Rocks & mirror
Encyclopedia of Marine and Energy Technology

Weld defects


The most common type of discontinuities are: cracks, incomplete fusion, slag inclusions, porosity, undercut. Imperfections of welding connections can be isolated or clustered.

Further reading: ABS Guide for “Nondestructive Inspection of Hull Welds” (2002), can be downloaded from

Cracks – Cracking in welded joints can be classified as either hot or cold cracking. Hot cracking is a function of chemical composition. Cold cracking is the result of inadequate ductility or the presence of hydrogen in hardenable steels. Welds in which radiographs exhibit any type of cracks are to be considered unacceptable.

- Incomplete fusion – The failure to fuse adjacent beads of the weld metal and the base metal. This condition can be localised or it may be extensive, and it can occur at any point in the welding groove.

- Porosity – Gas pockets or voids in the weld metal. The voids come from gas that is formed due to certain chemical reactions that take place during welding.

Slag inclusions – The oxides and nonmetallic solids that sometimes are entrapped in weld metal, between the adjacent beads, or between the weld metal and the base metal.

- Undercut – This term is used to describe two situations. One is the melting away of the sidewall of a welding groove at the edge of the bead, thus forming a sharp recess in the sidewall in the area in which the next bead is to be deposited. The other one is the reduction in thickness of the base metal at the line where the beads in the final layer of weld metal tie into the surface of the base metal (e.g., at the toe of the weld).