Study On The Optimization Of Mould Electromagntic Stirring Process Parameters

Electromagntic stirring (EMS)can transform electromagntic power into rotary power of molten steel and drive the the molten steel rotating.Because of these,it can control solidification structure of molten steel, crystal state,inclusion, skin blowhole and intergranular and center segregation effectivly.Finally,the quality of steel can be improved.Mould electromagntic stirring (M-EMS) technology has been carried out on No.1 and No.5 billets caster in Chongsteel.The technical parameters are mainly from plant providing EMS technology.With the increase of steel grades , output and casting speed of No.1 and No.5 casters, in order to meet the requirement of steel quality, the further study must be done to make sure the better matching between M-EMS process parameter and continuous casting process.Based on the magnetic induction intensity of 150mm×150mm and 150mm×210mm cross sections been measured, the electromagnetic process parameters of tipical steel grades were analyzed.By industrial field tests,the optimal process parameters which assure the better steel subcutaneous quality and crystal structure were obtained. The study results provided the theoretical and practical foundation for M-EMS technology applied properly at Chongsteel.The test results of electromagnetic stirring magnetic field of two cross sections showed that the maximums of magnetic induction of both cross sections were both at 100mm from mould upper port,that is the nearby center of mould.At 100mm from mould upper port (at meniscus),the magnetic induction of both cross sections were less than 50Gs,and the stirring current and frequency change had little effects on magnetic induction. At the mould upper half part , the increasing trend of magnetic induction of 150mm×210mm was stronger than that of 150mm×150mm.At 200mm from mould summit,that is 100mm from meniscus,the magnetic induction of 150mm×210mm was about 400Gs,but the magnetic induction of 150mm×150mm was only 150Gs at 300mm from mould summit,The magnetic induction was little larger at mould wall than at center,and with the increase of magnetic induction ,the difference was bcome larger.Using numerical simulation,the distribution feature of fluid profile under the function of electromagnetic force field was analysed.By analysing the strand quality with different electromagnetic stirring process parameters in Chongsteel,when the electrical current is 4Hz, the optimal process parameters of typical steel grades were obtained:the optimal electrical current of 70steel was 360A; the optimal electrical current of 40Cr,45A were both 320A; the optimal electrical current of 20CrMnTi was from 280A; the optimal electrical current of AM3 steel was 230A.