How Granulation Processes Enhance AgWC(12)C(3) Performance?

Researchers at Fudar Alloys have found that different granulation processes significantly impact the material's performance. Among these, dry granulation technology performs particularly well.

What are AgWC(12)C(3) Electrical Contacts?

AgWC(12)C(3) electrical contacts are made using a powder metallurgical process. The material consists of 85% silver, 12% tungsten carbide (WC), and 3% graphite (C). This material is typically used as a static contact. It is paired with a dynamic contact material, such as AgW(50) or AgWC(40), in circuit breakers with rated currents of 63A and above.

Its main performance requirements include:

- Low resistivity: Improve the conductivity of the contacts and reduce the temperature rise.

- High flexural strength: Enhance the contact's resistance to arc burnout and improve electrical life.

-Long electrical life: Maintain reliable performance under frequent on-off operations.

Comparison of Three Granulation Processes

To explore the effect of the granulation process on the properties of AgWC12C3, the following three methods were used in the study:

1. Powder sintering granulation

• After sintering at high temperatures, the powder is formed by sieving through a granulator.
• lAdvantages: Simple process, suitable for mass production.
• lDisadvantage High-temperature treatment reduces the activity of the powder and affects the sintering performance.

2. Glue mixing granulation

• lAdding binder to the powder and forming granules by sieving.
• lAdvantage: Low operating temperature.
• lDisadvantage: Binder residue may form porosity and reduce sintering activity.

3. Dry granulation

• lDDirectompression of powders into granules by CIP(ColdIsostaticPressing).
• lAdvantages: Avoids the influence of high temperatures or binders and maintains the powder activity.
• Disadvantages: Higher process equipment requirements.

Experimental results and analysis

Mechanical and Physical Properties
The hardness, density, resistivity, and flexural strength of the samples prepared by the three processes (1#, 2#, and 3#) were compared. The results are as follows:

Sample No.	Hardness (HBW)	Density (g/cm³)	Electrical Resistivity (μΩ·cm)	Flexural Strength (MPa)
1# Powder sintering granulation	56.5	9.69	3.08	248
2# Glue mixing granulation	58.0	9.69	2.90	276
3# Dry granulation	59.0	9.71	2.78	305

Findings:

- Electrical resistivity: The dry granulation sample had the lowest electrical resistivity, which was 9.7% lower than the powder sintering granulation.

-Flexural strength: The dry granulation sample was the highest, with a 23% increase over the powder sintering granulation.

Metallographic Organisation and Fracture Analysis

- Metallographic organization: The samples prepared by the three processes showed uniform tissue distribution. The dry granulation samples had the least porosity.




- Fracture Morphology: The fracture of the dry granulation samples was fine and smooth, indicating a high degree of sintering. In contrast, the sintered granulation samples had more incompletely sintered particles.

Electrical Life Test

The samples were assembled into 250A molded case circuit breakers (MCCB) for an electrical life test. The results are as follows:

- 1# Powder SinteringGranulation: The failure life is 4479 cycles.
- 2# Glue Mixing Granulation: The failure life is 5980 cycles.
- 3# Dry Granulation: Tested to 8000 cycles without failure.

Why is Dry Granulation Superior?

The advantages of dry granulation stem from the fact that it maintains the high sintering activity of the powder during the granulation process:

- Avoidance ohigh-temperature sinteringng: Reduces particle growth and agglomeration and improves sintering properties.
- No binder residue: Avoids the formation of pores and improves the density and strength of the material.

Application Prospects and Conclusion

The experimental results show that the AgWC12C3 material prepared by dry granulation technology has the best overall performance. Compared to powder sintering granulation, the resistivity is reduced by 9.7%. The flexural strength is increased by 23%, and the electrical life improves by more than 78%.

Optimizing the granulation process has significantly improved the comprehensive performance of AgWC12C3 electrical contacts. Specifically, dry granulation technology reduces the material's resistivity and greatly enhances mechanical strength and electrical life. This makes it well-suited for high-performance static contacts in modern circuit breakers. As the performance requirements for electrical equipment continue to improve, dry granulation technology will have broad application prospects in the field of high-performance electrical contact materials. If you have any questions about granulation processes, please feel free to contact us.