Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : September 27, 2023 - September 29, 2023
Aged and as received KA-STPA28, Japanese standard of Gr. 91 steel for high temperature piping, steel were tested by standard and ultra miniature creep (UMC) testing method. Time dependence of creep rate of each test were compared and the results were discussed with scanning electron microscopy (SEM) observation results of fracture surfaces and cross section of specimens. Creep rate of UMC specimens at the initial stage of tests were about 5 times higher than those of round bar specimens. By comparing relationship between modified minimum creep rate and rupture time of each tests, in case of UMC specimen, excessive creep strain corresponded to those at 3% of rupture time was considered to be accumulated during initial stage of tests. Duration time between when specimen showed corresponded to minimum creep rate and rupture was relatively longer in case of UMC specimen because of higher ductility showed at fracture. Specimen surface oxidation was well suppressed by employing appropriate Ar gas flow rate.
