Vol.16, No.3, 2016, pp.171–178
UDC  620.178.2:669.14-112.81

The CTOD toughness evaluation of repaired weld joints (presence of two weld deposits, complex mechanical heterogeneity and high residual stresses) requires some modifications of commonly used specimen geometry and testing procedure. This paper presents the results of the single edge bend (SENB) specimens with shallow (a/W = 0.16) and deep notches (a/W = 0.3-0.5) extracted from 20 and 30 mm thick multipass submerged arc welded (SAW) joints repaired with hyperbaric (16 bar) welding process at the toe region of the original SAW weld deposits. The results show that an acceptable toughness level can be achieved for hyperbaric repair weld metals deposited at 16 bar (160 m water depth). The repaired single-bevel joint on 30 mm thick StE 445.7 TM steel contained low toughness HAZ (LBZ) regions, whereas another repaired X-joint on 20 mm thick StE 52 steel produced high toughness. The CTOD toughness evaluation (according to BS 5762 standard and CTOD (δ5) technique) of both plates contained a series of shallow and deep cracked SENB specimens notched (through thickness and surface) at various locations of the repaired welded joints. The directly measured CTOD (δ5) values are consistent with the calculated CTOD BS5762 values. An effect of weld metal overmatching on through thickness shallow cracked SENB specimen results was observed as these specimens can produce low CTOD values despite their lower crack tip constraint.

Keywords: CTOD toughness, hyperbaric repair weld, submerged arc welding, StE steel