Two Alloys in the SB111 Family
ASME SB111, matching ASTM B111, covers seamless copper and copper-alloy condenser tubes and ferrule stock. Within it, C44300 admiralty brass and C70600 90/10 copper-nickel are both widely specified, but they serve different service conditions. C44300 is a copper-zinc-tin alloy with arsenic, while C70600 is a copper-nickel alloy with iron and manganese.
Chemical Composition
| Element | C44300 Admiralty Brass | C70600 Copper Nickel |
|---|---|---|
| Copper | 70.0-73.0 percent | About 90 percent |
| Zinc | Balance | 1.0 percent max |
| Tin | 0.9-1.2 percent | - |
| Arsenic | 0.02-0.06 percent | - |
| Nickel | - | 9.0-11.0 percent |
| Iron | 0.06 percent max | 1.0-1.8 percent |
| Manganese | - | 1.0 percent max |
Mechanical Properties
C70600 has higher strength than C44300. Annealed C70600 tube provides a minimum tensile strength of 40 ksi and a minimum yield strength of 15 ksi, with higher values in drawn tempers. C44300 in the O61 temper has a minimum tensile strength of 45 ksi with a yield of 15 ksi. In practice, the copper-nickel grade sustains higher pressure and temperature ratings in seawater systems.
Corrosion Resistance
C44300 resists corrosion in slow-moving, stagnant, and moderately polluted water and clean seawater, which suits low-velocity condenser service. C70600 forms a protective film in seawater and resists erosion, impingement, and biofouling, making it the standard choice for high-velocity seawater piping, shipbuilding, and offshore installations.
Thermal Performance and Formability
C44300 has higher thermal conductivity than C70600, which favors heat transfer in condensers and exchangers. C44300 also has excellent cold formability for bending and tube rolling. C70600 offers better mechanical properties and long-term corrosion margins in marine environments, at a higher material cost.
How to Choose
Select C44300 for condensers and heat exchangers cooled by fresh, salt, or brackish water at moderate velocity, and for feed-water heaters and refinery exchangers. Select C70600 for seawater cooling systems, shipboard piping, offshore platforms, and other applications where velocity, erosion, or long-term marine exposure dominates the design.
Frequently Asked Questions
Q: What does SB111 stand for?
A: SB111 is the ASME designation matching ASTM B111, covering seamless copper and copper-alloy condenser tubes and ferrule stock.
Q: Which is stronger, C44300 or C70600?
A: C70600 copper-nickel has higher strength and supports higher pressure and temperature ratings.
Q: Which has better seawater corrosion resistance?
A: C70600 is preferred for high-velocity and long-term marine service; C44300 suits lower-velocity condenser duty.
Q: Can both be used in heat exchangers?
A: Yes, both are heat exchanger tube materials; C44300 offers higher thermal conductivity and C70600 greater corrosion margin.
Q: What is the copper content of each?
A: C44300 has 70 to 73 percent copper and C70600 about 90 percent copper.
Q: Which is more economical?
A: C44300 admiralty brass is generally the lower-cost option for fresh and brackish water condenser service.
