LR AH40 Steel Coil
LR AH40 Shipbuilding Steel Coil: High-Strength Marine Structural Steel
LR AH40 shipbuilding steel coil is a high-strength structural steel for marine applications, offering minimum yield strength of 390 MPa, excellent weldability, and reliable low-temperature toughness per Lloyd's Register specifications.
Hot rolling, controlled rolling, normalising, thermomechanical controlled processing (TMCP), cutting, forming, welding, machining
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LR AH40 Steel Coil Introduction
LR AH40 is a high-strength hull structural steel grade defined by Lloyd's Register (LR) Rules for the Manufacture, Testing and Certification of Materials. With a minimum yield strength of 390 MPa and tensile strength in the range of 510–650 MPa, it provides an optimal balance of strength, ductility, and toughness for demanding marine environments. The steel is designed with controlled chemical composition, including micro-alloying elements such as Nb, V, and Ti, to achieve fine grain refinement and improved mechanical properties. It is typically supplied as coil, plate, or strip in as-rolled, normalised, or thermomechanical controlled rolled (TMCP) conditions. AH40 exhibits good weldability and formability, making it suitable for critical structural components in shipbuilding and offshore engineering. The 'A' designation indicates that impact testing is conducted at 0°C, ensuring sufficient notch toughness for ordinary service temperatures. This grade is widely recognized internationally and has direct equivalents across all major classification societies, facilitating global procurement and design harmonization.
LR AH40 Steel Coil Chemical Composition
The chemical composition limits for LR AH40 steel are specified to ensure adequate strength, toughness, and weldability. The values represent ladle analysis as per Lloyd's Register requirements.
| Element | Specified Value | Remarks |
|---|---|---|
| C | ≤ 0.18 | |
| Si | ≤ 0.50 | |
| Mn | 0.90 - 1.60 | |
| P | ≤ 0.035 | |
| S | ≤ 0.035 | |
| Al (acid soluble) | ≥ 0.015 | Fine grain practice |
| Nb | ≤ 0.05 | |
| V | ≤ 0.10 | |
| Ti | ≤ 0.02 | |
| Cu | ≤ 0.35 | |
| Cr | ≤ 0.20 | |
| Ni | ≤ 0.40 | |
| Mo | ≤ 0.08 | |
| N | ≤ 0.012 | If Al is not added |
LR AH40 Steel Coil Thermal and Electrical Physical Properties
The following physical properties are typical for carbon and low-alloy steels similar to AH40. They are not mandatory requirements of LR rules but are provided for engineering design reference.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20 °C |
| Modulus of Elasticity (E) | 200 | GPa | 20 °C |
| Shear Modulus (G) | 76.9 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.3 | - | |
| Thermal Expansion Coefficient (α) | 12.0 | 10⁻⁶/K | 20 - 100 °C |
| Thermal Conductivity (λ) | 52 | W/(m·K) | 20 °C |
| Specific Heat Capacity | 0.47 | J/(g·°C) | 20 °C |
| Electrical Resistivity (ρ_e) | 0.16 | µΩ·m | 20 °C |
LR AH40 Steel Coil Mechanical Properties
The mechanical properties of LR AH40 steel are evaluated according to LR Rules. Tests are carried out at room temperature unless otherwise stated. The values apply to products with thickness ≤ 100 mm.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 390 | MPa | Transverse, t ≤ 100 mm |
| Tensile Strength (Rm) | 510 - 650 | MPa | Transverse, t ≤ 100 mm |
| Elongation (A) | ≥ 20 | % | l0=5.65√S0, transverse |
| Impact Energy (KV) | ≥ 34 (longitudinal) | J | 0 °C, longitudinal Charpy V-notch |
| Impact Energy (KV) | ≥ 24 (transverse) | J | 0 °C, transverse Charpy V-notch |
| Bend Test | No cracks, 180° | - | Bend diameter 3t for t ≤ 25 mm |
LR AH40 Steel Coil Equivalent Material Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | IACS URS W11 | AH40 | Unified requirement for classification societies |
| United States | ABS | AH40 | American Bureau of Shipping |
| Norway/Germany | DNV | NV A40 | Det Norske Veritas (now DNV) |
| France | BV | AH40 | Bureau Veritas |
| China | CCS | AH40 | China Classification Society |
| Korea | KR | AH40 | Korean Register |
| Japan | NK | KA40 | Nippon Kaiji Kyokai |
| Italy | RINA | AH40 | Registro Italiano Navale |
| Russia | RS | AH40 | Russian Maritime Register of Shipping |
LR AH40 Steel Coil Application Introduction
LR AH40 steel coil is a versatile material for marine and offshore structures where high strength and good toughness are required. Its combination of mechanical properties and weldability allows for efficient fabrication of lightweight structures without compromising safety. Typical applications include the construction of hulls, decks, and critical load-bearing members in ships and offshore platforms. It can be used in both stiffened and unstiffened components, and its availability in coil form facilitates continuous production of shaped profiles and long structural elements.
Product Applications: Container ships, Bulk carriers, Crude oil tankers, Chemical tankers, Offshore platforms (jack-ups, semi-submersibles), FPSO hulls, Ice-going vessels (with additional requirements)
Processed into products: Hull plating, Main deck plating, Bulkhead plates, Longitudinal stiffeners, Transverse frames and webs, Bracket plates, Keel plates, Stringer plates, Support structures for offshore modules
Application industries: Shipbuilding, Offshore Oil & Gas, Marine Engineering, Port and Harbor Construction
LR AH40 Steel Coil Similar or Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Lloyd's Register | LR | DH40 | Higher toughness; impact test at -20 °C, same strength level |
| Lloyd's Register | LR | EH40 | Higher toughness; impact test at -40 °C, same strength level |
| Lloyd's Register | LR | FH40 | Higher toughness; impact test at -60 °C, same strength level |
| Lloyd's Register | LR | AH36 | Lower strength grade (yield ≥ 355 MPa), same impact temperature |
| Any Classification Society | Various | D40 / E40 | Equivalent strength with enhanced toughness for lower service temperatures |
Notes:
- AH40 steel can be supplied in normalized or TMCP condition to achieve fine grain size and improved notch toughness. TMCP delivery often allows reduced carbon equivalent, enhancing weldability.
- Welding should follow recognized procedures, such as those approved by Lloyd's Register. Preheat may be required for thicknesses above 30 mm to avoid hydrogen-induced cracking.
- Post-weld heat treatment (PWHT) is generally not required for this grade but may be considered for thick sections under specific service conditions.
- Permissible rolling and dimensional tolerances are in accordance with the relevant LR rules or international standards (e.g., EN 10029).
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