Filed Of Invention:
This invention is related to welding fabrication and welding engineering. Also
relates to joining of materials using arc and beam energy with or without filler
addition and in particular relates to joining of materials by laser, electron beam
and gas tungsten arc welding processes.
Prior Art:
Welding of similar or dissimilar materials are performed with or without filer
addition, depending on type of materials to be welded, available resources and
the application requirements. Most of the welding is carried out using filler
addition. However, in case of beam process like laser and electron beam welding
or in case of arc welding like gas metal arc welding , no filler is used unless other
wise necessary. With the above welding process, the filler addition is
necessitated by the need to fill the weld gap in order to create a complete weld.
However, in beam process addition of filler material is a highly difficult and costly
affair in particular confronted with a lot of operational difficulties. In laser
welding, sufficient work has been carried out regarding the modalities of filler
addition for the past two decades. The possible technique of filler addition in

case of laser welding is addition of cold wire, to the laser beam in the focal area,
positioning of suitable metallic inserts in the location of proposed weld, addition
of filler in hybridization with an arc melting process like plasma, gas metal arc
and metal inert gas welding. The filler addition can also be facilitated by
supplying powdered materials to the weld location or pre-placing the same prior
to welding. Finally, oscillation can also be used to melt the material available in
the proximity to fill the weld gap. In this regard, some of the important and
relevant prior art are as follows:
United States Patent 4546230 describes welding in a square groove with laser
beam assisted by additional filler, cold wire addition , to fill the groove volume
under the title "Welding process using laser with filler metal". This invention uses
a welding process with a laser beam for joining metals such as steel plates along
a see-through groove such as a square groove formed by laser welding between
opposed edge of the two metals. The filler wire is supplied to the see-through
groove to increase the permissible gap of the see-through groove. A spot of laser
beam with a power density of 5xl05 w/cm22 or above is formed in the see-
through groove on the same level as the surface of the metals. The filler wire is
inserted into a point coincident with the spot of the laser beam, or the spot of
the laser beam focal point. As the filler wire is melted by the laser beam, a
globule or droplet is formed. It proceeds to the weld groove and deposited on

the opposed edge faces defining the groove to form the weld portion and thus
enabling a complete weld.
A method of laser welding with inserts is described in United States Patent
4527040. It defines a method of welding two steel members to produce a weld
joint having improved impact toughness. The surface to be welded are first
machined, roto-blasted and cleaned with acetone. Then, an insert of Inconel 600
is provided and cleaned with acetone. Next, the Inconel 600 insert is introduced
between the laser welding beam is applied to the Inconel 600 insert to weld
together the assembly of steel members and insert.
United States Patent 7241971 describes "Laser/arc hybrid welding process for
ferritic steels with filler wire" for joining of materials using a laser in conjunction
with an arc process. In this, a method and an apparatus for a hybrid laser beam
and electric arc welding process is detailed. A laser beam, an electric arc, a
shielding gas and a consumable welding wire are used to create a weld on a
steel work piece by melting the welding wire with the energy available arc and
laser beam. The welding wire, either solid welding or cored welding wire is used
to create a weld on a steel work piece by melting the welding wire with the
energy available through arc and laser beam. The welding wire is either solid
welding wire or cored welding wire, and may contain elements, in varying
percentages of titanium, manganese, iron, nickel, boron, molybdenum, carbon or
chromium, depending on application requirement.

Another way to add filler in hybridization with plasma welding is dealt in United
States Patent 5866870, title "Enhanced laser beam welding with plasma
welding". In this invention, an arc augmented laser welding apparatus has a
welding head which comprises a housing , a focusing system in the housing for
focusing a laser beam through a laser opening in the housing onto a work piece
and a plasma torch nozzle, through which a plasma arc is established between
an electrode and the workpiece. A first power source applies a high voltage
across the electrode and nozzle to strike a pilot arc which is then sustained by
power from a second source. A third power source applies a high amperage
signal to strike the main plasma arc between the electrode and the workpiece.
The nozzle has a tip which is adapted to constrict the plasma arc and restrict its
impingement on the workpiece. The nozzle and the focusing system are
arranged to cause the focused laser beam and the constricted plasma arc to
impinge on the workpiece at predetermined relative positions which may coincide
or may be slightly spaced apart. The power sources and the laser beam are
controlled by a microprocessor in accordance with a predetermined programme
in dependence on the type and thickness of material to be welded.
For carrying out laser plasma hybrid welding, a United States Patent 5700989,
titled" Combined laser and plasma arc welding torch" describes the construction
of a plasma torch for this purpose. Under this invention, a welding torch

. 6
combines features of both laser and plasma-arc welding torches. A laser beam is
directed by an objective lens so that it is co-linear with the central axis of a
plasma-arc torch. The laser beam passes through a planar or conical cathode
electrode placed at the bottom orifice of the torch. A coaxial hole having a
diameter less than of the laser beam is drilled into the cathode to allow the laser
beam to pass through the cathode. A constricting nozzle is placed under the
cathode, with the laser beam passing through the axis of the nozzle. As with a
standard plasma-arc torch, a gas is forced through a chamber having the
cathode and nozzle at its bottom end. As the cathode is heated by the laser
radiation, the gas is ionized and a plasma-arc is formed. As the laser beam
passes through the nozzle, it comes to a focus and interacts with the plasma-arc
formed between the cathode and a workpiece. The resulting interactions
between the plasma-arc and laser beam form a plasma-laser discharge which
acts to additionally constrict the laser beam and plasma-arc and increase the
energy density of the welding spot formed on the workpiece.
Addition of power as filler is described in a United States Paten 4835357, titled
"Sheet metal laser welding with powdered filler material". It describes a method
for the welding of contiguous sheet metal elements comprising the steps of
directing a defocused laser beam at the joint formed there between so as to
plasticize the areas there of proximate thereto with a substantial portion of

the energy thereof, and simultaneously feeding a powdered filler material into
and about the joint so as to fully encompass the area of laser beam impingement
thereupon, with a portion of the filler material being heated to a plastic state by
the remaining portion of the beam's energy. The powdered filler material thus
partially shields the sheet from the direct impingement of the beam's full energy
thereupon, whereby the likelihood of sheet burn-through and /or excessive heat
distortion is greatly reduced. The plasticized filler material thereafter attaches to
the plasticized area proximate with the joint and builds thereupon a
homogeneous weld seam characterized by excellent weld fusion and a high joint
efficiency.
Laser-hybrid welding with beam oscillation is described in a United States Patent
7154065. This deals with a method of welding metal components together
including moving a laser beam in a first direction along an interface between a
pair of metal components such that in the vicinity of the focused beam, metal
from each component is vaporized to produce a keyhole in a pool of molten
metal. The laser beam is oscillated in a direction different from (e.g., transverse
to) the first direction such that the keyhole oscillates through the pool of molten
metal and molten metal fills into the keyhole as the position of the keyhole
changes.

However, all the above variants require to add extra filler materials in one form
or the other to compensate the volume of weld gap or intentionally created weld
groove for obtaining a complete full penetration joint.
This invention totally differs from the above concept for meeting the filler
addition requirement and proposes to derive the additional material volume
required for filling the gap or groove by introducing a novel joint design on the
materials involved. The proposal is explained with relation to an application
example of tube to fin welding application practiced in power, transportation and
process industries.
Objectives Of The Invention:-
The main object of the invention is to develop suitable joint design which will be
acting as self melting filler for achieving an acceptable joint during autogenous
arc and beam welding processes.
Another object of the proposal is to fill the weld gap or groove without addition
of extra filler in the form of wire, insert and or powder.
Yet another of object of the invention is to bridge the weld gap or groove
between two faying edges without beam or arc oscillation, with or without filler.

Further object of the proposal is to eliminate the under-fill in the weld zone by
completely filling the weld gap or groove without any addition of any type of
extra filler in any form.
Still further object of the invention is to develop straight butt and chamber type
self melting edge preparation on any one of the weld assembly element itself.
Description Of The Invention:
In this invention, a novel method of designing a self melting edge preparation is
proposed to simulate the addition of filler materials for facilitating joint filling
during welding of components by a autogenous welding process, more
particularly, laser beam welding process.
In case of welding autogenous laser welding, the joint gap or groove may not be
fully filled leaving an undesired under-fill in the weld zone resulting in a
incomplete weld. This is true for butt and fillet welding of plates, butt welding of
different profiled components like, tube to flat welding often used in engineering
applications. Tube to fin welding example is quite complicated as compared to
simple butt and fillet welding of plates. Hence, the proposed invention is
explained with tube to fin welding application. Filler addition is done in the
conventional process of joint fit-up for tube to fin welding. However, the joint
shall not be fully filled up, ,i.e. weld, in case filler material is not used with this

type of joint design. This under-fill may result in weld defects like undercut and
subsequent cracking during operation or working.
To avoid such weld failure during autogenous laser welding of tube to fin
welding, it is proposed to modify the edges so as to have self melting portion
incorporated on to a participating member of the component itself.
Description Of The Accompanying Drawing:-
Fig.l illustrates the conventional joint design for welding of tube to fin by arc or
beam process. The welding is to performed between the tube and fin edge.
Fig.2 illustrates the straight butt design of self melting configuration. In this
proposal, the extra material required for filling the weld gap is obtained from the
fin itself.
Fig.3 illustrates chamfer design self melting fin. The self melting chamfer width
and thickness provide the required volume for filling the weld gap.
Detailed Description Of The Invention:
The invention will now be described with help of the accompanying drawings
which depict exemplary embodiments of the invention. However, there can be
several other embodiments, all of which are deemed covered by the description.
The invention is explained with tube to fin welding and fin is selected to have the
self melting provision. In case of butt and fillet welding of plates, a simple flare is

proposed on any one side of the plate to derive the additional material to fill the
anticipated weld gap or groove.
The first alternative is to make a straight butt provision at the ends of flat/fin,
where the flat is coming in contact with the tube or the proposed weld is to be
located as illustrated in Fig.2. The width and the thickness of self melting
provision depends on the (OD) of tube to be welded and the weld fit up between
tube and flat. Work has been carried out with 40 to 60mm OD tubes of various
wall thicknes ranging from 4 to 8mm with carbon steel. Cr alloyed steel and high
strength low alloy steels. The fin shall be of carbon steel or alloyed steel suitable
for high temperature application, incase of power plant components. Fin of 20 to
30mm width and 3 to 6mm thickness was employed for this work. The fit-up was
ensured with adequate fixturing to with stand deformation forces during
solidification of weld. It is observed that the width of the self melting portion
carried between 0.5 to 2mm and the thickness of the self melting portion varied
between 0.5 to 2mm depending on the laser beam power employed. The laser
beam power was varied from 800wats to 1800watts with scanning speed/
welding speed of 400to 1000mm/min. The beam diameter was varied from 0.4
to 1.0mm. The above operating range resulted in a complete fusion of the self
melting portion and filling up of the gap between the tube surface and the fin
edge completely. The health of the weld joint was verified by analyzing sufficient
number of randomly selected weld cross sections with the

help of optical microscope with magnification ranging from 50 to 400X. The
results showed that the weld is fully homogenous without any incomplete
fusion/penetration with side walls of fine and tube.
The second alternative of this invention is to introduce a chamfer in the fin as
shown in Fig. 3. This can be accomplished by machining and subsequent surface
cleaning with cleaning agents like acetone. Variation in chamber angle results in
various self melting width and thickness of the fin as indicated in the drawing.
The width of the chamfer was varied from 1 to 2mm and the thickness also from
1 to 2mm. The chamfer angle varied from 30 to 60deg to enable various
geometry of self melting feature. The results, as in the case of working with
straight butt self melting provision, resulted in acceptable, healthy weld.
The invention resulted in utilizing the material available in one of the assembly
elements rather than introducing an extra filler in the form of wire, strip, insert,
powder or similar geometry or in combination with either one or all.
Some Relevant Features Of The Invention:-
• A self melting joint design on any one of the weld assembly element
itself, instead of an extra filler addition to fill the weld gap or groove.
• A straight butt type self melting joint design on flat/ plate/fin while
carrying out butt, fillet or tube to fin welding using autogenous arc or
beam welding processes.

• A chamfer type self melting joint design on flat/plate/fin while carrying
out butt fillet or tube to fin welding using autogenous arc or beam
welding processes.
• Self melting joint designs for complete filling of weld gap or groove
without the addition of external or extra filler materials in any form.
• Elimination of under-fill in weld gap or groove by adapting self melting
joint designs.
• Elimination of weld cracking due to undercut and under-fill by adapting
the technique with self melting joint design mentioned in is done
effectively.
• Non availability of matching filler shall be substituted or overcome by
adapting the technique with self melting joint.
• The technique avoids incompatibility of weld with base material and thus
ensures consistent weld quality.
• The technique with self melting joint designs shall be applied for welding
fabrication of high strength joint and high pressure joints during arc and
beam welding.

We Claim:-
1. Method of autogenous laser welding without addition of filler providing self
melting joint comprising steps:-
-making a self melting joint for welding as for example with tube to fin/flat,
where the tube comes in contact for welding;
- checking of the weld fit-up between tube and flat/fin;
- ensuring the fit-up with adequate fixing to withstand deformation forces during
solidification of weld;
- setting of laser beam power and beam diameter for complete fusion of the self
melting portion and filling up of gap between the tube surface and the fin edge
completely;
- verification of health of welding by analyzing randomly selected weld cross-
sections with the help of optical microscope with magnification ranging from 50
to 400X;
characterized in that the self melting joint on any of the weld assembly element
itself, obviates the necessity of any extra filler addition to fill the weld gap or
groove completely and incompatibility of weld with base material for a consistent
weld quality.

2. Method of welding as claimed in claims 1, wherein the self melting joints arc
of two types (a) a straight butt joint at the end of the flat/fin and (b) a chamfer
in the fin.
3. Method of welding as claimed in claims 1 and 2, wherein the straight butt joint
of self melting type is built up on flat/plate/fin while carrying butt, fillet or tube
to fin welding applying autogenous arc or beam welding process.
4. Method of welding as claimed in claims 1 and 2, wherein the chamfer joint of
self melting type on flat/plate/fin while carrying out butt, fillet or tube to fin
welding applying autogenous arc or beam welding process.
5. Method of welding as claimed in claims 1, wherein the self melting joints
having measurement for its width for example 20-30mm and thickness for
example 3-6mm are ascertained depending on the OD (outside diameter) of tube
for example the range of 40 to 60mm to be welded and the weld fit-up between
tube and flat for example wall thickness in the range of 4 to 8mm with carbon
steel, Cr alloyed steel and high strength low alloy steels.

6. Method of welding as claimed in claim 1, wherein the fin/flat employed having
width in the range of 20-30mm and thickness ranging from 3-6mm, is of carbon
steel or alloyed steel suitable for high temperature application.
7. Method of welding as claimed in claims 1 and 2, wherein said chamfer in the
fin is accomplished by machining and subsequent surface cleaning with cleaning
agents like acetone.
8. Method of welding as claimed in claims 1 and 2, wherein said chamfer having
chamfer angle, which varies for example in the range of 30-60 degree, to get
various geometry self melting features like width, as for example in the range 1-
2mm and thickness, say in the range of also l-2mm.

9. Method of welding as claimed in claims 1 and 2, wherein said self melting
joint, by adapting the technique of which, elimination of defects of welding such
as under-fill in weld gap or groove, weld cracking due to under-cut and under fill,
is done effectively.
10. Method of welding as claimed in claim 1 wherein setting of laser beam made
in the range of 800watts to 1800watts with scanning speed/welding speed of
400 to lOOOmm/min.

11. Method of welding as claimed in claim 1 and 9, wherein said melting joint
technique is applied for welding fabrication of high strength joints and high
pressure joints during arc and beam welding.

Method of autogenous laser welding without addition of filler providing self
melting joint of a straight butt at the end of the flat/fin or a chamfer in the fin
comprising steps:-
-making a self melting joint for welding as for example with tube to fin/flat,
where the tube comes in contact for welding;
- checking of the weld fit-up between tube and flat/fin;
- ensuring the fit-up with adequate fixing to withstand deformation forces during
solidification of weld;
- setting of laser beam power and beam diameter for complete fusion of the self
melting portion and filling up of gap between the tube surface and the fin edge
completely;
- verification of health of welding by analyzing randomly selected weld cross
sections with the help of optical microscope with magnification ranging from 50
to 400X;
characterized in that the self melting joint on any of the weld assembly element
itself, obviates the necessity of any extra filler addition to fill the weld gap or
groove completely and incompatibility of weld with base material for a consistent
weld quality.