FIELD OF THE INVENTION
The present invention relates to a flux composition which improves penetration
during TIG welding of mild steel.
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 for example 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. DCEN (direct
current electrode negative) is the preferred current and polarity for welding of
mild steel.
Weld penetration is the distance that the fusion line extends below the surface of
the material being welded. Normally, penetration is directly related to welding
current. An increase or decrease in the current correspondingly influences the
weld penetration.

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. TIG welding is the preferred method for ensuring good quality of
weld joint but when compared to other welding processes, the TIG suffers from
low productivity i.e., deposition rate. However in recent years, considerable
research has taken place to improve the productivity of TIG welding. Such a high
penetration depth can be achieved by the improved TIG welding process, 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.
US 2010068559 (Al) discloses a penetration Enhancing Activating Flux (PEAF) in
paste form for autogenous TIG welding of austenitic stainless steels adapted for
ready application with a brush on top weld surface prior to conducting
autogenous TIG welding to favour single weld pass, of austentic stainless steels
of AISI 304LN and AISI 316LN varieties with weld bead penetration up to a

section thickness of 12 mm. Importantly, the above (PEAF) paste based TIG
welding of the invention achieves an increase in weld bead penetration of about
300% over the conventional TIG process without activating flux. The PEAF paste
based TIG welding also favours higher productivity and high quality apart from
being cost-effective due to less requirement of consumables and controlled heat
input to arrest distortion.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a flux composition
to achieve increased penetration during TIG welding of mild steel without
resorting to high current.
SUMMARY OF THE INVENTION
Accordingly, there is provided a welding flux to achieve increased penetration in
TIG welding of mild steel, comprising:

a paste consisted of a welding flux and acetone / industrial alcohol, wherein the
composition of the paste consisting of:
TI02 : 10wt%
K20T102 : 7wt%
Cr203 : 10 wt %
Si02 : 73wt%
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Experiment was carried out with several chemicals and commercially available
fluxing materials to increase penetration during TIG welding of MS sheets.
According to the invention, TIG welding was carried out using a mechanized
welding device. The power source used was a "drooping characteristic" power
source, the non-consumable electrode being made of thoriated / ceriated
tungsten, using a conventional TIG welding torch. The speed of welding and
current are varied depending on thickness of a base material and autogenous
welding (no external filler was added) was carried out.

Mechanized TIG welding using DCEN (direct current electrode negative) using a
drooping characteristic power source (as in normal in TIG welding) was used.
Commercial purity titania powder, potassium tianate powder, silica powder,
green chromium trioxide Cr203 powder and mixtures thereof were used as per
the following range:
Titania : 7.5 to 12.5wt%
Potassium titanate : 5-10 WT %
Green Chromium
Trioxide : 7.5-12.5 wt%
Silica : 70 to 75 wt %
Fluxing material powder was mixed with acetone / industrial alcohol and the
thick paste was applied on the 7 mm mild steel sheet on the top side of joint
surface.
The fluxes and acetone / industrial alcohol form a paste. The consistency of the
paste was adjusted by use of suitably adjusting quantities of acetone of the flux.

Acetone / alcohol, being volatile liquids even at room temperature evaporate
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.
With the individual components of the flux, it was found that when the following
quaternary mixtures were used, a high penetration was achieved:
TIO2 : 10 wt %
K20T102 : 7 wt %
Cr203 : 10 wt %
Si02 : 73wt%
After welding, cutting and metallographic preparation, and etching it was
observed that the use of fluxes 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 coating).

WE CLAIM:
1. A welding flux to achieve increased penetration in TIG welding of mild
steel, comprising:
a paste consisted of a welding flux and acetone / industrial alcohol,
wherein the composition of the paste consisting of:
TIO2 : 10wt%
K20T102 : 7 wt %
Cr203 : 10wt%
Si02 : 73wt%
2. The welding flux as claimed in claim 1, wherein the welding flux
consisting of the following commercial purity powders in a dry mixture:
Titania : 7.5 to 12.5wt%
Potassium titanate : 5-10 wt%
Green Chromium trioxide : 7.5-12.5 wt%
Silica : 70to75wt%

3. An improved TIG welding process in particular applicable for joining thin
M.S. sheets to achieve increased penetration, comprising:
applying a thick layer of the welding flux as claimed in claim 1 on
the weldable faces of the M.S. sheets;
autogenously running the welding arc along the joint surfaces,
wherein the weld joint surfaces are butted together without any
edge preparation.
4. The process as claimed in claim 3, wherein the autogenous TIG welding is
carried out with DCEN current, and without filler wire.

A welding flux to achieve increased penetration in TIG welding of mild steel,
comprising: a paste consisted of a welding flux and acetone / industrial alcohol,
wherein the composition of the paste consisting of:
TIO2 : 10wt%
K20T102 : 7 wt %
Cr203 : 10wt%
Si02 : 73wt%