著者

相原 安津夫

出版者

The Iron and Steel Institute of Japan

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.67, no.1, pp.35-46, 1981-01-01 (Released:2009-06-19)

著者

Nobuo Nakada Norihide Fukuzawa Toshihiro Tsuchiyama Setsuo Takaki Tamotsu Koyano Takashi Iwamoto Yasuhiro Omori

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.53, no.1, pp.139-144, 2013 (Released:2013-01-15)

参考文献数

22

被引用文献数

10 13

---

In order to understand the mechanism of isothermal transformation of Fe–N alloy, the isothermal transformation microstructure that forms in a wide temperature range below Ae1 was investigated in Fe–2.6 mass%N hypereutectoid alloy by means of the electron back scatter diffraction method in addition to the conventional microstructural observation methods. High-nitrogen austenite fully decomposed to ferrite and Fe4N over the entire temperature range, and the time-temperature-transformation (TTT) diagram had a C shape with a nose temperature around 700 K. The hardness linearly increased with decreasing transformation temperature because the microstructure became finer, but the morphology of the (ferrite + Fe4N) structure changed discontinuously at around 800 K. From the microstructural and crystallographic analyses, it was concluded that the microstructure formed at higher temperature is a lamellar eutectoid structure, braunite, while the other is an upper bainitic structure containing bainitic ferrite formed through a displacive mechanism and Fe4N formed by concentration and ordering of the nitrogen. Since Fe4N is a counterpart of the cementite in Fe–C alloy, the respective structures are similar to pearlite and upper bainite in carbon steel.

著者

北野 智靖 田川 哲哉 粟飯原 周二 Mirco Daniel CHAPETTI 宮田 隆司

出版者

The Iron and Steel Institute of Japan

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.83, no.6, pp.401-406, 1997-06-01 (Released:2009-06-19)

参考文献数

19

被引用文献数

2 1

---

The influence of microstructure on non-propagating behavior of fatigue crack below the fatigue limit was investigated using low carbon steels with three different microstructures simulated heat affected zone of welds. Notched round bar specimens with different stress concentration factors were fatigued under axial loading at the stress ratios R=-1 (tension-compression). Fractographic and metallographic observations of non-propagating cracks at the stress level below fatigue limit were examined, and correlation between non-propagating crack and microstructures was investigated. Non-propagating cracks could be classified as Stage I or Stage II, depending on the microstructure and notch root radius. In the case of dull-notched specimens, where the notch factor in fatigue is proportional to stress concentration factor, the non-propagating crack is Stage I type regardless the microstructure, although Stage II type cracks were observed in sharp notched specimens for particular materials. The criteria for both Stage I and Stage II type non-propagating crack were discussed on the basis of the point stress model and fracture mechanics.

著者

C. E. LOO

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.45, no.4, pp.436-448, 2005 (Released:2006-01-27)

参考文献数

45

被引用文献数

48 63

---

The main purpose of iron ore sintering is to produce a strong agglomerate for the blast furnace. This is achieved by partially melting a sinter mix at high temperature and then allowing the melt to solidify into a bonding phase for the unreacted material. The melt formation and subsequent solidification processes are highly dependent on the composition of the blended mix. This paper summarises the differences in sintering behaviour between hematite ores and goethitic ores based on past research programs carried out at BHP Billiton. From a fundamental evaluation of the sintering process, it is clear that productivity can be an issue with goethitic ores because of their low bulk density and high porosity. This paper recommends steps towards overcoming losses in productivity. The effect of goethitic ores on coke rates is also a matter of general concern and this study shows that the addition energy required to dehydrate goethites and remove the additional water introduced into the system is comparatively small. The properties of melts have been shown to be particularly important in determining yield from a sinter machine and it is evident that the easy-melting properties of goethitic ores will also have an impact on this area. This paper also reviews our current understanding of how goethitic ores can influence sinter quality. The implication of fundamental knowledge on practical sinter plant operation is discussed throughout and collated at the end of the paper.

著者

Yasuko Furunushi Kazuhiro Nagata

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.54, no.5, pp.1074-1079, 2014-05-15 (Released:2014-06-12)

参考文献数

10

被引用文献数

2 6

---

Ancient Japanese low-carbon steel, called “Hocho-tetsu” or “Wari-tetsu”, was made in “Okaji” process by decarburizing pig iron named “Zuku” produced in “Tatara” process. It is known that the low-carbon steel had higher corrosion-resistance and was much easier to forge-and-weld than modern steel. Japanese iron nails, called “Wakugi”, were made from “Hocho-tetsu” and had been used in shrines and temples until the Meiji period. The low carbon steel tends rapidly to make thin film of magnetite, called “Kurosabi”, on the surface to protect against corrosion under wet atmosphere or heating. The magnetite film is produced from the reaction of iron and oxygen. The oxygen and carbon concentrations in the iron matrix of ferrite in “Wakugi” were measured using EPMA to be about 0.15 to 0.38 mass% and 0.02 mass%, respectively. The oxygen concentration is over-saturated from the oxygen solubility of αFe and γFe. The over-saturated concentration of oxygen in “Wakugi” was caused from “Okaji” process without deoxidation of steel.

著者

Jan Bohacek Abdellah Kharicha Andreas Ludwig Menghuai Wu

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.54, no.2, pp.266-274, 2014-02-15 (Released:2014-03-11)

参考文献数

26

被引用文献数

11 15

---

In order to simulate the mold filling and solidification of the outer shell of large work rolls being cast by horizontal centrifugal casting, the shallow water equations were adopted to solve the 2D average flow dynamics of the melt spreading inside the cylindrical mold. The model accounts for centrifugal force, Coriolis force, shear force, gravity and convective and diffusive energy transport. The solidification front was tracked by fulfilling the Stefan condition. Radiative and convective heat losses were included from both, the free surface and the outer wall of the mold. By introducing a stochastic factor to account for the irregular filling jet behavior an uneven spreading of liquid from the center of the mold towards the extremities was predicted. Thus, the formation of the first solid layer also happens unevenly. However, when the mold is covered everywhere with a solid layer, the solidification rate decreases and further filling increases the height of the liquid layer. With increase liquid height the amplitude of the free surface waves also increases.

著者

福山 誠司 横川 清志 山田 良雄 飯田 雅

出版者

The Iron and Steel Institute of Japan

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.78, no.6, pp.860-869, 1992-06-01 (Released:2009-05-29)

参考文献数

43

被引用文献数

8 14

著者

西野 知良 本間 浩夫

出版者

The Iron and Steel Institute of Japan

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.56, no.7, pp.859-868, 1970-06-01 (Released:2010-10-12)

参考文献数

66

被引用文献数

2 1

---

The dependence of the yield stress of mild steel at low temperatures on grain size, strain rate and temperature was studied mainly by compressive deformation test.(1) The following equation relating strain rate (ε), temprature (T) and frictional stress (σt) of Petch equation was obtained;This is applicable when at is in the range of 8.7 to 28.2 kg/mm2. Strain rate exponent n and activation energy E are constant, both being independent on temperature, strain rate or stress. Above this stress level, n becomes larger but E is substantially invariable.(2) According to the study on BCC metals, it can be said that they behave in a similar manner to mild steel. That is, is is in the range of 7 to 9, being constant and specific to BCC metals, and in addition, E is approximately proportional to an energy of μb3, where μ is the shear modulus and b the Burgers vector.(3) The relations between strain rate, grain size and ductile-brittle transition temperature were studied by using the above equation, and the calculated temperatures are generally in accordance with the measured values.

著者

成瀬 亘

出版者

The Iron and Steel Institute of Japan

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.64, no.5, pp.650-658, 1978-04-01 (Released:2010-02-22)

参考文献数

15

著者

徳田 昌則 吉越 英之 大谷 正康

出版者

The Iron and Steel Institute of Japan

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.56, no.14, pp.1899-1915, 1970-12-01 (Released:2010-10-12)

参考文献数

123

被引用文献数

21 9

著者

Takayuki MAEDA Yoichi ONO

出版者

The Iron and Steel Institute of Japan

雑誌

Transactions of the Iron and Steel Institute of Japan (ISSN:00211583)

巻号頁・発行日

vol.25, no.12, pp.1191-1193, 1985 (Released:2006-09-08)

参考文献数

2

被引用文献数

17 18

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The reduction behavior of constituent minerals of iron ore sinter has been investigated microscopically by using two kinds of commercial sinter having different basicity and FeO content. The results are summarized as follows:(1) There is a difference in reducibility between hematite and magnetite, and hematite is reduced faster than magnetite.(i) Both hematite and magnetite are reduced rapidly to wustite, but there is a difference in the rate of reduction from wustite to iron.(ii) The reduction of wustite reduced from hematite does not proceed topochemically but homogeneously. Although the reduction of the wustite is comparatively fast in the almost whole period of reduction, part of the wustite becomes surrounded by dense iron and left unreduced in the final stage of reduction.(iii) In the reduction of wustite reduced from magnetite, almost all grains of wustite are surrounded by dense iron from the early stage of reduction, which causes the retardation of reduction.(2) Calcium ferrite is reduced much faster than the wustites mentioned above, which is shown by the fact that many grains of wustite are left unreduced even after calcium ferrite is reduced completely.(i) The reduction of calcium ferrite proceeds topochemically.(ii) Iron produced by the reduction of calcium ferrite is very porous and not sintered, which does not cause the retardation of reduction.(3) In many cases, reduction begins with the surface of mineral grains facing a macro-pore, which serves as a passage of reducing gas to each mineral grain to be reduced.

著者

Reon Ando Takashi Matsuno Tomoko Matsuda Norio Yamashita Hideo Yokota Kenta Goto Ikumu Watanabe

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.61, no.1, pp.473-480, 2021-01-15 (Released:2021-01-16)

参考文献数

21

被引用文献数

3

---

Herein, we investigated the local preliminary hardening of ferrite near the ferrite–martensite interfaces in a dual-phase (DP) steel. Geometrically necessary dislocations (GNDs), generated due to interfacial misfit between different phases, may cause preliminary hardening of ferrite around such interfaces. However, for nano-hardness distribution, the hardened zone was not evidently detected by scattering measurement. Thus, we factorized nano-hardness scattering to estimate the actual ferrite hardness near ferrite–martensite interfaces.First, nano-hardness was measured around a martensite island using a conical nano-indenter in the DP steel containing 10% martensite by volume. Taking into account the scattering, the nano-hardness measurement converged to the hardness of ferrite, exceeding the distance corresponding to the nano-indenter radius. Thus, a preliminary hardening zone was not detected. Subsequently, the surface of the nano-indented microstructure was polished and observed using scanning electron microscopy (SEM) by analyzing electron back scattering diffraction (EBSD). This analysis confirmed the presence of the nano-indented microstructure under ferrite. Moreover, it established that the majority of the irregularly higher nano-hardness was caused by the buried martensite under ferrite. The value of the kernel average misorientation (KAM), which is proportional to the GND density for other irregularly higher nano-hardness points, was higher for the nano-indented microstructure as compared to that of the buried martensite. On the other hand, the ferrite was expanded under the nano-indented points for the majority of the irregularly lower nano-hardness, with some exceptions. Further, soft martensite was observed to induce irregularly lower nano-hardness locally around the interface.

著者

Toshiyuki Hirosawa Akinori Murao Nobuyuki Oyama Shiro Watakabe Michitaka Sato

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.55, no.6, pp.1321-1326, 2015-06-15 (Released:2015-06-20)

参考文献数

12

被引用文献数

4 6

---

The use of high reactivity coke is a technology that dramatically improves the reaction efficiency in blast furnaces by decreasing the temperature of the thermal reserve zone. In this study, a blast furnace shaft simulator was developed to estimate the temperature of the thermal reserve zone and the distributions of the temperature and gas composition in the blast furnace when using cokes with different reactivity. The shaft simulator combines an experimental reaction furnace and a calculation model. Chemical reaction and mass/heat transfer phenomena in the blast furnace are considered in the calculation model so as to calculate the ore and coke reaction rate and the distribution of temperature and gas composition. Relatively small amounts of packed coke and sinter specimens are reacted with the temperature and gas composition controlled based on the calculation results. The coke gasification rate is fed back to the calculation model, and it is then possible to estimate the temperature of the thermal reserve zone and the distributions of the temperature and gas composition in the blast furnace. Shaft simulator experiments with high reactivity coke, such as CIC (Carbon Iron Composite), showed that the temperature of the thermal reserve zone is 140 K lower with high reactivity coke than with conventional coke.

著者

Yusuke Kashihara Yuki Iwai Natsuo Ishiwata Nobuyuki Oyama Hidetoshi Matsuno Hiroyuki Horikoshi Koji Yamamoto Minoru Kuwabara

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.57, no.4, pp.665-672, 2017-04-15 (Released:2017-04-19)

参考文献数

29

被引用文献数

4 6

---

Improved permeability and increased gas utilization have been desired in order to achieve low coke rate operation of blast furnaces. Coke mixed charging in the ore layer is one of the effective measures for realizing these improvements. A new charging technique for mixing small coke in the ore layer at a blast furnace with a center feed type bell-less top was developed and investigated in an experiment with a 1/18.8 scale model of an actual blast furnace at JFE Steel. By the new charging technique that small coke was charged in the determined port of the upper bunker before ore was charged in the upper bunker, the discharge pattern of the mixed small coke discharged from the bell-less top was improved, and the radial distribution of the mixed small coke ratio at the furnace top after the mixed materials were charged in the blast furnace was also improved. The new charging technique was applied to an actual blast furnace at JFE Steel, and improvement of gas permeability and a decrease in the coke rate were confirmed.

著者

Kazuhira Ichikawa Yusuke Kashihara Nobuyuki Oyama Toshiyuki Hirosawa Jun Ishii Michitaka Sato Hidetoshi Matsuno

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.57, no.2, pp.254-261, 2017-02-15 (Released:2017-02-16)

参考文献数

22

被引用文献数

11 14

---

Recently, low coke rate blast furnace operation has been required in response to the rising cost of coking coal. However, the thickness of the coke layer decreases in low coke rate operation. Since it is known that the gas permeability of the blast furnace deteriorates as the coke layer thickness decreases, it is important to determine the minimum coke layer thickness for stable blast furnace operation. On the other hand, the minimum coke layer thickness has not been clarified due to a lack of equipment capable of measuring the effect of the coke layer thickness on permeability.In this study, a new experimental device called the cohesive zone simulator was developed to clarify the minimum coke layer thickness. In the cohesive zone, gas flows horizontally along the coke layer. In order to quantify the effect of the coke layer thickness on permeability, this horizontal gas flow should be simulated. Therefore, this simulator simulates a horizontal gas flow.Next, the effect of the coke layer thickness was quantified by using the cohesive zone simulator. The results showed that melting iron ore penetrated into the coke layer and closed part of the layer. These phenomena caused a deterioration of permeability under thin coke layer thickness conditions.Finally, a pressure drop estimation model considering penetration of the coke layer by melting ore was developed with the aim of quantifying the minimum coke slit thickness.

著者

Naoyuki Takeuchi Yuji Iwami Takahide Higuchi Koichi Nushiro Nobuyuki Oyama Michitaka Sato

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.54, no.4, pp.791-800, 2014-04-15 (Released:2014-06-05)

参考文献数

31

被引用文献数

11 16

---

In the recent operation of blast furnace, it is supposed that high gas permeability of burden is important for low RAR and high PCR operation. In this work, sinter quality for improvement in gas permeability of blast furnace was investigated with reduction degradation and under-load-reduction tests. As the results, the reduction degradation of sinter is deteriorated by increasing H2 concentration in the reduction gas under the condition of below 3.8 vol% H2. However, over 3.8 vol% H2, increase of H2 has no effect on the reduction degradation because the diffusion of reduction gas in the sinter is limited. On the other hand, from the under-load-reduction test, there is possibility that increase in H2 concentration of reduction gas and decrease in slag ratio in sinter are effective to improve gas permeability of lower part of blast furnace rather than reducibility of sinter. Due to adoption of these experimental results to a 2-dimentional mathematical simulation model, the precision of pressure drop calculation of blast furnace was improved. It is considered from the evaluation by this model calculation that the RDI, a slag ratio and the slag viscosity as the sinter properties are greatly influence on the permeability of blast furnace.

著者

林 武志

出版者

The Iron and Steel Institute of Japan

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.64, no.13, pp.2037-2056, 1978-11-01 (Released:2010-02-22)

参考文献数

29

被引用文献数

2 2

著者

福島 英二

出版者

The Iron and Steel Institute of Japan

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.61, no.10, pp.2501-2513, 1975-08-01 (Released:2010-10-12)

参考文献数

54

被引用文献数

1 1

著者

Hirokazu Natsumeda Amane Kitahara Shunichi Hashimoto

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.57, no.5, pp.945-952, 2017-05-15 (Released:2017-05-16)

参考文献数

32

被引用文献数

3 6

---

Recently, 5% Mn steel has been focused on as one of the promising candidates for third generation AHSS by showing an excellent TS (Tensile Strength)-El (Elongation) relationship. The excellent TS-El relationship is brought about by a large volume fraction of retained austenite through the enrichment of austenite stabilizing elements such as C and Mn in retained austenite. The effect of the microstructure of mother hot band on the changes in microstructure and mechanical properties was compared with the intercritical annealing time in this study. The steel containing about 10% of retained austenite in a mother hot band exhibited a higher volume fraction of retained austenite and higher strength after intercritical annealing. On the other hand, the steel which did not contain retained austenite in a mother hot band exhibited excellent TS-El combination. The difference of work hardening behavior in these steels was analyzed and thought to be brought about by the difference of transformation behavior during deformation determined by the stability of retained austenite affected by Mn concentration. Although the precipitation of cementite was intended to effectively act as a nucleus of reverted austenite formation and to accelerate its formation, this affirmative result was not obtained. Since the volume fraction of cementite in a short annealing time is nearly the same in all hot rolling conditions, the higher volume fraction in hot band did not act to increase retained austenite during intercritical annealing.

著者

Abbas Mohammadi Motomichi Koyama Gregory Gerstein Hans Jürgen Maier Hiroshi Noguchi

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

pp.ISIJINT-2019-510, (Released:2020-05-25)

参考文献数

42

被引用文献数

4

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Hydrogen-assisted crack growth of pre-strained twinning-induced plasticity (TWIP) steel was investigated using artificial defects (micro-drilled holes), which acted as artificial crack initiation sites. Hydrogen was introduced into the specimens by electrochemical hydrogen charging during slow strain rate tensile test. The quasi-cleavage crack propagation observed was due to repeated crack initiation near the crack tip and subsequent coalescence. Crack initiation near the crack tip occurred after plastic deformation of the crack tip, and pre-straining facilitated plasticity-driven crack initiation. The early stage of plasticity-driven crack growth was sensitive to the crack length and remote stress level. Accordingly, the crack growth rate in the early stage increased with the increase in the initial defect size. In the following stage of the crack growth, the crack growth rate exhibited a complicated trend with respect to the crack length, which is possibly due to the plastic-wake-altered stress field around the crack tip, which depends on the initial defect size.