This Presentation covers the basic concepts of EBW in a easy version. For more information, please refer the books mentioned in the references slide.... Thank you

1. Electron Beam
Welding
Melwin D’mello
M.E (Welding Engineering)
Department of Manufacturing Engineering,
ANNAMALAI UNIVERSITY
Presented by

2. What is the need ?

3. Discovery
• William Rontengen in 1800s found that beam of
electron is suddenly stopped by impact with target, then
it start heating and melting the target.
• Dr. Karl Heinz (German) – Development of first practical
welding machine in 1958.

4. Introduction
• It is fusion welding process in which a beam of high velocity
electrons is applied to two materials to be joined.
• Free electrons in vacuum can be accelerated, with their
paths controlled by electric and magnetic fields.
• In this way narrow beams of electrons carrying high kinetic
energy can be formed.
• which upon collision with atoms in solids transform their
kinetic energy into heat.

5. Principle
• Electron beams are composed of electrons that are
charged particles and can be accelerated in electron
guns to high velocities, giving them high kinetic energies.
• At 10 kV, electrons travel at approximately 20% of the
speed of light, while at 200 kV they travel at
approximately 70% the speed of light.
• Electron beam welding process is carried out in vacuum.
In this process, electrons are emitted from the heated
filament called electrode.

6. Principle
• These electrons are accelerated by applying high
potential difference (30 kV to 175 kV) between cathode
and anode.
• The higher the potential difference, the higher would be
the acceleration of the electrons. The electrons get the
speed in the range of 50,000 to 200,000 km/s.
• When high kinetic energy electron beam strikes the work
piece, high heat is generated resulting in melting of the
work material. Molten metal fills into the gap between
parts to be joined.

7. EBW Setup
An EBW set up consists of the following major parts
1. Electron Gun
2. Power Supply Unit
3. Vacuum Chamber
4. Work piece Handling Device

8. EBW Setup

9. 1. Electron Gun
• The electron beam is most often formed by a triode style
electron gun under high vacuum conditions.

10. 1. Electron Gun
• The triode assembly consists of a cathode, a heated source
(emitter) of electrons that is maintained at some high negative
potential.
• A grid cup, a specially shaped electrode that can be negatively
biased with respect to the hot cathode emitter (filament);
• And an anode, a ground potential electrode through which the
electron flow passes in the form of a collimated beam.
• The hot cathode emitter (filament) is made from a high- emission
material, usually tungsten or tantalum, which is usually available in
wire, ribbon, or sheet form.

11. Triode Diode

12. Types of Electron Guns
• Self accelerated
o Electrons are accelerated by applying potential
difference between the cathode and anode.
• Work accelerated
o potential difference is applied between work piece and
anode (Diode type).

13. • Emitter/Filament : It generates electrons on heating.
• Anode: Positively charged element near cathode across which
high voltage is applied to accelerate electrons.
o For high voltage equipment's potential difference 70-150 kV & for
low voltage equipment’s potential difference is 15-30 kV.
• Grid Cup: Negative voltage with respect to cathode is applied.
Grid cup controls the beam.

14. Electron Beam Focusing
• It has two parts, An Electron
focusing lens and deflection
coil.
• Electron focusing lens focuses
the beam into work area.
• The focusing of the electrons
can be carried out by
deflection of beams.

15. Electron Beam Focusing
• This focusing lens reduces the diameter of the electron beam
and focuses the beam down to a much smaller beam cross
section in the plane of the Work piece.
• Thus reduction of beam diameter results into producing very
small high intensity beam spot.
• Deflection coil can be employed to “bend” the beam, thus
providing the flexibility to move the focused beam spot.

16. Beam Focusing

17. Power Supply
• It mainly consisting high power DC power supply source for
gun, focusing and deflection coil.
• It provides power supply for acceleration of the electrons.
• The potential difference for high voltage equipment ranges
from 70-150 kV and for low voltage equipment 15-30 kV.
The current level ranges from 50-1000 mA.
• The amount of current depends upon the diameter and type
of the filament.

18. Vacuum Chamber
• Generally EBW performed in vacuum.
• The gun portion of an electron gun/column assembly
generally is isolated from the welding chamber through the
use of valves when desired.
• Vacuum in the gun region is needed to maintain gun
component cleanliness, prevent filament oxidation, and
impede high-pressure short circuiting between the cathode
and the anode.

19. EBW Equipment

20. Vacuum Chamber
• Maintenance of this degree of vacuum is important
because of the effect that ambient pressure has on both
the beam and the weld produced.
• Based on vacuum intensity the EBW have following 3
types
1.Non vacuum EBW – atmospheric pressure
2.Medium Vacuum EBW – (10-3 to 25 torr)
3.High Vacuum EBW– (10-6 to 10-3 torr)

21. Effect of Vacuum on Beam
Beam scatter due to collision of electrons with
atmospheric molecules

22. Effect of Vacuum on Penetration
Increase in the beam diameter reduces the power &
produces welds with greater width and less penetration.

23. Beam Diameter

24. Penetration Vs Vacuum
Depth of penetration vs Vacuum in prescribed time

25. Penetration Vs Vacuum

26. Work piece Handling
• Quality and precision of the weld profile depends upon
the accuracy of the movement of work piece.
• There is also provision for the movement of the work
piece to control the welding speed.
• The movements of the work piece are easily adaptable
to computer numerical control (CNC )

27. Process Parameters
Major Process Parameters are,
1. Accelerating voltage
2. Beam current
3. Welding speed
4. Beam Focusing

28. Accelerating Voltage
• A value of electrical potential, usually expressed in kilovolts, being utilized to
accelerate and increase the energy of the electrons being emitted by an electron
beam gun.
• Increase in the voltage results into increase in the speed of electrons.
• At 10 kV electrons travel at approximately 20% of the speed of light, while at 200
kV they travel at approximately 70% the speed of light.

29. Electron Beam Current
• Close relation between
electron beam current and
depth of penetration.
• Beam current: measure of
the quantity of usually
expressed in units of mill
amperes (mA),that flow per
unit time in an electron
beam

30. Cont.

31. Welding speed
• Welding speed directly
affects on depth of
penetration of electron beam
into work piece.
• Higher speeds results into
lower depth of penetration.

32. Advantages
• High penetration to width can be obtained.
• High welding speed is obtained.
• Material of high melting temperature can be welded.
• Superior weld quality due to welding in vacuum i.e. welds are
corrosion free.
• Distortion is less due to less heat affected zone.
• Very wide range of sheet thickness can be joined (0.025 mm to
100 mm).

33. Disadvantages
• Transportation of equipment is not easy.
• Vacuum is required.
• Skilled person is needed.
• X-rays generated during welding
• 60 kV 4 kW (610 mm3) electron beam welding machine
including CNC controlled work manipulation systems
costs £220,000.00 i.e. 17609882.40 INR (1 £ = 80.02
INR)

34. Applications of EBW
• Mostly used in joining of refectory materials like columbium,
tungsten, ceramics.
• High Precision Welding of electronics components.
• welding of nuclear fuel elements.
• Special alloy components of jet engines.
• Pressure vessels for rocket.
• Joining of Dis similar metals.
• Welding of Titanium medical implants.

35. References
• Text Book : “Welding Process and Technology” by Dr.
R.S Parmar, 2015 edition.
• Text Book : “Welding Engineering and Technology” by Dr.
R.S Parmar, 2015 edition