LR AH69 Shipbuilding Steel
LR Grade AH69 Shipbuilding Steel Plate – High-Strength Offshore & Marine Steel
Explore the full material data for LR Grade AH69 shipbuilding steel plate as per Lloyd's Register rules, including chemical composition, mechanical properties, thermal & electrical physical properties, and international equivalent grades.
Thermo-mechanical controlled processing (TMCP), quenching & tempering (Q&T)
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LR AH69 Shipbuilding Steel Introduction
LR Grade AH69 is an ultra-high-strength shipbuilding steel plate classified under Lloyd's Register (LR) rules and conforming to IACS UR W28. It belongs to the high-strength hull structural steel family with a minimum specified yield strength of 690 MPa. The 'A' designation indicates that the steel is impact tested at 0°C (longitudinal), ensuring reliable notch toughness for demanding marine environments.
This grade is primarily supplied in the quenched and tempered (Q&T) or thermo-mechanically controlled processed (TMCP) condition, offering an excellent combination of high strength, good weldability, and formability. It is extensively used in critical structural components of large container ships, offshore platforms, jack-up rig legs, and crane booms where weight reduction and high load-bearing capacity are crucial.
The steel offers superior resistance to brittle fracture, even in thick sections, and is produced with strict control over residual elements and microalloying additions such as Nb, V, and Ti to achieve its fine-grained microstructure. Typical delivery condition is TMCP or Q&T, and Lloyds Register certification ensures full traceability and compliance with the strictest maritime safety standards.
LR AH69 Shipbuilding Steel Chemical Composition
The chemical composition conforms to LR Rules and IACS UR W28. Values are maximum unless otherwise indicated or ranges are shown. Microalloying elements (Nb, V, Ti) may be added singly or in combination for grain refinement and precipitation strengthening. The carbon equivalent (CEV) is controlled to ensure weldability.
| Element | Content (max, unless range) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.20 | Ladle analysis |
| Silicon (Si) | ≤ 0.55 | Ladle analysis |
| Manganese (Mn) | 0.70 – 1.70 | Ladle analysis |
| Phosphorus (P) | ≤ 0.025 | Ladle analysis |
| Sulfur (S) | ≤ 0.025 | Ladle analysis |
| Copper (Cu) | ≤ 0.35 | Residual element limit |
| Nickel (Ni) | ≤ 0.80 | |
| Chromium (Cr) | ≤ 0.30 | |
| Molybdenum (Mo) | ≤ 0.25 | |
| Aluminium (Als, acid soluble) | ≥ 0.015 | Minimum required for fine grain practice |
| Niobium (Nb) | ≤ 0.05 | Microalloying, singly or in combination |
| Vanadium (V) | ≤ 0.10 | Microalloying, singly or in combination |
| Titanium (Ti) | ≤ 0.05 | Microalloying, singly or in combination |
| Nitrogen (N) | ≤ 0.012 | Unless sufficient amount of nitride-forming elements present |
| Boron (B) | ≤ 0.0005 | If added, for hardenability |
LR AH69 Shipbuilding Steel Thermal and Electrical Physical Properties
The following values are typical for quenched and tempered AH69 shipbuilding steel at room temperature unless noted. They are not mandatory specification requirements but are useful for design, simulation, and welding planning. Actual values may vary slightly depending on chemistry and heat treatment.
| Property | Typical value | Unit | Test condition / reference |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20 °C |
| Modulus of elasticity (E) | 205 – 210 | GPa | 20 °C, tensile |
| Shear modulus (G) | ≈ 80 | GPa | 20 °C, calculated |
| Poisson's ratio (ν) | 0.29 – 0.30 | — | Elastic range |
| Thermal expansion coefficient (α) | 11.5 – 12.5 | ×10⁻⁶ /K | 20 – 100 °C |
| Thermal expansion coefficient (α) | 12.5 – 13.5 | ×10⁻⁶ /K | 20 – 200 °C |
| Thermal conductivity (λ) | 35 – 45 | W/(m·K) | 100 °C |
| Thermal conductivity (λ) | 30 – 40 | W/(m·K) | 300 °C |
| Specific heat capacity (cp) | 460 – 480 | J/(kg·K) | 20 °C |
| Electrical resistivity (ρe) | 0.25 – 0.35 | µΩ·m | 20 °C |
LR AH69 Shipbuilding Steel Mechanical Properties
Mechanical properties are determined on test pieces taken in the transverse or longitudinal direction as per LR Rules. Tensile and impact requirements depend on plate thickness. Impact test temperature for grade A is 0°C. Bending test is required over an appropriate former diameter without cracking.
| Property | Requirement / Value | Unit | Test Condition |
|---|---|---|---|
| Yield strength (ReH) | ≥ 690 | MPa | Thickness ≤ 50 mm, transverse |
| Yield strength (ReH) | ≥ 690 | MPa | Thickness 50 < t ≤ 100 mm, transverse |
| Yield strength (ReH) | ≥ 670 | MPa | Thickness 100 < t ≤ 150 mm, transverse |
| Tensile strength (Rm) | 770 – 940 | MPa | Thickness ≤ 100 mm, transverse |
| Tensile strength (Rm) | 760 – 930 | MPa | Thickness 100 < t ≤ 150 mm, transverse |
| Elongation (A5) | ≥ 14 | % | Gauge length 5.65√So, longitudinal, t ≤ 100 mm |
| Elongation (A5) | ≥ 14 | % | Gauge length 5.65√So, longitudinal, t > 100 mm |
| Charpy V-notch impact (KV2) longitudinal | ≥ 41 (average), ≥ 28 (single) | J | Standard 10×10 mm specimen, 0°C, t ≤ 70 mm |
| Charpy V-notch impact (KV2) longitudinal | Proportionally reduced values | J | Sub-size specimens for t > 70 mm, 0°C |
| Bend test (180°) | No cracks or ruptures | — | Bend diameter 3t for t ≤ 25 mm; 4t for t > 25 mm |
LR AH69 Shipbuilding Steel Full Equivalent Standards and Substitutable Grades
| Country / Region | Standard / Classification Society | Grade | Remarks |
|---|---|---|---|
| United Kingdom | Lloyd's Register (LR) | AH69 | Base specification |
| USA | American Bureau of Shipping (ABS) | AH69 | IACS UR W28 equivalent |
| Norway / Germany | DNV | AH69 | IACS UR W28 equivalent |
| France | Bureau Veritas (BV) | AH69 | IACS UR W28 equivalent |
| China | China Classification Society (CCS) | AH69 | IACS UR W28 equivalent |
| South Korea | Korean Register (KR) | AH69 | IACS UR W28 equivalent |
| Japan | Nippon Kaiji Kyokai (NK / ClassNK) | AH69 | IACS UR W28 equivalent |
| Italy | RINA (Registro Italiano Navale) | AH69 | IACS UR W28 equivalent |
| Russia | Russian Maritime Register of Shipping (RS) | AH69 | Upon agreement |
LR AH69 Shipbuilding Steel Application Introduction
LR Grade AH69 is designed for critical load-bearing structures in shipbuilding and offshore engineering. Its ultra-high strength allows substantial weight savings while maintaining structural integrity, making it ideal for large modern vessels and deep-water equipment. Typical applications include:
- Ship hulls: deck, bottom, and side shell plating of ultra-large container ships and bulk carriers.
- Offshore platforms: legs, spudcans, and rack chords of self-elevating (jack-up) rigs.
- Heavy-lift cranes: main chords and lattice booms of offshore cranes.
- Pressure vessels: offshore pressure vessels operating at low temperatures.
- Marine structures: structural components of FPSOs and semi-submersibles.
Product Applications: Large container ships (e.g., 20,000 TEU and above), Self-elevating drilling units (jack-up rigs), Floating cranes and heavy-lift vessels, Offshore substructures (jackets, topsides), Deck equipment for offshore service vessels
Processed into products: Main deck and bottom plates, Leg chords and rack plates for jack-up rigs, Crane boom flanges and webs, Transverse frames and longitudinal stiffeners in hulls, Pressure hull components for submersibles, Heavy-duty lifting lugs and padeyes
Application industries: Shipbuilding and ship repair, Offshore oil & gas exploration and production, Heavy engineering and crane manufacturing, Renewable energy (offshore wind turbine foundations and installation vessels)
LR AH69 Shipbuilding Steel Similar / Comparable Alternative Steels
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-6 | S690QL / S690QL1 | Quenched and tempered structural steel; yield 690 MPa; requires separate approval for marine use. |
| International | ISO 4950-3 | E690 | High yield strength flat products; similar strength level. |
| USA | ASTM A514 / A514M | Grade Q (and others) | High-yield-strength quenched and tempered alloy steel plate; 690 MPa min yield; commonly used in cranes and structures. |
| USA | API 2W / 2Y | Grade 60 (690) | Steel plates for offshore structures, produced to API standards, similar strength. |
| China | GB/T 712 | AH690 | Chinese shipbuilding steel for marine use; direct IACS counterpart. |
| Japan | JIS G 3128 | SHY 685 (modified) | High yield strength steel for welded structures; slightly lower yield (685 MPa) but comparable applications. |
Notes:
Specific impact testing temperatures and acceptance criteria may be modified as per the purchaser's requirements (e.g., to D (-20°C) or E (-40°C) grades). All plates are subject to Lloyds Register survey and stamping. Welding consumables must be matched to the steel, and preheat/interpass temperature control is essential to avoid hydrogen cracking. Users should refer to the latest LR Rules and IACS UR W28 for complete details, as the above values represent a summary based on common practice and published specifications.
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