Continuous casting method of high-silicon electrical steel based on liquid level periodic circulation movement control

Abstract

The invention provides a continuous casting method for high-silicon electrical steel based on liquid level periodic circulation movement control, and belongs to the field of continuous casting. The method comprises the following steps: injecting molten steel of high-silicon electrical steel into a crystallizer from a tundish through a submersed nozzle; casting powder is added to the surface of the molten steel in the crystallizer; controlling the liquid level of the molten steel in the crystallizer to periodically move up and down along a preset liquid level line so as to dynamically break the nucleation and growth processes of the casting powder on the wall of the crystallizer; and the molten steel is solidified to form a casting blank, and the casting blank is pulled out from an outlet of the crystallizer. The liquid level of the molten steel is controlled by the servo stopper rod system to periodically move up and down along the preset liquid level line, so that the nucleation growth process of the casting powder on the crystallizer wall is dynamically broken, the growth of slag strips is effectively inhibited, and the problem of pits formed by stripping of the slag strips is avoided. Therefore, the surface defect rate of the casting blank of the high-silicon electrical steel is reduced by inhibiting slag inclusion of the casting powder on the surface of the casting blank, so that the iron loss of the high-silicon electrical steel is reduced, and the magnetic performance is improved.

Description

Technical Field

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

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

[0003] However, due to the combined effects of factors such as non-optimized microstructure, chemical composition characteristics limitations, unstable magnetic domain structure, and insufficient preparation process of high-silicon electrical steel in the prior art, it is difficult to further improve the iron loss value of high-silicon electrical steel at medium and high frequencies. Therefore, how to improve the magnetic property iron loss value of high-silicon electrical steel is a technical problem that urgently needs to be solved at present. Summary of the Invention

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

[0005] An embodiment of the present application provides a continuous casting method for high-silicon electrical steel based on liquid level periodic cyclic movement control. The method includes: Injecting the molten steel of high-silicon electrical steel from the tundish into the mold through a submerged nozzle, and controlling the depth of the submerged nozzle inserted into the molten steel and the flow rate of argon blown through the stopper rod; Adding protective slag to the surface of the molten steel in the mold; Controlling the liquid level of the molten steel in the mold 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 protective slag on the mold wall; wherein, the liquid level movement trajectory of the up and down periodic movement is uniform or stepped. The up and down periodic movement includes the following parameters: the movement amplitude m1 above the preset liquid level line is 5 mm to 50 mm, the movement amplitude m2 below the preset liquid level line is 5 mm to 50 mm, the movement period t0 is 100 s to 600 s, the movement speed v is 5 mm / min to 25 mm / min, the pause movement time t1 after the liquid level moves up to the set movement amplitude m1 is 0 to 60 s, and the pause movement time t2 after the liquid level moves down to the set movement amplitude m2 is 0 to 60 s; and Solidifying the molten steel into a slab through the mold, and pulling out the slab from the outlet of the mold at a set casting speed.

[0006] Optionally, the immersion nozzle is inserted into the molten steel to a depth of 120 mm to 180 mm.

[0007] Optionally, the argon blowing flow rate of the stopper rod is 3 L / min to 8 L / min.

[0008] Optionally, the superheat of the molten steel of the high-silicon electrical steel in the tundish is 15 °C to 25 °C.

[0009] Optionally, the set casting speed is 0.8 m / min to 1.6 m / min.

[0010] Optionally, the basicity of the mold powder is 0.6 to 0.8.

[0011] Optionally, the melting point of the mold powder is 1050 °C to 1080 °C.

[0012] Optionally, the viscosity of the mold powder at 1300 °C is 0.25 Pa·s to 0.35 Pa·s.

[0013] Optionally, the chemical composition of the mold powder includes: CaO, SiO 2 , Al 2 O 3 , Na 2 O, NaF, CaF 2 , and C; wherein, by mass fraction, the content of CaO is 25% to 44%, the content of SiO 2 is 40% to 45%, the content of Al 2 O 3 is 2.5% to 5%, the content of Na 2 O is 5% to 10%, the sum of the contents of NaF and CaF 2 is 7% to 15%, and the content of C is 2.5% to 5%.

[0014] Optionally, the depth of the surface pits of the continuous casting billet is ≤ 1.0 mm, and the diameter of the surface pits of the continuous casting billet is ≤ 1.1 mm; the incidence rate of linear defects of the finished high-silicon electrical steel is ≤ 0.5%.

[0015] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art: The embodiment of the present application provides a continuous casting method for high-silicon electrical steel based on liquid level periodic cyclic movement control. The method includes: injecting the molten steel of high-silicon electrical steel from the tundish into the mold 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; adding the protective slag to the surface of the molten steel in the mold; controlling the liquid level of the molten steel in the mold to move up and down periodically along a preset liquid level line through the servo stopper rod system to dynamically interrupt the nucleation and growth process of the protective slag on the mold wall; wherein, the liquid level movement trajectory of the up and down periodic movement is uniform or stepped; solidifying the molten steel into a slab through the mold, and pulling out the slab from the outlet of the mold at a set casting speed. By controlling the liquid level of the molten steel to move up and down periodically along a preset liquid level line through the servo stopper rod system, the nucleation and growth process of the protective slag on the mold wall is dynamically interrupted, the growth of slag bars is effectively inhibited, and the pitting problem caused by the peeling of slag bars is avoided. Thus, by suppressing the inclusion of the protective slag on the surface of the slab, the surface defect rate of the slab of high-silicon electrical steel is reduced, and further the iron loss of high-silicon electrical steel is reduced, and the magnetic properties are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a schematic flow chart of a continuous casting method for high-silicon electrical steel based on liquid level periodic cyclic movement control provided by the embodiment of the present application; Figure 2 It is a schematic diagram of the liquid level movement trajectory of the up and down periodic movement provided by the embodiment of the present application; Figure 3 It is a schematic diagram of the nucleation of slag bars with up and down periodic movement provided by Embodiment 1 of the present application; Figure 4 It is a schematic diagram of the nucleation of slag bars with a traditional static liquid level provided by Comparative Example 1 of the present application; Figure 5 It is a surface morphology diagram of the slab of high-silicon electrical steel provided by Embodiment 1 of the present application; Figure 6 It is a surface morphology diagram of the slab of high-silicon electrical steel provided by Comparative Example 1 of the present application; Reference numerals: 1 - liquid slag layer; 2 - solid slag strip (block); 3 - mold copper plate; 4 - molten steel; 5 - solidified shell. Detailed implementation manners

[0019] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0020] The various embodiments of the present application may exist 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 construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub - ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has 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., and individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0021] In addition, in the description of the specification of the present application, terms such as "including" and "comprising" mean "including but not limited to". In this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this text, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. In this text, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one of the following (items)" or similar expressions refer to any combination of these items, including any combination of single item (s) or plural item (s). For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both mean: a, b, c, a-b (that is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple respectively. The "parts representation method" such as parts by weight and parts by mass represents the proportional relationship between each component. In the proportional relationships involved in this text, the parameters that need to be described by proportion should be understood as the antecedents of the proportion formula in the order of description, and the proportional numbers should be understood as the consequents of the proportion formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportion 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.

[0022] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present application can be obtained through market purchase or can be prepared by existing methods.

[0023] Figure 1 It is a schematic flow chart of a continuous casting method of high-silicon electrical steel based on liquid level periodic cyclic movement control provided for the embodiments of the present application.

[0024] As Figure 1 shown, the present application provides a continuous casting method of high-silicon electrical steel based on liquid level periodic cyclic movement control, and the method includes: S1. Inject the molten steel of high-silicon electrical steel from the tundish into the mold through the submerged nozzle, and control the depth of insertion of the submerged nozzle into the molten steel and the flow rate of argon blown through the stopper rod; In some embodiments, the superheat of the molten steel of high-silicon electrical steel in the tundish is 15°C to 25°C.

[0025] Superheat affects the solidification behavior of molten steel and the efficiency of inclusion floating. The superheat of the molten steel of high-silicon electrical steel in the tundish is limited to 15°C to 25°C to ensure that the molten steel solidifies quickly in the crystallizer, forms a shell of a certain strength as soon as possible, and reduces the probability of surface block slag inclusions. Exemplarily, the superheat of the molten steel 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.

[0026] In some embodiments, the submerged nozzle is inserted into the molten steel to a depth of 120 mm to 180 mm.

[0027] The insertion depth of the submerged nozzle directly affects the flow state of the molten steel and the stability of the liquid surface. The depth of the submerged nozzle inserted into the molten steel is limited to 120-180mm, which balances the impact force of the steel flow and the uniformity of the billet shell, avoids violent fluctuations in the liquid surface, and reduces the probability of slag formation. If the insertion is too shallow (<120mm), the steel flow will impact the liquid surface violently, which is easy to roll slag and cause the protective slag to be drawn into the molten steel, forming inclusion defects; if the insertion is too deep (>180mm), the steel flow will weaken the scouring of the narrow surface of the crystallizer, the thickness of the solidified billet shell is uneven, and the crystallizer liquid surface is not active enough, which affects the melting of the protective slag. Exemplarily, the depth of the submerged nozzle inserted into the molten steel can be 120mm, 130mm, 140mm, 160mm, 170mm, 180mm, etc.

[0028] In some embodiments, the stopper rod argon blowing flow rate is 3 L / min to 8 L / min.

[0029] Argon is blown into the nozzle through the core tube of the stopper rod. The stopper rod argon blowing flow rate is limited to 3-8L / min. Argon can stabilize the steel flow and uniform temperature, while inhibiting the deposition of high melting point inclusions on the inner wall of the nozzle. At the same time, the argon bubble diameter is ≤1mm to ensure that the liquid surface velocity at 1 / 4 of the plate width is ≥0.2m / s. Exemplarily, the stopper rod argon blowing flow rate can be 3L / min, 4L / min, 5L / min, 6L / min, 7L / min, 8L / min, etc.

[0030] S2, adding protective slag to the surface of the molten steel in the crystallizer; 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.

[0031] In some embodiments, the viscosity of the mold slag at 1300° C. is 0.25 Pa·s to 0.35 Pa·s.

[0032] In some embodiments, the chemical composition of the mold slag includes: CaO, SiO 2 、Al 2 O 3 、Na2 O, NaF, CaF 2 , and C; wherein, by mass fraction, the content of CaO is 25% - 44%, SiO 2 the content of which is 40% - 45%, Al 2 O 3 the content of which is 2.5% - 5%, Na 2 O the content of which is 5% - 10%, the sum of the contents of NaF and CaF 2 is 7% - 15%, and the content of C is 2.5% - 5%.

[0033] The low - basicity mold powder has a lower melting point and a higher tendency to vitrify. The traditional basicity (1.0 - 1.2) mold powder is prone to form high - melting - point phases (such as calcium aluminate), resulting in the generation of solid slag bars. In the embodiments of the present application, the basicity (CaO / SiO 2 ) of the mold powder is 0.6 - 0.8. The solidification temperature of the mold powder can be reduced by 70 - 120 °C, quickly forming a liquid slag layer (target melting speed 20s - 25s), and reducing the nucleation chance of slag bars. Exemplarily, the basicity of the mold powder can be 0.6, 0.65, 0.7, 0.75, 0.8, etc. The melting point of the mold powder can be 1050 °C, 1055 °C, 1060 °C, 1065 °C, 1070 °C, 1075 °C, 1080 °C, etc.

[0034] Fluorides significantly reduce the melting point and viscosity of the mold powder. The synergistic effect of NaF and CaF 2 keeps the viscosity at 0.25 Pa·s - 0.35 Pa·s at 1300 °C, ensuring that the liquid slag layer uniformly covers the surface of the molten steel, isolating air and lubricating the billet shell. Exemplarily, the sum of the contents of NaF and CaF 2 can be 7%, 8%, 9%, 10%, 11%, 12%, 14%, 15%, etc.

[0035] Carbon, as the framework material of the mold powder, controls the melting speed and the structure of the slag layer. If the carbon content < 2.5 wt%, the mold powder melts too fast, the liquid slag layer is too thick, and it is easily involved in the steel flow to form slag inclusions; if the carbon content > 5 wt%, the slag layer melts insufficiently, the proportion of solid slag increases, and the growth of slag bars is aggravated. Exemplarily, the content of C can be 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0036] S3. Through the servo stopper system, control the liquid level of the molten steel in the mold to move up and down periodically along a preset liquid level line, so as to dynamically interrupt the nucleation and growth process of the mold powder on the mold wall; wherein, the liquid level movement trajectory of the up - and - down periodic movement is uniform or stepped; The high silicon electrical steel in the prior art has a low liquidus temperature of molten steel (≤1480℃) and weak shell strength in the initial 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, they are pressed into the shell to form pits (pits) with a depth of ≥2mm. After rolling, they evolve into linear defects on the surface of the finished electrical steel (incidence rate ≥20%), affecting the surface yield rate. 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 The existing technology can only partially improve the slag entrainment by optimizing the melting point of the protective slag or the amount of argon blowing, and cannot completely solve the above problems.

[0037] In the embodiment of the present application, the height of the crystallizer liquid level line is preset before casting, and then pouring is started. After the liquid level in the crystallizer reaches the preset liquid level line and stabilizes, the "liquid level movement" operation described in the present application is started. The periodic movement of the liquid level causes the nucleation position of the protective slag on the crystallizer wall to continuously shift, so that the nucleation growth dynamics conditions of the crystallizer slag strip (block) are continuously broken, and the slag strip (block) is inhibited from growing to a critical size (≥3mm). At the same time, the movement speed is slow to avoid severe disturbance of the liquid surface causing slag rolling.

[0038] It should be noted that the preset liquid level line refers to the liquid level of the molten steel in the crystallizer that is preset artificially during the continuous casting process. For example, if the height of the crystallizer is 1000mm, the liquid level height is set to 850mm during pouring, that is, when pouring begins, the liquid level of the molten steel injected into the crystallizer is stabilized at a height of 850mm and remains slightly fluctuating 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 height of the liquid level under the static liquid level.

[0039] The uniform moving trajectory means that the actual molten steel level moves up or down at a constant speed at the preset liquid level line position under the control of the servo stopper system. This movement mode is characterized by stable speed and does not change with time, so the change of the liquid level presents a linear and continuous feature.

[0040] The step-type movement trajectory means that the actual molten steel level moves up or down at a constant speed at the preset liquid level line position under the control of the servo stopper system. When it moves to a new liquid level, it can pause and hold for a certain period of time, continue to move up or down at a constant speed, and then hold and move again at the second liquid level, and repeat this process. The characteristic of this movement mode is that the liquid level remains stable for a period of time on each step, and then transitions to the next step at a constant speed, forming a similar step-like liquid level change.

[0041] The "liquid level movement" mentioned in this application refers to the slow up-and-down movement of the molten steel level in the mold controlled by the subjective will of the operator. The movement speed is slow, 5 - 25 mm / min, and the movement amplitude is large, ±5 mm - 50 mm. Different from the traditional "liquid surface fluctuation" in the mold, the traditional liquid surface fluctuation is a passive behavior caused by the movement of the molten steel pouring flow field, with a short fluctuation period and easy to cause slag entrainment. Generally, the control target is <±3 mm.

[0042] This application supports uniform or stepped movement trajectories, which are adapted to different steel grades and mold powder characteristics. At the same time, the servo stopper system realizes liquid level precision control at the ±0.3 mm level, combined with AI real-time monitoring to ensure process stability.

[0043] It should be noted that through the servo stopper system, the implementation method and process of controlling the molten steel level in the mold to move up and down periodically along the preset liquid level line can be diversified. An example of a feasible implementation method is given in the embodiments of this application: The servo stopper system consists of an electric cylinder, an encoder, a PLC, and a liquid level sensor. The electric cylinder drives the stopper to lift and lower through a high-precision servo motor, adjusts the molten steel flow rate from the tundish to the mold, and thus controls the liquid level height. The sensor technology uses a Co-60 radiation source or an eddy current sensor to monitor the liquid level in real time, with an accuracy of ±1 mm. The signal is processed by a repeater (such as FB100) and shielded to resist interference. The encoder monitors the stopper displacement (inner loop), and the liquid level sensor feeds back the liquid surface height (outer loop). The stopper opening is dynamically adjusted through the PID algorithm to form a closed-loop control. The liquid level movement trajectory is set through PLC programming, including uniform speed, sine curve, or stepped fluctuation. For example, the sine wave trajectory can optimize the uniformity of molten steel flow, and the stepped type is suitable for intermittent control of specific processes. Thus, the servo motor drives the stopper to lift and lower at a set speed, with a control accuracy of ±0.3 mm. A double closed-loop feedback is formed through the encoder and the liquid level sensor (such as an eddy current sensor) to dynamically adjust the molten steel flow rate.

[0044] In some embodiments, a laser rangefinder + AI image recognition system is used to real-time feedback the liquid level movement trajectory.

[0045] Figure 2 It is a schematic diagram of the liquid level movement trajectory of the up-and-down periodic movement provided by the embodiments of this application.

[0046] As Figure 2 shown, in some embodiments, the up-and-down periodic movement includes the following parameters: The movement amplitude m1 above the preset liquid level line is 5 mm - 50 mm; The movement amplitude m2 below the preset liquid level line is 5 mm - 50 mm; The movement period t0 is 100 s - 600 s; Moving 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 to 60s; The pause movement time t2 after the liquid level moves down to the set movement amplitude m2 is 0 to 60s.

[0047] 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.

[0048] Under the traditional static liquid level, the slag strips continue to grow at a fixed position to a critical size (≥3mm), and eventually peel off to form pits. In the embodiment of the present application, the nucleation conditions of the protective slag on the wall of the crystallizer are destroyed by large-scale and long-period liquid level movement. The movement amplitude m1 above the preset liquid level line is limited to 5mm~50mm, and the movement amplitude m2 below the preset liquid level line is limited to 5mm~50mm, which can make the slag strip nucleation position periodically shift and inhibit its growth to the critical size; the movement period t0 is limited to 100s~600s, which can 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~25mm / min, and the slow movement speed avoids severe disturbance of the liquid surface. If the speed is <5mm / min, the liquid level movement effect is not obvious, and the slag strip growth cannot be effectively interrupted; if the speed is >25mm / min, the liquid level fluctuation amplitude increases (>±3mm), which is easy to cause slag rolling. The pause movement time (pause time) is limited to 0 to 60 seconds. It can pause after moving to the set amplitude to balance the 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.

[0049] 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.

[0050] In some embodiments, the set casting speed is 0.8 m / min to 1.6 m / min.

[0051] The casting speed affects the solidification thickness of the billet shell and the surface quality. By limiting the casting speed of the continuous casting billet to 0.8 m / min to 1.6 m / min, the billet shell thickness is uniform. Combining with dynamic liquid level control, the depth of surface pitting ≤ 1.0 mm. Exemplarily, the casting speed of the continuous casting billet can be 0.8 m / min, 0.9 m / min, 1.1 m / min, 1.3 m / min, 1.5 m / min, 1.6 m / min, etc.

[0052] In some embodiments, the depth of surface pitting of the continuous casting billet ≤ 1.0 mm, and the diameter of surface pitting of the continuous casting billet ≤ 1.1 mm; The incidence rate of linear defects in the finished product of the high-silicon electrical steel ≤ 0.5%.

[0053] In the embodiments of the present application, through the collaborative optimization of the immersion nozzle depth, argon blowing flow rate and the physical properties of the mold powder, combined with the liquid level periodic movement technology, the depth of surface pitting of the continuous casting billet of high-silicon electrical steel ≤ 1.0 mm, the incidence rate of linear defects in the finished product of electrical steel is reduced from more than 20% to less than 0.5%, and the magnetic properties are improved by more than 3%. It greatly improves the surface quality and magnetic property level, and is applicable to production scenarios with different silicon contents (2.5% to 4.5%) and plate widths (800 mm to 1600 mm).

[0054] In summary, through the dynamic liquid level control, the optimization of the physical properties of the mold powder and the coordination of process parameters in the embodiments of the present application, the problems of surface defects and deterioration of magnetic properties caused by slag bars in the continuous casting process of high-silicon electrical steel are solved, a breakthrough with a defect rate ≤ 0.5% and an iron loss reduction of more than 3% is achieved. At the same time, it adapts to the production requirements of large thickness-width ratios (800 mm to 1600 mm), and provides a high-cost-effective material solution for fields such as new energy vehicles and high-frequency devices.

[0055] Specifically, a continuous casting method of high-silicon electrical steel based on liquid level periodic cyclic movement control provided by the embodiments of the present application has the following advantages: (1) Optimize the molten steel flow and solidification: By precisely controlling the insertion depth of the immersion 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 mold is ensured, thereby reducing the probability of surface massive slag inclusions.

[0056] (2) Reduce the melting point and viscosity of the mold powder: By using a mold powder with a specific alkalinity and melting point, and optimized chemical composition, the melting point and viscosity of the mold powder are significantly reduced, which matches the low liquidus temperature of high-silicon steel, ensures that the liquid slag layer can uniformly cover the surface of the molten steel, effectively isolates the air and lubricates the billet shell, and controls the slag bars from growing and being pressed in.

[0057] (3) Dynamically interrupt the growth of slag bars: By controlling the molten steel level in the mold to move up and down periodically along the liquid level line through the servo stopper system, the nucleation and growth processes of the mold powder at fixed positions on the mold wall are dynamically interrupted, effectively inhibiting the growth of slag bars and avoiding the pit problems caused by the peeling of slag bars.

[0058] (4) Improve the surface quality of the billet: Combining the above optimization measures, the depth and diameter of the surface pits of the billet are effectively controlled, significantly improving the surface quality of the billet.

[0059] (5) Reduce the incidence of linear defects: Due to the optimization of molten steel flow, solidification, and mold powder behavior, as well as the application of the liquid level periodic movement technology, the incidence of linear defects in the finished high-silicon electrical steel is significantly reduced, from more than 20% to less than 0.5%.

[0060] (6) Improve magnetic properties: The optimized continuous casting process not only improves the surface quality of the billet but also significantly enhances the magnetic properties of the electrical steel, which is of great significance for the application of electrical steel.

[0061] (7) Wide applicability: This method is applicable to production scenarios with different silicon contents (2.5% - 4.5%) and slab widths (800 mm - 1600 mm), and has strong versatility and practicality.

[0062] The following further elaborates on this application in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate this application and not to limit the scope of this application. The experimental methods without specific conditions noted in the following embodiments are usually determined according to industry standards. If there is no corresponding industry standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0063] This application provides a continuous casting method for high-silicon electrical steel based on liquid level periodic cyclic movement control, and the method includes: S1. Inject the molten steel of high-silicon electrical steel from the tundish into the mold through an immersion nozzle, and control the depth of the immersion nozzle inserted into the molten steel and the flow rate of argon blown through the stopper; S2. Add the mold powder to the surface of the molten steel in the mold; S3. Through the servo stopper system, control the liquid level of the molten steel in the mold to move up and down periodically along the preset liquid level line to dynamically interrupt the nucleation and growth processes of the mold powder on the mold wall; S4. Solidify the molten steel into a billet through the mold, and pull out the billet from the outlet of the mold at a set casting speed.

[0064] The specific process parameters of the continuous casting method for high-silicon electrical steel in the examples are shown in Tables 1 to 3, and the specific process parameters of the continuous casting method for high-silicon electrical steel in the comparative examples are shown in Tables 4 and 5.

[0065] Among them, Examples 1 to 8, Comparative Example 1, and Comparative Example 2 are for producing non-oriented electrical steel with a thickness of 0.30 mm, Si = 3.3% (plate width 1100 mm); Examples 9 and Comparative Example 3 are for producing ultra-thin non-oriented electrical steel with a thickness of 0.20 mm, Si = 3.4% (plate width 1250 mm); Examples 10 and Comparative Example 4 are for producing non-oriented electrical steel with a thickness specification of 0.35 mm, Si = 3.4% (plate width 1000 mm). Comparative Examples 1 to 4 adopt fixed liquid level operation without performing periodic up and down movement of the liquid surface.

[0066] Table 1 Chemical composition (wt.%) and performance parameters of the mold powder for the continuous casting method of high-silicon electrical steel in the examples Table 2 Periodic up and down movement parameters of the continuous casting method of high-silicon electrical steel in the examples Table 3 Process parameters of the continuous casting method of high-silicon electrical steel in the examples Table 4 Chemical composition (wt.%) and performance parameters of the mold powder for the continuous casting method of high-silicon electrical steel in the comparative examples Table 5 Process parameters of the continuous casting method of high-silicon electrical steel in the comparative examples The billets of high-silicon electrical steel obtained from Examples 1 to 10 and Comparative Examples 1 to 4 were subjected to performance measurement. At the same time, according to the existing preparation method of high-silicon electrical steel, the billets of high-silicon electrical steel were prepared into high-silicon electrical steel, and at the same time, the finished product performance of the high-silicon electrical steel was measured. The results are shown in Table 6.

[0067] Table 6 Performance of the billets and finished products of high-silicon electrical steel As can be seen from Table 6, the surface quality and magnetic property P1.0 / 400 of the non-oriented electrical steel with a thickness of 0.30 mm 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 property P1.0 / 400 of the non-oriented electrical steel with a thickness of 0.20 mm produced in Example 9 of the present invention are significantly better than those of the corresponding Comparative Example 3; the surface quality and magnetic property P1.0 / 400 of the non-oriented electrical steel with a thickness of 0.35 mm produced in Example 10 of the present invention are significantly better than those of the corresponding Comparative Example 4.

[0068] Figure 3 Schematic diagram of the slag strip nucleation moving up and down periodically provided in Embodiment 1 of the present application; Figure 4 Schematic diagram of the slag strip nucleation of the traditional static liquid level provided in Comparative Example 1 of the present application.

[0069] From Figure 3 and Figure 4 By comparison, it can be seen that by adopting the up-and-down liquid level moving operation of the embodiment of the present application, the dynamic up-and-down movement of the liquid level can effectively destroy and inhibit the formation of large slag strips (blocks).

[0070] Figure 5 Surface morphology diagram of the continuous casting billet of high-silicon electrical steel provided in Embodiment 1 of the present application; Figure 6 Surface morphology diagram of the continuous casting billet of high-silicon electrical steel provided in Comparative Example 1 of the present application.

[0071] From Figure 5 and Figure 6 By comparison, it can be seen that the surface slag inclusion of the continuous casting billet in Example 1 is significantly controlled, the size and depth of the slag pit are greatly reduced, and the depth of the slag pit is reduced from a maximum of more than 3 mm in Comparative Example 1 to <1.0 mm in Example 1.

[0072] In addition, one or more technical solutions in the embodiments of the present application at least further have the following technical effects or advantages: In the embodiments of the present application, through the liquid level movement with a long period (100 s to 600 s) and a wide amplitude (±5 to 50 mm), the nucleation and growth process of the mold powder on the mold wall is dynamically interrupted, breaking through the limitation of the traditional static liquid level operation.

[0073] In the embodiments of the present application, uniform speed, stepped, and sinusoidal curve moving trajectories are supported, adapting to different steel grades and mold powder characteristics.

[0074] In the embodiments of the present application, the servo stopper system realizes the liquid level accuracy control of ±0.3 mm level, combined with AI real-time monitoring, ensuring the process stability.

[0075] In the embodiment of the present application, the depth of surface pits of the high-silicon electrical steel continuous casting billet is ≤ 1.0 mm. The incidence rate of linear defects in the finished electrical steel is reduced from more than 20% to less than 0.5%, and the magnetic properties are improved by more than 3%. The surface quality and magnetic property level are greatly improved, and it is applicable to production scenarios with different silicon contents (2.5 - 4.5%) and plate widths (800 - 1600 mm).

[0076] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

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 the tundish into the crystallizer through the submerged nozzle, and controlling the depth of the submerged nozzle inserted into the liquid steel and the argon blowing flow rate of the stopper rod; adding protective slag to the surface of the molten steel in the crystallizer; The liquid level of the molten steel in the crystallizer is controlled to move up and down periodically along a preset liquid level line through a servo stopper system, so as to dynamically interrupt the nucleation and growth process of the protective slag on the wall of the crystallizer; wherein the liquid level movement trajectory of the up and down periodic movement is uniform or step-type, 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 movement time t1 after the liquid level moves up to the set movement amplitude m1 is 0-60s, and the pause movement time t2 after the liquid level moves down to the set movement amplitude m2 is 0-60s; and 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.

2. The method according to claim 1, characterized in that The immersion nozzle is inserted into the molten steel to a depth of 120 mm to 180 mm.

3. The method according to claim 1, characterized in that The stopper rod argon blowing flow rate is 3L / min to 8L / min.

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

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

6. The method according to claim 1, characterized in that The basicity of the protective slag is 0.6-0.

8.

7. The method according to claim 1, characterized in that The melting point of the protective slag is 1050°C to 1080°C.

8. 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.

9. The method according to claim 8, 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%~44%, the SiO2 content is 40%~45%, the Al2O3 content is 2.5%~5%, the Na2O content is 5%~10%, the sum of the NaF and CaF2 contents is 7%~15%, and the C content is 2.5%~5%.

10. The method according to claim 1, characterized in that 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 incidence of linear defects in the finished product of the high-silicon electrical steel is ≤0.5%.

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