Grade Overview
UNS C26000, known commercially as cartridge brass or 260 brass, is a single-phase alpha copper-zinc alloy with a nominal 70/30 copper to zinc ratio. It is one of the most versatile of all the brasses: it can be cold reduced to a high degree, it takes an attractive yellow finish, it solders and brazes readily, and it resists corrosion in ordinary indoor and mild outdoor atmospheres. Those properties explain its long association with drawn cartridge cases and its continuing use across hardware, electrical and decorative products.
Because the alloy gains strength from cold work, the delivered temper is the single most important purchasing variable. Specify the temper, the applicable product standard and the direction of test wherever the part will be formed or loaded.
Chemical Composition
| Element | Composition (% by weight) | Comment |
|---|---|---|
| Copper (Cu) | 68.5 - 71.5 | Narrow band controls phase structure |
| Zinc (Zn) | Remainder | Principal alloying element |
| Lead (Pb) | 0.07 max | Kept low for ductility and lead control |
| Iron (Fe) | 0.05 max | Residual |
| Other elements | 0.15 max total | Within the limits of the product specification |
Common Product Forms and Dimensions
| Form | Typical thickness or diameter | Typical width |
|---|---|---|
| Sheet and strip | 0.2 - 6.0 mm | 50 - 600 mm |
| Plate | 6.0 mm and above | Up to 1000 mm |
| Rod and bar, round | 3 - 50 mm diameter | Straight lengths or coils |
| Wire | 0.3 - 12 mm | Coils |
| Tube | 10 - 150 mm outside diameter | 1 - 12 mm wall |
Strip is normally supplied in coil with a specified temper and grain size, while rod and bar are supplied straight in standard lengths or in coils for subsequent drawing. Tube is available as seamless or welded and drawn stock depending on the pressure and appearance requirements of the application.
Tempers and Typical Mechanical Properties
| Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|
| Annealed | 300 - 400 MPa | 100 - 150 MPa | 55 - 70 % | 50 - 70 HV |
| Cold worked, half hard (H02) | 450 - 550 MPa | 350 - 420 MPa | 15 - 25 % | 100 - 130 HV |
| Cold worked, hard (H04) | 550 - 650 MPa | 480 - 550 MPa | 5 - 12 % | 140 - 180 HV |
Typical physical values for the alloy are a density of about 8.53 g/cm³, a melting range of approximately 915 to 955 C, an electrical conductivity of about 28 per cent IACS and a thermal conductivity of about 120 W/m.K at room temperature. Modulus of elasticity is approximately 110 GPa.
Forming, Annealing and Joining
Deep drawing and stamping. The alloy's signature capability. Use annealed stock for the first draw, plan interstage anneals for heavy reductions, and control lubricant film carefully to prevent galling.
Annealing. A recrystallisation anneal between about 425 and 600 C restores ductility after cold work. Atmosphere control matters because the zinc can be lost from the surface at high temperature.
Machining. Use sharp tooling with lubricant and avoid dwelling in the cut, which work-hardens the surface and causes chatter.
Welding. TIG and resistance welding can be used with appropriate fume extraction, but zinc volatilisation must be managed and joint designs that concentrate heat should be avoided.
Surface finishing. Polishing, plating, lacquering and passivation are all readily applied, which is why the grade is common in visible decorative parts.
Service Limits to Respect
The alloy should not be used in contact with acetic acid, moist ammonia or ammonium compounds, hydrochloric or nitric acid, or concentrated alkalis. Components that have been heavily cold formed and will see ammoniacal service should be stress-relief annealed to reduce the risk of stress-corrosion cracking. In continuously immersed seawater service, dezincification can occur over long periods, so cupro-nickel or aluminium brass grades should be used for condenser and heat exchanger tubing instead. Where a lead-free material is required for potable water contact, confirm the applicable limit before ordering, since the alloy is specified with a maximum lead content rather than as a lead-free composition.
Typical Applications
Drawn cartridge cases and ammunition components
Hardware: fasteners, springs, hinges and catches
Plumbing valve components and fittings for non-potable duties
Electrical connectors, terminals and shielding components
Architectural trim, jewellery findings and decorative hardware
Radiator cores, tanks and general pressings
FAQ
Q: What does the UNS C26000 designation cover?
It covers the 70/30 alpha brass composition in all wrought product forms. The designation fixes the composition range only; strength and temper come from the product specification and the ordered condition.
Q: Is 260 brass the same as cartridge brass?
Yes. Cartridge brass, 260 brass and UNS C26000 are different names for the same alloy, so called because of its traditional use in drawn cartridge cases.
Q: Which temper should be ordered for deep drawing?
Start with fully annealed stock and specify grain size, which governs drawability more directly than hardness. Interstage annealing is then used as drawing reduction accumulates.
Q: How is the alloy hardened?
By cold work only. There is no precipitation or quench hardening, so the final properties are fixed by the last cold reduction and any subsequent anneal must be avoided.
Q: Can C26000 be used for potable water fittings?
The composition is low in lead but is specified with a maximum lead content rather than as lead-free. Check the local lead limit and any required certification before specifying it for drinking water contact.
Q: What causes cracking in formed C26000 parts?
Usually residual stress combined with an aggressive environment, or excessive cold reduction without an interstage anneal. Stress-relief annealing and controlled reductions both reduce the risk.
