Magnetic-Pulse-Weldingfor the right applications.SOLUTIONS with Effective, Practical Advice
Although its origins are pushed back to more than a century ago when essentially similar processes were used for metal forming, the renewed interest and development for welded applications is much more recent, supported in large measure by the needs of the automotive industry. (Sponsored Links) Short notes referring to Magnetic-Pulse-Welding were published in the past Issues PWL#018, PWL#043 and PWL#046 of Practical Welding Letter, mentioning a few applications. Magnetic-Pulse-Welding, a high speed, single pulse welding process, is suitable for cold welding together electrically conductive metals, not only identical but even dissimilar, as the absence of fusion makes the bonding without producing brittle intermetallic compounds. One of the most common configurations consists of a lap joint where a tubular exterior element surrounds an inner one, either tubular or solid. Before welding, a measurable gap is present between the two elements. Due to the collision generated, one of the elements looks deformed by the process after joining took place. A less common joint geometry consisting in overlapping sheet metal sections is aggressively pursued by automakers because of the intrinsic capabilities of this cold weld and applicability to dissimilar materials. Magnetic-Pulse-Welding is performed by accelerating a definite region of one of the parts to impact at high speed with much force against the other. This movement is the result of a high repulsive force generated into the workpiece by the opposing transient magnetic fields, one associated with the current flowing in the primary coil, the other produced by the eddy currents induced in the opposite direction in the conductive material nearby. The powerful current is generated by the sudden discharge of energy, from a bank of capacitors storing the charge at high voltage, through the primary coil designed to exhibit low inductance and high conductivity. The peak current can reach a very high level of amperes, measured in the millions, while the pulse width is limited to tens of microseconds. Magnetic-Pulse-Welding has some features in common with Explosion Welding: the gap through which the material of one element impacts at an angle with the surface of the second element, the local plastic deformation of one of the parts and the formation of a powerful jet at the point of collision, that cleans the surfaces by effectively removing all contaminants. As a consequence also the appearance of the wavy interface after welding, in metallographic sections across the welds is very similar for both processes as seen under a microscope. Magnetic-Pulse-Welding has therefore all the advantages that promote its application for mass production of welds in repetitive parts:
The limitations include:
Aluminum and Copper, because of their high conductivity, are among the most used materials that are joined by Magnetic-Pulse-Welding to most of the other commercial metals for ever expanding applications in all industries. Designers of tubular joints intended for parts to be mass produced are urged to explore Magnetic-Pulse-Welding for its low cost high productivity. Any questions or comments or feedback? Write them down and send them to us by e-mail.Click on the Contact Us button in the NavBar at top left of every page.
To reach a Guide to the collection of the most important Articles from Past Issues of Practical Welding Letter, click on Welding Topics. Friction Welding Processes Important Announcementa rich collection of valuable information on Materials, Volume 1, and Metals Welding, Volume 2, from expert Internet Sources, is now available. Buy It Now! at Metals Knowledge.
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