A method for improving the underlayer watermark of grain-oriented silicon steel

Abstract

This invention relates to a method for coiling steel coils, specifically a method for improving watermarks on the underside of grain-oriented silicon steel. The method involves controlling the coil's tightness coefficient r during the coiling process after the grain-oriented silicon steel has been coated with a release agent and dried, ensuring that r1 ≤ r ≤ r2; the tightness coefficient r is calculated according to the formula r = M / (d 2 -d0 2 The calculation yields M, representing the winding mass in tons; d, representing the real-time winding diameter in meters; and d0, representing the initial winding diameter in meters. Real-time control of the winding of the oriented silicon steel coil ensures stable and unobstructed interlayer gaps, reducing the area of ​​watermarks on the oriented silicon steel.

Description

Technical Field

[0001] This invention relates to a method for winding steel coils, and more specifically to a method for improving the watermark on the bottom layer of grain-oriented silicon steel. Background Technology

[0002] Grain-oriented silicon steel is a soft magnetic material with special magnetic properties, mainly used in the manufacture of core components for electrical equipment such as power transformers and inductors. Its surface typically has two layers: a magnesium silicate underlayer on the silicon steel substrate, and an insulating coating on top of the magnesium silicate underlayer. The magnesium silicate underlayer is formed by the reaction of the silica oxide layer on the substrate surface with a release agent (mainly magnesium oxide) coated on it under high-temperature conditions. During high-temperature annealing, a low-temperature holding process is first performed to remove moisture contained in the release agent. However, when the coil is wound too tightly or the coil is significantly deformed, moisture cannot escape properly and accumulates inside the coil, participating in the underlayer reaction. The underlayer formed in the area where moisture participates in the reaction is darker in color and is called a watermark. The significant color difference between the watermarked area and the non-watermarked area affects the appearance quality of the grain-oriented silicon steel. Watermarks not only affect the surface insulation resistance but also the surface uniformity. Therefore, it is necessary to minimize, or even completely eliminate, the area of ​​watermarks on grain-oriented silicon steel.

[0003] Currently, most solutions to the watermark problem in grain-oriented silicon steel are to improve it by adjusting the high-temperature heat treatment process. However, the high-temperature heat treatment process is closely related to the formation of grains in grain-oriented silicon steel and cannot be significantly adjusted, so the methods are relatively limited.

[0004] From a perspective beyond the heat treatment process, the tightness of the steel coil before high-temperature heat treatment has a significant impact on watermark formation. Currently, the main method for adjusting coil tightness is to establish a fixed coiling tension curve. For example, CN104342548A discloses a coiling method for oriented silicon steel MgO-coated coils, which uses a fixed 5-segment tension for coiling. However, practical observation has shown that even with the same specifications of material and the same coiling curve, the tightness of the coiled coils can still vary. Therefore, a new coiling method is needed to ensure stable and unobstructed interlayer gaps during coiling. Summary of the Invention

[0005] The present invention aims to solve the above problems and provides a method to improve the watermark on the bottom layer of grain-oriented silicon steel. By controlling the winding of the grain-oriented silicon steel coil in real time, the gap between the winding layers can be kept stable and unobstructed.

[0006] According to the technical solution of the present invention, the method for improving the watermark on the bottom layer of oriented silicon steel involves controlling the tightness coefficient r of the steel coil to satisfy r1≤r≤r2 during the winding process after the oriented silicon steel is coated with a release agent and dried. The tightness coefficient r is calculated according to the formula r=M / (d) 2 -d02 The calculation yields M, which is the winding mass in tons; d, which is the real-time winding diameter in meters; and d0, which is the initial winding diameter in meters.

[0007] Furthermore, when r exceeds the range of r1-r2, the winding tension is increased or decreased based on the set winding tension, maintained for 3-6 minutes, and then adjusted back to the set winding tension.

[0008] Furthermore, when r decreases to r1+0.05, the winding tension is increased based on the set winding tension, maintained for 3-6 minutes, and then adjusted back to the set winding tension. When r rises to r2-0.05, reduce the winding tension based on the set winding tension, maintain it for 3-6 minutes, and then adjust it back to the set winding tension.

[0009] Furthermore, the range for increasing or decreasing the winding tension is 20-50 kg.

[0010] Furthermore, r1 and r2 are set according to the thickness t of the grain-oriented silicon steel, the amount of release agent coating m after drying, and the moisture content k in the release agent after drying.

[0011] Furthermore, when t ≥ 0.21 mm, r1 = 4.20 + 3.0t + 0.1m 0.5 -0.3lgk, r2=4.50+3.0t+0.1*m 0.5 -0.3lgk; When t < 0.21 mm, r1 = 3.48 + 6.5t + 0.1m 0.5 -0.3lgk, r2=3.78+6.5t+0.1*m 0.5 -0.3lgk; Where t is the thickness of the grain-oriented silicon steel plate, in mm; m is the amount of release agent coated after drying, in g / m. 2 k represents the moisture content in the release agent after drying.

[0012] Furthermore, When the plate thickness t = 0.27 mm, r1 = 5.01 + 0.1 * m 0.5 -0.3lgk, r2=5.31+0.1*m 0.5 -0.3lgk; When the plate thickness t = 0.23 mm, r1 = 4.89 + 0.1 * m 0.5 -0.3lgk, r2=5.19+0.1*m 0.5 -0.3lgk; When the plate thickness t = 0.20 mm, r1 = 4.78 + 0.1 * m0.5 -0.3lgk, r2=5.08+0.1*m 0.5 -0.3lgk; When the plate thickness t = 0.18 mm, r1 = 4.65 + 0.1 * m 0.5 -0.3lgk, r2=4.95+0.1*m 0.5 -0.3lgk; Where m is the amount of release agent applied after drying, in g / m. 2 k represents the moisture content in the release agent after drying.

[0013] Furthermore, the amount of release agent applied after drying, m, is 4.0~8.0 g / m. 2 .

[0014] Furthermore, the moisture content k in the dried release agent is 1.0%~3.0%.

[0015] Compared with the prior art, the technical solution of the present invention has the following advantages: The present invention introduces the concept of tension coefficient, and achieves the stability of the interlayer gap by controlling the tension coefficient during the winding process, rather than a set tension curve, which can effectively avoid differences in tension; tension adjustment based on the tension coefficient can better distinguish whether the winding effect during the winding process has achieved the expected goal, making the process adjustment more purposeful, thereby achieving a stable and smooth interlayer gap during winding and reducing the area of ​​watermarks on oriented silicon steel; the setting of the tension coefficient fully considers the amount of release agent coating, the moisture content in the release agent, and the steel coil specifications (plate thickness), reducing the impact of various factors on the winding effect during the production process. Attached Figure Description

[0016] Figure 1 This is a tension curve diagram from Example 1.

[0017] Figure 2 This is a curve of the tightness coefficient in Example 1.

[0018] Figure 3 This is a tension curve diagram from Example 3.

[0019] Figure 4 This is a curve showing the tightness coefficient in Example 3.

[0020] Figure 5 This is a tension curve diagram from Comparative Example 1.

[0021] Figure 6 This is a curve showing the tightness coefficient in Comparative Example 1. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0023] This invention provides a method for improving the watermark on the bottom layer of grain-oriented silicon steel. During the winding process after the grain-oriented silicon steel is coated with a release agent and dried, the tightness coefficient r of the steel coil is controlled to satisfy r1≤r≤r2.

[0024] The aforementioned tightness coefficient r is based on the formula r = M / (d 2 -d0 2 The values ​​are calculated as follows: M is the winding mass in tons, which can be calculated based on the winding length (directly read by the system) and the unit length mass of the oriented silicon steel (in the following examples, the unit length mass of 0.27mm oriented silicon steel is 2.31kg / m, the unit length mass of 0.23mm oriented silicon steel is 1.97kg / m, the unit length mass of 0.20mm oriented silicon steel is 1.71kg / m, and the unit length mass of 0.18mm oriented silicon steel is 1.54kg / m); d is the real-time winding diameter in meters, which can be obtained through real-time detection, such as using a laser rangefinder; d0 is the initial winding diameter in meters, which is generally directly taken as the outer diameter of the winding sleeve. In the following examples, d0 is 0.54m.

[0025] To maintain the coil tension coefficient r within the range of r1-r2 during the winding process, the winding tension needs to be adjusted when r exceeds the range of r1-r2. Specifically, the winding tension can be increased or decreased based on the set winding tension, maintained for 3-6 minutes, and then adjusted back to the set winding tension.

[0026] The set winding tension in this invention is the set tension during the normal winding process. Its tension control mode is generally a fixed multi-segment tension, such as the 5-segment tension disclosed in CN104342548A.

[0027] It is conceivable that when adjusting the winding tension, the timing for returning to the set winding tension can be determined not only by setting the holding time, but also by the recovery of r, such as the intermediate value of r1 and r2, so as to ensure that r is always within the range of r1-r2.

[0028] In some preferred embodiments, to ensure that r is within the range of r1-r2, the tension can be adjusted in advance: When r decreases to r1+0.05, increase the winding tension based on the set winding tension, maintain it for 3-6 minutes, and then adjust it back to the set winding tension. When r rises to r2-0.05, reduce the winding tension based on the set winding tension and maintain it for 3-6 minutes before adjusting it back to the set winding tension.

[0029] When adjusting the winding tension, the range is 30-50 kg, such as 30 kg, 40 kg, 45 kg, 50 kg, etc. The specific setting depends on the winding situation, aiming to achieve a rapid recovery of the tension coefficient without affecting the winding process. In certain circumstances, the tension adjustment value can exceed the 30-50 kg range.

[0030] Since the raw materials and production process themselves have unavoidable fluctuations, after comprehensive consideration and weighing, the setting range of the tightness coefficient r of this invention is determined by the plate thickness t of the oriented silicon steel, the amount of release agent coating m after drying, and the moisture content k in the release agent after drying. That is, the values ​​of r1 and r2 are calculated based on t, m, and k.

[0031] Specifically: When t≥0.21mm, r1 = 4.20 + 3.0t + 0.1m 0.5 -0.3lgk, r2=4.50+3.0t+0.1*m 0.5 -0.3lgk; When t < 0.21 mm, r1 = 3.48 + 6.5t + 0.1m 0.5 -0.3lgk, r2=3.78+6.5t+0.1*m 0.5 -0.3lgk; Where t is the thickness of the grain-oriented silicon steel plate, in mm; m is the amount of release agent coated after drying, in g / m. 2 k represents the moisture content in the release agent after drying.

[0032] Based on the above calculation method, during the implementation process, it is first necessary to determine the amount of release agent applied per unit area after drying and the moisture content in the release agent, because different release agent dosages and different moisture contents require different drainage conditions. Then, the tightness of the winding should be adjusted in real time to ensure the stability of the winding tightness.

[0033] Specifically, the release agent used is magnesium oxide, a commonly used release agent in this field. The coating amount and moisture content can be sampled and tested at the beginning of the roll. For example, the coating amount can be measured by laser-cutting multiple (e.g., 3) sample pieces (each with an area of ​​400-600 cm²). 2 The weight is reduced and weighed, and the average value is taken as the final test result. The moisture content can be stored in a sealed bag immediately after scraping off the release agent powder on site to avoid water absorption affecting the test results. The drying and weighing temperature can be 880~920℃, and the drying time can be 2~3 minutes.

[0034] For the specifications (plate thickness) of commonly used grain-oriented silicon steel in this field, r1 and r2 are set as follows: When the plate thickness t = 0.27 mm, r1 = 5.01 + 0.1 * m 0.5 -0.3lgk, r2=5.31+0.1*m 0.5 -0.3lgk; When the plate thickness t = 0.23 mm, r1 = 4.89 + 0.1 * m 0.5 -0.3lgk, r2=5.19+0.1*m 0.5 -0.3lgk; When the plate thickness t = 0.20 mm, r1 = 4.78 + 0.1 * m 0.5 -0.3lgk, r2=5.08+0.1*m 0.5 -0.3lgk; When the plate thickness t = 0.18 mm, r1 = 4.65 + 0.1 * m 0.5 -0.3lgk, r2=4.95+0.1*m 0.5 -0.3lgk.

[0035] The amount of release agent coating *m* after drying and the moisture content *k* in the release agent after drying are generally sampled and tested at the beginning of the roll, and need to be controlled within the following range: the amount of release agent coating *m* after drying is 4.0~8.0 g / m. 2 The moisture content (k) in the drying release agent is 1.0%~3.0%.

[0036] In the following embodiments, the release agent was prepared by water, magnesium oxide, titanium dioxide, and boron in a mass ratio of 1600:200:10:5. After winding, high-temperature annealing was performed, and the watermark area ratio was calculated. The high-temperature annealing adopted a commonly used process in the art. Specifically, under a nitrogen atmosphere, the temperature was increased to 700°C at a heating rate of 200°C / h, then switched to a 3:1 hydrogen-nitrogen mixture and held for 20 h, then increased to 1200°C at a heating rate of 18°C / h, then switched to a pure hydrogen atmosphere and held for 20 h. After annealing, the temperature was first lowered to 670°C in a 3:1 hydrogen-nitrogen mixture, and then continuously lowered in nitrogen. Example 1

[0037] The release agent coating amount and moisture content of the coil head of 0.27mm oriented silicon steel coil were tested. Three 20×20cm samples were laser-cut, and the release agent coating amount of each sample was weighed. The results were 6.85g / m². 2 6.72 g / m 2 6.69g / m 2 The final result of the release agent coating amount test was 6.75 g / m². 2 Take 0.54g of the release agent powder, dry it in a muffle furnace at 920℃ for 3 minutes, and the moisture content is measured to be 2.36%. According to the calculation, the tightness coefficient of this roll should be maintained at 5.76~6.06.

[0038] During the production process, the tension of the roll is adjusted according to the real-time tension coefficient (tension curve as shown). Figure 1 As shown, when the tension coefficient first dropped to 5.81, the tension was increased by 30 kg and maintained for 5 minutes; when the tension coefficient second dropped to 5.81, the tension was increased by 30 kg and maintained for 4 minutes. The final tension coefficient ranged from 5.81 to 5.91 (tension coefficient curve shown). Figure 2 As shown), it is within the required range.

[0039] The watermark area percentage after high-temperature annealing of this volume is approximately 4.54%, which is relatively low. Example 2

[0040] The release agent coating amount and moisture content of the coil head of 0.23mm oriented silicon steel coil were tested. Three 24×24cm samples were laser-cut, and the release agent coating amount of each sample was weighed. The results were 6.08g / m². 2 6.19 g / m 2 6.32g / m 2 The final result of the release agent coating amount test was 6.20 g / m². 2 Take 0.43g of the release agent powder, dry it in a muffle furnace at 900℃ for 2 minutes, and the moisture content is measured to be 1.94%. According to the calculation, the tightness coefficient of this roll should be maintained at 5.65~5.95.

[0041] During the production process, the tension of the roll was adjusted according to the real-time tension coefficient (when the tension coefficient rose to 5.95, the tension was reduced by 40 kg and maintained for 5 minutes). The final tension coefficient ranged from 5.72 to 5.95, which did not exceed the required range.

[0042] The watermark area percentage after high-temperature annealing of this volume is approximately 3.19%, which is relatively low. Example 3

[0043] The release agent coating amount and moisture content of the coil head of 0.20mm oriented silicon steel coil were tested. Three 20×20cm samples were laser-cut, and the release agent coating amount of each sample was weighed. The results were 4.19 g / m². 2 4.16 g / m 2 4.21g / m 2 The final result of the release agent coating amount test was 4.19 g / m². 2 Take 0.57g of the release agent powder, dry it in a muffle furnace at 880℃ for 3 minutes, and the moisture content is measured to be 1.15%. According to the calculation, the tightness coefficient of this roll should be maintained at 5.57~5.87.

[0044] During the production process, the tension of the roll is adjusted according to the real-time tension coefficient (tension curve as shown). Figure 3 As shown, when the tension coefficient first rises to 5.82, the tension is reduced by 40 kg and maintained for 4 minutes; when the tension coefficient rises to 5.82 again, the tension is reduced by 40 kg and maintained for 3 minutes. The final tension coefficient range is 5.73~5.82 (tension coefficient curve shown). Figure 4 As shown), it is within the required range.

[0045] The watermark area percentage after high-temperature annealing of this volume is approximately 2.98%, which is relatively low. Example 4

[0046] The release agent coating amount and moisture content of the coil head of 0.18mm oriented silicon steel coil were tested. Three 20×20cm samples were laser-cut, and the release agent coating amount of each sample was weighed. The results were 5.98 g / m². 2 5.78g / m 2 5.69g / m 2 The final result of the release agent coating amount test was 5.82 g / m². 2 Take 0.42g of the release agent powder, dry it in a muffle furnace at 900℃ for 2 minutes, and the moisture content is measured to be 1.84%. According to the calculation, the tightness coefficient of this roll should be maintained at 5.41~5.71.

[0047] During the production process, the tension of the roll was adjusted according to the real-time tension coefficient (when the tension coefficient rose to 5.66, the tension was reduced by 20 kg and maintained for 6 minutes). The final tension coefficient ranged from 5.52 to 5.66, which did not exceed the required range.

[0048] The watermark area percentage after high-temperature annealing of this volume is approximately 4.24%, which is relatively low. Comparative Example 1

[0049] The release agent coating amount and moisture content of the coil head of 0.27mm oriented silicon steel coil were tested. Three 20×20cm samples were laser-cut, and the release agent coating amount of each sample was weighed. The results were 7.84 g / m². 2 7.82 g / m 2 7.74g / m 2 The final result of the release agent coating amount test was 7.80 g / m². 2 Take 0.54g of the release agent powder, dry it in a muffle furnace at 920℃ for 3 minutes, and the moisture content is measured to be 2.90%. According to the calculation, the tightness coefficient of this roll should be maintained at 5.75~6.05.

[0050] During the production process, the tension of this roll was not adjusted according to the real-time tension coefficient (tension curve as shown). Figure 5 As shown), the final tension coefficient ranges from 5.71 to 5.92 (tension coefficient curve is shown in the figure). Figure 6 As shown, this exceeds the required range.

[0051] The watermark area of ​​this volume after high-temperature annealing is approximately 20.16%, which is relatively high.

[0052] The results show that by using the winding method of the present invention, based on the control of the tightness coefficient, the gap between steel coil layers can be effectively controlled, thereby reducing the watermark area of ​​oriented silicon steel.

[0053] Obviously, the above embodiments are merely illustrative examples for clear explanation 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 here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for improving watermarks on the underside of grain-oriented silicon steel, characterized in that, During the winding process of oriented silicon steel after coating with a release agent and drying, the tightness coefficient r of the steel coil is controlled to satisfy r1≤r≤r2; The tightness coefficient r is calculated according to the formula r=M / (d) 2 -d0 2 The calculation yields M, which is the winding mass in tons; d, which is the real-time winding diameter in meters; and d0, which is the initial winding diameter in meters.

2. The method for improving watermarks on the underlying layer of grain-oriented silicon steel as described in claim 1, characterized in that, When r exceeds the range of r1-r2, increase or decrease the winding tension based on the set winding tension, maintain it for 3-6 minutes, and then adjust it back to the set winding tension.

3. The method for improving watermarks on the underlying layer of grain-oriented silicon steel as described in claim 1, characterized in that, When r decreases to r1+0.05, increase the winding tension based on the set winding tension, maintain it for 3-6 minutes, and then adjust it back to the set winding tension. When r rises to r2-0.05, reduce the winding tension based on the set winding tension, maintain it for 3-6 minutes, and then adjust it back to the set winding tension.

4. The method for improving watermark on the underlying layer of grain-oriented silicon steel as described in claim 2 or 3, characterized in that, The range for increasing or decreasing the winding tension is 30-50 kg.

5. The method for improving watermarks on the underside of grain-oriented silicon steel as described in claim 1, characterized in that, r1 and r2 are set according to the thickness t of the grain-oriented silicon steel, the amount of release agent coating m after drying, and the moisture content k in the release agent after drying.

6. The method for improving watermarks on the underlying layer of grain-oriented silicon steel as described in claim 5, characterized in that, When t≥0.21mm, r1=4.20+3.0t+0.1*m 0.5 -0.3lgk,r2=4.50+3.0t+0.1*m 0.5 -0.3lgk; When t < 0.21 mm, r1=3.48+6.5t+0.1*m 0.5 -0.3lgk,r2=3.78+6.5t+0.1*m 0.5 -0.3lgk; Where t is the thickness of the grain-oriented silicon steel plate, in mm; m is the amount of release agent coated after drying, in g / m. 2 k represents the moisture content in the release agent after drying.

7. The method for improving watermarks on the underlying layer of grain-oriented silicon steel as described in claim 5, characterized in that, When the plate thickness t = 0.27 mm, r1 = 5.01 + 0.1 * m 0.5 -0.3lgk, r2=5.31+0.1*m 0.5 -0.3lgk; When the plate thickness t = 0.23 mm, r1 = 4.89 + 0.1 * m 0.5 -0.3lgk, r2=5.19+0.1*m 0.5 -0.3lgk; When the plate thickness t = 0.20 mm, r1 = 4.78 + 0.1 * m 0.5 -0.3lgk, r2=5.08+0.1*m 0.5 -0.3lgk; When the plate thickness t = 0.18 mm, r1 = 4.65 + 0.1 * m 0.5 -0.3lgk, r2=4.95+0.1*m 0.5 -0.3lgk; Where m represents the amount of release agent applied after drying, in g / m. 2 k represents the moisture content in the release agent after drying.

8. The method for improving watermarks on the underlying layer of grain-oriented silicon steel as described in claim 5, 6, or 7, characterized in that, After drying, the amount of release agent applied (m) is 4.0~8.0 g / m. 2 .

9. The method for improving watermarks on the underside of grain-oriented silicon steel as described in claim 5, 6, or 7, characterized in that, The moisture content (k) in the dried release agent is 1.0%~3.0%.

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