Softening
The loss of strength and hardness in cold-worked materials through thermal processes such as recovery or recrystallization. Dislocation densities are drastically reduced in the process.
Softening occurs when a cold-worked material becomes soft due to heat. During welding, this often happens in the heat-affected zone when you weld a cold-worked sheet. The cold working is lost and the structure recovers or recrystallizes, which reduces the strength at that spot. If you have to weld cold-formed parts, keep the heat input as low as possible. Don't weld more than necessary, let the weld cool, and weld in short sections. For some materials, annealing beforehand helps, but you have to decide depending on the material. If softening has already occurred, you can often only reverse it by heat treatment or cold working.