S355JR is a high-strength, low-carbon structural steel grade (EN 10025) known for its good weldability and toughness, with "S" for structural, "355" for its minimum 355 MPa yield strength, and "JR" indicating it passed a Charpy impact test at room temperature (20°C) with 27 Joules of energy absorption. It's used widely in construction, bridges, heavy machinery, and shipbuilding for load-bearing components requiring strength and durability.
Key Characteristics
Strength: High tensile and yield strength (≥355 MPa).
Weldability: Excellent, due to low carbon content, making it easy to weld.
Toughness: Good impact resistance, guaranteed by the "JR" test.
Classification: Non-alloy, hot-rolled structural steel.
Breakdown of the Name
S: Structural Steel.
355: Minimum Yield Strength in MPa (for thicknesses ≤16mm).
JR: Result of the Charpy impact test (27 Joules at +20°C).
Is S355JR equivalent to ASTM A572 Grade 50?
No, S355JR is not a direct equivalent to ASTM A572 Grade 50, although they are often compared due to their similar strength levels. Key differences exist in standardization, mechanical property details, and testing requirements.
Direct Comparison:
| Property | S355JR (EN 10025-2) | ASTM A572 Grade 50 (USA) |
|---|---|---|
| Minimum Yield Strength | 355 MPa (for thickness ≤ 16 mm) | 345 MPa (50 ksi) |
| Tensile Strength | 470 – 630 MPa | 450 – 550 MPa (min 450 MPa) |
| Impact Toughness | Mandatory: 27 J at +20°C | Not required by default (only if supplementary Charpy requirements are specified) |
| Governing Standard | European (EN) | American (ASTM) |
| Material Type | Non-alloy structural steel | High-strength low-alloy (HSLA) steel, often micro-alloyed with Nb/V |
| Typical Thickness Effect | Yield strength decreases for thicker sections per EN table. | Yield strength remains 345 MPa for all thicknesses up to 100 mm (plates). |
| Primary Use Case | General construction in temperate climates where room-temperature toughness is sufficient. | High-strength structural applications where weight reduction is prioritized, with optional toughness for cold conditions. |
Why They Are Not Direct Equivalents:
Strength & Thickness Rules:
S355JR starts at a slightly higher yield strength (355 vs. 345 MPa) for thin sections but reduces with thickness.
A572 Grade 50 maintains constant yield strength (345 MPa) across thicknesses up to 100 mm for plates, making it simpler for design.
Toughness Requirements:
S355JR includes mandatory Charpy impact testing at +20°C, ensuring basic toughness at room temperature.
A572 Grade 50 has no mandatory impact properties unless supplementary requirements are specified (e.g., for bridges or cold service).
Material Composition:
S355JR is a non-alloy steel with controlled carbon and manganese.
A572 Grade 50 is an HSLA steel, often micro-alloyed for strength and may have different weldability considerations.
Regional Standards & Codes:
The grades belong to different regulatory systems (EN vs. ASTM) and are specified under respective regional codes (Eurocodes vs. AISC/ASCE). Substitution requires code approval and potential recalculation.
1. What is S355JR steel?
S355JR is a non-alloy structural steel grade per EN 10025-2, with a minimum yield strength of 355 MPa and guaranteed impact toughness at room temperature (+20°C).
2. What is the yield strength of S355JR?
The minimum yield strength of S355JR is 355 MPa for nominal thickness up to 16 mm, decreasing for thicker sections as per EN 10025-2.
3. What does the 'JR' in S355JR mean?
The 'JR' indicates Charpy V-notch impact testing at +20°C, ensuring a minimum absorbed energy of 27 Joules for basic toughness.
4. Is S355JR equivalent to ASTM A572 Grade 50?
Not exactly. While both have similar yield strength (~345 MPa for A572 Gr 50 vs. 355 MPa for S355JR), they belong to different standards and have different chemical and testing requirements.
5. What are the main applications of S355JR?
It is widely used in heavy construction, bridges, industrial buildings, cranes, machinery frames, and offshore structures requiring higher strength than S275 grades.
6. What is the difference between S355JR and S355J2?
S355JR is impact tested at +20°C, while S355J2 is tested at -20°C, making J2 suitable for cold climate applications.
7. Can S355JR be welded?
Yes, S355JR has good weldability using common methods, though preheating may be required for thicker sections or strict service conditions.
8. What is the chemical composition of S355JR?
Typical composition includes max 0.24% Carbon, max 1.60% Manganese, and controlled phosphorus/sulfur (e.g., P ≤ 0.035%, S ≤ 0.035%).
9. Is S355JR corrosion resistant?
No, it is not corrosion-resistant. Protective coatings such as painting or galvanizing are necessary for outdoor or corrosive environments.
10. What is the difference between S355JR and S275JR?
The main difference is strength: S355JR has a higher minimum yield strength (355 MPa vs. 275 MPa), allowing lighter or stronger designs.
11. What are the mechanical properties of S355JR?
Key properties include yield strength ≥355 MPa (t≤16mm), tensile strength 470-630 MPa, and minimum elongation of 20-22% depending on thickness.
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.
