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

Tetsu-to-Hagané Vol. 73 (1987), No. 9

  • Selective Refining of Metals by Chlorine Gas

    pp. 1077-1081

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  • The Present Situation of the Mechanics of Granular Materials

    pp. 1082-1088

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  • Research and Development of Residual Life Prediction Technique for High Temperature Structural Materials

    pp. 1089-1095

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  • Microwave Application on Measurement and Control

    pp. 1096-1102

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  • Revision of the Methods for Chemical Analysis of Fluorspar for Iron and Steel Making (JIS M 8514-1976)

    pp. 1103-1108

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  • Manganese Distribution between Lime-or Soda-based Slags and Liquid Iron Containing High Carbon

    pp. 1109-1116

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    The manganese distribution between lime-or soda-based slags and liquid iron containing about 4%C was examined at 1350, 1400, or 1500°C. The effect of calcium halides on the distribution ratio of manganese was examined for lime-based slags.
    The distribution ratios of manganese for CaO-SiO2-Al2O3 slag were nearly the same order of magnitude as those for soda-based slags. The distribution ratios increased by the addition of less than 14% CaF2 or CaCl2 to the CaO-SiO2-Al2O3 slags, while they decreased with increasing CaF2 content for CaF2-based slags containing a small amount of SiO2 or free of SiO2.
    As a result of the comparison of the oxygen activities in equilibrium with Mn, Si and C in the iron, the equilibrium for the reactions in which carbon participated, e.g. (MnO) + C = Mn + CO(g), was considered not to be established in the reaction time given here when the slag of high silica was used. However, the quasi-equilibrium was estimated to be attained for the displacement reaction between Mn and Si. Then, the apparent equilibrium constant, K'Mn-Si= (% MnO)[% Si]1/2/[% Mn](% SiO2)1/2, for CaO-SiO2-Al2O3-CaF2, CaCl2 slags could be expressed by the following equation;
    log K' Mn-Si = - 0.84{( % CaO)/(% SiO2)-0.067( % CaF2), - 0.025 ( % CaCl2)} - 0.29
  • The Mechanism of Post Combustion in Converter

    pp. 1117-1124

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    A study has been made on the mechanism of post combustion by the hot metal experiment using 250 t converter and O2-CO experimental combustion furnace. In addition to these experiments, the decarburization experiment has been pursued using 10 t ladle.
    Post combustion ratio "α" observed is well explained by the post combustion model presented in this report. The equations to estimate post combustion ratio are as follows.
    αi≅ 0.1 ( h/d0 )0.3-(h/d0)-0.7+0.01
    α= Σiji × βij × FO2i) / ΣiFO2i
    ijFO2ijiFO2j = 0 (-1 ≤ βij≤ 1 ))
  • Influence of Ingot Shape and Chemical Composition on the Inverse-V Segregation in Killed Steel Ingots

    pp. 1125-1132

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    Aluminum-killed-steel slab ingots, whose weight was 5 to 40 t with various chemical compositions, were cast in order to investigate the influence of ingot shape and chemical composition on the formation of inverse-V segregation.
    Manganese content in the cross section of segregated streakes were obtained by line analysis with EPMA.
    The results were as follows:
    1) The average number of inverse-V segregation in the ingots had a relationship with ingot thickness D(mm) and density-change coefficient(ε), as shown in the next formula.
    N2070 = - 21.57 + 52.84 ε + 0.025D
    2) Inverse-V segregation streakes concentrated below the hot top in big-end-up ingots of larger wide face taper and taller ingots.
    3) Inverse-V segregation was assumed to be formed by the interdendritic fluid flow in the region which had the fraction of solid between 0.51 and 0.86.
    x

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    3. Critical conditions for the Formation of "A" Segregation in Forging Ingots Tetsu-to-Hagané Vol.75(1989), No.1
  • Wear Rate of Fused Silica Submerged Nozzle for Continuous Casting

    pp. 1133-1137

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    In order to estimate the wear rate and the campaign life of fused silica submerged nozzle for continuous casting of Mn steel, investigations were made of used nozzle retrieved from actual continuous casting machine and laboratory corrosion test of fused silica refractories in molten steel with various Mn concentration.
    As a result, it was found that the wear rate was proportional to the difference between bulk Mn concentration and equilibrium Mn concentration, and flow velocity of molten steel through the nozzle.
    The wear rate is expressed as follows;
    υ (cm/min)= 0.46 (4.5×10-2U+1.2){13.9 ([Mn]0-[Mn]e) + 1.1} × 10-3
    where U is flow velocity of molten steel through the nozzle(cm/min), [Mn]0 is bulk Mn concentration in steel, and [Mn]e is equilibrium Mn concentration for the reduction reaction of SiO2 by Mn in steel.
  • Production of Rapidly Solidified Fe-C-Si Alloy Powder by the Rotating-Water-Atomization Process and Its Structure

    pp. 1138-1145

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    The rotating-water-atomization process (RWAP) developed by the authors was applied to produce rapidly solidified powder of a large number of ternary Fe-C-Si alloys with 0.42 to 4.8 mass% C and 0 to 7.15 mass% Si. The particle shape was not spherical unless Si was free. The particle size was distributed in logarithmic normal and the mean particle diameter was in the range of 100 μm and 150 μm. Total oxygen content of powder was about 1 500 ppm for Si free alloys and it drastically decreased with increasing Si content. It was about 400 ppm for alloys with 2 mass% Si. Rapidly solidified particles consisted of ferrite(δ), cementite, austenite and martensite which were achieved by conventional quenching techniques. In addition to the above, metastable ε (hcp) and new X1 and X2 phases were also formed at high carbon and silicon contents. Crystallographic structures of X1 and X2 were not yet identified. The DSC curves of X1 and X2 were quite similar to those of ε and austenite, respectively inspite of having different crystal structures. The formation of these phases depended on the cooling rate. In a Fe-2.79C-5.06Si alloy, austenite and ε phases were dominant at higher cooling rate, on the other hand at lower cooling rate X2 were preferentially formed. A large exothermic reaction of 84 J/g due to the decomposition of austenite to ferrite and cementite was observed upon heating Fe-1.89C-2.97Si powder.
  • Deformation and Recrystallization Behavior of Austenitic Stainless Steel in High Speed Hot Rolling

    pp. 1146-1153

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    The recrystallization behavior of austenitic stainless steel in high speed hot rolling has been investigated in relation to the strain distribution through the thickness of the rolled strip. The strip of which the size was 2.1 × 20 × 760 mm was rolled at the temperatures from 900°C to 1100°C and at the mean compressive strain rate of 600 s-1 with or without lubrication. The rolled specimen was quenched in water at the interval of 60 ms after rolling. The redundant shear strain caused by friction forms severely sheared region beneath the surface with the thickness of about 100 μm. The maximum equivalent strain εmax in rolling without lubrication is always larger than that in lubricated rolling.
    A band of extremely fine recrystallized grains (d= 27 μm) are formed in severely sheared region when εmax exceeds the critical value, which is dependent on Zener-Hollomon parameter Z0 at the mid-thickness of the strip and independent of lubrication condition. The size of the recrystallized grains is strongly dependent on Z0 and independent of εmax. It cannot be made clear from this experiment whether this recrystallization occurs dynamically or statically. It seems, however, that dynamic recrystallization possibly takes place because the recrystallized grains appear even in the strip quenched after a short holding time of 3.5 ms.
  • Statistical Analysis about Crack and Spalling on Work Roll for Hot Strip Mill Finishing Rear Stands

    pp. 1154-1161

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    Concerning cracks and spallings of high alloy grain cast iron roll for hot strip mill finishing rear stands, we have been trying to clarify their originating processes by the field data of rolls. From the analysis of reports about types of failure, roll operating and maintenance conditions for 80 pieces of damaged rolls, the followings became clear ralating to the mechanism of crack and spalling.
    When a crack is introduced on a roll body by cobble, quick roll change will result in a small damage. However, when the cracked roll is used continuously for rolling, we will get a heavy damage such as a large spalling, which is over 100 mm in width and over 50 mm in root depth. Sometimes, a breaking short on a roll body took place by the propagation of crack by cobble.
    It is important to find out the crack quickly after cobble to avoid the heavy damage of the roll. The roll material with higher resistance to thermal shock and load caused by cobble has to be manufactured. Introducing an eddy current testing method to find out a small crack, gives rise to effective decrease in roll damage.
  • Effect of Rolling in Low Temperature Austenite Region on Strength, Ductility and Toughness of Rail Steels

    pp. 1162-1169

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    For the purpose of improving the ductility and toughness of pearlitic eutectoid steel, such as rail steel, controlled-rolling was carried out. In this paper, controlled-rolling means the rolling in low temperature austenite ( γ ) region. The effects of rolling conditions and alloy additions on the microstructure and mechanical properties were investigated.
    The results are summarized as follows:
    (1) γ grains of the eutectoid steels controlled-rolled are refined or elongated, consequently, pearlite colonys become refined.
    (2) Also in eutectoid steel, the addition of Nb and V has a retardation effect on recrystallization. Cr addition also has the effect a little. Si addition does not show any such effects.
    (3) The nucleation rate of γ→ pearlite transformation in the unrecrystallized γ grain boundaries is higher than that in the recrystallized ones.
    (4) As for eutectoid steel, in general, the ductility and the toughness increase accompanying with decrease in yield strength accordingly as the controlled-rolling intensifies more. Only the steel to which Nb was added shows an improvement in ductility and toughness without a decrease in strength.
    (5) Si addition improves the fracture toughness markedly.
    (6) The combination of the complex addition of Nb, Si and the intensified controlled-rolling is effective for the improvement of ductility and toughness of rail steels.
  • Stress Relaxation and Hot Ductility of Steels in Intermittent Tensile Deformation at Temperatures from 700 to 1300°C

    pp. 1170-1177

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    In order to understand the effects of straightening points of continuous caster on the surface cracking susceptibility of the slabs, stress relaxation during hot deformation of low alloy steel austenite and austenitic steels has been studied by means of intermittent tensile testing at temperatures ranging from 700 to 1300°C. The processes of deformation to given strains at a slow strain rate of 4 × 10-4s-1and subsequent stress relaxation for 3 min were repeated. Stress relaxation is largely suppressed by lowering the deformation temperature especially in Nb steels because of the dynamic precipitation of NbC. Although the carbonitride precipitates nucleating dynamically can grow into considerably coarser particles in the subsequent relaxation process, the dynamic precipitetion introducing the ductility loss can occur in the next deformation. Thus the ductility in the intermittent deformation is completely the same as in the continuous deformation, indicating that increasing the straightening points will enhance the dynamic precipitation because of lowering the average strain rate, resulting in significant enhancement effect on the surface cracking frequency. While at higher temperatures, since the stress relaxation can occur much easily, the multipoint straightenng could give considerable improvement effect on internal cracking which is usually formed at temperatures close to the solidus.
  • Low Cyclic Fatigue Behavior of 32%Mn Nonmagnetic Steel and the Effects of C and N in Liquid Nitrogen and Liquid Helium

    pp. 1178-1185

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    The effects of testing temperature, C, and N on the low cyclic deformation behavior of 32% Mn nonmagnetic steels have been investigated in ambient air, liquid nitrogen, and liquid helium. It was observed that several problems exsisted in fatigue tests in liquid helium due to special phenomena occurred at very low temperatures. The steel containing 0.3 % N, which showed large fatigue softening at room temperature, increased the trend toward the softening at low temperatures. The steel containing 0.14% C and 0.13% N also increased the tendency of softening with the temperature decrease, while it was not so large at room temperature. Dislocation configuration in steels showing the softening tended to be mainly planar at very low temperatureas same as at room temperature. The steel with a very low content of C and N, the 0.3%C steel, and the 0.12% N steel did not show the softening at low temperatures, but showed only fatigue hardening. The hardening of the former two steels increased remarkably as the temperature decreased. This phenomenon was attributable to ε martensite induced by the cyclic deformation. The fatigue softening behavior observed at low temperatures could qualitatively be explained with the hypothesis that the softening occurred through the breakdown of solid solution strengthening due to IS complexes during the cyclic deformation.
  • Hot-hardness and Indentation Creep Characteristics of Pure Metals

    pp. 1186-1192

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    In this study, eighteen kinds of polycrystalline pure metals were provided to investigate the hot-hardness and the indentation creep characteristics at elevated temperatures.
    The inflection temperatures where the hot-hardness started to decrease quickly with increasing temperature were observed in the range from 0.35 to 0.68 Tm (where Tm was melting point on the absolute scale), and were calculated as 0.49 Tm on the average.
    However, in some semi-conductor metals such as Si or Ge, the second inflection temperature appeared.
    The slope of the plot of logHV-logt (t was indentation creep time in sec.) which was defined as "indentation creep rate" was the largest in Mo and the smallest in Si at 0.60 Tm. There was a tendency for the indentation creep rate to increase linearly with increasing homologous temperature, and the slope of the line was the largest in bcc and it became smaller with fcc and cph systems.
    On the other hand, in the case of semiconductors the indentation creep rate decreased with increasing temperature up to the second inflection temperature.
    The activation energies of pure metals calculated from the indentation creep were close to those for selfdiffusion.
  • Nucleation and Growth of Bubbles in Hydrogen Attack of 2.25Cr-1Mo Steel Determined by Hydrogen Permeation and Steel Density Measurements at Lower Temperatures

    pp. 1193-1198

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    The quations to estimate the density and the radius of bubbles formed in the incubation period for hydrogen attack of 2.25 Cr-1 Mo steel were proposed. By relating the hydrogen diffusivity and the change in density of steel with the bubble density ρs and the bubble radius γ, it is derived that
    ρs=LAK3/72πΔγ3(-Δρ/ρ)2 γ=3Δγ(-Δρ/ρ)/K
    where Δρ/ρ is the change in density caused by bubbles, Δγ is the thickness of shell around each bubble which acts as trapping site of hydrogen atoms, K is the total volume of the shells and LA is the mean intercept length of prior austenite grains.
    The hydrogen diffusivity and the change in density were measured on the quenched and tempered steel which had been exposed to high temperature and high pressure hydrogen atmosphere. ρs and γ obtained by substituting these values into the above equations agreed well with the microscopical observation.
  • 日中大学比較あれこれ

    pp. 1199-1201

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  • 会社は今美容整形中/ある日の研究ノ-トから/岩手の桜

    pp. 1201-1201,1209

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