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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 64 (1978), No. 1

  • 1978年の新年を迎えて

    pp. 1-2

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    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Production and Technology of Iron and Steel

    pp. 3-24

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  • Removal of Fine Particles in Ores for Blast Furnace by Pneumatic Classifier of Horizontal Type

    pp. 25-33

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    A pneumatic classifier of horizontal type is used instead of the wire sieve in order to eliminate fines in ores charged into blast furnace. The former is very convenient because it is free from troubles such as choking of the meshes and the breakdown in the case of the wire sieve. The removal of fines in sintered ores with increasing the mixing ratio (feed quantity to air quantity) was experimentally and theoretically examined in consideration of the scattering of the apparent specific weight and drag coefficient for the particles.
    The results obtained are as follows:
    (1) The classification is effectively carried out in when a distinct difference in horizontal travelling distance according to particle size can be made, even if the apparent specific weight and drag coefficient scatter in some extent.
    (2) With increasing the mixing ratio, the classification accuracy is lowered due to increasing of the collision frequency among the particles within the classification region. It is possible to avoid to some extent by thinning the thickness of feed particle bed.
    (3) The removal of fines is considerably successful by decreasing the cross section area of duct and increasing the air velocity in the case of classifing under condition of the same feed quantity and the same air quantity.
    (4) For the increase of the mixing ratio, it is practically economical to shorten the height of the duct and to make a calm zone within the classifing region without lowering the classification accuracy remarkably.
  • Effects of Electric and Magnetic Forces on the Solidified Structure

    pp. 34-41

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    To clarify the effects of the electric and magnetic forces on the solidified structure, the solidification experiments were systematically conducted on the Sn-10%Pb alloy. A direct or an alternative electric currents, magnetic currents and the currents combined them were introduced into the molten metal. The alloy was solidified under the nine different conditions.
    The effects of the electric field, the magnetic field and the combined field on each solidified structure were examined on the basis of the solidified structure and the theoretical considerations of the fluid flow caused under each experimental condition.
    It is concluded that the columnar structure can be developed by preventing the fluid flow and the fine equi-axed zone can be obtained by the forced fluid flow.
  • Estimation of Solute Concentration Distribution Accompanied by Interdendritic Solidification

    pp. 42-51

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    A peculiar break point in the cooling curves was experimentally observed. This point may be resulted from the rapid progress of solidification caused by the supercooling of interdendritic liquid.
    For studying the mechanism mentioned above mathemaical models for estimating the distribution of the solute concentration in the interdendritic liquid have been developed. The models are described for three cases where the liquid-solid interface is plain, cylindrical surface, and spherical one, respectively. Two models for the second and the third cases, which represent the state of the liquid surrounded with the dendrite arms, show that the difference between the liquid concentrations at the liquid-solid interface and those at the midpoint of adjacent dendrites increase when the solid fraction increases at the constant ratio. And it may be understood that the concentration difference results in the supercooling. While for the first model the difference of the concentrations decreases.
    Furthermore, by the use of the third model the measured temperatures where the break point occurs can be explained.
  • Effect of Nitrogen Content on Deep Drawability of Rimmed Low Carbon Cold Rolled Steel Sheet

    pp. 52-59

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    In the production of rimmed steel sheet, its nitrogen content converged to a constant level at box annealing process. Therefore increased nitrogen in steel making did not affect the strain aging properties of the sheet, but deteriorated the drawability or the r-value of the sheet.
    To clarify the effect of nitrogen on recrystallization texture formation, the nitrogen content at cold rolling and that at recrystallization annealing were varied by atmospheric reaction at 350-400°C after cold rolling and then recrystallization textures were compared. Amounts of {111} and {110} components of the recrystallization texture were markedly affected by the nitrogen content at annealing, whereas they were not affected by that at cold rolling. Meanwhile, neither the amount of {100} component nor recrystallized grain size was influenced by nitrogen content.
    It was supposed that high nitrogen content at the ladle in steel making induced larger amounts of nitrogen atoms as interstitials at recovery or recrystallization stage of the cold rolled steel, which promoted the recrystallization of {110} component and suppressed the development of {111} component at recrystallization annealing.
  • The Effect of Warm Tensile Working on the Stress Relaxation Value in the Carbon Steel

    pp. 60-69

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    In order to clarify the effect of warm tensile working on the stress relaxation value ΔP/P0 (ΔP: relaxed load, P0: initial load) at room temperature in a carbon steel (ferrite+lamellar pearlite), the effect of predeformation temperature (20°C-320°C), strain and structure have been studled, The results obtained are as follows:
    (1) The decrease in the stress relaxation value is observed on specimens which predeformed in the temperature rahge from about 220°C to 270°C. These predeformation tcmperature correspond to the temperature where the strain aging increases with increasing dissolution of the iron nitride and carbide owing to predeformation.
    (2) When the lamellar cementite have partially been broken by the predeformation in the temperature range from 20°C to 220°C, the relation between the relaxation value and logarithmic time is a snaky curve and then the relaxation value is shown its maximum value.
    (3) While the linear relation is observed for the steel with bended and broken lamellar cementite, in this case the relaxation value increases proportionally with increasing predeformation strain.
    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer

    pp. 70-77

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    When an immersion method is used for the cooling of heated steel products, it is important that the characteristics of this method are made clear. In order to measure the values of heat transfer coefficient between a specimen and coolant, and to clarify the influence of coolant stirring on heat transfer, 28×550×1000mm3 steel plates of about 930°C have been immersed into still water or stirred water.
    The main results obtained are summarized as follows:
    (1) When a specimen is immersed vertically into water, the maximum of heat transfer coefficient between the specimen and water (α) is, in kcal/mm2·h·deg, (5-7) ×103 for still water, (7-9) ×103 for stirred water by air flow, and (10-12) ×103 for stirred water by water flow.
    (2) In a vertical immersion into still water, α is considered to be a function of the surface temperature of a specimen, θs, and the height from the lower edge, H, as indicated below.
    α=10 (a+b·θs) · [1.0-k (H-10)]
    Where a, b, and k are constants which depend on θs.
    (3) When a specimen is immersed vertically into still water, αdecreases with increasing the size of the specimen.
    (4) The stirring of coolant by fluid flow is effective for the accelaration of the heat transfer and the water flow method is superior to the air flow one.
    x

    Readers Who Read This Article Also Read

    1. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. Laboratory Evaluation of Physical and High Temperature Properties of Commercial Pellets Tetsu-to-Hagané Vol.65(1979), No.3
  • Static Tensile Properties of Mixed Structure of Martensite and Residual Ferrite in Ni-Cr-Mo Steels Containing Medium Carbon

    pp. 78-87

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    A study has been made to clarify the effect of residual ferrite on static tensile properties of Ni-Cr-Mo steels containing medium carbon. Results obtained are summarized as follows:
    (1) The 0.2% proof stress approximately follows the calculated law of mixture up to 14% of residual ferrite, but becomes to deviate significantly from it beyond 14%.
    (2) Both elongation and reduction in area remarkably decrease with an increase in residual ferrite.
    (3) From the analyses of true stress-strain diagrams and microfractographs, a detrimental effect on ductility results from the fact that, in low volume fraction of residual ferrite, microcracks are initiated by fracturing of the residual ferrite in a brittle manner due to higher plastic restraining of it by martensite in the process of plastic deformation, and that with increasing in the residual ferrite microcracks which are initiated by fracturing of it, this mainly resulting from stress concentration in the neiborhood of interfaces between martensite and residual ferrite due to ununiform deformation, become to be simultaneously propagated through embrittled martensite.
  • Precipitation Hardening Produced by Ausaging of 245kg/mm2 Grade 18% Ni Maraging Steel

    pp. 88-94

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    Ausaging behavior in 245kg/mm2 grade maraging steels has been investigated. Appreciable precipitation-hardening is produced by ausaging at temperatures below about 625°C. The precipitation hardening is considered to be due to relatively high titanium content. It is also observed that elongation and reduction of area are decreased with increasing ausaging temperature. The decrease in ductility is considered to be caused by the formation of coarse precipitates at the austenite grain boundaries. The coarse precipitates are greatly suppressed when ausaging temperature is decreased to about 550°C. After ausaging at 550°C from 3000min to 6000min, the following mechanical properties are obtained; ultimate tensile strength: 200-210kg/mm2, elongation: 10-15%, reduction of area; 60-65%. However, the ductility of specimens ausaged at 550°C for longer times tends to decrease because of the formation of relatively coarse precipitates at the austenite grain boundaries.
    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Precipitation of Intermetallic Compounds in Austenite and Its Effects on Toughness of As-Quenched Martensite in 13%Ni Maraging Steel

    pp. 95-104

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    The precipitation of intermetallic compounds in austenite and its effects on the toughness of as-quenched martensite in 13%Ni maraging steel have been studied by means of Charpy impact tests and structural observations. The heat-treatment process investigated comprises intermediate isothermal holding in the temperature range from 800°C to 1100°C after homogenization at 1200°C reheating of the martensite to the austenite region below 1100°C after quenching to room temperature from 1200°C.
    Not only the intermediate holding but also the reheating introduced a drastic decrease in Charpy impact energy of the as-quenched martensite. Structural observations revealed the coarse precipitates on prior austenite grain boundaries and within the grains for both heat-treatments. Prolonged intermediate isothermal holding was necessary to cause the precipitation within the grains. However, when the martenisite was reheated to the range between Af and the austenite recrystallization temperature, the precipitation within the grains was promoted in short time, due to the presence of the nucleation sites formed in martensite on the heating up to the austenitic region, or probably to the internal strains of the reverted austenite.
    These precipitates were considered to be intermetallic compounds of Fe2Mo or (Fe, Co) 7Mo6. The major loss in the toughness of as-quenched martensite of 13%Ni maraging steel was associated with the precipitation of intermetallic compound containning Mo during holing in the austenite regions.
  • The Effect of Second Phase Particles on the Tensile Properties of Ferritic Iron at Low Temperature

    pp. 105-112

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    The effect of two kinds of the finely dispersed particles with different elastic modulus from iron matrix (∈-Cu and TiN) on the low temperature ductility of ferritic iron was investigated.
    ∈-Cu particles were uniformly dispersed in the matrix by aging of Fe-1.83% Cu allay at 700°C for 96h, whereas TiN particles were uniformly dispersed by internal nitriding of Fe-0.1% Ti alloy at 700°C for 4h. By the presence of TiN particles, the elongation at 77K of ferritic iron with 150μ grain diameter increased by about 20%, whereas, by the presence of ∈-Cu particles, the elongation at 77K of ferritic iron with 60μ grain diameter decreased by about 20%. The reason is considered that the presence of TiN particles favors cross slip of screw dislocation around these particles which changes the deformation mode of coarser grained ferritic iron from twinned to slipped, whereas ∈-Cu particles do not work so.
    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • The Influence of Solution and Precipitation Behavior of M23 (C, B) 6 on the Hardenability of Boron Steels

    pp. 113-120

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    Cu-Ni-Cr-Mo-B low alloy steels whose total boron content exceeds a certain limit show superior hardenability when they are austenitized at lower temperatures (≤900°C), although their hardenability decreases with higher austenitizing temperatures and longer holding times. As M23 (C, B) 6 in these steels is partly undissolvable at lower austenitizing temperatures, B content in solid solution is not determined uniquely from Fe-B-Al-N equilibrium state but rather regulated by the solubility product of M23 (C, B) 6.
    At lower temperatures (≤900°C) boron content in solid solution which balances with M23 (C, B) 6 is considered appropriate for hardenability. At higher temperatures (>900°C), boron content in solution which equilibriates with M23 (C, B) 6 increases and exceeds the limit over which the hardenability of boron steels decreases. Heating below Ac1 for a long period, while M23 (C, B) 6 is enriched with C, Mn, and Mo atoms, austenitizing condition appropriate for the hardenability is transferred to higher temperatures and longer periods. This is because the solubility product of M23 (C, B) 6 is lessened and the particles grow coarsed.
    Boron content in solid solution which balances with M23 (C, B) 6 is determined approximately from the relation among the decrease of hardenability, quenching temperature, and boron content in solution calculated from the Fe-Al-B-N system. The result is as follows: 880°C-3ppm, 900°C-6ppm and 930°C-8ppm.
    These values are considered to depend strongly on Cr, Mn, and Mo contents and prior heat treating history. In excess boron containing steels, boron constituents are observed on the prior austenite grain boundaries at distances longer than 15mm from the quenched end of Jominy end quench test specimens, when they are quenched from 930°C.
  • Reduction Test of Hematite Ore Powder by Gas Flowing High Pressure DTA Method

    pp. 121-127

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    The effect of reduction condition of hematite ore (32-60mesh) under high pressure (0-100kg/cm2) H2 flow was studied using dynamic gas flow type high pressure DTA equipment. Besides usual nonisothermal DTA method, new attempt on isothermal DTA method was made by the equipment.
    The results obtained are as follows:
    (1) The rate of reduction was high when reduction temperature was raised from 500°C to 850°C. The lowering of reduction rate around 700°C, which was pointed out in some papers, was not observed.
    (2) The effect of an increase of H2 pressure on reduction rate became very small at a pressure upper than 15kg/cm2. The effect of H2 pressure was relatively large under a reduction condition of low temperature and low gas pressure.
    (3) The rate of reduction increased with increasing H2 (STP) gas flow rate. It was found that the effect of gas flow rate on the rate of reduction was remarkably larger than the effect of gas pressure under the experimental conditions in this study.
  • Mechanical Properties of 12% Cr Steel Forging for Large Steam Turbine

    pp. 128-134

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    In order to develop a new rotor forging, for compact designed larger steam turbine, which has higher mechanical properties than 1Cr-1Mo-0.25V rotor at elevated temperature, an investigation has been carried out on the mechanical properties and the uniformity of 12Cr-Mo-V-Ta-N model rotor and high and intermediate pressure rotor for 375 MW steam turbine.
    12Cr-Mo-V-Ta-N rotor has better room temperature tensile strength and impact value than 1Cr-1Mo-0.25V rotor, in the part of shaft, body surface and body center. Creep rupture strength of 12Cr-Mo-V-Ta-N rotor, one of the most important properties, is also higher than 1Cr-1Mo-0.25V rotor and it uniformity is excellent.
    It is expected that a newly developed 12Cr-Mo-V-Ta-N rotor with good mechanical properties andsoundness can be applicable for larger steam turbine.
  • LNG Tank-Its Structure, the Materials and Welding Techniques

    pp. 135-144

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  • Controlling Sulfide Shape with Rare Earths or Calcium during the Processing of Molten Steel

    pp. 145-154

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  • Preparation and Quality Test of Minor Element Series B of Japanese Standards of Iron and Steel

    pp. 155-164

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  • A Future Trend of Research and Development in Steel Industry of Japan

    pp. 165-170

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  • Some Impressions in USA and Canada

    pp. 171-174

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  • 抄録

    pp. 175-179

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