S355N and S355NL are European standard (EN 10025-3) high-strength, low-alloy structural steels with the same minimum yield strength (355 MPa) but differ in their guaranteed low-temperature impact toughness: S355N is tested at -20°C, while S355NL is tested at a tougher -50°C, making S355NL superior for cold climates (arctic, offshore) and S355N suitable for moderate conditions (bridges, general construction). Both are normalized, weldable, fine-grain steels, with the 'NL' designation signifying excellent sub-zero performance.
S355NL (EN 10025-3)
S355NL is a fine-grain structural steel, normalized or normalized rolled, with:
S: Structural steel.
355: Minimum yield strength of 355 MPa (≤16 mm).
NL: Normalized, with impact toughness tested at -50°C for low-temperature applications.
Its superior toughness suits cold climates like arctic offshore platforms.
S355N (EN 10025-3)
S355N is also a fine-grain structural steel, normalized or normalized rolled, with:
S: Structural steel.
355: Minimum yield strength of 355 MPa (≤16 mm).
N: Normalized, with impact toughness tested at -20°C.
S355N is designed for moderate-temperature environments, such as general construction in milder climates.
Chemical Composition Comparison
|
Element |
S355NL (Ladle, max %) |
S355N (Ladle, max %) |
|---|---|---|
|
Carbon (C) |
0.18 |
0.20 |
|
Silicon (Si) |
0.50 |
0.50 |
|
Manganese (Mn) |
0.90-1.65 |
0.90-1.65 |
|
Phosphorus (P) |
0.025 |
0.030 |
|
Sulfur (S) |
0.015 |
0.025 |
|
Nitrogen (N) |
0.015 |
0.015 |
|
Aluminum (Al) |
0.02 (min, total) |
0.02 (min, total) |
|
Niobium (Nb) |
0.05 |
0.05 |
|
Vanadium (V) |
0.12 |
0.12 |
|
Titanium (Ti) |
0.05 |
0.05 |
|
Chromium (Cr) |
0.30 |
0.30 |
|
Nickel (Ni) |
0.30 |
0.50 |
|
Molybdenum (Mo) |
0.10 |
0.10 |
|
Copper (Cu) |
0.55 |
0.55 |
Mechanical Properties Comparison
|
Property |
S355NL (EN 10025-3) |
S355N (EN 10025-3) |
|---|---|---|
|
Yield Strength (min, MPa) |
||
|
≤16 mm |
355 |
355 |
|
16 |
345 |
345 |
|
40 |
335 |
335 |
|
Tensile Strength (MPa) |
470-630 |
470-630 |
|
Elongation (min, %) |
22 (≤40mm) |
22 (≤40mm) |
|
Impact Energy (min, J) |
27 @ -50°C (longitudinal) |
27 @ -20°C (longitudinal) |
Welding and Heat Treatment
S355NL: CEV ≤0.43% ensures excellent weldability with GMAW or SAW (EN 1011-2). Preheating (100-150°C) for >20 mm; PWHT (550-650°C) optional. Consumables: ER70S-6 (GMAW), EM12K flux with EH14 wire (SAW).
S355N: Identical CEV (≤0.43%) and welding properties, though slightly higher sulfur and phosphorus may require marginally more care during welding.
The S355N S355NL welding difference is negligible, with S355NL's lower impurities offering a slight edge.
Applications
S355NL:
Offshore platforms in cold marine environments.
Wind towers in sub-zero climates.
Bridges and cranes in arctic regions.
Its -50°C toughness ensures reliability in extreme cold. See EN 10025-3 S355NL normalized structural steel plate.
S355N:
Building frameworks in temperate climates.
Bridges and machinery in moderate conditions.
General structural applications where cold toughness is less critical.
The S355NL vs S355Nlo application difference highlights S355NL's suitability for colder environments and S355N's cost-effectiveness for milder ones.
Equivalent Grades
S355NL: ASTM A633 Grade E, Q345E (China), StE 355 (DIN).
S355N: ASTM A572 Grade 60, Q345D (China), StE 355 (DIN).
