Inspect incoming C10200 oxygen-free copper billets. Test chemical composition, electrical conductivity, hardness and surface integrity by spectrometer. Check for internal porosity, slag inclusion, cracks and severe oxidation. Record inspection data; unqualified billets will be isolated and returned to supplier.
2.Hot Extrusion Forming:
Load qualified copper billets into heating furnace, heat uniformly to the target extrusion temperature under inert protective atmosphere. Transfer heated billets to the extrusion press, extrude through precision circular die under stable hydraulic pressure. Control extrusion speed and temperature curve to avoid local overburning, surface tearing and uneven grain structure, obtaining preliminary solid round copper bar blank.
3.Multi-pass Cold Drawing Sizing:
Take extruded copper blanks for sequential multi-pass cold drawing. Match different drawing dies step by step to reduce cross-section incrementally. Strictly control drawing speed and lubrication condition, to achieve required outer diameter tolerance, improve roundness, straightness and surface finish of the round bar.
4.Intermediate Stress Relief Annealing:
After each cold drawing pass, carry out protective atmosphere annealing. Heat the copper bar to the specified temperature and keep constant for required holding time, then cool slowly. This step eliminates residual cold working stress, restores ductility of C10200 copper, avoids cracking during subsequent drawing and forming, and stabilizes material internal grain structure.
5.Finishing & Surface Treatment:
Straighten the copper bar on straightening machine to correct bending deformation. Cut to custom fixed lengths. Remove burrs, oxide film and surface scratches by buffing and pickling cleaning. Rinse thoroughly with clean water and dry completely, ensure uniform bright copper surface without oil stain, water mark and oxidation spots.
6.Final Inspection & Packaging:
Conduct comprehensive finished product inspection: dimensional tolerance check, visual surface inspection, conductivity test, hardness test and grain check. Label qualified bars with material grade, specification and batch number. Wrap with anti-scratch protective film, arrange neatly and pack into fumigated wooden cases, add moisture-proof desiccant for safe transportation.