The effect of the weld fusion zone shape on residual stress in submerged arc welding

A new multiple-electrode submerged arc welding
technique has been developed that imparts improved frac-
ture toughness properties in the heat affected zone, produces
a narrower weld bead geometry, and can also be employed
with lower heat inputs than conventional SAW. This study
examines how the difference in the weld fusion zone pro-
file affects residual stresses for weldments of API X70 steel
made using the same consumable, heat input and restraint,
varying only the shape of the weld fusion zone. The con-
tour method and neutron diffraction have been employed
to map and compare longitudinal and transverse residual
stresses. Results show peak longitudinal stresses in the weld
are within 50 MPa for both, and this is believed to be
because they have the same heat input and hence similar
heat affected zone size. By contrast, the peak stress in the
transverse direction is 120 MPa lower for the new SAW technique.
The reduction in transverse stress is attributed
to a narrower fusion zone profile. The new SAW technique
opens up the possibility of producing high quality narrower
welds with lower heat input which could lead to significant
reductions in residual stress.