The dependence of ductile-brittle transition (DBT) behavior of welded A533B pressure vessel steel (PVS) on the specimen size and location of notch in the heat affected zone (HAZ) has been investigated utilizing small specimen technique. Submerged arc welded thick plate for plant-use was supplied by Japan Steel Works, LTD. Standard size, one-third size and 1.5mm size Charpy V-notch (CVN) specimens were prepared so as to place the notches at the base metal (M15) and the deposit (D15) 15mm away from fusion boundary and 1 mm inside the base metal (M1) from the boundary. It is interesting that the M1 specimen shows better DBT behavior, namely a larger upper shelf energy (USE) and a lower ductile-brittle transition temperature (DBTT), than the M15 and D15 specimens independent of the specimen size. To investigate the dependence of the DBT behavior on the location of notch in the HAZ in more detail, impact tests were carried out for the one-third size specimens with notches at different distance from the fusion boundary (x=0), that is, x= -15, -6, -5, -4, -3, -2, -1, 0, +1, +2, +3, +15mm from the boundary. Again the DBTT is the lowest and the USE is the highest for the M1 specimen. On the contrary, impact properties are the worst at a HAZ location 4mm away from the boundary (M4).
Normalization of the USE is successfully done by a curve fitting method. There observed linear relationships between DBTTs obtained using standard and sub-sized specimens of base metal, deposit and HAZ.