This document discusses various solid-state welding processes including cold welding, diffusion bonding, explosive welding, hot pressure welding, roll welding, ultrasonic welding, and friction stir welding. Each process is characterized by its methods, applications, advantages, and disadvantages, highlighting their use in industries such as aerospace, automotive, and nuclear. The document emphasizes the differing techniques and applications associated with each welding type while outlining the conditions necessary for successful welding.

1. PR 8592 WELDING TECHNOLOGY -UNIT -3
P.VENGALA KUMAR ME.,MBA
TF/MECHANICAL ENGG.,
UNIVERSITY VOC COLLEGE OF ENGINEERING
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2. UNIT III SOLID STATE WELDING
PROCESSES
• Cold welding,
• Diffusion bonding,
• Explosive welding,
• Hot pressure welding,
• Roll welding
• Ultrasonic welding,
• Friction welding,
• Forge welding,
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3. Cold welding or contact welding
• Cold welding or contact welding is a solid-
state welding process in which joining takes
place without fusion/heating at the interface of
the two parts to be welded.
• Unlike in the fusion-welding processes,
no liquid or molten phase is present in the
joint.
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• Cold welding was first recognized as a general
materials phenomenon in the 1940s. It was then
discovered that two clean, flat surfaces of
similar metal would strongly adhere if brought
into contact under vacuum. Newly discovered
micro and nano-scale cold welding has already
shown great potential in the latest nano
fabrication processes.

5. DIFFUSION WELDING
-INTRODUCTION
• It is a solid state welding technique used in metal
working, capable of joining similar and dissimilar
metals.
• It operates on the principle of solid state diffusion,
wherein the atoms of two solid, metallic surfaces
intersperse themselves overtime.
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7. WORKING PRINCIPLE
• Diffusion means movement of molecules or atoms
from high concentration region to low concentration
region.
• This is fundamental principle of diffusion welding.
• In this welding process both the welding plates are
placed one over other in high pressure and
temperature for a long period of time.
• This high pressure force starts diffusion between
interface surfaces.
• This diffusion can be accelerated by the application
of high temperature.
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8. • The temperature range is about 50-60% of melting
temperature.
• This whole process takes place in vacuum or in inert
environment which protects the welding plates form
oxidation.
• Moderate pressure of about 10MPa is applied to
carefully cleaned surfaces of the workpiece at an
elevated temperature below the melting point.
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9. STAGES IN DIFFUSION WELDING
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10. ADVANTAGES
• Plastic deformation at surface is minimal.
• Dissimilar materials may be welded.
• There is no limitation in the thickness of the
workpieces.
• Welds of high quality obtained.
DISADVANTAGES
• It is a time consuming process due to low
productivity.
• Time required for diffusion can range from seconds to
hours.
• It requires relatively high initial investment in
equipment.
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11. APPLICATION
• It is used in joining of high strength and refractory
metals based on titanium in aerospace and nuclear
industries.
• Diffusion welding is most commonly used to join
sheet metal structures in nuclear and electronics
industries.
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12. EXPLOSIVE WELDING-INTRODUCTION
Explosive welding (EXW) is a solid state
welding process that uses a controlled
application of large pressure generated by the
detonation of applied explosives.
 In explosive welding parts are metallurgically
bonded as a result of oblique impact pressure
exerted on them by a controlled detonation of
an explosive change.
The following teams are frequently uses in the
explosive welding.
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14. Specification details
• Cladding metal or Cladder -Thinner plate,
direct contact with the explosive, Shielded by
flyer plate from the explosive
• Flyer plate - sacrificial plate placed between
cladder and explosive, it protect the cladder
metal.
• Inner layer - thin metal layer which sometime
placed between cladder and base plate to
enhance joining.
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15. Specification details
• Base plate or backer – This plate that the cladder
is being joining.
• Anvil – surface on which backer rests during the
joining operation.
• Standoff - The distance between cladder and base
plate prior to the joining operation.
• Bond window – The range of process variable
such as velocity, dynamic bend and standoff
distance that result in a successful weld.
• Bonding operation – The detonation of the
explosive which result in the weld.
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16. PREPARATION:
• The first step of the cladding operation is the
preparation of the two surfaces that are to be
bonded together.
• These surfaces are ground or polished to
achieve a uniform surface finish with a
roughness, dependent upon the metals
combination and thicknesses.
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17. BONDING OPERATION:
• The explosive composition and type is selected
to yield a specific energy release and a specific
detonation rate
• The speed at which the detonation front travels
across the explosive layer.
• The detonation rate must be subsonic to the
acoustic velocities of the metals.
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18. BONDING OPERATION
• The explosive, which is generally granular, is
uniformly distributed on the cladding plate
surface filling the containment frame.
• It is ignited at a predetermined point on the
plate surface using a high velocity explosive
booster.
• The detonation travels away from the initiation
point and across the plate surface at the
specified detonation rate.
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19. BONDING OPERATION
• The gas expansion of the explosive detonation
accelerates the cladding plate across the
standoff gap resulting in an angular collision at
the specified collision velocity.
• These pressures travel away from the collision
point at the acoustic velocity of the metals.
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20. • Since the collision is moving forward at a
subsonic rate, pressures are created at the
immediately approaching adjacent surfaces,
which are sufficient to spall a thin layer of metal
from each surface and eject it away in a jet.
• The surface contaminants, oxides and impurities
are stripped away in the jet.
• Although there is much heat generated in the
explosive detonation, there is no time for heat
transfer to the metals.
• The result is an ideal metal-metal bond without
melting or diffusion.
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21. Cladding and Base metals
• Copper to steel
• Nickel to steel
• Aluminum to steel
• Tungsten to steel
• Copper to aluminum
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22. TYPES OF EXPLOSIVE WAVES
Deflagration
Detonation
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23. Deflagration
• Deflagrations travel at subsonic velocity
depending on the rates of chemical reaction,
thermal diffusion and mass diffusion.
• Typical deflagrations are gas-air mixture in a
gas stove, fuel-air mixture in an internal
combustion engine and gunpowder in a firearm
or pyrotechnic device.
.
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24. Detonation
• A detonation travel at supersonic velocity
exceeding the sonic velocity of the understand
explosive.
• The detonation wave consists of shock front
compresses heats the explosive following by
region of rapid chemical reaction
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25. Advantages
• It ensures high quality bonding such as high strength,
no distortions, no porosity.
• No change of the metal microstructure.
• There is no diffusion.
• Only, minor melting occur.
• Large surfaces may be welding.
• It is less costly.
• Surface preparation is not required .
• Explosive welding is much suited to cladding
application.
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26. Limitations
• Brittle materials cannot be welded.
Thickness of flyer plate may be limited.
Safety and security aspects of storage and
using explosive are difficult.
• Metals must have high enough impact
resistance and ductility.
• The geometrics welded must be simple in the
shape of flat, cylinder and conical shapes.
Noise and blast.
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27. Application
• This process is applied to welding of tubes and
tube plate in heat exchangers, feed water
heaters and boiler tubes to clad tube plate.
• It is used manufacturing clad tubes and pipes,
pressure vessels, aerospace structure, heat
exchanger, bi metal sliding, ship structure and
weld transition.
• It is used fixing cooling fins.
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28. HOT PRESSURE WELDING PROCESS
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29. INTRODUCTION
• Hot pressure welding is a solid state welding process
which produces coalescence of materials with heat
and the application of pressure sufficient to produce
macro deformation of the base metal.
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31. WORKING PRINCIPLE
• Hot pressure welding is similar to both friction
welding and flash welding although the source of
heating is different. The surface should be machined
square and cleaned for obtaining the best result.
• Some beveling is used to control the amount of upset.
The process can be performed by a manual operation.
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32. • The materials to be welded must exhibit hot
ductility or forgeability. Castiron cannot be hot
pressure welded.
• The materials commonly joined by hot
pressure welding are carbon steels, low alloy
steels and cretain nonferrous metals. some
dissimilar materials combination are weldable
by hot pressure welding.
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34. ADVANTAGES
• Welding process is simple.
• It needs simple joint preparation.
• Low cost equipment.
• It ensures quick weld production.
• There is no filler metal.
DISADVANTAGES
• Not all metals are weldable.
• It is not easily automated.
• Length of cycle is dependent on time for heating.
• Only simple sections are readily butt weldable.
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35. APPLICATIONS
• It is used in aerospace industry.
• It is used in plastic welding.
• It is used for producing medical devices.
• It is used in automotive industries.
• It is used in ship building.
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36. ROLL WELDING
.• Roll welding is a solid state welding process in which
pressure sufficient to cause coalescence is applied by
mean of rolls, either with or without external heat.
• If the welding is done without applying heat, is called
cold roll welding and if the heat is used for welding, it
is called hot roll welding.
• This process is similar to forge welding except the
pressure applied by means of rolls rather then by means
of hammer blows.
• Coalescence occurs at the interface between two parts
by means of diffusion at the faying surface
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38. • Parts to be welded should be ductile and free
of work hardening.
Before the welding is carried out, the surface
to be joined should be cleaned.
• If the part to be welded are small, the pressure
applied by rolls is done by using simple hand
operated tools.
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39. • For heavier sizes of parts, power presses are
apply pressure.
Only of the major uses of this process is the
cladding of mild or low-alloy steel with a high
- alloy materials such as stainless steel.
• It is also used for making bimetallic materials
for the instrument industry.
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40. Advantages
.• Metals such as soft aluminum, copper, gold
and silver can be easily welded by roll welded.
The operation is easy and it used simple
equipment.
• There is no need of using flux and filler metal.
• It is smooth and clean process.
• Less time is required.
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41. Limitation
• It needs extreme pressure to perform the
welding process.
• The cost of equipment is high.
• Weld quality is less as compared to fusion
welding.
• It is limited to welding of flat shapes
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42. Applications
• It is used in cladding of stainless steel to mild
steel for corrosion resistance.
• It is used in making bimetallic strips.
• Roll welding is used to produce sandwich
strips to convert it into coins
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43. Ultrasonic welding
• Ultrasonic welding is an industrial technique
wherebyhighfrequency ultrasonic acoustic vibr
ations are locally applied to workpieces being
held together under pressure to create a solid-
state weld.
• It is commonly used for plastics and metals,
and especially for joining dissimilar materials.
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44. Ultrasonic welding
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45. Friction Stir Welding (FSW)
• Friction Stir Welding (FSW), was invented by W.
Thomas and his colleagues at The Welding
Institute (TWI), UK, in 1991
• Friction stir welding (FSW) is a solid-state joining
process that uses a non-consumable tool to join
two facing workpieces without melting the
workpiece material.
• Heat is generated by friction between the rotating
tool and the workpiece material, which leads to a
softened region near the FSW tool.
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46. • While the tool is traversed along the joint line,
it mechanically intermixes the two pieces of
metal, and forges the hot and softened metal
by the mechanical pressure, which is applied
by the tool, much like joining clay, or dough.
• FSW is capable of joining aluminium alloys,
cooper alloys, titanium alloys, mild steel,
stainless steel and magnesium alloys.
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47. MATERIALS USED IN FSW:
Alluminum and aluminum alloy.
Steel and steel alloy.
Cast iron materials.
Copper and bronze.
All ferrous materials and their alloys.
PARAMETER:
Welding speed (mm/min) 10 - 100
Tool rotation speed (RPM) 600 -1200
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48. WORKING
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49. WORKING
• A rotating cylindrical tool with a profiled probe is fed
into a butt joint between two clamped workpieces, until
the shoulder, which has a larger diameter than the pin,
touches the surface of the workpieces.
• The probe is slightly shorter than the weld depth
required, with the tool shoulder riding a top the work
surface. After a short dwell time, the tool is moved
forward along the joint line at the pre-set welding
speed.
• Frictional heat is generated between the wear-resistant
tool and the work pieces.
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50. • This heat, along with that generated by the mechanical
mixing process and the adiabatic heat within the
material, cause the stirred materials to soften without
melting.
• As the tool is moved forward, a special profile on the
probe forces plasticised material from the leading face
to the rear, where the high forces assist in a forged
consolidation of the weld.
• This process of the tool traversing along the weld line
in a plasticised tubular shaft of metal results in severe
solid-state deformation involving dynamic
recrystallization of the base material
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51. ADVANTAGES:
1.Good mechanical properties in the as-welded condition.
2.Improved safety due to the absence of toxic fumes or the spatter of molten
material.
3.No consumables - A threaded pin made of conventional tool steel.
4.Easily automated on simple milling machines - lower setup costs and less
training.
5.Can operate in all positions (horizontal, vertical, etc.), as there is no weld
pool.
6.Generally good weld appearance and minimal thickness under/over-
matching, thus reducing the need for expensive machining after welding.
7.Can use thinner materials with same joint strength.
8.Low environmental impact.
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52. DISADVANTAGES:
1.Exit hole left when tool is withdrawn.
2.Large down forces required with heavy-duty
clamping necessary to hold the plates together.
3.Less flexible than manual and arc processes
(difficulties with thickness variations and non-
linear welds).
4.Often slower traverse rate than some fusion
welding techniques, although this may be
offset if fewer welding passes are required.
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53. APPLICATION:
1.Ship building
2.Aerospace
3.Automotive
4.Railways
5.Fabrication
6.Robotics
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