What is S355N?
S355N is a high-strength, non-alloy structural steel grade standardized under EN 10025-3.
"S" = Structural steel
"355" = Minimum yield strength of 355 MPa
"N" = Supplied in normalized condition, providing good dimensional stability, toughness, and weldability
It is widely used in bridges, building structures, and heavy engineering applications, offering higher strength than S275N while maintaining excellent weldability and low-temperature performance.
1. Mechanical Properties
| Property | S355N Value / Requirement | Standard / Notes |
|---|---|---|
| Yield Strength (ReH) | ≥ 355 MPa | EN 10025-3 |
| Tensile Strength (Rm) | 470–630 MPa | EN 10025-3 |
| Elongation (A5) | ≥ 20% | Typical for structural steel |
| Impact Energy (Charpy V-notch) | ≥ 27 J at 20°C | Standard grade |
| Hardness (HB) | 140–190 HB | Brinell hardness |
| Density | 7.85 g/cm³ | Standard steel value |
| Modulus of Elasticity | 210 GPa | Typical for structural steel |
2. Chemical Composition (Typical % by weight)
| Element | C | Si | Mn | P | S | N |
|---|---|---|---|---|---|---|
| % | 0.22 | ≤0.55 | 1.60 | ≤0.035 | ≤0.035 | ≤0.012 |
Can S355N be used in cold environments?
Key Points About S355N in Cold Conditions
Normalized Condition
The "N" in S355N indicates the steel is normalized, providing uniform mechanical properties, good toughness, and dimensional stability.
Impact Toughness
S355N typically has Charpy V-notch impact energy of ≥27 J at 20°C.
For low-temperature applications, ensure the steel grade or variant meets the required impact energy at the target temperature. For colder environments, S355NL or S355J2 may be preferred, as these have tested impact toughness at –20°C.
Applications in Cold Environments
Building frameworks and roof trusses in cool climates
Bridges or structural steelwork exposed to moderate cold
Heavy engineering where extreme sub-zero performance is not critical
How is S355N tested for quality and compliance?
1. Mechanical Testing
| Test Type | Purpose | Standard / Notes |
|---|---|---|
| Tensile Test | Measures yield strength (ReH), tensile strength (Rm), and elongation (A5) | EN 10025-3 |
| Impact Test (Charpy V-notch) | Checks toughness, particularly normalized steel behavior at specified temperatures | EN 10025-3; S355N typically tested at 20°C |
| Hardness Test | Confirms surface and bulk hardness | Brinell (HB) or Rockwell |
2. Chemical Composition Verification
| Method | Purpose | Notes |
|---|---|---|
| Spectrometry / Optical Emission Spectroscopy (OES) | Measures elements C, Si, Mn, P, S, N | Ensures compliance with EN 10025-3 chemical limits |
| Carbon Equivalent (CE) Calculation | Assesses weldability | CE ≤ 0.45% typical for good weldability |
3. Dimensional and Visual Inspection
Thickness, width, and flatness are checked against order specifications.
Surface defects (cracks, laminations, inclusions) are inspected visually or with non-destructive testing (NDT) such as ultrasonic testing.
GNEE Steel also supplies a variety of high-strength steel plates, such as A514 Grade F, A572 Grade 50, A588 Grade A, S355JR, S690Q, SS400, S690QL, Q345B, Q345E, etc. If you want to know more about other types of steel plates, you can call the consultation hotline at +8615824687445 or send an email to info@gneesteels.com. You are welcome to consult us, and we are very willing to answer your questions.
