Key Considerations for Welding S355K2G2W Weathering Steel Plates

Welding S355K2G2W isn't complicated—but treat it like ordinary mild steel, and you might run into trouble. This grade combines strength, low-temperature toughness, and corrosion resistance. Your weld needs to preserve all three.

Choose the right filler. Match the consumable to the base material's weathering characteristics. For most applications, use a low-hydrogen electrode or solid wire with similar copper, chromium, and nickel content—think filler grades like AWS A5.18 ER70S-6 for GMAW (though verify corrosion matching) or basic-coated electrodes like AWS A5.5 E7018-1 for SMAW. Avoid high-hydrogen rods at all costs. They invite cold cracking.

Control heat input. Keep interpass temperature below 250°C (ideally 150–200°C). Too much heat slows cooling, which can coarsen grain structure in the heat-affected zone (HAZ) and reduce impact toughness. Use multiple small passes rather than one large, hot pass.

Preheat when needed. For plates under 12mm at room temperature, preheat isn't mandatory. But when thickness exceeds 15mm, shop temperatures drop below 5°C, or moisture is present, preheat to 100–150°C. This drives off hydrogen and reduces cooling rate.

Post-weld care. Let the joint cool in still air. No quench—that invites cracking. After welding, don't grind the weld reinforcement flat unless absolutely necessary. The weathering patina forms best on slightly rough surfaces. And never paint over fresh welds unless the design requires it.

Don't forget edge prep. Clean mill scale, oil, and rust from the weld zone. But don't over-grind the surrounding base metal—that patina chemistry needs to stay intact just outside the joint.