In this third article in our series we’ll cover TIG welding, which many people consider the most desirable of the welding processes. TIG welding offers unsurpassed control, with the ability to weld virtually any metal, and it has the potential to make a weld with that prized “stack of dimes” look.
The downsides are that TIG welding equipment is more expensive, and the learning curve is steeper. Nevertheless, if your goal is to do work where the weld beads are featured as part of the design, or if you want to weld exotic materials, it could be worth the time and money it takes to develop proficiency with this process. TIG welding has particular benefits for sheetmetal work since the welds are small and relatively soft, making them easy to work with a hammer and dolly.
All welding processes are fundamentally methods for applying heat to the metals being joined in a controlled manner. TIG welding accomplishes this with a tightly focused electric arc, shielded from the atmosphere with an inert gas. The better TIG machines allow you to change the heat “on the fly”—either with a foot pedal or with a knob or slider on the torch body. This ability to make continual adjustments as you weld is one of the keys that make TIG welding so precise.
There is a broad range of equipment made for TIG welding. The least-expensive machines are DC only, which will work for most metals, but it you want to weld aluminum or magnesium, you need a machine that can output AC, too. Most mid- or upper-range machines have both modes. Another feature that’s nice to have is a high-frequency circuit, which allows the arc to be started without touching the electrode to the workpiece. Some entry-level machines require “scratch” starting, which involves dragging the electrode across the metal to be welded and then pulling it a short distance away to establish the arc. While this reduces the complexity and cost of the machine, the downside is that the electrode is easily contaminated while being “scratched,” and welding with a contaminated electrode causes significant problems.
It’s worth mentioning that Miller Electric Manufacturing Company has developed a Touch-Start process where the arc is started by touching the electrode to the metal (which the machine holds at a very low current setting) and then retracting it slightly. Once the arc is established, the machine automatically ramps up to the welding current you’ve set. This is an interesting middle ground between the problematic scratch-start process and the more expensive high-frequency-start systems, and it has unique benefits in situations where the high-frequency circuitry in the welder could cause interference with delicate electronic systems in use near the machine.
One of the reasons that it’s challenging to learn TIG welding is because you need to control several things simultaneously, like modulating the welding current, holding the torch at the right angle, maintaining the right gap between the electrode and the work, moving the torch in a consistent manner, adding filler rod at just the right time, and “dabbing” the rod in the right place. If you have trouble chewing gum and walking, TIG welding may not be for you.
The “feel” of TIG welding is quite similar to gas welding, which we covered in the first installment of this series (Oct. ’17 issue). They both use a handheld torch to create and move the puddle, while the filler rod if added as needed with your other hand. One key difference is that when gas welding the torch is pulled farther from the workpiece to reduce the heat, while with TIG welding you can use the hand or foot control to change the heat and pulling the electrode away from the weld causes a number of problems.
Let’s take a closer look at some of the important details of the TIG welding process.
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