A131 low-temperature resistant marine steel plates

The embrittlement of steel at low temperatures does not occur gradually. As a material with a body-centered cubic (BCC) crystal structure, hull steel undergoes a ductile-to-brittle transition: once the temperature drops into a specific range, its impact energy (toughness) plummets. The "low-temperature resistance" of A131 steel essentially means that the entire transition curve is shifted to a temperature range below the design temperature; the distinction between Grade D and Grade E lies in the specific positioning of these curves.

While the Charpy V-notch impact test captures only a single point on this curve, the Nil-Ductility Transition (NDT) temperature—determined via the drop-weight test—serves as the primary benchmark for assessing the risk of brittle fracture. Certain projects involving polar or ice-covered regions may require both tests. The most hazardous operating conditions involve a combination of low temperatures and dynamic loading—such as the collisions and crushing forces encountered in icy waters during winter—which can push the material into the brittle regime. This explains why ice-class vessels are subject to stricter steel-grade temperature requirements than ships operating on conventional routes.

BBN Steel supplies A131 steel in low-temperature resistant grades, including D, E, DH36, and EH36. We can provide Charpy impact and drop-weight testing tailored to your specific design temperature. When requesting a quote, please specify the design temperature, plate thickness, and whether drop-weight test data is required; this will ensure an accurate and comprehensive quotation from the outset.