Common Weld Defects can be defined as the irregularities emerge in the welded work piece due to non-compliant welding or faulty welding patterns.
1. Introduction
Welding defects emerge either outside or inside the weld metal. Some of the defects may be allowed if the defects are under acceptance criteria set within the welding quality control guideline but other defects such as cracks are never accepted. The defect may occur from the desired weld bead shape, size, and quality
2. External Welding Defects
- Weld Crack
Weld Cracks weaken a weld, and sometimes they tend to grow at a rapid rate making the defect worse. Most types of weld cracking emerge when the shrinkage strains that occur as the weld metal cools.
- Undercut
An undercut is an accidental groove running along the weld bead. It is a long trough in the base metal at the edge of the weld.
- Spatter
During the welding, the molten material droplets may have splashed through the welding zone causing formation of modules on the work piece.
- Porosity
Porosity is the presence of voids in the weld work piece caused by the freezing of gas released from the weld as it solidifies. Porosity can occur on the surface of a weld or within the weld bead.
- Overlap
Overlap is a discontinuity of the weld when molten metal flows over the metal surface and then freezes without fusing with the base material. Generally overlap happens where there is excess weld metal and low welding speed.
3. Internal Welding Defects
- Incomplete Fusion
When the welder does not properly weld the material and weld lacks to fill all the weld pool. Possible reasons are the low welding speed, too big weld pool or improper bead position.
- Incomplete Penetration
Incomplete Penetration forms when the root of the weld bead does not connect the base of the joint to the other surface in the part. Increasing the current, decreasing the welding speed, or altering the joint geometry can prevent the occurrence of this defect.
4. Conclusion
It is essential to know the defects types and their causes in order to execute a proper welding. A proper welding quality control and appropriate welding tests will help to identify and correct all the defects of welding present in the work piece therefore welders should be properly trained.
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