Cyclic Hardening
Cyclic hardening is the process where metals become stronger under repeated loading. This happens through microscopic changes in the crystal lattice.
Physicochemical mechanism of action
Under cyclic loading (as in welding or mechanical stress), microscopic restructuring and dislocation pile-ups occur in the metal's crystal lattice. These changes lead to increased stress amplitude and greater flow resistance.
Metallurgical relevance & risks in welding
Cyclic hardening can have both advantages and disadvantages. Positive aspects are improved strength and toughness of the weld. However, it can also lead to increased stress pickup, which can cause cracks or wear issues over time. It's important to respect the material's stress limits.
Workshop practice & action items
To handle cyclic hardening effectively, take the following measures:
• Temperature control: Make sure the weld cools in an optimal temperature range (e.g., t8/5 between 10 and 20 seconds for many steel grades).
• Stress optimization: Avoid excessive stress by carefully planning mechanical loads.
• Material selection: Choose materials with low cyclic hardening if the application requires it.