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

Tetsu-to-Hagané Vol. 61 (1975), No. 9

  • これからの企業研究のあり方

    pp. 2149-2150

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  • A Study of Non-isothermal Reduction of Iron Ores

    pp. 2151-2159

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    Studies of iron oxide reduction are quite many, and the mechanism and kinetics of reaction have also been reported. Many of these reports, however, are concernei with the iso-thermal reductions, and only a few reports on the non-isothermal reduction have been published. Then, the authors investigated the reduction of non-isothermal type; from room temperature to 1050°C by simple H2 gas and mixed gases which approximate the distribution of gases in the B.F.
    Moreover, a non-isothermal fluidized bed reduction was tried, and an empirical formula n=γ00F/RT2) dT/dtΔt was presented and analyses were performed by this formula.
    The results are as follows.(1) The non-isothermal reduction in comparison with isothermal case is quick to finish the reduction.(2) In the reduction by mixed gases of CO, CO2, and H2 the effect of reducing temperature is greater than that of the concentration of CO.(3) The non-isothermal fluidized bed reduction is possible up to near 1000°C without sintering of reduced powders.(4) The rate of non-isothermal reduction can be expressed as n=γ00F/RT2) dT/dt·Δt.
  • The Reduction of Iron Oxide Single Crystal

    pp. 2160-2166

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    The change of crystal structure during the reduction of iron oxide and the growth mechanism of fibrous iron were investigated. In order to elucidate the crystallographic transition of Fe2O3 during the reduction, platelets of Fe2O3 single crystal with flat (0001) plane (approx. 5 mm in width and 0.5 mm in thickness) were used as samples. Each of Fe3O4, FeO, and Fe was prepared by the reduction of the Fe2O3 sample at 750°C in the CO-CO2 mixture with an appropriate composition for each. The structures of the products were analyzed by X-ray diffraction including the Lane methods and scanning electron microscopy (SEM).
    The X-ray diffraction revealed that (0001) plane of Fe203 changed to (111) plane of Fe3O4 and (111) plane of FeO by epitaxial reactions. SEM revealed that as the reduction proceeded, steps parallel to (0001) plane of Fe2O3 appeared remarkably, and fibrous iron grew from some nuclei on the steps. The fibrous iron was never seen on (0001) plane of Fe2O3, and the direction of most active growth was [2110] of Fe2O3.
  • Calcium Deoxidation and Aluminium Desulphurization of Liquid Iron and Liquid Iron Alloy with a Lime Crucible

    pp. 2167-2181

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    Using a lime crucible and an induction furnace in vacuum as well as at pressure, a study was made to clarify the deoxidation and the desulphurization processes of liquid iron and iron-base alloys by iron clad calcium or aluminium alone.
    The experimental results are summarized as follows.
    (1) Calcium addition to liquid iron in a magnesia or alumina crucible greatly influenced the rate of deoxidation and the deoxidizing power owing to the reaction of the crucible material with calcium.
    (2) The CaO-FeO oxide which was formed for liquid iron in a lime crucible immediately after the calcium addition seemed to grow and to be separated from the melt with time.
    (3) At 1 600°C in 1 atm argon, the concentration of calcium dissolved in liquid iron was estimated to be 0.024 wt pct. The equilibrium constants were calculated as follows. log Kca=log aca.ao=-8.23 and K′ca= [%Ca]×[%O] =2.16×10-6,
    (4) It is presumed that the aluminium desulphurization of liquid iron in a lime crucible is caused by the formation of highly basic reaction product layer such as 3CaO.Al2O3 on the surface of the crucible.
  • Optimizing of Dimensions of Flat-ingot Mould on the Basis of Thermal Stress Analysis

    pp. 2182-2197

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    Thermal stresses originated in ingot moulds during solidification of ingots in contact were analyzed by the two dimension thermo-elastic theory. The unsteady temperature distribution was estimated using a finite difference method on the nodal points of mesh screen representing a mould cross section. The thermal stress distribution on imaginary dividing elements of the mould was subsequently calculated by a finite element method. A thermal stress parameter, the ratio of the thermal stress in an element to the tensile strength of the element, was then calculated to investigate the influence of the thermal stress on the life of the mould.
    A subsequent analysis was made of the thermal stress parameter for flat shape moulds with different ratios of cross section of the mould to that of a corresponding 23 tingot and with differeat ratios of the wide-face thickness to the narrow-face thickness of the mould.
    The above analysis has made it possible to derive an optimum mould shape, for which thermal stress becomes minimum, for the flat shape 23 t ingot.
  • The Effect of Fluid Flow on the Macrosegregation in Steel Ingot

    pp. 2198-2213

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    It is possible to show quantitatively the macrosegregation in steel ingot if the flow velocity of bulk liquid during solidification can be obtained. It is found that the flow velocity of bulk liquid is determined by applying the hydrodynamical method known as Taylor's vortex flow to the solidification. Using this method, the following relation is introduced,
    U/V=7500Sh/(1-Sh) where U is the How velocity, V the solidification rate, and Shthe fraction of solid depending on the washed depth. The effective distribution coefficiemt, ke is theoretically deduced on the basis of the mass transferwith turbulent mixing in the solidifying zone, which is composed of solid and liquid. It is expressed as follows:
    ke=1-Bl/L(1-K0)(1-Sh) U/V
    where B is an expaimental constant of 0.81×10-2, hhe primary dendrite arm spacing, L the thickness of the solidifying zone, and k0 the equilibium distributioncoefficient. There is a limit fbr the degree of washing against the solidifying zone because of the growimg dendritc morphology, and the limiting fraction of solid is about 0.67. Furthermore the relatiGn among the deflection angle of dendrite, the solidiflcation rate, and the How velocity Gf bulk liquid is obtained.
  • Distributions of the Temperature and Thermal Stress in the Slab Mill Roll

    pp. 2214-2225

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    The temperature distributions in the slab mill roll were measured experimentally, and the thermal stresses in roll were calculated from the temperature distributions. The following results were obtained.
    1. The maximum temperature measured in this experiment is 220°C; inside 3mm from the surface.
    2. The maximum temperature at the center of the roll is 120°C.
    3. The thermal stress in the roll surface layer by the rolling with cooling water after rolling withoutcolling water is tensile and less than 10kg/mm2.
    4. The thermal stress at the center of the roll is tensile and less than 20kg/mm2.
    5. The neutral point where the sign of stress changes is about 16cm from the roll surface.
    6. The required properties of the roll are as follows;
    (1) The surface layer (0-1mm from the surface); strength to heat checking,
    (2) The middle part (1-250mm); fatigue strength, and
    (3) The inner part (250mm-center); toughness.
  • Effects of Small Pre-Strain and Austenitizing Condition on the γ→α Martensitic Transformation of Iron Alloys

    pp. 2226-2237

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    Grain refimng and plasticity induced by martensitic transformation are thought to be important for developing high strength steels with ductility. The phenomena are connected with the nucleation process of martensite, although the nucleation mechanism of martensite has been still obscure.
    In order to get some infbrmations of the nucleation effects of small pre-strain and austenitizing conditions on γ→α martensitic transformation of iron alloys have been investigated by measuring electric resistivity and hardness, and by optical-and electron-microscopy. A part of experimental results have been analyzed numerically by reaction rate equation. Merits and demerits of hitherto suggested models of martensitic nucleation are discussed comparing with the results of thiswork and adirection of future investigation is proposed.
  • Effect of Nitrogen and Austenite Grain Size on the Ductilities of Eutectoid Carbon Steels

    pp. 2238-2245

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    This paper presents the results of an investigation performed to determine the effect of free nitrogen (solute nitrogen in matrix) content on the tensile ductilities of as-patented eutectoid carbon steels with reference to the prior austenite grain sizes. The results obtained are as follows.
    (1) Reducing the free nitrogen content of as-patented steels improves the tensile ductilities under the condition of constant prior austenite grain size.
    (2) The refinement of prior austenite grain size also improves the ductilities of as-patented steels with constant free nitrogen content.
    (3) These effects mentioned in (1) and (2) are remarkable for fine pearlitic steels transformed at relatively low temperatures but tend to be less notable as the transformation temperature rises.
    These results are discussed in relation to metallurgical structure.
  • Effects of Heating Rate, N Contents, and Mn Contents on Recrystallization Texture of Aluminum-Killed Steel Sheets

    pp. 2246-2262

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    Low carbon Al-killed steels for deep drawing quality, containing various amount of N and Mn, were cold rolled 65% and annealed up to 700°C at various heating rates.
    Steels annealed at the adequate heating rate (peak heating rate) showed large elongated grain and strong {111}‹011› oriented recrystallization texture, while those annealed at the other heating rates showed fine grain with {554}‹225›+ {111}‹011› oriented recrystallization texture.
    The peak heating rate was affected not only by sol. A1 contents but also by N contents and by Mn contents.Increase of N contents induced the peak heating rate faster and {111} intensity at the peak higher, on the other hand, increase of Mn contents induced the peak heating rate faster and {111} intensity at the peak lower.
    Discussions were made concerning the difference in recovery and recrystallization behaviour among the peak heating rate and the other, and the roles of N contents and Mn contents on the peak heating rate. N contents were thought to have an effect on AIN precipitation rate, while Mn contents were thought to have effects on recovery and recrystallization rate of cold rolled structures. The change of the peak heating rate was supposed to be caused by those effects of N and Mn.
  • Effect of Boron on Long Period Creep Rupture Strength of 12%Cr Heat Resisting Steel

    pp. 2263-2273

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    The effect of boron on creep rupture properties of steels has been investigated in order to develop new 12% Cr heat resisting steel with improved strength at elevated temperatures.
    1) The creep rupture strength of a 12% Cr-Mo-V-Nb steel is improved by boron addition. Especially, the creep rupture life of the steel containing 0.037% boron is five to six times as long as that of the steel free from boron in long term creep rupture tests at 650°C and above.
    2) Boron forms boro-carbide M23 (C, B) 6, substituting some amounts of carbon in carbide, type M23C6. It is observed under electron microscope that M23 (C, B) 6 is finer than M23C6 at elevated temperature. This is one of the reason for that the 12% Cr-Mo-V-Nb-B steel has superior creep rupture strength to the 12% Cr-Mo-V-Nb steel.
  • Alloy Design of Nickel-Base Precipitation Hardened Superalloys

    pp. 2274-2294

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    A new method of alloy design which consists of theoretical analysis and experimental examination has been applied to development of turbine blade materials of gas turbines.
    Oianed practical performance of the materials to be developed is settled at the beginning, and property factors affecting practical performance are analysed.
    Theoretical analysis involves decision of the most promissing alloy type, analysisof structural factors affecting property factors, analysis of production factors affecting structural factors, limitation of the range of the structural factors and computation of effective chemical compositions.
    In experimental examination, factors which can not be determined through theoretical analysis are investigated and practically valuable alloys are finally selected from the compositions extracted through theoretical analysis.
    In conclusion, 22 kinds of precipitation hardened nickel base alloys have been developed and the method of alloy design used in this study has been proved to be an effective means to develop complicated alloys.
  • Review of Iron and Nickel Base Alloys for Nuclear Reactor

    pp. 2295-2308

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  • 抄録

    pp. 2309-2314

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