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Chemical composition of high strength hull structural steel

Low carbon: in order to ensure better toughness, weldability and plasticity, the carbon content of high strength hull structural steel is mostly below 0.20%.

Low alloy: with manganese as the main alloy element, Mn can delay the precipitation of ferrite when austenite is cooled, effectively strengthen the solid solution of ferrite and refine the grain. When the content of manganese is less than 1.8%, the high strength hull structural steel plasticity and toughness can be kept high under the condition of low carbon.

Niobium or vanadium can be added as alloy elements to form carbides or carbonitrides. On the one hand, austenite grain growth is prevented during hot rolling, on the other hand, carbonitride precipitates out during cooling, further improving the strength of high strength hull structural steel. In order to improve the corrosion resistance, copper (0.71-0.5%) and phosphorus (0.05-0.10%) were added. High strength hull structural steel has excellent corrosion resistance.