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

Tetsu-to-Hagané Vol. 93 (2007), No. 12

  • World Outlook for Iron Source Demand —Comparison with Energy Outlook—

    pp. 715-727

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    DOI:10.2355/tetsutohagane.93.715

    To maintain the sustainable use of iron source, there are global challenges due to mass effect such as the recent rapid growth in steel consumption, a large impact on climate change etc. Although R&D of iron and steel has been made for years, there is still significant potential of technological innovation to solve those challenges with a greater unified effort by the industry-academic-government. Therefore, it is necessary for deciding the amount of R&D's investment to share the common world-wide iron source demand outlook based on engineered researches of mathematical modeling and continual improvement, which lag behind those of energy. As it is expected to improve models of long-term forecasting of world iron source demand, priority issues are to specify the driver which governs the demand, and formulate a simple and rational hypothesis of the linkage.
  • Numerical Analysis of Microscopic Coke Strength Factors Using a Homogenization Method

    pp. 728-735

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    DOI:10.2355/tetsutohagane.93.728

    To investigate the effect of microscopic structures on coke strength, the stress analysis using a homogenization method is carried out for coke with different microscopic textures and pores with various shapes. Analytical results show that stress concentration for pores affects stress field in microscopic region of coke, on the other hand, the diameter and arrangement of inert in coke matrices hardly affects the stress field. The stress concentration for pores is the main factor of lowering coke strength since the interference of the stress concentration causes an increase in the maximum stress and a decrease in the homogenized elastic modulus. Especially, the existence of pores with low roundness causes a decrease in the homogenized elastic modulus of coke drastically and its effect on coke strength is bigger as the pore size is larger. Thick pore wall gives a decrease in maximum stress and an increase in the homogenized elastic modulus. In addition, in the case of pores with low roundness, the existence of big pores counteracts an increase in the homogenized elastic modulus with thick pore wall.
  • Analysis of Fracture Behavior in Metallurgical Coke Using Rigid Bodies-Spring Model

    pp. 736-742

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    DOI:10.2355/tetsutohagane.93.736

    In this study, fracture behavior of coke is investigated using 4-point bending tests and numerical analyses of Rigid Bodies-Spring Model.
    In 4-point bending tests, it is shown that the fracture behavior of coke is brittle fracture. The fracture occurrs at the middle of the bottom face of the coke specimen and a crack propagates vertically upwards. Finally, the coke specimen collapses with the powder.
    The fracture analyses using RBSM (Rigid Bodies-Spring Model) assuming 4-point bending tests were carried out for two cases in order to investigate the effect of existence of pores on fracture behavior of coke. In case 1, pores are not arranged in the analytical object and the effect of pores is considered by a decrease in the macro material constants. In case 2, the effect of pores is considered by arranging pores in the analytical object. Analytical results of case 2 reproduce the fracture behavior better than those of case 1. In addition, varying the inner structure and input data such as elastic modulus, yield criterion and so on, leads to improve the precision of fracture analyses of coke.
  • Generation Mechanisms of Non-metallic Inclusions in High-cleanliness Steel

    pp. 743-752

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    DOI:10.2355/tetsutohagane.93.743

    There have been many research reports regarding the deoxidation and oxygen reduction in steel since around 1970, some reports have discussed the genesis, growth and separation mechanisms of individual oxide inclusions in steel during refining.
    However, most of the investigation of deoxidation dealt with the steel with high oxygen content, where the sum of such base-metal oxides as FexO, MnO and Cr2O3, in the secondary refining slag amounted to 5 to 10 mass%, or higher.
    In this research, the behavior of the inclusions in clean steel practice was investigated, where the base metal oxides in slag do not exceed 1 mass%.
    It has been found that there are two important mechanisms of oxide inclusion generation other than “Deoxidation reaction” and “slag trapping” which are often assumed to be the origins of oxides during secondary refining.
    One is “Desulfurization reaction”; the amount of alumina formed by desulfurization after deoxidation is greater than that by the deoxidation reaction.
    The other is, namely, “Intrinsic reaction”; lime-bearing inclusions are formed by deoxidation/oxidation reactions of CaO and Al.
  • Development of Simplified Model for Gauge and Plate Crown on Work Roll Shift Mill

    pp. 753-762

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    DOI:10.2355/tetsutohagane.93.753

    In the work roll shift mill, a wide control range of the plate crown can be achieved by using an unsymmetrical work roll profile. The roll deformation of the mill has effected by not only the rolling load and the bending force of the work roll but also the work roll shift position and the work roll profile.
    The authors have formulated the simplified models of the gauge and the plate crown considering the above effects. These models consist of the mill housing deformation, the roll deformation in the kiss roll state and the roll deformation in the plate rolling, and are derived by dealing strictly with the roll deformation and the mill stretch.
    The accuracy of the new models has been compared with the point matching method and the actual plate rolling data.
    It is verified that these models can flexibly follow up the work roll shifting and the unsymmetrical work roll profile.
  • Effect of a Small Amount of Mo, W and Sn Additives on the Morphology and Orientation of Electrodeposited Zn

    pp. 763-768

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    DOI:10.2355/tetsutohagane.93.763

    Zn electrodeposition was carried out on a steel sheet galvanostatically at 1500 A/m2 in an agitated sulfate solution of pH 2 at 40°C to investigate the effect of a small amount of Mo, W and Sn additives on the morphology, crystal orientation and lightness of deposited Zn. No Mo and W codeposited with Zn, and hardly showed any effect on the morphology of deposited Zn. Mo and W increased the orientation of (0001) plane of Zn irrespective of not changing the overpotential for Zn deposition. Sn codeposited with Zn, and the platelet crystals of Zn was disappeared. Sn increased the crystal orientation of (0001) and (1013) plane of Zn due to a decrease in overpotential for Zn deposition. The lightness of deposited Zn depended on the crystal orientation and surface roughness of Zn. At coating weight of 20 g/m2, Sn, Mo and W enhanced the lightness of Zn due to an increase in orientation of (0001) and (1013) plane. However, with increased coating weight, since the surface roughness became large by addition of Mo, W and Sn, the enhancement of lightness by an increase in (0001) and (1013) plane was canceled.
  • Investigation on Mn Distribution between Ti2O3 and Austenite-iron

    pp. 769-774

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    DOI:10.2355/tetsutohagane.93.769

    Ti2O3 inclusions in steels have notable abilities as nuclei for intragranular ferrite (IGF) formations and bring grain refinement and high strength of steel. Most probable mechanism for the promotion of the IGF transition by Ti2O3 inclusions has been suggested that those absorb austenite stabilizing element of manganese from the steel phase and give the preferential ferrite formation from austenite due to raising its transition temperature. In the present work, manganese partitions between Ti2O3 and austenite-Fe were investigated at 1373-1573K for understanding the manganese absorbing behavior by Ti2O3 from the steel phase. It was clarified that the low titanium content of steel and the low heating temperature are the suitable conditions for manganese absorption by Ti2O3 and accordingly for IGF formations.
  • Giga-cycle Fatigue Properties of Induction Hardened 0.40% C Carbon Steels

    pp. 775-781

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    DOI:10.2355/tetsutohagane.93.775

    Giga-cycle fatigue tests were conducted for two heats of induction hardened 0.40% C carbon steels. The fatigue testing types were rotating bending at 100 Hz and ultrasonic at 20 kHz. The fatigue test specimens were uniformly induction hardened from the surface to the center. The induction hardened 0.40% C carbon steels revealed fish-eye fractures whose origins were mostly a TiN inclusion in case of heat A and entirely an Al2O3 inclusion in case of heat B. In case of rotating bending fatigue tests of heat A, surface fractures also occurred at over 108 cycles, while that type of the surface fracture never occurred in case of the ultrasonic fatigue tests. When the ultrasonic fatigue tests were compared with the rotating bending, focusing on the results of fish-eye fracture, the ultrasonic type showed slightly higher fatigue strength in case of heat A in spite of good agreements in case of heat B. However, the difference in case of the heat A was so small as to be in scattering of the results of heat B. Moreover, effects of pre-treatments before the induction hardening were also investigated in heat B. In this case, the fatigue tests were additionally conducted for induction hardened specimens with a pre-treatment condition of only normalizing (N-IH), while other tests were of normalizing, quenching and tempering (Q-IH). As the result, difference between N-IH and Q-IH was negligible, showing no influence of the pre-treatment condition.
  • Estimation of Steel Consumption and Obsolete Scrap Generation in Japan and Asian Countries in the Future

    pp. 782-791

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    DOI:10.2355/tetsutohagane.93.782

    In this paper the present flows of steel scraps in Japan, China, South Korea and Taiwan are clarified, and a dynamic model which analyzes future scraps flows is developed. To estimate the amount of collected obsolete scraps, a Population Balance Model (PBM) was used for Japan, South Korea and Taiwan. PBM is a model which estimates the amount of discards dynamically by taking into account the steel input to a society by end-uses and the lifetime distributions of each end-use. For China, a Leaching Model was used to estimate the amount of collected obsolete scraps. This model uses the amount of steel stocked in a society and the collection ratio of obsolete scraps. Three different methods were applied to predict future steel inputs for each country. The first method is applying the assumption that steel demand in the future remains constant at the present level. The second method is applying a logistic curve for future steel stocks. The third method is applying regression equations to future steel inputs by each end-use. GDP and population were used as variables. Finally the results of the steel input predictions by each method were substituted into the collected obsolete scraps estimation model. Under the logistic curve method, it was estimated that in 2030 the amount of collected obsolete scraps would be 29 million tons in Japan, 83 million tons in China, 20 million tons in South Korea and 3.7 million tons in Taiwan.
  • Changes in Carbon Content of Materials of the Japanese Sword under Traditional Forging Process

    pp. 792-798

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    DOI:10.2355/tetsutohagane.93.792

    The Japanese sword has excellent strength-toughness balance given by two traditional processes. One process is compounding of inner tough iron and outer strong steel. And the other process is cooling-rate control quenching by using thickness of clay-coating before quenching. However, it is a precondition for acquiring high strength-toughness that carbon content of sword parts are regulated in proper quantities. Carbon content of sword parts is very important and controlled under forging process which contains TSUMI-WAKASHI (forge-welding piled steel chips) work and fold-forging.
    Therefore, changes in carbon content of TAMA-HAGANE steels and carbon steels under traditional forging process were investigated in this study. Changes in carbon content depended on enclosing decarburized or carburized surface in steel as forge-weld interface. Total changes in carbon content were proportional to total layers of included surface in steel. Changes in carbon content per one forge-welded layer. “d (mass%/layer)” was ruled by carbon content of raw materials “C0 (mass%)”. When C0 is over 0.2 mass%, carbon content of forged steel is decreasing and the more C0, the more |d |. C0 is under 0.2 mass%, carbon content is increasing. The mass of forged steels is 4% increasing per one fold-forging cycle, but d is not affected by changes in mass of them.
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