Materials – C91100 + Graphite Plugs Disc Plate

Solid Bronze Calotte with Solid Lubricant for Heavy-Duty Applications

Product: Calotte (Disc Plate / Spherical Disc)

1. What Is a Calotte (Spherical Disc Plate)?

A Calotte, also known as a spherical disc plate, is a precision sliding and load-bearing component designed to handle high contact loads and angular misalignment. It is widely used in disc spring assemblies, spherical seating systems, and heavy-duty mechanical joints where reliable load transfer and controlled movement are required.

Thanks to its spherical geometry, a calotte provides:

• Automatic self-alignment under misalignment conditions

• Even load distribution across the contact surface

• Reduced edge loading, fretting, and surface fatigue

Typical applications include:

• Heavy industrial machinery

• Structural and mechanical assemblies with angular motion

• Low-speed, high-load sliding contact

• Installations with limited, unreliable, or no lubrication

2. Material Specification – C91100 Bronze with Graphite Plugs

Base Material:

• UNS C91100 High-Leaded Tin Bronze

Solid Lubricant:

• Embedded Graphite Plugs

This combination creates a solid bronze self-lubricating disc plate, specifically engineered for boundary lubrication and dry-running conditions, where conventional grease lubrication is difficult to maintain.

3. C91100 Bronze – Key Material Characteristics

C91100 is a proven high-lead tin bronze alloy commonly used in traditional bearing and sliding components due to its forgiving tribological behavior.

Main material advantages:

• Excellent embeddability, allowing debris to be absorbed without damaging mating parts

• Very good anti-seizure and anti-galling performance

• High conformability, accommodating surface imperfections and misalignment

• Moderate mechanical strength, ideal for low to medium speed and medium load conditions

Typical chemical composition (approximate):

• Copper (Cu): Balance

• Tin (Sn): 7–9%

• Lead (Pb): 15–25%

• Zinc (Zn): ≤ 3%

C91100 bronze is especially suitable for applications where:

• Contact stress is high

• Angular misalignment cannot be avoided

• Liquid lubrication is insufficient or unreliable

4. Role of Graphite Plugs in Self-Lubrication

The addition of graphite plugs significantly upgrades the performance of standard bronze calottes.

During operation:

• Graphite functions as a solid lubricant

• A lubricating transfer film forms on the sliding surface

• Friction is reduced under:

  • Dry-running conditions

  • Frequent start-stop operation

  • High load and low speed movement

As a result, the calotte can operate:

• With minimal or no grease

• In dusty, dirty, or high-temperature environments

• With a longer service life compared to plain bronze disc plates

5. Typical Installation Position and Working Conditions

A C91100 + Graphite Plugs Calotte is commonly installed at:

• Spherical contact and seating interfaces

• Load transfer and alignment points

• Disc spring stack assemblies

• Pivot or angular compensation locations

The calotte typically runs against:

• Hardened carbon steel

• Alloy steel

• Stainless steel counterfaces

Its primary functions are to:

• Allow controlled angular movement

• Reduce surface stress concentration

• Maintain stable and predictable friction behavior

6. Material Selection – Comparison and Alternatives

7. Why Choose C91100 + Graphite Plugs for Calotte Applications?

• ✔ Ideal for low-speed, high-load sliding contact

• ✔ Compensates effectively for misalignment and surface irregularities

• ✔ Performs reliably under poor or absent lubrication

• ✔ Reduces maintenance costs and downtime

• ✔ A proven solution for traditional and heavy-duty industrial systems

8. Conclusion

The C91100 + Graphite Plugs Calotte combines the forgiving tribological properties of high-lead bronze with the maintenance-reducing benefits of solid graphite lubrication. This makes it an excellent material choice for disc plates and spherical sliding components operating in demanding industrial environments.

For applications where reliable performance, long service life, and reduced lubrication dependency are critical, this material grade offers a well-balanced and cost-effective solution.