Abstract
The ductile-brittle transition behavior of neutron-irradiated welded A533B C1.1 pressure vessel steel has been investigated by means of small specimen test technique. Current surveillance test method is discussed on the basis of the obtained results.The submerged arc welded thick plate for plant-use was fabricated. Standard size, one-third size and 1.5mm 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 irradiations were performed in JMTR with fluence of 0.75 and 1.3×1024n/mm2 (E>1MeV). In both the cases before and after the irradiations, ductile-brittle transition temperature (DBTT) is lower and the upper-shelf energy (USE) is higher for so-called HAZ (M1) specimen, which has a V-notch 1mm away from the fusion boundary, than base metal and weld metal. However, it is revealed that DBTT of the HAZ (M4) specimen with a V-notch 4mm away from the boundary is higher than that of base metal. Hence the HAZ (M4) specimen shows rather higher DBTT, that is, lower toughness. Surveillance of HAZ specimen is potentially important and should not be omitted in case that impact property of HAZ cannot be represented by base metal.
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