In the field of power switchgear and high-voltage electrical appliance manufacturing, copper, with its excellent electrical conductivity, thermal conductivity, and processing performance, has become the core material for manufacturing circuit breaker contacts, connectors, and conductive components. Cold extrusion, as a highly efficient and precise metal forming technology, can produce copper stamps with complex shapes and high dimensional accuracy while maintaining the integrity of the material's grain lines. However, the quality of copper cold extrusion largely depends on the level of the pretreatment process. Scientific and systematic pretreatment can not only remove surface contaminants and oxide layers but also improve the material's surface condition and optimize lubrication conditions, thereby ensuring that the cold-extruded copper stamping meets the stringent requirements of power applications for high conductivity, strong wear resistance, and arc resistance.
Core Objectives of Pretreatment
The fundamental purpose of pretreatment for cold extrusion of Copper Stamping Parts is to achieve "three cleans and one optimization":
Removing oil stains: Removing residual grease, fingerprints, and rust inhibitors from processing.
Removing oxide layers: Stripping away naturally formed or high-temperature formed Cu₂O/CuO films.
Removing particulate impurities: Eliminating stamping debris, dust, and other embedded substances.
Optimizing surface condition: Providing a high-adhesion substrate for subsequent lubrication film, ensuring continuous grain flow lines and no tearing during cold extrusion.
Detailed Explanation of the Four-Stage Precision Pretreatment Process
1. Targeted Degreasing and Cleaning: Utilizing a 60–70℃ composite alkaline degreasing solution containing complexing agents and corrosion inhibitors, this process effectively emulsifies grease while protecting the Stamping Copper Sheet substrate from corrosion. Combined with 40kHz ultrasonic vibration, it effectively removes deep pores, bends, and particulate impurities larger than 5μm. After cleaning, it undergoes multi-stage rinsing with pure water and is tested for surface resistance (≤0.5mΩ, refer to ASTM B201) to ensure no ion residue remains.
2. Gradient Oxide Layer Removal: Traditional strong acid cleaning can easily lead to grain boundary corrosion and even hydrogen embrittlement. The modern process uses a micro-etching system composed of 10% dilute sulfuric acid and hydrogen peroxide, reacting precisely at room temperature for 90–120 seconds to uniformly remove the oxide film without damaging the Custom Copper Stamping substrate. The key innovation lies in the addition of a grain boundary corrosion inhibitor, which effectively inhibits intergranular corrosion and avoids microcracks caused by stress concentration during cold extrusion. After treatment, an activation layer of 0.5–1.5 μm is formed on the surface with moderate roughness, significantly improving the adhesion of subsequent phosphating films.
3. Power Industry-Specific Phosphating Treatment: Unlike ordinary rust-preventive phosphating, power industry phosphating needs to balance lubricity and conductivity. A medium-temperature (45–55℃) zinc-calcium phosphating solution for Metal Stamping Parts Electric Copper is used to generate a porous phosphate film 5–8 μm thick, with a film weight controlled at 3–5 g/m². By adjusting the formula, the film porosity is maintained at 30%–40%, which can store lubricant without excessively blocking current. Metallographic analysis shows that a high-quality phosphating film is mainly composed of plate-like crystals (accounting for >80%), which can continuously release lubricating components during cold extrusion, reducing frictional heat and metal adhesion for Copper Sheet Stamping.
4. Composite Lubrication Enhancement Immediately: after phosphating, a saponification sealing treatment is performed for Electrical Copper Stamping Parts, where sodium stearate solution penetrates the micropores to form a metallic soap layer. Subsequently, a nano-graphite dispersion is coated to form a solid lubricating film of 0.2–0.5 μm, reducing the cold extrusion friction coefficient to below 0.08. Finally, it is dried with hot air in an environment of 60°C and ≤15% humidity to prevent moisture retention from causing subsequent oxidation.
As the reliability requirements of power equipment continue to increase, the pretreatment process for Copper Strip Stamping cold extrusion is also being continuously optimized. In terms of power failure prevention, optimization of the phosphate film pore conductivity model reduces the generation of micro-sparks at electrical contacts; grain boundary passivation technology suppresses the risk of stress corrosion cracking in Copper Stamped Components during cold extrusion. These improvements directly enhance the long-term operational stability of power contacts.
In terms of green manufacturing, the application of a waste liquid regeneration system enables copper ion recovery rates to reach over 90%, meeting the requirements of RoHS and other environmental standards. Simultaneously, the extended bath life reduces waste liquid generation, making the pretreatment process more environmentally friendly while ensuring quality.
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