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.
When NOT to Use Class 2 (and What to Use Instead)
Class 2 is the workhorse for ~80% of applications — but it's not for projection.
❌ Don't use Class 2 if:
- It's projection welding of nuts/studs — The projections require A LOT of pressure to collapse and "bury" themselves. Class 2 can't handle the mechanical stress.
- Projection on UHSS/hot stamping — Even worse. The nut (softer) must bury into ultra-hard steel = extreme pressure. They even use capacitive welders for this.
- Heavy galvanizing with frequent sticking — Class 1 conducts better and requires less heat.
📋 Plant examples:
✓ Use this instead:
- Class 3 (C17510/C18000) — For projection. Higher hardness to handle mechanical stress.
- Elkonite/CuW (Class 10-12) — For heavy automotive projection or extreme wear.
- Class 1 (C15000) — If the problem is sticking with galvanized, not wear.
⚡ Quick Checklist (30 sec):
Quick rule: Sheet-to-sheet = Class 2. Projection = Class 3 or Elkonite.
Tell me: process type, material to weld, and current problem, and I'll confirm if Class 2 is right.
Validate my application →What We See in Real Applications
In our experience with automotive and manufacturing plants:
- Caps and shanks for BIW lines: Class 2 is the standard. Works well for spot welding on any type of steel, including UHSS when it's sheet-to-sheet.
- Curved and special electrodes: Class 2 is the most common choice for its balance of conductivity and mechanical strength.
- Projection = different world: Projections require high pressure to collapse. That's where Class 2 struggles — better to use Class 3 or Elkonite.
- Tip dressing: With a good dressing program, Class 2 caps maintain consistent geometry for thousands of welds.
If you have questions about which material is right for your specific application, let's review it together.