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

Tetsu-to-Hagané Vol. 62 (1976), No. 2

  • 鉄鋼工学セミナーについて

    pp. 165-166

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  • Effect of Pre-reduction on the Reduction of Hematite Powder by H2-H2O Mixtures

    pp. 167-175

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    The effect of pre-reduction of sintered hematite powder on the subsequent reduction to iron was investigated. Both the pre-reduction and the subsequent reduction were carried out at 900°C, but the ratio of the partial pressures, pH2/pH2O, in the reducing gas mixtures changed very widely.
    When the hematite powder was pre-reduced to magnetite, the rate of the subsequent reduction from magnetite to wustite as well as that from wustite to iron was retarded significantly. And topochemical progress of iron-wustite interface could be observed as in the case of the reduction of original hematite without pre-reduction.
    By pre-reducing the hematite powder to wustite, the subsequent reduction proceeded much faster than the reduction of hematite without pre-reduction, especially when the concentration of hydrogen was much higher than that of water vapor. Under such conditions, the reduction from wustite to iron progressed nontopochemically. As the concentration of water vapor became high, however, the reduction began to progress rather topochemically.
    By plotting the rate of reduction from wustite to iron against the ratio of hydrogen to water-vapor concentrations, it was found that the equilibrium between wustite and iron shifted apparently to the side of high concentration of hydrogen by such pre-reduction.
  • Activities of FeO in the Ternary System SiO2-MgO-FeO and Constitution of SiO2

    pp. 176-181

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    Activities of FeO in the ternary system MgO-SiO2-FeO are measured by means of the levitation method in an induction furnace.
    Activities of MgO in the binary system MgO-SiO2 are calculated from the activities of FeO in this ternary system MgO-SiO2-FeO.
    Theoretical expressions derived for molecular size distributions in multichain polymers (polymer theory) are applied to this binary system Mg-O-SiO2, and the theoretical curve from the polymer theory fits the calculated values of activities of MgO in the system MgO-SiO2 when the equilibrium constant of the polymer theory (K11) is 0.01.
    Application of the polymer theory to the ternary system MgO-SiO2-FeO seems to be possible with several assumptions.
  • Fundamental Study on the Dissolution Rate of CaO into Liquid Slag

    pp. 182-190

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    The rate of dissolution of CaO into liquid slag was determined by measuring the decrease of diameter of rotating CaO cylinder dipped in CaO-SiO2-Al2O3 or FeO-CaO-SiO2 slag and the penetration of slag was examined. Also, the distribution of components in liquid slag adjacent to the solid-liquid interface was examined by the XMA technique.
    The rate of dissolution increased with temperature and with rotating speed of the cylinder and was expressed by the rate equation derived from the assumption that the rate was controlled by mass transport in the boundary layer of liquid slag.
    The dissolution rate into liquid slag containing FeO was several times greater than that into slag without FeO, bacause of the difference of physical properties of slag and, probably, of the difference of the mode of 2CaO. SiO2 formation.
    Slag components penetrated into solid CaO were mainly Al2O3 and FeO and the SiO2 content was very little. This may be explained by the formation of Al2O3 or FeO rich slag layer between solid GaO and 2CaO. SiO2 film.
  • Model Experiments on Mass Transfer in Gas Phase between an Impinging Jet of Gas and a Liquid Iron

    pp. 191-200

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    Experimental studies have been made in order to analyze the mass-transfer characteristics in the gas phase in the reactor used for chemical reactions between an impinging jet of gas and an inductively-stirred liquid iron. The methods which have been used for the experimental studies are (a) sublimation of naphthalene into a nitrogen stream, (b) evaporation of pure liquids into a nitrogen stream, and (c) absorption of ammonia from ammonia-nitrogen stream into water.
    The results obtained are as follows;
    1) Average Sherwood numbers in the region of H/d= (H/d) c are correlated by the equation
    Sh=m (rs/d) -1Re0.66Sc0.5 (m=0.40±0.13),
    and (H/d) c is correlated by the equation
    (H/d) c=0.00464Re0.68 (rs/d) 1.5 exp (3.96 (d0/DT)) (exp (Sc)) /Sc,
    where H is the distance from nozzle to diffusing substance, rs is radius of diffusing substance, d is inside diameter of nozzle, d0 is outside diameter of nozzle, DT is inside diameter of vertical wall, Sh=kGd/D, Re=duρ/μ, Sc=μ/ρD, kG is mass-transfer coefficient for gas phase, u is average velocity of gas in nozzle, ρis density of gas, and μ is viscosity of gas.
    2) Average Sherwood numbers calculated from published data on the rate of decarburization are correlated by the equation
    Sh=m′ (rs/d) -1Re0.66Sc0.5 (m′=0.23±0.07).
    x

    Readers Who Read This Article Also Read

    1. Gas-phase Mass Transfer by Impinging Jet on Liquid Surface in Crucible Tetsu-to-Hagané Vol.70(1984), No.1
    2. Activities of FeO in the Ternary System SiO2-MgO-FeO and Constitution of SiO2 Tetsu-to-Hagané Vol.62(1976), No.2
  • Effect of Interfacial Factors on Distribution of Oxides Sprayed into Molten Steel

    pp. 201-209

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    For the purpose of approaching to the dispersion strengthened steel, an investigation was undertaken to study in detail the relation between the distribution of oxides, which were sprayed into molten steel by force, and interfacial factors.
    The main results obtained are summarized as follows:
    1) The distribution of oxides depends on both the contact angle of molten steel on various oxides and the interfacial tension. The oxides particle size in steel increases with the contact angle and the interfacial tension.
    2) The effect of carbon in steel on the distribution of oxides is not remarkable. This result may indicate that carbon is less surface-active.
    3) Addition of alloying elements which have a large standard free energy of oxide formation (-ΔG°) is very effective in lowering the oxide particle size. This can be attributed to the selective adsorption of the alloying element in steel at the interface and the interfacial reaction of its element with sprayed oxide.
    4) The oxide particle size shows a sharp decrease on additions of niobium, which is the most effective element in lowering the oxide particle size, but changes only slightly above 0.7 at% niobium.
  • Model Study of the Continuous Casting of Slab

    pp. 210-219

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    A simulation study has been made of the continuous casting of slab using potassium chloride solution. Solidification profiles from the meniscus to the bottom of a mushy zone, the regions of forced convection caused by the inlet stream and the temperature distribution in the slab have been observed under the various casting speed by the use of a straight nozzle and a bifurcated nozzle, respectively.
    Experimental results show that there exist some differences between the profile of liquidus line in the region of the forced convection for the run with a straight nozzle and that with a bifurcated nozzle. It may be considered that such differences are caused from the differences in the flow patterns and the temperature distributions in a liquid pool for each run mentioned above.
    Furthermore, it has been found that the differences in the profiles of solidus line for each run are almost negligibly small and that the primary dendrite arm spacings in the region being affected by the forced convection are different between the runs with each nozzle.
    Solidification profiles obtained in these experiments are compared with the profiles predicted by the mathematical model which was priviously presented by the authors.
  • Effects of Austenite Grain Size and Cold Rolling Prior to Aging on Tensile Properties of 18 Pct Ni Maraging Steels

    pp. 220-227

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    The influence of austenite grain size on the tensile properties of 18 Ni maraging steels has been investigated. The austenite grain size of these steels can be remarkably refined by annealing of the cold worked specimens at relatively low solution temperatures.
    Improvement in strength, ductility and toughness through austenite grain refinement is observed in aged conditions. The ductility of the 175 and 210 kg/mm2 grade maraging steels is relatively high even in coarse grained matrix. The austenite grain size of the 245 kg/mm2 grade maraging steel should be refined in order to improve the mechanical properties such as tensile strength, reduction in area, notch sensitivity and impact value because of its distinct low ductulity in coarse grained matrix.
    An appreciable increase in strength is found when solution treated specimens is cold worked and then aged. This strength increase is caused by work hardening of the martensite. Refining the austenite grain size of solution treated specimens increases work hardening.
    The 210 kg/mm2 grade maraging steel can be strengthened to the strength level of 245 kg/mm2 by a combination of work hardening and precipitation hardening, moreover its notch sensitivity is lower than that of the 245 kg/mm2 grade maraging steel. In the 245 kg/mm2 grade maraging steel, fine grained specimens show higher strength and tend to improve the notch sensitivity compared to those obtained in coarse grained ones when cold worked and then aged.
  • The Effect of Environment on the Oxidation Behaviour of Rimmed and Killed Steels at Elevated Temperature

    pp. 228-237

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    High temperature oxidation tests of rimmed and killed steels have been carried out in the CO2-CO, air, 3%O2, 300 ppm O2 and CO gas atomospheres in the temperature range from 350 to 530°C under the pressurized condition up to 42 kg/cm2. The oxide scales formed have been analized by mean of a scanning electron microscopy, X-ray diffraction, EPMA and measurements of electric resistance and porosity. The results obtained are summarized as follows:
    (1) Oxidation resistance of the killed SS41 steel is superior to the rimmed SS41 steel in the all tested atmospheres.
    (2) The above described tendency is remarkable especially in the cases of 3% O2 and CO2-CO atmosphere. It is considered that the former is due to the electro-chemical effect of Si in Fe2O3 and the latter the suppression of Boudouard's reaction (2CO→CO2+C) by Si at the interface of scale/matrix.
    (3) It is possible that the excrescences appear in CO or CO2 gas, but the excrescences don't appear in the oxygen only atmosphere.
    (4) It is considered from the results of EPMA and electrical resistivity measurement that Si doesn't exist at the scale/matrix interface as a layer of SiO2.
  • Photoelectric Emission Spectrochemical Analysis of C, Si, Mn, Mo, Cu, Ti, Nb and Al in Stainless Steel with Fixed Time Integration Technique

    pp. 238-246

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    The fixed time integration technique of photoelectric emission spectrochemical analysis was employed to determine C, Si, Mn, Mo, Cu, Ti, Nb and Al in various kinds of stainless steels with the same calibration curves for each element.
    The spectral intensities were measured in 3 seconds of fixed time integration without internal standard of Fe.
    It was confirmed with using Fe-X binary alloys that the following elements interfered to the spectral lines of analytical elements; Al for C I line, Mo for Si I line, Mo and Nb for Ti II line, Mo, W, V, and Ti for Nb II line and Mo for Al I line. No interference was found for Mn II Mo and Cu I lines in this method.
    The above seven elements except carbon were determined with the calibration curves which were corrected the above interference and independent of the kinds of stainless steels. Only the calibration curve of carbon was consisted of two curves of austenitic and ferritic stainless steels.
    Although the instrument was not designed for the fixed time integration method, good accuracy and reproducibility were obtained.
  • Quick Tapping BOF Operation

    pp. 247-253

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    No. 2 Steel-making Plant of Muroran Works, Nippon Steel Corporation has developed a new technique of L.D. converter operation, that is, sampling and temperature measurement has come to be executed by sub-lance with a unique senser without tilting the vessel, which is named “Quick Tapping”. Effects of Q.T. operation are as follows. (1) By the elimination of temperature measuring and sampling operation, considerable labor can be saved. (2) By the reduction in temperature measuring and sampling time, increase in production can be expected. (3) As no molten steel flows out when temperature measuring and sampling are executed, reduction in yield can be prevented. (4) Since the molten steel stays in the furnace for a shorter time, the life of the furnace can be prolonged. (5) As the temperature of the refract-tories does not drop the target tapping temperature can be lowered. (6) There is no disastrous accident which is related to safety and tilting operation. Q.T. operation was put into practice in November of 1972 and completed for all heats in September of 1973. Q. T. operation has largely contributed to high productivity. No. 2 Steel-Making plant made a new record of 111 heats per day in October 16th in 1973.
  • Manufacture, Mechanical Properties and Rolling Performance of Large Cast Steel Rolls with High Strength and Toughness

    pp. 254-266

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    This study is concerned with the manufacture and mechanical properties of large cast steel roll with new compositions (0.5C-1.25Cr-1.0Ni-0.5Mo-0.4V) which have been developed for prevention of roll breakage in service. The optimum heat treatment has been established to obtain high strength and good tough-ness. Four large cast steel rolls, two rolls for slabbing mill and two rolls for break down mill, have been manufactured by applying the results of the experiments. Mechanical properties of the rolls are superior to those of conventional cast steel rolls in characters of strength and toughness at both normal and elevated temperatures.
    At present, about one hundred rolls made of the new material are under service and for a slabbing mill they show excellent rolling performance irrespective of very severe rolling condition.
  • On the Deformability Fundamentals of Ductile Fracture and Prediction of Workability Limit

    pp. 267-280

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  • Recent Topics on the Martensitic Transformation

    pp. 281-293

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  • 第1回鉄鋼工学セミナー報告

    pp. 294-299

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  • 抄録

    pp. 300-307

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