Below is a glossary of terms commonly associated with the electron beam welding process. This reference is provided to bring clarity to some terms you may encounter on our website or in general research of the electron beam welding process and the EB welding equipment used to perform it.
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accelerating voltage: value of electrical potential, usually expressed in kilovolts, being utilized to accelerate and increase the energy of the electrons being emitted by an electron beam gun
additive manufacturing: an emerging technology utilizing electron beam melted wire-fed material, that is precisely layered according to programmed instructions to produce near-net part shapes that reduce the amount of raw material used and final machining required
alignment coil: electromagnetic coil, located directly below the electron beam gun, used to ensure electron beam produced by gun follows a path down through electron beam column which coincides with the column's centerline
anode: electrically positive element of the electron beam gun, commonly connected to the ground potential of the machine, through which the electron beam exits the gun
arcing: a condition usually in the gun area that is caused by impurities which produce a breakdown of the isolation between high voltage and ground resulting in a high current surge
beam current: 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 current control: special electronic circiutry used for regulating the level of beam current being emitted by the electron beam gun
beam deflection: movement of an electron beam being produced either by electromagnet coil or by the presence of undesirable, random magnetic or electric fields. This movement, when specifically induced by applying a direct or alternating current applied to the electronmagnetic deflection coil, can be used to provide a simple movement of the beam off from its normal position (dc), and/or a continuous oscillatory motion (ac) of the beam.
beam modulation: any periodic change in the beam current
beam power: measure of the beam energy being delivered per unit time; usually expressed in terms of watts, a rate of energy flow of a joule per second, it is equal to the product of the beam voltage times the beam current. In equation form;
P = V x I
P = Beam Power, watts (W)
V = Beam Voltage, kilovolts (kV)
I = Beam Current, milliamperes (mA)
beam spot size: beam diameter produced at point where beam impinges on surface of the workpiece; beam spot will either be equal to or larger than the minimum focal spot achievable in that plane from the focusing lens
bias voltage: value of negative potential difference being applied between gun filament and grid cup elements in order to regulate the value of beam current being emitted; as bias voltage decreases current increases
cathode: the source of electrons; commonly a filament of tungsten or tantalum directly heated to a temperature which initiates thermionic emission. Other forms and materials used as thermionic emitters include indirectly heated buttons or rods of tungsten, tantalum, lanthanum hexaboride, and rare earth oxides.
CNC: acronym for Computerized Numerical Control systemspresently used in modern EB welding systems for controlling a variety of both mechanical and electronic functions
column valve: a vacuum valve between the electron gun and the work chamber, used to seperate and maintain vacuum in the gun area when the chamber is vented
conduction mode welding: welding at a power density level below the threshold value required to form a "keyhole", and where the primary method of producing joint fusion is by the conduction of heat through the material being welded
corona clear: a technique for removing contamination from the electron beam gun area by briefly applying a slightly higher than normal beam voltage to the gun. Sometimes referred to as performing glow discharge cleaning or gun clearing.
corona ring: a highly polished ring around the cathode insulator that helps reduce arcing being produced by the gun's compressed electric field lines becoming compressed in that area
cosmetic pass: a partial penetration weld pass made primarily to enhance surface quality and appearance
data acquisition system: used in EB Welding to capture and save active weld parameters and values such as beam current, beam voltage, vacuum levels, focus coil and deflection current, etc.
deflection coil: electromagnetic coils used to change the path of the electron beam in either a stationary or oscillatory fashion
defocus: to locate the focal spot above or below the workpiece surface level when welding
degauss: to demagnetize a part or fixture in order to reduce or eliminate unwanted magnetic fields
electron beam: a stream of electrons accelerated and shaped into a directed beam by an electric potential being applied to an electron beam gun
electron beam braze welding (EBrazeTM): a hybrid process, developed by Dresser Rand/PTR-Precision Technologies, employing an electron beam to simultaneously accomplish welding and brazing to enhance the structural integrity of the T-joint welds in Dresser Rand impellers.
electron beam gun: a device for producing, accelerating, and forming a directed stream of electrons
electron beam gun column: the electron beam gun plus auxillary mechanical, optical and electrical components such as viewing optics and beam alignment, focus, and deflection coils
electron beam drilling (EBD): a process in which densely focused, high kinetic energy from accelerated electrons and high speed control of the electron beam enables fast and accurate hole drilling in workpieces
electron beam welding (EBW): a welding process that melts and fuses materials with the heat obtained from the kinetic energy of a concentrated beam of high-velocity electrons impinging on the joint
external gun: an electron beam gun mounted outside the welding chamber. The beam passes through an opening in the chamber wall and the workpiece is moved to accomplish welding. This type of gun is commonly used in high voltage electron beam welding systems.
electron optical viewing: a technique comparable to that used in SEM (Scanning Electron Microscope) devices, which employs the beam generation system to create a low current electron beam that uses a collector to image the work piece with back scattered electrons.
farraday cup: an isolated beam capture device used to determine beam efficiency
fast focus coil: an additional dynamic focus lens which provides ultra-fast changes in beam focal position; capable of delivering both static and dynamic focus currents it is available on SST-Steigerwald 150 kV and PTR 60kV EB generators
filament: a wire or ribbon which is the electron emitting component (i.e. the cathode) of an electron beam gun
filament current: current being used to directly heat wire or ribbon material being employed as cathode
focal spot: location where the electron beam has the smallest cross-sectional area. Also referred to as sharp focus or focal point.
focus: converging an electron beam to form a focal spot using electromagnetic or electrostatic forces
focus coil: electromagnetic coil, coaxial to the electron beam, acting as a lens to converge the beam’s electrons radially to form a focal spot. Sometimes referred to as focusing lens
grid cup: component of a triode gun, more electrically negative than the cathode, used as a grid to control the beam current and shape the beam. Also called bias cup.
hermetic seal weld: a weld design primarily used to provide a specific degree of tightness against air and gas leakage
high-vacuum electron beam welding (HV-EBW): an electron beam welding process mode in which welding is accomplished at a pressure of 10-4 to 10-1 Pascal (approximately 10-6 to 10-3 torr)
high-voltage EB welding: a relative term normally used to identify electron beam equipment employing a beam voltage in excess of 60kV, but under 1 MeV
high-voltage tank: a container, usually filled with insulating oil, which encloses and isolates the high-voltage generating components of an electron beam system
high speed beam deflection: beam deflection speeds typically greater than 50 kHz used for beam splitting, multipool processing, advanced pattern generation, joint seam tracking and electron optical viewing
joint scanning: preweld joint sensing, using a low-power electron beam, employed for both seam location and tracking
Karl-Heinz Steigerwald: the "Father of EB", a German physicist from Stuttgart, West Germany who developed the electron beam welding process while conducting experiments with his electron beam microscope. He inadvertently discovered when trying to increase the power of the scope that the specimen being examined would disappear. Later he determined that by regulating the power settings, the specimen would melt and resolidify- thus the electron beam welder was born.
keyhole mode welding: the classic high energy beam welding technique that employs a concentrated heat source with sufficient intensity to instantly vaporize workpiece material, thereby resulting in the formation of a vapor channel (“keyhole”), surrounded by molten material; this channel penetrates deeply into (or through) the workpiece and molten material flows around it as it is advanced solidifying at its trailing edge to produce a continuous weld.
low voltage EB welding: a relative term, normally used to identify electron beam equipment employing a beam voltage of 60 kV or less
mobile gun: electron beam gun that may be moved within the welding chamber and typically operates at 60 kV or less
multipool welding: using a single beam and high speed deflection to weld at two or more locations simultaneously without collapse of the keyhole
non-vacuum electron beam welding (NV-EBW): an electron beam welding process mode in which welding is performed in atmosphere; sometimes referred to as atmospheric electron beam (AEB) welding
optics: lens/prism system for magnified real time viewing of the weld utilizing either camera or eye-piece designed with parallax correction
oscillation frequency: the frequency at which the electron beam is deflected.
partial vacuum electron beam welding (PV-EBW): an electron beam welding process mode in which welding is accomplished at a pressure of 10-1 to 10+3 Pascal (approximately 10-3 to 25 torr)
pulsing: a brief, controlled on/off oscillation of beam-input energy generally performed in repetition
pump-down time: the time required for the vacuum pumps to evacuate the weld chamber down to high or medium vacuum levels (10-4 to 10-1 pascal)
pumped column: an electron beam gun with its own seperated evacuation system
radiation shielding: material to protect personnel from exposure to harmful radiation. Typically lead shielding or heavy-section steel is used.
reticle: sealed cross-hairs contained within the optics
ripple: AC portion of an applied DC voltage
specific power: power density in the electron beam, usually expressed in units of watts per square centimeter
spiking: a condition in partial penetration welding where the depth of fusion is nonuniform and changes abruptly
stigmator coil: a device used to compensate for irregularities in the beam caused by spurious astigmatism of lenses or defelction systems
switch mode power supply: the high voltage energy source for electron beam welding systems operating at a very high frequency, with low noise and low ripple, enabling very precise welds.
target: a piece of material, usually copper or tungsten, used for electron beam impingement while setting welding parameters and during radiation leakage checks
triode gun: an electron gun configuration utilizing a bias electrode (commonly called a grid cup), in addition to standard cathode/anode elements of diode gun, allowing beam current to be regulated independent of beam voltage.
vacuum chamber: air-tight enclosure which gets evacuated during pump-down and is integrated into all high and partial-vacuum electron beam welding systems. The vacuum chamber, sometimes referred to as weld chamber,contains a fixturing table that holds the workpiece and is where the EB welding actually takes place.
vapor plating: condensation of metal vapors evolved during welding
vapor shield: a glass partition that protects the optical prism from heat and vapor from the weld
wire feeder: unit for providing 'filler material' to introduce metal(s) for achieving desired metallurgical properties in the joint, to help fill large joint gaps or to provide material in additive manufacturing processes for near net-shape build ups
X-rays: when pertaining to EBW, any time an electron beam is stopped by a target ( your workpiece) X-rays are generated. The higher the voltage of the electron beam, the more X-rays that are being emitted. However, the total energy converted to X-rays is only a few percent of the electron beam's energy. At higher beam voltages, the X-rays are "harder" meaning they penetrate more and are not as readily absorbed. Therefore radiation checks must be done at the machines highest beam voltage using a target made of tungsten.
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