What Brass Is and How the Alloy Families Divide
Brass is a copper-zinc alloy, and almost every question about brass begins with the zinc content, because zinc controls the structure. Up to about 36 to 37% zinc the alloy is single-phase alpha brass: soft, ductile and easy to cold form, which is why it is used for tube, strip and deep-drawn parts. Between roughly 37 and 45% zinc a second beta phase appears and the alloy becomes duplex alpha-beta brass, stronger and easier to hot work but less ductile cold. Above that range the structure is increasingly beta, harder and more difficult to process, and such alloys are usually encountered as castings rather than as wrought product.
Small additions beyond zinc and copper do most of the application-specific work. Lead improves machinability by acting as an internal chip breaker. Tin raises strength and resistance to seawater. Arsenic in trace amounts suppresses dezincification in admiralty and aluminum brass. Aluminum in about 2% transforms performance in chloride-bearing water, which is why aluminum brass dominates seawater condenser service.
Standard Grades and Where They Are Used
| Grade | Nominal composition | Typical use |
|---|---|---|
| C26000 | 70% Cu, 30% Zn, cartridge brass | Deep-drawn cartridge cases, strip, tube, radiator cores |
| C27000 | 65% Cu, 35% Zn, yellow brass | General purpose sheet, tube and hardware |
| C28000 | 60% Cu, 40% Zn, Muntz metal | Condenser tube plates, architectural work, hot-worked parts |
| C36000 | About 61.5% Cu, 3% Pb, free-cutting brass | Screw machine parts, fittings, valves, connectors |
| C38500 | About 57% Cu, 3% Pb, architectural bronze | Extruded architectural sections, hardware, trim |
| C44300 | About 71% Cu, 1% Sn, arsenical admiralty brass | Condenser and heat exchanger tube in clean seawater |
| C68700 | About 77% Cu, 2% Al, aluminum brass | Seawater condenser and heat exchanger tube |
| C46400 | About 60% Cu, 0.75% Sn, naval brass | Marine hardware, propeller shafts, tube plates |
The table also settles a common naming confusion. The familiar 60/40 brass is Muntz metal, designated C28000. Cartridge brass is the 70/30 alloy, C26000. Both are alpha-beta or near-alpha alloys, but they behave very differently in drawing and forming, so the names are not interchangeable when a specification is written.
Properties That Decide Selection
Machinability: C36000 free-cutting brass is the reference material for machinability ratings in the copper alloy family, rated at 100% by convention. It is the standard choice where high-speed screw machine output matters, including fittings, valve bodies and electrical connectors.
Strength: duplex brasses and the tin-bearing and manganese-bearing grades are considerably stronger than cartridge brass. The strongest wrought brasses use combinations of zinc, manganese, iron and aluminum, and the high-strength cast manganese bronzes are stronger again. Where a specific strength figure is required, it must be confirmed against the standard and temper for the exact product form.
Ductility and forming: the alpha grades such as C26000 are the deep-drawing and bending materials; adding zinc reduces the elongation available for cold work.
Thermal and electrical conductivity: brass conducts heat and electricity well, but much less than pure copper. Cartridge brass is typically around 28% IACS electrically, which makes it suitable for connectors and terminals where strength and spring behaviour matter more than minimum resistance.
Magnetic response: brass is not magnetic. Copper and zinc are both non-ferrous, so the alloy is not attracted to a magnet unless it contains an unusual iron contamination.
Corrosion Behaviour and Failure Modes
Two mechanisms deserve attention. Dezincification is the selective removal of zinc from the alloy, leaving a porous copper-rich residue. It is most aggressive in stagnant, chloride-bearing water and at elevated temperature, and it is countered by choosing an inhibited grade: arsenical admiralty brass C44300 or aluminum brass C68700 for seawater tube, and dezincification-resistant brass compositions for potable water fittings. The second mechanism is stress corrosion cracking, sometimes called season cracking, which affects cold-worked high-zinc brass in an ammonia or amine-bearing environment. The remedy is stress relief annealing after cold forming and avoiding exposure to ammonia in storage and service.
Both failures are design and specification issues rather than random material defects, so they are controlled before the order is placed. State the medium, the temperature, the flow condition and the required service life, and select the alloy family accordingly rather than defaulting to the most machinable grade.
Specifying and Verifying Brass Products
Order by UNS number and temper, with the product form, dimensions and tolerances, because two brasses with similar zinc content can behave very differently in machining or forming.
State the lead requirement explicitly where the part touches potable water. Modern limits restrict lead in wetted surfaces, and lead-free compositions are available where the application demands them.
Require a certificate of analysis for the heat, and check zinc, lead, tin and any inhibitor element against the ordered grade.
For tube and sheet, confirm temper by hardness and tensile test; for machined parts, confirm the machining allowance and surface condition.
Where the part will be exposed to ammonia or to a stagnant chloride environment, record the stress relief requirement and the packaging condition so the material is not degraded before installation.
FAQ
Q: How many types of brass are there?
There are well over sixty standard copper-zinc compositions in commercial use. They divide first into single-phase alpha brass, generally below about 37% zinc, and duplex alpha-beta brass between roughly 37 and 45% zinc, then subdivide by the tin, lead, aluminum, manganese or arsenic additions that tailor the alloy for a specific duty.
Q: What is the best grade of brass?
There is no single best grade, only the best grade for the duty. C36000 free-cutting brass is the standard choice where machining output dominates, while C26000 cartridge brass is preferred for deep drawing and bending, and inhibited grades such as C44300 and C68700 are preferred in seawater.
Q: Which brass is the strongest?
The strongest wrought brasses are the high-strength duplex compositions that combine zinc with manganese, iron and aluminum, and the manganese bronzes in cast form are stronger again. Specifications should be written against the standard and temper for the exact form required, because strength depends on condition as much as on chemistry.
Q: What is 60/40 brass called?
60/40 brass is Muntz metal, designated C28000. Cartridge brass is a different alloy, the 70/30 composition designated C26000, and the two are not interchangeable in forming operations.
Q: Is brass magnetic?
No. Copper and zinc are both non-ferrous, so brass is not attracted to a magnet. A magnetic response indicates contamination, usually iron picked up during processing or scrap sorting.
Q: Does brass contain lead?
Many free-cutting grades do, because lead improves machinability, and the content is stated in the standard for that grade. Where a product contacts potable water, lead in the wetted surface is limited by regulation and lead-free compositions should be specified.
