Brass is a metal with unique properties, making it ideal for many applications in various industries. Though not a pure metal like iron, lead or tin, it is a mixture of copper and zinc, and has a distinct yellow-golden color.
Brass is an alloy of copper and zinc and usually contains 60% copper 40% zinc or ranges between 55-95% copper with 45 – 5% zinc.
The range of composition makes different types of brass alloys popular, some of which are popular for their excellent corrosion resistance and others for their antibacterial properties.
In this complete guide to brass, you’ll learn about various brass alloys, brass properties (mechanical and physical) and their popular use in manufacturing and machining. In the end, you’ll also find engineering tips to help you with brass machining.
What Is Brass?
Brass is a copper-zinc alloy and there are many types of brasses according to their composition. Since brass is an alloy, the color and appearance can change depending on the composition of the alloying metals.
Brass generally has a yellow-gold color, but a higher copper content can produce reddish brass. Brass has good corrosion resistance, machinability, workability and durability making it ideal for casting and machining.
For CNC machining, brass is generally categorized into:
High Brass
High brass has zinc content above 35% zinc and has a golden color. It is strong but less ductile and used in springs and parts.
Medium-Zinc Brass
Medium zinc brass has zinc in the range of 20 % to 30 % and balances ductility and machinability. It is used in cartridges and musical instruments. C26000 is a standard medium brass alloy, sometimes called cartridge brass.
Source: Copper Development Association
Low Brass (red brass)
Low brass has a high copper composition and a red appearance. Due to the high copper percentage, low brass is soft and ductile.
What Is The UNS Code for Brass?
The Unified Numbering System (UNS) code was developed by ASTM International to standardize metal alloy identification. UNS code is not unique to brass but a broader identification scheme used for all metal alloys.
Brass is identified using the letter “C” in the UNS codes, followed by a five-digit number. Because there are many types of brass, and some are classified according to their applications like cartridge brass, free-cutting brass, and naval brass, the UNS code helps engineers and manufacturers identify the exact type of brass.
Reading the Brass UNS code.
The first digit identifies the copper alloy
Next two digits identify the alloy group (composition: tin, lead, aluminum)
Last two digits identify the exact alloy.
For example, for C26000:
2: Wrought alloy
60: High zinc
00: no other element like aluminum or tin.
| UNS Code | Name | Use |
| C21000 | Gilding metal | Coinage, jewelry |
| C22000 | Commercial bronze | Architectural, jewelry |
| C36000 | Free machining brass | Screw machine parts |
| C44300 | Admiralty brass | Heat exchangers |
Commercial Copper Alloys; Source: Science Direct
Crystal Structure of Brass
Both zinc and copper have different crystal structures (arrangement of atoms). The brass crystal structure depends on how much zinc dissolves with the copper while making the alloy. The crystal structure is also temperature-dependent.
The crystal structure is important because it can identify alloys that are suitable for different manufacturing and machining processes.
Alpha Brass
Alpha brasses contain up to 38% zinc and have a face-centered cubic (FCC) crystal structure. The zinc atoms fit into the copper lattice, making a single-phase solid solution (uniform, consistent mixture).
Alpha brasses have consistent properties like ductility, corrosion resistance, and strength.
Alpha Beta Brass
Alpha-beta brasses have zinc in a moderate range (36% to 45%) and have a two-phase mix because of the high zinc ratio that causes a shift in the lattice. Both FCC and BCC structures exist in the alloy at the same time.
Alpha-beta brasses are stronger than alpha brass and more suitable for forging extrusion and other hot working processes. Alpha brass is ductile and suitable for cold working.
Alpha-beta brass includes grades like C28000 and C46400 (naval brass).
Beta Brass
Beta brasses have a zinc content of around 45% with a body-centered cubic structure. The zinc content in copper is so high that the FCC phase completely transitions to the BCC of the zinc. The BCC structure is less dense and more open, making beta brasses strong enough to resist deformation and brittle.
Types of Brass Alloys
Leaded Brass
Lead can be added to brass to improve its mechanical and physical properties. Most notably, adding lead can improve the machinability of brass.
Lead does not dissolve into the crystal structure and, during machining, acts as a chip breaker. The softened brass can be easily machined due to lesser friction, heat, and shorter chips.
The advantage of leaded brass is longer tool life and high machinability index.
Strength: Adding lead lowers the tensile strength and ductility.
Ductility: Adding lead makes the brass more brittle. Leaded brass is ideal for machining not cold working and forming.
Corrosion resistance: Lead does not add to the corrosion resistance of brass. Leaded brass is less corrosion-resistant in salt water.
Free-cutting brass like C36000 has a mixture of BCC and FCC structure (alpha beta), which reduces the ability of the alloy to be cold-worked. The lead makes it one of the most machinable brasses and C36000 is also called free machining brass.
Applications
Leaded brass is used in fasteners like screws, bolts, and nuts. It is relatively easy to cut threads into leaded brass. Leaded brass is also used in pipe fittings and valves under heavily regulated lead percentage as lead is poisonous for human consumption.
Leaded brass like C38500 is used in automobiles for small gears and bushings.
Lead-Free Brass
Lead free brass is an alternative to leaded brass because of its popular use in water supply and transport systems. Under health regulations, brass manufacturing now uses lead free brass alternatives.
The typical range of lead by weight in lead-free brass is 0.25% for safe drinking components. Lead-free brass uses other elements to achieve similar properties to leaded brass. Lead-free brass often contains silicon, tin, or bismuth to improve machinability and chip breaking.
Strength: Similar or higher than leaded brass using silicon as an alloying element
Machinability: Less machinable
Corrosion resistance: Improved over leaded brass
Ductility: Less ductile
Depending on the percentage of zinc, lead-free brass can have alpha (FCC) or alpha-beta crystal structure.
C27450 is a lead-free brass alloy often referred to as yellow brass. It is suitable for cold working and has decent machinability. Other notable lead-free brass alloys include the corrosion-resistant C46500 or a type of naval brass with seawater resistance. Instead of lead, tin adds corrosion resistance.
Tin Brass
Brass alloyed with tin has a tin content between 0.5 % to 2 %. The tin improves the physical and mechanical properties of brass alloys, making them useful in harsh environments, especially seawater.
Effect of Tin in Brass
Many corrosion-resistant brass alloys use tin as an alloying element because tin improves brass’s resistance to oxidation by forming a mixture of tin oxide and copper oxide layer. The tin oxide (SnO2) is stable and durable in harsh conditions, and the tin resists the dezincification of brass alloys.
Strength: Alloying brass with tin increases the tensile strength and hardness.
Machinability: Less machinable
Corrosion resistance: Improved corrosion resistance brass alloy
Ductility: Less ductile than alpha brasses
Tin brasses have an alpha crystal structure (FCC) with low zinc and a high zinc alloy like V46200 (naval brass) can have an alpha-beta crystal structure. Tin also increases the wear resistance of brass alloys.
C44300 (admiralty brass) has a tensile strength of around 450 MPa and a machinability of 50% with an alpha FCC structure; it is typically used for heat exchangers. C90500 (Gunmetal) has 10% zinc and 2% tin used for bearings and other brass components.
Aluminum Brass
Aluminum brass is another common type of brass alloyed with aluminum 1% – 2% along with copper and zinc. Aluminum is naturally corrosion resistant and making it a brass metal alloying element gives additional resistance to corrosion.
Strength: Aluminum strengthens the metal lattice and changes the grain structure
Corrosion resistance: It has good corrosion resistance and erosion resistance. Making it important in applications like brass pipes.
Corrosion resistance: Improved corrosion resistance brass alloy
Ductility: Less ductile
C68700 (Aluminum Brass) has moderate machinability but excellent corrosion resistance. C68800 brass grade is a high-strength brass alloy and can be used in critical structural applications, including brass fittings.
Manganese Brass
In manganese brass alloys, the manganese can range from 0.5 % to 4%, apart from copper and zinc, which make up the balance. Manganese alters the grain structure of the copper-zinc alloys. Manganese increases the hardness, corrosion resistance, wear resistance,
Unlike aluminum and tin, manganese forms no oxide but stabilizes the alloy and preserves the zinc.
Strength: Manganese acts as a solution strengthener in the molten brass dissolving into the brass matrix.
Corrosion resistance: It has good corrosion resistance in acidic environments.
Wear resistance: Reduces friction and any surface deformation compared to other metals.
Ductility: Less ductile because manganese can push the brass to alpha beta phases.
C66700 has an alpha crystal structure and is a versatile wrought alloy. CZ114 is a high-tensile strength used in bridge pins and structural fittings.
Advantages of Brass
High Corrosion Resistance
Brass has a natural resistance to oxidation and corrosion. It performs better than iron and pure copper in air and neutral water. Many brass grades have enhanced corrosion resistance performance in marine applications.
Brass has a long lifespan in plumbing and outdoor applications.
Workable Brass Material
Brass is a highly workable material. It’s not too hard and has a relatively low melting point but not as high as iron (1538°C) or steel, making alloying brass feasible. Brass material can be shaped through forging, casting, rolling, drawing, and other processes.
High Machinability
Brass is an ideal material for CNC machining. Leaded brass has one of the highest machinability ratings, making workpiece brass production efficient and precise.
Aesthetic
Brass has a shiny golden color, and higher copper can produce reddish brass, making it a visually pleasing material. Combining the aesthetic appeal of brass with its mechanical and physical properties makes brass useful for decorative and functional parts like door knobs and lamps.
Acoustic Material
Brass has long been used for musical instruments. Brass produces clear tones and sounds because of its density, elasticity and physical properties. Alpha brass allows sound to travel with minimal dampening.
High-quality musical instruments use precision-machined brass parts.
Mechanical and Electrical Properties
Brass has an electrical conductivity ranging between 25 – 40%. Red brass, with the most copper and highest conductivity, is 37% as conductive as copper.
Antibacterial
Brass is an antibacterial material. It does not allow bacterial growth because copper ions interfere with bacterial cells. Brass maintains hygienic standards and stops the spread of germs.
Disadvantages of Brass
Dezincification
For brass grades with a high zinc content, there is a risk that the zinc can leach out of the brass alloy in corrosive environments like prolonged exposure in seawater, leaving behind copper.
Lead Concern
Leaded brass had many health concerns and lead leaching into water has led to health care regulation bans on leaded brass.
Brittle
Higher zinc content or unproportioned alloying elements can produce brittle brass. Many high zinc brass alloys cannot be cold-worked, limiting their use.
Common Brass Grades and Their Applications
Cartridge Brass
Cartridge brass (C26000) is named after ammunition casings. It has good ductility and can form thin casings that can hold shape and gunpowder. Brass instruments are mainly made of cartridge brass because it can be worked into thin tubes.
Free Machining Brass
C36000 free machining brass has excellent machinability and is the ideal material to cut small features and thin walls using cutting tools. Free machining brass is used to make screws (threads), bolts and nuts.
Precision machining brass can produce accurate valves and connectors of complex shapes. It is also easy to mass-produce brass gears and components with tighter tolerances.
Naval Brass
Naval brass has a 60/40 copper zinc split with high corrosion resistance and hot working abilities. Naval brass is used in valves, pumps and propellers.
C46400 thrives in seawater and is commonly used in ship hulls as a filling material.
Red Brass
C23000 (red brass) has a reddish hue and high ductility. Brass jewellery often uses red brass, and it is also used in electrical connectors.
Muntz Brass
C28000 (muntz metal) is a cost-effective, strong, hot, workable brass alloy. Muntz brass is often used in elevators, doors, decorative elements, and for architectural purposes. Muntz metal is also architectural brass and is used in architectural trim panels.
Different Forms of Brass
Specific applications require different types of brass depending on the industry. Brass comes in many shapes, and although many parts are made from casted brass, brass sheets, brass foil, brass bars, and brass strips are all made from molten metal brass.
Brass Wire
Brass wire is not a common form of brass metal. It is often made from grades like C26000 and is a thin, drawn form of brass.
Brass Sheets
Brass sheets are popular in the architectural and design industries. Brass sheets are produced by rolling the brass into thin sheets. These sheets have high ductility and are used on roofs and claddings.
Brass Plates
Brass sheets are similar to brass plates but have a larger thickness. The grades of brass lean towards alpha-beta, and often, other alloying elements are used in these plates to increase their machinability.
Which Brass Grade Is Right For You?
The right brass grade choice depends on your machining, drawing, or casting requirements. These small tips can help you choose the right grade for your project.
Free cutting brass (C36000) is great for quick production of precise parts. It is ideal for CNC machining but lacks water use due to lead.
Cartridge brass (C26000) is a ductile and affordable brass alloy used for drawing applications and blanking.
Naval brass has high corrosion resistance and is ideal for use in corrosive environments and saltwater.
Aluminium brass has high strength and corrosion resistance. It has additional erosion resistance, making it ideal for prolonged used for heat exchanger tubes carrying fluids.
Conclusion
Brass is a historic alloy that started as a simple copper and zinc mixture. Today, brass can be altered to match your particular needs with alloying elements like tin, aluminum and silicon. It balances machinability, strength and natural resistive abilities.
Brass can be heat treated to further increase its strength and refine grain structure. It has been use in various industries, from automobiles and music to ammunition casings.
Many brass alloys can be confused with bronze, and you can learn more about brass vs bronze.