Laser Beam Welding
Introduction:
Laser Beam Welding (LBW) is a modern welding process; it is a high energy
beam process that continues to expand into modern industries and new applications
because of its many advantages like deep weld penetration and minimizing
heat inputs. The turn
by the manufacturers to automate the welding processes has also caused
to the expansion in using high technology like the use of laser and computers
to improve the product quality through more accurate control of welding
processes.
How it works:
The focal spot is targeted on the workpiece surface which will be welded.
At the surface the large concentration of light energy is converted into
thermal energy. The surface of the workpiece starts melting and progresses
through it by surface conductance. For welding, the beam energy is maintained
below the vaporization temperature of the workpiece material, because
hole drilling or cutting vaporization is required.
Because
the penetration of the workpiece depends on conducted heat, the thickness
of the materials to be welded is generally less than 0.80 inches if the
ideal metallurgical and physical characteristics of laser welding must
be realized.
Concentrated energy produces melting and coalescence before a heat affected
zone is developed and when the materials to be welded are thick and have
high thermal conductivity like for example aluminum the advantage of having
a minimal heat affected zone can be seriously affected.
Because the heat source in this type of welding process is the energy
of light, the workpiece will be welded purely which means the fatigue
strength of the welded joint will be excellent.
Energy distribution across the beam is generated by the design of the
resonant cavity, including mirror curvatures or shape and their relative
arrangement. This combination results in photon oscillation within the
cavity specific output beam energy patterns, these patterns are called
Transverse Energy Modes (TEMs).
The function of all laser beam welding processes whether they be gas (carbon
dioxide, helium, neo, etc.) or other lasing sources is based on the principles
of the excitation of atoms using intense light, electricity, electron
beams, chemicals, etc., and the spontaneous and stimulated release of
photons.
The role of focusing lenses in this process is really important because
it concentrates the beam energy into a focal spot as small as 0.005 in
diameters or even less.
Like mentioned above there are many types of Laser Beam Welding (LBW)
but the most popular types in the industry are:
1-Nd:YAG (neodymium-yttrium aluminum garnet) Laser:
The Nd:YAG laser uses a man-made crystal as its active medium and produces
light with a 1.06-micron wavelength.
2-Carbon Dioxide Lasers:
The CO2 laser uses a mixture of gases including CO2 as the active medium
and produces light with a 10.6-micron wavelength.
3-The Diode Laser:
The diode laser uses a semi-conductor diode material as its active medium
can be manufactured to produce one of several wavelengths.
Industries Served:
1- Aerospace.
2- Defense/military.
3- Electronics.
4- Research & development.
5- Medical.
6- Sensors & instrumentation.
7- Petrochemical refining.
8- Communications & energy.
Advantages:
1-Deep and narrow welds can be done.
2-Absence of distortion in welds created.
3-Minimal heat affected zones in welds created.
4-Excellent metallurgical quality will be established in welds.
5-Ability to weld smaller, thinner components.
6-Increased travel speeds.
7-Non-contact welding.