1. Pre-Welding Preparation
Material Selection
Use Corten-compatible filler metals:
AWS E7018-G (low-hydrogen, matching strength).
Special weathering electrodes (e.g., Lincoln Outershield 71A81).
MIG/TIG: ER70S-6 (with post-treatment for corrosion resistance).
Joint Design & Cleaning
Remove mill scale & rust (grind to bright metal).
Avoid moisture (prevents hydrogen-induced cracking).
Bevel thick plates (V or U-groove for full penetration).
2. Welding Process & Parameters
| Process | Recommended Method | Key Settings |
|---|---|---|
| SMAW (Stick) | AWS E7018-G, E7015-G | 90–120 A (3.2mm) |
| MIG (GMAW) | ER70S-6 (with 75% Ar + 25% CO₂) | 18–22V, 150–200 IPM |
| TIG (GTAW) | ER70S-2 (for precision work) | DCEN, 80–120 A |
Preheat & Interpass Temperature
Preheat: 100–150°C (212–302°F) for thickness > 12mm.
Interpass Temp: Keep below 250°C (482°F) to avoid brittleness.
Post-Weld Heat Treatment (PWHT)
Stress relief: 595–675°C (1100–1250°F) for critical structures.
Not always required for thin sections (<20mm).
3. Avoiding Common Welding Defects
Hydrogen Cracking (Cold Cracking)
Cause: Moisture, high P content.
Solution: Use low-hydrogen rods, preheat, and store electrodes properly.
Weld Metal Porosity
Cause: Contaminants (oil, rust).
Solution: Clean base metal thoroughly.
Reduced Corrosion Resistance in Weld Zone
Cause: Uneven patina formation.
Solution:
Grind welds smooth to promote uniform rusting.
Use weathering-resistant filler metals (e.g., AWS E7018-W).
4. Post-Welding Treatment
Rust Patina Development
Natural weathering: Let Corten steel rust naturally (takes 6–24 months).
Accelerated patina: Use water spray + drying cycles to speed up oxidation.
Painting (If Required)
For high-corrosion zones (e.g., marine environments), apply breathable coatings (e.g., clear acrylic).
Avoid standard paints (traps moisture, causes peeling).
5. Comparison: Corten vs. Carbon Steel Welding
| Factor | Corten Steel | Carbon Steel |
|---|---|---|
| Preheat Needed? | Yes (if >12mm thick) | Rarely (unless thick) |
| Filler Metal | Must match weathering properties | Standard E7018 OK |
| Corrosion Risk | Weld zone may rust differently | Uniform corrosion |
Conclusion
Use low-hydroden electrodes & preheat to avoid cracking.
Clean joints thoroughly to prevent porosity.
Allow natural rusting or use weathering-compatible coatings.
