What does S355JR stand for?

Gangsteel, a leading manufacturer and exporter of structural steel plates, supplies premium EN 10025-2 S355JR steel plates for construction, bridges, and heavy machinery applications. S355JR is a widely used grade in the EN 10025-2 standard for hot-rolled structural steels, known for its high strength, good weldability, and versatility. The designation "S355JR" is not just a random code but a specific identifier that conveys essential information about the steel's properties and performance. This article provides a detailed explanation of what S355JR stands for, breaking down each component of the grade designation, along with its chemical composition, mechanical properties, applications, and comparisons with other grades. This comprehensive guide will help engineers, fabricators, and procurement specialists understand the significance of S355JR and its suitability for various projects.

The EN 10025-2 Standard and S355JR Overview

The EN 10025-2 standard is a European specification for hot-rolled non-alloy structural steels, defining technical delivery conditions for products like plates, bars, and sections. It includes grades such as EN 10025-2 S235J0, EN 10025-2 S275JR, EN 10025-2 S275J0 steel, and higher strength options like EN 10025-2 S355JR. S355JR is one of the most popular grades in this standard, offering a balance of strength and ductility for general structural use.

The grade designation "S355JR" is a coded system where each part provides specific information:

• S: Stands for "Structural steel," indicating the steel is intended for structural purposes, such as load-bearing components in buildings or bridges.
• 355: Refers to the minimum yield strength in MPa for plates up to 16 mm thick. This value decreases slightly for thicker plates (e.g., 345 MPa for 16–40 mm), ensuring the steel can withstand significant stress without permanent deformation.
• JR: Indicates the impact toughness, requiring a minimum Charpy V-notch impact energy of 27 J at +20°C (room temperature). This ensures the steel resists brittle fracture in standard conditions.

This designation system allows quick assessment of the steel's capabilities. For example, compared to EN 10025-2 S275J2 steel (yield 275 MPa), S355JR offers higher strength, while its "JR" rating is sufficient for most general applications without extreme cold exposure.

Chemical Composition of S355JR

The chemical composition of S355JR is optimized for strength, weldability, and toughness, with low carbon content to prevent brittleness during welding. The table below shows the chemical composition limits (% by weight) as per EN 10025-2 for S355JR (maximum values unless specified):

Key Notes on Chemical Composition:

• Carbon (C): Capped at 0.24% to ensure good weldability and ductility, reducing the risk of hardness in the heat-affected zone.
• Manganese (Mn): Up to 1.60% enhances strength and toughness, crucial for load-bearing applications.
• Phosphorus (P) and Sulfur (S): Both limited to 0.035% to improve impact resistance and reduce brittleness, especially important for the JR toughness rating.
• Silicon (Si) and Copper (Cu): Provide moderate corrosion resistance, allowing the steel to form a protective patina in atmospheric exposure.

This composition makes S355JR a low-alloy steel with excellent formability. Gangsteel’s S355JR plates are produced with precise chemical control, often with lower impurities for enhanced performance. For lower grades, consider EN 10025-2 S235J2 steel.

Mechanical Properties of S355JR

S355JR exhibits robust mechanical properties, suitable for structural engineering. The table below summarizes its key properties for plates up to 16 mm thick, as per EN 10025-2 (values decrease for thicker plates):

Key Notes on Mechanical Properties:

• Yield Strength: 355 MPa min allows for high-load applications, with values for thicker plates (e.g., 345 MPa for 16–40 mm).
• Tensile Strength: 470–630 MPa provides excellent resistance to breaking under tension.
• Elongation: 20% ensures good ductility for forming and welding.
• Impact Toughness: 27 J at +20°C guarantees resistance to brittle failure in standard conditions.
• Hardness: 150–200 HB indicates moderate hardness, easy to machine while durable.

These properties make S355JR reliable for welded structures. For higher toughness, consider EN 10025-2 S355J2 steel or EN 10025-2 S355K2 steel from Gangsteel.

Weldability and Fabrication Properties of S355JR

S355JR has excellent weldability due to its low carbon equivalent (CEV max 0.45 for thicknesses up to 30 mm), allowing for welding without preheating in many cases. It is compatible with common welding methods like SMAW (using low-hydrogen electrodes such as E7018), GTAW, and SAW. For thicker plates (>40 mm), preheating to 100–150°C is recommended to avoid cracking in the heat-affected zone (HAZ).

Fabrication properties include good machinability and formability, with the normalized condition reducing distortion during heat treatment. Post-weld heat treatment (PWHT) at 600–650°C is advised for stress relief in ASME-coded applications. Gangsteel’s S355JR plates are supplied with optimized bonding, ensuring reliable welding, similar to EN 10025-2 S355JR+N.

Physical Properties of S355JR

Physical properties of S355JR contribute to its usability in various environments:

• Density: 7.85 g/cm³, typical for carbon steels, ensuring predictable weight calculations in design.
• Thermal Conductivity: 50 W/m·K at room temperature, suitable for heat transfer in structural components.
• Coefficient of Thermal Expansion: 11–13 × 10^-6 /K, allowing for stable performance in temperature-varying conditions.
• Modulus of Elasticity: 210 GPa, providing stiffness for load-bearing structures.
• Poisson's Ratio: 0.3, indicating typical elastic behavior under stress.

These properties make S355JR versatile for both static and dynamic loads, with good resistance to thermal expansion in construction. For offshore use, consider EN 10025-2 S355K2 steel.

Corrosion Resistance and Durability of S355JR

S355JR has moderate corrosion resistance in non-aggressive environments, enhanced by silicon and copper additions that form a protective patina in atmospheric exposure. For corrosive conditions, it can be painted or galvanized. Its durability is evident in its fatigue resistance and toughness, with a fatigue limit around 150–200 MPa for cycles up to 10^7. In low-temperature applications, its +20°C impact toughness prevents brittle failure, extending service life in mild cold climates. Gangsteel offers clad or coated S355JR plates for enhanced durability in harsh environments, such as EN 10025-2 S235J2 steel for lower strength needs.

Comparison with Other EN 10025 Grades

EN 10025 S355JR is part of the S355 family, offering higher strength than S275 grades but less toughness than S355J2 (tested at -20°C). The table below compares S355JR with other EN 10025-2 grades:

S355JR's +20°C toughness makes it cost-effective for general use, while S355J2 is better for cold applications. For higher strength, consider EN 10025-2 S450J0 steel.

Applications of S355JR Steel Plate

S355JR is versatile and widely used in applications requiring high strength and good toughness:

1. Construction: For high-rise buildings, bridges, and stadiums, where its yield strength and ductility are essential.
2. Offshore Engineering: In platforms and wind turbines, leveraging its corrosion resistance and impact toughness.
3. Heavy Machinery: For cranes, excavators, and mining equipment, where durability under dynamic loads is critical.
4. Shipbuilding: In hulls and superstructures, benefiting from its weldability and strength.
5. Energy Sector: For pipelines and storage tanks, offering reliability in varying temperatures.

Gangsteel’s S355JR plates are available in thicknesses from 6–300 mm, with options for cut-to-size and cladding for specialized applications like EN 10025-2 S355K2 steel.

Why Choose Gangsteel for S355JR Steel Plates?

Gangsteel is a trusted supplier of S355JR and equivalent plates, offering:

• Certified Quality: Plates undergo ultrasonic testing, Charpy impact tests at +20°C, and chemical analysis to meet EN 10025-2 standards.
• Customization: Available in thicknesses from 6–300 mm, with options for normalization, cut-to-size, and beveling.
• Global Supply: Competitive pricing and reliable delivery from China to worldwide markets.
• Technical Support: Guidance on selecting S355JR versus other grades like EN 10025-2 S355J0 or EN 10025-2 S355K2 steel.

Gangsteel Solution

S355JR is a structural steel grade where "S" means structural, "355" indicates minimum yield strength of 355 MPa, and "JR" denotes 27 J impact energy at +20°C. Gangsteel’s high-quality S355JR plates ensure reliability for your projects. For equivalent standards, explore our BS EN 10025-2 material grade guide.

Gangsteel

This article explains what S355JR stands for, detailing the grade designation, chemical composition, mechanical properties, and applications.

Keywords: S355JR meaning, EN 10025 S355JR, S355JR properties, S355JR applications