S235JR Carbon Steel: Structural Steels (EN 10025 Series)
S235JR carbon steel, designated under the EN 10025 series (equivalent to ASTM A283 Grade C or A36 in some contexts), is a non-alloy structural steel widely utilized in construction and engineering for its favorable strength-to-weight ratio and cost-effectiveness. With a minimum yield strength of 235 MPa, it offers good weldability, machinability, and formability, making it ideal for load-bearing structures, bridges, and machinery components. This article explores its chemical composition, mechanical properties, manufacturing processes, applications, and comparative advantages.
1. Core Chemical Composition (EN 10025-2 Standard)
| Element | Content Range | Function |
|---|---|---|
| Carbon (C) | ≤ 0.17% (for t ≤ 40mm) | Provides basic strength; controlled to ensure weldability and ductility |
| Manganese (Mn) | ≤ 1.40% | Enhances toughness and hardenability; improves deoxidation during smelting |
| Phosphorus (P) | ≤ 0.040% | Limited impurity; excess reduces ductility and impact resistance |
| Sulfur (S) | ≤ 0.040% | Controlled to prevent hot shortness and ensure good hot working properties |
| Silicon (Si) | ≤ 0.55% | Aids in deoxidation; contributes to improved strength and elasticity |
| Nitrogen (N) | ≤ 0.012% (with Al stabilization) | Restricted to avoid brittleness; aluminum addition for grain refinement |
| Copper (Cu) | ≤ 0.55% (total with other elements) | Improves corrosion resistance in atmospheric conditions |
2. Key Mechanical Properties (Room Temperature)
- Yield Strength (ReH): ≥ 235 MPa (for thickness ≤ 16mm; decreases slightly for thicker sections)
- Tensile Strength (Rm): 360-510 MPa (ensures adequate load-bearing capacity in structural applications)
- Elongation (A): ≥ 26% (longitudinal; supports forming and bending operations)
- Impact Toughness (KV): ≥ 27 J at 20°C (Charpy V-notch; suitable for general structural use)
- Hardness (HB): ≈ 120-150 (Brinell; facilitates machinability and welding)
3. Manufacturing Process Characteristics
- Smelting: Basic oxygen furnace (BOF) or electric arc furnace (EAF) with ladle refining to control impurities and achieve fine grain structure.
- Hot Rolling: Rolled at 900-1200°C into plates, sections, or bars; controlled cooling to normalize microstructure and meet strength requirements.
- Heat Treatment: Optional normalizing at 880-950°C followed by air cooling to refine grains and improve uniformity; stress relieving for welded components at 550-650°C.
- Cold Forming: Suitable for bending and rolling with radii based on thickness (e.g., 2t for 90° bends); annealing if excessive work hardening occurs.
- Surface Treatment: Pickling and oiling for plates to remove scale; shot blasting for sections to enhance surface quality and corrosion protection.
4. Typical Application Fields
Construction and Infrastructure
Beams, columns, girders, and reinforcement bars in buildings, bridges, and offshore platforms — compliant with Eurocode standards for structural integrity.
Machinery and Equipment
Frames for agricultural machinery, conveyor systems, crane components, and storage tanks — offers cost-effective strength for dynamic loads.
Piping and Fabrication
Welded pipes, pressure vessels (non-critical), and fabricated structures in oil & gas and mining — excellent weldability with no preheating required for thicknesses up to 20mm.
General Engineering
Automotive chassis parts, shipbuilding elements, and general fabrication — versatile for cutting, drilling, and assembly processes.
5. Difference from Similar Grades (S235JR vs S275JR vs S355JR)
| Grade | Min. Yield Strength (MPa) | Key Advantage | Suitable Scenario |
|---|---|---|---|
| S235JR | 235 | Cost-effective; good formability | Light-duty structures and general fabrication |
| S275JR | 275 | Higher strength; balanced toughness | Medium-load buildings and bridges |
| S355JR | 355 | Superior strength for weight savings | Heavy-duty construction and high-stress applications |
6. Selection & Usage Precautions
- Corrosion Protection: Prone to rust in harsh environments; apply galvanizing, painting, or weathering steel variants for outdoor exposure.
- Welding Guidelines: Use matching fillers (e.g., E7018 electrodes); no preheating for thin sections, but control heat input to avoid cold cracking.
- Thickness Considerations: Properties vary with thickness (e.g., yield drops to 215 MPa for t > 100mm); select based on design loads per EN 1993.
- Quality Assurance: Verify with mill certificates (EN 10204 3.1) for chemical and mechanical compliance; perform ultrasonic testing for critical sections.
7. Get a Carbon Steel Quote
If you need customized S235JR carbon steel products (plates, sections, bars, or coils) or require a detailed price quote, contact our team. We offer professional technical support and competitive pricing tailored to your project needs.