EN 10025-3 S420N High-strength Low-alloy (HSLA) Steel Plate

EN 10025-3 S420N is a hot-rolled weldable fine-grain structural steel that is normalized or normalized-rolled under the European standard. It offers good weldability, formability, and impact resistance, along with high strength and improved atmospheric corrosion resistance.

Standard and Grade Designation

Standard: EN 10025-3 (Hot-rolled products of structural steels – Part 3: Technical delivery conditions for normalized/normalized rolled weldable fine grain structural steels)

Grade: S420N

"S" stands for Structural steel

"420" indicates the minimum yield strength (420 MPa)

"N" means the steel is supplied in the normalized or normalized rolled condition

Key Features of S420N Steel Plate：

1. High Strength:Minimum yield strength (ReH) = 420 MPa, Tensile strength (Rm) = 520–680 MPa

2. Fine Grain Structure:Achieved through normalizing/normalized rolling and microalloying (Nb, V, Ti).

3. Good Toughness at Low Temperatures:Charpy V-notch impact ≥ 40 J at -20°C (higher than standard carbon steels).

4. Weldability:Low carbon equivalent (CEV ~0.40–0.45) allows welding without preheating in most cases (thicker plates may require controlled procedures).

5. Corrosion Resistance:Better than mild steel due to alloying elements, but not equivalent to weathering steels like S355J2W.

✔ Heavy construction (bridges, cranes, high-rise buildings)

✔ Offshore structures (platforms, shipbuilding)

✔ Pressure vessels & storage tanks

✔ Mining & earthmoving equipment

✔ Industrial machinery requiring high strength-to-weight ratio

Processing Condition:

Normalized/Normalized rolled (improves toughness and weldability).

Welding & Fabrication:

Weldable with common methods (SMAW, GMAW, SAW)

Preheating may be required for thick sections to avoid cracking.

Similar Grades:

S420NL (improved low-temperature toughness, tested at -50°C)

S355N (lower strength but better weldability)

ASTM A572 Gr. 60 (similar yield strength, but different standard)

Conclusion:

EN 10025-3 S420N is a high-strength, weldable HSLA steel plate ideal for structural applications requiring toughness and durability. Its normalized condition ensures uniform properties, making it suitable for dynamic loads and low-temperature environments.