Weld
porosity
Porosity is the presence of
cavities in the weld metal caused by the freezing in of gas released from the
weld pool as it solidifies.
Porosity
If shape of porosity is rounded holes,it is called spherical
porosity or just porosity.
Wormholes
if
elongated porosity is noticed with a height or width , the terminology is wormholes or piping.
As per ISO 5817 - 2006
Different types of porosity or gas pore
1.
Gas
pore uniformly distributed Cluster (localised)
porosity
2.
Liner
porosity
3.
Elongated
cavity – worm holes – height of the cavity
Acceptance based on ISO 5817 -2006
Gas pore or porosity - acceptance based on diameter
d ≤ 0.2 s
Worm hole or elongated cavity - acceptance is based on height
or width h ≤ 0.2 s
For
gas pore-- acceptance
based on diameter the
cavity
Ex. 10 mm thick plate, if pore size is d= 1.5 mm
- Acceptance based on pore dimensions d ≤0.2 s , s = nominal butt weld thickness
- Acceptance based on pore dimensions is 0.2 x 10mm = 2mm ,
Hence acceptable d is less than 2mm
Acceptance based on pore area Area ≤ 1% for 10mm plate
=1mm
For a worm hole-- acceptance
is based on height or width
Ex.10 mm thick plate, If the Height of worm
hole is 5 mm
- Acceptance based on pore dimensions h ≤ 0.2 s ,& l ≤ s
- Acceptance based on pore dimensions is 0.2 x 10mm = 2mm.
Therefore worm hole h=5 mm is not
acceptable
BS EN ISO 6520
Gas cavity----
Cavity
formed by entrapped gas.
Gas pore ----- Gas
cavity of essentially spherical form.
Worm Hole--- Tubular
cavity in weld metal caused by release of gas.
Porosity in welding is a result of dissolved gases or
gases released during the welding process, being trapped in the metal when
there is insufficient time to escape prior to solidification.
Complied by LRC Nov 15 2013
