The document discusses several welding techniques including explosive welding, ultrasonic welding, electron beam welding, laser beam welding, electrofusion, and plasma arc welding. Explosive welding uses detonation to join metals by forcing them together at high speed. Ultrasonic welding uses high frequency vibrations to create solid-state welds without other joining methods. Electron beam and laser beam welding use focused beams of electrons or laser light to melt materials together. Electrofusion uses electric heating elements in plastic pipe fittings to melt and fuse pipes. Plasma arc welding uses an ionized gas to generate an arc between an electrode and workpiece to produce welding heat.

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3. Friction heat caused by the motion of
one surface against another enables
plastic deformation and atomic
diffusion at the interface.
Used by the automotive industry for
decades in the manufacture of a range
of components.
The weld is formed across the entire
cross-sectional area of the interface in
a single shot process.
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4. • Dissimilar metals can be joined
• No fusion zone
• Can be used under water
• Very high reproducibility - an essential requirement for a mass
production industry
• Excellent weld quality, with none of the porosity that can arise in
fusion welding
• environmentally friendly, because no fumes or spatter are generated,
and there is no arc glare or reflected laser beams with which to contend
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5. •Welding produced by
explosively forcing one plate (or
component) against the one to
which it is to be joined at an
approximate angle of incidence,
known as the impact angle.
•Methods:
1.Inclined gap method
2. Parallel gap method
In parallel gap method,
detonation velocity should be
equal to or less than the speed of
sound in the metal being welded.
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6. Explosive Detonation
velocity, m/s
RDX (Cyclotrimethylene trinitramine, C3
H6
N6
O6
8100
PETN (Pentaerythritol tetranitrate, C5
H8
N12
O4
) 8190
TNT (Trinitrotoluene, C7
H5
N3
O6
) 6600
Tetryl (Trinitrophenylmethylinitramine, C7
H5
O8
N5
) 7800
Lead azide (N6
Pb) 5010
Detasheet 7020
Ammonium nitrate (NH4
NO3
) 2655
Explosives
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7. • Cladding plates
• Joining of pipes and tubes
• Major areas of the use of this method are heat exchanger
tube sheets and pressure vessels
• Tube Plugging
• Remote joining in hazardous environments
• Joining of dissimilar metals - Aluminium to steel,
Titanium alloys to Cr – Ni steel, Cu to stainless steel,
Tungsten to Steel, etc.
• Attaching cooling fins
• Other applications are in chemical process vessels, ship
building industry, cryogenic industry, etc.
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8. 1. Can bond many dissimilar, normally unweldable metals.
2. Minimum fixturing/jigs.
3. Simplicity of the process.
4. Extremely large surfaces can be bonded.
5. Wide range of thicknesses can be explosively clad
together.
6. No effect on parent properties.
7. Small quantity of explosive used.
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9. 1. The metals must have high enough impact resistance,
and ductility.
2. Noise and blast can require operator protection,
vacuum chambers, buried in sand/water.
3. The use of explosives in industrial areas will be
restricted by the noise and ground vibrations caused
by the explosion.
4. The geometries welded must be simple – flat,
cylindrical, conical.
5. Area should be cleaned and sound grounded for
explosion.
6. Licences are necessary to hold and use explosives.
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10. Ultrasonic welding is an industrial technique whereby high-
frequency ultrasonic vibrations are locally applied to
workpieces under pressure to create a solid-state weld. It is
commonly used for plastics, and especially for joining
dissimilar materials. In ultrasonic welding, there are no
connective bolts, nails, soldering materials, or adhesives
necessary to bind the materials together.
•Empirical relation for a ultrasonic welding:
E=k(HT)3/2
Where, E = Electrical energy
k = Constant for given welding system
H = Vickers hardness
T = Thickness of the work piece
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11. Ultrasonic welding control
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12. Advantages:
•Energy efficiency
•High productivity with low costs and ease of automated
assembly line production
Disadvantages:
The maximum component length that can be welded by a single
horn is approximately 250 mm. This is due to limitations in the
power output capability of a single transducer, the inability of the
horns to transmit very high power, and amplitude control
difficulties.
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13. Electron beam welding (EBW) is
a fusion welding process in
which a beam of high-velocity
electrons is applied to two
materials to be joined. The
workpieces melt and flow
together as the kinetic energy of
the electrons is transformed into
heat upon impact. EBW is often
performed under vacuum
conditions to prevent dissipation
of the electron beam.
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14. • Advantage: Very deep penetration can be achieved. For
example, joining of 200 mm aluminium plates requires 600
passes when conventional gas metal arc process requires
over 100 passes even using specially developed narrow-
grove process. By using the EB process, the same plate can
be welded in only 2 passes.
• Disadvantage: Dealing with the vacuum needed for the
process
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15. Laser beam welding (LBW) is a welding
technique used to join multiple pieces of metal
through the use of a laser. The beam provides a
concentrated heat source, allowing for narrow,
deep welds and high welding rates. The
process is frequently used in high volume
applications, such as in the automotive
industry.
LBW is a versatile process, capable of welding
carbon steels, HSLA steels, stainless steel,
aluminum, and titanium. Due to high cooling
rates, cracking is a concern when welding
high-carbon steels. The weld quality is high,
similar to that of electron beam welding.
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16. • The laser beam can be transmitted through air rather than
requiring a vacuum
• The process is easily automated with robotic machinery
• x-rays are not generated
• LBW results in higher quality welds
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17. • The LaserStar® Workstation is an Nd:YAG laser. The
host material is a cylindrical crystal of yttrium-
aluminum -garnet (Y3Al5O12), YAG doped by weight
with neodymium (Nd3+) ions. Laser emission takes
place at 1.064 μm (infrared).
LASERPOWER
• Joules: The “hot light” energy output is measured in
joules. This industry term by definition is “ the
capacity for doing work”. Hot light energy output is
determined by the amount of voltage and pulse-
length selected by the operator
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19. • Electrofusion is a method of
joining MDPE, HDPE and other plastic pipes
using special fittings that have built-in
electric heating elements which are used
to weld the joint together.
• The pipes to be joined are cleaned, inserted
into the elusion ectroffitting (with a
temporary clamp if required) and a voltage
(typically 40V) is applied for a fixed time
depending on the fitting in use. The built in
heater coils then melt the inside of the fitting
and the outside of the pipe wall, which weld
together producing a very strong
homogeneous joint. The assembly is then left
to cool for a specified time.
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20. Plasma arc welding is an arc welding process wherein coalescence is
produced by the heat obtained from a constricted arc setup between a
tungsten/alloy tungsten electrode and the water-cooled (constricting)
nozzle (non-transferred arc) or between a tungsten/alloy tungsten
electrode and the job (transferred arc). The process employs two inert
gases, one forms the arc plasma and the second shields the arc plasma.
Filler metal may or may not be added.
At least two separate (and possibly three) flows of gas are
used in PAW:
Plasma gas – flows through the orifice and becomes ionized.
Shielding gas – flows through the outer nozzle and shields the molten
weld from the atmosphere
Back-purge and trailing gas – required for certain materials and
applications.
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Plasma arc welding is an advancement over the GTAW process. PAW
can be used to join all metals that are weldable with GTAW. Difficult-
to-weld in metals by PAW include bronze, cast iron, lead and
magnesium. Several basic PAW process variations are possible by
varying the current, plasma gas flow rate, and the orifice diameter,
including:
Micro-plasma (< 15 Amperes)
Melt-in mode (15–100 Amperes)
Keyhole mode (>100 Amperes)
Plasma arc welding has a greater energy concentration as compared to
GTAW.
PAW requires relatively expensive and complex equipment as compared
to GTAW.
Welding procedures tend to be more complex and less tolerant to
variations in fit-up, etc.
Operator skill required is slightly greater than for GTAW.

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