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Welder’s Handbook
Cavities
Cavities are weld discontinuities consisting of rounded holes of various types, either within the weld or at the surface of the weld. Porosity and wormholes are cavity types formed by gases. Shrinkage voids are a cavity types formed by contraction of the weld material during solidifcation.
Porosity
Cavities
Porosity occurs when gas bubbles accumulate and get trapped inside the weld, weakening it. During welding, gases like steam, hydrogen, and carbon dioxide are produced and can't escape. Porosity creates small holes, while blowholes are comparatively larger holes or cavities. They can be found on the surface or inside the weld metal and may occur alone or in groups, known as cluster porosity.
Shrinkage Voids
Worm Holes
Shrinkage voids are holes that appear when the metal cools and shrinks, often running parallel to the root of the weld.
Wormholes are elongated or tubular cavities caused by excessive entrapped gas.
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