C260 (UNS C26000) is a binary copper-zinc alloy commonly known as cartridge brass or 70/30 brass, with approximately 70% copper and 30% zinc. It is widely used for electrical components, electronic parts and mechanical fasteners. The alloy has good strength and excellent cold-forming properties, but its stress-relaxation characteristics are poor, so it does not make a particularly good spring material. Although it has good conductivity, the solderability of the alloy is severely impaired by its high zinc content.
Chemical Composition (UNS C26000)
| Element | Content, % |
|---|---|
| Copper (Cu) | 68.5 – 71.5 |
| Lead (Pb) | 0.07 max |
| Iron (Fe) | 0.05 max |
| Zinc (Zn) | Balance |
Physical Properties
| Property | Value |
|---|---|
| Annealing range | 800 – 1400 °F |
| Density | 0.308 lb/in³ (8.53 g/cm³) |
| Electrical resistivity (annealed) | 37 Ω·cir-mil/ft @ 68 °F |
| Electrical conductivity (annealed) | 28% IACS @ 68 °F |
| Thermal conductivity | 70 Btu/ft²/ft/hr/°F @ 68 °F |
| Coefficient of thermal expansion | 11.1 × 10⁻⁶/°F (68–572 °F) |
| Modulus of elasticity (tension) | 16,000 ksi (110 GPa) |
| Modulus of rigidity | 6,000 ksi (39 GPa) |
| Melting point (solidus) | 1,680 °F (915 °C) |
| Melting point (liquidus) | 1,750 °F (955 °C) |
Note: typical values; guaranteed properties depend on product form and the applicable product specification (for example ASTM B36 sheet/strip, B134 wire, B135 tube).
Temper and Tensile Strength (Round Wire, Typical)
| Temper Name | Temper Code | Tensile Strength (ksi) |
|---|---|---|
| 1/8 Hard | H00 | 50 – 65 |
| 1/4 Hard | H01 | 62 – 77 |
| 1/2 Hard | H02 | 79 – 94 |
| 3/4 Hard | H03 | 92 – 107 |
| Hard | H04 | 102 – 117 |
| Extra Hard | H06 | 115 – 129 |
| Spring | H08 | 120 min |
Standard Designations
C26000 (UNS) is equivalent to CuZn30 (EN), H68 (Chinese GB standard) and C2600 (Japanese JIS). The chemical composition (Cu ~70%, Zn ~30%) and key properties are essentially identical across these standards.
Typical Applications
- Ammunition cartridge cases and shells.
- Deep-drawn housings, stampings and radiator tanks.
- Locks, hinges, hardware and fasteners.
- Electrical and electronic components requiring good formability.
FAQ
What is the difference between C260 and C360 brass?
C260 (cartridge brass) is a binary Cu-Zn alloy with excellent cold-forming properties (deep drawing, bending) but fair machinability (about 20% of free-machining brass). C360 (free-cutting brass) contains about 61% Cu, 35% Zn and 3% Pb, giving dramatically better machinability (the 100% industry reference) at the cost of poorer cold workability and ductility. Use C260 for formed parts and C360 for extensive drilling, turning or milling.
What is the difference between C2600 and C2680 (JIS)?
C2600 (JIS) is the direct equivalent of C26000 - CuZn30 with excellent cold workability. C2680 is CuZn35 (65/35 brass): slightly stronger and cheaper, but with reduced ductility and cold-forming capability; it suits simpler stamped parts, hinges and plumbing fixtures.
Why is C260 called cartridge brass?
The name comes from its traditional use in ammunition cartridge cases, where its combination of deep-drawing formability, strength and corrosion resistance is required.
Can C260 be soldered?
Yes, but the high zinc content impairs solderability compared with copper; proper flux selection and surface preparation are required for reliable joints.
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