SS330: Low-Strength General Structural Carbon Steel
SS330, specified under the JIS G 3101 standard, is a low-strength carbon steel grade designed for general structural applications. With a maximum carbon content of 0.15%, it offers good weldability, moderate formability, and cost-effectiveness, making it suitable for non-critical load-bearing structures in construction and machinery. This article explores its chemical composition, mechanical properties, manufacturing processes, applications, and key considerations for use.
1. Core Chemical Composition (JIS G 3101 Standard)
| Element | Content Range | Function |
|---|---|---|
| Carbon (C) | ≤ 0.15% | Provides basic strength; low content enhances weldability and ductility |
| Manganese (Mn) | ≤ 0.60% | Improves hardenability and tensile strength while aiding deoxidation |
| Phosphorus (P) | ≤ 0.050% | Controlled impurity to prevent brittleness and ensure toughness |
| Sulfur (S) | ≤ 0.050% | Limited to minimize hot shortness and promote good hot working properties |
| Silicon (Si) | ≤ 0.40% | Acts as a deoxidizer and enhances strength without reducing weldability |
2. Key Mechanical Properties (Room Temperature)
- Tensile Strength (σb): 290 – 420 MPa (provides adequate load capacity for general structures)
- Yield Strength (σ0.2): ≥ 205 MPa (ensures deformation resistance under moderate loads)
- Elongation (δ): ≥ 26% (sufficient ductility for bending and forming operations)
- Hardness (HB): Approximately 120 – 140 (Brinell; facilitates machining and fabrication)
- Impact Toughness: Suitable for ambient conditions; not recommended for cryogenic or high-impact applications
3. Manufacturing Process Characteristics
- Smelting: Basic oxygen furnace (BOF) or electric arc furnace (EAF) with ladle refining to achieve low impurity levels and consistent chemistry.
- Hot Rolling: Rolled at 850-950°C to produce plates, sheets, or sections, followed by controlled cooling to achieve desired microstructure.
- Cold Forming: Optional cold reduction for thinner gauges, with annealing at 650-700°C to relieve stresses and restore formability.
- Heat Treatment: Normalizing at 880-920°C for improved uniformity; no quenching required due to low hardenability.
- Surface Treatment: Pickling in acid solutions to remove scale; optional shot blasting for enhanced surface cleanliness in fabrication.
4. Typical Application Fields
Construction and Building
Beams, columns, and framing for low-rise buildings, bridges, and temporary structures — economical choice for non-seismic zones.
Machinery and Equipment
Supports, brackets, and housings for agricultural machinery, conveyor frames, and light-duty vehicles — good weldability for assembly.
Piping and Fabrication
Low-pressure pipes, fittings, and welded assemblies in water supply systems and general fabrication — compliant with basic structural codes.
General Industrial Use
Racks, platforms, and enclosures for warehousing and storage — cost-effective for moderate-strength requirements.
5. Difference from Similar Grades (SS330 vs SS400 vs SS490)
| Grade | Tensile Strength (MPa) | Key Advantage | Suitable Scenario |
|---|---|---|---|
| SS330 | 290 – 420 | High weldability and formability; lowest cost | Low-load general structures (e.g., supports, frames) |
| SS400 | 400 – 510 | Balanced strength and ductility; versatile | Medium-load applications (e.g., buildings, machinery) |
| SS490 | 490 – 610 | Higher strength for demanding loads | High-stress structures (e.g., heavy beams, bridges) |
6. Selection & Usage Precautions
- Load Limitations: Not suitable for high-stress or fatigue-prone applications — opt for SS400 or higher for increased safety margins.
- Welding Guidelines: Use low-hydrogen electrodes (e.g., E7018); preheating not typically required, but post-weld stress relief for thick sections.
- Corrosion Protection: Apply primer or galvanizing in humid or outdoor environments, as inherent corrosion resistance is moderate.
- Quality Assurance: Verify compliance with JIS G 3101 via mill certificates, including tensile tests and chemical analysis.
7. Get a Quote for SS330 Steel
If you need customized SS330 carbon steel products (sheets, plates, sections, bars) or a detailed price quote, contact our team. We provide professional support and competitive pricing tailored to your project needs.