The effects of thermal annealing on fracture toughness of low upper-shelf welds

Experimental results are presented from a study of the effects of thermal annealing on recovery of fracture toughness of low upper-shelf submerged-arc welds (weld designations 61W through 67W) from the Heavy-Section Steel Irradiation (HSSI) Program Second and Third Irradiation Series. Most of the study was conducted to evaluate the effects of annealing on the J-R curves of the submerged-arc welds. The recovery of fracture toughness in the transition range as the result of annealing was studied for welds 63W, 64, and 65W only. Compact specimens of 12.7- and 20.3-mm-thick (0.5T and 0.8T, respectively) were tested in this study. The specimens had been previously irradiated at the Oak Ridge National Laboratory (ORNL) Bulk Shielding Reactor. Each weld was irradiated to a certain value of neutron fluence in the range from 0.4 to 1.3 × 10¹⁹ neutrons/cm² (> 1 MeV) in the average temperature range of 275 to 300°C. Annealing of the irradiated specimens was done at 454°C for 168 h. Fracture toughness tests were performed at temperatures selected to match those of the previously conducted unirradiated and irradiated tests.