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The hull or shell of a ship is a structural frame made of steel plates which, when assembled, form the outer surface of a ship and insure the watertightness. A process known as heat rolled steel plates or ‘shipplates’ is used in producing the plates for shipbuilding, which produce plates of a uniform and consistent thickness and with a homogenous quality.
Heat rolled steel plates are typically made from the low-carbon steel grade A, Grade B or Grade D with other plates also made from higher grade steels. The chemical composition of the grade A steel plates is usually so mild as to allow for its welding and general workability. It is typically used in the construction of steel containments, tanks and tubes. Grade B steel is a high carbon steel that is used where extreme strength is required, while the difference between Grade A and Grade B steel is mainly the carbon content.
Heat rolled steel plates are produced by rolling semi-finished slabs of steel, which are red hot in temperature and of a controlled thickness, through a sequence of rolls. The rolls are aligned so that each reduces the slabs thickness equally. Each slab is heated in an oven or furnace to a temperature of around 500-1200 °C and is then passed through the various rolls by passing them between two series of linked stands.
The process begins with the rolling performance of the first two stands which are conjoined and work the slab from the edges backwards. This creates the basic shape of the plate, with the edges pressing the metal to the desired thickness for the plate. As the plate enters the middle stands further rolls are used to further reduce the slab. The end stands are then used to flatten the metal and reduce the plate to the required thickness and shape. The plate then passes into an annealing chamber to cool.
The annealing process is necessary for the plates to be finished and also known as ‘normalizing’, ‘anneal’, ‘temper’ or ‘treat’. Its purpose is to relieve the stresses created during the rolling process, to reduce the propensity for brittleness, and at the same time to adjust the properties of the plates to ensure their suitability for use in shipbuilding. In the annealing chamber, the plates cool slowly and unevenly, and this produces the desired properties of strength and malleability.
Heat rolled steel plates are typically used in the fabrication, installation and assembly of ship shells or hulls. Their malleability and strength make them ideal for creating a frame around which the outer surface of a ship can be laid and for indoor installation. Reliability and strength that heat rolled steel plates provide make them ideal for the construction of ships. Their uniformity ensures that the shell of a vessel will be constructed correctly, and this is an important factor in the success of any marine venture. The malleability of the steel alloy also allows for the plates to be formed into structural components that increase the strength of the hull and ensure the safety of the vessel.
In summary, heat-rolled steel plates are vital components in ensuring the success of ships and, as a result, it’s important to ensure that the quality, uniformity and malleability of the plates is of the highest standard. They provide strength and reliability, which are property that are essential for the construction and performance of any vessel.
