Electron Beam Welding vs Laser Beam Welding

When comparing electron beam welding (EBW) to laser welding (LW) it is important to note that both processes fall under a general heading of power beam welding.

Electron beam welding uses a finely focused stream or beam of electrons, and lasers use monochromatic coherent light, photons. In both cases, the energy of the electrons or photons are turned into heat energy when they impinge upon the surface of metal.

Of the two techniques, electron beam welding is probably less well known than lasers. This is not because it is an inferior process to laser, but probably due to people’s perceptions. Most have heard about or have seen Star Wars, James Bond, and a host of other hi-tec Sci-fi films that have bombarded our screens over many years and coupled with the high profile many respected institutions have been putting forward, unfortunately, electron beam has taken a back seat.

The following table examines some of the differences:

 

Electron Beam Welding in Vacuum Laser Welding with Shielding Gas
Single Pass Welding of Thick Sections
  • 6 kW beam power at 60 kV achieves over 20 mm penetration in stainless steel
  • Up to 300 mm thickness can be welded in a single pass
  • For steels approximately 1 kW per mm depth of weld is required
  • Limited availability and high cost of high power laser systems is a factor
Welding Speed
  • Deep penetration welds possible over a wide range of speeds
  • High welding speeds are required due to the plume of metal vapour formed
Automated Process
  • Can be highly automated with evacuation time of the chamber in a few seconds
  • Typical cycle times found within the automotive industry 40 seconds per component
  • Time is dependent upon length and complexity of weld
  • Can be highly automated with high production rates
  • No waiting time for chamber evacuation
  • Beam splitting and beam sharing are also possible
Component Size
  • Component size is restricted by the size of vacuum chamber
  • Chamber volumes are kept to a minimum to reduce evacuation times
  • Not restricted by component size
  • Fibre optic delivery systems can be used allowing the welding head to be remote from the power source
Vacuum Environment
  • Vacuum aids in the weld quality, as it tends to pull contamination away from the weld pool
  • Operator not exposed to hazardous environment
  • Laser conventionally uses atmosphere with additional shielding gas
  • Laser welding in vacuum significantly increases the depth of weld
Weld Quality
  • High quality weld due to inert atmosphere, very stable and repeatable
  • Deep penetration welds on a wide variety of materials
  • Joint finding and imaging using back scattered electrons is an option
  • Needs a shielding gas, typically nitrogen or argon, to prevent oxidisation of the weld area and stability of the weld pool
  • Real time monitoring of weld depth and quality are expensive options
Shielding Gas
  • Not required as the process is done in either high or low vacuum
  • Essential consumable and expensive
  • Fume extraction may be an issue
Wearing Components
  • Filaments
  • Metal vapours can deposit on viewing prism with no effect on weld characteristics
  • Prism can be cleaned
  • Optical devices such as mirrors and lenses can be coated by metal vapour produced during the welding process leading to drop in beam power
Power Efficiency
  • Typically 85% conversion of electrical power
  • Up to 40% for modern fibre and disc lasers
Cost Comparison
  • More expensive than tungsten inert gas (TIG) and metal inert gas (MIG) welding
  • More expensive than TIG & MIG
  • Price increases steeply with increasing power
Turnkey solutions
  • EB systems includes chamber, fully automatic vacuum system, work handling and control system
  • Usually requires a systems integrator to provide an integrated solution as the laser source does not include work manipulation and control system

 

The best process to use is often dependent on the given application.

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