Methods to improve the surface roughness of semi-finished electrical steel

Abstract

This application discloses a method for improving the surface roughness of semi-finished electrical steel, including uncoiling, pickling, annealing, and leveling of hot-rolled steel coils. In the leveling process, chrome-plated work rolls with a roughness of 3.5±0.5μm, a diameter of 400mm to 440mm, and a chrome plating thickness of 5.0±0.5μm are used. The leveling elongation of the strip is controlled to be 4.5±0.5%. The method of this application can reduce the decay rate of the surface roughness of semi-finished electrical steel, improve the surface roughness of semi-finished electrical steel, and improve the surface roughness uniformity of semi-finished electrical steel.

Description

Technical Field

[0001] This application belongs to the field of steel rolling technology, and in particular relates to a method for improving the surface roughness of semi-processed electrical steel. Background Technology

[0002] Semi-process electrical steel, also known as semi-finished electrical steel, has the advantages of fewer processes, shorter production flow, and lower cost compared to fully-processed electrical steel. As the stator and rotor of motor cores, semi-process electrical steel can improve the energy utilization efficiency of small and medium-sized motors. Therefore, semi-process electrical steel is widely used in small and medium-sized motors both domestically and internationally.

[0003] The oxide layer on the surface of semi-finished electrical steel is typically used as an insulating layer for the stator and rotor of motor cores to reduce eddy current losses and improve equipment efficiency. The higher the surface roughness of the semi-finished electrical steel, the stronger the adhesion between the oxide layer and the strip steel substrate. However, using conventional leveling processes, semi-finished electrical steel may exhibit problems such as rapid surface roughness decay and poor roughness uniformity, failing to meet the requirements of certain products. Summary of the Invention

[0004] This application provides a method for improving the surface roughness of semi-finished electrical steel and a semi-finished electrical steel with high surface roughness. The method can reduce the decay rate of the surface roughness of the semi-finished electrical steel, improve the surface roughness of the semi-finished electrical steel, and improve the surface roughness uniformity of the semi-finished electrical steel.

[0005] In a first aspect, embodiments of this application provide a method for improving the surface roughness of semi-processed electrical steel, comprising: uncoiling, pickling, annealing in a bell, and leveling treatment of hot-rolled steel coils to obtain leveled strip steel; wherein the leveling elongation of the leveled strip steel is 4.5±0.5%; the working roll of the leveling machine used in the leveling process is a chrome-plated working roll; the roughness of the chrome-plated working roll is 3.5±0.5μm; the diameter of the chrome-plated working roll is 400mm~440mm; and the thickness of the chrome plating layer of the chrome-plated working roll is 5.0±0.5μm.

[0006] According to an embodiment of the first aspect of this application, the method further includes rewinding the leveled strip to obtain semi-processed electrical steel with high surface roughness; the tensile elongation of the rewinding is 0.2% to 0.4%.

[0007] According to the embodiments of the first aspect of this application, the roll roughness of the final stand of the pickling and rolling process is 4.0 μm to 4.2 μm; the reduction rate of the pickling and rolling process is 70% to 85%.

[0008] According to an embodiment of the first aspect of this application, the annealing temperature of the annealing process is 700±10℃, and the holding time of the annealing process is 6±1h.

[0009] According to an embodiment of the first aspect of this application, the diameter of the chrome-plated work roller is 400 mm to 435 mm.

[0010] According to the embodiment of the first aspect of this application, the pretreatment process of washing the chrome-plated work roll is included before the leveling process. The rolling force of the pretreatment process of washing the roll is 200t to 300t, and the washing time is 3min to 5min.

[0011] According to an embodiment of the first aspect of this application, the material of the working roller of the leveling machine is Cr5.

[0012] Secondly, this application provides a semi-process electrical steel with high surface roughness, prepared according to the method of the embodiment of the first aspect of this application, wherein the surface roughness of the semi-process electrical steel is 1.3μm to 2.5μm.

[0013] According to an embodiment of the second aspect of this application, the iron loss of the semi-processed electrical steel is ≤4.2W / kg, and the magnetic permeability is ≥2000Gs / Oe.

[0014] According to an embodiment of the second aspect of this application, the average oxide layer thickness of the semi-finished electrical steel is 5 μm to 7 μm, and the surface insulation resistance of the semi-finished electrical steel is 500 Ω·mm. 2 / piece ~600Ω·mm 2 / piece.

[0015] The method for improving the surface roughness of semi-finished electrical steel according to the embodiments of this application includes uncoiling, pickling, annealing and leveling of hot-rolled steel coils. In the leveling process, chrome-plated work rolls with a roughness of 3.5±0.5μm, a diameter of 400mm to 440mm and a chrome plating layer thickness of 5.0±0.5μm are used, and the leveling elongation of the strip is controlled at 4.5±0.5%. The method of this application can reduce the decay rate of the surface roughness of semi-finished electrical steel, improve the surface roughness of semi-finished electrical steel, and improve the surface roughness uniformity of semi-finished electrical steel. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the leveling machine provided in the embodiments of this application.

[0018] Figure 2 This is a metallographic image of the strip steel product with volume number D200928310 in Embodiment 1 of this application. Detailed Implementation

[0019] To make the purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the implementation details described in this specification are merely for illustrative purposes and are not intended to limit the scope of this application.

[0020] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0021] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0022] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application). Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C and the test pressure is standard atmospheric pressure.

[0023] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0024] In current technologies, the oxide layer on the surface of semi-finished electrical steel is typically used as an insulating layer for the stator and rotor of motor cores to reduce eddy current losses and improve the efficiency of motors and other equipment. The higher the surface roughness of the semi-finished electrical steel, the stronger the adhesion between the oxide layer and the strip substrate, thus placing high demands on the surface roughness of the strip. The inventors discovered that using conventional leveling processes results in a rapid decrease in the surface roughness of the semi-finished electrical steel, with significant differences in roughness between the upper and lower surfaces, and between the edges and the middle. Generally, after producing 4-5 coils of steel, the surface roughness of the semi-finished electrical steel drops below 1.0 μm, making it difficult to meet the requirements of certain products.

[0025] To address the problems in the prior art, this application provides a method for improving the surface roughness of semi-processed electrical steel, comprising: uncoiling, pickling, annealing in a bell, and leveling the hot-rolled steel coil to obtain a leveled strip; wherein the leveled strip has a leveling elongation of 4.5±0.5%; the leveling machine work rolls used in the leveling process are chrome-plated work rolls; the roughness of the chrome-plated work rolls is 3.5±0.5μm; the diameter of the chrome-plated work rolls is 400mm~440mm; and the thickness of the chrome plating layer on the chrome-plated work rolls is 5.0±0.5μm. A schematic diagram of the leveling machine used in this application embodiment is shown below. Figure 1 .

[0026] For example, the roughness of the chrome-plated work roll is 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, and 4.0μm.

[0027] For example, the thickness of the chrome plating layer of the chrome-plated work roll is 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5.0μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, and 5.5μm.

[0028] This application embodiment performs uncoiling, pickling, annealing, and leveling treatments on hot-rolled steel coils. In particular, the leveling process uses chrome-plated work rolls with a roughness of 3.5±0.5μm, a diameter of 400mm to 440mm, and a chrome plating thickness of 5.0±0.5μm. Furthermore, the leveling elongation of the strip is controlled at 4.5±0.5%. By using the method of this application, the decay rate of the surface roughness of semi-processed electrical steel can be reduced, the surface roughness of semi-processed electrical steel can be improved, and the surface roughness uniformity of semi-processed electrical steel can be enhanced.

[0029] In some optional embodiments, the method further includes rewinding the leveled strip to obtain semi-processed electrical steel with high surface roughness; the rewinding has a tension leveling elongation of 0.2% to 0.4%.

[0030] In this embodiment, by rewinding the flattened strip and controlling the tensile elongation rate of the rewinding to 0.2% to 0.4%, the strip can be guaranteed to have a good shape and the rough surface of the strip can be effectively prevented from being worn flat.

[0031] In some optional embodiments, the roll roughness of the final stand in the pickling and rolling process is 4.0 μm to 4.2 μm; the reduction rate of the pickling and rolling process is 70% to 85%.

[0032] For example, the roll roughness of the pickling mill stand in the pickling process is 4.0μm, 4.01μm, 4.02μm, 4.03μm, 4.04μm, 4.05μm, 4.06μm, 4.07μm, 4.08μm, 4.09μm, 4.10μm, 4.15μm, and 4.2μm.

[0033] For example, the reduction rates of the pickling and rolling process are 70%, 75%, 78%, 79%, 79.5%, 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 84%, and 85%.

[0034] This application embodiment improves the surface roughness of cold-hardened strip steel to above 0.8μm by pickling hot-rolled strip steel and controlling the roll roughness of the final pickling stand to be 4.0μm to 4.2μm and the reduction rate to 70% to 85%, thereby ensuring that the strip steel can have a high surface roughness replication rate in the subsequent leveling process.

[0035] In some optional embodiments, the annealing temperature of the hood annealing process is 700±10℃, and the holding time of the hood annealing process is 6±1h.

[0036] In this embodiment, by controlling the annealing temperature of the bell-type annealing process to 700±10℃ and the holding time of the bell-type annealing process to 6±1h, it is possible to ensure that the average grain size of the cold-hardened strip steel after recrystallization annealing is 7-8 grade. This not only eliminates cold rolling work hardening and internal stress, but also ensures that the strip steel has a high surface roughness replication rate in the subsequent leveling process.

[0037] In some alternative embodiments, the diameter of the chrome-plated work roll is 400 mm to 435 mm.

[0038] For example, the diameters of the chrome-plated work rolls are 400mm, 405mm, 408mm, 410mm, 412mm, 413mm, 414mm, 415mm, 416mm, 417mm, 418mm, 419mm, 420mm, 422mm, 424mm, 426mm, 428mm, 430mm, 432mm, 433mm, 434mm, and 435mm.

[0039] The embodiments of this application control the diameter of the chrome-plated work roll to 400mm to 435mm, which can increase the rolling force and improve the surface roughness replication rate of the strip, thereby giving the strip a higher surface roughness.

[0040] In some optional embodiments, a pretreatment process of washing the chrome-plated work rolls is included before the leveling process. The rolling force of the pretreatment process is 200t to 300t, and the washing time is 3min to 5min.

[0041] In this embodiment, the chrome-plated work rolls undergo a pre-treatment process of washing. By controlling the rolling force of the pre-treatment process to be 200t to 300t and the washing time to be 3min to 5min, the surface roughness of the chrome-plated work rolls can be made more uniform, ensuring that they are more wear-resistant and have better roughness uniformity when rolling strip steel.

[0042] In some alternative embodiments, the work rolls of the leveling machine are made of Cr5.

[0043] This application also provides a semi-process electrical steel with high surface roughness, which is prepared according to the aforementioned method, and the surface roughness of the semi-process electrical steel is 1.3μm to 2.5μm.

[0044] In some alternative embodiments, the semi-processed electrical steel has an iron loss ≤4.2W / kg and a magnetic permeability ≥2000Gs / Oe.

[0045] In some optional embodiments, the average oxide layer thickness of the semi-processed electrical steel is 5 μm to 7 μm, and the surface insulation resistance of the semi-processed electrical steel is 500 Ω·mm. 2 / piece ~600Ω·mm 2 / piece.

[0046] Example

[0047] The following embodiments describe the disclosure of this application in more detail. These embodiments are for illustrative purposes only, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0048] Example 1

[0049] 1. Preparation of semi-process electrical steel:

[0050] Hot-rolled steel coils are uncoiled, pickled, annealed in a bell, and leveled to obtain leveled strip. Specific parameters for the pickling process are shown in Table 1, for the bell annealing process in Table 2, and for the chrome-plated work rolls used in the leveling process in Table 3. Prior to the leveling process, a pre-treatment process of washing the chrome-plated work rolls is included. The rolling force for the pre-treatment process is 200t, and the washing time is 3.5min.

[0051] Table 1

[0052]

[0053]

[0054] Table 2

[0055]

[0056] Table 3

[0057] Roller number Roller diameter (mm) Roller surface roughness (μm) Chromium plating thickness (μm) Roll material upper roller CPW326 421.933 3.5 5.1 Cr5 Lower roller CPW325 421.915 3.5 5.1 Cr5

[0058] 2. Surface roughness test results of semi-finished electrical steel:

[0059] The flattening elongation of the strip steel after leveling is 4.6%. The surface roughness of the semi-processed electrical steel was tested according to the standard GB_T 2523-2022_Measurement Method of Surface Roughness, Peak Number and Waviness of Cold Rolled Metal Sheets and Strips. The test results of the surface roughness of the semi-processed electrical steel are shown in Table 4.

[0060] Table 4

[0061]

[0062]

[0063] illustrate:

[0064] In the table, WS20 indicates the roughness measured 20mm from the left side of the working side of the strip, and DS20 indicates the roughness measured 20mm from the right side of the working side of the strip; the rolling sequence number indicates the roughness sampled and measured for the 1st, 3rd, 5th, 7th, 9th, and 11th rolls in the rolling plan.

[0065] As can be seen from Table 4, after rolling 11 coils of steel according to this plan, the surface roughness of the strip still meets the requirement of 1.3-2.5μm. Among them, Figure 2 The image shown is a metallographic diagram of the strip steel with roll number D200928310. Its average grain size is grade 7.5, which ensures a high surface replication rate and qualified magnetic properties of the finished product.

[0066] Example 2

[0067] 1. Preparation of semi-process electrical steel:

[0068] The only difference between this embodiment 2 and embodiment 1 is the work roller used in the leveling process. The specific parameters of the chrome-plated work roller used in the leveling process of this embodiment 2 are shown in Table 5.

[0069] Table 5

[0070] Roller number Roller diameter (mm) Roller surface roughness (μm) Chromium plating thickness (μm) Roll material upper roller CPW331 417.93 3.5 4.9 Cr5 Lower roller CPW330 417.918 3.5 4.9 Cr5

[0071] 2. Test results of magnetic properties of semi-finished electrical steel:

[0072] The flattening elongation of the strip after leveling is 4.6%. The magnetic property test results of the semi-processed electrical steel are shown in Table 6.

[0073] Table 6

[0074]

[0075] Comparative Example 1

[0076] 1. Preparation of semi-process electrical steel:

[0077] The only difference between Comparative Example 1 and Example 1 is the work roll used in the leveling process. Comparative Example 1 uses a common work roll, specifically a steel roll containing 5% Cr. The specific parameters of the work roll used in the leveling process of Comparative Example 1 are shown in Table 7.

[0078] Table 7

[0079] Roller number Roller diameter (mm) Roller surface roughness (μm) Roll material upper roller CPW310 415.449 3.5 Cr5 Lower roller CPW311 415.534 3.5 Cr5

[0080] 2. Surface roughness test results of semi-finished electrical steel:

[0081] The flattening elongation of the strip steel after leveling is 4.6%. The surface roughness test results of the semi-processed electrical steel are shown in Table 8.

[0082] Table 8

[0083]

[0084] illustrate:

[0085] In the table, WS20 indicates the roughness measured 20mm from the left side of the working side of the strip, and DS20 indicates the roughness measured 20mm from the right side of the working side of the strip; the rolling sequence number indicates the roughness measured for the 1st, 3rd, and 5th rolls in the rolling plan.

[0086] As can be seen from Table 8, after rolling 5 coils of steel, the surface roughness of the strip steel was <1.0μm, which did not meet the minimum roughness requirements of some customers (minimum roughness requirement 1.0-2.6μm, target requirement 1.3-2.5μm). Therefore, it is necessary to change the rolls before semi-process electrical steel can be produced.

[0087] Comparative Example 2

[0088] 1. Preparation of semi-process electrical steel:

[0089] The only difference between Comparative Example 2 and Example 1 is the work roller used in the leveling process. The chrome-plated work roller used in Comparative Example 2 has a chrome plating thickness of 3.2 μm. Specific parameters of the chrome-plated work roller used in the leveling process of Comparative Example 2 are shown in Table 9.

[0090] Table 9

[0091] Roller number Roller diameter (mm) Roller surface roughness (μm) Chromium plating thickness (μm) Roll material upper roller CPW506 412.718 3.5 3.2 Cr5 Lower roller CPW505 412.712 3.5 3.2 Cr5

[0092] 2. Surface roughness test results of semi-finished electrical steel:

[0093] The flattening elongation of the strip steel after leveling is 4.6%. The surface roughness test results of the semi-processed electrical steel are shown in Table 10.

[0094] Table 10

[0095]

[0096]

[0097] illustrate:

[0098] In the table, WS20 indicates the roughness measured 20mm from the left side of the working side of the strip, and DS20 indicates the roughness measured 20mm from the right side of the working side of the strip; the rolling sequence number indicates the roughness measured for the 1st, 3rd, and 5th rolls in the rolling plan.

[0099] As can be seen from Table 10, after rolling 5 coils of steel in this plan, the surface roughness of the strip is less than 1.3 μm (with some points less than 1.0 μm), which does not meet the minimum roughness requirements of some customers (minimum roughness requirement 1.0-2.6 μm, target requirement 1.3-2.5 μm).

[0100] Comparative Example 3

[0101] 1. Preparation of semi-process electrical steel:

[0102] The only difference between Comparative Example 3 and Example 1 is the work roller used in the leveling process. The chrome-plated work roller used in Comparative Example 3 has a diameter of less than 400 mm. Specific parameters of the chrome-plated work roller used in the leveling process of Comparative Example 3 are shown in Table 11.

[0103] Table 11

[0104] Roller number Roller diameter (mm) Roller surface roughness (μm) Chromium plating thickness (μm) Roll material upper roller CPW411 390.036 3.5 4.6 Cr5 Lower roller CPW416 390.045 3.5 4.6 Cr5

[0105] 2. Surface roughness test results of semi-finished electrical steel:

[0106] The flattening elongation of the strip steel after leveling is 4.6%. The surface roughness test results of the semi-processed electrical steel are shown in Table 12.

[0107] Table 12

[0108]

[0109]

[0110] illustrate:

[0111] In the table, WS20 indicates the roughness measured 20mm from the left side of the working side of the strip, and DS20 indicates the roughness measured 20mm from the right side of the working side of the strip; the rolling sequence number indicates the roughness measured for the 1st, 3rd, 5th, 7th, and 9th rolls in the rolling plan.

[0112] As can be seen from Table 12, after rolling 9 coils of steel in this plan, the surface roughness of the strip is less than 1.3 μm (with some individual points less than 1.0 μm), which does not meet the minimum roughness requirements of some customers (minimum roughness requirement 1.0-2.6 μm, target requirement 1.3-2.5 μm).

[0113] Comparative Example 4

[0114] 1. Preparation of semi-process electrical steel:

[0115] The only difference between Comparative Example 4 and Example 1 is the work roll used in the leveling process and the leveling elongation. The leveling elongation in Comparative Example 4 is 3.0%. The specific parameters of the chrome-plated work roll used in the leveling process of Comparative Example 4 are shown in Table 13.

[0116] Table 13

[0117] Roller number Roller diameter (mm) Roller surface roughness (μm) Chromium plating thickness (μm) Roll material upper roller CPW331 417.93 3.5 4.9 Cr5 Lower roller CPW330 417.918 3.5 4.9 Cr5

[0118] 2. The surface roughness test results of the semi-processed electrical steel are shown in Table 14.

[0119] Table 14

[0120]

[0121] illustrate:

[0122] In the table, WS20 indicates the roughness measured 20mm from the left side of the working side of the strip, and DS20 indicates the roughness measured 20mm from the right side of the working side of the strip; the rolling sequence number indicates the roughness measured for the 1st, 2nd, and 3rd rolls in the rolling plan.

[0123] As can be seen from Table 14, after rolling 3 coils of steel, the surface roughness of the strip steel was <1.0μm, which does not meet the customer's minimum roughness requirements (minimum roughness requirement 1.0-2.6μm, target requirement 1.3-2.5μm). Therefore, it is necessary to change the rolls before semi-process electrical steel can be produced.

[0124] 3. Test results of magnetic properties of semi-finished electrical steel:

[0125] Please see Table 15 for the test results of the magnetic properties of the semi-finished electrical steel.

[0126] Table 15

[0127]

[0128] The comparison between Table 6 and Table 15 shows that the flattening elongation is low (3.0%), the magnetic permeability is low, and some rolls have unqualified magnetic permeability. At the same time, the iron loss is also higher than that of the flattening elongation of 4.6% (50LW600 judgment standard: iron loss ≤ 4.2W / kg, magnetic permeability ≥ 2000Gs / Oe).

[0129] Comparative Example 5

[0130] The effect of surface roughness of semi-processed electrical steel on the iron oxide layer and surface insulation resistance of the finished product is shown in Table 16.

[0131] Table 16

[0132]

[0133] As can be seen from Table 16, a small surface roughness results in a thin oxide layer and low surface insulation resistance, which is detrimental to the product's rust prevention performance and temperature rise process.

[0134] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A method for improving the surface roughness of semi-finished electrical steel, characterized in that, include: Hot-rolled steel coils are uncoiled, pickled, annealed in a bell, and leveled to obtain leveled strip steel. The flattening elongation of the strip after leveling is 4.5±0.5%; the working roll of the leveling machine used in the leveling process is a chrome-plated working roll; the roughness of the chrome-plated working roll is 3.5±0.5μm; the diameter of the chrome-plated working roll is 400mm~440mm; and the thickness of the chrome plating layer of the chrome-plated working roll is 5.0±0.5μm. The method further includes rewinding the flattened strip to obtain semi-processed electrical steel with high surface roughness. The elongation of the rewound tension leveling is 0.2%~0.4%; The roll roughness of the final stand in the pickling and rolling process is 4.0 μm to 4.2 μm; the reduction rate of the pickling and rolling process is 70% to 85%.

2. The method according to claim 1, characterized in that, The annealing temperature of the bell-type annealing process is 700±10℃, and the holding time of the bell-type annealing process is 6±1h.

3. The method according to claim 1, characterized in that, The diameter of the chrome-plated work roller is 400mm~435mm.

4. The method according to claim 1, characterized in that, The leveling process is preceded by a pre-treatment process of washing the chrome-plated work rolls. The rolling force of the pre-treatment process is 200t~300t, and the washing time is 3min~5min.

5. The method according to claim 1, characterized in that, The working rollers of the leveling machine are made of Cr5.

6. A semi-processed electrical steel with high surface roughness, characterized in that, The semi-processed electrical steel prepared according to any one of claims 1-5 has a surface roughness of 1.3 μm to 2.5 μm.

7. The semi-process electrical steel according to claim 6, characterized in that, The semi-processed electrical steel has an iron loss ≤ 4.2 W / kg and a magnetic permeability ≥ 2000 Gs / Oe.

8. The semi-process electrical steel according to claim 6, characterized in that, The average oxide layer thickness of the semi-processed electrical steel is 5μm~7μm, and the surface insulation resistance of the semi-processed electrical steel is 500Ω•mm² / piece~600Ω•mm² / piece.

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