CCS Grade EQ51 Shipbuilding Steel Plate
CCS Grade EQ51 Shipbuilding Steel Plate - High-Strength Quenched and Tempered Hull Structural Steel
Comprehensive data sheet for CCS EQ51 shipbuilding steel plate: chemical composition, mechanical properties, thermal and electrical physical properties, international equivalents, and application guidance for marine and offshore engineering.
Hot rolling followed by quenching and tempering (QT); suitable for cutting, forming, welding, and machining after heat treatment
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CCS Grade EQ51 Shipbuilding Steel Plate Introduction
CCS Grade EQ51 steel plate is a high-strength quenched and tempered steel for ship and offshore structures, certified by China Classification Society (CCS). It complies with CCS Rules for Materials and Welding. EQ indicates quenching and tempering heat treatment, while 51 denotes a minimum yield strength of 510 MPa. The steel offers excellent weldability, good low-temperature impact toughness, and high resistance to brittle fracture, making it suitable for critical hull components, offshore platforms, and marine equipment operating in harsh environments.
CCS Grade EQ51 Shipbuilding Steel Plate Chemical Composition
Ladle analysis according to CCS Rules. Elements such as Nb, V, Ti, Al, N, and Mo may be added for grain refinement and hardenability. The carbon equivalent (CEV) is controlled to ensure weldability. CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 ≤ 0.52% typically for EQ51.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.18 | Heat analysis |
| Silicon (Si) | 0.10 – 0.55 | |
| Manganese (Mn) | 0.90 – 1.65 | |
| Phosphorus (P) | ≤ 0.025 | |
| Sulfur (S) | ≤ 0.015 | |
| Chromium (Cr) | ≤ 0.30 | Optional, may be specified |
| Nickel (Ni) | ≤ 0.40 | Optional |
| Molybdenum (Mo) | ≤ 0.20 | Optional |
| Copper (Cu) | ≤ 0.30 | Optional |
| Niobium (Nb) | 0.02 – 0.05 | Grain refinement |
| Vanadium (V) | 0.05 – 0.12 | |
| Titanium (Ti) | 0.007 – 0.05 | |
| Aluminum (Al) total | ≥ 0.015 | Grain refinement and deoxidation |
| Nitrogen (N) | ≤ 0.012 |
CCS Grade EQ51 Shipbuilding Steel Plate Thermal and Electrical Physical Properties
Typical physical properties at room temperature unless otherwise noted. These values are indicative for quenched and tempered low-alloy steels and may vary slightly depending on exact composition and manufacturing process.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20°C |
| Elastic Modulus (E) | 210 | GPa | At 20°C |
| Shear Modulus (G) | 81 | GPa | Estimated |
| Poisson's Ratio (ν) | 0.3 | - | Typical for steel |
| Thermal Expansion Coefficient (α) | 12.0 (20-100°C); 13.0 (20-200°C); 13.8 (20-400°C) | 10⁻⁶/K | Mean coefficient over temperature range |
| Thermal Conductivity (λ) | 36 (at 20°C); 35 (at 100°C); 33 (at 200°C) | W/(m·K) | Typical for QT alloy steel |
| Specific Heat Capacity (Cp) | 460 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρ_e) | 0.25 | µΩ·m | At 20°C |
CCS Grade EQ51 Shipbuilding Steel Plate Mechanical Properties
Mechanical properties for quenched and tempered plates with thickness (t) ≤ 50 mm. Properties depend on plate thickness; for thicknesses 50< t ≤ 100 mm, minimum yield strength is reduced to 460 MPa and tensile strength to 570–720 MPa. Charpy impact test temperatures: -40°C for EQ grades. Longitudinal and transverse tests may be specified.
| Property | Standard Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 510 (thickness ≤ 50 mm) | MPa | Transverse, room temperature |
| Yield Strength (ReH) | ≥ 460 (thickness 50< t ≤ 100 mm) | MPa | Transverse, room temperature |
| Tensile Strength (Rm) | 610 – 770 (thickness ≤ 50 mm) | MPa | Transverse, room temperature |
| Tensile Strength (Rm) | 570 – 720 (thickness 50< t ≤ 100 mm) | MPa | Transverse, room temperature |
| Elongation (A5) | ≥ 16 (thickness ≤ 50 mm) | % | Gauge length 5.65√So, transverse |
| Elongation (A5) | ≥ 15 (thickness 50< t ≤ 100 mm) | % | Gauge length 5.65√So, transverse |
| Charpy Impact Energy (KV2) | ≥ 33 (longitudinal) | J | -40°C, average of 3 specimens |
| Charpy Impact Energy (KV2) | ≥ 20 (transverse) | J | -40°C, average of 3 specimens |
| Bending Test (180°) | No cracks, d=3a (thickness ≤ 50 mm) | - | d = mandrel diameter, a = specimen thickness |
CCS Grade EQ51 Shipbuilding Steel Plate Completely Equivalent Material Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | CCS Rules | EQ51 | Base grade |
| International | IACS UR W31 | E690 (Q) | High-strength QT marine steel |
| Norway/Germany | DNV | NV E690 (QT) | Equivalent yield strength 690 MPa |
| USA | ASTM A514/A517 | Grade S | Similar strength, requires careful comparison; yield 690 MPa, but chemistry differs |
| Japan | JIS G 3128 | SHY685 | Yield 685 MPa, similar application |
| Europe | EN 10025-6 | S690QL (1.8928) | Equivalent strength, charpy at -40°C possible |
CCS Grade EQ51 Shipbuilding Steel Plate Application Introduction
EQ51 steel is specifically designed for marine and offshore engineering where high strength-to-weight ratio and excellent low-temperature toughness are required. Its applicability extends to:
Product Applications: Container ship hatch coamings and upper deck structures, Jack-up rig legs and spudcans, Heavy-lift crane booms and pedestals, Icebreaker hulls and ice belt zones, Offshore platform nodes and braces, Mine sweepers and patrol boats
Processed into products: Transverse frames and girders, Bulkhead stiffeners, Deck plates under high stress, Crane pedestal reinforcement, Structural transition pieces for wind turbines
Application industries: Shipbuilding (military and commercial), Offshore oil & gas platforms, Renewable energy (offshore wind turbine foundations), Heavy construction machinery, Pressure vessels and storage tanks
CCS Grade EQ51 Shipbuilding Steel Plate Similar or Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 712 | EH690 | Chinese high-strength shipbuilding steel, similar mechanical properties |
| Korea | KR Rules | EQ51 | Identical designation, KR certified |
| UK | LR Rules | EQ51 | Identical designation, Lloyd's Register |
| France | BV Rules | EQ51 | Identical designation, Bureau Veritas |
| Italy | RINA Rules | EQ51 | Identical designation |
| Russia | GOST 5520 | 10KhSND-Sh / similar | Requires translation; high-strength marine steel |
Notes:
Fabrication considerations: EQ51 requires precise preheating before welding (typically 100–150°C depending on thickness), strict control of heat input, and post-weld heat treatment may not be necessary for thin sections. Low-hydrogen welding consumables are mandatory. Certification: Material to be supplied with CCS surveyor's certificate and test reports including chemical analysis, tensile, impact and bend tests. Supplementary testing such as CTOD or through-thickness (Z35) properties may be specified by the purchaser. Anti-corrosion: Suitable coatings and cathodic protection should be applied in marine environments.
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