Numerical simulation on solidification behavior and structure of 38CrMoAl large round bloom using CAFE model

A coupled cellular automaton-finite element model was developed to simulate the solidification behavior and structure of 38CrMoAl large round bloom,in which mold electromagnetic stirring+final electromagnetic stirring was taken into consideration,under different superheat,casting speeds,and secondary cooling water flow.Industrial trials for infrared temperature measurement and macro etch experiments of the post-test round bloom samples were used to verify the simulated solidification structure and temperature field.The simulation results show that superheat and secondary cooling water flow have little influence on the surface temperature,center temperature,and center solid fraction while casting speed has a more obvious influence on solidification behavior.With the increase in the casting speed of 0.02 m min^(-1),the solidification position is prolonged by about 1.64 m.With the increasing specific water ratio by 0.02 L kg^(-1) each,the surface temperature of the secondary cooling zones decreases by about 18℃,and the solidification position shortens by about 0.11 m.As the superheat increases from 10 to 40℃,the ratio of the equiaxed crystal zone decreases from 35.98% to 23.98%.The casting speed and secondary cooling water flow increase the equiaxed crystal ratios of the large round bloom,but neither is significant,both being about 2%.

Flow field, heat transfer and inclusion behavior in a round bloom mold under effect of a swirling flow submerged entry nozzle

Flow field,heat transfer and inclusion behavior in a 700 mm round bloom mold under the effect of a swirling flow submerged entry nozzle(SEN)were investigated with the aim to enhance the casting process.The results indicate that the impinging flow phenomenon,which is commonly observed in conventional single-port SEN casting,was completely suppressed by the swirling flow SEN coming from a novel swirling flow generator design in tundish.Steel from the SEN port moved towards the mold wall in 360 direction,leading to a uniform temperature distribution in the mold.Compared to a conventional single-port SEN casting,the steel super-heat was decreased by about 5 K at the mold center,and the temperature was increased by around 3.5 K near the meniscus.In addition,the removal ratio of inclusions to the mold top surface in the swirling flow SEN casting was found to be increased.Specifically,the removal ratio of spherical inclusions with diameters of 1,10,50 and 100μm was increased by 18.2%,18.5%,22.6% and 42.7%,respectively.Furthermore,the ratio was raised by 18.2%,20.8%,21.5% and 44.1%for non-spherical inclusions,respectively.

Application of the Largest Movable Mold EMS on a Large Section Size CC Bloom

The largest movable mold EMS developed by POSCO in collaboration with Daineli-Rotelec for improving internal quality of a large CC bloom is being used at a large size bloom caster of POSCO since 2011.Internal quality of carbon steel CC bloom of 700×700 mm~2 section size with the mold EMS was much improved compared with without the mold EMS.Equiaxed zone ratio increased from 50%to 100%and the grain of equiaxed structure became globular and fine.Top shrinkage was also much reduced by applying the movable mold EMS.