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

Tetsu-to-Hagané Vol. 66 (1980), No. 5

  • Theoretical Study on Effective Diffusivities of Bi-disperse Porous Solids at Constant Pressure

    pp. 449-458

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    For predicting effective diffusivities of bi-disperse porous media, an improved model in which tortuosity factors of the macro- and micro-pore are taken into account is proposed on the basis of the WAKAO and SMITH random pore model. The diffusion rates of binary gases at constant pressure and the effective diffusivities are derived according to the model.
    By the use of the experimental data of WAKAO and SMITH and HENRY et al, tortuosity factors of their porous solids are determined approximately on the basis of the model. The theoretical effective-diffusivities calculated by using the tortuosity factors agree rather well with the experimental ones than those calculated on the basis of the random pore model over the pressure range 0.0006 to 12 atm.
    In order to examine the influence of an inert gas on the diffusion process, solutions to the Stefan-Maxwell diffusion equations for equimolar counter diffusion in a ternary gas mixture through bidisperse porous media are derived on the basis of the model: The diffusion rates and the effective diffusivities in this system are given.
    The expressions for the simple one-dimensional diffusion mentioned above are extended to those for the radial diffusion in a spherical shell.
  • Charging Behavior and Gas Distribution Considering Blast Furnace Aerodynamics

    pp. 459-468

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    The transitional behavior of the burden and gas distribution in the blast furnace has been studied aerodynamically by a blast furnace model.
    When ore is charged, the coke colume is formed in the central region, named the central coke column. The formation process of its column is modeled as the following three steps from the experimental observation.
    1) With the progressive covering of the stack surface from the periphery to the center by ore, the furnace gas is concentrated in the central region.
    2) The coke layer is expanded in the area where the gas velocity exceeds the minimum fluidization velocity of coke layer.
    3) Some of the expanded coke is pushed into the central part by the charged ore.
    The central coke column is easily formed at pellets charging rather than at sinter charging. The concentrated gas velocity in the central part is related to the ore thickness and the area of ore layer and the permeability ratio of ore to coke, and is expressed by the following equations
    Uc/Uav=1/{AC/AT+(AW/AT)/(UC/UW)}……(1)
    UC/UW=C0{(H/R)·(K1/K2)0.778·(AC/AT)-0.483}n……(2)
    where, A is the sectional area and U is the gas velocity, and suffix C and W express the central part without ore and the peripheral part with ore covered, respectively, and suffix T is the throat and av is the average. H is the ore thickness, R is the throat radius, K1 and K2 are the permeability indicies of coke and ore, respectively, and C0 and n are constants.
    The area of central coke column is estimated to be about 0.114 dimensionless radius from Eqs. (1) and (2).
    The pressure drop in the stack of blast furnace is decreased by formation of central coke column, while the distribution of gas through the coke layers in the softening-melting zone hardly changes.
  • Effect of Dissolved Oxygen on the Rates of Evaporation of Liquid Iron and Copper

    pp. 469-477

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    The rates of evaporation of liquid iron and copper under reduced pressure of 0.001600 mmHg Ar were measured at several temperature levels by using a recording micro-balance.
    In the pressure range of residual gas below 0.1 mmHg Ar, the rates of evaporation are independent of pressure, although the rates at above 0.1 mmHg Ar decrease with increasing the pressure of argon, probably because of the collision between the evaporated metal atom and argon as described already by previous investigators.
    It is also found that the rates for both metals decrease with increasing oxygen concentration in liquid metal. Considering that oxygen dissolved in liquid metal behaves as a surface active element, it seems reasonable to regard that the rates are controlled by the evaporation reaction at metal surface where oxygen adsorbes. Namely the present results suggest that most of metal atoms vaporize through the oxygen free site.
    Moreover, it is confirmed that the values of surface tensions of liquid metals estimated from the present work agree approximately with those in the literatures.
  • Model Experiment on Continuous Degassing with Inner Circulation and Its Analysis

    pp. 478-487

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    (1) Residence time distribution function E(t) in continuous degassing reactor was theoretically derived from the assumption that mixing in vessel was expressed as recirculation model with plug flow and perfect mixing.
    The equation was shown as follows:
    E(t)=dn=0bn/n!{t-(h+nc)}n·e-a{t-(h+nc)}
    th+nc
    The constants were determined by flow rate at inlet υ, circulating rate υ1, real flow rate in flow bath υ2, volume of vacuum bath V1, and volume of flow bath V2; The constants are shown as follows:
    θC=V11, θB=V22, a=1/(1-pC, b21(1-pC
    c=pθCB, d=υ/υ1(1-pC, h=pθC
    p is plug flow ratio in vacuum bath.
    (2) Mixing characteristics in model apparatus were measured by concentration pulse response under similarity of Fr number and Re number.
    The results of measurement of pulse response and tracing of flow pattern showed the presence of minor part of by-passing and dead space, and showed relatively close agreement with the above-mentioned theoretical equation.
    (3) From these results, percent conversion of continuous degassing under assumption of perfect mixing in reators was estimated and it was in approximate agreement with the results of RH degassing process when mean residence time was properly selected and at least two unit reactors were connected in series.
  • Mass Spectrometric Study of the Activity in Liquid Fe-Si Alloys at 1 600°C

    pp. 488-495

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    The activities of Si and Fe have been determined in the Fe-Si system at 1 600°C by the use of a combination of a mass spectrometer and a Knudsen-cell. In order to surpress the production of SiO gas, ThO2 was used for cell material.
    The range of composition of Si was 0.05<Nsi<0.5, and Belton-Fruehan's equation was used to estimate the activity coefficient and the interaction coefficient, log γ°si, and εSiSi from measured ion current ratios; log γ°Si=-3.1±0.2
    εSiSi=11.5±1.5
  • Characteristics of Plasticine Used in the Simulation of Slab in Rolling and Continuous Casting

    pp. 496-505

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    Simulation by plasticine is carried out to estimate various stress distributions and deformations of steel in hot rolling and to prevent internal or surface crack of slab in cotinuous casting.
    In this report, first of all, the following dynamic properties of plasticine is treated to establish the foundation of simulation: i) Static properties (stress-strain relation, its reliance on temperature and criterion of yielding etc.) ii) Kinetic proterties (reliance of stress on strain rate etc) iii) Friction with metal surface.
    From the above investigation, it became clear that, there exists the following relation between stress σ(kgf/cm2), logarithmic strain ε, strain rate ε (1/s) and temperature T (°K), in the region of T=253323°K, ε=0.020.3 and ε=10-210°1/s;
    σ=1.15×10-5ε0.085ε0.12 exp(3 530/T)
    Then the above result is compared with the deformation resistance of steel in high temparature (about 1 000°C). And it is confirmed that plasticine has enough properties to simulate not only the deformation of steel in high temparature but also the stress distribution.
  • Boron-Containing Precipitates Formed on the Prior Austenite Grain Boundaries in High Strength Low Alloy Steels

    pp. 506-513

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    This paper deals with the identification of boron constituent and its transition to other ferrous boroncarbides during heat treatment. In order to observe boron constituent clearly, the present authors adopted a new technique by which boron constituent on intergranular fractured surface is observed without performing etching.
    Boron constituent forms at austenite grain boundaries by step quenching, but this boron constituent begins to transform to fine M23(CB)6 particles from the periphery during holding below AC1. Boron constituent never forms in carbon free steels, and thus it must contain carbon atoms.
    It is considered that the boron constituent is not identical with M23(CB)6 bacause of 1) the above mentioned transition during heat treatment and 2) the difference in response to etching between them.
    Globular M23(CB)6 directly forms from ferrite by reheating at temperature below AC1 after the specimen is quenched with so high cooling rate that martensite is produced from austenite without forming boron constituent.
  • Effect of Cold Working and Heat Treatment on Stress Corrosion Cracking Behavior of SUS 304 Stainless Steel

    pp. 514-522

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    The effects of cold work and heat treatment on the stress corrosion cracking (SCC) behavior of SUS 304 stainless steel wire were studied in boiling 42%MgCl2 solution under the applied stress of 25kg/mm2.
    The SCC susceptibility of the specimen which was subjected to a cold work greatly decreased with lowering the working temperature when the degree of cold work was 7% or above, but has a tendency to increase in the case of a less working or an as-subzero treatment. It seems that the change of such an SCC susceptibility was closely related to the formation of stress-induced martensite. It was found that the intergranular SCC (IGSCC) was observed under the condition of cold work or assubzero treatment which increased SCC susceptibility. The above results suggest that there is a correlation between the SCC mode and the working condition, and the IGSCC was due to the formation of ε-type martensite. In the specimens which were aged at 470 or 530°C for short time after the solution treatment, the SCC susceptibility was increased, and the IGSCC was observed, whereas it was not observed after aging at 600, 700 or 850°C for more than 0.5hr in the solution treated or cold worked specimens.
  • Tensile Properties of a 0.2%C-Ni-Cr-Mo Steel Having Mixed Structure of Martensite and Bainite

    pp. 523-531

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    A study has been made of room-temperature tensile properties of a 0.2%C-Ni-Cr-Mo steel having mixed structure of martensite and bainite.
    When B-III and B-II type bainite, which precipitated acicularly so as to partition prior austenite grains, associated with lath martensite, a detrimental effect was found on the strength and ductility regardless of volume fraction of the bainite and tempering conditions, as opposed to a desirable effect in the case of mixed structure of lenticular martensite and lower bainite precipitated acicularly.
    From the analyses of true stress-strain diagrams and microfractographs, the decrease in the ductility results from the fact that the bainite being elongated pararell to tensile axis fractures in brittle manner, it being attributed to higher stress concentration in the vicinity of twophase interface as a result of unequal strain in the two-phases durring plastic deformation.
    From the above results, it was assumed that the strength and ductility of steels having mixed structure of martensite and bainite were significantly affected not only by the shape and distribution of the bainite, but also by the morphology of co-existent martensite.
  • Observation of the Sliding Wear Trace of Bonded Steel

    pp. 532-538

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    The sliding wear tests were carried out under the condition of constant surface pressure without lubricant at room temperature, using the stationary test pieces of S45C borided steel and the rotary test pieces of low carbon steel. Those tests were carried out with constant sliding distance under various sliding velocity. The scanning electron microscopy and X-ray microanalysis were employed to investigate the wear surface trace of borided steel. The experimental results indicated that the morphology of the wear surface trace largely depended upon the wear mechanism such as oxidative wear, mechanical wear or melting wear. It was concluded that the wear mechanism or the wear life of borided steel could be estimated to some extent with the observation of wear surface trace.
  • A System for Continuous Measurement of Concentration of Nitrate Ion in Pickling Waste Water

    pp. 539-544

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    A new system for continuous measurement of concentration of NO3- in the waste water discharged when stainless steel sheets are treated in pickling bath has been developed. This system is based on the principle that NO3- is measured at 302 nm in the ultra violet region after the co-existing iron ion is eliminated as iron hydroxide. The measurement of NO3-in the proposed system is performed as follows: The waste water sample from the neutralization treatment bath is continuously filtered by a newly developed device and some hydroxide precipitates like iron hydroxide are removed. Then the sample is constantly passed through a debubbling device to flow-cell of an ultra violet monitor, and the absorbance of the sample is continuously measured at 302nm. Accuracy and responsibility of this system were good. This system was found to be suitable to continuous measueement of NO3- in pickling waste water.
  • Effect of the Kind of Iron Oxide in Reduced Iron Pellets on the Melting rate into Iron Melt

    pp. 545-551

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    TThe melting rate into iron melt of partly reduced iron pellets made from pure iron powder and iron oxide powder by pressing has been measured. The effects of the kind of iron oxides in pellets and the weight of pellets on the melting rate of pellets have been investgated. The following results are obtained:
    (1) FeO, Fe3O4 and Fe2O3 were identified in low reduction pellets produced commercially while only FeO was found in high reduction pellets.
    (2) The difference of melting rate among the pellets containing different iron oxides was small for the constant content of oxygen in reduced iron pellts.
    (3) The apparent activation energy of melting into iron melt of pellets containing FeO was 33 kcal/mol which was the same as that of those containing Fe2O3, while that of those containing Fe3O4 was 21 kcal/mol.
    (4) The maximum melting rate of pellets containing iron oxides was obtained at the range of 2.53.5%C in iron melt.
    (5) The melting rate of pellets into iron melt increased with increasing the weight of pellets.
  • Some Studies on the Determination of Trace Amounts of Carbon in Steel

    pp. 552-557

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    Some factors affecting the determination of trace amounts of carbon in steel were examined, and the following results were obtained:
    (1) Sucrose was satisfactory as the standard substance for the carbon determination.
    (2) In the case of using a high-frequency furnace, copper accelerator was better than tungsten, because the latter was fused into ferrotungsten with a part of steel sample and then caused the incomplete extraction of carbon.
    (3) Carbon recovery from stainless steel on the determination with a resistance furnace was lower than that with a high-frequency induction furnace.
    (4) Effect of the procedure of sample preparation was also significant on the determination of trace amounts of carbon. Electro-polishing procedure gave the lowest error which was due to surface impurities.
  • New Method for Cold-rolling the Step-sectioned Strip

    pp. 558-564

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  • Study on the Welding of 9% Ni Steel

    pp. 565-572

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  • 古代日本製鉄技術考

    pp. 573-577

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  • 抄録

    pp. 596-600

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