Electron Beam Welding 电子束焊接
Electron beam welding is a liquid state welding process. Liquid state welding are those welding processes in which, the metal to metal joint form in liquid or molten state. This is also classified as a new welding process because it uses electrons kinetic energy to fuse two metal work pieces. This welding is developed by the German physicist Karl-Heinz in 1958. In this welding process, a high jet of electrons strikes at welding plates where its kinetic energy converts into heat energy. This heat energy is sufficient to melt the work pieces and fuse them into one piece. This whole process carried out in vacuum otherwise the electrons collides with air particles and loses its energy.
电子束焊接是液态焊接工艺。液态焊接是那些金属与金属接头形成液态或熔融状态的焊接工艺。 这也被归类为一种新的焊接工艺，因为它使用电子动能来熔化两个金属工件。这种焊接是由德国物理学家Karl-Heinz于1958年开发的。在这种焊接过程中，高电子射流撞击焊接板，其动能转化为热能。这种热能足以熔化工件并将它们熔合成一体。 整个过程在真空中进行，否则电子与空气粒子碰撞并失去其能量。
1 Principle 原理
This welding works on same principle of electron beam machining. This process uses kinetic energy of electrons to produce heat. This heat is further used to weld two welding plates. When a high jet of electrons strike at welding plates, its kinetic energy converts into heat energy. This heat energy is sufficient to fuse two metal plates together to form a weld joint.
2 Equipment 设备
2.1 Power Supply 能源
This process uses a power source to supply continuous beam of electrons for welding process. The voltage range of welding is about 5 – 30 kV for low voltage equipment’s or for thin welding and 70 – 150 kV for high voltage equipment’s or for thick welding.
2.2 Electron Gun 电子枪
It is heart of electron beam welding. It is a cathode tube (negative pole) which generates electrons, accelerate them and focus it on a spot. This gun is mostly made by tungsten or tantalum alloys. The cathode filament heated up to 2500 degree centigrade for continuous emission of electrons.
2.3 Anode 阳极
Anode is a positive pole which is just after the electron gun. Its main function is to attract negative charge, (in this case electron) provide them a path and don’t allow them to diverge from its path.
2.4 Magnetic Lenses 磁透镜
There are a series of magnetic lenses which allows only convergent electrons to pass. They absorb all low energy and divergent electrons, and provide a high intense electron beam.
2.5 Electromagnetic lens and deflection coil 电磁透镜和偏转线圈
Electromagnetic lens used to focus the electron beam on work piece and deflection coil deflect the beam at required weld area. These are last unit of EBW process.
2.6 Work holding device 工件固定装置
EBW uses CNC table for hold work piece which can move in all three direction. The welding plates are clamped on CNC table with the use of suitable fixtures.
2.7 Vacuum Chamber 真空室
As we know, whole this process takes place in a vacuum chamber. Vacuum is created by mechanical or electric driven pump. The pressure ranges in vacuum chamber is about 0.1 to 10 Pa.
3 Working 工作
Its working can be summarized as follow.
- First the electron gun, which is a cathode, produces electrons. These electrons move towards anode which is positive charged and placed right after electron gun.
- The anode accelerates the electrons and form a electron jet which is further move towards magnetic lenses.
- The magnetic lenses are a series of lenses which are used to absorb low energy electrons and does not allow to divergent electron to passes through it. It provides a high intense electron jet.
- Now this electron beam passes through electromagnetic lens and defecting coil which are used to focus and deflect the electron beam at the required spot. This unit direct high velocity electron beam to the weld cavity where its kinetic energy converts into heat energy due to collision. This heat energy is used to create weld by fusion. This whole welding process carried out in a vacuum chamber otherwise the electrons collides with air particle in the way and loses its energy.
4 Application 应用
- It is used in aerospace industries and marine industries for structure work
- It is used to join titanium and its alloy.
- This type of welding is widely used to join gears, transmission system, turbocharger etc. in automobile industries.
- It is used to weld electronic connectors in electronic industries.
- This process is also used in nuclear reactors and in medical industries
5 Advantages and disadvantages 优点与缺点
5.1 Advantages 优点
- It can weld both similar and dissimilar metals.
- It provides high metal joining rate.
- Low operating cost because no filler material and flux are used.
- It provide high finish welding surface.
- It can used to weld hard materials.
- Less welding defects occur due to whole process carried out in vacuum.
5.2 Disadvantages 缺点
- High capital or set up cost.
- High skilled labor required.
- Frequently maintenance required.
- Work pieces size is limited according to vacuum chamber.
- It cannot do at site due to vacuum.