TPT January 2013

Technology News

Welding with arc voltage control ALTERNATING current (AC) welding of aluminium and its alloys with arc voltage control (AVC) using the Polysoude PC 350 AC/DC controller and Tetrix 351 source is now possible thanks to a collaboration between Polysoude (concerning AVC regulation) and EWM (concerning source regulation). the replication of parameters linked to the electronic control of power sources. This replication allows for the creation of an elaborated welding procedure resulting in constant high quality welds. In 90 per cent of all cases appearance of H2 is caused by contaminated surfaces or humidity absorbed by the oxide layer. In some cases H2 comes from the base material or the filler wire.

The main obstacle with aluminium AC welding is the AVC regulation which does not support any phase jumps. The availability of the AVC function in AC gives Polysoude great competitive advantage. The word “aluminium” is only a generic term used to describe, apart from pure aluminium, the entire range of alloys which the majority of applications are composed of. Orbital welding of tubing systems and pipelines in aluminium alloy prove to be particularly interesting in the case of cryogenic and nuclear applications, which require a high level of quality. The advantages of an automatic weld process lie in the traceability and

Recommendations: using exclusively clean and dry materials; thorough protection of filler wire against any contamination; milling of zones to be welded; good shielding gas cover; and preheating of workpieces (at a temperature of 100°C). AC current is used essentially for the welding of aluminium and its alloys. InAC mode, the tungsten electrode is switched between positive polarity (acting as a cathode) and negative polarity (acting as an anode). During positive polarity with the electrode as a cathode the oxide layer on the surface of the workpiece is

destroyed (cleaning sequence). During negative polarity with the electrode as anode the heat necessary to melt the material is transferred to the workpiece, the temperature of the electrode can decrease during this time (penetration sequence).

Polysoude – France Email: info@polysoude.com Website: www.polysoude.com

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J anuary 2013