Can welded tools be as strong as one piece metal tool?
Looking at the link, that is a stainless spade and appears to have been TIG welded. The main problem with welded tools is someone's repair weld. They weld without proper preparation and the weld holds forever, but the metal breaks around the weld due to heat stress. TIG welding does not over heat the metal the way MIG or ARC welding will, this will allow the tool to last a long time. Most steel tools that are welded are properly heat treated to prevent the weld from weakening the steel around the weld. If you think about a Hoe, most have a sheet metal blade that is just spot welded onto a piece of round rod.