GL D550 Shipbuilding Steel Plate
GL D550 Shipbuilding Steel Plate: Premium High-Strength Marine Structural Material
Comprehensive material properties and equivalent grades for GL Grade D550 high-strength shipbuilding steel plate, based on GL/DNV classification requirements and IACS UR W11.
Thermo-Mechanical Control Process (TMCP), Normalizing, Quenching and Tempering (Q&T), Controlled Rolling
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GL D550 Shipbuilding Steel Plate Introduction
GL Grade D550 is a high-strength structural steel plate specifically developed for shipbuilding and offshore applications, certified under the rules of Germanischer Lloyd (now DNV). It falls under the yield strength category of 550 MPa minimum, providing superior strength-to-weight ratios for large marine vessels and offshore platforms. The 'D' designation indicates that the steel has guaranteed impact toughness at a test temperature of -20°C. It is produced through controlled rolling and/or thermo-mechanical control process (TMCP), and may undergo normalizing or quenching and tempering, depending on thickness and manufacturer practices. Key characteristics include excellent weldability, good formability, and reliable low-temperature toughness, making it ideal for critical structural components in harsh marine environments. Typical delivery conditions include TMCP or QT, with plates available in a wide range of thicknesses up to 100 mm, fulfilling the stringent requirements of IACS UR W11 and the DNV GL rules for classification.
GL D550 Shipbuilding Steel Plate Chemical Composition
The chemical composition is set to meet the strength and toughness requirements of IACS UR W11 for high-strength shipbuilding steels with yield strength of 550 MPa. Values are maxima unless indicated as a range. Grain-refining elements such as Al, Nb, V, and Ti may be added singly or in combination. The carbon equivalent (Ceq) is controlled to ensure good weldability; typical Ceq ≤ 0.47%.
| Element | Nominal Value (max %) | Remarks |
|---|---|---|
| C | 0.20 | Carbon maximum |
| Si | 0.55 | Silicon maximum |
| Mn | 1.60 | Manganese maximum |
| P | 0.035 | Phosphorus maximum |
| S | 0.035 | Sulfur maximum |
| Cr | 0.20 | Residual maximum |
| Ni | 0.40 | Residual maximum |
| Mo | 0.08 | Residual maximum |
| Cu | 0.35 | Residual maximum |
| Al (acid soluble) | ≥0.015 | Grain refinement, minimum when used |
| Nb | 0.02–0.06 | Optional microalloy |
| V | 0.05–0.10 | Optional microalloy |
| Ti | ≤0.02 | Optional microalloy |
| N | ≤0.012 | Maximum nitrogen |
GL D550 Shipbuilding Steel Plate Thermal and Electrical Physical Properties
The following values are typical for high-strength low-alloy steels of this type and are not mandatory requirements of the standard. They are provided for design and engineering calculations. Slight variations may occur depending on the exact chemical composition and heat treatment.
| Property | Typical Value | Unit | Test Condition / Temperature |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20°C |
| Modulus of Elasticity (E) | 210 | GPa | 20°C |
| Shear Modulus (G) | 81 | GPa | 20°C |
| Poisson's Ratio (ν) | 0.3 | – | 20°C |
| Thermal Expansion Coefficient (α) | 12 × 10⁻⁶ | 1/K | 20–100°C |
| Thermal Conductivity (λ) | ~ 50 | W/(m·K) | 20°C |
| Specific Heat Capacity | ~ 460 | J/(kg·K) | 20°C |
| Electrical Resistivity (ρ_e) | ~ 0.20 | μΩ·m | 20°C |
GL D550 Shipbuilding Steel Plate Mechanical Properties
Mechanical properties are measured on test pieces taken in the transverse or longitudinal direction, depending on the specification. The values below refer to the longitudinal direction and apply to plates with thickness ≤50 mm unless otherwise noted. For thicker sections, slight reductions in elongation are permitted. Charpy impact toughness is guaranteed at -20°C (grade D). Bending test is performed to evaluate formability and soundness.
| Property | Required Value | Unit | Test Condition / Thickness |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 550 | MPa | t ≤ 50 mm, transverse/longitudinal |
| Tensile Strength (Rm) | 670 – 830 | MPa | t ≤ 50 mm |
| Elongation (A5) | ≥ 16 | % | Gauge length 5.65√So, t ≤ 50 mm |
| Elongation (A5) | ≥ 15 | % | 50 < t ≤ 75 mm |
| Elongation (A5) | ≥ 14 | % | 75 < t ≤ 100 mm |
| Charpy Impact Energy (KV, longitudinal) | ≥ 31 (average) | J | Test temp. -20°C, t ≤ 50 mm |
| Charpy Impact Energy (KV, transverse) | ≥ 21 (average) | J | Test temp. -20°C (if required) |
| Bend Test (180°) | No cracks | – | Bend diameter d = 3a (a = specimen thickness) |
GL D550 Shipbuilding Steel Plate Fully Equivalent Material Standards and Substitutable Grades
| Country / Region | Standard / Rules | Grade | Remarks |
|---|---|---|---|
| International | IACS UR W11 | D550 | Unified requirement for all IACS members |
| USA | ABS Rules | ABS DH550 | American Bureau of Shipping |
| France | BV Rules | BV DH550 | Bureau Veritas |
| China | CCS Rules | CCS DH550 | China Classification Society |
| Norway/Germany | DNV GL Rules | DNV DH550 | DNV GL – direct equivalent |
| South Korea | KR Rules | KR DH550 | Korean Register of Shipping |
| UK | LR Rules | LR DH550 | Lloyd's Register |
| Japan | NK Rules | NK DH550 | Nippon Kaiji Kyokai (ClassNK) |
| Italy | RINA Rules | RINA DH550 | Registro Italiano Navale |
| Russia | RS Rules | RS DH550 | Russian Maritime Register of Shipping |
GL D550 Shipbuilding Steel Plate Application Introduction
GL D550 is a highly versatile high-strength shipbuilding steel designed for primary structural components in marine and offshore engineering. Its excellent combination of strength, low-temperature toughness, and weldability enables lighter structures with improved fuel efficiency and payload capacity. Typical industries and applications are listed below.
Product Applications: Hull envelope plating (bottom shell, side shell, weather deck), Strength deck and stringer plate, Longitudinal and transverse bulkheads, Web frames and floors, Heavy-lift crane pedestals and slewing rings, Legs of self-elevating platforms
Processed into products: Inner/outer bottom plates, Bilge strakes, Keel plates, Hatch coaming and girder webs, Deck girders, Cantilever beams, Tubular joints and node cans for offshore structures
Application industries: Commercial shipbuilding (container ships, tankers, bulk carriers), Naval and defence shipbuilding, Offshore oil & gas (jack-ups, semi-submersibles, FPSOs), Marine renewable energy (offshore wind turbine foundations), Heavy civil engineering and bridge construction
GL D550 Shipbuilding Steel Plate Similar / Alternative Materials with Comparable Properties
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| EU | EN 10025-6 | S550Q / 1.8926 | Quenched and tempered steel; slightly different composition, similar strength. Requires separate approval for marine use. |
| USA | ASTM A514 / A514M | Grade Q (Type Quenched & Tempered) | High-strength steel up to 4 in (100 mm); comparable yield strength, different toughness verification. |
| USA | API 2H | Grade 50 (or higher) | Offshore structural steel; similar application but different grade designation. |
| International | ISO 4950-2 | E550DD | High-strength flat products; comparable YS, but delivered in thermomechanical rolled condition. |
Notes:
Weldability: Pre-heating and post-weld heat treatment may be required depending on thickness and carbon equivalent. Certification: Plates are supplied with 3.1 or 3.2 inspection certificates according to EN 10204. Surface condition: Unless otherwise specified, plates are delivered in as-rolled or shot-blasted condition with a shop primer compatible with marine coating systems. Thickness tolerances: In line with EN 10029 or classification society rules.
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