Types and Applications of Electron Beam Welding Explained

Classification of Electron Beam Welding

According to the vacuum level of the workpiece environment, electron beam welding can be divided into high vacuum electron beam welding, low vacuum electron beam welding, and non-vacuum electron beam welding. Figure 1-3 shows the three basic types of electron beam welding.

Figure 1-3 Basic Types of Electron Beam Welding

a) High Vacuum Electron Beam Welding
b) Low Vacuum Electron Beam Welding
c) Non-Vacuum Electron Beam Welding
1— Electron Gun
2— Upper Gun Body
3— Gun Body Valve
4— Observation Window
5— Electromagnetic Lens
6— Deflection Coil
7— Welding Chamber
8— Workpiece

(1) High Vacuum Electron Beam Welding

High vacuum electron beam welding is carried out in a vacuum of 10-4~10-1 Pa. It has good vacuum conditions, the electron beam is rarely scattered, and it can ensure the protective effect on the molten pool, preventing the oxidation and burning of metal elements. It is suitable for welding of reactive metals, refractory metals, and workpieces with high quality requirements. It’s also suitable for precision welding of various complex-shaped parts.

The limitation of this method is that the size of the workpiece is restricted by the volume of the vacuum chamber. Moreover, vacuuming requires additional time, which affects productivity.

(2) Low Vacuum Electron Beam Welding

Low vacuum electron beam welding is carried out in a vacuum range of 10-1~10Pa. As shown in Figure 1-4, when the pressure is 4Pa, the maximum values of beam current density and its corresponding energy density are not much different from those at high vacuum. Therefore, the beam current density and energy density of low vacuum electron beam welding are also high.

Because it only needs to be vacuumed to a low vacuum, it reduces the vacuuming time, thus speeding up the welding process, improving productivity, and is suitable for welding large volumes of parts and for use on production lines. For example, low vacuum electron beam welding is often used for the assembly gears of automobile transmissions.

Figure 1-4 Distribution of Electron Beam Spot Beam Current Density at Different Pressures

(3) Non-vacuum Electron Beam Welding

In non-vacuum electron beam welding, the electron beam is still generated under vacuum conditions (≤10-1 Pa), and then it passes through a set of apertures, gas resistance channels, and several pre-vacuum small chambers, shooting onto the workpiece under atmospheric pressure. When the pressure increases to 7~15Pa, the power density of the electron beam decreases significantly due to scattering.

Under atmospheric pressure, the electron beam scattering is even stronger. Even if the working distance of the electron gun is limited within the range of 20~50mm, the maximum depth-to-width ratio of the weld can only reach 5:1. As the pressure increases, the divergence gradually increases, and the depth-to-width ratio of the weld decreases. At present, the maximum melting depth that non-vacuum electron beam welding can reach is 30mm.

The advantage of this method is that it does not require a vacuum chamber, so it can weld large size workpieces with high productivity. The mobile vacuum chamber or local vacuum electron beam welding methods that have emerged in recent years maintain the high power density advantage of vacuum electron beam welding without requiring a vacuum chamber. They have great potential in welding projects for large workpieces.

The technical characteristics and application ranges of different types of electron beam welding are shown in Table 1-2.

Table 1-2 Technical Characteristics and Application Ranges of Different Types of Electron Beam Welding

TypesVacuum Level/PaTechnical CharacteristicsApplicability
High Vacuum Electron Beam Welding10-4 ~ 10-1Acceleration voltage is 15~175kV, with a maximum working distance of up to 1000mm. The electron beam power density is high, the focus size is small, and the weld seam has a high depth-to-width ratio and quality. This process prevents the oxidation of molten metal. However, the vacuum system is complex, the time to create a vacuum is long (tens of minutes), the production rate is low, and the size of the welded pieces is limited by the volume of the vacuum chamber.Suitable for welding reactive metals, refractory metals, high-purity metals, and dissimilar metals, as well as for welding workpieces with high-quality requirements.
Low Vacuum Electron Beam Welding10-1~10Acceleration voltage is 40~150kV, and the maximum working distance is less than 700mm. There is no need for a diffusion pump, the focus size is small, the time to create a vacuum is short (within tens of minutes), and the production rate is relatively high. This process can be used with a partial vacuum chamber to weld large pieces, and the process and equipment have been simplified.Suitable for mass production, such as the welding of electronic components, precision instrument parts, inner and outer bearing rings, turbine partitions, gearboxes, combined gears, etc.
Non-Vacuum Electron Beam WeldingAtmospheric PressureThere is no need for a vacuum chamber, and the welding is performed under normal atmospheric pressure. The acceleration voltage is 150~200kV, and the maximum working distance is around 30mm. This process can weld large pieces, with a high production rate and low cost. However, the power density is relatively low, scattering is severe, and the weld seam depth-to-width ratio is less than 5:1. Some materials require inert gas protection.Suitable for welding large workpieces, such as large containers, missile shells, boiler heat exchangers, etc. However, the depth of penetration in a single weld does not exceed 30mm.
Partial Vacuum Electron Beam WeldingDetermined Based on RequirementsThis is used for mobile vacuum chambers or for creating a partial vacuum at the welding part of the piece for welding.Suitable for welding large workpieces.

Application Range of Electron Beam Welding

Due to the significant welding penetration, excellent weld seam performance, minimal welding deformation, high welding precision, and high production rate of electron beam welding, it has been widely applied in various industries such as aerospace, automotive manufacturing, pressure vessels, power and electronics.

It can achieve the welding of special difficult-to-weld materials. Currently, electron beam welding can be applied to the following materials and structures.

(1) Weldable Materials

In the case of electron beam welding in a vacuum chamber, apart from materials containing a large number of high vapor pressure elements, generally all metals that can be fused welded, such as iron, copper, nickel, aluminum, titanium, and their alloys, can be used in electron beam welding. In addition, electron beam welding can also weld rare metals, reactive metals, refractory metals, and non-metallic ceramics.

It can weld dissimilar metals with significant differences in physical properties such as melting point, thermal conductivity, and solubility. When welding heat-treated strengthened or cold-work-hardened materials, the mechanical properties of the joint do not change. The adaptability of various metal materials to electron beam welding is shown in Table 1-3.

Table 1-3: Adaptability of Various Metal Materials to Electron Beam Welding

WeldabilityTypes of Metal Materials
Good WeldabilityLow Carbon Steel (Fully Killed), Austenitic Stainless Steel, Non-Hardenable Aluminum Alloys, Copper Alloys (Zinc-Free), Titanium Alloys, Tantalum, Niobium, Silver, Gold, Platinum, Lead, Uranium, and other Pure Metals
Average WeldabilityLow Carbon Steel (Semi-Killed), Medium Carbon Steel (Free-Cutting Steel), Low Alloy Steel, High-Temperature Nickel-Based or Solid Solution Alloys, Martensitic Stainless Steel, Zirconium Alloys
Poor WeldabilityHeat-Treated Tempered Steel, High-Strength Alloy Steel, High-Temperature Iron-Based or Precipitation Hardening Alloys, Hardened Aluminum Alloys, Beryllium, Molybdenum, Magnesium, Tungsten, etc.
Non-weldableLow Carbon Steel (Boiling Steel), Zinc-Containing Copper and Aluminum Alloys, Non-Demagnetized Steel

(2) Structure and Dimensions of the Weldments

Electron beam welding can single-pass weld non-alloy steel with a thickness exceeding 100mm or aluminum plates with a thickness exceeding 400mm, without the need for groove opening and the use of filler metals. It can also weld thin pieces with a thickness less than 2.5mm (even as thin as 0.025mm), as well as weldments with significantly different thicknesses.

During vacuum electron beam welding, the shape and size of the weldments must be controlled within the allowable range of the vacuum chamber volume; non-vacuum electron beam welding is not subject to this restriction, allowing for the welding of large welding structures.

However, the distance from the bottom of the electron gun exit to the surface of the weldment must be controlled between 12-50mm, and single-side welding generally does not exceed a thickness of 10mm.

(3) Weldments with Special Requirements or Structures

Electron beam welding can weld sealed parts that need to maintain internal vacuum, weldments near thermosensitive components, parts with complex shapes and precision, and it can also perform welding on weldments with two layers or multiple layers of joints simultaneously. In this case, the joint layers can be spaced several tens of millimeters apart.

Table 1-4 lists some application examples of electron beam welding.

Industrial FieldsApplication Examples
AerospaceJet engine parts, landing gears, cabin segment frames, precision transmission parts, fire screen boosters, high-pressure gas cylinders, fire screen engine parts, etc.
Nuclear Energy IndustryFuel components, reactors, pressure vessels and pipelines, accelerator parts, fuel rods, brackets, guide vanes, evaporators, etc.
Weapons IndustryRadar waveguides, balance arms, diesel engines, turbocharger turbines, etc.
Automotive ManufacturingTransmission gears, planetary gear frames, rear axles, cylinders, clutches, engine turbocharger turbines, etc.
ShipbuildingNaval engine, ship machinery repair, propeller spiral, torpedo components, submarine hulls.
Electronic ComponentsIntegrated circuits, sealed packaging, magnetic core memories of electronic computers, sensor components, micro relays, micro components, thin-film resistors, electron tubes, heaters, etc.
Energy and PowerCommutator segments for electric motors, bimetallic commutators, turbine rotors, turbine stators, turbine partitions, boiler valve bodies, etc.
Petrochemical EquipmentCopper cooling nozzles for steelmaking furnaces, pressure vessels, spherical tanks, heat exchangers, circular transmission belts, welding of pipes and flanges, etc.
Heavy MachineryThick plate welding, welding of ultra-thick plate pressure vessels, etc.
Medical EquipmentTitanium alloy brackets, artificial joints, artificial skeletons, etc.
RemanufacturingRepair and restoration of defective containers, crack repair welding, reinforcement welding, build-up welding, etc.

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