The use of electrodes with a nominal strength lower than that of base metal has been considered to be effective in preventing weld cracks, although the use of electrodes with a nominal strength higher than that of base metal is in common. K. Satoh and M. Toyoda have analyzed the tensile behavior of undermatching welded joint and have demonstrated the appropriateness of this joint to heavy plates of HT 80 steel.
However, heavy plates of HT 60 steel are more common in heavy electric industrial structures, so that the strength of undermatching welded joint of HT 60 steel has been investigated in this paper. The results of investigations are summarized as follows:
(1) Undermatching welded joint of wide and heavy plates of HT 60 steel, where the weld metal has appropriate tensile strength, fractures in the base plate and exhibits significant ductility under tensile load even if the weld reinforcement is machined out, according to the increase in tensile strength of the joint caused by the hardening area in heat affected zone.
(2) Cylindrical pressure vessel has bursted at base plate region about 10 nun apart from the toe of the welded joint in the axial direction and it has been observed that the stress-strain curve for the weld metal of the joint locates in higher stress-strain region than that for the weld metal itself and it seems to approach to that for the base metal as the strain becomes larger.