LR Grade DH40 Shipbuilding Steel Plate
LR Grade DH40 Shipbuilding Steel Plate - High-Strength Low-Temperature Toughness
Comprehensive material properties of LR Grade DH40 shipbuilding steel plate, including chemical composition, mechanical and thermal characteristics, international equivalents, and application guidance for marine and offshore structures.
Hot rolling, normalising, quenching and tempering (optional), thermo-mechanical controlled processing (TMCP), welding, cutting, forming
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LR Grade DH40 Shipbuilding Steel Plate Introduction
LR Grade DH40 is a high-strength shipbuilding structural steel plate classified under the Lloyd's Register (LR) rules. It is designed for hull construction and offshore engineering applications requiring enhanced notch toughness at sub-zero temperatures (typically -20°C).
- Minimum yield strength of 390 MPa
- Excellent weldability with controlled carbon equivalent
- Delivered in normalized or thermo-mechanically controlled processed (TMCP) condition
- Strictly compliant with LR Rules for Materials, Chapter 3
LR Grade DH40 Shipbuilding Steel Plate Chemical Composition of LR DH40
Chemical composition limits as specified in LR Rules for DH40 grade. Microalloying elements such as niobium, vanadium, and titanium may be used individually or in combination to achieve mechanical properties.
- Aluminium acts as a grain refiner and deoxidiser.
- Carbon equivalent (Ceq) is usually ≤ 0.40% to ensure good weldability.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.18 | Ladle analysis; lower in TMCP delivery |
| Manganese (Mn) | 0.90 – 1.60 | Higher content for strength and toughness |
| Silicon (Si) | ≤ 0.50 | Deoxidiser |
| Phosphorus (P) | ≤ 0.035 | Maximum |
| Sulfur (S) | ≤ 0.035 | Maximum |
| Aluminium (Al) acid soluble | ≥ 0.015 | When used as grain refining element |
| Niobium (Nb) | ≤ 0.05 | Optional microalloying |
| Vanadium (V) | ≤ 0.10 | Optional microalloying |
| Titanium (Ti) | ≤ 0.02 | Optional microalloying |
| Copper (Cu) | ≤ 0.35 | Residual; may be specified for corrosion resistance |
| Chromium (Cr) | ≤ 0.20 | Residual |
| Nickel (Ni) | ≤ 0.40 | Residual |
| Molybdenum (Mo) | ≤ 0.08 | Residual |
| Nitrogen (N) | ≤ 0.012 | Max for fine grain steel; higher if Nb/V/Ti added |
LR Grade DH40 Shipbuilding Steel Plate Thermal and Electrical Physical Properties
Physical properties are typical for DH40 steel and are not part of the mandatory delivery conditions. Values are valid for ambient temperature unless otherwise noted.
- Density and modulus are standard for structural steels.
- Thermal expansion and conductivity are important for welding distortion analysis.
| Property | Standard Reference Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20°C |
| Modulus of Elasticity (E) | 200 | GPa | At 20°C |
| Shear Modulus (G) | 80 | GPa | Calculated from E and Poisson's ratio |
| Poisson's Ratio (ν) | 0.3 | - | Typical for steel |
| Thermal Expansion Coefficient (α) | 11.3 × 10⁻⁶ | K⁻¹ | Between 20°C and 100°C |
| Thermal Conductivity (λ) | 52 | W/(m·K) | At 20°C |
| Specific Heat Capacity (cp) | 470 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρe) | 0.16 × 10⁻⁶ | Ω·m | At 20°C |
LR Grade DH40 Shipbuilding Steel Plate Mechanical Properties of LR DH40
Mechanical properties are guaranteed for plates in normalized or TMCP condition in accordance with LR Rules. Charpy V-notch impact tests are performed at -20°C.
- Yield and tensile values depend on plate thickness.
- Elongation requirement reduces slightly for thicker plates.
| Property | Standard Required Value | Unit | Test Condition / Thickness Range |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 390 | MPa | t ≤ 50 mm |
| Yield Strength (ReH) | ≥ 370 | MPa | 50 mm < t ≤ 70 mm |
| Yield Strength (ReH) | ≥ 360 | MPa | 70 mm < t ≤ 100 mm |
| Tensile Strength (Rm) | 510 – 650 | MPa | All thicknesses |
| Elongation (A) | ≥ 20 | % | Gauge 200 mm (80 mm gauge length) - t ≤ 50 mm |
| Elongation (A) | ≥ 19 | % | 50 mm < t ≤ 70 mm |
| Elongation (A) | ≥ 19 | % | 70 mm < t ≤ 100 mm |
| Charpy V-notch Impact (KV2) longitudinal | ≥ 41 | J | At -20°C (average of 3 tests, single min ≥ 70% avg) |
| Charpy V-notch Impact (KV2) transverse | ≥ 27 | J | At -20°C (where specified) |
LR Grade DH40 Shipbuilding Steel Plate Fully Equivalent Material Standards and Replaceable Grades
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | IACS UR W11 | DH40 | All IACS member classification societies |
| USA / ABS | ABS Rules | ABS DH40 | American Bureau of Shipping |
| Norway / DNV | DNV-GL Rules | DNV DH40 | Det Norske Veritas Germanischer Lloyd |
| France / BV | BV Rules | BV DH40 | Bureau Veritas |
| China / CCS | CCS Rules | CCS DH40 | China Classification Society |
| Japan / NK | NK Rules | NK DH40 | Nippon Kaiji Kyokai (ClassNK) |
| Korea / KR | KR Rules | KR DH40 | Korean Register |
| Italy / RINA | RINA Rules | RINA DH40 | Registro Italiano Navale |
| Russia / RS | RS Rules | RS DH40 | Russian Maritime Register of Shipping |
| India / IRS | IRS Rules | IRS DH40 | Indian Register of Shipping |
LR Grade DH40 Shipbuilding Steel Plate Application Introduction
LR DH40 steel plates are primarily used in critical shipbuilding and offshore structural components. The grade offers a well-balanced combination of high strength and excellent low-temperature notch toughness, making it suitable for hulls of ice-strengthened vessels, large container ships, and offshore wind turbine foundations.
- Used in areas subject to moderate-low temperature service.
- Excellent weldability allows efficient fabrication with minimal preheat.
Product Applications: Hull plates, Deck stringers, Bulkheads, Longitudinal and transverse frames, Keels, Rudders and rudder horns, Offshore platform legs, bracings, and nodes
Processed into products: Ship hull outer shell plates (ice belt), Weather deck plates, Bottom and side shell plates, Strength deck plates, Bilge keels, Stern frames, Hatch coamings, Wind turbine tower flanges and transition pieces, Jacket structures and piles
Application industries: Shipbuilding (commercial and naval), Offshore oil & gas platforms, Offshore wind energy foundations, Port and harbor structures, Bridge engineering
LR Grade DH40 Shipbuilding Steel Plate Similar / Alternative Material Recommendations
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | IACS UR W11 | EH40 | Higher toughness: -40°C with same strength; may substitute DH40 with owner's approval |
| International | IACS UR W11 | FH40 | Even higher toughness: -60°C; over-specified for DH40 applications |
| European | EN 10025-4 | S420ML | Thermo-mechanically rolled weldable fine grain structural steel; similar yield but different impact temperature requirements (-50°C) |
| European | EN 10025-3 | S420NL | Normalized fine grain steel; similar strength, higher impact energy, but different standard scope |
Notes:
LR DH40 plates are typically supplied with Lloyds Register certification (material certificates type 3.1 or 3.2). Additional testing such as ultrasonic examination, Z-grade through-thickness testing, and CTOD fracture toughness can be ordered. For plate thicknesses above 20 mm, normalising or TMCP is mandatory; for thinner plates, as-rolled condition may be accepted if impact requirements are met. Consult the latest LR Rules for any updates on specifications.
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