FIELD OF THE INVENTION
The invention relates to a synergic tandem wire SAW process using two different
wire feeders assembly in a single motor shaft with a single Direct current
constant voltage power source for butt joint/ hardfacing of different combination
of filler wires by adapting an improved single/tandem wire submerged arc
welding machine. More particularly, the invention relates to an improved
single/tandem wire submerged are welding machine for butt joint and hardfacing
in grooves with width of different sizes and a high dilution process.
BACKGROUND OF THE INVENTION
A conventional tandem submerged arc welding equipment is essentially
characterized by the adaptation of one additional wire feeder with an Alternate
Current power source which is synchronized with a Direct current constant
voltage power source, a wire feeder with control system controlling the wire feed
rate and delivering the two different DC/AC arcs simultaneously using said two
different power sources for butt joint or hard facing of different or same
combination of filler wires.
In conventional tandem SAW process the heat input energy is calculated by the
average energy of two different DC/AC arcs, and thus less plate is melted as
wire.

When two welding arcs are running close together, an anomally known as "arc
blow" occurs as the magnetic fields created by the high currents repel each other
and actually blow molten metal out of the weld puddle.
Conventional welding equipment is limited to phase relationship only but without
the ability of phase synchronization.
United States Patent 7166818 discloses an electric arc welding apparatus
comprising at least a first consumable electrode and a second consumable
electrode movable in unison along a welding path between the edges of two
adjacent, mutually grounded plates, a first power supply for passing a first
welding current at a first low frequency between the first electrode and the two
plates, a second power supply for passing a second welding current at a second
low frequency between the second electrode and the two plates, where each of
the power supplies includes a three phase voltage input operated at line
frequency, a rectified to convert the input voltage to a DC voltage link and a high
frequency switching type inverter converting the DC voltage link to a high
frequency AC current, and output rectifier circuit to provide a positive voltage
terminal and a negative voltage terminal, and an output switching network
operated at a given low frequency for directing a pulsating welding current at the
given low frequency from the two terminals across one of the electrodes and the
plates, and a circuit for independently adjusting the given low frequency so the
value of the first low frequency of the first power supply is different from the
second low frequency of the second power supply.

United States Patent 4,572,936 discloses a method for making multiple wire
welding in a submerged arc multiple wire welding system. In the method, only
one or two of the welding wires used are 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.
In absence of further description in US 4572936, it appears that the wires are
separately fed using different power sources and different wire feeders as
mentioned in the Examples 1 to 4 of US patent. " The first wire is connected to
810 A at 30 V. The second wire is connected at 790 A at 33 V. The third wire is
connected to 680 A at 34 V.
The cited reference JP 3238173 teaches "ONE SIDE SUBMERGED ARC
WELDING METHOD" relates to ARC welding method to form a fine bead by
arranging two welding wires having the specified diameter in parallel with a weld
line to form one electrode, using this as a first electrode and making a root gap
specified times the size of the wire diameter.
In the disclosed method, square groove multiple electrode one-side submerged
arc welding is performed by using a small diameter welding wire 1 and large
diameter welding wire 2. The two welding wires having 1.0-3.5 mmphi diameter

(d) are then arranged in parallel with the weld line. The same welding power
source, a wire feed machine 3 of a wire feed mechanism and a feed roller 4 for
the twin wires are then held commonly for these wires to form the one electrode.
This is used as the first electrode and the root gap is made to 1.2-1.5 times the
size of the wire 1 diameter. Consequently, square grooves welding can be easily
performed at high speed.
Cited reference US 20070145028 entitled "WELDING UNIT AND WELDING
METHOD BY MEANS OF WHICH AT LEAST TWO DIFFERENT WELDING
PROCESSES MAY BE COMBINED" discloses a welding unit including a welding
apparatus with a welding torch unit connectable thereto via a hose pack. At least
one control device, a welding current source and optionally a wire feeder unit are
arranged in the welding apparatus. The welding torch unit is formed by at least
two separate welding torches intended to carry out at least two independent,
separate welding processes. The first welding torch is configured to carry out a
welding process and at least a second welding torch is configured to carry out a
cold-metal transfer welding process with a forward-backward movement of a
welding wire, and that a device for synchronizing the welding processes carried
out by the at least two welding torches is provided.

Cited reference DE 19611583 entitled "APPARATUS FOR WELDING WITH TWO
WIRES" relates to the apparatus for welding with two wires incorporates a single
current source (1) serving for production of pulsed direct current, spools (2,4)
respectively for wire electrodes (3,5), a wire feed unit (6), a holder (7) with
contact nozzles (8), and a delivery pipe for protective gas. The contact nozzles
accommodated by the holder are commercially available, changeable nozzles
fixed in the holder by clamping elements.
Cited reference CN 2199002 entitled "AUTOMATIC SUBMERGED-ARC WELDER
FOR ANGLE AND DOWNWARD WELDING OF TWO WIRES AUTOMATIC
SUBMERGED-ARC WELDER FOR ANGLE AND DOWNWARD WELDING OF TWO
WIRES" discloses a utility model relating to an automatic submerged-arc welder
for angle and downward welding of two wires. A welding tractor is provided with
two wire feeding devices which can work independently, a wire welding plate,
and a set of welding flux feed device for the joint use of the two wires. The
automatic submerged-arc welder for angle and downward welding of two wires
is composed of a gear box body, a welding gun, a conveying pipe, a control
circuit, etc. The automatic submerged-arc welder for angle and downward
welding of two wires can conduct angle welding to workpieces on horizontal
position, and can be convenient to conduct downward welding.

OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a synergic tandem
wire SAW process for butt joints which reduces the cycle time.
Another object of the present invention is to propose an improved single/tandem
wire submerged arc welding equipment which can be adapted in the process.
A still another object of the present invention is to propose a synergic tandem
wire SAW process which has the ability to avoid arc blow.

A further object of the present invention is to propose a synergic tandem wire
saw process for hardfacing of similar/dissimilar fillers using tandem wires
technique which is capable of creating a common weld pool to achieve a new
deposit chemistry according to the code of highest quality welds, including
achieving a considerable manufacturing economics.
Yet another object of the present invention is to propose an improved welding
equipment which can be configured by interfacing one additional wire feeder
roller and torch along with the main wire feeder with the existing control system
and drive motor using single direct current constant voltage power source.
SUMMARY OF THE INVENTION
In the synergic tandem submerged arc welding process, a newly designed wire
feeder(R), the existing main wire, and an additional wire are fed simultaneously
using two different feeder assemblies and nozzles. The wires in the contact
nozzles are arranged tangential to the welding direction.
With the new synergic tandem SAW process the two DC arcs calculate the heat
input energy. It is therefore a high dilution process with approximately twice as
much plates are being melted as wire. This new synergic tandem SAW process is
one of the advanced techniques which makes use of single power source energy
available in the arc stream, and which increases the deposition rate equivalent to
that of a conventional tandem SAW process. Thus, the new synergic tandem

SAW can ensure increased transfer efficiency as compared to the other method.
The SYNERGIC TANDEM Arc system provides two arcs, which can be configured
as DC single power source system. The advantage of the SYNERGIC TANDEM
system is the control over the phase relationship.
The SYNERGIC TANDEM has the ability to synchronize the phase relationships
between multiple arcs allowing unprecedented control over the arc blow.
This results in a highest usable melting rate for given arc energy for good
penetration without arc blow. Thus the synergic tandem SAW technique will
result in 40% increase in deposition rate and better mechanical properties is
achievable over conventional Tandem submerged arc welding process. In new
synergic tandem SAW, for addition of one wire is required to interface one
additional wire feeder along with main wire feeder with the existing control
system in same wire feeder motor using single Direct current constant voltage
power source to attain the required chemistry and mechanical properties.
The invention is directed to a further development that, "The similar/dissimilar
wires combination as main wire and an additional wire fed simultaneously using
two different wire feeder assemblies and nozzles in a single integrated wire
feeder motor shaft with same control system drawing power from a single Direct
current constant power source with parameters of 800 A, 32 V and 0.5 m/min as
welding speed". The wires in the contact nozzles are arranged tangential to the
welding direction creating a single weld pool in which the required weld

chemistry were obtained from the use of two wires of different/same chemistry.
The results are savings in consumables cost, cycle time reduction and high
productivity.
The present invention produces a weld metal structure with a high proportion of
acicular structure, the surface proportions of acicular being 100 percent. The
inventive process performs a multi layer pass welding for reducing the number of
layers compared to conventional SAW process to enhance the mechanical
properties.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 is prospective view of an improved single/tandem wire submerged arc
welding machine adaptable to a synergic tandem wire SAW process for butt
welding/hardfacing.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in Fi.-1, an improved wire feeding system can be fitted to a
conventional submerged arc welding machine. The new machine essentially
allows achievement of same/different composition (1) of filler materials and weld
metal combination. The synchronous operation of two wire feeders (2) mounted
on an integral shaft (3) is shown in Fig 1. The dissimilar/similar wire combination

is fed using a two wire feeder assembly (2) with two nozzles (4) connected to a
single power source (6) which is coupled by a power cable (7) in parallel. A
single weld pool is created in which new weld chemistry is obtained by using two
wires of different chemistry. To attain the required hardness properties as well as
the required microstructure of the weld metal chemistry, twin submerged arc
welding can be used in which the common arc pool (5) is created. In the arc
cavity the filler wires with different/same chemical composition wires are fed
simultaneously in a two nozzle structure, as shown in Fig. 1.
By using the present invention, the welding current for heavy plates welding can
be between about 200 amperes to about 1250 amperes.
In accordance with the invention, the electric arc welder includes a first and
second consumable electrode, which electrodes are moved in unison along a
welding path between the edges of the grounded plate. Power supply from one
power source (6) is used for passing welding currents between the individual
electrodes and the plates forming the grounded work piece of the welding circuit.
The new design enables welding/surfacing to be carried out in grooves having a
width of different sizes. The new tandem submerged arc welding with special
wire feeder can be used for welding/hardfacing of butt joints and surfacing. This
technique can be used for both mechanized and as well as automatic mode. This
results in savings in flux cost, cycle time reduction and higher productivity.

WE CLAIM:
1. An improved single/tandem wire submerged arc welding machine for
butt joint and hardfacing in grooves with width of different sizes, the
improvement is characterized in that:
- at least one two-wire feeder means (2) synchronously feeding
dissimilar/similar wire combination to a conventional submerged
arc welding machine, each wire feeder of the two-wire feeder
means (2) is mounted on an integrated shaft (3); and
- the two wire feeder means (2) having a single control device
drawing power from a single direct current constant voltage
power source (6);
- at least two nozzles (4) connected to the power sources (6);
wherein the plates around the grooves are melted as wires at a
rate twice that of the existing melting rate, wherein a weld metal
structure with a high proportion of acicular microstructure is
produced, wherein the number of welding pass including number of
layers are reduced which in turn reduces the cycle time and
enhance the mechanical properties, and wherein the welding
machine includes a first and second consumable electrode, which
electrodes are moved in unison along a welding path between the
edges of the grounded plate, power supply from one power source
being used for passing welding currents between the individual
electrodes and the plates forming a grounded work piece of the
welding circuit.

2. A high dilution synergic tandem wire SAW process for butt
joint/hardfacing in grooves with width of different sizes, the process
comprising the steps of:
- providing an improved single/tandem wire submerged arc
welding machine having a main wire feeder;
- simultaneously feeding a similar/dissimilar wires combination as
main wire and additional wire via at least one two-wire feeder
means;
- placing the wires in respective contact nozzles of a two nozzle
arrangement tangential to the welding direction;
- allowing a common control device for both the wire feeder
means to draw power from a single direct current constant
voltage power source; and
- creating a single weld pool with new weld chemistry which is
feed in the arc cavity simultaneously with said nozzles,
wherein the plates around the grooves are melted as wires at a
rate twice that of the existing melting rate, wherein a weld metal
structure with a high proportion of acicular microstructure is
produced,
wherein the number of welding pass including number of layers are
reduced which in turn reduces the cycle time and enhance the
mechanical properties, and wherein the welding machine includes a
first and second consumable electrode, which electrodes are moved
in unison along a welding path between the edges of the grounded
plate, power supply from one power source being used for passing
welding currents between the individual electrodes and the plates
forming a grounded work piece of the welding circuit.

3. The process as claimed in claim 2, wherein the phase relationships
between multiple arc is synchronized to achieve a substantial control
over arc blow.
4. The process as claimed in claim 1, wherein the surface proportion of
the acicular structure is 100 percent.
5. The process as claimed in claim 2, wherein a multilayer pass welding is
performed for reducing the number of layers compared to conventional
SAW process.

ABSTRACT

TITLE: "AN IMPROVED SINGLE/TANDEM WIRE SUBMERGED ARC WELDING
MACHINE FOR BUTT JOINT AND HARDFACING IN GROOVES WITH WIDTH OF
DIFFERENT SIZES AND A HIGH DILLUTION PROCESS".
The invention relates to An improved single/tandem wire submerged arc welding
machine for butt joint and hardfacing in grooves with width of different sizes, the
improvement is at least one two-wire feeder means (2) synchronously feeding
dissimilar/similar wire combination to a conventional submerged arc welding
machine, each wire feeder of the two-wire feeder means (2) is mounted on an
integrated shaft (3); and the two wire feeder means (2) having a single control
device drawing power from a single direct current constant voltage power source
(6) ; at least two nozzles (4) connected to the power sources (6);wherein the
plates around the grooves are melted as wires at a rate twice that of the existing
melting rate, wherein a weld metal structure with a high proportion of acicular
microstructure is produced, wherein the number of welding pass including
number of layers are reduced which in turn reduces the cycle time and enhance
the mechanical properties, and wherein the welding machine includes a first and
second consumable electrode, which electrodes are moved in unison along a
welding path between the edges of the grounded plate, power supply from one
power source being used for passing welding currents between the individual
electrodes and the plates forming a grounded work piece of the welding circuit.