Solid Inclusion

Solid foreign substance entrapped in the weld metal

Slag Inclusion

Slag trapped during welding. The imperfection is of an irregular shape and thus differs in appearance form gas pore

Causes	Prevention
Incomplete slag removal from underlying surface of multipass weld	Improve inter-run slag removal
Slag flooding ahead of arc	Position work to gain control of slag. Welder needs to correct electrode angle
Entrapment of sl  ag in work surface	Dress work surface smooth

Cavities

a.      Gas Pore

A gas cavity of essentially spherical shape trapped within the weld metal.

This cavity can be present in various forms :

-         isolated

-         uniformly distributed porosity

-         clustered (localized) porosity

-         linear porosity

-         elongated cavity

-         surface pore

Crack

An imperfection produced by a local rupture in the solid state, which may arise from the effect cooling of stresses. Cracks are more significant than other types of imperfection, as their geometry produces a very large stress concentration at the crack tip, making them more likely to cause fracture.