Grade B vs Grade D steel plate
Both are 235 MPa normal-strength hull structural grades with identical tensile range and elongation — the difference is the impact-test temperature: Grade B is tested at 0°C, Grade D at −20°C, one step colder than Grade A which isn't impact-tested at normal thickness.
Spec comparison
| Property | B | D |
|---|---|---|
| Min. yield ReH | 235 MPa | 235 MPa |
| Tensile Rm | 400–520 MPa | 400–520 MPa |
| Elongation A5 | 22% | 22% |
| Impact test temp. | 0 °C | -20 °C |
| Availability | Core stock | Made to order |
How to choose
Grade B is the mill's core stock item in this family and the default choice where the structural drawing doesn't call for low-temperature toughness. Grade D is rolled to order and specified where the classification society's rule requires the −20°C rating, typically driven by plate thickness or the vessel's intended service area. Ordering Grade D adds the mill's rolled-to-order lead time compared with ex-stock Grade B, so confirm which the drawing specifies before quoting a delivery date.
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