Method for accurately controlling N element of oriented silicon steel

Abstract

The invention discloses a method for accurately controlling the N element of oriented silicon steel, and belongs to the technical field of ferrous metallurgy. The method covers key procedures such as converter smelting, RH refining and continuous casting, accurate regulation and control of the content of the N element in the oriented silicon steel are achieved through accurate control over core links of all the procedures, and therefore the product quality of the oriented silicon steel is improved. According to the method, the fluctuation range of the N content of the oriented silicon steel is successfully and strictly controlled within 35 ppm by comprehensively and systematically optimizing the steelmaking process, and compared with a traditional process, the control precision is greatly improved, the performance and quality stability of the oriented silicon steel are remarkably enhanced, and the strict requirement of the high-end market for the oriented silicon steel is powerfully met.

Description

Technical Field

[0001] The invention belongs to the technical field of steel metallurgy, and in particular relates to a method for accurately controlling the nitrogen element in oriented silicon steel. Background Art

[0002] Grain-oriented silicon steel, a low-carbon, ferrosilicon soft magnetic alloy crucial for the power, electronics, and military industries, is also one of the most produced functional metallic materials. With a silicon content of ≥0.8%, it undergoes complex hot and cold rolling processes to be rolled into sheets less than 1mm thick. Precisely controlling the nitrogen content is a challenging and critical step in the entire grain-oriented silicon steel production process.

[0003] The nitrogen element plays an important role in oriented silicon steel. On the one hand, an appropriate amount of nitrogen element can help improve the microstructure of oriented silicon steel under certain conditions and can have a positive effect on the magnetic properties of oriented silicon steel. However, on the other hand, if the nitrogen content is unstable or exceeds a reasonable range, it will bring many serious problems to the production of oriented silicon steel. In the subsequent rolling process, unstable nitrogen content will lead to uneven stress distribution inside the steel, which will in turn cause difficulties in plate shape control during the rolling process, resulting in problems such as excessive thickness deviation and plate warping, which seriously affect the stability and yield of rolling. From the perspective of final product performance, fluctuations in the nitrogen content will cause significant changes in key magnetic performance indicators such as magnetic permeability and iron loss of oriented silicon steel, reduce the consistency and stability of the product, and fail to meet the strict requirements of high-end application fields for the performance of oriented silicon steel.

[0004] Currently, existing steel metallurgical technologies have many shortcomings in controlling nitrogen content. Traditional process methods make it difficult to accurately stabilize the nitrogen content within the target range, resulting in a low nitrogen content hit rate. In actual production processes, the nitrogen content is often too high or too low. This not only requires additional processing or rework of the product, increasing production costs and production cycles, but even after processing, it is difficult to ensure that the performance and quality of the final product reach the ideal stable state. Therefore, developing a new method that can effectively improve the control accuracy of the nitrogen content is of great practical significance for improving the production level and product quality of grain-oriented silicon steel. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for precisely controlling the nitrogen element in oriented silicon steel. By comprehensively and systematically optimizing the steelmaking process, the fluctuation range of the nitrogen content in oriented silicon steel is successfully and strictly controlled within 35ppm. Compared with traditional processes, the control accuracy is greatly improved, the performance and quality stability of oriented silicon steel are significantly enhanced, and the stringent requirements of the high-end market for oriented silicon steel are effectively met.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for accurately controlling the nitrogen element in grain-oriented silicon steel, comprising:

[0008] 1) Converter process

[0009] During the tapping process, a carefully designed weak deoxidation method is adopted. 13-140kg of deoxidizer is added when 1 / 4 of the steel is tapped. The amount and timing of deoxidizer addition are strictly controlled to avoid excessive gas exchange between the molten steel and the outside air due to over-deoxidation, thereby preventing abnormal absorption of the nitrogen element. After tapping, the flow rate of argon gas blown from the bottom of the ladle is strictly controlled. Large argon stirring is strictly prohibited. The flow rate of argon gas blown from the bottom of the ladle is controlled to 120±5L / min.

[0010] 2) RH refining process

[0011] Preliminary treatment: In the early stage of RH refining, the ultimate vacuum is strictly controlled below 133 Pa. After 15-17 minutes of sufficient treatment, oxygen and nitrogen samples are accurately extracted. The test results of these oxygen and nitrogen samples will become the key basis for subsequent adjustments. They can accurately reflect the content of nitrogen and other key gas elements in the current molten steel.

[0012] Late-stage vacuum control: Based on the precise oxygen and nitrogen sample test results at the end of the early stage, the late-stage vacuum control mechanism is activated. If the nitrogen content detected in the early stage is low, the vacuum level is appropriately reduced to accurately adjust to 35-45kPa. If the nitrogen content detected in the early stage is high, the vacuum level is appropriately increased to 25-35kPa to further enhance the "extraction" of nitrogen from the molten steel, promoting its rapid escape and smoothly reducing the nitrogen content to the target range. This precise, flexible, and ingenious vacuum control method allows the nitrogen content to be stably controlled within the target range of 85-120ppm without the addition of silicon manganese nitride alloy, achieving precise and efficient control of the nitrogen element.

[0013] 3) Continuous casting process

[0014] In the key link of tundish pouring in the continuous casting process, a series of strict and meticulous protection pouring measures are taken; first, ensure that the long nozzle of the large ladle is set correctly at one time; strictly control the flow rate of the blown argon gas at 5-8m 3The flow rate is controlled at 2-5 L / min at the stopper and nozzle. This precise control helps maintain the flow rate and volume of the molten steel, ensuring stability and uniformity during the pouring process. Back pressure is maintained at 0.3-1.0 bar. This stable back pressure helps maintain the flow of the molten steel and prevent abnormalities such as cavitation. High-performance graphite seals further prevent air intrusion through their excellent sealing properties. A WT2 coating agent, specifically for grain-oriented silicon steel, produced by Tongyu, is added to the tundish. This coating forms a dense protective film on the molten steel surface, effectively preventing secondary oxidation and further blocking nitrogen intrusion. This comprehensive, multi-layered protective pouring measure keeps nitrogen content in the tundish within 5 ppm, ensuring that the nitrogen content in the finished product meets the stringent requirement of 85-120 ppm.

[0015] Furthermore, the ladle bottom blowing argon flow rate was controlled to 120 L / min.

[0016] Furthermore, during the steel-making process, 130-140 kg of deoxidizer is precisely added according to calculations for weak deoxidation, and the degree of deoxidation is strictly controlled.

[0017] Furthermore, during the steel-making process, 130 kg, 135 kg or 140 kg of deoxidizer is precisely added according to calculations for weak deoxidation, and the degree of deoxidation is strictly controlled.

[0018] Furthermore, in converter smelting, the molten iron after strict desulfurization treatment is accurately added to the converter. During the converter smelting process, active lime, light-burned dolomite, and iron balls are added in precise proportions. The blowing adopts an advanced top-bottom combined blowing mode, with nitrogen blowing from the bottom throughout the process to ensure uniform stirring of the molten steel and stable composition. During tapping, the argon flow rate from the ladle bottom is precisely controlled to 120L / min. During the tapping process, 135kg of deoxidizer is accurately added according to calculations for weak deoxidation, and the degree of deoxidation is strictly controlled.

[0019] RH refining: Nitrogen was used as the circulating gas throughout the entire process. This treatment mode was initially used, with the ultimate vacuum controlled at 70 Pa. After 15 minutes of thorough treatment, oxygen and nitrogen samples were taken, and the nitrogen content was tested to be 61 ppm. Later, based on the test results, the vacuum was adjusted to 41 kPa and maintained at this vacuum for 10 minutes, allowing the nitrogen content in the molten steel to gradually increase and stabilize. At the end of the RH refining process, the nitrogen content reached an accurate 90 ppm, successfully and stably controlled within the target range.

[0020] Continuous casting process: Use high-quality graphite sealing rings to ensure the sealing effect; the large ladle long nozzle is accurately aligned and argon is blown in at one time to accurately control the flow rate to 6.5m 3 / h, the flow rate of the stopper rod and the upper water inlet is precisely controlled at 2.6L / min, the back pressure is accurately maintained at 0.7bar, and a special covering agent for oriented silicon steel is added to the tundish for comprehensive protection of the casting; after strict testing, the nitrogen content of the tundish is only 3ppm;

[0021] The nitrogen content in the final finished steel is 93ppm, precisely meeting the strict requirement of 85-120ppm.

[0022] Furthermore, in converter smelting, the molten iron after strict desulfurization treatment is accurately added to the converter. During the converter smelting process, active lime, light-burned dolomite, and iron balls are added in precise proportions. The blowing adopts an advanced top-bottom combined blowing mode, with nitrogen blowing from the bottom throughout the process to ensure uniform stirring of the molten steel and stable composition. During tapping, the argon flow rate from the ladle bottom is precisely controlled to 125L / min. During the tapping process, 130 kg of deoxidizer is accurately added according to calculations for weak deoxidation, and the degree of deoxidation is strictly controlled.

[0023] RH refining: Nitrogen was used as the circulating gas throughout the entire process. This treatment mode was initially used, with the ultimate vacuum controlled at 81 Pa. After 16 minutes of thorough treatment, oxygen and nitrogen samples were taken, and the nitrogen content was tested to be 59 ppm. Later, based on the test results, the vacuum was adjusted to 42 kPa and maintained at this vacuum for 11 minutes, allowing the nitrogen content in the molten steel to gradually increase and stabilize. At the end of the RH refining process, the nitrogen content reached a precise 92 ppm, successfully and stably controlled within the target range.

[0024] Continuous casting process: Use high-quality graphite sealing rings to ensure the sealing effect; the large ladle long nozzle is accurately aligned and argon is blown in at one time, and the flow rate is accurately controlled to 6.0m 3 / h, the flow rate of the stopper rod and the upper water inlet is precisely controlled at 2.7L / min, the back pressure is accurately maintained at 0.8bar, and a special covering agent for oriented silicon steel is added to the tundish for comprehensive protection of the casting; after strict testing, the nitrogen content of the tundish is only 2ppm;

[0025] The nitrogen content in the final finished steel is 94ppm, precisely meeting the strict requirement of 85-120ppm.

[0026] Furthermore, in converter smelting, the molten iron after strict desulfurization treatment is accurately added to the converter. During the converter smelting process, active lime, light-burned dolomite, and iron balls are added in precise proportions. The blowing adopts an advanced top-bottom combined blowing mode, with nitrogen blowing from the bottom throughout the process to ensure uniform stirring of the molten steel and stable composition. During tapping, the argon flow rate from the ladle bottom is precisely controlled to 125L / min. During the tapping process, 130 kg of deoxidizer is accurately added according to calculations for weak deoxidation, and the degree of deoxidation is strictly controlled.

[0027] RH refining: Nitrogen was used as the circulating gas throughout the entire process. This treatment mode was initially used, with the ultimate vacuum controlled at 81 Pa. After 16 minutes of thorough treatment, oxygen and nitrogen samples were taken, and the nitrogen content was tested to be 59 ppm. Later, based on the test results, the vacuum was adjusted to 42 kPa and maintained at this vacuum for 11 minutes, allowing the nitrogen content in the molten steel to gradually increase and stabilize. At the end of the RH refining process, the nitrogen content reached a precise 92 ppm, successfully and stably controlled within the target range.

[0028] Continuous casting process: Use high-quality graphite sealing rings to ensure the sealing effect; the large ladle long nozzle is accurately aligned and argon is blown in at one time, and the flow rate is accurately controlled to 6.0m 3 / h, the flow rate of the stopper rod and the upper water inlet is precisely controlled at 2.7L / min, the back pressure is accurately maintained at 0.8bar, and a special covering agent for oriented silicon steel is added to the tundish for comprehensive protection of the casting; after strict testing, the nitrogen content of the tundish is only 2ppm;

[0029] The nitrogen content in the final finished steel is 94ppm, precisely meeting the strict requirement of 85-120ppm.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] The present invention realizes precise regulation of the N content in oriented silicon steel through precise control of the core links of each process, thereby improving the quality of oriented silicon steel products. DETAILED DESCRIPTION

[0032] The present invention will be further described below by way of examples.

[0033] Example 1

[0034] Converter Smelting: Molten iron, after rigorous desulfurization treatment, is precisely added to the converter. During the converter smelting process, slag-forming materials such as active lime, light-burned dolomite, and iron balls are added in precise proportions. The blowing process utilizes an advanced top-bottom combined blowing method, with nitrogen blowing throughout the entire process to ensure uniform mixing and stable composition of the molten steel. During tapping, the ladle bottom argon flow rate is precisely controlled at 120 L / min. During the tapping process, 135 kg of deoxidizer is precisely added for weak deoxidation, strictly controlling the degree of deoxidation.

[0035] RH refining: Nitrogen was used as the circulating gas throughout the entire process. Initially, this process was employed, maintaining a maximum vacuum of 70 kPa. After 15 minutes of thorough refining, oxygen and nitrogen samples were collected, revealing a nitrogen content of 61 ppm. Later, based on these test results, the vacuum was adjusted to 41 kPa and maintained at this level for 10 minutes, allowing the nitrogen content in the molten steel to gradually increase and stabilize. By the end of the RH refining process, the nitrogen content had reached a precise 90 ppm, successfully and stably within the target range.

[0036] Continuous casting process: Use high-quality graphite sealing rings to ensure the sealing effect. The large ladle long nozzle is accurately aligned and argon is blown in at one time to accurately control the flow rate to 6.5m 3 / h, the flow rate of the stopper and upper water inlet is precisely controlled at 2.6L / min, and the back pressure is accurately maintained at 0.7bar. A special covering agent for oriented silicon steel (manufactured by Tongyu, model WT2) is added to the tundish for comprehensive protection during pouring. After rigorous testing, the nitrogen content in the tundish is only 3ppm.

[0037] The nitrogen content in the final finished steel is 93ppm, precisely meeting the strict requirement of 85-120ppm.

[0038] Example 2

[0039] Converter Smelting: Molten iron, after rigorous desulfurization treatment, is precisely added to the converter. During the converter smelting process, slag-forming materials such as active lime, light-burned dolomite, and iron balls are added in precise proportions. The blowing process utilizes an advanced top-bottom combined blowing method, with nitrogen blowing throughout the entire process to ensure uniform mixing and stable composition of the molten steel. During tapping, the ladle bottom-blown argon flow rate is precisely controlled at 125 L / min. During the tapping process, 130 kg of deoxidizer is precisely added for weak deoxidation, ensuring strict control of the degree of deoxidation.

[0040] RH refining: Nitrogen was used as the circulating gas throughout the entire process. Initially, this process was employed, maintaining a maximum vacuum of 81 kPa. After 16 minutes of thorough refining, oxygen and nitrogen samples were collected, revealing a nitrogen content of 59 ppm. Later, based on these test results, the vacuum was adjusted to 42 kPa and maintained at this level for 11 minutes, allowing the nitrogen content in the molten steel to gradually increase and stabilize. At the end of the RH refining process, the nitrogen content reached a precise 92 ppm, successfully and stably within the target range.

[0041] Continuous casting process: Use high-quality graphite sealing rings to ensure the sealing effect. The large ladle long nozzle is accurately aligned and argon is blown in at one time to accurately control the flow rate to 6.0m 3 / h, the flow rate of the stopper and upper water inlet is precisely controlled at 2.7L / min, and the back pressure is accurately maintained at 0.8bar. A special covering agent for oriented silicon steel (manufactured by Tongyu, model WT2) is added to the tundish for comprehensive protection during pouring. After rigorous testing, the nitrogen content in the tundish is only 2ppm.

[0042] The nitrogen content in the final finished steel is 94ppm, precisely meeting the strict requirement of 85-120ppm.

[0043] Example 3

[0044] Converter Smelting: Molten iron, after rigorous desulfurization treatment, is precisely added to the converter. During the converter smelting process, slag-forming materials such as active lime, light-burned dolomite, and iron balls are added in precise proportions. The blowing process utilizes an advanced top-bottom combined blowing method, with nitrogen blowing throughout the entire process to ensure uniform mixing and stable composition of the molten steel. During tapping, the ladle bottom-blown argon flow rate is precisely controlled at 130 L / min. During the tapping process, 140 kg of deoxidizer is precisely added for weak deoxidation, ensuring strict control of the degree of deoxidation.

[0045] RH refining: Nitrogen was used as the circulating gas throughout the entire process. Initially, this process was employed, maintaining a maximum vacuum of 60 kPa. After 14 minutes of thorough refining, oxygen and nitrogen samples were collected, revealing a nitrogen content of 57 ppm. Later, based on these test results, the vacuum was adjusted to 44 kPa and maintained at this level for 12 minutes, allowing the nitrogen content in the molten steel to gradually increase and stabilize. At the end of the RH refining process, the nitrogen content reached a precise 97 ppm, successfully and stably within the target range.

[0046] Continuous casting process: Use high-quality graphite sealing rings to ensure the sealing effect. The large ladle long nozzle is accurately aligned and argon is blown in at one time to accurately control the flow rate to 6.1m 3 / h, the flow rate of the stopper and upper water inlet is precisely controlled at 2.9L / min, and the back pressure is accurately maintained at 0.9bar. A special covering agent for oriented silicon steel (manufactured by Tongyu, model WT2) is added to the tundish for comprehensive protection during pouring. After rigorous testing, the nitrogen content in the tundish is only 2ppm.

[0047] The nitrogen content in the final finished steel is 99ppm, precisely meeting the strict requirement of 85-120ppm.

[0048] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for accurately controlling the nitrogen element in grain-oriented silicon steel, characterized by: include: 1) Converter process During the tapping process, a carefully designed weak deoxidation method is adopted. 13-140kg of deoxidizer is added when 1 / 4 of the steel is tapped. The amount and timing of deoxidizer addition are strictly controlled to avoid excessive gas exchange between the molten steel and the outside air due to over-deoxidation, thereby preventing abnormal absorption of the nitrogen element. After tapping, the flow rate of argon gas blown from the bottom of the ladle is strictly controlled. Large argon stirring is strictly prohibited. The flow rate of argon gas blown from the bottom of the ladle is controlled to 120±5L / min. 2) RH refining process Preliminary treatment: In the early stage of RH refining, the ultimate vacuum degree is strictly controlled below 133 Pa; After 15-17 minutes of thorough treatment, oxygen and nitrogen samples are accurately extracted. The test results of these oxygen and nitrogen samples will become the key basis for subsequent adjustments. They can accurately reflect the current content of nitrogen and other key gas elements in the molten steel. Late-stage vacuum control: Based on the precise oxygen and nitrogen sample test results at the end of the early stage, the late-stage vacuum control mechanism is activated. If the nitrogen content detected in the early stage is low, the vacuum level is appropriately reduced to accurately adjust to 35-45kPa. If the nitrogen content detected in the early stage is high, the vacuum level is appropriately increased to 25-35kPa, further increasing the "extraction" of nitrogen from the molten steel, promoting its rapid escape and smoothly reducing the nitrogen content to the target range. This precise, flexible, and ingenious vacuum control method allows the nitrogen content to be stably controlled within the target range of 85-120ppm without the addition of silicon manganese nitride alloy, achieving precise and efficient control of the nitrogen element. 3) Continuous casting process In the key link of tundish pouring in the continuous casting process, a series of strict and meticulous protection pouring measures are taken; first, ensure that the long nozzle of the large ladle is set correctly at one time; strictly control the flow rate of the blown argon gas at 5-8m 3 / h, this precise flow control can form a stable argon protective barrier on the surface of the molten steel, effectively isolating the nitrogen element in the air from contact with the molten steel; The flow rate of the stopper rod and upper nozzle is controlled at 2-5L / min. By precisely controlling the flow at these two key locations, the flow rate and flow rate of the molten steel can be accurately adjusted, ensuring the stability and uniformity of the molten steel during the pouring process. The back pressure is maintained at 0.3-1.0 bar. The stable back pressure helps maintain the flow state of the molten steel and prevent abnormal phenomena such as cavitation. At the same time, the use of high-performance graphite sealing rings, whose excellent sealing performance further eliminates the intrusion of air. A WT2 type of coating agent for grain-oriented silicon steel produced by Tongyu Company is added to the tundish. This coating agent forms a dense protective film on the surface of the molten steel, which not only effectively prevents secondary oxidation of the molten steel but also further blocks the intrusion of nitrogen. Through this series of comprehensive and multi-level protective pouring measures, the nitrogen content in the tundish is strictly controlled within 5ppm, thereby ensuring that the nitrogen content in the finished product precisely meets the strict requirement of 85-120ppm.

2. The method for accurately controlling the nitrogen element in grain-oriented silicon steel according to claim 1, characterized in that: The argon flow rate from the ladle bottom was controlled at 120 L / min.

3. The method for accurately controlling the nitrogen element in grain-oriented silicon steel according to claim 1, characterized in that: During the steel-making process, 130-140 kg of deoxidizer is accurately added according to calculations for weak deoxidation, and the degree of deoxidation is strictly controlled.

4. The method for accurately controlling the nitrogen element in grain-oriented silicon steel according to claim 1, characterized in that: During the steel-making process, 130 kg, 135 kg or 140 kg of deoxidizer is accurately added according to calculations for weak deoxidation, and the degree of deoxidation is strictly controlled.

5. The method for accurately controlling nitrogen element in grain-oriented silicon steel according to claim 1, characterized in that: Converter smelting: Molten iron that has undergone rigorous desulfurization treatment is precisely added to the converter. During the converter smelting process, active lime, light-burned dolomite, and iron balls are added in precise proportions to form slag. The blowing process uses an advanced top-bottom combined blowing mode, with nitrogen blowing from the bottom throughout the process to ensure uniform mixing and stable composition of the molten steel. During tapping, the argon flow rate from the ladle bottom is precisely controlled to 120L / min. During the tapping process, 135kg of deoxidizer is precisely added according to calculations for weak deoxidation, strictly controlling the degree of deoxidation. RH refining: Nitrogen was used as the circulating gas throughout the entire process. This treatment mode was initially used, with the ultimate vacuum controlled at 70 Pa. After 15 minutes of thorough treatment, oxygen and nitrogen samples were taken, and the nitrogen content was tested to be 61 ppm. Later, based on the test results, the vacuum was adjusted to 41 kPa and maintained at this vacuum for 10 minutes, allowing the nitrogen content in the molten steel to gradually increase and stabilize. At the end of the RH refining process, the nitrogen content reached an accurate 90 ppm, successfully and stably controlled within the target range. Continuous casting process: Use high-quality graphite sealing rings to ensure the sealing effect; the large ladle long nozzle is accurately aligned and argon is blown in at one time to accurately control the flow rate to 6.5m 3 / h, the flow rate of the stopper rod and the upper water inlet is precisely controlled at 2.6L / min, the back pressure is accurately maintained at 0.7bar, and a special covering agent for oriented silicon steel is added to the tundish for comprehensive protection of the casting; after strict testing, the nitrogen content of the tundish is only 3ppm; The nitrogen content in the final finished steel is 93ppm, precisely meeting the strict requirement of 85-120ppm.

6. The method for accurately controlling nitrogen in grain-oriented silicon steel according to claim 1, characterized in that: Converter smelting: Molten iron that has undergone rigorous desulfurization treatment is precisely added to the converter. During the converter smelting process, active lime, light-burned dolomite, and iron balls are added in precise proportions to form slag. The blowing process uses an advanced top-bottom combined blowing mode, with nitrogen blowing from the bottom throughout the process to ensure uniform mixing and stable composition of the molten steel. During tapping, the argon flow rate from the ladle bottom is precisely controlled to 125L / min. During the tapping process, 130 kg of deoxidizer is precisely added according to calculations for weak deoxidation, strictly controlling the degree of deoxidation. RH refining: Nitrogen was used as the circulating gas throughout the entire process. This treatment mode was initially used, with the ultimate vacuum controlled at 81 Pa. After 16 minutes of thorough treatment, oxygen and nitrogen samples were taken, and the nitrogen content was tested to be 59 ppm. Later, based on the test results, the vacuum was adjusted to 42 kPa and maintained at this vacuum for 11 minutes, allowing the nitrogen content in the molten steel to gradually increase and stabilize. At the end of the RH refining process, the nitrogen content reached a precise 92 ppm, successfully and stably controlled within the target range. Continuous casting process: Use high-quality graphite sealing rings to ensure the sealing effect; the large ladle long nozzle is accurately aligned and argon is blown in at one time, and the flow rate is accurately controlled to 6.0m 3 / h, the flow rate of the stopper rod and the upper water inlet is precisely controlled at 2.7L / min, the back pressure is accurately maintained at 0.8bar, and a special covering agent for oriented silicon steel is added to the tundish for comprehensive protection of the casting; after strict testing, the nitrogen content of the tundish is only 2ppm; The nitrogen content in the final finished steel is 94ppm, precisely meeting the strict requirement of 85-120ppm.

7. The method for accurately controlling nitrogen in grain-oriented silicon steel according to claim 1, characterized in that: Converter smelting: Molten iron that has undergone rigorous desulfurization treatment is precisely added to the converter. During the converter smelting process, active lime, light-burned dolomite, and iron balls are added in precise proportions to form slag. The blowing process uses an advanced top-bottom combined blowing mode, with nitrogen blowing from the bottom throughout the process to ensure uniform mixing and stable composition of the molten steel. During tapping, the argon flow rate from the ladle bottom is precisely controlled to 125L / min. During the tapping process, 130 kg of deoxidizer is precisely added according to calculations for weak deoxidation, strictly controlling the degree of deoxidation. RH refining: Nitrogen was used as the circulating gas throughout the entire process. This treatment mode was initially used, with the ultimate vacuum controlled at 81 Pa. After 16 minutes of thorough treatment, oxygen and nitrogen samples were taken, and the nitrogen content was tested to be 59 ppm. Later, based on the test results, the vacuum was adjusted to 42 kPa and maintained at this vacuum for 11 minutes, allowing the nitrogen content in the molten steel to gradually increase and stabilize. At the end of the RH refining process, the nitrogen content reached a precise 92 ppm, successfully and stably controlled within the target range. Continuous casting process: Use high-quality graphite sealing rings to ensure the sealing effect; the large ladle long nozzle is accurately aligned and argon is blown in at one time, and the flow rate is accurately controlled to 6.0m 3 / h, the flow rate of the stopper rod and the upper water inlet is precisely controlled at 2.7L / min, the back pressure is accurately maintained at 0.8bar, and a special covering agent for oriented silicon steel is added to the tundish for comprehensive protection of the casting; after strict testing, the nitrogen content of the tundish is only 2ppm; The nitrogen content in the final finished steel is 94ppm, precisely meeting the strict requirement of 85-120ppm.