C10200 oxygen-free copper billets arrive with original mill test certificates. Our QC team first cross-checks the heat number, chemical composition and purity data against ASTM B98 requirements. Random sampling is conducted for spectrometer analysis to confirm ultra-low oxygen content (≤0.001%) and high copper purity. Ultrasonic inspection is performed to detect internal porosity, segregation and inclusions, while visual inspection screens surface cracks, scratches and oxidation defects. Qualified billets are labelled with batch information and transferred to the production area; defective billets are isolated and returned to suppliers to avoid mixing into production.
2.Heating, Hot Piercing and Hot Extrusion:
The qualified copper billet is loaded into a low-oxygen controlled heating furnace and heated uniformly to the target forming temperature, with strictly regulated holding time to prevent local overheating, burning and surface oxidation. The heated billet is processed on a rotary piercing mill to form a hollow tube shell. After piercing, the shell is fed into the extrusion press for hot extrusion. Technicians precisely control extrusion speed, mould preheating temperature and graphite lubrication volume, to ensure the extruded mother tube blank has uniform wall thickness, good roundness and stable internal metallographic structure.
3.Pickling, Lubrication and Multi-pass Cold Drawing:
Hot extruded tube blanks are transferred to pickling tanks to remove high-temperature oxide scale. After pickling, thorough water rinsing and air drying are carried out to eliminate residual acid liquid. Special drawing lubricant is evenly coated on the inner and outer surfaces of the tube blank. The blank goes through multi-pass cold drawing, with intermediate straightening after each drawing pass to eliminate bending and twisting deformation. Each pass gradually reduces outer diameter, inner diameter and wall thickness, bringing dimensions close to the final tolerance, and further improving surface finish and dimensional precision.
4.Bright Annealing Heat Treatment:
Cold drawn copper pipes are loaded into a closed bright annealing furnace filled with inert protective atmosphere. The pipes are heated to the specified annealing temperature and kept for a fixed holding time to fully release residual stress accumulated during cold drawing, restore the ductility of oxygen-free copper and stabilize electrical and thermal conductivity. The protective gas isolates air to prevent surface discoloration and oxidation. The temperature curve and holding parameters of each batch are automatically recorded for process traceability.
5.Cutting, Finishing and Multi-item Inspection:
Annealed pipes are cut to the required straight lengths by precision cutting equipment. Both ends of the pipe are deburred and chamfered smoothly to remove sharp edges. A full range of inspections is implemented: dimensional testing of outer diameter, inner diameter, wall thickness and straightness; visual inspection for surface scratches, pits and stains. Conductivity testing and air tightness leak testing can be arranged according to customer requirements. Non-conforming products are marked clearly and segregated for rework or scrapping.
6.Marking, Packaging and Shipment:
All pipes passing all inspection items are permanently marked with material grade, specification, heat number and ASTM standard. Plastic end caps are installed on both pipe ends to block dust and prevent edge damage. Pipes are bundled with soft separating materials to avoid friction scratches. Moisture-proof film wrapping and sturdy export wooden cases are adopted for packaging to resist collision and deformation during sea or land transportation. The matched MTR documents, including chemical analysis report, conductivity test record and dimensional inspection data, are prepared and delivered together with goods for complete quality traceability.