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UNS C68000 (RBCuZn-B) Filler Metal

C68000 brass is a copper-based filler metal for brazing. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. RBCuZn-B is the AWS designation for this material. C68000 is the UNS number.

It has the lowest thermal conductivity and a moderately high tensile strength among copper-based braze fillers.

The graph bars on the material properties cards below compare C68000 brass to: copper-based braze fillers (top), all copper alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Elastic (Young's, Tensile) Modulus

100 GPa 15 x 106 psi

Elongation at Break

27 %

Poisson's Ratio

0.3

Shear Modulus

40 GPa 5.8 x 106 psi

Tensile Strength: Ultimate (UTS)

390 MPa 57 x 103 psi

Tensile Strength: Yield (Proof)

140 MPa 20 x 103 psi

Thermal Properties

Brazing Temperature

880 to 980 °C 1620 to 1800 °F

Latent Heat of Fusion

170 J/g

Maximum Temperature: Mechanical

120 °C 250 °F

Melting Completion (Liquidus)

880 °C 1620 °F

Melting Onset (Solidus)

870 °C 1590 °F

Specific Heat Capacity

390 J/kg-K 0.092 BTU/lb-°F

Thermal Conductivity

96 W/m-K 56 BTU/h-ft-°F

Thermal Expansion

21 µm/m-K

Otherwise Unclassified Properties

Base Metal Price

23 % relative

Density

8.0 g/cm3 500 lb/ft3

Embodied Carbon

2.8 kg CO2/kg material

Embodied Energy

48 MJ/kg 20 x 103 BTU/lb

Embodied Water

330 L/kg 39 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

82 MJ/m3

Resilience: Unit (Modulus of Resilience)

95 kJ/m3

Stiffness to Weight: Axial

7.3 points

Stiffness to Weight: Bending

20 points

Strength to Weight: Axial

14 points

Strength to Weight: Bending

15 points

Thermal Diffusivity

31 mm2/s

Thermal Shock Resistance

13 points

Alloy Composition

Copper (Cu) 56 to 60
Zinc (Zn) 35.6 to 42.8
Tin (Sn) 0.75 to 1.1
Iron (Fe) 0.25 to 1.3
Nickel (Ni) 0.2 to 0.8
Manganese (Mn) 0.010 to 0.5
Silicon (Si) 0.040 to 0.15
Lead (Pb) 0 to 0.050
Aluminum (Al) 0 to 0.010
Residuals 0 to 0.5

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

AWS A5.8: Specification for Filler Metals for Brazing and Braze Welding

Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, ASM Handbook vol. 2, ASM International, 1993