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
| Cu | 56 to 60 | |
| Zn | 35.6 to 42.8 | |
| Sn | 0.75 to 1.1 | |
| Fe | 0.25 to 1.3 | |
| Ni | 0.2 to 0.8 | |
| Mn | 0.010 to 0.5 | |
| Si | 0.040 to 0.15 | |
| Pb | 0 to 0.050 | |
| Al | 0 to 0.010 | |
| res. | 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