A solution for porosity in welding

1. Porosity
 Porosity in welding can be defined as small gas holes or cavities or pores which are
present in the weld bead. These gas holes can vary in size and appear to be scattered all
over the weld bead in a random manner. These holes or pores can occur either over or
under the weld surface.
 Porosity in welds does not normally present a problem from the strength standpoint,
unless the weld is extremely porous. Uniformly distributed porosity that is microscopic in
size may be beneficial under some service conditions. In weld metal porosity is
categorized according to shape and location of occurrence.
 The gas cavities can be of spherical shape or elongated like worm holes which occur all
over the weld metal.
 Surface holes in the weld bead are undesirable from an appearance standpoint and can be
starting points for fatigue cracks or result in other defective weld conditions. Weld
imperfections closely related to porosity are blow holes, gas pockets and slag inclusions.
These conditions tend to weaken the weld much more than ordinary porosity.
 The various reason for the formation of pores are mentioned below
1. Contaminated electrodes, filler rods, wires, consumables, tungsten rod, work
surface etc.
2. Inadequate electrode deoxidant, In-appropriate flux.
3. Moisture, paint, oil, grease, chalk marks, chemicals used for NDT on open
work surface.
4. Improper Gas shield or too high gas flow.

2. 5. Laminations and other defects in base metal.
6. Too high arc length.
7. Incorrect surface treatments.
8. Improper welding procedure.
The causes and cures for the above weld defects are mentioned below
Contaminated surface:
Cause Cure
It generally occurs on the parent metal or
electrodes used during the welding process.
Porosity can be formed if the presence of
grease, oil or moisture which tends to form a
gas during welding temperature.
The metal wire, rod, powder or electrode
which is used during the welding process must
be cleaned and made free from oil, grease or
moisture. Base metal and material to be welded
to it should be free from grease, paints,
moisture, oil, grinding dust or any other
contaminant.
Inadequate electrode deoxidant:
Cause Cure
It is formed when excess amount of oxygen
comes out in from the weld metal which tends
to form carbon monoxide and leads to
formation of porosity. Lack of deoxidation
Before welding proper deoxidation process
must be done which removes all the oxygen
content from the weld metal and prevents the
metal from reaction with oxygen during the

3. causes porosity. process of welding. Proper deoxidant
electrodes must be used for welding purpose.
Open work surface:
Cause Cure
Whenever the metal is exposed to air, it gets
absorbed through the root opening and finally
entrapped by the welded surface and as a result
porosity is formed. Excessive hydrogen or
oxygen in welding atmosphere.
Weld metal must not be exposed to air to
ensure that it doesn’t enter into the weld metal
easily in order to avoid porosity. Change
electrode to avoid oxidation.
Improper Gas Shield:
Cause Cure
The gas shielding is one of most important
reason for porosity. If gas shielding is
improper during the process of welding air
easily gets entrapped into the weld metal and
results in formation of oxidation. Too much of
air flow and draughts in the area of welding is
may also be a reason for porosity.
Proper connection of gas pipelines or hoses
must be ensured before starting the welding. In
order to avoid too much of air flow during
welding some kind of shielding must be given
during the time of welding or the process can
be done inside a place where the flow of outer
air is less.
Too high gas flow:

4. Cause Cure
Due to high flow of gas during the time of
welding some amount of turbulence is formed
which sucks in external air enabling it to react
with the weld metal and finally results in
porosity. Ensure that there are no holes or
loose fittings in the gas hose from the gas
cylinders to the power source / welding torch /
Gun. This is because air is sucked into the gas
hose which will create porosity in the weld
pool.
Flow meters must be checked and optimized
before starting the process. The proper pressure
and flow setting of gas will v ensure proper
shielding of weld from the external
atmosphere.
In-appropriate flux:
Cause Cure
Generally welding fluxes , base metal , filler
rode , electrodes wires or powders have the
tendency to absorb moisture very easily . If
moisture is absorbed it may be the cause of
weld defects. Application of low activity flux
also results in porosity of the weld metal.
In order to avoid weld defects the fluxes and
base metal, filler rod, electrodes wires or
powders must be ensured to be moisture free
and in dry condition. Usage of fluxes with high
activity to ensure quality weld with no weld
defects especially with the absence of porosity.
Too high arc length:

5. Cause Cure
Improper arc length, current or manipulation Use correct arc distance (within recommended
voltage range), control welding technique
Incorrect surface treatments:
Cause Cure
Porosity happens when the surface of the metal
is subjected to chemical treatment or painting
such as zinc coating or galvanizing produces
gas which can lead to change in requirements
of weld parameters and procedure.
In order to avoid these problems the chemical
reactions of the material are to be predicted in
prior so that the defect can be avoided. Use
E6010 electrode.
Moist Electrodes:
Cause Cure
Excessive moisture in electrode or joint Use dry electrodes and dry materials
Base Metal:
Cause Cure
High sulphur base metal Use EXX15 – 16 electrodes.
Improper welding procedure:

6. Cause Cure
Porosity may occur due to improper WPS
decided before welding. Due to improper
setting of parameters in the machine and
welding procedure weld defects can occur
easily.
The WPS for welding a particular job must be
taken care. All the machine parameters are to
be checked prior of welding. Ensure machine is
calibrated for current and voltage readings on
the display panel.
.
General solution for prevention of porosity:
 Be sure the base metal is one that will produce a porosity free weld. High Sulphur,
phosphorus and silicon steel sometimes produce gaseous combinations which tend to
make blow holes and gas pockets. Non-ferrous material high in oxygen also tends to
result in porous welds. Base metal containing segregations and impurities contribute to
porosity.
 The welding procedure has much to do with the soundness of finished welds. Do not use
excessive currents but be sure that each layer of weld metal is completely free of slag and
flux before depositing another layer. Puddle the weld, keeping the metal molten
sufficiently long to allow entrapped gases to escape. Use a weaving pass in making the
weld since a series of stringer beads is apt to contain minute pin holes.
 Since some electrodes have a tendency to produce sounder welds than others, try to use
such electrodes in making welds. Most low-hydrogen electrodes will be found helpful in
eliminating porosity. When using the submerged arc process, be sure the flux is suited to

7. scavenging gaseous elements. When using bare electrodes, thorough drying of them or
selection of a type that has a copper flash coating will eliminate oxygen or hydrogen
being introduced into the weld from moisture on the surface of the electrode.