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

A fine dispersion of inclusion may be present within the weld metal, particularly if the MMA process is used. These only become a problem when large of sharp-edged inclusions are produced.

a.      Flux Inclusion

Flux trapped during welding. The imperfection is of an irregular shape and thus differs is appearance from a gas pore. Appear only in case of flux associated welding processes (i.e. MMA, SAW and FCAW).

Causes	Prevention
Unfused flux due to damaged coating	Use electrodes in good condition
Flux fails to melt and becomes trapped in the weld (SAW or FCAW)	Change the flux/wire. Adjust welding parameters i.e. current, voltage etc to produce satisfactory welding conditions.

b.      Oxide Inclusion

Oxides trapped during welding. The imperfection is of an irregular shape and thus differs in appearance from a gas pore.

Causes	Prevention
Heavy mill scale/rust on work surface	Grind surface prior to welding

A special type of oxide inclusion is puckering. This type of defect occurs especially in the case of aluminium alloys. Gross oxide film enfoldment can occur due to a combination of unsatisfactory protection from atmospheric contamination and turbulence in the weld pool.

c.       Tungsten Inclusion

Particles of tungsten can became embedded during TIG welding. This imperfection appears as alight area on radiographs due to the fact that tungsten is denser than the surrounding metal and absorbs larger amounts of X/gamma radiation.

Causes	Prevention
Contact of electrode tip with weld pool	Keep tungsten out of weld pool, Use HF start
Contact of filler metal with hot tip of electrode	Avoid contact between electrode and filler metal
Contaminating of electrode tip by spatter from the weld pool	Reduce welding current, adjust shielding gas flow rate
Exceeding the current limit for a given electrode size or type	Reduce welding current, replace electrode with a larger diameter one
Extension of electrode beyond the normal distrance from the collet, resulting in overheating of the electrode	Reduce electrode extension and/or welding current
Inadequate tightening of the collet	Tighten the collet
Inadequate shielding gas flow rate or excessive wind drafts resulting in oxidation of the electrode tip	Adjust the shielding gas flow rate, protect the weld area, ensure that the post gas flow after stopping
Splits or cracks in the electrode	Change the electrode, ensure the correct size tungsteen is selected for the given welding current used
Inadequate shielding gas (e.g. use of argon-oxygen or argom-carbon dioxide mixtures thet are used for MAG- welding)	Change to correct gas composition