Recrystallization process
The formation of a new, strain-free microstructure via nucleation and grain growth in a previously cold-worked material at elevated temperature, restoring the mechanical properties prior to deformation.
Recrystallization means: when you cold-form steel, the grains become fine and stressed. When heated, new, unstressed grains form from them – the structure becomes softer and more formable again. In welding, this happens automatically in the heat-affected zone. But if you do it deliberately, for example after cold straightening, you anneal the part so that the structure rebuilds. If you anneal too hot or too long, the grains grow strongly – then the material becomes coarse-grained and brittle. In practice, this means: you want to heat the part evenly, but not overdo it. Better to work controlled in an oven or with a heating mat than to go wild with a flame. When the structure is fine and uniform again, you've done everything right.