Overview
Brass is a copper-zinc alloy containing 5-45% zinc, producing a golden-colored metal that is stronger and more machinable than pure copper while retaining good corrosion resistance. The term "brass" covers a wide family of alloys; the most common industrial grade is 70/30 (cartridge brass, C26000) with 70% Cu and 30% Zn.
Mechanical Properties
| Property | Value (70/30 annealed) |
|---|---|
| Density | 8,500 kg/m³ |
| Young's Modulus | 110 GPa |
| Yield Strength | 100 MPa (15,000 psi) |
| Ultimate Tensile | 320 MPa (46,000 psi) |
| Elongation | 65% |
| Hardness | 60-70 BHN |
| Melting Range | 915-955°C |
Higher-zinc brasses (40% Zn, Muntz metal) are stronger (up to 450 MPa) but less ductile.
Key Properties
- Machinability: Free-cutting brass (C36000, leaded) is the benchmark for machinability (100% rating)
- Formability: 70/30 brass deep-draws extremely well — originally for cartridge cases
- Corrosion resistance: Good in atmosphere, fresh water; better than steel, slightly less than copper
- Antimicrobial: Inherent antimicrobial surface (like all copper alloys)
- Joining: Solders and brazes easily; weldable with proper filler
- Appearance: Polishes to a bright gold finish; lacquered for decorative use
Common Brass Alloys
| Alloy | Cu% | Zn% | Pb% | Common Name | Use |
|---|---|---|---|---|---|
| C26000 | 70 | 30 | — | Cartridge brass | Deep drawing, ammunition, radiators |
| C28000 | 60 | 40 | — | Muntz metal | Architectural, condenser plates |
| C36000 | 61 | 35 | 3 | Free-cutting brass | Screw machine parts, high-volume machining |
| C46400 | 60 | 39 | — | Naval brass | Marine hardware, shafts, valve stems |
| C35200 | — | — | — | DZR brass | Plumbing fittings, potable water |
Applications
- Valves & fittings: Gate/ball/globe valve bodies, plumbing fittings, compression fittings
- Fasteners: Screws, nuts, bolts, inserts (excellent thread rolling)
- Hardware: Locks, hinges, doorknobs, decorative trim
- Electrical: Connectors, terminals, socket contacts
- Musical instruments: Trumpets, trombones, cymbals, bells
- Ammunition: Cartridge cases (70/30)
- Marine: Propellers, through-hull fittings, underwater hardware (naval brass)
- Plumbing: Faucets, fixtures, stop valves
Joining and Fabrication
- Soldering: Excellent with tin-lead or lead-free solders; standard for plumbing
- Brazing: Strong joints with silver brazing alloys
- Machining: Free-cutting brass (C36000) allows very high cutting speeds, produces small chips, excellent surface finish
- Forging: Forging brasses (C37700) used for valve bodies and fittings
- Polishing: Buffs to mirror finish; clear lacquer prevents tarnish
Summary
Brass (density ~8500 kg/m³) adds zinc to copper for increased strength, machinability, and lower cost while retaining corrosion resistance and antimicrobial properties. It is the standard material for plumbing fittings, valves, decorative hardware, and high-volume machined parts. Free-cutting brass (C36000) is the reference material for machinability rating.