What are the defects in welding?

The lack of training to the operator or careless application of welding technologies causes discontinuities in welding. Infusion welding, defects such as porosity, slag inclusion, solidification cracks etc., deteriorates the weld quality and joint properties. Common weld defects found in welded joints:

These mistakes may result in sudden crashes which are unexpected as they give rise to stress intensities. The common weld defects include:-

i. Porosity 

ii. Lack of fusion 

iii. Inclusions 

iv. Cracking 

v. Undercut 

vi.Lamellar tearing 

i. Porosity

Porosity takes place when the solidifying weld metal has gases trapped in it. The presence of porosity in most off the welded joints is due to dirt on the surface of the metal to be welded or damp consumables.

ii. Lack of Fusion

Due to very little input or slow traverse of the welding torch, lack of fusion arises. A better weld can be obtained by increasing the temperature, by properly cleaning the weld surface before welding and by choosing the proper joint design and electrodes, a better. On extending the fusion zone to the thickness of the joints fully, a great quality joint can be achieved.

iii. Inclusions

Due to the trapping of the oxides, fluxes and electrode coating materials in the weld zone, the inclusions have occurred. Inclusions are caused while joining the thick plates in several runs using flux cored or flux coated rods and the slag covering a run is not completely removed after each run and before the next run starts. By maintaining a clean surface before the run is started, providing sufficient space for the molten weld metal between the pieces to be joined, the inclusions can be prevented.

iv. Cracking

Due to the strain at the time of phase change, cracks may occur in various directions and in various locations in the weld area. Due to poor design and improper procedure of joining high residual stresses, cracking is seen. A stage-wise pre-heating process and stage-wise slow cooling will prevent such type of cracks.

v. The undercut

The undercut is caused due to incorrect settings or using improper procedure. Undercutting can be detected by a naked eye and the excess penetration can be visually detected.

vi. Lamellar Tearing

Due to non-metallic inclusions, the lamellar tearing occurs through the thickness direction. This is more evidently found in rolled plates. As the fusion boundary is parallel to the rolling plane in T and corner joints, the lamellar tearing occurs. By redesigning the joint and by covering the weld area with ductile material, the lamellar tearing can be minimized.