Many buyers wonder why marine steel costs more. Is it really different from ordinary steel used in construction?
Marine steel plate differs from ordinary steel in strength, corrosion resistance, toughness, and certification, making it suitable for demanding shipbuilding environments.
To clarify these differences, let’s compare their chemical composition, mechanical properties, and usage scenarios, so buyers can make the right material decision.
What Makes Marine Steel Plate Unique?
Using the wrong material in shipbuilding can result in corrosion, cracks, or even vessel failure.
Marine steel plate is specially designed with alloying elements and certifications to ensure seawater resistance, toughness, and weldability for ships.
Marine steel plate is manufactured with strict control over carbon, manganese, and microalloying elements. This balance delivers high strength and low-temperature toughness, critical for marine environments.
Chemical Composition Comparison
| Element | Marine Steel Plate | Ordinary Carbon Steel | Purpose |
|---|---|---|---|
| Carbon (C) | ≤ 0.18% | 0.20–0.25% | Lower C improves toughness |
| Manganese (Mn) | 0.9–1.6% | 0.5–0.8% | Increases strength & hardness |
| Silicon (Si) | ≤ 0.5% | ≤ 0.35% | Improves corrosion resistance |
| Microalloys (Nb, V, Ti) | Trace | None | Grain refinement, toughness |
The controlled composition ensures marine steel plates meet requirements of ABS, CCS, LR, BV, DNV, making them suitable for global shipbuilding projects.
How Do Mechanical Properties Differ?
Strength and toughness define how steel performs under pressure. Ordinary steel often fails to meet marine standards.
Marine steel plates offer yield strength of 315–390 MPa and impact toughness at -20°C, while ordinary steel lacks low-temperature resistance and certification.
Mechanical performance is the core difference. Ordinary steel used in buildings does not face seawater corrosion or extreme impact, while ships face constant stress.
Mechanical Property Comparison
| Property | Marine Steel Plate | Ordinary Carbon Steel |
|---|---|---|
| Yield Strength | 235–390 MPa | 200–250 MPa |
| Tensile Strength | 400–620 MPa | 370–500 MPa |
| Impact Toughness | -20°C to -40°C tested | Usually room temperature only |
| Weldability | Excellent, low crack sensitivity | Limited, prone to cracking |
| Certification | ABS, CCS, LR, DNV, BV | No international marine approval |
This explains why marine steel lasts decades at sea, while ordinary steel would corrode or fracture quickly in the same conditions.
Which Applications Require Marine Steel Instead of Ordinary Steel?
Some buyers try to cut costs by using standard steel in shipbuilding. But this shortcut can be dangerous.
Marine steel is required for ship hulls, decks, offshore platforms, and other critical structures, while ordinary steel is only suitable for inland construction projects.
Ordinary steel may be cheaper, but it cannot guarantee safety in marine environments. Seawater accelerates rust, reducing lifespan dramatically. Marine steel ensures safety and compliance with international shipping laws.
Application Comparison
| Application | Marine Steel Plate | Ordinary Carbon Steel |
|---|---|---|
| Ship Hull | ✅ Required | ❌ Not allowed |
| Deck & Cabin | ✅ Required | ❌ Not suitable |
| Offshore Platforms | ✅ Required | ❌ Not suitable |
| Buildings & Bridges | Possible but costly | ✅ Common choice |
| Inland Machinery | Not economical | ✅ Suitable |
Using certified marine steel is not just about safety; it also ensures insurance coverage, compliance with maritime law, and long-term operational savings.