2004 年 45 巻 8 号 p. 2638-2640
Microstructures and tensile properties of a martensitic steel F82H (Fe-8Cr-2W-0.1C-0.2V-0.04Ta) were examined as a function of time and temperature of tempering. A heat treatment was performed at temperatures from 750 to 800°C for 0.5 h after the normalizing at 1040°C for 0.5 h. The tempering time at 750°C was varied from 0.5 to 10 h. The tensile specimens were irradiated at 250°C to a neutron dose of 1.9 dpa in the JMTR (Japan Materials Testing Reactor), and tensile tests were carried out at 250°C after the irradiation. The microstructures of the non-irradiated specimens were observed by a transmission electron microscope. The density of dislocations decreased with increasing time and temperature of the tempering, and the size of M23C6 carbide increased with it. While the yield stress of the non-irradiated specimens decreased with increasing time and temperature of tempering, the yield stress of the irradiated specimens tended to increase with increasing temperature of the tempering. The yield stress of the irradiated F82H steel changed from about 525 to 750 MPa and depended on the conditions of tempering treatment before irradiation.
