A composite side spiral electromagnetic stirring device

Abstract

The present invention relates to a composite side spiral electromagnetic stirring device, comprising a yoke group, a yoke fixing sleeve, a rotating magnetic field coil and a traveling wave magnetic field coil; when the alternating current applied by the traveling wave magnetic field coil is positive, the alternating current is connected in the forward direction, and when the alternating current applied by the traveling wave magnetic field coil is negative, the alternating current is connected in the reverse direction, so that the direction of the magnetic pole alternately points to the two ends of the ingot; the rotating magnetic field coil generates a rotating electromagnetic force that moves circumferentially along the ingot and forms a rotating magnetic field; the traveling wave magnetic field coil generates a traveling wave electromagnetic force that is transmitted radially toward the center of the ingot and has an axial component force, and the formed traveling wave magnetic field causes the rotating magnetic field to tilt along the axial direction of the ingot, and the finally formed coupled magnetic field has a side spiral stirring effect that is inclined to the cross section of the ingot, effectively improving the phenomenon of negative segregation caused by excessive stirring intensity during the casting process of large-size ingots.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic metallurgy casting, and in particular to a composite side spiral electromagnetic stirring device. Background Art

[0002] Quality control is a paramount requirement in the metal casting process. The quality of the ingot is closely related to the flow, heat and mass transfer behavior of the molten steel during solidification. Electromagnetic fields offer advantages unmatched by other physical fields, most notably their ability to transfer heat and kinetic energy without direct contact with the molten steel, and without pollution. Therefore, electromagnetic stirring has become an effective means of controlling the flow of molten steel to improve ingot quality. This technology can promote mixing of the molten steel at the solidification front, homogenize the composition and temperature of the unsolidified zone, improve the cleanliness of the molten steel, expand the equiaxed crystal zone, and improve porosity and segregation. In recent years, it has been widely used in continuous casting, semi-solid casting, and directional solidification processes.

[0003] Rotary electromagnetic stirring plays a crucial role in refining microstructure grains and homogenizing the circumferential temperature distribution of ingots. However, axial stirring is insufficient, resulting in a limited effective range. Furthermore, excessive stirring intensity can lead to negative segregation at the edges of ingots. Traveling-wave electromagnetic stirring can control and regulate the axial motion of molten steel within the ingot, promoting axial convection and expanding the axial stirring range, but its radial effect is limited. With the increasing demand for large-scale, high-quality alloy steel products in modern metallurgy, single-magnetic-field rotary stirring or traveling-wave stirring, due to limitations in stirring intensity and range, can no longer meet quality requirements. Therefore, spiral electromagnetic stirring, formed by superimposing two magnetic fields, has been proposed. Combining the advantages of rotary and traveling-wave stirring, spiral electromagnetic stirring induces a spiral motion in the molten steel, enhancing radial and axial heat and solute exchange, reducing temperature gradients between the center of the molten steel and the solidification front, and thus alleviating central segregation and porosity.

[0004] At present, there are three ways to achieve spiral electromagnetic stirring, namely, superposition of rotating magnetic field and traveling wave magnetic field inside and outside, vertical arrangement of rotating magnetic field, and circumferential arrangement of traveling wave magnetic field. For example, there are the technical solutions described in Chinese utility model patents with publication numbers CN201476606U ("Crucible spiral magnetic field electromagnetic stirrer") and CN87204232U ("Spiral magnetic field electromagnetic stirrer"), and Chinese patent applications with publication numbers CN87104014A ("Continuous cast steel electromagnetic stirring device") and CN86104510A ("Combined multifunctional liquid metal electromagnetic stirrer"). Alternatively, there are methods that involve changing the shape of the yoke to tilt the yoke end faces, or aligning the yoke end faces vertically relative to the yoke back. These include the technical solutions described in Chinese patent applications with publication numbers CN102825245A ("Spiral Electromagnetic Stirring Device"), CN102825242A ("Vacuum Suction Casting Apparatus and Method for High-Activity, High-Purity, and High-Melting-Point Alloys"), CN108515153A ("A Composite Magnetic Field Spiral Electromagnetic Stirring Device"), and CN107116191A ("A Composite Spiral Electromagnetic Stirrer"). While these technical solutions can achieve spiral stirring of molten steel, the composite structure and various yoke shapes increase equipment cost and operational difficulty. Furthermore, the magnetic fields generated by the various winding combinations can interfere with each other, affecting the actual effect of electromagnetic stirring. Furthermore, the spiral magnetic field stirring method only provides both radial and axial stirring of the ingot, which somewhat expands the agitator's range of action. However, it does not actually improve the disturbance in the ingot's core, resulting in insufficient shrinkage compensation for the molten steel in the core. As a result, the ingot's core is prone to a series of quality issues such as segregation, porosity, and even shrinkage cavities, which are particularly serious during the casting of large-sized ingots. Currently, the solution to these problems is to adjust the electromagnetic stirrer's current parameters to enhance the stirring intensity and range. However, as the stirring intensity increases, the degree of negative segregation increases, which is not conducive to effective spiral stirring. Summary of the Invention

[0005] The present invention provides a composite side spiral electromagnetic stirring device, which is a simple and efficient spiral electromagnetic stirring device. It adopts a special excitation current application method. The electromagnetic force synthesized after the rotating magnetic field and the traveling wave magnetic field are coupled with each other to produce side spiral stirring with an angle of -90° to 90° with the horizontal plane of the billet. It can enhance the stirring effect of the core of the billet and make the molten steel exhibit a side spiral trajectory movement, effectively improving the phenomenon of negative segregation caused by excessive stirring intensity during the casting process of large-sized billets.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A composite side spiral electromagnetic stirring device comprises a yoke group, a yoke fixing sleeve, a rotating magnetic field coil and a traveling wave magnetic field coil; the yoke fixing sleeve is a sleeve-shaped structure, which is sleeved on the periphery of the casting blank; the yoke group is evenly arranged on the inner side of the yoke fixing sleeve along the circumferential direction; the rotating magnetic field coil is wound on the corresponding yoke in the yoke group in the form of a concentrated winding, and adjacent rotating magnetic field coils are passed through with alternating currents of the same magnitude and opposite directions so that the magnetic pole direction of the rotating magnetic field points to the radial direction of the casting blank; a plurality of traveling wave magnetic field coils are coaxially arranged with the yoke fixing sleeve on the rotating magnetic field coil On the inside; when the alternating current applied by the traveling wave magnetic field coil is positive, the alternating current is connected in the forward direction; when the alternating current applied by the traveling wave magnetic field coil is negative, the alternating current is connected in the reverse direction, so that the direction of the magnetic pole alternately points to the two ends of the billet; the rotating magnetic field coil generates a rotating electromagnetic force that moves along the circumferential direction of the billet and forms a rotating magnetic field; the traveling wave magnetic field coil generates a traveling wave electromagnetic force that is transmitted radially toward the center of the billet and has an axial component. The traveling wave magnetic field formed causes the rotating magnetic field to tilt along the axial direction of the billet, and the coupled magnetic field finally formed has a side spiral stirring effect that is inclined to the cross section of the billet.

[0008] The yoke fixing sleeve is a sleeve-shaped structure with a circular cross section, and the casting blank is a cylindrical casting blank.

[0009] The cross section of the yoke in the yoke group is rectangular, and the yoke group consists of 4 or 6 yokes.

[0010] The inner side of the magnetic yoke is provided with a plurality of slots along the axial direction of the magnetic yoke fixing sleeve for fixing the traveling wave magnetic field coils; the number of the traveling wave magnetic field coils is 2, 4 or 6.

[0011] The angle between the electromagnetic force of the coupling magnetic field and the cross section of the casting billet is -90° to 90°.

[0012] The rotating magnetic field coil and the traveling wave magnetic field coil are both powered by a three-phase alternating power supply.

[0013] The phase angles of the currents flowing through the windings of adjacent rotating magnetic field coils and adjacent traveling wave magnetic field coils differ by 120°, the current frequency is 1 to 10 Hz, and the current intensity is 0 to 1000A.

[0014] The current intensity of the traveling wave magnetic field is 1 / 2 to 2 / 3 of the current intensity of the rotating magnetic field.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1) A special excitation current application method is used. The electromagnetic force synthesized by the coupling of the rotating magnetic field and the traveling magnetic field produces a side spiral stirring with an angle of -90° to 90° with the horizontal plane of the billet. This can enhance the stirring effect at the core of the billet and make the molten steel move in a side spiral trajectory, effectively improving the negative segregation phenomenon caused by excessive stirring intensity during the casting process of large-sized billets.

[0017] 2) The structure of the composite side spiral electromagnetic stirring device is similar to that of the traditional internal and external superimposed spiral electromagnetic stirrer. It is simple in structure, easy to implement, and cost-effective. In addition, there is no directional magnetic field conflict when the two types of magnetic fields are excited at the same time, and the magnetic field loss rate is low.

[0018] 3) By changing the number of coils, the intensity of the rotating force and the traveling wave force can be adjusted in a targeted manner to produce side spiral stirring effects of different angles and intensities, making the magnetic field more controllable;

[0019] 4) The unique side spiral stirring method solves the problems of insufficient stirring in the core of large-sized billets and negative segregation at the edges compared with the existing electromagnetic stirring device. It is more suitable for the production process of large-sized billets and has a significant improvement effect on defects such as segregation and looseness in the core of the billets. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the three-dimensional structure of the composite side spiral electromagnetic stirring device of the present invention.

[0021] Figure 2 yes Figure 1 Top view of .

[0022] Figure 3 It is a middle cross-sectional view of the composite side spiral electromagnetic stirring device of the present invention.

[0023] Figure 4a This is a schematic diagram of the excitation current application method of the traditional traveling wave magnetic field.

[0024] Figure 4b It is a schematic diagram of the excitation current application method of the traveling wave magnetic field of the present invention.

[0025] Figure 5a It is a schematic diagram of the electromagnetic force distribution of the rotating magnetic field in the cross section of the casting billet according to the present invention.

[0026] Figure 5b It is a schematic diagram of the electromagnetic force distribution of the traveling wave magnetic field in the cross section of the casting billet according to the present invention.

[0027] Figure 5c It is a schematic diagram of the electromagnetic force distribution of the coupled magnetic field in the cross section of the casting billet according to the present invention.

[0028] Figure 6a This is a schematic diagram of the magnetic pole change of the traveling wave magnetic field in the longitudinal section of the casting billet according to the present invention. Figure 1 .

[0029] Figure 6b This is a schematic diagram of the magnetic pole change of the traveling wave magnetic field in the longitudinal section of the casting billet according to the present invention. Figure 2 .

[0030] Figure 7 It is a schematic diagram of the electromagnetic force distribution of the coupled magnetic field in the longitudinal section of the ingot according to the present invention.

[0031] Figure 8 It is a three-dimensional streamline diagram inside the casting billet under the action of the coupling magnetic field described in the present invention.

[0032] In the figure: 1. Ingot 2. Yoke fixing sleeve 3. Yoke assembly 4. Rotating magnetic field coil 5. Traveling wave magnetic field coil DETAILED DESCRIPTION

[0033] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0034] like Figure 1 、 Figure 2 As shown, the composite side spiral electromagnetic stirring device of the present invention comprises a yoke group 3, a yoke fixing sleeve 2, a rotating magnetic field coil 4 and a traveling wave magnetic field coil 5; the yoke fixing sleeve 2 is a sleeve-shaped structure, which is sleeved on the outer periphery of the ingot 1; the yoke group 3 is evenly arranged on the inner side of the yoke fixing sleeve 2 along the circumferential direction; the rotating magnetic field coil 4 is wound on the corresponding yoke in the yoke group 3 in the form of a concentrated winding, and adjacent rotating magnetic field coils 4 are passed through alternating currents of the same magnitude and opposite directions so that the magnetic pole direction of the rotating magnetic field points to the radial direction of the ingot 1; a plurality of traveling wave magnetic field coils 5 are coaxially arranged with the yoke fixing sleeve 2 On the inner side of the rotating magnetic field coil 4; when the alternating current applied by the traveling wave magnetic field coil 5 is positive, the alternating current is connected in the forward direction, and when the alternating current applied by the traveling wave magnetic field coil 5 is negative, the alternating current is connected in the reverse direction, so that the direction of the magnetic pole alternately points to the two ends of the ingot 1; the rotating magnetic field coil 4 generates a rotating electromagnetic force that moves circumferentially along the ingot 1 and forms a rotating magnetic field; the traveling wave magnetic field coil 5 generates a traveling wave electromagnetic force that is transmitted radially toward the center of the ingot 1 and has an axial component. The traveling wave magnetic field formed makes the rotating magnetic field tilted axially along the ingot 1, and the finally formed coupled magnetic field has a side spiral stirring effect that is tilted to the cross section of the ingot 1.

[0035] The yoke fixing sleeve 2 is a sleeve-shaped structure with a circular cross section, and the casting blank 1 is a cylindrical casting blank.

[0036] The cross section of the yokes in the yoke group 3 is rectangular, and the yoke group 3 is composed of 4 or 6 yokes.

[0037] like Figure 3 As shown, a plurality of slots are provided on the inner side of the magnetic yoke along the axial direction of the magnetic yoke fixing sleeve 2 for fixing the traveling wave magnetic field coils 5; the number of the traveling wave magnetic field coils 5 is 2, 4 or 6.

[0038] The angle between the electromagnetic force of the coupling magnetic field and the cross section of the casting billet 1 is -90° to 90°.

[0039] The rotating magnetic field coil 4 and the traveling wave magnetic field coil 5 are both powered by a three-phase alternating power supply.

[0040] The phase angles of the currents flowing through the windings of adjacent rotating magnetic field coils 4 and adjacent traveling wave magnetic field coils 5 differ by 120°, the current frequency is 1-10 Hz, and the current intensity is 0-1000A.

[0041] The current intensity of the traveling wave magnetic field is 1 / 2 to 2 / 3 of the current intensity of the rotating magnetic field.

[0042] The composite side spiral electromagnetic stirring device of the present invention is used for electromagnetic stirring of the ingot, and is arranged on the periphery of the ingot 1 when in use. Figure 1 、 Figure 2 As shown, the composite side spiral electromagnetic stirring device includes a yoke group 3, a yoke fixing sleeve 2, a rotating magnetic field coil 4 and a traveling wave magnetic field coil 5. The yoke group is composed of a plurality of yokes, the cross section of the yoke is rectangular, the number of yokes is an even number, preferably 4 or 6, and each yoke is evenly arranged on the inner side of the yoke fixing sleeve 3 along the circumference of the yoke fixing sleeve. A plurality of gaps (such as Figure 3 ), used to secure traveling wave magnetic field coils 5. The number of traveling wave magnetic field coils 5 is an even number, preferably 2, 4, or 6, and the traveling wave magnetic field coils 5 are arranged longitudinally along the ingot 1. The rotating magnetic field coils 4 and the traveling wave magnetic field coils 5 can be made of copper wire or hollow copper tube.

[0043] The structure of the composite side spiral electromagnetic stirring device described in the present invention is similar to that of the traditional internal and external superimposed spiral electromagnetic stirrer. The rotating magnetic field coil 4 is wound on the magnetic yoke in the form of a concentrated winding. The adjacent rotating magnetic field coils 4 are passed through an alternating current of the same magnitude and opposite direction, so that the magnetic pole direction of the rotating magnetic field coil 4 points to the radial direction of the billet 1, and the electromagnetic force is controlled to rotate along the circumference of the billet 1 (such as Figure 5a As shown). The traveling wave magnetic field coil 5 is arranged linearly along the axial direction of the yoke fixing sleeve 2 and fixed to the inner side of the yoke group 3. However, the application method of the excitation current in the traveling wave magnetic field coil of the present invention is different from that of the traditional traveling wave magnetic field (the application method of the excitation current is as shown). Figure 4a As shown, that is, the alternating current of equal magnitude and same direction is different. Figure 4b As shown, in the present invention, when the alternating current applied to the traveling wave magnetic field coil 5 is positive, the alternating current is connected in the forward direction. On the contrary, when the alternating current applied to the traveling wave magnetic field coil 5 is negative, the alternating current is connected in the reverse direction, so that the magnetic pole direction alternately points to the two ends of the casting billet 1, and the electromagnetic force is controlled to be transmitted radially toward the center of the casting billet 1 (as shown in FIG. Figure 5bDue to the characteristics of the alternating current, the magnetic pole direction of the traveling magnetic field is reversed along the axial direction of the billet 1 within a unit cycle. During this process, the angle between the magnetic pole direction of the traveling magnetic field and the magnetic pole direction of the rotating magnetic field is -90° to 90°. Under the mutual coupling effect of the two, the combined electromagnetic force ultimately generates a coupled magnetic field, which forms a side spiral stirring effect with an angle of -90° to 90° with the cross-section of the billet 1.

[0044] The composite side spiral electromagnetic stirring device described in the present invention is characterized in that a special traveling wave magnetic field excitation current access method is adopted to transmit the rotating electromagnetic force in the ingot 1 toward the core of the ingot 1 along the inclined direction, thereby enhancing the stirring effect of the core of the ingot 1 and improving the negative segregation problem that is common when using traditional electromagnetic stirring devices.

[0045] In the present invention, the power supply devices for the rotating magnetic field and the traveling wave magnetic field both use three-phase alternating current power supplies. The phase angles of the currents flowing through the windings of adjacent rotating magnetic field coils and adjacent traveling wave magnetic field coils differ by 120 degrees, the current frequency is 1 to 10 Hz, and the current intensity is 0 to 1000 A. Because the molten steel has a certain gravity and viscosity, the stirring effect is best when the current intensity of the traveling wave magnetic field is 1 / 2 to 2 / 3 of the current intensity of the rotating magnetic field. The rotating magnetic field coil 4 and the traveling wave magnetic field coil 5 can be powered separately by two sets of power supply equipment. According to the actual needs of the production site, by adjusting the intensity of the rotational force and centripetal force in the coupled magnetic field, it can be applied to the casting of high-alloy steels of various cross-sectional sizes.

[0046] Large-section ingots are prone to problems such as center segregation, looseness, and even shrinkage holes due to the slow solidification process and insufficient shrinkage compensation of the core molten steel. At this time, stronger core stirring is required to improve the quality of the ingot. When using a traditional electromagnetic stirring device, in order to increase the stirring intensity of the core of the ingot, the stirring intensity can only be increased, but this will lead to negative segregation problems. The composite side spiral electromagnetic stirring device described in the present invention adopts a unique inclined centripetal stirring method. While enhancing the stirring effect of the core of the ingot, the inclined stirring can even out the longitudinal composition and temperature of the ingot, expand the circulation area of ​​the molten steel, effectively improve the negative segregation problem, and provide technical support for the production of larger-section ingots.

[0047] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the protection scope of the present invention is not limited to the following examples.

[0048] [Example]

[0049] like Figure 1As shown, in this embodiment, the ingot 1 is a round ingot with a cross-sectional dimension of 800 mm. The composite side-spiral electromagnetic stirring device utilizes a structure composed of six magnetic yokes, six rotating magnetic field coils, and six traveling magnetic field coils. The yoke fixing sleeve 2 is a thin-walled cylindrical structure with an inner diameter of 1650 mm, an outer diameter of 1800 mm, and a height of 440 mm. The yoke assembly is made of high-permeability grained silicon steel. The yoke is a cubic structure measuring 350 mm × 220 mm × 440 mm, with five 40 mm wide grooves on the inside to secure the traveling magnetic field coils 5.

[0050] Both the rotating magnetic field coil 4 and the traveling-wave magnetic field coil 5 are made of hollow copper tubes, which can be cooled by cooling water. Power is supplied by two separate power supplies at a frequency of 3 Hz. The excitation currents for the rotating magnetic field coil 4 and the traveling-wave magnetic field coil 5 are 400A and 250A, respectively, with 30 turns each. Together, the rotating magnetic field coil 4 and the traveling-wave magnetic field coil 5 generate a side helical magnetic field.

[0051] In this embodiment, the excitation current of the traveling wave magnetic field is applied in the following manner: Figure 4b As shown, the alternating electromagnetic force is transmitted perpendicularly to the surface of the casting billet 1 toward the center (as shown in FIG. Figure 5b shown), in Figure 5a Under the combined action of the rotating magnetic field shown in Figure 5c The centripetal stirring force shown enhances the stirring effect at the core of the ingot 1 .

[0052] When the traveling wave magnetic field of the present invention works alone, the variation law of the magnetic flux lines within a unit period is as follows: Figure 6a 、 Figure 6b As shown, the magnetic poles alternately point to the two ends of the ingot, interacting with the rotating magnetic field rotating circumferentially within the ingot 1 to synthesize a coupling magnetic field that obliquely stirs the molten steel, as shown in FIG. Figure 7 shown.

[0053] Under the action of the composite side spiral electromagnetic stirring device, the three-dimensional streamlines of the molten steel in the ingot are as follows: Figure 8 As shown in FIG. 1 , the molten steel is subjected to inclined stirring under the action of the coupled magnetic field. In this embodiment, the inclined stirring angle is 33.7°.

[0054] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A composite side spiral electromagnetic stirring device, characterized in that: The magnetic field coil comprises a yoke assembly, a yoke fixing sleeve, a rotating magnetic field coil, and a traveling wave magnetic field coil. The yoke fixing sleeve is a sleeve-shaped structure and is mounted on the outer periphery of the ingot. The magnetic yoke assembly is uniformly arranged on the inner side of the yoke fixing sleeve along the circumference. The rotating magnetic field coil is wound around the corresponding magnetic yoke in the yoke assembly in a concentrated winding form. Adjacent rotating magnetic field coils are supplied with alternating currents of equal magnitude and opposite directions, so that the magnetic poles of the rotating magnetic field point in the radial direction of the ingot. Several traveling wave magnetic field coils are coaxially arranged on the inner side of the rotating magnetic field coil with the yoke fixing sleeve. When the alternating current applied to the traveling wave magnetic field coil is positive, the alternating current is connected in the forward direction. When the alternating current applied to the traveling wave magnetic field coil is negative, the alternating current is connected in the reverse direction, so that the magnetic poles point alternately toward the two ends of the ingot. The rotating magnetic field coil generates a rotating electromagnetic force that moves along the circumference of the ingot and forms a rotating magnetic field. The traveling wave magnetic field coil generates a traveling wave electromagnetic force that is transmitted radially toward the center of the ingot and has an axial component. The resulting traveling wave magnetic field causes the rotating magnetic field to tilt along the axial direction of the ingot. The resulting coupled magnetic field has a side spiral stirring effect that is inclined to the cross section of the ingot.

2. A composite side spiral electromagnetic stirring device according to claim 1, characterized in that: The yoke fixing sleeve is a sleeve-shaped structure with a circular cross section, and the casting blank is a cylindrical casting blank.

3. The composite side spiral electromagnetic stirring device according to claim 1, characterized in that: The cross section of the yoke in the yoke group is rectangular, and the yoke group consists of 4 or 6 yokes.

4. A composite side spiral electromagnetic stirring device according to claim 1 or 3, characterized in that: The inner side of the magnetic yoke is provided with a plurality of slots along the axial direction of the magnetic yoke fixing sleeve for fixing the traveling wave magnetic field coils; the number of the traveling wave magnetic field coils is 2, 4 or 6.

5. The composite side spiral electromagnetic stirring device according to claim 1, characterized in that: The angle between the electromagnetic force of the coupling magnetic field and the cross section of the casting billet is -90° to 90°.

6. The composite side spiral electromagnetic stirring device according to claim 1, characterized in that: The rotating magnetic field coil and the traveling wave magnetic field coil are both powered by a three-phase alternating power supply.

7. The composite side spiral electromagnetic stirring device according to claim 1, characterized in that: The phase angles of the currents flowing through the windings of adjacent rotating magnetic field coils and adjacent traveling wave magnetic field coils differ by 120 degrees, the current frequency is 1 to 10 Hz, and the current intensity is 0 to 1000A.

8. The composite side spiral electromagnetic stirring device according to claim 1, characterized in that: The current intensity of the traveling wave magnetic field is 1 / 2 to 2 / 3 of the current intensity of the rotating magnetic field.

Images