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

Tetsu-to-Hagané Vol. 79 (1993), No. 5

  • Recent Trend of Nickel Extractive Metallurgy

    pp. 537-547

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    1. 第57回講演大会講演大要4 Tetsu-to-Hagané Vol.45(1959), No.3
  • Current Method and Problem on X-ray Fluorescence Spectrometric Analysis for Blast Furnace Slag

    pp. 548-554

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    Readers Who Read This Article Also Read

    1. CO2 Recycling for a Carbon Resource Tetsu-to-Hagané Vol.78(1992), No.8
    2. Reaction Rate of Methane Formation for the Catalyst of Reduced Iron Pellets Tetsu-to-Hagané Vol.78(1992), No.11
    3. Outlook of Kinetic Studies on the Combustion of Pulverized Coal in a Blast Furnace Tetsu-to-Hagané Vol.78(1992), No.8
  • Sintering Condition and Characteristics of NiO-MgO Solid Solution

    pp. 555-560

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    The effects of the temperature and MgO content on the sintering characteristics of NiO were investigated by measuring the porosity, the specific surface area and the grain size. NiO compacts containing 0 to 20mol%MgO were sintered over the temperature range 1273 to 1773K in air.
    The results were summarized as follows.
    1) The sintering proceeded remarkably at higher temperature than 1473K.
    2) Both of the prosity and the specific surface area decreased with increasing the temperature and MgO content. The effect of MgO addition on the decrease in the specific surface area was more significant than that on the decrease in the porosity.
    3) Grain growth was expressed as 1/3 power function of time. The addition of MgO accelerated both the grain growth and the closed pore formation.
    4) Sintering mechanism was explained by bulk diffusion of oxygen ion.
    5) Lattice constant increased linearly with MgO content.
  • Estimation of Liquid and Bubble Rising Velocities in Bottom Blowing Bubbling Jet

    pp. 561-568

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    A mathematical model for estimating liquid and bubble rising velocities in metallurgical reactors subject to bottom gas injection was proposed. The mass conservation of gas and the momentum conservations of gas and liquid were employed as governing equations. Radial profiles of gas holdup and liquid velocity were assumed to be Gaussian distribution. Axial distributions of center line value and half-value radius of gas holdup were given by empirical correlations. The ratio of half-value radius of gas holdup to that of liquid velocity was also given by empirical one. The slip flow model and the drift flux model were employed for estimating bubble rising velocity. Concerning the liquid velocity, the results of this study agreed well with experimental results published so far. For the bubble rising velocity, in the region near the nozzle where the inertia force of injected gas prevails and the gas holdup on the center line, αCl, is higher than about 10%, it is hard to define which model is more adequate, but in the region far from the nozzle where αCl is lower than about 10% as a result of very high turbulent mixing, the slip flow model would be better.
  • Evaluation of the Critical Gas Flow Rate Using Water Model for the Entrapment of Slag into a Metal Bath Subject to Gas Injection

    pp. 569-575

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    Entrapment of slag into a metal bath at the slag-metal interface in a ladle or an iron bath of smelting reduction process is of practical importance. Cold model experiments were performed to make clear the critical flow rate of injected gas causing the entrapment of slag under bottom gas injection. Water and salt water were used as models of metal, while liquid paraffin, three kinds of silicone oils with much different kinematic viscosity, and n-pentane as models of slag. Air was injected through a centric bottom nozzle into the bath. Entrapment of slag was judged from visual observation. An empirical correlation for the critical gas flow rate was derived as a function of density and kinematic viscosity of slag and metal, interfacial tension between slag and metal, bath diameter, inner diameter of nozzle and bath depth. This correlation could predict the critical gas flow rate for previous hot model experiments as well, provided that the flow patterns in the baths were similar to the present case.
  • Influence of Casting Conditions on Molten Steel Flow in Continuous Casting Mold at High Speed Casting of Slabs

    pp. 576-582

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    Slab subsurface defects caused by mold powder entrapment tend to occur at high speed castig. Behavior of molten steel flow in continuous casting mold of steel slab was investigated with water model experiments and casting tests at actual continuous caster.
    The results obtained are as follows:
    (1) the level fluctuation of molten steel in a mold has various frequency waves and long period waves (0.1 to 0.2 Hz) are related to surface velocity of molten steel.
    (2) water model experiments reveal that the level fluctuation of molten steel is able to be controlled by the optimization of submerged nozzle desigh and other casting parameters.
    (3) a parameter expressing the level fluctuation of molten steel near the narrow side mold (F value), which was derived from various casting conditions, was found and a method to select casting parameters optimizing the range of the F value was devised.
    These findings have been contributing to the clean steel production at a high speed casting in Fukuyama No.5 continuous casting machine.
  • Effects of Surface Oxidation on Cooling Characteristics during Quenching of Heated Metals in Subcooled Water

    pp. 583-589

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    The effect of surface oxidation on the cooling characteristics of silver, nickel, SUS304 stainless steel and pure iron cylindrical specimens during quenching in still subcooled water has been investigated. It is shown that the oxidation of specimen surface has very little effect on the cooling characteristics at the initial solid-liquid contact stage and the vapor blanket stage, but has a very strong influence on the characteristic temperature, i.e. the lower limit temperature of the vapor blanket stage. In general, surface oxidation causes the rise of the characteristic temperature, and this tendency is more remarkable for high subcooling of water. In particular, the presence of a thick layer of porous oxides on specimen surface results in the remarkable rise of the characteristic temperature. The characteristic temperature would be unaffected by surface wettability, but significantly affected by low thermal conductivity and roughness of oxide layer on specimen surface.
  • Influence of Si Added Hot Rolled Steel Surface Condition on Galvanizing Reaction

    pp. 590-596

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    The hot dip galvanizing mechanism of Si added hot rolled Al killed steel sheets with various surface conditions were investigated. It was found that various factors of steel surface conditions affected the galvanizing reaction. The Zn coating appearance and galvanizing reaction of Si added hot rolled steel sheets were improved by mechanical grinding after pickling. According to the results of AES and ESCA analysis, it seemed that the residual subscale layer (inner oxide layer) of Si added hot rolled steel sheet after pickling was removed by grinding. Therefore Zn coating appearance was improved. Furthermore increase of residual strain and stress on the Si added steel surface by grinding were also observed by X-ray diffraction method. It seemed that active sites such as the lattice deffects of substrate increased by mechanical grinding, and therefore Zn-Fe reaction increased.
  • Effects of Si, Mn and C Content on Scale Properties of Steel Plates Oxidized at High Temperature

    pp. 597-603

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    Oxide scale properties on reheating slabs were studied from the point of steel compositions and oxidation conditions. The gas atmosphere was simulated to combustion gas of butane. Increase in scale thickness, the apparent porosity and the mean pore diameter in scale under the influence of oxidation temperature and time were investigated. The main results are summarized as follows. Si in steel had an important effect upon the behavior of scale formation of Fe2SiO4 between the iron substrate and the scale. When Si content in steel is more than 0.2%, the oxidation slowed down below 1170°C, which is the eutectic temperature of FeO and Fe2SiO4. Above 1170°C, scaling became heavy and the pores in scale became large by their agglomeration. C in steel resulted in a greater pore formation because of CO gas formation on oxidation. Mn in steel dissolved in scale uniformly but had a minor effect on the scale properties.
  • Sintering Rate of Creep Cavities in Heat Resisting Steel

    pp. 604-610

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    Experimental measurements of kinetics of creep cavity elimination by annealing and compressive creep are reported for a 1.3Mn-0.5Mo-0.5Ni steel. Samples of the steel were crept to implant creep cavities in the grain boundaries. The mean cavity size and spacing were obtained after measuring approximately 200 cavities and used for theoretical sintering rate calculation. The samples were then annealed for 800h at 550-700°C and compressively crept for 400h under 59-235 MPa and at 550-600°C to make the cavities shrink, and the creep cavity sintering rates were monitored using the highly sensitive density measurement technique.
    The results showed that sintering rates under compressive creep are rapid and depend proportionally on compressive creep rates, whereas annealing causes only slight sintering. Two models of diffusional and constrained cavity growth were applied for the calculation of sintering rate, and it was shown that the sintering rates calculated using the constrained cavity growth model coincides with the experimental data. This coincidence means that the contraction in the neighborhood of cavitied grain boundary due to the atom flow from grain boundary to cavity surface during sintering is costrained by the adjoining grain, causes local tensile strain in the neighborhood, and decreases the sintering rate drived by surface energy of creep cavity. Therefor it was indicated that the local tensile strain must be removed by compressive creep in the adjoining grains for progressive sintering.
  • Grain Refinement by Low Temperature Rolling and Subsequent Annealing Process

    pp. 611-617

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    In the process of cold rolling and subsequent annealing of Fe-36wt%Mn, Cu, Cu-0.03wt%P and Cu-1.25wt%Sn-0.08wt%P alloys, the effect of rolling temperature on the recrystallized grain size and mechanical properties was investigated. Cold rolling at 77K suppressed the dynamic recovery during rolling providing high stored energy which gives a driving force for recrystallization. Fe-36wt%Mn and Cu alloys having the grain size of about 1μm were obtained by cold rolling at 77K and subsequent annealing. Additions of alloying elements which decrease the stacking fault energy are effective in the refining of grains. Higher strength without loss of ductility was accomplished by the grain refinement.
  • Theory and Application of Thermo-Magneto Hydro Dynamics (III)

    pp. N327-N342

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  • Cupola Melting Technique, Transition and Recent Improvement

    pp. N343-N351

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    Readers Who Read This Article Also Read

    1. CO2 Recycling for a Carbon Resource Tetsu-to-Hagané Vol.78(1992), No.8
    2. Reaction Rate of Methane Formation for the Catalyst of Reduced Iron Pellets Tetsu-to-Hagané Vol.78(1992), No.11
    3. Outlook of Kinetic Studies on the Combustion of Pulverized Coal in a Blast Furnace Tetsu-to-Hagané Vol.78(1992), No.8
  • Current Status of Tubular Connections for OCTG

    pp. N352-N355

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