Due to the harsh working environment of ships, the hull is subject to chemical and electrochemical corrosion of seawater, and the corrosion of Marine organisms and microorganisms. The hull bears large wind and wave impact and alternating load; The shape of the ship makes the processing method complicated, so the steel for the hull structure is strictly required. First of all, good toughness is the most critical requirement. In addition, high strength, good corrosion resistance, welding performance, processing and molding performance and surface quality are required.
In order to guarantee quality and toughness, Mn/C of chemical composition is required to be above 2.5, and there are strict requirements for carbon equivalent, and it is produced by steel mills approved by shipping inspection department. Structural steels for ship hulls are divided into strength classes according to their minimum yield point: normal strength structural steels and high strength structural steels. Hull structural steels are classified into general strength steels and high strength steels. General strength steels are classified into four grades according to quality: A, B, D and E. High strength steel is divided into two strength grades and three quality grades; AH32, DH32, EH32, AH36, DH36, EH36.
China Classification Society standard of general strength structural steel is divided into: A, B, C, D four quality grades (CCSA, CCSB, CCSC, CCSD); China Classification Society standard of high strength structural steel for three strength grades, four quality grades.
