RWMA CLASS 2

Copper Class 2 – Copper Chromium Zirconium (C18150)

Q: What is the difference between Copper Class 2 C18150 and C18200?

Both are Class 2 Copper per AWS J1.3. C18150 (CuCrZr) contains chromium + zirconium with higher softening resistance, ideal for MFDC and AHSS. C18200 (CuCr) contains only chromium, is more economical. C18150 represents 90% of applications in OEM automotive plants.

Q: Why is C18150 better for MFDC welders?

MFDC welders operate with fast cycles and high currents. C18150 has higher softening temperature (475°C) thanks to zirconium, better dimensional stability under cyclic thermal loads, and superior resistance to mushrooming.

Q: What does AWS J1.3 mean for welding electrodes?

AWS J1.3 is the Specification for Materials Used in Resistance Welding Electrodes and Tooling from the American Welding Society. It defines minimum conductivity and hardness properties by RWMA class, allowed chemical compositions, and standardized test methods.

Q: When should I use Class 3 instead of Class 2?

Use Class 3 Copper when welding ultra high strength steels (UHSS >1000 MPa), when higher hardness (>90 HRB) is required, when working with nut/stud projection welding, or when the electrode needs to withstand higher mechanical loads.

The MOST used material in resistance welding. Optimal balance between conductivity and hardness. Ideal for MFDC technology and AHSS steels. Specifications per AWS J1.3.

Technical Specifications

Conductivity

≥75% IACS

Hardness

≥75 HRB

Temperature

475°C

Standard

AWS J1.3

Properties Table (AWS J1.3)

Property	Value	Unit
RWMA Class	Class 2	-
UNS Code	C18150	-
Composition	Cu + 0.5-1.5% Cr + 0.02-0.20% Zr	% wt
Electrical Conductivity	≥80	% IACS
Hardness	≥75	HRB
Thermal Conductivity	330	W/m·K
Softening Temperature	475	°C
Density	8.89	g/cm³

The Industry Standard Material

C18150 (CuCrZr) represents 90% of resistance welding applications. Its combination of chromium and zirconium provides:

Higher softening resistance than pure C18200
Excellent thermal balance for MFDC (Medium Frequency DC) welding
Better AHSS/UHSS performance than materials without zirconium
Sticking resistance on galvanized better than pure copper
Optimal cost-benefit for high-volume automotive production

Main Applications

OEM Automotive Welding

Body panels, structural reinforcements in OEM and TIER 1 plants

MFDC Technology

Medium frequency DC welders. C18150 withstands rapid cycles and high currents

AHSS/UHSS Steels

Ultra high strength steels for lightweight vehicles. Require high hardness electrodes

Galvanized Steels

Zinc requires materials with good alloying resistance. C18150 outperforms C18200

C18150 vs C18200: C18150 contains zirconium (Zr) that precipitates during heat treatment, providing higher softening resistance and hardness. For very demanding applications on AHSS steels, consider Class 3 (CuNiBe - C17510).

Frequently Asked Questions about Copper Class 2 C18150

What is the difference between Copper Class 2 C18150 and C18200?

Both are Class 2 Copper per AWS J1.3, but:

C18150 (CuCrZr): Contains chromium + zirconium. Higher softening resistance, better MFDC and AHSS performance. It is the current automotive industry standard.
C18200 (CuCr): Contains only chromium. More economical, suitable for less demanding applications.

C18150 represents 90% of applications in OEM automotive plants.

Why is C18150 better for MFDC welders?

MFDC (Medium Frequency DC) welders operate with fast cycles and high currents that generate more heat in the electrode. C18150 has:

Higher softening temperature (475°C) thanks to zirconium
Better dimensional stability under cyclic thermal loads
Superior resistance to "mushrooming" (contact face deformation)

What does AWS J1.3 mean for welding electrodes?

AWS J1.3 is the "Specification for Materials Used in Resistance Welding Electrodes and Tooling" from the American Welding Society. It defines:

Minimum conductivity and hardness properties by RWMA class
Allowed chemical compositions
Standardized test methods

At ALCAVIL, all our materials comply with AWS J1.3 - this is our quality guarantee and the reason OEMs trust us.

When should I use Class 3 instead of Class 2?

Class 3 Copper is recommended when:

Welding ultra high strength steels (UHSS >1000 MPa)
Higher hardness (>90 HRB) is required to resist deformation
Working with nut/stud projection welding
The electrode needs to withstand higher mechanical loads

See our Class 3 Copper (C17510) page for more details.