What ASTM B111 C44300 Admiralty Brass Tube Is
ASTM B111, also issued as ASME SB111, is the specification that covers seamless copper and copper-alloy condenser tubes and ferrule stock. UNS C44300 is the inhibited Admiralty brass grade inside that family. The alloy is a copper-zinc brass with a nominal copper content of about 71%, roughly 1% tin and a deliberately controlled trace of arsenic. The tin addition raises resistance to flowing seawater, and the arsenic addition inhibits dezincification, the selective leaching of zinc that destroys uninhibited brasses in polluted or stagnant water. Tubes are produced from cast billets that are pierced and extruded, then cold drawn to the ordered temper, and they are normally supplied as straight lengths for surface condensers, evaporators, feed-water heaters and ferrule stock.
Chemical Composition of UNS C44300
The limits below are those tabulated for C44300 in ASTM B111 / ASME SB111. Zinc is the balance of the alloy. Nickel and manganese are not required additions, and the total of unnamed residual elements is held to a low maximum so that the corrosion behaviour of the alloy stays predictable.
| Element | Limit (wt.%) |
|---|---|
| Copper, including silver | 70.0 - 73.0 |
| Tin | 0.9 - 1.2 |
| Arsenic | 0.02 - 0.06 |
| Lead | 0.07 max |
| Iron | 0.06 max |
| Zinc | Remainder |
| Nickel, manganese | Not required |
Mechanical Properties and Tempers
Admiralty brass condenser tube is most often ordered in the O61 annealed temper, which gives the softest condition and the highest ductility for rolling into tube sheets and for flaring and bending. Higher-strength tempers such as light-drawn or hard-drawn conditions raise tensile and yield strength at the expense of elongation, and the applicable minimum values are those tabulated in the specification for the ordered temper and wall thickness.
| Property, O61 annealed | Minimum value |
|---|---|
| Tensile strength | 310 MPa (45 ksi) |
| Yield strength, 0.5% extension under load | 105 MPa (15 ksi) |
| Elongation | Specified by the standard as a function of temper and wall thickness |
| Grain size | Controlled for the ordered annealed temper |
Because the elongation requirement in ASTM B111 is tied to tube wall thickness and temper rather than being a single figure, tube mills qualify each order against the row of the specification table that matches the ordered size and condition, and the mill test report should be read on that basis.
Corrosion Behaviour and Dezincification Resistance
The arsenic range of 0.02 - 0.06% is the defining feature of inhibited Admiralty brass. In aerated chloride-bearing water, arsenic interferes with the electrochemical mechanism by which zinc is preferentially dissolved, so the tube develops a protective copper-rich surface film instead of becoming porous. That is why C44300 remains serviceable in fresh water, seawater and brackish cooling water where an uninhibited 70/30 brass would fail within a few years of service. The alloy is nevertheless susceptible to stress-corrosion cracking in ammonia-bearing or ammoniacal condensate atmospheres, so cold-worked tubes must receive a low-temperature stress-relief anneal and impurity content must be controlled during hot working. Limiting cooling water velocity to the range recommended for Admiralty brass, avoiding stagnant pockets and keeping the water side free of ammonia contamination all extend service life.
Applications of C44300 Condenser and Heat Exchanger Tubes
Marine engineering: surface condenser tubes, desalination piping, auxiliary heat exchangers and subsea valve components.
Power generation: steam condenser tubes in thermal plants, cooling circuits and refinery exchangers where sulfur compounds and contaminated water attack tube surfaces.
HVAC and refrigeration: refrigerant condensers and chlorinated hot water circuits.
Process industry: feed-water heaters, evaporator tube bundles and ferrule stock for tube-sheet connections.
General engineering: deep-drawn pins and springs, corrosion-resistant bearing bushes and machined fittings.
Selection, Installation and Inspection Points
Dimensions, wall thickness and length tolerances come from the ordered specification, and the usual commercial range for condenser duty is an outside diameter from about 6 mm to 76 mm with walls from 0.5 mm to 3.75 mm. When placing an order it is worth stating the UNS number, temper, dimensions, quantity, the required eddy-current acceptance level and whether ASME SB111 applies. Seamless tube should be delivered with a hydrostatic or pneumatic test, an eddy-current examination and a mill test report traceable to the heat number, including chemical analysis, tensile results and grain size. Roller expansion into a tube sheet needs enough residual wall section to hold the joint, and tube ends should be annealed where severe flaring is required. Store tubes dry and away from ammonia-bearing atmospheres so that stress-corrosion cracking does not begin before installation.
FAQ
Q: What does the arsenic addition in C44300 actually do?
Arsenic in the range 0.02 - 0.06% inhibits dezincification, so the tube resists the selective loss of zinc that would otherwise make plain brass porous in seawater and polluted cooling water.
Q: How does C44300 differ from C68700 aluminium brass?
C44300 is a tin-bearing Admiralty brass, while C68700 contains 1.8 - 2.5% aluminium instead of tin. Aluminium brass is stronger and more resistant to erosion-corrosion, so it is chosen for higher seawater velocities.
Q: Which temper is used for condenser and heat exchanger tubes?
The O61 annealed temper is standard because it offers the ductility needed for rolling into tube sheets; light-drawn tempers are selected only where extra strength is required for a specific design.
Q: Can C44300 be used in high-velocity seawater?
It performs well at moderate velocities. Above the range recommended for Admiralty brass, aluminium brass or copper-nickel grades such as C70600 are usually selected because their resistance to erosion-corrosion is higher.
Q: What testing is normally supplied with the tubes?
Hydrostatic or pneumatic pressure testing, eddy-current examination, tensile testing, chemical analysis and grain size measurement, all reported on a mill test certificate traceable to the heat number.
Q: What is the ASME equivalent of ASTM B111?
ASME SB111 is technically identical to ASTM B111, and the closest European designation for the same alloy family is CuZn28Sn1As in EN 12451, with C4430 appearing in the JIS H3300 series.
