DNV F420 Shipbuilding Steel Coil
DNV F420 Shipbuilding Steel Coil: Properties, Equivalents & Applications
Comprehensive material data for DNV F420 shipbuilding steel coil including chemical, mechanical and thermal properties with international equivalents like ABS EH420.
Hot rolling, Thermomechanical controlled processing (TMCP), Normalizing
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DNV F420 Shipbuilding Steel Coil Introduction
DNV F420 is a high-strength shipbuilding structural steel grade certified by DNV (Det Norske Veritas). It belongs to the normalized or thermomechanically rolled fine-grain steels with a minimum yield strength of 420 MPa. This steel is designed for critical ship hull and offshore structures operating in low-temperature environments, designated with the -40°C impact test requirement (F-grade). The material is primarily supplied as hot-rolled coils or plates. Key features include:
- Excellent weldability with controlled carbon equivalent
- Good toughness at temperatures as low as -40°C
- High strength-to-weight ratio for light-weight design
- Consistent properties through strict mill production
DNV F420 is widely used in merchant ships, naval vessels, offshore platforms and heavy marine machinery.
DNV F420 Shipbuilding Steel Coil Chemical Composition
The ladle analysis shall comply with the limits given in the table. Grain-refining elements such as Nb, V, Ti, or Al must be added singly or in combination. The carbon equivalent (CEV) is typically controlled to ensure weldability and is calculated as CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. Actual CEV values are usually ≤ 0.43 for thickness up to 50 mm.
| Element | Standard Value (max, wt%) | Remarks |
|---|---|---|
| Carbon (C) | 0.18 | |
| Silicon (Si) | 0.10 - 0.50 | |
| Manganese (Mn) | 0.90 - 1.60 | |
| Phosphorus (P) | 0.025 | |
| Sulfur (S) | 0.025 | |
| Aluminium (Alt) | ≥ 0.015 | Total aluminium, acid-soluble |
| Niobium (Nb) | 0.02 - 0.05 | Optional grain refiner |
| Vanadium (V) | 0.05 - 0.10 | Optional grain refiner |
| Titanium (Ti) | ≤ 0.02 | Optional grain refiner |
| Copper (Cu) | ≤ 0.35 | |
| Chromium (Cr) | ≤ 0.20 | |
| Nickel (Ni) | ≤ 0.40 | |
| Molybdenum (Mo) | ≤ 0.08 | |
| Nitrogen (N) | ≤ 0.012 | If Ti or other nitride formers are present, higher N may be allowed |
DNV F420 Shipbuilding Steel Coil Thermal and Electrical Physical Properties
The following physical constants are representative for high-strength low-alloy structural steels similar to EN 10025-4 S420ML. Actual values may vary slightly depending on the exact chemical composition and heat treatment condition. Thermal properties are essential for welding simulation and fire design.
| Property | Standard Required Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7850 | kg/m³ | At 20°C |
| Elastic Modulus (E) | 210 | GPa | Tensile, room temperature |
| Shear Modulus (G) | 80.8 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.3 | - | Room temperature |
| Thermal Expansion Coefficient (α) | 11.1 (20-100°C) | 10⁻⁶·K⁻¹ | Range 20°C to 100°C |
| Thermal Expansion Coefficient (α) | 11.9 (20-200°C) | 10⁻⁶·K⁻¹ | Range 20°C to 200°C |
| Thermal Expansion Coefficient (α) | 12.5 (20-300°C) | 10⁻⁶·K⁻¹ | Range 20°C to 300°C |
| Thermal Conductivity (λ) | 45 | W/(m·K) | At 20°C |
| Thermal Conductivity (λ) | 42 | W/(m·K) | At 100°C |
| Specific Heat Capacity (cp) | 460 | J/(kg·K) | At 20°C |
| Specific Heat Capacity (cp) | 500 | J/(kg·K) | At 200°C |
| Electrical Resistivity (ρe) | 0.23 | μΩ·m | At 20°C |
DNV F420 Shipbuilding Steel Coil Mechanical Properties
Mechanical properties are determined on test pieces prepared from the final delivery condition. The specified values apply for plate/coil thicknesses up to 100 mm. Charpy V-notch impact tests are performed at -40°C; the energy values depend on specimen orientation and thickness. For thicknesses > 100 mm, lower yield and tensile values might apply as per DNV rules. The bending test is performed with a 180° bend over a diameter specified by the required elongation.
| Property | Standard Required Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 420 | MPa | Thickness ≤ 100 mm |
| Tensile Strength (Rm) | 530 - 680 | MPa | |
| Elongation (A5) | ≥ 18 | % | Gauge length 5.65√S0, thickness ≤ 100 mm |
| Bend Test (Bend Diameter) | 3a (t ≤ 25 mm), 4a (t > 25 mm) | - | a = specimen thickness, 180° bend |
| Impact Energy (KV) - Longitudinal | ≥ 24 (average), ≥ 17 (individual) | J | Temperature: -40°C, thickness 5-10 mm: 5x10x55 mm sub-size specimen |
| Impact Energy (KV) - Transverse | ≥ 17 (average), ≥ 12 (individual) | J | Temperature: -40°C, full-size specimen 10x10x55 mm |
DNV F420 Shipbuilding Steel Coil Equivalent Material Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | DNV Rules | F420 | Base grade |
| USA | ABS Rules | EH420 | Identical requirements |
| France | BV Rules | EH420 | Identical requirements |
| China | CCS Rules | EH420 | Identical requirements |
| UK | LR Rules | EH420 | Identical requirements |
| Japan | NK Rules | EH420 | Identical requirements |
| Italy | RINA Rules | EH420 | Identical requirements |
| Korea | KR Rules | EH420 | Identical requirements |
| Russia | RMRS Rules | F420 | Equivalent, minor test differences |
DNV F420 Shipbuilding Steel Coil Application Introduction
DNV F420 steel is purpose-designed for demanding marine and offshore environments. Its high strength and excellent low-temperature toughness make it suitable for critical structural applications where safety and durability are paramount. The TMCP delivery condition ensures good weldability without sacrificing strength.
- Heavy ship structures in Arctic and ice-class vessels
- Offshore platform legs, decks and modules
- High-stress hull members such as keels, bilge strakes
- Pressure hulls for submersibles
- Heavy-lift crane structures and marine gear
Product Applications: Hull plates and stiffeners, Deck plating, Bulkheads and floors, Jack-up rig legs, Floating production storage and offloading (FPSO) hulls
Processed into products: Transverse frames and webs, Longitudinal stiffeners, Keel plates, Rudder horns, Shaft brackets, Mooring brackets, Crane pedestals, Heavy lifting lugs
Application industries: Shipbuilding (commercial, naval, icebreakers), Offshore oil & gas, Marine engineering, Port and harbor construction, Renewable energy (offshore wind foundations)
DNV F420 Shipbuilding Steel Coil Similar/Comparable Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| European Union | EN 10025-4 | S420ML/ S420MLO | Thermomechanical rolled; not specifically certified for marine but equivalent mechanical properties; -50°C impact (ML) available |
| European Union | EN 10025-3 | S420N/S420NL | Normalized; NL has -50°C impact; may replace F420 when normalizing is specified |
| China | GB/T 712 | DH420, EH420 | EH420 matches the -40°C toughness of F420 |
| International | IACS UR W11 | EH420 | Unified requirements for ordinary and high-strength hull structural steel; EH420 is covered |
| USA | ASTM A572/ A573? | Not direct match | No US ASTM standard directly covers high-toughness 420 MPa ship steel; ABS EH420 is the reference |
Notes:
Note: The chemical composition and mechanical properties are in accordance with DNV Rules for Classification of Ships (July 2022 edition). Actual mill certificates may show tighter controls. For thicknesses above 100 mm, the yield strength may be reduced to 390 MPa. Additionally, the steel is typically supplied with ultrasonic testing (UT) according to DNV Class I or II. Surface quality and dimensional tolerances are in agreement with EN 10029 or equivalent.
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