Electromagnetic stirrer, electromagnetic stirrering, EMS-Hunan Kemeida Electric Co., Ltd

General Description of Electromagnetic Stirrer

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EMS is regularly used on CCM(continuous casting machine of bloom/billet), installed in the mould, strand or final. Most EMS are installed outside or inside the mould, which depends on the conditions of your casters. You can also use Mould-EMS + Final EMS together to achieve a better metallurgical effects.

An inductive Electromagnetic Stirrer is the stator of an asynchronous motor, the rotor of which is the liquid core of the continuously cast product in CCM. This stator produces either a rotating or a traveling magnetic induction field, which induces eddy current perpendicular to magnetic field. The stirrer creates mobile magnetic fields, which penetrate into the liquid steel, and creates eddy current. The magnetic induction field and the eddy current combine to create an electro-magnetic force, which causes the stirring motion in the liquid steel. During cooling and solidification of liquid steel, columnar dendrites are formed which are oriented along the direction of temperature gradient. This causes central segregation and inter-columnar cracking when the solid shell is subjected to tensile strains during solidification. Electro magnetic stirring of liquid steel facilitates quicker dissipation of superheat and the formation of an equi-axed structure in the cast product. Stirring of liquid pool will improve the internal structure due to better heat transfer between solidification front and liquid metal pool. The equi-axed zone in the cast product will increase whereas the central segregation will reduce. It will also help in reduction of breakouts during operation of CCM due to better dissipation of heat. (Refer to drawing below):

1. Mould Electromagnetic Stirrer (M-EMS): EMS is mounted outside or side the mould.
2. Strand Electromagnetic Stirrer (S-EMS): EMS is mounted outside the strand.
3. Final Electromagnetic Stirrer (F-EMS): EMS is mounted outside the final strand.
At present, M-ESM are widely used on CCM. The metallurgical effects differ from different locations.

Metallurgical effect of EMS for Billet

STIRRER LOCATION	METALLURGICAL EFFECTS	Steel Grades
Outside/inside the mould (M-EMS)	Increase equiaxed zone Reduce air holes, pinholes and inclusion in the surface and subsurface Equalize Billet Crust Reduce central porosity a little Reduce central segregation a little	Low alloy steel Spring steel Cold rolling steel Medium and high carbon steel
in the strand (S-EMS)	Increase Equiaxed Zone Inprove Central Segregation Reduce Inner Cracks Reduce central porosity and shringkage	stainless steel tool steel
in the final (F-EMS)	Make equiaxed zone fine Reduce central segregation Reduce central porosity and shringkage	spring steel bearing steel special high carbon steel

Photos of Cross Section of Billet and round


Without EMS(carbon steel)	With EMS(carbon steel)

Without EMS (stainless steel)	With EMS (stainless steel)

Metallurgical Effect of EMS for Slab Caster

NAME	METALLURGICAL EFFECT	STEEL GRADES
EMBR	IReduce slag Improve inner struction Reduce wave of liquid metal	Thin slab
MEMS		Medium and thick slab
SEMS	Make equiaxed zone fine Reduce central porosity and segregation Improve inner quality	Medium and thick slab

Sulfur Print Photos of Section


Without EMS	With M-EMS	With M+S-EMS

Technical Features of KEMEIDA EMS
*A new algorithm has been developed by KEMEIDA and GL Electromagnetic Field Software Co., names AGILD EM STIRRING ALGORITHM, which uses New Strip Magnetic Field Differential Integral Equation.
*This software can design electromagnetic parameters optimized. EMS shall be with high magnetic induction and stirring force. So stirring effect shall be great.
*Stirring force can be calculated by this software according different freq and current. So the best freq and current can be provided for user.
*Optimized design shall be done for L/D. Iron Core length shall be increased properly. So stirring effect shall be improved.
*Kemeida has also other software for designing F-EMS to calculate best position of F-EMS.
*KEMEIDA EMS uses low voltage and large current, which can avoid damage of peak voltage to insulation. It shall make reduce current leakage and prolong EMS life.
*Freq range shall be widened for choosing the best freq.
*Put EMS lower properly to make magnetic field around meniscus as little as possible to ensure strong magnetic field.


AGILD MAGNETIC FIELD VIRTUAL DIAGRAM	ROTATING MAGNETIC FIELD DISTRIBUTION DIAGRAM