1. Selection of solid state welding processes
Process Selection
Selection of solid state welding processes
depends on the following factors :
Performance of the welding processes under existing conditions
Advantages of the processes involved
Durability of the welds produced
Materials to be welded
Economic viability of the process

2. Solid state welding
Diffusion welding(DFW): Two parts are held together under pressure at elevated temperature.
Friction welding(FRW): By heat of friction between two surfaces two parts joined.
Ultrasonic welding(USW):Moderate pressure between two parts hold together and an ultrasonic oscillation frequency send through in the direction parallel to the surface of contact.
Forge welding(FOW): Heat and pressure applied. First the item is heated and hammered.
Cold welding(CW):Only pressure is applied.
Explosion Welding (EXW):A layer of explosives placed between layers of materials.

3. Advantages of Solid State Welding
1.Eliminates liquid phases
Example: cold welding, friction welding, ultrasonic welding, diffusion welding and explosion welding
3.Can be performed with little or no deformation in some cases
Example: diffusion welding
4.Some solid state processes can weld large areas in a single welding operation
Examples: diffusion welding and explosion welding
2.Makes the joining of many dissimilar metal combinations possible
Example: friction welding, explosion welding, diffusion welding.
5.Some solid state welding processes are relatively rapid
Example: ultrasonic welding, cold welding and friction welding

5. Ultrasonic Welding

6. Ultrasonic welding
Uses rapid vibrations to break up surface films and heat the surfaces, allowing them to bond
Figure : Ultrasonic welding (USW): (a) general setup for a lap joint; and (b) close‑up of weld area.

7. Ultrasonic Welding
In this high frequency ( ultrasonic ) vibrating energy is
applied to overlapping metals into weld area to be joined
The parts to be joined are clamped together between a
Welding tip and a supporting member ( anvil )
2. The core if ultrasonic transducer is coupled to work through
A bar having suitably-shaped tip ( welding tip )
3. The tip applies a transverse pressure between work pieces
and simultaneously ultrasonic vibration ( KHz ) is then
applied to tip
4. It causes vibration in metal molecules to raise temperature
Sufficient to form a strong union between the face of the material
In contact which results in spot type weld due to localized
heating by high velocity rubbing.

8. Ultrasonic Welding Advantage
This process doesn’t require any flux or filler metals,
electric arc
Disadvantage
It is only used for welding thin strips and foils

9. Uses pressure and frictional heat caused by mechanical rubbing, usually by rotation
Figure : Friction welding (FRW): (1) rotating part, no contact; (2) parts brought into contact to generate friction heat; (3) rotation stopped and axial pressure applied; and (4) weld created.

10. Friction Welding In friction welding process, the parts to be
welded are kept in contact and rotated relative
to each other. The interface is heated up due
To rotating friction ( sliding & rubbing )
The two pieces ( perfectly clean ) to be welded
Together are mounted in chucks on same
horizontal Axis ( perfectly axial alignment ) .and are
brought in contact face to face. One piece
is held
rigidly by fixed chuck and other is rotated by rotating
Chuck at the desired speed with help of motor
After the desired temp is attained , an axial
pressure is applied to complete the weld.
After welding is completed, the welded parts
Rotate together as one piece until stopped

11. The process is mainly used for joining round
bars face to face
Friction Welding

12. Explosion Welding (EXW)
process in which rapid coalescence of two metallic surfaces is caused by the energy of a detonated explosive
No filler metal used
No external heat applied
No diffusion occurs - time is too short
Bonding is metallurgical, combined with mechanical interlocking that results from a wavy interface between the metals
Commonly used to bond two dissimilar metals, in particular to clad one metal on top of a base metal over large areas

13. Figure Explosive welding (EXW): (1) setup in the parallel configuration, and (2) during detonation of the explosive charge.

14. Definition of Explosion Welding
Detonator
Explosive
standoff
distance
A solid-state welding process that produces coalescence by high velocity interaction of the work pieces produced by a controlled detonation.
prime
component
Base
component
Component arrangement
for explosion welding

15. Principles of Explosion Welding
Detonator
Welding arrangement consists of three components -
Base component
Prime component
Explosive.
Base component remains stationary, supported by anvil.
Explosive
prime
component
Base
component
Component arrangement
for explosion welding

16. Principles of Explosion Welding
Prime component is placed either parallel or at an angle to the base.
Explosive is distributed over top surface of prime component.
Upon detonation, prime component collides with base component to complete welding.
Detonation
Prime
component
Weld
Jet
Base
component
Action between components
during explosion welding.

18. Process Variables and Controls
Explosive Pressure
Variables
Collision Velocity
Collision Angle
Prime Component Velocity
These are Controlled By:
Component Mass
Explosive Charge
Initial Geometry - Standoff Distance or Angle
V = charge velocity

19. Explosives Used for Welding
High Velocity ft/s
Trinitrotoluene (TNT)
Cyclotrimethylenetrinitramine (RDX)
Pentaerythritol tetranitrate (PETN)
Composition B
Composition C4
Primacord
Low to Medium Velocity ft/s
Ammonium nitrate
Ammonium nitrate sensitized with fuel oil
Ammonium perchlorate
Amatol
Amatol and sodatol diluted with rock salt to 30 to 35%
Dynamites
Nitroguanidine
Dilute PETN

20. Effect of Velocity on Explosion Weld Geometry

21. In Parallel Arrangement
Standoff = 1/2 to 1.0 times clad

22. In Angular Arrangement
Angle = 1 to 8 Degrees

23. Wave Height
Larger Standoff and Greater Angle Generally Leads
to Greater Wave Heights

24. Wavy weld interface

25. Applications of Explosion Welding
Any metal of sufficient strength and ductility can be joined.
Cladding flat plates constitutes the major commercial application.
Can be used to clad cylinders on inside or outside surface.
Transition joints can be made.
Tube to tube sheet joints in heat exchangers.

26. Finished vessel fabricated from explosion clad plate.
Explosion welded 12 inch diameter
3003 aluminum to A106 grade B
steel tubular transition joint.

27. Forge welding
Forge welding(FOW): Heat and pressure applied. First the item is heated and hammered.

28. Diffusion welding
Diffusion welding(DFW): Two parts are held together under pressure at elevated temperature
process uses heat and pressure, usually in a controlled atmosphere, with sufficient time for diffusion and coalescence to occur
Limitation: time required for diffusion can range from seconds to hours