Post-Weld Treatment

After welding, let the weld cool and sit first so the structure can settle. Then smooth the surface with an angle grinder or polisher to remove notches and unevenness – they're the classic cause of cracking. If you have high stresses in the component, you can also stress-relieve the weld, but that's more for the furnace or torch flame, depending on what you've got. Main thing is the surface is clean and without sharp transitions, then the weld will hold.