The welding of A423 weathering steel requires specific precautions to maintain its corrosion resistance and mechanical properties. Here are the key special requirements:
1. Welding Process Selection
Preferred Methods:
SMAW (Shielded Metal Arc Welding): Use low-hydrogen electrodes (E7018 or equivalent).
GMAW (MIG/MAG): ER70S-6 or weathering steel-matched wires (e.g., Cu-bearing fillers).
FCAW (Flux-Cored Arc Welding): E71T-1 or similar low-hydrogen flux-cored wires.
2. Preheating Requirements
Thickness > 20mm: Preheat to 100–150°C (212–302°F) to avoid hydrogen cracking.
Low Ambient Temp (<5°C/41°F): Mandatory preheat, even for thinner sections.
3. Interpass Temperature Control
Max 250°C (482°F) to prevent HAZ (Heat-Affected Zone) softening.
4. Post-Weld Heat Treatment (PWHT)
For Thick Sections (>25mm): Stress relief at 550–600°C (1022–1112°F) for 1 hour per 25mm thickness.
Not Typically Needed for thin sections (<25mm) or non-critical applications.
5. Filler Metal Selection
Match Base Metal Corrosion Resistance:
Use weathering-resistant fillers (e.g., AWS A5.29 E80C-Ni1 for enhanced corrosion protection).
Avoid standard carbon steel fillers (they'll corrode faster than the base metal).
6. Post-Weld Cleaning & Surface Treatment
Remove Slag/Spatter: Prevents localized corrosion.
Allow Natural Weathering: No painting needed; the weld will develop a patina matching the base metal.
For Coastal/High-Salt Areas: Apply weathering-resistant primer on welds if patina formation is compromised.
7. Critical Avoidances
No Cellulosic Electrodes (e.g., E6010)-high hydrogen risk.
No Rapid Cooling-increases cracking susceptibility.
