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

Tetsu-to-Hagané Vol. 67 (1981), No. 11

  • Productivity of the Japanese Iron and Steel Industry

    pp. 1867-1875

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  • Hydrogen Energy and Metallurgy

    pp. 1876-1886

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  • Computer Calculation of Phase Diagrams of Iron Alloys (1)

    pp. 1887-1898

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  • On the Recent Developments of Solid Electrolyte Sensors

    pp. 1899-1908

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  • Recent Approaches in Process Systems Control

    pp. 1909-1916

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  • Metallic Resources Series -Vanadium-

    pp. 1917-1924

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  • Hydrogen Reduction of Pulverized Iron Ore by High Pressure Fluidized Bed

    pp. 1925-1933

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    The pulverized iron are has been reduced by H2 with a batch type fluidized bed reactor of 60 mm I.D. The reduction pressure and temperature are 5-36 kg/cm2 and 700-900°C, respectively. On the basis of the experimental results obtained at 700°C, the effects of pressure and gas velocity on the reduction rate have been analyzed according to the bubbling bed model. In the region of the partial reduction between 0 and 70%, the experimental result can be explained well by the present analysis.
    The analytical results are summarized as follows:
    (1) When the pressure is increased at the constant gas velocity, the reduction rate increases linearly with the pressure, independently of whether the gas supply determines the over-all rate or not.
    (2) When the gas velocity is increased at the constant pressure, the increase proportion of the reduction rate decreases with the increase of the gas velocity.
    (3) When the pressure is increased at the constant gas flow rate at the standard temperature and pressure, the reduction rate increases exponentially with the pressure, but the increase of the reduction rate saturates as the gas supply approaches the rate determining stage.
  • Influence of Pore Structure in Coke on the CO and NO Formation during Coke Combustion

    pp. 1934-1942

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    Two types of coke samples, being different in pore structure, were prepared as follows:
    a) Pulverized coke was moulded to the desired rectangular shape after mixed with inorganic binder. This sample maintained the almost same pore structure as the packed column of pulverized particles.
    b) The sample cut from lumpy coke was held in the stream of CO2/N2 mixed gas at 1 200°C until carbon in coke was consumed to the required amount. Innumerable small hollows were made on the wall surface of the tubular pores.
    The former aggregate sample was most effective for decreasing the NO formation. As to the latter samples, NO formation was reduced with increasing the porosity of the sample. The blockage of the outer pores with fine incombustible particles was not desirable. Absorption of KOH showed the good effect on the elimination of NO when the combustion temperature rose.
    The analytical results of the conversion ratio of organic nitrogen to NO indicated that most of nitrogen oxides were formed inside of the outer surface in the case of porous samples, namely in pores. High CO/O2 atmosphere was considered to be produced there and to be brought to the decrease of NO formation.
  • Experimental Study of the Resistance Due to the Rate of Gas Flow on the Reduction of an Iron Oxide Pellet

    pp. 1943-1951

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    Single basic hematite-pellets (porosity 24%) are reduced in two reactors of 54 and 156 mm I.D. over a temperature range from 600° to 1 000°C and a flow-rate range 0.1 to 20 Nl/min. In the initial stage of reduction, hydrogen is diluted by nitrogen which flows through a reactor until it reaches a set temperature, and the reaction retards especially at low flow rates. In the course of reduction, hydrogen is also diluted by the product gas (H2O). For these dilution processes, the dispersion model has been introduced into the unreacted-core shrinking model for one interface in consideration of the resistance due to the rate of gas flow proposed by Clair.
    Contribution of this resistance, denoted by κ (0≤κ≤1, κ=0 and 1 imply the analyses without and with the resistance proposed by Clair, respectively), is examined by comparing calculated reduction curves with experimental ones: The value of κ increases as the flow rate decreases. With appropriate selection of kinetic constants, the modified model produces a greatly improved fit to experimental data.
  • Mass Spectrometric Study of the Thermodynamic Properties of Liquid Fe-Sn, Fe-Sn-Cu Alloys

    pp. 1952-1961

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    The activities, interaction parameter and partial molar heats of solution in the Fe-Sn system at 1 550 and 1 600°C and the interaction parameter in the Fe-Sn-Cu system at 1 560-1 610°C have been determined by use of the combination of a mass spectrometer and a Knudsen-cell. The liquid miscibility gap in the Fe-Sn system is not observed in this study in the temperature range from 1 550 to 1 610°C. The ion current ratios for the alloy components are measured from 1 200 to 1 610°C, the concentration of tin Nsnbeing kept 0.50, and the temperature of critical mixing is determined to be about 1 505°C.
    The obtained thermodynamic quantities are as follows:
    The Fe-Sn system;
    1 600°C:γ°Sn=2.58, γ°Fe=4.86
    1 550°C:γ°Sn=2.68, γ°Fe=5.00
    1 600°C:εSnSn=-0.29±0.06
    The Fe-Sn-Cu system;
    1 560-1 610°C:εCuSn=-42 500/T+16.27(±0.04)
  • Development of Low Carbon-Niobium Steel with Ultra-deep Drawability

    pp. 1962-1971

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    A study has been made to develop deep-drawing sheet steel which can be produced by continuous annealing as well as box annealing, giving clean surface free from inclusions and orange peel-free surface in deeply drawn condition. To develop this type of steel, the following matters have been taken into consideration : (i) To obtain high ductility as well as favorable texture, ultra low carbon steel is adopted. (ii) Carbide-forming elements are added to fix interstitial carbon and nitrogen and whereby to obtain nonageing properties. (iii) To achieve clean sheet surface and avoid hardening the amount of alloying element is reduced as small as possible. (iv) Not all interstitial C and N do not precipitate by the addition of carbide-forming element. N is fixed as AIN by adding Al, which, in turn, together with carbides provide for the nucleation sites for the precipitation of remained free C. Ultra low carbon, niobium steel with Nb to C ratio of 1 in atomic weight is found to possess excellent properties. It shows high Lankford value, low yield, but relatively high tensile strength. The excellent properties are obtained in continuously annealed condition as well as box-annealed one.
  • Numerical Method for Violent Change of Temperature and Application to a Simple Model

    pp. 1972-1980

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    Synopsis:
    In order to improve the accuracy and computing time of the numerical simulation for a heat transfer problem where the rate of temperature change is extremely high, the authors have developed a unique method which is proposed in this paper.
    The method, for a non-steady heat transfer equation, has a distinctive feature that two fundamental equations on the heat transfer phenomena, that is,
    q=-λgradθ,
    and
    ∂θ/∂t=-1/ρc div q
    are utilized respectively in computation. In this way, it mainly becomes much easier to determine the increment time of computing cycle, Δt which considerably affects to the accuracy as well as computing time of the numerical simulation.
    The detail of the method and discussion on results of some simulations are described here.
  • Formation and Composition of π-phase Nitride in a High Chromium-high Nickel Austenitic Steel Containing 0.4% Nitrogen

    pp. 1981-1989

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    The microstructural change in a 25%Cr-28%Ni-0.4%N austenitic stainless steel during aging at 800 °C for up to 10 000 h was studied by means of optical microscopy and lattice parameter measurement. A dichromium nitride, Cr2N, precipitated at an earlier stage of aging both as intergranular precipitation and as cellular precipitation. Further aging caused π phase (a nitride with the structure of β-manganese type) precipitation, accompanied by redissolution of Cr2N. A nitride transformation from Cr2N to π phase started at 100 h and completed after 10 000 h aging in solution specimens without prior cold deformation. Cold rolling prior to aging accelerated the nitride reaction. A coarse dispersion of Cr2N produced by aging at 900°C retarded considerably the nitride reaction at 800°C. The chemical composition of the π phase formed after 10 000 h aging was determined to be Cr12(Ni0.5Fe0.4Cr0.1)8N4. The solubility of nitrogen corresponding to Cr2N and π phase was 0.15 and 0.125 wt%, respectively, in this austenitic steel at 800°C.
  • Characteristics of Precipitates and Austenite Grain Growth in Nb and Ti Bearing High Strength Steels

    pp. 1990-1999

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    A relation between austenite grain growth and characteristics of precipitates formed has been studied in the steels containing Nb and Ti.
    Ti supresses austenite grain growth more remarkably than Nb. It was demonstrated, however, that such a powerful effect of Ti was reduced by simultaneous addition of Nb at the temperatures up to 1 250°C. X-ray analysis revealed that under these situations, two kinds of precipitate compounds were formed at the same time, that is, one is (Ti, Nb)N where Nb is dissolved in TiN, another is (Nb, Ti)C where Ti is dissolved in NbC. Electron micrographs, however, indicated that there existed little fine cubic precipitates characteristic of (Ti, Nb)N, but only large grobular ones. So, it was speculated that the coalescence of (Ti, Nb)N and (Nb, Ti)C took place. Furthermore, the amount of (Ti, Nb)N unexpectedly decreased with decreasing temperature below about 1 250°C. This is owing to the increase of(Nb, Ti)C which causes short of Ti to form (Ti, Nb)N.
    It has been concluded that larger austenite grains of Nb and Ti bearing steels can be attributed to the reduction of (Ti, Nb)N and the presence of larger grobular precipitates.
  • The Effect of Temperature, Strain Rate, and Carbon Content on Hot Deformation of Carbon Steels

    pp. 2000-2009

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    High temperature tensile deformation of carbon steels containing from 0.036 to 1.09 wt% C was studied in the temperature range 873 to 1 373 K over a wide range of strain rates between 1 and 10-5 s-1. The shape of true stress-true strain (σ-ε) curves in the austenite (γ) range is expressed solely in terms of the first stress peak (σp) or Z in the following equation, and the relation is almost independent of C content. σp can be correlated with temperature (T) and strain rate (ε) by the following equation in the range of stresses below 110420 MPa;
    Z=ε·exp(Q/RT)=A·σmp
    in which A, m, and Q decrease with C content. The activation energies for deformation (Q) are nearly the same as those for self-diffusion. These results being almost the same as those of 0.16% C steel reported previously8)9), it is concluded that the high temperature deformation of carbon steels in the γ range is controlled by the dynamic recrystallization process assisted by the diffusion of vacancy.
    σp in the γ range decreases with C content in the whole range of Z used. This solid solution softening is considered to be attributed to the enhanced dynamic recrystallization process caused by increased diffusivity of vacancy due to the addition of C in the γ range.
    The flow stress maximum (α; ferrite) or the first stress peak (γ), σp, of mild steel (or iron) changes discontinuously near the A3 point, and σp at a Z is always larger in the γ range than in the α range. This is considered to be attributed to the differences of vacancy diffusivity and of the dynamic restoration process (i.e., recrystallization in the γ and recovery in the α) which may be caused by the difference in the stacking fault energy.
    The flow stress in the initial work hardening region (σε) is larger in the γ range than in the α range in the lower Z, but σε in the both ranges can be expected to become equal with an increase in Z. This is caused by the difference of strain hardening behavior in the both ranges and the lower strain rate (or Z) dependence of σε in the γ range.
  • Tensile and Impact Properties of 25Mn-5Cr-1Ni Austenitic Steel at Liquid Helium Temperature

    pp. 2010-2018

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    In order to examine the applicability of the 25Mn-5Cr-1Ni austenitic steel at cryogenic services, the tensile and impact properties of the steel were investigated at liquid helium temperature, and were compared with those of a typical austenitic stainless steel, SUS 304. The 25Mn-5Cr-1Ni steel exhibited, 0.2%proof stress (PS) of 103.5 kgf/mm2, tensile strength (TS) of 183.3 kgf/mm2 and elongation (El) of 31.4% in tensile test, and impact energy absorption (vE) of 12 kg-m and lateral expansion (LE) of 1.0 mm in Charpy impact test. Pestrained and aged specimen also showed good toughness. The austenite phase in the steel was stable through the testing carried out in this work. 0.2% PS of the steel was approximately twice as high as that of SUS 304 and depended extremely on temperature; it increased with lowering temperatures. This can be considered due to the solid solution hardening of matrix by carbon, nitrogen etc., and also the grain refinement resulting from niobium addition. The discontinuity of the first stage in the plastic deformation region of the load-displacement curve was considered to be resulted from slip by extended dislocation with stacking faults. It was suggested that the serration of the following stage resulted from the formation and disappearance of the deformation twin and ε phase. The rate of deformation hardening was not large in this case. High TS of SUS 304 was considered to be due to the deformation hardening followed by the deformation induced martensite transformation.Both steels showed equally high dependence of TS on temperature. vE and LE decreased with lowering temperature. Nevertheless, the toughness of the 25Mn-5Cr-1Ni steel was kept high at liquid helium temperature, due to the stable austenite phase without any sign of martensite transformation. From the above results, it was shown that the 25Mn-5Cr-1Ni steel was applicable to cryogenic service.
  • Stress Corrosion Cracking at the Weldments of 18-8 Austenitic Stainless Steels in High Temperature Deionized Water

    pp. 2019-2028

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    Stress corrosion cracking (SCC) behavior of several commercial 18-8 stainless steels (SUS 304, 304L, 304ELC, 321, and 347) in high temperature deionized water, has been studied in connection with microstructures on the welded joints with various heat inputs using double U-bend specimens. The influence of cooling time and prestrain at the welding on SCC was also investigated on SUS 304 heat treated to simulate the welding thermal cycle. Besides, the correlation between the susceptibility to intergranular stress corrosion cracking (IGSCC) and the susceptibility to intergranular corrosion in the Strauss solution was investigated on the weldments of these steels.
    Both deep IGSCC and shallow transgranular stress corrosion cracking (TGSCC) were recognized. The IGSCC was observed in the heat affected zone of SUS 304 weldment with high heat input (Ca. 25 000 Joule/cm) and SUS 321 weldment with any heat input (10 00025 000 Joule/cm). Although the weldments of SUS 304L, 304ELC, and 347 were immume to IGSCC, they were susceptible to TGSCC. It was concluded that reducing the carbon content in steel was most beneficial to prevent the IGSCC irrespective of non-stabilized and stabilized steel but this was not an effective means to prevent the TGSCC in high temperature deionized water.
  • Oxidation of Fe-Ni Alloys at High Temperatures

    pp. 2029-2038

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    The oxidation of five Ni-Fe alloys with Ni of 5-50% has been studied in air at 8001 300°C for 15120 min. The scales consisted of the external scale and the subscale.
    The external scales had stratified structures of either α-Fe2O3/Fe3O4 or α-Fe2O3/Fe3O4/(FeO+Fe3O4), depending on the conditions such as the nickel contents in the alloy, the oxidation temperature and the time of exposure. Their thicknesses decreased with increasing nickel contents in the alloys. FeO grew with a characteristic shape in the scales of the 530% Ni alloys oxidized at 1 0001 200°C.
    The subscales consisted of the metal/oxide mixed zone and the intergranular attacked zone. Morphological studies showed that the subscale was formed by the very local oxidation at the grain boundaries and at the alloy/mixed zone interface. Both zones grew according to the parabolic rate law. The effect of nickel contents in the alloy on the subscale growth rate was studied.
    On the basis of the above results, the aspects of the oxidation of Fe-Ni alloys were discussed.
  • Quantitative Phase Analysis in Textured Steels by Continuous X-ray Diffraction Method with Energy Analysis System

    pp. 2039-2048

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    X-ray diffraction method is widely used for determining the relative proportions of phases in a multiphase steel specimen. However, the intensities of the particular reflections are influenced by the preferred orientations and it is necessary to use an appropriate method in order to get accurate results when the specimen has preferred orientations in one or more of constituent phases. The continuous X-ray diffraction method with energy analysis system is presented here, in order to determine the volume fractions of α(or α')and γ phases by adequately averaging the intensities of diffraction lines belonging to a large number of diffraction planes with different hkl. The method, so far, has not been investigated for the quantitative phase analysis in textured steels. Results obtained by the method were compared with those obtained by the characteristic X-ray method. The results are as follows: (1) The volume fraction of phases in twophase synthetic speciments and two-phase stainless steel determined by the continuous X-ray diffraction method agree well with the one by the other methods, and the present method gives a rapid measurement. The determination of volume fractions by the present method, however, is less accurate than the monochromatic one. (2) This continuous X-ray diffraction method is applied to determine the depth-composition profile for the volume fraction of strain induced martensite in cold-worked tube of stainless steel, SUS 304.
  • 日本の研究費(その1)主要国との比較/日本の研究費(その2)主要国の研究費の対国民所得比の推移/日本の研究費(その3)研究費に対する技術導入額の比率の推移/80年代に発展,派生が期待される新たな産業分野

    pp. 2053-2053,2057

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  • 過剰品質の功罪

    pp. 2054-2057

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  • 抄録

    pp. 2063-2070

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