GL E550 Marine Steel Plate
GL E550 Marine Steel Plate: Superior Strength and Toughness for Shipbuilding and Offshore Structures
Comprehensive material datasheet for GL Grade E550 high-strength shipbuilding steel, including chemical composition, mechanical properties, thermal and electrical physical properties, international equivalents, and application guidelines.
Welding (preheat recommended), flame/plasma/laser cutting, cold and hot forming, machining
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GL E550 Marine Steel Plate Introduction
GL Grade E550 is a high-strength quenched and tempered structural steel plate specifically designed for shipbuilding and offshore applications, certified under the rules of Germanischer Lloyd (now part of DNV). This grade belongs to the extra high-strength category, with a minimum specified yield strength of 550 MPa, making it ideal for heavily loaded marine structures where weight savings and high toughness at low temperatures are critical. The E designation indicates that the steel is intended for use at sub-zero temperatures, with guaranteed impact toughness down to -40°C.
Typical features include:
- Excellent combination of high strength and good weldability.
- Fine-grained microstructure achieved by controlled rolling and heat treatment.
- High resistance to brittle fracture, suitable for harsh marine environments.
- Available in thicknesses up to 100 mm or more, with through-thickness properties (Z-quality) on request.
The material complies with GL Rules for Materials and Welding, Part 2, Chapter 1, and is often used in critical components such as main decks, side shells, bulkheads, and offshore platform topsides. Its performance ensures structural integrity under dynamic loads, cyclic stresses, and low-temperature service conditions.
GL E550 Marine Steel Plate Chemical Composition
The chemical composition is based on GL requirements for grade E550. Microalloying elements such as Nb, V, Ti, and Al are added for grain refinement and precipitation strengthening. Maximum limits are given unless a range is specified. Note: Carbon equivalent (CEV) is typically controlled to ensure weldability.
| Element | Standard Value (max. unless range) | Remarks |
|---|---|---|
| C | ≤0.20 | |
| Si | ≤0.55 | |
| Mn | ≤1.70 | |
| P | ≤0.025 | |
| S | ≤0.025 | Lower S may be specified for improved Z-properties |
| Cr | ≤0.25 | |
| Ni | ≤0.25 | |
| Cu | ≤0.35 | |
| Mo | ≤0.08 | |
| V | ≤0.10 | Microalloying for strength |
| Ti | ≤0.02 | Grain refinement |
| Nb | ≤0.05 | Grain refinement |
| N | ≤0.012 | |
| Altot | ≥0.020 | Aluminum, total; for deoxidation and grain refinement |
| CEV | Typically ≤0.43 | Carbon equivalent: C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15 |
GL E550 Marine Steel Plate Thermal and Electrical Physical Properties
The following physical properties are typical for quenched and tempered high-strength structural steel of the E550 class. Variations may occur depending on exact chemical composition and heat treatment condition. These values serve as reference for engineering calculations.
| Property | Typical Value | Unit | Test Conditions / Remarks |
|---|---|---|---|
| Density (ρ) | 7850 | kg/m³ | At 20°C |
| Modulus of Elasticity (E) | 210 | GPa | At 20°C, static loading |
| Shear Modulus (G) | ≈80 | GPa | Derived from E and Poisson's ratio |
| Poisson's Ratio (ν) | 0.3 | - | Within elastic range |
| Thermal Expansion Coefficient (α) | 11.5 × 10⁻⁶ | K⁻¹ | 20–100°C |
| Thermal Expansion Coefficient (α) | 12.5 × 10⁻⁶ | K⁻¹ | 20–200°C |
| Thermal Expansion Coefficient (α) | 13.5 × 10⁻⁶ | K⁻¹ | 20–400°C |
| Thermal Conductivity (λ) | 45 | W/(m·K) | At 100°C |
| Specific Heat Capacity (cp) | 460 | J/(kg·K) | At 20–100°C |
| Electrical Resistivity (ρe) | 0.20 × 10⁻⁶ | Ω·m | At 20°C |
GL E550 Marine Steel Plate Mechanical Properties
Mechanical properties are determined on quenched and tempered test coupons taken from plates. Minimum values are guaranteed by the classification society. Impact toughness is tested at -40°C (E grade). All values are transverse unless otherwise stated. Bend test requirements are based on a 180° bend without cracking.
| Property | Standard Requirement | Unit | Test Conditions |
|---|---|---|---|
| Yield Strength (ReH) | ≥550 | MPa | t ≤100 mm, transverse, room temperature |
| Tensile Strength (Rm) | 670 – 830 | MPa | t ≤100 mm, transverse |
| Elongation (A) | ≥16 | % | L0=5.65√S0, transverse |
| Impact Energy (KV, longitudinal) | ≥27 (average) | J | -40°C, Charpy V-notch |
| Impact Energy (KV, transverse) | ≥20 (average) | J | -40°C, Charpy V-notch |
| Bending Test | 180° unbend over former of 3t (t ≤20mm) or 4t (20| - | Mandrel diameter depends on thickness; no cracks permitted | |
GL E550 Marine Steel Plate Full Equivalents – International Standards and Replaceable Grades
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | DNV Rules for Ships / OS-B101 | DNV E550 | Identical material; most common direct substitute |
| International | ABS Rules for Materials and Welding | ABS E550 | Same mechanical and toughness requirements |
| International | Bureau Veritas Rules | BV E550 | Equivalent in all respects |
| International | CCS Rules for Materials and Welding | CCS E550 | Chinese classification society equivalent |
| International | Korean Register Rules | KR E550 | Equivalent Korean grade |
| International | Lloyd's Register Rules | LR E550 | Equivalent for UK-classed ships |
| International | RINA Rules | RINA E550 | Italian classification society equivalent |
| European | EN 10025-6 | S550Q / S550QL / S550QL1 | Base quenched and tempered structural steel; supplementary marine testing may be required |
| International | ASTM A514 / A517 | Grade Q (modified) | Not a direct marine grade but comparable strength; may need requalification |
GL E550 Marine Steel Plate Application Introduction
GL E550 is engineered for demanding structural applications where high strength, low-temperature toughness, and weldability are essential. Its typical usage extends across shipbuilding and offshore engineering, often replacing lower strength grades to reduce weight without compromising safety. Key design considerations:
- Preheating before welding is mandatory; interpass temperature control is critical.
- Post-weld heat treatment (PWHT) may be required for thick sections.
- Low-hydrogen welding consumables (E7018, ER70S-6, etc.) are strongly recommended.
- Through-thickness properties (Z35) should be specified for joints subjected to high restraint or lamellar tearing risk.
Product Applications: Hull plates for container ships, tankers, and bulk carriers, Deck structures and superstructures of naval vessels, Topside modules and jacket legs for offshore platforms, Telescopic crane booms for heavy-lift operations, Reinforced pressure vessels for deep submergence, Structural components of jack-up rigs
Processed into products: Transverse web frames and longitudinal stiffeners, Bottom and side shell plating, Watertight bulkheads and collision bulkheads, Hatch coamings and deck openings reinforcement, Crane pedestals and slewing rings, Pad-eyes and lifting lugs for offshore modules, Chord and bracing members in lattice structures, Padeyes for floating production systems
Application industries: Shipbuilding, Offshore oil & gas platform construction, Heavy-lift crane manufacturing, Pressure vessel fabrication, Bridge building, Mining and earthmoving equipment
GL E550 Marine Steel Plate Similar / Alternative Materials with Comparable Performance
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| European | EN 10025-6 | S690Q / S690QL | Higher yield strength (690 MPa); similar toughness class; often used as upgrade |
| International | ABS Rules | ABS EQ70 | Higher strength (690 MPa) marine steel; similar weldability considerations |
| Asian | JIS G 3128 | SHY 685 | Japanese high-strength quenched and tempered steel; adjusted thickness ranges |
| International | API 2Y | Grade 60 | Offshore structural steel with min. yield 415 MPa (lower strength); may suit less demanding applications |
| International | ASTM A709 | Grade 100 (690) | Bridge steel with comparable strength; not certified for marine use without additional testing |
Notes:
- For thicknesses above 50 mm, ultrasonic testing (UT) according to EN 10160 or equivalent is often required.
- Through-thickness tensile properties (Z-quality) can be ordered per GL rules as Z25, Z35, etc.
- Preheating temperature depends on plate thickness and carbon equivalent; typically 100–150°C for thin sections and 150–200°C for thick sections.
- Plates can be supplied with normalized or stress-relieved condition upon request, but standard delivery is quenched and tempered.
- Surface condition is usually as-rolled, shot-blasted and primed available.
- Maximum recommended service temperature is around 400°C for short-term exposure; prolonged exposure above 250°C may affect temper condition.
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