High temperature deformation behavior of Q355NE H-shaped steel for marine engineering and its influence on microstructure
A deep study was conducted on the thermal deformation behavior of marine steel Q355NE under 870-1 170 ℃ and 0.1-10 s-1 conditions using a Gleeble-3800 thermal simulation testing machine.The microstructure evolution of experimental steel under different hot working conditions was observed using techniques such as metallographic microscopy,electron backscatter diffraction,and transmission electron microscopy,non-dimensional Z-parameters were introduced,and a critical strain model for dynamic recrystallization of Q355NE steel was successfully established based on work hardening rate and flow stress curve.The results show that during the hot compression process,the flow stress of Q355NE steel shows a significant decreasing trend with the increase of deformation temperature or the decrease of strain rate;meanwhile,higher deformation temperature and lower strain rate are more conducive to the appearance of dynamic recrystallization characteristics,and the calculated activation energy Q for hot deformation is about 368.022 kJ/mol.A critical strain model for Q355NE steel under low lnZ conditions has been established.The deformation temperature has a significant impact on the microstructure and mechanical properties of Q355NE steel.Under the condition of strain rate of 5s-1,as the temperature decreases within the experimental temperature range,the refinement degree of ferrite grains is significantly improved,the proportion of large angle grain boundaries increases,and the dislocation density inside the ferrite grains increases.This is conducive to the precipitation of small and dispersed Ti and Nb carbon nitride second phase particles,and effectively suppresses or avoids the formation of Weinstein structure,thereby improving the low-temperature impact toughness and strength of Q355NE steel.
new offshore steelQ355NEthermomechanical treatmentcritical strain modelmicrostructure
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