What Is Phosphor Bronze

Phosphor bronze is an alloy of mainly copper, tin and phosphorus that is widely known for its strength, durability, fine grain and low coefficient of friction. It is usually manufactured it in the form of wires, tubes, bars, plates and sheets. It comes in a wide range of grades and has a moderate price ^[7].

Composition ^[2]

Copper	93.4-95.32%
Tin	4.2-5.8%
Zinc	0.30% (max)
Iron	0.10% (max)
Lead	0.05% (max)
Phosphorus	0.030-0.35%

Properties and Characteristics of Phosphor Bronze

The alloy has great fluidity and castability in the molten state owing to the presence of phosphorus. Tin increases its corrosion resistance and strength ^[8].

Physical Properties
Color/appearance	Reddish (in most cases) [7]
State at room temperature	Solid [7]
Melting point/freezing point	880-1025°C [3]
Density	8800 kg m3 [3]
Machinability	20% [3]
Thermal Conductivity	50 W/(m K) [3]
Electrical Conductivity (relative to copper)	15% [9]
Heat capacity	0.38 J/g °C [3]
Resistivity	13 micro-ohm-cm [4]
Hardness (Rockwell B)	85 [3]
Tensile strength (ultimate)	550 MPa [3]
Yield strength	450 MPa [3]
Young’s modulus	110 GPa [3]
Modulus of elasticity	110 GPa [3]
Friction coefficient (with steel)	0.35 [6]
Coefficient for thermal expansion	17.8X10-6/0C [5]

Uses

1. Typically for making springs, sleeve bushings, bearings, welding rods, nuts, bolts, etc ^{[7, 8]}.
2. To make the suspension coil of moving coil galvanometers because it doesn’t oxidize easily, is non-magnetic and has low torsional constant ^[8].
3. Making jewelry, knife and lock washers, guitar strings, harmonica reeds, dental bridges ^[7]

Is It Dangerous

The fumes or dust of the alloy is toxic to humans. Hence, contact with skin, clothing and eyes should be avoided. In solid form, the material is not hazardous ^[1].

Interesting Facts

• When exposed to air, a beautiful patina forms on its surface that makes it suitable for artistic applications ^[10].

References
1. Phosphor Bronze Alloy Material Safety Data Sheet – Fiskalloy.com
2. Phosphor Bronze Physical & Chemical Properties – Meadmetals.com
3. Phosphor Bronze 510 – Elginfasteners.com
4. Ness Engineering Technical Data Metal/Alloy Resistivity – Nessengr.com
5. Co-efficient of Thermal Expansion Data – Repairengineering.com
6. Friction and Friction Coefficients – Engineeringtoolbox.com
7. Phosphor Bronze Powder – Americanelements.com
8. Alloy: C51000 Phosphor Bronze 5% A Spec Sheet – Concast.com
9. Electrical Conductivity of Materials – Bluesea.com
10. Henley’s Twentieth Century Formulas Recipes Processes Vol1 – Chestofbooks.com