LR Grade AH42 Shipbuilding Steel Plate
LR Grade AH42 Shipbuilding Steel Plate: High Strength Hull Structural Steel
LR Grade AH42 is a high strength shipbuilding steel plate certified by Lloyd's Register, offering minimum yield strength of 420 MPa and excellent toughness at 0°C.
Hot rolling, controlled rolling (TMCP), normalizing, quenching and tempering
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LR Grade AH42 Shipbuilding Steel Plate Introduction
LR Grade AH42 is a high strength structural steel for shipbuilding, governed by Lloyd's Register Rules. It offers a minimum yield strength of 420 MPa and good weldability. Designed for hull structures, it withstands low-temperature service at 0°C with guaranteed impact toughness. Typical thickness up to 100 mm, supplied in normalized, TMCP or quenched and tempered condition.
- High strength: ReH ≥ 420 MPa
- Good toughness: KV at 0°C ≥ 34J
- Excellent weldability with controlled carbon equivalent
LR Grade AH42 Shipbuilding Steel Plate Chemical Composition
Chemical composition according to Lloyd's Register Rules for AH42. Carbon equivalent (CEV) is controlled to ensure weldability. Grain refining elements such as Al, Nb, V are added.
| Element | Specification | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.18 | |
| Manganese (Mn) | 0.90 - 1.60 | |
| Silicon (Si) | 0.10 - 0.50 | |
| Phosphorus (P) | ≤ 0.030 | |
| Sulfur (S) | ≤ 0.030 | |
| Aluminum (Al) | ≥ 0.015 (acid soluble) | Total Al may be specified |
| Niobium (Nb) | 0.02 - 0.05 | |
| Vanadium (V) | 0.05 - 0.10 | |
| Titanium (Ti) | ≤ 0.02 | |
| Copper (Cu) | ≤ 0.35 | |
| Chromium (Cr) | ≤ 0.20 | |
| Nickel (Ni) | ≤ 0.40 | |
| Molybdenum (Mo) | ≤ 0.08 | |
| Nitrogen (N) | ≤ 0.009 | If Al or Nb added |
| Carbon Equivalent (CEV) | ≤ 0.43 (typical) | Depends on thickness |
LR Grade AH42 Shipbuilding Steel Plate Physical Properties
Physical properties for high strength structural steel at room temperature unless noted. Values are approximate and for general guidance.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7850 | kg/m³ | 20°C |
| Modulus of Elasticity (E) | 206 | GPa | 20°C |
| Shear Modulus (G) | 79.3 | GPa | 20°C |
| Poisson's Ratio (ν) | 0.3 | 20°C | |
| Thermal Expansion Coefficient (α) | 11.5 x 10⁻⁶ | K⁻¹ | 20 - 100°C |
| Thermal Conductivity (λ) | 52 | W/(m·K) | 100°C |
| Specific Heat Capacity | 460 | J/(kg·K) | 20°C |
| Electrical Resistivity (ρ_e) | 0.18 x 10⁻⁶ | Ω·m | 20°C |
LR Grade AH42 Shipbuilding Steel Plate Mechanical Properties
Tensile and impact properties at ambient temperature and 0°C. Properties apply to thickness ≤ 100 mm. Yield strength and elongation may vary with thickness.
| Property | Specification | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 420 | MPa | Transverse, Thickness ≤ 100 mm |
| Tensile Strength (Rm) | 530 - 680 | MPa | Transverse |
| Elongation (A) | ≥ 20 | % | Gauge length 5.65√So |
| Bend Test | d = 3a | 180° bend, no cracks, a = thickness ≤ 25mm | |
| Charpy V-notch Impact (KV) | ≥ 34 (longitudinal) | J | at 0°C, standard 10x10 mm specimen |
| Charpy V-notch Impact (KV) | ≥ 24 (transverse) | J | at 0°C, standard 10x10 mm specimen |
LR Grade AH42 Shipbuilding Steel Plate Exact Equivalent Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | ABS | AH42 | American Bureau of Shipping |
| International | DNV | AH42 | Det Norske Veritas |
| International | BV | AH42 | Bureau Veritas |
| International | CCS | AH42 | China Classification Society |
| International | NK | AH42 | Nippon Kaiji Kyokai |
| International | KR | AH42 | Korean Register |
| International | RINA | AH42 | Registro Italiano Navale |
LR Grade AH42 Shipbuilding Steel Plate Application Introduction
LR Grade AH42 steel is widely used in ship and offshore construction where high strength and good weldability are required. Typical applications include:
Product Applications: Hull structures (bottom, side, deck plating), Bulkheads and frames, Stiffeners and girders, Jack-up rig legs (for low temperature service select DH/EH/FH), Deck houses
Processed into products: Ship plates (flat and curved), Longitudinal and transversal stiffeners, Webs and flanges of built-up sections, Brackets and connection plates
Application industries: Shipbuilding, Offshore oil & gas platforms, Marine engineering, Port machinery
LR Grade AH42 Shipbuilding Steel Plate Similar/Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | API | 2H Grade 50 | Offshore structural steel, similar strength |
| European | EN 10025-4 | S420M/ML | Thermomechanical rolled, comparable strength |
| International | IACS | DH42 / EH42 / FH42 | Higher toughness grades for lower temperatures |
| China | GB/T 712 | AH420 | Chinese standard shipbuilding steel |
Notes:
Note: Impact test temperature is 0°C for AH grades. For lower service temperatures, DH42 (-20°C), EH42 (-40°C), or FH42 (-60°C) should be selected. The steel shall be desoxidized (fully killed) and fine grain treated. Weldability is enhanced by controlling carbon equivalent (typically CEV ≤ 0.43 for thickness ≤ 50mm). Delivery condition may affect mechanical properties; TMCP is commonly used to achieve the required properties without additional heat treatment.
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