1. Raw Material Annealing (Primary Annealing)
Application Stage
Performed after the initial processing of raw materials (e.g., copper rods, plates via rolling, drawing, or casting) and before forming processes (e.g., stamping, cold heading).
Primary Objectives
Eliminate work hardening caused by prior processing (e.g., cold rolling, drawing) to restore material plasticity and ductility.
Refine grain structure and ensure uniformity, providing optimal mechanical properties for subsequent forming.
Reduce material hardness to minimize cracking or deformation risks during shaping.
Process Characteristics
Higher temperature range (typically 500–700°C) with longer soaking times (adjusted based on material thickness).
Often requires a protective atmosphere (e.g., nitrogen, hydrogen) to prevent oxidation and hydrogen embrittlement.
Slow cooling (e.g., furnace cooling) post-annealing to avoid reintroducing stress.
2. Secondary Process Annealing (Intermediate/Final Annealing)
Application Stage
Conducted after forming processes (e.g., cold stamping, cold heading, machining), either as an intermediate step or a final treatment.
Primary Objectives
Relieve residual stresses and work hardening from forming, preventing deformation or cracking in service.
Adjust final product properties (e.g., hardness, conductivity, fatigue resistance).
Improve surface quality (e.g., reduce grain boundary oxidation, enhance corrosion resistance).
Process Characteristics
Lower temperature range (300–500°C) with shorter soaking times to prevent excessive grain growth.
Strict atmosphere control (e.g., vacuum or high-purity gas) to ensure oxidation-free surfaces.
Flexible cooling methods (e.g., air cooling or rapid cooling) to balance hardness and ductility.
Key Differences Summary
Practical Considerations
Oxidation Control: Secondary annealing demands stricter surface quality to avoid compromising conductivity or sealing.
Grain Size: Raw material annealing allows moderate grain growth for plasticity, while secondary annealing limits coarsening to preserve strength.
Energy Efficiency: Secondary annealing often prioritizes cost-effectiveness, balancing performance and production costs.
By optimizing annealing parameters for both stages, oxygen-free copper gaskets can achieve excellent form ability, conductivity, fatigue resistance, and dimensional stability.
Post time: Apr-16-2025