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

Tetsu-to-Hagané Vol. 59 (1973), No. 6

  • 材料産業と環境問題

    pp. 691-692

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  • Agglomeration of Hematite from Aqueous Suspensions

    pp. 693-701

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    The agglomeration of hematite from aqueous suspensions by use of coal tar as a bridging liquid has been studied. It is necessary to treat the hematite with a Na-oleate aqueous solution prior to the agglomeration in order to make the surface of the hematite hydrophobic. The application of this method to the formation of hematite pellets containing coal has also been investigated together with the test of the reducibility of these pellets.
    Main results obtained are summarized as follows.
    1) Finely-divided hematite, which was pretreated with a Na-oleate solution, in aqueous suspensions can be agglomerated by applying suitable agitation in the presence of a small amount of coal tar.
    2) When the surface of hematite particles is covered by the complete mono molecular film of oleateions, the agglomeration efficiency becomes maximum.
    3) With an increase of the amount of coal tar added, the agglomeration efficiency and the pellet size increase but the strength of green pellets becomes weaker; the use of an excessive amount of coal tar results in no agglomerates formation. Thus, the amount of coal tar should be optimized.
    4) The agglomeration efficiency, determined by the amount of coal tar added to the hematite in aqueous suspensions, is not influenced by the pulp density of suspensions.
    5) The dry strength of the pellets rises up to 70kg/cm2.
    6) The agglomeration efficiency is improved and size of pellets becomes large (more spherical) by using coal together with coal tar.
    7) When the hematite pellets containing 20% coal agglomerates are reduced with 10% coke, the degree of metallization of the pellets is about 90%
  • Characteristics of Single-Blowing Operation in Hot-Blast Stoves

    pp. 702-714

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    The effects of five nondimensional factors of a hot-blast stove presented in the previous paper on the thermal efficiency and longitudinal distribution of brick temperature have been evaluated. On the basis of the approximate analysis shown in the previous paper, the conditions necessary to realize a balancedcycle operation have been given, and the existence region of a balanced cycle has been illustrated in this paper.
    To clarify the characteristics of balanced-cycle operations in a single blowing, the effects of the operating conditions on the blast temperature have been estimated numerically. Furthermore, by the use of the approximate method mentioned above, design procedures for the flow rate of hot gas and the surface area of checker brick have been shown under the conditions of balanced-cycle operation.
  • Diffusion of Oxygen in Various Binary and Ternary Liquid Oxide Systems

    pp. 715-724

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    The oxygen diffusion coefficients in various liquid oxide melts have been measured from the EMF meas-urement on oxygen concentration cells with solid or liquid electrolytes. This method can determine the diffusion coefficient without the solubility data of oxygen in liquid.
    The liquid solutions, without transition metal oxides, having compositions of Na2-GeO2, PbO-SiO2, PbO-GeO2, and CaO-SiO2-Al2O3, were studied at 1000 to 1450°C. The liquid solutions, with transition metal oxide, having compositions of FeO -PbO-SiO2 and V2O5-PbO were studied at 800 to 1300°C.
    It was discussed that the diffusion rate of oxygen in a liquid oxide system without a transition metal was determined by the diffusion rate of diatomic oxygen dissolved in the liquid oxides, and that the diffusion mechanism of oxygen in a liquid oxide system with a transition metal oxide could be explained by the quasi -lattice defects model.
  • The Behavior of Al2O3 Inclusions under the Mushy State

    pp. 725-737

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    In order to clarify the behavior of Al2O3 inclusions during the solidification process, an Fe-1%P alloy which contained fine Al2O3 inclusions was held in the temperature range where the liquid and the solid coexisted. The results obtained are as follows:
    1) Al2O3 inclusions were found to grow even under the mushy state of the alloy.
    2) Most of the Al2O3 inclusions existed in the liquid region of the alloy.
    3) Al2O3 inclusions in the liquid could move pretty freely and made clusters by uniting each other.
  • Relations between Wear Resistance and Heat Treatment or Structure of High Speed Steels

    pp. 738-751

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    Relations between the wear resistance and heat treatment conditions or structures of tool steels have not been made clear. In the present paper, studies were made to clarify the wear caused by slidingifriction, using speed steels heat-treated at various temperatures.
    The results can be summarized as follows:
    1) The wear rate at low sliding speeds depended on the hardness of the steels, decreasing with increasing the hardness. At a higher sliding speed it depended on the carbide content in the steel, decreasing with increasing carbide content.
    2) A maximum wear rate was obtained for the steels tempered at 300-400°C.
    3) At low sliding speeds, the retained austenite increased the wear rate, but did not affect the rate at a higher speed.
    4) When the steel is used at a high sliding speed, it should be quenched at lower temperatures and tempered at higher temperatures, even though a lower hardness may be obtained.
  • Effect of Heat Treatment in the Ferrite-Austenite Region on Notch Toughness of 6% Nickel Steel

    pp. 752-763

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    In order to improve the low temperature toughness of a newly developed 6% Ni steel, a new process of the heat treatment has been studied. By this new heat treatment, the steel is partially austenitized at the temperature range of the ferrite-austenite region and is quenched. When this special heat treatment is added between the conventional process of quenching and tempering, the low temperature toughness of nickel bearing steels is remarkably improved.
    The reasons why this special heat treatment remarkably improves the low temperature toughness are as follows. Firstly, a large amount of finely dispersed austenite islands, which are stable at a low temperature as -196°C, are formed by adding this heat treatment before tempering. These stable austenite islands act as a shock absorber and provides a resisting force against the propagation of brittle fracture. Secondly, temper brittleness is depressed since the embrittled prior austenite boundaries are covered by tempered martensite which is formed by this new process. Thirdly, the ductilicy of ferrite matrix is improved through the scavenging effect due to the formation of austenite during this heat treatment.
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  • Effects of Aluminium, Nitrogen, Carbon, Silicon, and Manganese on Austenite Grain Size of Steels

    pp. 764-790

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    The present investigation was carried out to know the effect of alloying elements on austenite grain size of high purity iron alloys. The single or combined effects of alloying elements i.e. aluminium, nitrogen, carbon, silicon, and (or) manganese were examined. The results obtained are summarized as follows.
    1) A ustenite grain size of pure iron-nitrogen alloys was somewhat refined as the content of acid soluble nitrogen was increased up to about 0.02% while that of pure iron-aluminium alloys was not infl uenced with an increase of acid soluble aluminium of less than 0.5%.
    2) The austenite grain size of pure iron alloys was not affected by the increase in AlN and the coarse grains of nearly the same size were observed.
    3) Carbon had a strong effect on the austenite grain refinement in the range of concentration of less than about 0.05%, while in the range from 0.1 to 0.5% the fine grained austenite was not affected by a furtheri ncrease in carbon content, and there was a trend for the grains to be coarsened when the content of carbon was increased beyond 0.5%.
    4) Carbon did not show any function to prevent or disturb the austenite grain coarseni ng.
    5) The grain size of the fine grained austenite in iron-carbon alloys was not influenced by the presence of nitrogen, aluminium or by the precipitated AlN. It was controlled mainly by the carbon content itself.
    6) The austenite grain was refined by the addition of silicon in the range less than 0.2%, while it was coarsened by the presence of silicon more than 0.2% in the range less than 2.1%.
    7) The austenite grain was slightly refined by the addition of manganese in the range less than 13.7%.
    8) The austenite grain was finest and the grain size number was 8 to 10 in the alloys containing more than two of carbon, AlN, silicon, and manganese. Carbon played a main role for the grain refinement also in these alloys.
    9) The presence of AlN was effective to raise the coarsening temperature, though it was not effective to to the austenite grain refinement.
  • Effect of the Cross-sectional Area on the Tensile Properties of Iron Whiskers

    pp. 791-799

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    The tensile test and the creep test of the iron whiskers having [100] and [111] growth directions which were produced by the reduction of iron chloride were carried out.
    The cross-sectional area dependence of the feature of the stress-strain curves and the creep curves of iron whiskers was observed. Work hardening did not appear on the stress-strain curves of [111] iron whiskers, which were similar to the curves calculated from the Johnston-Gilman theory on LiF single crystal.
    The equation for the relation between stress and strain of the iron whisker was derived from the Johnston-Gilman theory. The equation was solved under the condition of various initial mobile dislocation densities and dislocation multiplication rates. The result showed that the calculated stress-strain curves coresponded with the experimental stress-strain curves of [111] iron whiskers under the assumption that the initial mobile dislocation density and dislocation multiplication rate were reduced with a reduction of the cross-sectional area of iron whisker.
  • Corrections for the Background in Atomic Absorption Analysis for Iron and Steel

    pp. 800-807

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    For the determination of trace elements in iron, steel and iron are by atomic absorption analysis, the state of and the correction for influences by “the brackground” are studied.
    Following three methods for the correction for backgrounds are suggested.
    1) Correction with blank-test of pure iron treated in the same way as provided samples.
    2) Correction with the transmittance of several elements other than the objective ones in provided solutions by the use of the emissive line near the analytical line.
    3) Correction with the transmittance of several elements at the analytical line in the continuous spectrum by H2 hollow cathode lamp.
    The first can be applied with satisfaction to the correction for the background of Fe, but not for other coexisting elements. The second can be applied to any coexisting elements, but not at the analytical lines influenced with the spectrum interference. The third cannot be applied to the samples contining much Fe, because of the spectrum interference by the analytical line of Fe on the measurement at continuous spectrum.
  • Frictional Properties of Plastics Bearing Materials on Special Cast Steels

    pp. 808-815

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    The friction tests of variously heat-treated special cast steels against several kinds of plastics bearing materials were carried out, by the use of a friction testing machine in the absence of lubricant.
    1) In regard to all the plastics bearing materials employed, with the fine structure of cast steel shaft material the sliding friction showed a lower coefficient of friction, and the coefficient of friction increased with a decrease in the hardness of cast steel shaft material.
    2) With P. T. F. E. on all the tested cast steels, the sliding friction showed the lowest value, and the variations of frictional force with time were very small.
    3) With nylon and phenolic plastics on cast steels, the coefficient of friction increased with decreasing load and sliding speed in the stable condition. The probable reason for this may be due to thermal properties of plastics and ‘stick-slip’ process.
  • Removal of Alumina Clusters from Molten Steel by Tellurium Addition

    pp. 816-821

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    Effects of tellurium addition on the removal of alumina clusters from molten steel were investigated. The results obtained are summerized as follows:
    (1) Experiments were performed on 0.5kg melt, and it was observed that telluerium had a remarkable effect of ejecting alumina clusters from molten steel.
    (2) A small amount of tellurium (about 0.002%) was sufficient to obtain this effect.
    (3) The ejection of alumina clusters by tellurium was considerably rapid.
    (4) Sulfur and selenium also showed similar effects; nevertheless tellurium showed the most remarkable effect among them.
    This phenomenon was also observed in the case of 50kg and 500kg ingots
  • Precipitation Hardening in Maraging Steels

    pp. 822-841

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  • 第84回講演大会討論会報告

    pp. 842-850

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  • 抄録

    pp. 851-857

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