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

Tetsu-to-Hagané Vol. 60 (1974), No. 1

  • 1973 Perspective of Production and Technique of Iron and Steel in Japan

    pp. 3-19

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  • Reduction of Fine Particle of Iron Oxides by H2-H2O Mixture

    pp. 20-28

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    Small α-hematite particles with mean diameter of 8.1μ were reduced at 900°C in a gas stream of hydrogen and water-vapour. The investigation was forcused on the effect of water-vapour on the reduction of wüs-wustite. The appearance of product iron, its growth, and the change of pore shapes were examined with both scanning electron and optical microscopes. The reduction rate was obtained by measuring the weight change of the solid sample due to the reduction.
    When the partial pressure of water-vapour was less than 0.32 atm, the reduction rate was first order to the hydrogen partial pressure. Under those conditions, many spots of metallic iron could be observed on the surface of wastite particle. Then, they covered the whole surface in the early stage of reduction. After that, the reduction proceeded shell-likely.
    However, when the partial pressure of water-vapour was more than 0.32atm, the reduction was retarded significantly by the water-vapour, especially at low fractional reduction, although the reductiontemperature was as high as 900°C. This gave remarkably sigmoid reducing curves. Under those conditions, a part of the outer surface of wastite particle was not covered with metallic iron, even when the reduction already proceeded into the inner part of wastite particle. It could be concluded that this kind of partial growth of product iron was one of the important factors to make the reducing curves sigmoid.
  • Surface Tension of Liquid Fe-C-Si Alloys

    pp. 29-37

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    The surface tension of liquid iron, iron-carbon, iron-silicon and iron-carbon-silicon alloys was measured by sessile drop method. The surface tension and the density of pure liquid iron at 1550°C were 1735dyne/cm and 7.05g/cm3, respectively. The surface tension of iron-carbon alloy's decreased linearly with tem temperature and the carbon content, and the temperature coefficient decreased with increase of carbon content. The surface tension and the density of iron-silicon alloys decreased with increase of silicon content, but abnormal phenomena were found at 50 at % Si, that is, the temperature coefficients of surface tension and density were positive. The surface tension of iron containing carbon reached a maximum value when some amounts of silicon was added, although individual addition of carbon or silicon decreased the surface tansion of iron.
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    Readers Who Read This Article Also Read

    1. Viscosity of Liquid Fe-C-Si-Alloy Tetsu-to-Hagané Vol.60(1974), No.1
    2. Structural Change of Liquid Iron Observed on Viscosity Measurement Tetsu-to-Hagané Vol.56(1970), No.13
  • Viscosity of Liquid Fe-C-Si-Alloy

    pp. 38-44

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    Viscosity of liquid Fe-C-Si alloys was determined by measuring the logarithmic decrement of oscillation of the crucible containing liquid alloy in the temperature range between 1300 and 1650°C Empirical equation obtained by water, mercury and liquid tin was applied to the calculation of viscosity of liquid alloys.
    In binary alloys, viscosity of liquid iron decreased almost linearly with carbon content and decreased slightly with silicon content. Any abnormal or abrupt change of viscosity was not observed. Activation energy of viscous flow, also, decreased with increase of carbon or silicon. But, in the case of ternary alloys, viscosity of Fe-C alloys increased with silicon content, especially in higher carbpn alloys and activation energy showed a tendency to increase. Some considerations were given to the experimental results, though it was difficult to explain the cause of the increase of viscosity in ternary alloys.
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    Readers Who Read This Article Also Read

    1. Structural Change of Liquid Iron Observed on Viscosity Measurement Tetsu-to-Hagané Vol.56(1970), No.13
    2. Surface Tension of Liquid Fe-C-Si Alloys Tetsu-to-Hagané Vol.60(1974), No.1
  • Deoxidation with Calcium-silicide in Liquid Iron

    pp. 45-57

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    Complex deoxidation with calcium-silicide was made in pure iron melted with a high frequency furnace. Kinetics of the deoxidation process was analyzed to evaluate the growth rate and the separation rate of the primary inclusion. The compositions of the deoxidation products were determined by X-ray microanalyzer.
    The experimental results are as follows:
    1) Calcium-silicide reacts effectively as the deoxidizer when the atmospheric pressure on the melt is kept higher than the vapour pressure of calcium.
    2) In the initial stage of deoxidation with calcium-silicide, the content of oxygen in liquid iron is remarkably decreased by the formation and the floating up of such primary inclusions as Feo-SiO2 and CaO-SiO2.
    3) There after a number of fine silica particles remain in liquid iron without separation. Consequently the rate of deoxidation becomes smaller with the lapse of time.
    4) The deoxidation behaviour caused by calcium silicide is clarified in relation to the change in the content of oxygen in liquid iron and the change in the size of inclusion.
    5) Oxide inclusions formed in liquid iron are classified into the following four types, e. g. FeO-SiO2, CaOSiO2 containing a large amount of FeO, CaO-SiO2 including a small amount of FeO and fine SiO2.
  • The Ms-Temperature and the Martensite Structure of Fe-C Alloys Containing Mn, Si or Cr under High Pressure

    pp. 58-70

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    The effect of Mn, Si or Cr on the Ms-temperature and the martensite structure of Fe-0.3%C alloywere examined under hydrostatic pressure up to 41kbar using a “girdle” type high pressure apparatus.
    The results obtained are as follows;
    (1) The Ms-temperature was lowered approximately 40°C/10kbar in all alloys and its tendency wasnot significantly affected by alloying elements.
    (2) The measured Ms-temperatures at 1 atm (≈0.001 kbar), 29 and 38.5kbar are in reasonable agreementwith those calculated by the Predmore's equation concerning the free energy change for γ-α transformation.
    (3) The plate-like structure was observed as a result of the martensite transformation above 38.5kbar.The reason for the appearance of this structure can be explained qualitatively by P-T diagram of iron.
    (4) The hardness of martensitic structures increases with an increase of pressure. This tendency can beinterpreted by the fact that the Ms-temperature is lowered by pressure, accompanying with the change of martensite structure.
  • Effects of Niobium on Microstructures and Hardness of 15Cr-14Ni Heat Resisting Steels

    pp. 71-84

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    The effects of niobium on the microstructures and hardness of 0.15C-15Cr-14Ni heat resisting steels, after solution treatment and isothermal aging, have been studied by means of optical and electron microscopy, electrolytic isolation technique, X-ray diffraction method, and Vickers hardness testing. Theresults are as follows:
    The carbon solubility for the Nb free steel, and the solubility products of niobium carbide for the 1.03%Nb steel and the 2.02%Nb steel are determined by the electrolytic isolation method. The undissolvedcarbides, mainly NbC and M23C6, tend to become coarse with the increase of solution temperature or withthe increase of the niobium content. The distribution density of undissolved particle has a maximum at1.0%Nb, and decreases with the increase of the solution temperature. The distribution density of undissolvedcarbide affects the hardness and the austenite grain size of the steels solution treated. On agingthe steels with niobium less than 1.03% in the range 600°C to 750°C, massive, cubic and libbon-like M23C6, and thread-like NbC precipitate. In the 2.02%Nb steel, only thread-like NbC precipitates. From theresults of the microstructure observation and hardness testing, we find that there is a direct relationshipbetween the distribution density of cubic M23C6 and the increase in hardness. The measurements of thechange in the diameter of cubic M23C6 and the change in the width of thread-like NbC during isothernalaging show that the coarsening process of cubic M23C6 is controlled by the diffusion of chromium in matrix, and the coarsening process of thread-like NbC is controlled by the diffusion of niobium.
  • Relationship Between Austenitizing Time and Mechanical Properties of the Alloy Tool Steel SKD11

    pp. 85-95

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    In the earlier paper, the relationship between the austenitizing time and the mechanical properties ofhigh-speed tool steels was reported. In this paper, a similar relationship for the alloy tool steel SKD11 whichis austenitized at 960°C-1080°C for 10-3000sec and tempered at 150°C-550°C has been studied by thesame methods as in the previous paper. The results obtained are as follows;
    1. The preferable mechanical properties of the steel SKD11 for cold working are generally obtainedin the hardness range of Rockwell C58 to 60 (Hv 650 to 700) and in the bend strength of over 350kg. Theseproperties can be obtained by the next heat-treatments. A: Austenitized for a long time at lower temperaturenear 1000°C and tempered between 150°C and 200°C. B: Austenitized for a short time at highertemperature between 1040°C and 1080°C and tempered between the same temperatures as A. C: Austenitizedfor a long time at 1040°C to 1080°C and tempered above 500°C.
    2. Degrees of austenitizing in the microstructure seems to become larger in the order of B→A→C. Specimensby the treatment A are almost completely austenitized and those by B include some residual ferritein austenite. Those by the treatment C are completely austenitized and have partial grain growth.
    3. A specimen by A which has been austenitized for 3000sec at 960°C and tempered at 150°C has themost preferable mechanical properties for cold work tools. This has been confirmed by industrial tests.
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    Readers Who Read This Article Also Read

    1. Amount of Aluminium Addition Required in Continuous Galvanizing Baths Tetsu-to-Hagané Vol.60(1974), No.1
    2. Report of the Photoelectric Emission Spectrochemical Analysis Subcommittee Tetsu-to-Hagané Vol.60(1974), No.13
    3. 焼戻脆性・高張力鋼 Tetsu-to-Hagané Vol.60(1974), No.4
  • Reaction of Dross Formation in Continuous Galvanizing

    pp. 96-103

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    A study has been carried out on the dross formation in continuous galvanizing in relation to the aluminiumcontent in the bath.
    Iron and aluminium concentrations in drosses formed in conventional galvanizing lines are determined.In the laboratory, Zn alloys containing 0.22% Pb, 0.13-4.60% Al and 0.066-0.24% Fe are molten ingraphite crucibles and held at 465°C for 40hrs before cooling. Using the sectioned ingots, spectroscopic analysisof the portions free from dross and quantitative microscopy analysis of dross compounds are performed:
    On the basis of these results, the amount of dross and that of aluminium consumed in the dross formationreaction in conventional processes are estimated. Conclusions derived are as follows:
    Drosses contain two compounds, namely δ and Fe2Al5.
    When the aluminium content in the bath is in the range of 0.09-0.14%, δ and Fe2Al5 can coexist. Inthis case the higher the aluminium content, the lower the fraction of δ-compound. When the aluminiumcontent is higher than 0.15% the δ-compound can not be found.
    The amount of the bottom dross is estimated to decrease rapidly with increasing the aluminium contentin the bath up to 0.14% and becomes negligible above 0.15% Al. The amount of the top dross, however, increasesrapidly with increasing the aluminium content up to 0.14% and decreases gradually above 0.15% Al.
    The amount of aluminium consumed in the dross formation reaction is estimated proportional to the amount of iron dissolved from sheets.
  • Amount of Aluminium Addition Required in Continuous Galvanizing Baths

    pp. 104-107

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    As the aluminium in galvanizing bath is consumed through the reaction of dross and the alloy-layer formation, it is usually difficult to keep the aluminium content in the bath at a predetermined value. On the basis of our recent results, the aluminium content in tailored zinc required to keep the aluminium content in the bath at a desired level has been calculated.
    The aluminium content in tailored zinc (yT) can be expreessd as the sum of the aluminium concentration in liquid zinc (y) and the amount of aluminium consumed, in concentration, through dross and alloy- layer formations:
    yT=y+(aΔW1+bΔW2)·200/w
    where w is coating weight of sheet, and ΔW1 and ΔW2 are iron dissolved and iron in alloy layer, respectively.
    Under conditions of sheet temperature of 470°C, line speed of 100m/min and coating weight of 305g/m2-sheet, the aluminium content in tailored zinc is estimated to be 0.31% to maintain the bath at 0.14% Al. When the coating weight is in the range of 305±60g/m2, to increase the aluminium content in the bath by 0.01% the aluminium content in tailored zinc should be increased by 0.05-0.08% under the operational condition of 0.10-014% Al in the bath.
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    Readers Who Read This Article Also Read

    1. Report of the Photoelectric Emission Spectrochemical Analysis Subcommittee Tetsu-to-Hagané Vol.60(1974), No.13
    2. Relationship Between Austenitizing Time and Mechanical Properties of the Alloy Tool Steel SKD11 Tetsu-to-Hagané Vol.60(1974), No.1
    3. 焼戻脆性・高張力鋼 Tetsu-to-Hagané Vol.60(1974), No.4
  • Determination of Nitride and Dissolved Nitrogen in Steel by Hydrogen Hot Extraction

    pp. 108-120

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    A coulometric nitrogen analyser for the fractional determination of metallurgically dissolved nitrogen and various nitride precipitates in steel by hydrogen hot extraction has been developed. Nitrogen as NH3 in a hydrogen stream is successfully determined continuously by every 0.5μg and printed integrally by the analyser. Blank values of the determination are less than 0.5μg N.
    Aluminium-killed steel with dissolved nitrogen and precipitated nitrogen is heated in a hydrogen stream through a wide range of temperatures from 50°C to 1000°C, with the combined application of the newly developed nitrogen analyser and isochronous heating, in place of both photometric analysis which yields the only one determination of total extracted nitrogen and isothermal heating that has been adopted by many investigators, and the extracted nitrogen as NH3 provides separate and quantitative determinations of dissolved and precipitated nitrogen.
    Dissolved nitrogen is extracted at about 265°C, which corresponds to the reduction temperature of oxide film on specimens by hydrogen stream. Precipitated nitrogen as AlN is extracted mainly at about 800°C, and partially at the temperature between 425 to 950°C depending on the particle size and stability of the precipitates. Variations of extraction temperatures, therefore, also provide separative determinations of unstable fine precipitates and stable coarse nitride particles. Above mentioned experimental results are confirmed electron-micrographically and supported by the considerations of the reaction mechanism and the free energies of oxide film and nitride in the steel.
  • Recent Advances in the Mechanism of Stress Corrosion Cracking

    pp. 121-133

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  • Report of the 4th Japan-USSR Joint Symposium on Physical Chemistry of Metallurgical Processes 1973

    pp. 134-153

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  • 抄録

    pp. 154-158

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