If you are stamping electrical socket shells, deep-drawing ammunition casings, or crafting decorative jewelry, you need a metal that is both easy to shape and visually appealing. 260 brass—also known as cartridge brass, alloy C26000, or 70/30 brass—is the industry standard for these applications. With its precise balance of 70% copper and 30% zinc, it offers exceptional formability, good strength, and a bright, gold-like appearance. This guide explains its properties, applications, and how it compares to other materials.
Introduction
For manufacturers and designers, material selection often comes down to finding a metal that can be shaped into complex forms without cracking. 260 brass was developed to excel in this area. Its 70/30 copper-zinc ratio provides a unique combination of high ductility and moderate strength. This allows it to be stretched, bent, and stamped into intricate shapes while maintaining its structural integrity. Its warm golden color and ability to take a high polish also make it a favorite for decorative applications. From the ammunition that powers a firearm to the jewelry worn every day, 260 brass is a versatile and proven material.
What Defines 260 Brass?
The performance of 260 brass is rooted in its simple but carefully controlled chemistry and its response to cold working. It is designed to be shaped, not machined, and its properties are tailored for forming operations.
What Is in the Alloy?
The chemical composition of 260 brass is defined by its copper and zinc content, with strict limits on other elements to ensure consistency and safety.
| Element | Content Range (%) | Its Role in the Alloy |
|---|---|---|
| Copper (Cu) | 68.5 – 71.5 | Provides strength, ductility, and the characteristic warm, golden color. |
| Zinc (Zn) | Remainder (approx. 29%) | Enhances formability and reduces material cost. |
| Lead (Pb) | ≤ 0.07 | Kept very low to meet RoHS compliance standards for safety in consumer products. |
| Iron (Fe) | ≤ 0.05 | Minimized to prevent brittleness during forming. |
A leading ammunition manufacturer in Colorado relies on 260 brass for its cartridge cases. They choose it because its high ductility allows the case to stretch under pressure without cracking during firing, while its strength ensures it holds its shape. The low lead content also makes the spent casings safer for the environment.
What Are Its Key Mechanical and Physical Properties?
260 brass’s properties are highly dependent on its temper, which is controlled by the amount of cold work applied.
| Property | Annealed (Soft) | Cold-Worked (Hard) | Why This Matters |
|---|---|---|---|
| Tensile Strength | 300 – 360 MPa | Up to 500+ MPa | Strong enough for applications like radiator cores and ammunition casings. |
| Yield Strength | 75 – 150 MPa | 280 – 400 MPa | Low yield strength in the annealed state makes it easy to form; cold working hardens it for final strength. |
| Elongation | 66% | 5 – 15% | Exceptional ductility. It can stretch to nearly twice its original length before breaking, ideal for deep drawing. |
| Hardness | 55 – 70 HRB | 80 – 100 HRB (Spring Temper) | Soft for forming; can be work-hardened to a spring temper for parts like clips. |
| Density | 8.53 g/cm³ | 8.53 g/cm³ | Heavier than aluminum, lighter than steel, providing a solid feel for decorative items. |
| Electrical Conductivity | 28% IACS | 28% IACS | Adequate for electrical applications like socket shells and terminals. |
| Annealing Temperature | 427 – 482°C | N/A | Heating to this range softens the metal after cold work, restoring its formability. |
How Is 260 Brass Formed and Shaped?
260 brass is renowned for its exceptional cold working and formability. It is one of the most formable brasses available, making it the go-to choice for operations that involve significant shaping without heat.
Deep Drawing and Stamping
This is where 260 brass truly excels.
- Deep Drawability: It can be pulled into deep, thin-walled shapes like ammunition casings, small bowls, and radiator tanks without cracking. Its high elongation (66%) allows for multiple drawing steps.
- Stamping: It is ideal for stamping complex shapes like electrical socket shells, decorative trim, and jewelry components. The metal flows well under pressure, filling intricate die details.
- Minimal Earing: It exhibits very little “earing”—the small bumps that can form on the edge of drawn parts. This reduces the need for costly trimming and finishing operations.
Work Hardening and Annealing
As 260 brass is formed, it work-hardens. This means it becomes stronger and harder with each shaping operation. While this is useful for achieving final strength, it can also make the metal too brittle to continue forming. To solve this, the metal is annealed. It is heated to 427-482°C and then cooled. This process softens the metal, restoring its ductility so it can be shaped further.
A musical instrument maker uses this process to create trumpet tubes. They roll-form the brass into long, curved shapes. As the metal work-hardens, they anneal it to keep it flexible enough to be bent into the instrument’s unique, complex design.
Where Is 260 Brass Used?
The combination of formability, strength, and attractive appearance makes 260 brass a staple across many industries.
Ammunition and Automotive
- Cartridge Cases: This is the classic application. The 70/30 brass balance provides the perfect combination of strength to contain the explosion and ductility to expand and seal the chamber.
- Radiator Cores and Tanks: A radiator manufacturer uses 260 brass for its radiator cores. Its high elongation allows them to form thin, complex tubes, while its thermal conductivity helps transfer heat efficiently.
- Electrical Connectors: Its good conductivity and formability make it suitable for terminals and connectors.
Decorative and Consumer Goods
- Jewelry: A jewelry brand in California makes affordable wedding bands from 260 brass. They stamp the metal into rings, polish it to a bright gold shine, and coat it with a protective layer to prevent tarnishing—all at a fraction of the cost of gold.
- Lamp Fixtures and Decorative Trim: Its warm color and ability to be formed into intricate shapes make it a popular choice for lighting and architectural accents.
- Musical Instruments: Trumpets, trombones, and tubas rely on 260 brass for their tubes and bells. It produces a warm tone and bends easily into the required shapes.
Industrial Applications
- Heat Exchanger Tubes: Its high thermal conductivity and corrosion resistance to water make it suitable for heat exchangers.
- Flexible Hoses: Its ductility allows it to be formed into corrugated, flexible hoses that can handle bending without cracking.
How Does 260 Brass Compare to Other Alloys?
Choosing the right material often means comparing 260 brass to its alternatives. The table below provides a clear breakdown.
| Alloy | Formability | Machinability | Lead Content | Relative Cost | Best Application |
|---|---|---|---|---|---|
| 260 Brass (C26000) | Excellent (100%) | 65% (Fair) | <0.07% (RoHS) | 100% (Baseline) | Formed parts: stampings, deep-drawn components, jewelry |
| 360 Brass (C36000) | 40% (Poor) | Excellent (100%) | 3.1% (High) | 100% | Machined parts: fittings, valves, gears |
| 110 Copper | 80% (Good) | 40% (Fair) | 0% | 120-150% | Electrical components requiring maximum conductivity |
| 304 Stainless Steel | 30% (Poor) | 30% (Poor) | 0% | 150-200% | Corrosive environments, outdoor parts, high-strength applications |
| 5052 Aluminum | 90% (Very Good) | 50% (Fair) | 0% | 50-70% | Lightweight formed parts, automotive trim |
Analysis: For a deep-drawn part like a radiator tank or an ammunition casing, 260 brass is the superior choice due to its unmatched formability. For a part that requires extensive machining, like a threaded valve fitting, the free-machining 360 brass is a better option. For an outdoor component exposed to saltwater, stainless steel would be more appropriate.
Conclusion
260 brass is a material defined by its exceptional formability. Its 70% copper, 30% zinc composition provides a unique combination of high ductility and good strength, allowing it to be stamped, deep-drawn, and formed into complex shapes that other metals cannot achieve. Its bright, gold-like appearance and ability to take a high polish make it equally valued for decorative applications. While it is not the best choice for machining or for highly corrosive environments, its performance in forming operations is unmatched. For any project that requires intricate shaping, a warm aesthetic, and reliable performance, 260 brass is a proven, cost-effective, and versatile solution.
FAQ
Does 260 brass tarnish?
Yes, like all brasses, 260 brass will tarnish over time when exposed to air and moisture, developing a darker patina. To prevent this and maintain its bright finish, it can be coated with a clear protective layer such as lacquer. Regular polishing can also remove tarnish.
Can 260 brass be welded?
It is not ideal for welding. The zinc content in 260 brass can vaporize at the high temperatures required for welding, creating porosity and weak joints. For applications requiring welding, a lower-zinc brass like 464 naval brass or a different material like stainless steel is a better choice.
What is the difference between 260 brass and 70/30 brass?
There is no difference. 260 brass is the alloy designation (UNS C26000), while 70/30 brass describes its nominal composition of 70% copper and 30% zinc. Both terms refer to the same material.
What is the best way to anneal 260 brass?
To anneal (soften) 260 brass after it has work-hardened, heat it to a temperature between 427°C and 482°C (800-900°F) and then allow it to cool. This process will restore its ductility for further forming operations. Avoid overheating, as this can cause grain growth and weaken the metal.
Is 260 brass RoHS compliant?
Yes, standard 260 brass is typically RoHS compliant. Its lead content is strictly limited to less than 0.07% , which meets the requirements of the Restriction of Hazardous Substances (RoHS) directive for use in electronics and consumer products.
Discuss Your Projects with Yigu Rapid Prototyping
Selecting the right material for a formed part is critical for production efficiency and final product quality. At Yigu Rapid Prototyping, we have extensive experience with 260 brass and a wide range of other formable alloys. Whether you need custom-stamped components, deep-drawn parts, or guidance on temper selection and annealing, our team can help. Contact us to discuss your next project.