FIELD OF INVENTION
This invention relates to a method of TIG welding of aluminium for increased
penetration using a novel flux.
BACKGROUND OF THE INVENTION
TIG welding or tungsten inert gas welding uses a non-consumable Tungsten
electrode to establish the welding arc and welding can be performed with or
without filler material. An inert gas like argon or helium is used to shield the weld
metal from atmospheric contamination. When the welding is carried out without
addition of filler it is known as autogenous TIG welding AC (alternating current)
is the preferred current for welding of aluminium because of its ability to
breakdown the oxide layer.
Weld penetration is the distance that the fusion line extends below the surface of
the material being welded. Welding current is of primary importance to
penetration. Weld penetration is directly related to welding current. An increase
or decrease in the current will increase or decrease the weld penetration
respectively.

In conventional TIG welding, there is no scope or role for flux. The primary task
of protection of weld metal from atmospheric contamination is done by the
shielding gas. However in recent years, considerable research has taken place to
improve the productivity of TIG welding. In case high penetration depth can be
achieved even with lower or normal range of welding currents, thin sheets can
be welded in one or two passes instead of the large number of passes needed in
conventional TIG welding thereby improving productivity.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a method of TIG
welding of aluminium for obtaining increased penetration using a novel flux
which eliminates the shortcoming of prior art.
Another object of the present invention is to propose a method of TIG welding of
aluminium for obtaining increased penetration using a novel flux which uses
normal current.
A further object of the present invention is to propose a method of TIG welding
of aluminium for obtaining increased penetration using a novel flux which
reduces numbers of pass.

A still further object of the present invention is to propose a method of TIG
welding of aluminium for obtaining increased penetration using a novel flux
which is eco-friendly.
SUMMARY OF THE INVENTION
All welding processes rely on either gas shielding or slag shielding (produced
from a welding flux) or a combination thereof. Thus the SMAW (shielded metal
arc welding) process uses fluxes as a coating. In SAW (submerged arc welding)
the welding arc is buried under a blanket of flux which on melting protects the
weld metal and is finally discarded as slag.
As mentioned earlier, there is no need to use a flux in conventional TIG welding.
But due to low deposition rate per hour, TIG process suffers from low
productivity. It is also a fact that penetration depth in normal TIG welding is low.
This means that even for relatively low sheet thicknesses like 3.15 mm, 4, 5, 6.3
and 8 mm several runs are needed to fill the joint.
A novel welding flux was invented which significantly enhances welding
penetration during joining /TIG welding of aluminium thin sheet. It has been
found that Calcium Oxide (CaO), used as a flux, on the aluminium plate results a
siginificantly higher penetration.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Several materials testing was carried out for their ability to increase penetration
during TIG welding of commercially pure aluminium sheets. TIG welding was
carried out using a mechanized welding setup. The speed of welding and current
are varied for a given base material thickness and autogenous welding (no
external filler was added) was carried out using bead-on-plate trials.
Mechanised TIG welding using alternating current using a drooping characteristic
power source (as in normal in TIG welding) was used. Calcium oxide (CaO)
powder was mixed with acetone and was applied on the 8 mm aluminium plate.
(No other material was mixed with the calcium oxide powder).
Calcium oxide and acetone form a paste. The consistency of the paste was
adjusted by use of suitably adjusting quantities of acetone and the flux. The
paste was applied on the plate surface in 2 variants: one with a thin coating,
another with a thick coating, corresponding roughly to the coating applied once
and twice respectively. Acetone, being a volatile liquid even at room temperature
evaporates leaving a dry coating even prior to welding. On this dry coating, the
TIG welding arc is run autogenously. A run without any flux coating was also run
to record the normal penetration in the absence of a flux. After welding the
section was cut and prepared through metallographic methods and etched to
reveal the depth of penetration.

After welding, cutting and metallographic preparation, it was found after etching
that the use of calcium oxide as flux had improved penetration significantly i.e.
about 100 percent when the flux was applied as a thick layer with suitable
consistency (compared to the TIG welding without flux, and the "single coat"
thin layer coating).

WE CLAIM
1. A method of TIG welding for aluminium using a novel flux comprising the
steps of:
(a) preparation of surface to qualify for welding;
(b) application of novel flux using a brush;
(c) completion of TIG welding;
Characterised in that the novel flux comprises of a mixture of calcium oxide
powder and liquid acetone in the form of a paste that imparts an increase in
penetration of welded metal.
2. The novel flux as claimed in claim 1, wherein CaO used entirely of
commercially pure form (nearly 100%)
3. The novel flux as claimed in claim 1, wherein the paste of flux is used as a
thick layer.
4. The TIG welding as claimed in claim 1, wherein an autogenous TIG
welding carried out with AC current.

All welding processes rely on either gas shielding or slag shielding (produced
from a welding flux) or a combination thereof. Thus the SMAW (shielded metal
arc welding) process uses fluxes as a coating. In SAW (submerged arc welding)
the welding arc is buried under a blanket of flux which on melting protects the
weld metal and is finally discarded as slag.