A stopper for suppressing a confluence vortex and a method thereof

Abstract

The application discloses a stopper rod for inhibiting confluence vortex and a method thereof, and belongs to the technical field of water gap flow control of continuous casting tundish in metallurgy technology. The stopper rod comprises a stopper rod shell, a stopper rod core is embedded in the stopper rod shell, a magnetic field generating device is arranged on the outer circumferential wall of the stopper rod core, and the magnetic field generating device is used for exciting a magnetic field directly above the water gap. The magnetic field generating device is an electromagnetic coil or a rotating magnetic field stirrer. The application can effectively inhibit the generation of confluence vortex at the end of pouring by adding an electromagnetic field to make the molten steel generate induced current. Meanwhile, the magnetic field excited by the application is formed directly above the water gap and has the maximum strength at the vortex forming position, so that the inhibition effect of the magnetic field on the confluence vortex is more direct, the inhibition effect is obvious, and energy waste is avoided.

Description

Technical Field

[0001] This invention belongs to the field of sprue flow control technology in continuous casting tundish, and more specifically, relates to a sprue flow control plug rod to prevent the generation of converging vortices during casting in the continuous casting tundish. Background Technology

[0002] The tundish is one of the most important reaction vessels in the continuous casting process. As the last refractory vessel in the steelmaking process, the flow state of molten steel within the tundish has a significant impact on the continuous casting quality and directly affects the cleanliness of the steel. The tundish comprises two areas: the pouring zone and the outlet zone. The pouring zone is where molten steel is poured into the tundish through a long nozzle; the outlet zone is the nozzle area at the bottom of the tundish. The bottom of the tundish typically has one or more submerged entry nozzles through which molten steel flows into the crystallizer, preventing contact with air and ensuring that secondary oxidation does not occur. Because the submerged entry nozzle is a straight cylindrical channel, converging vortices are generated at the nozzle during molten steel pouring into the tundish. This phenomenon has many adverse effects on the continuous casting process, such as slag entrainment and slag runoff. It entrains slag from the surface of the molten steel into the interior, increasing the impurity content and significantly affecting the purity of the steel. Simultaneously, the presence of vortices causes the molten steel to continuously scour the ladle lining and nozzle, reducing their lifespan.

[0003] Converging vortices are vortices that form when the fluid level drops to a certain height (generally called the critical height or vortex height) during the discharge process of a container. In the steelmaking process, the converging vortices formed when the molten steel flows out of the tundish will entrain the slag covering the surface of the molten steel and inclusions in the steel into the interior of the molten steel, causing a serious decline in the quality of the tail billet obtained at the end of casting or making it scrap, reducing the metal yield. When the liquid level is below a certain height, the converging vortices will also entrain air, causing secondary oxidation of the molten steel, which seriously affects the quality of the billet. At present, metallurgists have found that the factors affecting the converging vortices in the tundish mainly include the following aspects: (1) Fluid settling: After the fluid has been settling for a period of time, the critical height decreases and the time when the vortex appears becomes later. (2) Fluid injection direction: When the fluid settling time is short, the critical height for the formation of vortices is lower when the fluid is injected axially, and it is not easy to form vortices; while the critical height of the fluid injected tangentially is higher, and it is easier to generate vortices. (3) Outlet eccentricity: Vortices are generated earlier when the fluid flows out from the center, and it is more difficult to form vortices when the fluid flows out from the eccentricity. (4) Outlet diameter: The larger the outlet diameter, the easier it is for vortices to form. (5) Rise or fall of liquid level: Vortices are more likely to form when the liquid level rises. (6) Shape of stopper rod: In actual production, the critical height of vortices is slightly smaller when using a stopper rod than when using a sliding nozzle, but the effect is limited, and vortices will still form around the stopper rod. (7) Air blowing at the nozzle: Introducing a gas jet along the axial direction around the nozzle can suppress the formation of vortices. In the actual tundish casting process, when the molten steel level is poured to the critical height, the casting will be stopped to maintain a high liquid level and avoid vortex slag entrainment. However, this will leave a large amount of molten steel in the tundish, reducing the metal yield and increasing production costs.

[0004] Currently, the commonly used devices for suppressing vortices in tundishes are stopper rods and sliding gate nozzles. Stopper rods or sliding gate nozzles are typically installed directly above the bottom nozzle of the tundish to control the molten steel flow. Stopper rod control alters the flow pattern of the molten steel near the nozzle by raising and lowering the stopper rod, reducing the formation of vortices. While stopper rods are more effective at controlling vortices than sliding gate nozzles, their effectiveness is still limited, and for some steel grades, their vortices-preventing effect is far from sufficient. Therefore, researching and improving stopper rod control for nozzle vortices is of great significance for process control in unsteady-state casting processes in tundishes and for clean steel production.

[0005] A search revealed Chinese patent number ZL201310075580.6, with an authorization announcement date of May 3, 2015, entitled "A Flow Control Device for Preventing Swirling Flow in a Continuous Casting Tundish." The application describes a drain pipe extending through the bottom of the tundish into its interior, with one end fixedly connected to an inlet plate. The top and sides of the inlet plate are sealed, and the bottom surface of the inlet plate has one or more downward-facing guide holes connected to the hollow portion inside the drain pipe. A flow control plug is positioned directly below the guide holes, its outer diameter matching the inner diameter of the corresponding guide hole. The flow control plug is vertically positioned and fixed to the bottom of the tundish. A lifting mechanism is installed at one end of the drain pipe outside the tundish, controlling the lifting and lowering movement of the drain pipe and the inlet plate. This application can prevent the formation of swirling flow and improve the cleanliness of the molten steel. However, the combination of the inlet tray and the flow control rod in this application is complex and the manufacturing cost is high, resulting in poor practicality.

[0006] Patent No. 201721686999.5, authorized on July 6, 2018, is a utility model entitled "A Flow Control Device for Preventing Converging Vortexes During Continuous Casting Tundish Pouring." The application describes a flow control nozzle that extends through the bottom of the tundish and into its interior, with an immersion nozzle connected to its bottom. A stopper rod is installed above the flow control nozzle, with a concave lower end. An automatic lifting mechanism is mounted on the stopper rod, controlling its vertical movement. A molten steel level measuring instrument is installed on the upper part of the tundish. The molten steel level measuring instrument measures the molten steel level; the flow control nozzle controls the flow of molten steel; the concave stopper rod controls the generation of converging vortices; and the automatic lifting mechanism controls the position of the concave stopper rod. This utility model can prevent the formation of backflow vortices and improve the cleanliness of the molten steel. However, the concave lower end design of the stopper rod significantly reduces its lifespan and easily leads to secondary contamination of the molten steel. Summary of the Invention

[0007] 1. The problem to be solved

[0008] Existing stopper rods are ineffective at preventing vortex confluence, which can negatively impact the purity of molten steel. This invention provides a stopper rod and method for suppressing vortex confluence. By introducing an electromagnetic field, an induced current is generated in the molten steel, effectively solving a series of problems caused by vortex confluence that are detrimental to the continuous casting process. Furthermore, the magnetic field generated by this invention forms directly above the nozzle and has the highest intensity at the vortex formation location, making the magnetic field's suppression effect on vortex confluence more direct, effective, and energy-efficient.

[0009] 2. Technical Solution

[0010] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] The present invention provides a stopper rod for suppressing confluence vortices, comprising a stopper rod shell, a stopper rod core disposed within the stopper rod shell, and a magnetic field generating device disposed along the outer peripheral wall of the stopper rod core, the magnetic field generating device being used to generate a magnetic field directly above the water inlet.

[0012] Furthermore, the magnetic field generating device includes an electromagnetic coil wound around the core of the stopper rod. When the electromagnetic coil is energized, it generates a magnetic field at the water inlet position that is perpendicular to the tangential velocity of the confluence vortex.

[0013] Furthermore, the stopper rod core is a steel pipe processed from ordinary carbon steel round steel, and the electromagnetic coil is covered with refractory material.

[0014] Furthermore, the magnetic field generating device is a rotating magnetic field stirrer, which includes an annular yoke, a winding coil, and a housing. The annular yoke is sleeved on the outer peripheral wall of the stopper rod core, and the winding coil is wound on the annular yoke.

[0015] Furthermore, the rotating magnetic field stirrer is installed near the head of the stopper rod, and three sets of the rotating magnetic field stirrer are arranged vertically, with each set of three sets of rotating magnetic field stirrers using three-phase symmetrical alternating current.

[0016] Furthermore, the winding coil is a copper tube coil and adopts the core Clam winding method, and cooling water is circulated through the copper tube coil.

[0017] The method for suppressing vortex confluence using the aforementioned plug rod is characterized by comprising the following steps:

[0018] Step 1: Place the electromagnetic coil or rotating magnetic field stirrer on the outer peripheral wall of the stopper rod core, and then embed the whole into the stopper rod shell;

[0019] Step 2: Place the assembled stopper rod in the corresponding position inside the intermediate package;

[0020] Step 3: After the magnetic field generator is powered on, a magnetic field can be generated directly above the water inlet to suppress the converging vortex above the water inlet.

[0021] Furthermore, in step one, before winding the electromagnetic coil, a formula is used...

[0022]

[0023] Calculate the number of turns of the electromagnetic coil;

[0024] Where L is the average length of one turn of wire in the coil; r is the core radius; δ is the air gap length; h is the coil height; b is the coil width; J is the current density in the electromagnetic coil; U is the power supply voltage; ρ is the resistivity of the conductor material; F is the magnetomotive force of the magnetic circuit; N

[0025] Where is the number of turns, and K is the winding tightness factor.

[0026] Furthermore, in step one, the magnetic induction intensity of the rotating magnetic stirrer is 0.17–0.2 T.

[0027] Furthermore, using the formula

[0028]

[0029] The electromagnetic force generated in the molten steel was calculated.

[0030] Where B is the magnetic flux density; B0 is the magnetic flux density amplitude of the stirrer cavity; r is the radius of the tundish cavity; r0 is the radius of the stirrer cavity; and p is the number of pole pairs. σ is the current density; σ is the conductivity of the molten steel. For induced electromotive force; This refers to the slip velocity, which is the velocity of the magnetic field relative to the molten steel. It is electromagnetic force. 3. Beneficial effects

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) The present invention provides a stopper rod and method for suppressing converging vortices. A magnetic field generating device is added inside the stopper rod. By adding an electromagnetic field, an induced current is generated in the molten steel, which effectively suppresses the converging vortices generated at the nozzle position when the molten steel level is lower than the critical height at the end of the casting process. This solves a series of problems that are detrimental to the continuous casting process caused by converging vortices. At the same time, the magnetic field generated by the present invention is formed directly above the nozzle and has the greatest strength at the vortex formation position, making the magnetic field more direct in suppressing the converging vortices. The suppression effect is not only obvious but also does not cause energy waste.

[0033] (2) The present invention provides a stopper rod for suppressing converging vortices. An electromagnetic coil is wound around the core of the stopper rod. When the electromagnetic coil is energized, the core of the stopper rod and the electromagnetic coil form an electromagnet. The two ends of the stopper rod are N and S poles, respectively. Magnetic field lines pointing from the N pole to the S pole are generated around the stopper rod. When the molten steel is below the critical height, converging vortices begin to form near the nozzle. The rotating molten steel cuts the longitudinal magnetic field lines, generating a tangential force opposite to the direction of the vortex, which cancels out the tangential velocity that originally existed in the molten steel, thereby suppressing the formation of converging vortices in the molten steel. When no vortex is generated in the molten steel, no external force is applied to the molten steel, and no disturbance is caused to the molten steel, avoiding slag layer vibration on the surface of the molten steel, which is conducive to the smooth floating of inclusions. At the same time, when the molten steel is stationary, the power of the external power supply of the electromagnetic coil can be adjusted to use the electromagnetic thermal effect to perform thermal compensation on the molten steel at the end of the pouring process, effectively solving the problem of molten steel temperature drop at the end of the pouring process, improving the cleanliness of the molten metal and increasing the metal yield, thus ensuring smooth subsequent pouring.

[0034] (3) A stopper rod for suppressing vortex converging according to the present invention, wherein the rotating magnetic field stirrer is provided in three sets and each uses three-phase symmetrical alternating current. When the rotating magnetic field excited by the rotating magnetic field stirrer cuts the molten steel at a synchronous speed, an induced current is generated in it. The induced current interacts with the molten steel to generate electromagnetic force. Since the stirrer is cylindrical, the electromagnetic force induced in the molten steel is paired on the left and right and opposite in direction, forming an electromagnetic torque. The two adjacent sets of rotating magnetic field stirrers excite opposite magnetic fields. The three sets of rotating magnetic fields at different heights cause the molten steel to rotate in opposite directions, thereby suppressing the formation of vortices. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the magnetic field distribution of the magnetic field generating device in Embodiment 1 of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of a plug rod for suppressing converging vortices in Embodiment 1 of the present invention;

[0037] Figure 3 This is a top view of a stopper rod for suppressing confluence vortices according to Embodiment 1 of the present invention;

[0038] Figure 4 This is a schematic diagram of the structure of a plug rod for suppressing converging vortices in Embodiment 2 of the present invention;

[0039] Figure 5 This is a top view of a stopper rod for suppressing confluence vortices in Embodiment 2 of the present invention.

[0040] In the diagram: 1. Stopper rod shell; 2. Stopper rod core; 3. Electromagnetic coil; 4. Rotating magnetic field stirrer; 41. Annular yoke; 42. Winding coil; 43. Shell. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments.

[0042] Example 1

[0043] Combination Figure 1 , Figure 2 , Figure 3 As shown, this embodiment of a stopper rod for suppressing converging vortices includes a stopper rod body and an electromagnetic coil 3 disposed within the stopper rod body. The stopper rod body comprises a stopper rod shell 1, a stopper rod core 2, a sleeve brick, and a stopper head brick. The stopper rod core 2 is a steel tube processed from plain carbon steel round bars, and the electromagnetic coil 3 is wound around the stopper rod core 2. After the electromagnetic coil 3 is connected to a power source, it constitutes a magnetic field generating device. Simultaneously, the stopper rod core 2 is covered with refractory material to protect the electromagnetic coil 3 from direct exposure to high temperatures. When the electromagnetic coil 3 is energized, it generates a magnetic field perpendicular to the tangential velocity of the converging vortex at the water inlet position.

[0044] This embodiment describes a stopper rod for suppressing converging vortices. During the final stage of tundish pouring, when the molten steel is about to reach a critical height, an electromagnetic coil 3 is energized. At this time, the stopper rod core 2 and the electromagnetic coil 3 form an electromagnet, with the two ends of the stopper rod being the N and S poles, respectively. Magnetic field lines pointing from the N pole to the S pole are generated around the stopper rod. When the molten steel falls below the critical height, converging vortices begin to form near the nozzle. The rotating molten steel cuts the longitudinal magnetic field lines, generating a tangential force opposite to the direction of the vortex, counteracting the tangential velocity already present in the molten steel, thereby suppressing the formation of converging vortices in the molten steel.

[0045] Meanwhile, the magnitude and direction of the magnetic field can be changed by adjusting the magnitude and direction of the current flowing through the electromagnetic coil 3. Furthermore, since the electromagnetic force required to suppress vortices in actual production is not large, the number of turns of the electromagnetic coil 3 that provides the electromagnetic force required to suppress vortices can be calculated based on the dimensions of the stopper rod core 2.

[0046] Let the magnetomotive force of the magnetic circuit be F, the height of the coil be h, the width be b, the cross-sectional area of ​​the coil conductor be A, the number of turns be N, and the winding tightness be K, then:

[0047]

[0048] The current density in the electromagnetic coil is:

[0049]

[0050] The coil width is then:

[0051]

[0052] The average length of one turn of wire in the electromagnetic coil is L:

[0053] By Ohm's Law

[0054]

[0055]

[0056] again:

[0057]

[0058] Substituting equation (6) into equation (5), we get:

[0059]

[0060] Substituting equations (3) and (6) into equation (5), we get:

[0061]

[0062] The number of turns N in the coil is:

[0063]

[0064] Where I is the current intensity (A); U is the power supply voltage (V); R is the winding resistance (Ω); ρ is the resistivity of the conductor material (Ω·m); δ is the air gap length (m); and r is the core radius (m).

[0065] The method for suppressing confluence vortices using the stopper rod of this embodiment specifically includes the following steps:

[0066] Step 1: Based on the dimensions of the plug rod core 2, calculate the number of turns of the electromagnetic coil required to generate the electromagnetic force needed to suppress the vortex confluence.

[0067] Step 2: Wind the electromagnetic coil 3 around the outer peripheral wall of the stopper rod core 2, and then embed the whole into the stopper rod shell 1; then place the assembled stopper rod in the corresponding position in the intermediate package;

[0068] Step 3: After the electromagnetic coil 3 is energized, a magnetic field perpendicular to the tangential velocity of the converging vortex will be generated at the water inlet position to suppress the converging vortex above the water inlet.

[0069] This embodiment describes a method for suppressing converging vortices. The molten steel within the vortex rotates and cuts magnetic field lines, generating a tangential force opposite to the vortex's direction of rotation. Therefore, a force is applied to the molten steel only when vortices are generated; when vortices are not generated, no external force is applied, thus preventing disturbance. This avoids slag layer vibration on the molten steel surface, facilitating the smooth floating of inclusions. Simultaneously, the electromagnetic thermal effect is used for thermal compensation of the molten steel at the end of casting, effectively solving the problem of temperature drop in the molten steel at the end of casting, improving the cleanliness of the molten metal and increasing metal yield, thus ensuring smooth subsequent casting.

[0070] Example 2

[0071] Combination Figure 3 , Figure 4 As shown, this embodiment of a stopper rod for suppressing converging vortices includes a stopper rod body and a rotating magnetic field stirrer 4 disposed within the stopper rod body. The stopper rod body consists of a stopper rod shell 1, a stopper rod core 2, a sleeve brick, and a stopper head brick. The rotating magnetic field stirrer 4 consists of a sensor and a non-magnetic stainless steel shell 43. The sensor is used to excite the rotating magnetic field, and the non-magnetic stainless steel shell 43 is used to protect the sensor and block radiant heat. The sensor includes an annular yoke 41 and a winding coil 42. The winding coil 42 is wound on the annular yoke 41, and the annular yoke 41 is sleeved on the outer peripheral wall of the stopper rod core 2.

[0072] The rotating magnetic field stirrer 4 is installed near the head of the stopper rod. Three sets of these stirrers 4 are arranged vertically, each using a three-phase symmetrical alternating current, which provides the best anti-vortex effect. Of course, the number of rotating magnetic field stirrers 4 is not limited to three sets.

[0073] The rotating magnetic field stirrer 4 employs a toroidal iron core Cram winding, with the winding material being copper tubing. All 12 winding coils 42 are wound around the toroidal yoke 41. The rotating magnetic field stirrer 4 is cooled by water, with water flowing through the copper tubing in the windings. Of course, the winding method is not limited to Cram windings; if a salient pole type is used, the winding material is copper flat wire, with an O-type winding wound around each salient pole. The number of pole pairs used in the rotating magnetic field stirrer 4 includes, but is not limited to, the two pole pairs in this embodiment; it can also be four, six, eight, or even more pole pairs.

[0074] In this embodiment, the three sets of rotating magnetic field stirrers 4 each employ three-phase symmetrical alternating current to generate three sets of sinusoidally distributed magnetic fields along the circumference at different heights within the tundish. When the generated rotating magnetic field cuts the molten steel at a synchronous speed, an induced current is generated within it. This induced current interacts with the molten steel to produce an electromagnetic force. Because the stirrer is cylindrical, the electromagnetic forces induced in the molten steel are paired and opposite in direction, forming an electromagnetic torque that causes the molten steel to rotate. The distribution of the internal magnetic field is as follows:

[0075]

[0076] Where B0 is the magnetic induction intensity amplitude on the surface of the stirrer cavity; r is the radius of the cavity; r0 is the radius of the surface of the stirrer cavity; and p is the number of pole pairs.

[0077] The rotating magnetic field stirrer 4 operates in an alternating forward and reverse manner. Each phase winding of the rotating magnetic field stirrer 4 is supplied with a current of the same frequency and intensity, and the phase sequence is changed at set intervals. This causes the excited magnetic field to alternate between forward and reverse directions according to the set time, resulting in the molten steel rotating intermittently clockwise and counterclockwise to eliminate vortices. Furthermore, magnetic fields in opposite directions are excited between adjacent groups, causing the molten steel to move in opposite directions to achieve the best anti-vortex effect.

[0078] In this embodiment, the rotating magnetic field stirrer 4 requires low power, has a significant suppression effect, and a large magnetic field influence area. Because the iron core of the rotating magnetic field stirrer 4 is closed, the magnetic circuit is also closed, generating an axisymmetric rotating magnetic field in the inner cavity, producing electromagnetic force in the molten steel. Almost all of the induced power is used to drive the movement of the molten steel, resulting in very high efficiency.

[0079] As the magnetic field increases, the formation of vortices decreases significantly. When the magnetic induction intensity reaches 0.17–0.2 T, the formation of vortices is significantly suppressed.

[0080] Specifically, when the rotating magnetic stirrer 4 is fed with three-phase alternating current, a rotating magnetic field is excited within it, rotating around its axis. This magnetic field not only has a certain rotational speed and intensity but also exhibits alternating changes in direction. When it cuts molten steel, an induced current is generated within it, namely:

[0081]

[0082] In the formula: σ is the current density; B is the conductivity of the molten steel; and σ is the magnetic flux density. For induced electromotive force; The slip velocity is the speed at which the magnetic field moves relative to the molten steel.

[0083] The interaction between the induced current generated in molten steel and the local magnetic field produces an electromagnetic force, namely:

[0084]

[0085] This embodiment provides a method for suppressing converging vortices, which specifically includes the following steps:

[0086] Step 1: Place the rotating magnetic stirrer 4 onto the outer peripheral wall of the stopper rod core 2, and then embed it entirely into the stopper rod shell 1; then place the assembled stopper rod in the corresponding position inside the intermediate package;

[0087] Step 2: When the molten steel is about to reach the critical height, the three sets of rotating magnetic field stirrers 4 are simultaneously connected to a three-phase symmetrical sinusoidal alternating current. Electromagnetic force is applied to the molten steel to make it move clockwise and counterclockwise intermittently to suppress the formation of vortices.

[0088] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A stopper rod for suppressing converging vortices, comprising a stopper rod housing (1), wherein a stopper rod core (2) is embedded within the stopper rod housing (1), characterized in that: The stopper rod core (2) is provided with a magnetic field generating device along its outer peripheral wall. The magnetic field generating device is used to generate a magnetic field directly above the water inlet. The magnetic field generating device is a rotary magnetic field stirrer (4), which includes an annular yoke (41), a winding coil (42) and a housing (43). The annular yoke (41) is sleeved on the outer peripheral wall of the stopper rod core (2), and the winding coil (42) is wound on the annular yoke (41). The rotating magnetic field stirrer (4) is arranged in multiple sets along the vertical direction. The multiple sets of rotating magnetic field stirrers (4) adopt three-phase symmetrical alternating current and operate in a forward and reverse alternating mode. The magnetic fields in opposite directions are generated between two adjacent sets of rotating magnetic field stirrers (4).

2. The plug rod for suppressing converging vortices according to claim 1, characterized in that: The rotating magnetic field stirrer (4) is installed near the head of the stopper rod. There are three sets of the rotating magnetic field stirrer (4) arranged in the vertical direction. The three sets of rotating magnetic field stirrers (4) are respectively powered by three-phase symmetrical alternating current.

3. A stopper rod for suppressing converging vortices according to claim 2, characterized in that: The winding coil (42) is a copper tube coil and adopts the core Klamm winding method. Cooling water is passed through the copper tube coil.

4. A method for suppressing converging vortices using a stopper rod as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Place the rotating magnetic stirrer (4) on the outer peripheral wall of the stopper rod core (2), and then embed it entirely inside the stopper rod shell (1); Step 2: Place the assembled stopper rod in the corresponding position inside the intermediate package; Step 3: After the magnetic field generator is powered on, a magnetic field can be generated directly above the water inlet to suppress the converging vortex above the water inlet.

5. The method for suppressing converging vortices according to claim 4, characterized in that: In step one, the magnetic induction intensity of the rotating magnetic stirrer (4) is 0.17~0.2T.

6. The method for suppressing converging vortices according to claim 5, characterized in that: Using formula ， ， ， The electromagnetic force generated in the molten steel was calculated. in, magnetic induction intensity denoted as , where is the magnetic induction intensity amplitude within the stirrer cavity; denoted as r is the radius of the tundish cavity. denoted as , where is the radius of the stirrer cavity; p is the pole pair number. Current density; The electrical conductivity of molten steel; For induced electromotive force; This refers to the slip velocity, which is the velocity of the magnetic field relative to the molten steel. It is electromagnetic force.

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