鉄と鋼
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
早期公開論文
早期公開論文の10件中1~10を表示しています
  • 新垣 之啓, 髙島 稔, 早川 康之
    原稿種別: 論文
    論文ID: TETSU-2020-093
    発行日: 2021年
    [早期公開] 公開日: 2021/02/13
    ジャーナル フリー 早期公開

    Influence of the initial crystal orientation and carbon content on rolling texture was investigated using quasi-single crystals in 3.2 mass% Si steel. These specimens had {110}<001> and {110}<113> crystal orientation which were known for the near surface texture of the hot-rolled band.

    In the case of the ultra low-carbon specimens, initial {110}<001> rotated to {111}<112> after 66 % reduction cold rolling and initial {110}<113> rotated to near {211}<124>. It was thought that the crystal rotation from {110}<113> to near {211}<124> caused by an activation of {110} slip system which had the second largest schmid factor. {211}<124> was not known for the stable rolling texture, however {211}<124> in-tensity in present experiment was extremely strong. In addition, {211}<124> has geometric character that if it rotates by an activation of one slip system, it will revert to the initial crystal orientation {211}<124> by an activation of another slip system.

    In the case of the specimens containing carbon, {110}<001> rotated to {111}<112> and {100}<011> caused by deformation twinning. On the other hand, {110}<113> rotated to {211}<113>-{111}<112> during the cold rolling. The deformation twinning was also observed. It was thought that the crystal orientation in the deformation twinning ro-tated to near {111}<112> by an activation of {110} slip system.

  • 嶋村 純二, 泉 大地, 寒沢 至, 伊木 聡
    原稿種別: 論文
    論文ID: TETSU-2020-121
    発行日: 2021年
    [早期公開] 公開日: 2021/02/09
    ジャーナル フリー 早期公開

    TMCP (thermo-mechanical controlled process) linepipes have been long used for severe sour environment, but recently sulfide stress cracking (SSC) caused by local hard zones has become a concern. In order to clarify the hardness threshold that leads to SSC, four-point bend (4PB) SSC tests as per NACE TM0316 were conducted under several H2S partial pressure conditions. For 1 bar and higher H2S partial pressure conditions, the surface hardness threshold (at 0.25 mm from surface) observing 4PB SSC specimens without SSC cracking was approximately correlated to a maximum acceptable hardness level of 250 HV0.1. By suppressing the hard lath bainite (LB) and obtaining the soft granular bainite (GB) microstructure, stable low surface hardness of 250 or less HV0.1 was achieved, resulting in superior SSC-resistant property. On the other hand, it was found that SSC crack propagated when the surface hardness increased with increasing the volume fraction of LB microstructure. In the case of 16 bar H2S partial pressure condition, the crack growth rate increased in the sour environment, and hydrogen embrittlement by H2S was promoted. However, in the 4PB SSC test at 16 bar, since the shape of localized corrosion is semicircular due to low localized corrosivity, it was considered that the stress concentration and transition to crack were suppressed. This may be the reason why the SSC susceptibility was similar to 1 bar condition, especially in the 4PB SSC test using the samples with lower surface hardness level of 250 or less HV0.1.

  • 溝口 友樹, 小山 元道, 野口 博司
    原稿種別: 寄書
    論文ID: TETSU-2020-106
    発行日: 2021年
    [早期公開] 公開日: 2021/01/25
    ジャーナル フリー 早期公開

    Compact tension tests for fatigue crack growth were carried out on transformation-induced plasticity (TRIP) maraging steel with two different annealing times (1 h and 8 h). Interestingly, resistance to the long crack growth increased with increasing annealing time at a ΔK ranging f rom 33 to 50 M Pa∙m1/2, while short crack growth resistance, e.g., crack growth in a smooth specimen, was reported to show an inverse trend. It is also noteworthy that increasing annealing time in TRIP-maraging steel decreases both yield and tensile strengths. Namely, the resistance to the long crack growth showed totally inverse trend to the tensile properties, in terms of annealing time. The major microstructural change by increasing annealing time was retained austenite fraction. Specifically, increasing annealing time increases austenite fraction, which may have assisted TRIP-related phenomena and associated resistance to the long crack growth, e.g. transformation-induced crack closure.

  • 丸岡 伸洋, 久保 裕也
    原稿種別: 論文
    論文ID: TETSU-2020-082
    発行日: 2021年
    [早期公開] 公開日: 2021/01/21
    ジャーナル フリー 早期公開

    It is necessary to develop an innovative iron-making technology for low-grade iron ore containing a high concentration of P. In this study, we propose a new process for enriching phosphorus in the C2S phase by mixing high-P iron ore, CaO, and graphite in appropriate proportions and partially reducing it. In this study, high-P iron ore adjusted to various basicities and reducing agent ratios was heated at 1573 K in Ar atmosphere, and the obtained sample was analyzed by EPMA. The results showed that in the reduced sample obtained under the conditions of C/S = 2.0 and Target FetO = 60%, more than 95% of P was distributed to the C2S phase, and the P content in metallic iron was sufficiently low.

  • 森 健一, 橋本 翔太朗, 宮原 光雄
    原稿種別: 論文
    論文ID: TETSU-2020-109
    発行日: 2021年
    [早期公開] 公開日: 2020/12/29
    ジャーナル フリー 早期公開

    Cyclic fatigue, dwell fatigue and crack growth properties were evaluated in the axial direction (L) and transversal direction (T) of Ti-6Al-4V forged round bar. In the SN curve where the stress is normalized by 0.2% proof stress, the cyclic fatigue life in the L/T direction is almost the same, whereas the dwell fatigue life in the T direction is as short as 1/5. In dwell fatigue, ductile fracture occurred when the maximum stress was higher than 95% of 0.2% proof stress. At stresses below 870 MPa, the inelastic strain range and the strain increase rate in the T direction gradually decreased with decreasing stress, and the fracture mode transitioned to that with fatigue crack growth. The gradual change must have been caused by the mixture of anisotropic microtexture regions. At stresses below 825 MPa, the fracture mode transitioned rapidly in the L direction, where the soft oriented microtexture regions were dominant. In the low ΔK region (≤15MPa√m), the crack growth rate in the axial direction was about twice that in the radial direction of the bar. The shorter dwell fatigue life in the T direction under stress conditions showing fatigue crack growth was explained by the significantly earlier crack initiation compared to that in cyclic fatigue and the faster crack growth along the microtexture in the axial direction of the bar.

  • 原野 貴幸, 根本 侑, 村尾 玲子, 木村 正雄
    原稿種別: 論文
    論文ID: TETSU-2020-098
    発行日: 2021年
    [早期公開] 公開日: 2020/12/26
    ジャーナル フリー 早期公開

    The mass fraction of each crystalline phase in inorganic materials can be investigated using the Rietveld refinement of the X-ray diffraction (XRD) patterns. For quantitative analysis, differences in the values of the linear absorption coefficient, μ, among the crystalline phases must be considered when certain X-ray sources are used, because such differences often affect their mass fractions. Herein, we evaluate the effects of the differences between the Cu and Co X-rays on the mass fractions of the crystalline phases in iron sintered ores using the XRD-Rietveld method by performing two types of XRD measurements. Type 1 samples modeled materials with two different particle size combinations of α-Fe2O3 and ZnO. Type 2 samples used powder mixtures to simulate iron sintered ores composed of α-Fe2O3, and synthesized SFCA and SFCA-I in various mass fractions. Moreover, a correction method was developed using the Taylor-Matulis (TM) correction that considers the μ of each phase and the average particle diameter of each crystalline phase determined by scanning electron microscopy with energy dispersive spectroscopy. For type 1 samples, results that were in good agreement with the initially-charged mass fractions could be obtained using the TM correction, even in the presence of significant differences in R between α-Fe2O3 and ZnO. The results for type 2 samples confirmed that quantitatively accurate mass fractions could be obtained using the TM correction with an accuracy of approximately ±3 mass% for Cu and Co sources, whereas the error was greater than ±3 mass% for Cu source when the TM correction was not applied.

  • 村尾 玲子, 木村 正雄
    原稿種別: 論文
    論文ID: TETSU-2020-077
    発行日: 2021年
    [早期公開] 公開日: 2020/12/19
    ジャーナル フリー 早期公開

    Reduction behavior of various multi-component calcium ferrites at 900°C were investigated by using in situ X-ray diffraction (XRD) and X-ray absorption spectroscopy. Intermediate components were determined by XRD, and change in X-ray absorption spectra of Fe and Ca K-edges were analyzed to determine reaction rate constants. SFCA-I (Ca3(Ca,Fe)(Fe,Al)16O28) and SFCA (Ca2(Fe,Ca)6(Fe,Al,Si)6O20) consist of layered structure of spinel and pyroxene. Early stage of reduction reaction, diffraction peaks of spinel structure were observed which indicating SFCA-I and SFCA decomposed into these units at the first step of the reduction reactions. The spinel was reduced sequentially into FeOx then Fe. Intermediate component, Ca2(Fe,Al)2O5 originated in pyroxene module was hard to reduce and reaction was controlled by decomposition of this phase. Reduction of SFCA-I started later than SFCA (with 5.7 mol% Al2O3) under hydrogen gas reduction condition at 900°C. SFCA with a high aluminum content indicated lower reducibility than that with a low one.

  • 仲村 英也, 河田 晟生, 馬場 智也, 大崎 修司, 綿野 哲
    原稿種別: 論文
    論文ID: TETSU-2020-079
    発行日: 2021年
    [早期公開] 公開日: 2020/12/04
    ジャーナル フリー 早期公開

    There is a great demand for understanding the layering granulation of coarse and fine iron ore particles. For the understanding, a numerical simulation can be powerful approach. We here proposed a numerical simulation method, by which the deposition of fine particles with water on the surface of a coarse particle can be simulated. In the proposed model, surface of a coarse particle was modeled as a flat surface. The fine particles and water droplets were then deposited on the flat surface with minimizing the surface energy of the liquid and potential energy of the particles, resulting in a bed of the deposited particles with water under the equilibrium state with considering the influence of the physicochemical properties of the particles and liquid. First, an experiment of the deposition of spherical polymer beads with water droplet on the flat polymer sheet was performed. The simulation results showed an agreement with the experimental result, demonstrating the validity of the proposed simulation method. Second, influences on the liquid amount and contact angle (i.e., wettability) of the particles were analyzed. The simulation results suggest that the smaller contact angle (good wettability) can result in more rigid bed with less ungranulated particles.

  • 村上 太一, 中村 周矢, 丸岡 大佑, 葛西 栄輝
    原稿種別: 論文
    論文ID: TETSU-2020-061
    発行日: 2021年
    [早期公開] 公開日: 2020/11/18
    ジャーナル フリー 早期公開

    Depletion of high-grade iron ore resources leads to increasing use of ore concentrates as raw materials for sinter. One of the methods to effectively utilize such concentrates is Mosaic EmBedding Iron Ore Sintering (MEBIOS), which pre-granulated green pellets are charged into sintering bed with the mixture of other raw materials. In this study, effects of the ore type and gangue mineral components on the strength of sintered pellet prepared of fine concentrates were examined. Green pellets were prepared using hematite and magnetite ores, burnt lime and alumina and mullite reagents, and then sintered at 1300°C. The strength of sintered pellet increases with increasing basicity (CaO/SiO2, C/S) at lower basicity region. The pellet using hematite ore with C/S above 1.5 showed higher strength than 980 N. It can be attributed to the melt formation during sintering. On the other hand, when using magnetite ore, higher strength than 980 N was obtained above C/S = 1.0. The reason is an acceleration of solid-state sintering by the volume expansion due to oxidation of magnetite to hematite. Increasing Al2O3 content leads to decreasing the strength of pellet because oxidation of magnetite is prevented by the increasing amount of formed melt.

  • 平 健治, 原 恭輔
    原稿種別: 論文
    論文ID: TETSU-2020-068
    発行日: 2021年
    [早期公開] 公開日: 2020/09/11
    ジャーナル フリー 早期公開

    For achieving high sinter yield and quality, various technologies are being implemented and developed to control the heat pattern during the sintering reaction. Further improvements in these technologies necessitate detailed time-course profiles of temperature at all sinter-bed heights; however, no technique has yet been reported for determining the temperature distribution in the top layers of the sinter bed at high spatial and time resolutions. Herein, detailed heat patterns in these layers were visualized by a newly developed pot test apparatus having ~300-mm sinter-bed height. The developed apparatus demonstrated the effect of ignition time on heat patterns during combustion and immediately after ignition. Ignition times of 30, 60, and 90 s demonstrated that the high-temperature holding time increased with an increase in ignition time, and this effect is more evident in the top layer. All parameters, including high-temperature holding time, flue gas composition, and sinter yield, suggest that a longer ignition time intensified coke combustion in the top half layer. The developed technique to measure the temperature in the top layer will quantitatively clarify the effect of segregation or ignition condition on the heat pattern in the top layer.

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