AWS J1.3 Technical Specifications
| Property | Value | Unit |
|---|---|---|
| UNS Designation | C17510 | - |
| Composition | Cu + 0.2-0.6% Be + 1.4-2.2% Ni | % wt |
| Electrical Conductivity | ≥45 | % IACS (AWS J1.3 min) |
| Hardness | ≥90 | HRB (AWS J1.3 min) |
| Thermal Conductivity | 208 | W/m·K |
| Softening Temperature | 550 | °C |
| Tensile Strength | 760-900 | MPa |
Recommended Applications
The Thermal Balance Principle
The formula Q = I²Rt (Joule's Law) governs resistance welding. When the material being welded has high resistivity (like AHSS or stainless), we need an electrode with lower conductivity to balance the heat generated.
- Higher hardness (96-102 HRB) resists deformation under high pressure
- 550°C softening temperature for high energy cycles
- Superior tensile strength for projection applications
- Less electrode "mushrooming" in intensive production
When NOT to Use Class 3 (and What to Use Instead)
Class 3 is for HARDNESS — but it sacrifices conductivity. Lower current = better conduction.
❌ Don't use Class 3 if:
- Machine at 80%+ current, validated electrode, still won't weld properly — That's a conductivity problem, not hardness. Go DOWN to Class 2, not up.
- Class 2 already works for you — If you don't have abnormal wear or deformation, don't change. Class 3 costs more and conducts less.
- You're welding uncoated low carbon steel — Class 2 is sufficient and has better conductivity (75% vs 45% IACS).
- You have sticking with galvanized — The problem is zinc-copper interaction, not hardness. Use Class 1 with upslope.
📋 Plant Examples:
- Automotive cell at 85% current, cold welds, electrodes validated → Problem is conductivity. Moving to C3 would make it worse. Solution: go DOWN to Class 2 and optimize parameters.
- Projection station with electrodes deforming after 500 welds → That IS a hardness problem. Solution: evaluate C18000 (beryllium-free Class 3) or Elkonite.
✓ Use this instead:
- Class 2 (C18200/C18150) — If you need more conductivity or C2 already works for you.
- Class 1 (C15000) — If the problem is sticking, not wear.
- Elkonite (CuW) — If C3 is not enough for projection wear.
⚡ 30-Second Checklist:
- □ Do I have wear/deformation problems on electrodes? → C3 may help
- □ Am I at high current and still cold welding? → C3 will make it WORSE
- □ Do I have beryllium restrictions? → Use C18000 (beryllium-free)
- □ Is C2 working fine for me? → Don't change
Not sure if Class 3 is right for your application? Tell us your parameters and we'll help you decide →
The 3 Class 3 Variants
All meet AWS J1.3 Class 3 specification (≥45% IACS, ≥90 HRB), but there are key differences:
- C17500 (CuCoBe): The hardest of all. More expensive and sometimes out of stock. For when you need maximum wear resistance.
- C17510 (CuNiBe): The beryllium standard. Good balance hardness/conductivity. Permanent stock.
- C18000 (CuCrNiSi): BERYLLIUM-FREE. Slightly lower hardness than C17510, but more economical and without beryllium restrictions. Excellent entry point to Class 3 — big mechanical difference vs Class 2, but similar price.
Selection logic:
1. Beryllium restrictions? → C18000 (beryllium-free)
2. Want the hardest and budget allows? → C17500 (CuCoBe)
3. Standard without complications? → C17510 (CuNiBe)
4. Good price/hardness balance without beryllium? → C18000
What We See in Real Applications
In our experience with automotive plants:
- AHSS/UHSS: Class 3 does make a difference when Class 2 deforms quickly from the heat generated.
- Nut projection: The higher hardness helps resist the mechanical pressure of the process.
- Gradual transition: Many plants start with C18000 (beryllium-free) before moving to beryllium-containing options.
- It's not magic: If your problem is parameters or setup, Class 3 won't solve it. First validate that the process is properly configured.
If you have questions about whether Class 3 is right for you, let's discuss your specific application.