An apparatus and method for improving temperature uniformity of high temperature annealed silicon steel coils

Abstract

The application discloses a kind of equipment and method for improving temperature uniformity of high-temperature annealing steel coil of oriented silicon steel, equipment includes annealing furnace;The annealing furnace includes furnace lining and bottom plate arranged in furnace lining;The bottom of the bottom plate is provided with heating cavity for heating oriented silicon steel coil, the inner cover for covering oriented silicon steel is arranged on the bottom plate, and the diameter of the bottom plate is greater than the outer diameter of the inner cover;The heating cavity is internally provided with annularly arranged burner and thermocouple for measuring the temperature in the heating cavity;The annularly arranged burner and thermocouple are respectively connected with the heating cavity furnace temperature control system, and the heating cavity furnace temperature control system controls the combustion state of the burner in the heating cavity according to the temperature measured by the thermocouple.The application adds heating cavity at the bottom of annealing furnace, and is equipped with thermocouple, realizes the control to heating cavity temperature, to greatly improve the problem of poor temperature uniformity of oriented silicon steel coil in high-temperature annealing process.

Description

Technical Field

[0001] This invention relates to the field of grain-oriented silicon steel technology, and more specifically, to an apparatus and method for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils. Background Technology

[0002] Grain-oriented silicon steel, an indispensable soft magnetic material in the power and defense industries, relies on a core technology that effectively suppresses the normal growth process of primary recrystallized grains by utilizing finely dispersed second-phase particles. Simultaneously, it fully leverages the interfacial energy differences between grains of different orientations to successfully achieve secondary recrystallization during high-temperature annealing, resulting in an extremely sharp Goss texture. It is worth noting that high-temperature annealing, besides its crucial role in promoting secondary recrystallization, also serves other important metallurgical purposes. For example, it promotes a chemical reaction between the MgO coating on the steel surface and the SiO2 in the surface oxide film, successfully forming a Mg2SiO4 underlayer; and it purifies the steel, effectively removing impurities such as N, S, and Al. This series of processes is crucial for improving the performance and quality of grain-oriented silicon steel, laying a solid foundation for its widespread application in related industrial fields.

[0003] The general process flow for grain-oriented silicon steel encompasses several key steps: First, the steelmaking process provides the basic raw materials for subsequent production; next, continuous casting is performed to initially form the steel billet; the subsequent hot rolling step causes plastic deformation of the billet and improves its microstructure; normalizing and pickling are used to optimize material properties and remove surface impurities; cold rolling further refines the grains and adjusts material properties; decarburization annealing effectively controls the carbon content; MgO coating creates favorable conditions for subsequent high-temperature annealing; and high-temperature annealing, as a crucial step, is typically carried out in equipment such as bell-type annealing furnaces, annular annealing furnaces, and tunnel annealing furnaces. Currently, the high-temperature annealing operation of grain-oriented silicon steel increasingly utilizes annular annealing furnaces, with specific structures exhibiting a facility layout based on annular annealing furnaces. Figure 1 The features shown are as follows: Heating burners are precisely installed on the furnace wall of this annular annealing furnace. These burners can directly inject various combustion media such as natural gas and coal gas into the furnace, thereby achieving efficient heating. At the same time, thermocouples are reasonably installed on the furnace top to accurately control the furnace temperature. This ensures the stability and reliability of the high-temperature annealing process, providing a solid guarantee for achieving the final performance of the grain-oriented silicon steel.

[0004] Combination Figure 1As shown, the high-temperature annealing process involves annealing the entire coil of steel strip coated with MgO in a high-temperature annealing furnace. The main heat conduction of the vertical steel coil occurs through the upper and lower end faces, resulting in significant temperature non-uniformity at different locations within the coil. Xia Tian et al. conducted a simulation study on the temperature state of various parts of the steel coil during the heating process of grain-oriented silicon steel, and the results are as follows... Figure 2 As shown in the figure, the temperature difference between the cold and hot spots can reach over 300℃. This significant temperature difference may have a considerable impact on the microstructure evolution and performance optimization of grain-oriented silicon steel during high-temperature annealing. Therefore, it becomes one of the key factors that needs to be focused on and studied in depth in this production process, so as to take effective control measures to reduce the adverse effects of temperature non-uniformity and improve the quality stability and consistency of grain-oriented silicon steel products.

[0005] During high-temperature annealing, the uneven temperature distribution of steel coils can cause numerous problems. Firstly, the asynchronous nature of the secondary recrystallization process between cold and hot spots significantly reduces the uniformity of the magnetic properties of the final strip in both the transverse and longitudinal directions. Since secondary recrystallization is a crucial factor determining the magnetic properties of grain-oriented silicon steel, differences in crystallization at different locations directly disrupt the uniformity of the magnetic domain structure, severely interfering with the strip's magnetic performance in different directions and weakening its reliability and stability in applications such as power and defense industries. Secondly, significant differences in drainage and additional oxidation between cold and hot spots in the steel coil make the underlying layer of the strip at these locations highly susceptible to watermarks and bright spots. In the complex environment of high-temperature annealing, poor drainage and excessive oxidation can lead to uneven distribution of the underlying material and changes in the surface microstructure, respectively, resulting in noticeable quality defects on the strip surface. This not only affects the appearance of the strip but may also negatively impact its bonding performance with other materials and subsequent processing techniques. Third, the uneven and asynchronous thermal expansion and contraction at different locations of the steel coil exacerbates the problem, leading to sheet defects such as "elephant feet" and edge waviness. Furthermore, due to the significant temperature differences, the magnetic properties of different parts of the steel coil exhibit marked variations. This uncoordinated thermal expansion and contraction causes uneven stress distribution within the strip. When the stress exceeds the material's yield strength, it leads to plastic deformation of the strip, resulting in various sheet defects. Simultaneously, these internal stress variations further affect the arrangement and orientation of magnetic domains, intensifying magnetic differences and causing significant dispersion in the electromagnetic properties of the strip at different locations, thus reducing the overall quality of the product.

[0006] Chinese patent CN202786362U relates to a HITT single-coil stacked bell-type annealing furnace specifically used for the heat treatment of grain-oriented electrical steel. This annealing furnace mainly consists of a furnace platform, an inner bell-shaped cover mounted on the furnace platform, and a heating or cooling bell-shaped cover surrounding the inner bell-shaped cover. A sealing element is installed on the furnace platform, and the inner bell-shaped cover is sealed to the sealing element via a hydraulic clamping device, thus creating a closed annealing space between the furnace platform and the inner bell-shaped cover. Furthermore, the furnace platform is equipped with a blowing pipe for purging the furnace body with atmosphere, and the heating bell-shaped cover has a corresponding heating system. When this annealing furnace performs heating or cooling operations on the coils, the coils are placed on the furnace platform in a single-coil stacked manner. From a technical advantage perspective, this technology can significantly reduce the consumption of protective atmosphere, and its processing temperature can reach up to 1200℃. It can also effectively shorten the time span required to reach the maximum cooling temperature required for unloading, which is significant for improving annealing efficiency. In addition, this technology also helps to improve the uniformity of annealing temperature and can shorten the overall annealing time. Through specific structural design, a relatively ideal heat transfer effect can be achieved between the inner cover and the surface of the coil. This not only helps reduce energy consumption but also ensures that the entire coil load achieves maximum flexibility and temperature uniformity. However, it should be noted that the above-mentioned technologies mainly focus on the design and function of the inner cover. Although they have achieved certain results in many aspects, the degree of improvement in the temperature uniformity of the steel coil is still quite limited. It is difficult to fundamentally solve a series of key problems caused by uneven temperature during the heat treatment of steel coils, such as differences in magnetic properties, plate defects, and underlying quality flaws.

[0007] Chinese Patent Publication No. CN103667874A discloses an innovative production method for shortening the furnace time during high-temperature annealing of grain-oriented silicon steel. This method encompasses several consecutive steps: first, a smelting process to lay the foundation for subsequent material forming; then, hot rolling to shape the initial form of the material; followed by normalizing and pickling to optimize the internal structure and surface condition of the material; then, cold rolling to further refine the grains and adjust the material properties; next, a decarburization annealing process to precisely control the carbon content; then, the crucial high-temperature annealing stage; and finally, stretching and leveling annealing. In this entire process, the technology utilizes a specific cold rolling method—one (or two) cold rolling processes with a high reduction rate—which facilitates the formation of Gaussian texture and the nucleation process. Furthermore, nitriding treatment is performed in the early stages of high-temperature annealing to promote the formation of sufficient (Al, Si)N inclusions. The strong inhibitory effect of these inclusions creates favorable conditions for the smooth progress, stable maintenance, and gradual improvement of secondary recrystallization. Meanwhile, two steps were carefully designed during the low-holding stage of high-temperature annealing, a design that, to some extent, facilitates the uniform distribution of temperature within the steel coil. These two targeted measures effectively shorten the overall high-temperature annealing time, thereby ensuring the stability and improvement of the magnetic properties of the grain-oriented silicon steel and the quality of the surface magnesium silicate underlayer, ultimately achieving the dual goals of increasing production efficiency and reducing production costs. However, it should be clearly pointed out that this technical solution primarily focuses on the heating process of high-temperature annealing. While it has achieved some success in shortening time and improving certain properties, its effect on improving the temperature uniformity of the steel coil is relatively limited. It cannot fundamentally and comprehensively solve a series of complex and critical problems caused by uneven steel coil temperature, such as excessive differences in magnetic properties, plate defects, and fluctuations in the quality of the underlayer.

[0008] Chinese patent CN205398688U focuses on the field of silicon steel production technology, specifically researching a device aimed at improving the temperature uniformity of steel coils in an annular furnace. This device mainly consists of a top cover and a bottom plate. The top cover is securely positioned above the steel coil, its key function being to effectively seal the upper end of the coil and, due to its inherent properties, to insulate against heat radiation. This reduces the temperature difference between cold and hot spots at the upper end of the coil, thus contributing to improved temperature uniformity. Simultaneously, a first reinforcing rib is carefully designed on the upper end of the bottom plate, which is positioned below the top cover, and the steel coil is placed on top of this rib. This creates a specific gap between the lower end of the steel coil and the bottom plate, which facilitates heat dissipation. This design also helps improve the temperature uniformity of the steel coil, thereby ensuring the surface quality of the strip steel. However, this technology has certain drawbacks in its implementation. Because this device improves temperature uniformity by adding it to the upper and lower ends of the steel coil, it can easily damage these ends in the complex environment of high-temperature annealing. This damage may cause difficulties in uncoiling in subsequent processes, negatively impacting the continuity and stability of the production flow. Furthermore, while the device has some positive effects on improving the temperature uniformity of the steel coil, its overall effectiveness in this area remains limited, making it difficult to completely solve the problem of uneven temperature caused by various factors during high-temperature annealing.

[0009] Chinese patent application number 202310275252.4 discloses a grain-oriented silicon steel and a corresponding method and apparatus for improving the uniformity of its high-temperature annealing temperature. In this apparatus system, one of the core components is an electrically heated chassis, whose main function is to electrically heat the grain-oriented silicon steel coil placed on it. This electrically heated chassis is precisely positioned on a support structure within the inner shroud of the annealing furnace, and is equipped with multiple electrically heated modules and multiple second temperature-measuring thermocouples. A circular hole is located at the center of the electrically heated chassis, within which a first temperature-measuring thermocouple is placed. Furthermore, the apparatus includes an annular sleeve, whose main purpose is to enclose the grain-oriented silicon steel coil placed on the electrically heated chassis. This annular sleeve is located between the inner shroud of the annealing furnace and the grain-oriented silicon steel coil on the electrically heated chassis, and its top is designed as an annular dome with a circular hole. By employing an electrically heated chassis and incorporating an added sleeve design, and precisely controlling the heating process of each module within the chassis, the problem of poor temperature uniformity in steel coils during high-temperature annealing can be effectively improved to a significant extent, thus positively contributing to the overall quality improvement of grain-oriented silicon steel. However, this technology is not without its flaws. Since it uses electricity as its energy source, this inevitably increases energy costs significantly during high-temperature heat treatment, putting considerable pressure on companies' production cost control. Furthermore, the embedded resistance wire structure of the electrically heated chassis reduces its strength, and its manufacturing process is relatively more difficult. These factors combined significantly increase the operating cost of the chassis equipment, limiting the large-scale promotion and application of this technology in actual production. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide an apparatus and method for improving the temperature uniformity of oriented silicon steel coils during high-temperature annealing. By adding a heating chamber at the bottom of the annealing furnace and equipping it with thermocouples, the temperature of the heating chamber can be controlled, thereby significantly improving the problem of poor temperature uniformity of oriented silicon steel coils during high-temperature annealing.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A first aspect of the present invention provides an apparatus for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils, including an annealing furnace;

[0013] The annealing furnace includes a furnace lining and a base plate disposed within the furnace lining;

[0014] The bottom of the chassis is provided with a heating cavity for heating the oriented silicon steel coil, and the chassis is provided with an inner cover for covering the oriented silicon steel, the diameter of the chassis being larger than the outer diameter of the inner cover;

[0015] The heating chamber is equipped with annularly arranged burners and thermocouples for measuring the temperature inside the heating chamber. The annularly arranged burners and thermocouples are respectively connected to the heating chamber furnace temperature control system. The heating chamber furnace temperature control system controls the combustion state of the burners inside the heating chamber based on the temperature measured by the thermocouples.

[0016] Preferably, the heating chamber includes an inner support and an outer support arranged in a ring; the outer support is disposed outside the inner support, and a gap is provided on the outer support for discharging high-temperature exhaust gas; the annularly arranged burner is disposed between the inner support and the outer support.

[0017] Preferably, the outer support comprises a plurality of support members made of refractory bricks, with gaps between adjacent support members; the diameter of the outer support is the same as the diameter of the inner cover.

[0018] Preferably, the inner cover and the chassis are isolated from each other by a fire-resistant insulating material.

[0019] Preferably, the fire-resistant insulating material is a fire-resistant fiber blanket.

[0020] Preferably, the upper part of the furnace lining is provided with an upper burner, and a thermocouple for temperature measurement is provided at the top. The upper burner and the thermocouple are connected to the furnace top temperature control system. The furnace top temperature control system controls the upper burner according to the temperature measured by the top thermocouple.

[0021] The second aspect of the present invention provides a method for improving the temperature uniformity of high-temperature annealed silicon steel coils. This method employs the equipment described in the first aspect of the present invention for improving the temperature uniformity of high-temperature annealed silicon steel coils. After the silicon steel coil is loaded into the furnace, it is covered with an inner cover. The silicon steel coil undergoes high-temperature annealing treatment through a heating chamber and an upper burner. The burner in the heating chamber is controlled by closed-loop feedback based on the temperature measured by thermocouples within the heating chamber. The heating time in the heating chamber is from the time the silicon steel coil enters the furnace until the high-temperature holding and homogenization ends. Afterwards, a leveling annealing treatment is performed.

[0022] Preferably, in the oriented silicon steel coil loading furnace, a layer of refractory insulating material is placed along the lower edge of the inner cover to isolate the atmosphere inside and outside the inner cover.

[0023] Preferably, in the high-temperature annealing process, the upper burner performs closed-loop feedback control based on the inner shroud temperature measured by the thermocouple at the top of the furnace lining.

[0024] Preferably, the high-temperature annealing treatment includes a preheating section, a primary heating section, a primary soaking section, a secondary heating section, and a secondary soaking section; the set temperatures of the heating chambers in the primary heating section, primary soaking section, secondary heating section, and secondary soaking section are the same as the set temperature of the inner furnace shroud; or

[0025] The high-temperature annealing process includes a preheating section, a primary heating section, a primary homogenizing section, a secondary heating section, and a secondary homogenizing section; the set temperature of the heating chambers in the primary heating section, the primary homogenizing section, and the secondary heating section is higher than the inner furnace temperature, and the set temperature of the heating chamber in the final homogenizing section is the same as the inner furnace temperature.

[0026] Preferably, during the high-temperature annealing treatment, the difference between the cold point and hot point temperature of the oriented silicon steel coil is ≤130℃.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. The present invention eliminates the burners at the bottom of the annealing furnace and adds a heating chamber under the chassis of the annealing furnace. The burners are arranged in a ring in the heating chamber, which can effectively avoid excessive local temperature of the chassis. In addition, the outer support of the heating chamber structure has a suitable gap to facilitate the discharge of high temperature exhaust gas from combustion.

[0029] 2. The present invention modifies the chassis and inner cover of the annealing furnace by increasing the diameter of the chassis and reducing the size of the inner cover, and ensuring that the inner cover can be placed on the chassis. At the same time, refractory insulating material is placed along the lower edge of the inner cover during furnace loading to ensure that the temperature and pressure inside the furnace meet the process requirements.

[0030] 3. The present invention configures thermocouples in the heating chamber and uses thermocouple temperature measurement to perform closed-loop feedback control of the heating chamber temperature, thereby controlling the temperature in the heating chamber to meet the high-temperature annealing requirements of oriented silicon steel, improving the underlying defects and magnetism of the product. Attached Figure Description

[0031] Figure 1 This is a schematic cross-sectional view of an annular annealing furnace or a tunnel annealing furnace in the prior art;

[0032] Figure 2 A simulation diagram of the internal temperature field of a vertically coiled high-temperature annealed steel coil.

[0033] Figure 3 This is a schematic diagram of the arrangement of temperature measuring points inside the embedded coupler roll;

[0034] Figure 4 It is a graph showing the temperature changes of cold and hot spots in the embedded coupler.

[0035] Figure 5 This is a schematic diagram of the structure of the device for improving the temperature uniformity of high-temperature annealed oriented silicon steel coils according to the present invention;

[0036] Figure 6 This is a schematic diagram of the heating cavity of the present invention;

[0037] In the diagram, 1. Furnace lining; 2. Upper burner; 3. Lower burner; 4. Thermocouple; 5. Inner cover; 6. Chassis; 7. Support; 8. Grain-oriented silicon steel coil; 10. Annealing furnace; 11. Furnace lining; 12. Upper burner; 13. Thermocouple; 14. Inner cover; 15. Inner support; 16. Outer support; 17. Burner; 18. Thermocouple; 19. Chassis. Detailed Implementation

[0038] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0039] In the high-temperature annealing process of grain-oriented silicon steel, in order to characterize the temperature uniformity of the steel coil, based on the simulation results of high-temperature annealing in an annular furnace by Xia Tian et al., the inventors determined the highest and lowest temperature points in the steel coil during high-temperature annealing to characterize the temperature uniformity of the steel coil: During the high-temperature annealing heating process, the temperature difference between different positions of the steel coil is relatively large. The outer ring near the upper end face has the fastest heating rate and is counted as the hot spot. Due to the heat insulation effect of the MgO coating during high-temperature annealing, the heat transfer between the layers of the steel coil is hindered by MgO, resulting in a large thermal resistance. Therefore, the main heat conduction of the steel coil is through the upper and lower end faces. Thus, the heating rate at the center of the steel coil is the slowest and is counted as the cold spot.

[0040] To understand the temperature distribution at different locations during the high-temperature annealing process of the steel coil, embedded thermocouples were used to measure the temperatures of cold and hot spots at locations on the steel coil after decarburization annealing. The layout of the embedded thermocouple measurement points is shown in the diagram. Figure 3 As shown. The embedded coupler coils were subjected to high-temperature annealing in a high-temperature annealing furnace. Measurements showed that point ③ of the embedded coupler coil heated the fastest, while point ⑤ heated the slowest. The heating curves and temperature differences are shown in [reference needed]. Figure 4 As shown in the figure, the maximum temperature difference between the cold and hot spots reached 260℃, and this occurred within the first 30 hours of high-temperature annealing. The temperature uniformity of the steel coil is reflected by the temperature changes and differences between the cold and hot spots during the high-temperature annealing process.

[0041] Therefore, the present invention provides an apparatus and method for improving the temperature uniformity of high-temperature annealed steel coils of oriented silicon steel. By designing and adding a heating chamber below the chassis and controlling the temperature of the heating chamber, the problem of poor temperature uniformity of steel coils during high-temperature annealing is significantly improved.

[0042] Combination Figure 5As shown, this invention provides a device for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils, including an annealing furnace 10; the annealing furnace includes a furnace lining 11 and a chassis 19 disposed within the furnace lining; a heating chamber for heating the grain-oriented silicon steel coil is provided at the bottom of the chassis, and an inner cover 14 for covering the grain-oriented silicon steel is provided on the chassis, the diameter of the chassis being larger than the outer diameter of the inner cover; annularly arranged burners 17 and thermocouples 18 for measuring the temperature inside the heating chamber are provided inside the heating chamber; the annularly arranged burners and thermocouples are respectively connected to a heating chamber temperature control system, which controls the combustion state of the burners inside the heating chamber based on the temperature measured by the thermocouples. This invention eliminates the lower burners of the annealing furnace, adds a heating chamber under the chassis, and equips the heating chamber with thermocouples for temperature measurement, thereby achieving closed-loop feedback control of the heating chamber temperature and solving the problem of poor temperature uniformity of the steel coil during high-temperature annealing.

[0043] Combination Figure 5 , Figure 6 As shown, the present invention modifies the lower part of the annealing furnace chassis 19 by adding a heating chamber below the chassis. The heating chamber includes an annularly arranged inner support 15 (i.e., the original support of the annealing furnace chassis) and an outer support 16; the outer support is located outside the inner support, and gaps are provided on the outer support to allow high-temperature exhaust gas to be discharged; annularly arranged burners 17 are located between the inner and outer supports. In a specific embodiment, the outer support includes multiple support members made of refractory bricks, with suitable gaps between adjacent support members for the discharge of high-temperature exhaust gas generated during burner combustion; the diameter of the outer support is the same as the diameter of the inner cover.

[0044] Combination Figure 5 As shown, this invention modifies the inner cover and chassis of the annealing furnace. On the one hand, the chassis size is increased, changing from a chassis diameter smaller than the inner diameter of the inner cover to a chassis diameter larger than the outer diameter of the inner cover. Increasing the chassis size allows the inner cover to be placed above the chassis, reserving space for heating of the lower heating chamber and exhaust of waste gas. On the other hand, the height of the inner cover is reduced (the inner cover does not need to cover the steel coil chassis and the heating chamber below the chassis), and the placement of the inner cover is adjusted from the furnace platform to a position above the chassis, ensuring that the top of the inner cover is slightly lower than the burner position of the upper part of the furnace lining, thereby ensuring the furnace temperature of the inner cover during high-temperature annealing.

[0045] In a specific embodiment, the inner cover and the chassis are isolated from each other by a refractory insulating material to ensure that the pressure of the inner cover reaches the process requirements during high-temperature annealing; the aforementioned refractory insulating material can be a refractory fiber blanket.

[0046] Combination Figure 5As shown, the upper part of the furnace lining 11 is equipped with an upper burner 12, and a thermocouple 13 for temperature measurement is mounted on top. The upper burner and the thermocouple are connected to the furnace top temperature control system. The furnace top temperature control system controls the combustion state of the upper burner based on the temperature measured by the top thermocouple. The furnace top temperature control system is independent of the heating chamber temperature control system and can control the temperature of the corresponding area separately.

[0047] This invention also provides a method for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils, employing... Figure 5 The device shown improves the temperature uniformity of high-temperature annealed silicon steel coils. After the silicon steel coils are loaded into the furnace, they are covered with an inner cover. The silicon steel coils are subjected to high-temperature annealing through a heating chamber and an upper burner. The burner in the heating chamber is controlled by closed-loop feedback based on the temperature measured by the thermocouple in the heating chamber. The heating time in the heating chamber is from when the silicon steel coil enters the furnace until the high-temperature heat preservation and homogenization ends.

[0048] When loading silicon steel coils into furnaces, a layer of refractory insulating material is placed along the lower edge of the inner shroud to isolate the atmosphere inside and outside the shroud, so as to ensure that the pressure of the inner shroud reaches the process requirements during high-temperature annealing; the aforementioned refractory insulating material can be refractory fiber blanket.

[0049] In the high-temperature annealing process, the upper burner is controlled by closed-loop feedback based on the inner shroud temperature measured by the thermocouple at the top of the furnace lining.

[0050] During the high-temperature annealing process, the upper burner and the burner in the heating chamber can be controlled to ensure the smooth progress of the high-temperature annealing process. The high-temperature annealing process includes a preheating section, a primary heating section, a primary soaking section, a secondary heating section, and a secondary soaking section. In a specific embodiment, the set temperatures of the heating chambers in the primary heating section, the primary soaking section, the secondary heating section, and the secondary soaking section can be controlled to be the same as the set temperature of the inner furnace. Alternatively, the set temperatures of the heating chambers in the primary heating section, the primary soaking section, and the secondary heating section can be controlled to be higher than the inner furnace temperature, while the set temperature of the heating chamber in the final soaking section is the same as the set temperature of the inner furnace.

[0051] In the method of the present invention, the temperature difference between the cold and hot spots of the steel coil is significantly improved during high-temperature annealing, and the temperature difference between the cold and hot spots of the oriented silicon steel coil is ≤130℃.

[0052] The grain-oriented silicon steel coils obtained by the above method show significantly improved uniformity of the bottom layer, reduced area of ​​bright spot defects, and improved magnetic differences in various parts of the coil. Compared with grain-oriented silicon steel coils annealed in a conventional ring furnace, the grain-oriented silicon steel coils prepared by this invention have a bright spot defect to watermark defect area ratio reduced by more than 65%, and an iron loss difference between the outer and middle rings of the coil reduced by more than 29%.

[0053] Example 1

[0054] This embodiment produces decarburized annealed steel coils according to conventional grain-oriented silicon steel manufacturing methods. The production steps include: smelting in a converter or electric furnace; continuous casting into slabs; slab heating; hot rolling; hot-rolled plate annealing; cold rolling to a thickness of 0.23 mm; decarburization annealing; and obtaining decarburized annealed coils after coating with MgO.

[0055] The annealed coil has an inner diameter of 520mm, an outer diameter of 1800mm, and a height of 1100mm.

[0056] The equipment and method for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils in this embodiment are as follows:

[0057] (1) The lower burner of the annular annealing furnace is removed, and the furnace temperature is controlled by the upper burner through closed-loop feedback by the temperature measurement of the thermocouple at the top of the furnace.

[0058] (2) Add a heating chamber under the chassis.

[0059] Heating chamber burners: The heating chamber is equipped with ring-shaped burners and thermocouples for temperature measurement, as well as a heating chamber furnace temperature control system, which can effectively prevent the local temperature of the chassis from becoming too high.

[0060] Heating chamber structure: Specifically, multiple support components are made using high-strength refractory bricks as the support material. An outer support is added below the chassis, and the diameter of the outer support is the same as that of the inner cover. The outer support, the inner support (original support), and the chassis constitute the heating chamber. The outer support has appropriate gaps for the discharge of high-temperature exhaust gas from combustion.

[0061] Heating chamber temperature control: The heating chamber temperature control system is independent of the furnace top temperature control system. The heating chamber is equipped with thermocouples to measure the furnace temperature inside the heating chamber. The thermocouple temperature measurement is used for closed-loop feedback control of the heating chamber temperature.

[0062] The heating chamber is put into operation from the time the steel coil enters the furnace until the high-temperature heat preservation and homogenization ends.

[0063] (3) Chassis: The chassis diameter was increased from 1950mm to 2100mm;

[0064] (4) Inner cover: The inner cover size is reduced from 2250mm to 1650mm. During high-temperature annealing, the inner cover is placed on top of the chassis.

[0065] In addition, nitrogen and hydrogen protective gases need to be circulated inside the inner cover during high-temperature annealing. In order to ensure that the pressure of the inner cover reaches the process requirements during high-temperature annealing, the original inner cover was placed in a sealed sand tank. The solution in this embodiment eliminates the sealed sand tank. When the steel coil is loaded into the furnace, a layer of refractory isolation material (such as refractory fiber blanket) is placed along the lower edge of the inner cover to isolate the atmosphere inside and outside the inner cover, so as to ensure that the pressure of the inner cover reaches the process requirements during high-temperature annealing.

[0066] According to the aforementioned Figure 3Temperature measurement was performed at the embedded point locations shown, followed by high-temperature annealing. The temperature changes and temperature differences at the embedded points of the coil were recorded. After annealing by the leveling unit, the finished product was obtained. The bottom layer and magnetic properties of the finished steel coil were evaluated. The results are shown in Table 1.

[0067] Table 1

[0068]

[0069] As shown in Table 1, Comparative Examples 1 to 5 were subjected to high-temperature annealing in a conventional annular annealing furnace. The temperature difference between the cold and hot points was large, with an average of about 242°C. The bottom layer defects were more severe, with the area ratio of watermarks and bright spots reaching 8.5%. The iron loss difference between the outer and middle rings of the steel coil was about 9.2%. Examples 1-5 describe the equipment and method of the present invention for improving the temperature uniformity of high-temperature annealed oriented silicon steel coils. Closed-loop feedback control of the furnace temperature in the heating chamber is implemented, ultimately resulting in a temperature difference between cold and hot spots of 100-130°C, with an average of 112°C. The ratio of watermark to bright spot defect area is 0.4-0.9%, with an average of 0.7%. The iron loss difference between the outer and middle rings of the coil is 1.1-2.0%, with an average of 1.5%. Compared to conventional annular furnace coils in Comparative Examples 1-5, using the equipment and method of the present invention, the proportion of bottom-layer defects in the finished oriented silicon steel coil decreases by approximately 91.72%, and the iron loss difference between the outer and middle rings of the coil decreases by 83.70%. Therefore, the magnetic properties of the finished oriented silicon steel coils prepared in the embodiments of the present invention are significantly improved, resulting in a product grade improvement of approximately 1-2 grades.

[0070] Example 2

[0071] This embodiment produces decarburized annealed steel coils according to conventional grain-oriented silicon steel manufacturing methods. The production steps include: smelting in a converter or electric furnace; continuous casting into slabs; slab heating; hot rolling; hot-rolled plate annealing; cold rolling to a thickness of 0.23 mm; decarburization annealing; and obtaining decarburized annealed coils after coating with MgO.

[0072] The annealed coil has an inner diameter of 520mm, an outer diameter of 1900mm, and a height of 1200mm.

[0073] The equipment and method for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils in this embodiment are as follows:

[0074] (1) The lower burner of the annular annealing furnace is removed, and the furnace temperature is controlled by the upper burner through closed-loop feedback by the temperature measurement of the thermocouple at the top of the furnace.

[0075] (2) Add a heating chamber under the chassis.

[0076] Heating chamber burners: The heating chamber is equipped with ring-shaped burners and thermocouples for temperature measurement, as well as a heating chamber furnace temperature control system, which can effectively prevent the local temperature of the chassis from becoming too high.

[0077] Heating chamber structure: Specifically, multiple support components are made using high-strength refractory bricks as the support material. An outer support is added below the chassis, and the diameter of the outer support is the same as that of the inner cover. The outer support, the inner support (original support), and the chassis constitute the heating chamber. The outer support has appropriate gaps for the discharge of high-temperature exhaust gas from combustion.

[0078] Heating chamber temperature control: The heating chamber temperature control system is independent of the furnace top temperature control system. The heating chamber is equipped with thermocouples to measure the furnace temperature inside the heating chamber. The thermocouple temperature measurement is used for closed-loop feedback control of the heating chamber temperature.

[0079] The heating chamber is put into operation from the time the steel coil enters the furnace until the high-temperature heat preservation and homogenization ends.

[0080] The ring furnace heating process is mainly divided into the following stages: preheating → primary heating → primary homogenization → secondary heating → secondary homogenization. This embodiment compares the heating processes.

[0081] Heating process 1: The heating chamber temperature of the heating section and the soaking section is set to be the same as the inner furnace temperature;

[0082] Heating process 2: The set temperature of each heating chamber in the first heating is 50°C higher than the inner furnace temperature in the same zone. The set temperature of each heating chamber in the first homogenization is 20°C higher than the inner furnace temperature in the same zone. The set temperature of each heating chamber in the second heating is 50°C higher than the inner furnace temperature in the same zone (the highest temperature of the second heating does not exceed the temperature of the second homogenization). The set temperature of each heating chamber in the second homogenization is equal to the inner furnace temperature in the same zone.

[0083] (3) Chassis: The chassis diameter was increased from 1950mm to 2100mm;

[0084] (4) Inner cover: The inner cover size is reduced from 2250mm to 1650mm. During high-temperature annealing, the inner cover is placed on top of the chassis.

[0085] In addition, nitrogen and hydrogen protective gases need to be circulated inside the inner cover during high-temperature annealing. In order to ensure that the pressure of the inner cover reaches the process requirements during high-temperature annealing, the original inner cover was placed in a sealed sand tank. The solution in this embodiment eliminates the sealed sand tank. When the steel coil is loaded into the furnace, a layer of refractory isolation material (such as refractory fiber blanket) is placed along the lower edge of the inner cover to isolate the atmosphere inside and outside the inner cover, so as to ensure that the pressure of the inner cover reaches the process requirements during high-temperature annealing.

[0086] According to the aforementioned Figure 3 Temperature measurement was performed at the embedded point locations shown, followed by high-temperature annealing. The temperature changes and temperature differences at the embedded points of the embedded coil were recorded. After annealing by the leveling unit, the finished oriented silicon steel coil was obtained. The bottom layer and magnetic properties of the finished steel coil were evaluated. The results are shown in Table 2.

[0087] Table 2

[0088]

[0089] As shown in Table 2, Comparative Examples 6-10 were subjected to high-temperature annealing in a conventional annular annealing furnace. The temperature difference between the cold and hot points was large, with an average of 250°C. The uniformity of the bottom layer was poor, and the area ratio of watermarks and bright spots was 18.3%. The magnetic differences between different parts of the steel coil were obvious, and the iron loss difference between the outer and middle rings of the steel coil was 12.7%.

[0090] As shown in Table 2, Examples 6-10, using the equipment and heating process 1 of the present invention, significantly improved the temperature difference between the cold and hot points of the oriented silicon steel coils, especially the cold point temperature, which increased significantly. The temperature difference between the cold and hot points was 110-120°C, with an average of 112°C. The uniformity of the bottom layer of the product was significantly improved, the area of ​​bright spot defects was significantly reduced, and the ratio of bright spot defects to watermark defects was 4.3-9.1%, with an average of 6.4%. The magnetic differences between different parts of the steel coil were significantly improved, and the iron loss difference between the outer and middle rings of the steel coil was 5.8-11.8%, with an average of 9.0%. Compared with the conventional ring furnace steel coils of Comparative Examples 6-10, Examples 6-10, using the equipment and method of the present invention, reduced the proportion of bottom layer defects in the finished oriented silicon steel coils by 65.03%, reduced the iron loss difference between the outer and middle rings of the steel coil by 29.13%, significantly improved magnetic properties, and improved the product grade by approximately 1-2 grades.

[0091] Referring to Table 2, Examples 11-15, using the equipment and heating process 2 of the present invention, further improved the temperature difference between the cold and hot spots of the oriented silicon steel coils. The temperature difference between the cold and hot spots was 90-110°C, with an average of only 96°C. The uniformity of the bottom layer was further improved, the area of ​​bright spot defects was reduced, and the proportion of bright spot defects and watermark defects was 1.7-3.6%, with an average of 2.5%. The magnetic difference between different parts of the steel coil was further improved, and the iron loss difference between the outer and middle rings of the steel coil was 2.2-4.5%, with an average of 3.4%. Compared with the conventional annular furnace steel coils of Comparative Examples 6-10, Examples 11-15, using the equipment and method of the present invention, reduced the proportion of bottom layer defects in the finished oriented silicon steel coils by 86.34%, reduced the iron loss difference between the outer and middle rings of the steel coil by 73.23%, significantly improved magnetic properties, and improved the product grade by approximately 1-2 grades.

[0092] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A device for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils, characterized in that, Including annealing furnaces; The annealing furnace includes a furnace lining and a base plate disposed within the furnace lining; The bottom of the chassis is provided with a heating cavity for heating the oriented silicon steel coil, and the chassis is provided with an inner cover for covering the oriented silicon steel, the diameter of the chassis being larger than the outer diameter of the inner cover; The heating chamber is equipped with annularly arranged burners and thermocouples for measuring the temperature inside the heating chamber. The annularly arranged burners and thermocouples are respectively connected to the heating chamber furnace temperature control system. The heating chamber furnace temperature control system controls the combustion state of the burners inside the heating chamber based on the temperature measured by the thermocouples.

2. The equipment for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils according to claim 1, characterized in that, The heating chamber includes an inner support and an outer support arranged in a ring; the outer support is located outside the inner support, and a gap is provided on the outer support to discharge high-temperature exhaust gas; the annularly arranged burner is located between the inner support and the outer support.

3. The equipment for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils according to claim 2, characterized in that, The outer support comprises multiple support members made of refractory bricks, with gaps between adjacent support members; the diameter of the outer support is the same as the diameter of the inner cover.

4. The equipment for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils according to claim 1, characterized in that, The inner cover and the chassis are isolated from each other by a fire-resistant insulating material.

5. The equipment for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils according to claim 4, characterized in that, The fire-resistant insulating material is selected from fire-resistant fiber blankets.

6. The equipment for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils according to claim 1, characterized in that, The upper part of the furnace lining is provided with an upper burner, and a thermocouple for temperature measurement is provided at the top. The upper burner and the thermocouple are connected to the furnace top temperature control system. The furnace top temperature control system controls the upper burner according to the temperature measured by the top thermocouple.

7. A method for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils, characterized in that, The equipment for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils as described in any one of claims 1 to 6 is used. After the grain-oriented silicon steel coils are loaded into the furnace, they are covered with an inner cover. The grain-oriented silicon steel coils are subjected to high-temperature annealing treatment through a heating chamber and an upper burner. The burner in the heating chamber is controlled by closed-loop feedback based on the temperature measured by the thermocouple in the heating chamber. The heating time in the heating chamber is from when the grain-oriented silicon steel coil enters the furnace until the high-temperature holding and homogenization ends. After that, a leveling annealing treatment is performed.

8. The method for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils according to claim 7, characterized in that, In the oriented silicon steel coil loading furnace, a layer of refractory insulating material is placed along the lower edge of the inner cover to isolate the atmosphere inside and outside the inner cover.

9. The method for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils according to claim 7, characterized in that, In the high-temperature annealing process, the upper burner performs closed-loop feedback control based on the inner shroud temperature measured by the thermocouple at the top of the furnace lining.

10. The method for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils according to claim 7, characterized in that, The high-temperature annealing treatment includes a preheating section, a primary heating section, a primary homogenization section, a secondary heating section, and a secondary homogenization section; the set temperatures of the heating chambers in the primary heating section, primary homogenization section, secondary heating section, and secondary homogenization section are the same as the set temperature of the inner furnace shroud; or The high-temperature annealing process includes a preheating section, a primary heating section, a primary homogenizing section, a secondary heating section, and a secondary homogenizing section; the set temperature of the heating chambers in the primary heating section, the primary homogenizing section, and the secondary heating section is higher than the inner furnace temperature, and the set temperature of the heating chamber in the final homogenizing section is the same as the inner furnace temperature.

11. The method for improving the temperature uniformity of high-temperature annealed grain-oriented silicon steel coils according to claim 7, characterized in that, During the high-temperature annealing treatment, the difference between the cold point and hot point temperature of the oriented silicon steel coil is ≤130℃.

Images