ABS Grade AQ51 Quenched and Tempered Shipbuilding Steel Coil
ABS Grade AQ51 Quenched and Tempered Shipbuilding Steel Coil - Properties and International Equivalents
Comprehensive material data for ABS AQ51 shipbuilding steel coil covering chemistry, mechanical and thermal properties, complete equivalents, and typical applications.
Hot rolling, cold rolling (if applicable), welding, bending, cutting
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ABS Grade AQ51 Quenched and Tempered Shipbuilding Steel Coil Introduction
ABS Grade AQ51 is a quenched and tempered high-tensile shipbuilding steel defined by the American Bureau of Shipping. It offers a minimum yield strength of 355 MPa (51 ksi) and excellent notch toughness, with impact testing at 0°C for the 'A' class designation. The steel is primarily supplied as coils or plates and is used in critical structural components of ships and offshore units. Its balanced chemistry, controlled carbon equivalent, and fine grain practice ensure good weldability and reliability in low-temperature service. Available in a range of thicknesses, AQ51 meets strict classification requirements and has direct equivalents in other major classification societies.
ABS Grade AQ51 Quenched and Tempered Shipbuilding Steel Coil Chemical Composition
The chemistry is tightly controlled to achieve the required strength and toughness while maintaining good weldability. Carbon equivalent (CEV) limits apply for thickness and toughness class. Typical elements include micro-alloying additions (Nb, V, Ti) for grain refinement and precipitation strengthening.
- CEV = C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15, ≤0.43% for t ≤ 50 mm.
| Element | Standard Value | Remarks |
|---|---|---|
| Carbon (C) | ≤0.18 % | Ladle analysis |
| Manganese (Mn) | 0.90 – 1.60 % | Range |
| Silicon (Si) | 0.10 – 0.50 % | Range |
| Phosphorus (P) | ≤0.030 % | |
| Sulfur (S) | ≤0.030 % | |
| Chromium (Cr) | ≤0.20 % | |
| Nickel (Ni) | ≤0.40 % | |
| Molybdenum (Mo) | ≤0.08 % | |
| Copper (Cu) | ≤0.35 % | |
| Niobium (Nb) | ≤0.05 % | Optional grain refiner |
| Vanadium (V) | ≤0.10 % | Optional micro-alloy |
| Titanium (Ti) | ≤0.02 % | |
| Aluminium (Al) | ≤0.06 % | Acid soluble |
| Nitrogen (N) | ≤0.012 % | |
| Carbon Equivalent (CEV) | ≤0.43 % | For thickness ≤ 50 mm |
ABS Grade AQ51 Quenched and Tempered Shipbuilding Steel Coil Thermal and Electrical Physical Properties
The physical constants represent typical values for low‑alloy structural steels at room temperature unless otherwise noted. These values are not part of the ABS specification but are useful for engineering design.
- Thermal expansion coefficient given for the range 0 – 100°C.
| Property | Standard Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Elastic Modulus (E) | 205 | GPa | Room temperature |
| Shear Modulus (G) | 80 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.3 | — | Room temperature |
| Thermal Expansion Coeff. (α) | 11.5 × 10⁻⁶ | /K | 0 – 100 °C |
| Thermal Conductivity (λ) | 52 | W/(m·K) | At 20 °C |
| Specific Heat Capacity (cp) | 460 | J/(kg·K) | At 20 °C |
| Electrical Resistivity (ρe) | 0.15 × 10⁻⁶ | Ω·m | At 20 °C |
ABS Grade AQ51 Quenched and Tempered Shipbuilding Steel Coil Mechanical Properties
Tensile and impact properties are tested on specimens taken in the longitudinal or transverse direction as agreed. Values below apply to thickness ≤ 50 mm in quenched and tempered condition. Impact test temperature for grade AQ51 is 0°C.
- Longitudinal Charpy V‑notch: average min 34 J, single min 24 J.
- Transverse Charpy V‑notch: average min 24 J, single min 17 J.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 355 | MPa | Ambient, thickness ≤ 50 mm |
| Tensile Strength (Rm) | 490 – 620 | MPa | Ambient |
| Elongation (A) | ≥ 15 | % | Gauge length 50 mm, thickness ≤ 50 mm |
| Bending Test | 180° bend, d=3t | — | Thickness ≤ 25 mm |
| Bending Test | 180° bend, d=4t | — | Thickness > 25 to 50 mm |
| Charpy Impact (KV, longitudinal) | ≥ 34 (ave) / ≥ 24 (min) | J | Tested at 0 °C |
| Charpy Impact (KV, transverse) | ≥ 24 (ave) / ≥ 17 (min) | J | Tested at 0 °C |
ABS Grade AQ51 Quenched and Tempered Shipbuilding Steel Coil Exact Equivalent Material Standards and Replaceable Grades
| Country/Region | Standard / Classification Society | Grade | Remarks |
|---|---|---|---|
| International | Bureau Veritas (BV) | AQ51 | Identical designation |
| International | DNV | VL AQ51 | Identical designation |
| International | Lloyd's Register (LR) | AQ51 | Identical designation |
| International | ClassNK (NK) | AQ51 | Identical designation |
| International | RINA | AQ51 | Identical designation |
| International | China Classification Society (CCS) | AQ51 | Identical designation |
ABS Grade AQ51 Quenched and Tempered Shipbuilding Steel Coil Application Introduction
ABS AQ51 steel is engineered for demanding marine and offshore environments where high strength, good low-temperature toughness, and weldability are essential. It is used in thickness ranges typically from 6 mm to 50 mm as hot‑rolled coil or plate. Common fabrication methods include flame cutting, cold forming, and welding with appropriate low‑hydrogen consumables.
Product Applications: Hull plates, Longitudinal and transverse stiffeners, Bulkheads, Decks and deck girders, Superstructure components, Offshore platform modules
Processed into products: Longitudinal frames and webs, Transverse web frames, Shell plates (bottom, side, strength deck), Hatch coamings, Brackets and connections, Cargo tank boundaries
Application industries: Shipbuilding, Marine and Offshore Engineering, Structural Engineering (heavy fabrication)
ABS Grade AQ51 Quenched and Tempered Shipbuilding Steel Coil Similar / Alternative Substitute Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-6 | S355Q (1.8901) | Close strength match; requires additional classification society approval for shipbuilding. Typical delivery condition: QT. |
| International | ABS Rules | AQ47 | Quenched and tempered grade with lower minimum yield strength (355 MPa vs 355 MPa? Actually 47 ksi ~ 325 MPa). Suitable where lower strength is acceptable but toughness remains similar. Note: AQ47 yield is 325 MPa, not directly equivalent but often used in similar applications if strength allowables permit. |
Notes:
Welding considerations: Preheating may be required for thick sections or under low ambient temperatures. Typical maximum hardness in the heat‑affected zone should be monitored to avoid cold cracking. The steel is supplied with full classification society certification including mill test certificates (MTC). Dimensional standards: Coils are usually ordered to specified thickness, width, and coil weight, with flatness and surface quality per ABS requirements. Corrosion protection: In service, coating systems or cathodic protection are applied as per ship design.
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