Critical Deformation Threshold
The critical deformation threshold is the minimum degree of deformation at which recrystallization occurs in a material. Below this threshold, only recovery takes place.
Physical-Chemical Mechanism of Action
The critical deformation threshold is the point at which the atomic structure of a material is so strongly altered that a new crystal structure forms through recrystallization. This process requires more energy and leads to a new, less defective microstructure.
Metallurgical Relevance & Welding Risks
If deformation stays below the critical threshold, the material lattice cannot fully reorganize. This leads to a fine-grained structure and increases stresses in the weld, which can cause cracks and hot cracks. Additionally, the toughness of the material may decrease.
Workshop Practice & Action Instructions
To reach the critical deformation threshold, ensure sufficient deformation during the welding process. This can be achieved with appropriate stress and adequate heat treatment time. For steels with a high deformation threshold (premium steel grades), make sure deformation is not too low to ensure complete recrystallization.