1. Q355NH has good weldability and is fully weldable
2. Recommended welding methods for Q355NH plates (matching thickness)
Thin plates (3–12 mm): TIG/MIG welding (low heat input), spot welding, laser welding - ideal for landscape products (flower boxes, sculptures) and building cladding, with neat weld seams and minimal post-weld deformation.
Medium/heavy plates (14–100 mm): MAG welding, submerged arc welding - suitable for light/heavy structural components (steel frames, bridge accessories), providing high joint strength and stable welding effect for load-bearing parts.
On-site field welding: Manual metal arc welding (MMA) - easy to operate with portable equipment, matching on-site installation needs of large components.
3. Key welding precautions (to maintain performance)
Match weathering welding materials: Use low-alloy weathering steel welding wires/electrodes (matching Cu/Cr/Ni composition, e.g., E5015-G, ER50-G) - avoids ordinary welding materials leading to poor patina formation and accelerated corrosion in the weld zone.
Control heat input: Adopt low heat input and fast welding speed; for plates ≥30 mm, preheat to 80–150℃ before welding to prevent cold cracking and reduce weld zone softening.
Post-weld simple treatment: Grind weld seams to remove spatter and burrs; passivate/cote thin transparent sealer on cutting/welding edges - prevents temporary micro-corrosion at unprocessed edges and ensures uniform patina formation across the whole plate.
Avoid excessive post-weld heat treatment: High-temperature annealing is unnecessary; it will eliminate the steel's inherent structural properties, and only stress relief treatment (≤200℃) is needed for heavy plates to reduce welding residual stress.
4. Weld zone performance retention
Mechanical strength: Weld joint yield/tensile strength is consistent with the base material, meeting the load-bearing requirements of structural and non-structural applications.
Corrosion resistance: The weld zone forms the same dense protective patina as the base material in outdoor environments, with no obvious difference in rust color and corrosion rate, ensuring the whole component's long-term anti-corrosion effect.
