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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 74 (1988), No. 4

  • Growth Kinetics and Alloying Element Partition of Proeutectoid Ferrite

    pp. 591-600

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  • Hydrogen-Defect Interactions and Hydrogen-Induced Embrittlement in Iron and Steel (1)

    pp. 601-608

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  • Computer Control of Mechanical Properties for Manufacture of Steel Plate-Present State and Future Problem

    pp. 609-616

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  • Manufacturing Techniques for Rolled Clad Products

    pp. 617-623

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  • Disintegration of Coke by Mechanical Impact under Gasification Reaction

    pp. 624-631

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    In order to clarify the behavior of fines in blast furnace, fundamental experiments were performed on the disintegration of coke during gasification reaction accompanied by mechanical impact.
    The following results were obtained :
    (1) Coke fines of high ash content are generated with the progress of gasification, which suggests the close correlation between generation of coke fines and gasification.
    (2) Generation of coke fines increases remarkably when the mechanical impact strength is beyond a critical value.
    (3) Reaction temperature, gas composition and coke size also affect the generation of coke fines by varying the rate of gasification.
    A mathematical model is made using the rate equation of coke fine generation deduced from the experimental results. The calculated results agree well with the experimental results. The model, therefore, can be applied for the investigation of the bahavior of coke fines in blast furnace.
  • The Solubility of the Chromite in MgO-Al2O3-SiO2-CaO Melts at 1 600°C in Air

    pp. 632-639

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    The solubility of the picrochromite MgO·Cr2O3 into MgO-Al2O3-SiO2 melts were measured at 1 600°C in air, to understand the bahavior of smelting reduction of chromite ore. The solubility of picrochromite were 1.1-4.5wt% Cr2O3 in MgO-SiO2-Cr2O3 melts. In MgO-CaO melts, they were as much as 40-55wt% CrOx, although more than 50% of chromium exists as Cr6+ in the high CaO and low MgO region. The solubility of the picrochromite increased from 0.2-0.8wt% Cr2O3 to 0.5-2.6wt% Cr2O3 by adding CaO to the MgO-Al2O3-SiO2 melts. For Al2O3 containing melts, the chromium in the chromite MgO·Cr2O3 was substituted by aluminum in proportion to Al2O3 content in the melt.
  • Copper Distribution between Na2S Bearing Fluxes and Carbon Saturated Iron Melts

    pp. 640-647

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    Copper distribution between NaS0.5 bearing fluxes and carbon saturated iron melts was measured at 1 200°C. Coefficients LCu and KCu which are defined below were used to discuss the decopperization behavior of different sulfide fluxes with different sulfur content in carbon saturated iron melts. LCu≡(%Cu)/[%Cu] KCu≡(%CuS0.5)/[%Cu]·[%S]1/2
    The results are summarized as follows.
    1) The distribution ratio LCu was between 11 and 21.5 for the NaS0.5-FeS-CuS0.5 system at 1 200°C. The maximum KCu was 213 for the 95%NaS0.5-5%FeS system with LCu=17 and [%S]=0.01.
    2) The temperature dependence of KCu, from 1 170°C to 1 325°C for the melts containing 79.9-88.5%NaS0.5+10.7-19.4%FeS+0.55-0.76%CuS0.5 can be expressed by the following equation.
    lnKCu=1.25×104/T-3.07
    3) NaS0.5 was found to be the best component for the decopperization among five sulfides FeS, NaS0.5, KS0.5, CaS, CuS0.5 investigated in the present work.
  • Wettability of Solid Oxides by Liquid Iron Alloys under Reduced Pressure

    pp. 648-655

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    Wettability of solid oxides by liquid iron alloys has been studied under reduced pressure. Measurements of surface tension and contact angle of liquid iron alloys on solid oxides (MgO, Al2O3) have been carried out with the sessile drop method.
    1) Different values of surface tension and contact angle were obtained by different furnaces whose heating elements were molybdenum and graphite, respectively. This can be explained by a difference in partial pressure of oxygen in the furnaces.
    2) The values of surface tension obtained by the furnace whose heating element was graphite was considerably higher than previous works. It should be caused by an extremely low oxygen pressure in this work compared with those in previous works.
    3) The difference in the wetting of Al2O3 and MgO with liquid iron alloys can be attributed to the difference in solubilities of Al and Mg in liquid iron.
  • Activities of Components in Iron oxysulphide Melt in Equilibrium with Solid Iron

    pp. 656-663

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    Equilibrium between H2-H2O-H2S mixtures and iron oxysulphide melts in coexistence of solid iron was accomplished by means of the gas circulating method. The temperature range of measurements was 1 000 to 1 200°C, and the mole fractions of oxygen and sulphur in the melt were No =00.35 and Ns= 0.180.43, respectively. The oxygen pressure in gas was measured by oxygen galvanic cell using calcia-stabilized zirconia as a solid electrolyte. The sulphur pressure in gas was determined by chemical analysis.
    The activities of oxygen and sulphur in the melt showed slightly positive deviation from the fractional concentration of each anion i, N'i =Ni/(No+Ns) modified by a solution model.
    The partial molar quantities of species in the solution at 1 100°C were calculated from results of the activities. It was shown that oxygen exothermically dissolves into the solution and has a small inclination of imperfect mixing at N'o=0.2, whereas sulphur plays nearly an ideal behavior in the solution.
    The sulphur potential in equilibrium with iron, wustite and the melt was in close agreement with those in earlier works.
  • Development of Automatic Blowing Technique in BOF Based on a Mathematical Model

    pp. 664-671

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    For the endpoint control and the estimation of steel compositions at the end point in BOF with top and bottom blowing, a mathematical model suitable for online application has been developed on the following procedure.
    (1) The basic equations of oxygen consumption ratio and temperature increase ratio have been developed. These equations have comprehensive characteristics in both low and high carbon ranges at the final stage of blowing.
    (2) An endpoint control model for coinciding the carbon content and temperature at the end point with their aimed values has been developed on the basis of the above mentioned basic equations.
    (3) Equations for the estimation of manganese and phosphorus contents at the end point have been developed by using the values obtained by analysis of the steel sampled by sub-lance measurement during blowing and the amount of oxygen which was not consumed for decarburization during the period from sublance measurement to the end point.
    At No. 2 BOF shop in Wakayama Steel Works, the models are being used for the automatic blowing and contributes to the reduction of reblow ratio and the improvement of quick tapping ratio.
  • Quantitative Estimation about the Influence of Various Factors on the Smelting Reduction Rate of Cr-ore by Top-and-bottom Blowing Converter

    pp. 672-679

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    Smelting reduction rate of Cr-ore in top-and-bottom blowing converter was quantitatively estimated by 600 kg scale fundamental experiment and 100 t scale industrial furnace (LD-OB). The change of Cr oxide in slag with time showed zero-order reaction kinetics and the following points were clarified on the reduction rate.
    1) The rate was in propotion to ε0.5 and L1.0, where ε was stirring energy, L was diameter of furnace.
    2) The activation energy was about 210 kJ/mol.
    3) The rate were not cleary affected by the kind of Cr-sources, namely, pellets, briquettes of powder ore, carbon containing briquettes and lump ore.
    4) The rate increased with the increase in amount of carbon for reduction and the decrease of [%Cr].
    According to these results, it was posturated that the transfer of Cr oxide in molten slag phase to the carbon-slag and the metal-slag interfaces was the rate controlling step. The reduction rate was formulated as a function of ε., L, [%Cr], temperature and the containing ratio of carbon for reduction in slag. The results of calculation showed fairly good agreement with the observed values.
  • Smelting Reduction of Chrome Ore Pellet in Stirred Bath

    pp. 680-687

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  • Stress Analysis of Grooved Rolls Having Closed Passes and Discussion on Their Groove Shapes by photoelastic Methods

    pp. 688-695

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    There was a breaking accident of a solid grooved roll having closed passes, which seemed to be broken at a groove bottom mainly by mechanical stresses.
    The stresses were analyzed by a three-dimensional photoelastic method and the cause of the breakage was studied. The effect of groove shapes on the stress distribution of the grooved roll was investigated by a two-dimensional photoelastic method. The main results obtained are as follows :
    1) As a result of the stress analysis of the solid grooved roll having closed passes, it became clear that the breakage was caused by too large mechanical working stresses.
    2) To prevent the breaking accident of the grooved roll at a groove fillet, it is most effective to make the diameter of the groove and collar as large as possible.
  • Development of a Simulation Testing Machine for Evaluating the Lubricity of Lubricant in Cold Sheet Rolling

    pp. 696-702

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    The new simple simulating tests have always been desired strongly in order to evaluate the lubricity of lubricant in cold sheet rolling, because of complexity and cost of experimentation with actual rolling processes. The purpose of the study is to develop a new simulation testing machine. In the new type of simulating test, it is necessary to deform, the workpiece material plastically which is different from the simulating test such as Timken test. The contact behavior between rolls and workpiece is undoubtedly closer to that in rolling practice. The roll can be rotated at a high relative speed and moreover, the normal force and tangential force can be measured individually. The new simulation testing machine developed is sufficient for these necessary conditions. The apparatus is very simple and the cost for experiments is cheap. This machine is effective for evaluation of the lubricity of lubricant in cold sheet rolling.
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  • Transvers and Longitudinal Yield Strength of Hot-rolled Seamless Linepipe

    pp. 703-709

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    The transverse yield strengths of hot-rolled seamless linepipes were studied with respect to the different test methods, including the tensile tests with cold-flattened strap and unflattened round specimens. These results were compared with the longitudinal yield strength and the yield strength obtained by the ring ex pansion test, and were discussed in relation to yielding of a pipe under triaxial stress state. The following conclusions are reached from the experimental results and discussion.
    (1) There is little difference between the longitudinal and transverse tensile properties of hot-rolled seamless linepipe.
    (2) The cold-flattened strap specimen does not represent the true material properties, because of the pipe-size effect on the yield strength.
    (3) The transverse yield strength, which is obtained with the cold-flattened strap specimen, can be well explained with the combination of work-hardening and the Bauschinger effect.
    (4) As for the hot-rolled seamless linepipe, the use of longitudinal tensile specimens should be recommended as the most reliable practical method for the purpose of quality control.
  • Fabrication of Silicon-Carbide Continuous Fiber Reinforced Carbon (SiC/C) Composites Using Hot Press Process and the Effects of Fiber Forms on the Strength

    pp. 710-717

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    Silicon-carbide continuous fiber reinforced carbon (SiC/C) composites was fabricated using a simple hot press process. Three forms of SiC fiber reinforcement, that is, cloth, mat and unidirectional long fibers (UD fibers) were employed. Fine pulverized coke mixed with carbonaceous bulk mesophase (BM) was used as matrix. In this process, SiC fibers were laminated alternately with the matrix admixture in a die, and then heated to 600°C under a pressure of 49 MPa.
    The results were as follows:
    (1) The maximum strengths of the composites were the greatest for the UD fiber reinforcements at 121.5 MPa while the cloth and mat reinforcements showed appreciably lower strengths.
    (2) After secondary heat treatments at 800°C to 1 500°C, the composite reinforced with UD fibers showed excellent strengths above 106 MPa which were greater than that of an as-fabricated commercial C/C composite. The strengths of the composites reinforced with cloth and mat, however, were significantly reduced by the heat treatments.
  • Visual Observations of Fatigue Crack Propagation of a Low Alloy Steel in High Temperature Pressurized Water

    pp. 718-724

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    Visual observations of fatigue crack propagation of a low alloy steel in an autoclave filled with pressurized water at high temperatures simulating a boiling water reactor environment were conducted. The observation system consisted of a distant focusing relay lens, a camera and a picture control device. A sapphire single crystal rod was employed as solid light path in high temperature water in order to reduce the image distortion due to convection. Observations were carried out at temperatures ranging from room temperature to 288°C. The total resolution power of the observation system decreased with increasing temperature but satisfied a requirement of ASTM standard even at temperature of 288°C.
    Crack growth curves were successfully obtained from the successive pictures and compared with those obtained by a compliance method using LVDT for the same specimen. A good coincidence was obtained between both measurements.
  • Fretting Fatigue of High Strength Steels for Chain Cables in Sea Water

    pp. 725-732

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    Fretting fatigue tests of high strength steels having ultimate tensile strengths of 490, 690 and 880 MPa were carried out in sea water under free corrosion condition, and the effect of fretting damage on fatigue life was investigated. At high stress amplitude, the higher the strength of steel, the longer the fretting fatigue life. At low stress amplitude, the fretting fatigue life of all the steels decreased to 10-20% of the conventional corrosion fatigue life and showed almost the same life irrespective of the strength of steel. The fretting fatigue life in sea water was much shorter than that in air, and the fretting fatigue strength at 107 cycles was lower in sea water than in air. The saturation of fretting fatigue damage occurred beyond a certain number of fretting cycles. The ratio of the smallest number of fretting cycles to the fretting fatigue life for the saturation to occur in sea water was less than 0.005%, but that in air was about 30%. It was shown that the fatigue life in sea water was lowered by the fretting damage of a small number of fretting cycles.
  • Phase Diagram of Fe Rich Side of Fe-Mo System under High Pressure

    pp. 733-740

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    High-pressure phase diagrams of the iron-rich Fe-Mo system were determined by a diffusion-couple method and the results were compared with the calculated phase diagrams. Under high pressure the α-phase region became narrower, while the γ-region wider. When the pressure was about 3.2 GPa, the γ-loop was no more present and instead the contracted γ-field appeared in the Fe-Mo system.
  • Measurements of Hydrogen Content at Inside Wall of Crack in Stress Corrosion Cracking

    pp. 741-743

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  • ファインセラミックスの研究開発

    pp. 747-748

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