Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Volume 79 , Issue 10
Showing 1-16 articles out of 16 articles from the selected issue
  • Tohru MURASE, Naoe HIRAI
    1993 Volume 79 Issue 10 Pages 1129-1137
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
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  • Toshiro MATSUI, Yutaka OSAJIMA
    1993 Volume 79 Issue 10 Pages 1138-1144
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
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  • Takaho OTOMO, Noboru TAGUCHI, Eiki KASAI, Yasuo OMORI, Takazo KAWAGUCH ...
    1993 Volume 79 Issue 10 Pages 1145-1150
    Published: 1993
    Released: February 16, 2010
    JOURNALS FREE ACCESS
    Sintering experiments were carried out in order to clarify the mechanism of formation of large pore in the assimilated part in the sintering process of pisolite ore. Modeled briquette which consisted of disk-shaped pisolite ore as core and fine mixture of hematite ore and limestone as shell layer was used in the present experiments. The results obtained are summarized as follws :
    1) When the shell layer was melted, large pore was formed in the assimilated part around the core ore.
    2) The large pore in the assimilated part was formed by using not only unfired core ore but also that calcined at 800°C or 1300°C. It suggests that the water vapor generated by the dissociation of combined water in the ore was not only the cause of the large pore formation.
    3) A mechanism of the formation of large pore in the assimilated part can be described by ; ( i ) The combined water in core ore is dissociated by heating, and macro-pores and/or cracks were formed in core ore. ( ii ) Gas in macro-pores and cracks in core ore is liberated because of its volume expansion during heating and by assimilation of core ore to the melt. ( iii ) The gas is caught around the ore because the viscosity of melt is increased by assimilation of the ore to melts. ( iv ) After cooling, the large pore in the assimilated part is formed around the core ore.
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  • Kentarou NOZAWA, Koichiro SHIBATA, Masakata SHIMIZU, Heinrich Wilhelm ...
    1993 Volume 79 Issue 10 Pages 1151-1156
    Published: 1993
    Released: February 16, 2010
    JOURNALS FREE ACCESS
    The knowledge on the microscopic reduction behavior of fine iron are in hot reducing gas flow is indispensable to accurate description of the extremely complex raceway combustion zone induced by PCI(Pulverized Coal Injection) and OI(fine iron Ore Injection) from blast furnace tuyeres. In the studies using the vertical flow reactor and the tube type reactor where fine materials were transported by the pressure difference in the gas chambers, and thereby a short residence time and a rapid heating rate of fine materials in the raceway combustion zone were simulated, the reduction degree of fine iron are as well as the reduction morphology were investigated in detail under the conditions of the combined injection(PCI+OI) and the carbon coated are injection. The experimental results revealed that the in-flight reduction degree of fine iron are was significantly increased mainly by the improved efficiency of contact of fine ore particles with reducing agents. And the carbon coating of the fine are surface achieved the most excellent condition for promoting the in-flight smelting reduction.
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  • Saburo KOBAYASHI, Masahiro ISHIGAKI, Shin-ichi INABA
    1993 Volume 79 Issue 10 Pages 1157-1163
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
    The pneumatic conveying is a useful technique which is used to provide powder materials such as fine coals, ores or fluxes to the metallurgical furnaces. The present paper describes the monitoring technique to distinguish between the two flow regimes of solid particles ; the dispersive and the sliding flows in the reverse T-type tube junction where alumina particles fall vertically and are conveyed by a horizontal nitrogen flow.
    The flow regimes of the alumina particles were monitored by means of two kinds of indexes; the pressure difference fluctuation of the gas in the tube and the acoustic effect on the tube wall. For this purpose, two pressure transducers were equipped to the tube and two acceleration pick up sensors were touched directly on the outer surface of the tube.
    In the range of Froud number greater than 8, the pressure index is significantly large for the dispersive flow, while small for the sliding flow. In the range of Froud number less than 8, the acoustic index is, in contrast to the above, significantly large for the sliding flow, while small for the dispersive flow. The simultaneous application of both indexes will increase the monitoring reliability.
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  • Shigeta HARA, Hiroshi SUGANO, Kazumi OGINO
    1993 Volume 79 Issue 10 Pages 1164-1168
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
    Solubility of carbon dioxide to melts in the system (BaO+ CaO)-(BaF2+ CaF2) was measured at 1673K by using the thermo-balance method. Itwas found that solubility of CO2 in the melts does not change proportionally with initially mixed BaO content in fluxes, since an reciprocal reaction, (BaO)+(CaF2) = (CaO) + (BaF2) may be established in the melts. Assuming that the equilibrium constant, Kp is 6.7 for the reciprocal reaction, solubility of carbon dioxide in the melt proportionally depends on BaO content in the melts calculated by using Kp = 6.7. It is also shown that experimental works on dephosphorization of Fe-2%C-15%Cr liquid alloy by BaO-CaO-CaF2 and NaF-CaF2 fluxes reported by Inoue et al.can be interpreted with consideration of the reciprocal reaction.
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  • Kohichi YAMAMOTO, Toshiei HASEGAWA, Jin-ichi TAKAMURA
    1993 Volume 79 Issue 10 Pages 1169-1175
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
    The effect of B on microstructure and toughness at the heat affected zone after welding thermal cycle simulations, has been investigated in steels containing titanium oxide particles. The titanium oxide is identified as Ti2O3 with cation vacanies, which contribute to preferential nucleation of MnS and TiN precipitates on Ti2O3. The Mn-depleted zone is formed around Ti2O3 after the MnS precipitation. The Ti2O3 particles with TiN and Mn-depleted zone act as preferential nucleation sites for intra-granular ferrite. The segragation of B at austenite grain boundaries suppresses effectively the nucleation of grain boundary ferrite. While ferrite nucleation at the interface between Ti2O3 and austenite matrix, is not affected by B addition because of B-depleted zone arisen from the diffusion of segregated B into Ti2O3, via cation vacancies. Consequently the B addition to steels with Ti2O3 promotes the formation of fine intragranular ferrite grains so that the heat affected zone toughness is improved even after large heat input welding.
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  • Tetsuya TAGAWA, Takashi MIYATA, Syuuji AIHARA, Kentarou OKAMOTO
    1993 Volume 79 Issue 10 Pages 1176-1182
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
    Formation of martensitic islands is one of the most significant causes of deterioration in toughness of multi-pass weld heat-affected zone of high tensile strength steels. This paper presents the influence of the size and the volume of the martensitic islands on the primary mechanical properties and the cleavage fracture toughness of steels simulated to intercritically reheated grain coarsened HAZ of multi-pass weld. Various thermal cycles simulated to HAZ were applied to five kinds of laboratory melted steels produced by hot rolling, direct quenching and tempering process to reproduce of different states of the martensitic islands. The states of the martensitic islands represented by the average and the maximum size, the volume fraction and the aspect ratio were investigated in correlation with the thermal cycles. The yield and tensile strength increased with the increase of the volume fraction of the martensitic islands. However, the toughness was so sensitive to the formation of the martensitic islands that small amount of the martensitic islands significantly decreased the toughness.
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  • Tetsuya TAGAWA, Takashi MIYATA, Syuuji AIHARA, Kentarou OKAMOTO
    1993 Volume 79 Issue 10 Pages 1183-1189
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
    In the previous work, the state of the martensitic islands and its influence on the fracture toughness in low carbon steels simulated to the heat affected zone of multi-pass weld were investigated.
    It has been shown by the authors that cleavage fracture toughness of steels can be described in terms of the cleavage fracture stress and yield stress of materials.
    In the present work, experimental results in the previous work were analyzed along with the local criterion approach, and successful correlations were obtained. Through this correlation, the influence of the martensitic islands on the deterioration in toughness was investigated. It was suggested that the maximum size of martensitic islands was not an unique metallurgical factor which deteriorated the toughness, and mean free path and the statistical distribution of the martensitic islands had also a great influence on cleavage fracture toughness.
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  • Jianping Mo, Akira SHIBATA, Kazuya MIYAHARA, Yuzo HOSOI
    1993 Volume 79 Issue 10 Pages 1190-1196
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
    The effects of thermomechanical treatments (TMT;warm working and ausforming) on the high temperature deformation behaviors of high carbon and high chromium steels (SKD11 die steels with 1.5%C-12%Cr) are investigated. Thermomechanically treated steels yield very fine ferrite grains of 0.3 to 0.6μm. When tensile tested just below the Ac1 temperature, the elongation of non-thermomechanically treated material is 130%, whereas, the ausformed material shows 320% elongation. The raise in ductility indicates the beneficial effect of TMT due to the refinement of microstructure. Image analysis on the grain-elongation during deformation of the materials shows that the degree of grain-elongation along the tensile axis in the finer grained material is smaller. This means that in the relatively finer grained materials, the contribution of the grain-elongation to the deformation of the materials is smaller but the contribution of grain boundary sliding is larger, compared to that of deformation of coarse grain materials.
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  • Yakichiro KAWAMO, Shozaburo NAKASHIMA, Kunihide TAKASHIMA, Jiro HARASE
    1993 Volume 79 Issue 10 Pages 1197-1203
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
    A study was made on the effect of the inter-pass aging during cold rolling on the secondary recrystallization of the grain-oriented electrical steel with Sn produced by the single-stage cold rolling process. The following conclusions were obtained.
    (1) The specimen without Sn yields a perfect secondary recrystallization structure in case of no inter-pass aging and 200°C inter-pass aging, but no secondary recrystallization in case of 300°C inter-pass aging. This failure of secondary recrystallization is attributed to the smallest amount of the product of {110} and {111} densities in the primary texture, that is, the smallest opportunity of meeting for Goss nuclei with easily consumable grains by them. The specimen with Sn yields a perfect secondary recrystallization structure in all cases of the inter-pass aging mentioned above. This is attributed to the small size of primary grains, the large amount of the product of {110} and {111} densities in the primary texture, and the large amount of effective inhibitors.
    (2) The core loss of the specimen with Sn cold rolled with the inter-pass aging is very small because of the high magnetic flux density and the small size of secondary grains.
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  • Nobuyuki NAKAMURA, Setsuo TAKAKI, Masatomo KAMADA, Youichi TOKUNAGA
    1993 Volume 79 Issue 10 Pages 1204-1209
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
    Sintering and nitriding behaviors of 12mass% Cr ferritic stainless steel (SUS410L) powder compacts in nitrogen gas atmosphere were investigated by means of optical microscopy and chemical analysis. Kinetics of the austenitization by nitriding was also discussed in terms of nitrogen diffusion within austenite grain and along grain boundaries.
    The results obtained are as follows:
    (1) At sintering temperature of 1473K in nitrogen gas atmosphere, about 0.26mass% of nitrogen is absorbed into the steel powders through open pores during heating to the sintering temperature, and ferritic phase changes to austenite owing to nitrogen absorption. Therefore, sintering proceeds in the state of austenitic structure at 1473K and then austenite transforms to martensite on cooling to room temperature after the sintering treatment.
    (2) Grain boundaries within powder particles play a role of free path for nitrogen diffusion, so that the austenitization by nitriding in ferrite powder particles proceeds not only from the particle surface but also from grain boundaries within each powder particle.
    (3) Nitriding rate greatly depends on the grain size within powder particles, although it is dependent on particle size itself when particles are of single crystal. As the grain size within powder particles becomes smaller, nitriding rate is increased.
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  • Kiyoshi KUSABIRAKI, Itaru HAYAKAWA, Takayuki OOKA
    1993 Volume 79 Issue 10 Pages 1210-1216
    Published: 1993
    Released: February 16, 2010
    JOURNALS FREE ACCESS
    The growth behavior of cellular δ phase in Ni-base alloy, modified Inconel X-750 type alloy (X-750M), was investigated mainly by optical and transmission electron microscopy.
    The values of n in Johnson-Mehl's equation for the growth of the cellular δ phase in X-750M aged in various conditions after a solution heat treatment were estimated to be 1.69-1.84.
    The values of n in the case of pre-aged X-750M at 943K for 253ks after a solution heat treatment followed by aging in various conditions, were estimated to be 1.44-1.67. The obtained value of n suggested that the growth of the cellular δ phase in X-750M after the pre-aging treatment obeyed a volume diffusion rate control with zero nucleation rate. Transformation curves of γ + γ'' phases to the cellular δ + γ phases in the specimens aged after the pre-aging treatment were consistent with a theoretical one. The apparent activation energy for the growth of the cellular δ phase in X-750M aged after the pre-aging treatment was estimated to be 232kJ/mol, which is nearly equal to those for diffusion of solute atoms in the alloy.
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  • Mitsunobu KURITA
    1993 Volume 79 Issue 10 Pages N704-N710
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
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  • Yoichi ONO
    1993 Volume 79 Issue 10 Pages N711-N715
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
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  • Kei-ichiro FUWA
    1993 Volume 79 Issue 10 Pages N716-N720
    Published: 1993
    Released: June 30, 2009
    JOURNALS FREE ACCESS
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