Annealing C10100 is about more than just softening the metal; it is a delicate balance of restoring ductility while preventing excessive grain growth. Because C10100 Oxygen-Free Electronic copper lacks the alloying elements that pin grain boundaries, it is highly sensitive to time and temperature during heat treatment.
If you over-anneal, you end up with a "large grain" structure that causes an "orange peel" surface during bending and creates mechanical weak points in high-pressure vacuum systems. For engineers working with 99.99% pure copper, controlling the grain size is the only way to ensure the material remains both workable and structurally sound.
What is the optimal C10100 annealing temperature?
The recrystallization of C10100 begins at relatively low temperatures compared to other alloys. While standard stress relieving can occur as low as 200°C to 250°C, a full anneal typically requires higher temperatures depending on the amount of prior cold work.
Stress Relieving: 200°C to 300°C (390°F - 570°F).
Full Annealing: 375°C to 650°C (700°F - 1200°F).
For a C10100 Round, Square & Flat Bar that has been heavily cold-worked, an annealing temperature of 500°C for 30 to 60 minutes is usually sufficient to restore the material to an O60 (Soft Anneal) temper without causing runaway grain growth.
Effect of Annealing Temperature on C10100 Grain Size
| Temperature (°C) | Resulting Grain Size (mm) | Surface Quality After Bending | Search Intent |
| 375°C | 0.015 - 0.025 | Very Smooth (Fine) | stress relieving C10100 |
| 500°C | 0.035 - 0.050 | Smooth (Standard) | heat treating OFE copper |
| 650°C | 0.070 - 0.110 | Orange Peel (Coarse) | grain size of C10100 |
| > 700°C | Rapid Growth | Structural Weakness | Over-annealing risk |
Consult GNEE Engineers: Optimize Your C10100 Annealing Curve
Why is the annealing atmosphere critical for OFE copper?
Maintaining 99.99% purity requires a non-oxidizing atmosphere. Even though C10100 is immune to hydrogen embrittlement (due to its less than 5 ppm oxygen content), you should still avoid heating it in open air.
Vacuum Annealing: The gold standard for electronics. Prevents surface tarnish and preserves the 101% IACS conductivity.
Inert Gas (Nitrogen/Argon): Prevents oxidation but requires high-purity gas to avoid surface "smut."
Hydrogen/Dissociated Ammonia: Safe for C10100 but dangerous for standard ETP copper.
As we discussed in our guide on C10100 bending and forming, if the grain size becomes too large during annealing, the material will fail during subsequent forming operations. Ensuring your material meets ASTM B170 Grade 1 standards includes verifying the grain size limits specified in your purchase order.
Controlling Work Hardening in C10100 Foil and Wire
For manufacturers using C10100 Foil, annealing is often performed between multiple rolling passes. If the grain size is not controlled, the foil will develop pinholes or tear during the final thin-gauge reduction.
Similarly, in fine wire drawing, localized annealing is used to prevent the wire from becoming too brittle. Controlling the C10100 annealing temperature ensures that the wire remains ductile enough for high-speed winding while maintaining its high electrical efficiency.
Annealing C10100 is a precise engineering step, not just a furnace cycle. By keeping your grain size between 0.025 and 0.050 mm, you ensure the best balance of ductility and surface finish. GNEE METAL provides certified Grade 1 OFE copper in various tempers, and we can provide specific heat treatment data to help you integrate our material into your production line without the risks of over-annealing or surface oxidation.
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GNEE METAL Product Range
| Product Type | Shapes Available | Common Grades | Diameter/Thickness Range | Length/Width Range | Applications |
|---|---|---|---|---|---|
| Copper Tubes | Round, Square, Rectangular, Coiled | C10100, C10200, C11000, C12200, C12000 | OD: 0.5mm - 300mm Wall: 0.1mm - 20mm | Up to 6000mm or custom | HVAC, Plumbing, Heat Exchangers, Refrigeration, Hydraulic Lines |
| Copper Plates & Sheets | Flat Sheets, Perforated, Embossed, Tread Plate | C10100, C11000, C12200, C23000, C26000 | Thickness: 0.1mm - 200mm | Width: Up to 2500mm Length: Up to 6000mm | Electrical Busbars, Roofing, Cladding, Gaskets, Transformers |
| Copper Bars & Rods | Round Bar, Square Bar, Hexagonal Bar, Flat Bar | C10100, C11000, C14500, C17200, C18200 | Diameter: 1mm - 300mm | Length: 1000mm - 4000mm | Machined Components, Electrical Contacts, Busbars, Fasteners |
| Copper Wires | Round Wire, Flat Wire, Square Wire, Stranded, Braided | C11000, C11600, C17200, C17510 | Diameter: 0.05mm - 12mm | Coil weights: 1kg - 500kg | Electrical Wiring, Cables, Springs, Mesh, Welding Wire |
| Copper Strips & Coils | Thin Strip, Foil, Slit Coil, Profile Strip | C11000, C12200, C19400, C26000, C26800 | Thickness: 0.03mm - 5mm | Width: 2mm - 1000mm Coil ID: 300mm - 600mm | Transformers, Radiators, Shielding, Terminals, Connectors |
About Our Factory
We operate a full range of production lines including extrusion presses, cold drawing benches, high-speed rolling mills, slitting lines, and precision CNC machining centers, enabling us to produce copper tubes, plates, bars, wires, and strips entirely in-house. For quality assurance, we maintain a dedicated inspection laboratory equipped with spectral analyzers, universal testing machines, hardness testers, surface roughness testers, and optical measuring instruments. Every batch is tested for chemical composition, mechanical properties, and dimensional accuracy before shipment. Our production capacity reaches 500+ tons per month, and we hold ISO 9001:2015 certification with full traceability from raw material to finished product. Whether you need standard mill stock or custom-processed components, we deliver precision copper products with short lead times and complete material certification.
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