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Kitagawa, Yoshihiro; Shirahama, Takuma*; Kisohara, Naoyuki; Tsuboi, Akihiko
Dai-96-Kai Reza Kako Gakkai Koen Rombunshu (Internet), p.91 - 96, 2022/01
Laser scanning quenching is a locally and rapidly heat-treated process and has an advantage of no coolant required. Compared with conventional technique such as induction quenching, the region of laser quenching is about 0.5
0.7mm in depth and it needs to be expanded for more applications or durability. For this purpose, the temperature distributions and transitions in materials during laser irradiation have been revealed by using a 3D heat transfer computer code, micro-structural observation and hardness transitions in depth direction. The results indicate the laser irradiation with low power and low scan speed condition allows deeper quenching area, but it also suggests the hardness of the deepest quenching area is degraded due to slow temperature decreasing rate after laser heat scanning. Multiple times continuous irradiation have been proposed and studied to resolve this hardness degradation, and maximum quenching depth of 1.4mm is obtained under three times irradiation and controlling its power and scan speed properly.
Saruta, Koichi; Shirahama, Takuma*; Yamaguchi, Toshihiko; Ueda, Masashi
E-Journal of Advanced Maintenance (Internet), 10(2), p.1 - 8, 2018/08
Mihalache, O.; Yamaguchi, Toshihiko; Shirahama, Takuma; Ueda, Masashi
E-Journal of Advanced Maintenance (Internet), 9(2), p.60 - 65, 2017/08
Mihalache, O.; Yamaguchi, Toshihiko; Shirahama, Takuma; Ueda, Masashi
Proceedings of 3rd International Conference on Maintenance Science and Technology (ICMST 2016) (Internet), 2 Pages, 2016/11
Sato, Yuji; Shirahama, Takuma*; Ishibashi, Junichi*; Muramatsu, Toshiharu
no journal, ,
no abstracts in English
Ishiguro, Takahiro; Hattori, Shushi*; Hattori, Tsukasa*; Shirahama, Takuma*; Ueda, Masashi
no journal, ,
In sodium cooled fast-reactors, opaque and highly chemical reactive sodium is used as coolant. Therefore, in the event of a loose part (dropped part) occurring, it is difficult to search and recover them under liquid sodium, potentially stopping the plant operation for a long time. The paper presents a prototype of the recovery mechanism, which is an important component of recover device for loose parts, and reports measurements and testing of it in liquid sodium.
Sato, Yuji; Shirahama, Takuma*; Ishibashi, Junichi*; Muramatsu, Toshiharu
no journal, ,
no abstracts in English
Ueda, Masashi; Ishiguro, Takahiro*; Hattori, Shushi*; Hattori, Tsukasa*; Shirahama, Takuma*
no journal, ,
Sodium-cooled fast reactors need special maintenance technologies such as remote maintenance, under sodium viewer etc., because sodium is opaque, chemically active and the maintenance works must be performed in high temperature. To acquire basic knowledge for remote maintenance technology in liquid sodium, a trial product of recover device for loose parts was fabricated and tested in sodium. The positions of loose parts were approximately estimated by using ultrasound, and the parts were recovered by the device successfully.
