A traveling wave electromagnetic stirring device and current application method for improving surface quality of small-section casting blank

Abstract

The application relates to a kind of surface quality of small section casting blank of improving traveling wave electromagnetic stirring device and current application method, traveling wave electromagnetic stirring device body is arranged on the backflow area of crystallizer, the traveling wave electromagnetic stirring device body includes several coil fixing sleeves and several traveling wave magnetic field coils, several traveling wave magnetic field coils are all set on the copper pipe of crystallizer, and sequentially superimposed arrangement is formed annular structure along the axial direction of copper pipe of crystallizer;Several coil fixing sleeves are arranged on the annular structure formed by several traveling wave magnetic field coils, and several coil fixing sleeves are distributed around the circumference of copper pipe of crystallizer;Same direction cosine alternating current is applied to several traveling wave magnetic field coils, and traveling wave electromagnetic force is formed upwards along the axial direction of casting blank in unit time;The application can accelerate the flow of molten steel in the upper part of crystallizer, promote the bubble and inclusion of solidification front to float, improve the ability of crystallizer liquid surface slag, reduce the skin bubble and surface carbon-rich defects of casting blank.

Description

Technical Field

[0001] This invention relates to a traveling wave electromagnetic stirring device and current application method for improving the surface quality of small cross-section cast billets, belonging to the field of iron and steel smelting technology. Background Technology

[0002] When continuously casting small-section billets, the casting speed is usually high. The outlet flow velocity of the straight-through nozzle is high, and the impact depth of the nozzle jet is deep. The diameter of the submerged entry nozzle is large. There is often a flow "dead zone" in the upper region of the crystallizer near the meniscus. The upper circulation is very weak, the steel surface activity is poor, and the high-temperature steel in the lower part is difficult to exchange with the "dead zone". The temperature in the upper region is low, which makes it difficult for inclusions and bubbles to float. The slag formation effect on the liquid surface is poor, which affects the lubrication and heat transfer effect of the protective slag. This can easily cause uneven growth of the initial billet shell, cracks, bubbles, carbon enrichment and other quality problems on the billet surface.

[0003] To address this issue, parameters such as the coil structure, current intensity, frequency, and installation position of the electromagnetic stirrer in the crystallizer are typically adjusted to control the growth and heat transfer uniformity of the continuously cast billet shell, promote the rising of bubbles and inclusions in the molten steel, and reduce the risk of cracks on the billet shell surface caused by thermal stress and compositional inhomogeneity. Examples include application CN109909467A, "Layered Coil Crystallizer Electromagnetic Stirrer," and application CN109158563B, "Continuous Casting Crystallizer Electromagnetic Stirrer with Composite Magnetic Field." The technical solutions mentioned above all improve the floating environment of inclusions and bubbles and enhance the surface quality of the cast billet by changing the winding method of the electromagnetic stirring coil in the crystallizer. The application with publication number CN109165469A, "Simulation Setting and Optimization Method of Electromagnetic Stirring Parameters in Square Billet Continuous Casting Crystallizer", and the application with publication number CN117620108A, "An Electromagnetic Stirring Method for Improving the Homogenization of Cast Billet", achieve optimal control of the surface quality of the continuously cast billet by improving the application method of the excitation current of the electromagnetic stirring in the crystallizer.

[0004] However, the rotating magnetic field generated by the applications with publication number CN109909467A and authorization announcement number CN109158563B is radial, and the axial stirring momentum generated by the stirring method is very small. Given the significant impact depth of the billet in traditional small-section straight-through nozzle castings, the installation position of the electromagnetic stirrer in the crystallizer is relatively far from the liquid surface, making it difficult to transfer the stirring momentum to the liquid surface of the crystallizer, thus hindering the exchange between the lower high-temperature molten steel and the upper low-temperature molten steel. Furthermore, blindly increasing the intensity of the electromagnetic stirring in the crystallizer will inevitably lead to significant fluctuations in the liquid surface, which may in turn cause slag entrapment and secondary oxidation.

[0005] Meanwhile, regarding the melting and activity of the top slag in the crystallizer, traditional continuous casting processes typically add a certain amount of fluxing agents, such as Na2O, CaF2, TiO2, LiO2, B2O3, MgO, and MnO, to the protective slag according to the steel grade requirements. This is exemplified by the technical solutions mentioned in applications CN108927502A ("A Low-Melting-Point Protective Slag for Centrifugal Casting") and CN114965934A ("A Method for Determining the Influence of Rare Earth Content in Molten Steel on the Viscosity of Crystallizer Protective Slag"). However, this approach involves complex reactions, has a limited range of applicable steel grades, and requires high fluxing agent content and basicity. It necessitates extensive industrial experiments to determine the optimal ratio of each component in the protective slag, which is difficult and lacks broad applicability.

[0006] Therefore, it is necessary to provide a traveling wave electromagnetic stirring device and its usage method to solve the problem of surface quality of small cross-section continuous casting billets. Summary of the Invention

[0007] This invention provides a traveling wave electromagnetic stirring device and current application method for improving the surface quality of small cross-section billets. It can accelerate the flow of molten steel in the upper part of the crystallizer, promote the floating of bubbles and inclusions at the solidification front, improve the slag formation ability of the crystallizer liquid surface, and reduce defects such as subcutaneous bubbles and surface carbon enrichment of the billet.

[0008] The technical solution adopted by this invention to solve its technical problem is:

[0009] A traveling wave electromagnetic stirring device for improving the surface quality of small-section cast billets is disclosed. Molten steel is injected into the crystallizer through a straight-through nozzle from the tundish. The cast billet is initially formed and grows downward within the copper tube of the crystallizer. The traveling wave electromagnetic stirring device body is installed in the reflux area of ​​the crystallizer. The traveling wave electromagnetic stirring device body includes several coil fixing sleeves and several traveling wave magnetic field coils.

[0010] Several traveling wave magnetic field coils are all sleeved on the copper tube of the crystallizer, and are stacked sequentially along the axial direction of the copper tube of the crystallizer to form a ring structure;

[0011] Several coil fixing sleeves are set on a ring structure formed by several traveling wave magnetic field coils, and the coil fixing sleeves are distributed around the circumference of the crystallizer copper tube.

[0012] Applying cosine alternating currents in the same direction to several traveling wave magnetic field coils generates a traveling wave electromagnetic force that moves upward along the axial direction of the billet per unit time.

[0013] Furthermore, the traveling wave electromagnetic stirring device body is positioned within a range of 200-600mm from the liquid surface of the crystallizer;

[0014] Furthermore, the traveling wave magnetic field coil is arranged in n layers, n = 2, 4, 6, and the number of turns of each layer of traveling wave magnetic field coil is 10-30 turns;

[0015] Furthermore, several grooves are provided along the central axis direction on the inner ring of the coil fixing sleeve, and the grooves are used to hold the traveling wave magnetic field coil.

[0016] The spacing between adjacent trenches is the same, and the number of trenches is equal to the number of traveling wave magnetic field coil layers;

[0017] Furthermore, the inner cavity shape of the traveling wave magnetic field coil matches the cross-sectional shape of the cast billet;

[0018] The current application method of the traveling wave electromagnetic stirring device for improving the surface quality of small cross-section cast billets involves applying a cosine alternating current to the traveling wave magnetic field coil, wherein the phase angle between adjacent phase currents is... The current intensity is 500-2000A, and the current frequency is 5-12Hz;

[0019] Furthermore, a cosine alternating current is applied within a period of 2π, with the phase of the current increasing sequentially from the straight-through inlet of the crystallizer to the bottom of the crystallizer. The cosine alternating current is:

[0020]

[0021]

[0022] In the above formula, i n I represents the cosine alternating current applied to each traveling wave magnetic field coil. m ω represents the amplitude of the current intensity, t represents the angular frequency, and n = 2, 4, 6.

[0023] By employing the above technical solutions, the present invention has the following beneficial effects compared to the prior art:

[0024] 1. The traveling wave electromagnetic stirring device for improving the surface quality of small cross-section cast billets provided by the present invention generates an upward electromagnetic force in the reflux area of ​​the crystallizer, enhances the development of reflux in the crystallizer, thereby promoting the floating of inclusions and bubbles accumulated at the solidification front of the cast billet, and increasing the upflow velocity in the small swirling zone around the nozzle, thereby enhancing the flow field activity at the steel-slag interface.

[0025] 2. The traveling wave electromagnetic stirring device for improving the surface quality of small cross-section billets provided by the present invention can ensure that no slag is generated on the surface of the crystallizer and that the top solid slag is efficiently melted by controlling the parameters of the traveling wave magnetic field coil.

[0026] 3. The traveling wave electromagnetic stirring device for improving the surface quality of small cross-section cast billets provided by the present invention, compared with the traditional crystallizer electromagnetic stirring technology, generates a smaller electromagnetic force intensity and a single direction under the same parameters, mainly concentrated at the front of the cast billet solidification, and has almost no effect on the reflux pattern of molten steel and the core flow field.

[0027] 4. The current application method of the traveling wave electromagnetic stirring device for improving the surface quality of small cross-section billets provided by the present invention, when used in conjunction with the traveling wave electromagnetic stirring device body, solves the problem of insufficient axial stirring momentum of traditional crystallizer electromagnetic stirring and improves the floating efficiency of inclusions and bubbles. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Figure 1 This is a schematic diagram of the main body structure of the traveling wave electromagnetic stirring device with a rectangular cross-section for casting billets provided by the present invention.

[0030] Figure 2 This is a cross-sectional view of the body of the traveling wave electromagnetic stirring device with a rectangular cross-section of the billet provided by the present invention along the axial direction of the billet.

[0031] Figure 3 This is a schematic diagram of the main body structure of the traveling wave electromagnetic stirring device with a circular cross-section for casting billets provided by the present invention.

[0032] Figure 4 This is a schematic diagram of the change of magnetic pole direction within a unit period according to a preferred embodiment of the present invention, wherein (a) 0°, (b) 60°, (c) 120°, (d) 180°, (e) 240°, and (f) 300°;

[0033] Figure 5 This is a schematic diagram of the electromagnetic force of the traveling wave electromagnetic stirring device body in the longitudinal section of the billet in a preferred embodiment of the present invention.

[0034] Figure 6 This is the steel flow trace of the straight-through nozzle billet in the crystallizer region in the preferred embodiment of the present invention;

[0035] Figure 7 This is a diagram showing the axial velocity distribution of molten steel at the center of the traveling wave electromagnetic stirring device in a preferred embodiment of the present invention.

[0036] Figure 8 This is a preferred embodiment of the present invention, showing the flow velocity distribution of molten steel in the corner region of the crystallizer under the action of a traveling wave electromagnetic stirring device and without a magnetic field. In this embodiment, 8(a) is the flow velocity distribution at the steel-slag interface, 8(b) is the flow velocity distribution at a position 5 mm below the steel-slag interface, and 8(c) is the flow velocity distribution at a position 10 mm below the steel-slag interface.

[0037] In the diagram: 1 is a straight-through nozzle, 2 is a copper tube for the crystallizer, 3 is a traveling wave magnetic field coil, 4 is a coil fixing sleeve, and 5 is a casting billet. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings. In the description of this application, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of the present invention.

[0039] As described in the background section, there are currently two main drawbacks in the production of small-section billets by continuous casting: insufficient axial stirring momentum of the traditional electromagnetic stirring structure for crystallizers and complex formulation of protective slag in crystallizers.

[0040] A careful analysis of the crystallizer reveals that it is located at the top of the continuous casting machine and is the first part to come into contact with molten steel during the continuous casting process. Molten steel is poured into the crystallizer from the tundish. The crystallizer has a special cooling structure, and under the cooling effect of the copper walls, the molten steel begins to solidify near the inner wall, forming a thin shell. This shell moves downwards with the traction of the casting device and gradually leaves the crystallizer. In other words, the billet is the product of initial shaping in the crystallizer, which continues to grow downwards through subsequent casting operations. Therefore, the crystallizer can be seen as the "mold" from which the billet begins to solidify and take shape. Addressing the two drawbacks mentioned in the background technology, this application enhances the development of backflow in the crystallizer by incorporating an upward-directed traveling wave electromagnetic stirring device in the reflux region.

[0041] The specific structure provided in this application is a traveling wave electromagnetic stirring device body, which includes several coil fixing sleeves and several traveling wave magnetic field coils. The traveling wave magnetic field coils are all sleeved on the copper tube of the crystallizer and are sequentially stacked along the axial direction of the copper tube to form a ring structure. Several coil fixing sleeves are set on the ring structure formed by the traveling wave magnetic field coils, and the coil fixing sleeves are distributed around the circumference of the copper tube of the crystallizer. When a cosine alternating current with the same direction is applied to several adjacent traveling wave magnetic field coils, the magnetic poles alternately point to both sides along the axial direction of the casting billet, ultimately forming a traveling wave electromagnetic force upward along the axial direction of the casting billet per unit time. This enhances the reflux development in the crystallizer, improves the efficiency of inclusion and bubble flotation, and promotes the activity of the steel-slag interface and the melting of the top slag.

[0042] The shape and size of the crystallizer's inner cavity determine the basic shape of the cast billet. If the crystallizer's inner cavity is rectangular, then the cross-section of the cast billet is also basically rectangular; if it's a circular crystallizer, the cross-section of the cast billet is circular. Therefore, the winding shape of the traveling wave magnetic field coil can be changed according to the cross-sectional shape of the cast billet, which allows the electromagnetic stirring device to be well adapted to small-section cast billets of various shapes. Figure 1 , Figure 3 As shown, examples with rectangular and circular cross-sections are given respectively. When the coil winding shape matches the cross-sectional shape of the billet, it ensures that the strength of the magnetic field transmitted into the billet is consistent, and the electromagnetic force can act more effectively on the molten steel. Compared with the potential force loss or unevenness that may occur when stirring billets of different shapes with a fixed-shape coil, this design with an adjustable winding shape can improve the efficiency of electromagnetic stirring, making the flow of molten steel in the billet more in line with the requirements for improving surface quality.

[0043] The coil fixing sleeve is used to fix several layers of traveling wave magnetic field coils. Here, we take a cast billet with a rectangular cross-section as an example. Figure 2 As shown, several grooves are provided along the central axis of the inner ring of the coil fixing sleeve. These grooves are used to hold the traveling wave magnetic field coil. The spacing between adjacent grooves is the same, and the number of grooves is equal to the number of traveling wave magnetic field coil layers. The uniformly distributed traveling wave magnetic field coils can generate a relatively uniform magnetic field, thereby subjecting the cast billet to a relatively balanced electromagnetic stirring force in all directions of the circumference. This avoids localized differences in the surface quality of the cast billet caused by uneven stirring.

[0044] If the traveling wave magnetic field coil has n layers, then n = 2, 4, or 6, and each layer has 10-30 turns. The traveling wave magnetic field coil can be wound with copper wire or hollow conduit. This multi-layer and variable-turns design provides the possibility of flexibly adjusting the electromagnetic stirring intensity. By increasing or decreasing the number of layers and adjusting the number of turns, the intensity of the magnetic field can be changed. For different steel grades, different casting speeds, and different small-section billet sizes, the intensity of electromagnetic stirring can be flexibly changed according to actual needs. It is important to emphasize that setting the traveling wave magnetic field coil to an even number of layers can better ensure the symmetry of the magnetic field distribution. This is because during the electromagnetic stirring process, even-numbered layers of coils can be arranged in pairs opposite each other, so that the magnetic fields generated in the circumferential direction can be balanced and symmetrical, ensuring that the molten steel receives a uniform electromagnetic stirring force within the billet, which helps to improve the surface quality of the billet.

[0045] In actual operation, the traveling wave electromagnetic stirring device is positioned within a range of 200-600mm from the liquid surface of the crystallizer. This position can be adjusted based on parameters such as the shape and size of the billet cross-section, casting speed, and the depth of the submerged entry nozzle. This is because the flow state of the molten steel in the upper reflux area of ​​the crystallizer is closely related to the distribution of inclusions, making it a critical area affecting the surface quality of the billet. By precisely adjusting the position of the electromagnetic stirring device, ensuring that the device is located in the upper reflux area of ​​the molten steel in the crystallizer, the electromagnetic stirring force can be accurately applied to this critical area, improving the stirring effect and effectively improving the surface quality of small-section billets.

[0046] As mentioned above, to generate a traveling wave electromagnetic force along the axial direction of the billet within a unit time, a cosine alternating current needs to be applied to the traveling wave magnetic field coil. Due to factors such as different steel grades, casting speeds, and the initial state of the molten steel in the crystallizer, the fluctuation range and flow velocity at the slag-steel interface will vary. By adjusting the current intensity and frequency, the magnitude and frequency of the electromagnetic stirring force can be effectively controlled, thus adapting to different working conditions. Therefore, to achieve the technical objective of this application, the phase angle between adjacent current phases is set to be... The current intensity is 500-2000A, the current frequency is 5-12Hz, and it can be adjusted according to the fluctuation range of the slag-steel interface and the flow rate.

[0047] Specifically, a cosine alternating current is applied within a period of 2π, with the phase of the current increasing sequentially from the straight-through nozzle 1 of the ladle to the bottom of the crystallizer. The cosine alternating current is:

[0048]

[0049]

[0050] In the above formula, i n I represents the cosine alternating current applied to each traveling wave magnetic field coil. m ω represents the amplitude of the current intensity, t represents the angular frequency, and n = 2, 4, 6.

[0051] Example:

[0052] To verify the feasibility of the traveling wave electromagnetic stirring device and current application method for improving the surface quality of small cross-section cast billets provided above, this application provides the following specific examples.

[0053] Similarly Figure 1For example, the billet 5 is a 140mm × 140mm square billet with a 10mm radius corner. The diameter of the straight-through nozzle 1 is 23mm, and the insertion depth is 110mm. The thickness of the copper tube 2 in the crystallizer is 8mm, and the length is 800mm. The electromagnetic stirring device body is installed at a position 350mm from the liquid surface of the crystallizer. It is formed by combining 4 coil fixing sleeves and 6 layers of traveling wave magnetic field coils. The coil fixing sleeves 4 are arranged at equal intervals along the winding direction of the traveling wave magnetic field coils 3, and 6 grooves with a width of 20mm are opened on the inner side to fix the traveling wave magnetic field coils 3. Each layer of traveling wave magnetic field coils has 10 turns, for a total of 60 turns.

[0054] The traveling wave magnetic field coil 3 is made of copper wire. The adjacent traveling wave magnetic field coils are supplied with cosine alternating currents in the same direction, and the phase angles are all 60° apart (here, six layers of traveling wave magnetic field coils are set, so the phase angles of adjacent currents are calculated to be 60° apart). The excitation current is 1500A and the frequency is 3Hz, forming a traveling wave electromagnetic force along the axial direction of the billet 5 in one unit cycle.

[0055] The applied cosine alternating current is as follows:

[0056] i A =I m cosωt

[0057] i B =I m cos(ωt+π / 3)

[0058] i C =I m cos(ωt+2π / 3)

[0059] i D =I m cos(ωt+π)

[0060] i E =I m cos(ωt+4π / 3)

[0061] i F =I m cos(ωt+5π / 3)

[0062] Among them, i A i B i C i D i E i F These are the alternating currents applied to each traveling wave magnetic field coil, I m ω is the amplitude of the current intensity, ω is the angular frequency, and t is the time.

[0063] Figure 4The figure shows the magnetic pole changes within a unit period in this embodiment. Figure 4 Within the casting, from (a) to (f), the phase angles range from 0°, 60°, 120°, 180°, 240° to 300°. It's important to note that the current direction is arbitrary, either clockwise or counterclockwise, but the phase sequence affects the direction of the electromagnetic force. Therefore, the phase angles increase sequentially along the casting direction. As the phase angles change, the magnetic field direction alternately points towards both sides of the casting slab 5, ultimately forming the following... Figure 5 The electromagnetic force shown is an upward-directed traveling wave. From Figure 5 As can be seen, the electromagnetic force is mainly concentrated on the surface area of ​​the billet, which can effectively flush out bubbles and inclusions at the solidification front of the billet and improve the surface quality of the billet.

[0064] Figure 7 This represents the axial velocity distribution along the diagonal of the billet at the center of the traveling wave electromagnetic stirring device. The negative direction represents the jet direction of the straight-through nozzle, and the positive direction represents the return flow direction on the crystallizer (e.g., Figure 6 As shown in the figure, it can be seen that compared with the case without a magnetic field, the magnetic field in this embodiment can significantly enhance the reflux velocity on the crystallizer, by about 33 mm / s under the parameters described in this embodiment.

[0065] Figure 8 Figures 8a, 8b, and 8c show the steel flow velocity distribution at the corners of the billet at positions 0mm, 5mm, and 10mm from the liquid surface in the crystallizer, respectively. It can be seen that under the action of the traveling wave electromagnetic stirring device provided in the embodiment, the steel flow velocity near the liquid surface in the crystallizer is significantly increased, which effectively improves the activity of the liquid surface in the straight-through nozzle, helps the protective slag in the crystallizer to smoothly slag and lubricate the outer surface of the billet shell, and improves the surface quality of the billet.

[0066] In summary, the traveling wave electromagnetic stirring device and current application method for improving the surface quality of small cross-section cast billets provided in this application are simple in equipment and easy to install. They avoid the drawbacks of insufficient axial stirring momentum and complex mold flux ratio of traditional crystallizer electromagnetic stirring structures. Furthermore, they can enhance the circulation intensity of molten steel in the crystallizer, effectively promote the floating of bubbles and inclusions, improve slag formation on the liquid surface, and improve the surface quality of the cast billet.

[0067] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0068] The meaning of "and / or" as used in this application includes situations where each exists alone or both exist simultaneously.

[0069] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0070] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for applying current to a traveling wave electromagnetic stirring device to improve the surface quality of small-section cast billets, characterized in that: Molten steel is injected into the crystallizer through a straight-through nozzle in the tundish. The billet is initially formed and grows downward inside the copper tube of the crystallizer. A traveling wave electromagnetic stirring device body is set in the reflux area of ​​the crystallizer. The traveling wave electromagnetic stirring device body includes several coil fixing sleeves and several traveling wave magnetic field coils. The several traveling wave magnetic field coils are all sleeved on the copper tube of the crystallizer and are arranged in a ring shape along the axial direction of the copper tube of the crystallizer. Several coil fixing sleeves are set on a ring structure formed by several traveling wave magnetic field coils, and the coil fixing sleeves are distributed around the circumference of the copper tube of the crystallizer; a cosine alternating current with the same direction is applied to several traveling wave magnetic field coils to form a traveling wave electromagnetic force upward along the axial direction of the billet per unit time; The traveling wave electromagnetic stirring device body is positioned within a range of 200-600mm from the liquid surface of the crystallizer; the traveling wave magnetic field coil is set... layer, The number of turns in each traveling wave magnetic field coil is 10-30. The cosine alternating current applied to the traveling wave magnetic field coil has a phase angle between two adjacent phase currents of 1. The current intensity is 500-2000A, and the current frequency is 5-12Hz; In a cycle A cosine alternating current is applied internally, with the phase of the current increasing sequentially from the straight-through inlet of the crystallizer to the bottom of the crystallizer. The cosine alternating current is: ， In the above formula, This represents the cosine alternating current applied to each traveling wave magnetic field coil. Indicates the amplitude of current intensity. Represents angular frequency. Indicates time, .

2. The traveling wave electromagnetic stirring device for improving the surface quality of small cross-section cast billets according to claim 1, characterized in that: Several grooves are provided along the central axis on the inner ring of the coil fixing sleeve. The grooves are used to hold the traveling wave magnetic field coil. The spacing between adjacent trenches is the same, and the number of trenches is equal to the number of traveling wave magnetic field coil layers.

3. The traveling wave electromagnetic stirring device for improving the surface quality of small cross-section cast billets according to claim 2, characterized in that: The inner cavity shape of the traveling wave magnetic field coil matches the cross-sectional shape of the billet.

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