A manufacturing method of high-magnetic-induction low-iron-loss ultra-thin oriented silicon steel

Abstract

The application belongs to the technical field of ultra-thin oriented silicon steel processing, and particularly relates to a manufacturing method of high-magnetic-induction low-iron-loss ultra-thin oriented silicon steel. The bottom-layer-free oriented silicon steel base material is subjected to cold rolling, alkali washing, nitriding annealing, high-temperature annealing, insulating layer coating, heat-resistant laser marking, nitriding process is used to nitride the base body, the aluminum and silicon elements in the base material are combined to form an effective inhibitor, the growth of non-Goss grains is inhibited during high-temperature annealing, the accurate Goss is promoted to grow abnormally, and finally the Goss texture with uniformity and small deviation is obtained. After coating and heat-resistant laser marking, the magnetic domain is effectively refined, and the loss is further reduced. The application avoids the growth of non-Goss orientation or large-deviation Goss orientation grains in the process of manufacturing the ultra-thin oriented silicon steel by the primary recrystallization method, accurately induces the abnormal growth of Goss by the inhibitor, and combines the tension coating and heat-resistant laser marking to reduce the iron loss, thereby manufacturing the high-magnetic-induction low-iron-loss ultra-thin oriented silicon steel.

Description

Technical Field

[0001] This invention belongs to the field of ultra-thin oriented silicon steel processing technology, specifically a method for manufacturing ultra-thin oriented silicon steel with high magnetic induction and low iron loss. Background Technology

[0002] Ultra-thin grain-oriented silicon steel refers to steel with a thickness of less than 0.1 mm and a {110} dimensional index. <001> Goss textured oriented silicon steel sheets have excellent magnetic properties under medium and high frequency conditions. They are generally used to make the cores of various transformers and reactors above 400Hz, such as high frequency transformers and pulse generators. They are soft magnetic materials with special functions in the fields of power, aviation and military.

[0003] Traditionally, grain-oriented silicon steel with a thickness ≥0.15mm typically employs an inhibitor-induced Goss texture secondary recrystallization method. However, when the thickness is reduced to below 0.1mm, the inhibitor easily becomes ineffective due to surface effects, making secondary recrystallization extremely unstable and ultimately resulting in poor magnetic properties. Ultra-thin grain-oriented silicon steel is generally considered to have three preparation methods: the most commonly used is the primary recrystallization method. This method uses finished grain-oriented silicon steel sheets as raw materials, undergoing a single cold rolling and primary recrystallization annealing process. It mainly utilizes the inherited Goss texture, meaning that after 50%–70% cold rolling deformation, the Goss texture... <110> / / Rotate the TD axis 35° to {111} <112> The texture, after initial recrystallization, reverts to the Goss texture. The initial recrystallization process is simple, easy to control, and allows for continuous production, making it the primary technical means for the current industrial production of ultra-thin grain-oriented silicon steel. Patent CN1562511A discloses a method for manufacturing ultra-thin grain-oriented silicon steel strips, using ordinary grain-oriented silicon steel as raw material, employing asynchronous rolling to prepare 0.06–0.1 mm ultra-thin strips, followed by initial recrystallization annealing at 700–980℃. Patent CN108315542A discloses an ultra-thin grain-oriented silicon steel sheet and its preparation method, using a base material without a bottom grain grain-oriented silicon steel, and preparing 0.01–0.1 mm ultra-thin grain-oriented silicon steel through cold rolling, recrystallization annealing, and coating. Patent CN111004903A discloses a method for increasing the η-texture occupancy rate in ultra-thin grain-oriented silicon steel strips, achieving an η-texture occupancy rate of 76–85% through emulsion-based hot rolling and protective atmosphere annealing. However, due to differences in Goss orientation in the base material and a certain gradient in the deformation process, a gradient exists in the cold-rolled texture. After recrystallization annealing, it is inevitable that Goss grains with large deviations and {411} will form. <148> Non-Goss textures, and even {110} <110> Gamma textures, which are detrimental to magnetic properties, are present in ultrathin oriented silicon steel. Current solutions involve using high-magnetic-induction oriented silicon steel as the base material and improving rolling and annealing processes. The former aims to increase the initial Goss texture orientation, while the latter can only maximize the proportion of Goss texture and cannot completely prevent the formation of non-Goss orientations due to uneven deformation. Therefore, improving the Goss orientation and proportion in ultrathin oriented silicon steel becomes crucial for enhancing its magnetic properties.

[0004] The second method is the conventional secondary recrystallization method. This method uses inhibitors to induce perfect secondary recrystallization of Goss grains. However, when the thickness is reduced, on the one hand, excessive cold rolling reduction is not conducive to the inheritance of Goss texture, and the number of deviated Goss or non-Goss oriented grains increases. On the other hand, the thinner the steel plate, the more obvious the surface effect. During high-temperature annealing, the inhibitor is easily coarsened, and the grains are prone to normal growth, making secondary recrystallization difficult. The third method is the surface energy-induced tertiary recrystallization method. This method utilizes the surface energy difference between {110} and {100} oriented grains. However, this method is extremely sensitive to the purity of the steel plate, annealing atmosphere, temperature, etc., and can only be prepared under laboratory conditions, making it difficult to achieve stable industrial production. Patent CN104726669A proposes a method for preparing low-iron-loss medium-frequency oriented silicon steel strips. The finished 0.15-0.35mm oriented silicon steel is cold-rolled to 0.03-0.1mm, and then coated with a release agent before being subjected to high-temperature annealing in a bell. However, it is foreseeable that, due to the lack of inhibitors, large deviations in Goss or non-Goss oriented grains will inevitably form during high-temperature annealing. Therefore, how to fully utilize the heritability of Goss texture and use inhibitors to induce accurate Goss formation and perfect secondary recrystallization becomes the key to manufacturing high magnetic induction, low iron loss, ultrathin oriented silicon steel. Summary of the Invention

[0005] The purpose of this invention is to provide a method for manufacturing ultrathin oriented silicon steel with high magnetic induction and low iron loss, which solves the technical problems of low Goss texture ratio, non-Goss oriented grain growth, and difficulty in balancing magnetic properties and overall quality in ultrathin oriented silicon steel, and achieves simultaneous improvement in Goss orientation degree and proportion in ultrathin oriented silicon steel.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] A method for manufacturing ultrathin grain-oriented silicon steel with high magnetic induction and low iron loss includes the following steps:

[0008] (1) Preparation of base material: Select non-oriented silicon steel with a thickness of 0.18 to 0.30 mm as raw material. The magnetic induction B8 of the non-oriented silicon steel is 1.85 to 1.94 T and the iron loss P is 0. 1.7 / 50 ≤1.2W / kg, the mass fraction of acid-soluble aluminum (Als) in the parent material is 0.01%~0.04%;

[0009] (2) Cold rolling: For silicon steel without bottom layer orientation, 3 to 6 passes of reciprocating rolling are used, with the first pass reduction rate of 30% to 55%; the total cold rolling reduction rate shall not exceed 90%;

[0010] (3) Alkali washing: Alkali washing is performed on the cold-rolled steel plate to remove oil and impurities from the surface of the steel plate;

[0011] (4) Nitriding annealing: The steel plate after alkaline washing is nitrided and annealed in a mixed atmosphere of nitrogen, hydrogen and ammonia. The nitriding temperature is 750-850℃ and the nitriding time is 30-240s. The nitriding amount ∆[N] is controlled in three stages according to the mass fraction of aluminum Als dissolved in the base material.

[0012] When the base material [Als] content is 0.01% ≤ [Als] ≤ 0.02%, the nitriding amount ∆[N] should be controlled within the range of 80–150 ppm; when the base material [Als] content is 0.02% < [Als] ≤ 0.03%, the nitriding amount ∆[N] should be controlled within the range of 150–250 ppm; when the base material [Als] content is 0.03% < [Als] ≤ 0.04%, the nitriding amount ∆[N] should be controlled within the range of 250–300 ppm.

[0013] (5) High-temperature annealing: After nitriding annealing, the steel plate is first coated with a magnesium oxide isolation layer, and then high-temperature annealing is carried out;

[0014] (6) Coating an insulating layer and heat-resistant laser marking: After high-temperature annealing, an inorganic insulating layer is first coated, and then heat-resistant laser marking is performed; the heat-resistant laser marking is stress-relief annealing laser marking, which processes linear physical grooves on a silicon steel substrate, with a marking depth of 10% to 20% of the steel plate thickness and a spacing of 2 to 8 mm between adjacent grooves;

[0015] The above steps are used to prepare ultrathin oriented silicon steel with a thickness of 0.03 to 0.10 mm.

[0016] In the manufacturing method of the high magnetic induction, low iron loss, ultrathin oriented silicon steel, in step (1), the substrate without a bottom layer of oriented silicon steel has {110} <001> Goss texture, grain-oriented silicon steel without a magnesium silicate underlayer on the surface, is obtained by pickling finished grain-oriented silicon steel with a magnesium silicate underlayer to remove the magnesium silicate underlayer and insulating coating, or by grain-oriented silicon steel that originally had no magnesium silicate underlayer during the manufacturing process.

[0017] In the manufacturing method of the high magnetic induction and low iron loss ultra-thin oriented silicon steel, in step (2), the cold rolling is a continuous production of 3 to 6 passes, or a stress-relief annealing is performed once in the middle pass of the cold rolling. The stress-relief annealing temperature is 650 to 750°C and the holding time is 1 to 5 minutes.

[0018] In the manufacturing method of the high magnetic induction and low iron loss ultra-thin oriented silicon steel, in step (4), by volume percentage, the mixed atmosphere contains 10% to 20% ammonia, 60% to 70% hydrogen, and the remainder is nitrogen.

[0019] In the manufacturing method of the high magnetic induction and low iron loss ultrathin oriented silicon steel, in step (4), the average grain size of the steel plate after nitriding annealing is 10-40 μm.

[0020] The manufacturing method of the high magnetic induction and low iron loss ultra-thin oriented silicon steel, in step (5), the high temperature annealing process includes: first, holding at 620-680℃ for 3-5 hours, then slowly raising the temperature to 1120-1200℃ at 20-40℃ / h under a mixed protective atmosphere of 60%-80% hydrogen and 20%-40% nitrogen by volume; after reaching the target temperature, switching to a pure hydrogen atmosphere and holding at 1120-1200℃ for 20-28 hours; after the holding period, slowly cooling with the furnace to below 300℃ at 20-40℃ / h, and then air-cooling to room temperature after being taken out of the furnace.

[0021] The manufacturing method of the high magnetic induction, low iron loss, ultra-thin oriented silicon steel, after the high temperature annealing treatment in step (5), the average grain size of the steel plate is 6-25 mm.

[0022] In the manufacturing method of the high magnetic induction, low iron loss, ultra-thin oriented silicon steel, in step (6), the sum of the thickness of the magnesium silicate underlayer generated by high-temperature annealing and the subsequent coated inorganic insulating layer is no greater than 4μm.

[0023] The manufacturing method of the high magnetic induction and low iron loss ultrathin grain-oriented silicon steel described above results in an ultrathin grain-oriented silicon steel product with a magnetic induction B8 of 1.88~1.95T and an iron loss P 1.5 / 400 =8.5~12.0W / kg.

[0024] The design concept of this invention is:

[0025] Ultra-thin grain-oriented silicon steel is typically manufactured using a primary recrystallization method. However, due to differences in Goss orientation within the base material and the incomplete uniformity of the deformation-annealing process, significantly deviated Goss grains and {411} grains inevitably form in the ultra-thin grain-oriented silicon steel. <148> Non-Goss textures are addressed by existing solutions that use high-magnetic-induction oriented silicon steel as the base material and improve rolling and annealing processes, but these still cannot completely prevent the formation of non-Goss orientations caused by uneven deformation. This invention addresses the heritability of Goss texture by introducing a nitriding annealing process into the cold-rolled ultrathin silicon steel matrix. The nitriding process introduces 80–300 ppm nitrogen into the matrix, and the amount of nitriding is controlled according to the acid-soluble aluminum content of the base material. This allows the introduced nitrogen to combine with aluminum and silicon elements in the base material to form an effective inhibitor (AlN). During high-temperature annealing, this inhibits the growth of non-Goss grains and promotes the formation and perfect abnormal growth of precise Goss grains, ultimately obtaining a uniform and low-deviation Goss texture, which improves magnetic induction. Simultaneously, post-processing steps involving coating an insulating layer and heat-resistant laser etching effectively refine magnetic domains while ensuring insulation performance and plate shape, further reducing losses and ultimately achieving stable preparation of high-magnetic-induction, low-iron-loss ultrathin oriented silicon steel.

[0026] The advantages and beneficial effects of this invention are:

[0027] 1) The technology of this invention fully utilizes the Al and Si elements present in the base material through the nitriding process to form an effective inhibitor. During the high-temperature annealing process, the inhibitor induces the abnormal growth of accurate Goss grains, avoiding the growth of non-Goss oriented or significantly deviated Goss oriented grains in the process of manufacturing ultra-thin oriented silicon steel by the primary recrystallization method, and effectively improving the degree and proportion of Goss orientation in ultra-thin oriented silicon steel.

[0028] 2) This invention employs tension coating and heat-resistant laser etching, which can effectively refine magnetic domains to further reduce iron loss, achieving the manufacture of ultra-thin grain-oriented silicon steel with even lower iron loss. 1.5 / 400 Control it within 8.5–12.0 W / kg.

[0029] 3) Further, the present invention sets the nitriding amount according to the Al content in the base material. Too low a nitriding amount will not form sufficient inhibitors; too high a nitriding amount will easily form coarse precipitates, failing to effectively pin the normal growth of grains. Therefore, the graded nitriding scheme of the present invention fully and efficiently utilizes the Al element in the base material to form sufficiently fine and uniform inhibitors, hindering normal grain growth and ensuring that accurately oriented Goss grains undergo perfect secondary recrystallization. Through perfect secondary recrystallization, a high proportion of accurate Goss texture is achieved, and the finished product's magnetic induction B8 can reach 1.88–1.95T.

[0030] 4) Compared with existing processes for manufacturing silicon steel strip, the ultra-thin oriented silicon steel strip manufactured by this invention exhibits better overall performance, meeting the application requirements of medium- and high-frequency electrical equipment. Furthermore, it offers a wider manufacturing process window, higher production efficiency, and stronger feasibility. Attached Figure Description

[0031] Figure 1 This is a process flow diagram of the present invention.

[0032] Figure 2 This is a metallographic diagram of the finished product from Embodiment 1 of the present invention.

[0033] Figure 3 The metallographic structure diagram of the finished product for Comparative Example 1 is shown. Detailed Implementation

[0034] like Figure 1 As shown, the present invention uses 0.18-0.30mm thick non-grained silicon steel as raw material, and sequentially processes cold rolling, alkaline washing, nitriding annealing, high-temperature annealing, coating with an insulating layer, and heat-resistant laser marking to prepare ultra-thin grained silicon steel with a thickness of 0.03-0.10mm.

[0035] 1. Non-grained silicon steel: refers to steel with a matrix having {110} <001> Goss texture, a type of grain-oriented silicon steel without a magnesium silicate underlayer, is produced by acid etching to remove the surface magnesium silicate underlayer and insulating coating from conventional finished grain-oriented silicon steel with a magnesium silicate underlayer, or by creating native grain-oriented silicon steel without a magnesium silicate underlayer during manufacturing. The Goss texture and magnetic properties within the matrix are preserved. The purpose of selecting this material is to eliminate the adverse effects of the magnesium silicate layer on cold rolling while ensuring that nitrogen can successfully penetrate into the steel matrix during the nitriding process.

[0036] 2. Heat-resistant laser marking: Also known as stress-relief annealing-resistant laser marking, this method uses a laser to create regular linear physical grooves on the surface of a grain-oriented silicon steel substrate. The static magnetic energy introduced by these grooves refines magnetic domains and reduces iron loss. Subsequent stress-relief high-temperature annealing does not cause the groove morphology to disappear, thus preserving the effects of magnetic domain refinement and iron loss reduction. In this invention, heat-resistant laser marking is performed after high-temperature annealing and coating with an inorganic insulating layer. The marking grooves penetrate the insulating layer and cut into the silicon steel substrate. The marking depth is controlled to be 10%–20% of the steel plate thickness, and the groove spacing is 2–8 mm. This achieves both magnetic domain refinement and reduced iron loss while avoiding excessive etching that could lead to insulation failure, deterioration of the plate shape, and a reduction in the stacking factor.

[0037] 3. The high-temperature annealing process includes: first, holding at 620-680℃ for 3-5 hours to fully remove the crystal water from the magnesium oxide isolation layer; then, under a mixed protective atmosphere of 60%-80% hydrogen and 20%-40% nitrogen by volume, slowly heating to 1120-1200℃ at a rate of 20-40℃ / h; after reaching the target temperature, switching to a pure hydrogen atmosphere and holding at 1120-1200℃ for 20-28 hours to provide conditions for the perfect secondary recrystallization of Goss grains; after the holding period, slowly cooling with the furnace to below 300℃, and then air-cooling to room temperature after being removed from the furnace.

[0038] 4. After nitriding, a magnesium oxide isolation layer is applied to the steel plate before high-temperature annealing. During high-temperature annealing, the magnesium oxide isolation layer undergoes a solid-phase reaction with the silica on the steel plate surface to form a magnesium silicate underlayer. Therefore, after high-temperature annealing, the underlayer on the steel plate surface is a magnesium silicate underlayer. The sum of the thickness of the magnesium silicate underlayer formed by high-temperature annealing and the subsequently coated inorganic insulating layer should not exceed 4 μm. The thickness of the magnesium silicate underlayer is generally 0.5–1.5 μm, and the thickness of the inorganic insulating coating is generally 1.0–2.5 μm, as long as the sum of the two does not exceed 4 μm.

[0039] 5. This invention avoids the growth of non-Goss oriented or significantly deviated Goss oriented grains during the primary recrystallization process for manufacturing ultra-thin oriented silicon steel. It induces abnormal growth of accurate Goss grains through inhibitors and combines this with tension coating and heat-resistant laser etching to reduce iron loss, resulting in high magnetic induction and low iron loss ultra-thin oriented silicon steel. This invention achieves a finished ultra-thin oriented silicon steel with perfect secondary recrystallization, where the Goss texture area accounts for approximately 85%–95%, and the

[001] rolling orientation deviation angle of the Goss grains is generally no greater than 7°. Samples with imperfect secondary recrystallization will show a significantly reduced proportion of Goss texture.

[0040] The present invention will be further described in detail below with reference to specific embodiments.

[0041] Example 1

[0042] In this embodiment, a method for manufacturing ultrathin oriented silicon steel with high magnetic induction and low iron loss includes the following steps:

[0043] 1) Base material preparation: 0.27mm non-gravity oriented silicon steel is used as the base material. The acid-soluble aluminum [Als] of the base material is 0.02%, the magnetic induction B8=1.88T, and the iron loss P 1.7 / 50 =1.0W / kg;

[0044] 2) Cold rolling: Cold rolled to 0.08mm in 3 passes, with a reduction rate of 40% in the first pass;

[0045] 3) Alkaline washing: Cold-rolled steel sheets undergo surface alkaline washing to remove surface oil and impurities;

[0046] 4) Nitriding annealing: Nitriding annealing was carried out in a mixed atmosphere of nitrogen, hydrogen, and ammonia. By volume percentage, the mixed atmosphere consisted of 15% ammonia, 60% hydrogen, and the remainder nitrogen. The nitriding temperature was 780℃, the nitriding time was 60s, the nitriding amount ∆[N] was 150ppm, and the average grain size after nitriding was 25μm.

[0047] 5) High-temperature annealing: The nitrided plate is first coated with a magnesium oxide isolation layer, and then subjected to high-temperature annealing. The high-temperature annealing is first held at 650℃ for 4 hours, and then slowly heated to 1150℃ at 20℃ / h in a mixed atmosphere of 70 vol% hydrogen and 30 vol% nitrogen. Then it is held at 1150℃ for 24 hours in a pure hydrogen atmosphere. After that, it is slowly cooled to below 300℃ in the furnace and then air-cooled to room temperature. The average grain size after high-temperature annealing is 20 mm.

[0048] 6) Coating the insulating layer and laser marking: After high-temperature annealing, an inorganic phosphate insulating layer is coated, and the sum of the thickness of magnesium silicate and the insulating layer is controlled to be less than 3μm; then heat-resistant laser marking is performed, and the marking depth is controlled to be 10μm and the groove spacing is 5mm to obtain ultra-thin oriented silicon steel finished products.

[0049] In this embodiment, the finished product undergoes perfect secondary recrystallization, with magnetic induction B8 = 1.92T and iron loss P. 1.5 / 400 =11W / kg.

[0050] Examples 2-20

[0051] Compared to Example 1, the changes in the base material characteristics of Examples 2 to 20 are shown in Table 1, and the changes in process parameters are shown in Table 2. Among them, Example 13 involved 5 passes of cold rolling, followed by stress-relief intermediate annealing after the third pass at a temperature of 700°C for 3 minutes.

[0052] Table 1. Characteristic parameters of the base material in Examples 1-13

[0053]

[0054] As can be seen from Table 1, the characteristic parameters of the base material used in the 13 sets of embodiments include base material thickness, base material magnetic induction B8, and base material iron loss P. 1.7 / 50 The four indicators of acid-soluble aluminum in the base material are as follows: base material thickness range: 0.18–0.30 mm; base material magnetic induction B8 range: 1.85–1.92 T; base material iron loss P. 1.7 / 50 The range is 0.8 to 1.2 W / kg, and the acid-soluble aluminum content ranges from 0.016% to 0.035%.

[0055] Table 2 Process parameters for Examples 1-13

[0056]

[0057] As shown in Table 2, the process parameters corresponding to the 13 sets of embodiments include: cold rolling passes, first pass reduction rate, final thickness, nitriding temperature, nitriding time, nitriding amount, average grain size after nitriding, high-temperature annealing temperature, sum of thickness of the underlayer and insulating layer, groove depth, and groove spacing. The cold rolling passes are 3 to 5, the first pass reduction rate is 30% to 55%, the final thickness of the finished product is 0.03 to 0.10 mm, the nitriding temperature is 780 to 850 ℃, the nitriding time is 25 to 80 s, the nitriding amount is 100 to 290 ppm, the average grain size after nitriding and annealing is 15 to 30 μm, the high-temperature annealing temperature is 1120 to 1200 ℃, the sum of thickness of the magnesium silicate underlayer and insulating coating is 2.2 to 4.0 μm, the groove depth is 4 to 15 μm, and the groove spacing is 4 to 8 mm.

[0058] Comparative Examples 1-5

[0059] Compared to Example 1, the changes in the characteristics of the base materials in Comparative Examples 1 to 5 are shown in Table 3, and the changes in the process parameters are shown in Table 4.

[0060] Table 3 Characteristic parameters of the base materials in Comparative Examples 1–5

[0061]

[0062] As shown in Table 3, the characteristic parameters of the base material used in the five comparative examples include base material thickness, base material magnetic induction B8, and base material iron loss P. 1.7 / 50 The four indicators of acid-soluble aluminum in the base material are as follows: base material thickness range: 0.18–0.30 mm; base material magnetic induction B8 range: 1.88–1.90 T; base material iron loss P. 1.7 / 50 The range is 0.83 to 1.20 W / kg, and the acid-soluble aluminum content ranges from 0.020% to 0.030%. The parameters of the comparative example base material are close to those of the corresponding embodiment.

[0063] Table 4 Process parameters for Comparative Examples 1-5

[0064]

[0065] As shown in Table 4, the process parameters corresponding to the 13 sets of embodiments include: cold rolling passes, first pass reduction rate, final thickness, nitriding temperature, nitriding time, nitriding amount, average grain size after nitriding, high-temperature annealing temperature, sum of thickness of the underlayer and insulating layer, groove depth, and groove spacing. The cold rolling passes are 3 to 7, the first pass reduction rate is 25% to 50%, the final thickness of the finished product is 0.03 to 0.05 mm, the nitriding temperature is 780 to 850 ℃, the nitriding time is 25 to 65 s, the nitriding amount is 75 to 320 ppm, the average grain size after nitriding and annealing is 15 to 35 μm, the high-temperature annealing temperature is 1120 to 1140 ℃, the sum of thickness of the magnesium silicate underlayer and insulating coating is 2.2 to 6.0 μm, the groove depth is 4 to 12 μm, and the groove spacing is 7 to 10 mm.

[0066] The grain size and magnetic properties of the ultrathin oriented silicon steel corresponding to Examples 1-13 and Comparative Examples 1-5 are shown in Table 5.

[0067] Table 5. Average grain size and magnetic properties of Examples 1-13 and Comparative Examples 1-5

[0068]

[0069] Table 5 shows the average grain size and magnetic performance data corresponding to the 13 sets of examples and 5 sets of comparative examples, including the average grain size of the finished product, magnetic induction B8 and iron loss P. 1.5 / 400 Among them, the performance parameter ranges of the finished products in the 13 sets of examples are as follows: average grain size of the finished board is 10-25mm, magnetic induction B8 is 1.88-1.95T, and iron loss P is... 1.5 / 400 The value is 8.5–12.0 W / kg. Performance parameters of the five comparative examples are as follows: average grain size of the finished plates is 5–18 mm, magnetic induction B8 is 1.82–1.90 T, and iron loss P... 1.5 / 400The value is 11.0–15.0 W / kg. As can be seen in the comparison, the finished product of the embodiments of the present invention has a larger grain size, higher magnetic induction, and lower iron loss, achieving superior magnetic performance.

[0070] like Figure 2 As shown, in Example 1, the finished plate underwent secondary recrystallization of perfected Goss grains, with an average grain size of 20 mm.

[0071] like Figure 3 As shown, no perfect secondary recrystallization occurred in the finished product of Comparative Example 1, and some grains grew normally with an average grain size of 5 mm.

[0072] The results show that the cold rolling, alkaline washing, nitriding annealing, high-temperature annealing, coating of insulating layer, and heat-resistant laser marking process designed according to this invention can obtain ultra-thin oriented silicon steel with perfect secondary recrystallization and good magnetic properties. In the comparative examples, the nitriding amount in Comparative Example 1 was lower than the lower limit of the design value, which failed to form sufficient inhibitors, resulting in coarse average grains after nitriding, incomplete secondary recrystallization, and abnormal growth of some deflected Goss grains; Comparative Example 2 also had too low a nitriding amount, and ultimately failed to achieve significant secondary recrystallization; In Comparative Example 3, there were too many rolling passes, a low reduction rate in the first pass, and the nitriding amount was higher than the upper limit of the design value, resulting in relatively coarse inhibitors that could not effectively inhibit the growth of non-Goss grains, and ultimately failed to achieve perfect secondary recrystallization; In the heat-resistant laser marking process in Comparative Example 4, the marking depth was too deep and the groove spacing was too large, which on the one hand caused the insulating layer to fall off and the insulation resistance to be low, and on the other hand introduced large stress, resulting in poor plate shape and poor stacking coefficient; In the coating of insulating layer process in Comparative Example 5, the insulating layer thickness was too thick, which reduced the stacking coefficient. In the comparative examples above, improper control of the nitriding process, laser marking process, or insulating layer coating process all resulted in deteriorated magnetic properties. This invention addresses different requirements for ultra-thin oriented silicon steel by setting the nitriding amount according to the Al content in the base material, forming an effective inhibitor, ultimately obtaining a uniform and minimally skewed Goss texture, thus improving magnetic induction. Furthermore, coating and heat-resistant laser marking effectively refine the magnetic domains, further reducing losses. It is highly feasible, has high production efficiency, and produces excellent magnetic properties.

Claims

1. A method for manufacturing ultrathin grain-oriented silicon steel with high magnetic induction and low iron loss, characterized in that, Includes the following steps: (1) Preparation of base material: Select non-oriented silicon steel with a thickness of 0.18 to 0.30 mm as raw material. The magnetic induction B8 of the non-oriented silicon steel is 1.85 to 1.94 T and the iron loss P is 0. 1.7 / 50 ≤1.2W / kg, the mass fraction of acid-soluble aluminum (Als) in the parent material is 0.01%~0.04%; (2) Cold rolling: For silicon steel without bottom layer orientation, 3 to 6 passes of reciprocating rolling are used, with the first pass reduction rate of 30% to 55%; the total cold rolling reduction rate shall not exceed 90%; (3) Alkali washing: Alkali washing is performed on the cold-rolled steel plate to remove oil and impurities from the surface of the steel plate; (4) Nitriding annealing: The steel plate after alkaline washing is nitrided and annealed in a mixed atmosphere of nitrogen, hydrogen and ammonia. The nitriding temperature is 750-850℃ and the nitriding time is 30-240s. The nitriding amount ∆[N] is controlled in three stages according to the mass fraction of aluminum Als dissolved in the base material. When the base material [Als] content is 0.01% ≤ [Als] ≤ 0.02%, the nitriding amount ∆[N] should be controlled within the range of 80–150 ppm; when the base material [Als] content is 0.02% < [Als] ≤ 0.03%, the nitriding amount ∆[N] should be controlled within the range of 150–250 ppm; when the base material [Als] content is 0.03% < [Als] ≤ 0.04%, the nitriding amount ∆[N] should be controlled within the range of 250–300 ppm. (5) High-temperature annealing: After nitriding annealing, the steel plate is first coated with a magnesium oxide isolation layer, and then high-temperature annealing is carried out; (6) Coating an insulating layer and heat-resistant laser marking: After high-temperature annealing, an inorganic insulating layer is first coated, and then heat-resistant laser marking is performed; the heat-resistant laser marking is stress-relief annealing laser marking, which processes linear physical grooves on a silicon steel substrate, with a marking depth of 10% to 20% of the steel plate thickness and a spacing of 2 to 8 mm between adjacent grooves; The above steps are used to prepare ultrathin oriented silicon steel with a thickness of 0.03 to 0.10 mm.

2. The manufacturing method of high magnetic induction, low iron loss, ultra-thin grain-oriented silicon steel as described in claim 1, characterized in that, In step (1), the substrate of the non-grained silicon steel has {110} <001> Goss texture, grain-oriented silicon steel without a magnesium silicate underlayer on the surface, is obtained by pickling finished grain-oriented silicon steel with a magnesium silicate underlayer to remove the magnesium silicate underlayer and insulating coating, or by grain-oriented silicon steel that originally had no magnesium silicate underlayer during the manufacturing process.

3. The method for manufacturing high magnetic induction, low iron loss, ultra-thin grain-oriented silicon steel as described in claim 1, characterized in that, In step (2), cold rolling is a continuous production of 3 to 6 passes, or a stress-relief annealing is performed once in the middle pass of cold rolling. The stress-relief annealing temperature is 650 to 750°C and the holding time is 1 to 5 minutes.

4. The method for manufacturing high magnetic induction, low iron loss, ultra-thin grain-oriented silicon steel as described in claim 1, characterized in that, In step (4), by volume percentage, the mixed atmosphere contains 10% to 20% ammonia, 60% to 70% hydrogen, and the remainder is nitrogen.

5. The method for manufacturing high magnetic induction, low iron loss, ultra-thin grain-oriented silicon steel as described in claim 1, characterized in that, In step (4), the average grain size of the steel plate after nitriding annealing is 10-40 μm.

6. The method for manufacturing high magnetic induction, low iron loss, ultrathin grain-oriented silicon steel as described in claim 1, characterized in that, In step (5), the high-temperature annealing process includes: first, holding at 620-680℃ for 3-5 hours, then slowly raising the temperature to 1120-1200℃ at 20-40℃ / h under a mixed protective atmosphere of 60%-80% hydrogen and 20%-40% nitrogen by volume; after reaching the target temperature, switching to a pure hydrogen atmosphere and holding at 1120-1200℃ for 20-28 hours; after the holding period, slowly cooling with the furnace to below 300℃ at 20-40℃ / h, and then air-cooling to room temperature after being taken out of the furnace.

7. The method for manufacturing high magnetic induction, low iron loss, ultrathin grain-oriented silicon steel as described in claim 1, characterized in that, After the high-temperature annealing treatment in step (5), the average grain size of the steel plate is 6-25 mm.

8. The method for manufacturing high magnetic induction, low iron loss, ultrathin grain-oriented silicon steel as described in claim 1, characterized in that, In step (6), the sum of the thicknesses of the magnesium silicate underlayer generated by high-temperature annealing and the subsequently coated inorganic insulating layer is no greater than 4 μm.

9. The method for manufacturing high magnetic induction, low iron loss, ultra-thin grain-oriented silicon steel as described in claim 1, characterized in that, The magnetic induction B8 of ultra-thin grain-oriented silicon steel products is 1.88~1.95T, and the iron loss P is... 1.5 / 400 =8.5~12.0W / kg.

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