What is S355ML?
S355ML is a thermo-mechanically rolled, fine-grain structural steel specified in EN 10025-4.
It provides:
Minimum yield strength: 355 MPa
Enhanced low-temperature toughness
Excellent weldability and formability
The "ML" designation means:
M = Thermo-mechanically rolled
L = Guaranteed low-temperature impact toughness (–50°C)
S355ML is commonly used in bridges, offshore structures, cranes, wind towers, and cold-climate engineering.
1. Chemical Composition (Typical Values, %)
| Element | C (max) | Si | Mn | P (max) | S (max) | Nb | V | Ti |
|---|---|---|---|---|---|---|---|---|
| S355ML | 0.22 | ≤ 0.55 | 1.00–1.60 | 0.025 | 0.020 | ≤ 0.06 | ≤ 0.12 | ≤ 0.03 |
2. Mechanical Properties
| Property | Value |
|---|---|
| Yield Strength (≤16 mm) | 355 MPa |
| Yield Strength (40–100 mm) | 345–355 MPa |
| Tensile Strength | 470–630 MPa |
| Elongation (A5) | ≥ 22% |
| Charpy Impact | ≥ 27 J at –50°C |
| Density | 7.85 g/cm³ |
What is S355NL?
S355NL is a normalized/normalized-rolled, fine-grain high-strength structural steel specified in EN 10025-3.
It provides:
Minimum yield strength: 355 MPa
Guaranteed low-temperature impact toughness at –50°C
Good weldability and formability
The "NL" designation means:
N = Normalized or normalized-rolled
L = Guaranteed low-temperature toughness
S355NL is typically used in offshore structures, bridges, cranes, and cold-climate engineering projects.
1. Chemical Composition (Typical Values, %)
| Element | C (max) | Si | Mn | P (max) | S (max) | Nb | V | Ti |
|---|---|---|---|---|---|---|---|---|
| S355NL | 0.22 | ≤ 0.55 | 1.00–1.60 | 0.025 | 0.020 | ≤ 0.06 | ≤ 0.12 | ≤ 0.03 |
2. Mechanical Properties
| Property | Value |
|---|---|
| Yield Strength (≤16 mm) | 355 MPa |
| Yield Strength (40–100 mm) | 345–355 MPa |
| Tensile Strength | 470–630 MPa |
| Elongation (A5) | ≥ 22% |
| Charpy Impact | ≥ 27 J at –50°C |
| Density | 7.85 g/cm³ |
What is the difference between S355ML and S355NL?
Both S355ML and S355NL are high-strength, fine-grain structural steels with a minimum yield strength of 355 MPa and low-temperature toughness guaranteed at –50°C, but they differ in rolling method, which affects toughness, flatness, and fabrication properties.
| Feature | S355ML | S355NL |
|---|---|---|
| Rolling Method | Thermo-mechanically rolled (TMCP) | Normalized / normalized-rolled |
| Impact Toughness | Guaranteed at –50°C | Guaranteed at –50°C |
| Plate Flatness & Thickness Control | Better flatness and dimensional control | Slightly less flatness for thick plates |
| Weldability | Excellent, consistent due to TMCP | Excellent, standard for normalized steels |
| Applications | Bridges, offshore, cranes, cold-climate structures | Bridges, offshore, cranes, cold-climate structures |
| Mechanical Consistency | More uniform due to TMCP process | Standard normalized properties |
Summary
S355ML: Thermo-mechanically rolled, better flatness, and more uniform mechanical properties, ideal for critical structural applications.
S355NL: Normalized/normalized-rolled, still strong and tough, suitable for low-temperature and offshore structures, slightly less dimensional uniformity.
Both are excellent for bridges, offshore platforms, cranes, and cold-region engineering, with the choice depending on fabrication preferences and thickness requirements.
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.
