KR Grade A47 Shipbuilding Steel Plate
KR Grade A47 Shipbuilding Steel Plate – High-Strength Hull Steel for Polar and Severe-Environment Vessels
Complete material data sheet for KR Grade A47 shipbuilding plate: chemical composition, mechanical properties, thermal and electrical characteristics, international equivalents, and typical applications in ice-class vessels and offshore structures.
Hot rolling followed by normalizing (N), thermomechanical controlled processing (TMCP), or quenching and tempering (Q&T) according to thickness and required properties
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KR Grade A47 Shipbuilding Steel Plate Introduction
KR Grade A47 is a high-strength, normalized or thermomechanically rolled shipbuilding structural steel certified by the Korean Register (KR). It belongs to the AH/ DH/ EH family of extra-high-strength hull steels with a minimum yield strength of 460 MPa (47 kgf/mm²). This grade is specifically designed for critical structural components in large container ships, icebreakers, Arctic tankers, and heavy offshore platforms where high load-bearing capacity, excellent weldability, and reliable low-temperature toughness are required.
Key attributes include:
- Minimum yield strength of 460 MPa, enabling weight reduction without sacrificing structural integrity
- Controlled carbon equivalent (Ceq) for superior weldability in thick sections
- Fine-grain microstructure through microalloying (Nb, V, Ti) and advanced rolling practices
- Toughness guaranteed at 0 °C (longitudinal Charpy V-notch impact energy ≥ 34 J) for safe operation in cold waters
- Compliance with KR Rules Pt. 2, Ch. 1 and the latest IACS UR W11 requirements
Plates are typically supplied in thicknesses from 6 mm to 100 mm, in as-rolled, normalized, or TMCP condition depending on thickness and customer specification.
KR Grade A47 Shipbuilding Steel Plate Chemical Composition
The composition limits for KR Grade A47 are defined in the KR Rules and follow the general requirements of IACS UR W11 for high-strength hull steels. The values below are maxima unless a range is indicated. The steel is fully killed and fine-grain treated with aluminium (acid-soluble Al ≥ 0.015 %). Microalloying elements (Nb, V, Ti) may be added singly or in combination to achieve the required strength and toughness. Hydrogen content, nitrogen, and carbon equivalent (Ceq or Pcm) are controlled to ensure weldability; typically Ceq (IIW) ≤ 0.45 % for thicknesses ≤ 50 mm.
| Element | Standard Requirement (wt. %) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.21 | For thickness > 50 mm, C may be limited to 0.20 % by agreement |
| Silicon (Si) | 0.10 – 0.55 | Killed steel, sufficient deoxidation |
| Manganese (Mn) | 1.00 – 1.70 | Higher Mn provides strength without excessive carbon |
| Phosphorus (P) | ≤ 0.030 | Strict control for low-temperature toughness |
| Sulfur (S) | ≤ 0.030 | Low sulfur for cleanliness and through-thickness properties |
| Aluminium (Al, acid soluble) | ≥ 0.015 | Grain refining; total Al typically 0.020–0.050 % |
| Niobium (Nb) | ≤ 0.05 | Grain refinement and precipitation strengthening |
| Vanadium (V) | ≤ 0.10 | Optional microalloy element |
| Titanium (Ti) | ≤ 0.02 | Optional; used for inclusion shape control |
| Copper (Cu) | ≤ 0.35 | Residual allowed; may be specified for corrosion resistance |
| Chromium (Cr) | ≤ 0.20 | Residual element |
| Nickel (Ni) | ≤ 0.40 | Residual; higher Ni can be added for improved toughness |
| Molybdenum (Mo) | ≤ 0.08 | Residual; may be specified in Q&T condition |
| Nitrogen (N) | ≤ 0.012 | Controlled for consistent grain refinement if Ti is added |
KR Grade A47 Shipbuilding Steel Plate Thermal and Electrical Physical Properties
The following physical properties are typical for quenched and tempered or TMCP high-strength steels with similar composition. They are not part of the formal delivery requirements but serve as design data for engineering calculations. Slight variations may occur depending on the exact chemical composition and heat treatment condition.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7850 | kg/m³ | At room temperature (20 °C) |
| Elastic Modulus (E) | 210 | GPa | Room temperature, static |
| Shear Modulus (G) | 81 | GPa | Room temperature, calculated from E and ν |
| Poisson's Ratio (ν) | 0.3 | – | Room temperature, elastic range |
| Thermal Expansion Coefficient (α) | 11.5 × 10⁻⁶ | K⁻¹ | Temperature range 20–100 °C |
| Thermal Expansion Coefficient (α) | 12.2 × 10⁻⁶ | K⁻¹ | Temperature range 20–200 °C |
| Thermal Expansion Coefficient (α) | 13.0 × 10⁻⁶ | K⁻¹ | Temperature range 20–400 °C |
| Thermal Conductivity (λ) | 42 | W/(m·K) | At 20 °C |
| Thermal Conductivity (λ) | 38 | W/(m·K) | At 200 °C |
| Thermal Conductivity (λ) | 34 | W/(m·K) | At 400 °C |
| Specific Heat Capacity (cp) | 460 | J/(kg·K) | At 20–100 °C |
| Specific Heat Capacity (cp) | 520 | J/(kg·K) | At 200 °C |
| Specific Heat Capacity (cp) | 600 | J/(kg·K) | At 400 °C |
| Electrical Resistivity (ρe) | 0.16 × 10⁻⁶ | Ω·m | At 20 °C |
KR Grade A47 Shipbuilding Steel Plate Mechanical Properties
The mechanical properties are determined on specimens taken transverse to the rolling direction unless otherwise specified. Yield strength (ReH) and tensile strength (Rm) vary with plate thickness. The elongation (A) is measured on a gauge length of 5.65√So (A5). Charpy V-notch impact energy (KV) is specified for longitudinal specimens at 0 °C (grade A). Bending test is carried out with a 180° bend around a mandrel diameter specified relative to the plate thickness. All values meet or exceed IACS UR W11 requirements.
| Property | Specified Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 460 | MPa | Thickness ≤ 50 mm, transverse |
| Yield Strength (ReH) | ≥ 440 | MPa | Thickness 50–70 mm, transverse |
| Yield Strength (ReH) | ≥ 420 | MPa | Thickness 70–85 mm, transverse |
| Yield Strength (ReH) | ≥ 400 | MPa | Thickness 85–100 mm, transverse |
| Tensile Strength (Rm) | 570 – 720 | MPa | All thicknesses, transverse |
| Elongation (A5) | ≥ 17 | % | Thickness ≤ 50 mm, transverse |
| Elongation (A5) | ≥ 16 | % | Thickness 50–70 mm, transverse |
| Elongation (A5) | ≥ 16 | % | Thickness 70–85 mm, transverse |
| Elongation (A5) | ≥ 16 | % | Thickness 85–100 mm, transverse |
| Charpy Impact Energy (KV) at 0 °C | ≥ 34 (average), ≥ 24 (single) | J | Longitudinal, V-notch, thickness ≤ 50 mm |
| Charpy Impact Energy (KV) at 0 °C | ≥ 34 (average), ≥ 24 (single) | J | Longitudinal, V-notch, thickness 50–70 mm (by agreement) |
| Charpy Impact Energy (KV) at 0 °C | ≥ 34 (average), ≥ 24 (single) | J | Longitudinal, V-notch, thickness 70–85 mm (by agreement) |
| Bend Test (180°) | No cracks or defects | – | Mandrel diameter = 3t (t = specimen thickness), flat specimen |
KR Grade A47 Shipbuilding Steel Plate Fully Equivalent Material Standards and Replaceable Grades
The KR Grade A47 is a ship classification society grade. Equivalent grades are found under the parallel rules of other major classification societies that adopt IACS UR W11. These grades are fully interchangeable as they share identical chemical and mechanical requirements for the same thickness ranges.
| Country / Region | Standard / Classification Society | Grade Designation | Remarks |
|---|---|---|---|
| International | American Bureau of Shipping (ABS) | ABS AH47 | Identical strength and toughness class |
| International | DNV (Norway/Germany) | DNV AH47 | Same as NV A47 under old DNV notation |
| International | Lloyd's Register (UK) | LR AH47 | Fully equivalent IACS UR W11 grade |
| International | Bureau Veritas (France) | BV AH47 | Fully equivalent |
| International | China Classification Society (CCS) | CCS AH47 | Same requirements |
| International | ClassNK (Japan) | NK AH47 | Fully equivalent under IACS unified requirements |
| International | Russian Maritime Register (RS) | RS AH47 | Recognized as equivalent |
| International | RINA (Italy) | RINA AH47 | Equivalent for high-strength ship plate |
KR Grade A47 Shipbuilding Steel Plate Application Introduction
KR Grade A47 is engineered for the most demanding structural roles in shipbuilding and marine construction. Its high strength-to-weight ratio allows designers to reduce scantlings while maintaining safety margins, and its controlled toughness makes it suitable for service in cold climates and ice-infested waters. Common applications include:
Product Applications: Arctic and polar class ships (icebreakers, research vessels), Ice-capable LNG carriers and oil tankers, Large container ships (upper deck, hatch coamings, and sheer strakes), Semi-submersible platforms and jack-up rigs (column structures, bracings), Heavy-lift vessels and crane barges, Naval auxiliaries and patrol boats requiring high strength
Processed into products: Shell plates in ice belts and forward collision zones, Longitudinal stiffeners and main deck framing, Bottom and side plates in high bending moment regions, Web frames and deep girders of double hulls, Reinforced brackets and transition joints, Offshore platform leg chords and rack plates, Turret and mooring structural components
Application industries: Shipbuilding (commercial and naval), Offshore oil & gas exploration and production, Renewable offshore (wind turbine foundations and substations), Heavy civil and bridge engineering (in specialized cases)
KR Grade A47 Shipbuilding Steel Plate Similar or Closely Related Substitute Materials
Where ship classification society certification is not mandatory, these grades offer comparable strength and toughness and can be considered for structural engineering applications. Always verify weldability and thickness-dependent properties when substituting.
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-6 | S460Q / S460QL / S460QL1 | Quenched and tempered structural steel with min. 460 MPa yield; similar mechanical range; check toughness temperature class for parity with AH47 (Q, QL offer –20°C or –40°C options) |
| Europe | EN 10225 | S460G2+M | Weldable structural steel for offshore structures; TMCP delivery; similar strength and good through-thickness properties |
| USA | ASTM A514 | Grade Q | Quenched and tempered high-strength plate; min. 690 MPa tensile, strength overmatching AH47 but often substituted in heavy machinery; may require evaluation of toughness |
| USA | ASTM A709 | Grade HPS 70W | High-performance structural steel with 485 MPa yield minimum; improved weathering resistance; not a direct substitute for ship plates but used in similar environments |
| Japan / International | JIS G 3106 | SM570 (SM570W) | Rolled steel for welded structures with min. 570 MPa tensile; not directly a ship plate but shares comparable chemistry for high-strength applications |
| China | GB/T 712 | AH47 (CCS certified) | Harmonized with IACS; essentially the same as KR AH47 |
Notes:
Material certification must include mill test reports showing ladle chemistry and mechanical test results for each plate or heat, as per KR surveyor requirements. For plates ordered with enhanced through-thickness properties (Z-quality), Z15, Z25, or Z35 ductility classes can be specified according to the customer's needs. Welding consumables and procedures must be qualified to match the base metal properties; preheating and interpass temperature control are recommended for thick sections to avoid hydrogen-induced cracking.
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