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

Tetsu-to-Hagané Vol. 58 (1972), No. 12

  • 情報処理

    pp. 1555-1556

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  • The Countercurrent Reduction of Iron Ore in a Fluidized Rotary Bed

    pp. 1557-1566

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    In a rotary furnace, an are bed was fluidized when the centrifugal force acting on are particles was equal to the force of gravity. In this bed, all cross-sectional area inside the tube was covered with moving are particles. Therefore contact of gas with are particles was improved as a conventional fluidized bed. Ore particles could be reduced in a countercurrent gas flow by inclining the rotary tube.
    Small sized hematite, magnetite and sintered are were reduced in the countercurrent fluidized bed. The results were as follows;
    1) The tendency of are sintering was lessened by using a reducing tube of larger diameter.
    2) Effect of gas film on the reduction was small.
    3) Under the condition of the same quantity of are in fluidizing zone, the utilization coefficient was constant whether the diameter of reducing tube was large or not.
    4) The calculation values of reduction were in good agreement with the experimental values.
    5) As the are size was smaller, the reducing rate per unit inner volume became larger.
  • Investigations of the Sintering Process by Applying of Mathematical Simulation

    pp. 1567-1578

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    In the sintering process of iron ore, various phenomena take place simultaneously, i. e. combustion, heat transfer, decomposition, fusion, and solidification. In order to clarify the relations between each phenomena, a simplified comparison between the results of the experiment by the use of sintering pot and of the calculation by the use of mathematical simulations was carried out, and the following conclusions were deduced.
    (1) The heat-front speed was influenced by mass velocity of gas and heat-transfer coefficient.
    (2) The reaction velocity of coke combustion in sintering layer was lower than that proposed by HoTTEL for carbon sphere.
    (3) From the result of examination of the heat-transfer coefficient calculated and observed, it was concluded that the heat transfer by radiation and combustion should be taken into consideration.
    (4) The fusion and solidification were represented as a mathematical expression in the model. The portion of not-fused are grain, remained lime stone and pore in sintered ores were measured and these vlaues agreed with the calculated results.
  • High-Temperature Thermodynamic Properties in Ti-0 System

    pp. 1579-1593

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    For the establishment of liquid iron-titanium-oxygen equilibria, a thermodynamic study on Ti-O system was achieved. For this purpose, EMF measurements onoxygen concentration cells involving thoria base solid electrolytes were made, in the temperature range from 900 to 1550°C, using Fe/FeO, Cr/Cr203, Ta/Ta205 and “TiO”/“Ti2O3” as reference electrodes.
    The po2-composition isotherms and the free energy change for titanium oxide formation were deduced from experimental results in Ti-0 system (O/Ti ratio; 0.6, -3/4-2.0, 900, -3/4-4 600°C).
  • A Fundamental Study of Titanium Deoxidation of Steel

    pp. 1594-1602

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    Liquid iron-titanium-oxygen equilibria has been established by equilibrium measurements between liquid iron-titanium alloys and synthesized titanium oxide crucibles and by the thermodynamic data reported previously by the authors.
    The results obtained are summerized as follows:
    1) It has been shown to be necessary to consider solid solubility of iron into, and nonstoichiometric be-haviour of deoxidation products for the estimation of titanium deoxidation equilibria and activity coefficient of titanium and interaction parameter between titanium and oxygen in liquid iron.
    2) Relation between titanium content and deoxidation products has been found to be as follows;
    [%Ti]<0.01; titanium oxides (0/Ti=1.7-1.87, [%Fe]<13)
    [%Ti] =0.013-0.25; Ti3O3 ([%Fe]<1.2)
    [%Ti] =0.25-4.8; Ti2O3
    [Ti]>4.8; TiO
    Besides, deoxidation products have been found to change its composition in its existing range in 0/Ti ratio and/or iron content corresponding titanium content in liquid iron.
    3) Interaction parameters and activity coefficient have been deduced;
    e(Ti)O=0.31, e(O)Ti=-0.93, γ0Ti=0.016, e(Ti)Ti=0.042
    4) A simplified equation for oxygen solubility is;
    log[%O]=-0.60log[Ti%]-3.22, at 1600°C, and 0.013-4.25[%Ti].
  • Kinetics of Decarburization of Liquid Iron by Ar-CO2 Gas Mixture

    pp. 1603-1611

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    A study has been made on the kinetics of the decarburization of liquid iron in Ar -CO2 atmospheres at 1600°C. The study has been especially directed towards determining the rate -controlling steps at low carbon contents of the melt.
    In the concentration range above 0.02-0.05% C (depending upon the partial pressure of CO2), the rate of decarburization is influenced by the gas flow rate. On the other hand, in the concentration rangebelow 0-02-0-05% C (depending upon the partial pressure of CO2), the rate of decarburization no longer depends on the gas flow rate, if it is higher than 1300 cc/min.
    The aspects on the mechanism of decarburization under the latter condition are summarized as follows;
    (1) The decarburization by blowing gas of pCO2 below 0.1 is controlled by chemical reaction. The rcactions conceived here are;. The results can be explained reasonably by the model based on the simultaneous reactions except for the range where FeO is formed on the surface of melt. The rate constants obtained here are; K1′= (1-2.5)×10-6mol/cm2sec atm2, k2= (2-3)×10-5 mol/cm2 sec atm.
    (2) At pCO2≥0-1, the rate-determining factor changes gradually. It is shown that at pCO2, ≥0.2, the rate of decarburization is determined by the mass transfer of carbon in liquid iron, mass transfer coefficient kc being 0.036 cm/sec.
  • Effect of Vanadium and Nitrogen Addition on the Recrystallization of Cold Rolled Low Carbon Steel

    pp. 1612-1622

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    Recrystallization of cold rolled steels with approximately 0-02wt% nitrogen and with vanadium is to a large extent affected by the variation of vanadium content. When the ratio of vanadium content (Cv) to nitrogen content (CN) is approximately 1, that is CV (a/o)/CN (a/o)≈1, recrystallization is much retarded; in the strip annealed for 3 hours at 750°C, unrecrystallized parts are found under an electron microscope. The annealing texture shows high concentrations around the (100) and (112) poles, and is rather similar to a cold rolling one. The steels have small grains, high yield points, and small elongations.
    When Cv/CN=10, the recrystallization of steels occurs more easily than that of the steels containing vanadium at the ratio of about Cv/CN, ≈1. The annealing texture is composed mainly of {111}‹110›+ {111}‹112› orientations.
    Similar but small effects are also observed by vanadium addition in the steels with approximately 0-002% nitrogen.
  • Effect of Nb, Ti, Mo and B on Creep Rupture Strength of 16Cr-10Ni Heat Resisting Steel with Vanadium

    pp. 1623-1631

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    The influence of individual and combined additions of molybdenum, niobium, boron and titanium on the creep rupture strength and the rupture elongation of 16Cr-10Ni-0.4V heat resisting steel, and their correlation with microstructures have been studied.
    Chemical composition of the steels used has been selected by the design of experiment and the relationship between the creep rupture strength and the chemical composition has been analysed by computer. Aregression equation has been developed which satisfactorily predicts the 700°C1000 hr creep rupture strength from the chemical composition. The additions of molybdenum, niobium and boron to this steel have a remarkable effect in increasing the creep rupture strength. Molybdenum, boron and titanium additions have been found to improve the creep rupture elongation.
    It has been presumed from electron microscopic studies that molybdenum accelerates slightly the coarsening of the precipitated carbide, but increases the creep rupture strength through the so-called solid solution strengthening, and that niobium and boron make a distribution of precipitated carbide more uniform in matrix, that is one of the causes of their strenghthening effect.
  • Effect of Carbide Stabilizing Elements Ti, Nb and V on the High Temperature Strength and Microstructural Change of 180/0Cr-100/0Ni Austenitic Steel

    pp. 1632-1645

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    The influences of titanium, niobium and vanadium on the creep rupture strength have been studied using 0.1%C-18%Cr-10%Ni stainless steels. The correlation of the strength to the microstructural change during creep has also been discussed.
    The highest value of 700°C-104 hr rupture strength in a titanium and niobium series (steels containing various amounts of titanium and niobium, respectively) is obtained at Ti/C and Nb/C atomic ratios of 0.8 and 0.2-0.4, respectively. On the other hand, in a vanadium series, the creep rupture strength of the steel shows its maximum at V/C atomic ratio of about unity at test temperature of 700°C and 800°C, but at 600°C, the strength increases monotonicaly with vanadium content up to 1.53%.
    The high strengths of the steels containing proper amounts of titanium, niobium, or vanadium can mainly be attributed to the fine distribution of M23C6 precipitates which is caused by the acceleration of nucleation due to the foregoing precipitation of an MC type carbide within austenite grains. It is deduced that the solid solution strengthening effect of vanadium contributes also to the remarkable increase in the rupture strength of the vanadium steel at 600°C.
  • Transverse Rupture Strength of the High Speed Steel Produced by Means of Powder Forging

    pp. 1646-1652

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    A study of the mechanical properties of a high speed steel, JIS SK H-2, made by powder forging and conventional processes has been carried out by transvere rupture test, hardness test and both optical and electron microscopies.
    The results are as follows;
    1) The strength of powder forged steel depended upon particle size, sintering temperature and pressure.
    2) Apparent density of gas atomized powder is higher than that of water atomized powder.
    3) Compressibility of water atomized powder is higher than that of gas atomized powder.
    4) The optimum sintering temperature range is between 1200°C and 1300°C and the holding time is 1hr.
    5) Transverse rupture strength of powder forged steel is 17% higher than that of commercial steel.
    6) Carbide distribution of powder forged steel is fine and uniform, but that of commercial steel is banding structure.
  • Age Hardening Behaviors of Low Nickel Stainless Steel Containing Aluminum

    pp. 1653-1662

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    From previous studies on 17-7 PH stainless steel and on Nitralloy-N steel, it had been expected that steels having martensitic or ferritic structure and containing proper amounts of Ni and Al might be hardened by aging at about 500°C, and therefore, age hardening behaviors of low carbon 16% Cr-2 or 3% Ni stainless steel containing 1% Al were investigated. The steel containing 0-19 C-16 Cr-3 Ni-1 Al (R1) exhibited a remarkable hardening by aging at about 500°C after solution treatment at I 100°C, and a tensile strength over 150kg/mm2 was obtained after aging for 1 to 10 hrs at 500°C. This steel, even if tempered at 700°C, was remarkably hardened by aging after the tempering. A steel containing 0.10 C-16 Cr-2Ni-1 Al (Si) also exhibited almost the same age hardening behavior as that of steel RI, but its tensile strength obtained was somewhat less than that of steel R1. A CsC1 type structure with a lattice constant of about 2-9 Å was found in the overaged specimens of steel R1 by means of the electron diffraction technique.
    It was concluded that this phase was intermetallic compound NiAl (α′) and the remarkable age hardening properties observed in steels investigated could be attributed to the precipitation of the α′ phase from martensitic or ferritic matrix.
  • Precipitation Hardening of 18%, 20%, and 25%Nickel Maraging Steels

    pp. 1663-1673

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    Precipitation hardening and reversion behaviours in 18%nickel maraging steels bearing molybdenum and cobalt and 20%, 25%nickel maraging steels bearing titanium have been investigated by measuring the electrical resistivity at liquid nitrogen temperature and tensile strength. Transmission electron microscopic studies have also been carried out. The results obtained are summarized as follows.
    (1) The 18%nickel maraging steels show a good combination of strength and toughness in aged conditions. The strength after aging is considerably increased by adding relatively small amounts of titanium, the upper limit of the content of titanium is considered to be nearly 1.5%to avoid the drop in toughness after aging.
    (2) A considerable drop in toughness is observed in the aged 20%nickel maraging steels. This fact may be interpreted in terms of the existence of relatively coarse precipitates accompanying precipitation-free zones formed mainly at grain boundaries. The aging brittleness can be reduced by heavy cold working before aging. Addition of relatively small amounts of molybdenum or tungsten is also effective to reduce the aging brittleness.
    (3) A marked reversion phenomenon is observed in 18%nickel maraging steel bearing 5%molybdenum and 9%cobalt, pre-aged at 375°. However, the reversion in 25%nickel maraging steel bearing 1.8%titanium, pre-aged at 375°, is inconsiderable. From these results it may be concluded that a meta-stable phase is precipitated at a lower aging temperature in nickel maraging steels bearing molybdenum and cobalt but not in those bearing titanium.
  • Influence of Carbides and Nitrides on the Recrystallization Behavior in Cold Rolled Steel Sheets

    pp. 1674-1692

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    To clarify the effect of carbides and nitrides on the formation of recrystallization texture in low carbon steel sheets, the changes in recovery, recrystallization and grain growth processes during isochronal annealing have been investigated from the view point of crystallographic orientation dependency, using commercial Al-killed steel, Ti-stabilized steel, rimmed steel, and vacuum-melted 0.02%C-Fe alloy as materials.
    The formation of the proper recrystallization texture in Al-killed steel may be explained by the crystallographic orientation dependency of recrystallization rate, which is originated from the retardation of recovery due to the precipitation of AIN. In rimmed steel, the treatment resulted in structures with fine cementite dispersion before cold rolling causes the crystallographic orientation dependency of grain size distribution just after primary recrystallization, and the recrystallization texture is developed by the preferential growth of {ill} grains during the normal grain growth. In Ti-stabilized steel, the behavior is more complicated but it might be affected by the precipitation of TiC.
  • Mechanical Properties of TRIP Steels for Room Temperature Use

    pp. 1693-1704

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    TRIP steels (Transformation Induced Plastity) recently developed by V. F. ZACHAY, et al., have aroused a considerable interest because of a good combination of high strength, high ductility and high fracture tough-ness. This investigation is concerned with mechanical properties of TRIP steels for room temperature use having compositions of 0.25%C-2%Si-2%Mn-8%Cr-4%Mo as a base and its modifications. The results are as follows:
    (1) The steel with the basic composition is found to be excellent in the combination of strength, ductility and toughness and in corrosion resistance but to be inferior in delayed failure and notch fatigue properties.
    (2) In relations between processing and mechanical properties, cold working is more effective than subzero treatment to increase strength without losing ductility.
    (3) A partial substitution of Cr for Ni and Mo in the basic composition results in a little improvement in mechanical properties.
    (4) The mechanical properties of TRIP steels are closely related to their MD points and it is useful to apply a Ni equivalent shown below in the estimation the relation between mechanical properties and alloy-ing elements.
    Nieq=%Ni+0.65%Cr+0.98%Mo+1.05Mn+0.35%Si+1.26%C
  • Conjecture of Salamander Penetration into the Blast Furnace Hearth Refractories Using Infrared Camera

    pp. 1705-1717

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    The salamander penetration profile may be obtained by means of thermography (measurement of temperature distribution pattern) outside the blast furnace mantle using an infrared camera. There are two points in the study;(1) introduction of wear index ξ, (2) computer simulation of the process of penetration. In connection with a problem that the measuring condition is not constant during taking thermographs, ξ was introduced, which was so taken as to avert those changes of the condition in processing a quantitative analysis of obtained thermographs. Computer simulation was carried out on a process of salamander penetration, assuming a model of stress concentration in hearth refractory body. Changing two major parameters within the model, the computation turned out simulated penetration profiles and value of e. The latter was compared with the values of ξ obtained from measured thermographs. This procedure enables us to determine the above two parameters, and to estimate the salamander penetration profile. A good agreement was obtained beteeen the estimated salamander penetration profiles and results of destructive survey of hearth refractories after operation-down.
  • Estimation of the Japanese Standard Sample of Iron and Steel (JSS) for Instrumental Analysis by Photoelectric Emission Spectrochemical Analysis

    pp. 1718-1728

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  • Solid State Electrochemistry at High Temperature and Chemistry of Iron and Steel Making

    pp. 1729-1745

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  • 抄録

    pp. 1746-1750

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