a. Slag Inclusion
Slag trapped during welding. The imperfection is of an irregular shape and thus differs in appearance form gas poreCauses | Prevention |
Incomplete slag removal from underlying surface of multipass weld
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Improve inter-run slag removal
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Slag flooding ahead of arc
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Position work to gain control of slag. Welder needs to correct electrode angle
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Entrapment of slag in work surface
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Dress work surface smooth
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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
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Use electrodes in good condition
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Flux fails to melt and becomes trapped in the weld (SAW or FCAW)
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Change the flux/wire. Adjust welding parameters i.e. current, voltage etc to produce satisfactory welding conditions.
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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
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Grind surface prior to welding
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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
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Keep tungsten out of weld pool, Use HF start
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Contact of filler metal with hot tip of electrode
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Avoid contact between electrode and filler metal
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Contaminating of electrode tip by spatter from the weld pool
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Reduce welding current, adjust shielding gas flow rate
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Exceeding the current limit for a given electrode size or type
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Reduce welding current, replace electrode with a larger diameter one
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Extension of electrode beyond the normal distrance from the collet, resulting in overheating of the electrode
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Reduce electrode extension and/or welding current
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Inadequate tightening of the collet
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Tighten the collet
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Inadequate shielding gas flow rate or excessive wind drafts resulting in oxidation of the electrode tip
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Adjust the shielding gas flow rate, protect the weld area, ensure that the post gas flow after stopping
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Splits or cracks in the electrode
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Change the electrode, ensure the correct size tungsteen is selected for the given welding current used
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Inadequate shielding gas (e.g. use of argon-oxygen or argom-carbon dioxide mixtures thet are used for MAG- welding)
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Change to correct gas composition
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