The GMAW process in Short Circuit transfer mode has the increased ability to deposit weld metal that is in close proximity to adjacent metal or the groove faces but may not be fused to it.

The radiographic process does not detect discontinuities that do not show a decrease in density of the material. Also any discontinuity that is parallell to the film plane is undectable. So if weld metal is just laying on top of other weld metal or the bevels, the radiographic process cannot detect that interface.

An example would be substituting glass for the plates and also the weld but having 3 different pieces. Just looking at them 90 degrees from the surface of the plate would not show that they are not joined together if they are touching.

So lack of fusion between passes and also the bevels may be difficult to detect. Guided bend tests will often open these defects and allow them to be viewed.


Ultrasonic testing could also reveal these types of defects but I don't know if it is allowed for welder qualification testing.


Hope this helps,

Gerald Austin
Weldinginspectionsvcs.com

Just to support what Gerald is saying:

The major defect for GMAW using short circuit transfer, is lack of side wall fusion. This defect is seldom detectable using radiographic techniques. It is however readily detected by bend tests.

Regards
Niekie