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

Tetsu-to-Hagané Vol. 92 (2006), No. 8

  • Initiation Time of Vortex and its Arrival Time to Impeller under Mechanical Agitation

    pp. 469-474

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    Experimental investigations have been carried out on the initiation time of a vortex and its arrival time to the impeller in a mechanically agitated water bath. The vortex initiation time is defined as the period from the start of impeller rotation to the initiation of a vortex, and the vortex arrival time is defined as the period from the start of impeller rotation to the moment at which the vortex arrives at the impeller. Empirical equations are proposed for the two characteristic times as functions of the rotation frequency of impeller and the geometrical parameters such as the depth of the water bath and the height of the impeller position.
  • Effect of Slag on Swirling Liquid Jet in Transient Period

    pp. 475-480

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    A swirl motion of a cylindrical water bath agitated by a bottom blown liquid jet has been investigated. Silicone oil or normal pentane on water is used as model fluid for molten slag. Boundary of occurrence region, the starting time and period of the swirl motion are determined.
  • The Characteristics of Catalyst-coated Highly Reactive Coke

    pp. 481-489

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    The development of production and utilization technology of highly reactive coke is significant in order to improve blast furnace reaction efficiency. In this report, the characteristics of catalyst-coated highly reactive coke produced by 'post-addition of catalyst to coke' method were investigated. First, the catalytic effect of Fe and Ca on graphite and deashed coke during the C-CO2 reaction was investigated. Fe and Ca addition increased the reaction rate and decreased the reaction beginning temperature. Secondly, it was shown that the reaction rate of Fe or Ca coated coke was kept high until the weight loss reached 10 percent. This means that the catalytic effect is maintained high in the thermal reserve zone of the blast furnace. Furthermore, it was proved that 70% of the catalyst coated on the coke surface still remains after drop impacts and it is considered that the loss of catalyst during coke handling and transportation is small. Catalyst-coated highly reactive coke seems to be promising to improve blast furnace reaction efficiency.
  • Analytical Performance of Argon Spark Discharge Plasma under Reduced Pressures

    pp. 490-494

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    The emission intensities, the signal-to-background ratios (SBR), and the relative standard deviations (RSD) for Cu I 324.75 nm and Cu II 224.70 nm were measured in spark discharge optical emission spectrometry (SD-OES) when the argon plasma was operated under reduced pressures. The SBRs increase with decreasing argon pressures, yielding about 4-times larger values compared to those in the ambient-pressure condition. In these cases, the RSDs are less altered at argon pressures of 10-40 kPa. The reason for this effect is that the background intensities are drastically reduced because the continuum by electron collisions decreases under the reduced-pressure conditions. The reduced-pressure argon plasma would contribute to the improvement in the analytical performance in SD-OES.
  • Adhesion between Paint and Steel Sheet in Paint-coated Steel Sheet System and Interaction at Interface between Paint and Chromate-coated Steel Sheet

    pp. 495-500

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    The interface between paint and chromate-coated steel sheet in the paint-coated steel sheet system were investigated using ATR IR spectroscopy technique to elucidate interactions between the paint and steel sheet. The paint composed of a mixture of alkyd resin and melamine resin, and the steel sheet modified with chromic acid were used as specimens for the experiments. In order to observe IR spectra at the paint/ chromate-coated steel sheet interface, the paint layer coated on the chromate-coated steel sheets was sandpapered to make thin layer of less than 1 μm thickness, which was smaller than the penetration length of Evanescent wave. The paint at the paint/ chromate-coated steel sheet interface showed different IR spectrum from the bulk of the paint layer. C=O absorption (1722 cm-1) in the alkyd resin showed weak intensity, and a new absorption at 1600 cm-1 appeared. Such changes in the IR spectrum indicate that C=O groups in alkyd resin could interact with the steel sheet to contribute to adhesion of the paint/chromate-coated steel sheet adhesive joints.
  • Effect of Polyethylene Glycol on the Morphology of Zn Electrodeposited on Steel Sheet

    pp. 501-506

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    Zn electrodeposition was carried out on a steel sheet galvanostatically at 1500 A/m2 in un-agitated sulfate solution of 40°C to investigate the effect of Polyethylene Glycol (PEG) addition on the morphology of Zn. In situ observation by atomic force microscopy showed that the growth of deposited Zn proceeded through the advance of macro-steps in platelet crystals to the [2130] direction. The addition of PEG to the solution brought about a decrease in size and macro-step height and an increase in inclination of platelet crystals of deposited Zn. In PEG-containing solution, the crystal orientation index of (0001)Zn decreased, while those of (1120), (1011), (1010)Zn correspondingly increased. This change in the crystal orientation generally corresponds to the macro morphology of deposited Zn. The surface roughness of initially deposited Zn was larger in PEG-containing solution than in PEG-free solution due to the decrease in orientation index of (0001)Zn. However, with increased coating weight, the roughness was smaller in PEG-containing solution due to the decrease in size of Zn platelet crystals.
  • Improvement of Corrosion Resistance, Toughness and Weldability of SUS329J4L for Large Thick Plate Applied for Canister of Spent Fuel Storage

    pp. 507-515

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    SUS329J4L equivalent to ASTM A240 S31260 is selected for the candidate material of canister for the dry interim storage of spent fuels, for that shows excellent hot workability to manufacture into wide and thick plate and good corrosion resistance for canister usage at the present time. In order to improve the corrosion resistance, toughness and electron beam weldability which is applicable in future, candidate steel is investigated to obtain the suitable chemical compositions within the specification requirements, and the following results are obtained.
    (1) Some experimental alloys were melted in the laboratory to obtain the best balance of N and Ni contents for suitable toughness and corrosion resistance, as the contents of Cr and Mo contributed for corrosion resistance are maintained at upper limit of the specification requirements. The best balance is obtained more than 0.2 mass% in N and more than 6.5 mass% in Ni within the specification requirements.
    (2) The practical hot rolled plate melted with suitably selected compositions at 3 m in wide and 20 mm in thickness was manufactured with no defects in spite of higher nitrogen contents. The improved plate has satisfactory strength, high toughness and excellent corrosion resistance equivalent to austenitic super stainless steels.
  • Yield Stress Anisotropy by Straining and Baking of Bake-hardenable Steel

    pp. 516-522

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    Bake-hardenable steel sheets have been applied in exterior body panels of automobiles for thickness reduction without deteriorating the panel dent-resistance. The increase in flow yield stress due to bake hardening depends largely on the amount of prestrain and strain path changes, before and after baking. In the present study, the strain-path effects on bake hardening properties have been examined by changing the direction of subsequent tensile tests after uniaxial tension, plane-strain and equi-biaxial stretching as prestrain for a ferrite based bake-hardenable steel sheet. The yield stress showed a strong anisotropy by prestraining. However, the anisotropy caused by prestraining was weakened by bake hardening treatments. The Taylor-theory calculations of yield stress based on the texture measurements revealed that the evolution of texture due to the prestraining is not responsible for the strong anisotropy prestrained materials observed in the experiments. The strain path changes can be characterized by a scalar product of previous and current strain-rate mode tensors. The subsequent yield stress after strain path changes of different combination could be qualitatively estimated by using this parameter, which showed a correlation between the strong anisotropy of the yield stress after prestraining and the microstructural evolution in the prestraining.
  • Fatigue Properties of Plasma Nitrided Ultrafine Ferrite-Cementite Steels

    pp. 523-529

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    Fatigue tests were conducted for a series of plasma-nitrided ultrafine ferrite-cementite steels under rotating bending. The plasma-nitriding was conducted at 500°C for 16 h. 4 types of the base ultrafine ferrite-cementite steels were prepared, i.e., 15C, 45C, 15C-P and 45C-P. 15C and 45C were contained 0.15 and 0.45 mass% of carbon, respectively. 15C-P and 45C-P were 0.1 mass% phosphorus-added versions of them. All of the nitrided specimens had a hardened area of 1 mm in depth and many of the nitrided specimens showed internal fracture in and beneath the hardened area in the rotating bending fatigue tests. In case of 45C and 45C-P of the nitrided specimens, the ferrite grains successfully remained ultrafine and the fatigue strengths were largely improved by the plasma-nitriding. On the other hand, the ferrite grains beneath the hardened area were enlarged in case of 15C and 15C-P during the plasma-nitriding and increase of fatigue strengths were small. Although the origins of the internal fractures were inclusions located in and beneath the hardened area, fatigue strength of the nitrided specimens appeared to be dependent on hardness at around the origin. In nitriding the ultrafine ferrite-cementite steels, therefore, preventing the ferrite grain growth beneath the hardened area was required to improve the fatigue strength. For this purpose, precipitation of particles, such as cementite, was found to be useful to pin the ferrite grain boundaries.
  • Grinding Sludge Recycling to Reduce Environmental Load

    pp. 530-534

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    Companies like bearing maker use many grinding machines, then by-produce a lot of grinding sludge, most of which is dumped into landfills now. Being ISO14001-certified company, it is responsible for helping establish recycling technology and contributing to our recycle-based society. Report of "No. 2 Development of practical machine and test results" proved that it was possible to separate coolant from grinding sludge economically and grinding swarf and coolant were able to be reused for environmental load reduction at practical use level after one year long run test. But it was found that there were many kinds of sludge which were similar to grinding sludge but impossible to separate coolant from sludge with the same method of grinding sludge separation. For further environmental load reduction, honing sludge was picked up for the next target. Basic test proved that it was possible to separate coolant from honing sludge by adding paper filters to the method of grinding sludge separation. Based on those test results, practical machine was developed and it was confirmed that it was possible to achieve recycling and cost-reduction at the same time for honing sludge also.
  • Grinding Sludge Recycling to Reduce Environmental Load

    pp. 535-538

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    Most of grinding sludge is dumped into landfills now. It is responsible to establish recycling technology which enables to reduce environmental load and contribute to our recycle-based society. But it is very difficult to recycle grinding sludge because it contains a lot of coolant.From our previous researches, it was confirmed that it was possible to separate coolant from grinding sludge economically by pressing it in a cylinder. After squeezing coolant out, pressure rod compress grinding swarf with high pressure, then push it out as briquettes of grinding swarf.
    Usually briquette can keep its shape because grinding swarf is curly and entangle each other. That helps to handle it easily as law material after transporting to steel maker, but sometimes briquette can't keep its shape just after briquetting. So grinding swarf and briquette were observed microscopically to clarify the cause. These observation found that it made difficult to keep briquette's shape if grinding sludge contained small amount of fine rusted particles. For this problem, it was proved that small additional cellulose was effective to keep briquette's shape.

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