Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Volume 87 , Issue 4
Showing 1-6 articles out of 6 articles from the selected issue
  • Takehiko KUMAGAI, Manabu IGUCHI
    2001 Volume 87 Issue 4 Pages 159-166
    Published: April 01, 2001
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    As a fundamental study on the dissolution process of gas into molten metal, a model experiment was done to reveal the effects of liquid flow velocity and turbulence intensity near a gas-liquid interface on the mass transfer coefficient from gas phase. To obtain the mass transfer coefficient, the dissolution rate of CO2 gas into water was measured by using a lance under several flow conditions of different flow velocities and different turbulence intensities. On the basis of the present experimental results, an empirical correlation for the mass transfer coefficient was proposed as a function of the turbulence intensity in addition to the usually used Reynolds number and Schmidt number. Another correlation for the mass transfer coefficient under stagnant conditions was proposed as a function of the diffusion coefficient of CO2 gas into water.
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  • Masafumi MORISHITA, Masahiko KOGITA, Takehiro NAKAOKA, Toshiya MIYAKE
    2001 Volume 87 Issue 4 Pages 167-174
    Published: April 01, 2001
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    An electromagnetic brake (EMBR) has been developed in order to reduce non-metallic inclusions in slab by means of reducing downward molten steel flow in a continuous casting machine. However, it was reported that the conventional EMBR, which imposes static magnetic field parallel to slab thickness direction, had a problem that the non-metallic inclusions in the vicinity of width edges werenot effectively reduced, especially when the slab width was small. The reason is considered that the electromagnetic force is not strong enough to prevent the downward flow from carrying the inclusions deep into the strand in the vicinity of the width edges, though the downward flow velocity is highest in the region. The force in the region is weak because electric current parallel to the slab width direction is small.
    In this study, a new EMBR, which imposes static magnetic field parallel to slab width direction, has been proposed as a countermeasure for the reported problem. By computer simulations and model experiments using liquid gallium, it was demonstrated that the new EMBR suppressed the downward flow more effectively than the conventional. The region where the downward velocity was high was extinguished. By using the new EMBR, upward electromagnetic force induced by the magnetic field parallel to slab width direction and the electric current parallel to slab thickness direction brakes the downward flow effectively in the vicinity of the width edges.
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  • Hiroyuki IWASHITA, Shun-ichi MORITA, Atsuo TANAKA
    2001 Volume 87 Issue 4 Pages 175-182
    Published: April 01, 2001
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    Polyester film laminated steel for can container will gradually replace lacquer coated steel sheet from environmental concern and cost consideration. The process of lamination is characterized by partial melting of the film on the surface of steel during lamination by pressing the supplied films between both sides of heated steel and a couple of cooled rubber rolls. Various characteristics of film laminated steel for can use are strongly influenced by the degree of biaxial orientation and the thickness of amorphous layer of the laminated film, and the characteristics are greatly influenced by several laminating conditions.
    Therefore, this report deals with the result of numerical analysis applied to characterize heat transfer in laminating process, in order to estimate the variation of orientation of the laminated film. From the result of numerical analysis, we found that the cross-sectional temperature distribution in roll nip greatly changes within extremely short time, and the distribution contributes to the formation of double layered structure of amorphous and biaxially oriented layers.
    Moreover, it was found important to form the double layered structure of the laminated film by keeping an appropriate temperature profile of film in roll nip. The thickness of amorphous layer with the numerical analysis obtained by the cross-sectional variation of maximum temperature of film in the roll nip agrees well with the one observed by polarizing microscope. The estimation of the thickness of amorphous layer was found possible by this method with a good accuracy.
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  • Yukio INOKUTI
    2001 Volume 87 Issue 4 Pages 183-189
    Published: April 01, 2001
    Released: January 18, 2010
    JOURNALS FREE ACCESS
    The texture formation of very thin (0.05 μm) TiN, TiCN and TiC films at the incipient stage during plasma coating of (011)[100] single crystals of silicon steel was investigated using the electron back scattering diffraction (EBSD) method, and that of 1.0 μm was measured using the solid state detector (SSD) auto pole figure apparatus. These ceramic films were also measured using the grow discharge spectroscopy (GDS).
    The orientation of very thin TiN film parallel to the normal direction (ND) exhibited separate (111) and (100) colonies of about 20-30 μm areas with low angles, whereas that to the rolling direction (RD) also exhibited separate <111> and <110> colonies.
    In contrast, the orientation of very thin TiCN and TiC films parallel to the ND and the RD was randam as evidenced by the black color areas which detected no orientation and high angles due to the existence of large strain etc. Black color area of TiC was larger than that of TiCN.
    1.0 μm thick TiN film exhibited a high {111} pole intensity and a good misfit, whereas TiCN and TiC films exhibited weaker {111} pole intensities and poor misfits in the order of TiCN, TiC.
    It should be noted that the smaller misfits of ceramic films and single crystals of silicon steel makes colonies coherent to the ND or the RD orientation at the incipient stage during plasma coating.
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  • Masaharu UEDA, Koichi UCHINO, Takehide SENUMA
    2001 Volume 87 Issue 4 Pages 190-197
    Published: April 01, 2001
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    It has been reported that the characteristic of rolling contact wear of rail steels varies depending on the microstructure and carbon content of steels. However, the reasons for such variations have not been fully elucidated yet. Accordingly, the authors conducted two-cylinder rolling contact wear test by using pearlitic steels with carbon content in the range from 0.8 to 1.0 mass% and studied the effects of carbon content of pearlitic steels on the rolling contact wear. In addition, the authors examined the dominating factor of the rolling contact wear in pearlitic steels and the effects of carbon content on this factor. The main findings obtained are as follows: (1) The wear resistance of pearlitic steels improves with increasing carbon content. (2) The rolling contact wear of pearlitic steels is dominated by the rolling contact surface hardness (RCSH). (3) The improving wear resistance of pearlitic steels is attributable to an increase in RCSH due to raising work-hardening rate of the rolling contact surface with increasing carbon content. (4) The reason why the work-hardening rate of the rolling contact surface of pearlitic steel rises with increasing carbon content is considered as follows: An increase in the cementite density (carbon content) increases the amount of dislocation in the matrix ferrite and promotes the grain refinement of the matrix ferrite. Moreover, the solid solution of carbon in the matrix ferrite takes place due to the decomposition of cementite. As a result, the matrix ferrite is strengthened through the promotion of dislocation hardening, grain refinement and solid solution of carbon.
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  • Toshihiko KUWABARA, Shuuya YAMADA, Eiji IIZUKA, Takaaki HIRA
    2001 Volume 87 Issue 4 Pages 198-204
    Published: April 01, 2001
    Released: June 19, 2009
    JOURNALS FREE ACCESS
    Biaxial tensile tests of seven kinds of rolled sheet steels with different r-values were carried out. Cruciform specimens were deformed under linear stress paths in a servo-controlled biaxial tensile testing machine. The stress ratios (R.D.: T.D.) adopted were 1:0, 2:1, 1:1, 1:2 and 0:1. Plastic orthotropy remained coaxial with the principal stresses throughout every experiment. Stress points consisting of contours of equal plastic work, (σYx, σYy), were measured and compared with Hill's quadratic and Logan-Hosford yield loci in the principal stress space. The results obtained are as follows. (i) Logan-Hosford yield criterion can predict (σYx, σYy) with an error of several percent and the directions of incremental plastic strain rate vectors with an error of 5 degrees at most. (ii) The (σYx, σYy) of sheet steels with an average r-value larger than 1.5 exhibit a tendency to approach Hill's yield locus in the directions of stress ratios 1:1 and 2:1 as the material work-hardens. This phenomenon has been also observed in the past literature and seems to be the common differential hardening characteristics of sheet steels having rather high r-values. (iii) The differential hardening of sheet steels is not caused by texture development, but rather governed by the work-hardening characteristics of slip systems.
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