To maintain the corrosion resistance and mechanical properties of Q460NH, follow these critical welding guidelines:
1. Pre-Welding Preparation
Material Cleaning:
Remove mill scale, rust, and contaminants from joint areas (use grinding or brushing).
Avoid oil/grease residues to prevent porosity.
Preheat:
100–150°C for thicknesses >20mm to avoid hydrogen-induced cracking (HIC).
Interpass temperature: ≤250°C.
2. Filler Metal Selection
Matching composition: Use weathering steel-compatible electrodes:
AWS E8018-W2 (for SMAW) or ER80S-G (for GMAW).
Ensure filler metals contain Cu, Cr, Ni to match Q460NH's patina-forming ability.
Avoid standard carbon steel fillers (e.g., E7018), which compromise corrosion resistance.
3. Welding Techniques
Low Heat Input:
Limit heat input to 15–25 kJ/cm to minimize HAZ brittleness.
Use short-arc or pulsed MIG for better control.
Joint Design:
Avoid sharp notches; use grinded weld toes to reduce stress concentrations.
Full penetration welds preferred for load-bearing joints.
4. Post-Weld Treatment
Slag Removal: Clean thoroughly to prevent crevice corrosion.
Grinding: Smooth weld seams to match base metal contour.
Patina Restoration:
Accelerate rust formation on welds via water spraying or weathering accelerants.
In aggressive environments, apply weathering steel primers (e.g., Tectyl 506) on welds.
5. Quality Control & Standards
Non-Destructive Testing (NDT):
UT/RT for critical joints (per ISO 17635).
Dye penetrant testing for surface cracks.
Certification: Welds should meet ISO 9606-1 or AWS D1.1 standards.
Environmental Considerations
Coastal/Industrial Areas:
Increase inspection frequency (e.g., annual UT for weld zones).
Use sealants at weld overlaps to block chloride ingress.
