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

Tetsu-to-Hagané Vol. 92 (2006), No. 9

  • Effects of Slag Content and Composition on the Reducibility of Iron Oxide Including CaO-SiO2-FetO Slag

    pp. 539-543

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    In the sintering with lower slag ratio, the melt quantity decreases, and the agglomeration do not progress sufficiently. It is necessary to secure the melt quantity by silicate melt mainly composed of FexO-SiO2 system and to control ideally the composition and the generation place of the melt. In the present study, iron ore sinter is simulated by an iron oxide pellet added with (CaO-)SiO2-FetO slag particles, and the effects of the slag content, the composition, the holding time at 1573K and the slag particle size on the hydrogen reduction behavior of the iron oxide pellet including (CaO-)SiO2-FetO slag particles have been investigated at 1173K. In the initial stage of reduction, the fractional reduction is higher when the slag content is higher. With proceeding the reduction, the fractional reduction of the sample with the higher slag content becomes lower than the sample with the lower slag content. The reduction rate decreases with the increase of the slag content. The ratio of the pore area with over 100 μm pore size increases with the increase of slag content. On the other hand, the final fractional reduction decreases with the increase of the slag content. From this fact, it is considered that the microporosity under 100 μm is related to the reducibility and becomes an influential factor. On the slag composition, the final fractional reduction of the pellet including FetO-SiO2 slag is better. This is because that the silicate slag is difficult to permeate nor block up the pore.
  • Water-model Experiment on Melting Powder Trapping by Vortex in the Continuous Casting Mold

    pp. 544-550

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    Water-model experiments have been carried out to understand the behavior of mold powder trapping phenomena by vortex in continuous casting mold. The following findings are obtained.
    (1) Mold powder trapping by the vortex occurs irregularly near the immersion nozzle. It occurs only in the wake of the immersion nozzle.
    (2) As for the occurrence frequency ratio of the vortex, the maximum value appears in the water flow rate regime ranging from 61.4 to 70.2 L/min. This regime is supposed to have a lose relationship with water flow velocity change near the immersion nozzle.
    (3) An empirical equation is proposed for the length of the molten mold powder entrapped by the vortex.
  • Effect of Crystal Structure on the Lightness of Zinc Electroplated Steel Sheet

    pp. 551-556

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    The lightness of Zn surface electrodeposited with different supporting electrolytes was investigated from the viewpoint of crystal structure and surface morphology using EBSP, AFM and GIXD (Grazing Incidence X-ray Diffraction) techniques. In pulsed current electrolysis containing sodium sulfate for supporting electrolyte, the lightness decreased according to crystal growth of Zn. On the other hand, the lightness remained almost constant in electrolysis containing aluminum sulfate. As for this difference, the usual positive correlation between lightness and preferred orientation of Zn crystal basal plane was not recognized. And GIXD analysis suggested that the crystallographic c axes of Zn electrodeposit using sodium sulfate and aluminum sulfate were roughly oriented perpendicular to the substrate surface, but that there was a small angle deviation inclined in the particular direction to the surface of Zn electrodeposit using sodium sulfate. In contrast, the particular directional deviation was not observed in the surface of Zn electrodeposit using aluminum sulfate. Furthermore, polarization curves of Zn electrodeposition suggested that nuclear generation was enhanced by using aluminum sulfate for supporting electrolyte in comparison with sodium sulfate. From these results, it is presumed that the unregulated crystal growth direction and fast nucleation of Zn crystals with aluminum sulfate caused fine crystal grain. And so, Zn surface possessed excellent smoothness due to its fine crystal facet confirmed by AFM analysis. As a result, it is considered that the lightness is mainly dominated surface smoothness, and that the high lightness of Zn electrodeposit was obtained using aluminum sulfate.
  • Measurements of Volume Fraction and Carbon Concentration of the Retained Austenite by Neutron Diffraction

    pp. 557-561

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    The time-of-flight method of neutron diffraction was employed to measure the volume fraction and carbon concentration of the retained austenite in four TRIP-DP steels. The results obtained before and after tensile deformation are compared with those measured by the conventional X-ray diffraction method. It is found that the neutron diffraction method is superior to X-ray in order to evaluate the bulky average of volume fraction because the stress-induced martensitic transformation occurs easily at the surface compared with the interior of a specimen. The stress-induced transformation is influenced not only by carbon concentration but also by microstructural topology.
  • Development of Fe-Mn-Si-Cr Shape Memory Alloy Machining Chips Reinforced Smart Composite

    pp. 562-566

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    Fe-Mn-Si-Cr shape memory alloy (SMA) machining chips reinforced smart composites are developed. The smart composites consist of SMA machining chips and plaster matrix. Because SMA waste machining chips are used as its reinforcements, the smart material can be treated as ecomaterial. In this study, fabrication method and mechanical properties of the smart composite, which can be used in architectural and civil engineering applications, are reported. Fe-Mn-Si-Cr SMA machining chips are subjected to pretensile strain at room temperature, and are embedded into plaster matrix. The Fe-Mn-Si-Cr SMA machining chips/plaster composites are then heated up to 250°C (above As) compressive residual stress in the matrix. Three-point bending test is performed for the mechanical property characterization. To discuss fracture behavior of Fe-Mn-Si-Cr SMA machining chips/plaster composites, Fe-Mn-Si-Cr SMA coils/plaster composites using SMA fibers are also fabricated and mechanical tested as model material. SMA machining chips have the property of shape recovery regardless of its heavy deformation due to machining. Therefore, SMA machining chips are available for reinforcement material as well as SMA fiber. It is found that SMA machining chips with prestrain improve the bending strength of composite. By using the Fe-Mn-Si-Cr SMA machining chips for the reinforcement of the SMA composite, one can obtain materials for practical engineering applications at low cost.
  • Assessment of the Zn/Al Metal Spraying Technology without Blast Treatment

    pp. 567-571

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    Recently, in the view of maintenance-free type corrosion prevention of steel bridges, thermal spraying with good durability and long life is desired. Zn/Al metal spraying is spotlighted due to its low life cycle cost (LCC). Zn/Al metal spraying without blast treatment, one of corrosion prevension methods, has better efficiency and environmental property, such as less fume, than the conventional method based on JIS H 8305. In this paper a comparison was made on the properties of the Zn/Al sprayed coating without blast treatment and the coating of the conventional method. In the results, it was shown that the coating of Zn/Al metal spraying without blast treatment had the same properties as conventional method based on JIS H 8305. This Zn/Al metal spraying was applied to steel bridges and they showed the good corrosion resistance.
  • Attachment of an Annular Bubble to an Orifice Placed in Gas-Liquid Two-phase Flow and Velocity of Liquid Flow

    pp. 572-574

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  • Attachment of an Annular Bubble to an Orifice Placed in Gas-Liquid Two-phase Flow and Loss Coefficient of Orifice

    pp. 575-577

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