Recovery Processes
Thermally activated processes prior to actual recrystallization, where lattice defects and dislocations rearrange and annihilate, releasing a portion of the stored strain energy.
Stress relieving is the heat treatment after welding that relaxes the structure. Dislocations in the lattice rearrange and partially reduce, which lowers internal stresses in the weld and heat-affected zone. This is done by controlled heating and slow cooling. If you skip it, the weld stays hard and stressed. Under load, it can crack or distort more easily. Especially for thicker parts or high-alloy materials, it's a must, otherwise you'll have trouble later. In practice, that means: heat the weld, hold the temperature for a while to let the process run, then cool slowly. Don't quench, but give it time. The exact values depend on the material, you have to look it up or ask the foreman if in doubt.