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

Tetsu-to-Hagané Vol. 47 (1961), No. 12

  • 製鉄工業と輸送問題

    pp. 1663-1664

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  • Reduction of Iron Ores by a Reformed Mixed Gas (Natural Gas+Carbon Dioxide)

    pp. 1665-1669

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    In the previous reports (ib., Tetsu-to-Hagane Vol.41, 1955, p.5-11; Vol.41, 1955, p.1149-4155), the authors reported the experiment on the reduction process of iron are by natural gas, and it was recognized that the reduction power of the gas was very strong when its decomposition was found. Then it was found that its decomposition was increased with increase of the reducing degree of iron are too.
    Then, the authors examined the reformation of natural gas by CO2 gas and the reduction of iron are by its reformed gas.
    Results obtained were as follow;
    (1) The reforming ratio was varied from 60 to 90% by the reducing degree of iron sand pellets which were fixed in the reforming furnace.
    (2) Using the unreduced iron sand pellets, the reforming ratio at 850°C was greater than at 900, 950°C.
    (3) Using completly reduced pellets, the reforming ratio was 90% of more.
    (4) When the volume ratio (CH4: CO2) of mixed gas was about 1: 1, reforming ratio was greatest and the reduction of iron are by reforming mixed gas was rapid, and the degree of reduction reached 90-100%.
  • A Consideration on Deoxidation Equilibrium Caused by Carbon in Vacuum Induction Melting

    pp. 1670-1675

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    As pointed out in previous report, (Tetsu-to-Hagane, Vol 47 (1961) pp.715-720), the degassing effect in vacuum induction melting by carbon should be considered with the study of the phenomenon of the kinetics.
    Standing on this point, series of melts of iron-base alloys containning chromium have been made in magnesia crucibles in vacuum by carbon degassing practice, and some fundamentals such as the carbon-oxygen relationship, influence of the hydrostatic pressure on degassing effect, the process of CO bubble formation, crucible reaction and effect of Si during the procedure were investigated.
    The results were as follows:
    (1) The oxygen in the melt was rapidly reduced down with vigorous boiling. After the boiling was completed, the oxygen reached nearly the constant value. In the author's experiments, the critical value of Pco at this stage obtained by substitution of the experimental activities of carbon and oxygen was some 10mmHg regardless of the alloy composition melted.
    (2) The oxygen level attainable by carbon degassing process was not influenced by changing the hydrostatic pressure in the vacuum tank in range of 1μHg-10mmHg.
    (3) Comparing the change in the carbon and oxygen contents during the melt, the carbon lost was far in excess of that necessary to account for the observed oxygen drop.
    (4) The abovementioned results could be explained as follow:
    The rapid removal rate of oxygen, at the early stage of the melting, was mainly dependent on the high value of the Pco. As the internal pressure of CO bubbles was gradually reduced and attained to the summed value of the factors, the hydrostatic pressure and surface tension of the molten metal, that limits growth of the bubbles, the bath became quiescent. It was presumed that an equilibrium state might be set up at the stage when the rate of removal of oxygen from the melt was equal to the rate of solution from the refractory.
    (5) In vacuum melting of austenitic stainless steel, the residual oxygen after the carbondegassing process was determined by the dynamic equilibrium relationship. In this case, the presence of silicon was apt to lower the residual oxygen in comparing with silicon free melts. Such an effect seemed to be attributed to the vaporization of silicon as Si suboxide gas in vacuum.
  • On Measurement of Rolling Pressure and Rolling Torque of Roughing Stands in an All-Continuous Wire-Rod Mill

    pp. 1676-1681

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    The rolling pressure and the rolling torque were measured at the roughing stands of all continous wire rod mill. When four billets of mild steel were rolled at once, the rolling pressure of each stand fell in the range of about 9-37 ton per billet.
    The rolling pressure of oval rolling stands was considerably higher than that of square rolling stands. And the effect of back or front tension between stands on the rolling pressure was found at the threading or the deliverying of billets.
    The measured torque was considerably higher than the calculated torque from the measured pressure. The rolling efficiency of roughing stands was about 71%, which, was derived from the measured rolling torque and motor torque. Moreover the load distribution of each stand to the main motor was obtained.
    At the end of this paper the relation between the mean specific pressure and some factors of rolling was discussed.
  • Effect of Cold Working on Carbide Precipitation of Hadfield Steel

    pp. 1682-1688

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    Effects of isothermal heating temperature and holding time on carbide precipitations of cold-rolled 13% Mn Hadfield steels, which had three kinds of carbon content 1.2%, 0.9%, and 0.65% were studied by micrography. In addition, effects of the cold-working ratio on carbide precipitations in heating process of both elongated and hammered Hadfield steels were studied by thermal dilatometry.
    By cold working, isothermal carbide precipitations of steels were started quickly at all precipitation temperature ranges. When steels were heated isothermally at about 500° firstly the carbide films were formed at a slip plane and on grain boundary in steels, and gradually they were grown up to the shape of platelet carbides. As the holding time increases, pearlitic constituents were nucleated at around the platelet carbide and the grain boundary carbide in steels, and gradually they were grown up to the shape of nodular forms. Recrystallized grains were nucleated in deformed austenite grains at carbide precipitation temperature. Therefore, the recrystallized grains were coexistent with the precipitates in steels. With heavy-worked steels, the precipitation of carbides in heating process were started at a lower temperature than in the case of light-worked or none-worked steels, and the more the working ratio was increased, the more the precipitates was increased. But, the severely worked standard Hadfield steels apparently did not precipitate the carbide at temperature below 350° in continuous heating process.
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  • Minor Phases in the Gamma-Type Fe-Co-Cr-Ni Base Heat-Resisting Alloy, LCN-155 Aged and Effect of Additional Elements on These Phases

    pp. 1689-1696

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    The precipitates in the commercial LCN-155 alloy aged at a temperature between 500°C and 950°C for a time up to 3, 000 hours were identified by the electrolytic extraction method. Further, the effect of additional elements such as N, Mo, W, and Cb on these phases was examined.
    The results obtained were as follows:
    1. The phases which were identified in the commercial LCN-155 alloy were the carbides, Cb (C, N), M23C6, X phase and M6C, and the intermetallic compound, Laves phase. These phases changed as follows by aging:
    Cr23C6→(Cr, Mo, W) 23C6→ X phase→ M6C→ Laves phase
    2. The stable Cb compound, Cb (C, N), was detected in the almost examined alloys containing Cb, but, as an exceptional case, it was unstable in a narrow range between about 750°C and 850°C in the alloys containing Cb, Mo, and W.
    3. The principal precipitates which contributed to age-hardening were the carbides M23C6. and X phase. Though the carbide M23C6 was stable in the alloys without N, it was less stable than X phase in the alloys with N, Mo, and W.(The X phase was a new type secondary phase which was detected by authors.)
    4. The carbide M6C and the Laves phase were identified in alloys of this type containing Mo, W, and Cb aged at a higher aging temperature above about 750°C for a longer time, and scarcely made a contribution to hardening.
    5. At about 500°C, no precipitate was found by aging in spite of producing a remarkable volume-change so called as the 1st stage in the tempering process.
    6. It was considered that the two steps of age-hardening in the LCN-155 alloy were caused by carbide reaction changing from M23C6 to X phase and the excellent age-hardenability of this type alloy containing N, Mo, and W would be due to a nature of the X phase.
  • Influence of Matrix Compositions on High-Temperature Properties of Gamma-Prime Precipitated Heat-Resisting Alloys.

    pp. 1697-1704

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    The series of eleven gamma-prime precipitated heat-resisting alloys of various matrix compositions were studied from the view point of correlation of high-temperature load-carrying ability and structural stability.
    The matrix compositions of specimens were different between Ni-base alloys and Fe-base alloys. Air-and vacuum-arc melted and forged 16mm ∅; bars were used for solution annealing, age hardening, short-time tensile, high-temperature creep-rupture tests, X-ray diffraction and -electron metallography.
    The identification of precipitated phases were carried out with the specimens aged for 1, 000 hours at 732 and 815°C, respectively.
    The changes of matrix-lattice parameters by aging treatments, γ′-matrix lattice mismatch and the growth of γ′ phase particles were also measured in these specimens. As the Co -content in Ni-base alloys was enhanced increased, high-temperature strength properties and γ′- matrix lattice mismatch of these alloys were increased and the growth of γ′ particles was delayed. High-temperature strength properties and lattice mismatch were decreased with -these alloys, as the Fe content in Ni-base alloys was raised.
    On the other hand, with Fe-base alloys high-temperature strength, age-hardening properties and lattice parameters of matrix in aged specimens were decreased markedly, as the Co content was increased.
    It was found that the deterioration of high-temperature characteristics in Fe-base alloys was principally caused by a precipitation of massive β phase.
  • Application of a Supplementary Low-Velocity Electron Gun to Electron-Diffraction Reflection

    pp. 1704-1707

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    Utility of electron -diffraction reflection method has been shown by the present authors, for identification of the nonmetallic inclusions constituting sand-marks in steels. However, when the nonmetallic inclusions are large enough to charge the electron on them, their electron diffraction patterns cannot be obtained because of irregular scattering of the diffracted electron beam. This phenomenon is usually observed in the electron-diffraction of a poor electric conductive material.
    To overcome this weak point of the electron-diffraction, it is adequate to apply the lowvelocity electron bombardment on the specimen in operating the electron-diffraction. In the present work, it was recognized that good results were obtained by the electron-diffraction reflection method using the supplementary low-velocity electron gun to identify the macroscopic nonmetallic inclusions constituting sand-marks in steel, and the usefulness of this method were shown.
  • Present Status of Recuperators for Reheating Furnaces in a Rolling Mill

    pp. 1708-1735

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  • 抄録

    pp. 1736-1740,1744

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  • 参考文献

    pp. 1741-1744

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  • 鉄鋼ニューズ

    pp. 1745-1746

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