LR AH42 Shipbuilding Steel Coil
LR AH42 Shipbuilding Steel Coil - High Strength Marine Grade | Chemical & Mechanical Properties
Comprehensive material data for LR AH42 shipbuilding steel coil, including chemical composition, mechanical and thermal properties, international equivalents, and application guide.
Welding, cutting, bending, cold forming, machining
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LR AH42 Shipbuilding Steel Coil Introduction
LR AH42 is a high-strength shipbuilding structural steel grade certified by Lloyd's Register (LR), United Kingdom. It is designed for use in the construction of marine vessels and offshore structures where high strength, good weldability, and excellent low-temperature toughness are essential.
- Minimum yield strength of 420 MPa ensures structural integrity under high stress.
- Charpy impact energy of at least 34 J at -40°C provides reliable performance in cold environments.
- Controlled processing (TMCP or normalized) refines grain structure for improved mechanical properties.
- Complies with IACS UR W11 for hull structural steel.
LR AH42 Shipbuilding Steel Coil Chemical Composition
The chemical composition of LR AH42 shipbuilding steel must comply with the requirements of Lloyd's Register Rules and IACS UR W11. Fine grain practice using aluminium, niobium, vanadium, or titanium is required. The carbon equivalent (CEV) is typically limited to 0.45% max to ensure good weldability.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.21 | |
| Silicon (Si) | 0.10 – 0.50 | |
| Manganese (Mn) | 0.90 – 1.60 | May be higher depending on thickness |
| Phosphorus (P) | ≤ 0.035 | |
| Sulfur (S) | ≤ 0.035 | |
| Chromium (Cr) | ≤ 0.25 | |
| Nickel (Ni) | ≤ 0.40 | |
| Copper (Cu) | ≤ 0.35 | |
| Molybdenum (Mo) | ≤ 0.08 | |
| Aluminium (Altotal) | ≥ 0.015 | Grain refining element |
| Niobium (Nb) | ≤ 0.05 | Grain refining element |
| Vanadium (V) | ≤ 0.10 | Grain refining element |
| Titanium (Ti) | ≤ 0.02 | Grain refining element |
| Nitrogen (N) | ≤ 0.009 |
LR AH42 Shipbuilding Steel Coil Thermal and Electrical Physical Properties
The following physical properties are typical for low-carbon high-strength structural steels and can be used for engineering calculations for LR AH42. Actual values may vary slightly depending on the exact composition and manufacturing route.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Modulus of Elasticity (E) | 205 | GPa | Room temperature |
| Shear Modulus (G) | 80 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.3 | – | |
| Thermal Expansion Coefficient (α) | 12.0 x 10⁻⁶ | K⁻¹ | 20 – 100°C |
| Thermal Expansion Coefficient (α) | 12.5 x 10⁻⁶ | K⁻¹ | 20 – 200°C |
| Thermal Conductivity (λ) | 50 | W/(m·K) | 20°C |
| Specific Heat Capacity (c) | 460 | J/(kg·K) | 20°C |
| Electrical Resistivity (ρ_e) | 0.18 | µΩ·m | 20°C |
LR AH42 Shipbuilding Steel Coil Mechanical Properties
The mechanical properties of LR AH42 are determined in accordance with LR Rules and IACS UR W11. Testing is performed on transverse specimens. The Charpy V-notch impact test is carried out at -40°C for grade AH42. Thickness-dependent properties are indicated below; for thicknesses beyond 50 mm, values may be subject to agreement.
| Property | Standard Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 420 | MPa | Thickness ≤ 50 mm |
| Yield Strength (ReH) | ≥ 410 | MPa | Thickness > 50 mm to 70 mm |
| Yield Strength (ReH) | ≥ 400 | MPa | Thickness > 70 mm to 100 mm |
| Tensile Strength (Rm) | 530 – 680 | MPa | |
| Elongation after fracture (A) | ≥ 19 | % | Thickness ≤ 50 mm, gauge length 5.65√S0 |
| Elongation after fracture (A) | ≥ 19 | % | Thickness > 50 mm to 70 mm |
| Elongation after fracture (A) | ≥ 18 | % | Thickness > 70 mm to 100 mm |
| Impact Energy (KV2), -40°C | ≥ 34 (average), ≥ 24 (single) | J | Transverse Charpy V-notch |
| Bend Test (mandrel diameter) | 3a (180°) | – | a = specimen thickness |
LR AH42 Shipbuilding Steel Coil Fully Equivalent Material Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International (IACS) | IACS UR W11 | AH42 | Baseline standard for classification societies |
| UK (Lloyd's Register) | LR Rules | AH42 | Original certification |
| USA (ABS) | ABS Rules | AH42 | Identical requirements |
| France (BV) | BV Rules | AH42 | Identical requirements |
| China (CCS) | CCS Rules | AH42 | Identical requirements |
| Norway/Germany (DNV) | DNV Rules | AH42 | Identical requirements (formerly DNV GL) |
| Japan (NK/ClassNK) | NK Rules | AH42 | Identical requirements |
| South Korea (KR) | KR Rules | AH42 | Identical requirements |
| Italy (RINA) | RINA Rules | AH42 | Identical requirements |
| Russia (RS) | RS Rules | AH42 | Identical requirements |
LR AH42 Shipbuilding Steel Coil Application Introduction
LR AH42 is specifically designed for demanding marine and offshore environments. Its high strength-to-weight ratio enables lighter ship designs with improved deadweight capacity. The excellent low-temperature toughness makes it suitable for ice-class vessels navigating cold regions.
- Widely used in critical structural components of commercial ships, naval vessels, and offshore platforms.
- Compatible with all conventional shipbuilding fabrication methods including welding, cutting, and forming.
- Certification by Lloyd's Register ensures global acceptance in the marine industry.
Product Applications: Hull plates and stiffeners, Decks and bulkheads, Longitudinals and frames, Web frames and stringers, Hatch covers, Boss plates, Keel plates, Rudder stocks and stem bars, Offshore platform legs and bracings
Processed into products: Hull shell plates (inner and outer), Longitudinal and transverse stiffeners, Web frames and floor plates, Bracket plates, Deck plating and beams, Watertight bulkheads, Engine room structural elements, Superstructure support elements, Padeyes and lifting lugs (with additional thickness consideration)
Application industries: Commercial shipbuilding (containers, bulk carriers, tankers, cruise ships), Naval and defense shipbuilding, Offshore oil and gas (jack-up rigs, FPSO, platform structures), Offshore wind energy (transition pieces, foundation structures), Heavy engineering and bridge construction where marine environment certification is required
LR AH42 Shipbuilding Steel Coil Similar / Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 712 | AH420 | Chinese shipbuilding steel, equivalent mechanical properties but require class society certification for marine use |
| China | GB/T 1591 | Q420D/Q420E | High-strength low-alloy structural steel, similar strength but not class-certified for shipbuilding |
| EU | EN 10025-4 | S420ML | Thermo-mechanically rolled weldable fine grain structural steel, similar yield strength with -50°C impact; marine application requires additional certification |
| EU | EN 10025-3 | S420NL | Normalized weldable fine grain steel, similar strength and low-temperature toughness; supplementary testing needed for ship classification |
| Japan | JIS G 3106 | SM490B/SM490C | Welded structural steel, similar tensile range but lower minimum yield (325-365 MPa); can be upgraded to AH42 by proprietary processing |
Notes:
LR AH42 shall be supplied with an inspection certificate per EN 10204 Type 3.1 or equivalent as required by Lloyd's Register rules. Full traceability and marking according to LR regulations are mandatory. For thicknesses above 100 mm, mechanical properties must be specially agreed. When used for offshore structures, compliance with additional NACE standards for sour service may be requested. Welding consumables should be matched to achieve equivalent strength and toughness. Preheating and post-weld heat treatment may be required based on thickness and service conditions.
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