04aD01P
水中爆接タングステン被覆材の耐熱衝撃特性及び、機械的特性に関する研究
Research on mechanical property and resistance to thermal shock of tungsten
cladded steels by underwater explosive welding
森大知1、権暁星1、笠田竜太1、小西哲之1、谷川博康2、森園靖浩3、外本和幸3
Daichi Mori1, Hyoseong Gwon1, Ryuta Kasada1, Satoshi Konishi1 ,Hiroyasu Tanigawa2, Yasuhiro Morizono3, Kazuuki Hokamoto3
1
京都大学、2日本原子力開発機構、3熊本大学
1
Kyoto University, 2JAEA, 3Kumamoto University
1.

Introduction

The plasma facing components using tungsten-coated
reduced-activation ferritic (RAF) steels are key
technologies to realize the fusion reactor because thesecomponents will be used in severe environments withenergetic particle irradiation at high temperatures. It isknown that explosive welding is a solid-state welding
using a controlled energy of a detonating explosive on
the material surface. Generally, explosive welding isperformed in the atmosphere by placing an explosive on
the one surface of the flyer plate located away from thebase plate to achieve a desired velocity during collisionof the plates. The underwater explosive welding
developed by one of the authors has been successfully
applied in the joining of many kinds of similar or
dissimilar materials including a tungsten foil on a copper
base plate. In the last report, the underwater explosive
welding was successfully used to clad tungsten on F82H.
The present study reports mechanical properties andresistance to thermal shock of tungsten cladded steels
made by underwater explosive welding.
2. Experimental Method
Underwater explosive welding was carried out at ShockWave and Condensed Matter Research Center,
Kumamoto University. The base plate used for theunderwater
explosive
weldingisF82H-IEA(Fe-8Cr-2W-V-Ta-0.1C) with 50 mm × 50 mm × 3 mm
thickness. The flyer plate used is tungsten foil, purchasedfrom the Nilaco Co., with 30 mm × 30 mm × 0.2 mm
thickness. Details are described by bibliography [1]about an explosive and a setup of under explosive
welding. After joining, the specimens were cut as3mm×0.4mmt for small punch (SP) tests. Moreover, thelaser-thermal shock test were performed.
3. Result and Discussion
The load-deflection curves obtained from SP tests areshown in Fig. 1. The load-deflection curve of the“fracture” specimen shows two sudden drops of load
which may correspond to the occurrence of crack in thespecimen. Therefore the other tests were terminated after
the first drop and the second drop. The result ofcross-sectional observation on first drop specimen
revealed that the first crack during the SP test occurred in

the middle of tungsten part as a perpendicular one to theloading direction at a load of approximately 350-400 N
under the bending with a constraint of the joint interface..
In the second drop specimen, the cracks propagated into
both the surface of tungsten and the interface. Finally, theboth tungsten and F82H was completely ruptured asshown in the Fig. 2 “fracture” specimen. These results
imply that the interface have an good bonding strengthcompared with the strength of tungsten under the small
punch loading. Results of laser-thermal shock test will beshown in the conference.

Fig.1 The fractographic
study result in SP
examination
4. Conclusion

Fig. 2 Fracture specien

Underwater explosive welding was successfully utilizedto clad tungsten on F82H RAF steel. SP tests on thewelded specimens resulted in the cracking in thetungsten part firstly followed by the propagation into thesurface of tungsten and the interface.
Reference[1] K.Hokamoto, K.Nakata, A.Mori, S.Tsuda,
T.Tsumura, A.Inoue, “Dissimilar material welding of
rapidly solidified foil and stainless steel plate using
underwater explosive welding technique”, Journal of
Alloys and Compounds 472 (2009) 507-511