Cartridge Brass, commonly known as 70/30 Brass (approximately 70% copper and 30% zinc), is one of the most widely used brass alloys. It is renowned for its exceptional ductility, corrosion resistance, and superior cold-working behavior.
The name “Cartridge Brass” originates from its traditional use in ammunition cartridge cases, where extreme formability, fatigue resistance, and dimensional stability are essential.
Chemical Composition
| Element | Typical % | Role |
|---|---|---|
| Copper (Cu) | 68.5 – 71.5 | Ductility, corrosion resistance |
| Zinc (Zn) | 28.5 – 31.5 | Strength, hardness |
| Lead (Pb) | ≤ 0.07 | Maintains formability |
| Iron (Fe) | ≤ 0.05 | Grain refinement |
| Others | Trace | Controlled impurities |
Key Point: Very low lead and impurity levels make cartridge brass ideal for severe cold deformation and food or potable-water applications.
Physical Properties
| Property | Typical Value |
|---|---|
| Density | ~8.53 g/cm³ |
| Melting Range | 900 – 940 °C |
| Electrical Conductivity | 26 – 28% IACS |
| Thermal Conductivity | ~120 W/m·K |
| Thermal Expansion | 20.4 µm/m·°C |
| Magnetic Property | Non-magnetic |
| Color | Bright yellow-gold |
Mechanical Properties (By Temper)
| Property | Annealed (O) | Half-Hard (H02) | Hard (H04) |
|---|---|---|---|
| Tensile Strength | 300 – 360 MPa | 440 – 520 MPa | 600 – 680 MPa |
| Yield Strength | 100 – 150 MPa | 300 – 400 MPa | 500+ MPa |
| Elongation | 55 – 65% | 20 – 30% | 5 – 10% |
| Hardness (HV) | 80 – 95 | 120 – 150 | 170 – 200 |
| Elastic Modulus | ~105 GPa | ||
Cartridge brass is not heat-treatable; all strength is obtained through cold working.
Strengthening & Metallurgical Behavior
✔ Single-phase alpha (α) brass with FCC lattice
✔ No brittle beta phase → extreme ductility
✔ Solid-solution strengthening by zinc
✔ Primary strengthening via strain hardening
✔ Recrystallization annealing at 450–650 °C restores ductility
Key Characteristics
✔ Outstanding cold formability and deep drawability
✔ High fatigue resistance
✔ Smooth surface finish after forming
✔ Excellent corrosion resistance
✔ Non-magnetic and food-safe
✔ Easily soldered and brazed
Available Forms
Sheets, plates, strips, and coils
Rods and bars
Tubes and pipes
Wires and precision blanks
Thickness range: Foil (<0.1 mm) to heavy plates (>25 mm)
Applications
Ammunition cartridge and shell cases
Electrical terminals and connectors
Radiator and heat exchanger components
Decorative architectural panels and fittings
Musical instruments
Food-processing and safe plumbing components
Advantages
✔ Superior formability
✔ Excellent surface quality
✔ Stable mechanical behavior
✔ Corrosion resistant without coating
✔ Long service life
✔ Cost-effective compared to copper
✔ Fully recyclable
Why Choose Cartridge Brass?
Choose Cartridge Brass (C260) when your application demands severe cold working without cracking, deep drawing of complex shapes, consistent mechanical performance, and a clean, low-lead alloy with excellent finish.
Engineering Insight:
Cartridge brass is the benchmark alloy for cold-formed copper alloys
and is commonly used as the reference material
for evaluating drawability and forming limits.