The Composition Design And Performance Of New-Generation 440MPa Steel For Surface Combatant Ship

There are two kinds of 440MPa grade steels used for surface ships in China, whose symbols are 903 and 945. But steel 903 is facing replacement, and steel 945 has so high carbon equivalent for its composition of Ni, Cr, Mo,V that it is difficult to be welded and expensive to produce. Along with the development of naval ships to higher technical and tactical ability, the steels used for them must be developed in advance or at least keeping up with the step. So it is imperative under the situation to develop new generation steels of surface ships. While the composition design and production technology research of new generation 440MPa grade steels of surface ships are the keys.The author designed 10 kinds of test steels with different composition. After steel-making and rolling, the microstructures and mechanical properties are observed. A serial tests are made according to different steels, including the influence of TMCP and alloy element on the microstructure and property. At last, reasonable composition is decided. By applying some new technology, such as lowering the temperature of terminal, increasing the reduction and enhancing the cooling rate after rolling, a new generation 440MPa grade steel of surface ships is developed, which has low cost, good weld ability and stable property. The work in the laboratory has made a firm foundation for the commercial test.