Hot deformation behavior and hot processing map of 18Cr2Ni4W steel
Under the conditions of deformation temperature of 850-1200 ℃,strain rate of 0.005-0.5 s-1 and true strain of 0.8,the Gleeble-3800 thermal simulation testing machine was used to conduct hot compression tests on 18Cr2Ni4W steel.Based on the analysis of the true stress-strain curves and the hyperbolic sine function,the hot deformation constitutive equation of the 18Cr2Ni4W steel was established.Hot processing map of the 18Cr2Ni4W steel at true strain of 0.8 was established using a dynamic material model(DMM).The results show that the 18Cr2Ni4W steel undergoes dynamic recrystallization during hot processing,the flow stress decreases with the increase of deformation temperature and increases with the increase of strain rate,and the peak stress decreases with the decrease of strain rate and the increase of deformation temperature.The instability zone is mainly distributed within the range of deformation temperature of 860-950℃ and strain rate of 0.03-0.5 s-1,its microstructure is an elongated strip structure along the deformation direction,with local fluidity,and the corresponding power dissipation value η is low,less than 0.2.The microstructure of the safety zone is a typical dynamic recrystallization microstructure,with a high power dissipation value η between 0.28 and 0.49.The optimal hot working process for the 18Cr2Ni4W steel at true strain of 0.8 is:deformation temperature of 975-1050 ℃,strain rate of 0.01-0.14 s-1,and deformation temperature of 1050-1200 ℃,strain rate of 0.01-0.5 s-1.
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