TRC Test for Steel in Underwater Wet Welding (Report 1)

Abstract

The initiation and propagation of root cracks in steel have been investigated with oblique y, straight Y and 45° single bevel grooves of the TRC test in the underwater wet welding process with covered electrode. Welding experiments are carried out by using HT 60 steel and D5003 covered electrode.
The following results are obtained:
(1) The diffusible hydrogen quantity reaches to the constant volume in about 2.4 x 10⁴ min. (about 408 hrs.), where in air, it is about 30 cc/ 100 g Fe, and in underwater, about 70 cc/100 g Fe, i.e., the more root cracks occur in underwater welding.
(2) The maximum hardness of the heat-affected zone is about Hv 350 in air, and Hv 440 in underwater, thus the crack sensitivity is higher in underwater welding.
(3) In the TRC test, the lower critical stress of straight Y groove is higher than that of 45° single bevel groove in both air and underwater welding.
(4) As for no-fracture specimens in the TRC test in underwater welding, there are many microfissure at the martensitic structure in the coarse grained zone near the bond.
(5) The fracture surface shows predominantly the dimple pattern in air welding, while in underwater welding, the quasi-cleavage of hydrogen embrittlement pattern is widely observed there and near the root it shows many intergranular patterns.