ABS steel plate means plate steel produced to the rules of the American Bureau of Shipping, one of the classification societies that set the material, welding and inspection requirements for ships, offshore units and marine structures. A plate carrying an ABS material grade is not a single steel: it is a steel that has been made, tested and marked under an approved mill scheme, so the classification society accepts it as suitable for a defined part of a hull or a marine structure.
Where the Rules Come From
The ABS Rules for Materials and Welding, Part 2, define the normal and higher strength hull structural steels, their chemical limits, their mechanical properties, the required tests and the marking. For normal strength plate the rule align with the widely used hull structural series also published as ASTM A131, while higher strength grades are identified by the letter A, D, E or F followed by the strength level 32, 36 or 40. The letter encodes the impact test temperature: A is tested at 20 °C, D at -20 °C, E at -40 °C, and F at -60 °C.
Grade Table for Common ABS Hull Plate
| Grade | Min. yield (MPa) | Tensile (MPa) | Charpy test temperature | Typical location |
|---|---|---|---|---|
| A | 235 | 400 - 490 | 20 °C | Internal structure, deck plating, non-critical panels |
| B | 235 | 400 - 490 | 0 °C | Hull plating, general structure |
| D | 235 | 400 - 490 | -20 °C | Shell plating, areas subject to low temperature |
| E | 235 | 400 - 490 | -40 °C | Shell plating, strength deck, exposed structures |
| AH32 / AH36 / AH40 | 315 / 355 / 390 | 440 - 590 / 490 - 620 / 510 - 650 | 0 °C | High stress zones, upper deck, hatch corners |
| DH32 / DH36 / DH40 | 315 / 355 / 390 | 440 - 590 / 490 - 620 / 510 - 650 | -20 °C | Shell and deck in colder service |
| EH32 / EH36 / EH40 | 315 / 355 / 390 | 440 - 590 / 490 - 620 / 510 - 650 | -40 °C | Ice-class, exposed shell and strength deck |
| FH32 / FH36 / FH40 | 315 / 355 / 390 | 440 - 590 / 490 - 620 / 510 - 650 | -60 °C | Severe low temperature service |
Higher strength grades also carry a maximum carbon equivalent that becomes tighter as the strength level rises, because weldability in a shipyard is a production requirement and not an optional property.
Mechanical Behaviour That Matters at Sea
A hull sees a continuous load spectrum: wave bending, slamming, vibration, cargo pressure and thermal cycling from ballast water in cold climates. The grade system answers that with a guaranteed minimum yield strength, a bounded tensile range and a certificated Charpy energy at a fixed test temperature. The impact requirement is the part that distinguishes a marine grade from a general structural plate, because fracture in a welded ship structure almost always initiates at a notch in a region whose toughness has been reduced by welding or by low temperature.
Certification, Testing and Marking
Plate for a classed vessel must come from a mill approved by the society. Each plate is tested and marked with the grade, the heat number, the plate identification and the manufacturer mark, and the class certificate is issued against those tests. Ordinary survey involves the society's surveyor attending the mill or accepting the mill's approved test scheme, and the resulting certificate is the document a shipyard must be able to show during construction and at later surveys. Chemical analysis, tensile and yield tests, elongation, and Charpy impact tests at the specified temperature are the routine elements; ultrasonic examination, through-thickness testing and special notch toughness are ordered when the structure or the class notation requires them.
Practical Guidance for Buyers
The grade alone is not a sufficient order. State the strength level, the impact letter, the thickness, the plate size, whether the plate is to be normalized or thermo-mechanically rolled, and the class notation the material must satisfy. Confirm in advance that the producing mill holds the approval for the intended grade, because not every mill is approved for the higher strength and low temperature combinations. Finally, keep the plate marking intact through cutting and forming, since the link between the finished part and the certificate depends on that marking.
Frequently Asked Questions
Q: What does ABS steel plate mean exactly?
A: It means hull structural steel made to the ABS Rules for Materials and Welding and accepted by the classification society for a defined part of a ship or marine structure. The rules fix the chemistry, the mechanical properties, the testing and the marking.
Q: What is the difference between ABS grade A and ABS grade E?
A: Both are normal strength grades with a 235 MPa minimum yield strength, but grade A is impact tested at 20 °C while grade E is tested at -40 °C. The letter of the grade therefore indicates where the plate may be used.
Q: What do AH36, DH36 and EH36 mean?
A: They are higher strength grades with a 355 MPa minimum yield strength, tested at 0 °C, -20 °C and -40 °C respectively. The strength level is given by the number and the test temperature by the leading letter.
Q: Is ABS grade A the same as ASTM A131 grade A?
A: The normal strength hull grades share a common technical basis, and a plate may be dual certified to both schemes if the mill is approved and the tests are accepted. Always confirm dual certification in writing at the time of order.
Q: Does ABS plate have to come from an approved mill?
A: Yes. Class rules require the material to be produced under an approved manufacturing and testing scheme, and the resulting certificate is what makes the plate acceptable for a classed vessel.
Q: Why is the carbon equivalent limited?
A: It controls weldability and heat-affected zone hardness in yard welding. A lower carbon equivalent means fewer cold cracking risks and less preheat, which matters on a shipbuilding schedule.
