Cambridge Vacuum Engineering

630 Silver St Suite 7A
Agawam,  MA  01001-2940

United States
413-789-4600
http://www.camvaceng.com

• Booth: C13212

 Press Releases

• Ebflow Reduces 200mm Steel Welding Time to 3 Hours (Aug 23, 2022)

  Cambridge Vacuum Engineering (CVE)’s local vacuum electron beam welding system, Ebflow, welds steel nuclear pressure vessel of 200mm thickness in under 3 hours, revolutionising the assembly and welding of thick-sections for pressure vessel manufacture.

  OVERVIEW

  CVE’s ground-breaking local vacuum electron beam (EB) welding technology, Ebflow, achieved a continuous, fully penetrating weld in a 200mm thick, three-metre diameter demonstrator vessel section in low alloy steel.

  The weld was produced in a nuclear grade steel typical of that used in some proposed small modular reactor (SMR) designs, with a circumferential weld length of ~10m.

  The joint was completed in a single pass, reducing the predicted weld time from several months, using conventional arc welding, to ~140 minutes using Ebflow.

  This weld represents a breakthrough in the industrialisation of Ebflow for fabrication of thick-section materials, not only for the nuclear industry, but also for other applications – such as offshore wind and hydrogen production – transforming the global capacity to produce zero-carbon energy.

  PROJECT BACKGROUND

  The project is a continuing collaboration between CVE, Sheffield Forgemasters, TWI, Arc Energy Resources, NAMRC, University of Sheffield, University of Cambridge, and University of Manchester. There was also a steering committee consisting of the Ministry of Defence, Rolls-Royce submarines and SMR divisions, the UK Atomic Energy Authority and Cavendish Nuclear.

  The Department for Business, Energy, and Industrial Strategy (BEIS) part-funded the project under the £26m Advanced Manufacturing and Materials Programme within the BEIS Energy Innovation Programme. Engagement with the Office for Nuclear Regulation and Environment Agency was also instigated by BEIS as the project progressed.

  After years of highly-advanced engineering and process development, CVE has led Ebflow to market, achieving near commercial exploitation for pressure vessel applications, as well as offshore wind foundation structures.

  

  Figure 1. CVE Project Team.

  ACHIEVING A WELDING BREAKTHROUGH

  CVE and Sheffield Forgemasters carried out the factory acceptance testing (FAT) of the welding system, which verifies that the equipment was built and operating in accordance with design and safety specifications, at CVE’s site, before shipping to Sheffield.

  Sheffield Forgemasters’ aim to incorporate Ebflow as an advanced fabrication technique, offering significant savings on both processing time and cost, over the traditional arc welding methods, which typically can take months and includes numerous stages of non-destructive testing (NDT).

  Notably, the weld was performed without pre-heat or consumables and with an overall energy consumption of less than 100kWh. This represents a considerable saving in CO2 emissions, in comparison with to more conventional arc welding practice, which requires ~1,000kWh arc energy and pre-heat of ~180oC before welding can begin.

  

  Figure 2. 200mm single pass full penetration weld in SA 508 Gr. 3 Cl.1 steel.

  QUALIFICATION AND WELD PERFORMANCE ASSESSMENT

  The welded assembly was examined using several ultrasonic test methods including conventional pulse echo ultrasonic testing (UT) and time of flight diffraction (TOFD). TOFD is particularly well suited to the vertical EB weld joint preparation, resulting in a high level of accuracy in size and position of weld imperfections.

  The tests reported that the weld zone was free from any reportable indications, as defined by the ASME acceptance criteria.

  Test pieces representative of the welded assembly will be subjected to rigorous mechanical testing at Sheffield Forgemasters after appropriate heat treatment. It is intended that a sample will be removed and introduced into a campaign to assess the influence of exposure to the high levels of radiation anticipated in service.

  Determination of magnitude and distribution of residual stresses both as-welded and after heat treatment will be carried out using a contour method.

  

  Figure 3. Weld cap bead.

  

  Figure 4. Weld root bead.

  GROUND-BREAKING TECHNOLOGY

  Ebflow combines the use of a local vacuum system and a high power electron gun that produces a high intensity electron beam. The beam penetrates the full thickness of the vessel and fuses the two components prepared with a close-fitting square butt preparation to produce a welded joint in a single pass.

  The local vacuum approach allows the EB process to be applied to thick-walled large vessels, which cannot be practically contained within a vacuum chamber, and can operate at significantly higher vacuum pressure than in-chamber EB welding systems. This results in an improved process tolerance to cleaning and outgassing when welding big structures.

  The Ebflow system comprises:

  • A patented high power electron beam generator designed for long duration welding campaigns with consistent, reliable welding performance, particularly for very thick section materials.
  • Local vacuum chamber and pumping system with minimum volume designed for rapid pumping (5 minute pump down in the FAT, compared to hours for conventional in-chamber systems) and minimal energy consumption compared to in-chamber systems as only mechanical pumps are required.
  • Several configurations of local vacuum deployment for vessels and other structures including the use of vacuum jackets for different sized vessels, sliding local vacuum seals for modular construction of components and internally mounted guns for heavy wall pressure vessels.
  • Beam quality measuring station that permits characterisation of the welding beam before and after welding to demonstrate consistency and reliability and provide a quality assurance measure.

  In addition, all electrical data is monitored continuously and captured, so that it can be stored and uniquely linked to the welded part, providing a through life record of the welded component.

  The resulting weld is inspected in real-time with a temperature resistant ultrasonic test method to provide immediate information on weld quality indication where detailed examination may be needed on completion of welding. The outcome is in line with the industry 4.0 data management approach.

  

  Figure 5. Dimensional measurement.

  APPLICATIONS AND EXPLOITATION

  Ebflow has the potential for exploitation in many of the global SMR programmes for primary structures and associated pressure containing plants.

  It also has applications in low carbon energy, hydrogen production and storage, chemical and pressure plant industries.

• Welding Electrical Conductors for Electric Vehicles (Aug 23, 2022)

  REMOVING THE BOTTLENECK IN WELDING OF ELECTRICAL CONDUCTORS FOR ELECTRIC VEHICLES

  The need to increase the rate of joining electrically conducting components within the electric vehicle sector has become of critical importance as it is emerging to be the bottleneck of manufacturing.

  The components of significance are electrical connectors and wires which can be sub millimetre thick foils or several millimetre thick rectangular section wires.

  The material most used for these components is copper due to its low cost, high electrical conductivity, and plentiful availability. The high thermal conductivity of copper and low thermal input required for the components in proximity of the joining processes leads most manufacturers to choose laser welding for their high throughput manufacturing.

  LASER WELDING OF COPPER

  Laser welding of copper is challenging primarily due to the wavelengths of commercially available lasers typically being red and infrared, these do not easily couple into copper due to the high reflectivity.

  The reflectivity also contributes to limit the beam angle of incidence, meaning the process must integrate mechanical repositioning of the welding head.

  The short focal depth of field of a welding laser also creates a high failure rate in the manufacturing, it requires high precision of machines in the manufacturing line to ensure the parts are prepared and held accurately at the correct working distance so that the weld executes correctly, repeatably.

  These drawbacks experienced when laser welding copper are issues that are not relevant to electron beam welding.

  

  Figure 1. Motor stator with 192 welds.

  

  Figure 2. Copper hairpins.

  ELECTRON BEAM WELDING

  Electron beam welding suffers no reflectivity issues to prevent it coupling into materials, the focal depth is multiple times longer and is rapidly adjustable during the process as the focusing is performed by electromagnetic coils.

  The rapid speed of beam positioning by electromagnetic coils and commercial availability of significantly higher beam power supplies are the most important advantages in allowing electron beam to process hundreds of copper welds per minute.

  The rapid rate of processing means the seconds taken for the vacuum chamber to evacuate ready for welding become negligible, furthermore, the fact that the welds are performed in a vacuum chamber mean the resulting weld has no porosity and impurities in the connection, giving the best electrical performance and vehicle efficiency.

  FURTHER INFORMATION

  We build electron beam welding machines to order, and options include custom and precision work handling, vacuum systems tailored to specific process needs and productivity, wire-feed, automatic joint finding, backscattered electron imaging, automatic focus, alignment and stigmator adjustment, high-speed data capture, beam probes and QA reporting.

  This paper was presented at the 75th International Institute of Welding (IIW) Annual Assembly and Conference in Tokyo, Japan. Doc.IV-1506-2022 Removing The Bottleneck In Welding Of Electrical Conductors for Electric Vehicles, Alex O’Farrell, UK.

• Electron Beam vs Laser Welding (Aug 23, 2022)

  ELECTRON BEAM VS LASER WELDING EXPLAINED

  Electron beam welding (EBW) and laser beam welding (LBW) fall under the same category of power beam welding. Despite this, there are some fundamental variations between each welding process and its applications. This article, electron beam vs laser welding, will explore the similarities and differences between electron beam welding in a vacuum and laser welding with a shielding gas – helping you decide which welding machine is most suitable for your application.

  Overview

  1. What is the difference between electron beam and laser welding?
  2. Vacuum environment
  3. Shielding gas
  4. Component size
  5. Welding speed
  6. Weld quality
  7. Single pass welding of thick sections
  8. Automated process
  9. Wearing components
  10. Power efficiency
  11. Cost comparison
  12. Turnkey solutions

  WHAT IS THE DIFFERENCE BETWEEN ELECTRON BEAM AND LASER WELDING?

  EB welding uses a finely focused stream or beam of electrons, whereas laser welding uses monochromatic coherent light (photons). In both cases, the kinetic energy of the electrons or photons is turned into heat energy when they hit the surface of the metal.

  Electron beam welding is lesser-known than laser welding out of the two techniques. And this is not because it is inferior to laser but mostly because of people’s perceptions. Many have seen Star Wars, James Bond, and a host of other hi-tech sci-fi films that have been present on our screens over many years. Culture, coupled with the high profile many respected institutions have been putting forward, has unfortunately meant that the electron beam process has taken a back seat.

  VACUUM ENVIRONMENT

  EBW takes place in a vacuum chamber. This aids the weld quality, as it tends to pull contamination away from the weld pool. Welding in a vacuum also results in the operator not becoming exposed to the hazardous welding environment.

  Conventional laser welding takes place at atmospheric pressure, with additional shielding gas. However, you can laser weld in a vacuum, which significantly increases the depth of the weld.

  SHIELDING GAS

  Shielding gas is not required for electron beam welding as the process takes place in either a low or high vacuum.

  Laser welding at atmospheric pressure requires a shielding gas; it is an expensive but essential consumable. Fume extraction may also be an issue.

  COMPONENT SIZE

  The vacuum chamber on an electron beam welder restricts the component size, as parts must fit within it. Chamber volumes are kept to a minimum to reduce evacuation times.

  Laser welding with a shielding gas can accommodate any component size, as there is no vacuum chamber. Furthermore, you can use fibre optic delivery systems. This allows the welding head to be remote from the power source.

  WELDING SPEED

  Electron beam welding can achieve deep penetration welds over a wide range of speeds, whereas laser welding with a shielding gas always requires high welding speeds due to the plume of metal vapour that forms.

  WELD QUALITY

  Electron beam welding produces high-quality weld joints in a wide variety due to the inert atmosphere, which creates a very stable and repeatable environment. Joint finding and imaging using backscattered electrons are advanced options that can further increase the weld quality.

  Laser welding needs a shielding gas, typically nitrogen or argon, to prevent oxidisation of the weld area and ensure the stability of the weld pools. Real-time monitoring of weld depth and quality are expensive options, but they can improve weld quality.

  SINGLE PASS WELDING OF THICK SECTIONS

  Electron beam welding in a vacuum can achieve 20mm penetration in stainless steel when using 6kW beam power at 60kV, achieving up to 300mm thicknesses can in a single pass.

  Laser welding with shielding gas can achieve approximately 1kW per mm depth of weld in steel. However, limited availability and high cost of high-power laser systems is a factor.

  AUTOMATED PROCESS

  Electron beam welding can be highly automated with the evacuation time of the chamber in a few seconds. A typical cycle time in the automotive industry is 40 seconds per component. But time is dependent upon the length and complexity of the weld.

  Laser welding can also be highly automated with high production rates, in addition to there being no waiting time for chamber evacuation. Beam splitting and beam sharing are also possible.

  WEARING COMPONENTS

  The main wearing component within the electron beam welding process is the filament. Metal vapours can deposit on the viewing prism, but this has no effect on weld characteristics, and you can clean the prism.

  During laser welding, a metal vapour that the welding process produces can coat the optical devices such as mirrors and lenses, leading to a drop in beam power.

  POWER EFFICIENCY

  Electron beam welding is a very efficient process, typically converting 85% of electrical power.

  Laser welding typically converts up to 40% when using modern fibre and disc lasers.

  COST COMPARISON

  Electron beam welding is more expensive than Tungsten inert gas (TIG) and metal inert gas (MIG) welding.

  Laser welding is also more expensive than TIG and MIG, with prices increasing steeply with increasing power.

  TURNKEY SOLUTIONS

  Electron beam systems include a chamber, fully automatic vacuum system, work handling, and control system.

  Laser welding usually requires a systems integrator to provide an integrated solution, as the laser source does not include a control system or work manipulation.

  CONCLUSION

  The best process to use, electron beam vs laser welding, is often dependent on the given welding application. If you are not sure which system is best for your application, please get in touch! Our machines are built to order and manufactured at our Cambridge Headquarters. With 60-years of process know-how in providing turnkey solutions, we can find the right solution for your application.

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