- The GTAW process produces a aesthetically better if not the best looking weld beads compared to GMAW, which in one professional's opinion, tend to be brittle at some point and is associated with burn throughs.
- TIG weld beads lie flush or flows with the surface while MIG beads typically lay on top like a worm.
- TIG welding is the solution for more weld control and precision.
- Skill required for MIG is moderate, while TIG requires a higher degree.
Gas tungsten arc welding, especially in tubing applications, helps overcome some of the drawbacks of GMAW. Instead of needing to maintain a consistent travel speed or risk incomplete fusion, GTAW lets you control the heat input with a foot or hand control in reaction to the changing dynamics of the molten weld pool. This gives you more control over the shape of the weld bead, penetration, and HAZ - or Heat Affected Zone.
But taking control requires more coordination. You're doing four different things at once: holding your torch with your right or left hand, holding the filler metal in your opposite hand, using your foot control, and watching the joint and the weld pool. It is
extremely important to make sure your arms and elbows are braced yet relaxed (this is true with GMAW also, but especially with GTAW). Note that you want to establish the weld pool as quickly as possible. Dwelling too long in one spot increases the size of the HAZ, which is undesirable.
The only downside is that TIG welding necessitates a lot of practice to be able to develop that steady pulse and exchange between angle, heat distribution and feeding, while MIG just lets you zip right through whatever it is you're welding. Suffice to say, almost everyone who can keep a steady hand can, with little practice immediately lay down decent beads almost instantly. Which is why many beginners opt to choose this process over the tedious TIG counterpart.
It took a while for me to find the right beginning pulse, but still a lot more to keep it steady at that pace. Keeping the bead straight and clean is very difficult. I've done quite a heck of a lot of tests and am nearing depletion of my second tank used mainly for practice. Will experiment with Lathaniated (blue) tungsten this week, less of a hazard compared to the radioactive Thoriated (red) ones. Throwing in a couple of various sizes with the rod as well, particularly with 3/32.
One thing worth noting is that I should take notes when playing with my settings, as I do tend to lose everything when welding the next day. One day I'd be "oohhh, nice.." and the next I'd be "wtf foo?" (Old age? Nah..) So notes, notes, notes. Jot down settings for varying thickness and metals. Also, do test welds on pieces of the same material before moving on to the final pieces you'd be welding.
And lastly, destructive testing. There are a couple of ways to find out if you've created a nice sound weld - of which a large part relies mainly on hygiene (not you dummy, the metal's..) and how well you cleaned it prior to laying the beads down. Other than that, shielding the last bead as it cools to protect it from contamination. Let's see, anything else?
Personal notes. Not to be taken on a professional level. I just don't want to learn afterwards that sticking two pieces of tubes together does not equal to a good solid weld.
