A method for producing an ultra-wide oriented silicon steel with a good substrate
By optimizing the decarburization annealing and high-temperature annealing processes, the problem of uneven bottom layer formation in different parts of ultra-wide oriented silicon steel coils was solved, enabling efficient production of ultra-wide oriented silicon steel without surface defects.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 武汉钢铁有限公司
- Filing Date
- 2024-03-15
- Publication Date
- 2026-06-02
AI Technical Summary
In the production of ultra-wide grain-oriented silicon steel, the underlying layer of the steel coil is unevenly formed in different parts, resulting in surface defects such as watermarks, which affects the quality of the finished product and production efficiency.
By optimizing the decarburization annealing and high-temperature annealing processes, and by adopting segmented control of the protective atmosphere and temperature to form an atmosphere distribution with a specific partial pressure ratio, the oxide layer structure is optimized to ensure that the bottom layer of each part of the steel coil is well formed.
It significantly reduces the incidence of defects such as watermarks, improves finished product quality and production efficiency, and the proportion of watermark defects in the length of the whole roll is less than 5%, which is more than 13% less than conventional production processes.
Smart Images
Figure BDA0004742669840000151 
Figure BDA0004742669840000161
Abstract
Description
Technical Field
[0001] This invention belongs to the field of grain-oriented silicon steel production technology, specifically relating to a method for producing ultra-wide grain-oriented silicon steel with a good underlying layer. Background Technology
[0002] Low-temperature, high-magnetic-induction grain-oriented silicon steel is an excellent soft magnetic material used in transformer core manufacturing. Current low-temperature heating technologies often require nitriding in subsequent processes. The infiltration and overflow of nitrogen can affect the oxide layer or subsequent underlayer formation, leading to increased defects, particularly at the edges of the steel coil. Due to these edge defects, the finished product typically requires edge trimming. Therefore, for the same weight of steel coil, narrower plate widths and longer coil lengths result in greater losses after shearing, leading to lower yield. Furthermore, for the same coil weight, narrower plate widths and longer coil lengths increase the time spent on each production step, directly reducing production efficiency. On the other hand, for downstream transformer users, wider specifications allow for the production of larger power transformers, offering more flexible and efficient material utilization, resulting in significant cost reductions. Therefore, from both manufacturing and user perspectives, wider specifications are undoubtedly a more efficient choice.
[0003] However, as the width of the material increases, the difficulty of controlling the stability of the process increases, leading to problems such as uneven color of the finished sheet, watermarks, uneven magnetic properties along the width direction, and aggravated side cracks on the bottom plate. Compared to products with conventional widths (900-1100mm), ultra-wide products ≥1200mm experience greater temperature differences between the upper and lower ends and the inner and outer surfaces of the steel coil during high-temperature annealing. This also increases the difficulty of achieving fluidity and differences in the inner atmosphere and the interlayer atmosphere of the steel coil. These factors result in significantly different environments for the formation of the bottom layer on the upper end or outer surface of the steel coil compared to the bottom layer formation environment in the middle of the coil. Therefore, the formation time of the bottom layer varies in different parts of the steel coil during high-temperature annealing. If the oxide layer structure formed during decarburization annealing is unreasonable, it will lead to better bottom layer formation in some areas and poorer formation in others. Therefore, ensuring good bottom layer formation in different parts of the steel coil and reducing surface defects such as watermarks has become a new challenge in silicon steel production with increased width. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a production method for ultra-wide oriented silicon steel with a good underlying layer, which addresses the shortcomings of the existing technology. By optimizing the atmosphere and temperature of different parts of the furnace during the decarburization annealing process and the high-temperature annealing process, the generation of watermark defects on the surface of the steel coil is reduced.
[0005] To address the technical problem presented in this invention, this invention provides a method for producing ultra-wide grain-oriented silicon steel with a good underlying layer, comprising the following steps:
[0006] 1) Smelting and continuous casting
[0007] According to the chemical composition of grain-oriented silicon steel, slabs are smelted and continuously cast to obtain slabs;
[0008] 2) Hot rolling, pickling and normalizing, and cold rolling
[0009] The slab is heated and then hot-rolled, then pickled and normalized, and finally cold-rolled to the finished thickness;
[0010] 3) Decarburization annealing
[0011] The cold-rolled steel strip undergoes decarburization annealing in an annealing furnace, with protective gas introduced in stages and controls.
[0012] 4) Nitriding annealing
[0013] Nitriding is performed, followed by coating with MgO and drying.
[0014] 5) High-temperature annealing
[0015] The steel strip undergoes high-temperature annealing, which includes a primary heating section, a low-temperature holding section, a secondary heating section, a high-temperature holding section, and a cooling section.
[0016] 6) Stretching and leveling annealing
[0017] After leveling and annealing, an insulating coating is applied to obtain the finished grain-oriented silicon steel.
[0018] In the above scheme, the chemical composition of the oriented silicon steel by weight percentage is as follows: Si: 3.00-3.30%, C: 0.04-0.06%, Mn: 0.05-0.12%, P: 0.01-0.05%, S: 0.005-0.010%, N: 0.005-0.009%, Cr: 0.02-0.20%, Cu: 0.05-0.20%, Als: 0.0250-0.0315%, with the balance being Fe and unavoidable impurities.
[0019] In the above scheme, the heating temperature of the slab is 1120~1190℃.
[0020] In the above scheme, the thickness of the hot-rolled slab is 1.8 to 2.8 mm, and the width is 1200 to 1350 mm.
[0021] In the above scheme, the normalization is a two-stage normalization, with the first stage normalization temperature at 1100-1150℃ and the time at 10-30s, and the second stage normalization temperature at 850-950℃ and the time at 10-30s.
[0022] In the above scheme, the cold rolling is carried out in one rolling process, with intermediate passes performing effective rolling at 180-250°C.
[0023] In the above scheme, the thickness of the finished product is 0.18 to 0.3 mm.
[0024] In the above scheme, the decarburization annealing is carried out at a constant temperature of 800-900℃ for a duration of 1-3 minutes.
[0025] In the above scheme, the protective gas for decarburization annealing is a humidified mixture of N2 and H2, with a total flow rate of 400-600 m³ / h. 3 / h.
[0026] In the above scheme, the decarburization annealing is divided into three sections: the first section is the front end of the furnace, and its length accounts for 1 / 4 to 1 / 3 of the furnace length of the decarburization annealing section; the second section is the middle part of the furnace, and its length accounts for 1 / 3 to 1 / 2 of the furnace length of the decarburization annealing section; the third section is the rear end of the furnace, and its length accounts for 1 / 4 to 1 / 3 of the furnace length of the decarburization annealing section.
[0027] Furthermore, the protective air nozzles in each section are arranged at intervals of 2 to 3 meters.
[0028] Furthermore, the flow rate of protective gas is different for each stage: 9-17% of the total flow rate for the first stage, 30-53% for the second stage, and 37.5-63% for the third stage.
[0029] Furthermore, the flow rate of each nozzle is the same in the first section, the flow rate of each nozzle is the same in the third section, and the flow rate of the nozzles gradually increases from front to back in the second section according to a certain fixed value, with an increment of 0.3 to 1.2 m. 3 / h.
[0030] Furthermore, the humidification temperature and hydrogen content (volume fraction of hydrogen) of the protective gas are different for each stage. The first stage has a humidification temperature of 0-15℃ and a hydrogen content of 40-75%; the second stage has a humidification temperature of 35-50℃ and a hydrogen content of 45-65%; and the third stage has a humidification temperature of 65-75℃ and a hydrogen content of 40-65%.
[0031] In the above scheme, a set of detection points, numbered from 1 to n, are arranged from the front to the back of the decarburization annealing furnace. The detection points start 2-5m from the front of the furnace and are arranged at fixed lengths every 5-10m thereafter, satisfying 16≤n≤20. The protective gas is introduced non-uniformly in stages to ensure that the water-hydrogen partial pressure ratio at any detection point in the furnace satisfies the formula: 0.00988 + 0.03892X - 0.01471X. 2 +0.00188X 3 -0.00005771X 4 ≤P X ≤0.05886-0.02949X+0.01341X 2 -0.00048X 3 In the formula, X represents the detection point number, PX This indicates the water-hydrogen partial pressure ratio (P) measured at detection point X. H2O / P H2 ).
[0032] In the above scheme, the O content in the steel after decarburization annealing is 500-1400 ppm.
[0033] In the above scheme, the nitriding temperature is 750-910℃ and the duration is 15-30s.
[0034] In the above scheme, the nitriding atmosphere is a mixture of N2 + H2 + NH3 with a dew point of -20 to 30°C, wherein the volume ratio of N2 to H2 is 1:(2 to 3), and the flow rate of NH3 is 3 to 20 m³ / s. 3 / h.
[0035] In the above scheme, the heating rate of the first heating stage of the high-temperature annealing is ≥50℃ / h, and the temperature is raised to 750~800℃. During the heating process, a N2+H2 mixture is introduced, wherein the volume fraction of N2 is 75~100%.
[0036] In the above scheme, the total holding time of the low-temperature annealing stage is 15-20 hours; the holding temperature for the first 1 / 3 stage is 750-800℃, and a N2+H2 mixture is introduced, wherein the volume fraction of N2 is 75-100%; the holding temperature for the latter 2 / 3 stage is 650-700℃, and a N2+H2 mixture is introduced, wherein the volume fraction of H2 is 75-90%.
[0037] In the above scheme, the heating rate of the secondary heating section of the high-temperature annealing is 10-17℃ / h. First, a N2+H2 mixture is introduced, in which the volume fraction of H2 is 75-90%, until the temperature rises to 850-950℃. Then, the volume fraction of H2 in the mixture is adjusted to 50-75% until the temperature rises to 1170-1210℃.
[0038] In the above scheme, the high-temperature annealing high-temperature holding section is in a 100% H2 atmosphere, the holding temperature is 1170~1210℃, and the holding time is 20~30h.
[0039] In the above scheme, the cooling section of the high-temperature annealing is first cooled to 600-700°C in a 100% H2 atmosphere at a rate of 12-30°C / h; then naturally cooled to room temperature in a 100% N2 atmosphere at an unlimited rate.
[0040] In the above scheme, the temperature of the leveling annealing is 800-900℃.
[0041] The main technical concept of this invention is as follows:
[0042] Decarburization annealing is a crucial step in the production of grain-oriented silicon steel. Its main function is to adjust the dew point and hydrogen content of the atmosphere to create an oxidizing environment that removes carbon from the steel matrix. Simultaneously, a SiO2 oxide layer forms on the steel plate surface, followed by a coating of MgO. The MgO and SiO2 on the steel plate surface will form a Mg2SiO4 underlayer during the subsequent high-temperature annealing process. This underlayer protects the steel plates from sticking together during high-temperature annealing, provides a good adhesion carrier for the insulating coating applied to the finished product, and enhances magnetic properties through added tension. Therefore, a well-structured oxide layer in the decarburization stage is key to forming a good underlayer free of surface defects.
[0043] During the high-temperature annealing process of steel coils, the bottom layer is formed by the reaction of the oxide layer and the magnesium oxide coated on the surface. The reaction sequence of MgO and SiO2 is that MgO reacts first with the oxide surface layer and then gradually moves inward until all oxide layers are completely reacted, forming a Mg2SiO4 bottom layer covering the substrate surface. During the high-temperature annealing process, the outer ring of the steel coil has a higher temperature, and the interlayer atmosphere is similar to that inside the inner ring. The inner ring has a lower temperature, and the interlayer atmosphere is less volatile. The bottom layer inevitably forms from the outside in, with the outer ring forming first and the inner ring forming last. The different temperatures and atmospheres in different parts of the steel coil result in a lack of uniform oxide layer structure, which cannot meet the conditions required for good bottom layer formation in different areas.
[0044] Increasing the width of the steel coil leads to a greater temperature difference between the inside and outside of the coil, and a further reduction in the gas flow between the layers. This results in a more significant difference in the formation state of the bottom layer on the upper and lower ends and the outer ring of the coil compared to the interior of a coil of ordinary width. Therefore, the technical measures adopted in this invention mainly include:
[0045] The protective gas for decarburization annealing is introduced in stages and controlled to form a protective atmosphere with a specific partial pressure ratio in the furnace. The steel plate passes through areas with different partial pressure ratios in the furnace. Under low partial pressure ratio conditions, SiO2 is more likely to form, while under high partial pressure ratio conditions, Fe2SiO4 is more likely to form. Moreover, the SiO2 formed under different conditions also has different morphologies. Therefore, the oxide layer formed on the surface of the steel strip exhibits different structural characteristics, which can simultaneously satisfy the overflow of N in the outer and inner rings and the formation of a good bottom layer, thereby achieving the absence of watermark defects.
[0046] With the increase in the width of the steel coil, the difficulty of gas exchange between the layers increases. Therefore, in addition to optimizing the structure of the decarburized annealed oxide layer, it is also necessary to optimize the high-temperature annealing process. During the low-holding stage of high-temperature annealing, the molecular weight of N2 is relatively large. Increasing the N2 content can provide sufficient kinetic energy to quickly remove the high dew point atmosphere from the interlayer. Afterward, an atmosphere dominated by H2 is adopted, mainly because the molecular weight of H2 is smaller and it quickly occupies the top layer of the inner cover. The removed high dew point atmosphere will gradually sink until it is discharged from the sealing sand.
[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0048] This invention optimizes the oxide layer structure on the surface of grain-oriented silicon steel by creating a protective atmosphere with a specific partial pressure ratio in the decarburization annealing furnace. It also improves the drainage between layers of the steel coil through high-temperature annealing, which weakens the impact of increased width on the formation of the bottom layer on the surface of the grain-oriented silicon steel. This results in good bottom layer formation in all parts of the coil, significantly reducing the incidence of defects such as watermarks. The length of watermark defects accounts for less than 5% of the total coil length, which is more than 13% less than the incidence of watermarks compared to conventional production processes. Detailed Implementation
[0049] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.
[0050] Each embodiment of the present invention is manufactured according to the following process, including the following steps:
[0051] 1) Smelting and continuous casting
[0052] The chemical composition of grain-oriented silicon steel, by weight percentage, is as follows: Si: 3.00–3.30%, C: 0.04–0.06%, Mn: 0.05–0.12%, P: 0.01–0.05%, S: 0.005–0.010%, N: 0.005–0.009%, Cr: 0.02–0.20%, Cu: 0.05–0.20%, Als: 0.0250–0.0315%, with the balance being Fe and unavoidable impurities. The steel is then smelted and continuously cast to obtain a slab.
[0053] 2) Hot rolling, pickling and normalizing, and cold rolling
[0054] The slab is heated in a furnace at 1120–1190℃, then hot-rolled to a thickness of 1.8–2.8 mm and a width of 1200–1350 mm. It then undergoes pickling and normalizing in two stages: the first stage at 1100–1150℃ for 10–30 seconds, and the second stage at 850–950℃ for 10–30 seconds. Finally, it is cold-rolled in a single pass with intermediate passes at 180–250℃ to obtain a cold-rolled steel strip with a finished thickness of 0.18–0.3 mm.
[0055] 3) Decarburization annealing
[0056] Cold-rolled steel strip undergoes decarburization annealing in an annealing furnace at a constant temperature of 800–900℃ for 1–3 minutes. The protective gas for decarburization annealing is a humidified mixture of N2 and H2, with a total flow rate of 400–600 m³ / h. 3 / h;
[0057] The decarburization annealing section is divided into three sections according to the furnace length: the first section is the front end of the furnace, accounting for 1 / 4 to 1 / 3 of the furnace length; the second section is the middle part of the furnace, accounting for 1 / 3 to 1 / 2 of the furnace length; and the third section is the rear end of the furnace, accounting for 1 / 4 to 1 / 3 of the furnace length. Protective gas nozzles for each section are installed at 2-3m intervals, and the protective gas flow is controlled segment by segment.
[0058] a. The flow rate of protective gas is different in each stage: 9-17% of the total flow rate in the first stage, 30-53% in the second stage, and 37.5-63% in the third stage.
[0059] b. The flow rate of each nozzle is the same in the first and third sections. In the second section, the flow rate of the nozzles gradually increases from front to back according to a fixed value, with an increment of 0.3 to 1.2 m. 3 / h;
[0060] c. The humidification temperature and hydrogen content of the protective gas are different for each stage. The humidification temperature of the first stage is 0-15℃ and the hydrogen content is 40-75%; the humidification temperature of the second stage is 35-50℃ and the hydrogen content is 45-65%; the humidification temperature of the third stage is 65-75℃ and the hydrogen content is 40-65%.
[0061] A set of detection points, numbered from 1 to n, is set up from the front to the back of the furnace. The detection points begin 2-5 meters from the front of the furnace and are then spaced 5-10 meters apart at fixed lengths, ensuring that 16 ≤ n ≤ 20. Through segmented control, the water-hydrogen partial pressure ratio at any detection point inside the furnace satisfies the formula: 0.00988 + 0.03892X - 0.01471X. 2 +0.00188X 3 -0.00005771X 4 ≤P X ≤0.05886-0.02949X+0.01341X 2 -0.00048X 3 In the formula, X represents the detection point number, P X This indicates the water-hydrogen partial pressure ratio measured at detection point X;
[0062] After decarburization annealing, the oxygen content in the steel is 500–1400 ppm;
[0063] 4) Nitriding annealing
[0064] After decarburization annealing, nitriding is performed at a temperature of 750–910℃ for 15–30 seconds. The nitriding atmosphere is a mixture of N2, H2, and NH3 with a dew point of -20–30℃, wherein the volume ratio of N2 to H2 is 1:(2–3), and the flow rate of NH3 is 3–20 m³ / s. 3 / h, then coated with MgO and dried;
[0065] 5) High-temperature annealing
[0066] It includes a primary heating section, a low-temperature insulation section, a secondary heating section, a high-temperature insulation section, and a cooling section; among which:
[0067] The first heating stage rapidly heats the gas to 750-800℃ at a rate of ≥50℃ / h. During the heating process, a N2+H2 mixture is introduced, in which the volume fraction of N2 is 75-100%.
[0068] The total time for the low insulation section is 15-20 hours; the insulation temperature for the first 1 / 3 of the time is 750-800℃, maintaining the protective gas of the first heating section; the insulation temperature for the last 2 / 3 of the time is 650-700℃, and a N2+H2 mixture is introduced, in which the volume fraction of H2 is 75-90%.
[0069] The heating rate of the secondary heating section is 10-17℃ / h. During the heating process, the mixed gas in the last 2 / 3 of the low heat preservation section is maintained until the temperature rises to 850-950℃. Then the volume fraction of H2 in the mixed gas is adjusted to 50-75% until the temperature rises to 1170-1210℃.
[0070] The high-insulation section is in a 100% H2 atmosphere, with an insulation temperature of 1170-1210℃ and an insulation time of 20-30 hours.
[0071] The cooling section is first cooled to 600-700°C in a 100% H2 atmosphere at a rate of 12-30°C / h; then naturally cooled to room temperature in a 100% N2 atmosphere at an unlimited rate.
[0072] 6) Stretching and leveling annealing
[0073] After leveling and annealing at 800–900℃, an insulating coating is applied to obtain the finished grain-oriented silicon steel.
[0074] Example 1
[0075] The chemical composition of the oriented silicon steel in this embodiment is as follows (by weight percentage): Si: 3.1%, C: 0.05%, Mn: 0.08%, P: 0.01%, S: 0.005%, N: 0.007%, Cr: 0.02%, Cu: 0.05%, Als: 0.0260%, with the balance being Fe and unavoidable impurities.
[0076] A method for producing ultra-wide grain-oriented silicon steel with a good underlying layer includes the following steps:
[0077] 1) Smelting and continuous casting
[0078] According to the chemical composition of grain-oriented silicon steel, slabs are smelted and continuously cast to obtain slabs;
[0079] 2) Hot rolling, pickling and normalizing, and cold rolling
[0080] The slab is heated in a furnace at 1150℃ and hot-rolled to a thickness of 2.8mm and a width of 1200mm. It is then pickled and normalized in two stages: the first stage is normalized at 1100℃ for 25s, and the second stage is normalized at 850℃ for 10s. Finally, it is cold-rolled in one pass with an intermediate pass at 187℃ to obtain a finished cold-rolled steel strip with a thickness of 0.3mm.
[0081] 3) Decarburization annealing
[0082] The cold-rolled steel strip undergoes decarburization annealing in an annealing furnace at a constant temperature of 855℃ for 1.5 minutes. The protective gas for decarburization annealing is a humidified mixture of N2 and H2 with a total flow rate of 400 m³ / min. 3 / h;
[0083] The decarburization annealing section is divided into three sections: the first section is the front 1 / 4 of the furnace length, the second section is the middle 1 / 2 of the furnace length, and the third section is the rear 1 / 4 of the furnace length. The protective gas nozzles in each section are arranged at 2m intervals, and the protective gas supply is regulated in sections.
[0084] a. The flow rate of protective gas is different for each section: 12% of the total flow rate for the first section, 48% for the second section, and 40% for the third section.
[0085] b. The flow rate of each nozzle is the same in the first and third sections. In the second section, the flow rate of the nozzles gradually increases from front to back according to a fixed value, with an increment of 0.55m. 3 / h;
[0086] c. The humidification temperature and hydrogen content of the protective gas are different for each stage. The first stage has a humidification temperature of 0℃ and a hydrogen content of 40%; the second stage has a humidification temperature of 50℃ and a hydrogen content of 60%; and the third stage has a humidification temperature of 75℃ and a hydrogen content of 65%.
[0087] Inside the annealing furnace, a set of detection points, numbered 1 to 16, is set up from the front to the back of the furnace. The detection points begin 2 meters from the front of the furnace and are spaced 5 meters apart at fixed intervals. Through segmented control, the water-hydrogen partial pressure ratio at any detection point inside the furnace satisfies the formula: 0.00988 + 0.03892X - 0.01471X 2 +0.00188X 3 -0.00005771X 4 ≤P X ≤0.05886-0.02949X+0.01341X 2 -0.00048X3 In the formula, X represents the detection point number, P X This indicates the water-hydrogen partial pressure ratio measured at detection point X;
[0088] The measured results of the partial pressure ratio of water and hydrogen at each detection point are as follows:
[0089] Inspection point number X 1 2 3 4 5 6 7 8 <![CDATA[Water hydrogen partial pressure ratio P X > 0.039 0.045 0.06 0.1 0.17 0.23 0.27 0.32 Inspection point number X 9 10 11 12 13 14 15 16 <![CDATA[Water-hydrogen partial pressure ratio P X > 0.37 0.45 0.57 0.79 0.86 0.942 0.977 0.982
[0090] After decarburization annealing, the oxygen content in the steel is 680 ppm;
[0091] 4) Nitriding annealing
[0092] After decarburization annealing, nitriding is performed at a temperature of 750℃ for 15 seconds. The nitriding atmosphere is a mixture of N2, H2, and NH3 with a dew point of -20℃, where the volume ratio of N2 to H2 is 1:3 and the flow rate of NH3 is 10 m³ / s. 3 / h, then coated with MgO and dried;
[0093] 5) High-temperature annealing
[0094] The temperature is initially increased at a rate of 70℃ / h, with N2 + H2 as the introduced gas (75% N2). The temperature rises to 750℃, entering a low-temperature holding period. The total holding period is 15 hours. For the first third, the temperature is maintained at 750℃, using the same protective gas as the previous stage. For the remaining two-thirds, the temperature is maintained at 650℃, with N2 + H2 as the introduced gas (90% H2). A second temperature increase is then performed at a rate of 17℃ / h. The process involves maintaining the mixed gas from the previous stage until the temperature reaches 900℃, then adjusting the volume fraction of H2 in the mixed gas to 75% until the temperature reaches 1210℃, entering the high-temperature holding section; the high-temperature holding section is a 100% H2 atmosphere, with a holding temperature of 1210℃ and a holding time of 20 hours; entering the cooling section, it is first cooled to 600℃ in a 100% H2 atmosphere at a rate of 12℃ / h; then it is naturally cooled to room temperature in a 100% N2 atmosphere at an unlimited rate;
[0095] 6) Stretching and leveling annealing
[0096] The steel is annealed at 850℃ and then coated with an insulating coating to obtain the finished grain-oriented silicon steel.
[0097] Comparative Example 1
[0098] Comparative Example 1 is the same as Example 1 except for decarburization annealing and high-temperature annealing, except that:
[0099] Decarburization annealing: The decarburization annealing temperature is 855℃, and the duration is 1.5 min; the decarburization annealing nozzles are evenly arranged at 2 m intervals, the protective gas is a humidified N2 and H2 mixture, with H2 accounting for 50% by volume, the humidification temperature is 60℃, and the total flow rate is 400 m³ / min. 3 / h; A set of detection points numbered from 1 to 16 is set up from the front of the furnace to the back of the furnace. The detection points start from 2m in front of the furnace and are set up every 5m thereafter. The partial pressure ratio is 0.5±0.05; After decarburization, the O content in the steel is measured to be 710ppm.
[0100] High-temperature annealing: First, rapidly heat to 750℃ at a rate of 70℃ / h and hold for 15h. Then, slowly heat to 1210℃ at a rate of 17℃ / h. The mixed gas used in the above stages is a mixture of H2 and N2, with H2 accounting for 75%. After holding at 1210℃ for 20h, cool to 600℃ at a rate of 12℃ / h. The mixed gas used in the above stages is 100% H2. Finally, introduce 100% N2 and allow to cool naturally to room temperature at an unlimited rate.
[0101] Example 2
[0102] The chemical composition of the oriented silicon steel in this embodiment is as follows (by weight percentage): Si: 3.30%, C: 0.056%, Mn: 0.12%, P: 0.04%, S: 0.01%, N: 0.008%, Cr: 0.12%, Cu: 0.2%, Als: 0.0312%, with the balance being Fe and unavoidable impurities.
[0103] A method for producing ultra-wide grain-oriented silicon steel with a good underlying layer includes the following steps:
[0104] 1) Smelting and continuous casting
[0105] According to the chemical composition of grain-oriented silicon steel, slabs are smelted and continuously cast to obtain slabs;
[0106] 2) Hot rolling, pickling and normalizing, and cold rolling
[0107] The slab is heated in a furnace at 1190℃ and hot-rolled to a thickness of 2.6mm and a width of 1350mm. It is then pickled and normalized in two stages: the first stage is normalized at 1150℃ for 10s, and the second stage is normalized at 950℃ for 10s. Finally, it is cold-rolled in one pass with an intermediate pass at 221℃ to obtain a finished cold-rolled steel strip with a thickness of 0.27mm.
[0108] 3) Decarburization annealing
[0109] The cold-rolled steel strip underwent decarburization annealing in an annealing furnace at a constant temperature of 810℃ for 2.5 minutes. The protective gas for decarburization annealing was a humidified mixture of N2 and H2 with a total flow rate of 600 m³ / min. 3 / h;
[0110] The decarburization annealing section is divided into three sections: the first section is the front 1 / 3 of the furnace length, the second section is the middle 1 / 3 of the furnace length, and the third section is the rear 1 / 3 of the furnace length. The protective gas nozzles in each section are arranged at 3m intervals, and the protective gas supply is controlled in sections.
[0111] a. The flow rate of protective gas is different for each section: 16% of the total flow rate for the first section, 34% for the second section, and 50% for the third section.
[0112] b. The flow rate of each nozzle is the same in the first and third sections. In the second section, the flow rate of the nozzles gradually increases from front to back according to a fixed value, with an increment of 1.1m. 3 / h;
[0113] c. The humidification temperature and hydrogen content of the protective gas are different for each stage. The first stage has a humidification temperature of 15℃ and a hydrogen content of 75%; the second stage has a humidification temperature of 35℃ and a hydrogen content of 45%; and the third stage has a humidification temperature of 65℃ and a hydrogen content of 40%.
[0114] Inside the annealing furnace, a set of detection points, numbered 1 to 20, is set up from the front to the back of the furnace. The detection points begin 5 meters from the front of the furnace and are then spaced 10 meters apart at fixed intervals. Through segmented control, the water-hydrogen partial pressure ratio at any detection point inside the furnace is ensured to satisfy the formula: 0.00988 + 0.03892X - 0.01471X 2 +0.00188X 3 -0.00005771X 4 ≤P X ≤0.05886-0.02949X+0.01341X 2 -0.00048X 3 In the formula, X represents the detection point number, P X This indicates the water-hydrogen partial pressure ratio measured at detection point X;
[0115] The measured results of the partial pressure ratio of water and hydrogen at each detection point are as follows:
[0116] Inspection point number X 1 2 3 4 5 6 7 8 9 10 <![CDATA[Water-hydrogen partial pressure ratio P X > 0.04 0.044 0.052 0.061 0.08 0.097 0.126 0.156 0.25 0.31 Inspection point number X 11 12 13 14 15 16 17 18 19 20 <![CDATA[Water-hydrogen partial pressure ratio P X > 0.4 0.53 0.65 0.79 0.85 0.89 0.92 0.93 0.92 0.91
[0117] After decarburization annealing, the oxygen content in the steel was 856 ppm.
[0118] 4) Nitriding annealing
[0119] After decarburization annealing, nitriding is performed at a temperature of 850℃ for 10 seconds. The nitriding atmosphere is a mixture of N2 + H2 + NH3 with a dew point of 30℃, where the volume ratio of N2 to H2 is 1:2 and the flow rate of NH3 is 5 m³ / s. 3 / h, then coated with MgO and dried;
[0120] 5) High-temperature annealing
[0121] The temperature is initially increased at a rate of 75℃ / h, with 100% N2 gas introduced, until it reaches 800℃, at which point a low-temperature holding period begins. The total holding period is 20 hours. For the first third of this period, the temperature is maintained at 800℃, using the same protective gas as the previous stage. For the remaining two-thirds of this period, the temperature is maintained at 700℃, with N2 + H2 gas introduced, where H2 accounts for 75%. A second temperature increase is then performed at a rate of 10℃ / h, during which the temperature is initially maintained... The mixture from the previous stage is maintained until the temperature reaches 850℃. Then, the volume fraction of H2 in the mixture is adjusted to 50% until the temperature reaches 1170℃, entering the high-temperature holding section. The high-temperature holding section is a 100% H2 atmosphere, with a holding temperature of 1170℃ and a holding time of 30 hours. In the cooling section, the mixture is first cooled to 700℃ in a 100% H2 atmosphere at a rate of 30℃ / h. Then, it is allowed to cool naturally to room temperature in a 100% N2 atmosphere at an unlimited rate.
[0122] 6) Stretching and leveling annealing
[0123] The steel is annealed at 900℃ and then coated with an insulating coating to obtain the finished grain-oriented silicon steel.
[0124] Comparative Example 2
[0125] Comparative Example 2 is the same as Example 1 except for decarburization annealing and high-temperature annealing, except that:
[0126] Decarburization annealing: The decarburization annealing temperature is 810℃, and the duration is 2.5 min; the decarburization annealing nozzles are evenly arranged at 3 m intervals, the protective gas is a humidified N2 and H2 mixture, the volume percentage of H2 is 50%, the humidification temperature is 60℃, and the total flow rate is 600 m³ / min. 3 / h; A set of detection points numbered from 1 to 20 is set up from the front of the furnace to the back of the furnace. The detection points start from 5m in front of the furnace and are set up every 10m thereafter. The partial pressure ratio is 0.5±0.05. After decarburization, the O content in the steel is measured to be 885ppm.
[0127] High-temperature annealing: First, rapidly heat to 800℃ at a rate of 75℃ / h and hold for 20h. Then, slowly heat to 1170℃ at a rate of 10℃ / h. The mixed gas used in the above stages is a mixture of H2 and N2, with H2 accounting for 75%. Then, after holding at 1170℃ for 30h, cool to 700℃ at a rate of 30℃ / h. The mixed gas used in the above stages is 100% H2. Finally, introduce 100% N2 and allow to cool naturally to room temperature at an unlimited rate.
[0128] Example 3
[0129] The chemical composition of the oriented silicon steel in this embodiment is as follows (by weight percentage): Si: 3.25%, C: 0.05%, Mn: 0.08%, P: 0.04%, S: 0.008%, N: 0.0075%, Cr: 0.1%, Cu: 0.05%, Als: 0.0285%, with the balance being Fe and unavoidable impurities.
[0130] A method for producing ultra-wide grain-oriented silicon steel with a good underlying layer includes the following steps:
[0131] 1) Smelting and continuous casting
[0132] According to the chemical composition of grain-oriented silicon steel, slabs are smelted and continuously cast to obtain slabs;
[0133] 2) Hot rolling, pickling and normalizing, and cold rolling
[0134] The slab is heated in a furnace at 1170℃ and hot-rolled to a thickness of 2.4mm and a width of 1290mm. It is then pickled and normalized in two stages: the first stage is normalized at 1140℃ for 20s, and the second stage is normalized at 920℃ for 15s. Finally, it is cold-rolled in one pass with an intermediate pass at 245℃ to obtain a finished cold-rolled steel strip with a thickness of 0.23mm.
[0135] 3) Decarburization annealing
[0136] The cold-rolled steel strip undergoes decarburization annealing in an annealing furnace at a constant temperature of 845℃ for 2 minutes. The protective gas for decarburization annealing is a humidified mixture of N2 and H2 with a total flow rate of 500 m³ / min. 3 / h;
[0137] The decarburization annealing section is divided into three sections: the first section is the front 1 / 3 of the furnace length, the second section is the middle 1 / 3 of the furnace length, and the third section is the rear 1 / 3 of the furnace length. Protective gas nozzles for each section are installed at 2.5m intervals, and the protective gas flow is controlled segment by segment.
[0138] a. The flow rate of protective gas is different for each section: 14% of the total flow rate for the first section, 34% for the second section, and 52% for the third section.
[0139] b. The flow rate of each nozzle is the same in the first and third sections. In the second section, the flow rate of the nozzles gradually increases from front to back according to a fixed value, with an increment of 0.6m. 3 / h;
[0140] c. The humidification temperature and hydrogen content of the protective gas are different for each stage. The first stage has a humidification temperature of 10℃ and a hydrogen content of 55%; the second stage has a humidification temperature of 40℃ and a hydrogen content of 50%; and the third stage has a humidification temperature of 68℃ and a hydrogen content of 45%.
[0141] Inside the annealing furnace, a set of detection points, numbered 1 to 18, is set up from the front to the back of the furnace. The detection points begin 5 meters from the front of the furnace and are then spaced 10 meters apart at fixed intervals. Through segmented control, the water-hydrogen partial pressure ratio at any detection point inside the furnace is ensured to satisfy the formula: 0.00988 + 0.03892X - 0.01471X 2 +0.00188X 3 -0.00005771X 4 ≤P X ≤0.05886-0.02949X+0.01341X 2 -0.00048X 3 In the formula, X represents the detection point number, P X This indicates the water-hydrogen partial pressure ratio measured at detection point X;
[0142] The measured results of the partial pressure ratio of water and hydrogen at each detection point are as follows:
[0143] Inspection point number X 1 2 3 4 5 6 7 8 9 <![CDATA[Water hydrogen partial pressure ratio P X > 0.038 0.045 0.056 0.067 0.088 0.11 0.153 0.2 0.29 Inspection point number X 10 11 12 13 14 15 16 17 18 <![CDATA[Water-hydrogen partial pressure ratio P X > 0.42 0.58 0.75 0.87 0.94 0.99 1 0.99 0.98
[0144] After decarburization annealing, the oxygen content in the steel is 964 ppm;
[0145] 4) Nitriding annealing
[0146] After decarburization annealing, nitriding is performed at a temperature of 860℃ for 15 seconds. The nitriding atmosphere is a mixture of N2, H2, and NH3 with a dew point of 30℃, where the volume ratio of N2 to H2 is 1:3 and the flow rate of NH3 is 6 m³ / s. 3 / h, then coated with MgO and dried;
[0147] 5) High-temperature annealing
[0148] The temperature is initially increased at a rate of 70℃ / h, with N2 + H2 as the introduced gas (90% N2). The temperature rises to 750℃, entering a low-temperature holding period. The total holding period is 20 hours. For the first third, the temperature is maintained at 750℃, using the same protective gas as the previous stage. For the remaining two-thirds, the temperature is maintained at 700℃, with N2 + H2 as the introduced gas (80% H2). A second temperature increase is then performed at a rate of 15℃ / h. The process involves maintaining the mixed gas from the previous stage until the temperature reaches 950℃, then adjusting the volume fraction of H2 in the mixed gas to 65% until the temperature reaches 1200℃, entering the high-temperature holding section; the high-temperature holding section is a 100% H2 atmosphere, with a holding temperature of 1200℃ and a holding time of 25 hours; entering the cooling section, it is first cooled to 700℃ in a 100% H2 atmosphere at a rate of 20℃ / h; then it is naturally cooled to room temperature in a 100% N2 atmosphere at an unlimited rate;
[0149] 6) Stretching and leveling annealing
[0150] The steel is annealed at 850℃ and then coated with an insulating coating to obtain the finished grain-oriented silicon steel.
[0151] Comparative Example 3
[0152] Comparative Example 3 is the same as Example 1 except for decarburization annealing and high-temperature annealing, except that:
[0153] Decarburization annealing: The decarburization annealing temperature is 845℃, and the duration is 2 minutes; the decarburization annealing nozzles are evenly arranged at 2.5m intervals, the protective gas is a humidified N2 and H2 mixture, with H2 accounting for 50% by volume, the humidification temperature is 60℃, and the total flow rate is 500m³. 3 / h; A set of detection points numbered from 1 to 18 is set up from the front of the furnace to the back of the furnace. The detection points start from 5m in front of the furnace and are set up every 10m thereafter. The partial pressure ratio is 0.5±0.05. After decarburization, the O content in the steel is measured to be 929ppm.
[0154] High-temperature annealing: First, rapidly heat to 750℃ at a rate of 70℃ / h and hold for 20h. Then, slowly heat to 1200℃ at a rate of 15℃ / h. The mixed gas used in the above stages is a mixture of H2 and N2, with H2 accounting for 75%. After holding at 1200℃ for 25h, cool to 700℃ at a rate of 20℃ / h. The mixed gas used in the above stages is 100% H2. Finally, introduce 100% N2 and allow to cool naturally to room temperature at an unlimited rate.
[0155] Example 4
[0156] The chemical composition of the oriented silicon steel in this embodiment is as follows (by weight percentage): Si: 3.10%, C: 0.048%, Mn: 0.12%, P: 0.02%, S: 0.005%, N: 0.0069%, Cr: 0.12%, Cu: 0.2%, Als: 0.0315%, with the balance being Fe and unavoidable impurities.
[0157] A method for producing ultra-wide grain-oriented silicon steel with a good underlying layer includes the following steps:
[0158] 1) Smelting and continuous casting
[0159] According to the chemical composition of grain-oriented silicon steel, slabs are smelted and continuously cast to obtain slabs;
[0160] 2) Hot rolling, pickling and normalizing, and cold rolling
[0161] The slab is heated in a furnace at 1150℃ and hot-rolled to a thickness of 2.2mm and a width of 1250mm. It is then pickled and normalized in two stages: the first stage is normalized at 1140℃ for 15s, and the second stage is normalized at 900℃ for 12s. Finally, it is cold-rolled in one pass with an intermediate pass at 223℃ to obtain a finished cold-rolled steel strip with a thickness of 0.2mm.
[0162] 3) Decarburization annealing
[0163] The cold-rolled steel strip undergoes decarburization annealing in an annealing furnace at a constant temperature of 825℃ for 3 minutes. The protective gas for decarburization annealing is a humidified mixture of N2 and H2 with a total flow rate of 600 m³ / s. 3 / h;
[0164] The decarburization annealing section is divided into three sections: the first section is the front 1 / 4 of the furnace length, the second section is the middle 1 / 2 of the furnace length, and the third section is the rear 1 / 4 of the furnace length. The protective gas nozzles in each section are arranged at 3m intervals, and the protective gas supply is regulated in sections.
[0165] a. The flow rate of protective gas is different for each stage: 10% of the total flow rate for the first stage, 47% for the second stage, and 43% for the third stage.
[0166] b. The flow rate of each nozzle is the same in the first and third sections. In the second section, the flow rate of the nozzles gradually increases from front to back according to a fixed value, with an increment of 0.42m. 3 / h;
[0167] c. The humidification temperature and hydrogen content of the protective gas are different for each stage. The first stage has a humidification temperature of 5℃ and a hydrogen content of 50%; the second stage has a humidification temperature of 50℃ and a hydrogen content of 55%; and the third stage has a humidification temperature of 70℃ and a hydrogen content of 50%.
[0168] Inside the annealing furnace, a set of detection points, numbered 1 to 20, is set up from the front to the back of the furnace. The detection points begin 5 meters from the front of the furnace and are then spaced 10 meters apart at fixed intervals. Through segmented control, the water-hydrogen partial pressure ratio at any detection point inside the furnace is ensured to satisfy the formula: 0.00988 + 0.03892X - 0.01471X 2 +0.00188X 3 -0.00005771X 4 ≤P X ≤0.05886-0.02949X+0.01341X 2 -0.00048X 3 In the formula, X represents the detection point number, P X This indicates the water-hydrogen partial pressure ratio measured at detection point X;
[0169] The measured results of the partial pressure ratio of water and hydrogen at each detection point are as follows:
[0170] Inspection point number X 1 2 3 4 5 6 7 8 9 10 <![CDATA[Water-hydrogen partial pressure ratio P X > 0.037 0.046 0.062 0.092 0.15 0.21 0.25 0.32 0.38 0.44 Inspection point number X 11 12 13 14 15 16 17 18 19 20 <![CDATA[Water hydrogen partial pressure ratio P X > 0.51 0.6 0.69 0.78 0.88 0.93 0.98 1.02 1.01 0.97
[0171] After decarburization annealing, the oxygen content in the steel was 1259 ppm.
[0172] 4) Nitriding annealing
[0173] After decarburization annealing, nitriding is performed at a temperature of 800℃ for 15 seconds. The nitriding atmosphere is a mixture of N2 + H2 + NH3 with a dew point of 20℃, wherein the volume ratio of N2 to H2 is 1:3 and the flow rate of NH3 is 7m³. 3 / h, then coated with MgO and dried;
[0174] 5) High-temperature annealing
[0175] The temperature is initially increased at a rate of 75℃ / h, with 100% N2 gas introduced, reaching 750℃ before entering the low-temperature holding phase. The total holding time for this phase is 20 hours. For the first third of this phase, the temperature is maintained at 750℃, using the same protective gas as the previous stage. For the remaining two-thirds of this phase, the temperature is maintained at 650℃, with N2 + H2 gas introduced, where H2 accounts for 90%. Then, a second temperature increase is performed at a rate of 10℃ / h, maintaining the protective gas from the previous stage. The mixed gas from the previous stage is held until the temperature reaches 850℃. Then, the volume fraction of H2 in the mixed gas is adjusted to 50% until the temperature reaches 1190℃, entering the high-temperature holding section. The high-temperature holding section is a 100% H2 atmosphere, with a holding temperature of 1190℃ and a holding time of 25 hours. In the cooling section, the gas is first cooled to 600℃ in a 100% H2 atmosphere at a rate of 15℃ / h. Then, it is allowed to cool naturally to room temperature in a 100% N2 atmosphere at an unlimited rate.
[0176] 6) Stretching and leveling annealing
[0177] The product is oriented silicon steel by performing leveling annealing at 840℃ and applying an insulating coating.
[0178] Comparative Example 4
[0179] Comparative Example 4 is the same as Example 1 except for decarburization annealing and high-temperature annealing, except that:
[0180] Decarburization annealing: The decarburization annealing temperature is 825℃, and the duration is 3 minutes; the decarburization annealing nozzles are evenly arranged at 3m intervals, the protective gas is a humidified N2 and H2 mixture, with H2 accounting for 50% by volume, the humidification temperature is 60℃, and the total flow rate is 600m³. 3 / h; A set of detection points numbered from 1 to 20 is set up from the front of the furnace to the back of the furnace. The detection points start from 5m in front of the furnace and are set up every 10m thereafter. The partial pressure ratio is 0.5±0.05. After decarburization, the O content in the steel is measured to be 1140ppm.
[0181] High-temperature annealing: First, rapidly heat to 750℃ at a rate of 75℃ / h and hold for 20h. Then, slowly heat to 1190℃ at a rate of 10℃ / h. The mixed gas used in the above stages is a mixture of H2 and N2, with H2 accounting for 75%. After holding at 1190℃ for 25h, cool to 600℃ at a rate of 15℃ / h. The mixed gas used in the above stages is 100% H2. Finally, introduce 100% N2 and allow to cool naturally to room temperature at an unlimited rate.
[0182] The occurrence of defects on the surface of the oriented silicon steel products obtained in each embodiment and comparative example was tracked, and the results are as follows:
[0183]
[0184]
[0185] The above data shows that by adopting the production method of the present invention, the occurrence rate of watermarks can be significantly reduced, and the proportion of watermark defects in the length of the roll is less than 5%, which is more than 13% less than the occurrence rate of watermarks compared with conventional production processes.
[0186] The above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for producing ultra-wide grain-oriented silicon steel with a good underlying layer, characterized in that, Includes the following steps: 1) Smelting and continuous casting According to the chemical composition of grain-oriented silicon steel, slabs are obtained by smelting and continuous casting. 2) Hot rolling, pickling and normalizing, and cold rolling The slab is heated in a heating furnace at a temperature of 1120~1190℃, and then hot-rolled to a thickness of 1.8~2.8mm and a width of 1200~1350mm; subsequently, it is pickled and normalized, and then cold-rolled to a finished thickness of 0.18~0.3mm. 3) Decarburization annealing Decarburization annealing is carried out at a constant temperature of 800-900℃ for 1-3 minutes. The decarburization annealing is divided into three sections: the first section is the front end of the furnace, accounting for 1 / 4 to 1 / 3 of the furnace length; the second section is the middle part of the furnace, accounting for 1 / 3 to 1 / 2 of the furnace length; and the third section is the rear end of the furnace, accounting for 1 / 4 to 1 / 3 of the furnace length. The protective gas is introduced in stages, with different humidification temperatures and hydrogen content in each section: the first section has a humidification temperature of 0-15℃ and a hydrogen content of 40-75%; the second section has a humidification temperature of 35-50℃ and a hydrogen content of 45-65%; and the third section has a humidification temperature of 65-75℃ and a hydrogen content of 40-65%. Inside the decarburization annealing furnace, a set of detection points, numbered from 1 to n, is arranged from front to back. The detection points begin 2-5 meters from the front of the furnace and are then spaced 5-10 meters apart at fixed intervals. Through segmented control, the water-hydrogen partial pressure ratio at any detection point inside the furnace satisfies the formula: 0.00988 + 0.03892X - 0.01472X 2 +0.00188X 3 -0.00005771X 4 ≤P X ≤0.05886-0.02949X+0.01341X 2 -0.00048X 3 In the formula, X represents the detection point number, P X This indicates the water-hydrogen partial pressure ratio measured at detection point X; 4) Nitriding annealing The nitriding temperature is 750~910℃, the duration is 15~30s, then MgO is coated and dried. 5) High-temperature annealing It includes a primary heating section, a low insulation section, a secondary heating section, a high insulation section, and a cooling section; 6) Stretching and leveling annealing After leveling and annealing, an insulating coating is applied to obtain the finished grain-oriented silicon steel.
2. The method for producing ultra-wide grain-oriented silicon steel with a good underlying layer according to claim 1, characterized in that, The protective gas for the decarburization annealing is a humidified mixture of N2 and H2, with a total flow rate of 400~600 m³ / h. 3 / h, the first segment carries 9~17% of the total flow, the second segment carries 30~53% of the total flow, and the third segment carries 37.5~63% of the total flow.
3. The method for producing ultra-wide grain-oriented silicon steel with a good underlying layer according to claim 1, characterized in that, The protective gas nozzles for decarburization annealing are arranged at intervals of 2-3m. The flow rate of each nozzle in the first section is the same, and the flow rate of each nozzle in the third section is also the same. In the second section, the flow rate of the nozzles gradually increases from front to back according to a fixed value, with increments of 0.3-1.2m. 3 / h.
4. The method for producing ultra-wide grain-oriented silicon steel with a good underlying layer according to claim 1, characterized in that, The nitriding atmosphere is a mixture of N2 + H2 + NH3 with a dew point of -20 to 30°C, wherein the volume ratio of N2 to H2 is 1:(2~3), and the flow rate of NH3 is 3~20 m³ / s. 3 / h.
5. The method for producing ultra-wide grain-oriented silicon steel with a good underlying layer according to claim 1, characterized in that, The heating rate of the first heating stage of the high-temperature annealing is ≥50℃ / h, and the temperature is raised to 750~800℃. During the heating process, a N2+H2 mixture is introduced, wherein the volume fraction of N2 is 75~100%.
6. The method for producing ultra-wide grain-oriented silicon steel with a good underlying layer according to claim 1, characterized in that, The total holding time for the low-temperature annealing stage is 15-20 hours; the holding temperature for the first 1 / 3 of the time is 750-800℃, and a N2+H2 mixture is introduced, wherein the volume fraction of N2 is 75-100%; the holding temperature for the latter 2 / 3 of the time is 650-700℃, and a N2+H2 mixture is introduced, wherein the volume fraction of H2 is 75-90%.
7. The method for producing ultra-wide grain-oriented silicon steel with a good underlying layer according to claim 1, characterized in that, The heating rate of the secondary heating section of the high-temperature annealing is 10~17℃ / h. First, a N2+H2 mixture is introduced, in which the volume fraction of H2 is 75~90%, until the temperature rises to 850~950℃. Then, the volume fraction of H2 in the mixture is adjusted to 50~75% until the temperature rises to 1170~1210℃.
8. The method for producing ultra-wide grain-oriented silicon steel with a good underlying layer according to claim 1, characterized in that, The high-temperature annealing high-holding section is in a 100% H2 atmosphere, with a holding temperature of 1170~1210℃ and a holding time of 20~30h; the high-temperature annealing cooling section is first cooled to 600~700℃ in a 100% H2 atmosphere at a rate of 12~30℃ / h; then it is naturally cooled to room temperature in a 100% N2 atmosphere at an unlimited rate.
9. The method for producing ultra-wide grain-oriented silicon steel with a good underlying layer according to claim 1, characterized in that, The chemical composition of the oriented silicon steel, by weight percentage, is as follows: Si: 3.00~3.30%, C: 0.04~0.06%, Mn: 0.05~0.12%, P: 0.01~0.05%, S: 0.005~0.010%, N: 0.005~0.009%, Cr: 0.02~0.20%, Cu: 0.05~0.20%, Als: 0.0250~0.0315%, with the balance being Fe and unavoidable impurities.