-- Analysis of the Technological breakthroughs and Industrial Practices behind Customized Fasteners

In high-end equipment manufacturing, new energy vehicles, aerospace and other fields, special-shaped copper bolts, with their advantages of corrosion resistance, electrical conductivity and customized structure, are becoming key components to replace traditional standard bolts. Its manufacturing process integrates materials science, precision forming and surface treatment technology, forming a highly specialized production system. This article, based on industry practice, deeply analyzes the core processes and industrial trends of manufacturing special-shaped copper bolts.

I. Material Selection: Differentiated Applications of oxygen-free Copper and Brass
The material selection of special-shaped copper bolts directly affects their performance and applicable scenarios. At present, mainstream materials are divided into two categories:

Oxygen-free copper (OFC) : With a purity of over 99.99% and a conductivity exceeding 100%IACS, it is suitable for scenarios with extremely high requirements for conductivity, such as high-frequency electrical connections and precision instruments. For instance, the irregular-shaped copper bolts in the battery packs of new energy vehicles need to withstand large current transmission, and oxygen-free copper can ensure low resistance and stability.
Brass (H62/H65) : A copper-zinc alloy with high mechanical strength and resistance to salt spray corrosion, it is widely used in harsh environments such as Marine engineering and chemical equipment. A certain shipbuilding enterprise once experienced equipment failure due to bolt corrosion. After switching to brass special-shaped bolts, the service life was extended to over 10 years.
Technical challenge: The plastic deformation capacity and work hardening characteristics of copper materials need to be precisely controlled. For instance, oxygen-free copper is prone to cracking during cold heading. It is necessary to adjust the metallographic structure into fine spherical pearlite through spheroidizing annealing process to enhance plasticity.

Ii. Precision Forming: The four-step cold extrusion process breaks through traditional limitations
The complex structure of irregular-shaped copper bolts (such as multi-level steps and asymmetrical heads) poses extremely high requirements for the forming process. The traditional turning process is inefficient and causes serious material waste, while the cold extrusion process achieves near-net forming through multiple plastic deformations and has become the mainstream in the industry.

Typical case: The "four-stage cold extrusion process" developed by a certain enterprise can simultaneously complete the forming of screw sections, circular flanges, rectangular heads and ring grooves.

First cold extrusion: One end of the billet is pressed to the diameter of the billet before threading, and the axial deformation is controlled to be ≤15%.
Second cold extrusion: Preform the head, reserving allowance for subsequent deformation;
The third cold extrusion: The double flange structure is formed in steps to avoid cracking caused by metal accumulation.
The fourth cold extrusion: The final rectangular head is formed, and the ring groove is formed through the extrusion of the remaining material.
Technical advantages: This process reduces the number of machining procedures, increases the material utilization rate to over 92%, and the product dimensional accuracy reaches ±0.05mm, which is three times higher than that of traditional processes.

Iii. Surface Treatment: A Balance between Functionality and Environmental Friendliness
The surface treatment of special-shaped copper bolts should take into account corrosion resistance, electrical conductivity and environmental protection requirements. Common processes include:

Electroplated nickel/tin: When the nickel layer thickness is ≥5μm, the salt spray test can last up to 1000 hours without corrosion, making it suitable for Marine environments. Tin plating is used in food-grade equipment to prevent heavy metal contamination.
Passivation treatment: A protective film is formed through chromate or chromium-free passivation solution to enhance corrosion resistance while maintaining electrical conductivity. After a certain 5G base station supplier adopted the chromium-free passivation process, its products passed the EU RoHS certification and its export volume increased by 40%.
Dacromet coating: With zinc sheets, aluminum sheets and inorganic substances as the base materials, it has a temperature resistance of up to 300℃ and is suitable for high-temperature scenarios such as engine compartments.
Industry trend: With the advancement of the "dual carbon" goals, environmentally friendly processes such as water-based coatings and vacuum coating are gradually replacing traditional electroplating. For instance, a certain enterprise has developed a nano-ceramic coating with a thickness of only 2-3μm, which can achieve the same corrosion resistance effect and reduce VOC emissions by 90%.

Iv. Quality Control: Full-chain inspection from raw materials to finished products
The manufacturing of special-shaped copper bolts needs to pass through multiple quality checkpoints:

Spectral analysis: Detect the purity and impurity content of copper materials to ensure compliance with ASTM B152 standards;
Metallographic examination: Observe the morphology of pearlite after spheroidizing annealing to avoid cold heading cracking caused by coarse lamellar structures.
3D scanning: Compare the design model with the physical object to detect detailed deviations such as head fillets and thread profiles.
Fatigue test: Simulating the risk of loosening in a vibration environment, a certain car manufacturer requires that the preload loss of bolts after 10^6 cycles be no more than 15%.
Case inspiration: In 2025, Guangdong Fasite Precision Hardware obtained a patent for the "Assembly Process of Special-shaped Gaskets and Bolts". By optimizing the fit clearance between gaskets and bolts, the connection reliability was increased by 20%. This technology has been applied to the high-speed rail track fastening system.

V. Industry Outlook: The Integration of Customization and Intelligence
According to market research institutions' predictions, the global market size of special-shaped copper bolts is expected to grow at an average annual rate of 8.5% from 2025 to 2030, with the demand from the new energy vehicle and semiconductor equipment sectors accounting for more than 60%. Enterprises are building their competitiveness in the following ways:

Digital process library: Establish a database of material properties, forming parameters, and defect patterns to achieve rapid process optimization;
Flexible production line: It adopts multi-station cold heading machines in collaboration with robots, supporting rapid switching of small batches and multiple varieties.
Material innovation: Develop copper-based composite materials (such as copper-graphene) to enhance strength while maintaining electrical conductivity.
Conclusion: The manufacturing of special-shaped copper bolts has shifted from "experience-driven" to "data-driven", and their process accuracy and quality stability are becoming the "invisible cornerstone" of high-end equipment manufacturing. With the deep integration of materials science and intelligent manufacturing, this niche field will continue to drive industrial upgrading and inject new impetus into the global manufacturing industry.