What Is Electron Beam Machining?

Electron beam processing is the processing of materials using the thermal or ionizing effects of high-energy converging electron beams. The thermal effect of electron beam can be used to perform surface heat treatment, welding, etching, drilling, smelting, or directly sublimate the material. Electron beam exposure is a processing method that utilizes the effects of electron beam radiation.

The thermal effect of electron beam can be used to perform surface heat treatment, welding, etching, drilling, smelting, or directly sublimate the material. Electron beam exposure is a processing method that uses the effects of electron beam radiation (see

Electron beam power density up to

At W / cm2, the material where the electron beam strikes is locally melted; when the electron beam moves relative to the workpiece, the molten metal is continuously solidified. This phenomenon can be used to weld materials. Electron beam welding has the characteristics of deep penetration, and the aspect ratio of the weld can reach 20: 1 or even 50: 1. This is because when the power density of the electron beam is large, the power given to the welding area by the electron beam is much larger than the power guided away from the welding area. Using this feature of electron beam welding can realize a variety of special welding methods. Electron beam can be used to weld almost any material, including refractory metals (W, Mo, Ta, Nb), active metals (Be, Ti, Zr, U), super alloys and ceramics. In addition, the position of the electron beam welding is precise and controllable, the welding quality is high, and the speed is fast. It can be used as precision welding in nuclear, aviation, rocket, electronics, automotive and other industries. In heavy industry, the power of the electron beam welding machine has reached 100 kilowatts, and it can weld stainless steel plates with a thickness of 200 mm. When welding large workpieces, a large-volume vacuum chamber must be used, or a movable partial vacuum must be formed at the welding place.

Use the focusing method to obtain a very fine power density of

The electron beam of W / cm bombards the fixed points on the surface of the material periodically, and the ratio of the bombardment time and the rest time of the electron beam is appropriately controlled, so that the material at the bombardment site can be evaporated quickly and the surrounding materials can be avoided from melting. Etch, drill or cut. Compared with electron beam welding, the electron beam used for electric beam etching, drilling and cutting has a higher power density and a shorter action time. The electron beam can drill holes with a diameter of 1 to several hundred micrometers in a thin sheet of any material with a thickness of 0.1 to 6 mm, and can obtain a great depth-to-aperture ratio. For example, a diameter of 0.3 mm on a jewel bearing with a thickness of 0.3 mm 25 micron pores. Electron beams are also suitable for drilling large numbers of holes at high speeds on thin sheets, such as gas turbine blades.

The electron beam smelting method was invented in 1907, but it was not used to smelt refractory metals until the 1950s, and later it was used to smelt live metals (such as Ti ingots) and advanced alloy steels. Electron beam heating can keep the material in a molten state in vacuum for a long time, realize the degassing of the material and the selective evaporation of impurities, which can be used to prepare high-purity materials. Electron beam heating is one of the effective ways to convert electrical energy into thermal energy. About 50% of the power is used for melting and maintaining liquefaction. Electron beam smelting machines with a power below 60 kW can use direct heating tungsten wire as the cathode of the electron gun. The electron gun of the smelting machine above 60 kilowatts uses an indirect heat block tantalum cathode, which is heated to 2700K by the electron bombardment of the tungsten wire behind it, and can have an emission current density of several amps per square centimeter. The acceleration voltage of the electron gun is about 30 kV, so it is easy to prevent electrical breakdown and weaken X-ray radiation. The electron beam is magnetically focused and deflected. The electron gun and the melting chamber are evacuated by different vacuum pumps, and the vacuum degree is maintained at about 10 and 10 Pa, respectively. In the 1980s, 600 kilowatt-level electron guns were produced. For more power, several electron guns can work at the same time. Using electron beam heating, 100 tons of billet can be cast.

According to the generation principle of electron beam current, electron beam processing has the following characteristics: 1) the beam spot emitted by the electron beam emitter is extremely small and controllable, which can be used for precision processing; 2) for various different processed Material, its efficiency can be as high as 75% to 98%, and the required power is low; 3) the energy generation and supply source can be accurately and flexibly moved, and has high processing productivity; 4) the energy beam can be easily controlled , Realize processing automation; 5) the use of equipment has a high degree of flexibility, and can use the same equipment for electron beam welding, surface improvement treatment and other electron beam processing; 6) electron beam processing is performed in a vacuum state, the environment is almost No pollution ^[1] ; 7) E-beam processing has high requirements on the vacuum degree of equipment and systems, which makes electron beam processing expensive, which limits its application in production to a certain extent.