EN CC495K (CuSn10Pb10-C) Bearings: The High-Load, Machinable Bronze Deep Dive
In the demanding world of industrial machinery and heavy equipment, the choice of bearing material is critical. Components face immense pressure, friction, and wear. One alloy that consistently rises to the challenge, particularly where high loads and machinability are paramount, is EN CC495K, also known by its chemical designation CuSn10Pb10-C. This leaded tin bronze offers a unique blend of properties that make it a go-to material for numerous demanding applications, especially for custom-designed parts.
But what exactly makes CC495K tick? Let's move beyond the surface level and delve deep into its composition, properties, and most importantly, where its custom applications truly shine.
Decoding the Alloy: What is EN CC495K (CuSn10Pb10-C)?
EN CC495K is a leaded tin bronze alloy manufactured according to the European standard EN 1982. The designation tells us a lot:
Cu: Copper is the base metal.
Sn10: It contains approximately 10% Tin (Sn).
Pb10: It contains approximately 10% Lead (Pb).
-C: This indicates the material is produced via Continuous Casting, a process crucial for its final properties (more on this later).
The precise chemical composition is tightly controlled to ensure consistent performance:
Table 1: Chemical Composition of EN CC495K (CuSn10Pb10-C) (% Weight)
Element
Symbol
Range (%)
Key Role & Contribution
Copper
Cu
76 - 82
Base Metal: Provides overall structure, conductivity, and fundamental strength.
Tin
Sn
9.0 - 11
Primary Alloying Element: Significantly increases strength, hardness, wear resistance, and corrosion resistance compared to pure copper. Forms the bronze matrix.
Lead
Pb
8.0 - 11
Critical Differentiator: Improves machinability drastically by acting as a chip breaker. Provides emergency self-lubrication and seizure resistance by smearing under boundary lubrication conditions. Reduces friction.
Nickel
Ni
0 - 2.0
Can improve strength, corrosion resistance, and refine grain structure.
Zinc
Zn
0 - 2.0
Often added for castability, deoxidation, and can slightly improve strength/corrosion resistance. May reduce cost.
Antimony
Sb
0 - 0.5
Can slightly increase hardness.
Iron
Fe
0 - 0.25
Typically an impurity, kept low to avoid forming hard spots that reduce machinability.
Manganese
Mn
0 - 0.2
Acts as a deoxidizer and desulfurizer during casting.
Phosphorus
P
0 - 0.1
Potent deoxidizer, can increase fluidity and wear resistance (though less critical than in phosphor bronzes).
Sulfur
S
0 - 0.1
Impurity, kept low as it can negatively impact mechanical properties.
Silicon
Si
0 - 0.010
Impurity, kept very low.
Aluminum
Al
0 - 0.010
Impurity, kept very low as it can negatively impact bearing properties.
Note: Ranges represent permitted limits under EN 1982.
The Lead Factor: Advantage and Consideration
The significant lead content (8-11%) is what truly sets CC495K apart from many other bronzes (like phosphor bronzes, e.g., CuSn12).
Contrasting Logic: While lead-free bronzes are increasingly mandated in certain sectors (like food processing or potable water systems) due to environmental and health regulations, lead provides distinct engineering advantages in specific contexts:
CC495K allows faster machining speeds, better surface finishes, and lower tooling costs for complex parts.
Seizure Resistance
Excellent (Lead smears under pressure)
Good
CC495K offers better protection against catastrophic failure during momentary oil starvation or overload.
Embeddability
Good (Lead helps embed foreign particles)
Fair
Can tolerate slightly dirtier operating environments without scoring the shaft as easily.
Conformability
Good (Lead allows slight plastic deformation)
Fair
Can better conform to slight shaft misalignments.
Max Load/Strength
High
Potentially Higher (depending on specific alloy)
While strong, CC495K might have slightly lower ultimate tensile strength than some high-tin phosphor bronzes.
Environmental/Health
Restricted Use
Generally Unrestricted
Lead content restricts use in certain applications (food, water, RoHS compliance).
Key Properties & Benefits of EN CC495K Bearings
Derived from its composition and manufacturing process, CC495K offers:
High Load Capacity: The tin-bronze matrix provides excellent strength to withstand heavy static and dynamic loads.
Good Wear Resistance: Suitable for moderate speeds under high load conditions.
Exceptional Machinability: The lead content allows for easy cutting, drilling, milling, and threading, making it ideal for complex custom parts.
Excellent Seizure Resistance: The lead provides a safety net during boundary lubrication conditions, preventing catastrophic welding between the bearing and shaft.
Good Corrosion Resistance: Generally resistant to atmospheric corrosion, non-oxidizing acids, and seawater, though less so than aluminum bronzes.
Pressure Tightness: The continuous casting process (-C designation) minimizes porosity, leading to a dense structure suitable for hydraulic applications and components requiring pressure integrity.
