1 Common Annealing Temperature Range
For commercially pure copper (such as C10100, C11000, oxygen‑free copper, electrolytic tough pitch copper):
Low‑temperature stress relief annealing: 150–250 °C
Used only to reduce residual stress without obvious softening.
Full recrystallization annealing: 300 °C – 400 °C (573 K – 673 K)
This is the most commonly used industrial annealing temperature for pure copper after cold working.
2 Temperature Selection Principles
Below 200 °C: Only stress relief occurs, recrystallization is very slow or does not occur.
Around 250 °C: Recovery begins, but softening is limited.
300–400 °C: Full recrystallization completes rapidly. Pure copper becomes soft, ductile, and conductive.
Above 450 °C: Grain growth occurs, resulting in coarse grains. This reduces strength and surface quality, and may cause oxidation or even grain boundary weakening.
3 Holding Time and Cooling
Holding time is usually 30 minutes to 2 hours, depending on thickness and loading.
Cooling method:
For most electrical and general applications: furnace cooling or air cooling
For surface‑sensitive products: protective atmosphere or vacuum annealing to prevent oxidation
Conclusion
Annealing after cold working is essential for pure copper to eliminate work hardening, restore ductility, release residual stress, and improve conductivity. The optimal industrial annealing temperature is typically 300 °C – 400 °C, which achieves complete recrystallization without excessive grain growth. Properly annealed pure copper combines excellent formability, mechanical stability, and high electrical and thermal conductivity, meeting the requirements of mass production and high‑performance applications.
