By Clare GoldsBerry, associate editor

New technologies have made controlling gas tungsten arc (TIG) welding processes easier.

The technology used in gas tungsten arc welding – also known as TIG welding – has changed considerably in the last five years, and the changes that have been made can give welders new reasons to consider gas tungsten arc welding as an alternative technology.

The gas tungsten arc welding process, the materials and the equipment used in it, especially TIG inverters, have come a long way, and have made the process easier to use and more effective.

While TIG inverters are not new – they were developed in the 1970s – many of the recent developments in TIG welding have focused on them.

"The primary problem with inverters when they were first developed is that they were ahead of their time electronically speaking," Brent Williams, TIG welding product manager, for Miller Electric Manufacturing Co., (www.millerwelds.com) said. "As computers have improved over the past 20 years to accommodate improved electronics, so have inverters. The electronics have to be there to support the design of the welder. Micro-electronics have made inverters more robust, and we use more electronics to reduce the size of the inverter and to improve process control."

When comparing traditional TIG welding power sources to inverter technology, the differences become clear. A traditional gas tungsten arc welding power source uses a transformer to turn high voltage, low amperage primary power into the low voltage, high amperage power that the process requires , Williams said. An inverter power source changes AC input power to DC power, and, using fast solid-state switches, increases its frequency in ranges from 20,000 Hz to 100,000 Hz. Then the inverter transforms it into usable welding power through an advanced level of control over the arc.

"Inverter technology increases the pinpoint control of the arc," Williams said. "Using the high current density the welder can manipulate the arc, resulting in purity or cleanliness of the arc. High current density from the narrow, focused arc cone improves the welder's ability to manipulate the puddle, resulting in improved arc and weld bead control. TIG is a very clean process primarily shielded by inert argon gas. As a result, there are no sparks, no spatter, no slag to chip away. You'll see markets such as aerospace, tool and die repair using this technology."

TIG inverters with advanced controls, such as Miller Electric's new Dynasty 350, offer AC/DC TIG options and improved control over the welding arc. They allow the operator to tailor the bead profile, to improve arc starting, and to increase travel speeds. These advanced controls also perform better on thin materials and thinner sections, and provide more production benefits.

"The oxide layer on the outside melts faster at higher temperature than the base metal aluminum, and cleaning action from the arc helps to remove this thin layer and to improve the weldability of aluminum. We can manipulate the AC wave form and offset it for more or less cleaning for a wide or narrow arc – tailored for the operation. It used to be a one-size fit all, and the welder had to know the tricks. An inverter takes the black magic out and gives the control to the operator to adapt the arc to the application."

Neil Vesco, co-owner of Vesco Rugby Chairs (Chula Vista, CA), a maker of wheel chairs for athletes, recently purchased a Dynasty 350 after testing it for six months. "The technology has come leaps and bounds over the last eight years. It's so far above the original inverter, and does things we never thought we could do," Vesco said. Vesco is an experienced welder with 17 years of experience.

He said he likes the versatility that the new gas tungsten arc welding technology provides.

"Welding very thin to 1/2 in. thick aluminum with a combination of changing the frequency, and the AC balance to include more straight polarity allows us to keep a sharp tip on the tungsten electrode," Vesco said. "We get better penetration and cleaner welds," he added.

When welding in AC for aluminum, a conventional machine with square wave output becomes inefficient, he said.

"Transition times are slow when you square off the wave," Williams said. "When you start to manipulate the wave, they become inefficient. We can get a better weld output and a true square wave output with these inverters."

Miller also has a new inverter that was designed to improve DC TIG welding productivity and quality in industrial applications.

The company said its Maxstar 350 DC TIG/Stick inverter provides high speed pulsing capabilities – as much as 5,000 pulses per second – 50 amps more welding power, and its Auto-Line power management technology.

The newest inverters are smaller and weigh less than conventional power sources – 90 lbs. today compared to 400 lbs. 10 years ago – and they can be even smaller. The smaller size offers several advantages, Williams said. The large-sized TIG machines of the past required that the weld was brought to the welder.

"Now the welder can go where the weld has to be made to improve efficiency. What used to take hours and days to make a repair, now takes minutes," Williams said.

Additionally, electrical efficiency has improved, making today's inverters more appealing, and prices have come down.

"Conventional machines used to be much cheaper, but the rising costs of raw materials such as copper, aluminum and steel, as made inverters economical by comparison," Williams said.

"When we first had the 300 amp inverter five years ago, it was new technology. Users wanted to see if it was as robust as the larger, older models, and questioned why a smaller machine cost more money. Today inverter costs are in line with conventional power sources and reliability has improved, helping to build confidence that accompanies performance with our inverter product line."