What is Electron Beam Welding?
Electron-beam welding (EBW) is a fusion welding process in which a beam of high-velocity electrons is applied to two materials to be joined. The workpieces melt and flow together as the kinetic energy of the electrons is transformed into heat upon impact. EBW is often performed under vacuum conditions to prevent dissipation of the electron beam.
Electrons are generated via an electron gun and then accelerated to very high speeds using electrical fields. This high-speed stream of electrons is then focused using magnetic fields and precisely applied to the materials to be joined.
As the electrons impact the materials their kinetic energy is converted to heat, which causes the metals to melt and flow together. Electron beam welding generally occurs in a vacuum as the presence of gas molecules can scatter the beam.
Because of the high voltages involved in EB welding, and the required vacuum, the entire process is computer-controlled and heavily automated. The precise nature of the technology often calls for specialized fixtures to secure parts for joining, and CNC tables are commonly used to move the fixtures and workpieces within the welding chamber.
Electron beam welders are very expensive, must be tightly maintained, and the support required by the high voltage and high vacuum technologies can be demanding. However, electron beam welds are incredibly precise, strong, and pure, the entire process accurately repeatable, and for many applications and materials, electron beam welding is the best-joining technology there is.
A Typical Electron Beam Welding Procedure
While every Electron Beam welding job is different, there is a base procedure we follow at EB Industries that allows us to maintain both weld quality and production rate.
- The parts to be assembled are thoroughly inspected and cleaned;
- Fixtures to hold the parts securely in place during the welding process are devised. We try to maximize the number of parts that can be welded per vacuum cycle to maintain high production rates. If necessary, fixtures are custom made in our complete machine shop;
- Parts are loaded into their fixtures and the fixtures attached to the Electron Beam welder’s CNC table. The CNC table is programmed to precisely move the parts into position under the electron beam during the welding process;
- The vacuum chamber is secured and the air pumped out of it to achieve the necessary partial or full vacuum required by the customer specification;
- If necessary, test welds are performed to check for proper beam alignment and focus, beam power, weld penetration and overall quality of the weld. Parameters are adjusted as needed, and continually monitored during all welding operations;
- If it is a production weld cycle, the welding operator initiates the CNC table programming and Electron Beam firing cycle. The parts are then Electron Beam welded;
- At the end of the welding cycle, the vacuum chamber is pumped down and the parts and fittings are removed from the welder;
- The parts are carefully removed from their fixtures and then subjected to a full quality control inspection.
Working of Electron Beam Welding
Electron beam (EB) welding is a fusion welding process whereby electrons are generated by an electron gun and accelerated to high speeds using electrical fields. This high-speed stream of electrons is tightly focused using magnetic fields and applied to the materials to be joined. The beam of electrons creates kinetic heat as it impacts the workpieces, causing them to melt and bond together.
Electron beam welding is performed in a vacuum environment as the presence of gas can cause the beam to scatter. Due to it being a vacuum process and because of the high voltages used, this welding method is heavily automated and computer-controlled. As a result, specialized fixtures and CNC tables are used to move the workpieces inside the welding vacuum chamber.
Recent developments in electron beam welding machine technology have realized a local method of electron beam welding, whereby the electron beam gun is enclosed in a vacuum box on the side of the material to be joined, rather than placing the entire workpiece inside a vacuum chamber.
In Electron Beam welding, the electron is produced by the cathode of the electron gun. After the cathode, a cup grid is provided. It prevents the divergence of electrons and controls them. Because of the high voltage applied across the cathode and anode. The anode which is positively charged attracts the electron from the cup grid.
The anode accelerates the electron and its velocity increases and reaches the range of 50000 – 200000 km/s. From the anode, the high-velocity electron beam is passed through the magnetic lens and deflector coils.
The magnetic lens focuses the electron beam to the desired location on the workpiece. And the deflector coil deflects the beam to the required weld area. As the high-velocity electron beam strikes the workpiece, intense heat is produced and it melts the metal of the two workpieces and fills the weld area. The molten weld solidifies and forms a strong weld joint.
Application of Electron Beam Welding
- It is used in aerospace industries for manufacturing jet components, parts of structures, transmission parts and sensors.
- It is used in power generation industries.
- It is used in space industries to build titanium tanks and sensors.
- It is used in automobile industries to manufactures transmission systems, gears, and turbochargers.
- It used in electrical and electronic industries to manufactures parts of copper structures.
- The other areas where it is used are nuclear industries, medical, research centers, etc.
Advantages of Electron Beam Welding
- High welding speed.
- Welding of dissimilar metal can be done.
- High weld quality and precision.
- Less operating cost.
- Materials with high welding temperatures can be welded easily.
- Less distortion due to less affected heat zone.
- The cost of cleaning is negligible.
- It welds thicker sheets, ranges from .025 mm to 100 mm.
- It is capable of welding inaccessible joints.
Disadvantages of Electron Beam Welding
- The cost of equipment is very high.
- High skilled operator is required to operate it.
- A high vacuum is required.
- Due to operation in vacuum, large jobs cannot be welded.
- High safety measures are needed to work with it.