When selecting a welding power source for your garage or jobsite, the first place to start is usually determining which processes will be used most often. If you plan on switching between semi-automatic processes such as GMAW (MIG) and manual processes such as GTAW (TIG), you may want to consider a multi-process welding machine. This is because these power sources can switch between constant current (CC) and constant voltage (CV) outputs with the press of a button.
If you plan on doing TIG welding almost exclusively, renting a dedicated TIG welder may be a more attractive route. While you lose some versatility, a dedicated TIG welder typically offers an improved feature set for TIG than is available on many multi-process power sources. For example, alternating current (AC) output is critical for easily welding aluminum and magnesium. On dedicated power sources, AC output may even be square wave and have variable balance for improved arc stability and improved fine-tuning of the arc characteristics, respectively.
A Little Secret
Did you know that even dedicated TIG welding power sources are, in a sense, “multi-process”? This doesn’t mean you’ll be able to easily switch between TIG and MIG with good results; wire-fed processes such as MIG or flux-cored arc welding (FCAW) require a constant voltage output for reliable operation. But stick welding performs best with the constant current output produced by dedicated stick and TIG welding machines. This means that, if needed, you can attach a stick welding electrode holder in place of the TIG welding torch and produce high quality welds.
Why Use a TIG Machine for Stick Welding?
There are two primary answers to this question: speed when infrequently welding thick materials and convenience when performing infrequent field repairs.
Welding Thick Materials
TIG is a comparatively low deposition-rate welding process. It can be used for welding thick materials with minimal preparation, but high amperage is typically required which necessitates the use of larger (and pricier) welding power sources and water-cooled torches. Using a smaller power source requires that thick materials be beveled for good joint access and that additional filler metal is added a dab at a time.
When a particularly thick weldment is to be welded, stick may be worth considering due to its higher deposition rates and good penetration characteristics for a given amperage. This means that the job can be completed with good quality in less time. Of course, it is important to balance the need for post-weld cleanup (slag and spatter removal) against the time savings afforded by the improved deposition rate.
Field Welding
Field fabrication and repair welding is often more involved than welding in the shop environment: the weld joint may be located outside, with less-than-ideal equipment access, and/or some distance from mains power. TIG is often not the first choice of process for these applications. This is primarily due to the shielding gas that is required. Shielding gas cylinders must be transported relatively close to the workpiece and the shielding gas itself is susceptible to disruption in drafty environments.
Instead, the self-shielded processes—like stick welding—are preferable since less effort is required to adequately shield the weld from the atmosphere. Since both TIG and stick welding utilize a constant current waveform, the only additional equipment required is an electrode holder and enough weld cable to provide good electrode and work connections.
An Example
You spend most of your time welding relatively thin aluminum sheet metal, but you have a need to weld a thick aluminum plate onto a piece of equipment that can’t be easily transported to your shop. You rent a generator and gather your equipment. You could use TIG, but as mentioned, shielding gas can be quite inconvenient in the field and you are looking to cut down on welding time.
Your TIG welding power source provides an additional benefit: AC output. This allows you to not only perform stick welding but use aluminum stick electrodes which are typically designed for AC output only. This combination will help you complete the job quickly and get back to your typical welding operations.
Conclusion
In short, using a TIG machine for stick welding is perfectly reasonable for the occasional field repair or when an occasional job requires tackling particularly thick base material. The capability is inherent to the constant current output of the machine; it is not using the proverbial “wrench as a hammer”.
So, rent a TIG welder for your next project with the knowledge that you aren’t pigeonholed into a single process. But remember, if stick welding is the only process you intend to use, the feature set of an advanced dedicated TIG welder may be a source of unnecessary cost. When selecting the best piece of equipment for your application, be mindful of how much of your time will be spent with the primary use while staying mindful of alternate uses.
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