Understanding the Designation: EN CC762S (CuZn25Al5Mn4Fe3-C)
Understanding the Designation: EN CC762S (CuZn25Al5Mn4Fe3-C)
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CuZn25Al5Mn4Fe3-C, CuZn25Al5Mn4Fe3, and EN CC762S all refer to the same material. It is a high-strength special brass, often called manganese bronze, specifically designed for heavy-duty applications.
1. Understanding the Designation: EN CC762S (CuZn25Al5Mn4Fe3-C)
Let’s decode the name to understand the material’s composition and properties:
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EN: European Norm (Standard).
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CC762S: The specific material designation within the EN 1982 standard for copper alloy ingots and castings.
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CuZn25Al5Mn4Fe3: This is the chemical composition breakdown:
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Cu (Copper): The base metal.
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Zn25 (Zinc ~25%): The primary alloying element that makes it a brass.
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Al5 (Aluminum ~5%): Significantly increases strength, hardness, and corrosion resistance.
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Mn4 (Manganese ~4%): Acts as a deoxidizer and grain refiner. It dramatically increases strength, hardness, and wear resistance.
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Fe3 (Iron ~3%): Also a grain refiner, contributing to higher tensile strength and hardness.
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-C: This suffix is critically important. It stands for Continuously Cast. This manufacturing process produces a very fine, uniform grain structure with minimal porosity, which results in superior mechanical properties (especially fatigue strength) compared to other casting methods like sand casting (-S) or centrifugal casting (-GZ).
2. Application Analysis: Bearing Sleeves for Internal Combustion Engine Connecting Rods
Using CC762S for connecting rod bearings (specifically for the “small end” bushing where the piston pin sits, or sometimes for larger, lower-speed engines) is an excellent choice. Here’s why this material excels in this environment:
The Challenges of a Connecting Rod Bearing:
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Extreme Loads: The bearing must withstand immense, rapidly cycling compressive forces from the combustion stroke.
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High Sliding Velocity: There is constant high-speed sliding motion between the bearing and the crankshaft pin or piston pin.
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Risk of Lubrication Failure: During startup, shutdown, or extreme conditions, the protective oil film can temporarily break down, risking metal-to-metal contact (seizure).
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Fatigue: The cyclic loading can lead to fatigue failure over millions of cycles.
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Corrosion: Engine oil can become acidic over time due to combustion byproducts, attacking the bearing material.
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Heat: Friction and proximity to combustion generate significant heat that the bearing must tolerate and dissipate.
How CC762S (CuZn25Al5Mn4Fe3-C) Meets These Challenges:
| Property of CC762S | How It Benefits the Connecting Rod Application |
| High Compressive & Tensile Strength | The alloy’s high strength, derived from the combination of Al, Mn, and Fe, allows it to withstand the immense pressures of the combustion cycle without deforming or failing. |
| Excellent Wear & Seizure Resistance | The hard intermetallic compounds formed by manganese, aluminum, and iron create a durable surface that resists abrasion and galling. This is crucial for preventing catastrophic failure if the oil film is compromised. |
| Superior Fatigue Strength | The Continuously Cast (-C) process creates a dense, fine-grained microstructure. This is vital for resisting the cyclic stresses from the engine’s operation and preventing the formation of fatigue cracks. |
| Good Corrosion Resistance | The aluminum content forms a passive, protective oxide layer on the surface, making the bearing resistant to attack from acidic byproducts in the engine oil. |
| Good Embeddability & Conformability | While very strong, the brass matrix is softer than steel. It can embed small, hard contaminant particles from the oil, preventing them from scoring the more expensive steel crankshaft. |
| Good Thermal Conductivity | As a copper-based alloy, it effectively conducts heat away from the bearing surface, helping to prevent overheating and maintain the integrity of the lubricating oil. |
3. Technical Data for EN CC762S (CuZn25Al5Mn4Fe3-C)
Here are typical mechanical properties for the continuously cast (-C) version. These values highlight why it’s considered a high-performance material.
| Property | Typical Value | Unit |
| Tensile Strength (Rm) | > 750 | MPa |
| 0.2% Proof Strength (Rp0.2) | > 450 | MPa |
| Elongation (A) | > 10 | % |
| Hardness (HBW) | > 200 | HBW 10/3000 |
| Density | ~ 7.6 | g/cm³ |
| Thermal Conductivity | ~ 35 – 40 | W/(m·K) |
Summary
You have identified a top-tier material for high-load, high-wear bearing applications. CuZn25Al5Mn4Fe3-C (EN CC762S) is not a standard, simple brass; it is a complex, high-strength alloy engineered specifically for environments like an internal combustion engine’s connecting rod.
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Its complex chemistry (Al, Mn, Fe) provides exceptional strength and wear resistance.
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Its manufacturing process (Continuously Cast -C) provides the superior fatigue resistance needed to survive millions of engine cycles.
It is a perfect example of matching an advanced material to a highly demanding engineering challenge.
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