FC Mold II电磁制动中磁场匹配对金属液流影响

Electromagnetic brake(EMBr) affects the flow field in mold during the slab continuous casting process.Flow control moldⅡ(FC MoldⅡ) has been developed to resolve the defects of the third generation(flow control mold) of EMBr which the braking effect on meniscus is too strong to make the surface flow excessively stabilize and it would be prone to freezing and related defects.To gain a fundamental understanding of FC MoldⅡ,a mercury physical model was developed to investigate the influence of the magnetic field intensity match on metal flow in FC MoldⅡbased on the 1350 mm×230 mm slab continuous casting process in a factory.The flow regime and velocity distribution in mold were measured by ultrasound Doppler velocimeter(UDV) with the maximum magnetic field intensity of the upper pair of magnetic poles B_1=0.18,0.36 and 0.50 T respectively and the maximum magnetic field intensity of the down pair of magnetic poles B_2=0.50 T,while the mold casting speed is 0.41,0.52 and 0.82 m/min respectively corresponding to the practical casting speed 1.00, 1.30 and 2.00 m/min respectively.The influences of the magnetic field intensity match on the flow discharged from the nozzle,the flow near the meniscus and the washing intensity to the mold narrow wall were analyzed and studied.The results showed that,when the magnetic field intensity match of the upper and the lower pair of magnetic poles B_1/B_2≤1,with the continuous casting speed increasing, the value of B_1/B_2 should increase in order to get an ideal braking effect.The value of B_1/B_2 should be 0.36,0.72 and 1.00 respectively when the model casting speed is 0.41,0.52 and 0.82 m/min respectively.The increasing of the intensity of the magnetic field reduces the "flow passage" effect caused by EMBr,and is conducive to the formation of the plug flow under the electromagnetic braking region.