Control method for inhibiting periodic fluctuation of crystallizer liquid level in SPHC steel grade production

Abstract

The invention provides a control method for inhibiting the periodic fluctuation of the liquid level of a crystallizer in SPHC steel grade production, which is characterized in that when the SPHC steel grade is cast, low-carbon steel casting powder is used, and the depth of a submersed nozzle inserted into the liquid level of the crystallizer is 130-170mm; the pulling speed of the crystallizer is 1.0-2.0 m / min, the amplitude is 3-6 mm, and the vibration frequency is 170-150 times; wherein the treatment comprises crystallizer cooling treatment and secondary cooling treatment; when the periodic fluctuation value of the liquid level of the crystallizer is smaller than or equal to 10 mm, the cooling strength of the secondary cooling treatment is 0.8-0.9 L / kg; when the periodic fluctuation value of the liquid level of the crystallizer is greater than 10mm, the cooling strength of the secondary cooling treatment is 1.0-1.1 L / kg; by limiting the use of special casting powder for low-carbon steel during casting, the depth of the submersed nozzle inserted into the liquid level of the crystallizer, a crystallizer vibration model and a specific secondary cooling grading treatment method, the fluctuation value of the liquid level of the crystallizer can be reduced from original 10-20 mm to 3 mm or even has no fluctuation, and the technological requirements of slabs are met; and the periodic fluctuation of the liquid level of the crystallizer is effectively inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field of continuous casting of low-carbon steel, and in particular relates to a control method for suppressing periodic fluctuation of a crystallizer liquid level in the production of SPHC steel grades. Background Art

[0002] As the drawing speed of low-carbon steel continues to increase and the limit is constantly broken, continuous casting is also facing greater quality challenges, such as billet bulging and mold level fluctuation. Especially for SPHC series steels, the carbon content requirement is ≤0.06%. As the drawing speed continues to increase, billet bulging is more likely to occur, causing periodic fluctuations in the mold level, which has a greater impact on production, quality and cost.

[0003] The periodic fluctuation of the liquid level in the crystallizer causes slag to roll on the ingot and peeling or black lines to appear on the surface of the hot-rolled strip, which seriously affects the quality of the strip and poses a great quality risk. Summary of the invention

[0004] The invention provides a control method for suppressing periodic fluctuation of the liquid level of a crystallizer in the production of SPHC steel grades, which is used to solve the problem of periodic fluctuation of the liquid level of a crystallizer in the production of SPHC steel grades in the prior art.

[0005] The invention provides a control method for suppressing periodic fluctuation of a crystallizer liquid level in the production of SPHC steel grades, characterized in that, when casting the SPHC steel grades, low-carbon steel protective slag is used, the depth of the submerged nozzle inserted into the crystallizer liquid level is 130-170 mm; the casting speed of the crystallizer is 1.0-2.0 m / min, the amplitude is 3-6 mm, and the vibration frequency is 170-150 times; Among them, it includes crystallizer cooling treatment and secondary cooling treatment; when the periodic fluctuation value of the crystallizer liquid level is ≤10mm, the cooling intensity of the secondary cooling treatment is 0.8~0.9L / kg; when the periodic fluctuation value of the crystallizer liquid level is >10mm, the cooling intensity of the secondary cooling treatment is 1.0~1.1L / kg.

[0006] Compared with the prior art, the present invention is beneficial in that: the control method for suppressing the periodic fluctuation of the crystallizer liquid level in the production of SPHC steel provided by the present invention can reduce the crystallizer liquid level fluctuation value from the original 10-20 mm to 3 mm or even no fluctuation by limiting the use of low-carbon steel special protective slag during casting, the depth of the immersion nozzle inserted into the crystallizer liquid level, the crystallizer vibration model and the specific secondary cooling classification treatment method, which meets the slab process requirements, effectively suppresses the periodic fluctuation of the crystallizer liquid level, improves the casting quality, and ensures the rolling quality; and under the premise of keeping the existing equipment working conditions unchanged, the investment is small and the effect is fast, and it has certain promotion.

[0007] Furthermore, the basicity of the low carbon steel protection slag is 0.95±0.15, the viscosity is 0.2±0.1 Pa·S, and the moisture content is <0.5%.

[0008] Furthermore, the mass component contents of the low carbon steel protection slag include: CaO: 28.5±5.0%, SiO2: 31.0±5.0%, Al2O3: 4.5±3.0%, F: 8.0±3.0%, Tc: 6.0±3.0%, MgO: ≤5.0%.

[0009] Furthermore, the temperature of the middle package is 1550~1565℃, and the carbon content is ≤0.06%.

[0010] Furthermore, during the cooling process of the crystallizer, the water volume on the wide side is 3100~3300L / min, and the water volume on the narrow side is 460~500L / min.

[0011] Furthermore, full-process protective casting is adopted, the argon flow rate of the upper water inlet of the tundish is 2.2~3.2L / min, and the argon flow rate of the stopper rod is 1.0~2.5L / min.

[0012] Furthermore, the casting section thickness is 200~230mm and the width is 900~1235mm.

[0013] Furthermore, a crystallizer liquid level automatic control system was adopted, wherein the initial setting value of the KP system in the PID parameters was 1.0, and the initial setting value of the TI system was 0.5.

[0014] Furthermore, the depth of the submerged water inlet inserted into the liquid surface of the crystallizer is successively deepened to 130mm-150mm-170mm.

[0015] Furthermore, the liquid level of the crystallizer is automatically controlled using an eddy current probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the principle of periodic fluctuation of the liquid level in the crystallizer caused by the bulging of the casting billet in the present invention; Figure 2 It is a schematic diagram of periodic fluctuation of the liquid level of the crystallizer in the present invention; Figure 3 Schematic diagram of argon blowing casting for gathering inclusions on the water inlet and stopper rod; Figure 4 This is the actual casting picture of the crystallizer liquid level in the casting process of the present invention: Figure 5 This is a picture of periodic fluctuations in the liquid level of the crystallizer in the test example; Figure 6 This is an actual picture of slag inclusion on the surface of the ingot when the mold liquid level fluctuates periodically in the test example; Figure 7 This is an actual picture of the strip surface defects when the crystallizer liquid level fluctuates periodically in the test example; Figure 8 This is an actual picture of the casting billet after stripping when the mold liquid level fluctuates periodically in the test example; Fig. 9 This is a picture of the crystallizer liquid level without fluctuation in the test example; Fig.10 This is an actual picture of the surface of the ingot without defects when the liquid level in the crystallizer is not fluctuating in the test example; Fig.11 This is an actual picture of the strip surface without defects when there is no fluctuation in the crystallizer liquid level in the test example.

[0017] Description of reference numerals: 1. Roller; 2. Shell; 3. Nozzle; 4. Molten steel; 5. Argon pipe; 6. Stopper rod; 7. Crystallizer; 8. Upper water inlet; 9. Immersed water inlet; 10. Inclusions; 11. Argon in upper water inlet; 12. Argon in stopper rod; 13. Eddy current probe. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The invention provides a control method for suppressing periodic fluctuation of a crystallizer liquid level in the production of SPHC steel. When casting the SPHC steel, low-carbon steel protective slag is used, and the depth of the submerged water nozzle inserted into the crystallizer liquid level is 130-170 mm; the pulling speed of the crystallizer is 1.0-2.0 m / min, the amplitude is 3-6 mm, and the vibration frequency is 170-150 times; Among them, it includes crystallizer cooling treatment and secondary cooling treatment; when the periodic fluctuation value of the crystallizer liquid level is ≤10mm, the cooling intensity of the secondary cooling treatment is 0.8~0.9L / kg; when the periodic fluctuation value of the crystallizer liquid level is >10mm, the cooling intensity of the secondary cooling treatment is 1.0~1.1L / kg.

[0020] When casting SPHC steel grades, please refer to Figure 1 and Figure 2 When the billet passes through the roller 1, the billet shell 2 is too thin to resist the static pressure of the molten steel 4. The billet shell 2 bulges outward, and the molten steel 4 fills inward. The actual liquid level of the crystallizer drops. When the billet passes through the next roller 1, the billet shell 2 is squeezed, and the actual liquid level of the crystallizer rises, eventually forming a Figure 2 Sinusoidal periodic fluctuations in.

[0021] The control method for suppressing the periodic fluctuation of the liquid level of the crystallizer in the production of SPHC steel provided by the present invention can reduce the fluctuation value of the liquid level of the crystallizer from the original 10-20 mm to 3 mm or even no fluctuation by limiting the use of special protective slag for low carbon steel during casting, the depth of the immersion nozzle inserted into the liquid level of the crystallizer, the crystallizer vibration model and the specific secondary cooling classification treatment method, which meets the requirements of the slab process, effectively suppresses the periodic fluctuation of the liquid level of the crystallizer, improves the quality of the casting, and ensures the rolling quality; and under the premise of keeping the working conditions of the existing equipment unchanged, the investment is small and the effect is fast, and the method has certain promotion potential.

[0022] Furthermore, the basicity of the low carbon steel protection slag is 0.95±0.15, the viscosity is 0.2±0.1 Pa·S, and the moisture content is <0.5%.

[0023] By limiting the basicity, viscosity and moisture content of the mold slag, the ability to adsorb inclusions can be further improved, the heat transfer of the shell can be slowed down, the shell growth can be made more uniform, and it helps to further reduce fluctuations.

[0024] In a specific embodiment, the main mass components of the low carbon steel protective slag include: CaO: 28.5±5.0%, SiO2: 31.0±5.0%, Al2O3: 4.5±3.0%, F: 8.0±3.0%, Tc: 6.0±3.0%, MgO: ≤5.0%, and also include other components such as Fe2O3, Na2O, K2O, S and unavoidable impurities.

[0025] Furthermore, the temperature of the middle package is 1550~1565℃, and the carbon content is ≤0.06%.

[0026] The inventors have found that specifically limiting the tundish temperature helps to further control the crystallization process of the steel, thereby improving its microstructure and final properties and further reducing the liquid level fluctuation.

[0027] Furthermore, during the cooling process of the crystallizer, the water volume on the wide side is 3100~3300L / min, and the water volume on the narrow side is 460~500L / min.

[0028] The molten steel in the crystallizer needs to be quickly cooled by cooling water to form a solid shell. By further limiting the amount of cooling water on the wide and narrow sides of the crystallizer, the thickness of the ingot can be further increased, the liquid level fluctuation can be reduced, and the surface quality can be improved.

[0029] Specifically, full-process protective casting is adopted, the argon flow rate of the upper water inlet of the tundish is 2.2~3.2L / min, and the argon flow rate of the stopper rod is 1.0~2.5L / min.

[0030] By adjusting the argon flow rate of the upper water inlet and the stopper rod, the liquid level fluctuation in the crystallizer can be further controlled; the argon flow rate defined by the above parameters can further stabilize the liquid level in the crystallizer, avoiding problems such as slag curling or exposed molten steel caused by excessive liquid level fluctuation. At the same time, the adjustment of the argon flow rate helps to remove harmful gases and inclusions in the molten steel. The blowing of argon can not only make the protective slag slagging more uniform, but also promote the floating and removal of non-metallic inclusions in the molten steel, and improve the cleanliness of the molten steel; it can also timely flush out the inclusions in the water inlet, keep the water inlet unobstructed, and further improve the quality of the ingot.

[0031] In a specific embodiment, the casting section has a thickness of 200-230 mm and a width of 900-1235 mm.

[0032] It can be understood that appropriate thickness and width can ensure that a uniform and solid shell is formed during the solidification process of the ingot, further reducing liquid level fluctuations.

[0033] Optionally, a crystallizer liquid level automatic control system is used, wherein the initial setting value of the KP system in the PID parameters is 1.0, and the initial setting value of the TI system is 0.5.

[0034] It can be understood that appropriate KP (proportional gain) can reduce steady-state error and improve control accuracy. Increasing KP can increase the response speed of the system, allowing the control system to respond to deviations more quickly, while too large KP may cause system instability and oscillation. Increasing TI (integral time) can eliminate the steady-state error of the system and improve the steady-state accuracy of the system, while too large TI may cause the system to respond more slowly or even cause oscillation. It can be seen that selecting appropriate PID parameters is crucial to stabilizing the liquid level. The inventors have found that the above-defined parameters can further reduce liquid level fluctuations.

[0035] Furthermore, the depth of the submerged water inlet inserted into the liquid surface of the crystallizer is successively deepened to 130mm-150mm-170mm.

[0036] When the depth of the water inlet inserted into the crystallizer liquid surface is shallow, the tumbling of the crystallizer liquid surface is likely to cause liquid level fluctuations. Gradually increasing the depth of the insertion into the crystallizer liquid surface can further reduce the liquid level fluctuations.

[0037] Specifically, the crystallizer liquid level is automatically controlled using an eddy current probe.

[0038] See also Figure 3 In a specific embodiment, the control method provided by the present invention is specifically implemented as follows: S1: When casting SPHC steel, the liquid level of the crystallizer 7 is detected by the eddy current probe 13, and the stopper rod 6 controls the steel flow through the submerged nozzle 9 into the crystallizer 7 to cast the ingot.

[0039] S2: In order to ensure smooth casting and reduce the accumulation of inclusions 10 in the bowl of the upper nozzle 8, argon is blown into the upper nozzle 8 to form argon bubbles so that the inclusions 10 accumulated in the bowl of the upper nozzle 8 float up. Similarly, the inner wall of the submerged nozzle 9 is prone to accumulate inclusions 10. Argon is blown into the stopper rod 6 through the stopper rod argon pipe 5 to blow off the inclusions 10. The flow control range of the upper nozzle argon 11 is 2.2-3.2L / min, and the flow control range of the stopper rod argon 12 is 1.0-2.5L / min; the pulling speed control range is 1.0-2.0m / min, and the tundish temperature control range is 1550-1565℃.

[0040] S3: The cooling mode of crystallizer 7 is weak cooling, 3100L / min for the wide side and 460L / min for the narrow side; the secondary cooling is also weak cooling water, that is, the cooling intensity is 0.8L / kg.

[0041] S4: When the liquid level of the crystallizer 7 fluctuates periodically, the secondary cooling weak cold water meter is switched to the secondary cooling SPHC special water meter, that is, the cooling intensity is 1.05L / kg, which slows down the periodic fluctuation of the actual liquid level of the crystallizer 7 and ensures the stability of the liquid level.

[0042] The control method for suppressing periodic fluctuation of the mold liquid level in the production of SPHC steel grades provided by the present invention is described in detail below through specific test examples.

[0043] The following test cases were all conducted using the single variable method. The specific process conditions were as follows: the casting section thickness was 200 mm, the width was 1235 mm, the tundish temperature was 1550-1565 ° C; the casting speed of the crystallizer was 1.4 m / min, the amplitude was 4.1 mm, the vibration frequency was 161 times, the water volume of the wide surface of the crystallizer for cooling treatment was 3100 L / min, and the water volume of the narrow surface was 460 L / min; the cooling intensity of the secondary cooling treatment was 1.0 L / kg; the depth of the immersion nozzle inserted into the crystallizer liquid surface was successively deepened to 130 mm-150 mm-1 70mm; the flow rate of argon at the upper water inlet is 2.7L / min, and the flow rate of argon at the stopper rod is 1.5L / min; the initial setting value of the KP system in the PID parameters is 1.0, and the initial setting value of the TI system is 0.5; the mass component contents of the low-carbon steel protection slag include: CaO: 30.35%, SiO2: 31.45%, Al2O3: 3.61%, F: 10.35%, Tc: 6.16%, MgO: 3.31%, basicity is 0.97, viscosity is 0.123Pa·s, and moisture content is 0.3%.

[0044] Test Example 1 In this test example, the other process parameters remain unchanged. The effects of amplitude and frequency on the fluctuation of the crystallizer liquid level are compared when the pulling speed is 1.0~2.0m / min. The results are shown in Table 1.

[0045] Table 1 Pulling speed amplitude Frequency Negative slip time (s) Pulling speed amplitude Frequency Negative slip time (s) 1.0 3.5 165 0.146 1.0 2.5 175 0.137 1.1 3.7 164 0.146 1.1 2.6 174 0.138 1.2 3.8 163 0.147 1.2 2.7 173 0.139 1.3 4.0 162 0.148 1.3 2.8 172 0.140 1.4 4.1 161 0.149 1.4 2.9 171 0.140 1.5 4.3 160 0.150 1.5 3.0 170 0.141 1.6 4.4 159 0.151 1.6 3.1 169 0.142 1.7 4.6 158 0.152 1.7 3.2 168 0.143 1.8 4.7 157 0.153 1.8 3.3 167 0.144 1.9 4.9 156 0.154 1.9 3.4 166 0.145 2.0 5.0 155 0.155 2.0 3.5 165 0.145 It can be seen that when the pulling speed is 1.0-2.0m / min, the vibration amplitude of low carbon steel is 3.5-5.0mm, the frequency is 165-155 times, and the negative slip time is controlled at 0.146-0.155S; the negative slip time can be reduced by reducing the amplitude and increasing the frequency, the amplitude is reduced by 1-1.5mm, and the frequency is increased by 10 times, which reduces the friction between the billet shell and the inner wall of the crystallizer, making the billet shell grow evenly and smoothly, thereby reducing the liquid level fluctuation.

[0046] Test Example 2 In this test example, the other process conditions remain unchanged. The effect of the secondary cooling treatment on the crystallizer liquid level fluctuation is compared, and the results are shown in Table 2.

[0047] Table 2 Steel Type Carbon content% Cooling intensity of secondary cooling treatment (L / kg) Periodic fluctuation value of crystallizer liquid level mm Is the crystallizer liquid level fluctuation periodic? The test was conducted to determine whether the periodic fluctuation of the crystallizer liquid level was alleviated. SPHC 0.038 0.8 13 conform to fluctuation SPHC 0.043 0.8 13 conform to fluctuation SPHC 0.046 1.05 1.5 conform to Stablize SPHC 0.045 1.05 No fluctuation conform to The liquid level is stable without fluctuations SPHC 0.041 1.05 No fluctuation conform to The liquid level is stable without fluctuations SPHC 0.040 1.05 No fluctuation conform to The liquid level is stable without fluctuations It can be seen that under the premise that other process parameters remain unchanged, when the original secondary cooling weak water meter is used, the periodic fluctuation value of the crystallizer liquid level is about 13mm; after increasing the secondary cooling intensity and using the SPHC special water meter (i.e., the cooling intensity is 1.05 L / kg), the periodic fluctuation of the crystallizer liquid level is significantly reduced, and the fluctuation value is about 1.5mm, or even no fluctuation. Through experiments, it is found that increasing the secondary cooling intensity makes the billet shell thicker in the second cooling zone, which can resist the outward impact force of the static pressure of the molten steel on the billet shell under high drawing speed, thereby reducing the bulging of the casting billet, and effectively alleviating the periodic fluctuation of the crystallizer liquid level. The liquid level is stably controlled within the range of ±3mm or even without fluctuation. It has a significant effect on reducing the periodic fluctuation of the crystallizer liquid level. The crystallizer liquid level is stable and meets the process requirements within the range of ±3mm.

[0048] Test Example 3 In this test example, the other process conditions remain unchanged. The effect of the depth of the submerged nozzle inserted into the crystallizer liquid surface on the crystallizer liquid surface fluctuation is compared, and the results are shown in Table 3.

[0049] Table 3 When the depth of the water inlet inserted into the crystallizer liquid surface is shallow, the tumbling of the crystallizer liquid surface is likely to cause liquid level fluctuations. Gradually increasing the depth of the insertion into the crystallizer liquid surface can further reduce the liquid level fluctuations.

[0050] Test Example 4 In this test example, the other process conditions remain unchanged. The effect of the argon flow rate at the upper water inlet on the crystallizer liquid level fluctuation is compared, and the results are shown in Table 4.

[0051] Table 4 Steel Type Carbon content Argon flow rate at upper water inlet (L / min) Periodic fluctuation value of crystallizer liquid level mm Is the crystallizer liquid level fluctuation periodic? The test was conducted to determine whether the periodic fluctuation of the crystallizer liquid level was alleviated. SPHC 0.049 2.7 7 conform to There is relief SPHC 0.043 2.7 7 conform to There is relief SPHC 0.051 1.7 10 conform to fluctuation SPHC 0.052 1.7 11 conform to fluctuation SPHC 0.044 2.2 9 conform to There is relief SPHC 0.040 2.2 9.6 conform to There is relief SPHC 0.040 3.2 7 conform to There is relief SPHC 0.037 3.2 7 conform to There is relief SPHC 0.045 3.7 11 conform to fluctuation SPHC 0.046 3.7 12 conform to fluctuation SPHC 0.044 4.2 12 conform to fluctuation SPHC 0.045 4.2 12 conform to fluctuation Test Example 5 In this test example, the other process conditions remain unchanged. The results of comparing the effect of the stopper argon flow rate on the crystallizer liquid level fluctuation are shown in Table 5.

[0052] Table 5 Test Example 6 In this test case, the other process conditions remain unchanged. The effects of the original KP value of the PID parameter on the crystallizer liquid level fluctuation are compared, and the results are shown in Table 6.

[0053] Table 6 Test Example 7 In this test example, the other process conditions remain unchanged. The effects of the original TI value of the PID parameter on the crystallizer liquid level fluctuation are compared, and the results are shown in Table 7.

[0054] Table 7 Test Example 8 In this test example, the other process conditions remain unchanged. The effects of casting speed on the fluctuation of the crystallizer liquid level are compared, and the results are shown in Table 8.

[0055] Table 8 Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by equivalents. If these modifications and variations fall within the scope of the claims of the present invention and their equivalent technologies, they should be considered to be within the protection scope of the present invention.

Claims

1. A control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production, characterized in that: When casting SPHC steel, low carbon steel protection slag is used, and the depth of the submerged nozzle inserted into the crystallizer liquid surface is 130~170mm; the casting speed of the crystallizer is 1.0-2.0m / min, the amplitude is 3~6mm, and the vibration frequency is 170~150 times; Among them, it includes crystallizer cooling treatment and secondary cooling treatment; when the periodic fluctuation value of the crystallizer liquid level is ≤10mm, the cooling intensity of the secondary cooling treatment is 0.8~0.9L / kg; when the periodic fluctuation value of the crystallizer liquid level is >10mm, the cooling intensity of the secondary cooling treatment is 1.0~1.1L / kg.

2. The control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production according to claim 1, characterized in that: The basicity of low carbon steel protection slag is 0.95±0.15, the viscosity is 0.2±0.1Pa·S, and the moisture content is <0.5%.

3. The control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production according to claim 1, characterized in that: The mass component contents of low carbon steel protection slag include: CaO: 28.5±5.0%, SiO2: 31.0±5.0%, Al2O3: 4.5±3.0%, F: 8.0±3.0%, Tc: 6.0±3.0%, MgO: ≤5.0%.

4. The control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production according to claim 1, characterized in that: The temperature of the tundish is 1550~1565℃, and the carbon content is ≤0.06%.

5. The control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production according to claim 1, characterized in that: During the crystallizer cooling process, the water volume on the wide side is 3100~3300L / min, and the water volume on the narrow side is 460~500L / min.

6. The control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production according to claim 1, characterized in that: The whole process protection casting is adopted, the argon flow rate of the upper water inlet of the tundish is 2.2~3.2L / min, and the argon flow rate of the stopper rod is 1.0~2.5L / min.

7. The control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production according to claim 1, characterized in that: The casting section thickness is 200~230mm and the width is 900~1235mm.

8. The control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production according to claim 1, characterized in that: The crystallizer liquid level automatic control system is adopted, in which the initial setting value of the KP system in the PID parameters is 1.0, and the initial setting value of the TI system is 0.

5.

9. The control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production according to claim 1, characterized in that: The depth of the submerged water inlet inserted into the crystallizer liquid surface is successively deepened to 130mm-150mm-170mm.

10. The control method for suppressing periodic fluctuation of mold liquid level in SPHC steel production according to any one of claims 1 to 9, characterized in that: The crystallizer liquid level is automatically controlled using an eddy current probe.

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