In-Chamber Electron Beam Welding

Electron beam (EB) welding is a fusion welding process whereby electrons are generated by an electron gun and accelerated to high speeds using electric fields.

This high speed, precisely controlled stream of electrons is tightly focused using magnetic fields and directed at the materials to be joined. The beam of electrons creates kinetic heat as it impacts with the workpieces, causing them to melt and bond together. The localised nature of the beam means that there is a minimal heat affected zone and the process also requires less total heat input when compared to conventional arc welding methods such as TIG welding.

Electron beam welding is performed in a high vacuum environment as the presence of gas can cause the beam to scatter. Due to it being a vacuum process, and because of the high voltages used, this welding method is heavily automated and computer controlled. As a result, specialised fixtures and CNC tables are used for moving the workpieces inside the welding vacuum chamber, making it a highly repeatable process.

Advantages of In-Chamber Electron Beam Welding

In-chamber electron beam welding offers a number of advantages for industry, including:

Minimal distortion: The small heat-affected zone, created as a result of the high energy density and focused beam, minimises distortion and thermal stress
Low heat input: Because the process applies heat to a very small area, it is ideal for welding delicate materials and heat-sensitive components
High-quality welds with good penetration: The process creates clean, high-strength welds with deep penetration, while the vacuum environment prevents oxidation and contamination
High speed: Electron beam welding can achieve high welding speeds
Precise control: Being able to precisely control the electron beam makes this process suitable for intricate and complex designs
Wide material compatibility: The process can join both similar and dissimilar materials, including chemically active metals and those with high thermal conductivity, often without needing filler material or flux, making it suitable for a range of welding applications
Repeatability: The automatic control of welding parameters ensures consistent and reproducible weld quality

In-Chamber Electron Beam Welding at TWI

TWI provides in-vacuum-chamber electron beam (EB) welding and processing, such as brazing, as well as a range of related products and services.

Conventional EB welding takes place within a vacuum chamber, taking advantage of the clean, vacuum environment to produce high-integrity, high-productivity and low-distortion welded joints. Electron beam welds are autogenous and hence result in the parent metal composition in the joint.

With decades of experience in electron beam welding, our experts have been instrumental in a number of industry breakthroughs including the design and manufacture of the electron beam welding gun that created the first-ever autonomous weld in space.

Track Record

TWI has a strong track record in the development of EB processing, including:

1960s – Early 30kV EBW machine at TWI
1970s – High power electron guns (75kW)
1980s – Charged particle collection innovation and patent
1990s – Reduced Pressure EB
2000s – EB Surfi-Sculpt^® - first demonstration
2010s – Novel radio-frequency-excited plasma electron beam source
2020s – First autonomous weld created in space using electron beam gun designed and manufactured at TWI

Applications and Services

We offer a range of services, including:

Welding and brazing
Welding feasibility advice
Procedure qualification and development
Low volume, very high value adding, specialist production welding
Quality assurance (BeamAssure^TM)
Surface engineering technologies (Surfi-Sculpt®)

TWI is active in the development of new capability and the deployment of established in-chamber EB welding at a range of power levels, including:

High power – welding of thick-section material using a high accelerating potential (up to 175kV) and high beam power (up to 100kW) to penetrate steel up to 300mm thick, while achieving a stable weld keyhole in sections of 200mm or more. Application fields are often in the power sector, nuclear waste encapsulation and for value-adding in primary manufacture. Stainless and carbon-manganese (C-Mn) steels as well as copper and nickel-based super alloys are commonly welded
Medium power – the main users of medium power EB welding are the aerospace and automotive sectors. Here weld penetrations are typically between 1 and 20mm. Welds in turbine engine drums, control actuators, heat exchangers, gear clusters and turbochargers are common; many oil and gas industry instrumentation assemblies are also welded/hermetically sealed using the process, which is beneficial as the resulting welds, having been made with a very localised heat source that is consistent through the thickness being welded, typically have low distortion and allow parts to be welded at or very close to final size/geometry
Low power – EB welding machines may be configured to produce very fine, intense beams with spot sizes at the workpiece as small as 20µm. These beams may be used effectively to create very small welds, cuts, holes, and other features. Low power welding, as at higher powers, is a keyhole process; the subtractive processes are achieved through the use of pulsed beams which ablate and vaporise material in a controlled manner

Equipment

TWI facilities include a number of commercial and unique electron beam welding machines, which we can use to assist our Industrial Members as if it was their own equipment. Our electron beam machines have a range of accelerating voltage and power (from 60kV, 4kW up to 175kV, 100kW) and vacuum chamber sizes (from less than 1m³ up to more than 36m³). This enables processing of both small and large components with the capability of welding in excess of 200mm steel sections.

Core Research Programme (CRP) and Joint Industry Projects (JIP)

Core Research

Each year the TWI Core Research Programme (CRP) addresses challenges on behalf of our Industrial Members as well as developing specific technologies and processes. Each of the projects under the CRP is focussed on engineering, materials or manufacturing technologies.

Joint Industry Projects

TWI also conducts Joint Industry Projects (JIPs) that bring together groups of Industrial Members to share the cost of research activities in areas of mutual industrial interest, gaining exclusive access to the outcomes. These projects cover a broad range of topics.

Capabilities

Thickness range ( <0.1 to>200mm)

Single pass welding

Autogenous process (normally no filler)

Low heat input and distortion

Narrow, high aspect ratio, heat affected zone (HAZ)

High speed and productivity

Up to 100kW beam power

Non-contaminating atmosphere

Joins most metals and dissimilar combinations

Modelling and practice

Large welding chamber machines

Standards interpretation and application

Monitoring, quality assurance (QA) and calibration know-how

To find out more, and see how we can help solve your in-chamber electron beam welding challenges, please email contactus@twi.co.uk.