generally used to excite the lasing material in the laser
source, releasing photons. Photon energy is allowed to
build up in the laser or laser welding machine until the
desired level is reached. The energy is then released to
fuse the weld joint.
Fusion occurs at the point where the laser beam
strikes the weldment. Laser beams may be continuous
or pulsed. They can be focused with lenses to a very
small and accurate beam. Their direction can be
changed through the use of mirrors.
Electron Beam Welding (EBW)
Figure 29-14 shows the basic parts of an electron
beam welding (EBW) machine. Electrons are emitted
from the electron gun. They are then focused and
directed at the weld joint. The kinetic energy of the
electrons creates the heat for welding. Kinetic energy
is the energy of an object in motion. In this case, the
objects in motion are the electrons.
Electron beam welding may be done in a high vac-
uum, a partial vacuum, or under normal atmosphere
pressure. A vacuum is a condition in which atmos-
pheric pressure in a closed vessel has been decreased.
This is done by pumping out air. Figure 29-15 shows
an electron beam welder in use in industry. The
beam energy is easier to direct under high vacuum
conditions. Also, less energy is lost in a vacuum.
Advantages of Laser and Electron
Beam Welding
Laser and electron beam welding machines are
made in a variety of energy levels. The greater the elec-
trical energy input, the greater the energy output.
Nd:YAG lasers are produced in sizes from 100W–4000W
(watts). CO2 lasers are produced in sizes from
500W–25,000W. A 600W Nd:YAG laser will penetrate
steel .01″ (2.5 mm) in thickness.
Electron beam welding machines are produced in
sizes from 1kW–100kW (kilowatts). A 100kW EB
welding machine will produce 100% penetration on
steel 10″ (254 mm) thick. See Figure 29-16. Laser beam
and electron beam welding offer these advantages:
Welding Technology Fundamentals
358
Base metal Weld joint
High vacuum
Upper
column
Electron
gun
Column
valve
Optics
Magnetic lens
Deflection coil
Vacuum
chamber
3″
75 mm
Figure 29-14. The basic parts of an electron beam welding
machine shown in schematic form. Note that, in this machine,
the weldment is mounted in a vacuum chamber. (PTR-Precision
Technologies, Inc.)
Figure 29-15. This electron beam welding machine comes with
an optical viewing system, video, wire feed, vacuum chamber,
and CNC technology. (PTR-Precision Technologies, Inc.)
Figure 29-16. A cross section of an electron beam weld. Notice
how thin the weld is in relation to the metal thickness.
(PTR-Precision Technologies, Inc.)