C28000 is the UNS designation for the wrought 60/40 copper-zinc alloy that industry has called Muntz metal since the nineteenth century. The solid annealed condition, written O60 under the temper nomenclature of ASTM B601, is a fully recrystallised supply condition produced by a final anneal after cold rolling. Sheet supplied in this way combines moderate strength with very high ductility, which is why it is chosen whenever a component has to be deep drawn, spun, bent or coined before it enters service. This guide sets out the composition limits, equivalent designations, temper options, typical properties, stock sizes and fabrication behaviour of solid annealed C28000 sheet.
Composition of Wrought 60/40 Brass Sheet
The alloy is a copper-zinc solid solution with tightly controlled residuals. Because the zinc content is high, the material is a two-phase alpha-beta structure at room temperature, and that structure is what gives the sheet its useful balance of strength and formability.
| Element | Content, % by weight | Function or control point |
|---|---|---|
| Copper (Cu) | 59.0 - 63.0 | Principal alloying element, sets the alpha-beta ratio |
| Lead (Pb) | 0.30 max | Residual; low-lead melting practice can be supplied |
| Iron (Fe) | 0.07 max | Residual, controlled to protect ductility |
| Zinc (Zn) | Remainder | Balance of the composition |
| Other elements | 0.5 max total | Usual purchase specification limit |
Holding copper inside the 59.0 - 63.0 % window keeps the phase balance stable from heat to heat. Small shifts in that balance change both the annealed hardness and the rate at which the sheet work hardens, so the copper range is the single most important composition control for a forming operation.
Equivalent Designations and Product Standards
| System | Designation |
|---|---|
| UNS (USA) | C28000 |
| EN | CW509N, CuZn40 |
| DIN | 2.0360, CuZn40 |
| ISO | CuZn40 |
| BS | CZ109 |
| JIS | C2801 |
| GB (China) | H62 |
Sheet, plate and strip of this composition are ordered against ASTM B36/B36M, ASTM B152/B152M or EN 1652. Temper designation follows ASTM B601, mechanical testing is carried out to ASTM E8/E8M in tension and ASTM E18 for hardness, and grain size is reported to ASTM E112 when it is specified. In the JIS system the correct code for CuZn40 sheet is C2801; the similar-looking C3712 designation belongs to a leaded free-cutting brass family and must not be applied to this alloy.
What Solid Annealing Does to the Sheet
Cold rolling raises strength and hardness by accumulating dislocations in the lattice. Solid annealing reverses that work hardening through recrystallisation. Production anneals for 60/40 brass are normally run between roughly 425 °C and 650 °C, and the temperature and soak are chosen to hit a target grain size rather than simply to soften the metal. A coarse grain makes deep drawing easier but leaves an orange-peel surface after forming, while a fine grain yields a smoother finish at a slightly higher flow stress. Stress-relief treatments applied to parts that have already been formed are carried out much lower, in the 250 - 325 °C range, so that the strength gained from cold work is retained. Unlike the aluminium bronzes, this alloy does not harden appreciably on rapid cooling after anneal, so cooling rate is not a critical variable.
Typical Properties of O60 Annealed C28000
The figures below are representative of commercial O60 product and are given for design orientation only. Permissible minima and maxima are always those stated in the ordering specification.
| Property | Typical value, annealed (O60) |
|---|---|
| Tensile strength | 310 - 400 MPa (45 - 58 ksi) |
| Yield strength, 0.2 % offset | 105 - 275 MPa (15 - 40 ksi) |
| Elongation in 50 mm (2 in.) | 40 % and higher |
| Hardness | 45 - 65 HRB |
| Physical property | Typical value |
|---|---|
| Density | 8.39 g/cm³ (0.303 lb/in³) |
| Melting range | 900 - 940 °C (1652 - 1724 °F) |
| Thermal conductivity | about 120 W/(m·K) |
| Electrical conductivity | about 28 % IACS |
| Coefficient of thermal expansion | 20.6 µm/(m·°C) over 20 - 300 °C |
| Specific heat capacity | 377 J/(kg·K) |
| Modulus of elasticity | about 110 GPa (16 × 10&sup6; psi) |
Because the annealed temper is fully softened, properties are quoted as ranges: coil made to a coarse-grain target sits near the soft end of the tensile and hardness bands, while fine-grain product shows the higher yield figures.
Stock Sizes and Available Forms
| Form | Thickness | Width | Length |
|---|---|---|---|
| Sheet and plate | 0.3 - 50 mm | 300 - 1200 mm | 1000 - 3000 mm |
| Strip and coil | 0.05 - 3.0 mm | 10 - 500 mm | Coil, cut to length on request |
Sheet and plate are the primary forms for construction and fabrication work, while lighter strip feeds high-speed stamping and connector presses. Material is supplied with mill finish, or bright annealed, polished, oiled and brush-finished surfaces depending on the cosmetic and corrosion requirements of the end product.
Forming, Joining and Corrosion Notes
Bending: the soft temper tolerates a tight inside bend radius, of the order of half the sheet thickness for thin gauges; the radius must be increased as thickness grows or as the sheet is worked to a harder temper.
Deep drawing: high elongation allows multi-stage drawing, with interstage anneals scheduled before the material runs out of ductility.
Soldering and brazing: the alloy is readily joined by soft soldering and by brazing with silver-based or copper-phosphorus fillers; flux residues should be removed to avoid later staining.
Fusion welding: not recommended for 60/40 brass because zinc volatilises from the weld pool and produces porous joints; brazing, riveting or mechanical fastening is preferred.
Corrosion: C28000 is not inhibited against dezincification. For chloride-bearing, stagnant or marine water service an inhibited grade such as C44300 arsenical admiralty brass is the correct selection.
Typical Applications
Architectural and ornamental trim, grilles and decorative panels
Plumbing fixtures and fittings, including escutcheons and trim plates
General hardware, catches, hinges and stamped fittings
Small mechanical parts, brackets and lightly loaded machined components
Decorative items and signage produced by etching, embossing or spinning
Frequently Asked Questions
Q: Is C28000 the same material as Muntz metal?
Yes. Muntz metal is the traditional name for wrought 60/40 brass, nominally 60 % copper and 40 % zinc, and it is identical to UNS C28000, to EN CW509N and to CuZn40.
Q: What does the solid annealed condition mean in practice?
It means the sheet is delivered in the fully recrystallised O60 soft temper after a final anneal. The material is at its most ductile, with the lowest strength and hardness of the standard tempers.
Q: How does C28000 differ from C26000 cartridge brass?
C26000 is 70/30 brass with a higher copper content, better resistance to dezincification and lower strength. C28000 is 60/40 brass with more zinc, higher strength and a lower cost per kilogram, but reduced corrosion resistance in aggressive water.
Q: Which standards should be quoted on a purchase order?
Quote ASTM B36/B36M or ASTM B152/B152M for sheet, plate and strip, EN 1652 for European projects, plus the temper designation from ASTM B601 and the required grain size if the part is to be deep drawn.
Q: Can C28000 sheet be welded?
Fusion welding is not advised because zinc vaporises and the joint becomes porous. Brazing with silver-based filler, soft soldering or mechanical fastening all give reliable results.
Q: Is C28000 suitable for seawater piping or tube plates?
No. The un-inhibited 60/40 composition is prone to dezincification in chloride-bearing water. Inhibited admiralty brass such as C44300 is used for seawater-cooled exchangers and condensers instead.
