During CCM process, Electromagnetic stirrer (EMS) is used to eliminish some flaws of the billet and improve quality of steel product.
At present there are following types according to CCM type, section of billet and erection position of EMS.
By power supply, there is divided DC conduction type and AC induction type.
By EMS's excited magnetic method, there are constant magnetic field, rotating magnetic field, travelling magnetic field and helical magnetic field. A multifunctional EMS may have rotating, traveling waves or helical magnetic field function.
There are two phase type EMS or three phase EMS by its power supply.
The EMS can be installed in different positions of CCM, like at mould, second cooling area and trail end of solidification.
Application of the electric magnetic stirring technology can greatly improve the quality of billet and one may consider the following aspects to choose and implement EMS.
Steel grade: Alloy steel contains many alloy elements. In order to gain the same flow speed, magnet induction strength of stirring stainless steel should be higher than of carbon steel, because the cylindrical crystal of stainless steel is more developed than carbon steel, and breaking the branch crystal of stainless steel requires greater electromagnetic force.
Product quality: Main flaw types shall be determined according to product quality before choosing the proper EMS. For example, the flaws of thick plate show central loose and segregation. The main flaws of steel sheet are gas holes and inclusions.
Section of casting billet: The size of casting billet section will decide drawing speed and length of liquid core so that it will influence the position of the EMS.
EMS mode: That shall determine the right position to install the EMS by product type and consider single stirring mode or combine different stirring modes.
Parameters of the EMS: The parameters of the stirrer include mode, power, operation method and supply frequency, etc. Steel grade and technological data (like degree of superheat of steel liquid, drawing speed) shall be referenced to confirm the parameters of the EMS.
