Overview
Higher-strength hull steel designations are controlled by strength family, toughness class, thickness, delivery condition and classification approval. Selecting a higher strength notation does not itself prove weld procedure, fracture performance or suitability for every hull member.
Designation and acceptance
IACS Unified Requirements are minimum classification-society requirements. Grade notation, thickness, delivery condition, test temperature, plate approval and the ship’s class rules must be read together; notation alone does not create an interchangeable material approval.
Members and selection
| Designation | Selection context |
|---|---|
| FH36 | Higher-strength notation requiring project-specific toughness, thickness and delivery-condition confirmation. |
| DH40 | Higher-strength notation; verify the approved strength/toughness combination instead of comparing only the number. |
| EH40 | Higher-strength notation that needs class-approved product, testing and fabrication controls. |
Comparison framework
| Criterion | Decision context |
|---|---|
| Selection basis | Higher-strength groups need deliberate welding and fracture-control review, particularly as thickness and structural consequence increase. |
Performance
- Toughness class, thickness, delivery condition and approved testing must match the approved hull-member rule. Do not rank letter suffixes as a universal good-better-best scale.
Orderable product scope
- Shipbuilding plate, wide flat and sections must be quoted with class approval, grade notation, thickness, delivery condition, inspection and material certificates.
Processing
- Control welding procedure qualification, heat input, consumables, repair, NDT timing and identification through cutting and assembly in accordance with the approved shipyard and class requirements.
Applications
- Hull structural members and marine structures where the design, classification and fabrication documents approve the ordered steel.
Selection
- Start with the vessel type, hull-member location, design temperature, thickness and class rule, then choose the approved grade and delivery condition. Grade labels must not replace the class-approved material schedule.
Procurement
- State class society, rule edition, approved mill, grade notation, product form, thickness, delivery condition, impact-test requirement, Z-quality if ordered, certificates, marking, quantities, destination and inspection plan.