Transcript electron beam welding

ELECTRON BEAM WELDING
•The electron beam gun has a
tungsten filament which is heated,
freeing electrons.
•The electrons are accelerated
from the source with high voltage
potential between a cathode and
anode.
•The stream of electrons then
pass through a hole in the anode.
The beam is directed by magnetic
forces of focusing and deflecting
coils. This beam is directed out of
the gun column and strikes the
workpiece.
•The potential energy of the
electrons is transferred to heat
upon impact of the workpiece and
cuts a perfect hole at the weld
joint. Molten metal fills in behind
the beam, creating a deep finished
weld.
How an Electron Beam Machine Works
• The EB system is composed of an
electron beam gun, a power supply,
control system, motion equipment and
vacuum welding chamber. Fusion of base
metals eliminates the need for filler metals.
The vacuum requirement for operation of
the electron beam equipment eliminates
the need for shielding gases and fluxes.
• The electron beam stream and
workpiece are manipulated by means
of precise, computer driven controls,
within a vacuum welding chamber,
therefore eliminating oxidation,
contamination.
ELECTRON BEAM WELDING
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ELECTRON BEAM WELDING
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Electron Beam Welding
• Electron Beam Welding joins ferrous metals, light
metals, precious metals, and alloys, to themselves or
each other.
• Multi-axis EB control
• High ratio of depth-to-width
• Maximum penetration with minimal distortion
• Exceptional weld strength
• Ability to weld components up to 10 feet in diameter
• High precision and repeatability with virtually 0% scrap
• Versatility from .002" depth to 3.00" depth of
penetration
Electron Beam Welding Facts
• Electron Beam Welding Advantages
• Maximum amount of weld penetration with the least amount of heat
input reduces distortion
• Electron beam welding often reduces the need for secondary
operations
• Repeatability is achieved through electrical control systems
• A cleaner, stronger and homogeneous weld is produced in a
vacuum
• The electron beam machine's vacuum environment eliminates
atmospheric contaminates in the weld
• Exotic alloys and dissimilar materials can be welded
• Extreme precision due to CNC programming and magnification of
operator viewing
• Electron beam welding frequently yields a 0% scrap rate
• The electron beam process can be used for salvage and repair of
new and used components
Electron Beam Welding Speeds/Depth of Penetration
• Electron Beam
Welding
Limitations
• The necessity of an
electron beam
welding vacuum
chamber limits the
size of the workpiece
— EBTEC's
maximum chamber
size is 11' 4" wide x
9' 2" high x 12' deep
Electron Beam Welding Speeds/Depth of Penetration
• Electron Beam Welding (EBW) is a unique way of
delivering large amounts of concentrated thermal
energy to materials being welded. It became viable,
as a production process, in the late 1950's. At that
time, it was used mainly in the aerospace and
nuclear industries. Since then, it has become the
welding technique with the widest range of
applications. This has resulted from the ability to use
the very high energy density of the beam to weld
parts ranging in sizes from very delicate small
components using just a few watts of power, to
welding steel at a thickness of 10 to 12 inches with
100 Kilowatts or more. However, even today most of
the applications are less than 1/2" in thickness, and
cover a wide variety of metals and even dissimilar
metal joints
•
Two welding modes are used in the (EBW):
1-Conductance mode:
Mainly applicable to thin materials, heating of the weld joint to melting
temperature is quickly generated at or below the materials surface followed by
thermal conductance throughout the joint for complete or partial penetration.
The resulting weld is very narrow for two reasons:
a- It is produced by a focused beam spot with energy densities concentrated
into a .010 to.030 area.
b- The high energy density allows for quick travel speeds allowing the weld to
occur so fast that the adjacent base metal does not absorb the excess heat
therefore giving the E.B. process it's distinct minimal heat affected zone.
2-Keyhole mode:
It is employed when deep penetration is a requirement. This is possible since
the concentrated energy and velocity of the electrons of the focused beam are
capable of subsurface penetration. The subsurface penetration causes the
rapid vaporization of the material thus causing a hole to be drilled through the
material. In the hole cavity the rapid vaporization and sputtering causes a
pressure to develop thereby suspending the liquidus material against the
cavity walls. As the hole is advanced along the weld joint by motion of the
workpiece the molten layer flows around the beam energy to fill the hole and
coalesce to produce a fusion weld. The hole and trailing solidifying metal
resemble the shape of an old fashion keyhole.
Both the conductance and keyhole welding modes share physical features
such as narrow welds and minimal heat affected zone .The basic difference is
that a keyhole weld is a full penetration weld and a conductance weld usually
carries a molten puddle and penetrates by virtue of conduction of thermal
energy.