Recovery
Reduction of lattice defects and rearrangement of dislocations upon heating without forming new grain boundaries. It precedes recrystallization and partially relieves internal stresses.
When you weld cold-formed material, you heat the area in the heat-affected zone. This can partially anneal the hardening from cold forming, making the material softer and more relaxed. That's not necessarily bad, but you have to know that the strength there is then no longer that of the base material. The residual stresses from forming often remain partially and add to the welding stresses, increasing the risk of cracking. So keep the heat input as low as possible and don't let the part get too hot. If you want to get rid of the residual stresses beforehand, stress-relief annealing in an oven helps, but the whole part must be heated evenly. Local post-heating with a torch is usually counterproductive, as it creates new stresses.