Description
S355JR Steel is a structural grade steel widely used in construction and engineering projects. It is part of the EN 10025-2 European standard and is commonly referred to as a “structural steel” because of its broad applications in structural components such as beams, columns, and frameworks. The “S” stands for structural steel, while “355” refers to the minimum yield strength of 355 MPa. The “JR” designation indicates that the steel has passed a Charpy V-notch impact test at 27J at room temperature (+20°C), making it suitable for general structural applications.
Properties of S355JR Steel:
- Carbon Content: 0.22% (max)
- Manganese Content: 1.60% (max)
- Tensile Strength: 470–630 MPa (68,000–91,000 psi)
- Yield Strength: 355 MPa (51,500 psi)
- Impact Toughness: 27J at +20°C (JR condition)
- Elongation: ~20% (longitudinal)
- Hardness: 146-187 HB (Brinell)
- Weldability: Excellent, with no need for preheating in most applications
- Corrosion Resistance: Moderate (requires coatings for use in corrosive environments)
- Machinability: Good for structural steel
- Formability: Good (can be formed into various shapes and profiles)
S355JR is known for its high tensile and yield strength, excellent weldability, and good toughness at room temperature. It is ideal for use in structural applications where moderate strength and impact resistance are required but without the need for low-temperature toughness.
Grades of S355JR Steel:
S355JR is available in different forms, each designed to meet specific requirements, including surface finish, dimensional accuracy, and strength.
| Grade | Description |
|---|---|
| S355JR (Hot-Rolled) | Produced through hot rolling, providing good strength and toughness but with a rougher surface finish. Commonly used in large structural components like beams and girders. |
| S355JR (Cold-Rolled) | Cold-rolled version provides a smoother surface finish and higher precision, making it ideal for applications requiring tight dimensional tolerances and aesthetic quality. |
| S355JR+AR | The “+AR” indicates “as-rolled” condition, which means that the steel has not undergone additional heat treatment processes, such as normalizing. It’s commonly used for general structural purposes. |
Applications of S355JR Steel:
| Industry/Field | Applications |
|---|---|
| Construction | Used in structural components like beams, columns, and trusses for buildings, bridges, and other infrastructure due to its high strength and good weldability. |
| Engineering | Applied in frameworks and supports for heavy equipment, as well as in plant construction and industrial machinery due to its excellent strength-to-weight ratio. |
| Automotive | Employed in truck frames, chassis, and other structural components that require good strength and resistance to dynamic loads. |
| Railways | Used in railway track components, underframes, and structural parts of trains, where high strength and durability are essential. |
| Shipbuilding | Suitable for constructing decks, hulls, and structural components of ships and offshore platforms, especially for general structural use. |
| Wind Energy | Utilized in the construction of wind turbine towers and other components where strength and resistance to fatigue are important. |
| Agricultural Equipment | Ideal for manufacturing frames, supports, and heavy-duty equipment for agriculture, where durability and strength are key. |
| Cranes and Lifting | Used in cranes, hoists, and other lifting equipment, as it provides the necessary strength for load-bearing and dynamic applications. |
Advantages of S355JR Steel:
- High Yield Strength: S355JR offers a yield strength of 355 MPa, making it suitable for load-bearing structures.
- Good Impact Toughness: Its JR designation ensures it has been impact-tested at room temperature, making it resistant to sudden impacts or dynamic loads.
- Excellent Weldability: S355JR can be easily welded without the need for preheating, making it ideal for fabrication and assembly.
- Good Formability: The steel can be easily shaped and formed into various profiles, making it versatile for a wide range of structural applications.
- Widely Available: S355JR is one of the most commonly used structural steels, making it easy to source and cost-effective for many projects.
Limitations of S355JR Steel:
- Corrosion Resistance: Like most structural steels, S355JR does not have inherent corrosion resistance and typically requires surface treatments or coatings when used in outdoor or corrosive environments.
- Low-Temperature Toughness: S355JR is not specifically designed for low-temperature applications; for colder environments, grades like S355J2 (tested at -20°C) or S355K2 (tested at -40°C) are more suitable.
Comparison with Other Structural Steels:
| Steel Grade | Comparison with S355JR Steel |
|---|---|
| S275JR | S275JR has a lower yield strength (275 MPa), making S355JR more suitable for applications requiring higher strength and load-bearing capacity. |
| S355J2 | S355J2 offers better impact resistance at lower temperatures (-20°C) compared to S355JR, which is tested at room temperature. Suitable for colder climates and harsh conditions. |
| S235JR | S235JR is a lower-grade structural steel with a yield strength of 235 MPa, making S355JR stronger and more suited for heavy-duty applications. |
| A36 (ASTM) | A36 is an American standard low-carbon steel with lower yield strength compared to S355JR, often used in less demanding structural applications. |
Heat Treatment and Hardening of S355JR Steel:
- As-Rolled Condition (AR): S355JR is often supplied in its as-rolled condition, meaning no additional heat treatment has been applied after the steel is rolled. This condition provides good mechanical properties for general-purpose applications.
- Normalizing: Though S355JR is not typically heat-treated, normalization can be applied to improve toughness and homogeneity if required for specific applications.
