SS490: Medium-high strength structural carbon steel
SS490 structural carbon steel, governed by the JIS G3101 standard, is a medium-high strength grade widely utilized in construction and engineering applications. With a yield strength of approximately 245 MPa minimum for thicknesses up to 16 mm, it offers a robust balance of strength, weldability, and cost-effectiveness, making it ideal for buildings, bridges, and heavy machinery. This article explores its chemical composition, mechanical properties, manufacturing processes, applications, and comparisons with similar grades.
1. Core Chemical Composition (JIS G3101 Standard)
| Element | Content Range | Function |
|---|---|---|
| Carbon (C) | ≤ 0.20% (for t ≤ 16 mm) | Provides baseline strength; controlled to ensure good weldability and ductility |
| Manganese (Mn) | 0.60 – 1.50% | Enhances strength and toughness; improves hardenability |
| Phosphorus (P) | ≤ 0.050% | Limited to prevent brittleness and maintain impact resistance |
| Sulfur (S) | ≤ 0.050% | Controlled to avoid hot shortness and ensure hot workability |
| Silicon (Si) | ≤ 0.55% | Aids in deoxidation; contributes to improved strength and elasticity |
2. Key Mechanical Properties (Room Temperature)
- Yield Strength (σ_y): ≥ 245 MPa (for t ≤ 16 mm; decreases for thicker sections)
- Tensile Strength (σ_b): 400 – 510 MPa (provides reliable load-bearing capacity)
- Elongation (δ): ≥ 21% (adequate ductility for structural forming and welding)
- Impact Toughness: Not specified in standard, but typically ≥ 27 J at 20°C for normalized conditions
- Hardness (HB): Approximately 120 – 160 (easily machinable and weldable)
3. Manufacturing Process Characteristics
- Steelmaking: Basic oxygen furnace (BOF) or electric arc furnace (EAF) followed by ladle refining to achieve low impurity levels and uniform composition.
- Hot Rolling: Rolled at 900-1100°C to produce plates, sections, or bars; controlled cooling to refine grain structure and achieve desired mechanical properties.
- Normalization: Optional heat treatment at 850-900°C followed by air cooling to improve uniformity, especially for thicker sections.
- Cutting and Forming: Plasma or oxy-fuel cutting for shapes; hot bending feasible due to good formability in the normalized state.
- Surface Treatment: Shot blasting or pickling to remove scale; primer coating for corrosion protection in outdoor applications.
4. Typical Application Fields
Construction and Infrastructure
Building frameworks, bridge girders, steel piles, and transmission towers — offers cost-effective strength for seismic and load-bearing structures.
Machinery and Equipment
Heavy-duty frames for excavators, cranes, and agricultural machinery — reliable weldability supports fabrication of complex assemblies.
Transportation
Railway components, shipbuilding hull sections, and vehicle chassis — balances weight reduction with structural integrity.
General Fabrication
Storage silos, conveyor supports, and industrial platforms — suitable for low-to-medium corrosive environments with protective coatings.
5. Difference from Similar Grades (SS490 vs SS400 vs SS540)
| Grade | Yield Strength (MPa) | Key Advantage | Suitable Scenario |
|---|---|---|---|
| SS490 | ≥ 245 (t ≤ 16 mm) | Medium-high strength with good weldability | General structural applications requiring moderate toughness |
| SS400 | ≥ 235 (t ≤ 16 mm) | Lower cost, easier to source | Light-duty structures like non-critical building elements |
| SS540 | ≥ 295 (t ≤ 16 mm) | Higher strength for demanding loads | Heavy engineering where enhanced yield is essential |
6. Selection & Usage Precautions
- Corrosion Considerations: Prone to rust in moist or marine environments — apply galvanizing or epoxy coatings for longevity.
- Welding Practices: Use low-hydrogen electrodes (e.g., E7018); preheat to 100-150°C for thicknesses >20 mm to prevent cracking.
- Design Limits: Account for yield strength reduction in thicker sections (>40 mm); consult JIS G3101 for precise values.
- Quality Assurance: Verify with material certificates confirming JIS compliance; perform ultrasonic testing for internal defects in critical applications.
7. Contact Us for SS490 Quote
If you require SS490 structural carbon steel in plates, sections, or custom profiles, or need a competitive quote, contact our team. We offer professional sourcing and technical advice tailored to your project needs.