NK A40 Shipbuilding Steel Coil
NK A40 Shipbuilding Steel Coil - High-Tensile Grade for Marine Hull Structures
Comprehensive technical data for NK A40 shipbuilding steel coil as per ClassNK Rules, including chemical composition, mechanical properties, thermal performance and international equivalents.
Hot rolling, controlled rolling, normalizing, TMCP, cutting, bending, welding
- Phone : +8618037372205
- Email : [email protected]
- WhatsApp: Contact via Whtsapp
- WeChat: +8618037372205
NK A40 Shipbuilding Steel Coil Introduction
NK A40 is a high-strength shipbuilding steel grade defined by Nippon Kaiji Kyokai (ClassNK) for hull structures. It belongs to the AH40 family, requiring a minimum yield strength of 390 MPa and Charpy impact testing at 0°C. The coil form is widely used for continuous construction processes. Key features:
- Excellent weldability with controlled carbon equivalent
- High toughness at low temperatures for safe marine operations
- Good cold-forming capabilities
- Uniform mechanical properties across thicknesses
This grade is typically supplied in normalized or thermo-mechanically controlled processed (TMCP) condition, suitable for building container ships, bulk carriers, tankers and offshore platforms.
NK A40 Shipbuilding Steel Coil Chemical Composition
The chemical composition of NK A40 is strictly regulated to balance strength, toughness and weldability. Microalloying elements like Nb, V, Ti may be added singly or in combination to achieve grain refinement. Note: The values below are maximum unless a range is specified, in accordance with ClassNK Rules Part K, Chapter 3, Table K3.2.1 for product thickness ≤ 100 mm.
| Element | Standard Value | Remarks |
|---|---|---|
| C | ≤ 0.18 | Carbon equivalent Ceq ≤ 0.38% (optional) |
| Mn | 0.90 – 1.60 | Higher Mn improves strength and toughness |
| Si | ≤ 0.50 | Killed steel practice required |
| P | ≤ 0.035 | |
| S | ≤ 0.035 | |
| Cr | ≤ 0.20 | Residual element, may be added as alloy if agreed |
| Ni | ≤ 0.40 | Residual unless specified |
| Mo | ≤ 0.08 | Residual unless specified |
| Cu | ≤ 0.35 | Residual unless specified |
| Al (acid-soluble) | ≥ 0.015 | Grain refinement |
| Nb | 0.02 – 0.05 | Single or combined with V or Ti |
| V | 0.05 – 0.10 | Combined microalloying permitted |
| Ti | 0.007 – 0.05 | Controlled for HAZ toughness |
NK A40 Shipbuilding Steel Coil Thermal and Electrical Physical Properties
The physical properties listed below are typical for low-alloyed high-strength shipbuilding steels like NK A40. Actual values may vary slightly with processing route. These data are not part of the classification rule requirements but are essential for design and fabrication calculations such as heat transfer, thermal stress and corrosion prevention.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7850 | kg/m³ | Room temperature |
| Elastic modulus (E) | 205 | GPa | Room temperature |
| Shear modulus (G) | 80 | GPa | Calculated from E and ν |
| Poisson's ratio (ν) | 0.30 | – | Room temperature |
| Thermal expansion coefficient (α) | 12.0 | 10⁻⁶/K | 20 – 100°C |
| Thermal expansion coefficient (α) | 12.5 | 10⁻⁶/K | 20 – 200°C |
| Thermal expansion coefficient (α) | 13.2 | 10⁻⁶/K | 20 – 400°C |
| Thermal conductivity (λ) | 50 | W/(m·K) | 100°C |
| Thermal conductivity (λ) | 47 | W/(m·K) | 200°C |
| Specific heat capacity (cₚ) | 460 | J/(kg·K) | Ambient temperature |
| Electrical resistivity (ρₑ) | 0.20 | µΩ·m | Ambient temperature |
NK A40 Shipbuilding Steel Coil Mechanical Properties
Mechanical properties are verified on test specimens oriented transversely to the rolling direction unless otherwise agreed. The following values are the minimum requirements per ClassNK Rules for thicknesses up to 50 mm (for elongation) and 100 mm (for strength). Impact test temperature for A40 class: 0°C, with absorbed energy requirements dependent on specimen size.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield strength (ReH) | ≥ 390 | MPa | Ambient temperature |
| Tensile strength (Rm) | 510 – 650 | MPa | Ambient temperature |
| Elongation (A) | ≥ 20 | % | Gauge length 5.65√S₀, t ≤ 50 mm |
| Charpy impact energy (KV) (longitudinal) | ≥ 31 | J | 0°C, standard specimen |
| Charpy impact energy (KV) (transverse) | ≥ 24 | J | 0°C, standard specimen |
| Bend test (180°) | No cracks | – | Bend diameter 2t (t ≤ 25 mm), 3t (t > 25 mm) |
| Through-thickness reduction of area (optional) | Class Z25: avg ≥ 25, single ≥ 15 | % | If agreed, per ClassNK |
NK A40 Shipbuilding Steel Coil Completely Equivalent Material Standards and Alternative Designations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International (IACS) | IACS UR W11 | AH40 | Common IACS hull steel specification |
| USA | ASTM A131 / ABS | AH40 | American Bureau of Shipping equivalent |
| France | BV Rules | AH40 | Bureau Veritas equivalent |
| China | CCS Rules | AH40 (CCS A40) | China Classification Society |
| Norway/Germany | DNV Rules | AH40 (NV A40) | Det Norske Veritas equivalent |
| UK | LR Rules | AH40 (LR AH40) | Lloyd's Register equivalent |
| South Korea | KR Rules | AH40 | Korean Register equivalent |
| Italy | RINA Rules | AH40 | Registro Italiano Navale equivalent |
| Japan (JIS) | JIS G 3106 | SM490YA/SM490YB heat treated for 390 MPa yield, but not identical; refer to classification society grade | Chemical and property overlap exists |
NK A40 Shipbuilding Steel Coil Application Introduction
NK A40 steel coil is engineered for critical marine structures where high strength-to-weight ratio and dependable notch toughness are essential. It is typically used in shipbuilding yards for automated panel lines and continuous welding. Processing considerations:
- Preheat is rarely needed for thicknesses up to 50 mm due to controlled carbon equivalent
- Post-weld heat treatment (PWHT) is generally not required unless specified for thick sections
- Excellent formability allows cold bending of stiffeners and frames
- Compatible with all conventional shipyard welding processes
Product Applications: Container ships, Bulk carriers, Oil tankers, LNG / LPG carriers, Roll-on/roll-off passenger (RoPax) vessels, Semi-submersible drilling rigs, Jack-up rig legs, Floating production storage and offloading (FPSO) units
Processed into products: Main deck plating, Bottom shell plating and keel, Side shell strakes, Transverse watertight bulkheads, Longitudinal girders and stringers, Hatch coaming stiffeners, Web frames and bracket plates, Crane pedestal reinforcements, Rudder horn structures, Steering gear foundations
Application industries: Shipbuilding (commercial, naval), Offshore oil & gas platforms, Marine engineering, Bridge construction (secondary), Pressure vessel (with additional certification), Wind turbine support structures (offshore)
NK A40 Shipbuilding Steel Coil Similar / Alternative Materials with Slightly Different Properties
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| ClassNK | NK Rules | AH36 | Lower yield strength (min 355 MPa), otherwise similar composition and toughness at 0°C |
| ClassNK | NK Rules | DH40 | Same strength, impact test at -20°C instead of 0°C |
| ClassNK | NK Rules | EH40 | Same strength, impact test at -40°C, used for severe cold service |
| ClassNK | NK Rules | FH40 | Same strength, impact test at -60°C, high-cost premium grade |
| ClassNK | NK Rules | A40 (KA40) | Older designation, essentially same as AH40 |
| EN | EN 10025-4 | S420MLO / S420G1+QT (offshore structural steel) | Similar yield strength but different testing regime, not identical |
Notes:
Important notice: The data given are based on ClassNK Rules for the Survey and Construction of Steel Ships, Part K, Materials, Chapter 3. Actual supplied coil may have tighter internal mill specifications to meet total quality requirements. When ordering, it is essential to specify the exact product thickness, width, edge condition (mill or slit) and surface finish. For welded structures requiring through-thickness ductility, additional Z-testing according to ClassNK Z25, Z35 can be specified.
Tolerances: Thickness, width, and flatness tolerances follow JIS G 3193 unless otherwise agreed. Marking: Steel coils must be marked with the manufacturer's name, NK stamp, heat number, and grade.
- Share
