Tungsten electrical contact

copperfor circuit breakers

Product overview
Our tungsten-copper (WCu) materials combine the high-temperature stability of tungsten with the electrical and thermal conductivity of copper. WCu is the ideal material for arc erosion contacts in gas-insulated and air-insulated switchgear as well as high- and medium-voltage generator circuit-breakers. Arc temperatures during switching can reach ≥ 20,000 K.

Your advantages at a glance

• Excellent resistance to arc erosion
• Excellent electrical conductivity
• High strength
• Good resilience
• Very good thermal conductivity
• Low thermal expansion

Materials and manufacturing
We use Ni-activated sintering for WCu to ensure very low susceptibility to cracking while maintaining excellent electrical conductivity. The tungsten/copper ratio and the tungsten grain size are adjusted depending on switching voltage, current intensity and the required arc erosion resistance. Typical tungsten contents are set between about 60% and 90% by weight depending on application and economic considerations. The lowest arc erosion rates are achieved at about 80% tungsten by weight. Grain size selection (coarse, medium, fine) influences arc erosion behavior differently for cathode (C) and anode (A) roles in SF6 or air atmospheres.

Ready-to-install systems & services
We deliver ready-to-install WCu contact systems that reduce assembly time. Services include cost-efficient sintering, back-filling, machining, joining, coating and final assembly. Our engineering team supports contact design (FEM/CAD) to optimize making/breaking capacity and maximize service life.

Notes on arc erosion and microstructure
To optimize arc erosion performance we balance tungsten content and tungsten grain size. The selection is made to match the electrical and mechanical loading (voltage/current/atmosphere) of the application, ensuring minimal erosion while maintaining conductivity and mechanical integrity.

Typical properties / data table
Material | CG15 (A15Ni) | CG20 (A20Ni) | MG20 (A20NiF) | FG20 | CG25 | CG30 (A30Ni)
W (% by weight) | 85 | 80 | 80 | 80 | 75 | 70
Cu (% by weight) | 15 | 20 | 20 | 20 | 25 | 30
Alloying additions (% by weight) | ≤ 1.0 | ≤ 1.0 | ≤ 1.0 | ≤ 1.0 | ≤ 1.0 | ≤ 1.0
Grain size (µm)* | Up to 50 | Up to 50 | 20 - 25 | 4 - 8 | Up to 50 | Up to 50
Density (g/cm³) | 15.7 | 15.2 | 15.2 | 15.2 | 14.5 | 14.0
Hardness (HV30) | 205 | 200 | 190 | 220 | 190 | 135
Compressive strength (N/mm²) | 250 | 200 | 240 | 300 | 160 | 60
Electrical conductivity (m/Ωmm²) | 14 | 16 | 16 | 16 | 19 | 22

Additional technical notes
CG = Coarse grain; MG = Medium grain; FG = Fine grain; VFG = Vacuum fine grain.

caractéristiques / spécifications techniques

• Typical tungsten content: 60–90 wt% (typical optimized: ~80 wt% for minimal arc erosion)
• Copper content corresponding to tungsten (e.g., CG15: W 85% / Cu 15%)
• Alloying additions: ≤ 1.0% by weight (typical)
• Available grain sizes: coarse, medium, fine (example ranges in µm shown in table)
• Density range: approx. 14.0–15.7 g/cm³ depending on composition
• Hardness range (HV30): approx. 135–220 depending on grade
• Compressive strength range: approx. 60–300 N/mm² depending on grade
• Electrical conductivity range: approx. 14–22 m/Ωmm² depending on composition
• Manufacturing: Ni-activated sintering, back-filling, machining, joining, coating and assembly into ready-to-install contacts
• Design support: FEM/CAD analyses to optimize contact geometry, mechanical and thermal behavior