Copper alloys have served as bearing materials for over a century, prized for their excellent conformability, embeddability, and compatibility with steel shafts. From heavy-duty industrial bearings to precision instrument bushings, copper alloy bearing materials offer properties that make them suitable for diverse operating conditions.
Why Copper Alloys for Bearings?
- Conformability: Accommodates minor shaft misalignment without excessive wear
- Embeddability: Embeds small particles without scoring the shaft
- Compatibility: Resists galling and seizure against steel shafts
- Thermal conductivity: Efficient heat dissipation
- Corrosion resistance: Resists water and many chemical environments
Tin Bronze Bearings (SAE 65, C932)
Composition: 88% Cu, 8% Sn, 4% Pb, balance Zn. The most widely used general-purpose bearing bronze.
Properties: Hardness 65-75 HB, tensile strength 240-310 MPa, max load 8,000-12,000 psi, max temperature 260°C, max speed 1,200 fpm.
Applications: Agricultural equipment, construction machinery, machine tools, conveyors, and pumps.
High-Leaded Bronze (SAE 67, C943)
Composition: 78% Cu, 7% Sn, 15% Pb. Higher lead content for maximum conformability.
Properties: Hardness 50-60 HB, tensile strength 170-210 MPa. Excellent conformability and embeddability.
Applications: Rolling mill bearings, dam gate bearings, large slow-speed machinery. High lead creates soft bearing surface for boundary lubrication.
Copper-Lead Bearing Alloys (SAE 48, C964)
Composition: 70-75% Cu, 25-30% Pb. Lead exists as discrete particles in the copper matrix.
Properties: Hardness 45-55 HB, max PV value 40,000-50,000 psi·fpm, max speed 3,600 fpm.
Applications: High-speed, high-load applications in automotive and diesel engines. Main bearings and connecting rod bearings.
Lead-Tin Babbitt (White Metal)
Composition: Grade 1: 89% Sn, 8% Sb, 3% Cu (tin-base). Grade 7: 80% Pb, 15% Sb, 5% Sn (lead-base).
Properties: Hardness 20-30 HB (very soft), tensile strength 40-70 MPa, max load 1,000-2,000 psi, max temperature 135°C.
Applications: Cast as thin layer (1-3mm) over steel or bronze backing. Used in turbine, compressor, motor, and generator bearings.
Bearing Material Selection Guide
| Application | Recommended Material | Reason |
|---|---|---|
| General machinery | SAE 65 (C932) | Best all-around performance |
| High-speed engine bearings | Cu-Pb (SAE 48) | Fatigue resistance at high speed |
| Turbine/compressor bearings | Tin Babbitt on steel | Conformability for high-speed shafts |
| Heavy slow-speed loads | High-leaded bronze | Conformability under heavy loads |
| Food/pharmaceutical | Leaded-free bronze (C86300) | Lead-free, corrosion resistant |
| Marine applications | Manganese bronze (C86300) | Seawater corrosion resistance |
Summary
Copper alloy bearing materials span from soft babbitt metals for turbine bearings to high-strength copper-lead alloys for engine applications. Correct selection depends on load, speed, temperature, lubrication, and environmental factors.
CoreMetal Steel supplies copper and copper alloy products including bearing bronze bar, plate, and custom-machined bearing components.