S355J0WP (EN 10025‑5) has excellent weldability-low carbon, fine‑grained, and compatible with all common processes; welds match base‑metal strength, and preheat is rarely needed.
Core Welding Performance
1. Chemical Basis for Good Weldability
Low carbon (≤0.22%) + controlled P/S (<0.030%) → low hardenability, low cold‑crack risk.
Microalloyed (Nb, V, Ti) → fine grains, good toughness in HAZ.
Weathering elements (Cu, Cr, Ni, P) do not harm weldability; they just require matching filler for corrosion resistance.
2. Weldability Rating
Excellent for most structural applications; comparable to S355JR/J0 carbon steelArcelorMittal.
Low cold‑crack sensitivity; no mandatory preheat for typical thicknesses.
3. Applicable Welding Processes
All standard methods work well:
SMAW (E7018‑type weathering electrodes)
GMAW/MIG (solid wire, metal‑cored)
FCAW (flux‑cored)
SAW (submerged arc)
GTAW/TIG (thin sections)
4. Preheat & Interpass Temperature
Normally no preheat for thickness ≤20 mm at ambient >0°C.
Preheat only if:
Ambient <–5°C → preheat to ~100–150°C.
Thickness >30 mm or high restraint → 80–120°C.
Interpass ≤250°C to avoid HAZ grain coarsening.
5. Filler Metal Selection
For unpainted weathering service: Use weathering‑grade filler (e.g., E8018‑W, ER80S‑W) to match base‑metal corrosion resistance.
For painted/non‑exposed: Standard S355‑grade filler (E7018, ER70S‑6) is acceptable.
6. Weld & HAZ Properties
Weld strength: Matches base metal (≥355 MPa yield).
HAZ toughness: Good; J0 guarantees ≥27 J at 0°C in HAZ.
No significant loss of weathering resistance if using matching filler; patina forms across weldsArcelorMittal.
7. Key Precautions
Clean thoroughly: Remove mill scale, rust, oil, and paint within 10–20 mm of the joint.
Avoid excessive heat input: Prevents HAZ grain growth and toughness loss.
Post‑weld treatment: Not required for most cases; stress relief only for highly restrained thick sections.
Corrosion in crevices: Design to avoid water trapping; welds should be smooth to prevent moisture retention.
