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

Tetsu-to-Hagané Vol. 50 (1964), No. 6

  • わが半生の記

    俵 隆治

    pp. 871-872

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  • On the Rate of Decarburization of Molten Iron with 1-120-Ar Atmosphere

    Koin ITO, Kokichi SANO

    pp. 873-877

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    Abstract

    In the early paper of this series, the authors gave the rate equation for the dissolution of oxygen from I-I20-Ar atmosphere into molten iron, assuming that a gaseous diffusion layer exists above the gas-molten iron interface as well as metal phase-diffusion layer generally supposed. Here, as an example of gas-molten iron reactions, the authors measured the decarburization of molten Fe-C alloy with H20-Ar atmosphere and tried to apply the previous result under a similar assumption to this reaction.Modifying the rate equation in previous paper for the present reaction, we obtain
    -d%C/dt=1200DmFPH2O/VρδG……(7)
    which holds until an oxide film appears on the surface of molten iron.
    In the same range, experimental data showed that the rate of decarburization is independent of the carbon concentration in liquid iron and that Eq.7 is in good agreement with the results.Activation energy of this reaction was found to be 5.5+3 kcal/ mole.On the other hand, the activation energy of diffusion coefficient, Dm, is 1.8 kcal/mole and that of 1/σG is supposed to be about 1 kcal/mole on the basis of the kinetic theory of gas molecules and hydrodynamics.Accordingly, the activation energy of this reaction calculated from Eq. 7 is expected to become only several kcal/mole, and this value agreed approximately with experimental results.Several investigators have found some larger values for the activation energy of decarburization reaction with atmospheres.However, if any suitable corrections for the rate of decarburization with crucibles were done, the values would become smaller ones of the same order as the present result.

  • On Hydrogen Equilibria in the System Water Vapour-Molten Slag-Molten Iron

    Mitsuo IMAI, Hiroshi OOI, Toshihiko EMI

    pp. 878-887

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    Abstract

    In order to improve understanding of the behaviour of hydrogen in the system atmosphere-molten slag-molten steel in a steelmaking furnace, we already reported dissolution of water vapour in molten slags in the previous paper.
    In this experiment, as a next step, the form of hydrogen in slag has been determined by infra-red spectra measurements which have been carried out on the ternary and quaternary CaO-Si02-(mono, di, tri-valent metal oxide) systems.
    Then, simultaneous equilibria of hydrogen in the system water vapour-molten slag-molten iron have been investigated by equilibrating CaO-Si02 binary slag and pure iron with water vapour.
    The results obtained are as follows.
    1) Water vapour dissolves into molten slag as a free, hydrogen bonded and a strongly hydrogen bonded hydroxyl, and more than one half of total amount of hydroxyl exists in free form.The existence ratio of each form of hydroxyl to total amount of hydroxyl varies characteristically with different basicities.In the systems CaO-SiO2-MO, the existence ratio of free form becomes greater and those of two other forms become smaller with increasing ion-oxygen attraction force of Mu+.2) Dissolution formula and equilibrium constants of hydrogen equilibria in the system water vapour-molten slag-molten iron are determined as
    H2O (g)(O) =2 (OH) K1= (OH) 2/PH2O·(O) logK1=-2, 160/T+8.144
    (OH) =H+ (O) K2=H.(O)/(OH) logK2=-4, 800/T-0.835
    The hydrogen solubility of slag and iron under PH20 682 mmHg is found to be H 5'5ppm (H) 30'3ppm at 1550°C, H 6.3ppm (H) 33.5ppm at 1600°C
    respectively, and these are proportional to the square root of the partial pressure of water vapour.'I hus, CaO-Si02 slag which intervenes between water vapour and molten iron considerably decreases the solubility of hydrogen in iron.

  • Consideration on the Equilibrium between Silicon and Oxygen in the Liquid 18-8 Stainless Steel

    Yasushi KOJIMA, Kokichi SANO

    pp. 888-894

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    Abstract

    At several steps of stainless-steelmaking, the most important thing is the relation between chemical compositions of various elements, which are determined by the thermodynamic data. Practically, many elements dissolve from raw materials, fuel, and refractory, into liquid steel and the actual composition is different from the composition in the melt prepared in laboratory.
    It needs complicated calculations to know the equilibrium constants. Presence of too many elements in the liquid steel and the uncertainty of their activity coefficients make the results of the calculations not always satisfactory.
    Silicon is one of the important elements for the deoxidation in 18-8 stainless-steelmaking practice. Concerning the equilibrium relation between silicon and oxygen, the present authors obtained the following results.
    1) The effect of chromium concentration on the activity of dissolved oxygen, f(Cr)0, the temperature dependence of which has not yet been measured, is calculated by the solubilities of oxygen and silicon in the system Fe-Cr solution equilibrated with acidic slag saturated with silica.
    The value of f(Cr)0 obtained is in good agreement at 1600°C with that reported by SAKAO and SANO.
    The effects of both the concentration of chromium and the temperature on f(Cr)0 are expressed by the following empirical formula;
    log f(Cr)0=-(369/T-0.137)[%Cr]+0.0024[%Cr]1.75
    2) The equilibrium constant between silicon and oxygen in the liquid Fe-Cr system is calculated at 1600°C, 1650°C and 1700°C.The relationship between the equilibrium constant Ksi and the temperature is as follows:
    log KSi=-33210/T+13.01
    3) By using f(Cr)0 given above, the equilibrium constant Ksi is calculated for the liquid 8-8 stainless steel, which is practically produced in the steelmaking.
    The result agrees relatively well with that of Ksi in the Fe-Cr system.

  • Influence of the Ingot-Making Condition on Segregation of S and Mechanism of High Segregation in Rimmed Steel Slab Ingot

    Kozo MORINAGA, Kazutomo KITAGAWA, Susumu SATO, Soichi Izumi, Akira HOSHINO

    pp. 894-903

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    Abstract

    In order to establish the adequate method to reduce high segregation at the top center of rimmed steel ingot, the effect of the ingot dimension was investigated in the 1st report. In this paper, the effect of the capping method, the track time and sulphur content in the ladle which are connected with segregation during solidification are investigated; moreover, origins of the high segregation at the top center of the ingot and inverse U typed streak segregations are discussed.
    The obtained results are as follows.
    (1) It is scarcely possible to reduce the high segregation of a large ingot of low carbon rimmed steel (about 16t weight), by improving only the form of the ingot-cap (e.g.enlarging) and the capping method (e.g.put the cap earlier, water-cooling of the ingot top) as far as the normal open top ingot is concerned.
    (2) By shortening the track time, the high segregating zone is enlarged, as the is tpeak at the top center of the ingot is removed to top side, while the 2nd peak is done to bottom side, at the sametime the latter is often raised abnormally.It about 2hr and 50min.of the track time is nccessary (though complete solidifying time-about 30min) to prevent the increase of the segregating zone, as the thickness of the ingot is 800mm (ingot weight is about 14t).
    (3) It is effective for segregation to reduce sulphur content in the ladle, because the max.segregating ratio is increased linearly in accordance with the increase of sulphur content in the ladle, and its gradient is comparatively large, when sulphur content is 0.015 to 0.021% in the ladle.
    (4) It is assumed that there are two kinds of segregation which are made up of the high segregating zone at the top center of the ingot;the 1st peak appears mainly by the rising and concentration of sulphur in molten steel during rimming action and the adiabatic effect of trapped CO bubbles in the segregating zone, while the 2nd peak occurs through the coagulation and precipitation of sulphide in the final solidifying zone.And it seems that the rising of sulphur in that case is connected with inverse U type streak segregations which are heavily distributed in the core zone.

  • Nonmetallic Inclusion in Fe-Mn-O System and Fe-Cr-0 System

    Kiyoshi SEGAWA, Shiro WATANABE, Takashi FUKUYAMA, Hiroshi HARAGUCH

    pp. 904-910

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    Abstract

    The preparation, analysis, and microscopic examination of two series of ingots, made by adding oxygen and manganese or chromium to 6kg pure iron melt, are described.The analysis includes the chemical analysis of ingots, and chemical and X-ray analysis of non-metallic inclusions extracted by alcoholic-iodine or electrolytic method, and the estimation of chemical compositions of inclusions by an electron probe microanalyser.
    The following results are obtained.
    1) The product of deoxidation of iron by manganese is found to be a double oxide (Fe-Mn) 0, the composition of which varies continuously with increasing manganese content in an ingot.
    The microscopic appearance of inclusions in polished metal section varies from round to irregular particle with increasing MnO content of (Fe-Mn) O.
    2) The deoxidation product by chromium varies with chromium content in an ingot. FeO·Cr203 is formed in an ingot containing less than 5% Cr, and Cr203 is formed in one containing more than 5% Cr.Both of them have very similar appearance.
    3) Though (Fe·Mn) 0 which is low in MnO is deformed a little, (Fe-Mn) 0 which is high in MnO, FeO·Cr203 and Cr2O3 is not deformed by hot working.

  • Behavior of Niobium Carbides and Nitrides in Steel

    Toshisada MORI, Kiyohiko FUJITA, Masaharu TOKIZANE, Ko YAMAGUCHI

    pp. 911-917

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    Abstract

    High purity Fe-Nb-C, Fe-Nb-N and Fe-Nb-C-N alloys containing niobium up to 033% were vacuum-melted and cast into 2-5 kg ingots. The metallographic structure was investigated with these specimens which had been prepared from the samples by quenching in water after long-time holding at respective temperatures of 800 to 1250°C. At the same time, the precipitants were isolated from the3e specimens by 6N-HC1 solution an 1 identified by X-ray diffraction method.The quantitative determination of insoluble niobium was also investigated. Results obtained are as follows:
    1) The precipitation of niobium-carbonitrides or -carbides is recognized predominantly on austenite grain boundaries as finely dispersed particles, while the niobium-nitrides precipitate as comparatively large particles.
    2) The precipitants of niobium-carbides and-carbonitrides in these samples were identified to be f.c.c.δ5-phases with somewhat different lattice constants.
    3) Two types of hexagonal niobium-nitrides were recognized and identified to be ε-and δ'-phases, the ratio of ε- to δ'-phase seemed to be increased as the ratio of N to Nb in sample was increased.
    4) These precipitants can be quantitatively isolated from the iron matrix by dissolving the chips in 6N-HCl solution at room temperature.
    5) It is concluded from the results of analysis for insoluble niobium content in each specimen that the precipitation of niobium-carbides, -nitrides and-carbonitrides begins at high temperature such as 1200°C and is almost completed at about 900°C in these alloys.

  • Effects of Ti and Nb Additions on Structures and Properties of Cr-Ni Stainless Steels

    Yasuo OTOGURO, Yoshikuni KAWABE, Ryuichi NAKAGAWA

    pp. 918-924

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    Abstract

    Investigations were made on the effects of Ti and Nb additions on structures of Cr-Ni stainless steels and on the effects of the structures on mechanical properties and corrosion resistance.
    Experimental results obtained were as follows: 1) The specimens containing Ti were hardened by the formation of σ phase from δ ferrite and the precipitation of Ni3Ti. Those containing Nb were hardened only by the formation of σ phase from δ ferrite.
    Two peaks were observed in as-aged hardness versus time curves for the specimens containing Ti when they were solution treated at lower temperature.
    2) The chromium equivalences of Ti and Nb as a ferrite former were about 35 and 3'1 respectively. In the specimens contaning the largest amounts of Ti and Nb, Laves phase existed in the neighbourhood of δ ferrite. The chromium content of σ phase became low in specimens containing Nb as in specimens containing Ti and Mo.
    3) The degree of the solution hardening by Ti and Nb was considerably great. The effect of the solution hardening by Ti on tensile strength was larger than that by Nb. In specimens containing Ti, tensile strength increased with increasing Ti content at test temperatures below 700°C.
    4) Creep rupture strength reached minimum at certain contents of Ti and Nb. This was due to the combined effects of the solution hardening and the increment of the amount of δ ferrite with increasing contents of the alloying elements.
    5) The corrosion resistance to H2SO4 also reached minimum at certain contents of Ti and Nb, which was similar to the relationship between creep rupture strength and alloying content, as described above.

  • On the Condensed Film on the Inner Wall of the Apparatus for Vacuum Fusion Gas Analysis

    Takeji KOIZUMI, Fujio TSUGANE, Masataka KAMAKURA

    pp. 925-933

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    Abstract

    In the previous paper, the authors ascertained that when the steel samples containing Al or Mn were analysed by the vacuum fusion method, the O values decreased quantitatively with the increase of such elements.
    In this paper, the following are dealt with:(1) Relations between the above-mentioned phenomenon, the temperatures of the inner wall of the apparatus, of the Mo-hood covering the graphite crucible, and then the components (Fe, Al, or Mn) of the condensed film on the inner wall surface.(2) The analysis of the residues in the crucible revealed the increasing tendency of Mn and Al vaporization proportional to each content.
    On these experimental results, it is concluded that when the samples containing Al or Mn are molten, the vapour pressures of these elements are remarkably high comparing with other metals and so the vapourized quantities become larger.
    Consequently, a film containing Fe, Al or Mn is formed on the inner wall of the apparatus and adsorbs the extracted CO gas.Thus the 0 values determined are lowered.

  • On the Technical Development of Pelletizing and the Utilization of Pellet for Blast Furnace Practice

    Yasubumi Doi

    pp. 934-942

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  • Developement of Ingot Mold in Recent Years

    Eiro IWAMURA

    pp. 943-961

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  • The Development of the Heat Economy in Iron and Steel Industry Last 10 Years

    Ichiro FUJIMOTO, Kazuhiko KUWAHATA

    pp. 962-972

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  • 抄録

    pp. 973-975

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  • 参考文献

    pp. 976-977

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  • 鉄鋼ニューズ

    pp. 983-984

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  • © 1964 The Iron and Steel Institute of Japan

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