FIELD OF THE INVENTION
The invention relates generally to submerged arc welding, and in particular to a
process of narrow gap submerged arc welding with cold wire addition and an
apparatus for the same.
BACKGROUND AND PRIOR ART
Submerged Arc Welding (SAW) involves formation of an arc between a
continuously fed bare wire electrode and the workpiece. The process uses a flux
to protect the molten pool and form slag, and to add alloying elements to the
weld pool. A shielding gas is not required. Prior to welding, a flux is covered on
the arc zone in the workpiece surface. The arc moves along the joint line and as
it does so, unused flux is recycled via a hopper. Remaining fused slag layers can
be easily removed after welding. As the arc is completely covered by the flux,
the weld area is also not visible during welding. The welding is spatter free and
there is no need for fume extraction.

As the operator cannot see the weld-pool, greater reliance must be placed on
parameter settings.
Narrow gap SAW is a process variant, which utilizes a two or three bead per
layer deposition technique.
Narrow gap arc welding is particularly suitable for welding of thick-section
material.
Narrow gap submerged arc welding (SAW) presently uses different techniques
like tandem or multi-wire technique. However the above stated techniques used
for narrow gap welding involve either high cost or criticality to operate the
instruments, or both.
In tandem SAW for narrow gap welding, the following features of the welding
heads are needed, which is costly and need precision handling :
a) Massive frame for rigidity, current transfer and heat dissipation.
b) Controlled torch angle drives for programmable precision torch
placement and smooth transitions from pass to pass.

c) Controlled X and Z slides for precise, smooth height and cross-seam
(tracking) control.
d) Redundant, off-set wire straightening to ensure wire is straight for
consistent and accurate placement.
In multiple wire welding system, out of the wires used for welding one or two of
the welding wires used are over a microalloyed wires. The other wires are
commercially available unalloyed or low-alloyed solid wires. The process uses a
weld metal, which has unexpectedly high toughness value, used in single or
multi-pass welding operation.
Multiple wire welding process is described in the US Patent No.4,572,936 -
where wires are fed separately using different power sources for different wire
feeders. Hence requirement of individual power source with high current feed is
needed - which add to cost.
The above disadvantages are overcome in present invented process and
apparatus.

OBJECTS OF THE INVENTION
An object of the present invention is to provide a process for addition of cold
wire during narrow gap welding.
Another object of the invention is to provide a process of narrow gap submerged
arc welding which eliminates excess arc energy leading to deformation of micro-
structure, shrinkage and distortion of the main plate.
Yet another object of the present invention is to provide a process for increasing
the deposition rate by 50% and thereby achieving better mechanical properties.
A further object of the present invention is to provide a process which enables
savings of upto 70% in weld metal requirement compared to conventional
process.
Yet another object of the present invention is to provide an apparatus for cold
wire addition along through cold wire feeder with the main wire using narrow
gap nozzles.

A still further object of the invention is to provide a product for two wire feeders
with narrow gap nozzles to draw power from a single power source.
SUMMARY OF THE INVENTION
The invented process uses submerged arc-welding with cold wire addition for
narrow gap welding. Compared to conventional welding techniques, this process
employs near parallel-sided edge preparation. The included angle for joint will be
in the range of 2-4 deg. The width of the joint at the root will be approximately
18~25 mm depending upon the thickness of the material welded. Thus this
process enables savings of upto 70% in weld metal requirement.
The narrow-gap submerged arc welding process uses one additional wire feeder
with special narrow torch without any power source and it is interfaced with the
existing wire feeder with control system for controlling the wire feed rate. Along
with the main wire, the cold wire is fed either simultaneously with different wire
feed rate or at the same wire feed rate. The wires in the contact nozzles are
arranged tangentially to the welding direction.

In conventional SAW process the heat energy is distributed in such a way that
only 20-25% of the heat energy is used for melting the filler wire and the rest is
utilized in melting the flux, super heating the molten weld pool and melting the
parent plate. In this high dilution process twice as much plates are being melted
as wire, which is undesirable.
In the invented process, it makes use of the 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 the "cold wire" in the arc system increases the deposition rate,
thus increases transfer efficiency. This results in a highest usable melting rate for
a given arc energy and unwanted heat which causes heavy penetration,
unfavorable micro structure formation, high shrinkage and distortion of the main
plate is eliminated. Hence these defects of the prior art are avoided.
This invented process increases deposition rate by 50% and better mechanical
properties are achieved over conventional single/tandem narrow gap submerged
arc welding process.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWING:
Fig. 1: View of cold wire addition technique in narrow gap torch for single
submerged arc welding technique for butt welding of drum shell.
The invention now will be described in detail in an exemplary embodiment as
depicted in the accompanying drawings. There can however be other
embodiments of the same invention, all of which are deemed covered by this
description.
As best seen in Fig. 1
In the present invention as shown in Fig. l, a specially designed wire feeding
with control system with additional cold wire feeding using a narrow gap torch,
which is attached to a conventional submerged arc welding machine. Here same
or different composition (1) of filler materials weld metal combination can be
done effectively. In the present invention main wire is fed through feeder
assembly (2) and the cold wire is fed through the feeder assembly (3) in fig. 1.

The dissimilar / similar wire combination is fed using these two wire feeders with
two narrow gap nozzles (4) and (5). Both these nozzles draw power from a
single power source (6). A single weld pool is created in which the required weld
chemistry is obtained from the use of two wires of different chemistry. Common
arc pool gives the required microstructure of the weld metal and the weld joint
attains required hardness.
Not limiting the scope of the invention, the present invented product and process
can be applied for welding to be carried out in narrow grooves having different
width. The cold wire addition process, by using cold wire feeder with narrow gap
torch, can be used for welding of drum butt joints, valve wedges and seat rings
of different sizes. This process can be manual as well as mechanised mode.
This will result in savings in consumables cost, cycle time reduction and higher
productivity with savings of weld materials.

We claim:
1. A process of narrow gap submerged arc welding with cold-wire addition
comprises the steps of -
preparation of near parallel-sided edges for welding;
ensuring that the included angle for the joint is in the range of 2-4°
and width of the joint at the root is in the range of 18~25 mm;
feeding one additional wire with special narrow gap nozzle and
interfacing the additional wire-feeder with the existing wire feeder for
controlling the wire feed rate,
characterized in that the process enables savings of upto 70% in weld metal
requirement and in that the excess energy available in the arc cavity melts
the cold wire and eliminates heavy penetration, unfavourable micro-structure
formation, high shrinkage and distortion of the main plate.
2. A process of narrow gap submerged arc welding as claimed in claim 1,
wherein the cold wire is fed alongwith the main wire simultaneously either with a
different wire feed-rate or with the same wirefeed-rate.

3. A process of narrow gap submerged arc welding as claimed in claims 1
and 2, wherein the narrow gap nozzles are arranged tangentially to the welding
direction.
4. A process of narrow gap submerged arc welding as claimed in claim 1,
wherein a single pass welding is performed to avoid buffering layer of welding
and machinery.
5. An apparatus for the narrow gap submerged arc welding process as
claimed in claims 1 to 4 comprising:
main wire-feeder assembly (2)
cold wire feeder assembly (3)
narrow gap nozzles (4,5), and
single power source (6)
characterized in that cold wire is added to the weld through cold wire feeder
assembly (3) alongwith the main wire.
6. An apparatus for the narrow gap submerged arc welding as claimed in
claim 5, wherein the wires fed into the weld can be of similar or dissimilar
combination.

7. An apparatus for the narrow gap submerged arc welding as claimed in
claim 5, wherein the similar / dissimilar wire combination fed through wire
feeders with narrow gap nozzles creates a common weld pool for achieving
required chemistry and hardness.
8. An apparatus for the narrow gap submerged arc welding as claimed in
claim 5, wherein both the wire feeder assemblies (2,3) with narrow gap nozzles
draw power from a single power source (6).

A process of narrow gap submerged arc welding with cold-wire addition
comprises the steps of preparation of near parallel-sided edges for welding;
ensuring that the included angle for the joint is in the range of 2-4° and width of
the joint at the root is in the range of 18~25 mm; feeding one additional wire
with special narrow gap nozzle and interfacing the additional wire-feeder with
the existing wire feeder for controlling the wire feed rate, characterized in that
the process enables savings of upto 70% in weld metal requirement and in that
the excess energy available in the arc cavity melts the cold wire and eliminates
heavy penetration, unfavourable micro-structure formation, high shrinkage and
distortion of the main plate.