Device and method for regulating and controlling bias current in crystallizer through electromagnetic braking

Abstract

The invention relates to a device and method for regulating and controlling bias current in a crystallizer through electromagnetic braking, and belongs to the technical field of ferrous metallurgy continuous casting. The device comprises a regional electromagnetic braking device, a full-width two-section electromagnetic braking device, a liquid level wide-width nozzle local electromagnetic braking device and a narrow-width regional electromagnetic braking device, each electromagnetic braking device is composed of an iron core, a magnetic induction coil and a magnetic pole, a static magnetic field is applied to the wide face of a crystallizer, magnetic lines of force on the two sides of the submersed nozzle perpendicularly penetrate through the wide face of the crystallizer, and molten steel flowing is regulated and controlled; liquid level fluctuation and meniscus flow are inhibited, the impact depth of molten steel and the impact strength on a narrow surface are reduced, the problem of bias flow caused by nozzle nodulation is solved, the quality of a casting blank is improved, and smooth production is guaranteed; the method comprises the steps of monitoring a bias current phenomenon, selecting a proper device, and adjusting magnetic pole parameters to stabilize a flow field; the nozzle can effectively improve the flowing state of molten steel in the crystallizer, reduce slag entrapment and surface defects, prolong the service life of the nozzle, adapt to different nodulation degrees and pulling speed conditions, and have remarkable technical advantages and application prospects.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting technology in iron and steel metallurgy, and particularly relates to a device and method for electromagnetic braking to regulate the deflection flow inside a crystallizer. Background Technology

[0002] In the continuous casting process of iron and steel metallurgy, molten steel flows into the crystallizer through an immersion nozzle. Under the influence of turbulence, a large amount of acid-soluble aluminum solid inclusions adhere to the nozzle outlet or inner wall, causing nozzle blockage, also known as nodule formation. Because the nodule formation process is very complex, the mechanism is generally considered to include the following four parts: sintering of high-melting-point deoxidation products on the inner wall of the nozzle; precipitation of Al2O3 due to the decrease in molten steel temperature; and oxidation reaction between the molten steel and the refractory material. If the nozzle is not replaced in time, the blockage will cause different flow rates on both sides of the tapping surface, resulting in asymmetrical molten steel flow and liquid level imbalance within the crystallizer. This unilateral flow deviation significantly increases the downward impact velocity and depth of the molten steel, making it difficult for inclusions and bubbles to rise. After the molten steel deviates from its natural flow path within the crystallizer, the enhanced upward circulation leads to increased surface velocity, increasing the likelihood of slag entrapment. When the flow deviation is too severe, the flow field inside the crystallizer becomes unstable, leading to surface longitudinal cracks in the produced billet, and even melting of the solidified billet shell, resulting in a steel leakage accident. In the continuous casting process of slabs, the flow control of molten steel inside the crystallizer has a significant impact on the quality of the billet and production efficiency. As the production capacity of the continuous casting machine increases, the billet drawing speed continuously increases, leading to an increase in the kinetic energy of the molten metal jet, which in turn causes irregular flow of molten steel inside the crystallizer, forming two circulations: an upper circulation that dominates the flow of molten steel near the meniscus of the crystallizer, affecting the melting, spreading, and entrainment of the protective slag, and a lower circulation whose impact depth governs the rising and separation of inclusions and bubbles.

[0003] However, this complex flow pattern also brings many problems. First, the upward-flowing molten steel impacts the surface of the molten steel in the crystallizer, causing surface fluctuations, especially near the meniscus, which can easily lead to slag entrapment. Second, the downward-flowing molten steel penetrates to a greater depth, carrying non-metallic inclusions, bubbles, and other heterogeneous substances into deeper parts of the crystallizer. These heterogeneous substances are not easy to float to the surface and may be captured by the initial solidification shell leading edge of the billet, resulting in surface or subsurface defects on the continuously cast billet.

[0004] Furthermore, the molten metal flow at the nozzle under highly turbulent conditions can cause remelting of the solidified shell near the narrow face of the crystallizer, leading to uneven shell thickness distribution, subsurface inclusions in the continuously cast billet, and surface defects. These problems severely affect the quality and production efficiency of continuously cast billets, necessitating an effective technical means to control the flow of molten steel within the crystallizer and improve billet quality. Summary of the Invention

[0005] The objective of this invention is to provide a device and method for electromagnetic braking to regulate flow deviation within a slab mold. The flow of molten steel within the slab mold is predominantly turbulent. Under high-speed production conditions, increased molten steel flow can cause blockages in the submerged entry nozzle, leading to different steel outputs on both sides of the nozzle and asymmetry in the flow streams. This results in unbalanced liquid surface fluctuations and different impact depths of the backflow on both sides, ultimately causing flow deviation within the mold. Therefore, it is necessary to adjust the coil structure of the electromagnetic braking device, change the intensity of the direct current flowing through the coil, and control the magnetic induction intensity of the electromagnetic braking device to stabilize the electromagnetic braking effect. The electromagnetic braking device regulates the magnetic field under flow deviation conditions within the slab mold, mitigating the impact of molten steel flow deviation and improving the quality of the cast billet. The advantages of this invention are that it slows the growth rate of nozzle nodules, inhibits the erosion of the nozzle by protective slag, and extends the service life of the nozzle.

[0006] To accomplish the above tasks, the present invention adopts the following technical solution:

[0007] An electromagnetic braking device for regulating flow deviation within a crystallizer includes a regional electromagnetic braking device, a full-width two-stage electromagnetic braking device, a wide-area localized electromagnetic braking device for the immersion nozzle, and a wide-area narrow-area segmented electromagnetic braking device for the immersion nozzle. Each device consists of an iron core, a magnetic induction coil, and magnetic poles. The regional electromagnetic braking device comprises a U-shaped iron core and coil symmetrically arranged on both sides of the wide face of the crystallizer. The magnetic poles cover the surface of the molten steel on both sides of the immersion nozzle and near the narrow face. It is used to apply direct current to two excitation coils on the non-bulking side, causing the molten steel to pass through a stable magnetic field after exiting the nozzle, thus generating a braking effect. The full-width two-stage electromagnetic braking device consists of two sets of parallel long iron cores and coils installed on the free surfaces on both sides of the wide face of the thin slab crystallizer and near the outlet. The wide-width local area electromagnetic braking device and the wide-width narrow-width regional electromagnetic braking device respectively achieve the control of the flow of molten steel in the crystallizer by setting multiple sets of iron cores and coils at corresponding positions on both sides of the wide face of the thin slab crystallizer. Both devices control the flow of molten steel by applying a static magnetic field at the wide face of the crystallizer, so that the magnetic lines of force on both sides of the immersion nozzle pass perpendicularly through the wide face of the crystallizer. The magnetic pole position and magnetic induction intensity of each device can be adjusted.

[0008] Furthermore, the core of the regional electromagnetic braking device is U-shaped and symmetrically arranged on both sides of the wide face of the crystallizer. The coil is wound on the core, and the magnetic poles point to the molten steel area inside the crystallizer. It mainly covers the molten steel surface on both sides of the immersion nozzle and near the narrow face. By applying DC current to the two excitation coils on the non-bulging side, the molten steel on that side is braked in a constant magnetic field after being ejected from the nozzle, reducing the flow rate of the molten steel on that side, thereby adjusting the symmetry of the molten steel flow in the crystallizer.

[0009] Furthermore, the upper and lower sets of parallel long iron cores and coils of the full-width two-stage electromagnetic braking device are located on the free surfaces on both sides of the wide face of the thin slab crystallizer and near the outlet, respectively. By adjusting the magnetic induction intensity of the upper auxiliary magnetic pole and the lower main magnetic pole, the upper and lower reflux zones of the molten steel in the crystallizer can be controlled separately to improve the flow state of the molten steel in the crystallizer.

[0010] Furthermore, the upper and lower sets of parallel long iron cores and coils of the wide-area electromagnetic braking device for the liquid surface are set at corresponding positions on both sides of the wide surface of the thin slab crystallizer. By independently adjusting the current of each pair of coils, the electromagnetic braking effect on the molten steel on both sides of the crystallizer outlet is achieved, thereby controlling the flow rate of molten steel in the upper and lower reflux zones of the crystallizer, stabilizing the flow rate of molten steel in the lower part of the outlet, and reducing secondary eddies.

[0011] Furthermore, the wide-area, narrow-area, segmented electromagnetic braking device is equipped with two pairs of iron cores and coils above and three pairs of iron cores and coils below, located at corresponding positions on both sides of the wide face of the thin slab crystallizer. By adjusting the magnetic induction intensity of the auxiliary magnetic pole and the main magnetic pole, the electromagnetic braking effect on the backflow portion of the molten steel in the crystallizer is achieved, thereby improving the internal flow field of the crystallizer.

[0012] A method for controlling flow deviation within a crystallizer using electromagnetic braking includes the following steps: determining the degree of nozzle clogging by monitoring the height difference of the free liquid surface in the crystallizer; selecting a corresponding electromagnetic braking device based on the degree of clogging, wherein when the degree of clogging at one side of the crystallizer outlet is relatively mild, a static magnetic field is applied to the unclogged side or the side with a relatively mild clogging, while for the side with a severe clogging or even severe blockage, no static magnetic field may be applied or only a suitable static magnetic field may be applied; adjusting the magnetic pole parameters of the selected electromagnetic braking device to stabilize the flow field, including adjusting the magnetic induction intensity and magnetic pole position, specifically: for a regional electromagnetic braking device, when the clogging area on one side of the outlet accounts for 30%-50% of the outlet area, the magnetic induction... The intensity is adjusted to 0.1T-0.15T, and the magnetic pole installation position P is 125mm. When the nodule area accounts for 70% of the outlet area, the magnetic induction intensity must reach at least 0.2T, and the magnetic pole installation position P is 25mm. For the full-width two-stage electromagnetic braking device, when the nodule degree of the outlet on one side of the crystallizer is less than 40%, the magnetic induction intensity output by the upper auxiliary magnetic pole is 0.05T-0.3T, and the magnetic induction intensity output by the lower main magnetic pole is 0T-0.5T. When the nodule degree of the outlet reaches 60%, the magnetic induction intensity of both main magnetic poles is output simultaneously, and when the magnetic induction intensity output by the main magnetic pole reaches 0.3T, the symmetrical effect of the molten steel reflux zone in the crystallizer is better.

[0013] Furthermore, at a casting speed of 1.5 m / min, when the proportion of nodule formation on the right side of the crystallizer reaches 71% and the magnetic induction intensity is 0.15 T, the braking effect on the right-side flow field is better when the magnetic pole position P = 25 mm. At this time, the jet from the right-side crystallizer flows out horizontally, while the jet from the left side bends slightly upward. Applying a steady magnetic field only to the left side of the crystallizer can effectively suppress the flow of molten steel on the left side, reduce the flow velocity of the molten steel in the upper backflow zone and free surface in the crystallizer, and suppress liquid surface fluctuations.

[0014] Furthermore, for thin slab crystallizers, when the degree of nodule formation on one side of the crystallizer outlet is less than 40%, the output magnetic induction intensity of the main and auxiliary magnetic poles of the wide-range electromagnetic braking device at the liquid level outlet is adjusted to 0.1T or 0.2T respectively. This can suppress the backflow of rising molten steel, improve free surface fluctuations, and achieve better symmetry of molten steel on the left and right sides of the crystallizer. When the degree of nodule formation on one side of the outlet is 60%, the output magnetic induction intensity of the main and auxiliary magnetic poles needs to be adjusted to 0.5T to control the deflection of molten steel.

[0015] Furthermore, for the wide-range liquid level and narrow-range nozzle-divided electromagnetic braking device, when the degree of nodule formation on one side of the crystallizer outlet is less than 40%, the output magnetic induction intensity of both the main and auxiliary magnetic poles is set to 0.3T, which can maintain a better symmetrical double reflux of the molten steel in the crystallizer; when the degree of nodule formation on one side of the outlet is 60%, the output magnetic induction intensity of the main and auxiliary magnetic poles needs to be adjusted to 0.3T-0.5T to improve the internal flow field of the crystallizer under the condition of nodule formation.

[0016] Beneficial effects

[0017] Compared with the prior art, the present invention provides a device and method for electromagnetic braking to regulate the deflection flow in a crystallizer, which has the following beneficial effects:

[0018] 1. This invention employs various structural forms, including regional electromagnetic braking devices, full-width two-stage electromagnetic braking devices, wide-width liquid surface nozzle local regional electromagnetic braking devices, and wide-width liquid surface nozzle narrow-width sub-regional electromagnetic braking devices. By rationally designing the magnetic pole positions and magnetic induction intensity, it achieves precise control of the flow of molten steel in the crystallizer, effectively solving the problem that the vertical and horizontal magnetic pole structures in the prior art need further optimization.

[0019] 2. By setting electromagnetic braking devices on both sides of the wide face of the crystallizer, the present invention can effectively reduce the flow velocity of molten steel on both sides of the outlet, reduce liquid surface fluctuation, improve the symmetry of molten steel flow, effectively alleviate the growth rate of nodule deposits at the outlet, inhibit the erosion of the outlet by protective slag, and significantly extend the service life of the outlet.

[0020] 3. The electromagnetic braking device of the present invention adopts a modular design, which is convenient for maintenance. Moreover, through the adjustable magnetic induction intensity and magnetic pole position, the braking effect can be flexibly adjusted according to actual production needs, adapting to the needs of different steel grades and production processes.

[0021] 4. The wide-range electromagnetic braking device for the nozzle of the present invention can effectively control the flow rate of molten steel in the upper and lower reflux zones of the crystallizer, stabilize the flow rate of molten steel in the lower part of the nozzle, reduce secondary eddies, and significantly improve the quality of the cast billet and production efficiency.

[0022] 5. By rationally adjusting the magnetic field strength and distribution, this invention can effectively control the thickness distribution of the solidified billet shell near the narrow face of the crystallizer, reduce the probability of subsurface inclusions and surface defects in the continuously cast billet, and improve product quality. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the regional electromagnetic braking device in this invention;

[0024] Figure 2 Indicates the position of the magnetic poles;

[0025] Figure 3 This is a schematic diagram of the full-width two-stage electromagnetic braking device in this invention;

[0026] Figure 4 This is a schematic diagram of the wide-range electromagnetic braking device for the water inlet in this invention.

[0027] Figure 5 This is a schematic diagram of the electromagnetic braking device with a wide liquid level and a narrow water inlet in this invention.

[0028] Figure 6 The shape of the immersion nozzle for the slab crystallizer;

[0029] Figure 7 The shape of the immersion nozzle for a thin slab crystallizer;

[0030] Figure 8 The effect of free surface flow velocity under different magnetic induction intensities is shown in the figure for 50% nodule formation on one side of the slab crystallizer in this invention.

[0031] Figure 9 The invention describes the effect of molten steel flow under different magnetic induction intensities (0T, 0.1T, 0.2T) on a single-sided nozzle with 40% nodule formation in the thin slab crystallizer.

[0032] Figure 10 The effect of 35% unilateral nodule formation on the inner wall of the slab crystallizer nozzle in this invention on the molten steel flow rate under different magnetic pole positions;

[0033] Figure 11 This is a schematic diagram of the molten steel flow deviation within the crystallizer in this invention;

[0034] In the diagram: 1-Crystallizer; 2-Iron core; 3-Coil; 4-Sprue. Detailed Implementation

[0035] Example 1:

[0036] like Figure 1 As shown, the structure of the regional electromagnetic braking device in this invention is to add a set of symmetrical U-shaped iron cores and coils on both sides of the wide face of the crystallizer. The coverage area of ​​the magnetic poles is mainly the surface of the molten steel on both sides of the immersion nozzle and near the narrow face. By applying DC current to the two excitation coils on the non-bulging side, the molten steel can generate a braking effect after passing through the stable magnetic field after being ejected from the nozzle. The main structure of the device is small and the device is easy to maintain.

[0037] For a slab mold with a cross-sectional size of 1200mm × 230mm, a nozzle immersion depth of 300mm, a side outlet size of 50mm × 70mm, and a nozzle inclination angle of 0°, when nodule formation occurs at the right outlet of the mold, the nodule is located by blocking downwards for 50mm along the height of the outlet, corresponding to a nodule area accounting for 71% of the outlet area. To better control the steel flow deviation problem within the mold, this case only applies a static magnetic field to the stronger flow field on the left side, while not applying electromagnetic braking to the nodule-forming side. For a conventional slab mold, when unilateral nodule formation occurs at the outlet, the first device applies unilateral electromagnetic braking to the non-nodule-forming side of the mold's wide face. As the nodule formation at the outlet reaches 50%, ... Figure 8 The horizontal axis represents the distance from a point on the free surface of the crystallizer to the center line of the nozzle, and the vertical axis represents the steel flow velocity. The left figure shows the steel flow velocity curve on the left side of the crystallizer, and the right figure shows the steel flow velocity curve on the right side of the crystallizer. Adjusting the magnetic induction intensity of the device to 0-0.15T, with the corresponding magnetic pole installation position P=125mm, significantly controls the steel flow and effectively solves the problem of steel flow deviation under nodule formation. When the nodule formation degree reaches 70%, a magnetic induction intensity of at least 0.2T is required to temporarily slow down the steel flow deviation. When nodule formation occurs on the inner wall of the submerged nozzle, the first device applies electromagnetic braking to the wide face of the crystallizer. When the nodule formation degree reaches 14%, adjusting the magnetic induction intensity of the device to 0-0.15T, with the corresponding magnetic pole installation position P=125mm, provides the best control effect on the steel flow. When the nodule formation degree reaches 70%, a corresponding magnetic pole installation position P=25mm is required. When nodule formation occurs on one side of the inner wall of the submerged entry nozzle, the first type of device applies electromagnetic braking to the wide face of the mold. When the nodule area is 10%-26%, the magnetic induction intensity of the device is adjusted to 0-0.15T, corresponding to a magnetic pole installation position P=125mm, which can effectively reduce the degree of molten steel flow deviation in the mold. When the nodule degree reaches 35%, Figure 10In the figure, the horizontal axis represents the distance from a point on the free surface of the crystallizer to the center line of the nozzle, and the vertical axis represents the velocity of the molten steel. Under the condition that a magnetic field is applied only on the right side, the maximum surface velocity on the left side increases by about 40%. Overall, it is difficult to stabilize the flow of molten steel by changing the position of the magnetic poles and the intensity of the magnetic induction.

[0038] The positions of the magnetic field devices in Comparative Examples 1 and 2 are the same as those in Examples 1 and 2. The methods of applying the magnetic field in Comparative Examples 1 and 2 are the same as those in Examples 1 and 2. The difference lies in the magnitude of the magnetic field strength. According to the data in Table 1, when the proportion of duct nodules on one side of the water outlet is 30%, the magnetic field strength is guaranteed to be at least 0.1T after the electromagnetic braking device is adjusted, which can appropriately extend the service life of the water outlet under the nodulation state. When the area of ​​duct nodules on one side of the water outlet is 50%, weakening the magnetic field strength of the electromagnetic braking device will seriously shorten the service life of the water outlet.

[0039] Table 1. Effects of different nodulation conditions on the service life of the sluice gate.

[0040]

[0041]

[0042] At a casting speed of 1.5 m / min, when the proportion of nodule formation on the right side of the crystallizer reaches 71%, under the condition of magnetic induction intensity of 0.15T, the braking effect of the static magnetic field on the vertical flow velocity of the narrow face on the left side is basically the same when the magnetic pole position P = 25 mm and 125 mm. However, for the flow field on the right side, the braking effect is better when the magnetic pole position P is 25 mm. At this time, the jet from the right side of the crystallizer flows out horizontally, and the jet from the left side also bends slightly upward. Applying a constant magnetic field only to the left side of the crystallizer results in the best suppression effect on the flow of molten steel on the left side. This deflection control method can effectively reduce the flow velocity of molten steel in the upper backflow zone and free surface in the crystallizer and suppress liquid surface fluctuations.

[0043] The device brakes the molten steel flowing out of the nozzle to reduce the outflow velocity from both nozzles, thereby regulating the free surface fluctuation of the molten steel in the crystallizer, suppressing the flow at the meniscus, avoiding slag entrapment, and reducing the downward impact depth of the molten steel in the crystallizer and the impact intensity of the nozzle jet on the narrow face of the crystallizer.

[0044] Example 2:

[0045] like Figure 3 As shown, the full-width two-stage electromagnetic braking device structure in this invention involves adding two sets of parallel long iron cores and coils to the free surfaces on both sides of the wide face of the thin slab crystallizer and near the outlet.

[0046] When the degree of nodule formation at the outlet of the crystallizer is less than 40%, in this case, no static magnetic field is applied to the main magnetic pole area on one side of the outlet, while static magnetic fields are applied to both sides of the auxiliary magnetic pole. The magnetic induction intensity output by the auxiliary magnetic pole above the electromagnetic braking device is 0.05-0.3T, and the magnetic induction intensity output by the main magnetic pole below is 0-0.5T, which significantly improves the flow deviation problem. When the degree of nodule formation at the outlet is 60%, it is necessary to suppress the asymmetry of the flow field inside the crystallizer by simultaneously using both main magnetic poles.

[0047] For a thin slab crystallizer with a cross-sectional size of 1250mm × 73mm, a nozzle immersion depth of 230mm, a side outlet hole size of 160mm × 90mm, and a nozzle inclination angle of 0°, when nodule formation occurs at the left outlet of the crystallizer, the corresponding nodule area accounts for 60% of the outlet area. To better control the flow deviation of molten steel within the crystallizer, the magnetic induction intensity output by the upper auxiliary magnetic pole is 0.05T-0.3T; the magnetic induction intensity of the lower main magnetic pole is 0T-0.5T. In this case, no static magnetic field is applied to the main magnetic pole area on the left side of the outlet, while electromagnetic braking is applied to both sides of the auxiliary magnetic pole.

[0048] At a casting speed of 4.5 m / min and with a magnetic induction intensity of 0.2 T at the output of the main magnetic pole, the device can effectively improve the molten steel flow deviation and surface fluctuation in the thin slab crystallizer when the nozzle nodule formation ratio is less than 25%. When the magnetic induction intensity output of the main magnetic pole reaches 0.3 T, the symmetry effect of the molten steel flow reflux zone in the crystallizer is better, and the static magnetic field control effect of molten steel flow deviation in the crystallizer is optimal.

[0049] By independently controlling the magnetic field in two parts, the magnetic induction intensity of the secondary and primary magnetic poles is adjusted separately. This controls the flow velocity of molten steel at the meniscus and the velocity of molten steel ejected from the nozzle, reducing the impact depth and impact intensity on the narrow face of the crystallizer and the initial billet shell. This improves the magnetic field under the biased flow condition within the crystallizer and enhances the quality of the cast billet.

[0050] Example 3:

[0051] like Figure 4 As shown, the structure of the wide-area electromagnetic braking device in this invention is to add two sets of parallel long iron cores and coils on the free surfaces on both sides of the wide surface of the thin slab crystallizer and near the outlet.

[0052] When the degree of nodulation on one side of the crystallizer outlet is less than 40%, such as Figure 9 In (a), no electromagnetic braking is applied. Figure 9 In (b), the magnetic induction intensity of the main and auxiliary magnetic poles of the electromagnetic braking device is 0.1T. Figure 9 In (c), the output magnetic induction intensity of both the main and auxiliary magnetic poles of the electromagnetic braking device is 0.2T, wherein... Figure 9(c) shows that the auxiliary magnetic pole improves the free surface fluctuation by suppressing the backflow of rising molten steel, and the molten steel on the left and right sides of the crystallizer forms a better symmetry; when the outlet has 60% of unilateral nodule formation, the main and auxiliary magnetic poles of the electromagnetic braking device need to output a magnetic induction intensity of 0.5T in order to achieve the control of the molten steel deflection.

[0053] By independently adjusting each pair of coils, electromagnetic braking effect is achieved on the molten steel on both sides of the crystallizer outlet, controlling the molten steel flow rate in the upper and lower recirculation zones of the crystallizer, stabilizing the molten steel flow rate in the lower part of the nozzle, and reducing secondary eddies, so as to realize the electromagnetic braking technology of thin slab crystallizer at high casting speed.

[0054] Example 4:

[0055] like Figure 5 As shown, the structure of the wide-area liquid level and narrow-area water outlet segmented electromagnetic braking device in this invention is to add two pairs of iron cores and three pairs of coils on the free surfaces on both sides of the wide surface of the thin slab crystallizer and near the water outlet.

[0056] When the degree of nodule formation on one side of the crystallizer outlet is less than 40%, the output magnetic induction intensity of the main and auxiliary magnetic poles of the electromagnetic braking device is 0.3T, and the molten steel in the crystallizer can maintain a good symmetrical double reflux. When the degree of nodule formation on one side of the outlet is 60%, the output magnetic induction intensity of the main and auxiliary magnetic poles of the electromagnetic braking device needs to be 0.3-0.5T to improve the internal flow field of the crystallizer under the condition of nodule formation.

[0057] By adjusting the magnetic induction intensity of the secondary and primary magnetic poles, an electromagnetic braking effect is achieved on the reflux section of the molten steel inside the crystallizer, improving the internal flow field of the crystallizer, reducing the growth rate of nozzle nodules, inhibiting the erosion of the nozzle by the protective slag, and extending the service life of the nozzle.

[0058] After nodulation occurs in the immersion nozzle, the degree of nodulation can be determined by monitoring the height difference of the free liquid surface in the crystallizer using a wave height meter. However, the specific working principle of the wave height meter is irrelevant to this invention and will not be described further.

[0059] The above description is merely a specific example of how the present invention achieves better results. However, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A device for electromagnetic braking to regulate the bias flow within a crystallizer, characterized in that, These include regional electromagnetic braking devices, full-width two-stage electromagnetic braking devices, wide-width sprue nozzle localized regional electromagnetic braking devices, and wide-width sprue nozzle narrow-width segmented regional electromagnetic braking devices. Each device consists of an iron core, a magnetic induction coil, and magnetic poles. The regional electromagnetic braking device features a U-shaped iron core and coil symmetrically arranged on both sides of the wide face of the crystallizer. The magnetic poles cover the molten steel surface on both sides of the immersion nozzle and near the narrow face, used to control the molten steel on the non-bulging side. A DC current is applied to an excitation coil, causing the molten steel to pass through a constant magnetic field after being ejected from the nozzle, thus generating a braking effect. The full-width two-stage electromagnetic braking device consists of two sets of parallel long iron cores and coils set on the free surfaces on both sides of the wide face of the thin slab crystallizer and near the outlet. The wide-width nozzle local area electromagnetic braking device and the wide-width nozzle narrow area electromagnetic braking device respectively achieve the control of the flow of molten steel in the crystallizer by setting multiple sets of iron cores and coils at corresponding positions on both sides of the wide face of the thin slab crystallizer. Both devices control the flow of molten steel by applying a static magnetic field at the wide face of the crystallizer, so that the magnetic lines of force on both sides of the immersion nozzle pass perpendicularly through the wide face of the crystallizer. The magnetic pole position and magnetic induction intensity of each device can be adjusted.

2. The device for electromagnetic braking to regulate the bias flow within the crystallizer according to claim 1, characterized in that, The core of the regional electromagnetic braking device is U-shaped and symmetrically arranged on both sides of the wide face of the crystallizer. The coil is wound on the core, and the magnetic poles point to the molten steel area inside the crystallizer. It mainly covers the molten steel surface on both sides of the immersion nozzle and near the narrow face. By applying DC current to the two excitation coils on the non-bulging side, the molten steel on that side is braked in a constant magnetic field after being ejected from the nozzle, reducing the flow rate of the molten steel on that side, thereby adjusting the symmetry of the molten steel flow in the crystallizer.

3. The device for electromagnetic braking to regulate the bias flow within the crystallizer according to claim 1, characterized in that, The upper and lower sets of parallel long iron cores and coils of the full-width two-stage electromagnetic braking device are located on the free surfaces on both sides of the wide face of the thin slab crystallizer and near the outlet, respectively. By adjusting the magnetic induction intensity of the upper auxiliary magnetic pole and the lower main magnetic pole, the upper and lower reflux zones of the molten steel in the crystallizer can be controlled separately to improve the flow state of the molten steel in the crystallizer.

4. The device for electromagnetic braking to regulate the deflection flow within the crystallizer according to claim 1, characterized in that, The upper and lower sets of parallel long iron cores and coils of the wide-area electromagnetic braking device for the liquid surface are set at corresponding positions on both sides of the wide surface of the thin slab crystallizer. By independently adjusting the current of each pair of coils, the electromagnetic braking effect on the molten steel on both sides of the crystallizer outlet is achieved, thereby controlling the flow rate of molten steel in the upper and lower reflux zones of the crystallizer, stabilizing the flow rate of molten steel in the lower part of the outlet, and reducing secondary eddies.

5. The device for electromagnetic braking to regulate the deflection flow within the crystallizer according to claim 1, characterized in that, The wide-area, narrow-area, zoned electromagnetic braking device is equipped with two pairs of iron cores and coils above and three pairs of iron cores and coils below, located at corresponding positions on both sides of the wide face of the thin slab crystallizer. By adjusting the magnetic induction intensity of the auxiliary and main magnetic poles, the electromagnetic braking effect on the backflow section of the molten steel in the crystallizer is achieved, thereby improving the internal flow field of the crystallizer.

6. A method for controlling the bias current within a crystallizer using electromagnetic braking, characterized in that, Includes the following steps: The degree of nozzle formation is determined by monitoring the height difference of the free liquid surface in the crystallizer. The appropriate electromagnetic braking device should be selected based on the degree of nodulation. Specifically, when the nodulation at one side of the crystallizer outlet is mild, a static magnetic field is applied to the un-nodulated or mildly nodulated side. For the heavily nodulated or severely blocked side, no static magnetic field may be applied, or only a moderately applied one may be used. The magnetic pole parameters of the selected electromagnetic braking device are adjusted to stabilize the flow field, including adjusting the magnetic induction intensity and pole position. Specifically: for a regional electromagnetic braking device, when the nodulation area on one side of the outlet accounts for 30%-50% of the outlet area, the magnetic induction intensity is adjusted to 0.1T-0.15T, and the pole installation position P is 125mm; when the nodulation area accounts for 70% of the outlet area, the magnetic induction intensity must reach at least 0.2T, and the pole installation position P is 25mm; for a full-width two-stage electromagnetic braking device, when the nodulation at one side of the crystallizer outlet is below 40%, the upper auxiliary pole output magnetic induction intensity is 0.05T- 0.3T, the magnetic induction intensity output by the lower main magnetic pole is 0T - 0.5T; when the degree of nodule formation at the outlet reaches 60%, the magnetic induction intensity output by both main magnetic poles is simultaneously achieved, and when the magnetic induction intensity output by the main magnetic pole reaches 0.3T, the symmetry effect of the molten steel reflux zone in the crystallizer is better.

7. The method for controlling the bias flow within a crystallizer using electromagnetic braking according to claim 6, characterized in that, At a casting speed of 1.5 m / min, when the proportion of nodule formation on the right side of the crystallizer reaches 71% and the magnetic induction intensity is 0.15 T, the braking effect on the right side flow field is better when the magnetic pole position P=25 mm. At this time, the jet from the right side of the crystallizer flows out horizontally, while the jet from the left side bends slightly upward. Applying a steady magnetic field only to the left side of the crystallizer can effectively suppress the flow of molten steel on the left side, reduce the flow velocity of the molten steel in the upper backflow zone and free surface in the crystallizer, and suppress liquid surface fluctuations.

8. The method for controlling the bias flow within a crystallizer using electromagnetic braking according to claim 6, characterized in that, For thin slab crystallizers, when the degree of nodule formation on one side of the crystallizer outlet is less than 40%, the magnetic induction intensity of the main and auxiliary magnetic poles of the wide-range electromagnetic braking device at the liquid level outlet is adjusted to 0.1T or 0.2T respectively. This can suppress the backflow of rising molten steel, improve free surface fluctuations, and achieve better symmetry of molten steel on the left and right sides of the crystallizer. When the nodule formation on one side of the outlet is 60%, the magnetic induction intensity of the main and auxiliary magnetic poles needs to be adjusted to 0.5T to control the deflection of molten steel.

9. The method for controlling the bias flow within a crystallizer using electromagnetic braking according to claim 6, characterized in that, For the wide-range liquid level and narrow-range nozzle-type electromagnetic braking device, when the degree of nodule formation on one side of the crystallizer outlet is less than 40%, the output magnetic induction intensity of both the main and auxiliary magnetic poles is set to 0.3T, which can maintain a good symmetrical double reflux of molten steel in the crystallizer. When the degree of nodule formation on one side of the outlet is 60%, the output magnetic induction intensity of the main and auxiliary magnetic poles needs to be adjusted to 0.3T - 0.5T to improve the internal flow field of the crystallizer under the condition of nodule formation.

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