S355JR Carbon Steel: Structural Steels (EN 10025 Series)
S355JR carbon steel, designated under the EN 10025-2 standard (material number 1.0045), is a non-alloy structural steel widely utilized in construction and engineering for its high strength, good weldability, and cost-effectiveness. With a minimum yield strength of 355 MPa, it offers reliable performance in load-bearing applications. This article explores its chemical composition, mechanical properties, manufacturing processes, applications, and comparisons with related grades.
1. Core Chemical Composition (EN 10025-2 Standard)
| Element | Content Range | Function |
|---|---|---|
| Carbon (C) | ≤ 0.24% | Enhances strength and hardness; controlled to maintain weldability |
| Manganese (Mn) | ≤ 1.60% | Improves tensile strength and toughness; aids in deoxidation |
| Phosphorus (P) | ≤ 0.045% | Limited to prevent brittleness and ensure ductility |
| Sulfur (S) | ≤ 0.045% | Restricted to avoid hot shortness and improve machinability |
| Silicon (Si) | ≤ 0.55% | Acts as a deoxidizer; enhances strength without reducing ductility |
| Nitrogen (N) | ≤ 0.012% | Controlled to minimize brittleness in normalized conditions |
2. Key Mechanical Properties (Room Temperature)
- Tensile Strength (Rm): 470-630 MPa (EN 10025-2 standard)
- Yield Strength (ReH, min): 355 MPa for thicknesses ≤ 16 mm (provides robust structural support)
- Elongation (A, min): 22% (ensures sufficient ductility for forming and impact resistance)
- Impact Toughness (KV): ≥ 27 J at +20°C (Charpy V-notch; suitable for general ambient conditions)
- Hardness (HB): ≤ 170 (Brinell; facilitates welding and machining)
3. Manufacturing Process Characteristics
- Smelting: Basic oxygen furnace (BOF) or electric arc furnace (EAF) with ladle refining to achieve low impurity levels and fine grain structure.
- Hot Rolling: Rolled at 900-1200°C, followed by controlled cooling (air cooling or normalizing) to achieve desired mechanical properties.
- Heat Treatment: Normalized at 880-950°C to refine microstructure, enhance uniformity, and improve toughness.
- Cold Forming: Possible for thinner sections with subsequent stress-relief annealing (600-650°C) to prevent distortion.
- Surface Treatment: Shot blasting and priming for corrosion protection; optional galvanizing for enhanced durability in outdoor environments.
4. Typical Application Fields
Construction & Infrastructure
Beams, columns, and girders in buildings, bridges, and platforms — ideal for high-load structural frameworks.
Heavy Machinery
Frames for cranes, excavators, and industrial equipment — combines strength with weldability for fabrication.
Offshore & Marine Structures
Piles, walkways, and supports in non-corrosive marine settings — provides economic strength for coastal projects.
General Engineering
Pressure vessels, storage tanks, and transmission towers — versatile for bolted or welded assemblies.
5. Difference from Similar Grades (S235JR vs S355J2 vs S355JR)
| Grade | Yield Strength (min, MPa) | Key Advantage | Suitable Scenario |
|---|---|---|---|
| S355JR | 355 | High strength-to-weight ratio; good weldability | General structural use in ambient temperatures |
| S235JR | 235 | Lower cost; easier to form | Light-duty structures and non-critical applications |
| S355J2 | 355 | Superior low-temperature toughness (≥ 27 J at -20°C) | Cold climates, heavy fabrication, and impact-prone areas |
6. Selection & Usage Precautions
- Environmental Considerations: Suitable for mild atmospheres; apply protective coatings in corrosive or humid conditions to prevent rusting.
- Welding Guidelines: Preheat to 150-200°C for thicknesses >20 mm; use low-hydrogen electrodes (e.g., E7018) to avoid cracking.
- Design Factors: Account for fatigue in dynamic loads; ensure compliance with Eurocode 3 for structural design.
- Quality Assurance: Verify with material certificates confirming EN 10025-2 compliance, including CE marking for EU projects.
7. Get a Carbon Steel Quote
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