著者

前野 圭輝 田中 將己 吉村 信幸 白幡 浩幸 潮田 浩作 東田 賢二

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.98, no.12, pp.667-674, 2012 (Released:2012-11-30)

参考文献数

31

被引用文献数

7 27

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In order to elucidate the mechanism behind the decrease in the brittle-to-ductile transition (BDT) temperature with the addition of Ni, impact tests and tensile tests were performed at various test temperatures from 130K to 320K with Ni added ultra-low carbon steels. The dependence of absorbed impact energy on temperature and the Ni content indicates that the BDT temperature was decreased with the increasing Ni content, which suggests that the dislocation mobility at low temperatures was increased with the Ni content. The yield stress which is also influenced by the dislocation mobility was decreased at low temperatures while it was increased at room temperature with the Ni content. The values of the activation volume and the effective stress were measured at several temperatures, and then the dependence of the activation energy for dislocation gliding on Ni content was obtained by extrapolating the relation between temperature and the multiplication of the activation volume and the effective stress to 0K. The activation energy was found to decrease with the increasing Ni content, which suggests that the dislocation mobility was increased with the addition of Ni. Discrete dislocation dynamics simulation was also performed in order to calculate the dependence of fracture toughness on temperature and the Ni content, and it was clarified that the BDT temperature is decreased by increasing dislocation mobility.

著者

潮田 浩作 吉村 仁秀 海藤 宏志 木村 謙

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.100, no.6, pp.716-727, 2014 (Released:2014-05-31)

参考文献数

67

被引用文献数

7

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Steels have made remarkable progress in order to meet the strict requirements of today’s society. Such progress is based on scientific elucidation of the functions of alloying elements, their effective utilization, and the innovative production processes.Since natural resources are limited, it is important to increase their productivity for the continuous development of our society. Therefore, proper management taking into account the element strategy is becoming extremely important.Steel industries are highly dependent on rare metals. Therefore, they are easily influenced by the hazards of rare metals, avoidance of which is extremely crucial.This paper focuses on steels such as flat-rolled product, plate, pipe & tube and stainless steel, and historically reviews them from the aspect of changes in the surrounding market together with the technological developments such as new steel products and exploitation of rare metals for them. The functions of rare metals are classified into three types, i.e. the control of a) microstructures, b) mechanical properties and c) anti-corrosion properties, and the present understanding of them is discussed from a scientific perspective. Furthermore, the concrete future scientific and technological problems are surveyed. It is revealed that there are still many issues that need to be addressed. Exploitation of the advanced analytical techniques together with computational science is expected to contribute to solving the long standing problems and to stimulate a breakthrough in this field.

著者

玉木 輝幸 村上 健一 潮田 浩作

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.101, no.3, pp.211-220, 2015 (Released:2015-02-28)

参考文献数

13

被引用文献数

1

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A local curvature multi-vertex model was developed. This model is a straightforward two-dimensional topological network model based on physical principles that consider the local curvatures of grain boundaries and the grain boundary tensions at triple junctions. Virtual vertices are set on the grain boundaries in order to calculate the driving forces of grain boundary and triple junction migration. Therefore, the accuracy of the developed model is higher than that of the conventional curvature model and the vertex model. In the proposed model, the generation and annihilation of virtual vertices maintained a proper configuration of virtual vertices, and high accuracy is expected with a suitable set of simulation parameters. The proposed model was verified by the grain growth simulation using adequately determined parameters for the artificially generated specimens with 5040 grains.