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Welding Process for Copper‑Braided Belts Using Polymer Diffusion Welders
Aug 21,2026
Copper‑braided belts welded by polymer diffusion welders feature good flexibility and high vibration resistance. They are widely used for power connections in high‑low‑voltage distribution cabinets, transformers, new‑energy facilities and rail transit. Conventional welding of copper‑braided belts frequently causes strand fraying, cold joints, hardened terminals, strand blow‑off, unstable resistance and delamination‑peeling. Under long‑term heavy‑current operation, workpieces tend to overheat and detach with shortened service life.
I Welding Difficulties of Copper‑Braided Belts
Copper‑braided belts are interwoven from fine copper strands and feature loose structure and abundant inter‑layer gaps. Conventional fusion welding cannot fully eliminate internal gaps, which easily lead to hidden cold joints and voids.
II Welding Process Flow
1.Pre‑weld finishing and cleaning: Smooth out wrinkles and lifted strands on belt terminals, trim stray loose strands for neat strand arrangement. Remove surface oil, copper chips and black oxide layers to prevent impurity‑blocked atomic diffusion and fundamentally avoid cold joints and delamination.
2.Layer‑by‑layer smoothing and degassing: Smooth and compress multi‑layer braided belts layer by layer to fully expel inter‑strand and inter‑layer air. Never weld directly with residual gaps or loose sections, to avoid internal void interlayers.
3.Centered precise positioning: Place belt terminals centrally inside molds in upright posture without offset or one‑side suspension, securing even overall stress distribution and preventing local loose cold joints.
4.Low‑pressure pre‑press forming: Apply slow and gentle pressure to gradually compress loose copper strands, close micro‑gaps and achieve tight overall bonding of braided layers as foundation for even diffusion fusion.
5.Constant‑temperature constant‑pressure diffusion fusion: Maintain stable temperature and pressure for sufficient inter‑penetration and mutual fusion of copper‑strand atoms. The loose braided structure is integrated into one compact mass to eliminate local incomplete fusion.
6.Pressure‑held slow‑cool setting: Do not release pressure immediately upon welding completion. Cool slowly under pressure to eliminate spring‑back stress, lock flat terminal dimensions and prevent deformation, warpage and micro‑cracks.
III Core Parameter Tuning Logic
1.Excessive pressure crushes copper strands and hardens‑embrittles terminals; insufficient pressure fails to expel gaps completely and leads to delamination and cold joints.
2.Apply medium‑temperature constant‑temperature diffusion. Fine copper strands cannot sustain high temperature; high temperature hardens strands and eliminates flexibility. Moderate temperature enables gradual penetration‑fusion to secure sound welding while preserving material toughness.
3.Secure sufficient diffusion time. Multi‑layer braided belts feature long diffusion paths. Insufficient time brings hidden cold joints. Adequate heat‑holding enables thorough bonding of every copper‑strand layer and prevents post‑weld delamination and detachment.
IV Specification for Graphite‑Mold Usage and Maintenance
Mold conditions influence batch quality. Mold surfaces shall be flat, smooth, scratch‑free, carbon‑deposit‑free and free of bumps and dents. Periodically clear copper chips and impurities off mold surfaces to avoid isolating layers triggered by foreign bodies which cause cold joints. Maintain even mold temperature to prevent batch‑to‑batch quality fluctuation caused by large temperature difference.
V Common Defects
1.Frayed and hairy terminals: untidy pre‑weld strand finishing and insufficient pre‑pressing.
2.Terminal bulges, internal voids and delamination: loose braided layers, incomplete degassing and air‑trapping under high pressure.
3.Hardened terminals prone to fracture upon bending: excessive temperature and prolonged heat‑holding induce copper‑strand embrittlement.
4.Unstable resistance and over‑heating under current: surface impurities, insufficient diffusion and loose bonding.
5.Skewed forming and uneven thickness: placement offset, uneven pressure and uneven mold surfaces.
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Wuxi HAIFEI Intelligent Equipment Co., Ltd.
Wuxi HAIFEI Welding Equipment Co., Ltd.
Add: 28 Shuiyun Road, Yuecheng, Jiangyin, Jiangsu Province, China. (Postal Code: 214404)
Mobile: +86 18915302352
Email: wushijie@jshaifei.com