Electromagnetic Stirring Complete Device

I. Basic Principles

Electromagnetic stirring (abbreviated as EMS) is a new technology that enhances the movement of molten steel by utilizing the electromagnetic force generated in the liquid phase cavity of the casting blank, thereby improving the flow, heat transfer, and uniform distribution of alloy elements during the solidification process, and enhancing the internal quality of the casting blank. It plays a very important role in improving steel quality, achieving high-speed continuous casting, expanding the types of continuous casting steel, and relaxing continuous casting process conditions.
The principle of electromagnetic stirring is similar to that of a solid rotor asynchronous motor. Specifically, the alternating magnetic field generated by the stirrer penetrates into the liquid phase cavity of the casting blank, inducing a current within it. This induced current interacts with the magnetic field generated by the stirrer to produce electromagnetic force, thereby driving the molten steel movement. The electromagnetic stirrer is equivalent to the stator of a solid rotor asynchronous motor, while the molten steel is equivalent to the rotor of the motor.

II. Composition of Electromagnetic Stirring Complete Device

The composition of the electromagnetic stirring complete device includes: electromagnetic stirrer, variable frequency power supply, control equipment, and cooling water treatment system.

III. Combination Methods of Electromagnetic Stirring Complete Device

.IV. Metallurgical Effects

Through electromagnetic stirring, the internal structure of the steel blank can be improved, the surface quality of the casting blank can be enhanced, non-metallic inclusions in the molten steel can float up, central segregation and central porosity can be reduced, and the equiaxed crystal rate can be increased.

Different installation positions of the electromagnetic stirrer have different metallurgical effects. The main metallurgical effects of improving the quality of the casting blank are shown in the table.

V. Classification of Electromagnetic Stirrer

• Electromagnetic Stirring of the Mold

The electromagnetic stirrer for the mold is divided into built-in and external types based on its relative position to the mold.

• Built-in Electromagnetic Stirrer

The built-in electromagnetic stirrer is installed inside the water tank of the mold. Characteristics: The induction coil is close to the copper sleeve and water jacket of the casting blank, providing a good stirring effect; it requires a small power capacity and low operating costs; the mold is water-cooled without needing an additional cooling water system; each mold requires a stirring coil, resulting in many spare parts.

Built-in Electromagnetic Stirrer for the Crystallization Section

• External Electromagnetic Stirrer

The external electromagnetic stirrer is installed around the mold.

(1) Direct Water Cooling Type Characteristics: Convenient for replacing the mold; higher energy consumption and operating costs; fewer spare parts required; mold water cooling without needing an additional cooling water system.

(2) Hollow Copper Tube Internal Cooling Type Characteristics: Convenient for replacing the mold; internal cooling with hollow copper tubes, high cooling efficiency; fewer spare parts required; higher energy consumption and operating costs; requires a separate cooling water treatment system.

External Electromagnetic Stirrer for the Crystallization Section

Electromagnetic Stirrer for the Secondary Cooling Zone

The electromagnetic stirrer (SEMS) is installed in the secondary cooling zone of the continuous casting machine. The electromagnetic stirring in the secondary cooling zone for square billets generally adopts a single-sided traveling wave magnetic field type, installed on the inner arc side of the casting blank; there are also rotating magnetic field types. The electromagnetic stirring in the secondary cooling zone for slab billets usually uses a double-sided traveling wave magnetic field type.

Field Line Stirrer

Electromagnetic Stirrer for the Secondary Cooling Zone Slab

Electromagnetic Stirrer for the Solidification End

The electromagnetic stirrer is installed at the solidification end of the continuous casting machine, all using rotating magnetic field types, and can use low frequency or industrial frequency excitation based on the cross-section of the casting blank.

Electromagnetic Stirrer for the Solidification End

Combination Methods of Electromagnetic Stirrer      

Based on the situation of the electromagnetic stirrer for the root and river magnetic, its combination methods.

Model Description 

Model of Electromagnetic Stirrer (EMS) and its Meaning

Parameters to be Provided When Ordering
The selection of the electromagnetic stirrer is generally determined by the following conditions.
△ Continuous Casting Machine Model
△ Continuous Casting Steel Type
△ Continuous Casting Blank Cross-section
△ Installation Area
△ Built-in Type Requires Providing Mold Water Tank Size
△ External Type Requires Providing Mold Size and Flow Spacing
△ Water Jacket Size
△ Copper Tube Size and Thickness

Electromagnetic Stirring Control System 

The electromagnetic stirring control systems produced by our company are currently used in two main categories: one is the three-phase electromagnetic stirring control system for continuous casting of square and round billets and slabs, and the other is the two-phase orthogonal electromagnetic stirring control system for the intermediate ladle.
1. Three-phase electromagnetic stirring (EMS) control system for square and round billets and slabs continuous casting
The N-flow M-segment (where N represents the number of flows in the continuous casting machine, and M represents the number of segments for combined stirring) continuous casting electromagnetic stirring control system mainly consists of a monitoring system, a process control system, and NxM sets of three-phase low-frequency current systems (YSVF3), among other components. Its low-frequency power output is a three-phase low-frequency sine wave current.
2. Two-phase orthogonal electromagnetic stirring control system for the intermediate ladle
The electromagnetic stirring control system for the intermediate ladle mainly consists of a monitoring system, a process control system, and a two-phase low-frequency power system (YSVF2), among other components. Its low-frequency power output is a two-phase orthogonal low-frequency sine wave current.
3. Block diagram and outline of the electromagnetic stirring control system

4. Main features of the system

1. It adopts the latest achievements in power electronics technology and microcomputer control technology internationally, with advanced technology, excellent performance, simple operation, convenient maintenance, and long service life.
2. It has two operating locations: remote and on-site.
3. It has manual and automatic operation functions.
4. It can adopt three operating modes: continuous, intermittent, and alternating.
5. It has control functions for three magnetic field forms: rotating, traveling wave, and spiral.
6. The current and frequency of each low-frequency power system can be adjusted separately without mutual interference, allowing for current closed-loop control.
7. A complete electromagnetic compatibility design and protection function design make the system highly resistant to interference, stable, and reliable in operation.
8. It has good network communication flexibility.
9. The monitoring system has a general operation system with an industrial control interface type, and the general operation panel type is slightly lower in cost than the full industrial control interface type, allowing users to choose based on their situation.
10. Due to the use of an AC-DC-AC voltage type frequency conversion main circuit in the low-frequency power device, the frequency conversion and voltage transformation are achieved using DSP or microcontroller to implement high carrier SPWM modulation, and the inverter part uses fully controlled IGBT power modules or IPM intelligent power modules with three-phase or two-phase full-bridge output. This makes the entire device compact, with a high carrier frequency, good output waveform, and high power factor. The device can output a maximum current of 1200A, with an adjustable output frequency of 2-30Hz and a maximum output voltage of 460V.
11. The three-phase low-frequency power system has both domestically produced models and variable voltage variable frequency (VVVF) parts that use imported electromagnetic stirring dedicated frequency conversion cores. The domestically produced model is more cost-effective than the VVVF part that uses imported electromagnetic stirring dedicated variable voltage variable frequency cores, allowing users to choose based on their situation.

5. Explanation of electromagnetic stirring control system models

Note: The rated output capacity is the output capacity of a single low-frequency power system.

6. Selection explanation

The selection of the electromagnetic stirring control system is generally determined by the following factors:
1. The current, voltage, frequency, capacity, and phase number of the electromagnetic stirring coil.
2. The number of flows in the continuous casting machine or the number of intermediate ladles.
3. The number of physical quantity parameters that need to be detected and monitored in the water system.
4. The number of physical quantity parameters that need to be interlocked on the user's site.
5. Other specific requirements from the user.

Technical parameters of the complete set of continuous casting electromagnetic stirring devices

Continuous Casting Electromagnetic Stirring Device Technical Parameters