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

Tetsu-to-Hagané Vol. 60 (1974), No. 6

  • Investigation of Slag Flow in the Blast Furnace Hearth Based on the Fluid Dynamics and of Relation between Residual Slag Amount and Tapping-out Conditions

    pp. 607-621

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    In order to clarify the causes of the excess accumulation of molten materials in the blast furnace hearth which results in blast furnace troubles, such as hanging and slipping, the behaviour of flowing out and accumulation of slag in the furnace hearth is investigated.
    The results of model studies of slag flow in the furnace hearth during tapping were analyzed as the scaleup problem based on the theories of fluid dynamics. The dimensionless flow-out coefficient FL in eq.(32) has been found to be closely related to the slag residual ratio, i.e. the ratio of residual amount of slag at the end of tapping to that accumulated at the begining (Fig. 8).
    Further investigation using this relation shows that eight independent variables, i.e. viscosity, tapping amount, tapping rate and depth of slag, hearth diameter, effective hearth area, number of tapping and permeability of packed coke, determine the behaviour of flowing out and accumulation of slag in the furnace hearth. The results of investigations are as follows;
    1) The residual amount of slag and the depth of slag layer increase with the increase in slag tapping rate and of slag viscosity.
    2) The increase of the number of tapping operation is beneficial in maintaining the smooth furnace operation, if the tapping rate and/or slag viscosity increase.
  • Theoretical Analysis of Staggerd-Parallel Operation in Hot-Blast Stoves

    pp. 622-636

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    Staggerd-parallel operation in hot-blast stove is theoretically investigated on the basis of both numerical and analytical methods. The effects of non-dimensional factors in the mathematical model on the longitudinal distribution of brick temperature and on the fractional distribution of blast to each stove have been evaluated by means of the numerical computations.
    By applying the analogues method with the method used in the previous paper on the analysis of single blowing operation to a staggerd-parallel operation, the approximate solution and the necessary conditions relevant to a balanced cycle have been obtained. Although the analysis on a staggerd-parallel operation becomes rather difficult since the flow rate of air varies considerably during the cooling period, good agreements between the results obtained from the approximate solution and those from the numerical computation have been found.
    Several diagrams to be available for the rational stove design are drawn up on the basis of approximate solution mentioned above.
  • Effect of Surface Condition on The Abnormal Oxidation of Fe-Cr-Al Alloys

    pp. 637-646

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    Studies were made to investigate the reason for occurrence of the abnormal oxidation on heat-resistant Fe-Cr-Al alloys. The results are summarized as follows.
    (1) This anomalous oxidation was accompanied with nitrogen absorption and proceeded markedly at the temperature above 1000°C. The voluminous oxidation products comprising iron-base oxides (α-Fe2O3Fe3O4) were observed on the alloy surface and numerous massive blocks of aluminum nitrides (AIN) in the inner matrix.
    (2) It was found that the initiation of the anomalous oxidation depended not only on the chemical composition but also on the surface condition of an alloy, as observed in alloy C (Fe-18.2%Cr-3.7%AI). In this case needle-shaped AIN were observed on the surface of the alloy C before the oxidation test. The nitride formation decreased the contents of aluminum in the matrix (to ca. 0.5%), which was considered to be related in the remarkable deterioration of the oxidation resistance.
    (3) The anomalous oxidation of alloy C was able to be prevented by preliminary removal of the surface layer containing AIN or by preannealing at 900°C for the diffusion of Al and Cr.
  • Morphological Study of the Isothermal Martensitic Transformation of Iron Alloys

    pp. 647-660

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    Morphological study of the isothermal martensitic transformation of Fe-25-7%Ni-2.76%Cr, Fe-25.4%Ni-2.17%Mn, and Fe-25.3%Ni-4.52%Mo alloys with very few content of carbon and nitrogen has been carried out and the following results were obtained.
    (1) The typical isothermal martensite of these three iron alloys transformed at temperature range from room temperature to about-100°C were a lath type martensite having tangleddislocations.
    (2) AT gretaly lower temperature than-100°C, the martensitic transformation with burst-like mode occured.
    The martensite transformed in such manner had many twins other than dislocations, and it can be considered that Georgiyeva et al had regarded improperly such kind of martensite as the isothermal one.
    (3) The dislocations in the isothermal martensite lath were less closely tangled than that in the so-called packet type athermal martensite.
    (4) Some regions having different image contrasts were observed in the isothermal martensite laths by transmission electron microscopy. It is supposed that those implies a little change of the orientation during the transformation.
    (5) The lattice orientation relationship between the isothermal martensite and the austenite was analysed approximately as the so-called K-S relationship.(6) Some highly dislocated region was observed in the austenite surrounding the isothermal martensite. That region was extending into a characteristic direction.
    (7) These results drawn from this study give important informations about the interrelation among three types of γ→α' marteneite transformation in iron alloys.
  • Unification on Cooling Curves of Quenched Bars at Center

    pp. 661-670

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    Cooling curve of a specimen quenched into a still coolant varies with not only the cooling behaviour of coolant but also other factors such as dimension, shape and material of specimen. An examination was made to show the influence of these factors on cooling curves and the following expression was proposed.
    Values of NL and NM were determined experimentally by using the many cooling curves obtained from various sorts of coolants, and NL and NM were evaluated 1.31 and 0.215 respectively. Unification of the cooling curve was made by conversion of cooling time to t/{(D·W/S)nL·a-nM} for each shape, dimension and material.
    whree, t: cooling time of the central portion of a specimen during quenching,
    W/S: ratio of volume to surface area of a specimen for the unit size,
    a: thermal diffusivity, nL, nM experimental constants.
  • Method to Derive Cooling Curve of Specimen During Quenching

    pp. 671-681

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    A cooling curve whose scale of the abscissa is transformed to t/{(D-W/S)1.3α-0.215} wasproposed as a master cooling curve of the coolant used,
    where t is cooling time of a quenched bar
    D, W, and S are dimension, weight, and surface area of the bar, respectively, and
    a is thermal diffusivity.
    W/S is taken for a unit size bar similar to the quenched one.
    The curves for various coolants were obtained. A calculated cooling curve of a bar quenched into a still coolant was compered with the measured one of the same bar and in the samecoolant, and they coincided well with each other. The method to derive the master cooling curve could be applied for any quenching temperature. A cooling curve of a quenched bar at any inside position could also be infered by using the curve at the center.
  • The Work Hardening Behavior and Some Other Properties of High Silicon Two-Phase Stainless Steel Wires

    pp. 682-694

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    Two-phase stainless steel wires composed of austenite and ferrite were studied on their mechanical properties, stress corrosion cracking behavior and corrosion resistance against chloride or acidic solutions. The volume fraction of ferrite in the alloys used is 50 percent.
    The main results obtained are as follows:
    (1) At low reductions of cold drawing, the yield strength of two-phase stainless steel wires increases with increasing cold reduction with the same work hardening rate as that of single-phase austenitic stainless steel wires. After heavy cold drawing, the work hardening rate of two-phase alloys becomes an intermediate value of those of austenitic and ferritic stainless steels. This may be attributable to preferred strain concentration in the austenite with small reductions by drawing and a distribution of strain equal in the austenite and ferrite phases after heavy drawing.
    (2) A good combination of the tensile strength and reduction of area is obtained by aging between 300°C and 500°C after heavy drawing. The strengthening after aging at 500°C may be due to the (Fe, Cr)23C6 carbide precipitated in the austenite and ferrite phases.
    (3) The resistance against stress corrosion cracking of 20Cr-10Ni-4Si steel drawn is better than that of SUS 316 austenitic stainless steel wire.
    (4) The pitting and chemical corrosion resistances against chloride or acidic solusions are also excellent. This may be attributed to high silicon contents of the steels.
  • Effect of Carbon on the Determination of Nitrides in Steel by Cold Nitric Acid Method

    pp. 695-699

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    The effect of carbon on the quantitative determination of nitride-nitrogen in steel by dissolution in cold nitric acid has been investigated.
    (1) Nitrides are quantitatively extracted from steel with nitric acid aquaoud solutions at a temperature of -5°C and in the concentration range of 1:6 to 1:8.
    (2) The nitride-nitrogen in low carbon steel is accurately and rapidly determined by this method.
    (3) For the steel sample with a higher carbon content, the residue extracted by the method yields an erroneously higher result.
    (4) The reason for the erroneous result is that organic-nitrogen compounds are synthesized from the carbon in steel with nitric acid during the dissolution.
    (5) By heating the residue in a He stream to expel the organic-nitrogen compounds, the nitrogen in nitrides of Ti, Zr, V in steels is quantitatively determined.
  • Determination of Sulfur, Silicon, Nickel, Chromium and Cobalt in Ferro-nickel Containing High Carbon by X-ray Fluorescent Analysis

    pp. 700-704

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    A study has been made, by using the Shimazu-ARL X-ray quantometer, on the analytical precision of S, Si, Ni, Cr, and Co in Ferro-nickel containing high carbon as a raw material for stainless steels.
    Samples are prepared by pouring the melt into a metallic mold and grinded with No.80 emery paper after cutting them. No segregation of the above elements are found regardless of the high carbon content (2%<) in the sample.
    The multiple linear regression method is employed to improve the analytical precision of S, Si, Ni, Cr and Co.
    Si and C effect the determination of S. The precision and reproducibility of the above elements are as follows:
    (1) Precision.
    S:0.003%, Si:0.041%, Ni:0.137%, Cr:0.032% and Co:0.008%
    (2) Reproducibility.
  • Present Status and Future Aspect of Hot Dip Galvanized Steel Sheet

    pp. 705-722

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  • The Effect of Chromium on the Activity of Nitrogen in Fe-28% Ni Austenite at 1000°C

    pp. 723-725

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    A capsule technique was employed to investigate the effect of chromium on the activity of nitrogen in Fe-28%Ni-Cr-N austenite at 1000°C in a high chromium concentration range between 15 and 30%. The activity of nitrogen in the system is adequately described by the following equation:
    log aN=log (%N)+eCrN(%Cr)+eNiN(%Ni)+rCrN(%Cr)2+rCr, Ni(%Cr)(%Ni), where numerical values for eCrN and eNiN are evaluated from the data in Fe-Cr-N and Fe-Ni-N systems, respectively.
    The values of the secnd order interaction parameters, rCrN and rCr, Ni, determined in the present investigation, are 0.00213 and -0.00033, respectively, at 1000°C.
  • 抄録

    pp. 726-733

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