by Tim Wilson
TIG welding advances make for more efficient welding
TIG welding, also known as GTAW) or Heli-arc welding, has been around for a long time. It was developed before World War II, when it became the method of choice for welding aircraft parts. In the TIG welding process, a tungsten electrode is used to form an arc to the metal being welded, and a gas that is fed through the torch shields the weld pool and the electrode.
“TIG welding machinery has become more efficient, and that makes it more flexible than ever,” says Jay Ginder, a senior application engineer with ESAB Welding & Cutting Products. “Inverter-based welding equipment gives the welder greater control over the process. There is better control over the AC arc and heat, more programmability through advanced controls, and faster travel speeds.”
ESAB was an early player in this market, with its Heliarc line of AC/DC inverters staying competitive by being both light and small. As a result of new products like those from ESAB, the industry is seeing more consistent welding results, with less time to weld clean up. This is especially evident in challenging aluminum welding applications, where more advanced TIG welding equipment is making things easier and more cost effective.
“When welding aluminum with a pure tungsten electrode, a ball is typically formed at the end of the tungsten electrode, and that creates a broad bushy arc that can help increase heat input and improve travel speed for high quality aluminum welds,” says Dan Tadic, executive director, Canadian Welding Association. “Some newer power sources are capable of welding with a sharpened or pointed 2 per cent thoriated tungsten electrode–these can weld for a longer period of time, and therefore help increase productivity.”
New technology is also coming from Lincoln Electric, which has its Aspect 375 product, expected to launch this fall. The Aspect is an inverter-based product with a user-friendly interface, but with advanced capabilities such as AC wave-shape controls. These can adjust the negative and positive amplitude value, the AC balance, and the AC output frequency when welding aluminum.
“Inverter-based technology is generally more efficient than traditional transformer-based technology, as it requires less current for a given weld output,” says Ivan Gracic, a product manager at Lincoln Electric. “As well, conventional TIG technology is constrained to 60 hertz frequency, but with the Aspect we can manage the AC output frequency up to 400 hertz. By having the additional frequency range, the arc profile can be widened or narrowed, making it easier to weld around tight corners or in hard to reach areas.”
An inverter also allows for the ability to increase the pulse frequency–the Aspect 375 can get to 2,000 pulses per second in DC polarity.
“This is a benefit to the customer, in part, because with a higher pulse frequency one can better manage heat input on thin materials, and increase travel speed,” says Gracic. “We have received field-trial feedback indicating that the Aspect provides for enhanced arc control and stability, making it is easier for the operator to produce precise welds.”
This is crucial in areas like aerospace, where quality and accuracy reign supreme. Gracic gives the example of an aerospace application working with material at 7,000th of an inch–a truly incredible level of detail, given that a human hair is 4,00th of an inch.
For industry, the advantage of TIG welding is that it can be used in thin and thick materials to produce the highest quality welds. It’s a good choice for any application where weld size is critical because of its precision, and because of the control the welder has over the process.
“Because of the preciseness of the arc and because TIG provides an aesthetic surface finish that doesn’t need grinding, it’s used in the automotive/transportation industry, in the auto racing industry and for products like high-end bicycles,” says ESAB’s Ginder. “Aluminum and stainless steel applications are the most common, but TIG can be used for welding exotic materials such as titanium in aircraft manufacturing.”
There is a trade-off of sorts, because metal inert gas (MIG) welding is favoured for higher weld productivity, with better throughput. But for those applications where quality trumps speed, TIG is still the way to go. This is one reason why TIG is used in high-demand areas as space exploration: it can pass x-ray analysis for critical precision requirements, and was even used when making the Mars Rover.
“We also see it in food and beverage processing and the nuclear industry,” says Andrew Pfaller, product manager, TIG Solutions, Miller Electric. “Given that many alternative materials are being implemented to achieve specific metallurgical and mechanical properties, TIG continues to hold its relevance across a broad spectrum of markets.”
For its part, Miller has its inverter-based Dynasty products, which are helping lead the ongoing transition from transformer-based power sources to the higher performing inverter technology. The newer technology has the ability to increase portability, quality and productivity, while also reducing the large primary power draw. With these advances and other, TIG welding promises to remain relevant well into the 21st century. SMT
Tim Wilson is a contributing editor. [email protected]