11.4 GTAW Operation and Welding Techniques
Karl Fulton
Cleaning Tools
Cleaning is important for all welding, but it is accentuated with GTAW. Here are the tools recommended for cleaning.
- Sanding disk or belt sander: This is a great tool for removing mill scale from mild steel. It is not recommended for use with aluminum or stainless steel.
- Stainless steel wire brush: You will want to have one of these for each type of metal you weld. Label them with the material you have designated them for and only use them on that material to prevent cross-contamination. When wire brushing your material, only brush in one direction—and all the way across the surface of the material, if possible. When brushing aluminum, you will want to break through the oxide layer, and you’ll know you have done this when it starts to feel gummy as you brush the material.
- Acetone: Wipe down parts to be welded with acetone and a lint-free rag to remove any oil or other unknown contaminates from the surface of the metal. You may also want to wipe down your filler rod—it can be surprising how dirty filler rods can be.
Fit Up
As with all welding processes, the fit up (contact between parts) is critical. Most of the time, you will want the joints to be as tight as possible. An exception to this rule would be for an open root butt weld where 100% penetration is required. You will want to refer to the Welding Procedure Specifications for restrictions, but for practice and your own knowledge you can make adjustments in a few ways. You can bevel your parts to a knife edge that is where the bevel continues all the way to the edge. When using this technique, you will want the joints to be very close. You can also put a landing on the end of your bevel. This end of the bevel has a small flat spot to create a little thicker material for you to weld with a gap. The land and the gap between your parts should be about the same size as your filler rod.
Make sure your parts are tacked up in multiple spots before welding to reduce the possibility of the joint separating as you introduce heat and tension from the weld. This is very important, no matter the weld joint you are working on. The tension will increase in the direction you are welding.
For a fun experiment, weld a butt joint from one side to the other without tacking the side you are welding to. You will probably see the two parts pull themselves together or even overlap.
Feeding the Filler Rod
There are three options for feeding the filler rod. Try to find a technique that works best for you. The idea is to keep your hand the same distance from the molten puddle the entire time you weld as you feed the filler rod through your hand.
The first technique is to simply push with your thumb. This is good for slower-paced welding. Put the filler rod in the crux between your palm and thumb and between your ring and middle finger. Then use your thumb to push the rod forward. See Video 11.2 for a demonstration.
A second method is to pull t