① Requirements for strength. The higher strength can reduce the weight of the hull, reduce the welding workload, and increase the carrying capacity. The use of high-strength steel is restricted by the rigidity and corrosion resistance of the hull.
② The shape of the hull is relatively complicated. There are many types of single curves or hyperboloids, and various forming operations such as cold, hot bending and correction are required. The suitability of the steel to the shipbuilding process is required, including welding and repairing.
③ The requirements for plasticity and toughness are sufficient to compensate for the influence of work hardening and thermal cycles on the material due to various operations in the construction process. For important parts such as the bow, the part where the longitudinal bending stress of the hull is the largest, the bottom of the ship and the side crack arrester, high crack resistance is required, and it is required to have a low extension-brittle transition temperature and sufficient impact absorption under low temperature conditions. .
④ Seawater corrosion resistance.