Most Common Signs of Welding Imperfections and Problems17 April 2018
Problem welds are an open book to weld inspectors. Incomplete fusion or unacceptable weld profile, the signs are there to be read. Then, as these weld imperfections are deftly interpreted, a report is compiled. It informs the lead engineer of potential problems, defects that could structurally incapacitate the project. Obviously, then, the mastery of diagnostician-class weld sleuthing is an essential skill. Let’s see the results.
The smooth dome shape is broken by a series of pinholes. If the fused joint is enveloped in tiny material perforations, how can it function properly? Check for shield gas coverage and contaminants when weld porosity is indicated. Additionally, inspect the equipment, the welding consumables, and find the source of the contaminant.
Guard Against Incomplete Fusion
On the surface, the clues suggest a weld discontinuity. The edges are uneven, the filler isn’t fully occupying the weld zone, and the message is clear; it’s time to use a scanning instrument. An ultrasonic tester reveals the worst. That incomplete weld profile travels deep. If the weld isn’t cementing itself to the fusion faces, ugly gaps appear. Lack of root fusion material undermines weld integrity. The defect is real, so report this flaw immediately and repair the weakened join.
Unacceptable Fusion Profiles
There’s not enough material in the groove or angled join, so the weld can’t hold. Elsewhere, there’s excessive undercut or the join is bulging because too much filler has found its way to the weld zone. Structural stresses gather at undesirable fuse surfaces. They overlap and produce surface deformations. In some cases, the excess material can be eliminated by a grinding tool, but even that happy circumstance will impact site productivity.
Cracking Up Under Pressure
Weldment cracks require immediate attention, for the joint is on the verge of failing. Simply put, it’s not going to support a structural load. Strangely enough, cracks split into two distinct categories. There are cracks that propagate because of excess application heat and cracks that form because of rapid site cooling. Detect surface cracks with a visual inspection. If the fracture lines are still intact and embedded inside the weld, a radiographic test is advised, for liquid penetrants won’t always pick up these tight-lipped defects.
Even the weld inspector’s defect reporting talents are put to the test here, especially if the discontinuity is only cosmetically flawed. It’s the job of this expert individual to tell the difference between a cosmetic discontinuity and a potentially catastrophic weld defect. Training regimens shape that trained eye, as do the welding codes that the inspector follows to the very letter.
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