CuSn8 Bronze Bearing Material: Properties, Selection Guide & Applications
CuSn8 Bronze Bearing Material: Properties, Selection Guide & Applications
High-Performance Self-Lubricating Bronze Bushing Solutions & Technologies. Minimize downtime, extend service life, and reduce costs for dynamic applications.
CuSn8 Bronze Bearing Material:
Properties, Selection Guide & Applications
A consolidated engineering reference for CuSn8 (phosphor bronze) plain bearings and sleeve bushings with lubrication indents / grease reservoirs, with application analysis in material handling equipment.
1Material Overview
CuSn8 — also designated phosphor bronze or CuSn8P — is a tin-bronze alloy of nominally 92% copper and 8% tin with a small phosphorus addition for deoxidation and strength. It is one of the most widely specified materials for wrapped (rolled) plain bearings, sleeve bushings, flanged bushes and thrust washers, particularly where high load at low speed, oscillating motion and contaminated environments are expected.
Grade Equivalents
| System | Designation | Standard | Notes |
|---|---|---|---|
| EN / CEN | CuSn8 · CW453K | EN 1652 / CEN/TS 13388 | Strip & sheet copper alloy designation |
| DIN (Germany) | CuSn8 · 2.1030 (CuSn8P) | DIN 17662 | Cold-rolled tin-phosphor bronze strip |
| UNS (USA) | C52100 | ASTM B103 | Phosphor bronze strip, 8% tin |
| JIS (Japan) | C5210 | JIS H 3100 | Phosphor bronze sheet / strip / coil |
| GB/T (China) | QSn8-0.3 | GB/T 5231 | Tin-phosphor bronze strip equivalent |
| Structure codes | FB090 / FB092 / FB09G | DIN 1494 · ISO 3547 | Wrapped-bushing forms: diamond pockets / perforated / graphite-plugged |
2Chemical Composition
| Element | Nominal | Role |
|---|---|---|
| Tin (Sn) | 7.0 – 9.0 % | Primary alloying element; governs strength, elasticity and corrosion resistance |
| Copper (Cu) | Balance | Matrix; provides thermal / electrical conductivity and ductility |
| Phosphorus (P) | 0.03 – 0.35 % | Deoxidizer; refines the structure, improves fluidity and wear behaviour |
| Iron (Fe) | ≤ 0.10 % | Impurity control |
| Lead (Pb) | ≤ 0.02 % | Impurity control (RoHS / ELV compliant composition) |
Note: European suppliers typically specify Sn 7.5–8.5 % (EN CW453K), while strip standards allow 7.0–9.0 %. P is commonly quoted 0.1–0.3 % for bearing-grade strip. The alloy is compliant with RoHS and ELV directives.
3Technical Data
3.1 Mechanical & Physical Properties
| Parameter | Value / Range | Unit | Engineering Relevance |
|---|---|---|---|
| Tensile strength (soft state) | 390 – 450 | MPa | Resists hoop stress under press-fit; varies with temper (R370–R740) |
| Yield strength (Rp0.2, soft) | 180 – 220 | MPa | Low permanent set under shock load; work-hardened strip 250–280 MPa |
| Elongation | ≥ 35 | % | Conformability to shaft and housing under assembly |
| Hardness | 90 – 150 | HBW / HV | Wear resistance under boundary lubrication; work-hardened 125–150 |
| Fatigue strength (10⁷ cycles) | 150 – 180 | MPa | Oscillating and cyclic-load endurance |
| Density | 8.8 – 8.9 | g/cm³ | Thin-wall wrapped form reduces component mass vs. solid castings |
| Melting range | 950 – 1040 | °C | Process window for brazing / soldering |
| Thermal conductivity | 50 – 67 | W/(m·K) | Heat dissipation higher than steel-backed bimetal in dry duty |
| Electrical conductivity | 12 – 15 | % IACS | Applicable for current-carrying contacts / connectors |
| Linear expansion coefficient | 17.5 – 18.5 | 10⁻⁶/K | Input for running-clearance calculation across temperature shifts |
3.2 Friction, Wear & Operating Limits
| Parameter | Value | Condition |
|---|---|---|
| Coefficient of friction | 0.08 – 0.25 | Boundary / grease-lubricated running |
| Coefficient of friction (fluid film) | 0.03 – 0.08 | Oil-lubricated, fully developed film |
| Allowable dynamic load | ≤ 40 N/mm² | Continuous motion; reinforced pocket designs to ~100 N/mm² |
| Allowable static load | ≤ 120 N/mm² | Static holding, low-speed oscillation |
| Maximum sliding speed | ≤ 2.5 m/s | Grease-lubricated |
| PV limit | ≤ 2.8 N/mm²·m/s | Grease lubrication — primary safety constraint |
| Operating temperature | −100 … +200 °C | Lubricant-dependent; typical duty −40 … +150 °C |
| Wear rate (standard conditions) | < 0.5 μm/km | Lubricated, clean reference test |
Apply the PV value as the primary safety constraint rather than load or speed alone. For wrapped CuSn8 bushings the practical boundary-lubrication envelope is PV ≤ 2.8 N/mm²·m/s; applications beyond this range require steel-backed bimetal, cast bronze (CuSn10P / CuSn12) or aluminium-bronze evaluation.
4Lubrication Design: Grease Reservoirs
The sliding surface of CuSn8 wrapped bushings is engineered with indented lubrication pockets that act as grease reservoirs:
| Variant | Geometry | Function | Preferred duty |
|---|---|---|---|
| FB090 — diamond pockets | Diamond / spherical indents, ~20–30 % surface coverage | Retain grease, form a lubricant film at start-up, trap wear debris | General use; long relubrication interval; dirty environments |
| FB092 — through-holes | Uniform punched holes through the wall, Ø 2–5 mm | Feed grease from housing / shaft to the interface; flush contaminants | Heavy-load wheels, crane sheaves, conveyor idlers; central lubrication systems |
| FB09G — graphite plugs | Solid graphite plugs embedded in the matrix | Semi-self-lubricating; minimal maintenance | Hard-to-reach pivot points, intermittent duty |
Assembly guidance for wrapped bushings: press into an H7 housing; finished bore typically holds H9; recommend shaft tolerance e7 / f7 (machine bore to F7 if an h-shaft is used).
5Product Forms & Solution Comparison
| Solution | Structure | Load | Wear res. | Self-lube | Corrosion res. | Cost | Suitable scenario | Key consideration |
|---|---|---|---|---|---|---|---|---|
| Standard rolled bearing | Diamond oil pockets, rolled | ★★★★ | ★★★★ | ★★★ | ★★★★ | Economical | General conditions, periodic lubrication | Requires relubrication; limited in very dirty environments |
| Flanged bearing (deep pockets) | Flange location, deep oil storage | ★★★★★ | ★★★★ | ★★★★ | ★★★★ | Medium | Heavy load, low speed, dirty | Higher cost; not for high speed |
| CuSn8 + graphite | Embedded graphite particles | ★★★★ | ★★★★★ | ★★★★★ | ★★★★ | Medium | Medium load / speed, maintenance-free | Cost above standard type |
| CuSn8 + PTFE composite | PTFE coating or embedded layer | ★★★ | ★★★★ | ★★★★★ | ★★★★★ | High | Corrosive environment, ultra-low friction | Limited load; not heat resistant; higher cost |
| Cast bronze bearing | Cast forming, thick wall | ★★★★★ | ★★★★ | ★★ | ★★★★ | High | Ultra-heavy load, extreme conditions | Forced lubrication; longer manufacturing lead |
| Steel-backed composite | Steel backing + bronze layer | ★★★★★ | ★★★★ | ★★★ | ★★★ | Medium | High load with thin-wall / high-stiffness need | Steel backing rust risk in salt spray |
| Thin-wall bearing | Light-gauge rolled strip | ★★★ | ★★★ | ★★★ | ★★★★ | Economical | Light load, high speed, space limited | Not for heavy or impact loads |
| Machined oil-groove bearing | Machined grooves, forced lubrication | ★★★★ | ★★★★★ | ★★ | ★★★★ | Medium | High-speed continuous operation | Requires forced lubrication system |
6Application Matrix — Material Handling Equipment
| Equipment | Application position | Load type | Speed | Environment | Recommended form | Key requirement |
|---|---|---|---|---|---|---|
| Container wheel hub system | Hub bearing seat | Radial + axial | 0.2–0.5 m/s | Outdoor, dirty, corrosive | Flanged, deep oil groove | Load capacity, corrosion resistance |
| Rotating support shaft | Mainly radial | < 0.3 m/s | Outdoor, dusty | Rolled bearing | Impact resistance | |
| Fixed pin shaft | Radial + shear | Reciprocating | Outdoor, corrosive | Flanged bushing | Maintenance-free | |
| Electric forklift | Mast guide bearing | Radial + lateral | 0.5–1.5 m/s | Warehouse, clean | CuSn8 + graphite | Low friction, maintenance-free |
| Fork pivot bushing | Radial + bending | Swinging | Warehouse, general | Standard bearing | Load + impact resistance | |
| Steering knuckle bushing | Radial + torque | Swinging | Warehouse, clean | Thin-wall bearing | Low friction, flexible steering | |
| Lift hydraulic cylinder | Radial + axial | 0.1–0.5 m/s | Warehouse, clean | Guide sleeve | Precision guidance | |
| Diesel forklift | Drive shaft bearing | Radial | 1–3 m/s | Outdoor, high temp. | Rolled bearing | High-temperature resistance |
| Rear axle bushing | Radial + impact | < 1 m/s | Outdoor, dirty | Thick-wall bearing | Impact + load capacity | |
| Belt conveyor | Drum bearing seat | Radial | 1–4 m/s | Workshop, dusty | Rolled bearing | Wear resistance, long life |
| Tension pulley bearing | Radial + tension | 2–5 m/s | Workshop, clean | Standard bearing | Stability | |
| Idler bearing | Radial | 1–3 m/s | Workshop, dusty | Thin-wall bearing | Economical, low friction | |
| Chain conveyor | Sprocket bearing | Radial + impact | 0.5–2 m/s | Workshop, dirty | CuSn8 + graphite | Impact + wear resistance |
| Guide wheel bushing | Radial + lateral | 1–3 m/s | Workshop, general | Standard bearing | Guidance precision | |
| Gantry / bridge crane | Boom pivot | Radial + bending | Swinging | Outdoor, corrosive | Flanged bearing | High load, corrosion resistance |
| Sheave bearing | Radial | 0.5–2 m/s | Outdoor, dusty | Rolled bearing | Reliability | |
| Travel wheel bearing | Radial + axial | 0.2–0.8 m/s | Outdoor, rail track | Flanged bearing | Impact resistance | |
| Stacker / shuttle | Guide wheel group | Radial + lateral | 1–3 m/s | Warehouse, rail track | CuSn8 + PTFE | Low friction, guidance |
| Lift mechanism bearing | Radial + axial | 0.5–2 m/s | Warehouse, clean | Guide sleeve | Precision + load capacity | |
| Fork telescoping shaft | Radial + friction | 0.3–1 m/s | Warehouse, general | CuSn8 + graphite | Self-lubricating | |
| AGV / AMR | Drive wheel bearing | Radial + drive | 0.5–2 m/s | Workshop, clean | Thin-wall bearing | Long life, precision |
| Idler wheel bearing | Radial | 0.5–2 m/s | Workshop, clean | Standard bearing | Reliability | |
| Steering wheel pivot | Radial + torque | Swinging | Workshop, clean | CuSn8 + PTFE | Low friction, flexibility |
7Quick Selection Decision Matrix
| Working condition | Load | Speed | Environment | Lubrication | Preferred solution | Not recommended | Key consideration |
|---|---|---|---|---|---|---|---|
| Heavy load, low speed | High | Low | Dirty | Periodic | Flanged (deep pockets) | Thin-wall | Oil storage and load capacity are key |
| Heavy load, low speed | High | Low | Corrosive | Maintenance-free | CuSn8 + PTFE composite | Thin-wall | Prioritise corrosion resistance and self-lubrication |
| Medium load, medium speed | Medium | Medium | General | Maintenance-free | CuSn8 + graphite | Cast bronze | Balance performance and maintenance cost |
| Medium load, medium speed | Medium | Medium | Clean | Periodic | Standard rolled | CuSn8 + PTFE | Economy and reliability |
| Light load, high speed | Low | High | Clean | Oil | Machined oil groove | Cast bronze | Low friction and heat dissipation |
| Ultra-heavy load | Very high | Very low | Extreme | Forced | Cast bronze | Thin-wall | Extreme load capacity |
| Impact & vibration | High | Low–med | Dirty | Periodic | Flanged bearing | Thin-wall | Impact resistance and structural strength |
| Precision guidance | Medium | Medium | Clean | Self-lubricating | CuSn8 + graphite | Cast bronze | Low friction and dimensional precision |
8Maintenance, Diagnostics & Replacement Criteria
8.1 Periodic maintenance schedule
| Item | Frequency | Inspection content | Abnormal indication | Typical cause |
|---|---|---|---|---|
| Visual inspection | Weekly | Surface condition | Scratches, discoloration, rust | Insufficient lubrication, contamination |
| Lubrication check | Monthly | Grease condition and quantity | Grease dried, deteriorated | Long interval, seal failure, high temperature |
| Wear measurement | Quarterly | Bearing clearance | Excessive clearance, looseness | Normal wear, overload, poor lubrication |
| Temperature monitoring | During operation | Touch / thermometer | Temperature rise > 40 °C | Lubrication loss, excessive friction |
| Noise monitoring | During operation | Listen / vibration meter | Noise, vibration, sticking | Wear, contamination, misalignment |
| Seal inspection | Monthly | Seal integrity | Damage, aging, leakage | Seal aging, improper installation |
| Alignment check | Semi-annually | Shaft concentricity | Eccentricity, tilt | Improper installation, foundation deformation |
| Load assessment | Semi-annually | Actual load vs. design | Overload, frequent impact | Changing operating conditions |
8.2 Common fault diagnostics
| Fault | Severity | Diagnostic method | Emergency measure | Root-cause solution |
|---|---|---|---|---|
| Abnormal wear | High | Disassemble, measure wear | Add lubrication, reduce load | Identify cause, replace, improve lubrication |
| Overheating | High | Temperature monitoring | Stop, cool, check lubrication | Improve lubrication and cooling, check load |
| Noise / vibration | Medium | Listen, vibration measurement | Reduce speed, check tightening | Clean, lubricate, adjust installation |
| Sticking (seizure) | High | Manual rotation resistance check | Clean, lubricate, check assembly | Thorough cleaning, reassemble, check fit |
| Corrosion | Medium | Visual inspection | Clean, corrosion-protection treatment | Replace, improve sealing and protection |
| Installation damage | High | Disassemble, check damage | Irreparable — replace | Use dedicated installation tooling |
8.3 Replacement criteria
| Inspection item | Normal range | Warning value | Replacement at | Frequency |
|---|---|---|---|---|
| Radial clearance | 0.05 – 0.15 mm | 0.20 mm | ≥ 0.25 mm | Quarterly |
| Wear depth | < 0.2 mm | 0.3 mm | ≥ 0.5 mm | Semi-annually |
| Surface roughness | Ra 1.6 – 3.2 | Ra 6.3 | Ra > 12.5 | Semi-annually |
| Temperature rise | < 40 °C | 50 °C | ≥ 60 °C | During operation |
| Vibration intensity | < 2.8 mm/s | 4.5 mm/s | ≥ 7.1 mm/s | Monthly |
| Corrosion degree | None | Minor pitting | Obvious corrosion / flaking | Monthly |
| Deformation | None | Minor deformation | Obvious deformation / cracking | Semi-annually |
9Data Review Notes
During consolidation, the source data were cross-checked against independent references (EN 1652 / CW453K, UNI 2527, Aurubis CuSn8 datasheets, DIN 1494 / ISO 3547 wrapped-bushing catalogues). Three points merit attention in engineering use:
CuSn8 strip offers good resistance to fresh water and mild media, but resistance to seawater is limited; wrapped thin-wall phosphor bronze is not the first choice for continuous salt-spray duty. For marine / port applications subject to heavy salt exposure, specify aluminium bronze (e.g. CuAl10Ni5Fe4 / C95800) or apply a protective surface coating, and confirm the corrosion requirement with the manufacturer.
Source data cite both −40 … +150 °C (typical) and −100 … +200 °C (limit). The −100 … +200 °C window is the accepted envelope for the base alloy; the practical range is governed by the lubricant (grease typically limits duty to ≈ −40 … +150 °C). Specify the lubricant when defining the operating window.
Quoted dynamic limits vary by supplier and pocket design (40 N/mm² standard, up to ~100–120 N/mm² for reinforced designs). Treat the PV limit (≤ 2.8 N/mm²·m/s grease-lubricated) as the binding constraint and confirm the load figure against the specific product datasheet.
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