S355J2 is a widely used European standard (EN 10025-2) high-strength, low-carbon structural steel. It is characterized by its excellent weldability, toughness, and high yield strength.
Key Specifications & Meaning
The designation "S355J2" breaks down as follows:
S: Indicates Structural steel.
355: Represents the minimum Yield Strength of 355 MPa (for thicknesses ≤ 16mm).
J2: Specifies Impact Toughness. It must reach a minimum of 27 Joules during a Charpy V-notch impact test at -20°C.
1.0577: The numeric material number assigned under the EN system.
Mechanical & Physical Properties
Tensile Strength: Typically ranges from 470 to 630 MPa.
Weldability: Highly weldable with a maximum Carbon Equivalent Value (CEV) of approximately 0.47.
Common Delivery Conditions: Often supplied as S355J2+N, where "+N" indicates it has been normalized (rolled or heat-treated to a normalized state) to improve grain structure and toughness.
Global Equivalents
While not identical, S355J2 is often compared to the following international grades:
USA (ASTM): A572 Grade 50 is the closest equivalent.
UK (Former BS): 50D.
Germany (Former DIN): St52-3.
China (GB): Q355D or Q345D.
The mechanical properties of S355J2 structural steel are defined by the European standard EN 10025-2:2004. These are the minimum guaranteed values used for design. Actual test results from mill certificates are typically higher.
Here is a detailed breakdown:
1. Core Mechanical Properties (Thickness-Dependent)
The yield strength, tensile strength, and sometimes elongation vary with the product thickness.
| Nominal Thickness (*t* ) (mm) | Yield Strength, ReH (min.) MPa | Tensile Strength, Rm MPa | Elongation, A (min.) % (Longitudinal Test) |
|---|---|---|---|
| t ≤ 16 | 355 | 470 - 630 | 21 |
| 16 < t ≤ 40 | 345 | 470 - 630 | 21 |
| 40 < t ≤ 63 | 335 | 470 - 630 | 21 |
| 63 < t ≤ 80 | 325 | 470 - 630 | 20 |
| 80 < t ≤ 100 | 315 | 470 - 630 | 20 |
| 100 < t ≤ 150 (For flats) | 295 | 450 - 600 | 19 |
| 150 < t ≤ 250 (For flats) | 285 | 450 - 600 | 19 |
Note: For structural sections (beams, columns), the relevant thickness is the nominal thickness of the flange.
2. Impact Toughness (The Defining "J2" Property)
This is a mandatory and key property that distinguishes S355J2.
Test Standard: Charpy V-notch (ISO 148-1 or EN 10045-1).
Test Temperature: -20°C.
Minimum Impact Energy: 27 Joules.
Rule: The average of three transverse specimen tests must be ≥ 27 J. No single value may be below 70% of this average (i.e., ≥ 19 J).
3. Other Important Mechanical & Physical Properties
| Property | Typical Value / Information | Standard / Note |
|---|---|---|
| Modulus of Elasticity (Young's Modulus) | 210,000 MPa (210 GPa) | Standard design value for steel (EN 1993-1-1). |
| Shear Modulus | 81,000 MPa (81 GPa) | Standard design value for steel. |
| Poisson's Ratio | 0.3 | Standard value for steel. |
| Density | 7,850 kg/m³ | For mass calculations. |
| Bend Test | Must pass without cracking. | The internal bend radius is related to thickness and quality grade (specified in EN 10025-2). |
4. Chemical Composition & Weldability (Indirectly Influences Mechanical Behavior)
Carbon Equivalent (CEV): Has a specified maximum limit (typically ≤ 0.40 - 0.45 depending on thickness). This ensures good weldability, though proper procedures (preheat for thicker sections) are still required.
Key Elements: Controlled limits for Carbon (C), Manganese (Mn), Phosphorus (P), and Sulfur (S) ensure strength, toughness, and soundness.
Summary for Engineers and Designers:
Thickness is Critical: Always use the yield strength value corresponding to the actual thickness of the element in your design.
Toughness is Guaranteed: The -20°C impact toughness is a built-in safety feature for structures in cold climates or subject to dynamic loading.
For Precise Work: The mill test certificate (MTC) is the authoritative source for the actual properties of your specific batch of steel, which will meet or exceed these minimums.
Not a Stainless or Weathering Steel: S355J2 has no inherent corrosion resistance and requires protective coatings (paint, galvanizing) for most exterior applications.
This combination of strength, guaranteed low-temperature toughness, and good weldability makes S355J2 one of the most widely used structural steels for bridges, buildings, and offshore structures in temperate and cold regions.
1. What Is S355J2 Steel?
S355J2 is a European standard structural steel with a minimum yield strength of 355 MPa and guaranteed impact toughness of 27 Joules at -20°C, making it suitable for low-temperature applications.
2. What Is The Difference Between S355J0 And S355J2?
The key difference is the impact test temperature. S355J0 is tested at 0°C, while S355J2 is tested at -20°C, giving S355J2 better low-temperature toughness for colder environments.
3. What Does The 'J2' Mean In S355J2?
The 'J2' indicates the steel's impact toughness grade. 'J' means the minimum Charpy V-notch impact energy is 27 Joules, and '2' signifies the test is conducted at -20°C.
4. What Is The Yield Strength Of S355J2?
The minimum yield strength is 355 MPa for thicknesses up to 16mm, but it decreases for thicker sections (e.g., 345 MPa for 16-40mm, 335 MPa for 40-63mm) as per EN 10025-2.
5. Is S355J2 Equivalent To ASTM A572 Grade 50?
They are generally comparable in strength, but S355J2 has a mandatory toughness requirement at -20°C, while ASTM A572 Gr. 50 requires impact testing only if specified by the purchaser.
6. Can S355J2 Be Welded?
Yes, S355J2 has good weldability. However, proper procedures-such as using suitable low-hydrogen electrodes and applying preheat for thicker sections-must be followed to maintain its mechanical properties.
7. What Is S355J2+N?
The '+N' means the steel is supplied in a normalized or normalized rolled condition. This process refines the grain structure, improving toughness and making the steel more forgiving for welding, especially in thicker sections.
8. What Are The Chemical Properties Of S355J2?
S355J2 has controlled levels of carbon, manganese, silicon, phosphorus, and sulfur. Its maximum Carbon Equivalent (CEV) is also limited, typically around 0.40-0.45, to ensure good weldability.
9. What Is The Tensile Strength Of S355J2?
For common thicknesses (≤ 40mm), the tensile strength ranges from 470 MPa to 630 MPa, as specified in the EN 10025-2 standard.
10. Where Is S355J2 Steel Used?
It's widely used in structural applications exposed to colder climates, such as bridges, building frames, offshore structures, cranes, and heavy equipment where low-temperature toughness is critical.
11. What Is The Density Of S355J2?
Like most structural carbon steels, the density of S355J2 is approximately 7,850 kg/m³ (or 7.85 g/cm³).
12. Is S355J2 Corrosion Resistant?
No, S355J2 is not a corrosion-resistant (weathering) steel. It is a carbon steel that will rust if exposed to the elements unless protected by paint, galvanizing, or other coatings.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
