ASTM B111 C68700 Aluminum Brass Seamless Tube for Heat Exchanger and Condenser
ASTM B111 C68700 Aluminum Brass Seamless Tube for Heat Exchanger and Condenser
ASTM B111 C68700 copper alloy tube is a seamless aluminum brass tube manufactured for condenser, evaporator and heat exchanger applications.
UNS C68700 is classified as Aluminum Brass, Type B under ASTM B111/B111M. The alloy is a copper-zinc-aluminum material with controlled arsenic content. Its specified chemical composition includes 76.0–79.0% copper, 1.8–2.5% aluminum and 0.02–0.06% arsenic, with zinc as the balance.
The tube can be supplied in different tempers and dimensional configurations according to ASTM B111/B111M and project requirements. Typical applications include surface condensers, heat exchangers, evaporators and other industrial heat-transfer equipment.
Technical Specifications
| Item | Specification |
|---|---|
| Product Name | C68700 Aluminum Brass Seamless Tube |
| Standard | ASTM B111 / ASTM B111M |
| ASME Equivalent | ASME SB111 / SB111M when specified |
| UNS | C68700 |
| Alloy Type | Copper-Zinc-Aluminum Alloy |
| Common Description | Aluminum Brass Type B |
| Tube Type | Seamless |
| Manufacturing Process | Extrusion / Drawing / Annealing / Straightening as applicable |
| Outside Diameter | Up to 3-1/8 in. [80 mm] under ASTM B111 scope; other sizes by agreement |
| Wall Thickness | According to specification and project requirements |
| Length | Straight lengths, customized |
| Temper | O61 Annealed, Light Drawn, Hard Drawn or applicable condition |
| Surface | Mill Finish / Clean Surface |
| End Condition | Plain End or customized |
| Testing | Eddy Current, Hydrostatic, Pneumatic and applicable mechanical tests |
| Documentation | MTC and inspection documents |
C68700 Chemical Composition
The chemical composition of C68700 is controlled to the applicable ASTM B111 requirements.
| Element | ASTM B111 C68700 Requirement |
|---|---|
| Copper (Cu) | 76.0–79.0% |
| Aluminum (Al) | 1.8–2.5% |
| Arsenic (As) | 0.02–0.06% |
| Iron (Fe) | ≤0.06% |
| Lead (Pb) | ≤0.07% |
| Zinc (Zn) | Balance |
Mechanical Properties
Mechanical properties depend on the specified temper.
For C68700 O61 annealed tube, commonly referenced ASTM B111 minimum requirements include:
| Property | O61 Annealed Requirement |
|---|---|
| Tensile Strength | ≥345 MPa |
| Yield Strength | ≥125 MPa |
| Hardness | According to ASTM B111 temper requirements |
Manufacturing Process
C68700 seamless copper alloy tubes are manufactured through a controlled tube-production process.
1. Billet Preparation
Copper alloy material is prepared according to the specified C68700 chemical composition and heat identification requirements.
2. Extrusion and Piercing
The billet is processed to form a hollow tube suitable for subsequent drawing operations.
3. Cold Drawing
Cold drawing is used to achieve the required outside diameter, wall thickness and dimensional tolerances.
4. Heat Treatment
Annealing or other applicable thermal treatment is carried out according to the specified temper and ASTM B111 requirements.
5. Straightening and Cutting
The tubes are straightened and cut to the required length.
6. Final Inspection
Dimensional, surface and applicable mechanical and nondestructive testing are performed before shipment.
Tube Dimensions
C68700 aluminum brass tubes can be supplied in various combinations of outside diameter and wall thickness.
Typical order information includes:
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Outside diameter
-
Wall thickness
-
Tube length
-
Temper
-
Dimensional tolerances
-
End condition
-
Surface condition
-
Testing requirements
For condenser and heat exchanger projects, tube dimensions can be manufactured according to the customer's tube sheet drawing, equipment specification or tube schedule.
Heat Treatment and Temper
ASTM B111/B111M specifies several tube conditions, including:
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Annealed
-
Light Drawn
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Hard Drawn
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Hard Drawn and End Annealed
The selected temper affects the mechanical properties and forming characteristics of the tube. ASTM B111/B111M-24 specifically identifies these available conditions for copper and copper-alloy tubes.
For applications involving tube expansion, bending or tube-to-tubesheet installation, the appropriate temper should be confirmed during the engineering stage.
Testing and Quality Control
Quality control can be carried out according to ASTM B111/B111M and the customer's purchase requirements.
Chemical Inspection
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Heat chemical analysis
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Cu verification
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Al verification
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As verification
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Fe and Pb control
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Heat-number traceability
Mechanical Testing
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Tensile test
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Yield strength test where applicable
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Elongation
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Hardness
Tube Tests
Applicable ASTM B111 tests may include:
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Expansion test
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Flattening test
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Residual stress test
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Eddy-current test
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Hydrostatic test
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Pneumatic test
ASTM B111/B111M-24 specifically identifies expansion, flattening and residual stress testing together with eddy-current, hydrostatic and pneumatic testing within its product requirements.
Dimensional Inspection
Inspection can include:
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Outside diameter
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Wall thickness
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Length
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Straightness
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Ovality
-
End condition
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Surface condition
Applications
Surface Condensers
C68700 seamless tubes are specified for condenser tube applications covered by ASTM B111.
Heat Exchangers
The tubes can be used as heat-transfer tubing in shell-and-tube heat exchangers where C68700 aluminum brass is specified.
Evaporators
ASTM B111 includes evaporator applications within its scope for copper and copper-alloy seamless tubing.
Industrial Cooling Equipment
Typical equipment may include:
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Surface condensers
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Shell-and-tube heat exchangers
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Evaporators
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Industrial coolers
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Power-generation heat-transfer equipment
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Marine and process cooling equipment
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