Traveling wave electromagnetic stirring device for improving surface quality of small-section casting blank and current applying method

Abstract

The invention relates to a traveling wave electromagnetic stirring device for improving the surface quality of a small-section casting blank and a current applying method.The traveling wave electromagnetic stirring device body is arranged in a backflow area on a crystallizer and comprises a plurality of coil fixing sleeves and a plurality of traveling wave magnetic field coils; the plurality of traveling wave magnetic field coils are arranged on the crystallizer copper pipe in a sleeving manner and are sequentially overlapped and arranged in the axial direction of the crystallizer copper pipe to form an annular structure; a plurality of coil fixing sleeves are arranged on the annular structure formed by the traveling wave magnetic field coils, and the coil fixing sleeves are distributed around the circumference of the crystallizer copper pipe; cosine alternating currents in the same direction are applied to the traveling wave magnetic field coils, and upward traveling wave electromagnetic force in the axial direction of the casting blank is formed within unit time; molten steel flowing on the upper portion of the crystallizer can be accelerated, bubbles and inclusions on the solidification front edge are promoted to float upwards, the liquid level slagging capacity of the crystallizer is improved, and the defects such as subsurface bubbles and surface rich carbon of a casting blank are reduced.

Description

Technical Field

[0001] The invention relates to a traveling wave electromagnetic stirring device and a current applying method for improving the surface quality of a small-section casting blank, belonging to the technical field of steel smelting. Background Art

[0002] The pulling speed is usually faster when continuous casting is used to produce small-section ingots. The straight-through nozzle used has a large outlet flow rate, the impact depth of the nozzle jet is deep, the diameter of the submerged nozzle is large, and there is often a flow "dead zone" in the upper area of ​​the crystallizer close to the meniscus. The upper circulation is very weak, the activity of the molten steel surface is poor, and it is difficult for the high-temperature molten steel in the lower part to exchange with the "dead zone". The temperature in the upper area is relatively low, which makes it difficult for inclusions and bubbles to float up, and the slagging effect of the liquid surface is poor, which affects the lubrication and heat transfer effects of the protective slag, and easily causes uneven growth of the primary billet shell, cracks, bubbles, carbon enrichment and other quality problems on the surface of the ingot.

[0003] To address this problem, the coil structure, current intensity, frequency, and installation position of the electromagnetic stirring of the crystallizer are usually adjusted to control the growth of the continuous casting slab shell and the uniformity of heat transfer, promote the floating of bubbles and inclusions in the molten steel, and reduce the risk of cracks on the surface of the slab shell due to thermal stress and uneven composition, such as the application "Layered Coil Crystallizer Electromagnetic Stirrer" with publication number CN109909467A and the application "Continuous Casting Crystallizer Electromagnetic Stirrer with Composite Magnetic Field" with authorization announcement number CN109158563B. The technical solutions mentioned in the patent application are to change the coil winding method of the electromagnetic stirring of the crystallizer to improve the floating environment of inclusions and bubbles and improve the surface quality of the ingot; the application "Simulation setting and optimization method of electromagnetic stirring parameters of square billet continuous casting crystallizer" with publication number CN109165469A and the application "A crystallizer electromagnetic stirring method for improving ingot homogenization" with publication number CN117620108A achieve the best control of the surface quality of the continuous casting ingot by improving the crystallizer electromagnetic stirring excitation current application method.

[0004] However, the magnetic field force of the rotating magnetic field generated by the application with publication number CN109909467A and authorization announcement number CN109158563B is radial, and the axial stirring momentum generated by the stirring method is very small. In view of the significant impact depth of the traditional small-section straight-through water inlet casting, the installation position of the crystallizer electromagnetic stirring is far away from the liquid surface, which makes it difficult to transfer the stirring momentum to the crystallizer liquid surface, and it is difficult to exchange the lower high-temperature molten steel with the upper low-temperature molten steel. In addition, if the intensity of the crystallizer electromagnetic stirring is blindly increased, it will inevitably lead to significant fluctuations in the liquid level, which may cause slag rolling and secondary oxidation.

[0005] At the same time, in terms of the melting and activity of the top slag of the crystallizer, the traditional continuous casting process usually adds a certain amount of solvents to the protective slag according to the requirements of the steel grade, such as Na2O, CaF2, TiO2, LiO2, B2O3, MgO, MnO, etc. For example, the technical solutions mentioned in the application "A low melting point protective slag for centrifugal casting" with publication number CN108927502A and the application "A method for determining the influence of rare earth content in cast steel water on the viscosity of the crystallizer protective slag" with publication number CN114965934A, but this method has complex reactions and a small scope of application for steel grades, and has high requirements for the content of solvents and alkalinity. A large number of industrial experiments are required to obtain the optimal ratio of the content of each component of the protective slag, which is difficult to match and has no wide applicability.

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

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

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

[0009] A traveling wave electromagnetic stirring device for improving the surface quality of small-section ingots. Molten steel is injected into a crystallizer from a straight-through water inlet of a tundish. The ingot is initially formed in a copper tube of the crystallizer and extends downward. A traveling wave electromagnetic stirring device body is arranged in a reflux area on the crystallizer. The traveling wave electromagnetic stirring device body includes a plurality of coil fixing sleeves and a plurality of traveling wave magnetic field coils.

[0010] A plurality of traveling wave magnetic field coils are sleeved on the copper tube of the crystallizer, and are stacked and arranged in sequence along the axial direction of the copper tube of the crystallizer to form a ring structure;

[0011] A plurality of coil fixing sleeves are arranged on the annular structure formed by a plurality of traveling wave magnetic field coils, and the plurality of coil fixing sleeves are distributed around the circumference of the crystallizer copper tube;

[0012] Applying cosine alternating currents with the same direction to a plurality of traveling wave magnetic field coils to form a traveling wave electromagnetic force upward along the axial direction of the casting billet within a unit time;

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

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

[0015] Furthermore, a plurality of grooves are provided on the inner ring of the coil fixing sleeve along the central axis direction, and the grooves are used to clamp the traveling wave magnetic field coil;

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

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

[0018] The current application method of the traveling wave electromagnetic stirring device for improving the surface quality of small-section casting billets is characterized in that the cosine alternating current loaded on the traveling wave magnetic field coil has a phase angle between two adjacent phase currents of 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, and the phase of the current increases sequentially from the straight-through water inlet of the crystallizer to the bottom of the crystallizer. The cosine alternating current is:

[0020]

[0021]

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

[0023] Through the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The traveling wave electromagnetic stirring device for improving the surface quality of small-section ingots provided by the present invention forms an electromagnetic force in an upward direction in the reflux area on the crystallizer, thereby enhancing the development of reflux on the crystallizer, thereby promoting the floating of inclusions and bubbles gathered at the solidification front of the ingot, and increasing the rising flow velocity in the small whirlpool area around the water inlet, thereby enhancing the flow field activity at the steel-slag interface;

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

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

[0027] 4. The current application method of the traveling wave electromagnetic stirring device for improving the surface quality of small-section castings provided by the present invention is used in combination with the traveling wave electromagnetic stirring device body, which solves the problem of insufficient axial stirring momentum of conventional crystallizer electromagnetic stirring and improves the floating efficiency of inclusions and bubbles. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0029] Figure 1 It is a schematic diagram of the main structure of the traveling wave electromagnetic stirring device provided by the present invention, in which the cross section of the casting blank is rectangular;

[0030] Figure 2 It is a cross-sectional view of the main body of the traveling wave electromagnetic stirring device provided by the present invention, wherein the cross section of the casting billet is rectangular, along the axial direction of the casting billet;

[0031] Figure 3 It is a schematic diagram of the main structure of the traveling wave electromagnetic stirring device provided by the present invention, in which the cross section of the casting blank is circular;

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

[0033] Figure 5 It is a schematic diagram of the electromagnetic force of the traveling wave electromagnetic stirring device body in the longitudinal section of the casting billet in the preferred embodiment provided by the present invention;

[0034] Figure 6 It is the flow trace of molten steel in the crystallizer area of ​​the straight-through nozzle casting billet in the preferred embodiment provided by the present invention;

[0035] Figure 7 is a distribution diagram of the axial flow velocity of the molten steel at the center position of the traveling wave electromagnetic stirring device body in the preferred embodiment provided by the present invention;

[0036] Figure 8 It is a flow velocity distribution diagram of molten steel in the corner area of ​​the crystallizer in the preferred embodiment provided by the present invention using the traveling wave electromagnetic stirring device body and without the action of a magnetic field, wherein 8(a) is the flow velocity distribution at the slag interface, 8(b) is the flow velocity distribution at a position 5 mm below the slag interface, and 8(c) is the flow velocity distribution at a position 10 mm below the slag interface.

[0037] In the figure: 1 is a straight-through water inlet, 2 is a copper tube of a crystallizer, 3 is a traveling wave magnetic field coil, 4 is a coil fixing sleeve, and 5 is a casting. DETAILED DESCRIPTION

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

[0039] As described in the background technology, there are currently two main drawbacks in the continuous casting production of small-section ingots, namely, insufficient axial stirring momentum of the conventional crystallizer electromagnetic stirring structure and complex proportion of the crystallizer protective slag.

[0040] A careful analysis of the crystallizer shows that it is located at the top of the continuous casting machine and is the first part to come into contact with the molten steel during the continuous casting process. The molten steel is injected into the crystallizer from the tundish. There is a special cooling structure inside the crystallizer. Under the cooling effect of the copper wall of the crystallizer, the molten steel begins to solidify near its inner wall to form a thin shell. This shell moves downward with the traction of the billet drawing device and gradually leaves the crystallizer. That is, the billet is the product of the initial shape formed in the crystallizer, and then continues to extend and grow downward through subsequent operations such as billet drawing. Therefore, the crystallizer can be regarded as the "mold" where the billet begins to solidify and form. In view of the two disadvantages raised in the background technology, the present application sets a traveling wave electromagnetic stirring device with an electromagnetic force direction upward in the reflux area on the crystallizer to enhance the development of reflux on the crystallizer.

[0041] The specific structure provided in this application is a traveling wave electromagnetic stirring device body, which includes a plurality of coil fixing sleeves and a plurality of traveling wave magnetic field coils, wherein the plurality of traveling wave magnetic field coils are all sleeved on the copper tube of the crystallizer, and are sequentially stacked and arranged along the axial direction of the copper tube of the crystallizer to form a ring structure; a plurality of coil fixing sleeves are arranged on the ring structure formed by the plurality of traveling wave magnetic field coils, and the plurality of 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 a plurality of adjacent traveling wave magnetic field coils, the direction of the magnetic poles alternately points to both sides along the axial direction of the ingot, and finally a traveling wave electromagnetic force is formed upward along the axial direction of the ingot within a unit time, thereby enhancing the development of reflux on the crystallizer, improving the floating efficiency of inclusions and bubbles, and promoting the activity of the slag interface and the melting of the top slag.

[0042] The shape and size of the inner cavity of the crystallizer determine the basic shape of the ingot. If the inner cavity of the crystallizer is rectangular, the cross section of the ingot is basically rectangular; if it is a circular crystallizer, the cross section of the ingot is circular. Therefore, the winding shape of the traveling wave magnetic field coil can be changed according to the cross-sectional shape of the ingot, which makes the electromagnetic stirring device body well adapted to various shapes of small cross-sectional ingots. Figure 1 , Figure 3 As shown in the figure, examples of rectangular and circular cross-sections are given respectively. When the coil winding shape is adapted to the cross-sectional shape of the ingot, the strength of the magnetic field transmitted to the inside of the ingot is ensured to be consistent, and the electromagnetic force can act on the molten steel more effectively. Compared with the loss or unevenness of force that may occur when a coil of a fixed shape stirs ingots of different shapes, this design with a changeable winding shape can improve the efficiency of electromagnetic stirring and make the flow of molten steel in the ingot 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 the rectangular cross-section of the ingot as an example. Figure 2 As shown, a plurality of grooves are arranged along the central axis direction in the inner ring of the coil fixing sleeve, and the grooves are used to clamp the traveling wave magnetic field coil. Of course, the intervals between adjacent grooves are the same, and the number of grooves is equal to the number of traveling wave magnetic field coil layers. The evenly distributed traveling wave magnetic field coil can generate a relatively uniform magnetic field, so that the casting is subjected to a relatively balanced electromagnetic stirring force in all directions of the circumference, which can avoid local differences in the surface quality of the casting caused by uneven stirring.

[0044] If the traveling wave magnetic field coil is set to n layers, then n = 2, 4, 6, and the number of turns of each layer of the traveling wave magnetic field coil is 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 pulling speeds, and different small-section billet sizes, the intensity of electromagnetic stirring can be flexibly changed according to actual needs. It should be emphasized that the traveling wave magnetic field coil is set to an even number of layers, which can better ensure the symmetry of the magnetic field distribution. This is because during the electromagnetic stirring process, the even-numbered layers of coils can be arranged opposite to each other, so that the magnetic field generated in the circumferential direction can be balanced and symmetrical with each other, ensuring that the molten steel is subjected to uniform electromagnetic stirring force in the billet, which helps to improve the surface quality of the billet.

[0045] In actual operation, the traveling wave electromagnetic stirring device body is set within the range of 200-600mm from the crystallizer liquid surface, and can be adjusted in combination with parameters such as the cross-sectional shape, size, pulling speed, and immersion nozzle depth of the ingot. This is because the flow state of molten steel in the upper reflux area of ​​the crystallizer is closely related to the distribution of inclusions, and is a key area that affects the surface quality of the ingot. By accurately adjusting the position of the electromagnetic stirring device and ensuring that the electromagnetic stirring device body is located in the upper reflux area of ​​the molten steel in the crystallizer, the electromagnetic stirring force can be accurately applied to this key area, thereby improving the stirring effect and effectively improving the surface quality of the small-section ingot.

[0046] As mentioned above, if a traveling electromagnetic force is to be formed in the unit time along the axial direction of the ingot, a cosine alternating current needs to be loaded on the traveling magnetic field coil. Due to factors such as different steel grades, pulling speeds, and the initial state of the molten steel in the crystallizer, the fluctuation range and flow rate of the slag-steel interface will be different. By adjusting the current intensity and frequency, the magnitude and frequency of the electromagnetic stirring force can be effectively controlled to adapt to different working conditions. Therefore, in order to achieve the technical purpose of this application, the phase angle between the adjacent two-phase current is set to The current intensity is 500-2000A, the current frequency is 5-12Hz, and can be adjusted according to the slag-steel interface fluctuation range and flow rate.

[0047] Specifically, a cosine alternating current is applied within a period of 2π, and the phase of the current increases sequentially from the through-type water inlet 1 of the ladle to the bottom of the crystallizer. The cosine alternating current is:

[0048]

[0049]

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

[0051] Example:

[0052] In order to verify the feasibility of the above-mentioned traveling wave electromagnetic stirring device and current application method for improving the surface quality of small-section ingots, the present application provides the following specific cases.

[0053] Likewise Figure 1For example, the casting billet 5 uses a 140mm×140mm square billet with a fillet of 10mm, the straight-through water inlet 1 has a diameter of 23mm, an insertion depth of 110mm, and the crystallizer copper tube 2 has a thickness of 8mm and a length of 800mm. The electromagnetic stirring device body is installed at a position 350mm away from the crystallizer liquid surface, and is formed by a combination of 4 coil fixing sleeves and 6 layers of traveling wave magnetic field coils. The coil fixing sleeve 4 is arranged equidistantly along the winding direction of the traveling wave magnetic field coil 3, and 6 grooves with a width of 20mm are opened on the inside to fix the traveling wave magnetic field coil 3. Each layer of the traveling wave magnetic field coil has 10 turns, for a total of 60 turns.

[0054] The traveling wave magnetic field coil 3 is made of copper wire, and cosine alternating currents of the same direction are passed through adjacent traveling wave magnetic field coils, and the phase angles differ by 60° (six layers of traveling wave magnetic field coils are set here, so the calculated results of adjacent current phase angles differ by 60°). The excitation current is 1500A and the frequency is 3Hz, forming a traveling wave electromagnetic force axially upward along the ingot 5 within a unit period.

[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 are the alternating currents applied by each traveling wave magnetic field coil, I m is the current intensity amplitude, ω is the angular frequency, and t is the time.

[0063] Figure 4As shown, it is the magnetic pole change in the unit period of this embodiment. Figure 4 From (a) to (f), the phase angles range from 0°, 60°, 120°, 180°, 240° to 300°. It should be noted that the direction of the current is arbitrary, either clockwise or counterclockwise, but the phase sequence affects the direction of the electromagnetic force. Therefore, it increases in sequence along the billet drawing direction. As the phase angle changes, the direction of the magnetic field alternately points to the two sides of the billet 5, and finally forms the following: Figure 5 The traveling electromagnetic force is in the upward direction as shown. Figure 5 It can be seen that the electromagnetic force is mainly concentrated in the surface area of ​​the ingot, which can effectively flush out the bubbles and inclusions at the solidification front of the ingot and improve the surface quality of the ingot.

[0064] Figure 7 is the axial velocity distribution on the diagonal line of the ingot 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 reflux direction on the crystallizer (such as Figure 6 As shown, it can be seen that compared with the case without a magnetic field, the magnetic field in this embodiment can significantly enhance the reflux flow rate on the crystallizer. Under the parameter conditions described in this embodiment, the reflux flow rate is enhanced by about 33 mm / s.

[0065] Figure 8 Figures 8a, 8b and 8c are the distribution of molten steel flow rate at the corner of the ingot at 0mm, 5mm and 10mm away from the crystallizer liquid surface respectively. It can be seen that under the action of the traveling wave electromagnetic stirring device body provided in the embodiment, the molten steel flow rate near the crystallizer liquid surface is significantly improved, which effectively improves the liquid surface activity of the straight-through water inlet, helps the crystallizer protective slag to smoothly slag and lubricate the outer surface of the ingot shell, thereby improving the surface quality of the ingot.

[0066] In summary, the traveling wave electromagnetic stirring device and current application method for improving the surface quality of small-section ingots provided in the present application are simple in device and easy to install, avoiding the drawbacks of insufficient axial stirring momentum and complex ratio of crystallizer protective slag in the traditional crystallizer electromagnetic stirring structure, and can enhance the circulation intensity of the molten steel in the crystallizer, effectively promote the floating of bubbles and inclusions, improve the slag formation on the liquid surface, and improve the surface quality of the ingot.

[0067] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0068] The meaning of "and / or" described in this application means that the situations where each exists alone or both exist at the same time are included.

[0069] The term “connection” as used in this application may mean a direct connection between components or an indirect connection between components via other components.

[0070] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A traveling wave electromagnetic stirring device for improving the surface quality of small-section castings, characterized in that: Molten steel is injected into the crystallizer from the straight-through water inlet of the tundish. The ingot is initially formed in the copper tube of the crystallizer and extends downward. A traveling wave electromagnetic stirring device body is arranged in the reflux area of ​​the crystallizer. The traveling wave electromagnetic stirring device body includes a plurality of coil fixing sleeves and a plurality of traveling wave magnetic field coils. A plurality of traveling wave magnetic field coils are sleeved on the copper tube of the crystallizer, and are stacked and arranged in sequence along the axial direction of the copper tube of the crystallizer to form a ring structure; A plurality of coil fixing sleeves are arranged on the annular structure formed by a plurality of traveling wave magnetic field coils, and the plurality of 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 a number of traveling wave magnetic field coils, so that a traveling wave electromagnetic force is formed upward along the axial direction of the casting billet within a unit time.

2. The traveling wave electromagnetic stirring device for improving the surface quality of small-section casting according to claim 1, characterized in that: The traveling wave electromagnetic stirring device body is arranged within a range of 200-600 mm from the liquid surface of the crystallizer.

3. The traveling wave electromagnetic stirring device for improving the surface quality of small-section casting according to claim 1, characterized in that: The traveling wave magnetic field coils are arranged in n layers, where n=2, 4, 6, and the number of turns of each layer of the traveling wave magnetic field coils is 10-30 turns.

4. The traveling wave electromagnetic stirring device for improving the surface quality of small-section casting billets according to claim 1, characterized in that: A plurality of grooves are arranged on the inner ring of the coil fixing sleeve along the central axis direction, and the grooves are used to clamp the traveling wave magnetic field coil; The intervals between adjacent grooves are the same, and the number of grooves is equal to the number of traveling wave magnetic field coil layers.

5. The traveling wave electromagnetic stirring device for improving the surface quality of small-section casting billets according to claim 1, characterized in that: The inner cavity shape of the traveling wave magnetic field coil matches the cross-sectional shape of the casting billet.

6. The current application method of the traveling wave electromagnetic stirring device for improving the surface quality of small-section casting according to claim 3, characterized in that: The cosine alternating current loaded on the traveling wave magnetic field coil has a phase angle between two adjacent phase currents. The current intensity is 500-2000A and the current frequency is 5-12Hz.

7. The current application method of the traveling wave electromagnetic stirring device for improving the surface quality of small-section casting according to claim 6, characterized in that: A cosine alternating current is applied within a period of 2π, and the phase of the current increases sequentially from the straight-through water inlet of the crystallizer to the bottom of the crystallizer. The cosine alternating current is: In the above formula, i n Represents the cosine alternating current applied by each traveling wave magnetic field coil, I m represents the current intensity amplitude, ω represents the angular frequency, t represents the time, and n=2,4,6.

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