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

Tetsu-to-Hagané Vol. 71 (1985), No. 14

  • The Changing Scenes in Materials

    pp. 1569-1575

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  • Research and Education at the Universities in West Germany

    pp. 1576-1582

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  • Evaluation of New Energy Technologies with Net Energy Analysis

    pp. 1583-1588

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  • Carbonization of Coal and Coking Mechanism

    pp. 1589-1595

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  • Application of Laser in Steel Industry

    pp. 1596-1606

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  • Effect of Atmospheric Gases on the Reduction of Chromium Ore Pellet Containing Carbonaceous Material

    pp. 1607-1614

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    The reduction rate of chromium ore pellet containing coke powder was measured at various temperatures in flowing N2-CO, N2-CO-H2 and N2-CO-CO2 atmospheres.
    The pellet diameter and the grain size of coke only slightly influenced the reduction rate, while the effect of the grain size of chromium ore was greater.
    The reduction rate increased with the decrease in the partial pressure of CO and with the increase in that of H2. From the result of kinetic analysis based on a shrinking core model, such an effect was elucidated to be caused by the decrease in gaseous diffusion resistance through the pore in reduced layer formed on the surface of chromite grain.
    Although CO2 was contained at low concentration (for example, Pco2/Pco=0.02) in furnace atmosphere, it remarkably retarded the progress of reduction and consumed the coke contained in the pellet.
  • Continuous Hot Metal Pretreatment by Top Injection Method at Blast Furnace Runner

    pp. 1615-1622

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    A new continuous hot metal pretreatment by top injection method which is carried out at the blast furnace runner is examined. Emphasis is placed on the method of charging the reagents for desiliconization and dephosphorization. It is found that not only desiliconization but also dephosphorization can be accomplished at the charge point by employing the top injection method. The reactions are analyzed in terms of the kinetics and thermodynamic equilibria.
  • Mass Transfer between Gas and Liquid in a Gas-stirred Vessel

    pp. 1623-1630

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    Experimental and theoretical studies were made in order to discuss the characteristics of the mass transfer between gas and liquid in the gas-stirred system. Carbon dioxide was injected into water. The concentration of carbon dioxide in water was measured by the carbon-dioxide electrode.
    The volumetric coefficient (kLa) was defined by assuming the uniform concentration in the water, where kL is mass-transfer coefficient, and a is the specific area of the gas-liquid interface. The coefficients were obtained from the concentration change with time under the following conditions: gas-flow rate=1.67 × 10-51.67 × 10-4 m3/s, radius of vessel=0.0550.145 m, depth of water=0.10.4 m, and nozzle diameter=0.6 cm.
    A mathematical model for the mass transfer was proposed under the assumptions that the both masstransfer coefficients (kL) for bubbles and the free surface were given by the HIGBIE's penetration theory. The model consists of the equations for the continuity of solute with constant effective diffusivity and the equations for the flow field proposed previously. Although the computed concentration profiles were not uniform, it was shown that the relation between In((Ceq-Co)/(Ceq-C)) and time was linear and that the slope of the straight line was independent of the location in the vessel, where C is local concentration, Ceq is equilibrium concentration, and Co is initial concentration. Volumetric coefficients (kLa) obtained from the slope under the various conditions were consistent with those calculated by the HIGBIE's model, and also were roughly consistent with observed ones.
  • Production of High Carbon Chromium Bearing Steel by Vertical Type Continuous Caster

    pp. 1631-1638

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    Rolling contact fatigue life of bearing steel is improved with a decrease in oxide nonmetallic inclusions. The oxygen content of high carbon chromium bearing steel has been reduced to an average level of 5.8 ppm. This is accomplished through the combined processes of an electric arc furnace, a ladle furnace, an R-H vacuum degassing vessel and a continuous caster.
    Rolling contact fatigue life of high carbon chromium bearing steel thus manufactured and tested on the thrust type machine has accordingly doubled to tripled if compared with the conventional vacuum degassed, ingot cast steel.
    From an operational standpoint, the supply of extremely low oxygen steel to the caster has resulted in the elimination of such troubles as nozzle clogging and has been the main contributor to a record 10 000 tons of continuous cast high carbon chromium bearing steel from one tundish without interruptions.
    It has been demonstrated in the life tests that neither sulphur nor titanium influenced life when the levels of these elements were held down to a minimum in the high carbon chromium bearing steel. Life is further extended by the cold working inherent to cold pilgered tubes. The improvement in life has been found out in the tests to double to triple that of hot worked hollow tubes.
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    1. Generation Mechanisms of Non-metallic Inclusions in High-cleanliness Steel Tetsu-to-Hagané Vol.93(2007), No.12
  • Effect of Carbon on Hydrogen Attack of 21/4Cr-1Mo Steels

    pp. 1639-1646

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    Susceptibility to hydrogen attack of 2 1/4 Cr-1 Mo steel base metals and those simulated weld heat affected zone (HAZ) was investigated. Namely, tensile properties and a growth behavior of bubble cavities in the steels containing 0.05, 0.10 and 0.17% carbon were evaluated after an exposure to hydrogen at temperatures 200 to 650°C under a pressure of 300 kgf/cm2.
    The steel which contained 0.17% carbon exhibited a remarkable deterioration in reduction of area at an earier period of the hydrogen exposure and a more rapid growth rate of bubble formation along grain boundaries than the steels contained 0.05 and 0.10% carbon. It was presumed that M3C carbides densely precipitated along the grain boundaries played a role to accelerate the growth rate of bubble formation during a hydrogen exposure, especially in the simulated HAZ material.
    Incubation periods determined by the drop of reduction of area demonstrated an apparent linear decrease as increasing the carbon content. An activation energy was found to be 24 220 cal/mol in hydrogen attack of the 0.17% carbon containing steel.
  • Effects of Cold-rolling and Ni-equivalent on Mechanical Properties of Austenitic Stainless Steels at Cryogenic Temperatures

    pp. 1647-1654

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    Austenitic stainless steels, especially SUS304L and 316L, are candidate structural materials for cryogenic use. However, there are not enough data on Charpy absorbed energy at 4K nor reports on effects of coldrolling and Ni-equivalent on the tensile properties and absorbed energy for these steels. In this study, tensile and Charpy impact tests of cold-rolled SUS304L, SUS310S and SUS316L were carried out at 293 K, 77K and 4K. Microstructure and texture of the steels were also studied. Effects of cold-rolling and Ni-equivalent on low temperature mechanical properties of these stainless steels has been discussed. Results are summarized as follows;
    1) 0.2% proof stress and ultimate tensile strength increased as the reduction of cold-rolling increased. In the 40% cold-rolled steels, there were little difference in the proof stress between the steels investigated. As the Ni-equivalent increased, the proof stress increased and tensile strength decreased at low temperatures.
    2) The notch-to-unnotched ratio of tensile strengths increased as the cold-rolling reduction and Ni-equivalent increased.
    3) As the cold-rolling reduction increased, the absorbed energy decreased. The absorbed energy in 40% cold-rolled steels at 4K was 40-100J.
  • Measurement of Bundle Sizes of Martensite Structures and Facet Sizes of Brittle Fracture Surfaces by Applying a Technique of Texture Analysis

    pp. 1655-1662

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    Bundle sizes of the martensite structures and facet sizes of brittle fracture surfaces were measured in quenched and tempered 80 kgf/mm2 steels by applying a technique of texture analysis. The cooccurrence matrix derived by HARALICK was useful to analyse degital images of the martensite structures and the brittle fracture surfaces.
    The contrast parameter which is one of the parameters derived from the cooccurrence matrix, was found to have good relationships with the bundle size of the martensite structure and the facet size of the brittle fracture surface. Therefore, a bundle size and a facet size can be quantitatively known by measuring contrast parameters of a martensite structure and a brittle fracture surface, respectively.
  • Failure Analysis of Seamless Line Pipe during Transportation by Ship

    pp. 1663-1669

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    Break out had happened during field hydraulic test of unused line pipe. The observation of failure pipe indicated presence of the pre-damage at the broken portion. We supposed that the damage would have occurred during manufacturing or shipping. From analysis offracture surface and failure section, follow ing facts were revealed
    (1) The cracks propagate in wall thickness direction independently of the metal-flow of hot rolling direction.
    (2) The crack initiation sites are the external and the internal surfaces of the pipe and the cracks propagate stepwise with smooth fracture surface.
    (3) In the fracture surface, many corrosion products are observed and clear striations are locally recognized.
    It was concluded that the failure was caused by fatigue crack during shipment. This mechanism was confirmed by the pulsating bending fatigue test of pipes.
  • The Determination of Trace Amounts of Carbon in Iron and Steel by the Tube Furnace Combustion-Conductometric Method

    pp. 1670-1676

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    The useful method is described for the determination of trace amount of carbon in iron and steel by the conductometry with the aid of microcomputer. That is, the carbon dioxide is evolved by combustion of the sample in the stream of oxygen and then absorbed into the sodium hydroxide solution for measurement of conductivity. The following results were obtained:
    (1) The concentration of sodium hydroxide solution is decided by the theoretical calculation in order to measure the conductivity shift based on the absorption of the carbon dioxide below 100 μg as carbon and the reasonability of its concentration is also confirmed by the experiment. The optimum concentration is 0.0025 mol dm-3.
    (2) Carbon of 0.5 μg can be determined by the present method, because the output of the conductivity cell is treated by the micro computer to improve S/N ratio.
    (3) Carbon adsorbed on the sample surface can be eliminated by heating the sample at 430°C in oxygen stream or etching chemically the sample surface in the mixed acid solution.
    (4) The certified values of the certified reference materials on the market show generally tendencies to be on the high side in 48 ppm because of carbon adsorbed on their surfaces.
    (5) The present method is useful for the determination of carbon of ppm order in iron and steel because of the high sensitivity and the simplicity in the analytical procedure.
  • Development of Laser Welder for Production Process of Steel Sheet

    pp. 1677-1684

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    Two 5 kW CO2 Laser welders developed by Kawasaki Steel Corp. have been installed for pickling lines at both Mizushima and Chiba Works in 1983.
    Those are the first 5 kW Laser welder for sheet steel production floor, which can weld automatically any kind of steel strip measuring up to 1 880 mm in width and up to 6 mm in thickness, bringing about high yield of production on cold rolling process.
  • Development of X-ray Computed Tomographic Scanner for Iron and Steel

    pp. 1685-1691

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    X-ray computed tomography is extensively used in medicine, but has rarely been applied to non-medical purposes. Steel specimens pose particularly difficult problems-very poor transmission of X-rays and the need for high resolving capability. There has thus been no effective tomographic method of examining steel specimens.
    Due to the growing need for non-destructive, non-contact methods for observing and analyzing the internal conditions of steel microscopically, however, we have developed an X-ray Computed Tomographic Scanner for Steel (CTS) system, specifically for examination of steel specimens.
    Its major specifications and functions are as follows. Type: the second-generation CT, 8-channels, Scanning method: 6° revolution, 30-times traversing, Slice width: 0.5 mm, Resolving capability: 0.25 × 0.25 mm, X-ray source: 420 kV, 3 mA, X-ray detector: BGO scintillator, Standard specimen shape: 50 mm dia., 100 mm high, Measuring time: 10.5 min.
    Porosity of a stainless steel (SUS 304) bloom was examined three-dimensionally by the CTS system. Corrosion procedure of a steel slab was also examined.
  • Development of Industrial X-ray Computed Tomography and Its Application to Refractories

    pp. 1692-1699

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    An industrial X-ray computed tomography was developed under the influence of the rapid spread of the use of the X-ray CT scanner in the medical field and improvements of the equipment. Although current nondestructive testing machines of refractories use the ultrasonic inspection method or the X-ray fluoroscopic method, these equipments cannot produce a tomogram or cannot carry out quantitative evaluation.By using an industrial X-ray computed tomography, submerged nozzles for continuous casting of steel were analyzed with interesting results. The features of the industrial X-ray computed tomography applied for refractory nozzles are as follows:
    (1) It promptly detects interior defects.
    (2) It can measure dimensions and shapes.
    (3) It can numerically express the distribution of density.
    Accordingly, it is expected that the industrial X-ray computed tomography will widely be used in the fields of development and quality control of refractories and advanced ceramic materials.
  • 東南アジア鉄鋼協会の勤務を終えて(東南アジアにおける仕事と生活)

    pp. 1700-1702

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  • 抄録

    pp. 1707-1709

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