Pretty sure that "welding" is actually brazing/soldering. Quite poorly done. Once you've "blobbed" it on like that, it can be smoothed out with a flat bladed screwdriver then flashed with the flame to get penetration. Better surface prep. and it wouldn't have taken so many goes to get it to stick. I do have trouble getting enough heat into the piece though. Setting a conventional blowlamp generally warming the whole area while you use a more concentrated flame on the specific bit to be soldered helps.
It's something it's perfectly possible for the home mechanic to do with a bit of practice. You can buy the rods in B&Q.
I even managed to solder a couple of red bull cans together to make a mini alcohol stove using the stuff.
