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How can I avoid gun flashovers in EB welding, and prolong the filament life?


Frequently Asked Questions

Electron gun discharges, caused by the electrical breakdown between the high voltage gun and anode can cause severe defects which may, in some cases, require expensive repair welding or even demand the component to be scrapped. Discharges are produced when metal vapour or charged particles produced by the weld pool enter the gun electrode region and the effects are particularly severe when welding materials containing volatile elements. In addition, the ingress of such particles accelerates cathode wear which ultimately demands a higher percentage downtime for machine maintenance.

Magnetic Trap devices fit into the electron gun column below the anode plate. Within the trap there are several pairs of deflection coils which divert the beam through a channel off- axis, around a vapour stop and then back to its original axis. Once set up, the trap is essentially maintenance free and invisible to the machine operator.

Use of such a trap allows welding of materials with volatile elements (for example aluminium-magnesium alloy) with virtually no risk of gun electrode breakdown. These devices broaden the application of electron beam welding to areas where previously the scrap rate would have been unacceptable. In addition, they allow the useful cathode life of the gun to be extended and prevent damage to the gun electrodes.

Other methods of avoiding gun flashovers include the use of low stored energy, intelligent high voltage power sources and Reduced Pressure EBW.

For further information please see Joining Technologies or if you require any further information on TWI's magnetic traps, high voltage power supplies and Reduced Pressure EBW please contact us.

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