Sep 13 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesThermal PropertiesOther DesignationsFabrication and Heat treatment Machinability Welding Forging Hot Working Cold Working AnnealingApplications
Introduction
Copper beryllium alloys have high strength and good thermal and electrical conductivities. High conductivity alloys and high strength alloys are the two major types of copper beryllium 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 and the cast high-strength alloys contain up to 2.7% of beryllium. The wrought alloys are named as C17200 to C17400, and the cast alloys are designated as C82000 to C82800. C17200 alloys have high tensile strength of over 1380 MPa (200 ksi).
Copper beryllium alloys can be precipitation hardened or age hardened to achieve high strength. The cast alloys contain dendritic structure of alpha copper and beryllide phases. The wrought alloys have microstructure containing twinned grains of alpha copper with cobalt, nickel or cobalt and nickel beryllide particles dispersed in the structure.
The following section will discuss in detail about UNS C172 beryllium copper alloys, which are malleable, heat treatable and can be mill hardened.
Chemical Composition
The following table shows the chemical composition of UNS C172 copper alloys.
| Element |
Content (%) |
| Cu |
97.9 |
| Be |
1.9 |
| Co |
0.20 |
Physical Properties
The physical properties of UNS C172 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 C172 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) |
20% |
20% |
| Shear modulus |
50.0 GPa |
7250 ksi |
Thermal Properties
The following table shows the thermal properties of UNS C172 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 C172 copper alloys include:
- UNS C17200
- AMS 4651
- AMS 4725
- ASTM B194
- ASTM B196
- ASTM B197
- ASTM B570
- MIL C-21657
- SAE J461
- SAE J463
Fabrication and Heat Treatment
Machinability
The machinability rate of C172 copper alloys is 20%.
Welding
Welding techniques such as soldering, brazing, gas shielded arc welding, coated metal arc welding, spot welding, seam welding and butt welding are recommended for C172 copper alloys. For this type of alloys, oxyacetylene welding is not preferred.
Forging
Forging of C172 copper alloys is performed at temperature ranging from 649 to 816°C (1200 to 1500°F).
Hot Working
C172 copper alloys have good hot working property.
Cold Working
C172 copper alloys have excellent cold working property.
Annealing
Annealing is carried out in C172 copper alloys at temperature ranging from 774 to 802°C (1425 to 1475°F).
Applications
The following are the major applications of UNS C172 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 |