Classification societies publish rules and regulations for the strength of the ship
Mild steels
Mild steel or low carbon steel in several grades has been used as a ship structural material because of its mechanical properties and low cost
There are mainly four grades of steel specified by classification societies based on the degree of notch toughness (Notch toughness is the ability that a material possesses to absorb energy in the presence of a flaw).
Grade A
Grade B
Grade D
Grade E
Grade A is least toughness while grade D has great notch toughness.
High Tensile Steels which have higher strength than that of mild steel are employed in the more stressed regions of large tankers, container ships and bulk carriers
Aluminium Alloys: The major advantage of aluminium alloy over mild steel is its weight. Aluminium alloys are much lighter than steel. The most often used Al-alloys in shipbuilding are the 5083 type for plates and 6082 for extrusions
Shell Plating: Steel Plates
Superstructures: Aluminium alloys used in accommodation of passenger ship to reduce weight
Watertight doors: Mild steel or cast steel
Stern Frame: Cast, forged, or fabricated from steel plate
Rudder Stock: Cast or forged steel
Propellers: Copper alloys such as brass