Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Volume 77 , Issue 3
Showing 1-20 articles out of 20 articles from the selected issue
  • Yo TOMOTA
    1991 Volume 77 Issue 3 Pages 315-325
    Published: March 01, 1991
    Released: June 19, 2009
    JOURNALS FREE ACCESS
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  • Sumio SAKKA
    1991 Volume 77 Issue 3 Pages 326-335
    Published: March 01, 1991
    Released: June 19, 2009
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  • Shoji IKI
    1991 Volume 77 Issue 3 Pages 336-344
    Published: March 01, 1991
    Released: June 19, 2009
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  • Tsutomu TANAKA, Kohichi KURITA, Atsuhiko KURODA
    1991 Volume 77 Issue 3 Pages 345-352
    Published: March 01, 1991
    Released: May 07, 2010
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    For the better understanding of the phenomena in the cold crucible, advanced electromagnetic field models have been developed for both vertical and horizontal cross sections of the crucible. In the former model, the axi-symmetric sheet model was assumed and the influence of the number of slits was taken into account by the use of parameter representing the magnitude of the electromagnetic interaction. In the latter one, the conservation problem of the current density in a finite cell was successfully solved through the introduction of Newton method for the simultaneous convergence of both scalar and vector potentials. The validity of the models was confirmed through experimental measurements of the magnetic flux density, the coil voltage and the elevation height of the Al-Cu alloy melts.
    Regardless of the number of slits and the shape of the crucible, the induced current on the internal and external sheets of the crucible flows on the horizontal path. An increase in the number of slits resulted in the increase of the magnetic flux density. This is mainly explained by the reason that the partition ratio of the induced current into the segmented part of the crucible increases with the number of slits. Since the melt is expected to contact with the internal wall near the slit bottom in case of the straight type crucible, the solidification is preferable to be complete just above the bottom for the improvement of the ingot surface during continuous casting.
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  • Chao WANG, Jun HIRAMA, Tetsuya NAGASAKA, Shiro BAN-YA
    1991 Volume 77 Issue 3 Pages 353-360
    Published: March 01, 1991
    Released: June 19, 2009
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    Phase equilibria of Fe-S-C ternary melts have been studied to obtain the fundamental knowledges on the copper removal from liquid iron by FeS flux.
    Measurements were made to clarify the solubility of carbon and miscibility gap between iron and FeS melts at carbon saturation or unsaturation in Fe-S-C melts at temperature range from 1 473 to 1 873 K. Some thermodynamic considerations were tried by applying interstitial model. In order to determine the interaction parameter in Fe-C binary system, activity of iron in liquid Fe-C binary alloys was measured by the distribution of iron between liquid iron and silver.
    It was concluded that interstitial model was applicable to express thermodynamic relations in this system. By this model, phase diagram and iso-activity contour of constituents in Fe-S-C ternary melts were calculated.
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  • Shiro BAN-YA, Mitsutaka HINO, Atsushi SATO, Osamu TERAYAMA
    1991 Volume 77 Issue 3 Pages 361-368
    Published: March 01, 1991
    Released: June 19, 2009
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    Equilibrium oxygen, phosphorus and sulphur distribution between liquid iron and CaO-Al2O3-FetO slag saturated with CaO has been studied at the temperature range from 1 550 to 1 650°C in order to know the applicability of the slag to secondary refining of steel and the approximate validity of the regular solution model for the aluminate slag.
    As the results, it is guessed that CaO saturated CaO-Al-2O3-FetO slag would be useful the secondary refining of steel. It was confirmed that regular solution model was satisfied for oxygen distribution between liquid iron and aluminate slag as well as that between liquid iron and silicate or phosphate slag in our previous work. Sulphur distribution ratio and sulphide capacity of the aluminate slag were determined as the function of slag composition and temperature.
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  • Keiichi MAYA, Tohru MATSUO
    1991 Volume 77 Issue 3 Pages 369-376
    Published: March 01, 1991
    Released: June 19, 2009
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    Removal of chromium from molten steel is investigated with (CaO-MgO-MnO2)-(SiO2-Al2O3)-Fe2O3 flux in a laboratory scale test.
    By using the flux of about 50 kg/t, chromium 60 to 75% is removed from molten steel by oxidation refining, if (1)FeO activity is high, (2)slag basicity, (CaO + MgO + MnO)/(SiO2+ Al2O3) is 1.5 to 2.0, and (3)MgO is added to the flux as a component for accelerating removal of chromium.
    In addition, manganese loss in this treatment is suppressed, if (1)MnO2 is added to the flux or (2)carbon is added to the slag after removal of chromium.
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  • Han YETAO, Tadashi SAWADA, Masakazu KATO, Masamichi SANO
    1991 Volume 77 Issue 3 Pages 377-383
    Published: March 01, 1991
    Released: June 19, 2009
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    Kinetics of decarburization and oxygen absorption of molten iron of low carbon and oxygen concentrations has been studied. The decarburization and oxygen absorption experiments were performed by blowing Ar-O2 mixture (oxygen partial pressure 1.0×10-5<PO2(atm)<5.5×10-2 and gas-flow rate 1 000 (and 1 900) Ncm3/min) onto the melt surface. The rates of decarburization and oxygen absorption increase with increasing oxygen partial pressure ( PO2>1.0×10-2 atm). At oxygen partial pressures of PO2<1.0×10-4 atm, the oxygen concentration is kept almost constant. The total reaction rate of oxygen with the melt (=decarburization rate + oxygen absorption rate) is larger than the rate of oxygen absorption without decarburization and smaller than the rate calculated from a reaction model of oxygen diffusion in the gas phase. It is presumed that formation of oxide film on the melt surface has influence on the decarburization and oxygen absorption rates. A mathematical model is proposed to explain the rates of decarburization and oxygen absorption.
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  • Fujio ISHII, Shiro BAN-YA
    1991 Volume 77 Issue 3 Pages 384-390
    Published: March 01, 1991
    Released: June 19, 2009
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    The deoxidation of liquid nickel-copper and nickel-cobalt binary alloys with silicon has been studied at the temperatures ranging from 1 450°C to 1 650°C using silica crucible.
    On the nickel basis in nickel-copper binary, the deoxidation product, logK'Si(Ni-Cu), which increased with the addition of copper, was expressed to be :
    logK'Si(Ni)=logK'Si(Ni-Cu)+0.0342[%Cu]-0.0004[%Cu]2 Cu<40%, 0.5%Si, 1 550°C1 650°C.
    The effect of temperature on the equilibrium constants of the deoxidation reaction in copper, obtained by extrapolation, was estimated as follows :
    logKSi(Cu)=-15 680/T+2.16 1 450°C1 550°C
    while the value of logK'Si(Ni-Cu) on the copper basis was given by the expression :
    logK'Si(Ni-Cu)=logK'Si(Cu)+0.012[%Ni]-0.0001[%Ni]2 Ni<40%, 0.5%Si, 1 450°C1 550°C
    On the nickel basis in nickel-cobalt binary, logK'Si(Ni-Co) was represented to be as follows:
    logK'Si(Ni-Co)=logK'Si(Ni)+0.005[%Co] Co<20%, 0.55%Si, 1 550°C1 650°C
    The temperature dependence of the equilibrium constants for the deoxidation of cobalt was expressed to be:
    logK'Si(Co)=-15 270/T+1.81 1 550°C1 650°C
    whereas logK'Si(Ni-Co) on the cobalt basis was found to be :
    logK'Si(Ni-Co)=logK'Si(Co)-0.001[%Ni] Ni<60%, 0.55%Si, 1 550°C1 650°C
    Using the values of deoxidation product, the interaction parameters of various alloying elements were calculated.
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  • Akio IKESUE, Jhouki YOSHITOMI, Hiroshi SHIKANO
    1991 Volume 77 Issue 3 Pages 391-397
    Published: March 01, 1991
    Released: June 19, 2009
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    The chemical corrosion (static wearing condition ) and the mechamo-chemical corrosion (dynamic wearing condition) on magnesia-carbon refracrories were investigated by a high capacity induction furnace. In comparison with respective experiments, the specimens after dynamic wearing had large wearing rates and showed specific corrosion mechanism on microscopic observation. The corrosion resistance of specimen was determined by base material of refractories under static wearing condition. Through dynamic wearing condition, it was possible to mention that the corrosion resistance has influenced by both factors as base matetial and hot modulus of rupture.
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  • Noriaki USUKI, Akito SAKOTA, Shigeru WAKANO, Minoru NISHIHARA
    1991 Volume 77 Issue 3 Pages 398-405
    Published: March 01, 1991
    Released: June 19, 2009
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    The effects of titanium and manganese contents on the surface state and the phosphatability of cold rolled steel sheets have been investigated with ESCA and SEM analyses.
    The Mn-oxide and Ti-oxide are preferentially formed on the surface during annealing at 780°C in H2-N2 atmosphere. The surface concentration of Mn is three or four times as large as that of Ti on the 0.3 Mn-0.2 Ti added cold rolled steel sheet in this annealing condition.
    The bulk Ti and the surface Mn-oxide affect the phosphatability whereas the surface Ti-oxide of a few at% does not interfere the phosphating reaction. The bulk Ti is electrochemically oxidized to Ti-oxide during phosphating. This reaction, which is accompanied by the evolution of hydrogen, suppresses the precipitation of phosphate crystalline. On the other hand, the surface Mn-oxide is able to dissolve in phosphate solution, and this dissolution increases the pH of the solution, resulting in the acceleration of the phosphate film formation.
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  • Makoto NAKAZAWA, Minoru YONENO
    1991 Volume 77 Issue 3 Pages 406-413
    Published: March 01, 1991
    Released: June 19, 2009
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    The performance of the chromate conversion coatings applied on the electro-galvanized steel has been investigated in terms of the effects of phosphate and silica addition to the chromating solutions.
    It was found that in the presence of both additives, the chromate film exhibits clearer appearance, higher corrosion resistance, and better fingermarking resistance than when either additive is missing, while paint adhesion was not compatible with wet durability of adhesion even when the two additives coexisted.
    In order to optimize the dry and wet adhesion of the chromate to paint, the variations of the surface chemical properties and the performance of the chromate film with the changes in the amount of phosphate and/or silica addition were analyzed quantitatively. The hydrogen bonding component of surface tension was found to increase with increasing amount of silica addition because silica is polar and it segregates on the surface, and therefore, it resulted in improvement of dry adhesion and deterioration of wet adhesion. While the hydrogen bonding component once decreased with increasing phosphate addition due to the formation of chromium phosphate, but it was recovered when zinc phosphate began to be formed. The dry and wet adhesion was optimized when the surface contents of silica, zinc phosphate, and zinc chromate were balanced.
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  • Makoto NAKAZAWA, Minoru YONENO
    1991 Volume 77 Issue 3 Pages 414-421
    Published: March 01, 1991
    Released: June 19, 2009
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    In the previous papers, we examined the effects of phosphate and silica in chromate films on the performance of a chromate-treated electro-galvanized steels, and found that required properties except paint adhesion were improved by those elements. In this paper, we examined a small addition of water-soluble resin to phosphate-silica-chromate solution for improving the paint adhesion.
    It was found that the addition of resin less than 1.0mg/m2 enhances wet and dry adhesion of the paint remarkably, but adding an excess amount of resin deteriorates corrosion resistance of the chromate film.
    The role of the resin in the improvement of the paint adhesion was considered to be as follows ;
    The resin tends to be concentrated to the film surface and conceal polar elements such as silica and zinc phosphate. As a result, the hydrogen bonding force of surface tension of the chromate film is kept moderate, and the wet adhesion was improved. Instead, the dispersion force component of surface tension is increased by resin addition, which improves the dry paint adhesion.
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  • Tetsuo SOSHIRODA, Tsuyoshi INOUE
    1991 Volume 77 Issue 3 Pages 422-429
    Published: March 01, 1991
    Released: June 19, 2009
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    A CO2 continuous laser process was applied to Ni-5at%Cr-25at%Mo-6at%B alloy. The wear property was investigated under sliding wear conditions. The wear property was improved markedly by the laser treatment. The reason for this effect was explained by not only the high hardness of the laser treated layer but also the microstructure change by the laser treatment. The microstructure of the laser treated layer consisted of an f.c.c. Ni phase and an amorphous phase, and the good deformation ability of the amorphous phase brought about excellent wear property. Since the phase boundary between the f.c.c. and amorphous phases did not obstruct the deformation across those two phases, the wear property of the laser modified layer was superior to the non-treated one.
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  • Takashi FUKUDA, Mikio KUSUHASHI, Komei SUZUKI, Masanobu SATO, Yoshio U ...
    1991 Volume 77 Issue 3 Pages 430-437
    Published: March 01, 1991
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    Nuclear Reactor Pressure Vessel (RPV) suffers the neutron irradiation during operation, which results in preferential decrease of toughness in the internal side of RPV and generation of mechanical properties gradient through its wall thickness. It is expected that even if a crack initiates at the internal surface of such a RPV with gradient toughness under a hypothetical thermal transient, crack propagation will be arrested in the external portion of RPV where the higher toughness is maintained.
    In order to evaluate the crack arrest characteristics of RPV in laboratory scale, a steel plate with toughness gradient is needed. A 190 mm thick laminated steel plate has been successfully manufactured by hot roll bonding. As the results of mechanical tests on such a steel plate specimen, it is found that this three layer steel plate, can be regarded as a single integral material with toughness gradient through thickness and can be utilized satisfactorily as a testing material for evaluating crack arrest characteristics of RPV. It is also confirmed through the fracture test of this laminated steel plate that a running brittle crack is to be arrested at the layer with higher toughness.
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  • Yoshihiro OHKOMORI, Ikujirou KITAGAWA, Keigo SHINOZUKA, Toshiyuki TORI ...
    1991 Volume 77 Issue 3 Pages 438-445
    Published: March 01, 1991
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    The effects of nonmetallic inclusions and artificial corrosion pits on the fatigue strength of backup roll steel at two hardness levels are investigated. The crucial factors which control the fatigue strength of hard steels are the Vickers hardness (HV) and the square root of the projection area of inclusions or pits (√area). The fatigue strength prediction equation was proposed using HV and √area. The lower limit of large scatter in the fatigue strength was predicted by this equation using the maximum inclusion size, which is determined by the statistics of extreme values, and HV. The quantitative perspective to the reduction of maximum inclusion size in the steel making process was suggested on the basis of the prediction equation and the extreme value data. The proposed method was applied to a new backup roll steel with high fatigue resistance.
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  • Shohei HAMAI, Yukihiko SUGIURA
    1991 Volume 77 Issue 3 Pages 446-453
    Published: March 01, 1991
    Released: June 19, 2009
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    Ti-5Al-2.5Sn ELI alloy is one of the most promising cryogenic material whose use is expected to spread in near future. The alloy has been used for cryogenic application. But, cast parts are scarecely applied, and no data is available of mechanical properties of Ti-5Al-2.5Sn ELI cast material. Casting techniques is a part of the most important things to produce the complicated shapes and to save cost of titanium parts. The present work reports of the mechanical properties of the alloy tested both at room temperature and under cryogenic conditions. The materials were casted in rammed graphite mould and HIP'ed and heat treated under some conditions.
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  • Tomoyuki TAKEUCHI, Yoshio MONMA, Masao SAKAMOTO
    1991 Volume 77 Issue 3 Pages 454-461
    Published: March 01, 1991
    Released: June 19, 2009
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    A computer simulation system which calculates the high-temperature tensile deformation of austenitic stainless steel has been developed on the basis of a dislocation modeling. Plastic deformation by the external force is expressed by the flow of dislocations, and the load-deformation curves are computed as the reaction of material to a tensile testing machine. The formation of internal stress by work hardening and its recovery is represented by a cell structure model in which the framework is constructed by edge dislocation dipoles. The model also accounts for the temperature dependence of the effective stress by three types of dislocation motion ; free, pinning and dragging. The simulation system outputs computed curves of load-elongation and creep strain-time relation for the conventional tensile and creep tests. By selectiong suitable parameters in the model, the system is designed to allow us to predict the stress-strain and creep-rupture behavior of austenitic stainless steel. The model is so flexible that we can obtain good curve fitting to the experimental data of NRIM Creep Data Sheet.
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  • Zhou XU, Taku SAKAI
    1991 Volume 77 Issue 3 Pages 462-469
    Published: March 01, 1991
    Released: June 19, 2009
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    Effect of prior strain on the static softening taking place in hot deformed austenite was studied by means of interrupted tensile tests and metallographic observation. For this purpose a 0.15%C-1.5%Mn steel was deformed at a temperature of 1 133 K and a strain rate of 2×10-3s-1. The softening curve after dynamic recovery consists of two stages which can be controlled by classical recovery and recrystallization. By contrast, the softening curve after dynamic recrystallization (DRX) consists of three distinct stages accompanied, by three plateaus, and can not go to the full softening. These can be controlled by metadynamic recovery and recrystallization in addition to classical recovery and recrystallization. The softening ratio caused by each of the mechanisms can be roughly proportional to the volume fraction of DRX nuclei, growing DRX grains and strain hardened DRX grains. Metadynamically recovered grains which contain moderate dislocation density can exist stably at high temperature, leading to incomplete softening as well as relatively lower grain growth rate and relatively smaller grains.
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  • 1991 Volume 77 Issue 3 Pages N148
    Published: 1991
    Released: June 19, 2009
    JOURNALS FREE ACCESS
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