FH32-HD和FH36-HD高延性船板钢的开发及控冷工艺

Using the composition design of low C and Nb + Ti compound addition, two higher ductility ship plate steels FH32 and FH36 were developed by means of optimizing the controlled cooling process of "relaxation-laminar cooling-air cooling". The tensile properties and microhardness were tested, and the full-thickness A5 scale specimens were used for tensile testing. The micrestructure and inclusions of the tested steels were observed and analyzed by using SEM and EDS. The results show that with the reduction of the initial cooling temperature, that is, the extension of the relaxation time, the ferrite yield earlier, the average grain size and the ratio of soft-hard phases increase. Furthermore, the content of lamellar pearlite increases and the content of granular bainite decreases significantly. The overall elongation increases, but the strength margin greatly decreases. The decrease of the final cooling temperature make the pearlite lamellae reduce firstly and then enlarge, the content of bainite in the structure increases gradually, and the morphology changes from granular bainite to lath bainite. The strength shows an upward trend, but the elongation decreases significantly after reaching a peak at 600 °C.