Microsmicrostructure and Mechanical Properties of Simulate Fusion Line in Eh40 Ship Plate Steel for High Heat Input Welding

The microstructure and mechanical properties in simulate fusion line of EH40 ship plate steel with high heat inputs were investigated using welding thermal simulation test.The effects of inclusions on the grain size of original austenite and intragranular ferrite (IGF) were analyzed.The results indicate that impact energy of the steels at -20 was more than 150 J with a heat input of 800 kJ/cm (t 8/5 =730 s) and maximum temperature of 1400 for 30 s.The microstructures of the steel were composed of GBF, IPF and IAF, and the fraction of IAF was over 50%.Lath bainite and granular bainite were not observed.The type and concentration of inclusions were ideal which decreased the growth of GBF.Those inclusions whose diameter were 5-8 μm can also promote the formation of IGF, and sometimes IAF was also formed through the nucleation at Mn-depleted zone.