welding

2. Laser beam welding:Laser beam welding:
 High energy density input
process
Precisely controllable
(close tolerence: ±
0.002 in.)
 Low heat input produces
low distortion
 Does not require a vacuum
(welds at atmospheric
pressure)
 No filler metal required
Why do we need laser for welding?Why do we need laser for welding?
Traditional welding:Traditional welding:
 Natural limitations to speed
and productivity
 Thicker sections need multi-
pass welds
 A large heat input
 Results in large and
unpredictable distortions
 Very difficult to robotize

3. The term laser is an acronym for Light Amplification by
Stimulated Emission of Radiation.
A laser beam is a powerful, narrow, monochromatic and
directional beam of electromagnetic radiation.
Often, these beams are within the visible spectrum of
light.
A laser device excites the atoms in a lasing medium. The
electrons of these atoms move to a higher orbit, then
release photons, creating a laser beam.

4. Laser BasicsLaser Basics
Laser ComponentsLaser Components
Lasing Medium:Lasing Medium:
Provides appropriate transition and
Determines the wavelength (it must be in a
metastable state)
Pump:Pump:
Provides energy necessary for population
inversion
Optical Cavity:Optical Cavity:
Provides opportunity for amplification
and Produces a directional beam (with
defined length and transparency)
Properties of LaserProperties of Laser
CoherentCoherent (synchronized phase
of light)
CollimatedCollimated (parallel nature of
the beam)
MonochromaticMonochromatic (single
wavelength)
High intensityHigh intensity (~1014
W/m2
)
LLightight AAmplification bymplification by
SStimulatedtimulated EEmission ofmission of
RRadiationadiation

6. Laser beams are used in industry to cut and weld metal
and to survey land and construct buildings.
 In scientific research, they're used in laser spectroscopy
and chemical analysis.
They are used in medical procedures such as eye, cancer
and heart surgery, as well as in cosmetic procedures.
Dental applications include cavity treatment, nerve
regeneration and reshaping gum tissue.

7. Laser beams can measure distances with a high degree
of accuracy. Laser scanners in grocery stores save time
in pricing products and in processing the customer's
purchase.
 In industry, laser cutting and welding are faster and
more precise than other methods. In medical and dental
procedures, lasers do less damage than scalpels and
drills. Scientific research using lasers has led to real-
world advances, such as the use of fiber optics in
telephone communications and computer networking.

8. When overlaying with a laser an optical arrangement
is used to focus the laser beam on the work piece and
heat it. Simultaneously hardfacing material in the
form of powder is introduced into the laser beam and
melted. Due to the narrow heat affected zone and the
fast cooling rate the heat input is low, thereby
producing an almost stress free overlay.
The beam is focused towards the joint which
causes the materials to change from solid to liquid
state. Upon cooling it returns to a solid state.

9. Low heat input
Fast cooling
Almost stress free overlays
High hardness
Fine microstructure

12. lasers used for weldinglasers used for welding
 COCO22 Laser
 NdNd3+3+
:YAG:YAG Lasers
Lamp-Lamp-pumped
LD-LD-pumped
 DiskDisk Laser
 DiodeDiode Laser
 FiberFiber Laser

13. CO2 laser
 The carbon dioxide laser (CO2 laser) was one of the
earliest gas lasers to be developed in 1964[
, and is still one
of the most useful.
 Carbon dioxide lasers are the highest-power
continuous wave lasers that are currently available. They
are also quite efficient: the ratio of output power to pump
power can be as large as 20%.
 The CO2 laser produces a beam of infrared light with the
principal wavelength bands centering around 9.4 and 10.6
micrometers
CO2
Laser: Characteristics
Wavelength 10.6 µm; far-infrared ray
Laser Media CO2
–N2
–He mixed gas (gas)
Average
Power (CW)
45 kW (maximum)
(Normal) 500 W – 10 kW
Merits Easier high power (efficiency: 10–
20%)

14. Lamp-pumped YAG Laser: Characteristics
Wavelength 1.06 µm; near-infrared ray
Laser Media Nd3+
: Y3Al5O12 garnet (solid)
Average
Power [CW]
10 kW (cascade type & fiber-
coupling)
(Normal) 50 W–4 kW
Merits Fiber-delivery, and easier
handling (efficiency: 1–4%)
LD-pumped YAG Laser: Characteristics
Wavelength about 1 µm; near-infrared ray
Laser Media Nd3+
: Y3Al5O12 garnet (solid)
Average
Power
[CW] : 13.5 kW (fiber-coupling
max.)
[PW] : 6 kW (slab type max.)
Merits Fiber-delivery, high brightness,
and high efficiency (10–20%)
YAG Laser Application: AutomobileAutomobile
IndustriesIndustries
Lamp-
pumped
3 to 4.5 kW class; SI fiber
delivered (Mori, 2003)(Mori, 2003)
LD-pumped 2.5 to 6 kW
New
Development
(Bachmann(Bachmann
2004)2004)
Rod-type:Rod-type: 8 and 10 kW; Laboratory
Prototype
Slab-type:Slab-type: 6 kW; Developed by
Precision Laser Machining
Consortium, PLM
YAG Laser

15. Disk Laser: Characteristics
Wavelength 1.03 µm; near-infrared ray
Laser Media Yb3+
: YAG or YVO4 (solid)
Average
Power [CW]
6 kW (cascade type max.)
Merits Fiber-delivery, high
brightness, high
efficiency(10–15%)
Disk LaserDisk Laser
A thin disc is used as lasing medium… it is often called active mirror as
it is used as mirror with laser gain. Within resonator, it acts as end
mirror…

16. Fiber Laser: Characteristics
Wavelength 1.07 µm; near-infrared ray
Laser
Media
Yb3+
: SiO2 (solid), etc.
Average
Power [CW]
20 kW (fiber-coupling max.)
Merits Fiber-delivery, high
brightness, high
efficiency(10–25%)
Recent DevelopmentRecent Development (Thomy et.al. 2004; and
Ueda 2001):
 FiberFiber lasers of 10kW10kW or moremore are
commerciallycommercially available
 Fiber lasers of 100kW100kW and moremore are
scheduledscheduled
 FiberFiber laser at 6.9kW6.9kW is able to provide
deeply penetrateddeeply penetrated weld at highhigh speed
 FiberFiber laser is able to replacereplace high quality
(slab) COCO22 laserlaser for remoteremote or scanningscanning
welding
Fiber LaserFiber Laser
Fiber laser is meant to be lasers with optical fiber as gain medium….Fiber doped with
rare earth ions e.g. erbium, neodymium or ytterbium is used as gain medium and fiber
brag gratings made either directly in doped fiber or in an undopped fiber which is
spliced to an active fiber are commonly used as optical resonator

17. Types of LBWTypes of LBW
Conduction WeldingConduction Welding
DescriptionDescription
 Heating the workpiece above the melting temperature
without vaporizing
 Heat is transferred into the material by thermal
conduction.
CharacteristicsCharacteristics
 Low welding depth
 Small aspect ratio (depth to width ratio is around
unity)
 Low coupling efficiency
 Very smooth, highly aesthetic weld bead
ApplicationsApplications
Laser welding of thin work pieces like foils, wires, thin
tubes, enclosures, etc.

18. Types of LBWTypes of LBW
Keyhole WeldingKeyhole Welding
DescriptionDescription
 Heating of the workpiece above the vaporization
temperature and forming of a keyhole
 Laser beam energy is transferred deep into the
material via a cavity filled with metal vapor
 Hole becomes stable due to the pressure from vapor
generated
CharacteristicsCharacteristics
 High welding depth
 High aspect ratio (depth to width
ratio can be 10:1)
 High coupling efficiency

19. LaserLaser
Beam Delivery UnitBeam Delivery Unit
Workpiece Positioning UnitWorkpiece Positioning Unit
ProcessingProcessing
OpticsOptics
SchematicSchematic
DiagramDiagram
BeamBeam
DeliveryDelivery
unitunit
Lasers Beam WeldingLasers Beam Welding

20.  Low possibility of HAZ in the joint
 No need for filler metal
 Reduce Latency
 No tool wear
 LBW is not influenced by magnetic fields

21. Joints must be accurately positioned
Maximum weld penetration is limited (19-21mm)
High reflectivity and high thermal conductivity of
materials like Aluminum effect the weldability of
the joint