The low‑temperature impact toughness of S355J0WP can be further improved, by adjusting composition, rolling process, and heat treatment-without losing its weathering performance.
1. Alloy adjustment (most effective)
Reduce phosphorus (P)P seriously causes low‑temperature brittleness; lowering P greatly raises impact energy.
Add a small amount of nickel (Ni)Ni strongly lowers ductile‑brittle transition temperature and offsets P embrittlement.
Strictly limit sulfur (S)Reduces elongated MnS inclusions that start cracks at low temperature.
Micro‑alloy with Nb / Ti / AlRefines grains, which is the most direct way to boost toughness.
2. Optimize rolling process
Controlled rolling + accelerated coolingProduces finer ferrite grains and uniform microstructure.
Lower finishing rolling temperatureAvoids coarse grains, improves low‑energy impact resistance.
3. Heat treatment
NormalizingEliminates segregation, refines structure, significantly increases Charpy impact values at low temperatures.
4. Thickness control
Thinner plates naturally have better toughness; heavy thickness reduces it, so limiting plate size helps improvement.
Trade‑off note
Higher toughness usually means:
Slightly higher cost
A bit slower rust patina formation (due to lower P)
