A method of coating an oriented electrical steel with a magnesium oxide coating

Abstract

This invention belongs to the technical field of grain-oriented electrical steel, specifically relating to a method for applying a magnesium oxide coating to grain-oriented electrical steel, comprising the following steps: S1, obtaining grain-oriented electrical steel; S2, subjecting the grain-oriented electrical steel to alkaline washing; S3, applying a magnesium oxide coating to the grain-oriented electrical steel, wherein the coating amount of the magnesium oxide coating on the working side is 3.5~3.7 g / m². 2 The coating amount of the magnesium oxide coating on the transmission side is 3.8~4.0 g / m². 2 The coating amount of the magnesium oxide coating in the middle part is 3.3~3.5 g / m². 2 The water content of the magnesium oxide coating is 1.5%~2.0%; S4, the oriented electrical steel coated with magnesium oxide coating is dried to obtain oriented electrical steel with a thickness difference of less than or equal to 0.05μm; the present invention adjusts the coating amount on the working side, transmission side and middle part during coating preparation to make the coating more uniform during preparation, thereby obtaining oriented electrical steel with a small thickness difference between the coating and the plate.

Description

Technical Field

[0001] This invention belongs to the field of grain-oriented electrical steel technology, specifically a method for applying a magnesium oxide coating to grain-oriented electrical steel. Background Technology

[0002] Before high-temperature annealing, oriented electrical steel undergoes a magnesium oxide coating process. This serves two purposes: first, to prevent the steel strip from sticking together during high-temperature annealing; and second, to form a magnesium silicate underlayer during annealing, thereby increasing interlayer resistivity. The thickness and uniformity of the magnesium oxide coating directly affect the uniformity of the magnesium silicate underlayer, which in turn affects the uniformity of the finished product's magnetic properties, especially the fluctuation rate of iron loss.

[0003] Currently, there is no technology for strictly controlling the thickness of the coating, especially for controlling the thickness difference between the coating and the substrate. The thickness difference between the coating and the substrate affects the thickness uniformity of the magnesium silicate underlayer, thereby affecting the resistivity at different points and the magnetic uniformity of the finished electrical steel. It can also indirectly lead to crystal exposure problems. Therefore, controlling the thickness uniformity and thickness difference of the magnesium oxide coating in grain-oriented electrical steel is crucial for the production of grain-oriented electrical steel. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a method for applying a magnesium oxide coating to grain-oriented electrical steel, comprising the following steps: S1. Obtain oriented electrical steel, wherein the thickness of the oriented electrical steel is 0.1~0.2mm and the width is 0.8~1.5m; S2. The oriented electrical steel is subjected to alkaline washing; S3. Apply a magnesium oxide coating to the oriented electrical steel, wherein the coating amount on the working side is 3.5~3.7 g / m². 2 The coating amount of the magnesium oxide coating on the transmission side is 3.8~4.0 g / m². 2 The coating amount of the magnesium oxide coating in the middle part is 3.3~3.5 g / m². 2 The water content of the magnesium oxide coating is 1.5% to 2.0%. S4. Dry the oriented electrical steel coated with magnesium oxide coating to obtain oriented electrical steel with a thickness difference of less than or equal to 0.05 μm. The thickness of the magnesium oxide coating on the oriented electrical steel is 3~4 μm.

[0005] Furthermore, the coating range on the working side accounts for 1 / 4 to 1 / 3 of the width of the oriented electrical steel, the coating range on the transmission side accounts for 1 / 4 to 1 / 3 of the width of the oriented electrical steel, and the remaining part is the coating range of the middle part. Furthermore, the thickness of the oriented electrical steel is any one of 0.1mm, 0.12mm, 0.14mm, 0.16mm, 0.18mm, and 0.2mm, or a range between two of them; Furthermore, the width of the oriented electrical steel is any one of 0.8m, 0.9m, 1.0m, 1.1m, 1.2m, 1.3m, 1.4m, and 1.5m, or a range between two of them; Furthermore, the coating amount of the magnesium oxide coating on the working side is 3.5 g / m². 2 3.6g / m 2 3.7g / m 2 The range between any one or both of them; Furthermore, the coating amount of the magnesium oxide coating on the transmission side is 3.8 g / m². 2 3.9g / m 2 4.0g / m 2 The range between any one or both of them; Furthermore, the coating amount of the magnesium oxide coating in the intermediate portion is 3.3 g / m². 2 3.4g / m 2 3.5g / m 2 The range between any one or both of them; In step S2, the alkaline washing is performed using a NaOH solution with a concentration of 20% to 30%. Furthermore, the iron loss fluctuation value of the finished oriented electrical steel prepared by using the above-mentioned magnesium oxide coating method for oriented electrical steel is less than or equal to 5%.

[0006] This invention adjusts the coating amount on the working side, transmission side, and intermediate part during coating preparation to make the coating more uniform, thereby obtaining coated oriented electrical steel with very small differences within the same plate, and improving the effect of subsequent annealing. Detailed Implementation

[0007] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0008] This invention provides a method for applying a magnesium oxide coating to grain-oriented electrical steel, comprising the following steps: S1. Obtain oriented electrical steel, wherein the thickness of the oriented electrical steel is 0.1~0.2mm and the width is 0.8~1.5m; In the technical solution of this invention, the thickness of the oriented electrical steel before coating is 0.1~0.2mm, and the width is 0.8~1.5m. The coating range on the working side accounts for 1 / 4~1 / 3 of the width of the oriented electrical steel, and the coating range on the transmission side accounts for 1 / 4~1 / 3 of the width of the oriented electrical steel. If the width of the oriented electrical steel is too wide or too narrow, or if the coating range on the working side and the transmission side is too large or too small, it will affect the spreading of the magnesium oxide coating on the surface, thereby affecting the adhesion and uniformity. If the thickness of the oriented electrical steel is too thick or too thin, it will affect the penetration effect of the subsequent preparation of the finished oriented electrical steel, thus making it impossible to obtain the technical effect of the oriented electrical steel with a plate difference of less than or equal to 0.05μm as described in this invention.

[0009] S2. The oriented electrical steel is subjected to alkaline washing; This invention performs alkaline washing before coating preparation to ensure the surface of the oriented electrical steel is clean and the coating adheres evenly, thus guaranteeing uniform coating thickness. If the concentration of the alkaline washing solution is too low, it will result in incomplete alkaline washing, affecting the adhesion of the magnesium oxide coating. If the concentration of the alkaline washing solution is too high, it is easy to over-wash, causing the oriented electrical steel sheet to turn black and affecting the amount of coating adhesion on the surface.

[0010] S3. Apply a magnesium oxide coating to the oriented electrical steel, wherein the coating amount on the working side is 3.5~3.7 g / m². 2 The coating amount of the magnesium oxide coating on the transmission side is 3.8~4.0 g / m². 2 The coating amount of the magnesium oxide coating in the middle part is 3.3~3.5 g / m². 2 The water content of the magnesium oxide coating is 1.5% to 2.0%. This invention employs coating rollers for coating. The inventors discovered that inconsistent pressure from the coating rollers along the width of the strip leads to inconsistent coating thickness at different locations. Therefore, this invention achieves uniform thickness across the entire strip width by controlling the coating amount on the working side, the drive side, and the middle section. The drive side, affected by the equipment's transmission, experiences the highest extrusion pressure and the least amount of coating liquid adhered, thus requiring a larger coating amount. The working side experiences the lowest extrusion pressure, resulting in a slightly smaller coating amount compared to the drive side. The middle section, influenced by the flow of coating liquid on both sides, has a large coverage area, thus requiring the minimum coating amount. While coating liquid freely drips from the strip edges on both the drive and working sides, the middle side, constrained by the coating liquid on both sides, adheres mostly to the strip surface. The magnesium oxide coating is applied to the working side, the transmission side, and the middle part between the working side and the transmission side. When the water content of the magnesium oxide coating is greater than 2.0%, the fluidity is good, but the adhesion is poor, which will result in insufficient coating thickness. When the water content of the magnesium oxide coating is less than 1.5%, the fluidity is poor, and the difference in coating thickness between the working side and the plate is difficult to control, which will not achieve the technical effect of the present invention. In the present invention, the coating range on the working side and the transmission side accounts for 1 / 4 to 1 / 3 of the width of the oriented electrical steel, and the remaining part is the coating range of the middle part. If the range on the working side and the transmission side is too large or too small, the technical effect of the difference in thickness between the working side and the plate of the oriented electrical steel prepared by the present invention being less than or equal to 0.05 μm cannot be achieved.

[0011] S4. Dry the oriented electrical steel coated with magnesium oxide paint to obtain oriented electrical steel with a plate difference of less than or equal to 0.05μm.

[0012] Furthermore, the present invention also limits the coating thickness to 3~4μm. If the coating thickness is less than 3μm, the interlayer resistance is insufficient. If the coating thickness is greater than 4μm, the adhesion of the magnesium oxide coating will be poor, and the technical effect of the present invention cannot be achieved. Therefore, the coating thickness of the present invention is 3~4μm.

[0013] The greater the difference in coating thickness between the coating and the board, the greater the difference in coating thickness at different locations. This results in uneven thickness of the magnesium silicate underlayer, leading to uneven magnetic properties, especially greater fluctuations in iron loss.

[0014] This invention addresses the issue of controlling the uniformity of magnesium oxide coating thickness in existing technologies by controlling two key aspects: first, the overall coating thickness, which affects the thickness of the magnesium silicate underlayer and the interlayer resistance; and second, the coating thickness difference within the same board, i.e., the difference in coating thickness at different locations on the board surface. The smaller the difference, the better the coating uniformity. A large difference leads to significant variations in anti-adhesion properties and resistance fluctuations at different locations, and may even cause crystallization defects in the later stages.

[0015] The oriented electrical steel used in this embodiment of the invention has the following composition: Si 3.3wt%, Mn 0.2wt%, Al 0.2wt%, S 0.008wt%, N 0.02wt%, C 0.003wt%, with the balance being iron and unavoidable impurities.

[0016] Example 1 A method for applying a magnesium oxide coating to grain-oriented electrical steel includes the following steps: S1. Obtain oriented electrical steel, wherein the oriented electrical steel has a thickness of 0.1 mm and a width of 0.8 mm; S2. The oriented electrical steel is subjected to alkaline washing, wherein the alkaline washing is performed using a NaOH solution with a concentration of 20%. S3. Apply magnesium oxide coating to the oriented electrical steel, with the coating amount on the working side being 3.5 g / m². 2 The coating amount of the magnesium oxide coating on the transmission side is 3.8 g / m². 2 The coating amount of the magnesium oxide coating in the middle part is 3.3 g / m². 2 The water content of the magnesium oxide coating is 1.5%; S4. The oriented electrical steel coated with magnesium oxide is dried to obtain oriented electrical steel with a thickness difference of 0.04 μm and a magnesium oxide coating thickness of 3 μm.

[0017] Example 2 A method for applying a magnesium oxide coating to grain-oriented electrical steel includes the following steps: S1. Obtain oriented electrical steel, wherein the oriented electrical steel has a thickness of 0.2 mm and a width of 1.5 mm; S2. The oriented electrical steel is subjected to alkaline washing, wherein the alkaline washing is performed using a NaOH solution with a concentration of 30%. S3. The oriented electrical steel is coated with magnesium oxide coating, and the coating amount of magnesium oxide coating on the working side is 3.7 g / m. 2 The coating amount of the magnesium oxide coating on the transmission side is 4.0 g / m². 2 The coating amount of the magnesium oxide coating in the middle part is 3.5 g / m². 2 The water content of the magnesium oxide coating is 2%; S4. The oriented electrical steel coated with magnesium oxide is dried to obtain oriented electrical steel with a thickness difference of 0.05μm and a magnesium oxide coating thickness of 4μm.

[0018] Example 3 Finished grain-oriented electrical steel was prepared using the grain-oriented electrical steel obtained in Example 1, and its iron loss was tested. The iron loss P... 1.7 / 50 Volatility is 5%.

[0019] Comparative Example 1 Unlike Example 1, in step S1, the thickness of the electrical steel is 0.05 mm; In step S4, oriented electrical steel with a plate difference of 0.07 μm is obtained.

[0020] Comparative Example 2 Unlike Example 1, in step S1, the thickness of the electrical steel is 0.3 mm; In step S4, oriented electrical steel with a plate difference of 0.06 μm is obtained.

[0021] Comparative Example 3 Unlike Example 1, in step S3, the coating amount of magnesium oxide on the working side, transmission side, and intermediate part is 4.0 g / m². 2 ; In step S4, an oriented electrical steel with a thickness difference of 0.065 μm is obtained, and the thickness of the magnesium oxide coating on the oriented electrical steel is 4.5 μm.

[0022] Comparative Example 4 Unlike Example 1, in step S3, the coating amount of the magnesium oxide coating on the working side is 3.4 g / m². 2 The coating amount of the magnesium oxide coating on the transmission side is 3.6 g / m². 2 The coating amount of the magnesium oxide coating in the middle part is 3.2 g / m². 2 ; In step S4, an oriented electrical steel with a thickness difference of 0.048 μm is obtained, and the thickness of the magnesium oxide coating on the oriented electrical steel is 2.7 μm.

[0023] Comparative Example 5 Unlike Example 1, in step S3, the coating amount of the magnesium oxide coating on the working side is 3.8 g / m². 2 The coating amount of the magnesium oxide coating on the transmission side is 4.1 g / m². 2 The coating amount of the magnesium oxide coating in the middle part is 3.6 g / m². 2 ; In step S4, an oriented electrical steel with a thickness difference of 0.053 μm is obtained, and the thickness of the magnesium oxide coating on the oriented electrical steel is 4.2 μm.

[0024] Comparative Example 6 Unlike Example 1, in step S3, the water content of the magnesium oxide coating is 1%; In step S4, an oriented electrical steel with a thickness difference of 0.055 μm is obtained, and the thickness of the magnesium oxide coating on the oriented electrical steel is 4.7 μm.

[0025] Comparative Example 7 Unlike Example 1, in step S3, the water content of the magnesium oxide coating is 3%; In step S4, an oriented electrical steel with a thickness difference of 0.047 μm is obtained, and the thickness of the magnesium oxide coating on the oriented electrical steel is 2.6 μm.

[0026] Comparative Example 8 Unlike Example 3, the oriented electrical steel prepared in Comparative Example 1 was used to prepare the finished oriented electrical steel, and its iron loss was tested. The iron loss P was... 1.7 / 50 The volatility is 10%.

[0027] This invention adjusts the coating amount on the working side, transmission side, and intermediate part during coating preparation to make the coating more uniform, thereby obtaining coated electrical steel with very small differences within the same plate, and ensuring that the iron loss value of the electrical steel product after annealing fluctuates less.

[0028] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for applying a magnesium oxide coating to grain-oriented electrical steel, characterized in that, Includes the following steps: S1. Obtain oriented electrical steel, wherein the thickness of the oriented electrical steel is 0.1~0.2mm and the width is 0.8~1.5m; S2. The oriented electrical steel is subjected to alkaline washing; S3. Apply magnesium oxide coating to the oriented electrical steel, with the coating amount on the working side being 3.5~3.7 g / m². 2 The coating amount of the magnesium oxide coating on the transmission side is 3.8~4.0 g / m². 2 The coating amount of the magnesium oxide coating in the middle part is 3.3~3.5 g / m². 2 The water content of the magnesium oxide coating is 1.5% to 2.0%. S4. Dry the oriented electrical steel coated with magnesium oxide coating to obtain oriented electrical steel with a thickness difference of less than or equal to 0.05 μm. The thickness of the magnesium oxide coating on the oriented electrical steel is 3~4 μm.

2. The method for applying a magnesium oxide coating to grain-oriented electrical steel according to claim 1, characterized in that, In step S2, the alkaline washing is performed using a NaOH solution with a concentration of 20% to 30%.