FIELD OF INVENTION
The invention relates to an apparatus and process for alternating the shielding gas
supply to the arc in Gas Metal Arc Welding (GMAW) process to achieve improved weld
quality including reduction in shielding gas consumption. More particularly, the
invention relates to an apparatus to alternate the shielding gas supply to the GMAW
torch and optimization of gas pulsing frequency for improving weld quality.
BACKGROUND OF THE INVENTION:
GMAW is one of the important arc welding processing widely used in the fabrication
industries all over the world. This is an electric arc welding process, which produces
coalescence of metals by heating them with an arc established between a continuous
filler metal (consumable) electrode and the work. Shielding of the arc and molten
weld pool is obtained by an externally supplied gas, which may be inert, reactive or a
mixture of inert and reactive gases. The GMAW process is known as Metal Inert Gas
(MIG) welding, when the shielding gas used in inert, and also known as Metal Active
Gas

(MAG) welding when the shielding gas contains reactive gases, such
as O2 or CO. sub.2 or mixtures of inert and reactive gases. Each
shielding gas has its own properties, including ionization potential,
and produces unique arc characteristics. For instance, 100%CO2
shielding in mild steel application produces somewhat harsh arc with
associated spatter but gives better weld penetration. On the other
hand, 100% argon shielding for mild steel application produces very
stable arc but results in very poor bead wetting. In order to achieve
stable arc and also good bead wetting characteristics in ferrous
applications, a shielding gas mixture containing argon+CO2 or
argon+O2 of different proportions is used in the industries for over
two decades. Though GMAW with argon+CO2 and argon+O2 mixed
gas is successful in welding of ferrous metals, there are some
limitations.
The mixed gases used in industries are generally rich in argon (argon
> 80%) resulting higher shielding gas cost.
Variation in the mixing ratio particularly with gas mixing units Leads
to poor weld quality due to changes in arcing characteristics.

In conventional GMAW for welding of ferrous metals, it is standard
practice to use 100%CO2 or argon+CO2 gas mixture depending on
the quality requirement and application. The use of 100%CO2 or
argon+CO2 gas mixture produces a constant arc dynamics. The arc
pressure and weld pool fluidity remain constant.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an apparatus and
process for alternate supply of shielding gas to the GMAW torch.
Another object of the invention is to propose an apparatus and
process for alternate supply of shielding gas to the GMAW torch in
which the shielding gas can be directly supplied to the GMAW torch
to avoid mixing of the gas before entering the torch.
A further object of the invention is to propose an apparatus and
process for alternate supply of shielding gas to the GMAW torch in
which due to optimization of pulsing frequency of the gas supply
achieves improved weld quality.

A still further object of the invention is to propose an apparatus and process for
alternate supply of shielding gas to the GMAW torch inn which shielding gas can be
alternating supplied at different frequencies.
These and other object and advantages of the invention will be apparent from the
ensuring from the ensuring description.
At the outset of the description, which follows, it is to be understood that the ensuring
description only illustrates a particular form of this invention. However, such a
particular form is only an exemplary embodiment and the teachings of the invention
are not intended to be taken restrictively.
SUMMARY OF THE INVENTION
According to the invention, there is provided an apparatus and a process for
alternating supply of two shielding gases to a Gas Metal Arc Welding (GMAW) torch at
a preset alternating/pulsing frequency, comprising two hoses (3, 4) at least,
characterized in that the said hoses (3, 4) mainly for alternating two shielding gases
without mixing at controlled frequencies from two individual gas cylinders (1, 2),
connected to the respective input terminals (5,6) provided in the shielding gas
alternator (9); and the shielding gas alternator (9), containing at least two solenoid
valves (S1) S2 and two timer knobs (7, 8) and two gas outlets (10,11), connected to a
GMAW torch via two individual hoses (12, 13), characterized in that the length of
hoses (12, 13) is so selected as to optimize alternating and/or pulsing frequency of
the supplied shielding gas for improved weld quality.

PRIFF PESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from the
ensuing description when read in conjunction with the accompanying drawings
wherein:
Figure 1 (Schematic)- Shows an embodiment of the apparatus according to the
invention.
Figure 2- shows the diagram of the shielding gas alternator.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Referring now to the drawings. Wherein like reference numerals designate identical or
corresponding parts throughout the several views. Rg 1 shows the schematic of the
alternate gas supply system. At least two hoses (3,4) carrying argon and C02 gases
from two individual gas cylinders (1,2) are connected to the respective input terminals
(5,6) provided in a gas supply alternator (9). The duration of flow for each individual
gas is controlled through two timer knobs (7, 8) provided in the front panel of the
shielding gas alternator (9). Two gas outlets (10, 11) provided on the front panel of
the shielding gas alternator (9) is connected to a plurality of nipples (14,15).

Provided in a GMAW torch nozzle directly through two individual hoses (12, 13) for
each gas. The hose (12, 13) length from the shielding gas alternator (9) to the torch
is kept to a minimum to make it dynamically more responsive. Adjusting the timer
control(7,8) varies the shielding gas alternating /pulsing frequency.
As shown in Fig. 2 S1 and S2 are the two solenoid valves for alternating the shield
gas supply at a frequency range of 20-120 cycles/minutes through these valves and
F1 and T2 are the timers used for controlling the flow duration.
The alternate shielding gas supply process overcomes the limitations of mixed gas
method. The technology of alternate supply of shielding gas has influence on every
aspect of the arc welding. The alternate supply of shielding gas causes a dynamic
action on the molten weld pool, which results in improved weld quality both in terms
of fusions characteristics and bead appearance.
The alternate shielding gas supply technology causes multiple impacts to weld pool
resulting in much improved weld quality.

WE CLAIM:
1. An apparatus and a process for alternating supply of two shielding gases to a
Gas Metal Arc Welding (GMAW) torch at a preset alternating/pulsing frequency,
comprising:
- two hoses (3,4) at least, characterized in that the said hoses
(3,4) mainly for alternating two shielding gases without mixing
at controlled frequencies from two individual gas cylinders (1,2),
connected to the respective input terminals (5,6) provided in
the shielding gas alternator (9); and
- the shielding gas alternator (9), containing at least two solenoid
valves (S1) S2 and two timer knobs (7, 8) and two gas outlets
(10, 11), connected to a GMAW torch via two individual hoses
(12,13), characterized in that the length of hoses (12,13) is so
selected as to optimize alternating and/or pulsing frequency of
the supplied shielding gas for improved weld quality.
2. The apparatus as claimed in claim 1, wherein two different shielding gases is
selected from a combination of argon and carbon dioxide; argon and helium;
and argon and oxygen.

3. The apparatus as claimed in claim 1, wherein the shielding gas supply is
alternated at a frequency range of 20 to 120 cycles/minute through a solenoid
valve control (S1, S2);
4. The apparatus as claimed in claim 1, wherein the gas pulsing frequency is
controlled through timer circuit (7, 8) for controlling the duration of flow of
individual gases.
5. The apparatus, as claimed in Claim 1 wherein the apparatus is applicable for
alternating supply of two different shielding gases to a GMAW torch at a pre-
set alternating pulsing frequency.
6. A new version of (GMAW) process wherein the welding is carried out with
alternating supply of shielding gases for carbon steel, stainless steel and
aluminum as substantially described and illustrated herein with reference to the
accompanying drawings.

ABSTARCT

AN APPARATUS AND A PROCESS FOR ALTERNATING SUPPLY OF TWO
SHIELDING GASES TO A GAS METAL ARC WELDING (GMAW) TORCH AT A
PRE-SET ALTERNATING/ PULSING FREQUENCY
The invention discloses an apparatus and a process for alternating supply of two
shielding gases to a Gas Metal Arc Welding (GMAW) torch at a preset
alternating/pulsing frequency, comprising two hoses (3, 4) at least, characterized in
that the said hoses (3,4) mainly for alternating two shielding gases without mixing at
controlled frequencies from two individual gas cylinders (1,2), connected to the
respective input terminals (5,6) provided in the shielding gas alternator (9); and the
shielding gas alternator (9), containing at least two solenoid valves (S1) S2 and two
timer knobs (7, 8) and two gas outlets (10, 11), connected to a GMAW torch via two
individual hoses (12,13), characterized in that the length of hoses (12,13) is so
selected as to optimize alternating and/or pulsing frequency of the supplied shielding
gas for improved weld quality.