2. WELDING
Welding is a process in which two or more
parts of same or different material are
joined together with the help of heat or
pressure is known as welding. The joint
formed is known as welded joint.
4. THERMITE WELDING
Thermite welding is an exothermic welding process
that uses thermite to melt metal, which is poured
between two workpieces to form a welded joint.
5. REACTION
The aluminium reduces the oxide of another metal, most
commonly iron oxide, because aluminium is highly reactive.
The maximum reachable temperature is 3090 0C. The
products are aluminium oxide, free elemental iron, and a
large amount of heat. The reaction is used for thermite
welding, often used to join rail tracks.
Fe2O3 + 2Al → 2Fe + Al2O3
6. TEMPERATURE VARIATION
The reaction of the Thermite-
welding is started at about 1200 0C
using a special ignition powder. The
maximum reachable temperature is
3090 0C that has to be reduced
quickly to about 2480 0C by the
addition of non reacting pellets of
ferroalloy.
7. SLAG
At 2500 0C the aluminum
would vaporize. The aluminum
slag (Al2O3), that has to remain
liquid to float and separate
from the metal, would solidify
at 2040 0C (3700 0F) and less.
9. APPLICATION
•Thermite welding is mainly used in repair and
welding of large forgings and castings, pipes, mill
housings and heavy rail sections.
•Applications are used to repair heavy sections
•Often used to join rail tracks
•Field welding of track
10. ELECTRON BEAM WELDING
Electron Beam Welding (EBW) is
a fusion joining process that
produces a weld by impinging a
beam of high energy electrons to
heat the weld joint. (EBW) is
done in vacuum.
11. PROCESS
An EBW gun functions similarly to a TV picture
tube. The major difference is that a TV picture
tube continuously scans the surface of a
luminescent screen using a low intensity
electron beam to produce a picture. An EBW
gun uses a high intensity electron beam to
target a weld joint. The weld joint converts the
electron beam to the heat input required to
make a fusion weld.
12. EQUIPMENTS
• Electron gun, generating the electron beam
• Working chamber, mostly evacuated to "low"
or "high" vacuum
• Work-piece manipulator (positioning
mechanism)
• Supply and control/monitoring electronics
13. FUNCTION
The electron beam is always
generated in a high Although, high
vacuum welding will provide maximum
purity and high depth to width ratio
welds.
15. SOLID STATE WELDING
Solid State Welding is a welding process, in
which two work pieces are joined under a
pressure providing an intimate contact
between them and at a temperature
essentially below the melting point of the
parent material.
16. TYPES OF SOLID STATE WELDING
COLD PRESSURE WELDING
ULTRA SONIC WELDING
17. COLD WELDING
Cold 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.
18. PRINCIPLE
Cold welding is a method for joining non-ferrous
metals and their alloys without using heat, fillers or
fluxes. Round wire sections, dissimilar materials and
materials of different sizes can all be welded with
BWE's proven cold welding technology. A cold weld is
generally stronger than the parent material and has
the same electrical characteristics.
19. DIES IN COLD WELDING
The dies play an important role in
the cold weld process. Firstly, they
must grip the material firmly
and, therefore, the inside of the
cavity is either etched with an
electric pencil or, when the die is to
be used for welding large pieces of
aluminium, grip marks are put in the
cavity before the die is heat treated.
20. CHARACTERISTICS OF COLD WELDING
• At least one of the metals must be ductile without
excessive work-hardening
• Total absence of applied heating
• Dissimilar metals can be joined
• Surface preparation is important
21. COLD WELDING PROCESS
DESCRIPTION
• The parts to be welded are first
cleaned.
• A short section of the part is sheared
• The parts are clamped in a die with
some initial extension
• A forging force is applied to
complete welding.
25. APPLICATION
• Cold welded butt joints are used in the
manufacturing
of aluminum, copper, gold, silver, and platinum
wire
• Most commonly, successive reels of wire
are joined for continuous drawing to a smaller
diameter
• Aluminum alloys used in cold welding
26. ULTRASONIC WELDING
Ultrasonic welding is an industrial technique whereby
high-frequency ultrasonic acoustic vibrations are
locally applied to work pieces being held together
under pressure to create a solid-state weld.
27. Why to use US welding?
• First - Ultrasonic assembly uses ultrasonic vibratory
energy which is transmitted through the parts to melt
and bond thermoplastic materials And joining thin sheet
gauge metals and other lightweight materials
Second - This technique is fast, efficient, non-
contaminating and requires no consumables.
Third - In ultrasonic welding, there are no connective
bolts, nails, soldering materials, or adhesives necessary
to bind the materials together.
28. PRINCIPLE
In ultrasonic welding, frictional heat produced
by the ultrasonic waves and force is used for the
joining process. Ultrasonic waves (15 to 60 kHz)
are transferred to the material under pressure
with a sonometer. Welding times are lower than
3 s. The welding can proceed with or without
the application of external heat.
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35. ADVANTAGES
• Heat affected zone is minimized
• Very thin materials can be welded
• Surface deformation is minimum
• Welding of glass is also possible
• No defects due to gases, arc and filler metal
• Equipment is simple and moderate skill is enough
• Dissimilar materials can be joined
36. DISADVANTAGES
• Restricted to join thin materials
• Competitively not economical
• Materials being welded may tend
to weld to the tip and anvil
37. Application
• Manufacturing of toys
• Joining of electrical and electronic components
• Welding aluminium wire and sheet
• Mobiles, sports shoes , laminations, cars etc
• Packing , medical industries, computers.
