Everyone knows the TIG process is all about precision, control and quality. Unfortunately, with conventional TIG technology the arc doesn't always go exactly where planned. This can lead to oversized welds, excessive heat input, excessive melt-through, and a lack of fusion. The overall weld quality and productivity is highly dependent on the welder's skill.
Conventional TIG technology provides very limited tools for the welder to control the arc. A garden hose makes for another useful analogy. With a regular hose, all you can pretty much do is adjust the volume (the "amperage") of water flow. The shape of the water is fixed until you add an adjustable brass nozzle. That nozzle lets you direct the water from a focused driving spray to a gentle wide spray.
Advanced TIG technology gives you a host of "nozzles" to tailor the arc specifically to your application. Some benefits of being able to customize the arc to the application are listed in Figure 1.
High speed DC pulsed output ranging up to 5000 pulses per second can provide a benefit for DC applications. Increasing the number of pulses per second constricts and focuses the arc cone, which increases arc stability, penetration and travel speeds, as well as narrows the weld bead. Pulsing between a high peak and low background current reduces heat input (for less distortion), and it helps to minimize the heat affected zone.
The pulse of peak current ensures good penetration. As added benefits, high speed pulsing can produce a smoother ripple effect in the weld bead, enhancing weld cosmetics. High pulse rates also agitate the weld pool, enhancing the grain structure within the weld as it solidifies.
On the AC side, conventional TIG technology only offers one method to adjust the arc, where advanced TIG technology offers four primary tools to tailor the arc to the application: extended balance control, frequency control, independent amperage control and multiple waveform options (see Figures 2, 3).
Our engineers recently conducted a comparison of conventional and advanced TIG technology, as found in two popular 350 amp AC/DC TIG welders. These lab results present possible improvements. Adjusting multiple factors, especially with advanced AC TIG, generally improves results in most applications. In fact, in some cases, a 20 percent overall increase in productivity is common.
To determine the potential for advanced TIG technology in your facility, ask your local welding supply representative for a demonstration.
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Nick Peterson is a welding engineer for Miller Electric Mfg., 1635 West Spencer Street, P.O. Box 1079, Appleton, WI 54912-1079, 920-734-9821, www.millerwelds.com, firstname.lastname@example.org. He is also a columnist for Melting Point, a welding e-newsletter published each quarter by Fabricating & Metalworking.
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