Transcript Slide 1

LASER BEAM WELDING(LBW)
LASER- Light Amplification by Stimulated
Emission of Radiation
Focusing of narrow monochromatic light into
extremely concentrated beams (0.001 mm
even)
Used to weld difficult to weld materials, hard to
access areas, extremely small components, In
medical field to weld detached retinas back into
place
Laser Beam- coherent
Laser production- complex process.
Al2O3 + 0.05% Chromium
Laser Welding
• Laser Welding joins ferrous metals,
stainless steel, precious metals, and
alloys, to themselves or each other.
Features include:
• 5-axis laser control
• Extreme precision and minimal distortion
• Low heat input
• Excellent appearance
• No fillers or fluxes required
• Fast, cost-effective production
LASER WELDING
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LASER WELDING
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Laser Welding Facts
• Laser Welding Advantages
• Processes high alloy metals without difficulty
• Can be used in open air
• Can be transmitted over long distances with a minimal
loss of power
• Narrow heat affected zone
• Low total thermal input
• Welds dissimilar metals
• No filler metals necessary
• No secondary finishing necessary
• Extremely accurate
• Welds high alloy metals without difficulty
• CO2 Laser Welding Speeds
The LASER, an
acronym for "Light
Amplification by
Stimulated Emission of
Radiation," is a device
that produces a
concentrated, coherent
beam of light by
stimulating molecular
or electronic transitions
to lower energy levels,
causing the emission of
photons.
• The solid-state laser utilizes a single crystal rod
with parallel, flat ends. Both ends have reflective
surfaces. A high-intensity light source, or flash
tube surrounds the crystal. When power is
supplied by the PFN (pulse-forming network), an
intense pulse of light (photons) will be released
through one end of the crystal rod. The light
being released is of single wavelength, thus
allowing for minimum divergence
• One hundred percent of the laser light will be
reflected off the rear mirror and thirty to fifty
percent will pass through the front mirror,
continuing on through the shutter assembly to
the angled mirror and down through the focusing
lens to the workpiece.
• The laser light beam is coherent and has a high
energy content. When focused on a surface,
laser light creates the heat used for welding,
cutting and drilling.
• The workpiece and the laser beam are
manipulated by means of robotics. The laser
beam can be adjusted to varying sizes and heat
intensity from .004 to .040 inches. The smaller
size is used for cutting, drilling and welding and
the larger, for heat treating
Laser Welding Limitations
• Rapid cooling rate may cause
cracking in certain metals
• High capital cost
• Optical surfaces easily damaged
• High maintenance cost
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solid state RubyLaser- Neon flash tube emits light
into specially cut ruby crystals- absorbs light electrons of chromium atoms get stimulatedIncrease in stimulation ---- electrons increase from
normal(ground) orbit to an exited orbit. More
energy input- energy absorbed exceeds thermal
energy- no longer to heat energy.
Electrons drop back to intermediate orbit- emits
PHOTONS (light) called spontaneous emission
With continued emission, released photons
stimulate other exited electrons to release
photons- called stimulated emission
Causes exited electrons to emit photons of same wave
length.
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Power intensities > 10 kw/cm2
No physical contact between work and welding
equipment
2 mirrors- coherent light reflected back and forth,
becomes dense, penetrates partially reflective
mirror, focused to the exact point
Very little loss of beam energy
Solid state, liquid, semiconductor and gas lasers
used.
Solid state uses light energy to stimulate electrons
Ruby, Neodymium, YAG
Gas lasers use electrical charge to stimulate
electrons Gas lasers- higher wattage outputs. Used
for thicker sections - CO2, N2, He
Liquid- nitrobenzene; Gas- based on gallium
arsenide
• Laser beam cutting
• Along with beam, oxygen used to help
cutting. Ar, He, N, CO2 also for steel, alloys
etc.
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Two ways to weld
• Work piece rotated or moved past beam
• Many pulses of laser (10 times/sec)used.
• Narrow HAZ., speeds of 40 mm/sec to 1.5
m/sec
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Cooling system to remove the heat•
gas and liquid cooling used
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Klyston tubes (glass to metal sealing),
capacitor bank, triggering device, flash
tube, focusing lens, etc. in the setup.
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Cathode of molybdenum, tantalum or
titanium used.
1987
• Laser research begins - a unique method for depositing
complex metal alloys (Laser Powder Fusion).
2002
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From Linde Gas in Germany, a Diode laser using
process gases and "active-gas components" is investigated
to enhance the "key-holing" effects for laser welding. The
process gas, Argon-CO2, increases the welding speed and
in the case of a diode laser, will support the transition of
heat conductivity welding to a deep welding, i.e., 'keyholing'. Adding active gas changes the direction of the
metal flow within a weld pool and produces narrower,
high-quality weld.
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CO2 Lasers are used to weld polymers. The Edison
Welding Institute is using through-transmission lasers in
the 230-980 nm range to readily form welded joints. Using
silicon carbides embedded in the surfaces of the polymer,
the laser is capable of melting the material leaving a near
invisible joint line.