Low-hydrogen oxygen-control decarburization annealing method for copper-containing oriented silicon steel

Abstract

The invention discloses a low-hydrogen oxygen-controlled decarburization annealing method for copper-containing oriented silicon steel, which comprises the following steps: carrying out surface treatment on an oriented silicon steel primary cold-rolled sheet in a heating section of an annealing furnace, controlling the heating rate at 20-80 DEG C / s, and introducing H2 with the dew point less than or equal to-40 DEG C; decarburization is carried out in a soaking section of an annealing furnace in a low-hydrogen annealing atmosphere, the furnace temperature is controlled between 800 DEG C and 850 DEG C, the H2 content is reduced to 1%-10%, and the dew point in the furnace is adjusted to be smaller than or equal to 30 DEG C; accurate oxygen control is carried out on the tail end part of the soaking section of the annealing furnace, the furnace temperature is increased by 5-15 DEG C on the basis of the decarburization furnace temperature, and the oxygen content and the surface oxide layer structure of an annealing plate are controlled by adjusting H2 and the dew point. According to the method, the oxygen content and surface oxide layer substances of the oriented silicon steel decarburized plate are controlled by adopting a composite technology of decarburizing in the low-hydrogen annealing atmosphere and independently and accurately controlling the oxygen content after decarburization, the copper-containing oriented silicon steel plate with stable and excellent surface quality is prepared, the technical blank in the field is filled, and the method has great industrial application value.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material annealing process, and particularly relates to an annealing method for decarburization of oriented silicon steel, and more specifically to a low-hydrogen and oxygen-controlled decarburization annealing method for copper-containing oriented silicon steel. Background Art

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

[0003] The technical characteristics of copper-containing oriented silicon steel preparation are: adding about 0.5% Cu to the ingredients. The addition of Cu can increase the amount of austenite and reduce the solid solution temperature of AlN inhibitor. 2 S is used as an inhibitor, and the hot rolling heating temperature is reduced to 1250-1300℃; low C content facilitates complete decarburization during intermediate annealing, and even if secondary cold rolling is adopted, there is no need for decarburization annealing after the second cold rolling. Obviously, copper-containing oriented silicon steel belongs to the production process of oriented silicon steel with low production cost, and has received more and more attention and practical application. The secondary recrystallization grains of ordinary oriented silicon steel finished plates produced by this process are large, and the magnetic properties are higher than those of ordinary oriented silicon steel heated at high temperature.

[0004] The decarburization annealing process of copper-containing 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 completely decarburize the intermediate thickness. Studies have shown that under a suitable atmosphere, the plate temperature has oxidation ability starting from 400℃, and has decarburization ability in the period of 760-890℃. The surface carbon is oxidized to generate CO and overflow from the surface of the steel plate, the surface carbon potential begins to decrease, and the carbon inside the matrix diffuses to the surface. The decarburization reaction intensifies with the increase of temperature; oxidation reaction will inevitably occur during the decarburization process. At this time, oxidation will generate SiO 2 , Fe x O y and their complexes.

[0005] In the traditional decarburization annealing process of copper-containing oriented silicon steel, surface decarburization and oxidation reaction are intertwined processes. The decarburization process is accompanied by the control of surface oxides. The oxygen content and oxide composition structure of the product after annealing fluctuate greatly, resulting in fluctuations in the surface quality of the finished product. Therefore, surface quality control is the difficulty of the decarburization annealing process of copper-containing oriented silicon steel, among which accurate oxygen control is the key.

[0006] Existing patents such as Chinese patent application CN1978673A entitled “A production method for ordinary oriented silicon steel”, Chinese patent application CN101748258A entitled “A method for improving the magnetic properties of low-temperature GO oriented silicon steel”, Chinese patent application CN102534364A entitled “A production method for improving the magnetic properties of ordinary oriented silicon steel”, and Chinese patent CN102330021B entitled “The whole process of low-temperature oriented silicon steel production” have focused on the magnetic properties and process optimization of copper-containing oriented silicon steel, and disclosed content such as improving the magnetic properties of products and optimizing production processes, but none of them involve content related to precise oxygen control in the decarburization annealing process.

[0007] Existing relevant literatures, such as "Research on Decarburization Process of CGO Oriented Silicon Steel", "Determination of Complete Decarburization Annealing Process for Ordinary Cold-rolled Oriented Silicon Steel", and "Numerical Simulation Analysis of Decarburization Process of Oriented Silicon Steel", have studied the effects of decarburization temperature, atmosphere, furnace pressure difference and decarburization time on carbon content; they have also studied the microstructure, texture and decarburization effect after decarburization annealing by different processes with the help of scanning electron microscopy and electron backscatter diffraction technology; and further established a mathematical model of the decarburization process of oriented silicon steel by studying the decarburization reaction kinetics on the surface of silicon steel strip and the diffusion mechanism of carbon in the steel strip. However, it also does not involve the relevant content of precise oxygen control in the decarburization annealing process.

[0008] Existing patents such as Chinese patent application CN201910563069.8 entitled “A process for preparing low-temperature and high-magnetic induction oriented silicon steel”, Chinese patent application CN201611016468.5 entitled “A decarburization and nitriding annealing method for producing low-temperature and 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 target 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] In order to solve the above-mentioned technical problems existing in the prior art, the present invention provides a low-hydrogen and oxygen-controlled decarburization annealing method for copper-containing oriented silicon steel. By accurately controlling the oxygen content during the decarburization annealing process, the difficult problems of poor surface quality and surface quality stability of copper-containing oriented silicon steel are solved, filling the technical gap in this field.

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

[0011] Surface treatment is performed at the beginning of annealing, using a low dew point H 2 It is the main protective gas to prevent surface overoxidation;

[0012] Decarburization is performed in the middle of annealing to reduce H 2 Decarburization is performed when the content is ≤10% and the dew point of the furnace atmosphere is ≤30℃;

[0013] Independent oxygen control is performed at the end of annealing to adjust H 2 The oxygen content and the surface oxide layer structure can be precisely controlled by adjusting the content and dew point of the furnace atmosphere.

[0014] Furthermore, the above-mentioned low hydrogen and oxygen controlled decarburization annealing method for copper-containing oriented silicon steel comprises:

[0015] (1) Place the oriented silicon steel primary cold-rolled sheet into an annealing furnace, and perform surface treatment on the oriented silicon steel primary cold-rolled sheet in the heating section of the annealing furnace, wherein the heating rate of the annealing furnace is controlled between 20°C / s and 80°C / s, and H with a dew point of ≤-40°C is introduced. 2 , H 2 The content is controlled at 20% to 50% to prevent the surface of the oriented silicon steel primary cold-rolled sheet from overoxidation;

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

[0017] (3) Precise oxygen control is performed at the end of the soaking section of the annealing furnace, where the furnace temperature is increased by 5°C to 15°C based on the decarburization furnace temperature. 2 The content is adjusted to 5% to 50%, and the dew point of the furnace atmosphere is adjusted to 0 to 40°C to control the oxygen content and surface oxide layer structure of the annealed plate.

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

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

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

[0021] (1) The low-hydrogen and oxygen-controlled decarburization annealing method for copper-containing oriented silicon steel of the present invention adopts a composite technology of decarburization in a low-hydrogen annealing atmosphere and independent and precise control of the oxygen content after decarburization, thereby controlling the oxygen content and surface oxide layer substances of the oriented silicon steel decarburization plate, and preparing a copper-containing oriented silicon steel plate with stable and excellent surface quality, solving the problem of poor surface quality and surface quality stability of copper-containing oriented silicon steel, and filling the technical gap in this field;

[0022] (2) The present invention innovatively proposes low-hydrogen decarburization annealing, independent and precise oxygen control process and corresponding parameter control of annealing temperature, heating rate, annealing atmosphere and dew point, which greatly reduces the amount of hydrogen used and reduces energy consumption. It not only has low production cost, flexible and simple operation, and high control accuracy, but also can produce copper-containing oriented silicon steel decarburization annealed plates with oxygen content and surface oxide layer structure that meet the needs of different users, and ultimately promotes the formation of finished plates with stable and excellent surface quality, which has great industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a process flow chart of the low hydrogen and oxygen controlled decarburization annealing method of copper-containing oriented silicon steel of the present invention;

[0025] Figure 2 It is a metallographic diagram of the oxide layer structure of copper-containing oriented silicon steel after annealing using the prior art comparative example;

[0026] Figure 3 The metallographic diagram of the oxide layer structure of copper-containing oriented silicon steel annealed by the low-hydrogen and oxygen-controlled decarburization annealing method of the copper-containing oriented silicon steel of the present invention is shown. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] The low hydrogen and oxygen controlled decarburization annealing method for copper-containing oriented silicon steel of the present invention adopts a composite technology of decarburization in a low hydrogen annealing atmosphere and independent and precise control of the oxygen content after decarburization, thereby controlling the oxygen content and surface oxide layer substances of the oriented silicon steel decarburization plate, and preparing a copper-containing oriented silicon steel plate with stable and excellent surface quality. The main technical measures include: the initial stage of annealing is a surface treatment zone, and a low dew point H of ≤-40°C is used. 2 It is the main protective gas to prevent surface overoxidation; the middle stage of annealing is the decarburization zone, which reduces the H in the atmosphere of the annealing furnace soaking section. 2 Content to ≤10% and H 2 The dew point is reduced to ≤30℃ for decarburization. The end of annealing is the oxygen control zone. According to the different process requirements of subsequent steps, the atmosphere dew point is adjusted again to accurately control the oxygen content and the surface oxide layer structure.

[0029] Specifically, if Figure 1 As shown, the low hydrogen and oxygen controlled decarburization annealing method for copper-containing oriented silicon steel of the present invention comprises:

[0030] (1) placing a cold-rolled sheet of oriented silicon steel having 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 performing surface treatment on the cold-rolled sheet of oriented silicon steel in a heating section of the annealing furnace, wherein the heating rate of the annealing furnace is controlled between 20°C / s and 80°C / s, and the furnace temperature satisfies the requirement of passing H 2 After the conditions are met, introduce H with a dew point of ≤-40℃ 2 , H 2 The content is controlled at 20% to 50% to prevent overoxidation of the surface of the oriented silicon steel primary cold-rolled sheet.

[0031] (2) Decarburization annealing of oriented silicon steel sheet is carried out in a low hydrogen annealing atmosphere in the soaking zone of the annealing furnace. The furnace temperature is controlled between 800℃ and 850℃. 2 The content is reduced to 1% to 10%, and the dew point of the furnace atmosphere is adjusted to ≤30℃. 2 The partial pressure ratio is controlled at 0.25-0.50. The 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 facilitate the control of the surface oxide layer.

[0032] (3) Precise oxygen control is performed 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 sheet according to demand, so as to obtain a controllable and stable surface oxide layer. The furnace temperature is increased by 5°C to 15°C based on the decarburization annealing furnace temperature. 2 The content is adjusted to 5% to 50%, and the dew point of the furnace atmosphere is adjusted to 0 to 40°C to control the oxygen content and surface oxide layer structure of the annealed plate.

[0033] The low-hydrogen and oxygen-controlled decarburization annealing method for copper-containing oriented silicon steel of the present invention is used to carry out decarburization annealing treatment on the oriented silicon steel primary cold-rolled sheet, and then subjected to secondary cold rolling, magnesium oxide coating, high-temperature annealing and stretching and leveling annealing to prepare a copper-containing oriented silicon steel finished product. Surface quality inspection and performance inspection show that the surface quality of the finished product is excellent and stable, the adhesion reaches Class B, and the performance hit rate is also significantly improved.

[0034] The low hydrogen and oxygen controlled decarburization annealing method for copper-containing oriented silicon steel of the present invention is described in detail below in combination with comparative examples of the prior art and embodiments of the present invention.

[0035] Comparative Example

[0036] A Q120 grade oriented silicon steel cold rolled sheet containing 3.15% silicon by weight and 0.5% copper by weight was used for decarburization annealing, wherein the annealing furnace heating rate was 35°C / s, the furnace temperature was 835°C, and the H 2 Dew point is 30℃, H 2 The content is 35%.

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

[0038] Example 1

[0039] A Q120 grade oriented silicon steel primary cold-rolled sheet containing 3.15% silicon by weight and 0.5% copper by weight was first subjected to surface treatment in the heating section of an annealing furnace, wherein the annealing furnace was heated at a rate of 35°C / s and H with a dew point of -45°C was introduced. 2 As the main protective gas, it prevents the surface of the oriented silicon steel cold-rolled plate from being over-oxidized; then decarburization is carried out in a low-hydrogen annealing atmosphere in the soaking section of the annealing furnace, where the furnace temperature is 835℃ and H 2 The content is 5%, and the dew point of the furnace atmosphere is 22°C; 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°C and H 2 The content is 10%, and the dew point of the furnace atmosphere is maintained at 22°C.

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

[0041] Example 2

[0042] A Q120 grade oriented silicon steel primary cold-rolled sheet containing 3.15% silicon by weight and 0.5% copper by weight was first subjected to surface treatment in the heating section of an annealing furnace, wherein the annealing furnace was heated at a rate of 35°C / s and H with a dew point of -45°C was introduced. 2 As the main protective gas, it prevents the surface of the oriented silicon steel cold-rolled plate from being over-oxidized; then decarburization is carried out in a low-hydrogen annealing atmosphere in the soaking section of the annealing furnace, where the furnace temperature is 835℃ and H 2 The content is 5%, and the dew point of the furnace atmosphere is 22°C; 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°C~850°C, H 2 The content is 35% and the dew point of the furnace atmosphere is 30℃.

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

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

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

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

[0047] In addition, regarding the surface oxide layer structure, in the prior art, due to the lack of a surface treatment process before decarburization annealing as in the present invention, before the annealing temperature is reached (e.g., below 760°C), the oxygen diffused into the steel strip through the grain boundary of the steel sheet first reacts chemically with Si to form dense amorphous SiO 2 The oxide layer hinders the subsequent decarburization reaction and also hinders the subsequent oxidation reaction, resulting in an uneven surface oxide layer after annealing, such as Figure 2 In contrast, in the present invention, a surface treatment process is first performed in the heating section of the annealing furnace before decarburization annealing, and the atmosphere, H 2 The dew point and annealing furnace heating rate effectively prevent the product surface from overoxidation and eliminate the adverse effects on subsequent decarburization. In addition, during the decarburization annealing process, the H2 The content and dew point can not only ensure the decarburization requirements of the product, but also reduce the concentration of water vapor in the atmosphere and reduce the formation of surface oxides during the decarburization process; further, by accurately controlling the oxygen at the end of the soaking section of the annealing furnace, the oxygen content and the surface oxide layer structure can be accurately adjusted according to the needs to obtain a controllable and stable surface oxide layer, such as Figure 3 shown.

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

[0049] The low-hydrogen and oxygen-controlled decarburization annealing method for copper-containing oriented silicon steel of the present invention adopts a composite technology of decarburization in a low-hydrogen annealing atmosphere and independent and precise control of the oxygen content after decarburization, thereby controlling the oxygen content and surface oxide layer substances of the oriented silicon steel decarburization plate, and preparing copper-containing oriented silicon steel plates with stable and excellent surface quality, which 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.

[0050] The present invention innovatively proposes low-hydrogen decarburization annealing, independent and precise oxygen control process and corresponding parameter control of annealing temperature, heating rate, annealing atmosphere and dew point, which greatly reduces the hydrogen consumption and reduces energy consumption. It not only has low production cost, flexible and simple operation, and high control accuracy, but also can produce copper-containing oriented silicon steel decarburization annealed plates with oxygen content and surface oxide layer structure that meet the needs of different users, and ultimately promotes the formation of finished plates with stable and excellent surface quality, which has great industrial application value.

[0051] It should be noted that, in this article, the term "comprise" or any other variation thereof is intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A low hydrogen and oxygen controlled decarburization annealing method for copper-containing oriented silicon steel, characterized in that: include: Surface treatment is performed at the initial stage of annealing, wherein H2 with a low dew point of ≤-40°C is used as the main protective gas to prevent surface overoxidation; Decarburization is carried out in the middle of annealing, reducing the H2 content to ≤10% and the dew point of the furnace atmosphere to ≤30℃ for decarburization; Independent oxygen control is performed at the end of annealing to adjust the H2 content and the dew point of the furnace atmosphere to accurately control the oxygen content and the surface oxide layer structure.

2. The low hydrogen and oxygen controlled decarburization annealing method for copper-containing oriented silicon steel according to claim 1, characterized in that: include: (1) placing the oriented silicon steel primary cold-rolled sheet into an annealing furnace, and performing surface treatment on the oriented silicon steel primary cold-rolled sheet in the heating section of the annealing furnace, wherein the heating rate of the annealing furnace is controlled between 20°C / s and 80°C / s, and H2 with a dew point of ≤-40°C is introduced, and the H2 content is controlled to be 20% to 50% to prevent the surface of the oriented silicon steel primary cold-rolled sheet from being overoxidized; (2) Decarburization annealing of the oriented silicon steel sheet is performed in a low hydrogen annealing atmosphere in a soaking zone of an annealing furnace, wherein the furnace temperature is controlled between 800°C and 850°C, the H2 content is reduced to 1% to 10%, and the dew point of the furnace atmosphere is adjusted to ≤30°C; (3) Precise oxygen control is performed at the end of the soaking section of the annealing furnace. The furnace temperature is increased by 5°C to 15°C based on the decarburization furnace temperature. The oxygen content and surface oxide layer structure of the annealed sheet are controlled by adjusting the H2 content to 5% to 50% and the dew point of the furnace atmosphere to 0 to 40°C.

3. The low hydrogen and oxygen controlled decarburization annealing method for copper-containing oriented silicon steel according to claim 2, characterized in that: During decarburization annealing, the partial pressure ratio of water and H2 is controlled at 0.25-0.

50.

4. The low hydrogen and oxygen controlled decarburization annealing method for copper-containing oriented silicon steel according to any one of claims 1 to 3, characterized in that: The weight percentage of silicon in the oriented silicon steel primary cold-rolled plate is 2.9% to 3.3%, and the weight percentage of copper is 0.3% to 0.7%.

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