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

Tetsu-to-Hagané Vol. 91 (2005), No. 9

  • Numerizing of Heat Transfer Coefficient between Water Spray and Heated Metal Specimens

    pp. 685-693

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    The author made four kinds of water spray cooling experiments to numerize heat transfer coefficient h between water spray and a heated specimen as a function of water flux W, water pressure P and specimen surface temperature θs. In this report, the author described numerizing of the equation: h=f (W, P, θs). The specially fixed water flux Wd (W1 to W4), water pressure Pd (P1 to P4), specimen surface temperature θsd (50, 75, to 900°C), and the most probable values of heat transfer coefficient hsa obtained from these experiments were introduced for numerizing of the above-mentioned equation.
    The principal contents are as follows: (1) In each θsd, the exponents n1 to n4 of the equation: hsa=AWnd corresponding to Pd: P1 to P4 respectively were obtained (A is constant). The mean exponent n is (n1+…+n4)/4. (2)In each θsd, the exponents m1 to m4 of the equation: hsa=BPmd corresponding to Wd: W1 to W4 respectively were obtained (B is constant). The mean exponent m is (m1+…+m4)/4. (3) By using n and m, the equation: h=C(WnPm) among arbitrary W, arbitrary P and h was numerized in every θsd (C is constant). (4) hi and hi+1 corresponding to θsd: θsdi and θsdi+1 respectively were calculated by using the equation: h=C(WnPm). Next, by using the relations: [hi vs. θsdi] and [hi+1 vs. θsdi+1], the equation: hx=f(θsx) to obtain hx corresponding to an arbitrary θsx between θsdi and θsdi+1, was numerized.
  • Effect of Cold Working and Warm Working on Recrystallization and High Temperature Deformation Behaviors in SUS304

    pp. 694-699

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    The effect of strain-induced martensite and introduced strain was examined in thermo-mechanical treatment for grain refinement on the SUS304 metastable-austenitic stainless steel. By combining the cold working with warm working, the following were independently estimated : Effect of the strain and effect of the martensite.
    In spite of whether it added to before and after anyway of the martensite generation, the strain has the equivalent effect for grain refinement. Resembled microstructure and mechanical property in high temperature was shown.
  • Corrosion Behavior of 55%Al-Zn Alloy Coated Steel Sheet near its Shear Cut Edge in Salt Spray Test

    pp. 700-705

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    Hot-dip 55%Al-Zn alloy coated steel sheet has superior corrosion resistance in various atmospheric environments. However, the corrosion often occurs near the shear cut edge in continuous wet environments, for example, salt spray test (SST, JIS Z2371), whose behavior is different from in cyclic corrosion tests including dry process (CCT, ISO 14993). To make clear the behavior and the mechanisms of the corrosion of 55%Al-Zn alloy coated steel sheet near the cut edge in SST, cross-sectional observations after the corrosion tests by SEM and polarization measurements in addition to the corrosion tests were conducted.
    The time to the red rust occurrence near the cut edge of 55%Al-Zn coated steel sheet was made longer with increasing the coating weight and decreasing the steel thickness in SST. The corrosion near the cut edge in SST is caused by a galvanic attack between the coating as an anode and the steel exposed at the edge as a cathode.
    Moreover, in the case of SST, which has no drying process, the corrosion products almost never formed near the edge, while they were observed to be adhered on the surface in CCT. These differences can be explained by whether these tests have the drying process or not.
  • Dissolution Resistance of Rusts on Galvanized Steels in Atmospheric Environments

    pp. 706-711

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    Detailed examinations of the corrosion processes of galvanized steels have shown that the steels exhibit some corrosion resistance after the zinc has corroded away. This corrosion resistance has been ascribed to a protective nature of the corrosion products from the zinc layer. Rusts exposed to environments containing air and water are subject to dissolution, and the protective components in the rust must be resistant to dissolution to persist and play a protective role in steels. In this investigation, zinc oxide, zinc carbonate, basic zinc carbonate, zinc ferrite, magnetite, and hydrated iron(III) oxide were chosen as model corrosion products, and their solubilities in water were examined as a function of pH. The solubilities of zinc oxide, zinc carbonate, and basic zinc carbonate are similar and very large, indicating that these would be dissolved away in atmospheric environments. The values of the solubility products of zinc ferrite and magnetite have not been reported and were estimated from thermodynamic data for the solubility calculations. The solubilities of zinc ferrite, magnetite, and hydrated iron(III) oxide are very much smaller than those for zinc oxide and carbonates. At pH lower than 7 the solubility order is: zinc carbonate-zinc oxide-basic zinc carbonate>>zinc ferrite>magnetite>hydrated iron(III) oxide. The compounds containing iron(III) ions are likely to show the adequate resistance to dissolution and to form the protective film. It is known that protective rusts are composed of fine particles of low crystallinity.The protective nature of these compounds can be explained by the effect of zinc ions on the crystalinity, particle size, and other properties of the compounds during their formation and growth.
  • Evaluation of True Stress-True Strain Relationship after Local Necking by Stepwise Tensile Test

    pp. 712-718

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    The goal in this research is to evaluate the correct true stress-true strain curve after local necking up to a true strain of 1.0. To achieve this goal, a smooth round tension test was carried out by a stepwise method. Yield stresses of the materials tested ranged from 251 to 1182MPa. The tensile load-neck section diameter curve was measured in the stepwise test and was transformed into an average stress-true strain curve in the neck. The necking ratio-true strain relationship was determined by an optical microscope observation. The necking ratio was defined as the radius of the neck section divided by the radius of the neck curvature. The true stress-true strain curve after local necking can be evaluated from the average stress-true strain curve and the necking ratio-true strain relationship using an empirical equation up to a true strain of 1.0 regardless of the yield stress of the materials tested. In addition, circumferentially notched tension tests with different notch radii were carried out in a stepwise manner to evaluate the true stress-true strain curves in the neck.Regardless of the initial notch shape, the true stress-true strain relationship after local necking was similar in the notched tension test and in the smooth round tension test.
  • Dislocation Substructure of Single Crystal Nickel-base Superalloy CMSX-4 Creep Ruptured at 1273K

    pp. 719-725

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    To clarify the feature of the rotation of the crystal lattice in the single crystal nickel-base superalloy, CMSX-4, during the creep deformation, the crystal misorientation across the interface of γ/γ' phase and that misorientation in the area of the γ and γ' phase were investigated. Creep-rupture tests were conducted at 1273K, in the stress range of 200 to 320MPa. Microstructural observation by SEM indicated that the cuboidal γ' turns to the rafted one in all ruptured specimens. However, at the stresses higher than 250MPa, the interface between the γ/γ' was waved, while the interface between γ/γ' in the specimen crept at 200MPa remains straight one. The crystal misorientation across the interface of γ/γ' phase and misorientations in the area of the γ and γ' phase decreased with decreasing the stress. The average misorientation perpendicular and parallel to tensile directions across the interface of γ/γ' phase were zero, independent of stress. At the lower stress side, the cuboidal γ' has regularly line up before rafting. However, at the higher stress side, the rafted γ' was formed after large creep deformation, and the rotation of the crystal lattice was also large, and the cuboidal γ' seemed to turn to the random direction. Consequently, it was suggested that the origin of the crystal misorientaiton in a single crystal nickel-base superalloy was the γ' phase rotated by subjecting the creep deformation.
  • Examination on Recycling Possibility by Steel Manufacturing Based on Survey of Reducible Wastes

    pp. 726-733

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    Survey on wastes required for reduction in paper, house, food, printing, pharmaceutical manufacturing and glass manufacturing industries was carried out by a hearing method, and their recycling systems using manufacturing processes of steel products were examined in order to enhance process linkage between the different industries and to decrease wastes emission. Paper sludge in paper, construction and demolition waste wood and waste plaster board in house, waste ion exchange resin in food, incineration ash in printing, inorganic sludge in pharmaceutical manufacturing and chemical division of glass industries were found by hearing of each company. The paper sludge as a sinter material, the construction and demolition waste wood as a blast furnace reductant, and the incineration ash of municipal solid waste as a molten slag by a electric furnace for steelmaking are hopeful from the viewpoint of the progress of their technology, the large treatment amounts and their efficient delivery. The calculated CO2 emission of paper sludge utilization as the sinter material and that of scraped wood as the blast furnace is less than power generation by incineration, while that of molten slag of incineration ash utilized by electric furnace is larger than cement materials.
  • Hydrogen Methane Gas Mixture Recovery by Reactions of Carbonaceous Wastes in Supercritical Water along with CO2 Fixation

    pp. 734-738

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    Automobile Shredder Residue (ASR) and Refuse derived fuels (not carbonized and carbonized: YRDF and RDF) as carbonaceous wastes were reacted isothermally with sub-supercritical water (600695°C, 200atm) together with a CO2 fixation reagent Ca(OH)2 inside a closed metallic tube reactor (7cm3). Product gas mainly consisted of hydrogen gas and a little methane gas except YRDF. As a whole, gas generated more in order ASR, YRDF, and RDF. Addition of catalysis NaOH or KOH made product gas increase more. KOH was more effective to product gas than NaOH. X-ray diffraction followed that Ca(OH)2 and CaCO3 existed mainly in residues after reaction tests with a CO2 fixation reagent Ca(OH)2 or CaO. Therefore, it was supposed that an overall chemical reaction took place as shown below. BOF steelmaking slag for CO2 fixation provided maximum gas generation 1.42 times as much as molar carbon in a RDF sample with KOH.
    C+H2O+Ca(OH)2=CaCO3+2H2
  • Construction of Supply Chain Management with Packing Companies in the Surface Treatment Steel Manufacturing Plant

    pp. 739-743

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    Kudamatsu plant projected the three-year mid term managerial program in 2002, promoting the integration and reorganization of subsidiary companies and reviewing the material and supplemental material procurement operation.
    As a part of this program, manufacturing for packing material and packing operations, which work had been so far divided into 6 subsidiaries, were integrated and entrusted to a newly founded single company. Then we tied up S.C.M. (Supply Chain Management) with it.
    Practically, packing operation was not involved in production control system. That is the reason some troubles frequently occurred, such as delivery delays due to the packing stagnation and the conflicting imbalance between the production and the packing operational flow.
    Therefore, along with S.C.M. construction, packing operation was included into the production control system in which overall reformation was being made at the time.
    Our purpose was to establish a system of manufacturing and packing section that can link together in the time scheduling.
    Integration and reorganization of subsidiary companies started in October 2002. Packing control system started in October 2004, and now demonstrating noticeable results such as labor saving in packing worker, improvement of material flow, packing productivity, and delivery date achievement level.

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