FIELD OF THE INVENTION
The invention relates to a process for cold wire addition using cold wire feeder
for butt joint of pressure vessels/structural/hardfacing of different combination of
filler wires using single/twin/tandem wire submerged arc welding applications.
More particularly, the present invention relates to an improved method of cold
wire addition for long stem butt welding for pressure vessels joints in a
single/tandem submerged arc welding process.
BACK GROUND OF TOE INVENTION
The existing cold wire addition process essentially characterized by the use of
one additional wire feeder with out any power source is interfaced with the
existing wire feeder control system for controlling the wire feed rate. A single
wire feeder along with the main wires, feeds the cold wires simultaneously. The
wires in the contact nozzles are disposed tangentially in respect of the welding
direction. In conventional SAW process the heat energy are distributed in such
way that only 20-25% as consumed for melting the filler wire, the rest being
utilized in melting the flux, super heating the molten weld pool and melting the
parent plate. It is therefore a high dilution process with approximately twice as
much plates are being melted as wire. This cold wire addition is one of the
advanced technique to make use of excess energy available in the arc cavity for
addition of filler material in the form of wire. With addition of cold wire, the
excess heat energy is used efficiently for melting the wire. The addition of "cold
wire* in the arc stream

can increase the deposition rate. Thus, the addition of cold wire ensures
increased transfer efficiency compared to other method. This results in a highest
usable melting rate for a given arc energy and unwanted heat which causes
heavy penetration, unfavorable microstructures, high shrinkages and distortion.
Thus the prior art cold wire addition technique will results in 40% increase in
deposition rate and better mechanical properties over conventional single /
Tandem submerged arc welding process. In current practice, addition of cold
wire warrants interfacing one additional wire feeder along with main wire feeder
with control system to attain the required chemistry and mechanical properties.
US patent 4,572,936 discloses a submerged arc multiple wire welding system in
which only one or two of the plurality welding wires used constitute over or
microalloyed wires. The other wires are commercially available unalloyed or low-
alloyed solid wires. The process produces a weld metal which has unexpectedly
high toughness values, and can be performed more economically. This multiple
wire welding system is used in single or multiple-pass welding operations .
This process, although constitutes a multiple wire system, the step of feeding the
wires is accomplished by using different power sources and different wire feeders
as mentioned in the Examples 1 to 4 of the cited prior art. According to the
disclosure, the first wire is connected to 810 A at 30 V, the second wire is
connected at 790 A at 33 V, and the third wire is connected to 680 A at 34 V.
The cited invention further discloses that, a similar wire combination is fed using
a single wire feeder with two nozzle drawing power from a single power source
with parameters of 750 A, 32 V, 0.4 m/min as the welding speed.

OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to provide an improved method
of cold wire addition for long stem butt welding for pressure vessel joints in a
single wire, tandem submerged arc welding process, which reduces cycle time
and consumables.
Another object of the present invention is to provide an improved method of cold
wire addition for butt or fillet joint for, pressure vessels, in a two-wire submerged
arc welding process.
A further object of the present invention is to provide an improved method of
cold wire addition in a welding process for hardfacing of dissimilar fillers in a
two-wire submerged arc welding process which is capable of creating a common
weld pool to attain required chemistry according to the code of highest quality
welds, and which achieves considerable manufacturing economics.
SUMMARY OF THE INVENTION
Accordingly there is provided in one aspect of the invention, an improved method
of cold wire addition for pressure vessels joints in a single/tandem submerged
arc welding process. In a second aspect, the invention provides an improved
method of cold wire addition in a welding process for hardfacing of dissimilar
fillers in a two-wire submerged arc welding process
The invention provides a new configuration of the wire feeder, which enables
feeding of multi wire simultaneously in the same wire feeder in different feed
rate for different current rating. This new wire feeder substantially enhances the

production rate as compared to the conventional submerged arc welding
process. An integral shaft is designed and interfaced with the available DC wire
feeder for coupling the additional wire feeder for feeding the cold wire in the arc
cavity in SAW process. With this new wire feeder the cold wire addition can be
provided in both direction of welding. This results additional weld deposit with
same in-put heat energy available in the arc zone. Additional power source and
control system is not required for this new design of wire feeder. This new wire
feeder can be interfaced with the existing type of SAW machine.
According to the invention, single weld pool is created in which the required weld
chemistry is obtained by the use of three wires of same chemistry.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig. 1 is prospective view of the improved method of cold wire addition in
Tandem submerged arc welding for long seam butt welding of pressure vessel
components according to the present invention.
DETAILED DESCRIPTION QF THE INVENTION
The improved method of cold wire addition technology can be adapted to
conventional tandem submerged arc welding machine. By this method, a same
composition (1) of filler materials and weld metal combination can be used
effectively. The construction of special tandem wire feeding (2) and integral shaft

(3) assembly is shown in Figure 1. A similar wire combination (1,1) is fed using a
single wire feeder (2) with two nozzles (4) drawing power from a first power
source (6) with a parameters of 750 A, 32 V in DC, and a third wire (5) is fed
through a second power source (7) with 650A, 30V in AC and 0.4 m/min as
welding speed. A single weld pool (8) is created in which the required weld
chemistry is obtained by the use of three wires (1,1,5) of same chemistry. In this
technique, to attain the required hardness properties including the required
microstructure of the weld metal, the tandem wire with cold wire submerged arc
welding is adapted, in which the common arc pool (8) is created. In the arc
cavity, the fillers (1,1) with same chemical composition of same alloy wires are
fed simultaneously via a single wire feeder (2) with the two nozzles (4) using the
first power source (6). The direction of welding (9) is shown in Fig 1. i.e., one
after another which creates the common weld pool to give the desired weld
properties.
This new method enables carrying out welding / surfacing in grooves having
width of different sizes. The new method of tandem with cold wire addition can
further be adapted for drum butt welding for long seam butt welding including
circumferential butt welding of pressure vessels components of different sizes.
This method can also be used for both manual as well as for mechanical mode.
The method results in savings in consumables cost and cycle time and improved
mechanical properties.

WE CLAIM
1. An improved method of cold wire addition in long stem butt welding of
pressure vessels by tandem submerged arc welding process, the method
comprising the steps of:
- providing an integral shaft (3) being interfaced with a wire feeder (2),
having at least two nozzles (4);
- simultaneously feeding a similar wire-combination of two wires (1,1) via
the wire feeder (20, the at least two nozzles (4) of the wire feeder (2)
drawing power from a first power source; characterized by comprising :
- feeding a third wire (5) via a second power source (7), and;
- creating a common arc pool (8) by adapting the tandem wire (1,1) with
the third wire (5) in the submerged arc welding.

2. The method as claimed in claim 1, wherein the three wires (1,1,5), of
same composition are used.
3. The method as claimed in claim 1, wherein the first power source (6) has
operating parameters for example, 750A, 32V DC, and wherein the second
power source (7) comprises operating parameters for example, 650A, 30V
AC.

4. The method as claimed in claim 1 or 3, wherein the welding speed of the
third wire (5) is 0.4m/min.

ABSTRACT

TITLE : "AN IMPROVED METHOD OF COLD WIRE ADDITION IN LONG
STEM BUTT WELDING OF PRESSURE VESSELS"
The invention relates to an improved method of cold wire addition in long stem
butt welding of pressure vessels by tandem submerged arc welding process, the
method comprising the steps of providing an integral shaft (3) being interfaced
with a wire feeder (2), having at least two nozzles (4); simultaneously feeding a
similar wire-combination of two wires (1,1) via the wire feeder (20, the at least
two nozzles (4) of the wire feeder (2) drawing power from a first power source;
characterized by comprising feeding a third wire (5) via a second power source
(7), and; creating a common arc pool (8) by adapting the tandem wire (1,1) with
the third wire (5) in the submerged arc welding.