AH36 steel plate, DH36 steel plate and EH36 steel plate are higher-strength hull structural steels used for load-bearing structures in ships, offshore platforms and marine construction projects. These shipbuilding steel plates belong to the Grade 36 strength level, with a specified minimum yield strength of approximately 355 MPa. Their basic strength level is similar, while the AH, DH and EH designations define different low-temperature Charpy V-notch impact toughness requirements.
In practical fabrication, these plates are commonly used for ship hulls, bulkheads, upper decks and hatch covers, and they are widely applied in the construction of tankers, bulk carriers, container ships, LNG carriers and other marine structures. AH36 shipbuilding steel plate is commonly selected where general higher-strength hull performance is required, while DH36 steel plate and EH36 steel plate are used when lower design temperatures or stricter toughness requirements must be satisfied.
OCTAL Metals supplies AH36 DH36 EH36 steel plate for shipbuilding and offshore structural applications, with dimensions, delivery condition, processing and certification coordinated according to the purchase specification and project service conditions.
AH36, DH36 and EH36 Grades, Standards and Supply Range
ASTM A131/A131M covers structural steel products intended primarily for ship construction and includes ordinary- and higher-strength steel grades. ASTM A131 AH36 steel plate, together with DH36 and EH36, belongs to the higher-strength hull structural steel group.
| Supply Item | Available / Reference Range |
|---|---|
| Grades | AH36, DH36, EH36 |
| Main Specification | ASTM A131/A131M |
| Product Form | Shipbuilding steel plate |
| Strength Level | 355 MPa minimum yield class |
| Thickness | 5–150 mm |
| Width | 1500–3900 mm |
| Standard Lengths | 6 m, 12 m |
| Surface Condition | As specified for the order |
| Surface Protection | Anti-rust protection when required |
| Processing | Cutting and project-specified plate processing |
| Certification | According to project and classification requirements |
The listed dimensional range represents the general supply scope. Final availability depends on the selected grade, thickness, delivery condition and certification requirement. In particular, thicker marine steel plate may require different production routes and impact-test requirements from standard thickness material.
Shipbuilding Steel Grade Family
Shipbuilding structural steel includes ordinary-strength grades such as A, B, D and E, together with higher-strength AH, DH, EH and FH grade families. Higher-strength grades are further classified by strength level, including the 32, 36 and 40 series. AH36, DH36 and EH36 belong to the Grade 36 series, combining the same nominal strength level with different specified impact-toughness requirements.
| Grade Family | Representative Grades | Main Classification Basis |
|---|---|---|
| Ordinary Strength | A, B, D, E | 235 MPa class with grade-specific toughness requirements |
| Grade 32 | AH32, DH32, EH32 | Higher-strength 315 MPa class |
| Grade 36 | AH36, DH36, EH36 | Higher-strength 350/355 MPa class |
| Grade 40 | AH40, DH40, EH40 | Higher-strength 390 MPa class |
AH36 vs DH36 vs EH36: Impact Toughness and Grade Selection
AH36, DH36 and EH36 are sometimes incorrectly treated as progressively stronger grades. In fact, all three belong to the same Grade 36 shipbuilding steel strength level. Their main selection difference is the required Charpy V-notch impact toughness at different test temperatures. Current Grade 36 technical data uses a minimum specified yield strength of 51 ksi, approximately 355 MPa, for all three grades.
| Grade | Strength Level | Reference Charpy Test Temperature | Main Grade-Selection Basis |
|---|---|---|---|
| AH36 | 355 MPa class | 0°C | General higher-strength hull structures |
| DH36 | 355 MPa class | −20°C | Increased low-temperature toughness requirement |
| EH36 | 355 MPa class | −40°C | More demanding low-temperature toughness requirement |
Therefore, AH36 vs DH36 vs EH36 is primarily a toughness-selection question rather than a simple strength comparison. AH36 impact temperature requirements are less severe than those for DH36, while the EH36 impact temperature establishes the lowest test temperature of the three.
The Charpy test temperature should not be treated automatically as the minimum operating temperature of the finished vessel. Actual material selection also depends on structural category, plate thickness, design temperature, loading condition and the applicable ship classification rules.
Mechanical Properties, Chemical Composition and Impact Requirements
The performance of high strength shipbuilding steel depends on both strength and notch toughness. Controlled carbon, phosphorus and sulfur levels support weldability and toughness, while manganese, silicon, aluminum and, where applicable, microalloying additions contribute to the required steelmaking and grain-control practice.
Chemical Composition of AH36, DH36 and EH36
| Element (%) | AH36 | DH36 | EH36 |
|---|---|---|---|
| Carbon, Max | 0.18 | 0.18 | 0.18 |
| Manganese | 0.70–1.60 | 0.90–1.60 | 0.90–1.60 |
| Silicon | 0.10–0.50 | 0.10–0.50 | 0.10–0.50 |
| Phosphorus, Max | 0.040 | 0.040 | 0.040 |
| Sulfur, Max | 0.040 | 0.040 | 0.040 |
| Aluminum, Min | 0.015 | 0.015 | 0.015 |
Carbon control is particularly important because increasing carbon can improve strength but may reduce weldability and low-temperature toughness. For this reason, the chemical analysis, plate thickness and welding procedure should be evaluated together rather than using carbon content as an isolated acceptance criterion.
Mechanical and Impact Properties
The AH36 mechanical properties, DH36 mechanical properties and EH36 mechanical properties are similar in strength. The principal difference appears in the specified impact-test temperature.
For plates up to approximately 50 mm, the commonly referenced Grade 36 values are:
| Grade | Yield Strength, Min | Tensile Strength | Elongation, Min | Charpy Test Temperature | Longitudinal Average Energy | Transverse Average Energy |
|---|---|---|---|---|---|---|
| AH36 | 355 MPa | 490–620 MPa | 22% | 0°C | 34 J | 24 J |
| DH36 | 355 MPa | 490–620 MPa | 22% | −20°C | 34 J | 24 J |
| EH36 | 355 MPa | 490–620 MPa | 22% | −40°C | 34 J | 24 J |
The 355 MPa yield strength and approximately 490–620 MPa tensile strength define the common Grade 36 strength basis. By contrast, the Charpy V-notch impact test differentiates the low-temperature toughness level. For thicker plates, required impact energy and other mechanical-property conditions may change, so acceptance must follow the ordered thickness and governing specification. Current Grade 36 product data, for example, specifies higher minimum impact energy for thicker EH36 plate.
Delivery Condition and Welding of AH36, DH36 and EH36 Steel Plate
AH36, DH36 and EH36 steel plates achieve the required Grade 36 strength and impact toughness through controlled steel chemistry, grain refinement and an approved rolling or heat-treatment route. Depending on grade, plate thickness and project requirements, the material may be supplied in normalized or thermo-mechanically controlled conditions. The delivery condition is therefore confirmed together with the plate grade, thickness and applicable shipbuilding specification.
For AH36, DH36 and EH36 welding, procedure control is important because excessive or unsuitable heat input can affect the heat-affected zone and its toughness. Preheat and interpass temperature are determined from plate thickness, carbon equivalent, joint restraint, hydrogen control and the qualified welding procedure rather than from the AH36, DH36 or EH36 designation alone. Where low-temperature toughness is required, the welding procedure must also maintain the specified impact performance of the welded joint.
Applications of AH36, DH36 and EH36 Shipbuilding Steel Plate
Hull and Deck Structures
AH36, DH36 and EH36 are used as ship hull steel plate for side shell, bottom structures, decks and other primary load-bearing areas. Their 355 MPa strength class allows structural designers to use higher-strength steel where the hull design requires greater load capacity or controlled structural weight. Final grade selection depends on the required toughness category as well as strength.
Bulkheads and Internal Structural Members
These grades are also used for watertight bulkheads, longitudinal and transverse structural members, stiffened panels and other internal hull structural steel components. Structural location, plate thickness and specified impact category determine whether AH36, DH36 or EH36 is required.
Offshore and Marine Structures
Grade 36 offshore structural steel plate is used in selected structural parts of offshore units and marine structures where strength, weldability and notch toughness must be considered together. Typical applications for AH36/DH36/EH36 include shipbuilding and mobile offshore drilling units and structures.
Low-Temperature Structural Areas
Where the structure requires greater impact toughness at reduced temperature, DH36 or EH36 may be specified instead of AH36. The choice is based on the applicable structural category and toughness requirement; EH36 is not simply a “stronger AH36,” but a Grade 36 material qualified to a more demanding impact-test temperature.
Inspection, Certification and Ordering Requirements
Shipbuilding plate requires tighter coordination between material grade and project documentation than ordinary structural plate. The delivered material should be traceable to its heat identification and corresponding test documents. Chemical analysis, tensile properties and Charpy impact results are therefore key parts of material verification.
Classification Society Requirements
Shipbuilding projects may require material approval and certification according to the rules of a specified classification society. Common project requirements may reference ABS, BV, CCS, DNV, LR, KR, ClassNK, RINA or other recognized classification societies. The applicable society, steel grade, plate thickness, impact-testing requirement and certificate type should be confirmed in the purchase specification before production.
| Ordering Input | Information to Provide |
|---|---|
| Steel Grade | AH36 / DH36 / EH36 |
| Standard | ASTM A131/A131M or project specification |
| Classification Requirement | Specified classification society and rule |
| Plate Thickness | Required thickness |
| Width × Length | Finished plate dimensions |
| Impact Requirement | Grade and project toughness requirement |
| Delivery Condition | Normalized, TMCP or specified condition |
| Processing | Cutting, beveling or other processing |
| Surface Requirement | As-rolled or specified surface protection |
| Certification | MTC, class certificate and additional inspection requirements |
| Quantity | Pieces or total tonnage |
OCTAL Metals supplies AH36, DH36 and EH36 marine steel plate with project-specified dimensions, processing and documentation. Classification and certification requirements are confirmed according to the vessel or offshore project rather than assumed from the steel grade alone.
FAQ
Q: Can DH36 or EH36 steel plate automatically replace AH36?
A: No. AH36, DH36 and EH36 share the same 355 MPa strength class, but they have different toughness requirements. Any grade substitution should also match the project specification, plate thickness, delivery condition and classification approval requirements.
Q: Does the −40°C Charpy test for EH36 define its minimum service temperature?
A: No. −40°C is the specified Charpy V-notch impact-test temperature for EH36, not a universal minimum operating temperature for the vessel. Material selection must also consider plate thickness, structural location, design conditions and applicable class rules.
Q: Why must plate thickness be specified when ordering AH36, DH36 or EH36?
A: Thickness can affect available dimensions, impact-energy requirements and the applicable delivery or testing condition. For example, published EH36 data shows higher minimum Charpy energy requirements as plate thickness increases above about 50 mm.
Q: Is ASTM A131 compliance the same as ABS certification?
A: No. ASTM A131/A131M defines material requirements for structural steel used in ship construction, while ABS certification confirms compliance with applicable classification requirements. When ABS or another class is required, it should be stated separately in the purchase specification.