S355 steel plate refers to a high-strength low-alloy (HSLA) structural steel plate that conforms to the European standard EN 10025. This standard specifies the technical delivery conditions for non-alloy structural steels used in construction and engineering applications.

S355 steel is widely used in various industries and sectors due to its high strength, mechanical properties, and weldability. The 355 refers to a minimum yield strength of 355 megapascals (MPa).

These plates are available in different grades designated as S355JR, S355J0, S355J2 and S355K2. These grades determine the performance and suitability for different types of construction projects.