Transcript LASER Welding - City Tech OpenLab

Metal Repairs: Laser Welding
LASER
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“light amplification by stimulated emission
of radiation.”
Electrons are atomic particles that exist at specific
energy levels. These energy levels are unique and are
different for every atom or molecule.
Electrons in outer rings are at higher energy levels than
those in the inner rings. A flash of light can bump
electrons to higher energy levels by the injection of
energy. When an electron drops from an outer ring to an
inner ring or level, the excess of energy is given off as
light.
The wavelength or the color emitted is related to the
amount of energy released.
I. The LaserStar® Workstation
The LaserStar® Workstation is an
Nd:YAG laser. The host material is a
cylindrical crystal of yttriumaluminum -garnet (Y3Al5O12), YAG
doped by weight with neodymium
(Nd3+) ions. Laser emission takes
place at 1.064 μm (infrared).
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Part of the laser light passes through
the semi-reflecting mirror and performs
the welding function.
produces a very high energy density
light beam, many times higher than is
possible with normal light
The energy -“hot light”- created at the
focal point in a relatively short time
(0.5 to 20 ms) heats the metal beyond
its melting point and thus enables a
weld.
Laser Power
Joules: The “hot light” energy
output is measured in joules.
This industry term by
definition is “ the capacity
for doing work”. Hot light
energy output is determined
by the amount of voltage and
pulse-length selected by the
operator
Welding effects:
When a pulse of “hot light”
energy penetrates an
alloy, the resulting affect
creates gaseous, liquid,
and molten zones in the
bombardment area
Effect parameters while welding metals
is as follows:
• The voltage first influences the welding
depth.
• The pulse length predominantly influences
the diameter of the welding point.
• The focus influences the welding depth as
well as the diameter of the welding spot.
When increasing the diameter, the welding
depth is reduced at the same time.
Parameter Adjustments-Bombardment
Zone Results
Keypad
ON SYSTEM ON: This light comes on when the main
switch of the product is turned “on” and the key
switch is set to the “ON” position.
● CLOSE SHUTTER: This key closes the shutter. A
continuous indicator light indicates that the
shutter is closed.
O OPEN SHUTTER: This key enables the opening of
the laser shutter. Green indicator light flashes
when the shutter is ready to open; continuous
when the shutter has opened.
 ENTER KEY: To enter or accept system variables
and/or navigate menus.
OK Green light indicates laser is ready, Red: no pulse
can be released (recovery time) or the system is
still in the startup phase after being switched “on.”
! FAULT: System fault (yellow light). To reset fault
must be corrected.
↑/↓ To change system variables and navigate menus.
MENU To enter the menu mode.
Welding chamber/area controls
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Gas Flow Control These controls used to control the flow of inert gas. Right control for center
tube, left control for left tube.
Beam Expander: Focus setting: This changes the diameter of the focal spot (model dependant)
Safety Shutter (Open Shutter) Used to open laser shutter from inside the welding
chamber/area.
Brightness This control allows you to control the brightness of the lights in the welding
chamber/area.
+ / - When the joystick is pushed toward the + , this will increase the value in the display for the
parameter flashing. When the joystick is pushed toward the - , this will decrease the value in the
display for the parameter flashing.
< Menu The joystick is pushed toward the < Menu symbol to select the parameter to be changed
going to the left in the display.
Menu > The joystick is pushed toward the Menu > symbol to select the parameter to be changed
going to the right in the display.
Joining Metals
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Joint Preparation: To ensure a
strong laser welding joint it is
important to properly evaluate your
application and material thickness
first before selecting one of the joint
preparation methods
Bonding the joint: Strong
homogenous allow flow is achieved using
the appropriate parameter combinations
and the 50% overlap firing method. This
ensures a structurally sound joint while
virtually eliminating the possibility of
gaseous pockets or cold welds
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Surface filling the joint: laser
welding vaporizes some of the alloy.
Filler material is used to fill these
voids. The filler material should be the
same alloy if possible. Filler wire
diameter should be no lager than
0.50mm or .020”.
Welding a Connector
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Keyhole Weld- used for thick connectors
is a deep core penetrating weld that will
hold the part together. A proper keyhole
weld will penetrate at least halfway into
the gauge of the parts to be welded
Surface Weld- used for tin connectors.
Thin connectors need less penetration.
Therefore, a Surface weld is
recommended
Quadrant Method
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Quadrant Tacking
Metal contracts and expands during the
welding process. For this reason we must
tack the connector in diametrically
opposed quadrants.
Quadrant Welding
To maintain equal, consistent heating
and equal metal displacement of the
structure, we must weld the connector
in diametrically opposed quadrants as
well. This prevents distortion of the
metal during the weld process.
Filler Materials
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Large gaps: Require fabricating a
large insert (often thick wire or
casted piece) of the same material
Small gaps: often require a quick
application of a thin filler wire to
correct or complete the laser
welding application
Shallow blemishes: require a
quick application of a thin filler wire
to correct the laser welding
application
Porosity
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Deep porosity: can be repaired
in two steps: first using high
voltage-short pulse duration with
a tight beam diameter, burnout
any investment remaining and
expose the complete porosity
pocket; Second, use the filler
material to refill the porosity
pocket
Hammering and Smoothing
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After the core laser welding
process has been completed, it
is recommended to adjust to a
lower power, wide laser pulse
diameter and medium to fast
auto-pulsing setting. This will
smooth over or hammer the
surface which eliminates most
rough surfaces and reduces
secondary finishing techniques
to the laser welded area.