Page 16 - MetalForming March 2010

Tips for Improving
Gas-Tungsten- Arc-Welding Productivity
While extremely versatile, gas-tungsten-arc welding is not always easy to perform. Follow the five tips offered here to optimize your likelihood of success.
BY JACK FULCER
By its very nature, gas-tungsten-arc welding (GTAW) is a relatively slow process. But it also is a very versatile one. In fact, it can be used to weld more materials than any other process, even exotic and heavier alloyed metals. It’s also ideal for thin materials, as it results in a relatively low amount of heat input, to prevent burnthrough. Plus, no mat- ter the application, when performed properly GTAW can provide extremely high weld quality.
Jack Fulcer is marketing and product manager, Weldcraft, Appleton, WI: tel. 920/882-6800, www.weldcraft.com.
Achieving such positive results, how- ever, isn’t always easy—success is as much a matter of training and practice as it is simple patience. Fortunately, arming yourself with a few tips along the way can help you greatly improve the effectiveness of the process. After all, you don’t want an already slow welding process to become even slower.
Tip #1: Invert the Process
Using an inverter power source is one of the first steps a metalformer can take to improve GTAW efficiency. Inverters operate by switching high- voltage low-amperage alternating cur- rent (AC) into direct current (DC) back and forth at a very high rate of speed— up to 50,000 times/sec. The overall result is a smooth arc that provides consistent welding performance.
Inverters also have frequency con- trols that allow the welder to determine the length of time that it takes the unit to complete one full current cycle (the combined time spent on electrode pos-
itive and electrode negative), and to adjust the frequency from 20 to 400 Hz. (Note: transformer-based power sources only produce an output of 60 Hz, the same frequency that comes from a wall power receptacle).
The inverter’s frequency feature helps improve welding efficiency by narrow- ing the focus of the arc, creating a nar- row weld bead and minimal heat-affect- ed zone (HAZ). With this feature, welders will spend less time and con- sume less filler metal completing each weld. And, a smaller HAZ minimizes the likelihood of burnthrough and the need for rework—a definite cost saver in any welding application.
Inverters also feature a balance con- trol, which allows the welder to adjust how long the current spends in each part of the AC cycle—particularly use- ful when welding aluminum. He can adjust the balance control more toward the electrode-positive portion of the cycle, which helps to remove the oxide layer on the aluminum workpiece
14 METALFORMING / MARCH 2010
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