Method for eliminating liquid level disorder of molten steel in large-section slab crystallizer

Abstract

The invention relates to a method for eliminating liquid level disorder of molten steel in a large-section slab crystallizer, and belongs to the technical field of continuous casting methods in the metallurgical industry. According to the technical scheme, the structure of the submersed nozzle of the continuous casting crystallizer is optimized, and dynamic instability of a molten steel flow field is restrained; the water gap immersion depth is increased; pID parameters of the liquid level control system are adjusted, and the stability and applicability of the liquid level control system are improved; the stopper shaking function is started, the flowing state of molten steel in the nozzle is changed, and the liquid level disorder of the crystallizer is restrained. The method has the beneficial effects that the periodic disorder of the liquid level of the crystallizer can be effectively eliminated, the fluctuation of the liquid level of the crystallizer is controlled, the slag entrapment defect caused by the fluctuation of the liquid level is reduced, and the product quality of a casting blank is improved; and meanwhile, production accidents such as pouring stopping and steel breakout caused by liquid level disorder can be effectively reduced.

Description

Technical Field

[0001] The invention relates to a method for eliminating the disorder of liquid steel level in a large-section slab crystallizer, belonging to the technical field of continuous casting methods in the metallurgical industry. Background Art

[0002] The production of automotive sheet steel has very high requirements for the control of non-metallic inclusions in steel. This is because improper flow patterns of molten steel in the crystallizer can lead to instability of the crystallizer liquid level and slag rolls, which in severe cases affect the quality of the ingot and cause ingot defects.

[0003] With the efficient production of steel enterprises, the continuous casting speed has gradually increased, and some steel mills have exceeded 2.0 m / min. However, the increase in the casting speed has a significant impact on the flow of molten steel in the crystallizer, especially increasing the surface flow velocity of the molten steel in the crystallizer. When the surface flow velocity exceeds 0.5 m / s, it will easily cause liquid level fluctuations and cause quality defects of the ingot.

[0004] The traditional metallurgical process of automobile plate steel emphasizes the formation of balanced upper and lower reflux, in which the upper reflux mainly serves the following functions: (1) to supply heat to the molten steel above the crystallizer to facilitate the melting of the protective slag and reduce the unevenness of the primary shell; (2) to promote the upward movement of non-metallic inclusions with the upper reflux, so that they collide with each other and aggregate into larger inclusions, float out of the molten steel and are removed. For this reason, most automobile plate steel production steel companies use a smaller submerged nozzle outlet angle of 15° and a shallow nozzle immersion depth of 110-150 mm.

[0005] However, through the study of the flow characteristics of molten steel in the continuous casting crystallizer, it was found that the submerged nozzle with a smaller outlet angle, in addition to being easy to cause liquid level fluctuations and a large surface flow rate, also has the problem that due to the low turbulent kinetic energy of the molten steel in the area below the submerged nozzle, the lower reflux on both sides periodically gathers toward the center, making the turbulent kinetic energy of the area below the submerged nozzle stronger, and then dissipates to the outer area, resulting in periodic turbulence of the molten steel flow field in the crystallizer, horizontal swing of the liquid level, and increased fluctuations, increasing the possibility of the protective slag being involved in the molten steel and being captured by the solidified billet shell to become large and medium-sized inclusions in the steel. In particular, when the cross-section of the billet is greater than 1800 mm, the above problems are more serious. Therefore, how to effectively control the liquid level fluctuation in the slab continuous casting crystallizer by comprehensively optimizing the existing continuous casting technology and control method is a technical problem that technicians in this field need to solve urgently.

[0006] At present, domestic and foreign scholars and technicians lack systematic research on the periodic disturbance of liquid level caused by the unreasonable structure of the side holes of the water inlet in the conventional slab lower crystallizer. At the same time, no scholar or technician has studied the method of controlling different types of liquid level fluctuations in the crystallizer by comprehensively adjusting the PID control system and the rotation and shaking mode of the stopper rod. Summary of the invention

[0007] The object of the present invention is to provide a method for eliminating the turbulence of the liquid steel surface in a large-section slab crystallizer. By changing the nozzle structure, the nozzle insertion depth, adjusting the PID parameters of the liquid level control system and controlling the stopper rod shaking function, the periodic turbulence of the liquid level in the crystallizer can be effectively eliminated, the fluctuation of the liquid level in the crystallizer can be controlled, the slag rolling defects caused by the fluctuation of the liquid level can be reduced, and the product quality of the cast slab can be improved; at the same time, production accidents such as casting suspension and steel leakage caused by the turbulence of the liquid level can be effectively reduced, and the above-mentioned problems existing in the background technology can be effectively solved.

[0008] The technical solution of the present invention is: a method for eliminating the turbulence of the liquid steel level in the large-section slab crystallizer, comprising the following steps: (1) Optimize the structure of the submerged nozzle of the continuous casting mold to suppress the dynamic instability of the molten steel flow field; (2) Increase the immersion depth of the nozzle; (3) Adjust the PID parameters of the liquid level control system to improve the stability and applicability of the liquid level control system; (4) Turn on the stopper rod shaking function to change the flow state of the molten steel in the water inlet and suppress the turbulence of the crystallizer liquid level.

[0009] In the step (1), the inclination angle of the water inlet is increased from 15 degrees to 25 degrees, and the side hole shape of the immersion water inlet is made into an elliptical shape.

[0010] In the step (2), the insertion depth of the submerged nozzle, that is, the distance from the upper edge of the side hole to the liquid surface of the crystallizer, reaches 150 mm.

[0011] In step (3), when the crystallizer liquid level fluctuates periodically, the proportional gain part K of the control system is increased within the allowable range. P ; ② When the center value of the crystallizer liquid level fluctuation deviates from the standard value, reduce the integral gain part K within the allowable range I ; ③ When the vibration noise of the liquid level fluctuation of the crystallizer is high, reduce the differential gain part K within the allowable range D .

[0012] The proportional gain part K P The allowable range of adjustment is 0.6-2.0, the integral gain part K I The allowable range of adjustment is 0.08-0.3, the differential gain part K D The allowable range of adjustment is 0.05-0.2; Adjust the PID value of the liquid level control system. If the crystallizer liquid level is good and the fluctuation value is less than 5 mm, then K P =0.8, K D =0.5, K I=0.05; if the crystallizer liquid level is slightly worse, when the 20% liquid level fluctuation value is 5-8 mm, the PID parameter needs to be adjusted to K P =1.2, K D =0.15, K I =0.1; if the crystallizer liquid level fluctuation value is large, and 10% of the liquid level fluctuation value exceeds 10 mm, the PID parameter is adjusted to K P =1.5, K D = 0.1, K I =0.06; in the above case, when the liquid level fluctuation tends to be stable, adjust the PID parameters to the original values.

[0013] In the step (4), ① after the first furnace of the casting is completed, the timing starts from the time when the molten steel liquid level in the crystallizer is stable, and the stopper rod rotation and shaking function is turned on after 10 minutes; ② the stopper rod shaking of the first four furnaces of casting adopts mode 1, with a rotation frequency of 2 Hz, an up and down shaking frequency of 5 Hz, and a shaking amplitude of 1 mm; ③ after casting four furnaces, different stopper rod shaking modes are adopted according to the liquid level fluctuation of the crystallizer: a. if the liquid level fluctuation is in good condition, the stopper rod shaking mode 1 is maintained; b. if there are many jump points in the liquid level fluctuation curve, the stopper rod shaking is switched to mode 2, with a rotation frequency of 1 Hz, an up and down shaking frequency of 2 Hz, and a shaking amplitude of 1.5 mm; if the appearance of jump points cannot be improved, the stopper rod shaking is turned off; c. if the liquid level fluctuation curve shows irregular large fluctuations, the stopper rod shaking is switched to mode 3, with a rotation frequency of 5 Hz, an up and down shaking frequency of 10 Hz, and a shaking amplitude of 1.0 mm.

[0014] The beneficial effects of the present invention are as follows: by changing the nozzle structure, the nozzle insertion depth, adjusting the PID parameters of the liquid level control system and controlling the stopper rod shaking function, the periodic disturbance of the liquid level in the crystallizer can be effectively eliminated, the fluctuation of the liquid level in the crystallizer can be controlled, the slag roll defect caused by the liquid level fluctuation can be reduced, and the product quality of the ingot can be improved; at the same time, production accidents such as casting stoppage and steel leakage caused by liquid level disturbance can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of a 15-degree downward rectangular nozzle according to the background technology of the present invention; Figure 2 This is a schematic diagram of an elliptical nozzle pointing downward at 25 degrees according to the present invention; Figure 3 1. It is a graph showing the qualified rate of the crystallizer liquid level fluctuation under different water inlet inclination angles of the present invention; Figure 4 This is a crystallizer liquid level fluctuation diagram of the present invention when the water inlet is immersed at a depth of 110 mm; Figure 5This is a crystallizer liquid level fluctuation diagram of the present invention when the water inlet is immersed at a depth of 160 mm; Figure 6 It is a comparison diagram of the crystallizer liquid level fluctuation before and after the PID system parameter adjustment of the present invention; Figure 7 This is a diagram of the crystallizer liquid level fluctuation before the stopper rod is opened and shaken in the present invention; Figure 8 It is a diagram of the liquid level fluctuation of the crystallizer after the stopper rod is opened and shaken according to the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the invention implementation cases clearer, the technical solutions in the implementation cases of the present invention will be clearly and completely described below in conjunction with the drawings in the implementation cases. Obviously, the implementation cases described are only a small part of the implementation cases of the present invention, rather than all the implementation cases. Based on the implementation cases in the present invention, all other implementation cases obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0017] A method for eliminating the turbulence of the liquid steel level in a large-section slab crystallizer comprises the following steps: (1) Optimize the structure of the submerged nozzle of the continuous casting mold to suppress the dynamic instability of the molten steel flow field; (2) Increase the immersion depth of the nozzle; (3) Adjust the PID parameters of the liquid level control system to improve the stability and applicability of the liquid level control system; (4) Turn on the stopper rod shaking function to change the flow state of the molten steel in the water inlet and suppress the turbulence of the crystallizer liquid level.

[0018] In the step (1), the inclination angle of the water inlet is increased from 15 degrees to 25 degrees, and the side hole shape of the immersion water inlet is made into an elliptical shape.

[0019] In the step (2), the insertion depth of the submerged nozzle, that is, the distance from the upper edge of the side hole to the liquid surface of the crystallizer, reaches 150 mm.

[0020] In step (3), when the crystallizer liquid level fluctuates periodically, the proportional gain part K of the control system is increased within the allowable range. P ; ② When the center value of the crystallizer liquid level fluctuation deviates from the standard value, reduce the integral gain part K within the allowable range I ; ③ When the vibration noise of the liquid level fluctuation of the crystallizer is high, reduce the differential gain part K within the allowable range D .

[0021] The proportional gain part K P The allowable range of adjustment is 0.6-2.0, the integral gain part K IThe allowable range of adjustment is 0.08-0.3, the differential gain part K D The allowable range of adjustment is 0.05-0.2; Adjust the PID value of the liquid level control system. If the crystallizer liquid level is good and the fluctuation value is less than 5 mm, then K P =0.8, K D =0.5, K I =0.05; if the crystallizer liquid level is slightly worse, when the 20% liquid level fluctuation value is 5-8 mm, the PID parameter needs to be adjusted to K P =1.2, K D =0.15, K I =0.1; if the crystallizer liquid level fluctuation value is large, and 10% of the liquid level fluctuation value exceeds 10 mm, the PID parameter is adjusted to K P =1.5, K D = 0.1, K I =0.06; in the above case, when the liquid level fluctuation tends to be stable, adjust the PID parameters to the original values.

[0022] In the step (4), ① after the first furnace of the casting is completed, the timing starts from the time when the molten steel liquid level in the crystallizer is stable, and the stopper rod rotation and shaking function is turned on after 10 minutes; ② the stopper rod shaking of the first four furnaces of casting adopts mode 1, with a rotation frequency of 2 Hz, an up and down shaking frequency of 5 Hz, and a shaking amplitude of 1 mm; ③ after casting four furnaces, different stopper rod shaking modes are adopted according to the liquid level fluctuation of the crystallizer: a. if the liquid level fluctuation is in good condition, the stopper rod shaking mode 1 is maintained; b. if there are many jump points in the liquid level fluctuation curve, the stopper rod shaking is switched to mode 2, with a rotation frequency of 1 Hz, an up and down shaking frequency of 2 Hz, and a shaking amplitude of 1.5 mm; if the appearance of jump points cannot be improved, the stopper rod shaking is turned off; c. if the liquid level fluctuation curve shows irregular large fluctuations, the stopper rod shaking is switched to mode 3, with a rotation frequency of 5 Hz, an up and down shaking frequency of 10 Hz, and a shaking amplitude of 1.0 mm.

[0023] In practical applications, the present invention can effectively obtain stable liquid surface fluctuations and internal flow fields. The technical solution mainly includes the following detailed control processes: 1. Optimize the structure of the submerged nozzle of the continuous casting crystallizer to suppress the dynamic instability of the steel liquid flow field. ① The nozzle inclination angle is increased from 15 degrees to 25 degrees. Increasing the submerged nozzle inclination angle can effectively weaken the kinetic energy of the upper reflow zone and strengthen the inward gathering of the lower reflow zone. In addition to the significant reduction of liquid surface fluctuations and surface flow velocity, the low and uneven turbulent kinetic energy of the steel liquid in the area below the submerged nozzle has been significantly improved, thereby eliminating the phenomenon that the lower reflow on both sides periodically gathers to the center when the nozzle angle is too small, making the turbulent kinetic energy in the area below the nozzle stronger, and then dissipates to the outer area, resulting in periodic disorder of the flow field and intensified liquid surface fluctuations. ② The side hole shape of the submerged nozzle is optimized to an elliptical shape, which can effectively reduce the negative pressure area of ​​the nozzle side hole by 5%-10%, inhibit the accumulation of inclusions in the nozzle side hole, so as to ensure the symmetry of the flow field in the crystallizer as much as possible during the casting process, inhibit the formation of bias flow, and ensure a reasonable flow field morphology in the crystallizer.

[0024] 2. Increase the immersion depth of the nozzle. The insertion depth of the submerged nozzle (the distance from the upper edge of the side hole to the liquid surface of the crystallizer) reaches 150 mm. Increasing the insertion depth of the submerged nozzle can reduce the activity of the recirculation zone on the crystallizer, so that the surface flow rate of the molten steel in the crystallizer is controlled at about 0.2 m / s, which can ensure a reasonable consumption of protective slag and ensure that the crystallizer has a good flow field morphology and free liquid surface characteristics.

[0025] 3. Improve the stability and applicability of the liquid level control system. The basic principle of the liquid level control system of the slab continuous casting machine is to control the flow of molten steel by controlling the stopper position to keep the liquid level stable. Therefore, the corresponding parameters of the control system can be adjusted according to the fluctuation situation: ① When the liquid level of the crystallizer fluctuates periodically, increase the proportional gain part (K P value), which can improve the response speed of the control system and suppress periodic liquid level fluctuations; ② When the center value of the crystallizer liquid level fluctuation deviates from the standard value, the integral gain part (K I value), thereby eliminating the deviation between the center value and the standard value; ③ When the vibration noise of the liquid level fluctuation of the crystallizer is high, the differential gain part (K D value), can improve the dynamic characteristics of the control system and increase the control system's ability to resist interference.

[0026] According to the actual on-site production and different degrees of liquid level fluctuations, the following three control modes are provided for reference. You can also adjust the parameter values ​​​​by yourself according to the operating rules of the PID control parameters described above and the actual on-site conditions.

[0027]

[0028] 4. Turn on the stopper rod shaking function to change the flow state of the molten steel in the water nozzle and suppress the turbulence of the crystallizer liquid level. The steps to turn on the stopper rod shaking function mainly include: ① After the first furnace of the casting is completed, start the timing after the molten steel liquid level in the crystallizer is stable, and turn on the stopper rod rotation shaking function after 10 minutes. ② The stopper rod shaking of the first four furnaces of casting adopts mode 1 (rotation frequency is 2 Hz, up and down shaking frequency is 5 Hz, and shaking amplitude is 1 mm). ③ After casting four furnaces, different stopper rod shaking modes are adopted according to the liquid level fluctuation of the crystallizer: a. If the liquid level fluctuation is good, keep the stopper rod shaking mode 1. b. If there are many jump points in the liquid level fluctuation curve, switch the stopper rod shaking to mode 2 (rotation frequency is 1 Hz, up and down shaking frequency is 2Hz, and shaking amplitude is 1.5 mm). If the appearance of jump points cannot be improved, turn off the stopper rod shaking. c. If the liquid level fluctuation curve shows irregular large fluctuations, switch the stopper rod shaking to mode 3 (rotation frequency is 5 Hz, up and down shaking frequency is 10 Hz, and shaking amplitude is 1.0 mm).

[0029]

[0030] Among the four steps, step 1 and step 2 are permanent fixed measures, and step 3 and step 4 need to be adjusted in a targeted manner according to the situation of the crystallizer liquid level at the production site. Combining the above measures, the present invention forms a set of process methods that can effectively eliminate the disorder of the liquid level of molten steel in the slab crystallizer, greatly reducing the slab steel defects caused by liquid level fluctuations, and avoiding the excessive liquid level fluctuations caused by the instability of the crystallizer flow field. The excessive liquid level fluctuations and other malignant production accidents such as continuous casting leakage are avoided, solving the technical problems that have long plagued continuous casting production and ingot quality. Embodiment 1:

[0031] In this embodiment, the width of the crystallizer is 1900 mm, the thickness is 237 mm, the pulling speed is 1.2 m / min, and the on-site liquid level fluctuation detection system is used to find that the qualified rate of liquid level fluctuation ≤±3 mm is 93.5%.

[0032] In order to increase the proportion of liquid level fluctuation value ≤ ± 3 mm, such as Figure 1 and Figure 2 , the inclination angle of the submerged nozzle was increased from 15 degrees downward to 25 degrees downward, and the shape of the side hole of the submerged nozzle was optimized from rectangular to elliptical. The optimized nozzle was applied to the slab production line of a steel company. Under the process conditions of a crystallizer width of 1900 mm, a thickness of 237 mm, and a casting speed of 1.2 m / min, the on-site liquid level fluctuations of three months of production casting were statistically analyzed and found that, Figure 3 The qualified rate of liquid level fluctuation value ≤±3mm is 98.8%. Embodiment 2:

[0033] In this embodiment, the process conditions are as follows: the width of the crystallizer is 1800 mm, the thickness is 237 mm, the pulling speed is 1.3 m / min, and the shape of the crystallizer submerged water inlet is an elliptical side hole with a downward inclination of 25 degrees.

[0034] After the pulling speed was increased due to increased production, it was found from the on-site statistics of the liquid level fluctuation that compared with the crystallizer liquid level fluctuation when the pulling speed was 1.0 m / min, when the pulling speed was increased to 1.3 m / min, the surface flow rate of the crystallizer molten steel increased and the liquid level fluctuation intensified.

[0035] In order to control the surface velocity of the molten steel in the crystallizer and suppress the fluctuation of the liquid level in the crystallizer, the immersion depth of the nozzle was increased from 110 mm to 160 mm. The fluctuation of the liquid level was significantly suppressed. The liquid level fluctuation of the crystallizer was compared when the casting speed was 1.3 m / min and the immersion depth of the nozzle was 110 mm and 160 mm. Figure 4 and Figure 5 After increasing the immersion depth of the water inlet, the liquid level fluctuation value of the crystallizer was significantly reduced, and basically met the liquid level fluctuation value ≤±3mm. Embodiment three:

[0036] In this embodiment, the width of the crystallizer is 2000 mm, the thickness is 237 mm, the pulling speed is 1.2 m / min, the submerged water nozzle adopts a downward inclination of 25 degrees and an elliptical side hole, and the water nozzle immersion depth is 160 mm. Under this process condition, normal liquid level fluctuations are basically controlled within ±3 mm. However, when the nozzle in the secondary cooling section is blocked and the billet is cooled unevenly, it is easy to cause violent periodic fluctuations in the crystallizer liquid level caused by the bulging of the billet. When this kind of crystallizer liquid level fluctuation occurs, it is necessary to make targeted adjustments to the liquid level control parameter PID. In order to improve the response speed of the system, the proportional coefficient K P Adjusted from 0.8 to 1.0, it was found that the liquid level fluctuation was significantly suppressed. Subsequently, in order to continue to suppress the liquid level fluctuation, K I Reduce from 0.5 to 0.2, such as Figure 6 , the liquid level fluctuation basically returns to normal state, and can basically meet the liquid level fluctuation value ≤±3 mm. Embodiment 4:

[0037] In this embodiment, the width of the crystallizer is 1800 mm, the thickness is 237 mm, the pulling speed is 1.4 m / min, the submerged nozzle has a downward inclination of 25 degrees and an elliptical side hole, and the nozzle immersion is 160 mm.

[0038] When producing ultra-low carbon steel under this process condition, Figure 7As can be seen from the figure, there are many jump points with fluctuation values ​​exceeding ±3mm. Generally, this is because there are nodules on the plug rod head. During the steel casting process, the nodules will fall off with the flushing of the molten steel, which will cause the "jump point type" liquid level fluctuation in the crystallizer.

[0039] In order to suppress the occurrence of such liquid level fluctuations, the stopper rod shaking mode needs to be adjusted to mode 2, mainly to reduce the rotation and shaking frequencies of the stopper rod. The rotation frequency is adjusted to 1 Hz, the shaking frequency is adjusted to 2 Hz, and the vibration amplitude of the stopper rod is adjusted to 1.5 mm.

[0040] After the stopper rod shaking mode is adjusted, after about 10 minutes of casting, if Figure 8 , the crystallizer liquid level fluctuation returned to normal, there was no jump point in the liquid level fluctuation, and the fluctuation value was basically less than ±3 mm.

Claims

1. A method for eliminating the turbulence of the liquid steel level in a large-section slab crystallizer, characterized in that The following steps are involved: (1) Optimize the structure of the submerged nozzle of the continuous casting mold to suppress the dynamic instability of the molten steel flow field; (2) Increase the immersion depth of the nozzle; (3) Adjust the PID parameters of the liquid level control system to improve the stability and applicability of the liquid level control system; (4) Turn on the stopper rod shaking function to change the flow state of the molten steel in the water inlet and suppress the turbulence of the crystallizer liquid level.

2. The method for eliminating the turbulence of the molten steel level in a large-section slab crystallizer according to claim 1, characterized in that: In the step (1), the inclination angle of the water inlet is increased from 15 degrees to 25 degrees, and the side hole shape of the immersion water inlet is made into an elliptical shape.

3. The method for eliminating the turbulence of the liquid steel level in the large-section slab crystallizer according to claim 1, characterized in that: In the step (2), the insertion depth of the submerged nozzle, i.e. the distance from the upper edge of the side hole to the liquid surface of the crystallizer, reaches 150 mm.

4. The method for eliminating the turbulence of the molten steel level in a large-section slab crystallizer according to claim 1, characterized in that: In step (3), when the crystallizer liquid level fluctuates periodically, the proportional gain part K of the control system is increased within the allowable range. P ; ② When the center value of the crystallizer liquid level fluctuation deviates from the standard value, reduce the integral gain part K within the allowable range I ; ③ When the vibration noise of the liquid level fluctuation of the crystallizer is high, reduce the differential gain part K within the allowable range D .

5. The method for eliminating the turbulence of the liquid steel level in the large-section slab crystallizer according to claim 4, characterized in that: The proportional gain part K P The allowable range of adjustment is 0.6-2.0, the integral gain part K I The allowable range of adjustment is 0.08-0.3, the differential gain part K D The allowable range of adjustment is 0.05-0.2; Adjust the PID value of the liquid level control system. If the crystallizer liquid level is good and the fluctuation value is less than 5 mm, then K P =0.8, K D =0.5, K I =0.05; if the crystallizer liquid level is slightly worse, when the 20% liquid level fluctuation value is 5-8 mm, the PID parameter needs to be adjusted to K P =1.2, K D =0.15, K I =0.1; if the crystallizer liquid level fluctuation value is large, and 10% of the liquid level fluctuation value exceeds 10 mm, the PID parameter is adjusted to K P =1.5, K D = 0.1, K I =0.06; in the above case, when the liquid level fluctuation tends to be stable, adjust the PID parameters to the original values.

6. The method for eliminating the turbulence of the molten steel level in a large-section slab crystallizer according to claim 1, characterized in that: In the step (4), ① after the first furnace of the casting is completed, the timing starts from the time when the molten steel liquid level in the crystallizer is stable, and the stopper rod rotation and shaking function is turned on after 10 minutes; ② the stopper rod shaking of the first four furnaces of casting adopts mode 1, with a rotation frequency of 2 Hz, an up and down shaking frequency of 5 Hz, and a shaking amplitude of 1 mm; ③ after casting four furnaces, different stopper rod shaking modes are adopted according to the liquid level fluctuation of the crystallizer: a. if the liquid level fluctuation is in good condition, the stopper rod shaking mode 1 is maintained; b. if there are many jump points in the liquid level fluctuation curve, the stopper rod shaking is switched to mode 2, with a rotation frequency of 1 Hz, an up and down shaking frequency of 2 Hz, and a shaking amplitude of 1.5 mm; if the appearance of jump points cannot be improved, the stopper rod shaking is turned off; c. if the liquid level fluctuation curve shows irregular large fluctuations, the stopper rod shaking is switched to mode 3, with a rotation frequency of 5 Hz, an up and down shaking frequency of 10 Hz, and a shaking amplitude of 1.0 mm.

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