ASTM B111 C68700 Copper Alloy Seamless Tube For Heat Exchanger and Evaporators
ASTM B111 C68700 Seamless Tube – Overview
ASTM B111 C68700 refers to seamless brass tubes made from Arsenical Aluminum Brass (UNS C68700), designed primarily for condensers, heat exchangers, and marine applications. This standard specifies requirements for dimensions, mechanical properties, and chemical composition.
1. Key Features
(1). Chemical Composition (UNS C68700 / ASTM B111)
The composition is specified in weight percentages (wt. %):
| Element | Composition (wt. %) |
| Copper (Cu) | 76.0 – 79.0% |
| Zinc (Zn) | Remainder (balance) |
| Aluminum (Al) | 1.8 – 2.5% |
| Arsenic (As) | 0.02 – 0.10% |
| Iron (Fe) | ≤ 0.06% |
| Lead (Pb) | ≤ 0.07% |
| Other Impurities | ≤ 0.5% (total) |
Notes:
The arsenic (As) addition improves corrosion resistance, especially in seawater.
Aluminum (Al) enhances strength and oxidation resistance.
(2). Mechanical Properties (ASTM B111 C68700 Seamless Tube)
| Property | Condition | Value |
| Tensile Strength (min) | Annealed (O60) | ≥ 380 MPa (55,000 psi) |
| | Hard Drawn (H55, H58) | ≥ 485 MPa (70,000 psi) |
| Yield Strength (0.5% extension, min) | Annealed | ≥ 125 MPa (18,000 psi) |
| | Hard Drawn | ≥ 345 MPa (50,000 psi) |
| Elongation (min, % in 50mm) | Annealed | ≥ 45% |
| | Hard Drawn | ≥ 10% |
| Hardness (Rockwell B, typical) | Annealed | ~55 HRB |
| | Hard Drawn | ~80 HRB |
| Max. Working Temperature | — | ~260°C (500°F) |
Notes:
Annealed (O60): Soft, ductile, suitable for bending/flaring.
Hard Drawn (H55/H58): Higher strength, used for pressure applications.
Corrosion Resistance: Excellent in seawater, steam, and condensate systems.
2. Equivalent Standards
| Standard | Equivalent Material |
| UNS | C68700 |
| EN (Europe) | CW702R |
| DIN (Germany) | CuZn20Al2As |
| JIS (Japan) | C6870 |
3. Why Choose ASTM B111 C68700 Tubes?
✅ Excellent corrosion resistance (especially in seawater).
✅ High thermal conductivity (good for heat exchangers).
✅ Good mechanical strength (even at elevated temperatures).
✅ Seamless construction (no weak points from welding).
The ASTM B111 C68700 seamless tube (Arsenical Aluminum Brass) is specifically engineered for demanding environments where corrosion resistance, thermal conductivity, and mechanical strength are critical. Here are its primary applications:
1. Marine & Offshore Systems
- Seawater Condensers & Heat Exchangers
- Resists dezincification and biofouling in saltwater.
- Used in ship cooling systems, offshore oil rigs, and desalination plants.
- Propulsion & Cooling Pipes
- Withstands high-velocity seawater flow without erosion.
2. Power Generation
- Steam Condenser Tubes (Fossil & Nuclear Plants)
- Handles high-pressure steam and hot water (up to 260°C/500°F).
- Preferred in coal-fired, gas turbine, and nuclear power stations.
- Evaporators & Feedwater Heaters
- Efficient heat transfer with minimal scaling.
3. Chemical & Petrochemical Industry
- Cooling Systems for Refineries
- Resists sulfides, chlorides, and ammonia in process fluids.
- Heat Exchangers for Acidic/Caustic Media
- Aluminum content improves resistance to weak acids and alkalis.
4. HVAC & Refrigeration
- Chiller Tubes & Cooling Coils
- High thermal conductivity improves energy efficiency.
- Brine & Glycol Cooling Systems
- Compatible with antifreeze solutions.
5. Industrial Process Equipment
- Distillation Columns & Reboilers
- Used in ethanol, pharmaceutical, and food processing plants.
- Hydraulic & Pneumatic Systems
- Hard-drawn (H55/H58) tubes handle high-pressure fluids.
Why Choose C68700 Over Other Copper Alloys?
| Feature | C68700 (Arsenical Aluminum Brass) | Admiralty Brass (C44300) | Cupronickel (C70600) |
| Seawater Resistance | Excellent (As prevents dezincification) | Good (needs inhibitors) | Superior (best for high salinity) |
| Strength | High (Al adds strength) | Moderate | Moderate |
| Cost | Mid-range | Lower | Higher |
| Thermal Conductivity | Very High | High | Lower |
Key Advantages for These Applications
✔ Corrosion Resistance – Arsenic (As) and aluminum (Al) protect against saltwater, steam, and chemicals.
✔ Pressure Tolerance – Seamless construction avoids weak welds.
✔ Easy Fabrication – Can be bent, flared, or expanded (annealed condition).
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