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

Tetsu-to-Hagané Vol. 85 (1999), No. 3

  • Equilibrium between Aluminum and Oxygen in Fe-36%Ni Alloy and Liquid Iron at 1973K

    pp. 201-207

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    The deoxidation equilibrium for aluminum in liquid iron and Fe-36%Ni alloy were carried out under pressure controlled H2/H2O gas at 1973K.
    Within the composition range of [%O]<0.008 and [%Al]<0.018, the values for the interaction parameter between aluminum and oxygen in liquid iron and Fe-36%Ni alloy were determined as -9.5±5.9 and -26.2±8.7, respectively. The values of the equilibrium constant for the deoxidation reaction:
    Al2O3(s)=2Al(1 wt% in metal)+3O(1 wt% in metal)
    for liquid iron and Fe-36%Ni alloy were obtained to be -12.5±0.3 and -12.6±0.3 in logarithmic scale, respectively.
  • Formation Behavior of Iron Carbide Pellet with H2-CO Gas Mixture Including Small Amounts of H2S Gas

    pp. 208-215

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    Using a thermobalance, a hematite pellet was reacted with H2-CO mixtures at 9731073K to produce an iron carbide pellet. H2S of low pressures unable to form FeS was added to the mixtures. First, reduction of iron oxides proceeded and then carbidization of metallic iron occurred. Small amounts of H2S in gas led to iron carbides (Fe3C, Orthorhombic) with complete conversion rather than free carbon or metallic iron as final products. In later stage of carbidization, higher iron carbide (Fe2.5C, Monoclinic) appeared partially in lower temperatures. The conditions of higher temperature and low sulfur pressure provided high quality iron carbides having nearly less than 0.03 mass% S. The tests without H2S provided lower iron carbide contents with much free carbon or metallic iron. Carbidization rates of a reduced iron pellet were analysed by an unreacted core model to investigate this process. The carbidization proceeded more rapidly in lower temperatures.
  • Technologies for Producing the Ultra Low Carbon and Nitrogen Steel in RH Degasser

    pp. 216-220

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    Experimental and theoretical studies were carried out to understand the behavior of carbon content and nitrogen content during RH treatment.
    A new model for decarburization was developed to estimate the decarburization rate and to predict the carbon content. This model clarified the effects of carbon content, oxygen content, argon gas flow rate, the pressure in the vessel and the cross section area of the vessel on the decarburizaion rate. With helium detection, it was found that air invaded in molten steel through the down leg snorkel. A new snorkel with argon sealed protected the air suction, and it made possible to produce the ultra low nitrogen steel.
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    Readers Who Read This Article Also Read

    1. Development of Refining Process for Production of High Purity Ultra-low-carbon Steel Tetsu-to-Hagané Vol.76(1990), No.11
    2. Mathematical Model for Decarburization Process in RH Refining Process ISIJ International Vol.54(2014), No.7
    3. Mechanism of Decarburization in RH Degasser ISIJ International Vol.35(1995), No.12
  • The Characteristics of Spectral Radiation of the Small Size Blackbody

    pp. 221-228

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    Concerning about the thermal radiation, either theoretically or practically, the basis is the blackbody (full-radiator). The blackbody is an ideal body, and practically, an artificial blackbody i.e. blackbody furnace is made and used. Graphite used in the existing blackbody is oxidized, exhausted, and deformed on heated in the atmosphere, and it was necessary to heat up in the controlled atmosphere like nitrogen.
    In recent years, silicon carbide (SiC), silicon nitride (Si3N4), inconel, nickel, stainless steel etc. are used as blackbody materials which can be heated in the atmosphere. But a blackbody whose spectral emissivity is a little less than 1 is large in scale.
    This study is carried to develop a simple and small sized blackbody which can be heated in the atmosphere and has the traceability of the thermal radiation pyrometer or can be used as the thermal radiation pyrometer traceability. The blackbody is spherical and made of SiC, and the diameter of their aperture should be more than 20 mm. Spectral emissivity of the blackbody depends on the ratio of the diameter of the sphere D to the radius of the aperture r, i.e. the aperture ratio D/r. Thus three types of blackbody whose aperture ratio D/r is 150 mm/15 mm (=10), 90 mm/ 10 mm (=9), and 60 mm/10 mm (=6), respectively, are manufactured.
    Then we compare the characteristics of spectral radiation of this three types under the condition that the temperature range is 1000-1200°C and the wavelength region is 0.38-0.76 μm.
  • Longitudinal Cracking in Metastable Austenitic Stainless Steels during Cold Drawing

    pp. 229-235

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    Cracking parallel to the wire axis (longitudinal cracking) occurs during or after the drawing of metastable austenitic stainless steel wires. In this paper, the mechanism of cracking was investigated in relation to the behavior of deformation induced martensitic transformation, hydrogen content and residual stress in the steel wires drawn under different several conditions. Results obtained are as follows:
    (1) Martensite formed through deformation induced transformation is of lath-structure, but the lath-structure is broken and changed to dislocation cell structure during heavy drawing, which is characterized with the poor ductility.
    (2) Microcracks are formed around inclusions and carbide particles which are just in the heavily deformed martensite with dislocation cell structure. This leads to the cracking parallel to the wire axis.
    (3) Such a cracking occurs not only during drawing but also during aging at room temperature after drawing with the asist of residual stress and diffusive hydrogen.
    (4) Main reason for the cracking is thought to be stress concentration at inclusions and carbide particles which results in the formation of microcracks, and the structural change of martensite, existence of hydrogen and residual stress are secondary factors which promote the crack initiation.
  • Effect of Annealing Temperature on Adhesion of Polyester Film to Electrolytically Chromium Coated Steel

    pp. 236-240

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    Recently, Electrolytically Chromium Coated Steel (ECCS) laminated with biaxially oriented polyester films has been applied to container materials. These laminated materials for containers are usually subjected to heat treatments under dry and wet conditions in the can-making and filling processes. Sufficient adhesion of polyester film to ECCS is essential even under these severe conditions to fulfilling the required properties as a container material.
    In this paper we studied effects of annealing temperature between 50°C and 240°C on the adhesion of a polyethylene terephthalate (PET) film and a copolymerized ethylene terephthalate/isophthalate (PET/I) film to ECCS in connection with structural changes of the polyester. The adhesivity was evaluated by T-peel tests, and the properties of polyester were evaluated by density measurements, molecular weight and dynamic viscoelastic spectroscopy. The adhesivity of both the films related with crystallization and thermal degradation of polyester by annealing. The PET/I film showed better adhesivity than the PET film after annealing at temperatures between 160°C and 180°C, because the PET/I film has the more relaxed amorphous phase than the PET film in this temperature range, which exhibits a higher degree of an amorphous state.
  • Precipitation and Growth of γ″ Phase in a Ni-22Cr-9Mo-5Fe-4Nb Superalloy

    pp. 241-248

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    Hardening behavior due to precipitation of a Ni3Nb(γ″) phase during aging was experimentally studied for a Ni-22Cr-9Mo-5Fe-4Nb alloy. The alloy was homogenized at 1373K for 3.6ks and then quenched in water. The homogenized alloy was aged at temperatures between 894 and 1073K for up to 720ks. The aging was also carried out at 893 to 1033K for up to 720ks for the alloys cold rolled with reductions of 4, 10, 30 and 50% after the homogenization. The micro Vickers (MV) hardness test was made for the aged specimens. The microstructures of the specimens were observed by transmission electron microscopy (TEM).
    For the specimens without cold rolling, the MV hardness monotonically increases with increasing aging time at 893, 943 and 1073K. On the other hand, the MV hardness increases with increasing aging time and then reaches the maximum values at 36 and 72ks at 993 and 1033K, respectively. In the specimens with the maximum values of the MV hardness, disk-like γ″ precipitates with diameters of 30 to 35nm were observed in a γ matrix. Coarsening of the γ″ phase seems to obey the Ostwald ripening mechanism. The activation enthalpy for the coarsening was obtained to be 418kJ/mol. For the specimens with cold rolling, over-aging is rather restrained due to fine γ″ particles precipitated along dislocations.
  • Experimental Examination of the Validity of the Model for Predicting Ms, Temperature for Martensitic Stainless Steels

    pp. 249-254

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    Comparisons between the experimentally measured Ms and the calculated Ms temperatures for eleven martensitic stainless steels were performed on the basis of conventional models.
    Empirical formulae for the calculation of Ms temperature do not show enough ability to predict the Ms temperature of all martensitic stainless steels, i.e. available alloying elements and their composition ranges are restricted. While, the Ghosh and Olson model for the prediction of Ms temperature is shown to be reasonably good in estimating the Ms temperature for martensitic stainless steels except some conditions.
  • Stress Relaxation Behavior of SUS630 Stainless Steel at Room Temperature

    pp. 255-260

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    Creep and stress relaxation behavior at room temperature has been investigated for 17-4 PH martensitic stainless steel (SUS630: 17Cr-4Ni-3Cu-Nb) in comparison with a high-strength carbon steel for F10T high-tension bolts. Both steels showed creep strain at stresses around the 0.2% proof stress, and the creep curves followed a logarithmic creep law. Though the 0.2% proof stresses were almost the same, the creep strain of SUS630, which was precipitation hardened, was lower than that of F10T carbon steel. From the stress relaxation tests, it was confirmed that the stress relaxation property of SUS630 was superior because of the lower stress relaxation values at the same initial stress. The observed stress relaxation curves were compared with the ones predicted from the creep data by the time hardening theory and strain hardening theory. Though the calculated values of the stress relaxation from the creep data was consistent with the measured values at lower stresses below 800 MPa, the calculated values became larger at higher stresses. Since the deviation mainly occured at an early stage of the stress relaxation test, it was atributable to the difference in the velocity of loading before the tests.
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    Readers Who Read This Article Also Read

    1. Room Temperature Creep Behavior of Stainless Steels Tetsu-to-Hagané Vol.79(1993), No.1
    2. Effect of Strain Rates on Strength of Sheet Steels Tetsu-to-Hagané Vol.83(1997), No.11
    3. Relationship between Room Temperature Creep Behavior and Yield Strength in Austenitic Stainless Steels Tetsu-to-Hagané Vol.80(1994), No.2
  • Fracture Toughness Improvement Mechanism of Calcium Treated Steel

    pp. 261-268

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    The effect of Ca addition on fracture toughness has been examined by means of the analysis of fracture mechanics and tensile tests together with micro-structural observation. The Ca addition results in the spheroidization and reduction of the number of non-metallic inclusions, while the matrix structure does not show significant changes. Fracture mechanics test in terms of J-integral using a three point bending test shows the increase in the slope of the R-curve, indicating enhanced increase in the stable crack growth resistance. The dimple morphology on the ductile fracture surface is classified into two types, i.e. primary and secondary dimples. By Ca addition, the depth of the primary dimple and local shear area on the fracture surface increase. It implies that Ca addition causes increased local plastic deformation in the course of stable crack extension, resulting in the improvement of fracture toughness. On the other hand, effect of Ca addition does not appear in tensile test. It suggests that the effect of micro-structural factors on mechanical properties depends on the testing methods.
  • Some Characteristics of Creep Behavior in High Nitrogen 9Cr-2Co Steels

    pp. 269-275

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    Constant load creep tests have been conducted at 873K under an initial stress from 50 to 70MPa for 9Cr-2Co steels containing 0.06, 0.11, 0.16 or 0.19 mass% nitrogen. An increase of nitrogen concentration decreases creep rate and increases rupture life. Except for an early and a final stage of creep, the logarithm of creep rate ε was expressed as a linear function of strain in the form;
    lnε=lnε0+lnΩε,
    where ε0is imaginary initial strain rate and Ω is strain acceleration factor defined in the text, respectively. The stress dependence of ε0 was expressed by nth power of applied stress. The stress exponent, n decreased gradually with an increase in nitrogen concentration from 5.0 to 3.9. It was found that the linear-type primary creep appeared in some creep conditions. An analysis based on the concept of threshold stress and the formation of solute atmosphere consisting of nitrogen-chromium atom pair revealed semi-quantitatively that dislocations move in a viscous manner dragging solute atmospheres behind them in creep deformation of the present high nitrogen ferritic steels.
  • A Study of the Managerial Environment Evaluation in the East Asian Area and the Overseas Expansion of Japanese Steel Industry

    pp. 276-281

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    After it comes in the 90's, our country manufacture industries is increasing the amount of investment directly to the East Asian countries which continues the high growth. The inactivity of the rapid strong yen and the demand for a country can be given as this background. The economic confusion of ASEAN (the Association of Southeast Asian Nations) countries is a topic at present due to the fall of the Asian currency.
    However, after it has the economic growth which is still latently high, a Yen rate against the Asian currency is strong further in the East Asian countries. Therefore, the direct investment of advanced Japanese manufacture companies to the East Asian countries is thought to last from now on, too. The inside of such investment conditions put a focus on the investment movement and the plant investment directly of the steel industry, and an analysis was done by this research.
    At first, We calculated quantitatively a change in the management environment of each Asian country using AHP (Analytical Hierarchy Process), and next we estimated the scale to which the local corporation of each country could expand. Furthermore, a consideration was done about the production facilities of investing the Japanese steel industries, in consideration of the conditions of the production technology that each country possesses it.
  • Remote Experiment for the Design of Ni-base Superalloys Using Broadband Research Network

    pp. 282-287

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    An integrated materials research information system for Ni-base superalloys design, which consists of a characterization simulator, a data base, and a remote experimental system using MPEG1 tool and TV conference tool, has newly been developed. The goal of this system is to develop new alloys and to elucidate some phenomena occurring in the material field efficiently. In order to test the real performance of the system, the proof examination was carried out among National Research Institute for Metals (NRIM), Japan Science and Technology Corporation (JST) and Michigan State University (MSU) by using an exclusive broadband network of 45 Mbps. As a result, it has been proved that the real-time moving picture transfer system, the basic function of the remote experiment system, is eligible to the practical use for transferring ordinary moving pictures in the material field. It has also been found that the transfer rate has strongly depended on the machine performance of the receiving site rather than the network performance. This system may provide worldwide research environment for the promotion of design, development and evaluation of novel materials by accessing the alloy design program, evaluator and testing devices on the Web.

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