S355J2+N is a low-alloy high-strength structural steel according to the European standard (EN 10025-3). S355N+2 steel plate mainly follows the European standard: EN 10025-3: Hot rolled structural steel products – Part 3: Technical delivery conditions for weldable fine grain structural steel by normalizing/normalizing rolling.
S: Structural Steel
355: indicates a minimum yield strength of 355 megapascals (MPa). This is one of the most critical performance indicators of the steel, which means that it can withstand a stress of at least 355 MPa without permanent deformation when subjected to force.
N: Indicates the normal ignition state. This is the critical heat treatment state.
Normalization is the process of heating a steel plate to the austenitizing temperature (usually above 900 ° C), holding it for a period of time, and then cooling it in air.
The benefits of normalizing:
Refine grain size and improve microstructure.
Improve the toughness and plasticity of steel.
Eliminate internal stresses caused by rolling or welding.
Make the performance of steel more uniform and consistent.
+2: Indicate the impact toughness requirements at low temperatures of -20 ° C. In the European standard EN 10025-3, this numerical code specifies the testing temperature for impact energy:+1 represents that the impact test is conducted at -20 ° C.
+The impact test is conducted at -20 ° C and requires a more stringent average impact energy value (usually not less than 40 or 47 joules, depending on the thickness). +The impact test is conducted at -30 ° C.
+The impact test is conducted at -40 ° C. +The impact test is conducted at -50 ° C.
Therefore, S355N+2 ensures that the steel plate still has good resistance to brittle fracture in low temperature environments of minus 20 degrees, which is crucial for structures used in cold regions.
Chemical composition and mechanical properties (according to EN 10025-3)
The following is a rough range, with specific values depending on the thickness of the product.
Chemical composition (maximum%):
Element C (carbon) Si (silicon) Mn (manganese) P (phosphorus) S (sulfur)
Content ≤ 0.20 ≤ 0.55 ≤ 1.60 ≤ 0.035 ≤ 0.035
Note: It may also contain trace amounts of alloying elements such as Nb, V, Ti, etc. to refine the grain size.
Mechanical properties (example of thickness ≤ 16 mm):
Performance yield strength ReH (MPa) tensile strength Rm (MPa) elongation at break A (%) impact energy (KV), -20 ° C
Requirement: ≥ 355 470-630 ≥ 22 ≥ 40 J (average)
Application field
Due to its excellent comprehensive performance, S355N+2 steel plate is widely used in structures with high requirements for strength and toughness:
Bridge construction: especially for bridges located in cold regions or subjected to dynamic loads.
Heavy duty building steel structures: such as high-rise buildings, industrial plants, sports venues, etc.
Port machinery and lifting equipment, such as tower cranes, gantry cranes, etc.
Mining machinery:
Pressure vessels and pipelines (under specific standards and certifications).
Offshore platform modules (may require higher levels of resilience, such as+3 or+4).
Comparison with other similar grades
S355J2: S355J2 is also a common S355 grade steel, but it is “non alloy” and its performance is guaranteed through controlled rolling. S355N usually has more uniform and stable performance through normalizing treatment, especially for thicker sheets.
Vs. S355NL: S355NL is the “low-temperature” version of S355N, which has a lower impact testing temperature (-50 ° C) and stricter control over impurities such as phosphorus and sulfur, resulting in better low-temperature toughness.
Post time: Oct-11-2025