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Cr-Cu, W-Cu Contacts

Product descriptions

Application

Cr-Cu contacts are used in the vacuum arc-quenching chambers (VACs) of highly dependable, quick-acting vacuum circuit breakers capable of breaking large currents in high-voltage 6-35 kW electrical networks. Contacts are a key element in commutation switches (circuit breakers). Currently, the most common material used in contact pairs in VACs are Cr-Cu composites.

 

Contacts are subjected to the effects of short-circuit currents and fusing metals in various points of the surface due to the high density of the current in them; as a result, welding joints form in these zones. This problem was one reason that delayed the development of vacuum commutation technology for more than twenty years. The resistance of a VAC's contacts to welding is one of its key characteristics. The problem of welding was solved by developing special contact plates made from chromium-copper composites, which provided a high breaking capacity for circuit breakers in commutation networks, wear-resistance and resistance of contact pairs to welding together.

 

W-Cu contacts are used in VACs of vacuum contactors with a nominal voltage of 1.14 kW and higher in systems for remote control of electric drivers. The contacts are a long-lasting means of switching contactors in electric circuits on and off and ensure a low cut-off current in the system.

Characteristics of fabricated parts from chromium-copper materials

Grades, structure and chemical composition

Grade,standard Form and structure Chemical composition, mass %
Cr Cu O max N max S max
ERCr25Cu75-PM Single-layer chromium-copper disks 24-27 Base 0.07 0.005 ND
ERCr50Cu50-PM Single-layer chromium-copper disks Balance 48-53 0.07 0.005 ND
ERCr35Cu65-PM Single-layer chromium-copper disks 33-37 Base 0.07 0.005 ND
ERCr30Cu70-PM Two-layer disks: Cr-Cu and Cu Contact layer 27-33 Balance 0.05 0.005 0.007
Copper layer <1.0 Base 0.02 0.005 0.007
ERCr50Cu50-PM Contact layer 48-53 Balance 0.05 0.005 0.007
Copper layer <1.0 Base 0.02 0.005 0.007
Cr-Cu, W-Cu Contacts

PM – Powder Metallurgy

Dimensions

Grade Nominal dimensions, mm
Diameter Thickness
Disc Contact layer Copper layer
ERCr25Cu75-PM single-layer discs 90 8.0 to 20.0 - -
ERCr50Cu50-PM single-layer discs 48, 56, 66, 70, 80 8.0 to 20.0 - -
ERCr35Cu65-PM single-layer discs 42.0 to 90.0 7.0 to 13.0 - -
ERCr30Cu70-PM two-layer discs 32 4.0 2±0.5 2±0.5
48, 56, 60, 66, 80 6.0 3±0.5 3±0.5
ERCr50Cu50-PM two-layer discs 32 4.0 2±0.5 2±0.5
48, 56, 60, 66, 80 6.0 3±0.5 3±0.5
Cr-Cu, W-Cu Contacts

At the client's request, contact parts of other dimensions can be produced.

Physical and mechanical characteristics

Grade Minimum density, g/cm³ Minimum hardness HB* Minimum conductivity %**
ERCr25Cu75-PM single-layer discs 8.2 65.0 55.0
ERCr50Cu50-PM single-layer discs 7.8 90.0 40.0
ERCr35Cu65-PM single-layer discs 8.0 72.0 45.0
ERCr30Cu70-PM two-layer discs 8.35 70 55
ERCr50Cu50-PM two-layer discs 8.35 85 40
Cr-Cu, W-Cu Contacts

* Contact layer Brinell hardness HB 5/250

**Conductivity of the contact layer in % of standard copper.

Other types of contact parts

  • ERCr30Cu70-PM made from Cr30Cu70 material. Single-layer disks with the dimensions: Ø 50x16, 70x22 mm.
  • ERCr30Cu70-PM and ERCr50Cu50-PM Bimetallic disks with a contact layer made from Cr30Cu70 or Cr50Cu50 material and copper substrata.

Nominal product dimensions, mm: diameter 48, 56, 66, 80 thickness (height) 10. Thickness of contact layer 4.5±0.5 mm.

Contact parts with other dimensions can be produced at the client's request.

Controlled parameters: chemical composition, dimensions, density, hardness and conductivity.

Sample actual specifications of contact parts

Part Chemical composition, % ρ, g/cm³* HB** σ, %***
Cr Cu O max N max S max
ERCr30Cu70-PM Two-layer disk Ø48x10 Contact layer 30.69 Rem. 0.025 0.002 0.001 8.59 79 59.7
Copper substratum <0.05 Base 0.009 0.002 0.001 - - -
ERCr30Cu70-PM Two-layer disk Ø56x6 Contact layer 30.16 Rem. 0.026 0.002 0.001 8.54 77.1 58.7
Copper substratum <0.05 Base 0.01 0.002 0.001 - - -
ERCr50Cu50-PM Two-layer disk Ø66x6 Contact layer 50.3 Rem. 0.042 0.002 0.002 8.4 106 41.1
Copper substratum <0.05 Base 0.008 0.002 0.001 - - -
Cr-Cu, W-Cu Contacts

* ρ - part density

** HB - Contact layer Brinell hardness HB 5/250

*** σ - contact layer conductivity in % of standard copper.

Microstructure

In complex parts, material microstructure is monitored to prevent defects and the thicknesses of the contact layer and substratum are checked, along with the quality of the composite's transition layer.

Sample structures of complex contacts

Sample structures of complex contacts

fig. 1

Sample structures of complex contacts

fig. 2

*Fig.1: Complex 2-layer contact material structure ERCr 50Cu50 (fragment). ERCr50Cu50 contact layer and Cu substratum.

*Fig.2: Contact layer structure ERCr30Cu70 (fragment) of bimeitalic contact.

Specifications of electric contact parts made from tungsten-copper material

Grade, structure and chemical composition

Contract parts consist of two heterogeneous layers (bimetallic structure): a contact layer made from a tungsten-copper material and a substratum made from copper.

Grade, standard Part shape and structure Chemical composition, mass %
W Cu O max N max S max
W70Cu30-PM(elsend) Bimetallic disks made from W70Cu30 + Cu material Contact layer Balance 28-32 0.05 0.005 0.007
Copper layer - Base 0.02 0.005 0.007
Cr-Cu, W-Cu Contacts

PM – Powder Metallurgy

Dimensions

Grade Nominal dimensions, mm
Diameter Thickness
Disc Contact layer Copper layer
W70Cu30-PM 32, 48 4+2.0 2±0.5 2±0.5
Cr-Cu, W-Cu Contacts

Parts with contacts of other sizes can be produced at the client's request.

Physical and mechanical characteristics

Cr-Cu, W-Cu Contacts
Grade Minimum density, g/cm³ Minimum hardness HB* Minimum conductivity, %**
W70Cu30-PM 11.36 145 55

* Contact layer Brinell hardness HB 5/250

** Contact layer conductivity in % of standard copper.

Sample structure of complex contacts

The parts' material microstructure is monitored to prevent defects. The thicknesses of the layers and the quality of the composite's transitional zone are checked.

Sample structure of complex contacts

fig. 3

*Fig.3: Structure of bimetal contact layer material W70Cu30-PM (fragment).

Typical specifications:

density 8.86-8.88 g/cm3,
conductivity 87-92%,
hardness 130-140 HB.