates were obtained by various heat treatments, using HT140 steel. HY180 and 12%Ni-maraging steels were also used. The effect of metallurgical factors on cycles to failure, crack growth rate, and cyclic stress-strain curves was examined and discussed.
    The results are as follows:
    (1) Fatigue strength at 105 cycles increases with increase of cyclic yield strength and decrease of prior austenite grain size.
    (2) The difference of fatigue strength between various materials mainly depends on the difference of cycles required to initiate crack and behaviour of the very early crack growth.
    (3) The stage of intermediate crack growth is hardly influenced by metallurgical factors of steels.
    (4) The ratio of cyclic yield strength to monotonic one for steels peak-aged is lower than that for steels otherwise treated.
    x

    Readers Who Read This Article Also Read

    1. 日本鉄鋼協会第94回講演大会講演概要 Tetsu-to-Hagané Vol.63(1977), No.11
    2. 日本鉄鋼協会第94回講演大会講演概要 Tetsu-to-Hagané Vol.63(1977), No.11
    3. 日本鉄鋼協会第94回講演大会講演概要 Tetsu-to-Hagané Vol.63(1977), No.11
  • Role of Oxide and Sulfide Particles on Charpy Impact Properties in 10Ni-8Co Alloy Steels

    pp. 1709-1718

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    The influence of second phase particles such as oxide and sulfide on Charpy impact absorbed energy of 10Ni-8Co alloy steels (HT180) with various sulfur (0.002-0.015%) and oxygen (0.0006-0.0095%) contents was studied. The role of these particles in ductile fractures was discussed to be based on the variation of the dimple size and the relation between the impact energy and volume fractions of the particles. Charpy impact absorbed energy (Ev) in these steels decreases remarkably with an increase of the volume fraction (Vp) of oxide and sulfide. The relation between Ev and Vp is expressed by Ev=A·Vp-n, where nvalue indicating the dependence of Ev on Vp is 0.95 of 1/3 according to the change of size and spacing of the particles observed. When the dimple size on the fractured surface correpsonds to the spacing the particles obsEved, n-value is 0.95. When the dimple size smaller than the spacing of the paricles, n-value decreases to 1/3. The latter is the case for the coarse oxide. This can be explained by the fact that the voids nucleated by the coarse oxide are linked by the smaller voids nucleated by sulfide.
  • Rust Nucleation Sites in 18Cr-Ti Stainless Steel

    pp. 1719-1727

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    The aim of the present work is to study the sites of rust formation and mechanism of rusting on 18 Cr-Ti steels under the salt spray test. Rusts are preferentially initiated at cubic inclusions or precipitates with titanium (esp. TiN-TiC-Ti4C2S2 system, TiO2 (or Al2O3) -TiN-TiC-Ti4C2S2 system, TiN-TiC system). But no rusting occurs either at separate particles of titanium carbosulfide or at titanium cabonitride surrounded by a rim of carbosulfide. There exist primary microscopical crevices between the cubic inclusions and the matrix. At these sites crevice corrosion is able to initiate and causes the annular rusting around the cubic inclusions. Additions of titanium (about 0.2% or more in free Ti) in extra low carbon and nitrogen 18 Cr steels show a very pronounced effect on the resistance to rusting. The role of titanium in rust resistance is (1) to prevent the formation of manganese sulfide related to rusting and to lead the formation of carbosulfide resistant to the dissolution and (2) to shift the pitting potential to the noble direction.
  • Oxide Inclusions in Mild Steel Weld Metal

    pp. 1728-1737

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    Oxide inclusions in mild steel weld metal were investigated. Oxide inclusions isolated from mild steel weld metal by ultrasonic agitating dissolution method using I2-CH3OH solution were classified according to the size (5 microns over and under) by ultrasonic sieving method, and observed by optical microscope.
    Larger inclusion particles over 5 microns were analysed by electron-probe X-ray microanalyzer.
    It was found that inclusion particles over 5 microns were spheroidal (MnO·SiO2, SiO2, and (Mn, Fe) O), angular (SiO2), lumpy (SiO2), platy-shaped (SiO2), prismatic (Al-silicate), pine needle- or stick-shaped (Ca-silicate), and string-shaped (Ca-phosphate) in shapes (and compostions).
    The amount of inclusion particles less than 5 microns was about 90% in oxide inclusions, and the greater portion of these was MnO·SiO2, the size of which was about 1 micron.
    Ti-oxides which were confirmed by X-ray diffraction in inclusion particles less than 5 microns were α-Ti2O3, Ti2O3, and FeO·TiO2 when Fe-Ti was added to the flux of low hydrogen type, while TiO2 (anatase), Ti2O3, and FeO·TiO, when TiO2 (rutile) was added to titania and cellulose type in the compositions.
    The mechanism of formation of various oxide inclusion particles in the weld metal was considered.
  • Effect of High Temperature Aging on the Microstructure of Cr-Ni Austenitic Steels

    pp. 1738-1749

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  • Development and Future Trend of Alloys for Automobile Emission Control Devices

    pp. 1750-1757

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  • Long-term Energy Outlook

    pp. 1758-1770

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  • 抄録

    pp. 1771-1778

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    x

    Readers Who Read This Article Also Read

    1. 日本鉄鋼協会第94回講演大会講演概要 Tetsu-to-Hagané Vol.63(1977), No.11
    2. Effect of Metallurgical Factors on Fatigue Properties in 5.5Ni-Cr-Mo-V Steel Tetsu-to-Hagané Vol.63(1977), No.10
    3. 日本鉄鋼協会第94回講演大会講演概要 Tetsu-to-Hagané Vol.63(1977), No.11

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