CN112853052B - Control method for high-temperature annealing of oriented silicon steel - Google Patents
Control method for high-temperature annealing of oriented silicon steel Download PDFInfo
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/68—Temporary coatings or embedding materials applied before or during heat treatment
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- C—CHEMISTRY; METALLURGY
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
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Abstract
The invention discloses a control method of high-temperature annealing of oriented silicon steel, which comprises the steps of smelting in a molten steel converter or an electric furnace, continuously casting into a plate blank, heating the plate blank, carrying out hot rolling to form a hot rolled plate, annealing the hot rolled plate, cold rolling to the thickness of 0.23mm, carrying out decarburization annealing and nitriding treatment, coating an MgO coating on the surface to obtain a decarburization annealed steel coil, and then carrying out high-temperature annealing; in the high-temperature annealing process, the average cooling speed between the high heat preservation temperature and the glass film bottom layer forming temperature is controlled to be minus 6 ℃/h to minus 15 ℃/h; controlling the total cooling speed from the high heat preservation temperature to the tapping time to be-6 ℃/h to-25 ℃/h; and when the steel coil is cooled to be lower than the tapping temperature, tapping the steel coil, and then cooling the steel coil in an air cooling mode or an off-line cooling mode in a protective atmosphere, wherein the tapping temperature is less than or equal to 500 ℃. According to the invention, by reasonably controlling the cooling speed of high-temperature annealing, some plate-shaped defects of the oriented silicon steel after high-temperature annealing can be effectively reduced without increasing the manufacturing cost.
Description
Technical Field
The invention relates to a manufacturing method of oriented silicon steel, in particular to a control method of high-temperature annealing of oriented silicon steel.
Background
The oriented silicon steel is an indispensable soft magnetic material for electric power and national defense industry, and consists of crystal grains called Goss texture, wherein the Miller index of the Goss texture is used for expressing {110} <001>, the {110} crystal face of the crystal grains is parallel to a rolling plane, and the <001> crystal direction of the crystal grains is parallel to the rolling direction, so that the oriented silicon steel has better easy magnetization performance under an oriented magnetic field, and the best magnetic performance of a polycrystalline material is realized by fully utilizing magnetocrystalline anisotropy. The product with the magnetic induction B8 lower than 1.88T is common oriented silicon steel, CGO steel for short; the product with the magnetic induction B8 higher than or equal to 1.88T is high-magnetic-induction oriented silicon steel, namely HiB steel for short.
The core technology of the oriented silicon steel is to utilize fine dispersed second phase particles to inhibit the normal growth of primary recrystallized grainsAnd the secondary recrystallization is completed in the high-temperature annealing process by utilizing the interface energy difference of different oriented crystal grains, so that a sharp Goss texture is formed. In addition to accomplishing the secondary recrystallization, the metallurgical purposes of high temperature annealing include: MgO for coating steel plate surface and SiO in surface oxide film2A chemical reaction takes place to form Mg2SiO4The bottom layer can be combined with the insulating coating to improve the insulating property of the product, can prevent inhibitors such as AIN and the like from being oxidized or nitrided in the high-temperature annealing process to prevent the loss or reduction of the inhibition effect, and can be kept at the temperature of about 1200 ℃ for a long time for purification treatment to remove excessive impurity elements such as S, N and the like in the steel plate.
The high-temperature annealing process is usually completed in a bell-type furnace or a ring furnace, and the process flow can be divided into four stages: in the first stage, turning the decarburized horizontal steel coil into a vertical steel coil for charging, and discharging free water box combination water in MgO at 550-750 ℃; in a second stage, a bottom layer of magnesium silicate is formed and secondary recrystallization is developed, starting with the formation of Mg at a temperature of about 850 ℃ to 950 ℃2SiO4A bottom layer that begins to develop secondary recrystallization at about 950 ℃ to 1050 ℃; the third stage, after finishing the secondary recrystallization and forming the bottom layer, preserving the heat for more than 2 hours at about 1200 ℃, and finishing removing S, N and other impurity elements so as to eliminate the problem of magnetic aging of products caused by the impurity elements; and in the fourth stage, cooling the steel coil from about 1200 ℃ to room temperature. The four stages form a complete annealing cycle, and one cycle usually lasts for 6-8 days.
Because the high-temperature annealing process is complex, the annealing temperature is high, the duration time is long, the manufacturing cost of the working procedure is high, the important influence on the product quality is achieved, and a lot of researches are made around process realization, cost control, quality improvement and the like. For example: chinese patent CN106435102A discloses a continuous high-temperature annealing process for tunnel-type oriented silicon steel, which is characterized by comprising the following steps: the first step is as follows: charging; placing the prefabricated steel coil on a trolley, and fastening the steel coil by using a sealing cover to ensure that the steel coil is in a sealed environment; the second step is that: filling the furnace; moving the trolley loaded with the steel coil to the inlet of the annealing furnace through the auxiliary rail, and pushing the trolley into the annealing furnace through a hydraulic push rod; the third step: annealing treatment; comprises a low temperature area, a heating area and a high temperature area; the temperature of the low-temperature area is 550-600 ℃, the temperature is kept for 20-30 h, and nitrogen and ammonia decomposition gas are sequentially introduced into the low-temperature area sealing cover; the temperature in the heating area is increased from 550 ℃ to 1200 ℃ within 30-40 h, and ammonia decomposition gas is introduced into the heating area sealing cover; the temperature of the high-temperature area is 1100-1200 ℃, the temperature is kept for 15-25 h, and hydrogen is introduced into the high-temperature area sealing cover; the fourth step: cooling; comprises a natural cooling stage and a rapid cooling stage; the natural cooling stage is finished at the tail end of a high-temperature area of the annealing furnace, the gas of the annealing furnace is closed for natural cooling, the temperature is reduced to 800-1000 ℃, and nitrogen is introduced into the sealing cover in the natural cooling stage; the rapid cooling stage is completed in a cooling area of the annealing furnace, the cooling area and a high-temperature area are directly separated by a partition plate, a plurality of fans are arranged at the upper part of the annealing furnace in the rapid cooling stage, the cooling is carried out by ventilation of the fans, the temperature is reduced to 30-80 ℃ in the rapid cooling stage, and nitrogen is introduced into a sealing cover in the rapid cooling stage; the fifth step: discharging; pushing the cooled trolley out of the annealing furnace; and a sixth step: unloading; after the trolley is pulled to the unloading area of the auxiliary rail, the annealed steel coil is hung away; the seventh step: overhauling; after the trolley is pulled to the maintenance area of the auxiliary rail, whether the trolley is complete is maintained; if the furnace is complete, directly charging to prepare for next furnace charging, and if the furnace is incomplete, repairing, charging after repairing is completed, and preparing for next furnace charging; eighth step: and repeating the first step to the seventh step to realize continuous annealing treatment. The patent mainly focuses on the description of each stage of the high-temperature annealing production of the oriented silicon steel, does not describe the technical implementation scheme in the aspect of quality control of the cooling stage in the specific high-temperature annealing process, and does not describe the mechanism of defect control of the cooling stage in the high-temperature annealing process.
Chinese patent CN104726760 proposes a method for manufacturing an oriented electrical steel sheet, wherein the high-temperature annealing secondary recrystallization process is performed in a state of applying an electric field, and the magnitude of the electric field is 1kV/cm to 3 kV/cm. The manufacturing method can shorten the purification annealing time of high-temperature annealing, thereby improving the production efficiency.
Chinese patent CN101573458B proposes a method for producing oriented electrical steel sheet with excellent magnetic properties in high yield, wherein the temperature increase rate of high temperature annealing is set as two stages: the temperature range where the secondary recrystallization does not start is high speed, and the temperature rise speed is 18-75 ℃/h; the temperature range of the secondary recrystallization is a conventional speed, and the temperature rise speed is 10-15 ℃/h. The high-temperature annealing temperature rise time can be shortened under the condition of not influencing the magnetic performance of the finished product, so that the production efficiency can be improved. The main team of this patent is the shortening heating stage of oriented silicon steel high temperature annealing production, promotes production efficiency and describes, does not mention the technical scheme of cooling stage quality control.
Due to the long-time high-temperature annealing, the steel coil after the high-temperature annealing usually has some plate-shaped defects, such as: the defects of plate shapes, such as wave property on two sides of the strip steel, protruding camber of the inner ring, unevenness of the outer ring and the like, can be relieved through the subsequent stretching, flattening and annealing process, but can not be completely eliminated, and further the yield of the qualified products is reduced. The method for manufacturing the oriented silicon steel is provided, and particularly the method for manufacturing the oriented silicon steel by high-temperature annealing can effectively reduce some plate-shaped defects of the oriented silicon steel after the high-temperature annealing without increasing the manufacturing cost.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a control method for high-temperature annealing of oriented silicon steel, which can effectively reduce some plate-shaped defects of the oriented silicon steel after high-temperature annealing without increasing the manufacturing cost by reasonably controlling the cooling speed of the high-temperature annealing.
In order to realize the purpose, the invention adopts the following technical scheme:
a control method for high-temperature annealing of oriented silicon steel;
smelting the steel in a molten steel converter or an electric furnace, continuously casting the steel into a plate blank, heating the plate blank, carrying out hot rolling to form a hot rolled plate, annealing the hot rolled plate, cold rolling to the thickness of 0.15-0.35 mm, carrying out decarburization annealing and nitriding treatment, coating an MgO coating on the surface to obtain a decarburization annealed steel coil, and then carrying out high-temperature annealing; after the high-temperature annealing process, controlling the average cooling speed between the high heat preservation temperature and the glass film bottom layer forming temperature to be between-6 ℃/h and-15 ℃/h;
controlling the cooling speed between the high heat preservation temperature and the tapping temperature between-6 ℃/h and-25 ℃/h;
and when the steel coil is cooled to be lower than the tapping temperature, tapping the steel coil, and then cooling the steel coil in an air cooling mode or in a protective atmosphere in an off-line mode, wherein the tapping temperature is less than or equal to 500 ℃.
The protective atmosphere is 25% N2+75％H2。
The high heat preservation temperature is 1150-1250 ℃, and the temperature for forming the bottom layer of the glass film is 900-1050 ℃.
Preferably, the average cooling speed in the temperature range of 1050 ℃ -900 ℃ is controlled between-6 ℃/h and-15 ℃/h.
The bottom layer of the glass film is Mg2SiO4A bottom layer.
The steel coil can be selectively placed in an auxiliary device for off-line cooling.
The auxiliary device comprises a circular heat-insulating cover body, wherein the top of the circular heat-insulating cover body is connected with a polygonal support frame and is further provided with a plurality of heat dissipation windows, an interlayer is arranged in the side wall of the circular heat-insulating cover body, a base is arranged at the bottom of the side wall, and a plurality of lifting lugs are further arranged on the outer side of the side wall of the circular heat-insulating cover body.
According to the control method for the high-temperature annealing of the oriented silicon steel, provided by the invention, by reasonably controlling the cooling speed of the high-temperature annealing, the edge waves of the oriented silicon steel after the high-temperature annealing are small, the plate shape is excellent, and the magnetic property uniformity is good under the condition that the manufacturing cost is not increased.
Drawings
FIG. 1 is a schematic diagram of a cooling process curve of the control method of the present invention;
FIG. 2 is a schematic diagram illustrating the cause of plate-like defects in the high temperature annealing process of oriented silicon steel;
FIG. 3 is a schematic structural diagram of an auxiliary device in the control method of the present invention;
Fig. 4 is a top view of the supplemental device of fig. 3.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
The invention provides a control method for high-temperature annealing of oriented silicon steel, which comprises the following steps:
the average cooling speed between the high heat preservation Temperature T1(Temperature1) (1150-1250 ℃) and the glass film bottom layer forming Temperature is controlled between-6 ℃/h and-15 ℃/h. Preferably, the average cooling rate in the temperature range of 1050 ℃ to 900 ℃ is controlled to be between-6 ℃/h and-15 ℃/h, because the situation that the glass film tension sigma 2 in the local area of the steel coil is higher than the strip steel yield strength sigma 1 is most easily generated in the temperature range of 1050 ℃ to 900 ℃. In addition, the average cooling speed between the high heat preservation temperature T1 and the glass film bottom layer forming temperature is not controlled to be too low, and the high heat preservation time is increased when the temperature is lower than-6 ℃/h, so that the creep of a steel coil caused by self gravity and the like is aggravated.
The cooling speed from the high heat preservation temperature to the tapping is controlled to be lower than-25 ℃/h, recorded as C1 (average cooling speed maximum), and preferably between-6 ℃/h and-25 ℃/h. Because the average cooling speed between the high heat preservation temperature and the bottom layer forming temperature is controlled to be lower than minus 25 ℃/h, if the cooling speed is higher than minus 25 ℃/h, the cooling speed must be increased below the bottom layer forming temperature, and the investment of cooling equipment needs to be obviously increased; the cooling rate control is not as slow as possible, and if the cooling rate is lower than-6 ℃/h and is recorded as C2 (average cooling rate minimum), the whole production process of the steel coil is prolonged, the yield is reduced, and the energy consumption and the cost are increased.
In order to further shorten the time of the steel coil in the furnace, when the steel coil is cooled to be lower than the tapping Temperature T2(Temperature2) and less than or equal to 500 ℃, the steel coil can be tapped out of the furnace and then cooled off-line by air cooling or in a protective atmosphere. If the air cooling is carried out at the temperature higher than 500 ℃, because the bottom layer of the glass film is not completely compact, the surface of the strip steel can generate oxidation reaction, and the surface quality, the magnetic property and the bending property of a finished product are deteriorated.
In order to more effectively perform off-line cooling on the steel coil, the steel coil can be placed in an auxiliary device for off-line cooling. The auxiliary device can properly improve the tapping temperature of the steel coil, shorten the cooling time,
And reduces possible quality problems such as deformation or cracking of the lower end portion.
As shown in fig. 1, the cooling rate in the high-temperature annealing cooling stage is controlled between the maximum average cooling rate value C1 and the minimum average cooling rate value C2, and a uniform cooling rate is selected to meet the technical scheme for cooling, which is recorded as a mode i; the high-temperature annealing process is carried out with sectional cooling, the number of the sections is not limited, the method meets the technical scheme, and the method is recorded as a mode II; after the high-temperature annealing process is cooled to a certain temperature, the cooling auxiliary device is used for cooling, and the method is marked as a third mode.
Through a group of high-temperature annealing heating rate and cooling rate comparison tests, a vertical decarburization annealing steel coil coated with MgO conventionally is loaded into a bell-type furnace, the temperature is increased from room temperature to 1200 ℃ according to the heating rate listed in the following table 1, the temperature is kept for 25h, the steel coil is cooled to about 300 ℃ according to the cooling rate listed in the following table 1, then the steel coil is lifted off a furnace platform for air cooling, and the plate-shaped defects are evaluated after the steel coil is processed by a conventional hot-drawing leveling unit. The whole temperature rising and reducing process of high-temperature annealing adopts 25 percent N2+75％H2And (6) protecting.
The test results are listed in table 1, and it can be seen that the influence of the high-temperature annealing cooling speed on the plate-shaped defects is more obvious than the temperature rise speed; when the cooling speed is-6 ℃/h, the plate shape after high-temperature annealing has no plate shape defects or is very slight. However, reducing the cooling rate after the high-temperature annealing significantly reduces the production efficiency.
TABLE 1 comparative test of temperature rise rate and cooling rate in high-temperature annealing
Further combining with fig. 2, the temperature of the vertical steel coil is slowly raised from room temperature, and the yield strength σ 1 of the strip steel is continuously reduced in the process of raising the temperature; when the glass film is heated to t1(time1), a glass film bottom layer begins to be formed, because the expansion coefficients of the glass film bottom layer and the strip steel are different, tension sigma 2 begins to be generated in the strip steel, the strip steel continuously expands along with the continuous rise of the temperature, the soft glass film under high temperature is driven to extend, the tension sigma 2 is not obviously increased, and when the high temperature preservation is finished, the tension sigma 2 does not exceed the yield strength sigma 1 of the strip steel, so the influence of the stage on the plate shape defects is small.
After the high heat preservation is finished, the steel coil begins to be cooled, the yield strength sigma 1 of the strip steel is gradually improved, the strip steel contracts faster than the glass film, the tension sigma 2 generated by the glass film is converted from compressive stress to tensile stress and is rapidly increased when the time2 reaches t2, especially, the difference of the contraction rates of the two at the periphery of the steel coil is more obvious, if the tension sigma 2 in a local temperature area is increased to be higher than the yield strength sigma 1 of the strip steel, the strip steel is subjected to plastic deformation, and the plate-shaped defects are caused.
The forming temperature of the bottom layers of the glass films of different steel types is 900-1050 ℃, and if the forming temperature of the glass films is low, the tension of the glass films which can be formed during cooling can be increased, so that the plate-shaped defects are more likely to appear.
The actual process is far more complicated than the above process, for example, the vertical steel coil is also affected by the self-gravity, the temperature field, the uneven expansion curve and other factors, but this does not prevent the completion of the technical solution.
As shown in fig. 3 and 4, the auxiliary device used for off-line cooling of the steel coil by the control method of the invention comprises a circular heat-insulating cover body 1, wherein the top of the circular heat-insulating cover body is connected with a polygonal support frame 2, a plurality of fixing rods 3 are further connected in the polygonal support frame 2, and meanwhile, six heat-radiating windows 4 which are uniformly distributed are further arranged on the top of the circular heat-insulating cover body. All be provided with intermediate layer 5 in the circumference lateral wall of circular heat preservation cover body 1, base 6 is installed to the bottom of lateral wall, and the lateral wall outside upper end of circular heat preservation cover body 1 still is equipped with several lug 7, the hoist and mount of being convenient for.
The present invention will be further described with reference to the following examples.
Example 1
The decarburization annealed steel coil is produced according to a conventional oriented silicon steel manufacturing method, and the production steps comprise: smelting in a converter or an electric furnace; continuously casting into a plate blank; heating the plate blank; hot rolling; annealing the hot rolled plate; cold rolling to 0.23mm thickness; decarburization annealing and nitriding treatment; and coating the MgO coating to obtain the decarburization annealing coil. And turning the horizontal steel coil into a vertical steel coil, then placing the vertical steel coil in a bell-type furnace for high-temperature annealing, heating to 1200 ℃ at an average heating speed of 10 ℃/h, preserving the heat for 25h, cooling to about 300 ℃ at a cooling speed listed in the following table 2, and then hanging the steel coil off the furnace platform for air cooling. The whole temperature rising and reducing process of high-temperature annealing adopts 25 percent N 2+75％H2And (6) performing protection. And then uncoiling, coating an insulating coating, hot stretching, flattening and annealing to obtain a finished product, and evaluating the plate shape defects and magnetic properties of the finished product.
The decarburized annealed sheet prepared by the above method was subjected to the same high-temperature annealing temperature-raising process in a laboratory, samples were taken out at intervals of 10 ℃ in a temperature range of 860 ℃ to 1000 ℃, the formation of the bottom layer of the substrate was observed, and it was confirmed that the bottom layer formation temperature in the above process was between 900 ℃ and 930 ℃, thereby performing key control.
TABLE 2
In table 2, in invention examples 1 to 8, the average cooling rate between the high-temperature-maintaining temperature of 1200 ℃ and the glass film formation temperature of 900 ℃ is controlled to be-8 to-15 ℃/h, and the average cooling rate between 1050 ℃ and 900 ℃ is controlled to be-6 to-15 ℃/h, so that the corresponding plate-shaped defects after high-temperature annealing are relatively good, no serious defects occur, and the magnetic performance is good. In contrast, in comparative examples 1 to 4, since the cooling rate of 900 ℃ or higher was not controlled within the required range, the plate shape defect was relatively poor.
Example 2
The decarburization annealed steel coil is produced according to a conventional oriented silicon steel manufacturing method, and the production steps comprise: smelting in a converter or an electric furnace; continuously casting into a plate blank; heating the plate blank; hot rolling; annealing the hot rolled plate; cold rolling to 0.30mm thickness; decarburization annealing and nitriding treatment; and coating the MgO coating to obtain the decarburization annealing coil. And turning the horizontal steel coil into a vertical steel coil, then loading the vertical steel coil into a ring furnace for high-temperature annealing, heating to 1200 ℃, preserving heat for 25 hours, cooling to about 300 ℃ at the cooling speed listed in the following table 3, and then hanging the steel coil away from the furnace platform for air cooling. The whole temperature rising and reducing process of high-temperature annealing adopts 25 percent N 2+75％H2And (6) protecting. And then uncoiling, coating an insulating coating, hot stretching, flattening and annealing to obtain a finished product, and evaluating the plate shape defects and magnetic properties of the finished product.
TABLE 3
In table 3, in invention examples 1 to 6, the average cooling rate between 1200 ℃ and 900 ℃ is controlled to be-6 to-15 ℃/h, and the average cooling rate between 1200 ℃ and tapping is controlled to be-6 to-20.5 ℃/h, so that the corresponding plate-shaped defects after high-temperature annealing are relatively good, no serious defects appear, and the magnetic performance is good. In comparison, in comparative example 1, the cooling rate from 1200 ℃ to tapping is-4.5 ℃/h, the furnace time of the cooling section is obviously prolonged, the production efficiency is influenced, and the plate shape defect after high-temperature annealing is not obviously improved; in comparative example 2 and comparative example 3, the plate-shaped defects after the high-temperature annealing were deteriorated due to the excessively high cooling rate.
Example 3
The decarburization annealed steel coil is produced according to a conventional oriented silicon steel manufacturing method, and the production steps comprise: smelting in a converter or an electric furnace; continuously casting into a plate blank; heating the plate blank; hot rolling; annealing the hot rolled plate; cold rolling to 0.23mm thickness; decarburization annealing and nitriding treatment; and coating the MgO coating to obtain the decarburization annealing coil. The horizontal steel coil is turned into a vertical steel coil and then is loaded into a ring furnace for high-temperature annealing, the temperature is raised to 1200 ℃, the temperature is kept for 25 hours, and the steel coil is cooled according to the cooling speed listed in the following table 4 When the steel coil is discharged at different temperatures, the steel coil is lifted off the furnace platform for air cooling or N2The protective atmosphere is cooled off-line. The whole temperature rising and reducing process of high-temperature annealing adopts 25 percent N2+75％H2And (6) protecting. And then uncoiling, coating an insulating coating, hot stretching, flattening and annealing to obtain a finished product, and evaluating the plate shape defects, the surface color uniformity and the recurvation performance of the finished product.
TABLE 4
In table 4, in the invention examples 1 to 6, the tapping temperature is lower than 500 ℃, the corresponding plate-shaped defects after high-temperature annealing are relatively good, no serious defects appear, and the surface color of the finished product is uniform. In contrast, the tapping temperatures of comparative examples 1 to 3 were higher than 500 ℃ regardless of whether N was used or not2Protective atmosphere, product reverse bending or surface color deterioration.
It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be used as a limitation of the present invention, and that changes and modifications to the above described embodiments are within the scope of the claims of the present invention as long as they are within the spirit and scope of the present invention.
Claims (6)
1. A control method for high-temperature annealing of oriented silicon steel is characterized by comprising the following steps:
smelting the steel liquid in a converter or an electric furnace, continuously casting the steel liquid into a plate blank, heating the plate blank, carrying out hot rolling to form a hot rolled plate, annealing the hot rolled plate, carrying out cold rolling to the thickness of 0.15-0.35 mm, carrying out decarburization annealing and nitriding treatment, coating an MgO coating on the surface to obtain a decarburization annealed steel coil, and then carrying out high-temperature annealing;
After the high-temperature annealing process, controlling the average cooling speed between the high heat preservation temperature and the glass film bottom layer forming temperature to be-6 ℃/h to-15 ℃/h;
controlling the cooling speed between the high heat preservation temperature and the tapping temperature between-6 ℃/h and-25 ℃/h;
when the steel coil is cooled to the tapping temperature, the steel coil is tapped, and then the steel coil is cooled by air or off-line in a protective atmosphere;
the high heat preservation temperature is 1150-1250 ℃, and the temperature for forming the bottom layer of the glass film is 900-1050 ℃;
the average cooling speed in the temperature range of 1050-900 ℃ is controlled between-6 ℃/h and-15 ℃/h.
2. The method for controlling the high-temperature annealing of oriented silicon steel as set forth in claim 1, wherein: the tapping temperature is less than or equal to 500 ℃.
3. The method for controlling the high-temperature annealing of oriented silicon steel as set forth in claim 1, wherein: the protective atmosphere is nitrogen and hydrogen.
4. The method for controlling the high-temperature annealing of oriented silicon steel as set forth in claim 1, wherein: the bottom layer of the glass film is Mg2Si O4A bottom layer.
5. The method for controlling the high-temperature annealing of oriented silicon steel as set forth in claim 1, wherein: and the steel coil is placed in the auxiliary device for off-line cooling.
6. The method for controlling the high-temperature annealing of the oriented silicon steel as set forth in claim 5, wherein: the auxiliary device comprises a circular heat-insulation cover body, wherein the top of the circular heat-insulation cover body is connected with a polygonal support frame and is further provided with a plurality of heat dissipation windows, an interlayer is arranged in the side wall of the circular heat-insulation cover body, the bottom of the side wall is provided with a base, and the outer side of the side wall of the circular heat-insulation cover body is further provided with a plurality of lifting lugs.
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