Abstract
In order to improve surface quality of continuously cast steel, alternating magnetic field was applied through the copper mold to the early solidification zone of round billet. The mold has a number of slits and was specifically designed to achieve the efficient penetration of the field as well as high stiffness. A mold size is 0.18 m in internal diameter and is surrounded with a multi-turn induction coil. Casting velocity is 1.2m/min. The capacity of high frequency generator is 300kW and the frequency is 25kHz.
0.11% carbon steel was cast to investigate the effects of the intensity of magnetic field and the imposing area on the surface quality of billets. Even under the strong magnetic field, the meniscus level was controled precisely by RFLC method (Resonant Frequency Level Control Method) detecting the small shift of resonant frequency of high frequency generator.
Surface marks on the cast billets had three types by the imposition of electromagnetic field. Regular surface marks caused by the mold oscillation have disappeared by selecting the optimum meniscus level under suitable electric power. By the use of developed two fluids model based on VOF code, dynamics of meniscus shape at the early solidification zone during oscillation were studied theoretically. The model shows that the disappearance of oscillation marks is responsible for the stability of interfacial shape between flux and molten steel by the imposition of electromagnetic field.
