Effect of Location of V-Notch on Neutron Irradiation-Induced Shift in DBTT of HAZ of Welded Pressure Vessel Steel

Abstract

The effect of the location of the V-notch in the heat affected zone (HAZ) on the ductile-brittle transition behavior of neutron-irradiated welded A533B pressure vessel steel has been investigated utilizing the small specimen technique. Standard size, one-third size and 1.5 mm size Charpy V-notch specimens were prepared by changing the distance from the fusion boundary, so that a V-notch was located in the position to be evaluated. Neutron irradiation was performed in JMTR at 290°C up to 0.75 and 1.3 × 1024 n/m2. In both the cases before and after the irradiations, ductile-brittle transition temperature (DBTT) is lower and the upper-shelf energy is higher for so-called HAZ(M1) specimen, which has a V-notch 1mm away from the fusion boundary, than base metal and deposit. However, the DBTT of the HAZ(M4) specimen, with a V-notch 4 mm away from the boundary, is higher than that of base metal. As for the ΔDBTT, the HAZ(M1) and HAZ(M4) specimens showed equivalent and considerably larger ΔDBTT, respectively, than the base metal specimen; hence the HAZ(M4) specimen shows rather higher DBTT, that is, lower toughness. Micro-Vickers hardness measurements revealed that the M1 and M4 site showed the highest and lowest hardness, respectively.