A METHOD FOR FORMING A JOINT BETWEEN DISSIMILAR
METALS IN A LANCE ASSEMBLY
FIELD OF INVENTION
[001] The present subject matter described herein, relates to a method of
forming joints between dissimilar metals in a lance assembly. More
particularly, to a method of forming joint between ASTM A297 Grade HH
alloy and ASME SA 312 TP 321 steel in Lance Assembly using Automatic
orbital hot wire Gas Tungsten Arc welding process and optimization of
parameters associated with the method for obtaining defect-free dissimilar
metal welds. The method is applicable for welding joint between pipes
which is primarily of interest in manufacturing of Lance Assembly for coal
fired power plants.
BACKGROUND OF THE INVENTION:-
[002] In usual practice, lance assembly is designed with dissimilar
materials combination to withstand higher operating temperature for
reducing the cost of materials. A Nozzle assembly made up of Heat
Resistant Stainless ASTM A297 Grade HH alloy, the nozzle welded with
Stainless steel grade ASME SA 312 TP 321 and the other end of ASME SA
312 TP 321 tube welded with alloy steel. To increase the quality of such
joints, it is proposed to weld using tungsten insert gas welding process.
Further, to enhance the productivity a hot wire welding process is preferred.
[003] Highest level of quality may be obtained through an automation of
the welding process. Here, the major obstruction is posed by the length of
the specimen that is approximately 9 meters which requires more
sophisticated equipment in order to rotate the specimen and weld in 1G
position. Hence, to overcome the aforementioned problem it is usually
recommended to rotate the welding torch instant of job to perform the
welding at 5G position. Automation of 5G position welding has number of
challenges like the combination of overhead welding and vertical up

welding positions and it becomes important to further optimize welding
parameters to achieve defect free quality welding in 5G automatic welding.
PRIOR ART OF THE INVENTION:-
[004] Reference may be made to the following patents:
[005] The US Patent Application no. US20130301309A1 discloses a
procedure for obtaining dissimilar metal welds using buttering technique is
discussed in detail for applications related to welding large components
such as turbine rotor. In the method disclosed by this patent, dilution ratio of
buttering layer to metal is less than 50%. This can be employed for welding
large components such as turbine rotor.
[006] The US Patent Application no. US8308051B2 discloses, welding
method for welding dissimilar metals (i.e., one high melting point material
with one lower melting point material) were discussed using friction stir
welding process. The method involves presence of rotary tool which makes
the interface softer and later joins them to obtain a sound weld joint. Joints
between steel and aluminium were successfully obtained using this
technique.
[007] The US Patent Application no. US200880067214A1 discloses, a
novel method of having a transition for superheater or reheater tubes by
mechanical forming and hot isostatic pressing (HIP) is discussed. This
method eliminates the need for arc welding or other fusion welding
processes. The transition is from ferritic T11 or T22 steel (ASME A213
type) to TP347 or TP 304 type austenitic steels (which resist higher
temperatures).
[008] The WIPO Patent Application no. WO2001083151A1 discloses
joining dissimilar metals such as steels and aluminium using new technique.
In this invention, Aluminium is retrogressively heat treated locally at the
joint prior to electromagnetic forming (EMF) or magnetic pulse welding
(MPW). This technique led to development of stronger welds.
[009] All the aforementioned prior arts are capable of providing
development of dissimilar metal welds which are defect free. However, they
require sophisticated techniques such as HIP or EMF or MPW. None of

them can employ techniques as such with hot wire Tungsten Inert Gas
welding process.
OBJECTS OF THE INVENTION
[0010] It is therefore the object of the invention to overcome the
aforementioned and other drawbacks in prior art.
[001] The principal objective of the present invention is to provide for a
method for joining of dissimilar metals using fusion welding process.
[0011] Another object of the present invention is to provide for a defect
free joint between dissimilar metals using fusion welding process.
[002] Another object of the present invention is to producing defect free
weldments between ASTM A297 Grade HH alloy and SA 312 TP 321 pipes
with ER NiCr-3 filler material using Automatic 5G Gas Tungsten Arc
Welding Process.
[003] These and other objects and advantages of the present subject matter
would be apparent to a person skilled in the art after consideration of the
following detailed description taken into consideration with accompanying
drawings in which preferred embodiments of the present subject matter are
illustrated.
SUMMARY OF THE INVENTION
[004] One or more drawbacks of the conventional technology based on
existing apparatus and processes are overcome, and additional advantages
are provided through a novel method of forming joint between ASTM A297
Grade HH alloy and ASME SA 312 TP 321 steel in Lance Assembly using
Automatic orbital hot wire Gas Tungsten Arc welding process and
optimization of parameters associated with the method for obtaining defect-
free dissimilar metal welds. Additional features and advantages are realized
through the technicalities of the present disclosure. Other embodiments and
aspects of the disclosure are described in detail herein and are considered to
be a part of the claimed disclosure.

[005] In an embodiment of the present subject matter, a method for
forming a joint between dissimilar metals in a lance assembly is disclosed.
The method comprising rotating of welding torch over specimen to be
welded in 5G welding position in an automatic gas tungsten arc welding
(GTAW) system; preparing edge design in the specimen to be joined
wherein, the specimen is presumed to be a 12-hour clock and welding is
initiated at 11’O clock position set as 0 segment; controlling and setting
welding parameters; dividing the specimen into four segmented areas for
parameter programming, wherein 1st area (S1) starts at 11’O clock set as 0
segment and ends at 2’O clock 12 minutes set as 100° from 0 Segment, 2nd
area (S2) starts at 2’O clock set as 100° from 0 segment and ends at 5’O
clock set as 190° from 0 Segment, 3rd area (S3) starts at 5’O clock set as
190° from 0 Segment and ends at 7’O clock set at 240° from 0 Segment and
4th area (S4) starts at 7’O clock set as 240° from 0 Segment and ends at
11’O clock set as 365° from 0 Segment with 5° overlap on S1; performing
root pass welding further comprising steps of back purging with argon gas;
root passing without hot wire current and hot passing with hot wire pulsing
current.
[006] In an aspect of the present subject matter, the pressure during back
purging is between 5-7 LPM for avoiding weld metal suck back.
[007] In an aspect of the present subject matter, the dissimilar joints are
formed between ASTM A297 Grade HH alloy and SA 312 TP 321.
[008] In an aspect of the present subject matter, the filler material includes
ER NiCr-3.
[009] In an aspect of the present subject matter, the dimensions of pipes
are 90-115 mm outer diameter and thickness of 4 - 5.5 mm.
[0010] It is to be understood that the aspects and embodiments of the
disclosure described above may be used in any combination with each other.
Several of the aspects and embodiments may be combined to form a further
embodiment of the disclosure.
[0011] The foregoing summary is illustrative only and is not intended to be
in any way limiting. In addition to the illustrative aspects, embodiments, and
features described above, further aspects, embodiments, and features will

become apparent by reference to the drawings and the following detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] It is to be noted, however, that the appended drawings illustrate only
typical embodiments of the present subject matter, and are therefore not to
be considered for limiting of its scope, for the invention may admit to other
equally effective embodiments. The detailed description is described with
reference to the accompanying figures. In the figures, a reference number
identifies the figure in which the reference number first appears. The same
numbers are used throughout the figures to reference like features and
components. Some embodiments of system or methods or structure in
accordance with embodiments of the present subject matter are now
described, by way of example, and with reference to the accompanying
figures, in which:
[0013] Figure 1 illustrates a flowchart of the steps involved in the present
method in accordance with an embodiment of the present disclosure;
[0014] Figure 2 illustrates a schematic view of various geometric
parameters used for preparation of the edge for welding in accordance with
an exemplary embodiment of the present disclosure;
[0015] The figures depict embodiments of the present subject matter for the
purposes of illustration only. A person skilled in the art will easily recognize
from the following description that alternative embodiments of the
structures and methods illustrated herein may be employed without
departing from the principles of the disclosure described herein.
DETAIL DESCRIPTION OF INVENTION WITH REFERENCE TO
THE DRAWINGS OF THE PREFERRED EMBODIMENTS
[0016] The detailed description of various exemplary embodiments of the
disclosure is described herein with reference to the accompanying drawings.
It should be noted that the embodiments are described herein in such details
as to clearly communicate the disclosure. However, the amount of details

provided herein are not intended to limit the anticipated variations of
embodiments; on the contrary, the intention is to cover all modifications,
equivalents, and alternatives falling within the scope of the present
disclosure as defined by the appended claims.
[0017] It is also to be understood that various arrangements may be devised
that, although not explicitly described or shown herein, embody the
principles of the present disclosure. Moreover, all statements herein reciting
principles, aspects, and embodiments of the present disclosure, as well as
specific examples, are intended to encompass equivalents thereof.
[0018] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of example
embodiments. As used herein, the singular forms “a",” “an” and “the” are
intended to include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms “comprises,”
“comprising,” “includes” and/or “including,” when used herein, specify the
presence of stated features, integers, steps, operations, elements and/or
components, but do not preclude the presence or addition of one or more
other features, integers, steps, operations, elements, components and/or
groups thereof.
[0019] It should also be noted that in some alternative implementations, the
functions/acts noted may occur out of the order noted in the figures. For
example, two figures shown in succession may, in fact, be executed
concurrently or may sometimes be executed in the reverse order, depending
upon the functionality/acts involved.
[0020] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which example
embodiments belong. It will be further understood that terms, e.g., those
defined in commonly used dictionaries, should be interpreted as having a
meaning that is consistent with their meaning in the context of the relevant
art and will not be interpreted in an idealized or overly formal sense unless
expressly so defined herein.
[0021] The present invention discloses a method of forming joints between
dissimilar metals in a lance assembly particularly a method of forming joint

between ASTM A297 Grade HH alloy and ASME SA 312 TP 321 steel in
Lance Assembly using Automatic orbital hot wire Gas Tungsten Arc
welding process and optimization of parameters associated with the method
for obtaining defect-free dissimilar metal welds.
[0022] The method with optimized welding parameters is for obtaining
dissimilar joints between ASTM A297 Grade HH alloy and SA 312 TP 321
pipes of having 90 mm to 115 mm outer diameter and thickness of 4 mm to
5.5 mm with ER NiCr-3 filler material up to 0.8-1 mm diameter using
Automatic 5G Gas Tungsten Arc Welding Process. The method has been
observed to be repeatable in at least ten pairs of pipes, which may be
successfully welded using the method claimed in the present subject matter.
Hence, the method can be relied on for reproducibility. Moreover, the
weldments produced as a result of this welding procedure have qualified
side bend tests without showing up any cracks. The welding process is
hence, applicable not only for pipes but also for tubes, forged/casted
cylindrical sections, etc. where weldments of ASTM A297 Grade HH alloy
and SA 312 TP 321 pipes are envisaged. These weldments can be used for
manufacturing of Lance Assembly for coal fired power plants.
[0023] These and other advantages of the present subject matter would be
described in greater detail with reference to the following figures. It should
be noted that the description merely illustrates the principles of the present
subject matter. It will thus be appreciated that those skilled in the art will be
able to devise various arrangements that, although not explicitly described
herein, embody the principles of the present subject matter and are included
within its scope.
[0024] As illustrated in Figure 1 and 2, the present subject matter discloses
a method for forming joints between two dissimilar metals through fusion
welding process in a lance assembly. The method 100 for forming a joint
between dissimilar metals in a lance assembly comprising rotating 101 of
welding torch over specimen to be welded in 5G welding position in an
automatic gas tungsten arc welding (GTAW) system, preparing 102 edge
design in the specimen to be joined wherein, the specimen 200 is presumed
to be a 12-hour clock and welding is initiated at 11’O clock position set as 0
segment, controlling 103a and setting 103b welding parameters, dividing

104 the specimen 200 into four segmented areas for parameter
programming, wherein 1st area (S1) starts at 11’O clock set as 0 segment
and ends at 2’O clock 12 minutes set as 100o from 0 Segment, 2nd area (S2)
starts at 2’O clock set as 100o from 0 segment and ends at 5’O clock set as
190o from 0 Segment, 3rd area (S3) starts at 5’O clock set as 190o from 0
Segment and ends at 7’O clock set at 240o from 0 Segment and 4th area
(S4) starts at 7’O clock set as 240o from 0 Segment and ends at 11’O clock
set as 365o from 0 Segment with 5o overlap on S1, performing 105 root pass
welding further comprising steps of back purging 105a with argon gas, root
passing 105b without hot wire current and hot passing 105c with hot wire
pulsing current.
[0025] The value of purging pressure during back purging process is
maintained between 5- 7 LPM for avoiding weld metal suck back. Herein,
in an aspect the dissimilar joints are formed between ASTM A297 Grade
HH alloy and SA 312 TP 321, wherein the filler material includes ER NiCr-
3 up to a diameter of 0.8-1mm and the pipes have an outer diameter of 90-
115 m m and thickness of 4-5.5 mm. The specimen 200 of the present
method includes pipes, tubes, forged/casted cylindrical sections in different
embodiments of the present method. Root pass during welding is performed
without hot current (0 Amp) for reducing suck back at inner diameter side of
the specimen and hot pass is performed with pulsed hot current in
accordance with set parameter settings.
APPLICATION
[0012] The method as claimed in the present disclosure has a number of
applications in fossil-fired power plants such as boiler pipes, valves, boiler
tubes, turbine sections, etc. and can be applied on specimens of various
thickness and various geometries such as pipes, tubes, etc. with increasing
the number beads. The method is applicable for direct application at sites
such as power plant erection and commissioning areas and even directly at
shop floor in manufacturing sites etc.

WORKING EXAMPLE
[0013] In the preferred embodiment, the present disclosure relates to a
method for forming a joint between two dissimilar metals i.e. ASTM A297
Grade HH alloy and SA 312 TP 321 with ER NiCr-3 up to a diameter of
1mm being used as filler material during the automatic 5G welding process
i.e. Gas Tungsten Arc Welding process (GTAW). Herein, the pipes have an
outer diameter of 108 mm and thickness of 4.9 mm.
[0014] The method comprises the following steps of rotating 101 of
welding torch over specimen 200 to be welded in 5G welding position in an
automatic gas tungsten arc welding (GTAW) system, preparing 102 edge
design in the specimen to be joined wherein, the specimen 200 is presumed
to be a 12-hour clock and welding is initiated at 11’O clock position set as 0
segment, controlling 103a and setting 103b welding parameters , dividing
104 the specimen 200 into four segmented areas for parameter
programming, wherein 1st area (S1) starts at 11’O clock set as 0 segment
and ends at 2’O clock 12 minutes set as 100o from 0 Segment, 2nd area (S2)
starts at 2’O clock set as 100o from 0 segment and ends at 5’O clock set as
190o from 0 Segment, 3rd area (S3) starts at 5’O clock set as 190o from 0
Segment and ends at 7’O clock set at 240o from 0 Segment and 4th area
(S4) starts at 7’O clock set as 240o from 0 Segment and ends at 11’O clock
set as 365o from 0 Segment with 5o overlap on S1, performing 105 root pass
welding further comprising steps of back purging 105a with argon gas, root
passing 105b without hot wire current and hot passing 105c with hot wire
pulsing current. Back purging is performed using Argon gas to avoid
root side oxidation. The value of purging pressure during back purging
process is maintained below between 5-7 LPM for avoiding weld metal suck
back.
[0015] Table 1 below illustrates the values of Optimized welding
parameters employed during welding using Gas Tungsten Arc Welding
process and Table 2 below illustrates the average Test results of trials with
optimized welding parameters. During the trials ten trial defect free
weldments sample were prepared and 180°bend testing was carried out as
per ASME welding procedure qualifications.

ADVANTAGES
[0016] The present method has a high reliability in both shop and site
environments.
[0017] The present method delivers high speed welding with best quality
for site and shop floor fabrications.
[0018] It will be understood by those within the art that, in general, terms
used herein, and especially in the appended claims (e.g., bodies of the
appended claims) are generally intended as “open” terms (e.g., the term
“including” should be interpreted as “including but not limited to,” the term
“having” should be interpreted as “having at least,” the term “includes”
should be interpreted as “includes but is not limited to,” etc.). It will be
further understood by those within the art that if a specific number of an
introduced claim recitation is intended, such an intent will be explicitly
recited in the claim, and in the absence of such recitation no such intent is
present. For example, as an aid to understanding, the following appended
claims may contain usage of the introductory phrases “at least one” and
“one or more” to introduce claim recitations. However, the use of such
phrases should not be construed to imply that the introduction of a claim
recitation by the indefinite articles “a” or “an” limits any particular claim
containing such introduced claim recitation to inventions containing only
one such recitation, even when the same claim includes the introductory

phrases “one or more” or “at least one” and indefinite articles such as “a” or
“an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least
one” or “one or more”); the same holds true for the use of definite articles
used to introduce claim recitations. In addition, even if a specific number of
an introduced claim recitation is explicitly recited, those skilled in the art
will recognize that such recitation should typically be interpreted to mean at
least the recited number (e.g., the bare recitation of “two recitations,”
without other modifiers, typically means at least two recitations, or two or
more recitations). It will be further understood by those within the art that
virtually any disjunctive word and/or phrase presenting two or more
alternative terms, whether in the description, claims, or drawings, should be
understood to contemplate the possibilities of including one of the terms,
either of the terms, or both terms. For example, the phrase “A or B” will be
understood to include the possibilities of “A” or “B” or “A and B.”
[0026] It will be further appreciated that functions or structures of a
plurality of components or steps may be combined into a single component
or step, or the functions or structures of one-step or component may be split
among plural steps or components. The present invention contemplates all
of these combinations. Unless stated otherwise, dimensions and geometries
of the various structures depicted herein are not intended to be restrictive of
the invention, and other dimensions or geometries are possible. In addition,
while a feature of the present invention may have been described in the
context of only one of the illustrated embodiments, such feature may be
combined with one or more other features of other embodiments, for any
given application. It will also be appreciated from the above that the
fabrication of the unique structures herein and the operation thereof also
constitute methods in accordance with the present invention. The present
invention also encompasses intermediate and end products resulting from
the practice of the methods herein. The use of “comprising” or “including”
also contemplates embodiments that “consist essentially of” or “consist of”
the recited feature.
[0027] Although embodiments for the present subject matter have been
described in language specific to structural features, it is to be understood
that the present subject matter is not necessarily limited to the specific

features described. Rather, the specific features and methods are disclosed
as embodiments for the present subject matter. Numerous modifications and
adaptations of the system/component of the present invention will be
apparent to those skilled in the art, and thus it is intended by the appended
claims to cover all such modifications and adaptations, which fall within the
scope of the present subject matter.

We Claim:
1. A method (100) for forming a joint between dissimilar
metals in a lance assembly, the method comprising:
rotating (101) welding torch over specimen (200) to
be welded in 5G welding position in an automatic gas
tungsten arc welding (GTAW) system;
preparing (102) edge design in the specimen to be
joined;
controlling (103a) of welding parameters;
setting (103b) welding parameters;
dividing (104) the specimen (200) into four
segmented areas for setting of welding parameters;
back purging (105a) with argon gas;
root passing (105b) without hot wire current;
and
hot passing (105c) with hot wire pulsing
current.
2. The method as claimed in claim 1 comprising preparing
(102) edge design in the specimen to be joined, wherein the
specimen (200) is presumed to be a 12-hour clock and
welding is initiated at 11’O clock position set as 0 segment.;
controlling (103a) and setting (103b) welding parameters
comprising:
shielding gas flow rate between 11 - 12 LPM,
back Purging gas flow rate 5 - 7 LPM,
inter-pass temperature <150oC,
hot Current – Peak value 0 to 25A,
hot Current – Back ground 0 to 30A,
welding Current – Peak 110 to 130A,
pulse time high between 70 to 80 ms,
welding Current –Back ground between 60 to 75A,

pulse time Low between 70 to 80 ms,
welding speed between 35 to 50 mm/min based on segment,
wire feed between 600 to 1000 mm/min
dividing (104) the specimen (200) into four
segmented areas for setting the welding parameters,
wherein 1st area (S1) starts at 11’O clock set
as 0 segment and ends at 2’O clock 12 minutes set as 100°
from 0 Segment,
2nd area (S2) starts at 2’O clock set as 100°
from 0 segment and ends at 5’O clock set as 190° from 0
Segment,
3rd area (S3) starts at 5’O clock set as 190°
from 0 Segment and ends at 7’O clock set at 240° from 0
Segment and 4th area (S4) starts at 7’O clock set as 240°
from 0 Segment and ends at 11’O clock set as 365° from 0
Segment with 5° overlap on S1;
performing (105) root pass welding comprising steps
of
back purging (105a) with argon gas;
root passing (105b) without hot wire current; and
hot passing (105c) with hot wire pulsing current.
3. The method (100) for forming a joint between dissimilar
metals in a lance assembly as claimed in claim 2, wherein
dissimilar joints are formed between ASTM A297 Grade HH
alloy and SA 312 TP 321.
4. The method (100) for forming a joint between dissimilar
metals in a lance assembly as claimed in claim 2, wherein the
filler material includes ER NiCr-3.
5. The method (100) for forming a joint between dissimilar
metals in a lance assembly as claimed in claim 1, wherein the
specimen (200) includes pipes, tubes, forged/casted
cylindrical sections.

6. The method (100) for forming a joint between dissimilar
metals in a lance assembly as claimed in claim 2, wherein the
dimensions of pipes are 90 mm to 115 mm outer diameter
and thickness of 4 mm to 5.5 mm.