In this article, you learn what is EBM and working principle, equipment, applications, advantages with PDF and more.
Electron Beam Welding
Electron beam welding is a welding process that uses the heat produced by a beam of high energy electrons. Electrons hit the workpiece and their kinetic energy is transformed to the thermal energy heating the metal so that the sides of the workpiece can be joined and a weld can be formed after freezing.
The EBM is also a liquid state welding process. In which, the metal to the metal joint is formed in a liquid or molten state. It is also named as a welding process because it uses electrons kinetic energy to join two metal workpieces.
This welding was invented in 1958 by the German physicist Karl-Heinz. In this welding process, a high stream of electrons strikes the welding plates, where its kinetic energy is converted into heat energy.
This heat energy is enough to melt the workpieces and join them into one piece. This entire process takes place in a vacuum, otherwise, electrons collide with air particles and lose their energy.
The electron beam welding machine price is around $1,000,000 of EBW-112x102x66 available in Sciaky. The machine has a 30KW W2000 computer-controlled hard vacuum beam welder, with low voltage (60KV) gun.
Working Principle of Electron Beam Welding
It works on the principle of welding electron beam machining. This process uses the kinetic energy of electrons to generate heat. This heat is used to weld two welding plates.
When a high stream of electrons strikes the welding plates, its kinetic energy is converted into heat energy. This heat energy is enough to form a fused joint by joining two metal plates together.
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Equipment of Electron Beam Welding
Following are the equipment of EBM:
- Electron gun
- Magnetic lenses
- Electromagnetic lens and deflection coil
- Work holding device
- Vacuum chamber
- Power supply
1. Electron Gun
It is the important equipment of electron beam welding. It is a cathode tube (negative pole) that generates electrons, accelerates them and concentrates in one place. This gun is often made by tungsten or tantalum alloys. The cathode filament heated up to 2500°C for the continuous discharge of electrons.
The anode is a positive pole just behind the electron gun. Its main function is to attract a negative charge, (electrons in this case) giving them a path and not allowing them to deviate from their path.
3. Magnetic Lenses
There are a series of magnetic lenses that allow only the converging electrons to pass. They all absorb divergent electrons with low energy and provide a high intense electron beam.
4. Electromagnetic Lens and Deflection Coil
Electromagnetic lenses are employed to focus the electron beam onto the workpiece and deflection coil deflect the beam to the expected weld area. These are the final units of the EBW process.
5. Work Holding Device
This welding process uses CNC tables to hold workpieces that can rotate in all three directions. Welding plates are fastened to the CNC table with the use of suitable fixtures.
6. Vacuum Chamber
As you know, this entire process takes place in a vacuum chamber. The vacuum is produced by mechanical or electric-powered pumps. The pressure range in the vacuum chamber is about 0.1 to 10 Pa.
7. Power Supply
This EBM welding process uses a power source to supply a continuous beam of electrons for the welding process. The welding voltage range for low voltage equipment or for thin welding is about 5 – 30 kV and for high voltage equipment or 70 – 150 kV for thick welding.
Working of Electron Beam Welding
EBM is a welding process utilizing heat generated by a beam of high energy electron. The electrons hit the workpiece and their kinetic energy turns into thermal energy heating the metal so that sides of the workpiece are joined and a weld can be formed after freezing.
The process is carried out in the vacuum chamber at a pressure of about 2 x 10-7 to 2 x 10-6 psi (0.0013 to 0.0013 Pa). Such a high vacuum id required in order to prevent loss of the energy of the electron in collisions with air molecules.
The electrons are emitted by a cathode (electron gun). Due to a high voltage (about 150 kV) used between the cathode and the anode, the electrons are stimulated up to 30% – 60% of the speed of light. The kinetic energy of the electrons becomes sufficient for melting the targeted weld. Some of the energy of the electron transforms into X-ray irradiation.
Electrons stimulated by electric field are then focused into a thin beam in the focusing coil. The deflection coil moves the electron beam along the weld. The electron beam is capable to weld workpieces with thickness from 0.004″ (0.01 mm) up to 6″ (150mm) of steel and up to 20″ (500mm) of aluminium.
Electron beam welding can be used to join any metal, including metals that are rarely welded by other welding methods: refractory metals (tungsten, molybdenum, and niobium) and chemically active metals (titanium, zirconium, and beryllium).
Electron beam welding is also capable to join dissimilar metals. The arrangement is done as shown in the figure.
Advantages of Electron Beam Welding
Following are the advantages of EBM:
- Tight continuous weld.
- It has low distortion.
- Narrow weld and narrow heat-affected zone.
- Filler metal is not required.
- It can weld both uniform and diffusion metals.
- The electron beam welding process provides high metal joining rate.
- It can be used to weld hard materials.
- It provides high surface finish welding.
- The entire process in a vacuum has fewer welding defects.
Disadvantages of Electron Beam Welding
Following are the Disadvantages of EBM:
- Its equipment is very expensive.
- It has high production expenses.
- This type of welding has X-ray radiation.
- It has a high capital or installed costs.
- Regular maintenance is required.
- The size of the workpiece is limited according to the vacuum chamber.
- It requires highly skilled labour.
Applications of Electron Beam Welding
You may be wondering what is electron beam welding used for, following are the application of EBM:
- It is used in aerospace industries and marine industries for infrastructure work.
- This type of welding is generally used in automobile industries for connecting gears, transmission systems, turbochargers, etc.
- EBM is applied to join titanium and its alloys.
- It is used in electronic industries to weld electronic connectors.
- This EBM welding process is also used in nuclear reactors and medical industries.
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