AWS J1.3 Technical Specifications
| Property | Value | Unit |
|---|---|---|
| UNS Designation | C15000 | - |
| Composition | Cu + 0.10-0.20% Zr | % wt |
| Electrical Conductivity | ≥80 | % IACS (AWS J1.3) |
| Hardness | ≥65 | HRB |
| Thermal Conductivity | 365 | W/m·K |
| Softening Temperature | 525 | °C |
| Tensile Strength | 310-450 | MPa |
Recommended Applications
The Zinc Problem and the Class 1 Solution
When welding galvanized steels, the zinc coating melts at ~420°C and tends to alloy with the copper of the electrode, forming brass (CuZn). This phenomenon causes:
- Sticking of the electrode to the workpiece
- Build-up of material on the electrode face
- Accelerated wear and loss of geometry
- Inconsistency in nugget quality
The high conductivity of Class 1 dissipates heat more rapidly, keeping the electrode face temperature below the alloying point of zinc with copper.
When NOT to Use Class 1 (and What to Use Instead)
Class 1 is not the "basic" option — it's a specialized material and typically more expensive than Class 2.
❌ Don't use Class 1 if:
- You're experiencing rapid wear — Class 1 has lower typical hardness than Class 2 (depending on thermal conditions). If you're changing electrodes frequently due to wear, the problem is hardness.
- You're not working with galvanized or coated materials — High conductivity (≥80% IACS) only pays off when there's zinc, Al-Si, or other coatings causing sticking.
- Your process doesn't use low current — If you're using high currents on normal steel, Class 1 provides no advantage and you're overpaying.
- You're looking for the most economical option — Class 1 costs more than Class 2. If you don't have sticking problems, you're overpaying.
📋 Plant examples:
- Automotive galvanized + sticking → Yes, use Class 1. Better conductivity → less heat needed → less zinc alloying. Tip: adjust up-slope parameter before changing material.
- Automotive caps (e.g. LUVATA) → Class 1 is the standard. Well-tuned machines + low current + low pressure = best results.
- Uncoated steel + wear → Don't use Class 1. Use Class 2 or Class 3 for higher hardness.
✓ Use this instead:
- Class 2 (C18200/C18150) — Higher hardness, more economical, the standard for ~80% of steel applications.
- Class 3 (C17510/C18000) — If you also have UHSS, high pressure, or projection welding on top of wear issues.
⚡ Quick Checklist (30 sec):
Quick rule: Class 1 is for galvanized + sticking + low current. If you don't have that combination, Class 2 is probably the better choice.
Tell me: material, thickness, coating, and welder type, and I'll recommend the exact class.
Request technical recommendation →What We See in Real Applications
In automotive plants working with galvanized materials and medium frequency:
- Automotive caps: Brands like LUVATA use Class 1 in their caps. The key: well-tuned machines running at the lowest current and pressure possible.
- Why does it work? Lower pressure = more heat in the weld zone. Lower current = machine in good order. Class 1 conducts better, so it needs less heat to weld.
- Key parameter - Up-slope: Before changing material, adjust the up-slope. Many times sticking problems are solved with parameters, not material changes.
If you're not sure which material is right for your application, let's review it together before quoting.