The grades specified in the GB712-2011 ship and marine engineering structural steel standard are: Grade A, B, D, E, AH32, DH32, EH32, FH32, AH36, DH36, EH36, FH36, AH40, DH40, EH40, FH40, AH420, BV grade A ferry steel plate, DH420, EH420, FH420, AH460, DH460, EH460, FH460, AH500, DH500, EH500, FH500, AH550, DH550, EH550, FH550, AH620, DH620, EH620, FH620, AH690, DH690, EH690, FH690.
The main uses of flat steel are as follows. First, flat steel is used as a raw material for processing steel plates, which is convenient for transportation, takes up a small space, and can save transportation costs. Second, BV grade A ferry steel plate flat steel can be used as raw material for processing welded pipes. Flat steel can be a finished steel product, or it can be used as a billet for welded pipes and thin slabs for stacked sheets. Third, flat steel can be directly used as a steel structure. As a finished material, flat steel can be used for making hoop iron, tools and mechanical parts, and used as building frame structure and escalator in construction. Fourth, the flat steel has a smooth surface and a certain degree of beauty.
In order to obtain the seamless tube with smaller size and better quality, the method of cold rolling, cold drawing or the combination of the two must be used. Cold rolling is usually carried out on a two high mill, and BV grade A ferry steel plate pipes are rolled in a circular pass composed of a variable cross-section circular groove and a fixed conical head. Cold drawing is usually carried out on single chain or double chain cold drawing machines of 0.5-100t.
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