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RWMA Class 2

Copper Class 2 – Copper Chromium (C18200)

The most versatile alloy for resistance welding. Optimal balance between conductivity and hardness. Specifications per AWS J1.3.

AWS J1.3 Technical Specifications

Property Value Unit
UNS Designation C18200 -
Composition Cu + 0.6-1.2% Cr % wt
Electrical Conductivity ≥80 % IACS (AWS J1.3 min)
Hardness ≥75 HRB (AWS J1.3 min)
Thermal Conductivity 324 W/m·K
Softening Temperature 475 °C
Density 8.89 g/cm³

Recommended Applications

Low Carbon Steels Body panels, structures, sheets
Galvanized Steels Auto parts, appliances
High Volume Production OEM automated lines
Spot & Seam Welding Caps, shanks, forged wheels

Why Choose Class 2?

Copper Chromium Class 2 represents 80% of industrial applications in resistance welding. Its balance between electrical conductivity (≥75% IACS) and hardness (≥75 HRB) makes it ideal for:

  • Longer service life than Class 1 on low resistivity materials
  • Wear resistance in high volume production
  • Higher softening temperature (475°C vs 200°C of pure Cu)
  • Optimal cost-benefit for most automotive applications
Technical Note: For advanced high strength steels (AHSS/UHSS) with high resistivity, consider Class 3 (CuNiBe - C17510) for better thermal balance and higher hardness.

Frequently Asked Questions about Copper Class 2

What is RWMA Class 2 Copper?

Class 2 Copper is an RWMA (Resistance Welder Manufacturers Association) classification for precipitation-hardened copper alloys. According to the AWS J1.3 standard, Class 2 Copper must have a minimum electrical conductivity of 75% IACS and minimum hardness of 75 HRB. The most common alloy is Copper Chromium (C18200), composed of copper with 0.6-1.2% chromium.

What is the difference between C18200 and C18150?

Both are Class 2 Copper, but they have different compositions:

  • C18200 (CuCr): Copper-Chromium. More economical, excellent for general applications.
  • C18150 (CuCrZr): Copper-Chromium-Zirconium. Higher softening resistance, ideal for MFDC welders and high-strength galvanized steels.

For more details, see our Copper Chromium Zirconium C18150 page.

What materials can I weld with Class 2 electrodes?

Class 2 Copper is ideal for welding:

  • Low carbon steels (body panels, structures)
  • Galvanized steels (auto parts, appliances)
  • Stainless steels in thin to medium thicknesses
  • Coated sheets (zinc, aluminum-silicon)

For high strength steels (AHSS/UHSS), we recommend Class 3 Copper for its higher hardness.

Why does ALCAVIL use the AWS J1.3 standard?

The AWS J1.3 (Specification for Materials Used in Resistance Welding Electrodes and Tooling) standard is the international reference that defines minimum properties for resistance welding electrode materials. At ALCAVIL, all our technical information is backed by AWS J1.3 because:

  • It is the reference used by Tier 1 automotive OEMs
  • It defines verifiable minimum values for conductivity and hardness
  • It ensures consistency in material selection