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

Tetsu-to-Hagané Vol. 70 (1984), No. 14

  • Developments of Large Size High Quality Steels and Their Future Aspects as "Near Net Shape" Material

    pp. 1631-1639

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  • Fandamentals of the Kinetics of Metal-Slag Reactions

    pp. 1640-1647

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  • Nucleation and Growth of Proeutectoid Ferrite in Fe-C and Fe-C-X Alloys

    pp. 1648-1658

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  • The Composite Materials Used in Rockets

    pp. 1659-1665

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  • Analysis of Sintering Process of Ores by a Gas Velocity Distribution Model

    pp. 1666-1673

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    A model for sintering process has been developed and used to analyze the sintering operation and the response time of sintering process to a step-wise change in the pallet speed and the bed height. The unknown parameters are estimated by measuring the gas velocity at 4 points on the sinter strand.
    (1) The ratio of (flame front speed)/(gas velocity) decreases by increasing coke content and coke diameter. Therefore when they are increased, it is necessary to increase the suction gas velocity in order to keep the flame front speed constant. Consequently it leads to the increase in the quantity of heat transfer from the sinter to the gas at the cooling stage resulting in the rise in the cooling rate.
    (2) As to the unsteady state of sintering process caused by a step-wise change in the pallet speed and the bed height, the results of model calculation and the actual plant test show a good agreement to some extent. It is confirmed that the model is also valid for the analysis of the unsteady state of sintering process.
  • Cooling Down and Hot Idling of Silica Brick Hot Stove during Blast Furnace Relining

    pp. 1674-1680

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    Hot stoves using silica brick should either be cooled or hot-idled when the blast furnace is blown-out for relining or shut down for a long time. Noticing the thermal stress of the brick in a steady or a nonsteady state of temperature distribution and based on experimental and actual-furnace-operation data, the authors introduced the cooling rate suited for reducing the temperature difference between the inner side and the outer side of the silica brick in order to decrease the circumferential stress in the case of cooling. The authors also found the temperature range suited for reducing the radial stress and set the lower limit temperature of the brick at 450°C in the case of hot idling. Both these measures were applied to the hot stoves of the Kimitsu BF No. 3 achieving a large economic effect.
  • Rate of Dephosphorization of Liquid Iron by the Slag of CaO-SiO2-FeO System

    pp. 1681-1688

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    The rate of dephosphorization of liquid iron by the slag of CaO-SiO2-FeO system was investigated at temperatures of 1 570, 1 610 and 1 650°C.
    The rate of dephosphorization was analysed as a first order reaction equation. On the basis of the discussion on the effect of slag composition on the rate of dephosphorization, it was found that the reaction-rate constant was expressed as function of CaO and FeO content in the slag and temperature as follow:
    logk=1.67log(%CaO)+1.90 log(%FeO)-5 620/T-5.057
    It was obvious from this expression that the optimum composition of slag for the rate of dephosphorization is 47% CaO-53% FeO.
    The discussion was made on the rate determining step of the reaction, and it was considered that the diffusion of phosphorus from slag-liquid iron interface to slag phase controlls the rate of reaction. On the basis of the discussion on the rate determining step, the value of D(P)/δ was obtained to be
    0.1-7.0×10-4cm/s(1 570-1 650°C).
  • Rate of Reduction of Liquid Wustite with Hydrogen

    pp. 1689-1696

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    The reduction rate of liquid wustite in contact with solid iron with inert gas(N2, Ar or He)-hydrogen mixture was measured by using the thermobalance at 1 400, 1 450°C.
    (1) The apparent reduction rate of liquid wustite with hydrogen was proportional to PH2.
    (2) The apparent reduction rate was affected by the gas flow rate over the range of this experiment. The rate of chemical reaction between liquid wustite and hydrogen was so fast that the overall reduction was controlled by mass transfer in the stagnant film of gas phase in the range of flow rate, V<4l/min(N2-H2 and Ar-H2 mixture) or V<7l/min(He-H2 mixture). However, in the range of V=728l/min with He-H2 mixture, reduction was controlled by both two steps, i.e., mass transfer in gas phase and chemical reaction at the interface. The chemical reaction rate at the interface was estimated to be 1.6×10-2(g-oxygen/cm2·s·atm).
    (3) The chemical reaction rate estimated was about 20 times larger than that of solid wustite obtained in the present work.
  • Operation of Vacuum Slag Cleaner (VSC) for Casting Ladle

    pp. 1697-1703

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    BOF slag run into casting ladle at tapping gives disadvantageous effects in the succeeding steelmaking process, such as rephosphorization, low yield of alloy, and steel contamination in the form of inclusion at the stage of casting. Conventionally at NKK Fukuyama Works, dragger was applied to eliminate the slag mechanically. This mechanical method, however, had caused imperfect slag skimming, mechanical damage to casting ladle, steel loss, and temperature drop and so on.
    To solve these problems, introduction of vacuum slag cleaner (VSC) for casting ladle was made. In September, 1982, NKK started the operation of VSC. And the monthly production through VSC was increased up to 50 000 tons of steel. Various effects of VSC treatment, such as reduction of aluminum consumption, less rephosphorization and better cleanliness of the steel, are discussed quantitatively in this study.
  • Tundish Nozzle Constriction in Continuous Casting of Titanium Bearing Stainless Steel Slabs

    pp. 1704-1711

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    A study was made on the problem of tundish nozzle constriction in continuous casting of titanium bearing stainless steel slabs. The constriction becomes more severe as the percentage of alumina in the molten steel in the tundish, and subsequently the ratio of alumina to titanium nitride increases. The main origin of titanium nitride and alumina particles in the buildup are denitrification and deoxidation products in the molten steel. Alumina from the nozzle refractory and the reaction between aluminum in the steel and silica in the refractory, in addition to the deoxidation product, plays a significant part in buildup process at the initial stage. The buildup process is assumed to be a phenomenon involving not only deposition of the nonmetalics and freezing of the steel but also subsequent removal of the buildup.
  • Deformation and Strain Hardening of Martensite in 1.4% Mn Steels

    pp. 1712-1718

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    The effects of carbon content and tempering temperature on the deformation and the strain hardening of martensite in 0.11-0.43 percent carbon-1.4 percent manganese steels were investigated.
    (1) The deformation of the martensites as-quenched and tempered at 100°-400°C was composed of two or three kinds of fundamental deformation stages, e.g. the first and the third stages or the first, the third and the fourth stages.
    The strain hardening rates in the first stage (at ε=0.01, true plastic strain) and the third stage were raised in proportion to cm' (0.43-0.87) power of the carbon content. Those hardening rates were particularly high in the martensites as-quenched and tempered at 100°-200°C, while very low after tempering at 300°-400°C.
    (2) After tempering at 500°-700°C, the second stage appeared. The strain hardening rate in this stage had a linear relationship with f;/(1-f;), where f; represents the volume fraction of spheroidal cementite particles. The strain hardening rate in the third stage showed a little higher values than those after tempering at 300°-400°C.
    (3) Relative strain hardening rate 1/σ·dσ/dε of the martensites was affected by tempering temperature. This will influence on toughness of the steels.
  • Effect of Aluminum in Zinc on Alloying of Zinc Coating of Galvanized Steel

    pp. 1719-1726

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    By means of high temperature X-ray diffraction apparatus, was studied the effect of aluminum on the formation of alloy layers during heating of the galvanized steel sheet.
    (1) Aluminum additions result in the formation of Fe2Al4Zn on the Zn/Fe boundary and shift the formation temperature of the δ1 phase and Γ phase and the disappearance temperature of the η phase toward the higher side.
    (2) Aluminum additions necessary and sufficient for this are 0.12 per cent; greater addition would little affect the phase change.
    (3) Fe2Al4Zn expands the existence region of the single phase of δ1 and inhibits the formation of the Γ phase because it interferes with the interdiffusion of iron and zinc.
  • Alloying Behavior of Galvannealed Steel Sheets

    pp. 1727-1733

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    For galvannealed steel sheets, the properties such as adherence of coated layer depend upon the degree of alloying with base steel.
    It is necessary to know the moment of alloying of zinc surface in order to control the degree of alloying.
    That moment was detected in the laboratory by measuring the irregular reflection intensity and the emittance during galvannealing of the specimen.
    The behavior of irregular reflection intensity generally corresponds to the change of the surface roughness (Rmax) during the course of alloying. On the other hand, the emittance increases mainly when the liquid of zinc on the very surface of the coating changes to the crystalline solid such as ζ or δ1 phase. The change of the former precedes the latter.
    x

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  • Effect of Tramp Elements in Steel on the Adherence of Porcelain Enamel

    pp. 1734-1741

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    The effect of tramp elements in steel on the adherence of porcelain enamel has been studied using commercial products and specimens prepared from vacuum melting. Firstly, it was found that the steel sheet scarcely containing tramp elements showed very poor adherence. In order to obtain excellent adherence, it is effective for steel sheet to contain the appropriate quantities of Cu and S. Mn and Ni contents have no effect on the adherence, and the increase of P content gives negative effect on the adherence. It is considered that the adequate contents of Cu and S to obtain excellent adherence are more than about 0.03% and 0.01%, respectively.
    The presence of adequate contents of Cu and S is effective for uniform smut formation on steel surface in pickling, which roughens uniformly the steel surface in pickling, and causes fine Ni deposition in subsequent Ni flash. It is considered that these two effects due to uniform smut formation provide serrated enamel-steel interface in subsequent enamel firing, and finally give excellent adherence.
  • Development of Covered Arc-welding Electrodes for Stainless Steels of 18Cr-8Ni-0.2N-0.1Nb and 25Cr-13Ni-0.8Mo-0.35N

    pp. 1742-1749

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    Purpose of this study is to develop covered arc-welding electrodes for high strength stainless steel, 18Cr-8Ni-0.2N-0.1Nb (SUS 304N2) and pitting corrosion resistant stainless steel, 25Cr-13Ni-0.8Mo-0.35N.
    0.2% proof stress and tensile strength of 20Cr-9Ni-3Mn weld metal increase in proportion to increase of N content. Columnar structure of weld metal tends to become fine-grained by addition of small amount of Nb and Ti. The same also brings about extreme increase of 0.2% proof stress and tensile strength. Addition of 0.2% N, 0.05% Nb and 0.05% Ti results in 0.2% proof stress more than 35 kgf/mm2 and tensile strength more than 70 kgf/mm2 (specification values of SUS 304N2). Decrease of elongation, vEo°C and crack resistant property of weld metal associated with addition of above elements is found to be small and neglisible.
    Weight loss by pitting corrosion test (5%FeCl3+1/20 N HCl, 50°C, 48h) of 25Cr-14Ni-0.8Mo-0.30N weld metal (0.11.5g/m2·h) is slightly greater than that of base metal (less than 1 g/m2·h). Pitting potential V'c100 of weld metal (0.96 Vvc SCE) is almost same as that of base metal. It is concluded that initiation of pitting corrosion is almost same as that of base metal, while dissolution rate of pitting corrosion is slightly higher than that of base metal. In spite of increase of Mo and N contents up to 1.8% and 0.34 % respectively, there is no decrease of weight loss by pitting corrosion test. Crack ratio of weld metal decreases as ferrite content increases, while pitting corrosion resistant does not decrease by increase of ferrite content up to 5%.
    Various characteristics of welded joint of above two kinds of stainless steel are also described in this article.
  • Strength of Welded Joint in Maraging Steels Having Strength Levels from 200 to 300 kgf/mm2

    pp. 1750-1757

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    The strengh of electron beam welded joint in six maraging steels has been measured and discussed on the basis of microstructural features and the strength of weld metal.
    The strength of the welded joint of steels except No. 6 steel increases proportionally with the increase in the strength level of the base metal. In No. 6 steel the strength of the welded joint is remarkably lower comparing with the strength of the base metal. The joint efficiency is usually about 90%, but that of No. 6 steel is 75%.
    The lower joint efficiency in No. 6 steel can be explained by the fact that the weld metal have the low strength as the result of the formation of the large amount of the stable austenite. The amount and the stability of the austenite phase increase remarkably, when Ms temperature in the base metal is lower than 200°C.
    The maximum strength of base metal for which the strengthening is effective, is more than 300 kgf/mm2 if it is evaluated from smooth tensile test of welded joint. The maximum strength is 270 kgf/mm2 when welded joint is evaluated from notch tensile test of weld metal.
  • New Processing Method of the Waste Pickling Liquor in Steel Making with the Fluidized Bed Reactor

    pp. 1758-1764

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    Iron oxide (α-Fe2O3), a by-product of the steel industry, is widely used as a raw material of ferrite products in the electronics industry. This iron oxide is manufactured by oxidizing and thermal-decomposing spent hydrochloric acid pickling liquor (FeCl2) in steelmaking.
    A new process called Chemirite method was developed and it is summarized as follows:
    1. Fluidized bed reactor is used for thermal decomposition of the purified waste liquor.
    2. Energy-saving measures are effected at all levels of the equipment and operation of the plant.
    3. While plant operations are continuous, pollution control is given full consideration. Moreover, safety is assured.
    4. Hydrochloric acid is regenerated and reused with a higher recovery rate than other recovery processes. It also offers high purity.
    5. Iron oxide powder, as a by-product, is best suited for the raw material of soft ferrite products.
  • Extraction and Determination of Fe-M (M=Ti, Nb, or Mo) Phosphides in Steel

    pp. 1765-1772

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    Electrolysis method for extracting phosphides in Fe-P-M (M: Ti, Nb, or Mo) ternary alloys has been investigated. The experimental results obtained were as follows;
    (1) Solute P in steel is anodically oxidized by electrolysis, and reacts with ferrous ion and ion of alloying element to form Fe-P-M-O type compound insoluble in non-aquous electrolyte. This compound is produced in large quantities in 10% acetylacetone-1% tetramethylammoniumchloride-methanol, 4% methylsalicylate-0.5% salicylic acid-1% tetramethylammoniumchloride-methanol and 5% HCl-methanol, and gives positive error to the analytical results of P as phosphide.
    (2) By use of 20% calciumsalicylate-0.5% salicylic acid-1% LiCl-methanol solution (termed 20% CaSA electrolyte), developed in this study, formation of Fe-P-M-O type compound can advantageously be prevented.
    (3) FeMoP, FeNbP and FeTiP are found in Fe-Mo-P, Fe-Nb-P and Fe-Ti-P ternary alloys, respectively. These phosphides are found to be chemically stable in 20% CaSA electrolyte and to be quantitatively extracted, by controlled-current electrolysis.
    (4) It is proved that cold-work embrittlement in extra-low carbon titanium-added steel can be improved by decreasing the amount of solute P in the steel.
  • コークス製造研究の回顧と期待

    pp. 1773-1774

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  • 抄録

    pp. 1786-1788

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  • 住宅雑感

    pp. 1789-1790

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