ELECTRON BEAM WELDING

1. 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.

2. 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.

3. The electron beam stream and workpiece are manipulated by means of precise, computer driven controls, within a vacuum welding chamber, therefore eliminating oxidation, contamination.

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7. 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

8. 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

9. Electron Beam Welding Speeds/Depth of Penetration

10. 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

11. Electron Beam Welding (EBW) is a unique way ofdelivering 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

12. 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.