Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : October 07, 2017 - October 09, 2017
All atomic power plants in Japan have stopped its generation after the seismic East-Japan earthquake. Many aged thermal power plants restarted to supply sufficient electricity for the Japanese industry and daily activities. Reasonable guidelines for assessment of its integrity and estimation of remaining life have been required to operate them with a safety margin. Miniature Creep (MC) test is recognized as a semi-destructive technique to examine the degradation level of aged high temperature components. In this study, the MC thin plate specimen of 2.25Cr-1Mo steel and the similar one welded by Electron beam (EB) only for gauge part were employed to evaluate the validity of the EB welded MC specimen. A series of creep tests were conducted in vacuum at 600°C. After the comparison of these test results with those using the conventional uniaxial specimens, following conclusions were obtained: (1) Creep rupture lives of the MC thin plate specimens including the EB welded ones were nearly the same as those of conventional uniaxial ones. (2) Vickers hardness on the surface of the EB welded MC thin plate before/after the creep tests were measured. The HV in the welded zone rapidly decreased in a short time and reached to almost as the mother material or below it. (3) Rupture lives of the welded MC thin plate specimens were longer than that of the monolithic MC thin plate specimen at higher stress levels, because the HV in the welded part was a bit larger than those of mother materials.
