Magnetic pulse welding
Encyclopedia
Magnetic pulse welding is a welding
process that uses magnetic forces to drive two workpieces together and weld them together. The welding mechanism is most similar to that in explosion welding
.
") near an electrically conductive material (the "flyer"). An intense magnetic field
is locally produced that generates a secondary eddy current
in the flyer according to Lenz's Law
. The net effect of the secondary current moving in the primary magnetic field is the generation of a Lorentz force
, which accelerates the flyer at a very high velocity. A stationary material (base material) is positioned in the trajectory
of the flyer thus producing an impact which causes a solid state weld. Magnetic pulse welding may be used to join dissimilar metals.
Primary currents as high as 1 million ampere
s are used and flyer velocities
in the vicinity of 800 meters per second can be achieved over a distance of a few millimeters. The magnetic pulse welding system is a high frequency capacitor discharge circuit (RLC circuit) often with extreme energy and power characteristics. System energies as high as 100 kJ, power of up to 1 GW and magnetic field intensities of 50 teslas
and higher can be seen, which can propel certain materials at extreme velocities of 600 to 1000 m/s.
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
process that uses magnetic forces to drive two workpieces together and weld them together. The welding mechanism is most similar to that in explosion welding
Explosion welding
Explosion welding is a solid state process where welding is accomplished by accelerating one of the components at extremely high velocity through the use of chemical explosives. This process is most commonly utilized to clad carbon steel plate with a thin layer of corrosion resistant material...
.
Process
A very high AC current (the "primary current") is passed through a conductive coil (the "inductorInductor
An inductor is a passive two-terminal electrical component used to store energy in a magnetic field. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries...
") near an electrically conductive material (the "flyer"). An intense magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
is locally produced that generates a secondary eddy current
Eddy current
Eddy currents are electric currents induced in conductors when a conductor is exposed to a changing magnetic field; due to relative motion of the field source and conductor or due to variations of the field with time. This can cause a circulating flow of electrons, or current, within the body of...
in the flyer according to Lenz's Law
Lenz's law
Lenz's law is a common way of understanding how electromagnetic circuits must always obey Newton's third law and The Law of Conservation of Energy...
. The net effect of the secondary current moving in the primary magnetic field is the generation of a Lorentz force
Lorentz force
In physics, the Lorentz force is the force on a point charge due to electromagnetic fields. It is given by the following equation in terms of the electric and magnetic fields:...
, which accelerates the flyer at a very high velocity. A stationary material (base material) is positioned in the trajectory
Trajectory
A trajectory is the path that a moving object follows through space as a function of time. The object might be a projectile or a satellite, for example. It thus includes the meaning of orbit—the path of a planet, an asteroid or a comet as it travels around a central mass...
of the flyer thus producing an impact which causes a solid state weld. Magnetic pulse welding may be used to join dissimilar metals.
Primary currents as high as 1 million ampere
Ampere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...
s are used and flyer velocities
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
in the vicinity of 800 meters per second can be achieved over a distance of a few millimeters. The magnetic pulse welding system is a high frequency capacitor discharge circuit (RLC circuit) often with extreme energy and power characteristics. System energies as high as 100 kJ, power of up to 1 GW and magnetic field intensities of 50 teslas
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
and higher can be seen, which can propel certain materials at extreme velocities of 600 to 1000 m/s.
External links
- The Electromagnetic Pulse Technology (EMPT): Forming, Welding, Crimping and Cutting By R. Schäfer, P. A. Pasquale and S. W. Kallee
- Automotive Applications of Electromagnetic Pulse Technology (EMPT) By S. W. Kallee, R. Schäfer and P. A. Pasquale
- New materials, processes, and methods technology By Mel M. Schwartz