S355J0WP weathering steel generally does not require post-weld heat treatment (PWHT) for most applications, but it depends on welding parameters, component thickness, and service conditions. Here are key considerations:
1. When PWHT May Be Omitted
Thin Sections (<16 mm): Preheating (100–150°C) and controlled welding are usually sufficient.
Low-Restraint Joints: Simple fillet welds or non-critical structures.
Atmospheric Exposure: The steel's corrosion-resistant patina forms naturally after welding.
2. When PWHT Is Recommended
Thick Sections (≥25 mm): To relieve residual stresses and prevent cold cracking (especially in low-temperature service).
High-Restraint Joints: Complex geometries or highly constrained components.
Critical Applications: Load-bearing structures subject to dynamic stresses (e.g., railway bridges).
3. PWHT Parameters (If Required)
Temperature: 550–600°C (below Ac1 to avoid microstructure changes).
Holding Time: 1 hour per 25 mm thickness.
Cooling Rate: Slow cooling in air.
4. Alternatives to PWHT
Preheating: 150–200°C for thicker sections.
Low-Hydrogen Electrodes: Use E7018-W or similar to minimize hydrogen-induced cracking.
Peening: Light peening of weld passes to reduce residual stresses.
5. Corrosion Resistance After Welding
The heat-affected zone (HAZ) will develop a patina over time, matching the base metal's weathering performance.
For aesthetics, local surface treatments (e.g., rust accelerators) can synchronize patina formation.
