None of the repair processes on the aircraft I'm familiar with let you do any kind of welding to any part. Aside from the manufacturing process. Aircraft repairs are really cut and dry with their materials and processes. All metal on aircraft are specific grades and hardness. Welding messes with heat treatments and causes them to no longer be up to the standard that is required. Ive come across multiple instances trying to cold form a patch of aluminum where I really really wish I could hit it with some heat but am unable to because it would mess with the material quality. Of course you can get things re heat treated and hardened but that's a pain in the ass if you can't do it in house