Greg,
I've welded many springs over the years and it is a real crap shoot. The material almost always welds very well but the heat from the welding, in most cases makes the spring brittle. My advice is the same a DR. Bill, nothing ventured, nothing gained. Just be sure that if the spring breaks again it is not going to cause other damage inside the lock. If you do try to weld I would suggest that you use mild steel filler rod and make sure that the welder can get in and out quickly. The less heat, the better you chances of success.
Bill G.
