Electron Beam Welding and its Applications
The heat of welding distorts workpiece materials and alters their properties. Electron beam welding (EBW) minimizes these adverse impacts and provides a way of joining otherwise unwieldable materials and parts.
Impro Aerotek has EBW welding capabilities, which complement our other precision machining services. This blog explains what EBW is, its advantages, and when you might want to specify it or when we might recommend it.
The Problem of the Heat Affected Zone
Welding entails local melting of two adjacent workpieces in a way that fuses them together. Arc welding is the most widely used method, although laser welding is becoming more common.
A problem with these processes is that heat modifies material properties in a region around the weld. This heat affected zone (HAZ) results from thermal conductivity causing the heat of the arc to spread through the material. High temperatures can alter material properties like strength and ductility, and expansion leads to distortion. This happens as the weld pool cools and solidifies, which locks the workpiece into its expanded condition.
Increasing Power Density Shrinks the HAZ
HAZ issues like distortion are reduced by minimizing the energy put into the workpieces. At the same time, local melting is still needed to fuse them together.
EBW achieves this by using a beam of smaller diameter and high power density than laser welding. Putting more energy into a smaller area results in a higher depth-to-width ratio than is achievable with other welding processes. This reduces the time needed at high temperatures, which results in a smaller HAZ with less impact on material properties and less expansion and distortion.
The EBW Process
In EBW heat is delivered to the weld zone in the form of the kinetic energy of a stream of high velocity electrons. These are produced by an electron gun, similar in concept to the source at the rear of a cathode ray tube in an old TV. The electron gun has a filament, which forms the cathode, and a doughnut-shaped anode which attracts the electrons as they boil off the filament.
The electron beam passes through the center of anode, and then through a ring of magnetic focusing coils. These narrow the beam diameter to approximately 0.2mm just before it strikes the target.
EBW is performed in a vacuum to prevent any beam scatter. This also improves weld quality by eliminating oxide formation and weld embrittlement. However, it means placing the workpiece in a chamber where a vacuum is pulled prior to welding.
Owing to the need for vacuum and the high voltages involved, EBW machines operate with a high level of automation. This results in good part-to-part consistency.
When to Specify EBW
The cost and complexity of EBW machines make it a niche process used only when other welding processes can’t achieve the required results. It can also be viewed as a process for enabling designs that could not otherwise be manufactured. EBW is the preferred welding method in situations where:
- The pieces being joined are very thick (>100mm (4”))
- The pieces being joined are very thin
- Dissimilar metals with different melting points are being joined
- High melting point metals are being joined
- It’s essential to minimize distortion
- There are heat-sensitive components or materials very close to the weld
- The weld must be of the highest quality achievable
Applications for EBW
EBW is used to join components in industries from industrial and scientific equipment to aerospace and electronics. A partial list of products made by EBW includes:
- Bimetallic saw blades
- Transmission components
- Titanium and superalloy aerospace components
- Pressure vessels
- Electronic components
Ask Impro About EBW
Electron beam welding complements our precision machining services by enabling high quality, low distortion joining of CNC machined components. Not every job or workpiece needs EBW but for some it’s the only way of achieving a consistent, high quality joint.
If your designs need welding, bring them to us. We’ll use our experience with EBW to advise on an appropriate welding process. Contact us to start that discussion.