Types of welding defects

Written by george lawrence
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Types of welding defects
Improper techniques will likely lead to welding defects. (the electric welding image by Victor M. from Fotolia.com)

The bond created by welding two pieces of metal together is only as strong as the procedure used to create the weld in the first place. Welding defects are typically caused by improper welding procedure. Defects increase the chance that the weld will not hold. Once a welder understands the defect her or she is causing, the welder can assess what welding procedure he is using and fix the errors.

Lack of Fusion

If the weld heat was not high enough, the metals being welded together may not have become molten during the welding process and the two pieces did not join. "Lack of fusion" is characterised by edges that are still flat and smooth and show no signs of having once been molten metal, according to thermatool.com.


Welding along a line or using an arc voltage that is too low can produce a groove or a slight ditch in the metal right along the weld line. This is known as "undercutting." The size of the groove deepens the faster the arc travels along the weld line. Decreasing the arc speed reduces the depth of the groove and eventually eliminates it, according to esaban.com.


"Pinholes" refers to a welding defect caused by high welding temperatures. If the temperature of the arc making the weld is too high, tiny holes resembling pinholes may appear on the surface of the weld.


"Cracking" looks like ridges in the weld line that resemble an earthworm's body. This defect typically occurs because the welder was using the wrong type of wire electrode to make the weld.

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