What Is Electron Beam Welding?- Definition, & Process

What is Electron Beam Welding?

Electron-beam welding (EBW) is a form of fusion welding where a beam of high-speed electrons is used to join two materials.

The materials melt, and flow together as the kinetic energy of the high-speed electrons is converted to heat when they hit the materials. EBW is often performed in a vacuum chamber to prevent dispersion of the electron beam.

Electrons are produced from an electron gun and are accelerated to very high speeds using electrical fields. The high-speed stream of electrons are focused by magnetic fields and aimed at the materials to be joined.

As the beam of electrons impacts the surfaces of the workpieces, the kinetic energy of the electrons is converted to heat. This heat melts the metal and allows it to flow together. Electron beam welding is performed in a vacuum because gas molecules can scatter the electron beam and disrupt welding fusion.

Due to the high voltage in the electron beam welding, and the vacuum required for the process, EBW is a computer-controlled process and highly automated.

As noted, the high precision nature of the technology often requires the use of special holding fixtures to secure parts for joining, and CNC tables are often seen to move both the fixtures and work pieces through the welding chamber.

Electron beam welders are expensive, require stringent maintenance, and the support technology around high voltage high vacuum can be demanding.

While expensive, electron beam welds are very precise, very strong, very pure, very repeatable, and in many situations and with many materials, EBW is the best joining technology available.

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 components for assembly are thoroughly cleaned and checked for quality;
• Fixtures that hold the parts firmly in one position while welding is done are developed. Whenever possible, the program to load as many parts in each vacuum cycle is implemented to keep production rates high. If needed, fixtures are fabricated at our complete machine shop;
• Parts are loaded into the fixtures, and the fixtures are installed into the Electron Beam’s CNC table, and the CNC table is programmed to transfer the pertinent parts under the electron beam during the welding process;
• The vacuum chamber will be secured and the air evacuated out of the chamber until the partial or full vacuum is obtained as specified by the customer;
• If required, test welds will occur to check the beam is aligned and focused, the beam power, and the amount of penetration, and overall quality of the weld. The parameters will be adjusted as needed, and monitored through all welding;
• If it is a production weld cycle, the welding operator will start the CNC table program and Electron Beam firing cycle, and the parts are Electron Beam welded;
• At the end of the weld cycle, the vacuum chamber is pumped down, and the parts and fittings are removed from the welder;
• The parts will be carefully removed from the fixtures, and a full quality control inspection will proceed.

Working of Electron Beam Welding

Electron beam (EB) welding is a fusion welding process in which electrons are created by an electron gun and rapidly accelerated to high speeds using electrical fields. This beam of electrons is then tightly focused using magnetic fields and directed onto the materials to be welded.

In EB welding, the beam of electrons produces kinetic heat, which becomes sufficient to melt the workpieces and join them together.

EB welding is performed in a vacuum environment because if there were gas, the beam electrons would scatter. EB welding is heavily automated and computerized because it is a vacuum process, and due to the high voltage, special fixtures and CNC tables are used to move the workpieces in the welding vacuum chamber.

Important advances in electron beam welding machine technology have introduced a local beam welding process where the gun is enclosed in a ‘vacuum box’ on the side of the material to be welded, instead of 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, there is a cup grid. This prevents the electrons from diffusion and controls them. Because of the high voltage applied across the cathode and anode. The anode that is positively charged attracts the electron created from the cup grid.

The anode accelerates the electron, and it reaches a high velocity in range of 50000 – 200000 km/s. The anode sends the beam of high-velocity electrons through the magnetic lens and deflector coils.

The magnetic lens focuses the electrons to the workpiece location desired. The deflector coil deflects the electrons to the weld area. As the beam of high-speed electrons impacts the workpiece, very high heat is produced, and it melts the workpiece’s metal, filling the weld area. The molten weld cools and solidifies as a strong weld joint.

Application of Electron Beam Welding

• Usage of this technology is in the aerospace industries to manufacture components of jets, structures, transmission parts, and sensors.
• Usage of this technology is in the power generation industries.
• Usage of this technology is in the space industries to build titanium tanks and sensors.
• Usage of this technology is in the automobile industries to manufacture transmission systems, gears, and turbochargers.
• Usage of this technology is in the electrical and electronic industries to manufacture portions of copper structures.
• The other areas of usage are in the nuclear industries, medical, research centers, etc.

Advantages of Electron Beam Welding

• High welding speed.
• Welding of dissimilar metals 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, ranging 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.
• A high skilled operator is required to operate it.
• A high vacuum is required.
• Due to operation in a vacuum, large jobs cannot be welded.
• High safety measures are needed to work with it.

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