P355N, P355NH, and P275NH are non-alloy quality steels. They are models of steel plates. They are used in petroleum, chemical industry, power stations, boilers and other industries to make reactors, heat exchangers, separators, and balls. Tanks, oil and gas tanks, liquefied gas tanks, nuclear reactor pressure shells, boiler drums, liquefied petroleum cylinders, high-pressure water pipes in hydropower stations, turbine volutes and other equipment and components, the full name is: normalized weldable fine-grained steel plate.