Description
Structural steel plates or aluminum plates are fabricated and assembled to form the ship or erection units. Erection units are assembled to form ships. Steel plates are replaced during repair and conversion work.
Steel plates may be cut to size in a shop, and then transferred to the ship where they are welded into place. The steel plate may first be tacked or spot-welded to secure its position before the entire perimeter is welded. Alternatively, steel plate may be welded to form erection units that are later moved and assembled to form the ship. Welding has mostly replaced drilling and hot riveting.
Stainless steel is used extensively in building ships while aluminum is being used more often as a structural material.
To cut structural steel for fabrication in shipbuilding, and to remove worn or damaged steel plates in ship repair and conversion, oxy-acetylene, oxy-propane, and oxy-butane cutting torches are used. Steel plate may be treated by shot blasting, either using automatic machines, or, for small components, by hand. Angle steel “stiffeners” may be used to reinforce steel plates.
Portions of the ship that will be below the water line may be sand-blasted and painted before assembly into the hull.