High temperature annealing method of grain-oriented silicon steel

Abstract

The application provides a high-temperature annealing method of oriented silicon steel and relates to the technical field of steel material heat treatment, and the method comprises the following steps: in the case that a trolley is located at a first stage position in an annealing furnace, the volume ratio of nitrogen and hydrogen in the annealing furnace is adjusted to be 50% respectively; and the temperature in the annealing furnace is adjusted from low to high, and the temperature adjustment range is 700 DEG C to 1200 DEG C; in the case that the trolley is located at a second stage position in the annealing furnace, the volume ratio of hydrogen in the annealing furnace is adjusted to be 100%; and the temperature in the annealing furnace is adjusted from high to low, and the temperature adjustment range is 1200 DEG C to 660 DEG C; and the trolley is located at the first stage position and the second stage position in sequence.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for steel materials, and in particular to a high-temperature annealing method for grain-oriented silicon steel. Background Technology

[0002] The dual-car continuous annealing process enables more precise atmosphere control. During annealing, with the continuous operation of the two cars, the furnace atmosphere composition, concentration, and flow rate can be adjusted in real time according to the needs of different stages. In the early stages of annealing, a high-concentration reducing atmosphere is introduced to quickly remove the oxide layer on the silicon steel surface; in the later stages of annealing, the atmosphere composition is adjusted to promote the optimization of the silicon steel's crystal structure. In contrast, existing annealing processes struggle to achieve such precise atmosphere control. Furthermore, they often neglect the synergistic optimization of temperature control and atmosphere concentration, making it difficult to fully exploit the performance potential of silicon steel, resulting in bottlenecks in product yield and magnetic property improvement.

[0003] In the prior art, such as Chinese invention patent CN2521566Y, a single (double) row tunnel-type online gas protection hood continuous annealing furnace is disclosed. In the RP (Reverse Rotation) section, hot nitrogen is used to purge the cold air inside the hood to minimize the oxygen and moisture content. When the annealing train enters the heating tunnel, the online gas protection system continuously replenishes nitrogen to each annealing train, maintaining a slight positive pressure of nitrogen in each hood to achieve online gas protection. The annealing train moves slowly forward in sequence under the intermittent pushing of the trolley device. Several pairs of upper and lower burners inside the heating tunnel continuously heat the heat-resistant steel inner hood and the metal materials within it according to process requirements, using preheating, weak heating, strong heating, and uniform temperature control. However, the aforementioned prior art does not disclose the synergistic optimization of temperature control and atmosphere concentration. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the present invention aims to provide a high-temperature annealing method for grain-oriented silicon steel, which can be perfectly coordinated with existing temperature control through the differentiation of atmosphere concentration in each stage, thereby significantly improving the product qualification rate and magnetic properties.

[0005] To achieve the above-mentioned objective, this invention provides a high-temperature annealing method for grain-oriented silicon steel, the method comprising:

[0006] With the grain-oriented silicon steel in the first stage position in the annealing furnace, the volume ratio of nitrogen and hydrogen in the annealing furnace is adjusted to 50% each; and the temperature in the annealing furnace is adjusted from low to high, with the temperature adjustment range being 700℃~1200℃.

[0007] With the oriented silicon steel in the second stage position in the annealing furnace, the volume ratio of hydrogen in the annealing furnace is adjusted to 100%; and the temperature in the annealing furnace is adjusted from high to low, with the temperature adjustment range being 1200℃~660℃.

[0008] The oriented silicon steel is located in the first stage position and the second stage position respectively.

[0009] According to one technical solution of the present invention, it further includes:

[0010] When the grain-oriented silicon steel is in the zero stage position in the annealing furnace, the volume ratio of nitrogen in the annealing furnace is adjusted to 100%; and the temperature in the annealing furnace is adjusted from low to high, with the temperature adjustment range being 550℃~700℃.

[0011] The oriented silicon steel is located successively in the zero-stage position and the first-stage position.

[0012] According to one technical solution of the present invention, it further includes:

[0013] With the grain-oriented silicon steel in the third stage of the annealing furnace, the volume ratio of nitrogen in the annealing furnace is adjusted to 100%; and the temperature in the annealing furnace is adjusted from high to low, with the temperature adjustment range being 570°C to room temperature.

[0014] The oriented silicon steel is located in the second stage position and the third stage position respectively.

[0015] According to one technical solution of the present invention, the first stage location is the T3 to T16 positions inside the annealing furnace;

[0016] The parking space is the location of the trolley that carries the oriented silicon steel;

[0017] With the grain-oriented silicon steel located at positions T3 to T7, adjust the temperature inside the annealing furnace to 700℃±5℃;

[0018] With the grain-oriented silicon steel in position T8, adjust the temperature inside the annealing furnace to 775℃±5℃.

[0019] With the grain-oriented silicon steel in position T9, adjust the temperature inside the annealing furnace to 850℃±3℃.

[0020] With the grain-oriented silicon steel in position T10, adjust the temperature inside the annealing furnace to 925℃±3℃.

[0021] With the grain-oriented silicon steel in position T11, adjust the temperature inside the annealing furnace to 1000℃±3℃.

[0022] With the grain-oriented silicon steel in position T12, adjust the temperature inside the annealing furnace to 1050℃±3℃.

[0023] With the grain-oriented silicon steel in position T13, adjust the temperature inside the annealing furnace to 1100℃±3℃.

[0024] With the grain-oriented silicon steel in position T14, adjust the temperature inside the annealing furnace to 1180℃±3℃.

[0025] With the oriented silicon steel located at positions T15 to T16, adjust the temperature inside the annealing furnace to 1200℃±3℃.

[0026] According to one technical solution of the present invention, the second stage location is car positions T17 to T28 within the annealing furnace;

[0027] With the grain-oriented silicon steel located at positions T17 to T20, adjust the temperature inside the annealing furnace to 1200℃±3℃.

[0028] With the grain-oriented silicon steel in position T21, adjust the temperature inside the annealing furnace to 1140℃±3℃;

[0029] With the grain-oriented silicon steel in position T22, adjust the temperature inside the annealing furnace to 1080℃±3℃.

[0030] With the grain-oriented silicon steel in position T23, adjust the temperature inside the annealing furnace to 1020℃±3℃.

[0031] With the grain-oriented silicon steel in position T24, adjust the temperature inside the annealing furnace to 960℃±3℃;

[0032] With the grain-oriented silicon steel in position T25, adjust the temperature inside the annealing furnace to 900℃±3℃;

[0033] With the grain-oriented silicon steel in position T26, adjust the temperature inside the annealing furnace to 840℃±3℃.

[0034] With the grain-oriented silicon steel in position T27, adjust the temperature inside the annealing furnace to 750℃±3℃;

[0035] With the grain-oriented silicon steel in position T28, adjust the temperature inside the annealing furnace to 660℃±3℃.

[0036] According to one technical solution of the present invention, the zero-stage position is the T1 to T2 positions within the annealing furnace;

[0037] With the grain-oriented silicon steel in position T1, adjust the temperature inside the annealing furnace to 550℃±5℃.

[0038] With the grain-oriented silicon steel in position T2, adjust the temperature inside the annealing furnace to 700℃±5℃.

[0039] According to one technical solution of the present invention, the third stage is located at positions T29 to T31 inside the annealing furnace;

[0040] With the grain-oriented silicon steel in position T29, adjust the temperature inside the annealing furnace to 570℃±5℃.

[0041] With the grain-oriented silicon steel located at positions T30 to T31, adjust the temperature inside the annealing furnace to room temperature.

[0042] According to one technical solution of the present invention,

[0043] With the grain-oriented silicon steel located at positions T1 to T2, adjust the furnace pressure in the annealing furnace to 300 Pa.

[0044] With the oriented silicon steel located at positions T3 to T31, adjust the furnace pressure inside the annealing furnace to 200 Pa.

[0045] According to one technical solution of the present invention, the working time of the oriented silicon steel in each of the T1 to T31 parking spaces is 5 to 7 hours.

[0046] According to one technical solution of the present invention, when the oriented silicon steel is located in the T1 to T2 parking positions, nitrogen gas with a volume of 20 cubic meters under standard atmospheric pressure is introduced;

[0047] With the oriented silicon steel located in positions T3 to T9, nitrogen and hydrogen, each with a volume of 8 cubic meters under standard atmospheric pressure, are introduced.

[0048] With the oriented silicon steel located in positions T10 to T16, nitrogen and hydrogen, each with a volume of 6 cubic meters under standard atmospheric pressure, are introduced.

[0049] With the oriented silicon steel located in positions T17 to T22, hydrogen gas with a volume of 8 cubic meters under standard atmospheric pressure is introduced.

[0050] With the oriented silicon steel located in positions T23 to T28, 12 cubic meters of hydrogen gas at standard atmospheric pressure is introduced.

[0051] With the grain-oriented silicon steel located in positions T29 to T31, nitrogen gas with a volume of 20 cubic meters under standard atmospheric pressure is introduced.

[0052] The volume of the annealing furnace shroud corresponding to each parking space is 9.1 m³. 3 .

[0053] Compared with the prior art, the present invention has the following advantages:

[0054] This invention provides a high-temperature annealing method for grain-oriented silicon steel. Based on the characteristics of grain-oriented silicon steel, during a tunnel-type dual-carriage continuous high-temperature annealing process, precise control of the microstructure and properties of the grain-oriented silicon steel is achieved through staged atmosphere control. Regarding the control of the nitrogen and hydrogen concentration ratio, the optimal concentration ratio range of nitrogen and hydrogen at different annealing stages is precisely determined.

[0055] Precise matching of temperature control and atmosphere concentration. The annealing process is divided into multiple stages, and different atmosphere concentrations are set for the temperature characteristics of each stage. In the annealing preheating stage, a lower atmosphere concentration is used to avoid premature over-reaction on the silicon steel surface, while slow heating lays a stable foundation for subsequent processes. In the core stage of high-temperature annealing, the atmosphere concentration is increased to allow the silicon steel to fully complete key reactions such as recrystallization in a suitable atmosphere, promoting grain growth and texture optimization. In the cooling stage, the atmosphere concentration is adjusted again to prevent oxidation of the silicon steel surface and ensure its surface quality and magnetic properties.

[0056] By perfectly coordinating differentiated atmosphere concentrations across different sections with existing temperature control, product yield and magnetic properties can be significantly improved. On one hand, precise atmosphere concentration control reduces product defects caused by unsuitable atmospheres, thus increasing the product yield. On the other hand, the optimized atmosphere environment creates favorable conditions for improving the magnetic properties of silicon steel, effectively improving its permeability, reducing iron loss, and enabling the product to achieve a higher level of performance. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0058] Figure 1 This diagram schematically illustrates a parking area in a high-temperature annealing method for grain-oriented silicon steel according to an embodiment of the present invention.

[0059] Figure 2 The flowchart schematically illustrates a high-temperature annealing method for grain-oriented silicon steel according to an embodiment of the present invention. Detailed Implementation

[0060] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0061] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0062] like Figures 1-2 As shown, the present invention provides a high-temperature annealing method for grain-oriented silicon steel, the method comprising:

[0063] With the grain-oriented silicon steel in the first stage of the annealing furnace, the volume ratio of nitrogen and hydrogen in the annealing furnace is adjusted to 50% each; and the temperature in the annealing furnace is adjusted from low to high, with a temperature range of 700℃~1200℃.

[0064] When the grain-oriented silicon steel is in the second stage position in the annealing furnace, the volume ratio of hydrogen in the annealing furnace is adjusted to 100%; and the temperature in the annealing furnace is adjusted from high to low, with the temperature adjustment range being 1200℃~660℃.

[0065] Grain-oriented silicon steel is located in the first stage and the second stage, respectively.

[0066] In this embodiment, the oriented silicon steel semi-finished product is further processed by carrying the oriented silicon steel semi-finished product coil on a trolley and processing it in a high-temperature annealing furnace according to the following stage process.

[0067] Specifically, when the trolley is in the first stage position, it is in the preheating and heating stage of high-temperature annealing of oriented silicon steel. By precisely adjusting the ratio of N2 and H2, the hydrogen concentration ratio is stabilized at 50%, ensuring that the silicon steel can be heated steadily according to the predetermined heating rate. This avoids abnormal heating or process interruption caused by unsuitable atmosphere, improves the stability and continuity of the annealing process, and thus improves the overall production efficiency.

[0068] When the trolley is in the second stage, it is in the core stage of high-temperature annealing for grain-oriented silicon steel, ensuring a 100% hydrogen concentration. This creates an ideal atmosphere for the recrystallization and grain growth of the silicon steel. The pure H2 atmosphere helps promote uniform grain growth and texture optimization in silicon steel, effectively reduces iron loss, increases magnetic permeability, and significantly enhances the magnetic properties of grain-oriented silicon steel, meeting the demand for high-magnetic-performance silicon steel in high-end electrical equipment.

[0069] This embodiment provides a more suitable environment for silicon steel annealing through precise atmosphere control, effectively reducing the generation of defects such as oxidation, and improving the product qualification rate and the stability of magnetic properties.

[0070] High-temperature annealing methods for grain-oriented silicon steel also include:

[0071] When the grain-oriented silicon steel is in the zero stage position in the annealing furnace, the volume ratio of nitrogen in the annealing furnace is adjusted to 100%; and the temperature in the annealing furnace is adjusted from low to high, with the temperature adjustment range being 550℃~700℃.

[0072] Grain-oriented silicon steel is located in the zero stage and the first stage, respectively.

[0073] In this embodiment, the zero stage is the preheating stage. N2 is used to purge and replace the air in the furnace to prevent oxidation. This avoids the silicon steel from coming into contact with harmful gases such as oxygen during the annealing process, reduces the generation of defects such as surface oxidation and cracks, ensures the surface quality of the silicon steel, and improves the appearance quality and yield of the product.

[0074] High-temperature annealing methods for grain-oriented silicon steel also include:

[0075] With the grain-oriented silicon steel in the third stage of the annealing furnace, the volume ratio of nitrogen in the annealing furnace is adjusted to 100%; and the temperature in the annealing furnace is adjusted from high to low, with the temperature range being 570℃ to room temperature.

[0076] Grain-oriented silicon steel is located in the second stage and the third stage, respectively.

[0077] In this embodiment, the third stage is the cooling stage. By reintroducing N2 to prevent oxidation, the silicon steel is prevented from coming into contact with harmful gases such as oxygen during the annealing process. This reduces the generation of defects such as surface oxidation and cracks, ensures the surface quality of the silicon steel, and improves the appearance quality and yield of the product.

[0078] In the high-temperature annealing method for grain-oriented silicon steel, the first stage is located at positions T3 to T16 inside the annealing furnace;

[0079] The parking space is the location of the trolley that carries the oriented silicon steel;

[0080] With the grain-oriented silicon steel located at positions T3 to T7, adjust the temperature inside the annealing furnace to 700℃±5℃;

[0081] With the grain-oriented silicon steel in position T8, adjust the temperature inside the annealing furnace to 775℃±5℃.

[0082] With the grain-oriented silicon steel in position T9, adjust the temperature inside the annealing furnace to 850℃±3℃.

[0083] With the grain-oriented silicon steel in position T10, adjust the temperature inside the annealing furnace to 925℃±3℃.

[0084] With the grain-oriented silicon steel in position T11, adjust the temperature inside the annealing furnace to 1000℃±3℃.

[0085] With the grain-oriented silicon steel in position T12, adjust the temperature inside the annealing furnace to 1050℃±3℃.

[0086] With the grain-oriented silicon steel in position T13, adjust the temperature inside the annealing furnace to 1100℃±3℃.

[0087] With the grain-oriented silicon steel in position T14, adjust the temperature inside the annealing furnace to 1180℃±3℃.

[0088] With the oriented silicon steel located at positions T15 to T16, adjust the temperature inside the annealing furnace to 1200℃±3℃.

[0089] In this embodiment, the T3-T16 parking space stage is the preheating and temperature rise stage.

[0090] The T3-T16 positions mentioned above are the locations of the trolleys that carry the semi-finished coils of grain-oriented silicon steel; including the positions below, there are a total of T1 to T31 positions, which are arranged sequentially in the annealing furnace, with different positions where the trolleys are parked, and different positions are used for corresponding annealing processes.

[0091] In this embodiment, during the preheating and heating stages (T3-T16 positions), the ratio of N2 and H2 is precisely adjusted to stabilize the hydrogen concentration at 50%, ensuring that the silicon steel can be heated steadily at the predetermined heating rate. This avoids abnormal heating or process interruption caused by unsuitable atmosphere, improves the stability and continuity of the annealing process, and thus enhances overall production efficiency.

[0092] Specifically, the preheating and heating phase begins at car position T3. During this phase, the flow rates of N2 and hydrogen (H2) need to be gradually adjusted to maintain a stable hydrogen concentration of 50% and reduce the furnace pressure from 300 Pa to 200 Pa and maintain this level. At car position T3, the N2 flow rate is reduced to 8, and H2 begins to flow at 8. The N2 and H2 contents at subsequent car positions are then gradually fine-tuned according to the data in the table.

[0093] During operation, precise control of the N2 and H2 flow rates is crucial. By adjusting the flow control valves on their respective pipelines, and with real-time data feedback from the mass flow meter, it is essential to ensure the two gases are mixed in the correct proportions. For example, when adjusting the flow rate, the valves should be operated slowly to avoid excessive fluctuations in the hydrogen concentration ratio due to sudden flow changes. After each flow rate adjustment, wait 3-5 minutes for the gases to mix evenly and the system to stabilize. Then, recheck the hydrogen concentration ratio and furnace pressure. If the requirements are not met, continue fine-tuning. Simultaneously, closely monitor the furnace temperature rise, as changes in the atmosphere ratio affect the heating rate. Ensure the heating process is stable and meets process requirements.

[0094] During the initial reduction stage of annealing (T3-T9 stage), the hydrogen concentration is adjusted to 50% of the total gas ratio, and the nitrogen concentration is adjusted accordingly to 50% of the total gas ratio. The strong reducing properties of hydrogen are used to effectively remove the oxide layer on the surface of silicon steel, while inhibiting the formation of new oxide layers and ensuring the purity of the silicon steel surface.

[0095] During the crystal structure optimization stage in the middle of annealing (T9-T16), the concentrations of hydrogen and nitrogen can be fine-tuned according to the specific composition and performance requirements of the silicon steel. This provides a stable protective atmosphere for the growth of silicon steel crystals, promotes more regular crystal orientation, and significantly improves the magnetic permeability of the silicon steel.

[0096] The method described above for precisely controlling the ratio of nitrogen and hydrogen concentrations in stages is key to improving the performance of grain-oriented silicon steel, reducing hysteresis loss by 15%-20%. It also ensures the surface quality of the silicon steel, improving the product's appearance and yield.

[0097] In the high-temperature annealing method for grain-oriented silicon steel, the second stage is located at positions T17 to T28 within the annealing furnace.

[0098] With the grain-oriented silicon steel located at positions T17 to T20, adjust the temperature inside the annealing furnace to 1200℃±3℃.

[0099] With the grain-oriented silicon steel in position T21, adjust the temperature inside the annealing furnace to 1140℃±3℃;

[0100] With the grain-oriented silicon steel in position T22, adjust the temperature inside the annealing furnace to 1080℃±3℃;

[0101] With the grain-oriented silicon steel in position T23, adjust the temperature inside the annealing furnace to 1020℃±3℃.

[0102] With the grain-oriented silicon steel in position T24, adjust the temperature inside the annealing furnace to 960℃±3℃;

[0103] With the grain-oriented silicon steel in position T25, adjust the temperature inside the annealing furnace to 900℃±3℃;

[0104] With the grain-oriented silicon steel in position T26, adjust the temperature inside the annealing furnace to 840℃±3℃.

[0105] With the grain-oriented silicon steel in position T27, adjust the temperature inside the annealing furnace to 750℃±3℃;

[0106] With the grain-oriented silicon steel in position T28, adjust the temperature inside the annealing furnace to 660℃±3℃.

[0107] In this embodiment, the T17-T28 stage is the core stage of high-temperature annealing.

[0108] Specifically, this embodiment achieves a 100% hydrogen concentration during the core high-temperature annealing stage (T17-T28 positions), creating an ideal atmospheric environment for the recrystallization and grain growth of silicon steel. The pure H2 atmosphere helps promote uniform grain growth and texture optimization in silicon steel, effectively reducing iron loss, increasing magnetic permeability, and significantly enhancing the magnetic properties of grain-oriented silicon steel, thus meeting the demand for high-magnetic-performance silicon steel in high-end electrical equipment.

[0109] Car positions T17-T28 are in the core stage of high-temperature annealing. At this time, N2 is stopped and H2 is introduced completely, with the hydrogen concentration reaching 100%. The furnace pressure is maintained at 200 Pa to promote recrystallization and grain growth of silicon steel, thereby improving its magnetic properties. Starting from car position T17, the H2 introduction rate is gradually adjusted according to the data in the table. For example, the H2 introduction rate for cars T17 and T18 is 8, and the H2 introduction rate for cars T23-T28 is increased to 12.

[0110] During this stage of operation, first ensure the N2 valve is completely closed to prevent N2 from contaminating the H2 purity. Then, slowly increase the opening of the H2 valve to allow H2 to flow smoothly into the furnace. Because pure H2 atmosphere is flammable and explosive, extreme caution is required during operation; open flames, static electricity, and other ignition sources are strictly prohibited in the operating area. Simultaneously, continuously monitor the H2 flow rate, hydrogen concentration ratio, and furnace pressure to ensure the H2 flow rate remains stable at the set value, the hydrogen concentration ratio is consistently maintained at 100%, and the furnace pressure remains stable at 200 Pa. If any abnormal fluctuations in parameters are detected, immediately inspect the gas pipelines, valves, and instruments to eliminate potential faults and ensure the safe and efficient execution of the high-temperature annealing process.

[0111] In the high-temperature annealing method for grain-oriented silicon steel, the zero stage is located at positions T1 to T2 within the annealing furnace;

[0112] With the grain-oriented silicon steel in position T1, adjust the temperature inside the annealing furnace to 550℃±5℃.

[0113] With the grain-oriented silicon steel in position T2, adjust the temperature inside the annealing furnace to 700℃±5℃.

[0114] In this embodiment, the T1-T2 stage is the furnace purging and replacement stage.

[0115] At the T1-T2 positions, the main task at this stage is to purge the furnace with nitrogen (N2) to fully replace the air inside, creating an oxygen-free environment for the subsequent silicon steel annealing and preventing oxidation of the silicon steel. According to the table data, the N2 flow rate at positions T1 and T2 is set to 20 m³, H2 is kept off, and the furnace pressure is stabilized at 300 Pa.

[0116] In practice, first slowly open the N2 gas pipeline valve to allow the N2 gas to flow steadily into the furnace at a low flow rate, avoiding excessive impact force caused by excessive gas flow rate, which could damage the silicon steel coil. Simultaneously, monitor the oxygen content inside the furnace in real time. When the oxygen content drops below 1%, the air replacement in the furnace can be considered basically complete. Throughout the purging process, continuously observe changes in furnace pressure. Adjust the N2 inlet flow rate or exhaust valve to ensure the furnace pressure remains stable at 300 Pa, preventing abnormal furnace pressure from affecting the purging effect or causing safety issues.

[0117] In this embodiment, N2 is used to purge and replace the air in the furnace during the preheating stage (T1-T2 positions) to prevent oxidation. This avoids the silicon steel from coming into contact with harmful gases such as oxygen during the annealing process, reduces the generation of defects such as surface oxidation and cracks, ensures the surface quality of the silicon steel, and improves the appearance quality and yield of the product.

[0118] In the high-temperature annealing method for grain-oriented silicon steel, the third stage is located at positions T29 to T31 inside the annealing furnace;

[0119] With the trolley positioned at car T29, adjust the temperature inside the annealing furnace to 570℃±5℃.

[0120] With the trolley positioned between positions T30 and T31, adjust the temperature inside the annealing furnace to room temperature.

[0121] In this embodiment, the T29-T31 parking space stage is the cooling stage.

[0122] During the cooling phase at car positions T29-T31, the H2 valve must be gradually closed to stop the H2 supply, and N2 must be reintroduced to reduce the hydrogen concentration to 0%, maintaining the furnace pressure at 200 Pa to prevent oxidation of the silicon steel during cooling. At car position T29, the N2 supply is restored to 20, and the H2 supply is reduced to 0.

[0123] During operation, first slowly close the H2 valve, closely monitoring furnace pressure changes during the closing process to prevent pressure fluctuations caused by a sudden decrease in H2 flow. After the H2 valve is completely closed, slowly open the N2 valve, introducing N2 at a small flow rate. Once the furnace atmosphere stabilizes, adjust the N2 flow rate to the set value. Continuously monitor the furnace temperature and adjust the N2 flow rate and furnace pressure as needed based on the required cooling rate. Simultaneously, prepare for appearance and performance testing of the cooled silicon steel to ensure its quality meets standards. Throughout the entire cooling process, maintain a high level of safety awareness to prevent accidents caused by residual H2.

[0124] In this embodiment, N2 is reintroduced during the cooling stage (T29-T31 positions) to prevent oxidation. This avoids the silicon steel from coming into contact with harmful gases such as oxygen during the annealing process, reduces the generation of defects such as surface oxidation and cracks, ensures the surface quality of the silicon steel, and improves the appearance quality and yield of the product.

[0125] In the high-temperature annealing method for grain-oriented silicon steel, when the grain-oriented silicon steel is located at position T1 to position T2, the furnace pressure in the annealing furnace is adjusted to 300 Pa.

[0126] With the oriented silicon steel located at positions T3 to T31, adjust the furnace pressure inside the annealing furnace to 200 Pa.

[0127] In the high-temperature annealing method for grain-oriented silicon steel, the working time for grain-oriented silicon steel at each of the T1 to T31 positions is 5 to 7 hours.

[0128] In this embodiment, the working time for each parking space is 5 to 7 hours, which can be 6 hours, for a total working time of 31*6=186 hours.

[0129] In the high-temperature annealing method for grain-oriented silicon steel, when the grain-oriented silicon steel is located at T1 position to T2 position, nitrogen gas with a volume of 20 cubic meters under standard atmospheric pressure is introduced.

[0130] With the oriented silicon steel located in positions T3 to T9, nitrogen and hydrogen, each with a volume of 8 cubic meters under standard atmospheric pressure, are introduced.

[0131] With the oriented silicon steel located in positions T10 to T16, nitrogen and hydrogen, each with a volume of 6 cubic meters under standard atmospheric pressure, are introduced.

[0132] With the oriented silicon steel located in positions T17 to T22, hydrogen gas with a volume of 8 cubic meters under standard atmospheric pressure is introduced.

[0133] With the oriented silicon steel located in positions T23 to T28, 12 cubic meters of hydrogen gas at standard atmospheric pressure is introduced.

[0134] With the grain-oriented silicon steel located in positions T29 to T31, nitrogen gas with a volume of 20 cubic meters under standard atmospheric pressure is introduced.

[0135] The volume of the annealing furnace shroud corresponding to each parking space is 9.1 m³. 3 .

[0136] In summary, the atmosphere and furnace pressure settings for each stage of the present invention are shown in Table 1:

[0137] Table 1

[0138]

[0139] Furthermore, the temperature control range for each parking space is shown in Table 2:

[0140] Table 2

[0141]

[0142] The high-temperature annealing method for grain-oriented silicon steel of the present invention is capable of:

[0143] 1. Optimized Magnetic Properties: By precisely controlling the ratio of hydrogen (H2) and nitrogen (N2) at different annealing stages, such as achieving a 100% hydrogen concentration during the core high-temperature annealing stage (T17-T28), an ideal atmospheric environment is created for the recrystallization and grain growth of silicon steel. A pure H2 atmosphere helps promote uniform grain growth and texture optimization in silicon steel, effectively reducing iron loss, increasing magnetic permeability, and significantly enhancing the magnetic properties of grain-oriented silicon steel, meeting the demands of high-end electrical equipment for high-magnetic-performance silicon steel.

[0144] 2. Ensure surface quality: Atmosphere parameters are set reasonably at different stages of annealing. For example, in the preheating stage (T1-T2 positions), N2 is used to purge and replace the air in the furnace, and in the cooling stage (T29-T31 positions), N2 is reintroduced to prevent oxidation. This avoids the silicon steel from coming into contact with harmful gases such as oxygen during the annealing process, reduces the generation of defects such as surface oxidation and cracks, ensures the surface quality of silicon steel, and improves the appearance quality and yield of the product.

[0145] 3. Precise Process Matching: Based on the characteristics of each stage of silicon steel annealing, differentiated atmosphere schemes are designed and closely coordinated with process steps such as temperature control. For example, in the preheating and heating stages (T3-T16 positions), the ratio of N2 and H2 is precisely adjusted to ensure that the hydrogen concentration is stabilized at 50%, ensuring that the silicon steel can be heated steadily according to the predetermined heating rate. This avoids abnormal heating or process interruption caused by unsuitable atmosphere, improves the stability and continuity of the annealing process, and thus enhances overall production efficiency.

[0146] 4. Reduced process adjustment time: The atmosphere design scheme has been optimized, and the atmosphere parameters at each stage are clear and reasonable. In actual production, operators can quickly and accurately carry out the atmosphere introduction operation according to the scheme, reducing the time wasted in figuring out the atmosphere parameters, shortening the production preparation cycle, enabling the equipment to operate more efficiently, and increasing the output per unit time.

[0147] 5. Conserving Gas Resources: The use of N2 and H2 has been meticulously designed, with gas introduced only as needed at different stages. For example, H2 is not introduced during stages where it is not needed (T1-T2 parking spaces), and N2 is reused during the cooling stage, avoiding unnecessary gas consumption and reducing gas procurement costs. At the same time, rational gas use also reduces the amount of exhaust gas to be treated, lowering exhaust gas treatment costs.

[0148] 6. Reduced defect rate: This atmosphere design effectively improves product performance and surface quality, reducing the number of defective and scrap products caused by quality issues, thus reducing raw material waste and saving production costs. Simultaneously, improved product quality also reduces rework and repair costs in subsequent processing, further lowering overall production costs.

[0149] Table 3 shows the average product pass rate and product defects for HG27 specification products when the trolley is in the first stage position, using different hydrogen concentration ratios (PH2%). It indicates that different hydrogen concentration ratios show significant differences. The average pass rate reaches 73% at a hydrogen concentration of 50%, far exceeding other concentration levels (17% at 40%, 45% at 60%, and 38% at 75%), making it the optimal choice for quality performance among all production parameters. This data clearly verifies the decisive influence of hydrogen concentration on product quality and provides a clear parameter benchmark for production process optimization.

[0150] Table 3

[0151]

Claims

1. A method of high temperature annealing of an oriented silicon steel, characterized in that, The method comprises: In the case that the oriented silicon steel is located at the first stage position in the annealing furnace, the volume ratio of nitrogen and hydrogen in the annealing furnace is adjusted to be 50% respectively; and the temperature in the annealing furnace is adjusted from low to high, and the temperature adjustment range is 700-1200 DEG C; In the case that the oriented silicon steel is located at the second stage position in the annealing furnace, the volume ratio of hydrogen in the annealing furnace is adjusted to be 100%; and the temperature in the annealing furnace is adjusted from high to low, and the temperature adjustment range is 1200-660 DEG C; The oriented silicon steel is located at the first stage position and the second stage position in turn; The first stage position is T3-T16 in the annealing furnace; The position is the position of the trolley carrying the oriented silicon steel; In the case that the oriented silicon steel is located at T3-T7, the temperature in the annealing furnace is adjusted to be 700 DEG C; In the case that the oriented silicon steel is located at T8, the temperature in the annealing furnace is adjusted to be 775 DEG C ± 5 DEG C; In the case that the oriented silicon steel is located at T9, the temperature in the annealing furnace is adjusted to be 850 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T10, the temperature in the annealing furnace is adjusted to be 925 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T11, the temperature in the annealing furnace is adjusted to be 1000 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T12, the temperature in the annealing furnace is adjusted to be 1050 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T13, the temperature in the annealing furnace is adjusted to be 1100 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T14, the temperature in the annealing furnace is adjusted to be 1180 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T15-T16, the temperature in the annealing furnace is adjusted to be 1200 DEG C; The second stage position is T17-T28 in the annealing furnace; In the case that the oriented silicon steel is located at T17-T20, the temperature in the annealing furnace is adjusted to be 1200 DEG C; In the case that the oriented silicon steel is located at T21, the temperature in the annealing furnace is adjusted to be 1140 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T22, the temperature in the annealing furnace is adjusted to be 1080 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T23, the temperature in the annealing furnace is adjusted to be 1020 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T24, the temperature in the annealing furnace is adjusted to be 960 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T25, the temperature in the annealing furnace is adjusted to be 900 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T26, the temperature in the annealing furnace is adjusted to be 840 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T27, the temperature in the annealing furnace is adjusted to be 750 DEG C ± 3 DEG C; In the case that the oriented silicon steel is located at T28, the temperature in the annealing furnace is adjusted to be 660 DEG C.

2. The high temperature annealing method of an oriented silicon steel according to claim 1, characterized in that, Further comprising: In the case that the oriented silicon steel is located at the zero stage position in the annealing furnace, the volume ratio of nitrogen in the annealing furnace is adjusted to be 100%; And the temperature in the annealing furnace is adjusted from low to high, and the temperature adjustment range is 550-700 DEG C; The oriented silicon steel is located in the first stage position and the second stage position in sequence.

3. The high temperature annealing method of an oriented silicon steel according to claim 1, characterized in that, Further comprising: When the oriented silicon steel is located in the third stage position in the annealing furnace, the volume ratio of nitrogen in the annealing furnace is adjusted to 100%; and the temperature in the annealing furnace is adjusted from high to low, and the temperature adjustment range is 570 DEG C to room temperature; The oriented silicon steel is located in the first stage position and the second stage position in sequence.

4. The high temperature annealing method of oriented silicon steel according to claim 2, characterized in that, The first stage position is T1 parking space-T2 parking space in the annealing furnace; When the oriented silicon steel is located in T1 parking space, the temperature in the annealing furnace is adjusted to 550 DEG C; When the oriented silicon steel is located in T2 parking space, the temperature in the annealing furnace is adjusted to 700 DEG C.

5. The high temperature annealing method of oriented silicon steel according to claim 3, characterized in that, The third stage position is T29 parking space-T31 parking space in the annealing furnace; When the oriented silicon steel is located in T29 parking space, the temperature in the annealing furnace is adjusted to 570 DEG C; When the oriented silicon steel is located in T30 parking space-T31 parking space, the temperature in the annealing furnace is adjusted to room temperature.

6. The high temperature annealing method of the oriented silicon steel according to claim 5, wherein, When the oriented silicon steel is located in T1 parking space-T2 parking space, the furnace pressure in the annealing furnace is adjusted to 300 Pa; When the oriented silicon steel is located in T3 parking space-T31 parking space, the furnace pressure in the annealing furnace is adjusted to 200 Pa.

7. The high temperature annealing method of an oriented silicon steel according to claim 5 or 6, characterized in that, The operation time of the oriented silicon steel in each parking space of T1 parking space-T31 parking space is 5-7 h.

8. The high temperature annealing method of the oriented silicon steel according to claim 7, wherein, When the oriented silicon steel is located in T1 parking space-T2 parking space, 20 cubic meters of nitrogen at standard atmospheric pressure is introduced; When the oriented silicon steel is located in T3 parking space-T9 parking space, 8 cubic meters of nitrogen and hydrogen at standard atmospheric pressure is introduced; When the oriented silicon steel is located in T10 parking space-T16 parking space, 6 cubic meters of nitrogen and hydrogen at standard atmospheric pressure is introduced; When the oriented silicon steel is located in T17 parking space-T22 parking space, 8 cubic meters of hydrogen at standard atmospheric pressure is introduced; When the oriented silicon steel is located in T23 parking space-T28 parking space, 12 cubic meters of hydrogen at standard atmospheric pressure is introduced; When the oriented silicon steel is located in T29 parking space-T31 parking space, 20 cubic meters of nitrogen at standard atmospheric pressure is introduced; The volume of the inner cover of the annealing furnace corresponding to each parking space is 9.1 m 3 .

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