Dependence of Ductile-Brittle Transition Behavior on the Size of Charpy Specimen and The Location Of V-Notch in the Haz of Welded A533B PVS

Abstract

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.

Evaluation of impact properties of weld joint of reactor pressure vessel steels with the use of miniaturized specimens

“…The HAZ-1 specimen is defined as a surveillance specimen in the regulation code of surveillance test method as mentioned before. The HAZ-4 specimen, of which the notch is located at 4 mm away from fusion boundary, often showed the worst impact properties at the weld bond of ferritic steels [2], the worst position may depend on welding conditions. Charpy tests were carried out at temperatures from 73 K to 473 K. A specimen was set up in a cold bath filled with isopentane, which was cooled by liquid nitrogen, for tests at below ambient temperature, and with silica oil for tests at elevated temperatures.…”

“…The USE of sub-sized specimens is reduced primarily because of a decrease in the cross section of the specimen. Many previous works suggest that so-called volume normalization is suitable to estimate USE of standard size specimen from sub-sized specimen data [2]. The measured USEs of Steel-1 specimens are plotted against specimen width (B) as shown in Figure 7.…”

“…The measured USEs of Steel-1 specimens are plotted against specimen width (B) as shown in Figure 7. The relationship between USE, E and B, is expressed by the following function [2]:…”

“…However, it is well known that the Charpy impact properties depend on the specimen size as well as the notch location of the weld joint [1][2][3][4]. The HAZ of the weld bond was considered to have lower fracture toughness than the other regions because of the finely grained microstructures in this region [5].…”

“…In the most of regulation codes, the surveillance specimen of HAZ has a notch in base metal 1 mm away from the fusion line, which is called as HAZ-1 specimen hereafter, and the Japanese regulation requires the evaluation of irradiation embrittlement of HAZ-1 specimens. However, recent studies have shown that the fracture toughness of HAZ is better than that of base metal [2,3,6], suggesting that the HAZ-1 specimen is not always lowest in fracture toughness test among base metal, WM, and HAZ, and possibly represented by base metal or WM.…”