CuZn31Si1 (CW708R) Bearing and Bushing Material Solution
CuZn31Si1 (CW708R) Bearing and Bushing Material Solution
High-Performance Self-Lubricating Bronze Bushing Solutions & Technologies. Minimize downtime, extend service life, and reduce costs for dynamic applications.
CuZn31Si1 (CW708R) Bearing and Bushing Material Solution， CuZn31Si1 Copper
This guide presents a complete engineering solution for CuZn31Si1 (CW708R) when used in plain bearings and bushings. It includes the material’s composition, mechanical and tribological properties, design principles, lubrication methods, manufacturing process, and real-world application cases.
Designation
Name: Silicon Brass CuZn31Si1
International Designation: CW708R (German Standard), DIN 2.0490
Standards: DIN 17660, EN 12163, EN 12449.
Material designation
- EN CuZn31Si1
- CW708R
Chemical composition*
- Cu 68 %
- Si 1 %
- Pb 0.8 %
- Zn balance
- *Reference values in % by weight
-
Key Features
1. Excellent Machinability: Easy to cut, high flatness, suitable for hot/cold forming.
2. High Strength & Creep Resistance: Silicon enhances stress relaxation resistance at high temperatures.
3. Corrosion & Wear Resistance: Performs well in atmospheric, freshwater, seawater, and dilute sulfuric acid environments.
4. Conductivity: Ideal for electrical and thermal components.
5. Non-Magnetic: Suitable for anti-magnetic applications.
Material properties and typical applications
CuZn31Si1 is a special brass exhibiting high resistance to load and wear
due to embedded hard silicides and also good high-temperature strength.
CuZn31Si1 is primarily used in highload sliding applications (e.g. bearing bushings, sleeves and other sliding elements).
Symbol：CuZn31Si1
Number：CW708R
Category：EN Wrought Copper Alloy
Type：Silicon Brass
| Chemical Composition mass/% | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Cu | Sn | Al | Fe | Mn | Ni | Pb | Si | P | Zn |
| 66.0-70.0 | – | – | <0.4 | – | <0.5 | <0.8 | 0.7-1.3 | – | Rem |
| Mechanical properties | |||
|---|---|---|---|
| Tensile strength Mpa(Min) | Yield strength MPa(Min) | Elongation % | Brinell hardness(HB) |
| 460-600 | 250-370 | 30-12 | 115-170 |
CuSn8 vs. CuZn31Si1: Comparing Two High-Performance Copper Alloys
CuSn8 and CuZn31Si1 are both copper-based alloys widely used in bearing and mechanical engineering applications. Despite their similar uses, their compositions and performance characteristics differ significantly.
CuSn8 (Phosphor Bronze)
Composition: Copper–tin alloy with a small addition of phosphorus.
Key Properties:
-
Excellent wear resistance and sliding performance
-
Good corrosion resistance, particularly in seawater environments
-
Can be soldered and processed with ease
-
Offers high electrical conductivity (depending on temper and processing condition)
Typical Applications:
Ideal for plain bearings, electrical connectors, and components that require both durability and reliable sliding performance.
CuZn31Si1 (Silicon Brass)
Composition: Copper–zinc alloy with silicon as an alloying element.
Key Properties:
-
Excellent friction and wear behavior
-
Good machinability and weldability (especially for TIG welding)
-
High mechanical strength achievable through cold working
-
Corrosion-resistant and stable up to approximately 200°C
-
Silicon addition reduces susceptibility to stress corrosion cracking
Typical Applications:
Used for bearing bushings, guide elements, and other mechanical parts in machinery and plant construction, where a combination of strength, corrosion resistance, and smooth sliding behavior is required.
| Category | CuSn8 (Phosphor Bronze) | CuZn31Si1 (Silicon Brass) |
|---|
| Alloy Type | Copper–Tin–Phosphorus Alloy | Copper–Zinc–Silicon Alloy |
| Main Chemical Composition | Cu + ~8% Sn + P | Cu + ~31% Zn + ~1% Si |
| Typical Appearance | Reddish brown | Golden yellow |
| Key Characteristics | • High wear resistance • Excellent sliding properties • Good corrosion resistance (especially in seawater) • Solderable and weldable • High electrical conductivity (depending on temper) |
• Favorable friction and wear behavior • Good machinability and weldability (especially TIG welding) • High strength achievable through cold working • Good corrosion resistance • Silicon reduces susceptibility to stress corrosion cracking • Stable up to around 200°C |
| Typical Mechanical Properties | Tensile strength: 350–600 MPa Elongation: 10–25% |
Tensile strength: 400–650 MPa Elongation: 5–20% |
| Friction Performance | Excellent dry-running capability; ideal for sliding bearings | Low friction coefficient; suitable for medium-speed, moderate-load applications |
| Corrosion Resistance | Excellent, especially in marine or humid environments | Very good; silicon addition improves resistance to corrosion |
| Workability | Can be cold-worked, machined, and soldered | Easy to machine, weld, and cold-work for higher strength |
| Temperature Stability | Up to approx. 250°C | Up to approx. 200°C |
| Typical Applications | Plain bearings, bushings, electrical connectors, spring elements, conductive components | Bearing bushings, guide elements, mechanical parts, hydraulic components, general machinery construction |
1. Material Overview – CuZn31Si1 (CW708R)
| Element | Content (%) |
|---|---|
| Cu | 68.0 – 71.0 |
| Zn | Balance (~29–31) |
| Si | 0.8 – 1.8 |
| Pb | ≤ 0.1 (lead-free) |
| Fe | ≤ 0.3 |
| Others | ≤ 0.2 each |
Standards:
-
EN: CW708R
-
DIN: CuZn31Si1
-
UNS Equivalent: ~C87500 (similar but not identical)
Type: Silicon brass alloy (lead-free)
2. Why Choose CuZn31Si1 for Plain Bearings & Bushings?
| Property | Advantage |
|---|---|
| Wear Resistance | Silicon forms hard Cu–Si intermetallics → excellent for dry or boundary lubrication |
| Corrosion Resistance | Withstands seawater, brine, and mild acids |
| Load Capacity | PV limit up to 8–12 MPa·m/s (higher with oil or grease) |
| Thermal Conductivity | ~80 W/m·K ensures effective heat dissipation |
| Machinability | 70–80% of C36000 brass |
| Lead-Free Compliance | Meets RoHS and ELV environmental standards |
Summary: CuZn31Si1 is an eco-friendly, high-performance alternative to traditional leaded bronzes.
3. Design & Engineering Guidelines
A. PV Factor (Pressure × Velocity)
| Lubrication Type | Max PV (MPa·m/s) |
|---|---|
| Dry | 2.0 – 3.0 |
| Grease | 6.0 – 8.0 |
| Oil | 10.0 – 12.0 |
Rule of Thumb:
-
P ≤ 40 MPa (static)
-
V ≤ 2.5 m/s (continuous)
B. Recommended Wall Thickness (t) vs Shaft Diameter (d)
| Shaft Diameter (mm) | Wall Thickness (mm) |
|---|---|
| < 20 | 1.5 – 2.5 |
| 20 – 50 | 2.5 – 4.0 |
| > 50 | 4.0 – 6.0 |
C. Diametral Clearance
| Shaft Diameter | Clearance (mm) |
|---|---|
| < 30 mm | 0.03 – 0.08 |
| 30 – 80 mm | 0.05 – 0.12 |
| > 80 mm | 0.08 – 0.18 |
Recommended Fits: H7/g6 or H8/f7 for most bearing assemblies.
4. Lubrication Recommendations
| Type | Specification |
|---|---|
| Initial Grease | PTFE-based, NLGI 2 lithium or synthetic |
| Oil | ISO VG 68–150 (circulating or drip feed) |
| Solid Lubricant | Graphite or MoS₂ plugs |
| Self-Lubricating Option | Oil grooves + PTFE liner (PTFE-lined composite bush-type hybrid) |
Groove Design: Spiral, axial, or figure-8 patterns enhance lubricant retention.
5. Manufacturing Process for CuZn31Si1 Bushings
Typical Workflow:
Surface Finish:
Inner bore roughness ≤ Ra 0.8 μm for reduced friction and wear.
6. Real-World Applications
| Industry | Component | Benefit of CuZn31Si1 |
|---|---|---|
| Marine | Propeller shaft bushings | Excellent seawater corrosion resistance |
| Automotive | Brake cam & kingpin bushings | Durable, lead-free wear surface |
| Industrial Machinery | Conveyor roller bearings | Long life under grease lubrication |
| Hydraulic Systems | Rod eye bushings | Handles high PV with chemical stability |
| Railway | Bogie suspension links | Absorbs shock loads and resists corrosion |
7. Comparison with Alternative Materials
| Property | CuZn31Si1 | CuSn8 Bronze | Sintered Bronze | Polymer (DU) |
|---|---|---|---|---|
| Wear Resistance | ★★★★★ | ★★★★ | ★★★ | ★★ |
| Corrosion Resistance | ★★★★★ | ★★★ | ★★ | ★★★★★ |
| Load Capacity (PV) | ★★★★ | ★★★★★ | ★★★ | ★★ |
| Cost | $$ | $$$ | $ | $$ |
| Machinability | ★★★★ | ★★★ | ★★ | ★★★★★ |
Best Choice For:
Medium-to-high load applications, corrosive environments, and lead-free compliance.
8. Supplier & Specification Tips
Recommended Suppliers: Silicon Brass CuZn31Si1 viiplus.com, CW708R (German Standard), DIN 2.0490
Example Order Specification:
CuZn31Si1 (CW708R) – Turned & Honed Bushing – Ø50/Ø42 × 50L – Ra 0.6 – H8 bore – Grease grooves
Summary: CuZn31Si1 Bearing Solution
| Step | Action |
|---|---|
| 1 | Select CuZn31Si1 for lead-free, wear-resistant, corrosion-proof sliding performance |
| 2 | Design with PV < 8 MPa·m/s, correct clearance, and wall thickness |
| 3 | Use grease or oil lubrication with proper groove geometry |
| 4 | Manufacture via forging → machining → honing |
| 5 | Apply in marine, automotive, and heavy machinery environments |
Need design support?
We can provide 2D/3D CAD drawings, FEA simulations, or a PV calculation worksheet upon request.
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