Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Volume 74 , Issue 12
Showing 1-19 articles out of 19 articles from the selected issue
  • Kazuyoshi SEKINE
    1988 Volume 74 Issue 12 Pages 2231-2238
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
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  • Nobuo KAMIYA
    1988 Volume 74 Issue 12 Pages 2239-2246
    Published: December 01, 1988
    Released: May 29, 2009
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  • Osami TSUKAMOTO
    1988 Volume 74 Issue 12 Pages 2247-2253
    Published: December 01, 1988
    Released: May 29, 2009
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  • Hideyuki YAMAOKA, Yasuo KAMEI
    1988 Volume 74 Issue 12 Pages 2254-2261
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    A three dimensional mathematical simulation model has been developed to study on the scale up of a new ironmaking process (SC process) which consists of a shaft type reduction furnace and a cupola type melting furnace. Results obtained are as follows;
    1) The fuel rate of a 2 400 t/d plant with the productivity of 5 t/dm3 is estimated to be 525 kg/t.
    2) In this case, gas and solid flows tend to deviate from the uniform flow, which gives effects on the operational performance. Especially, discharging holes must be located at the appropriate positions of the reduction furnace to increase the gas utilization degree.
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  • Tsutomu TANAKA, Yoshimasa KAJIWARA, Takanobu INADA
    1988 Volume 74 Issue 12 Pages 2262-2269
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    A mathematical model, capable of describing the macroscopic movement of an assembly of discs in a hopper, was developed based on the constitutive equations described by Voigt-Kelvin rheological model with a slider and on the equations of motion for translation and rotation of each disc. The validity of the present model was confirmed by comparing the results, such as the order of discs discharged from the hopper, arrangement of discs after charging in the hopper and stress distribution at the wall, obtained from calculations with the corresponding ones obtained by experiments as well as JANSSEN'S equation.
    The present model was successfully applied to the macroscopic flow of the assembly of granular materials of different disc size, subjected to gravitational force in a hopper.
    The installation of a repulsion box in the upper part of the hopper was also simulated and resulted in the decrease in the variation of disc size during discharge through the suppression of small disc segregation during charge, while it had insignificant effect on the deposit profile and the order of discharge.
    The present model was found to precisely describe frictional wall effect in solid flow and abnormal flow behavior, such as bridge formation, in comparison with the conventional continuous potential flow model.
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  • Tomohiro AKIYAMA, Jun-ichiro YAGI
    1988 Volume 74 Issue 12 Pages 2270-2277
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    Exergy analysis was conducted on three ironmaking systems which were conventional ironmaking, direct reduction-electric furnace and smelting reduction systems. The exergy analysis is better than an enthalpy balance or a heat balance because exergy can express the quality of energy and evaluate different forms of energy like chemical, thermal, pressure and mixing energy by a unified measure.
    According to the calculated results for the specified conditions, the smelting reduction system was the lowest in net exergy loss, however, the highest in overall output exergy. The development of the efficient heat recovery process is therefore required for this system. The direct reduction-electric furnace system was the highest in net exergy loss. However, nonfired pellets were found to be effective to reduce net exergy loss. In the conventional ironmaking system, net exergy loss of its constituent processes significantly depended on the injection rate of pulverized coal and on the charging amount of nonfired pellets.
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  • Toshiyuki KOZUKA, Shigeo ASAI, Iwao MUCHI
    1988 Volume 74 Issue 12 Pages 2278-2285
    Published: December 01, 1988
    Released: May 29, 2009
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    The surface wave of molten metal is a triger to induce instabilities and surface defects in several processes such as twin roll, electromagnetic casting and conventional continuous casting.
    Molten metal is an electrically conducting fluid. So its surface wave motion is expected to be suppressed by imposing direct magnetic field.
    In this work, a direct magnetic field was imposed vertically to surface of liquid mercury and damping behavior of wave motion was measured by using laser slit beam. On the other hand, a damping coefficient of wave motion was derived on the basis of magnetohydrodynamics, and experimental data verified the theoretical results. Magnetic field intensity to completely suppress wave motion of molten steel is evaluated by use of the dispersion relation and the damping coefficient derived here.
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  • Takashi SAKURAI, Hitohisa YAMADA, Kazuo KITAMURA, Tomoo TAKENOUCHI
    1988 Volume 74 Issue 12 Pages 2286-2293
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    Iron-base superalloy A286 has been increasingly used for such application as components for power industry because of its high strength at high temperatures. In the ingot of this material, however, heterogeneities such as "A" segregation and Laves phase are easily formed to deteriorate the properties of the products.
    In this study, therefore, an ESR ingot 1 000 mm in diameter was produced and examined in search for measures to reduce these heterogeneities. By beeing based on the result, laboratory experiments were carried out reproducing "A" segregation in a small ingot. The result revealed that lowering Si and Ti contents and making liquid pool angle smaller, which corresponded to shallow liquid pool in actual ESR ingot, were favorable for reducing "A" segregation. From another series of experiments it was made clear that lowering Si and Ti contents was also favorable for reducing Laves phase which tended to appear in micro-segregated interdendrite.
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  • Takeshi TAKAWA, Tsutomu TAKAMOTO, Hiroshi TOMONO, Keigo OKUNO, Hirotak ...
    1988 Volume 74 Issue 12 Pages 2294-2299
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    For the improvement of quality of round billet, a mathematical model of secondary cooling process control has been developed on the following procedure.
    (1) Cylindrical heat transfer model suitable for round section is considered, and one dimensional difference equation along the billet radius is derived.
    (2) In regard to the boundary condition of billet surface, heat transfer coefficients which are suitable for mold area, direct cooling area and indirect cooling area respectively are selected.
    (3) The authors have developed a control method determining optimum water flow in order to keep the temperature fall pattern of billet surface at the aimed value by using the above mentioned model.
    This control method is being put into practice and improves the control accuracy of surface temperature of round billet, and it contributes to the reduction of degrading ratio due to surface defects and so on.
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  • Kazuo KONDO
    1988 Volume 74 Issue 12 Pages 2300-2306
    Published: December 01, 1988
    Released: May 29, 2009
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    Zinc-iron electrodeposited sheet steels have been widely adopted for automobile bodies for their improvements in the corrosion resistance and paintability.In principle, these properties depend on the crystal structure, morphology and microstructure of deposits.The deposits of various zinc contents have been prepared galvanostatically from sulfate baths and examined by scanning and transmission electron microscopes.The 99.5 at% zinc, η-single phase deposit exhibits a collective morphology of hexagonal plates thin in the direction of c-axis.With the increase of iron content, the Γ-phase forms in addition to the η-phase.The η-phase plates stack in the direction of c-axis and form the hexagonal columnar crystals which have triangular pyramidal shapes in morphology.The Γ-particles disperse within the grain and along grain boundaries of these η-phase plates.The Burgers orientation relationship holds between the η and Γ-particles.The 91.2 at% zinc hexagonal columnar crystals form steps on{10.0}η surfaces.An increase of iron content to 85.1 at% zinc, however, flattens the steps on {10.0}η surfaces.Further increase of iron content to 73.0 at% zinc produces a large amount of Γ-particles, which cannot be absorbed any more within the η-phase.These excess Γ-particles form granular crystals, and precipitate between the hexagonal columnar crystals.
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  • Masaru SAGIYAMA, Masaki KAWABE, Tsutomu WATANABE, Akira TONOUCHI, Tosh ...
    1988 Volume 74 Issue 12 Pages 2307-2314
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    Factors affecting zinc electrodeposition on conductor roll (CDR) in a horizontal electroplating cell were investigated. Zinc electrodeposition on CDR was basically attributed to leak current from anode to CDR through plating bath. Limiting current density of hydrogen evolution was also a dominant factor affecting zinc electrodeposition on conductor roll. A decrease in the leak current and an increase in the current density of hydrogen evolution reduced zinc electrodeposition on CDR. The leak current depended on electroplating cell parameters including the distance between CDR and anode, the electrode gap, anode length and solution level from strip. The current density of hydrogen evolution was affected by bath composition and pH of the bath. Decreasing pH of sulfate bath increased the current density of hydrogen evolution.Prevention of zinc electrodeposition on CDR was not achieved only by lowering pH of sulfate bath down to 1 in the cell used for the experiments. It was attained by applying CDR shielding method using covers made of insulator neighboring on CDR in addition to using sulfate bath of pH=1.
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  • Isao KUBOKI, Yoshinobu MOTOHASHI, Mamoru IMABAYASHI, Kenzou KATO
    1988 Volume 74 Issue 12 Pages 2315-2322
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    The Ni-30Cr-5Al alloy which is used for an ornamental material is relatively soft in an as-solid-solution state, and the alloy can be strengthened to about 600 in Vickers hardness by precipitation hardening. In the present study, a possibility of superplasticity in the alloy is examined by refining its microstructure using a thermomechanical treatment. The thermomecahnical treatment is composed of a cold rolling of at least 80% in rolling reduction followed by a precipitation and recrystallization at temperatures below 1225 K. A fine-grained dual phase microstructure in which fine round α-Cr phase particles are uniformly dispersing in γ-Ni phase matrix can be obtained by the treatment. An alloy which was undergone such treatments shows the total elongation of more than 500% and the strain-rate sensitivity index of about 0.4 when deformed at 1225 K. The deformation at temperatures below 1225 K obeys thermally activated process and the activation energy found is 251 kJ mol-1. It can therefore be concluded that the Ni-30Cr-5Al alloy which has undergone the above-stated thermomechanical treatment shows superplasticity.
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  • Masahiko ODA, Hiroshi KUBO, Osamu AKISUE, Kichi NAKAZAWA
    1988 Volume 74 Issue 12 Pages 2323-2329
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    The effect of hot rolling starting temperature on mechanical properties of Nb-containing low-carbon steels produced by continuous casting-direct rolling process was studied. Experiments were carried out by using a continuous casting machine and a hot strip mill at Hirohata works.
    As a result, when the hot rolling starting temperature was at 1 020°C, yield point and tensile strength of the hot band produced by direct rolling process were lower than those by conventional reheat process. When the hot rollling starting temperature was at 1130°C and finishing temperature was lower than 850°C, tensile strength and toughness of the hot band produced by direct rolling process were almost same as those by reheat process.
    In this condition, precipitates of Nb (C, N) were effectively formed during hot rolling, and these were usefull for grain refining.
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  • Saiji MATSUOKA, Susumu SATOH, Takashi OBARA, Kozo TSUNOYAMA
    1988 Volume 74 Issue 12 Pages 2330-2336
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    The effect of strain rate during hot-rolling below Aγ3 transformation temperature on the formation of recrystallization textures of Ti-added extra-low-carbon sheet steel has been investigated. The intensity of {222} component of recrystallized sheet steel increased with the increase of the strain rate. Textures of hot-rolled sheet steels, which were similar to those of cold-rolled sheet steels, didn't depend on the strain rate. The {222} residual strain of specimens hot-rolled at high strain rate was higher than that of lowstrain rate specimens while {211}, {200} and {110} residual strains were independent of the strain rate.{111}oriented grains of the high strain rate specimen recovered faster than those of the low strain rate specimen while no change in recovery rate of {100} oriented grains was observed. Based on the above results, it is concluded that high strain rate hot-rolling at the ferrite region provides high stored energy only in{111} oriented grains, with the result that {111} oriented grains recover swiftly and intense{111}recrystallization texture is formed.
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  • Masakatsu UENO, Kametaro ITOH
    1988 Volume 74 Issue 12 Pages 2337-2344
    Published: December 01, 1988
    Released: January 15, 2010
    JOURNALS FREE ACCESS
    As a direct quenching process has become into wide use, it becomes very important to investigate the effect of austenitizing conditions on the hardenability of a steel. In this study, in order to apply this process successfully to B-added steels, the effect of heating rate, austenitizing temperature and cooling rate in γ-phase on the hardenability of B-added steels has been carried out.
    The results obtained are as follows :
    1)The effect of B is an only function of free-B content [B] unless BN precipitates in γ-phase during cooling from a austenitizing temperature. In case of [B] ≤5 ppm, the effect of B increases with [B]. When [B] is more than 5 ppm, it becomes constant.
    2)The hardenability of B-added steels does not depend on the γ-grain size as well as the heating rate.
    3)When BN precipitates prior to γ→α transformation, the effect of B disappeares. The critical cooling velocity of precipitation of BN, VBN (°C/S) is shown as follows :
    log VBN=0.0042[B][N]-0.25
    where, the unit of [B] and [N] is "ppm".
    4)Therefore, the necessary conditions for B being effective are as follows :
    (1) When a B-added steel is austenitized, [B]must not be less than 5 ppm.
    (2) Vγ>VBN, where Vγ is the cooling rate of the steel in γ-phase after austenitizing.
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  • Akibumi FUJIWARA, Nobuya IWAMOTO
    1988 Volume 74 Issue 12 Pages 2345-2352
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    A Statistical technique was used to clarify the difference between the bending strength of small size specimens and the crack initiation stress value of blast furnace hearth model constructed by carbon blocks.
    By the Weibull's weakest link model, strength (size effect) and it's variance of carbon blocks of blast fur-nace hearth model were estimeted from those of small size bending specimen.
    To obtain the crack initiation stress value of the carbon block, 2-dimensional elastic-creep analysis and 3-dimensional elastic analysis were carried out. The stress value which caused cracks in the carbon block model became about 1/51/4 of the bending strength of small size specimens.
    Also, the variance of stress value was estimated from the variance of location of cracks in carbon blocks.
    By combining the size effect, strength-and stress-value variances, we clarified that the stress level of about 1/51/4 of bending strength is small size specimens is large enough to cause cracks in large blocks of the blast furnace hearth model.
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  • Hirofumi KURAYASU, Yasuo INOKUMA, Tsuyoshi NAKAYAMA
    1988 Volume 74 Issue 12 Pages 2353-2360
    Published: December 01, 1988
    Released: May 29, 2009
    JOURNALS FREE ACCESS
    It was found that the mixture of ammonium sulfate, cupric sulfate and sulfuric acid was suitable for the decomposition of BN in steel. Using this mixture, boron in steels and in the precipitates was analyzed and the precipitation behavior of boron in steels was discussed.
    1) BN isolated from steel was decomposed by fuming sulfuric acid in the above described mixture for 1 hour. The maximum quantity of coexisting water should be 0.2 ml to prevent the loss of boron.
    2) After steel matrix was dissolved by nitric acid, BN in the residue was decomposed by fuming sulfuric acid in the above mixture with the addition of phosphoric acid for 25 minutes.
    3) BN was precipitated in non-equilibrium state at various temperatures of heat treatment of steel. BN precipitated at 500°C changed into the dual phases comprising borocarbide and AIN with increasing the holding time or the holding temperature for heating of steel.
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  • Kazuki MORITA, Nobuo SANO, Toshio SUZUKI, Yasunori MIYATA
    1988 Volume 74 Issue 12 Pages 2361-2366
    Published: December 01, 1988
    Released: January 15, 2010
    JOURNALS FREE ACCESS
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  • [in Japanese]
    1988 Volume 74 Issue 12 Pages 2373
    Published: December 01, 1988
    Released: January 15, 2010
    JOURNALS FREE ACCESS
    Download PDF (158K)
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