Decarburization annealing method for copper-containing oriented silicon steel with low hydrogen control oxygen

Abstract

The application discloses a decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and oxygen control, which comprises the following steps: surface treatment of the oriented silicon steel primary cold-rolled plate is carried out in the heating section of an annealing furnace, the temperature rising rate is controlled within 20-80 DEG C / s, and H2 with a dew point of less than or equal to-40 DEG C is introduced; decarburization is carried out in the soaking section of the annealing furnace with a low-hydrogen annealing atmosphere, the furnace temperature is controlled within 800-850 DEG C, the H2 content is reduced to 1-10%, and the dew point in the furnace is adjusted to less than or equal to 30 DEG C; accurate oxygen control is carried out at the end part of the soaking section of the annealing furnace, the furnace temperature is increased by 5-15 DEG C based on the decarburization furnace temperature, and the oxygen content and surface oxide layer structure of the annealed plate are controlled by adjusting H2 and the dew point. The application adopts the composite technology of low-hydrogen annealing atmosphere decarburization and independent accurate oxygen content control after decarburization, controls the oxygen content and surface oxide layer material of the decarburized oriented silicon steel plate, and prepares the copper-containing oriented silicon steel plate with stable and excellent surface quality, thereby filling the technical blank in the field and having great industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of metal material annealing technology, and particularly relates to an annealing method for decarburizing oriented silicon steel, and more specifically to a low-hydrogen controlled oxygen decarburizing annealing method for copper-containing oriented silicon steel. Background Technology

[0002] The main production process of copper-containing oriented silicon steel is as follows: smelting → hot rolling → pickling → primary cold rolling → decarburization annealing → secondary cold rolling → magnesium oxide coating → high temperature annealing → stress coating and tensile leveling annealing → slitting and packaging.

[0003] The key features of copper-containing grain-oriented silicon steel manufacturing technology are: the addition of approximately 0.5% Cu, which increases austenite content and lowers the solution temperature of AlN inhibitors. Using AlN and Cu₂S as inhibitors, the hot-rolling temperature is reduced to 1250–1300℃. The low carbon content facilitates complete decarburization during intermediate annealing, eliminating the need for a second decarburization annealing process even with secondary cold rolling. Clearly, copper-containing grain-oriented silicon steel represents a low-cost production process and has gained increasing attention and practical application. The finished grains of ordinary grain-oriented silicon steel produced using this process exhibit larger recrystallized grains and higher magnetic properties than ordinary grain-oriented silicon steel heated at high temperatures.

[0004] The decarburization annealing process for copper-containing grain-oriented silicon steel is carried out after the first cold rolling. The decarburization annealing process uses a hydrogen atmosphere with a dew point between 25℃ and 55℃ and a volume percentage between 25% and 50% to achieve complete decarburization of the intermediate thickness. Studies have shown that under suitable atmosphere, the plate temperature begins to exhibit oxidizing capacity from 400℃, and decarburization capacity is achieved between 760 and 890℃. Surface carbon is oxidized to form CO, which escapes from the steel plate surface, and the surface carbon potential begins to decrease. Carbon from the matrix diffuses to the surface, and the decarburization reaction intensifies with increasing temperature. Oxidation inevitably occurs during the decarburization process, at which point SiO2 and Fe are generated. x O y And their complexes.

[0005] In the traditional decarburization annealing process for copper-containing grain-oriented silicon steel, surface decarburization and oxidation reactions are intertwined. The control of surface oxides is incidentally achieved during decarburization, resulting in significant fluctuations in the oxygen content and oxide composition of the annealed product, leading to variations in the surface quality of the finished product. Therefore, surface quality control is a key challenge in the decarburization annealing process for copper-containing grain-oriented silicon steel, with precise oxygen control being crucial.

[0006] Existing patents, including Chinese patent application CN1978673A entitled "A Production Method of Ordinary Grain-Oriented Silicon Steel", Chinese patent application CN101748258A entitled "A Method for Improving the Magnetic Properties of Low-Temperature GO Grain-Oriented Silicon Steel", Chinese patent application CN102534364A entitled "A Production Method for Improving the Magnetic Properties of Ordinary Grain-Oriented Silicon Steel", and Chinese patent CN102330021B entitled "Complete Production Process of Low-Temperature Grain-Oriented Silicon Steel", focus on research on the magnetic properties of copper-containing grain-oriented silicon steel and process optimization, disclosing content on improving product magnetic properties and optimizing production processes, but none of them involve the precise oxygen control in the decarburization annealing process.

[0007] Existing literature, including titles such as "Research on Decarburization Process of CGO Grain-Oriented Silicon Steel," "Determination of Intermediate Complete Decarburization Annealing Process for Ordinary Cold-Rolled Grain-Oriented Silicon Steel," and "Numerical Simulation Analysis of Decarburization Process of Grain-Oriented Silicon Steel," investigated the effects of decarburization temperature, atmosphere, furnace pressure difference, and decarburization time on carbon content. Furthermore, scanning electron microscopy and electron backscatter diffraction techniques were used to study the microstructure, texture, and decarburization effect after decarburization annealing using different processes. A mathematical model of the decarburization process of grain-oriented silicon steel was established by studying the decarburization reaction kinetics on the surface of silicon steel strip and the diffusion mechanism of carbon within the strip. However, this study did not address the precise oxygen control aspects of the decarburization annealing process.

[0008] Existing patents such as Chinese patent application CN201910563069.8 entitled "A process for preparing low-temperature high magnetic induction oriented silicon steel", Chinese patent application CN201611016468.5 entitled "A decarburization and nitriding annealing method for producing low-temperature high magnetic induction oriented silicon steel", and Chinese patent application CN202110441863.2 entitled "A decarburization annealing process for high magnetic induction oriented silicon steel" all focus on the decarburization and nitriding control technology of low-temperature heating high magnetic induction oriented silicon steel, and do not involve the relevant content of precise oxygen control in the decarburization annealing process. Summary of the Invention

[0009] To address the aforementioned technical problems in the prior art, this invention provides a low-hydrogen, oxygen-controlled decarburization annealing method for copper-containing oriented silicon steel. By precisely controlling the oxygen content during the decarburization annealing process, the method solves the problem of poor surface quality and surface quality stability of copper-containing oriented silicon steel, filling a technical gap in this field.

[0010] The decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and controlled oxygen provided by the present invention includes:

[0011] Surface treatment is performed in the initial stage of annealing, in which low dew point H2 (≤-40℃) is used as the main protective gas to prevent surface over-oxidation;

[0012] Decarburization is carried out during the mid-annealing process, reducing the H2 content to ≤10% and the furnace atmosphere dew point to ≤30℃.

[0013] Independent oxygen control is performed at the end of annealing, and the oxygen content and surface oxide layer structure are precisely controlled by adjusting the H2 content and the dew point of the furnace atmosphere.

[0014] Furthermore, the aforementioned decarburization annealing method for copper-containing grain-oriented silicon steel with low hydrogen and controlled oxygen includes:

[0015] (1) Place the oriented silicon steel cold-rolled sheet into the annealing furnace and perform surface treatment on the oriented silicon steel cold-rolled sheet in the heating section of the annealing furnace. The heating rate of the annealing furnace is controlled between 20℃ / s and 80℃ / s. H2 with a dew point ≤ -40℃ is introduced and the H2 content is controlled between 20% and 50% to prevent over-oxidation of the surface of the oriented silicon steel cold-rolled sheet.

[0016] (2) Decarburization annealing of oriented silicon steel sheets is carried out in the soaking zone of the annealing furnace with a low hydrogen annealing atmosphere. The furnace temperature is controlled between 800℃ and 850℃, the H2 content is reduced to 1% to 10%, and the dew point of the atmosphere in the furnace is adjusted to ≤30℃.

[0017] (3) Precise oxygen control is carried out at the end of the soaking section of the annealing furnace. The furnace temperature is increased by 5℃ to 15℃ based on the decarburization furnace temperature. The oxygen content and surface oxide layer structure of the annealing plate are controlled by adjusting the H2 content to 5% to 50% and the dew point of the furnace atmosphere to 0 to 40℃.

[0018] Furthermore, in the above-mentioned decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and controlled oxygen, the partial pressure ratio of water and H2 is controlled at 0.25 to 0.50 during decarburization annealing.

[0019] Furthermore, in the above-mentioned decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and controlled oxygen, the silicon weight percentage of the primary cold-rolled oriented silicon steel sheet is 2.9% to 3.3%, and the copper weight percentage is 0.3% to 0.7%.

[0020] The decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and controlled oxygen of the present invention has the following advantages and beneficial effects:

[0021] (1) The decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and oxygen control of the present invention adopts a composite technology of decarburization in low hydrogen annealing atmosphere and independent and precise control of oxygen content after decarburization. In this way, the oxygen content and surface oxide layer of the decarburized oriented silicon steel plate are controlled, and copper-containing oriented silicon steel plate with stable and excellent surface quality is prepared. This solves the problem of poor surface quality and surface quality stability of copper-containing oriented silicon steel and fills the technical gap in this field.

[0022] (2) This invention innovatively proposes a low-hydrogen decarburization annealing process, an independent and precise oxygen control process, and corresponding parameter control of annealing temperature, heating rate, annealing atmosphere and dew point. This significantly reduces hydrogen consumption and energy consumption. It not only has low production cost, flexible and simple operation, and high control precision, but also can produce copper-oriented silicon steel decarburized annealed plates with oxygen content and surface oxide layer structure that meet the needs of different users. Ultimately, it promotes the formation of finished plates with stable and excellent surface quality, which has significant industrial application value. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a process flow diagram of the decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and controlled oxygen according to the present invention.

[0025] Figure 2 The image shows the metallographic structure of the oxide layer of copper-containing oriented silicon steel after proportional annealing using existing technology.

[0026] Figure 3 The image shows the metallographic structure of the oxide layer of copper-oriented silicon steel after annealing using the low-hydrogen controlled oxygen decarburization annealing method of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] The decarburization annealing method for copper-oriented silicon steel with low hydrogen and controlled oxygen in this invention employs a composite technology of decarburization in a low-hydrogen annealing atmosphere and independent and precise control of oxygen content after decarburization. This controls the oxygen content and surface oxide layer of the decarburized silicon steel plate, resulting in copper-oriented silicon steel plates with stable and excellent surface quality. The main technical measures include: the initial annealing stage is the surface treatment zone, where low dew point H2 at ≤-40℃ is used as the main protective gas to prevent surface over-oxidation; the middle annealing stage is the decarburization zone, where the H2 content in the soaking zone of the annealing furnace is reduced to ≤10% and the H2 dew point to ≤30℃ for decarburization; and the final annealing stage is the oxygen control zone, where the atmosphere dew point is adjusted again according to the different process requirements of subsequent processes to precisely control the oxygen content and surface oxide layer structure.

[0029] Specifically, such as Figure 1 As shown, the decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and controlled oxygen according to the present invention includes:

[0030] (1) Place the oriented silicon steel cold-rolled sheet with a silicon weight percentage of 2.9% to 3.3% and a copper weight percentage of 0.3% to 0.7% into an annealing furnace and perform surface treatment on the oriented silicon steel cold-rolled sheet in the heating section of the annealing furnace. The heating rate of the annealing furnace is controlled between 20℃ / s and 80℃ / s. After the furnace temperature meets the conditions for H2 introduction, H2 with a dew point ≤ -40℃ is introduced. The H2 content is controlled between 20% and 50% to prevent over-oxidation of the surface of the oriented silicon steel cold-rolled sheet.

[0031] (2) Decarburization annealing of grain-oriented silicon steel sheets is carried out in the soaking zone of the annealing furnace with a low-hydrogen annealing atmosphere. The furnace temperature is controlled between 800℃ and 850℃, the H2 content is reduced to 1% to 10%, the dew point of the atmosphere in the furnace is adjusted to ≤30℃, and the partial pressure ratio of water and H2 is controlled between 0.25 and 0.50. This low-hydrogen annealing atmosphere can reduce the concentration of water vapor in the atmosphere while ensuring the decarburization requirements of the product, reduce the formation of surface oxides during the decarburization process, and make it easier to control the surface oxide layer.

[0032] (3) Precise oxygen control is carried out at the end of the soaking section of the annealing furnace to precisely adjust the oxygen content and surface oxide layer structure of the oriented silicon steel annealing plate according to the requirements, so as to obtain a controllable and stable surface oxide layer. The furnace temperature is increased by 5℃~15℃ on the basis of the decarburization annealing furnace temperature. The oxygen content and surface oxide layer structure of the annealing plate are controlled by adjusting the H2 content to 5%~50% and the dew point of the furnace atmosphere to 0~40℃.

[0033] The copper-oriented silicon steel sheet subjected to decarburization annealing treatment using the low-hydrogen controlled oxygen decarburization annealing method of the present invention is then subjected to secondary cold rolling, magnesium oxide coating, high-temperature annealing, and stretching and leveling annealing to prepare the finished copper-oriented silicon steel product. After surface quality testing and performance testing, the finished product has excellent and stable surface quality, adhesion reaches grade B, and the performance hit rate is also significantly improved.

[0034] The following describes in detail the low-hydrogen controlled oxygen decarburization annealing method for copper-containing oriented silicon steel of the present invention, in conjunction with comparative examples of existing technologies and embodiments of the present invention.

[0035] Comparative Example

[0036] Decarburization annealing was carried out on Q120 grade oriented silicon steel cold-rolled sheet with a silicon content of 3.15% by weight and a copper content of 0.5% by weight. The annealing furnace heating rate was 35℃ / s, the furnace temperature was 835℃, the H2 dew point was 30℃, and the H2 content was 35%.

[0037] After adopting the conventional annealing process, the oriented silicon steel cold-rolled sheet is then subjected to secondary cold rolling, magnesium oxide coating, drying, high-temperature annealing and stretching and leveling annealing to prepare copper-containing oriented silicon steel finished products. The surface quality test and performance test results of the finished products are shown in Table 1.

[0038] Example 1

[0039] Using Q120 grade grain-oriented silicon steel cold-rolled sheet with a silicon content of 3.15% by weight and a copper content of 0.5% by weight, the surface is first treated in the heating section of an annealing furnace, where the furnace heating rate is 35℃ / s and H2 with a dew point of -45℃ is introduced as the main protective gas to prevent over-oxidation of the grain-oriented silicon steel cold-rolled sheet surface. Then, decarburization is carried out in the soaking section of the annealing furnace in a low-hydrogen annealing atmosphere, where the furnace temperature is 835℃, the H2 content is 5%, and the furnace atmosphere dew point is 22℃. Finally, precise oxygen control is performed at the end of the soaking section of the annealing furnace, where the furnace temperature is raised to 840℃, the H2 content is 10%, and the furnace atmosphere dew point is maintained at 22℃.

[0040] After adopting the low-hydrogen controlled oxygen decarburization annealing process of Example 1, the oriented silicon steel primary cold-rolled sheet is then subjected to secondary cold rolling, magnesium oxide coating, drying, high-temperature annealing and stretching and leveling annealing processes to prepare copper-containing oriented silicon steel finished products. The surface quality test and performance test results of the finished products are shown in Table 1.

[0041] Example 2

[0042] Using Q120 grade grain-oriented silicon steel cold-rolled sheet with a silicon content of 3.15% by weight and a copper content of 0.5% by weight, the surface is first treated in the heating section of an annealing furnace, where the furnace heating rate is 35℃ / s and H2 with a dew point of -45℃ is introduced as the main protective gas to prevent over-oxidation of the grain-oriented silicon steel cold-rolled sheet surface. Then, decarburization is carried out in the soaking section of the annealing furnace in a low-hydrogen annealing atmosphere, where the furnace temperature is 835℃, the H2 content is 5%, and the furnace atmosphere dew point is 22℃. Finally, precise oxygen control is performed at the end of the soaking section of the annealing furnace, where the furnace temperature is raised to 840℃~850℃, the H2 content is 35%, and the furnace atmosphere dew point is 30℃.

[0043] After adopting the low-hydrogen controlled oxygen decarburization annealing process of Example 2, the oriented silicon steel primary cold-rolled sheet is then subjected to secondary cold rolling, magnesium oxide coating, drying, high-temperature annealing and stretching and leveling annealing processes to prepare copper-containing oriented silicon steel finished products. The surface quality test and performance test results of the finished products are shown in Table 1.

[0044] Table 1. Surface quality and performance test results of copper-containing grain-oriented silicon steel finished products.

[0045] Testing volume (tons) Surface adhesion Surface color difference Dewdrop Performance hit rate (%) Comparative Example 500 Class C have have 75 Example 1 1200 Grade B slight none 92 Example 2 1000 Grade B none slight 90

[0046] As shown in Table 1, compared with the conventional decarburization annealing process for copper-oriented silicon steel in the prior art, the copper-oriented silicon steel finished product prepared by the decarburization annealing treatment using the low-hydrogen controlled oxygen decarburization annealing method of the present invention has better surface quality and more stable magnetic properties after the primary cold-rolled sheet of the copper-oriented silicon steel is subjected to secondary cold rolling, magnesium oxide coating, high-temperature annealing and stretching and leveling annealing. The surface adhesion reaches grade B, there is almost no surface color difference, there is basically no crystal exposure, and the magnetic property hit rate is significantly improved (from 75% in the prior art to 90%).

[0047] Furthermore, regarding the surface oxide layer structure, in the prior art, due to the lack of a pre-decarburization annealing surface treatment process like that of the present invention, before reaching the annealing temperature (e.g., below 760°C), oxygen diffused into the steel strip through the grain boundaries first reacts chemically with Si to form a dense amorphous SiO2 oxide layer, hindering the subsequent decarburization reaction and also hindering the subsequent oxidation reaction, resulting in an uneven surface oxide layer after annealing, such as... Figure 2As shown. In contrast, in this invention, a surface treatment process is first performed in the heating section of the annealing furnace before decarburization annealing. By adjusting the atmosphere, H2 dew point, and annealing furnace heating rate, over-oxidation of the product surface is effectively prevented, eliminating the adverse effects on subsequent decarburization. Moreover, during the decarburization annealing process, lowering the H2 content and dew point can reduce the concentration of water vapor in the atmosphere while ensuring the decarburization requirements of the product, thus reducing the formation of surface oxides during decarburization. Furthermore, by precisely controlling oxygen at the end of the soaking section of the annealing furnace, the oxygen content and surface oxide layer structure are precisely adjusted according to requirements to obtain a controllable and stable surface oxide layer, such as... Figure 3 As shown.

[0048] In summary, compared with the prior art, the low-hydrogen controlled oxygen decarburization annealing method for copper-containing oriented silicon steel of the present invention has the following advantages and beneficial effects:

[0049] The present invention provides a low-hydrogen controlled oxygen decarburization annealing method for copper-oriented silicon steel. This method employs a composite technology of decarburization in a low-hydrogen annealing atmosphere and independent and precise control of oxygen content after decarburization. This controls the oxygen content and surface oxide layer of the decarburized silicon steel plate, resulting in copper-oriented silicon steel plates with stable and excellent surface quality. This solves the problem of poor surface quality and surface quality stability of copper-oriented silicon steel and fills a technological gap in this field.

[0050] This invention innovatively proposes a low-hydrogen decarburization annealing process, an independent and precise oxygen control process, and corresponding parameter control for annealing temperature, heating rate, annealing atmosphere, and dew point. This significantly reduces hydrogen consumption and energy consumption, resulting in low production costs, flexible and simple operation, and high control precision. Furthermore, it can produce copper-oriented silicon steel decarburized annealed plates with oxygen content and surface oxide layer structure that meet the needs of different users, ultimately leading to the formation of finished plates with stable and excellent surface quality. This invention has significant industrial application value.

[0051] It should be noted that, in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device.

[0052] It should also be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method for decarburizing copper-containing oriented silicon steel with low hydrogen and controlled oxygen, characterized in that, include: (1) Place the oriented silicon steel cold-rolled sheet into the annealing furnace and perform surface treatment on the oriented silicon steel cold-rolled sheet in the heating section of the annealing furnace. The heating rate of the annealing furnace is controlled between 20℃ / s and 80℃ / s. H2 with a dew point ≤ -40℃ is introduced and the H2 content is controlled between 20% and 50% to prevent over-oxidation of the surface of the oriented silicon steel cold-rolled sheet. (2) Decarburization annealing of grain-oriented silicon steel sheets is carried out in the soaking zone of the annealing furnace with a low-hydrogen annealing atmosphere. The furnace temperature is controlled between 800℃ and 850℃, the H2 content is reduced to 1% to 10%, and the dew point of the atmosphere in the furnace is adjusted to ≤30℃. (3) Precise oxygen control is carried out at the end of the soaking section of the annealing furnace. The furnace temperature is increased by 5℃~15℃ based on the decarburization furnace temperature. The oxygen content and surface oxide layer structure of the annealing plate are controlled by adjusting the H2 content to 5%~50% and the dew point of the furnace atmosphere to 0~40℃.

2. The decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and controlled oxygen as described in claim 1, characterized in that, In decarburization annealing, the partial pressure ratio of water to H2 is controlled at 0.25~0.

50.

3. The decarburization annealing method for copper-containing oriented silicon steel with low hydrogen and controlled oxygen as described in claim 1 or 2, characterized in that, The oriented silicon steel cold-rolled sheet has a silicon weight percentage of 2.9% to 3.3% and a copper weight percentage of 0.3% to 0.7%.

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