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Development of A32 and A36 High Strength Shipbuilding Steel Plates

Development of A32 and A36 High Strength Shipbuilding Steel Plates

Since the 1990s, China’s shipbuilding steel plates industry has entered the international market on a large scale, and the shipbuilding steel plates industry has gradually become one of the pillar industries in China. With the development of shipbuilding steel plates in the direction of large-scale and light-weight, the general strength ship plates can no longer meet the needs of the hull, and the proportion of high-strength ship plates will continue to increase. Therefore, the development of high-strength shipbuilding plates has broad market prospects. Structural steel for hull can be divided into general strength steel and high strength steel. A32 and A36 are one type of structural steel for high strength hull. With the development of the shipbuilding industry, the requirements for materials are becoming more and more demanding. At present, in the factory approval, besides the certification of the quality system, strict type tests must be carried out. Type test and test items and requirements attention is the ability to guarantee the physical and chemical properties of the product, and its technical requirements are mainly reflected in the following aspects.
The plasticity and toughness reserve is sufficient to withstand the crack propagation and brittle fracture of the hull during normal navigation or accidents. The toughness and plasticity index must have considerable room to compensate for the deterioration of material properties caused by various heat and cold processing during the construction process, especially for materials that require good crack resistance in important parts. For ships in unbounded areas, lower brittle transition temperatures at lower temperatures are required. Therefore, in the factory-approved type test, it is necessary to test the longitudinal and lateral series of Charpy V-type impact work (20 ° C, 0 ° C, -20 ° C, -40 ° C) and the drop weight test to measure the NDT brittle transition temperature. We should meet the adaptability of the shipyard’s processing technology in ship construction. The hull line type is more complex and has many types of curved surfaces. Therefore, on the one hand, the material must have good weldability, and the forming operation of the material such as cold, hot bending and water-fire bending of the material should be satisfied, and surface damage and fine cracks are not formed. Therefore, the factory type test must carry out the system welding test and the longitudinal and transverse cold bending test. The surface quality and dimensional tolerances are strictly controlled to ensure that the ship’s board is free of pitting after shot peening. All specifications ship plate thickness tolerance is ≤ 0.3mm. Seawater corrosion resistance should not be lower than ordinary carbon steel. A32 and A36 shipbuilding plate delivery state thickness ≥ 12.5mm specifications must use CR (controlled rolling delivery), N (normalizing) or TM (temperature-deformation controlled rolling).

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