What Is C26000 (CDA 260)?
CDA 260 is the Copper Development Association designation for UNS C26000, universally known as cartridge brass or 70/30 brass. It is a binary copper-zinc alloy containing approximately 70 percent copper and 30 percent zinc. The fully alpha microstructure gives C26000 the highest ductility of the yellow brass series, which is why it is the first choice for deep drawing, stamping, spinning, and other severe cold-forming operations.
Chemical Composition
| Element | Content (%) |
|---|---|
| Copper (Cu) | 68.5 - 71.5 |
| Iron (Fe), max | 0.05 |
| Lead (Pb), max | 0.07 |
| Zinc (Zn) | Balance |
Mechanical Properties by Temper
| Temper | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| Soft annealed (OS) | 320 - 370 | 100 - 150 | 50 - 62 |
| Quarter hard (H01) | 370 - 410 | 270 - 320 | 40 - 45 |
| Half hard (H02) | 420 - 460 | 350 - 400 | 20 - 30 |
| Hard (H04) | 500 - 560 | 430 - 480 | 8 - 15 |
| Extra hard (H06) | 590 - 650 | 445 - 480 | 3 - 8 |
The soft annealed condition is the reference state for forming: elongation above 50 percent allows deep cups, severe flanging, and complex press work without cracking. As strength rises with cold work, ductility falls, so parts needing both strength and form are often formed soft and then strength is achieved by the work itself or by controlled temper selection.
Available Product Forms and Specifications
| Form | Governing Specification |
|---|---|
| Bar and rod | ASTM B36, ASTM B19, SAE J463, SAE J461 |
| Plate and sheet | ASTM B19, ASTM B36, AMS 4505, AMS 4507 |
| Strip | ASTM B36, ASTM B569, ASTM B888 |
| Seamless tube | ASTM B135 |
| Welded tube | ASTM B587 |
| Wire | ASTM B134 |
C26000 vs C36000: Two Different Alloys
C26000 (cartridge brass) is a binary 70/30 alloy with excellent cold formability but modest machinability, rated about 30 percent of free-cutting brass. C36000 (free-cutting brass) contains about 61 percent copper, 35 percent zinc, and 3 percent lead; the lead makes it the machinability benchmark of the brass family, rated 100 percent, but the alloy cracks under severe bending and cannot be deep drawn. Selection is therefore simple: form it in C26000, machine it in C36000.
Applications
Deep-drawn shells, cups, and housings; the historical cartridge-case application.
Stamped electrical terminals, connectors, and socket components.
Radiator cores, heater cores, and heat exchanger fins.
Fasteners, springs, grommets, and eyelets formed at high speed.
Architectural trim, decorative hardware, and jewelry findings.
Frequently Asked Questions
Q: Why is C26000 called cartridge brass?
A: It was the standard material for ammunition cartridge cases because its high ductility permits deep drawing into thin-wall cups without cracking.
Q: What does 70/30 mean?
A: Approximately 70 percent copper and 30 percent zinc, the nominal composition of C26000.
Q: Is C26000 the same as C260?
A: Yes. C260 is the common shorthand for UNS C26000; the full designation is preferred in purchase documents.
Q: How does C26000 compare with C36000 for machining?
A: C36000 is rated 100 percent machinability and is the best choice for screw-machine parts. C26000 is rated about 30 percent and is chosen for forming, not heavy machining.
Q: What is the difference between soft and hard C26000 strip?
A: Soft strip has maximum ductility for deep drawing; hard strip has higher strength and springback for parts that must resist bending or flexing.
Q: Can C26000 be used in seawater?
A: No. High-zinc brass dezincifies in seawater. For marine service, use copper-nickel, aluminum brass, or naval brass.
