Aiming at the problem that Q500MEZ35 heavy plate is difficult to quench through due to the insufficient on-line cooling capacity,the 40 mm thickness plate was developed for trial production.In the process of steel smelting,the inclusion size can be reduced by controlling the mass fraction of S element less than 0.002％,adding Ca line and rare earth element Ce,etc.,so as to improve the Z-direction resistance to laminar-tear of plate.More and smaller(Ti,Nb,V)(C,N)second phase particles were pre-cipitated by the finishing rolling process with low temperature and large deformation,which provided more nucleation sites for the subsequent ferritic transformation.Through different final cooling temperatures(580-350 ℃)tests,it is found that with the decrease of final cooling temperature,the long-range diffusion ability of C atom is weakened,the stability of residual austen-ite is reduced,and the size of M/A island is reduced.At the same time,the ferrite grains nucleate in shear mode and grow up due to the limitation of C diffusion,and finally form fine lath acicular ferrite.When the final cooling temperature is 350 ℃,the main microstructure of the plate is fine granular bainite and acicular ferrite,and the impact property is the best.
Q500MEZ35 heavy plateinclusionslow temperature and large deformationfinal cooling temperatureacicular ferrite
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