Welding looks easy. I've tried it many times, it's really hard. There's a very small line between not fusing the metal and burning a big hole in the work.
Welding is very rare in aircraft because of the difficulty in verifying a correct weld.
Difficulty is relative and practice makes perfect. People love to compare difficulty of processes, metals, positions etc. They’re all hard without practice. They’re all easy with a lot of practice. If you just want to fuse some metal it can be very frustrating to fight with the welder and get nowhere. But if you’re deliberately practicing, getting hundreds of hours under the hood, you will get good. The other crucial component is that other humans have worked out how to weld metals effectively and have documented it. There are tons of handbooks and manuals, detailing which techniques and consumables you should be using for a given weld. Combine that with lots of time under the hood, and you’ll be making phenomenally good welds without difficulty.
> People love to compare difficulty of processes… they’re all easy with a lot of practice.
People also love to diminish the value of skilled trades and high quality craftspeople. If it takes thousands of hours to become a competent welder then it’s hard. It’s okay to say that things are hard.
I was doing pretty nice TiG welding after one class, which was probably around 2 hours per session times four sessions. Better than most of what I see with tradespeople in the area. That was true for most if not all of the students there.
A key was that the instructor was a master. He created amazing works of art by constructively adding metal. He was trained in all sorts of esoteric areas too, like underwater welding.
There's about a mile-wide gap between being able to fuse two pieces of metal without leaving a hole (which is fine for most professional work), and being able to make a tiny insect by building it out of little dots of metal. Learning to do what our instructor did would be like black magic.
However, what you're describing just consists of having proper technique and proper equipment. It's a very learnable skill.
I don't think you can get there by stumbling around yourself in a workshop, though.
(Unfortunately, it's also a forgettable skill if you don't practice, which I didn't)
I don't think it's difficulty in verifying, it's just not the right tool for the job in a lot cases on an airplane. Aircraft don't use much steel, and aluminum welds typically have a heat affected zone (HAZ) adjacent to the weld which is weaker and more prone to fatigue cracking. For this reason aluminum is often riveted or bolted.
Verification of inclusion and heat affected zones is indeed extremely difficult. It’s a very skill sensitive process that’s hard to get right 100% of the time
It's also capable of handling very thin material and it's very repeatable.
The https://en.wikipedia.org/wiki/GTW_Generation_15 trains also rely on it, as the weight limit stems from the track (to passively bank in curves, the cabin is underneath the rail (and there's only one rail as this arrangement is stable and just acts like a pendulum), so the track needs to be a bridge).
Welding is incredibly important in modern construction. All steel-framed buildings are held together by welding pretty much. Not surprisingly it is quite highly paid (at least in my country).
Welding is very rare in aircraft because of the difficulty in verifying a correct weld.