Secondary precipitation hardening
Secondary precipitation hardening increases strength by forming nanosized particles in the weld. They block dislocations and make the steel harder.
Physical-Chemical Mechanism of Action
Secondary precipitation hardening occurs when nanosized particles form in the weld from a supersaturated solid solution. These particles hinder the movement of dislocations in atoms, resulting in increased strength.
Metallurgical Relevance & Welding Risks
This hardening can contribute to increased toughness and improved mechanical properties. However, it can also lead to hot cracking if the weld is not cooled properly. Too fast cooling can prevent the particles from having enough time to form.
Workshop Practice & Action Guidelines
To take advantage of secondary precipitation hardening, it is important to ensure controlled cooling of the weld. The critical time span t8/5 should be between 10 and 20 seconds. This ensures the particles have enough time to form without the structure becoming too glass-hard.