Effect of heat treatments on tensile properties of F82H steel irradiated by neutrons

The dependence of irradiation hardening of F82H steel on tempering conditions was examined by JMTR and HFIR irradiation experiments. The JMTR and HFIR irradiations were performed to 2 dpa at 250 °C and 5 dpa at 300 °C, respectively. Irradiation hardening measured at 25–400 °C depended strongly on tempering conditions, and it basically increased with temperature and time of tempering. The increment of yield stress due to irradiation was negligible at 500 °C in the specimens tempered at 750 °C for 0.5–10 h, but was measured to be 130–200 MPa in the specimens tempered at 780 and 800 °C for 0.5 h. Irradiation hardening of F82H that was heat treated to produce a weld-like material was also examine. The weld-like material was annealed at 800, 860 and 920 °C for 0.5 h, and then continuously annealed at 700 °C. The level of irradiation hardening depended on the heat treatment conditions. From these results, it is suggested that the control of heat treatments such as tempering is useful to resist irradiation hardening and embrittlement.