S355N is a high-strength, low-alloy structural steel under EN 10025-3:2019, with a minimum yield strength of 355 MPa for plates up to 16 mm thick. Its designation, also known as material number 1.0545, breaks down as:
S: Structural steel.
355: Minimum yield strength in MPa.
N: Normalized or normalized rolled, tested for impact toughness at -20°C.
The normalization process refines the grain structure, enhancing S355N material properties for strength, toughness, and weldability, making it ideal for moderate climates. Compared to en 10025 3 s460n normalized structural steel plate, S355N offers lower strength (355 MPa vs 460 MPa) but is more cost-effective for general structural applications.
Chemical Composition Supporting S355N Material Properties
Element | Ladle Analysis (max %) | Product Analysis (max %) | Role in S355N Material Properties |
|---|---|---|---|
Carbon (C) | 0.20 | 0.22 | Enhances strength, kept low for weldability and toughness. |
Silicon (Si) | 0.50 | 0.55 | Aids deoxidation, improves strength and microstructure. |
Manganese (Mn) | 0.90-1.65 | 0.85-1.75 | Boosts strength and toughness for load-bearing capacity. |
Phosphorus (P) | 0.030 | 0.035 | Minimized to reduce inclusions, enhancing toughness. |
Sulfur (S) | 0.025 | 0.030 | Low levels prevent inclusions, improving weld quality. |
Nitrogen (N) | 0.025 | 0.027 | Controlled to avoid brittleness, supporting toughness. |
Aluminum (Al) | 0.020 (min, total) | 0.015 (min, total) | Refines grains for toughness, improves microstructure. |
Niobium (Nb) | 0.05 | 0.06 | Promotes fine-grain structure, enhancing strength and toughness. |
Vanadium (V) | 0.10 | 0.12 | Increases strength via precipitation hardening. |
Titanium (Ti) | 0.05 | 0.06 | Refines grains, supports toughness. |
Chromium (Cr) | 0.30 | 0.35 | Enhances corrosion resistance and strength. |
Nickel (Ni) | 0.50 | 0.55 | Improves toughness in moderate climates. |
Molybdenum (Mo) | 0.10 | 0.12 | Boosts strength and creep resistance. |
Copper (Cu) | 0.55 | 0.60 | Enhances corrosion resistance and strength. |
Carbon Equivalent (CEV): Capped at 0.43% for plates up to 63 mm, calculated as CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15, ensuring excellent weldability, similar to en 10025 3 s420n normalized structural steel plate.
Mechanical Properties of S355N Steel
Thickness (mm) | Yield Strength (min, MPa) | Tensile Strength (MPa) | Elongation (min, %) | Impact Energy (min, J @ -20°C) |
|---|---|---|---|---|
≤16 | 355 | 470-630 | 22 | 27 |
16<t≤40 | 345 | 470-630 | 22 | 27 |
40<t≤63 | 335 | 470-630 | 22 | 27 |
63<t≤80 | 325 | 470-630 | 22 | 27 |
80<t≤100 | 315 | 470-630 | 22 | 27 |
100<t≤150 | 295 | 450-610 | 22 | 27 |
150<t≤200 | 285 | 450-610 | 22 | 27 |
Yield Strength: Starts at 355 MPa for thin plates, ideal for moderate-load structures like bridges.
Tensile Strength: 470-630 MPa ensures durability under high tensile forces.
Elongation: ≥22% supports complex structural designs, offering better ductility than higher-strength grades like S460N.
Impact Toughness: ≥27 J at -20°C ensures reliability in moderate climates, comparable to en 10025 3 s355nl normalized structural steel plate.
Hardness: Typically 150-190 HB (Brinell), balancing machinability and durability.
Density: 7.85 g/cm³ (7850 kg/m³), standard for structural steels, aiding weight calculations.
These properties make S355N versatile for structural applications requiring a balance of strength and formability.
Welding and Heat Treatment
S355N material properties include excellent weldability with a low CEV (≤0.43%):
Welding: Compatible with GMAW and SAW per EN 1011-2. Preheating typically not required for plates <20 mm; optional for thicker plates (100-150°C); post-weld heat treatment (PWHT) at 550-650°C optional.
Consumables: ER70S-6 for GMAW, EM12K flux with EH14 wire for SAW.
Weld Quality: Matches en 10025 3 s355n normalized structural steel plate for reliable, high-strength joints.
Applications Leveraging
Bridges: Load-bearing components like girders and beams in moderate climates, leveraging 355 MPa yield strength.
Cranes: Structural parts for lifting equipment, benefiting from 470-630 MPa tensile strength.
Building Frameworks: Columns and trusses in temperate regions, supported by ≥22% elongation for complex designs.
Heavy Machinery: Durable components like chassis in industrial equipment, relying on -20°C toughness.
For colder climates requiring -50°C toughness, consider en 10025 3 s355nl normalized structural steel plate.
