This is a joint which would be found on a typical bicycle. I used a 7/8" hole saw mounted in my milling machine to notch the end of a tube. It fits up against another tube of the same diameter. I TIG welded at about 80 amps with a standard #7 gas cup, 15 cfh argon, 1/16" tungsten and rod.
The tube was originally chromed, but I ground the chrome off prior to welding.
After welding, I ground one side of the weld flat. Is this structurally sound? I don't know.