Material Overview
C44400 is a wrought copper alloy whose principal elements are copper, zinc and tin. Copper forms the matrix and provides the corrosion resistance and conductivity that characterise the copper alloy family; zinc lowers cost and contributes strength; tin dissolves in the copper-rich phase and strengthens it while improving resistance to seawater. A small, deliberately controlled antimony addition completes the specification by suppressing the selective leaching of zinc that otherwise limits the service life of brass in marine and chemical environments.
The alloy is produced and supplied as tube, pipe, rod, bar, plate, sheet, strip and wire, and it is most often selected when a component must combine the fabricability of brass with the corrosion behaviour of a more heavily alloyed copper material.
Chemical Composition
| Element | Weight % |
|---|---|
| Copper (Cu) | 70.0-73.0 |
| Tin (Sn) | 0.9-1.2 |
| Antimony (Sb) | 0.02-0.10 |
| Lead (Pb) | 0.07 max |
| Iron (Fe) | 0.06 max |
| Zinc (Zn) | Balance |
Two features of these limits deserve attention. First, lead and iron are held to very low maxima because both harm hot workability and toughness at these levels of tin; a supplier that permits higher residuals to reduce melting costs will produce an alloy that cracks during rolling or drawing. Second, the antimony range is narrow and must be met by analysis, because the whole corrosion benefit depends on it. The approved wrought forms are delivered to ASTM B111 for tube and to the corresponding plate, rod and strip specifications for other product forms.
Mechanical Properties
| Property | Value |
|---|---|
| Tensile strength, annealed tube | 275 MPa minimum |
| Elongation, annealed tube | 45% minimum |
| Tensile strength, cold worked | Increased with reduction, at the cost of elongation |
| Density | Approximately 8.5 g/cm³ |
The annealed condition is the reference state for heat exchanger and condenser tube. A minimum tensile strength of 275 MPa with at least 45% elongation gives the ductility needed to roller expand a tube into a tube sheet and to bend it without splitting, while still providing enough strength for normal operating pressures. Where higher strength is required, the alloy can be supplied lightly cold worked, and the resulting loss of elongation must then be considered in the installation procedure.
Corrosion Resistance
C44400 is primarily a seawater alloy. It resists general corrosion in salt water, brackish water and condensate, and the antimony addition specifically delays dezincification. The alloy also behaves well in mildly acidic and alkaline chemical environments, which extends its use into process equipment and chemical pipework.
Three limitations should be respected. Ammonia and ammonium compounds can cause stress corrosion cracking in copper-zinc alloys, so residual stress should be relieved and contact with such media avoided. High flow velocities cause impingement and erosion, so water velocity should be kept inside the design envelope. Stagnant conditions and deposits promote under-deposit attack in any inhibited brass, so drainage, cleaning and flow distribution matter as much as alloy choice.
Processing and Application Scenarios
Cold working. Excellent. The single phase alpha structure allows drawing, bending, flaring, swaging and cold forming with intermediate anneals, which is why the alloy is a tube and strip material.
Hot working. Performed above approximately 600 C. The low lead and iron limits widen the hot working window and reduce the risk of edge cracking.
Casting. The alloy casts well and can be used for fittings and valve bodies that are later machined.
Machining. Free of the high lead additions used in free-cutting brass, so cutting speeds are moderate and sharp tooling with lubricant is required.
Shipbuilding. Hull and deck fittings, seawater pipework, condenser and cooler tube, pump and valve components.
Electrical industry. Connectors, terminals and contacts that must survive humid or salt-laden atmospheres.
Process industries. Heat exchangers, evaporators and pipework in chemical and desalination plants.
Transport and equipment. Automotive, aerospace, electronic and general mechanical components where corrosion resistance and moderate strength are both needed.
Quality Control Points
Confirm chemistry by optical emission spectrometry, with antimony, tin, lead and iron all reported individually.
Confirm the temper by tensile and hardness testing against the ordered standard.
Verify tube dimensions, wall thickness and concentricity; wall variation governs both pressure rating and heat transfer performance.
Apply eddy current testing to tube destined for heat exchanger service, and hydrostatic testing where pressure integrity is critical.
Keep material identification through the works. Tin brasses and inhibited admiralty brasses look identical on the shop floor but are not interchangeable.
FAQ
Q: What makes C44400 different from ordinary brass?
It contains about 1% tin along with a controlled antimony addition and a higher copper content of 70-73%, which together give markedly better seawater corrosion resistance and resistance to dezincification than a plain copper-zinc brass.
Q: What are the mechanical values for annealed tube?
A minimum tensile strength of 275 MPa and a minimum elongation of 45% are the reference values for the annealed condition used in heat exchanger service, as reflected in the requirements of ASTM B111.
Q: Why are lead and iron limited so strictly?
Both elements embrittle the alloy and narrow the hot working window. Holding lead to 0.07% maximum and iron to 0.06% maximum keeps the material ductile enough for drawing and rolling.
Q: Can it be used in fresh water and steam condensate?
Yes. The alloy performs well in fresh water, condensate and brackish water, which is why it is widely used in cooling systems and in thermal desalination plants.
Q: How does it behave during machining?
Machinability is only moderate because the lead content is low and strictly limited. Use sharp carbide tooling, positive rake angles and an effective cutting lubricant, and expect longer chips than with a free-cutting brass.
Q: Which product forms are available?
Seamless tube and pipe, rod, bar, plate, sheet, strip and wire. Tube and pipe dominate because the main application is seawater and condensate handling, with plate and strip used for baffles, tube sheets and fabricated components.
