NK D51 Shipbuilding Steel Coil
NK D51 Shipbuilding Steel Coil - High Strength Marine Steel Properties
Detailed material data of NK D51 shipbuilding steel coil: chemical composition, mechanical properties, physical properties, international cross-reference equivalents, and application guide.
Hot Rolling, Controlled Rolling (CR), Normalizing (N), Thermomechanical Control Processing (TMCP)
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NK D51 Shipbuilding Steel Coil Introduction
NK D51 is a high-strength shipbuilding structural steel grade specified by ClassNK (Nippon Kaiji Kyokai) under its Rules for the Survey and Construction of Steel Ships. D denotes the toughness category, indicating an impact test temperature of -20 °C, while 51 refers to the minimum tensile strength of 510 MPa.
- Weldable fine-grain structural steel with excellent notch toughness at sub-zero temperatures.
- Controlled carbon equivalent (< 0.40%) ensures good weldability without preheating for moderate thicknesses.
- Supplied as hot-rolled coil, typically in controlled rolled, normalized or TMCP condition.
- Fulfills the requirements of major classification societies, making it widely accepted in global shipbuilding projects.
Typical applications include primary hull structures, decks, side shells, and offshore platforms.
NK D51 Shipbuilding Steel Coil Chemical Composition
The chemical composition is specified according to NK Rules Part K, Table K3.1.1-2 for high strength hull structural steel. Typical limits are given below; additional microalloying elements such as Nb, V, Ti may be added to achieve the required strength and toughness. Carbon equivalent (Ceq) shall be ≤ 0.40% for thicknesses up to 50 mm.
| Element | Standard Value | Remarks |
|---|---|---|
| C | ≤ 0.18% | Ladle analysis maximum |
| Mn | 0.90 – 1.60% | Higher Mn for increased strength |
| Si | ≤ 0.50% | Deoxidation element |
| P | ≤ 0.035% | Maximum allowed |
| S | ≤ 0.035% | Maximum allowed |
| Cr | ≤ 0.20% | Residual element |
| Ni | ≤ 0.40% | Residual element |
| Cu | ≤ 0.35% | Residual element |
| Mo | ≤ 0.08% | Residual element |
| V | ≤ 0.10% | Microalloy if added |
| Nb | ≤ 0.05% | Microalloy if added |
| Ti | ≤ 0.02% | Microalloy if added |
| Al (total) | ≥ 0.015% | Grain refining, if required |
| N | ≤ 0.012% | Maximum |
| Ceq | ≤ 0.40% | C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 |
NK D51 Shipbuilding Steel Coil Thermal & Electrical Physical Properties
Physical property values are representative of normalized or hot-rolled C-Mn steel similar to NK D51. Actual values may vary with manufacturing process and exact chemical composition; these data provide reliable engineering estimates for design calculations.
| Property | Typical Value | Unit | Condition / Notes |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Modulus of Elasticity (E) | 210 | GPa | Room temperature |
| Shear Modulus (G) | approx. 80 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.3 | - | Room temperature |
| Thermal Expansion Coefficient (α) | 11.8 × 10⁻⁶ | /K | 20 – 100 °C |
| Thermal Conductivity (λ) | approx. 50 | W/(m·K) | At 20 °C |
| Specific Heat Capacity (cₚ) | approx. 460 | J/(kg·K) | At 20 – 100 °C |
| Electrical Resistivity (ρₑ) | 0.20 – 0.25 | µΩ·m | At 20 °C |
NK D51 Shipbuilding Steel Coil Mechanical Properties
Mechanical properties are extracted from NK Rules for D51 grade with thickness ≤ 50 mm. Tensile testing is carried out transverse to the rolling direction. Impact testing uses Charpy V-notch specimens taken longitudinally. Bending test is with 180° angle and specified inside diameter, without cracks.
| Property | Specified Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 355 | MPa | Thickness ≤ 50 mm, room temperature |
| Tensile Strength (Rm) | 510 – 600 | MPa | Thickness ≤ 50 mm, room temperature |
| Elongation (A5) | ≥ 21 | % | Gauge length 5.65√S₀, thickness ≤ 50 mm |
| Bend Test (Diameter = 3t, 180°) | No cracks | - | t = specimen thickness |
| Charpy Impact KV₂ (-20 °C) | ≥ 27 (longitudinal) | J | Standard 10x10 mm V-notch specimen at -20 °C |
NK D51 Shipbuilding Steel Coil Fully Equivalent Material Standards & Replaceable Grades
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| International (IACS) | UR W11 | HT51 | Common high-strength standard; adopted by most classification societies |
| USA | ABS Rules | D51 (ABS D51) | ABS D51 matches the same strength and toughness level |
| United Kingdom | LR Rules | DH51 | Lloyd's Register DH51 - identical properties |
| France | BV Rules | DH51 | Bureau Veritas DH51 |
| Norway | DNV GL Rules | NV D510 | DNV D510 with similar tensile and impact requirements |
| China | CCS Rules | D51 | China Classification Society D51 |
| Korea | KR Rules | RD51 | Korean Register RD51 (equivalent high strength ship steel) |
| Italy | RINA Rules | ADH51 | RINA Grade ADH51 |
NK D51 Shipbuilding Steel Coil Application Introduction
NK D51 steel coil is designed for ships and marine structures where high strength combined with good low-temperature toughness is essential.
Typical processing: cutting, cold forming, bending, welding (SAW, SMAW, GMAW with low hydrogen consumables).
Industries:
Product Applications: Hull main plates, Deck plating, Side shell plates, Bottom plates, Offshore platform jackets and decks
Processed into products: Longitudinal stiffeners, Transverse frames, Bulkheads, Stringers, Web frames, Hatch coamings, Rudder horns, Sea fastening supports
Application industries: Shipbuilding, Offshore Oil & Gas Platforms, Marine Engineering, Heavy Structural Fabrication
NK D51 Shipbuilding Steel Coil Similar / Alternative Material Recommendations
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3106 | SM490YA / SM490YB | Tensile 490–610 MPa, similar to D51; check toughness requirement |
| Japan | JIS G3106 | SM520B / SM520C | Higher tensile 520–640 MPa; may substitute for D51 with adjusted design |
| EU | EN 10025-2 | S355J2+N / S355K2+N | 355 MPa yield, J2 has -20 °C impact; tensile 470–630 MPa |
| EU | EN 10025-3 | S355N/NL | Normalized fine-grain steel with improved toughness |
| China | GB/T 712 | DH36 | Yield ≥355 MPa, tensile 490–630 MPa; D51 is a tighter version of DH36 |
| China | GB/T 712 | DH40 | Higher yield (≥390 MPa) and higher tensile; may exceed D51 requirements |
| USA | ASTM A572 | Grade 50 (345 MPa) / Grade 55 | Structural steel; similar strength but may need additional toughness guarantee |
Notes:
D51 coil can be ordered with additional requirements such as Z-quality (through-thickness tensile properties), extra impact test temperatures (e.g., -40 °C or -60 °C as per E or F categories), or special surface finish. Tolerance on thickness and flatness shall be as per NK Rules or agreed standard EN 10029. The steel is suitable for painting, shot blasting, and welding with appropriate preheat depending on thickness and hydrogen control.
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