ASTM B111 UNS C68700 | Aluminum Brass Tubes

Superior heat exchange solution: ASTM B111 UNS C68700 tubes

ASTM B111 UNS C68700 arsenical aluminum brass seamless tubes supplied to Holland, OD19.05mm x WT2.11mm x L=7.62m, sea-worthy wooden case packaged.

Condenser tubes made of ASTM B111 UNS C68700, also known as “aluminum brass”, offer exceptional corrosion & erosion resistance, thermal conductivity, and mechanical properties, making them ideal for a wide range of heat exchange applications. UNS C68700 is an alloy containing nominally 77.5% copper, 2% aluminum, and 20.5% zinc with a trace of arsenic (0.04%) as an inhibitor. Brass are basically copper-zinc alloys. Aluminum additions incorporate an important constituent of the corrosion film onto a brass: aluminum oxide, which markedly increases resistance to impingement attack in turbulent high-velocity saline water. A trace of arsenic is added to the aluminum brass to “inhibit” its susceptibility to dezincification. Hence, tubes made of arsenical aluminum brass ASTM B111 UNS C68700 are frequently used for marine condensers and heat exchangers in which impingement attack by the high-velocity cooling water is likely to pose a serious problem.

Chemical Composition Requirements

Standard marking on the ASTM B111 UNS C68700 seamless tubes, supplied to Riyadh, Saudi Arabia.

The chemical composition requirements for ASTM B111 UNS C68700 are as follows:

• Copper (Cu): 76.0~79.0%
• Aluminum (Al): 1.8~2.5%
• Iron (Fe): ≤ 0.06%
• Lead (Pb): ≤ 0.07%
• Arsenic (As): 0.02~0.06%
• Zinc (Zn): Balance

Mechanical Properties

The ASTM B111 UNS C68700 seamless tubes shall be furnished in annealed condition with the temper designation of O61:

• Tensile strength: ≥ 50 ksi [345 MPa];
• Yield strength: ≥ 18 ksi [125 MPa];
• Elongation: ≥ 55%;
• Machinability rating: 30%.

International Equivalent & Annealing Temperature

The bright annealing facilities for copper alloy tubes in a factory located in Gansu province, China.

The arsenical aluminum brass ASTM B111 UNS C68700 has several international equivalent grades: HAL77-2 (China), CZ110 (BS), CuZn20Al2 (DIN), C6870 (JIS H). The tubes shall be bright annealed at a temperature between 425°C [800°F] and 600°C [1100°F].

Inspections & Tests

Hydrostatic testing facilities for aluminum brass tubes in a workshop of SJZ Metalsin.

For seamless tubes made of ASTM B111 UNS C68700, the following inspections and tests shall be performed to ensure compliance with the standard and the desired quality: chemical analysis, visual inspection, dimensional examination, tensile test, grain size examination according to ASTM E112, expansion test, flattening test, residual stress test, eddy current test, hydrostatic test, pneumatic test.