A continuous casting method for high silicon electrical steel based on liquid level periodic cyclic movement control

Abstract

The present application provides a continuous casting method for high-silicon electrical steel based on periodic cyclic movement control of the liquid level, which belongs to the field of continuous casting. The method comprises: injecting the molten steel of high-silicon electrical steel from the tundish into the crystallizer through the submerged water nozzle; adding protective slag to the surface of the molten steel in the crystallizer; controlling the liquid level of the molten steel in the crystallizer to move up and down periodically along the preset liquid level line, so as to dynamically interrupt the nucleation and growth process of the protective slag on the wall of the crystallizer; solidifying the molten steel to form a billet, and pulling the billet out from the outlet of the crystallizer. The servo stopper system controls the liquid level of the molten steel to move up and down periodically along the preset liquid level line, dynamically interrupting the nucleation and growth process of the protective slag on the wall of the crystallizer, effectively suppressing the growth of slag strips, and avoiding the problem of pits formed by slag strip peeling. Thus, by suppressing the inclusion of protective slag on the surface of the billet, the surface defect rate of the high-silicon electrical steel billet is reduced, thereby reducing the iron loss of the high-silicon electrical steel and improving the magnetic properties.

Description

Technical Field

[0001] The present application relates to the field of continuous casting technology, and in particular to a continuous casting method for high-silicon electrical steel based on periodic cyclic movement control of liquid level. Background Art

[0002] High silicon electrical steel is a soft magnetic alloy with a silicon content of ≥2.5%. High silicon content significantly reduces eddy current loss and hysteresis loss, especially at medium and high frequencies (such as 400Hz). 1.0 / 400 ) performance is outstanding, which is more than 30% lower than that of ordinary silicon steel. Therefore, high-silicon electrical steel is mainly used in high-frequency transformers, new energy vehicle drive motors, high-speed motors and other fields with strict requirements on energy efficiency and volume.

[0003] However, existing high-silicon electrical steels face challenges in achieving higher iron loss at medium and high frequencies due to factors such as suboptimal microstructure, limited chemical composition, unstable magnetic domain structure, and inadequate manufacturing processes. Therefore, improving the magnetic properties and iron loss of high-silicon electrical steels is a pressing technical challenge. Summary of the Invention

[0004] The present application provides a continuous casting method for high-silicon electrical steel based on periodic cyclic movement control of liquid level to solve the following technical problem: how to improve the magnetic property iron loss value of high-silicon electrical steel.

[0005] The present application provides a method for continuous casting of high-silicon electrical steel based on periodic cyclic movement control of liquid level, the method comprising:

[0006] Injecting high-silicon electrical steel liquid from the tundish into the crystallizer through the submerged nozzle, and controlling the depth of the submerged nozzle inserted into the molten steel and the argon blowing flow rate of the stopper rod;

[0007] adding mold slag to the surface of the molten steel in the crystallizer;

[0008] The servo stopper system is used to control the liquid level of the molten steel in the crystallizer to move up and down periodically along a preset liquid level line, so as to dynamically interrupt the nucleation and growth process of the protective slag on the crystallizer wall; wherein the liquid level movement trajectory of the up and down periodic movement is uniform or step-by-step, and the up and down periodic movement includes the following parameters: the movement amplitude m1 above the preset liquid level line is 5mm-50mm, the movement amplitude m2 below the preset liquid level line is 5mm-50mm, the movement period t0 is 100s-600s, the movement speed v is 5mm / min-25mm / min, the pause time t1 after the liquid level moves up to the set movement amplitude m1 is 0-60s, and the pause time t2 after the liquid level moves down to the set movement amplitude m2 is 0-60s; and

[0009] The molten steel is solidified into a cast billet through the crystallizer, and the cast billet is pulled out from the outlet of the crystallizer at a set pulling speed.

[0010] Optionally, the depth of the submerged nozzle inserted into the molten steel is 120 mm to 180 mm.

[0011] Optionally, the stopper rod argon blowing flow rate is 3 L / min to 8 L / min.

[0012] Optionally, the superheat degree of the molten high-silicon electrical steel in the tundish is 15°C to 25°C.

[0013] Optionally, the set pulling speed is 0.8m / min to 1.6m / min.

[0014] Optionally, the basicity of the protective slag is 0.6 to 0.8.

[0015] Optionally, the melting point of the protective slag is 1050°C to 1080°C.

[0016] Optionally, the viscosity of the protective slag at 1300° C. is 0.25 Pa·s to 0.35 Pa·s.

[0017] Optionally, the chemical composition of the mold slag includes: CaO, SiO2, Al2O3, Na2O, NaF, CaF2, and C; wherein, in terms of mass fraction,

[0018] The CaO content is 25% to 44%, the SiO2 content is 40% to 45%, the Al2O3 content is 2.5% to 5%, the Na2O content is 5% to 10%, the sum of the NaF and CaF2 contents is 7% to 15%, and the C content is 2.5% to 5%.

[0019] Optionally, the depth of the surface pits of the ingot is ≤1.0 mm, and the diameter of the surface pits of the ingot is ≤1.1 mm;

[0020] The incidence rate of linear defects in the finished product of the high-silicon electrical steel is ≤0.5%.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] An embodiment of the present application provides a continuous casting method for high-silicon electrical steel based on periodic liquid level movement control. The method comprises: injecting high-silicon electrical steel molten steel from a tundish through a submerged nozzle into a crystallizer, controlling the depth of the submerged nozzle inserted into the molten steel and the flow rate of argon blowing through a stopper rod; adding mold slag to the surface of the molten steel in the crystallizer; controlling the liquid level of the molten steel in the crystallizer to move up and down periodically along a preset liquid level line through a servo stopper rod system to dynamically interrupt the nucleation and growth process of the mold slag on the crystallizer wall; wherein the liquid level movement trajectory of the up and down periodic movement is uniform or stepped; solidifying the molten steel in the crystallizer to form a cast billet, and pulling the cast billet out of the crystallizer outlet at a set pulling speed. By controlling the liquid level of the molten steel to move up and down periodically along the preset liquid level line through the servo stopper rod system, the nucleation and growth process of the mold slag on the crystallizer wall is dynamically interrupted, effectively suppressing the growth of slag bars and avoiding the problem of pitting caused by slag bar peeling. Thus, by suppressing the inclusion of mold slag on the surface of the cast slab, the surface defect rate of the cast slab of high-silicon electrical steel is reduced, and the iron loss of the high-silicon electrical steel is further reduced, thereby improving the magnetic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 A schematic flow chart of a continuous casting method for high-silicon electrical steel based on liquid level periodic cyclic movement control provided in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of a liquid level movement trajectory that periodically moves up and down provided in an embodiment of the present application;

[0027] Figure 3 Schematic diagram of the slag strip nucleation with periodic up and down movement provided in Example 1 of the present application;

[0028] Figure 4 This is a schematic diagram of slag strip nucleation at a conventional static liquid level provided in Comparative Example 1 of this application;

[0029] Figure 5 This is a surface morphology image of the ingot of high-silicon electrical steel provided in Example 1 of the present application;

[0030] Figure 6This is a surface morphology of the ingot of high-silicon electrical steel provided in Comparative Example 1 of the present application;

[0031] Reference numerals:

[0032] 1-Liquid slag layer; 2-Solid slag bar (block); 3-Crystallizer copper plate; 4-Molten steel; 5-Solidified shell. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0035] In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be a single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationships discussed herein, the parameters that need to be described by ratio should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substances A, B, and C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0037] Figure 1 A schematic flow chart of a continuous casting method for high-silicon electrical steel based on periodic cyclic movement control of liquid level provided in an embodiment of the present application.

[0038] like Figure 1 As shown, the present application provides a continuous casting method for high-silicon electrical steel based on liquid level periodic cyclic movement control, the method comprising:

[0039] S1. Injecting molten high-silicon electrical steel from a tundish into a crystallizer through a submerged nozzle, and controlling the depth of the submerged nozzle inserted into the molten steel and the argon blowing flow rate of the stopper rod;

[0040] In some embodiments, the superheat degree of the molten high-silicon electrical steel in the tundish is 15°C to 25°C.

[0041] Superheat affects the solidification behavior of molten steel and the efficiency of inclusion flotation. The superheat of high-silicon electrical steel in the tundish is limited to 15°C to 25°C to ensure rapid solidification in the mold, quickly forming a shell of sufficient strength and reducing the likelihood of surface slag inclusions. For example, the superheat of high-silicon electrical steel in the tundish can be 15°C, 17°C, 19°C, 20°C, 22°C, 24°C, 25°C, etc.

[0042] In some embodiments, the depth of the submerged nozzle inserted into the molten steel is 120 mm to 180 mm.

[0043] The insertion depth of a submerged nozzle directly affects the flow state of the molten steel and the stability of the liquid surface. The insertion depth of the submerged nozzle into the molten steel is limited to 120-180 mm. This balances the impact force of the steel flow with the uniformity of the billet shell, avoids violent fluctuations in the liquid surface, and reduces the probability of slag formation. If the insertion depth is too shallow (<120 mm), the steel flow will violently impact the liquid surface, easily entraining slag and causing the mold slag to be drawn into the molten steel, forming inclusion defects. If the insertion depth is too deep (>180 mm), the steel flow will weaken the narrow surface of the crystallizer, resulting in uneven thickness of the solidified billet shell and insufficient mold surface activity, which will affect the melting of the mold slag. For example, the insertion depth of the submerged nozzle into the molten steel can be 120 mm, 130 mm, 140 mm, 160 mm, 170 mm, 180 mm, etc.

[0044] In some embodiments, the stopper rod argon blowing flow rate is 3 L / min to 8 L / min.

[0045] Argon is blown into the nozzle through the stopper core tube. The stopper argon flow rate is limited to 3-8 L / min. This stabilizes the steel flow, evens out the temperature, and inhibits the deposition of high-melting-point inclusions on the nozzle inner wall. The argon bubble diameter should be ≤ 1 mm to ensure a liquid surface velocity of ≥ 0.2 m / s at 1 / 4 the plate width. Exemplary stopper argon flow rates can be 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, etc.

[0046] S2, adding mold slag to the surface of the molten steel in the crystallizer;

[0047] In some embodiments, the basicity of the mold slag is 0.6-0.8, and the melting point of the mold slag is 1050°C-1080°C.

[0048] In some embodiments, the viscosity of the mold slag at 1300° C. is 0.25 Pa·s to 0.35 Pa·s.

[0049] In some embodiments, the chemical composition of the mold slag includes: CaO, SiO2, Al2O3, Na2O, NaF, CaF2, and C; wherein, in terms of mass fraction,

[0050] The CaO content is 25% to 44%, the SiO2 content is 40% to 45%, the Al2O3 content is 2.5% to 5%, the Na2O content is 5% to 10%, the sum of the NaF and CaF2 contents is 7% to 15%, and the C content is 2.5% to 5%.

[0051] Low-basicity mold slag has a lower melting point and a higher vitrification tendency. Traditional mold slags with a basicity of 1.0-1.2 are prone to forming high-melting-point phases (such as calcium aluminates), leading to the formation of solid slag strips. In this embodiment of the present application, the mold slag basicity (CaO / SiO2) is limited to 0.6-0.8. This can reduce the solidification temperature of the mold slag by 70-120°C, allowing for the rapid formation of a liquid slag layer (target melting speed 20s-25s), reducing the chance of slag strip nucleation. For example, the mold slag basicity can be 0.6, 0.65, 0.7, 0.75, 0.8, etc. The melting point of the mold slag can be 1050°C, 1055°C, 1060°C, 1065°C, 1070°C, 1075°C, 1080°C, etc.

[0052] Fluorides significantly reduce the melting point and viscosity of mold slag. The synergistic effect of NaF and CaF2 maintains a viscosity of 0.25 Pa·s to 0.35 Pa·s at 1300°C, ensuring a uniform layer of liquid slag covering the molten steel surface, isolating it from air and lubricating the shell. For example, the combined content of NaF and CaF2 can be 7%, 8%, 9%, 10%, 11%, 12%, 14%, 15%, etc.

[0053] Carbon serves as the mold slag's skeleton, controlling the melting rate and slag layer structure. If the carbon content is less than 2.5wt%, the mold slag melts too quickly, resulting in a thick liquid slag layer that is easily drawn into the steel stream and forms slag inclusions. If the carbon content is greater than 5wt%, the slag layer does not melt sufficiently, increasing the proportion of solid slag and exacerbating slag strand growth. For example, the carbon content can be 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0054] S3. Controlling the liquid level of the molten steel in the crystallizer to periodically move up and down along a preset liquid level line through a servo stopper system to dynamically interrupt the nucleation and growth process of the mold slag on the crystallizer wall; wherein the liquid level movement trajectory of the periodic up and down movement is uniform or stepped;

[0055] The high silicon electrical steel in the existing technology has a low liquidus temperature of molten steel (≤1480℃) and weak shell strength in the early stage of solidification. When the traditional continuous casting process adopts a fixed liquid level operation, the protective slag continues to nucleate and grow into solid slag strips (blocks) (length ≥30mm) at the wall of the crystallizer. After the slag strips are peeled off, it is pressed into the shell to form pits (pits) with a depth of ≥2mm. After rolling, it evolves into linear defects on the surface of the finished electrical steel product (incidence rate ≥20%), affecting the surface yield. At the same time, the pinning effect of the surface defects on the magnetic chips causes the magnetic properties to deteriorate, especially the iron loss value P of the medium frequency low magnetic field strength. 1.0 / 400 Existing technologies can only partially improve slag entrainment by optimizing the melting point of mold slag or the amount of argon blowing, but cannot completely solve the above problems.

[0056] In this embodiment, the mold liquid level is preset before casting, and then pouring begins. Once the liquid level in the mold reaches the preset level and stabilizes, the "liquid level shifting" operation described herein begins. This periodic liquid level shift continuously shifts the nucleation position of the mold slag on the mold wall, disrupting the dynamic conditions for the nucleation and growth of mold slag strips (lumps), inhibiting their growth to a critical size (≥3mm). Simultaneously, the movement speed is slowed to avoid slag entrainment caused by violent liquid level disturbances.

[0057] It should be noted that the preset liquid level line refers to the artificially preset liquid level of molten steel in the crystallizer during the continuous casting process. For example, if the crystallizer height is 1000mm and the liquid level is set to 850mm during pouring, the liquid level of the tundish steel injected into the crystallizer will stabilize at a height of 850mm when pouring begins and remain slightly above and below this height line. The preset liquid level line in the embodiment of the present application can be the position of the preset liquid level height under the static liquid level.

[0058] A uniform motion trajectory means that the actual steel level, under the control of the servo stopper system, moves up or down at a constant speed around the preset level. This motion method is characterized by a stable speed that does not change over time, resulting in a linear and continuous change in the level.

[0059] A stepped motion trajectory means that the actual steel level, under the control of the servo stopper system, moves up or down at a constant speed around a preset level line. After reaching a new level, the movement pauses for a certain period of time, then continues upward or downward at a constant speed. After reaching the next level, the movement is repeated, followed by another steady-state movement. This motion pattern is characterized by the liquid level remaining stable for a period of time at each step before transitioning to the next step at a constant speed, creating a similarly stepped level change.

[0060] The "liquid level movement" mentioned in this application is the slow up and down movement of the crystallizer steel liquid level controlled by human subjective will, with a slow movement speed of 5 to 25 mm / min and a large movement amplitude of ±5 mm to 50 mm; it is different from the traditional crystallizer "liquid level fluctuation". The traditional liquid level fluctuation is a passive behavior caused by the movement of the molten steel pouring flow field. The fluctuation period is short and it is easy to cause slag rolling. The general control target is <±3 mm.

[0061] This application supports uniform or stepped movement trajectories to accommodate different steel grades and mold slag characteristics. Furthermore, the servo stopper system achieves ±0.3mm liquid level accuracy, combined with AI real-time monitoring to ensure process stability.

[0062] It should be noted that the implementation methods and processes of controlling the liquid level of the molten steel in the crystallizer to move periodically up and down along the preset liquid level line through the servo stopper system can be diverse. The present application provides a feasible implementation method:

[0063] The servo stopper system consists of an electric cylinder, an encoder, a PLC, and a liquid level sensor. The electric cylinder, driven by a high-precision servo motor, raises and lowers the stopper, regulating the flow of molten steel from the tundish to the mold and thus controlling the liquid level. The sensor technology uses a Co-60 radioactive source or eddy current sensor to monitor the liquid level in real time with an accuracy of ±1mm. The signal is relayed (such as the FB100) and shielded to prevent interference. The encoder monitors stopper displacement (inner loop), while the liquid level sensor provides feedback on the liquid level (outer loop). A PID algorithm dynamically adjusts the stopper opening, creating a closed-loop control system. The PLC programmable liquid level trajectory can include uniform, sinusoidal, or stepped fluctuations. For example, a sinusoidal trajectory optimizes the uniformity of molten steel flow, while a stepped trajectory is suitable for intermittent control of specific processes. The servo motor then raises and lowers the stopper at a set speed with a control accuracy of ±0.3mm. The encoder and liquid level sensor (such as an eddy current sensor) form a dual closed-loop feedback loop to dynamically adjust the molten steel flow rate.

[0064] In some embodiments, a laser rangefinder + AI image recognition system is used to provide real-time feedback on the liquid level movement trajectory.

[0065] Figure 2 A schematic diagram of the liquid level movement trajectory that moves up and down periodically provided in an embodiment of the present application.

[0066] like Figure 2 As shown, in some embodiments, the up and down periodic movement includes the following parameters:

[0067] The movement range m1 above the preset liquid level line is 5mm to 50mm;

[0068] The movement range m2 below the preset liquid level line is 5mm to 50mm;

[0069] The moving period t0 is 100s to 600s;

[0070] Moving speed v is 5mm / min~25mm / min;

[0071] The pause time t1 after the liquid level moves up to the set movement amplitude m1 is 0 to 60s;

[0072] The pause movement time t2 after the liquid level moves down to the set movement amplitude m2 is 0 to 60s.

[0073] It should be noted that in Figure 2 In the figure, the movement amplitude OA above the preset liquid level line = m1, the movement amplitude OB below the preset liquid level line = m2, and the relationship between m1 and m2 can be: m1 = m2 or m1>m2 or m1<m2.

[0074] Under traditional static liquid levels, slag strips continue to grow at a fixed position to a critical size (≥3mm), eventually peeling off and forming pits. In the embodiments of the present application, large-scale, long-period liquid level movement is used to disrupt the nucleation conditions of the protective slag on the crystallizer wall. The movement amplitude m1 above the preset liquid level line is limited to 5mm to 50mm, and the movement amplitude m2 below the preset liquid level line is limited to 5mm to 50mm. This can cause the slag strip nucleation position to shift periodically, inhibiting its growth to a critical size. The movement period t0 is limited to 100s to 600s to match the slag strip growth dynamics and ensure that the nucleation process is interrupted multiple times. The movement speed v is limited to 5mm / min to 25mm / min, and the slow movement speed avoids severe disturbances in the liquid surface. If the speed is <5mm / min, the liquid level movement effect is not significant and cannot effectively interrupt the growth of the slag strip. If the speed is >25mm / min, the liquid surface fluctuation amplitude increases (>±3mm), which can easily cause slag coiling. The pause movement time (dwell time) is limited to 0 to 60 seconds. The machine can pause after moving to the set amplitude to balance process stability and slag suppression effect. Exemplarily, the movement amplitude m1 above the preset liquid level line can be 5mm, 10mm, 20mm, 30mm, 40mm, 50mm, etc., the movement amplitude m2 below the preset liquid level line can be 5mm, 10mm, 15mm, 20mm, 30mm, 40mm, 50mm, etc., the movement period t0 can be 100s, 200s, 300s, 400s, 500s, 600s, etc., the movement speed v can be 5mm / min, 10mm / min, 15mm / min, 20mm / min, 25mm / min, etc., the pause movement time t1 after the liquid level moves up to the set movement amplitude m1 is 0, 5s, 10s, 20s, 30s, 40s, 50s, 60s, etc., and the pause movement time t2 after the liquid level moves down to the set movement amplitude m2 is 0, 5s, 10s, 20s, 30s, 40s, 50s, 60s, etc.

[0075] S4. Solidify the molten steel into a cast billet through the crystallizer, and pull the cast billet out from the outlet of the crystallizer at a set pulling speed.

[0076] In some embodiments, the set pulling speed is 0.8 m / min to 1.6 m / min.

[0077] The drawing speed affects the solidified shell thickness and surface quality. The drawing speed is limited to 0.8m / min to 1.6m / min. The shell thickness is uniform, and combined with dynamic liquid level control, the surface pit depth is ≤1.0mm. For example, the drawing speed can be 0.8m / min, 0.9m / min, 1.1m / min, 1.3m / min, 1.5m / min, 1.6m / min, etc.

[0078] In some embodiments, the depth of the surface pits of the ingot is ≤1.0 mm, and the diameter of the surface pits of the ingot is ≤1.1 mm;

[0079] The incidence of linear defects in the finished product of the high-silicon electrical steel is ≤0.5%.

[0080] In the embodiment of the present application, through the coordinated optimization of the submerged nozzle depth, argon blowing flow rate and the physical properties of the protective slag, combined with the liquid level periodic movement technology, the depth of the pits on the surface of the high-silicon electrical steel continuous casting billet is ≤1.0mm, the incidence of linear defects in the finished electrical steel product is reduced from more than 20% to less than 0.5%, and the magnetic properties are improved by more than 3%, greatly improving the surface quality and magnetic performance level. It is suitable for production scenarios with different silicon contents (2.5% to 4.5%) and plate widths (800mm to 1600mm).

[0081] In summary, the embodiments of the present application solve the problems of surface defects and deterioration of magnetic properties caused by slag strips during the continuous casting of high-silicon electrical steel through dynamic liquid level control, optimization of protective slag properties and coordination of process parameters, achieving a breakthrough of defect rate ≤ 0.5% and iron loss reduction of more than 3%. At the same time, it adapts to the production needs of large width-to-thickness ratio (800mm~1600mm), providing cost-effective material solutions for new energy vehicles, high-frequency devices and other fields.

[0082] Specifically, the embodiment of the present application provides a continuous casting method for high-silicon electrical steel based on periodic cyclic movement control of the liquid level, which has the following advantages:

[0083] (1) Optimizing the flow and solidification of molten steel: By precisely controlling the insertion depth of the submerged nozzle and the argon blowing flow rate of the stopper rod, the flow state of the molten steel is optimized, the liquid level fluctuation is reduced, and the rapid solidification of the molten steel in the crystallizer is ensured, thereby reducing the probability of surface block slag inclusions.

[0084] (2) Lowering the melting point and viscosity of protective slag: Using protective slag with specific alkalinity and melting point, as well as optimized chemical composition, significantly lowers the melting point and viscosity of protective slag, matching the low liquidus temperature of high silicon steel, ensuring that the liquid slag layer can evenly cover the surface of the molten steel, effectively isolating the air and lubricating the shell, and controlling the slag strips from growing and being pressed in.

[0085] (3) Dynamic interruption of slag bar growth: The servo stopper system controls the molten steel level to move up and down periodically along the liquid level line, dynamically interrupting the nucleation and growth process of the protective slag at a fixed position on the crystallizer wall, effectively inhibiting the growth of the slag bar and avoiding the pitting problem caused by slag bar peeling.

[0086] (4) Improving the surface quality of the ingot: Combined with the above optimization measures, the depth and diameter of the surface pits of the ingot are effectively controlled, which significantly improves the surface quality of the ingot.

[0087] (5) Reduction of the incidence of linear defects: Due to the optimization of molten steel flow, solidification and protective slag behavior, as well as the application of liquid level periodic movement technology, the incidence of linear defects in finished products of high-silicon electrical steel has been greatly reduced from more than 20% to less than 0.5%.

[0088] (6) Improvement of magnetic properties: The optimized continuous casting process not only improves the surface quality of the ingot, but also significantly improves the magnetic properties of electrical steel, which is of great significance for the application of electrical steel.

[0089] (7) Wide applicability: This method is applicable to production scenarios with different silicon contents (2.5% to 4.5%) and plate widths (800 mm to 1600 mm), and has strong versatility and practicality.

[0090] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0091] The present application provides a continuous casting method for high-silicon electrical steel based on liquid level periodic cyclic movement control, the method comprising:

[0092] S1. Injecting molten high-silicon electrical steel from a tundish into a crystallizer through a submerged nozzle, and controlling the depth of the submerged nozzle inserted into the molten steel and the argon blowing flow rate of the stopper rod;

[0093] S2, adding mold slag to the surface of the molten steel in the crystallizer;

[0094] S3. Controlling the liquid level of the molten steel in the crystallizer to periodically move up and down along a preset liquid level line through a servo stopper system to dynamically interrupt the nucleation and growth process of the mold slag on the crystallizer wall;

[0095] S4. Solidify the molten steel into a cast billet through the crystallizer, and pull the cast billet out from the outlet of the crystallizer at a set pulling speed.

[0096] The specific process parameters of the continuous casting method of high silicon electrical steel of the embodiment are shown in Tables 1 to 3, and the specific process parameters of the continuous casting method of high silicon electrical steel of the comparative example are shown in Tables 4 and 5.

[0097] Examples 1 to 8, Comparative Examples 1, and 2 were used to produce non-oriented electrical steel with a thickness of 0.30 mm and a Si content of 3.3% (1100 mm wide); Example 9 and Comparative Example 3 were used to produce ultra-thin, high-grade, non-oriented electrical steel with a thickness of 0.20 mm and a Si content of 3.4% (1250 mm wide); and Example 10 and Comparative Example 4 were used to produce non-oriented electrical steel with a thickness of 0.35 mm and a Si content of 3.4% (1000 mm wide). Comparative Examples 1 to 4 employed fixed liquid level operation, without periodic vertical movement of the liquid level.

[0098] Table 1 Chemical composition (wt.%) and performance parameters of mold slag used in the continuous casting method of high silicon electrical steel in the embodiment

[0099]

[0100] Table 2 Up and down periodic movement parameters of the continuous casting method of high silicon electrical steel in the embodiment

[0101]

[0102] Table 3 Process parameters of the continuous casting method of high silicon electrical steel in the embodiment

[0103]

[0104] Table 4 Chemical composition (wt.%) and performance parameters of mold slag for continuous casting of high silicon electrical steel in comparative example

[0105]

[0106] Table 5 Process parameters of continuous casting method for high silicon electrical steel of comparative example

[0107]

[0108] The properties of the high-silicon electrical steel ingots obtained in Examples 1 to 10 and Comparative Examples 1 to 4 were measured. At the same time, according to the existing high-silicon electrical steel preparation method, the high-silicon electrical steel ingots were prepared to form high-silicon electrical steel. At the same time, the properties of the finished high-silicon electrical steel were measured. The results are shown in Table 6.

[0109] Table 6 Properties of high silicon electrical steel ingots and finished products

[0110]

[0111] As can be seen from Table 6, the surface quality and magnetic properties P1.0 / 400 of the 0.30 mm non-oriented electrical steel produced in Examples 1 to 8 of the present invention are significantly better than those of the corresponding Comparative Examples 1 and 2; the surface quality and magnetic properties P1.0 / 400 of the 0.20 mm non-oriented electrical steel produced in Example 9 of the present invention are significantly better than those of the corresponding Comparative Example 3; the surface quality and magnetic properties P1.0 / 400 of the 0.35 mm non-oriented electrical steel produced in Example 10 of the present invention are significantly better than those of the corresponding Comparative Example 4.

[0112] Figure 3 Schematic diagram of the slag strip nucleation with periodic up and down movement provided in Example 1 of the present application; Figure 4 This is a schematic diagram of slag bar nucleation at a traditional static liquid level provided in Comparative Example 1 of this application.

[0113] Depend on Figure 3 and Figure 4 By comparison, it can be seen that the upper and lower liquid level movement operation of the embodiment of the present application and the dynamic upper and lower movement of the liquid level can effectively destroy and suppress the formation of large slag strips (lumps).

[0114] Figure 5 This is a surface morphology image of the ingot of high-silicon electrical steel provided in Example 1 of the present application; Figure 6 This is a surface morphology diagram of the ingot of high-silicon electrical steel provided in Comparative Example 1 of the present application.

[0115] Depend on Figure 5 and Figure 6 By comparison, it can be seen that the surface slag inclusion of the ingot in Example 1 is significantly controlled, the size and depth of the slag pit are greatly reduced, and the slag pit depth is reduced from a maximum of more than 3 mm in Comparative Example 1 to <1.0 mm in Example 1.

[0116] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0117] In the embodiment of the present application, the nucleation and growth process of the protective slag on the crystallizer wall is dynamically interrupted by long-period (100s to 600s) and wide-range (±5 to 50mm) liquid level movement, breaking through the limitations of traditional static liquid level operation.

[0118] In the embodiment of the present application, uniform speed, stepped and sinusoidal movement trajectories are supported to adapt to different steel grades and protective slag characteristics.

[0119] In the embodiment of the present application, the servo stopper rod system achieves ±0.3mm level liquid level accuracy control and combines AI real-time monitoring to ensure process stability.

[0120] In the embodiment of the present application, the depth of the pits on the surface of the high-silicon electrical steel continuous casting billet is ≤1.0mm, the incidence of linear defects in the finished electrical steel product is reduced from more than 20% to less than 0.5%, and the magnetic properties are improved by more than 3%, which greatly improves the surface quality and magnetic properties. It is suitable for production scenarios with different silicon contents (2.5-4.5%) and plate widths (800-1600mm).

[0121] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A continuous casting method for high silicon electrical steel based on liquid level periodic cyclic movement control, characterized in that: The method comprises: Injecting high-silicon electrical steel liquid from a tundish into a crystallizer through a submerged nozzle, controlling the depth of the submerged nozzle inserted into the molten steel and the flow rate of argon blowing through the stopper rod, wherein the silicon content of the high-silicon electrical steel is 2.5-4.5%; adding mold slag to the surface of the molten steel in the crystallizer; The servo stopper system is used to control the liquid level of the molten steel in the crystallizer to move up and down periodically along a preset liquid level line, so as to dynamically interrupt the nucleation and growth process of the protective slag on the crystallizer wall; wherein the liquid level movement trajectory of the up and down periodic movement is uniform or step-by-step, and the up and down periodic movement includes the following parameters: the movement amplitude m1 above the preset liquid level line is 10mm-50mm, the movement amplitude m2 below the preset liquid level line is 10mm-50mm, the movement period t0 is 100s-600s, the movement speed v is 5mm / min-25mm / min, the pause time t1 after the liquid level moves up to the set movement amplitude m1 is 0-60s, and the pause time t2 after the liquid level moves down to the set movement amplitude m2 is 0-60s; and Solidifying the molten steel into a cast billet through the crystallizer, and pulling the cast billet out from the outlet of the crystallizer at a set pulling speed; The depth of the submerged nozzle inserted into the molten steel is 120 mm to 180 mm; The stopper rod argon blowing flow rate is 3L / min to 8L / min; The depth of the surface pits of the ingot is ≤1.0 mm, and the diameter of the surface pits of the ingot is ≤1.1 mm; The linear defect incidence rate of the finished product of the high-silicon electrical steel is ≤0.5%, and the magnetic properties are improved by more than 3%.

2. The method according to claim 1, characterized in that The superheat degree of the molten high-silicon electrical steel in the tundish is 15°C to 25°C.

3. The method according to claim 1, characterized in that The set pulling speed is 0.8 m / min to 1.6 m / min.

4. The method according to claim 1, wherein The basicity of the protective slag is 0.6-0.

8.

5. The method according to claim 1, wherein The melting point of the protective slag is 1050°C to 1080°C.

6. The method according to claim 1, characterized in that The viscosity of the protective slag at 1300° C. is 0.25 Pa·s to 0.35 Pa·s.

7. The method according to claim 6, characterized in that The chemical composition of the protective slag includes: CaO, SiO2, Al2O3, Na2O, NaF, CaF2, and C; wherein, in terms of mass fraction, The CaO content is 25% to 44%, the SiO2 content is 40% to 45%, the Al2O3 content is 2.5% to 5%, the Na2O content is 5% to 10%, the sum of the NaF and CaF2 contents is 7% to 15%, and the C content is 2.5% to 5%.

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