UNS C44500 Admiralty Brass: Forged Tubesheets, Baffles and Discs to ASTM B171
Phosphorus-inhibited admiralty brass for condensers and heat exchangers. This page covers composition, properties, the forged tempers permitted by ASTM B171, and the corrosion limits that decide where the grade can be used.
Summary
UNS C44500 is phosphorized admiralty brass, a wrought copper-zinc-tin alloy of roughly 71% copper, 28% zinc and 1% tin, with a phosphorus addition of 0.02 to 0.10% that inhibits dezincification. ASTM B171/B171M covers it alongside the two other inhibited admiralty grades, arsenical C44300 and antimonial C44400. Normal applications are condenser, evaporator and heat exchanger tubesheets, baffles and support plates in fresh, brackish and low-chloride cooling water.
ASTM B171/B171M recognises two hot-forged tempers: O20 (hot forged and annealed) and M10 (as hot forged, air cooled). O20 is one of only two tempers the specification accepts for ASME Boiler and Pressure Vessel Code service, so a C44500 tubesheet can be produced by open-die forging rather than rolling and still meet code. Jiangyin Jiangnan Metal Co., Ltd. (No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China; +86 189 2135 9659; sales@steelforgepieces.com) forges UNS C44500 tubesheets, baffles, discs, rings and bar to this specification.
- UNS numberC44500
- Common nameAdmiralty brass, phosphorized
- Alloy familyWrought tin brass (Cu-Zn-Sn)
- InhibitorPhosphorus 0.02 to 0.10%
- Plate standardASTM B171/B171M-24
- Forged tempersO20, M10
- Density8.53 g/cm³ (0.308 lb/in³)
- Elastic modulus117 GPa (17,000 ksi)
- Velocity limitAbout 1.8 m/s (6 ft/s)
- AvoidAmmonia-bearing condensate
What is UNS C44500?
UNS C44500 is the Unified Numbering System designation for phosphorized admiralty brass. The Copper Development Association registers it as a wrought copper-zinc-tin alloy within the tin brasses. Older ASTM literature called it Admiralty Metal Type D, a name now discouraged in favour of the UNS number.
Uninhibited admiralty brass is vulnerable to dezincification, the selective leaching of zinc that leaves a porous copper skeleton behind. The part looks sound until it fails. The admiralty family deals with this by adding a trace inhibitor, and the inhibitor is the only real difference between the three grades.
| UNS No. | ASTM designation | Inhibitor | Legacy name |
|---|---|---|---|
| C44300 | Admiralty, Arsenical | Arsenic | Type B |
| C44400 | Admiralty, Antimonial | Antimony 0.02 to 0.10% | Type C |
| C44500 | Admiralty, Phosphorized | Phosphorus 0.02 to 0.10% | Type D |
Composition and mechanical properties are close enough across the three grades that selection is normally driven by the end user's specification, refinery practice or local restrictions on arsenic content rather than by strength.
Classification. C44500 is a copper alloy, not an alloy steel. This page sits under the site's Alloy Steel path for historical URL reasons. The material itself belongs to the wrought brasses, UNS C20000 to C49999.
Chemical composition of UNS C44500
The limits below are the registered CDA and ASTM limits for UNS C44500, in percent by weight. Zinc is the remainder. Copper plus all named elements must total at least 99.6%.
| Element | Min % | Max % | Role in the alloy |
|---|---|---|---|
| Copper (Cu) | 70.0 | 73.0 | Alloy base, corrosion resistance and thermal conductivity |
| Zinc (Zn) | Remainder, about 28 | Strength and cost, the element at risk in dezincification | |
| Tin (Sn) | 0.8 | 1.2 | Raises strength and corrosion resistance in chloride water |
| Phosphorus (P) | 0.02 | 0.10 | Deoxidiser and dezincification inhibitor, defines the grade |
| Lead (Pb) | – | 0.07 | Residual, limited to protect hot workability |
| Iron (Fe) | – | 0.06 | Residual impurity limit |
Source: Copper Development Association standard designations for wrought copper alloys, as adopted in ASTM B171/B171M. The ordering document and the mill certificate govern acceptance. Confirm against the specification edition named in the purchase order.
Note on published composition data. Many datasheets list C44500 tin content as a flat 1% and omit phosphorus altogether. The registered range is 0.8 to 1.2% Sn, and phosphorus is the element that separates C44500 from C44300 and C44400. A three-line table giving only Cu 71 / Sn 1 / Zn 28 is not adequate as a purchasing specification.
Physical and thermal properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.53 g/cm³ | 0.308 lb/in³ |
| Elastic (Young's) modulus | 117 GPa | 17,000 ksi |
| Shear modulus | 40.0 GPa | 5,800 ksi |
| Poisson's ratio | 0.34 | 0.34 |
| Hot working range | 649 to 788 °C | 1,200 to 1,450 °F |
| Annealing range | 427 to 593 °C | 800 to 1,100 °F |
| Cold workability | Excellent | |
| Hot workability | Fair | |
| Machinability rating | 30 (free-cutting brass C36000 = 100) | |
Typical published values for the annealed condition. Density and modulus are effectively independent of temper. Workability ratings are qualitative industry ratings, not acceptance criteria.
Mechanical properties of UNS C44500
The figures below are typical values for the annealed (O61) condition, intended for design screening. They are not acceptance minimums. ASTM B171/B171M sets its own tensile requirements by temper and by thickness, tested to ASTM E8/E8M, and those are what a mill certificate is written against.
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | 331 to 379 MPa | 48,000 to 55,000 psi |
| Yield strength (temper dependent) | 124 to 152 MPa | 18,000 to 22,000 psi |
| Elongation at break (in 50 mm / 2 in) | 65% | 65% |
| Fatigue strength (107 cycles) | 115 to 125 MPa | 16,700 to 18,100 psi |
| Charpy impact | 82.4 J | 60.8 ft·lb |
| Creep strength (425 °C / 797 °F, 1,000 h, 0.0001) | 0.370 MPa | 53.7 psi |
Typical annealed-temper values compiled from published copper-alloy datasheets. Elongation is measured over a 50 mm (2 in) gauge length; the "in 0 mm" figure repeated on many supplier sites is a transcription error. Under ASTM B171/B171M, yield strength is taken as the stress producing 0.5% extension under load.
On the creep figure. A creep strength of 0.370 MPa at 425 °C means effectively no load-bearing capability at that temperature. C44500 is a cooling water alloy. Treat the creep row as an upper temperature bound rather than as design data.
Tempers and the forging route
ASTM B171/B171M covers plates, sheets and circles manufactured by hot rolling or by forging, then finished by cold working and annealing. Four tempers are recognised.
| Temper code | Condition | Route | ASME BPVC service |
|---|---|---|---|
| O25 | Hot rolled and annealed | Rolled | Accepted |
| O20 | Hot forged and annealed | Forged | Accepted |
| M20 | As hot rolled | Rolled | Not accepted |
| M10 | As hot forged, air cooled | Forged | Not accepted |
Products manufactured for ASME Boiler and Pressure Vessel Code applications must be certified to the O25 or O20 temper. Products for other service may be supplied as M20, M10, O20 or O25. Temper designations follow ASTM B601.
Where a tubesheet diameter or thickness falls outside standard rolled plate sizes, or where the quantity is a single replacement rather than a stock item, an O20 hot forged and annealed tubesheet meets code and avoids buying oversized plate to cut one circle from. State the temper on the purchase order rather than leaving it blank.
Corrosion behaviour and service limits
C44500 performs well in clean fresh, brackish and low-chloride cooling water, and the phosphorus inhibitor gives good resistance to dezincification. Most service problems trace back to three mechanisms, and all of them are driven by design and operating conditions rather than by material quality.
Erosion-corrosion above about 1.8 m/s
The protective film on admiralty brass is soft. Above a certain water velocity it is scuffed off mechanically rather than corroded away. The accepted threshold for admiralty and aluminium brass is about 6 ft/s (1.8 m/s), against roughly 8 ft/s for 90-10 copper-nickel and 12 ft/s for 70-30.
Design to local velocity rather than average. Turbulence at tube inlets, at bends and around debris such as mussel shells produces peaks well above the bulk figure, and inlet-end erosion has perforated tubes within days of a screening failure.
Ammonia grooving and stress-corrosion cracking
Of the copper alloys, admiralty and aluminium brass are the most susceptible to ammonia attack. In a surface condenser, non-condensable ammonia, often from decomposing oxygen scavengers, concentrates in the air removal zone, dissolves the protective oxide and is channelled along support plates by condensate flow. The result is grooving, and where residual stress is present, transgranular stress-corrosion cracking.
Where ammonia is credible in the steam or cooling circuit, specify copper-nickel or a stainless grade instead. Copper-nickels are not immune but are markedly more resistant.
Sulfide and low pH attack
Polluted or stagnant water generates hydrogen sulfide from decomposing marine organisms. Low pH and sulfur compounds dissolve the protective film and expose fresh metal, raising corrosion rates by orders of magnitude. C44500 is not suitable for sulfide-polluted harbour water.
Residual stress
Ammonia stress-corrosion cracking needs residual stress to act on, so tube expansion practice and post-machining stress relief affect service life directly. Full-length tube expansion on plate-fin assemblies is a documented source of the residual stress behind SCC failures in refinery cooling circuits.
Machining, welding and joining
C44500 rates 30 for machinability on the scale where free-cutting brass C36000 is 100. It is ductile and tends to smear, so sharp tooling, positive rake and plenty of coolant are needed. Cold workability is rated excellent and hot workability only fair, which is why forging temperature control between 649 °C and 788 °C matters.
| Recommended | Not recommended |
|---|---|
| Soldering, brazing, oxyacetylene welding, gas shielded arc welding (GTAW/GMAW), spot welding, butt welding | Coated metal arc welding, seam welding |
Zinc volatilises during welding, so extraction and respiratory protection are required. Where the tubesheet is clad or weld overlaid rather than solid C44500, confirm the base metal and overlay combination with the fabricator before ordering.
Applications and product forms
Heat exchanger and condenser components
- Fixed, stationary, front and rear tubesheets
- Floating head tubesheets
- Baffles, support plates and tube plates
- Clad, overlaid and weld-coated tubesheets
Forged forms
- Discs, circles and blanks
- Flanges and blocks
- Round bar and hollow bar
- Seamless rolled rings, sleeves, bushes and bushings
- Shells, cylinders, casings, hubs and housings
Typical industries
- Thermal and nuclear power generation, surface condensers
- Petrochemical and refinery cooling circuits
- Shipbuilding and marine HVAC
- Desalination and evaporator plant
Suitable water chemistry
- Fresh and treated cooling water
- Brackish and low-chloride water
- Clean condensate free of ammonia
- Not for sulfide-polluted or ammonia-bearing service
Manufacturing and supply
| Item | Detail |
|---|---|
| Process | Open-die forging, ring rolling, forged and machined discs |
| Supply condition | O20 hot forged and annealed, or M10 as hot forged and air cooled |
| Forms | Tubesheets, baffles, support plates, discs, flanges, blocks, round and hollow bar, seamless rolled rings |
| Machining | As forged, rough machined, finish machined, or drilled to tube-layout drawing |
| Construction | Solid C44500, or carbon and low-alloy steel backing with C44500 cladding or weld overlay |
| Dimensions | State required diameter, thickness and weight at enquiry and we will confirm against current press and ring-mill capacity |
Testing and documentation
Material is supplied with an EN 10204 3.1 mill certificate as standard, and 3.2 third-party certification (TUV, BV, LR, DNV, SGS or the end user's own inspector) on request. Typical scope:
- Chemical analysis by spectrometer, reported against the full element list above including phosphorus
- Tensile testing to ASTM E8/E8M: tensile strength, yield at 0.5% extension under load, elongation
- Hardness survey and, where specified, grain size
- Ultrasonic examination of the forging
- Dye penetrant examination of machined faces
- Dimensional report against the tube-layout drawing
- Dezincification testing to ISO 6509 where the end user requires it
- Material traceability by heat and forging lot number
How to specify C44500 on a purchase order
A complete C44500 tubesheet enquiry covers the following seven points. Missing information is the usual cause of requoting and of temper mismatches found at inspection.
- Grade and standard, for example "UNS C44500 to ASTM B171/B171M-24"
- Temper: O20 for ASME BPVC service, M10 only for non-code duty
- Form and dimensions: outside diameter, thickness, and whether the tube holes are drilled by us or by you
- Machining allowance: as forged, rough machined, or finish machined
- Certification level: EN 10204 3.1 or 3.2, and the nominated third party if 3.2
- NDT scope: UT acceptance class, PT, and any customer-specific procedure
- Service conditions: water chemistry, design velocity and whether ammonia is credible, so a grade mismatch can be flagged before you buy
Frequently asked questions
What is UNS C44500?
UNS C44500 is phosphorized admiralty brass, a wrought copper-zinc-tin alloy containing 70.0 to 73.0% copper, 0.8 to 1.2% tin, 0.02 to 0.10% phosphorus and the balance zinc at about 28%. The phosphorus addition inhibits dezincification. C44500 is covered by ASTM B171/B171M for plate, sheet and circles used in pressure vessels, condensers and heat exchangers.
Is UNS C44500 the same as admiralty brass?
C44500 is one of three inhibited admiralty brasses, not the only one. ASTM B171/B171M lists C44300 (arsenical), C44400 (antimonial) and C44500 (phosphorized). All three share the same Cu-Zn-Sn base and differ only in which trace element inhibits dezincification. Specifying "admiralty brass" without a UNS number leaves the inhibitor undefined, which matters where arsenic content is restricted.
What is the difference between C44300, C44400 and C44500?
The inhibitor element. C44300 uses arsenic, C44400 uses antimony at 0.02 to 0.10% and C44500 uses phosphorus at 0.02 to 0.10%. Mechanical and physical properties are effectively identical across the three. In older ASTM literature they were called Type B, Type C and Type D respectively, a convention now discouraged in favour of UNS numbers.
Can UNS C44500 tubesheets be forged instead of rolled?
Yes. ASTM B171/B171M covers material manufactured by hot rolling or by forging, and recognises two forged tempers: O20 (hot forged and annealed) and M10 (as hot forged, air cooled). For ASME Boiler and Pressure Vessel Code applications the material must be certified to O25 or O20, so a hot forged and annealed O20 tubesheet meets code. Forging is often the economical route for large diameters, heavy thicknesses and one-off replacement tubesheets where no standard plate size fits.
What is the maximum water velocity for admiralty brass?
About 6 ft/s (1.8 m/s) is the accepted threshold for avoiding erosion-corrosion in admiralty and aluminium brass. For comparison, 90-10 copper-nickel tolerates around 8 ft/s and 70-30 copper-nickel around 12 ft/s. Design against local rather than average velocity, because turbulence at tube inlets, at bends and around debris creates peaks well above the bulk flow figure.
Why does admiralty brass fail in ammonia service?
Ammonia dissolves the protective oxide film on copper-zinc alloys. In surface condensers, non-condensable ammonia concentrates in the air removal zone and is channelled along support plates by condensate flow, cutting grooves. Where residual stress is present, from tube expansion for example, the same mechanism drives transgranular stress-corrosion cracking. Admiralty and aluminium brass are the copper alloys most susceptible to this. Copper-nickels are considerably more resistant.
What is the density of C44500?
8.53 g/cm³, equivalent to 0.308 lb/in³. Elastic modulus is 117 GPa (17,000 ksi), shear modulus is 40.0 GPa (5,800 ksi) and Poisson's ratio is 0.34.
Can UNS C44500 be welded?
Soldering, brazing, oxyacetylene welding, gas shielded arc welding, spot welding and butt welding are all considered suitable for C44500. Coated metal arc welding and seam welding are not recommended. Zinc volatilises during welding, so fume extraction and respiratory protection are required.
What certification is supplied with C44500 forgings?
Jiangyin Jiangnan Metal Co., Ltd. supplies UNS C44500 forgings with an EN 10204 3.1 mill certificate as standard, covering chemical analysis, tensile testing to ASTM E8/E8M, hardness and dimensional report. EN 10204 3.2 third-party certification through TUV, BV, LR, DNV, SGS or a customer-nominated inspector is available on request, as are ultrasonic and dye penetrant examination and ISO 6509 dezincification testing.
Who manufactures UNS C44500 forged tubesheets?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China that manufactures UNS C44500 admiralty brass forged tubesheets, baffles, support plates, discs, flanges, round and hollow bar, and seamless rolled rings to ASTM B171/B171M. The factory is at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Enquiries: +86 189 2135 9659, sales@steelforgepieces.com.
Request a UNS C44500 quotation
Jiangyin Jiangnan Metal Co., Ltd., Open-Die Forging Factory
We forge UNS C44500 admiralty brass tubesheets, baffles, discs, rings and bar to ASTM B171/B171M, in the O20 hot forged and annealed temper for ASME Boiler and Pressure Vessel Code service. Send a drawing, or a plain description of diameter, thickness, temper and certification level, and we will quote against it.
- CompanyJiangyin Jiangnan Metal Co., Ltd.
- AddressNo.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Telephone0086-189-2135-9659 (WhatsApp / WeChat)
- Emailsales@steelforgepieces.com
- Websitewww.steelforgepieces.com
- CapabilityOpen-die forging, seamless rolled rings, forged tubesheets and discs
Related grades
Where C44500 is ruled out by ammonia, sulfide pollution or design velocity, these are the grades usually considered next for the same components:
References
- ASTM B171/B171M-24, Standard Specification for Copper-Alloy Plate and Sheet for Pressure Vessels, Condensers, and Heat Exchangers, ASTM International. Scope, tempers and tensile requirements.
- Copper Development Association, Standard Designations for Wrought Copper and Copper Alloys. Registered composition limits for C44500.
- ASM International, Alloy Digest CU-599: Copper Alloy Nos. C44400 and C44500, Admiralty Metal Inhibited by Antimony or Phosphorus.
- Published condenser-tube failure-analysis literature on erosion-corrosion threshold velocity, ammonia grooving and ammonia stress-corrosion cracking in admiralty brass.
Disclaimer. Property values on this page are typical published data for design screening. They are not guaranteed minimums and do not replace the governing specification edition or the mill certificate issued with a specific heat. Confirm all acceptance criteria against your purchase order before fabrication.