# 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 10 ^{6} psi*

Elongation at Break

27 *%*

Poisson's Ratio

0.3

Shear Modulus

40 *GPa* 5.8 *x 10 ^{6} psi*

Tensile Strength: Ultimate (UTS)

390 *MPa* 57 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

140 *MPa* 20 *x 10 ^{3} 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/cm ^{3}* 500

*lb/ft*

^{3}Embodied Carbon

2.8 *kg CO _{2}/kg material*

Embodied Energy

48 *MJ/kg* 20 *x 10 ^{3} BTU/lb*

Embodied Water

330 *L/kg* 39 *gal/lb*

## Common Calculations

Resilience: Ultimate (Unit Rupture Work)

82 *MJ/m ^{3}*

Resilience: Unit (Modulus of Resilience)

95 *kJ/m ^{3}*

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 *mm ^{2}/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