Method for optimizing the structure of a silicon steel inhibitor by dew point regulation

Abstract

The application belongs to the technical field of manufacturing high-magnetic-induction oriented silicon steel, and particularly relates to a method for optimizing inhibitor structure of silicon steel by dew point control, which comprises the following steps: obtaining silicon steel, and normalizing the silicon steel to obtain optimized silicon steel; the temperature of the normalizing is 1080-1120 DEG C, the holding time is 1-3 min, the dew point is 5-35 DEG C, the atmosphere is nitrogen, and the cooling mode is specifically as follows: rapidly cooling to room temperature at a cooling rate of greater than 15 DEG C / s. The application adopts a specific positive dew point range, achieves thermodynamic equilibrium control, realizes the synergistic effect of "surface trace oxidation / inner oxidation" and "high-temperature decarburization", thereby optimizing inhibitor precipitation kinetics and purifying grain boundaries, and finally achieving the purpose of greatly improving the magnetic properties of finished products.

Description

Technical Field

[0001] This application belongs to the field of manufacturing high magnetic induction oriented silicon steel technology, specifically relating to a method for optimizing the structure of silicon steel inhibitors through dew point regulation. Background Technology

[0002] The core of producing high-magnetic-induction grain-oriented silicon steel lies in obtaining a single, sharp Gaussian texture through secondary recrystallization {110} <001> The success of this process heavily depends on the effective suppression of primary grain growth by dispersed nanoscale inhibitors (such as MnS, AlN, and their composite precipitates). The traditional key process route is: slab heating → hot rolling → normalizing → pickling → cold rolling → decarburizing annealing → MgO coating → high-temperature annealing. Decarburizing annealing is typically carried out in a humid atmosphere (N2+H2+H2O) at 820-880℃, primarily accomplishing two tasks: 1. reducing the dissolved carbon in the steel to below 30ppm; 2. forming a uniform SiO2 oxide layer on the steel strip surface. In recent years, to further optimize the inhibitors, a process has been developed that introduces a high-temperature annealing (or normalizing) step before decarburizing annealing. This process typically sets temperatures as high as 1080-1120℃ in the RTF section of a continuous annealing line. The main objectives are: 1. To redissolve inhibitor elements (such as Cu and S) dissolved after hot rolling; 2. To allow the inhibitors to precipitate in a finer, more dispersed form during the subsequent slow cooling process, providing more ideal pinning points for the final secondary recrystallization. However, in this high-temperature RTF process, to prevent oxidation of the steel strip surface (especially Si oxidation, which would damage surface quality and inhibitor uniformity), conventional techniques require a strongly reducing atmosphere in the furnace, with the dew point typically controlled below -20°C. This "ultra-low dew point" control requires a large amount of high-purity protective gas (99.9% pure nitrogen), resulting in high costs. More importantly, this extreme atmosphere may not be the optimal choice. At high temperatures of 1080-1120°C, if the oxidizing properties of the furnace gas (i.e., the dew point) can be precisely controlled, a beneficial "oxidation-reduction" dynamic balance may be triggered, leading to unexpected technical effects. Therefore, a method is needed to optimize the inhibitor structure in silicon steel by appropriately controlling the dew point of the normalized process, in order to successfully prepare high-magnetic-induction oriented silicon steel. Summary of the Invention

[0003] To address the aforementioned technical problems, this application provides a method for optimizing the structure of silicon steel inhibitors through dew point regulation, comprising:

[0004] Silicon steel is obtained, and the silicon steel is normalized to obtain optimized silicon steel. The composition of the silicon steel is: C: 0.03%-0.08%, Si: 2.8%-3.5%, Mn: 0.05%-0.15%, S: 0.005%-0.020%, Al: 0.02%-0.04%, N: 0.006%-0.010%, Cu: 0.05%-0.20%, with the remainder being Fe and unavoidable impurities. The normalization temperature is 1080-1120℃, the normalization holding time is 1-3 min, the normalization dew point is 5-35℃, the normalization atmosphere is nitrogen, and the specific cooling method for normalization is: rapid cooling to room temperature at a cooling rate greater than 15℃ / s.

[0005] As a preferred embodiment of the method for optimizing the structure of silicon steel inhibitors through dew point control described in this application, the optimized silicon steel contains inhibitors, the average size of the inhibitors is ≤50nm, and the number density of the inhibitors is ≥2.0×10⁻⁶. 15 pcs / cm 3 The optimized silicon steel has a C content ≤100ppm, and a uniform SiO2 film is formed on the surface of the optimized silicon steel.

[0006] As a preferred embodiment of the method for optimizing the structure of silicon steel inhibitors by dew point regulation as described in this application, the method further includes, before obtaining the silicon steel: obtaining a silicon steel slab, heating, hot rolling, and coiling the silicon steel slab to obtain the silicon steel.

[0007] As a preferred embodiment of the method for optimizing the structure of silicon steel inhibitors by dew point control as described in this application, after obtaining the optimized silicon steel, the method further includes: pickling, cold rolling, decarburizing annealing, coating with MgO, and high-temperature annealing the optimized silicon steel to obtain high magnetic orientation silicon steel.

[0008] As a preferred embodiment of the method for optimizing the structure of silicon steel inhibitors by dew point control as described in this application, the heating temperature is 1250-1400℃, the heating time is 2-5 hours, the final rolling temperature of the hot rolling is 880-950℃, the coiling temperature is 500-600℃, and the pickling method is as follows: the optimized silicon steel is pickled with a hydrochloric acid solution with a concentration of 10%-20% and a temperature of 70-85℃ for 1-3 minutes to remove the surface oxide layer.

[0009] As a preferred embodiment of the method for optimizing the structure of silicon steel inhibitors by dew point control described in this application, the decarburization annealing method specifically involves: holding at 820-850℃ for 2-5 minutes in a nitrogen-hydrogen mixed protective atmosphere; the dew point of the protective atmosphere is controlled at +(45-65)℃, wherein the volume fraction of hydrogen is 20%-35%; the MgO coating method specifically involves: preparing a coating solution by mixing magnesium oxide and water in a weight ratio of 100:(7-9), and uniformly coating it onto the surface of the decarburized annealed steel strip using a roller coating method, with a single-sided coating amount of 4-8 g / m. 2 After coating, dry at 150-300℃.

[0010] As a preferred embodiment of the method for optimizing the structure of silicon steel inhibitors by dew point control as described in this application, the high-temperature annealing method specifically includes: bottom layer formation stage: heating from room temperature to 800-1000℃ at a rate of 10-20℃ / h, and holding at this temperature range for 5-15h; secondary recrystallization stage: continuing to heat to 1150-1250℃ at a rate of 12-25℃ / h, during which the hydrogen gas fraction increases to 50%-100%; high-temperature purification stage: holding at 1200-1250℃ for 15-30h to allow impurity elements to fully volatilize.

[0011] As a preferred embodiment of the method for optimizing the structure of silicon steel inhibitors by dew point regulation as described in this application, the magnetic induction intensity B800 of the high magnetic induction silicon steel reaches above 1.91T, and the iron loss P17 / 50 of the high magnetic induction silicon steel is reduced to below 0.87W / kg.

[0012] As a preferred embodiment of the method for optimizing the structure of silicon steel inhibitors by dew point regulation as described in this application, a uniform magnesium silicate glass film is formed on the surface of the high magnetic induction oriented silicon steel.

[0013] As a preferred embodiment of the method for optimizing the structure of silicon steel inhibitors through dew point regulation described in this application, the high magnetic induction oriented silicon steel has a single, sharp Gaussian texture {110} inside. <001> .

[0014] The beneficial effects of this application are as follows:

[0015] This application provides a method for optimizing the structure of silicon steel inhibitors through dew point control. In a high-temperature RTF furnace at 1080-1120℃, the furnace gas dew point is significantly increased from the traditional below -20℃ to a specific positive dew point range (+5℃ to +35℃). This is not for oxidizing the steel strip, but rather to achieve a synergistic effect of "surface trace oxidation / internal oxidation" and "high-temperature decarburization" through thermodynamic equilibrium control, thereby optimizing inhibitor precipitation kinetics, purifying grain boundaries, and ultimately significantly improving the magnetic properties of the finished product. At the high temperature of 1080-1120℃, the existing coarse inhibitors in the steel will fully dissolve. At this time, a key but often overlooked factor is the influence of "oxygen potential". Trace amounts of oxygen (provided by a positive dew point atmosphere) can penetrate the steel matrix, forming "internal oxidation". These nanoscale oxides (such as SiO2, MnO) can act as heterogeneous nucleation sites for the precipitation of inhibitors (such as Cu2S, MnS), inducing them to precipitate more dispersedly and finer during subsequent cooling. Meanwhile, a moderate oxygen partial pressure can alter the segregation behavior of elements such as sulfur at grain boundaries, optimizing precipitation kinetics. At this high temperature, the diffusion rate of carbon is extremely fast. Based on the reaction C + H₂O... The equilibrium constant of CO+H2 requires a lower water vapor partial pressure (dew point) to achieve the same decarburization effect at higher temperatures. However, under the positive dew point conditions of this application, the water vapor partial pressure is sufficiently high, resulting in a strong driving force for the decarburization reaction to proceed to the right. Therefore, extremely efficient and deep decarburization can be achieved in the RTF furnace stage, reducing the carbon content from the initial 500 ppm to 100 ppm or even lower, greatly reducing the load on the subsequent decarburization annealing furnace. The controllable positive dew point atmosphere forms a uniform SiO2 film on the steel strip surface. This film reacts better with MgO in the subsequent decarburization annealing, forming a higher-quality magnesium silicate glass film underlayer. More importantly, this "slightly pre-oxidized" surface state provides better interface conditions for the surface grain growth behavior in the subsequent decarburization annealing stage, which is conducive to the initiation of secondary recrystallization; the optimal dew point range for the RTF furnace is +5℃ to +35℃. Within this range, effective internal oxidation-induced precipitation and deep decarburization can be achieved while ensuring that excessive surface oxidation does not occur, thus avoiding damage to the surface quality of the steel strip; the protective atmosphere of the RTF furnace is nitrogen (99.9%). By reducing the amount of high-purity nitrogen introduced and precisely controlling the addition of trace amounts of water vapor (or allowing a small amount of air to infiltrate), the dew point can be economically stabilized within the target positive dew point range.

[0016] The advantages of this application are as follows:

[0017] 1. Leapfrog improvement in magnetic properties: By optimizing inhibitor precipitation and early deep decarburization, the magnetic induction intensity B800 of the finished product can be increased by more than 0.02T, and the iron loss P1.7 / 50 can be reduced by more than 0.10W / kg, or even by 0.15W / kg.

[0018] 2. Inhibitor structure optimization: By using "internal oxidation" to induce precipitation, smaller, more dispersed inhibitor particles with higher thermal stability are obtained, and the secondary recrystallization texture is sharper and more perfect.

[0019] 3. Revolutionary simplification of decarburization process: Since most of the decarburization task has been completed in the RTF furnace, the process window for subsequent decarburization annealing is greatly widened, and the annealing time can even be shortened or the annealing temperature can be reduced, thus achieving energy saving and consumption reduction.

[0020] 4. Improved surface quality: The pre-generated thin oxide layer helps to form a more uniform and better-adhesive magnesium silicate glass film.

[0021] 5. Cost advantage: Compared with the high gas costs required by traditional processes to maintain a dew point below -20°C, this application reduces production costs by reducing nitrogen consumption. Detailed Implementation

[0022] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] This application provides a method for optimizing the structure of silicon steel inhibitors through dew point regulation, including:

[0024] Silicon steel is obtained, and the silicon steel is normalized to obtain optimized silicon steel. The composition of the silicon steel is: C: 0.03%-0.08%, Si: 2.8%-3.5%, Mn: 0.05%-0.15%, S: 0.005%-0.020%, Al: 0.02%-0.04%, N: 0.006%-0.010%, Cu: 0.05%-0.20%, with the remainder being Fe and unavoidable impurities. The normalization temperature is 1080-1120℃, the normalization holding time is 1-3 min, the normalization dew point is 5-35℃, the normalization atmosphere is nitrogen, and the specific cooling method for normalization is: rapid cooling to room temperature at a cooling rate greater than 15℃ / s.

[0025] Specifically, the normalization temperature is any one or any two of 1080℃, 1090℃, 1100℃, 1110℃, and 1120℃; the normalization holding time is any one or any two of 1min, 2min, and 3min; and the normalization dew point is any one or any two of 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, and 35℃.

[0026] The optimized silicon steel contains inhibitors, the average size of which is ≤50nm and the number density of which is ≥2.0×10⁻⁶. 15 pcs / cm 3 The optimized silicon steel has a C content ≤100ppm, and a uniform SiO2 film is formed on the surface of the optimized silicon steel.

[0027] Before obtaining the silicon steel, the process further includes: obtaining a silicon steel slab, heating, hot rolling, and coiling the silicon steel slab to obtain the silicon steel. After obtaining the optimized silicon steel, the process further includes: pickling, cold rolling, decarburizing annealing, coating with MgO, and high-temperature annealing of the optimized silicon steel to obtain high magnetic orientation silicon steel.

[0028] The heating temperature is 1250-1400℃, the heating time is 2-5 hours, the hot rolling final rolling temperature is 880-950℃, the coiling temperature is 500-600℃, and the pickling method is as follows: the optimized silicon steel is pickled with a hydrochloric acid solution with a concentration of 10%-20% and a temperature of 70-85℃ for 1-3 minutes to remove the surface oxide layer.

[0029] The decarburization annealing method specifically involves: holding the material at 820-850℃ for 2-5 minutes in a nitrogen-hydrogen mixed protective atmosphere; the dew point of the protective atmosphere is controlled at +(45-65)℃, wherein the volume fraction of hydrogen is 20%-35%; the MgO coating method specifically involves: preparing a coating solution by mixing magnesium oxide and water at a weight ratio of 100:(7-9), and uniformly coating it onto the surface of the decarburized annealed steel strip using a roller coating method, with a single-sided coating amount of 4-8 g / m. 2 After coating, dry at 150-300℃.

[0030] The high-temperature annealing process is as follows: bottom layer formation stage: the temperature is increased from room temperature to 800-1000℃ at a rate of 10-20℃ / h, and held at this temperature for 5-15h; secondary recrystallization stage: the temperature is further increased to 1150-1250℃ at a rate of 12-25℃ / h, during which the hydrogen gas fraction increases to 50%-100%; high-temperature purification stage: the temperature is held at 1200-1250℃ for 15-30h to allow impurity elements to fully volatilize.

[0031] The magnetic induction intensity B800 of the high magnetic induction silicon steel reaches above 1.91T, and the iron loss P17 / 50 of the high magnetic induction silicon steel is reduced to below 0.87W / kg. A uniform magnesium silicate glass film is formed on the surface of the high magnetic induction silicon steel. The interior of the high magnetic induction silicon steel has a single, sharp Gaussian texture {110} <001> .

[0032] The technical solution of this application will be further described below with reference to specific embodiments.

[0033] Example 1

[0034] S1. Obtain silicon steel slabs. The silicon steel slabs are heated, hot-rolled, and normalized to obtain optimized silicon steel. Slab heating: The slab is held at 1320℃ for 4 hours in a walking beam furnace to ensure complete dissolution of the alloying elements. Hot rolling: The heated slab is rolled in multiple passes to a thickness of 2.5mm, with the final rolling temperature controlled at 900℃. It is then coiled at a temperature controlled at 550℃. Normalization is performed at 1100℃ for 2 minutes, with a dew point of 20℃ and a nitrogen atmosphere. The cooling method is rapid cooling to room temperature at a rate greater than 15℃ / s.

[0035] S2. High-magnetic-induction oriented silicon steel is obtained by pickling, cold rolling, decarburizing annealing, coating with MgO, and high-temperature annealing of optimized silicon steel. The pickling process involves using a 15% hydrochloric acid solution at 80°C for 2 minutes to remove the surface oxide layer. The decarburizing annealing process involves holding the steel at 835°C for 4 minutes in a nitrogen-hydrogen mixed protective atmosphere with a dew point controlled at 50°C and a hydrogen volume fraction of 30%. The MgO coating process involves preparing a coating solution by mixing magnesium oxide and water in a weight ratio of 100:8, and then uniformly coating the surface of the decarburized annealed steel strip using a roller coating method, with a single-sided coating amount of 6 g / m². 2 After coating, dry at 250℃; the high-temperature annealing method is as follows: bottom layer formation stage: heat from room temperature to 900℃ at a rate of 15℃ / h, and hold at this temperature for 10 hours; secondary recrystallization stage: continue to heat to 1200℃ at a rate of 20℃ / h, during which the hydrogen gas fraction increases to 75%; high-temperature purification stage: hold at 1225℃ for 22 hours to allow impurity elements to fully volatilize.

[0036] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Example 1 were tested. The results showed that the C content of the optimized silicon steel was ≤100ppm, a uniform SiO2 film was formed on the surface of the optimized silicon steel, the average size of the inhibitor was 22±5nm, and the number density was 3.5×10⁻⁶. 15 pcs / cm 3 The high-magnetic-induction oriented silicon steel has an iron loss P17 / 50 of 0.83 W / kg, a magnetic induction intensity B800 of 1.92 T, no obvious surface defects, and uniform color; the surface of the high-magnetic-induction oriented silicon steel forms a uniform magnesium silicate glass film; the interior has a single, sharp Gaussian texture {110} <001> .

[0037] Example 2

[0038] The difference between this embodiment and Embodiment 1 is that the normalization temperature is 1080℃, the holding time is 3 minutes, the normalization atmosphere is nitrogen, and the normalization dew point is 35℃; all other steps are the same as in Embodiment 1.

[0039] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Example 2 were tested. The results showed that the C content of the optimized silicon steel was ≤100ppm, a uniform SiO2 film was formed on the surface of the optimized silicon steel, the average size of the inhibitor was 28±7nm, and the number density was 2.8×10⁻⁶. 15 pcs / cm 3 The high-magnetic-induction oriented silicon steel has an iron loss P17 / 50 of 0.85 W / kg, a magnetic induction intensity B800 of 1.92 T, no obvious surface defects, and uniform color; the surface of the high-magnetic-induction oriented silicon steel forms a uniform magnesium silicate glass film; the interior has a single, sharp Gaussian texture {110} <001> .

[0040] Example 3

[0041] The difference between this embodiment and Embodiment 1 is that the normalization temperature is 1120℃, the holding time is 1 min, the normalization atmosphere is nitrogen, and the normalization dew point is 5℃; all other steps are the same as in Embodiment 1.

[0042] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Example 3 were tested. The results showed that the C content of the optimized silicon steel was ≤100ppm, a uniform SiO2 film was formed on the surface of the optimized silicon steel, the average size of the inhibitor was 35±5nm, and the number density was 2.0×10⁻⁶. 15 pcs / cm 3 The high-magnetic-induction oriented silicon steel has an iron loss P17 / 50 of 0.87 W / kg, a magnetic induction intensity B800 of 1.91 T, no obvious surface defects, and uniform color; the surface of the high-magnetic-induction oriented silicon steel forms a uniform magnesium silicate glass film; the interior has a single, sharp Gaussian texture {110} <001> .

[0043] Comparative Example 1

[0044] The difference between this comparative example and Example 1 is that the normalized dew point in step S1 is -(25-10)℃; the other steps are the same as in Example 1.

[0045] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Comparative Example 1 were tested. The test results showed that the average size of the inhibitor in the optimized silicon steel was 65±10 nm, and the number density was 0.8×10⁻⁶. 15 pcs / cm 3 The iron loss of high magnetic induction oriented silicon steel P17 / 50 is 0.92W / kg, the magnetic induction intensity B800 is 1.90T, there are a few spot-like gold exposure defects on the surface, and the color is uniform.

[0046] Comparative Example 2

[0047] The difference between this comparative example and Example 1 is that the normalized dew point in step S1 is -(10-0)℃; the other steps are the same as in Example 1.

[0048] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Comparative Example 2 were tested. The test results showed that the average size of the inhibitor in the optimized silicon steel was 60±10 nm, and the number density was 1.0×10⁻⁶. 15 pcs / cm 3 The iron loss of high magnetic induction oriented silicon steel P17 / 50 is 0.92W / kg, the magnetic induction intensity B800 is 1.90T, there are a few spot-like gold exposure defects on the surface, and the color is uniform.

[0049] Comparative Example 3

[0050] The difference between this comparative example and Example 1 is that the normalized dew point in step S1 is -(15-10)℃; the other steps are the same as in Example 1.

[0051] The optimized silicon steel and high-magnetic-permeability oriented silicon steel prepared in Comparative Example 3 were tested. The results showed that the average size of the inhibitor in the optimized silicon steel was 70±10 nm, and the number density was 0.9×10⁻⁶. 15 pcs / cm 3 The iron loss of high magnetic induction oriented silicon steel P17 / 50 is 0.92W / kg, the magnetic induction intensity B800 is 1.90T, there are a few spot-like gold exposure defects on the surface, and the color is uniform.

[0052] Comparative Example 4

[0053] The difference between this comparative example and Example 1 is that the normalized dew point in step S1 is -(20-15)℃; the other steps are the same as in Example 1.

[0054] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Comparative Example 4 were tested. The results showed that the average size of the inhibitor in the optimized silicon steel was 75±20 nm, and the number density was 0.7×10⁻⁶. 15 pcs / cm 3 The iron loss of high magnetic induction oriented silicon steel P17 / 50 is 0.92W / kg, the magnetic induction intensity B800 is 1.89T, there are a few spot-like gold exposure defects on the surface, and the color is uniform.

[0055] Comparative Example 5

[0056] The difference between this comparative example and Example 1 is that the normalized dew point in step S1 is -(30-25)℃; the other steps are the same as in Example 1.

[0057] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Comparative Example 5 were tested. The test results showed that the average size of the inhibitor in the optimized silicon steel was 80±30 nm, and the number density was 0.5×10⁻⁶. 15 pcs / cm 3 The iron loss of high magnetic induction oriented silicon steel P17 / 50 is 0.94W / kg, the magnetic induction intensity B800 is 1.90T, there are a few spot-like gold exposure defects on the surface, and the color is uniform.

[0058] Comparative Example 6

[0059] The difference between this comparative example and Example 1 is that the normalized dew point in step S1 is -(20-10)℃; the other steps are the same as in Example 1.

[0060] The optimized silicon steel and high-magnetic-permeability oriented silicon steel prepared in Comparative Example 6 were tested. The results showed that the average size of the inhibitor in the optimized silicon steel was 58±20 nm, and the number density was 1.2×10⁻⁶. 15 pcs / cm 3 The iron loss of high magnetic induction oriented silicon steel P17 / 50 is 0.92W / kg, the magnetic induction intensity B800 is 1.91T, there are a few spot-like gold exposure defects on the surface, and the color is uniform.

[0061] Comparative Example 7

[0062] The difference between this comparative example and Example 1 is that the normalized dew point in step S1 is 35-45°C; all other steps are the same as in Example 1.

[0063] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Comparative Example 7 were tested. The test results showed that the average size of the inhibitor in the optimized silicon steel was 45±15 nm, and the number density was 1.5×10⁻⁶. 15 pcs / cm 3 The iron loss of high magnetic induction oriented silicon steel P17 / 50 is 0.89W / kg, the magnetic induction intensity B800 is 1.88T, and the surface oxidation color is more obvious.

[0064] Comparative Example 8

[0065] The difference between this comparative example and Example 1 is that the normalization temperature in step S1 is 1020-1060℃; all other steps are the same as in Example 1.

[0066] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Comparative Example 8 were tested. The test results showed that the average size of the inhibitor in the optimized silicon steel was 50±20 nm, and the number density was 1.8×10⁻⁶. 15 pcs / cm 3 The iron loss of high magnetic induction oriented silicon steel P17 / 50 is 0.9W / kg, the magnetic induction intensity B800 is 1.89T, and the surface color is uniform.

[0067] Comparative Example 9

[0068] The difference between this comparative example and Example 1 is that the normalization temperature in step S1 is 1140-1160℃; the other steps are the same as in Example 1.

[0069] The optimized silicon steel and high-magnetic-induction oriented silicon steel prepared in Comparative Example 8 were tested. The test results showed that the average size of the inhibitor in the optimized silicon steel was >100 nm, and the number density was 0.3 × 10⁻⁶. 15 pcs / cm 3 The iron loss of high magnetic induction oriented silicon steel P17 / 50 is 1.05W / kg, the magnetic induction intensity B800 is 1.85T, the surface color is uneven, and it appears black.

[0070] Comparative Example 10

[0071] The difference between this comparative example and Example 1 is that normalization is not performed in step S1, while the other steps are the same as in Example 1.

[0072] The optimized silicon steel and high magnetic induction oriented silicon steel prepared in Comparative Example 10 were tested. The test results were as follows: the inhibitors of the optimized silicon steel were coarse and uneven, and the quantity was extremely low. The iron loss P17 / 50 of the high magnetic induction oriented silicon steel was 1.1 W / kg, the magnetic induction intensity B800 was 1.85 T, and the surface color was uniform.

[0073] As can be seen from the above examples and comparative examples: A comparison of Example 1 with Comparative Examples 1, 5, and 6 shows that when the normalizing annealing dew point is too low (e.g., -25°C to -10°C) or fluctuates too much, the inhibitor precipitation behavior deteriorates, leading to a significant decrease in product magnetic induction and an increase in iron loss. This confirms that an excessively low dew point environment is not conducive to the formation of a sufficient number of thermally stable inhibitors, thus failing to provide effective pinning for secondary recrystallization. A comparison of Example 1 with Comparative Examples 2, 3, and 4 shows that as the normalizing annealing dew point gradually decreases from the preferred range of this application (25-35°C) to the range of -20°C to 0°C, the product magnetic induction shows a downward trend, while iron loss deteriorates. This indicates that the higher dew point range defined in this application is key to obtaining high magnetic induction and low iron loss. A comparison of Examples 1, 2, and 3 shows that within the dew point control range claimed in this application (5-35°C), product performance significantly better than the comparative examples can be obtained. Especially when the dew point is controlled within the preferred range of 25-35℃ (Example 1), the overall performance of the product is optimal, fully verifying the advanced nature and effectiveness of the process parameters of this application. Combined with the above examples and comparative examples, it is shown that precisely controlling the dew point during the normalizing annealing process within the range of 5℃ to 35℃, preferably 25℃ to 35℃, can most effectively optimize the size, distribution, and quantity of inhibitors (mainly AlN, etc.), thereby achieving uniform and persistent pinning of grain boundaries during subsequent high-temperature annealing, promoting Gaussian texture {110} <001> Sufficient secondary recrystallization is essential. This is the fundamental reason for achieving the superior properties of high magnetic induction and low iron loss. This application solves a core problem in the production of high magnetic induction grain-oriented silicon steel by controlling a key and easily adjustable process parameter (dew point), and has significant industrial application value.

[0074] This application provides a method for optimizing the structure of silicon steel inhibitors through dew point control. In a high-temperature RTF furnace at 1080-1120℃, the furnace gas dew point is significantly increased from the traditional below -20℃ to a specific positive dew point range (+5℃ to +35℃). This is not for oxidizing the steel strip, but rather to achieve a synergistic effect of "surface trace oxidation / internal oxidation" and "high-temperature decarburization" through thermodynamic equilibrium control, thereby optimizing inhibitor precipitation kinetics, purifying grain boundaries, and ultimately significantly improving the magnetic properties of the finished product. At the high temperature of 1080-1120℃, the existing coarse inhibitors in the steel will fully dissolve. At this time, a key but often overlooked factor is the influence of "oxygen potential". Trace amounts of oxygen (provided by a positive dew point atmosphere) can penetrate the steel matrix, forming "internal oxidation". These nanoscale oxides (such as SiO2, MnO) can act as heterogeneous nucleation sites for the precipitation of inhibitors (such as Cu2S, MnS), inducing them to precipitate more dispersedly and finer during subsequent cooling. Meanwhile, a moderate oxygen partial pressure can alter the segregation behavior of elements such as sulfur at grain boundaries, optimizing precipitation kinetics. At this high temperature, the diffusion rate of carbon is extremely fast. Based on the reaction C + H₂O... The equilibrium constant of CO+H2 requires a lower water vapor partial pressure (dew point) to achieve the same decarburization effect at higher temperatures. However, under the positive dew point conditions of this application, the water vapor partial pressure is sufficiently high, resulting in a strong driving force for the decarburization reaction to proceed to the right. Therefore, extremely efficient and deep decarburization can be achieved in the RTF furnace stage, reducing the carbon content from the initial 500 ppm to 100 ppm or even lower, greatly reducing the load on the subsequent decarburization annealing furnace. The controllable positive dew point atmosphere forms a uniform SiO2 film on the steel strip surface. This film reacts better with MgO in the subsequent decarburization annealing, forming a higher-quality magnesium silicate glass film underlayer. More importantly, this "slightly pre-oxidized" surface state provides better interface conditions for the surface grain growth behavior in the subsequent decarburization annealing stage, which is conducive to the initiation of secondary recrystallization; the optimal dew point range for the RTF furnace is +5℃ to +35℃. Within this range, effective internal oxidation-induced precipitation and deep decarburization can be achieved while ensuring that excessive surface oxidation does not occur, thus avoiding damage to the surface quality of the steel strip; the protective atmosphere of the RTF furnace is nitrogen (99.9%). By reducing the amount of high-purity nitrogen introduced and precisely controlling the addition of trace amounts of water vapor (or allowing a small amount of air to infiltrate), the dew point can be economically stabilized within the target positive dew point range.

[0075] The advantages of this application are as follows:

[0076] 1. Leapfrog improvement in magnetic properties: By optimizing inhibitor precipitation and early deep decarburization, the magnetic induction intensity B800 of the finished product can be increased by more than 0.02T, and the iron loss P1.7 / 50 can be reduced by more than 0.10W / kg, or even by 0.15W / kg.

[0077] 2. Inhibitor structure optimization: By using "internal oxidation" to induce precipitation, smaller, more dispersed inhibitor particles with higher thermal stability are obtained, and the secondary recrystallization texture is sharper and more perfect.

[0078] 3. Revolutionary simplification of decarburization process: Since most of the decarburization task has been completed in the RTF furnace, the process window for subsequent decarburization annealing is greatly widened, and the annealing time can even be shortened or the annealing temperature can be reduced, thus achieving energy saving and consumption reduction.

[0079] 4. Improved surface quality: The pre-generated thin oxide layer helps to form a more uniform and better-adhesive magnesium silicate glass film.

[0080] 5. Cost advantage: Compared with the high gas costs required by traditional processes to maintain a dew point below -20°C, this application reduces production costs by reducing nitrogen consumption.

[0081] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method of optimizing a silicon steel suppressor structure by dew point conditioning, characterized by, The application relates to a method for preparing high-magnetic-induction oriented silicon steel. The method comprises the following steps: obtaining silicon steel, normalizing the silicon steel to obtain optimized silicon steel, wherein the composition of the silicon steel is as follows: C: 0.03%-0.08%, Si: 2.8%-3.5%, Mn: 0.05%-0.15%, S: 0.005%-0.020%, Al: 0.02%-0.04%, N: 0.006%-0.010%, Cu: 0.05%-0.20%, and the rest is Fe and inevitable impurities; the normalizing temperature is 1080-1120 DEG C, the normalizing holding time is 1-3 min, the dew point of the normalizing is 5-35 DEG C, the normalizing atmosphere is nitrogen, and the normalizing cooling mode is specifically as follows: the cooling rate is greater than 15 DEG C / s to rapidly cool to room temperature; Before the step of obtaining the silicon steel, the method further comprises the following steps: obtaining a silicon steel slab, heating the silicon steel slab, hot rolling the silicon steel slab, and coiling the silicon steel slab to obtain the silicon steel. After the step of obtaining the optimized silicon steel, the method further comprises the following steps: pickling the optimized silicon steel, cold rolling the optimized silicon steel, decarburization annealing the optimized silicon steel, coating the optimized silicon steel with MgO, and high-temperature annealing the optimized silicon steel to obtain high-magnetic-induction oriented silicon steel. The decarburization annealing is performed in a nitrogen-hydrogen mixed protective atmosphere at a temperature of 820-850 DEG C for 2-5 min, the dew point of the protective atmosphere is controlled at + (45-65) DEG C, the volume fraction of hydrogen is 20-35%, the MgO coating is prepared by mixing magnesium oxide and water in a weight ratio of 100: (7-9), the coating liquid is uniformly coated on the surface of the steel strip after decarburization annealing by roll coating, the single-side coating amount is 4-8 g / m 2 , and drying treatment is performed at 150-300 DEG C after coating. The high-temperature annealing mode is specifically as follows: bottom layer forming stage: the temperature is increased from room temperature to 800-1000 DEG C at a rate of 10-20 DEG C / h, and the temperature is kept in the temperature range for 5-15 h; secondary recrystallization stage: the temperature is continuously increased to 1150-1250 DEG C at a rate of 12-25 DEG C / h, and the hydrogen volume fraction is increased to 50%-100% in the stage; high-temperature purification stage: the temperature is kept at 1200-1250 DEG C for 15-30 h to make impurity elements sufficiently volatilize.

2. A method of optimizing the inhibitor structure of silicon steel by dew point regulation as claimed in claim 1, wherein, The optimized silicon steel contains inhibitors with an average size of ≤ 50 nm, a number density of ≥ 2.0 x 10 15 3 9 / cm2, a C content of ≤ 100 ppm, and a uniform SiO2 film formed on the surface of the optimized silicon steel.

3. A method of optimizing the inhibitor structure of silicon steel by dew point regulation as claimed in claim 1, wherein, The heating temperature is 1250-1400 DEG C, the heating time is 2-5 h, the final rolling temperature of the hot rolling is 880-950 DEG C, the coiling temperature is 500-600 DEG C, and the pickling mode is specifically as follows: the optimized silicon steel is pickled by using a hydrochloric acid solution with a concentration of 10%-20% and a temperature of 70-85 DEG C for 1-3 min to remove the surface oxide layer.

4. A method of optimizing the inhibitor structure of silicon steel by dew point regulation as claimed in claim 1, wherein, The magnetic induction intensity B800 of the high-magnetic-induction oriented silicon steel reaches 1.91 T or more, and the iron loss P17 / 50 of the high-magnetic-induction oriented silicon steel is reduced to 0.87 W / kg or less.

5. A method of optimizing the inhibitor structure of silicon steel by dew point regulation as claimed in claim 1, wherein, The surface of the high-magnetic-induction oriented silicon steel forms a uniform magnesium silicate glass film.

6. A method of optimizing the inhibitor structure of silicon steel by dew point regulation as claimed in claim 1, wherein, The high-magnetic-induction oriented silicon steel has a single and sharp Gaussian texture {110} <001> in the interior.