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

Tetsu-to-Hagané Vol. 55 (1969), No. 6

  • Relation between the Size Distribution of Crushed Product and the Rate of Loading for Iron Ore Crushing

    pp. 429-436

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    The relation between the size distribution of crushed product and the rate of loading for iron are crushing was studied.
    From the crushing tests in which the compression length and the compressing time for each compression length were kept constant, it was confirmed that the amounts of fine particles of the crushed product increased remarkably with the increase of the rate of loading.
    The breaking strength and the apparent YOUNG'S modulus of the glass and the iron ores were measured. The breaking strength and the apparent YOUNG'S modulus of the glass and the iron ores markedly increased as the rate of loading increased. The relationship between the rate of loading and the breaking strength was proposed by the PLANDTL'S equation.
    It was considered that the changes in the dynamical behaviors of the ores with the variation of the rate of loading closely relate to the production of fine particles of the crushed product.
    Thus, the rate of loading is one of the most important factors which have a great influence on the size distribution of the crushed product of iron ores.
  • On the Rates of Decarburization and Oxidation of Molten Iron Alloys with CO2-Ar Atmosphere

    pp. 437-445

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    The rates of decarburization of molten iron, containing Si, Cr and Mn, with CO2-Ar mixtures at 1600°C were measured, and the oxidations of the above-mentioned elements were also investigated. It was observed that the carbon concentration decreases linearly with time down to the critical value, Cf, where the oxide film appears on the surface of melt, and that the value of Cf increases with the amount of added elements and the partial pressure of CO2. The critical value Cf depends on the deoxidizing force of added elements. Carbon concentration on the reaction interface, Ci, corresponding to Cf, calculated from the equilibria, Me+O=(MeO) and C+O =CO, was used to estimate the thickness of diffusion layer in metal surface. Before the oxide film appears on the surface of melt, the rates of decarburization was proportional to the partial pressure of CO2 and independent of the amount and the kinds of added elements.
  • Mass Spectrometric Study of Desulfurization of Iron Alloys by Vacuum Melting

    pp. 445-453

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    To determine the sulfide species evaporated from iron alloys during vacuum melting, mass spectrometry was used. A small furnace was wound with tungsten wire and was coated with alumina. Specimens of materials to be investigated were placed in the furnace located close to the ion source of the mass spectrometer. The alloys investigated were Fe-C-S alloy (2.70%C, 1.32%S), Fe-Si-S alloy (3.40%Si, 0.5%S), Fe-C-Si-S alloy (3.42%C, 2.73%Si, 0.51%S), Fe-Al-S alloy (2.42%Al, 0.49%S) and Fe-S alloy 0.20%S). Temperature was measured by means of an optical pyrometer, and the range was 1000- 1400°C.
    In the Mass spetr* of Fe-C-S alloy the ions S+, S+2, CS+ and CS+2 were found and the proportion of S+ ion was, greatest. SiS+, S+ and S+2 ions were found in the mass spectra of Fe-Si-S alloy. In the mass spectra of Fe-C-Si-S alloy, SiS+, CS+, CS+2, S+2, S+ ions were found and of these ions the proportion of SiS+ is large compared with the others, and, in addition to the ions mentioned above, SiS+2 was also found at the high temperatures (above 1300°C). The ions S+ and S+2 were found in the mass spectra of Fe-Al-S and Fe-S alloys.
  • Influence of Crucible Materials on the Attained Oxygen Content after Deoxidation of Aluminium or Silicon in Stirred Liquid Iron

    pp. 454-459

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    The oxygen content after deoxidation by the addition of 0.5% Al or 0.5% Si in molten iron was studied using various oxide crucibles.
    The results obtained are as follows:
    1) Deoxidation proceeded not only by the flotation of oxide inclusions (deoxidation products) but also by the reaction of oxide inclusions with crucible material at the metal-crucible interface.
    2) The oxygen content decreased with increase of the difference of iron-oxygen attraction force (I=Z/a2) between oxide crucible and deoxidation product.
    3) X. M. A. line analysis of crucible wallmatter, Al-deoxidation indicated that deoxidation product alumina penetrated remarkably into the crucible wall in the case of CaO crucible, whereas it enriched only at the crucible surface in the case of SiO2 crucible.
  • Kinetic Study for Deoxidation of Molten Iron with Aluminum in the Combined Alumina-Silica Crucibles

    pp. 460-470

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    The deoxidation of molten iron with aluminum was investigated by using an alumina crucible, the inner wall of which was partially covered with silica.
    The deoxidation rate is analized on the basis of the kinetic theory with the following assumptions;(a) The deoxidation products (Al2O3) are nucleated homogeneously in the bulk of molten iron. Their agglomeration and growth are completed within about one minute after the aluminum addition.(b) Molten iron in the crucible follows the well?known flow pattern in the high frequency induction furnace.(c) The rising-out of the deoxidation products obeyed by the Stokes law takes place only in a thin layer close to the free surface of molten iron.(d) The deoxidation products are also separated through adsorption by the silica wall. This process is considered to take place through the bulk flow and the Brownian motion in a thin layer close to the side surface of molten iron.
    These assumptions lead to the rate equation given as [%O]=[%O]°exp-kt/(1+βt/§) 2, which is quantitatively in good agreement with the experiments.
    Here, t is the time after the completion of the agglomeration and growth, [%O] and [%O] the oxygen concentration at t=0 and t=t respectively, § the constant determined by the size distributions of the deoxidation products at t=0, β the constant associated with the Stokes law, and k represents the constant concerning to the adsorption process.
  • The Electrochemical Measurement of the Standard Free Energy of Formation of Niobium Oxides

    pp. 470-474

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    A modified cell arrangement has been used particularly for the purpose of measuring the standard free energy of formation of low oxygen potential oxides of niobium.
  • Formation of Equiaxed Zone in Ingots and Negative Segregation in Steel Ingots

    pp. 475-484

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    99.99% Al, 9911% Al containing 0.13% Fe and 0.07% Si, and Al-Cu alloys containing 0.1-4% Cu were solidified in static or dynamic moulds. Mechanical barriers were placed in the mould in some experiments. The equiaxed zone in castings was shown to derive from crystallites formed in the upper part of the advancing interface of solid shell during the initial stages of solidification. It was also shown that the crystallites sediment along the advancing interface of solid shell and are piled up on the bottom. The formation of these crystallites is probably due to partial remelting of dendrite casesed by the marked temperature fluctuations in the melt. The formation mechanism of negative segregation in steel ingots was explained based on the experimental results.
  • The Effect of Niobium and Tantalum on Grain Size of Steel

    pp. 485-496

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    The effects of niobium and tantalum on austenitic grain size and ferritic grain size of pure iron, Fe-C (C=0.1%) and Fe-N (N=0.02%) alloys have been studied and compared with each other. The austenitic grain size were revealed by thermal etching method. The effects of small addition of each element on the grain coarsening temperature of these alloys were also studied. The main results obtained are as follows;
    (1) Small addition of niobium or tantalum to Fe-C alloys is effective for austenitic grain size refining and this may be due to the precipitation of δ-niobium-carbide or δ-tantalum-carbide. Tantalum is required two times as much amounts (in wt%) as niobium is, to obtain the same fine grain size number such as No 7·5.
    (2) The addition of niobium or tantalum to pure iron and Fe-N alloys is also effective for austenitic grain size but the finer grain size than No 6 cannot be obtained in these cases.
    (3) An approximately linear relationship is observed between ferritic and austentic grain size in the series of niobium-added steels as well as of tantalum added steels.
    (4) Small addition of niobium or tantalum to Fe-C alloys is effective in retarding the austenitic grain coarsening.
    x

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  • The Calculation of the Amounts of the Carbide and Nitride Precipitates in the Steel at Temperature of the γ State

    pp. 497-503

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    A method of calculation was studied to determine the amounts of nitides and carbides in the steel to which various carbide or nitride forming elements were simultaneously added. According to the results obtained, the behaviours of these precipitates determined by the calculation were in accordance with thoseexperimentally determined in the specimen held at the temperature of austenite range, such as heating temperature of the slab, normalizing, or quenching temperatures.
    As an example, the behaviours of carbides and nitrides in y state of the steel containing niobium and aluminium are determined as follows by calculation.
    (1) In the range of carbon content of more than 0.10% and of nitrogen content of 0.006%, which corresponds to the chemical composition of commercial steel, niobium tends to form carbide3 than nitrides.
    (2) Only the precipitates of NbC and AIN are formed when carbon contant is more than 0.10% and nitrogen content lies between 0.006 and 0.01%.
  • Metallographic Analysis of Niobium in High Strength Steel

    pp. 503-511

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    A new, simple and reliable method has been develoed for metalloyaphic analysis of Nb in high strength steel.
    The procedure is as follows:
    1. Separation of Nb
    a) Dissolve 1 g of sample in 40ml of HC1 (1:1) at room temperature. Filter and wash with water.
    b) Dilute the filterate to 250ml with water, add 10ml of phytin solutiol (1%), and boil for 10min, and allow to, stand for 5min. Filter and wash 2 or 3 times with hot water.
    c) Return the paper and precipitate to the beaker, add 20ml of HNO3, 3ml of HCIO4, and 2ml of H2SO4 (1:1), and evaporate to a sirup, and determine Nb as solid solution as described in Section 2 a) to c). d) Transfer the paper and residue (Paragraph a) to the beaker, add 20ml of HNO3 (1:1) and 5ml of H202, and boil for 5min. Filter and wash 2 or 3 times with hot wlter.
    e) Add 2ml of H2SO4 (1:1) to the filterate and evaporate to a sirup, and determine Nb as carbonitride as described in Section 2a) to c).
    f) Transfer the paper and residue (Paragraph d) to the beaker, add 20ml of HNOB, S ml of HCI04, and 2ml of H2SO4 (1:1), and evaporate to a sirup, and determine Nb as oxide as described in Section 2 a) to c).
    2. Photometric determination of Nb
    a) Dissolve each of the salt of section 1 c), e) and f) in 20ml of tartaric acid solution (20%) and 10ml of HOI (1:1) and dilute to 100ml in a volumetric flask.
    b) Transfer 5ml portion of solution to 50 ml volumetric flask, add 15ml of water, and 2ml of thioglycollic acid solution (10%), mix, allow to stand for 2 min, and then, add 10ml of HCI (1: 1), 5ml of EDTA solution (1%), 5ml of aceton and 2ml of sulfochloro phenol S solution (0.05%).
    c) Warm to 60 to 70°C for 5 min, cool, dilute to the mark, and mix. Measure the absorbance against water at 650mμ.
  • Infrared Camera and Its Application to Steel Industry

    pp. 512-517

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    Recently the infrared camera has been used in various kinds of field, and useful applications to the steel industry are expected. Many interesting thermograms of blast furnace, hot stove etc. have been obtained by using the infrared camera (Barnes Co., Thermography T-4). The important points in practical use including the dust protection for the camera are described
  • 討論会集録

    pp. 518-536

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