Numerical And Physical Simulation On The Flow And Temperature Field Of Bloom Mould

Mold is the final metallurgical vessel which makes steel clean in the process of continuous casting.The fluid flow field and temperature field in mold affects inclusion removal,slag entrapment,solidified shell formation and solidification structure greatly.To optimize the flow field and temperature field in mold is very important for improving the quality of bloom and operation performance.A company plans to produce blooms sized 250mm×350mm and 250mm×300mm to meet the needs of practice and high-quality alloy steel production.The experiment is mainly based on physical and numerical simulation to study the effect of nozzle structures and electromagnetic stirring on the flow and temperature field,and additionally,design optimal nozzle structures and reasonable processing parameters.The main conclusions are as follows:(1)When casting speed is 0.7 m/min and immersion depth is 100mm with one-port SEN for producing bloom sized 250mm×350mm,the penetration depth is 518.8mm with mean wave height around 0.29mm.While bilateral and quadripuntal SEN are used,the penetration depth are 160.0mm and 150.8mm,with mean wave height around 1.29mm and 0.63mm respectively.Considering the effect of nozzle structure on level fluctation and penetration depth,quadripuntal SEN is more conducive to the production of high-quality bloom,especially the No.3 with optimal results.(2)When quadripuntal SEN is used,with the increase of casting speed and decrease of immersion depth,the penetration depth and the level fluctuation of the stream is also increased.When casting speed is 0.8 m/min and immersion depth is 90mm for producing bloom sized 250mm×350mm,the slag layer coverage is favourable.So the parameter under these conditions is selected to be the best process optimization parameters;when casting speed is 0.9 m/min and immersion depth is 90mm for producing bloom sized 250mm×300mm,the liquid surface appears a little slag entrapment.It is recommended that the immersion depth should be controlled more than 90mm under this casting speed.(3)Comparing with three kinds of nozzles,the high-temperature region with one-port SEN concentrates in the lower part of mold,with a main temperature of 1785.OK along the centerline of width and narrow face direction at free surface.However,the high-temperature region with No.10 bilateral SEN and No.3 quadripuntal SEN both concentrates in the upper part of mold.Temperature along the centerline of width and narrow face direction with No.10 bilateral SEN concentrates in 1788.2K and 1785.OK respectively at free surface,which generates difference of 3.2K,while the No.3 quadripuntal SEN both concentrates in 1788.2K.Obviously,the temperature distribution near the No.3 quadripuntal SEN is more uniform,more conducive to slag melting and uniform thickness of solidified shell.(4)Comparing with three kinds of nozzles,the solidified shell with one-port SEN almost linearly uniform grows initially,and then slowed with a thickness of 25.93mm and 23.29mm in the centerline of wide and narrow face at the outlet of mold respectively.However,the solidified shell with No.10 bilateral SEN and No.3 quadripuntal SEN grows a "platform" at the point of impingement.The thickness of solidified shell in the centerline of wide and narrow face at the outlet of mold with No.10 bilateral SEN is 32.93mm and 27.88mm respectively,while the No.3 quadripuntal SEN is 32.99mm and 30.48mm respectively.(5)When the casting speed is 0.7 m/min and immersion depth is 100mm with 300A of current intensity for producing bloom sized 250mm×350mm,the liquid steel produces horizontal rotary motion with a maximum of 0.342m/s in central cross-section of stirrer which significantly greater than 0.026m/s of no electromagnetic stirring.Even at 400mm distance from the outlet,the rotary motion still exists with a maximum of 0.178 m/s.considering the above results,the current intensity is recommended 300～400A.