Dr Hiroaki Mori
Associate Professor in the Department of Management of Industry and Technology, Graduate School of Engineering at the Osaka University Ph.D. in Engineering given from Osaka University in 1997 From 1997 to 2007, Assistant Professor in the Manufacturing Science Course in the Division of Materials and Manufacturing Science, Graduate School of Engineering at the Osaka University Since 2008, Associate Professor in the Department of Management of Industry and Technology, Graduate School of Engineering at the Osaka University In 2010, Visiting Scholar at the University of Waterloo, Canada Research interests are metallurgy and thermodynamics in welded joints of steels, high alloys and light metals. Current research themes have been mainly focused on metallurgical and numerical analyses for weld defects such as cracking and porosity.
Development of Welding Techniques for Reduced Activation Ferritic/martensitic Steel F82H to Construct Blanket Modules set on Inner Wall of Nuclear Fusion Reactors
The reduced activation ferritic/martensitic steel F82H has been specially modified 9Cr steel to be added reduced activation property and developed as a structural material of the blanket module, which is the device set on the inner wall of fusion reactors. In order to construct the modules, it’s necessary to establish the welding techniques for each joint shapes and plates’ thickness of F82H. Laser beam welding (LBW) and arc welding with single-pass and multi-passes will be adopted for thin plates and thicker ones, respectively. Hot and cold cracking should be concerned in welds during these welding processes, because the welds are usually hardened by martensite formed during welding thermal cycles. Hot crack susceptibility in LBW of F82H was measured by the side-bead test. The susceptibility was less than that of conventional austenitic stainless steels. Varestraint tests were conducted to evaluate hot crack susceptibility in the welds by single-pass and multi-passes arc welding. On the basis of test results, even though the crack susceptibility was raised with increase in Ta contents in the steels, the susceptibilities were less than those in the welds of 9Cr steels. On the other hand, cold crack susceptibility in welds was evaluated by hydrogen concentration, which is well known as a cause of cold cracking, and residual stress calculated by the developed numerical analysis method as compared with the measured criteria by a slow strain rate tensile (SSRT) test for hydrogen charged specimens. Based on the results, as compared with these calculated hydrogen contents and stress and the criteria, it was judged that cold cracking does not occur in this case. Actually, based on experimental verification, cold cracking could not be recognized in this study. These results suggest that the crack susceptibility may be sufficiently low and the cracking can be prevent in the welds of F82H.
Nuclear fusion reactor, Blanket module, Reduced activation ferritic/martensitic steel, Austenitic stainless steel, Welding, Cracking