Electromagnetic stirring device and method for secondary cooling zone during slab continuous casting

An electromagnetic stirring device and a method for a secondary cooling zone during slab continuous casting. The device has a main body, an opening adjustment assembly, and a secondary cooling assembly. The main body has a protection housing (3), a phase sequence control assembly, an iron core (4) and an electromagnetic coil (5) for carrying out variable-direction electromagnetic stirring on a molten steel by a three-phase current phase sequence transformation. The opening adjustment assembly has an air cylinder (7), a fixed base (8), a movable joint shaft (12) and a silicon steel sheet group insert (13) for adjusting online opening degree of the closed annular iron core by a movable joint structure. The secondary cooling assembly has a cooling water inlet (9) and a cooling water nozzle (10) for cooling the electromagnetic coil and spraying cooling water to a surface of a cast slab (1).