Shipbuilding steel plate is regulated by multiple classification society standards and international specifications. For buyers sourcing marine-grade steel, understanding the equivalencies and differences between ASTM A131, ABS (American Bureau of Shipping), and DNV (Det Norske Veritas) standards is essential to ensure compliance with vessel design requirements. This article provides a practical cross-reference guide.
ASTM A131 / A131M is the primary American standard covering structural steel plates for ship construction. It defines two strength levels:
Plate thickness ranges from 6 mm to 150 mm under this standard. Chemical composition limits are set for carbon, manganese, phosphorus, sulfur, silicon, and residual elements. Carbon equivalent (CEV) is calculated to control weldability.
The American Bureau of Shipping publishes its own Rules for Materials and Welding, which reference many ASTM A131 grades but add additional requirements for vessels classed by ABS. ABS Grade A, B, D, and E correspond directly to the ASTM A131 ordinary-strength equivalents. ABS AH36, DH36, and EH36 correspond to the higher-strength grades.
Key differences under ABS: all material used on ABS-classed vessels must come from ABS-approved mills and carry ABS surveyor endorsements. Plates above certain thickness thresholds may require through-thickness (Z-direction) tensile testing. ABS also mandates stricter surface quality and lamination inspection compared to baseline ASTM A131 supply to non-classed projects.
For buyers, the practical implication is clear: if the vessel or structure will be ABS-classed, specify ABS-grade plates procured from an ABS-approved supplier and confirm that an ABS surveyor will witness the material testing and stamp the mill certificates.
DNV (now DNV GL, rebranded as DNV) maintains its own shipbuilding steel specification under the DNV rules for classification of ships. DNV ordinary-strength grades (NV A, NV B, NV D, NV E) and higher-strength grades (NV A27, NV D27, NV E27, NV A32, NV D32, NV E32, NV A36, NV D36, NV E36, NV F36) follow similar strength levels to ASTM A131 and ABS.
DNV certification requires mill approval by DNV surveyors and is recognized internationally for vessels flagged under a wide range of registries. DNV-certified plate must carry the DNV stamp and surveyor-signed certificates. Some DNV grades specify tighter tolerances on thickness and flatness compared to ASTM A131, particularly for high-strength grades above 40 mm thickness.
The following table summarizes the most common equivalencies across the three standards:
| Strength Level | ASTM A131 | ABS | DNV | |---|---|---|---| | Ordinary, ambient | Grade A | ABS A | NV A | | Ordinary, -20°C | Grade D | ABS D | NV D | | Ordinary, -40°C | Grade E | ABS E | NV E | | Higher, 315 MPa, ambient | AH32 | ABS AH32 | NV A32 | | Higher, 315 MPa, -20°C | DH32 | ABS DH32 | NV D32 | | Higher, 315 MPa, -40°C | EH32 | ABS EH32 | NV E32 | | Higher, 355 MPa, ambient | AH36 | ABS AH36 | NV A36 | | Higher, 355 MPa, -20°C | DH36 | ABS DH36 | NV D36 | | Higher, 355 MPa, -40°C | EH36 | ABS EH36 | NV E36 | | Higher, 355 MPa, -60°C | FH36 | ABS FH36 | NV F36 |
FH36 / NV F36 (impact tested at -60°C) is specified for Arctic-service vessels and ice-class ships where steel must maintain toughness at extreme low temperatures.
All shipbuilding steel plate must ship with full material certification. Under ASTM A131, EN 10204 3.1 certificates (mill-issued) are the minimum requirement. For classed vessels, EN 10204 3.2 certificates with third-party surveyor endorsement (ABS, DNV, Lloyd's Register, BV, etc.) are mandatory. The certificate documents heat number, chemical composition, tensile properties, impact test results (temperature, absorbed energy, lateral expansion), and the surveyor's stamp.
Buyers should confirm at inquiry stage whether their project requires 3.1 or 3.2 certification, as 3.2-certified material carries a cost premium reflecting surveyor attendance at the mill and during testing.
When procuring shipbuilding plate, verify the mill holds current approval from the relevant classification society. The approval is heat- and thickness-range-specific, so confirm the mill's scope covers your required dimensions. Lead times for classed plate are typically 30–60 days for mill orders, though stock material in AH36 and DH36 is sometimes available from large distributors for immediate shipment.
Jinan Zunkai Materials supplies ASTM A131 and classed shipbuilding steel plate in ordinary-strength and higher-strength grades, including AH36, DH36, and EH36. Plates are available from 6 mm to 120 mm thickness with full classification society certification as required.
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