Glossary

A

Acceleration voltage

High voltage potential between cathode and anode which accelerates the electrons into an electron beam.

Additive manufacturing

EBOADD additive manufacturing is one of the most future-oriented manufacturing technologies. With electron beam technology, highly complex wire-based metallic workpieces can be produced cost-effectively and flexibly in just one process step. The workpieces are made up directly from the CAD data of the design or development department in EBOCAM electron beam machines developed for this purpose.

Air-lock machine

Electron beam welding machine with a separate chamber partition for loading/unloading in order to eliminate the evacuation time by operating parallel to processing time.

Anode

Grounded electrode within the electron beam generation system, forming an electrical potential with the cathode.

Atmosphere

In contrary to almost all other welding methods EB welding does not work on atmosphere but under vacuum. The NonVac welding process (NVEBW) is an exception.

Automation

EBW machines run fully automatic. For mass production they can be automatically linked to other equipment for pre and post electron beam process operations.

B

Bead on plate weld

Simulated EB welding run into material with no joint.

Beam adjustment

Magnetic alignment of the electron beam axis relative to the focus coil axis centre-line.

Beam current

The measure of the quantity of charge (ie: number of electrons), usually expressed in units of milliamperes (mA), that flow per unit time in an electron beam.

Beam energy

Kinetic energy of the electrons impinging the workpiece; a product of the elementary charge and the accelerating voltage. Sometimes confused with the term – electron beam power.

Beam generator

Source of an electron beam.

Beam power

The electron beam power is the product of beam current (mA) and high voltage (kV), measured in kilowatts (kW).

Beam profile

Envelope of the electron beam as it traverses its way from the beam generator to the workpiece. Typical are a beam waist extending over several millimeters (highest power density) and defocused areas above and below these. The radial geometry of the power density distribution, which should ideally correspond to a Gaussian distribution, is of particular importance.

C

Cathode

Part of the beam generating system of the electron beam generator, from which free electrons are emitted due to its high temperature. These electrons are then formed into a beam. Typical cathode materials are tungsten and Lanthanum hexaboride. A difference is made between direct heating of the cathode (by current flow) and indirect heating (by primary electron bombardment).

Chamber machine

Basic type of an electron beam welding machine having a suitably designed working chamber which can accessed by an opening and closing door.

Cleaning

Any kind of contamination of the parts to be electron beam welded will adversely affect the weld quality; therefore cleaning prior to welding is an essential step.

Consumption

The costs for the use of electron beam technology are defined as the consumption of electrical energy and compressed air, the replacement of cathodes, vacuum seals and pump oils during maintenance work. Electron beam welding is characterized by extremely moderate overall consumption costs.

Control

With the control of an electron beam machine, a fully automatic operation and programmed process flow is possible. In most cases, CNC controls are used, but for simpler applications as well as PLCs.

Cosmetics

Shallow welding run (with adapted parameters) to reduce or smooth-the crown or root part of the penetration weld.

Cycle time

Total time to perform a complete electron beam machine’s work-cycle, independent of the number of parts processed in doing so.

D

Deep welding effect

The extreme high-power density of the electron beam not only melts the workpiece metal but also evaporates it locally and forms a key hole. By this means the beam penetrates into the material up to a depth controlled by the parameters used. In moving the beam along the path, a deep weld is performed from the solidifying the molten material behind the key-hole.

Deflection

The beam of electrons can be deflected by magnetic (and/or more seldom electric) fields which are regulated by the machine’s control.

Deflection grid

Digital array of deflection positions which the electron beam can target on the workpiece.

Deflection pattern

Digital or analogue figure which can be transposed by electron beam onto the workpiece.

Deflection system

A system of magnetic coils and controlled constant current sources which produce static or dynamic electron beam deflection movement.

Deformation

In EB technology, highly intense energy input and the optimally parallel flanks of the seam profile reduce weld distortion to a minimum. This means that the component does mostly not have to be reworked after welding.

E

EB

Abbreviation for electron beam (English) or Elektronenstrahl (German)

EB brazing

Abbreviation for electron beam brazing

EB drilling

Abbreviation for electron beam drilling

EB generator

Abbreviation for electron beam generator

EB machine

Abbreviation for electron beam brazing

EB treatment

A short form for electron beam processing in electron beam technology, e.g. electron beam welding, electron beam drilling, electron beam perforating.

EB welding

Abbreviation for electron beam welding

Electron

Elementary particle having a mass of 9.1 x 10^-28 g and carrying a negative electrical charge of 1.6 x 10^-19 As.

Electron beam

Particle beam produced by an electron beam generator to process metallic materials.

Electron beam brazing

Fusion brazing by using the heat from an impinging electron beam.

Electron beam drilling

When the deep-welding capillary completely penetrates a sheet metal and then hits an underlying detonative substance (not an explosive, but a material with a low melting point), the melt is ejected at the top and a hole remains. This will work for thin and thicker wall thicknesses; the maximum hole frequencies for electron beam drilling depend on this, but can be several thousand holes per second.

Electron beam generator

Component of an electron beam machine for beam generation and shaping. In addition to the beam generating unit, the EB generator includes focusing and deflection systems, a high-vacuum pump system and an optical system for observing the workpiece and the process. The high voltage is supplied via an insulator. The EB generator can be mounted stationary or movable outside on the walls or on the ceiling of the working chamber of the electron beam machine. For large chambers, it can be mounted on the inside on a movement system.

Electron beam hardening

A special process to locally transform the surface by means of an electron beam – with the objective of increasing the hardness (especially without melting the surface). Self-quenching is performed without any additional cooling process.

Electron beam machine

Electron beam machine for processing with the electron beam; the design is determined by the concrete task(s).

Electron beam treatment

A generic term for all types of thermal processing of a workpiece with the electron beam. This includes electron beam welding, electron beam surface modification, electron beam drilling and other.

Electron beam welding

The most commonly used method of electron beam processing in EB technology. Typical is the deep welding effect. It enables to join large material cross-sections in a single layer. The joining partners are mainly welded without gaps by melting both contact zones. Weld metal is formed with a cross-sectional profile that can have very parallel flanks and a depth/width ratio of up to 40:1. Due to this seam profile and the overall minimal energy input, the resulting welding distortion is extremely low. This makes it possible to weld finished individual parts in the EB welding machine.

Energy input

The energy input in all types of electron beam processing is caused by the braking of the beam electrons in the material (metal), whereby the kinetic energy is transformed into heat. Compared to all other welding processes, the energy input is lowest in electron beam welding - related to a defined joining cross section.

Evacuation

Because the electron beam can only be generated under vacuum, the EB generator has to be evacuated (less than 10^-4 mbar). A vacuum is also required in the working chamber of the electron beam welding machine (10^-2 to 10^-6 mbar depending on the task). Mechanical pumps, oil diffusion pumps or cryopumps are used for vacuum generation.

Evacuation time

Time to achieve the necessary operating pressure for the electron beam treatment. This can be only a few seconds for an electron beam machine for mass production or many minutes for a large chamber electron beam welding machine. The evacuation time can be parallelised to the main time by vacuum locks.

F

Fast beam deflection

The EB technology EBO Jump is the so-called "fast beam deflection" developed by Steigerwald Strahltechnik. In comparison to the low-frequency deflection for affecting the welding capillary, an extremely fast deflection (up to 1 MHz from point to point) is mandatory for applications with multi-bath or multi-process technology.

Feasibility of welding

Property of a given metal or metal combination to achieve successful electron beam welding without unacceptable inclusions.

Filler material

Additional metal (generally in wire form) to fill gaps or to alloy the weld zone material.

Floor-to-floor time

Time to process one (1) workpiece from a machine or production line – used in mass production. In electron beam processing, it is not only defined by the real EB process, but also by the non-productive times. Machine types such as cycle machines and airlock machines are characterized by very low non-productive times.

Focus

The "point" on the axis of the electron beam where the highest power density is located. By focusing, the electrons are brought together there. The position of the focus relative to the workpiece surface is an essential parameter for all EB welding processes.

Focus coil

Electrically controlled toroidal coil in the electron beam generator, in which a magnetic field is formed inside that causes the focusing of the electron beam. Depending on the strength of the current in the focusing coil, the location of the focus is shifted.

Focussing

In electron beam technology, the divergent electron beam that passes through the anode is focused at one point by the magnetic field of the focusing coil. It is typical for the electron beam that the concentration does not only occur on one focal plane, but is effective over a specific range, the focus waist.

G

Gun column

Colloquial term for EB generator.

H

Hardening

Transformation of steel or cast-iron microstructure to martensite. Electron beam hardening can also be combined with a pre-executed thermo-chemical process, e.g. nitriding.

High voltage

Direct voltage between cathode and anode in the EB generator of an electron beam welding machine, which accelerates the electrons to a beam. Depending on machine type and application, the typical high voltages for EB processing are between 60 and 150 kV.

I

Indexing machine

High volume production electron beam machines equipped with an indexing table carrying a minimum of two stations for loading/unloading and processing, respectively.

Interlinking

This means the automated integration of an electron beam welding machine to other equipment within a production line.

J

Job shop

Plant for sub-contract electron beam production (welding, drilling), for both one off and mass production.

Joint preparation

Particularly the form of the joint edges. Most common type used in electron beam welding is a butt joint with theoretical zero-gap.

K

Key hole

Metal-vapour gas capillary opening developed in deep welding processing.

L

LENS

The focusing coil for generating the magnetic field is also known as a magnetic lens or lens coil.

M

Magnetic lens

See: focus coil

Mass production

EB systems with their advantages are also used in high volume production. Preferably cycle machines or airlock machines are used, which guarantee short non-productive times.

Material assembly

Electron beam technology can be used to join numerous metal combinations; in some cases, special techniques are required to achieve sufficient mechanical strength.

Material combinations

The electron beam can join not only parts from identical materials, but also from different materials. The weldability in the case of material combinations definitely depends on the metallurgy of the common (mixed) molten pool. Intermetallic phases can limit the strength; this effect can be suppressed by the use of filler material.

Metallurgy

The resultant microstructure resulting from the fusion process created by the electron beam treatment.

Microstructure

Composition and configuration of the basic elements within a metallic alloy or compound.

N

NonVac

Abbreviation for Nonvacuum electron beam welding

Nonvacuum electron beam welding

This is a special form of EB welding in which the workpiece is not located in an evacuated chamber. The special electron beam generator is equipped with pressure stages that allow the beam to emerge into the free atmosphere. Due to the collision of the electrons with the gas molecules of the atmosphere, the beam becomes somewhat wider than in a vacuum, which allows small workpiece tolerances to be compensated. With the NonVac electron beam, however, welding cannot be as deep and as narrow as in a vacuum, and the working distance is also limited.

O

Observation

The process area can be observed by means of light-optical systems (via TV camera) or by using reflected electrons from a scanned beam.

Operation costs

Low operation costs are a general characteristic of electron beam machines.

P

Production cell

EB machine interlinked to other operating units within a production cell.

Production line

Electron beam machine interlinked to other operating units within a production line

Protection gas

In contrast to all other fusion welding processes electron beam welding does not need any gas to protect weld metallurgy.

Pumping unit

Equipment to develop a vacuum within the electron beam machine, in order to develop and weld with the electron beam.

Q

Quality

In particular the properties of any electron beam processing. Quality levels are defined in certain norms.

R

Radiological protection

The electron beam produces unwanted X-rays as a by-product. Human have to be protected from high levels of X-radiation, this is achieved within the EB machine’s design concept.

Rotary indexing machine

See: indexing machine

S

Single-item production

Complex and expensive parts are processed as single electron beam processes in direct contrast to mass production.

Smoothing

See: cosmetics

Surface modification

By local heat treatment – without or with melting the surface – the electron beam can change the metallurgical structure within a certain depth of the surface. This includes hardening, remelting, alloying, embedding, structuring etc.

T

Technology

A set of parameters used within a special electron beam process or application.

V

Vacuum

In order to avoid scattering of the electrons by gas molecules the beam generator (~10^-4 mbar) as well as the working chamber (10^-2 to 10^-6 mbar) are evacuated.

Vacuum chamber

See: working chamber

W

Waist of beam

In contrast to a laser beam, the electron beam is not focussed to a precise level (a point) but exhibits a focus-waist (a few millimetres in length). Electron beam processes are therefore less sensitive to small tolerances in working distance.

Wall-plug efficiency

The so-called "wall-plug efficiency" of an electron beam machine includes both the highly effective beam generation itself as well as the expenditure for evacuation, movement and cooling etc. Depending on the machine type and the applied beam power, this total efficiency reaches values > 60%.

Wehnelt electrode

This solid grid cup (placed between cathode and anode within the electron beam generating system) controls the beam current by means of its negative field-potential.

Weld depth

The penetration depth of the key-hole determines the depth of the achievable weld.

Weld profile

The shape and form of the solidified metal seen in a transverse weld cross-section. The two fusion faces (flanks) of EB welds are typically parallel; therefore, reducing the angular shrinkage and workpiece distortion.

Weld with

Width of the two fusion faces of a weld profile (cross section) obtained by deep welding effect during electron beam welding.

Welding

In particular, processes and their result within the solidified melting pool with respect to the composition and properties of the weld metal. A filler material is often used in most conventional welding processes; this is not necessary for electron beam welding, but is also possible.

Welding technology

In particular, whole set of parameters used in a special welding task.

Working chamber

The evacuated of an EB machine the EB process takes place.

The evacuated chamber where the workpiece is processed in the electron beam machine. The walls of the chamber also protect against X-rays.

X

X-rays

Short-wave electromagnetic radiation which occurs parasitically with any electron beam process. Its “hardness” (ability for penetration) increases with the level of the accelerating high voltage. The X-ray radiation is safely shielded by the structure of the electron beam machine, so that no persons in its surroundings can be harmed.