Sep 18 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat treatment
Machinability
Welding
Forging
Hot Working
Cold Working
Annealing
Applications
Introduction
Copper beryllium alloys feature high strength and good thermal and
electrical properties. Two main types of copper beryllium alloys are
high conductivity alloys and high strength alloys. The high
conductivity alloys have 0.2-0.7% of beryllium and high cobalt and
nickel contents. The wrought high strength alloys consist of 1.6 to
2.0% of beryllium and nearly 0.3% of cobalt. While, the cast
high-strength alloys contain up to 2.7% of beryllium. The UNS
designations of the cast alloys are C82000 to C82800 and that of
wrought alloys are C17200 to C17400. The copper beryllium alloys can be
precipitation hardened or age hardened to improve its strength. The
tensile strength of C17300 alloys is over 1380 MPa (200 ksi).
The cast alloys contain alpha copper dendritic structure and
beryllide phases. The wrought alloys consist of a microstructure, which
have twinned grains of alpha copper with cobalt, nickel or cobalt and
nickel beryllide particles dispersed in the structure.
This article will outline the properties of UNS C17300 beryllium
copper alloys, which are heat treatable, ductile and capable of being
mill hardened.
Chemical Composition
The following table shows the chemical composition of UNS C17300
copper alloys.
| Element |
Content
(%) |
| Cu |
97.7 |
| Be |
1.9 |
| Co |
0.40 |
Physical Properties
The physical properties of UNS C17300 copper alloys are given in the
following table.
| Properties |
Metric |
Imperial |
| Density (during age hardening, 2% max. decrease
in length and 6% max. increase in density) |
8.25 g/cm3 |
0.298 lb/in3 |
| Melting point |
866°C |
1590°F |
Mechanical Properties
The mechanical properties of UNS C17300 copper alloys are tabulated
below.
| Properties |
Metric |
Imperial |
| Hardness, Rockwell B |
80.0 - 85.0 |
80.0 - 85.0 |
| Tensile Strength, ultimate |
515 - 585 MPa |
74700 - 84800 psi |
| Tensile Strength, yield |
275 - 345 MPa |
39900 - 50000 psi |
| Elongation at break |
15.0 - 30.0% |
15.0 - 30.0% |
| Modulus of elasticity |
125 - 130 GPa |
18100 - 18900 ksi |
| Poissons ratio |
0.3 |
0.3 |
| Machinability (UNS C36000 (free-cutting brass) =
100%) |
50% |
50% |
| Shear modulus |
50.0 GPa |
7250 ksi |
Thermal Properties
The following table shows the thermal properties of UNS C17300
copper alloys.
| Properties |
Metric |
Imperial |
| CTE, linear (@20.0 – 100°C /68.0 – 212°F) |
16.7 μm/m°C |
9.28 μin/in°F |
| CTE, linear (@20.0 – 200°C /68.0 – 392°F) |
17.0 μm/m°C |
9.44 μin/in°F |
| CTE, linear (@20.0 – 300°C /68.0 – 572°F) |
17.8 μm/m°C |
9.89 μin/in°F |
| Specific heat capacity |
0.420 J/g°C |
0.100 BTU/lb°F |
| Thermal conductivity (@20.0°C /68.0°F) |
105 - 130 W/m-K |
729 - 902 BTU-in/hr-ft2°F |
| Thermal conductivity (@200°C /392°F) |
130 - 133 W/m-K |
902 - 923 BTU-in/hr-ft2°F |
| Solidus |
865°C |
1590°F |
| Liquidus |
980°C |
1800°F |
Other Designations
Other designations that are equivalent to UNS C17300 copper alloys
include:
- UNS C17300
- ASTM B196
- ASTM B197
Fabrication and Heat Treatment
Machinability
The machinability rate of C17300 copper alloys is 20%.
Welding
Welding procedures such as soldering, brazing, gas shielded arc
welding, coated metal arc welding, spot welding, seam welding and butt
welding are preferred for C17300 copper alloys. Oxyacetylene welding is
not preferred for this type of alloys.
Forging
Forging is carried out in C17300 copper alloys at temperature
ranging from 649 to 816°C (1200 to 1500°F).
Hot Working
C17300 copper alloys have good hot working property.
Cold Working
C17300 copper alloys have excellent cold working property.
Annealing
Annealing of C17300 copper alloys is performed at temperature
ranging from 774 to 802°C (1425 to 1475°F).
Applications
The following are the major applications of UNS C17300 copper alloys:
| Bearings |
Precision screw machined parts |
| Plastic molds |
Electrical/electronic connectors |
| Welding electrodes |
Corrosion resistant components |
| Current-carrying springs |
Housings for magnetic sensing devices |