Non-oriented silicon steel and method for manufacturing the same

Abstract

This invention discloses a method for manufacturing non-oriented silicon steel. The non-oriented silicon steel comprises: steel material, a coating layer on the surface of the steel material, and an insulating layer on the surface of the coating layer; wherein the resistivity of the coating layer is greater than that of the steel material. The manufacturing method of the non-oriented silicon steel includes the following steps: S1. continuous casting; S2. hot rolling; S3. normalizing; S4. cold rolling; S5. annealing; S6. alloy coating; S7. insulating coating. The beneficial effect of this invention is that it provides a non-oriented silicon steel with P1.5 / 50 less than or equal to 2.15 W / kg, P1.0 / 400 less than or equal to 14.5 W / kg, and P1.0 / 1000 less than or equal to 48.5 W / kg, and its manufacturing method.

Description

Technical Field

[0001] This invention belongs to the field of non-oriented silicon steel, and more specifically, relates to a non-oriented silicon steel and its manufacturing method. Background Technology

[0002] With the development of drive motor technology, permanent magnet direct drive technology is being used more and more widely in mechanical transmission. Due to different load conditions, motors need to operate in different speed and frequency ranges. To ensure high-efficiency operation of the motor, it is required that the non-oriented silicon steel soft magnetic material used to make the motor core has low iron loss under power frequency (50Hz) conditions, and also has low iron loss performance under high frequency conditions.

[0003] Under high-frequency operating conditions, the core loss of motors is mainly composed of eddy current losses of non-oriented silicon steel. Conventional non-oriented silicon steel achieves the purpose of reducing iron loss by adding alloying elements such as Si, Mn, and Al. As the content of alloying elements increases, the resistivity of silicon steel increases, eddy current losses decrease, and total iron loss decreases. However, as the content of alloying elements increases to a certain value, the plasticity of non-oriented silicon steel decreases, cold working becomes difficult, and the risk of strip breakage during rolling increases.

[0004] Based on this, patent document 1 (CN108286014B) provides a method for preparing low-iron-loss, high-strength, non-oriented electrical steel. The core of this method is to strengthen the electrical steel by increasing the silicon content through solid solution and combine it with dislocation strengthening to improve the strength of the electrical steel, reduce its iron loss at high frequencies, and ensure magnetic induction. This solves the problems of poor toughness and plasticity, easy brittle fracture, and low magnetic induction caused by increasing Si content. Patent document 2 (CN113512635B) provides a method for producing low-iron-loss non-oriented electrical steel adapted to high-frequency operating conditions. The core of the solution is to control the process, especially the cold rolling step, by using a six-roll single-stand reciprocating mill to cold roll to the target thickness in five passes. In the first three passes of the cold rolling process, a variable-speed asynchronous rolling method is used to increase the dislocation density on the surface of the steel plate under shear stress. This results in finer grain size on the surface and coarser grains in the core after annealing. The method of this invention can produce electrical steel products with coarse equiaxed grains in the core and fine equiaxed grains in the surface. The iron loss of this product is less than or equal to 2.35 W / kg and P1.0 / 400 is less than or equal to 14.0 W / kg. Summary of the Invention

[0005] To address the issue of high iron loss when using non-oriented silicon steel as a motor core under high-frequency operating conditions, this invention provides a non-oriented silicon steel and its manufacturing method.

[0006] As a first aspect of the present invention, some embodiments of the present invention claim protection for a non-oriented silicon steel comprising: a steel material, a coating layer on the surface of the steel material, and an insulating layer on the surface of the coating layer; wherein the resistivity of the coating layer is greater than that of the steel material.

[0007] Furthermore, the coating layer is a silicon-iron alloy with a Si content of 8wt% to 20wt%.

[0008] Furthermore, the thickness of the coating layer is 0.05 mm to 0.1 mm.

[0009] Furthermore, the thickness of non-oriented silicon steel is less than or equal to 0.3 mm.

[0010] Furthermore, the steel comprises the following chemical composition by weight percentage:

[0011] Si: Greater than or equal to 3.0%;

[0012] Als: 0.20% to 0.60%;

[0013] Mn: 0.10% to 0.40%;

[0014] The C, S, N, and Ti contents are all less than 0.003% and the total C, S, N, and Ti contents are less than or equal to 90 ppm;

[0015] The balance consists of iron and unavoidable impurities.

[0016] Furthermore, the weight percentage of Si is 3.0% to 3.6%.

[0017] As a second aspect of the present invention, some embodiments of the present invention claim protection for a method for manufacturing non-oriented silicon steel, wherein the non-oriented silicon steel is the aforementioned non-oriented silicon steel; the method for manufacturing non-oriented silicon steel includes the following steps:

[0018] S1. Continuous casting;

[0019] S2. Hot-rolled;

[0020] S3. Normal heating;

[0021] S4. Cold rolled;

[0022] S5. Annealing;

[0023] S6. Alloy coating;

[0024] S7. Apply insulating coating.

[0025] Further, step S6. Alloy coating includes: heating the ferrosilicon alloy to a molten state by induction eddy current, and spraying the molten ferrosilicon alloy onto the steel surface using a spray gun to form a coating layer.

[0026] Furthermore, step S6. Alloy coating is carried out in a protective atmosphere to prevent oxidation of the ferrosilicon alloy.

[0027] Furthermore, the protective atmosphere is nitrogen and / or argon.

[0028] The beneficial effects of this invention are as follows:

[0029] The properties of the non-oriented silicon steel of the present invention are as follows: P1.5 / 50 ≤ 2.15W / kg, P1.0 / 400 ≤ 14.5W / kg, P1.0 / 1000 ≤ 48.5W / kg.

[0030] More specifically, some embodiments of the present invention may produce the following specific beneficial effects:

[0031] The coating layer of this invention has a higher resistance than steel, which makes the current distribution in non-oriented silicon steel more uniform. The skin effect when high-frequency current flows through non-oriented silicon steel is weakened, effectively reducing the eddy current loss on the skin surface of non-oriented silicon steel under high-frequency conditions, and also reducing the total loss of non-oriented silicon steel at high frequencies.

[0032] The non-oriented silicon steel of the present invention comprises steel in which the weight percentage of Si is 3.0% to 3.6%, which can improve the resistivity of the steel while ensuring the plasticity of the non-oriented silicon steel, avoiding the problems of cold working difficulties and increased risk of strip breakage during rolling. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention, making other features, objects, and advantages of the invention more apparent. The illustrative embodiments of the invention illustrated in the drawings and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0034] In the attached diagram:

[0035] Figure 1 The image shown is a scanning electron microscope image of the non-oriented silicon steel of the present invention, which mainly shows the surface microstructure of the non-oriented silicon steel.

[0036] Figure 2 This is an electron probe image of the non-oriented silicon steel of the present invention, mainly showing the structure such as the coating layer.

[0037] Meaning of the reference numerals in the attached figures:

[0038] 100. Non-oriented silicon steel;

[0039] 110. Steel; 120. Coating layer; 130. Insulation layer. Detailed Implementation

[0040] Embodiments of this disclosure will now be described in more detail. It should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0041] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0042] Reference Figure 1 and Figure 2 As shown, this embodiment provides a non-oriented silicon steel 100 and its manufacturing method. The non-oriented silicon steel 100 includes: a steel material 110, a coating layer 120 located on the surface of the steel material 110, and an insulating layer 130 located on the surface of the coating layer 120; wherein, the resistance of the coating layer 120 is greater than that of the steel material 110.

[0043] The above technical solution can reduce the eddy current loss of non-oriented silicon steel 100 because: the induced electromotive force increases with the frequency of alternating current, and the skin effect also becomes more pronounced with the frequency of alternating current. When a high-frequency current passes through the non-oriented silicon steel 100, it can be considered that the current flows only through a very thin layer on the surface of the non-oriented silicon steel 100, generating eddy current loss. Furthermore, due to the thermal effect of the current, the eddy current will cause the non-oriented silicon steel 100 to heat up, and if the temperature is too high, the non-oriented silicon steel 100 in the core will undergo thermal demagnetization. The lower the resistance of the non-oriented silicon steel 100, the larger the eddy current in the alternating electric field, and the greater the eddy current loss accordingly.

[0044] However, in this invention, a high-silicon coating layer 120 is added to the surface of the non-oriented silicon steel 100. Since the resistance of the insulating layer 130 is relatively high, its conductivity is negligible. Therefore, the coating layer 120 and the steel 110 jointly contribute to conductivity. As the surface of the conductive part of the non-oriented silicon steel 100, the coating layer 120 has a higher resistance than the internal steel 110. When a high-frequency current flows through the non-oriented silicon steel 100, it effectively reduces the surface eddy current loss caused by the skin effect, thereby reducing the total loss of the non-oriented silicon steel 100 at high frequencies.

[0045] The coating 120 described herein is a silicon-iron alloy with a Si content of 8wt% to 20wt%.

[0046] Using the above technical solution, such as the silicon content in the silicon-iron alloy described herein, the main influence of the resistance of the coating layer 120 and the coating effect is on the coating.

[0047] Therefore, as the silicon content increases, the resistance of the ferrosilicon alloy increases, and the resistance of the coating layer 120 also increases. However, excessively high silicon content will worsen the coating effect of the coating layer 120. Therefore, controlling the Si content between 8wt% and 20wt% ensures that the resistance of the coating layer 120 is sufficiently high while maintaining a good coating effect. For example, the Si content in the ferrosilicon alloy can be any value within any of the following ranges: 8wt%–20wt%, 8wt%–15wt%, 8wt%–10wt%, 10wt%–20wt%, 10wt%–15wt%, and 15wt%–20wt%.

[0048] More specifically, the thickness of coating 120 is 0.05 mm to 0.1 mm.

[0049] Using the above technical solution, the thickness of the coating layer 120, as described herein, mainly affects the resistance of the coating layer 120 and the total thickness of the non-oriented silicon steel 100. The higher the frequency of the alternating current, the stronger the skin effect of the non-oriented silicon steel 100, and the more concentrated the current is on the surface of the non-oriented silicon steel 100. Increasing the thickness of the coating layer 120 increases its resistance, which can correspondingly reduce iron losses due to the skin effect. However, increasing the thickness of the coating layer 120 also increases the overall thickness of the non-oriented silicon steel 100, leading to a corresponding increase in total losses. Therefore, increasing the thickness of the coating layer 120 has both positive and negative effects on the iron losses of the non-oriented silicon steel 100, which are contradictory.

[0050] Therefore, controlling the thickness of the coating layer 120 to be between 0.05 mm and 0.1 mm in this application can balance the positive and negative effects of increasing the thickness of the coating layer 120 on the iron loss of the non-oriented silicon steel 100, thereby minimizing the total iron loss of the non-oriented silicon steel 100. For example, the thickness of the coating layer 120 can be any value taken from any of the following sets of numerical ranges: 0.05 mm to 0.1 mm, 0.05 mm to 0.08 mm, or 0.08 mm to 0.1 mm.

[0051] More specifically, the thickness of the non-oriented silicon steel 100 is less than or equal to 0.3 mm.

[0052] Using the above technical solution, since the greater the thickness of the non-oriented silicon steel 100, the greater the eddy current loss due to the skin effect, and the higher the eddy current loss when its thickness is greater than 0.3 mm, the thickness of the non-oriented silicon steel 100 is controlled to be less than or equal to 0.3 mm to further ensure that the total loss of the non-oriented silicon steel 100 is reduced.

[0053] More specifically, steel 110 comprises the following chemical composition by weight percentage:

[0054] Si: Greater than or equal to 3.0%;

[0055] Als: 0.20% to 0.60%;

[0056] Mn: 0.10% to 0.40%;

[0057] The C, S, N, and Ti contents are all less than 0.003% and the total C, S, N, and Ti contents are less than or equal to 90 ppm;

[0058] The balance consists of iron and unavoidable impurities.

[0059] Using the above technical solution, the addition of Si, Als, and Mn can improve the resistivity of steel 110 and reduce the eddy current loss of non-oriented silicon steel 100. However, excessive Al content has detrimental effects: large, elongated aluminum compound precipitates form at grain boundaries, hindering grain coarsening. Simultaneously, excessive Mn also negatively impacts the magnetism of non-oriented silicon steel 100, as it deteriorates the texture and forms unwanted MnS precipitates. Therefore, controlling Al content between 0.20% and 0.60% and Mn content between 0.10% and 0.40% can improve the resistivity of steel 110 while mitigating the negative effects of excessive Al and Mn content.

[0060] More specifically, the weight percentage of Si is 3.0% to 3.6%.

[0061] By adopting the above technical solution, the resistivity of steel 110 can be improved while maintaining the plasticity of non-oriented silicon steel 100, avoiding problems such as difficulties in cold working and increased risk of strip breakage during rolling. The reason is that although a higher Si content results in a higher resistivity and lower eddy current loss in steel 110, excessive Si content can also make non-oriented silicon steel 100 brittle, leading to increased susceptibility to internal cracking during cold working. Therefore, the weight percentage of Si is controlled between 3.0% and 3.6%. For example, the weight percentage of Si can be any value within any of the following ranges: 3.0%–3.6%, 3.0%–3.4%, 3.0%–3.2%, 3.2%–3.6%, and 3.4%–3.6%.

[0062] More specifically, the manufacturing method of the aforementioned non-oriented silicon steel 100 includes the following steps:

[0063] S1. Continuous casting;

[0064] S2. Hot-rolled;

[0065] S3. Normal heating;

[0066] S4. Cold rolled;

[0067] S5. Annealing;

[0068] S6. Alloy coating;

[0069] S7. Apply insulating coating.

[0070] More specifically, molten steel with the required chemical composition is continuously cast into a billet in step S1; the billet is hot-rolled into a hot-rolled steel plate with a thickness of 1.5mm to 2.5mm in step S2; the hot-rolled steel plate is normalized in step S3 to obtain a cold-rolled raw material plate; the cold-rolled raw material plate is cold-rolled in step S4 to obtain a cold-rolled steel plate with a target thickness of 0.25mm to 0.30mm; the cold-rolled steel plate is annealed in step S5 to obtain steel 110; steel 110 is alloy coated in step S6 and coated with an insulating coating in step S7 to produce a finished non-oriented silicon steel 100 with a thickness of less than or equal to 0.3mm.

[0071] More specifically, step S1. Continuous casting includes the process of solidifying molten steel in a crystallizer to form a billet, which is carried out using electromagnetic stirring.

[0072] By adopting the above technical solution, electromagnetic stirring can reduce the proportion of columnar crystals in the billet and obtain a higher proportion of equiaxed grains. The increase in the proportion of equiaxed crystals can reduce the difficulty of the subsequent deformation process.

[0073] More specifically, in step S2, during hot rolling, the billet heating temperature is 1000–1250℃, with low-temperature heating being preferred.

[0074] By adopting the above technical solution, low-temperature heating can avoid the solid solution of large-sized liquid inclusions in the billet. This is because high temperature will cause the liquid inclusions in the billet to dissolve and disperse in the hot-rolled steel plate after cooling, thus affecting its performance.

[0075] More specifically, in step S3, the normalizing temperature is 850–950°C and the normalizing time is 2–5 minutes. In step S3, the normalizing process preferably adopts a low-temperature process.

[0076] Using the above technical solution, step S3. Normalizing with a low-temperature process can improve the microstructure of hot-rolled steel plates and enhance their cold working performance. This is because low temperature reduces the grain size in hot-rolled steel plates, thereby effectively improving their cold working performance.

[0077] More specifically, after step S3. normalizing and before step S4. cold rolling, the cold-rolled raw material plate is pickled in a turbulent pickling tank. The pickled cold-rolled raw material plate is then cold-rolled in six passes using a 20-roll single-stand reciprocating mill to obtain a cold-rolled steel plate with a target thickness of 0.25mm-0.30mm.

[0078] Using the above technical solution, pickling can achieve the following technical effects: removing iron oxide scale and dirt from the surface of cold-rolled raw material plates; inspecting and removing defects on the surface of cold-rolled raw material plates that are not conducive to cold rolling; and adjusting the weight of cold-rolled raw material plates.

[0079] More specifically, step S5. Annealing adopts a continuous annealing process. The continuous annealing temperature of the cold-rolled steel sheet is 920-990℃, and the continuous annealing time is 180-350s. During continuous annealing, the furnace is protected with a mixed gas of 10%-60% hydrogen and nitrogen, and the dew point of the mixed gas is less than or equal to -25℃.

[0080] Using the above technical solution, a mixture of 10% to 60% hydrogen and nitrogen gas as a protective gas can prevent the metal on the surface of cold-rolled steel sheet from being oxidized at high temperatures. The dew point of the mixture is required to be less than or equal to -25°C. This is because the lower the dew point of the mixture, the lower its oxygen content, and the better it can prevent high-temperature oxidation of the surface of cold-rolled steel sheet.

[0081] More specifically, in step S6, alloy coating, a ferrosilicon alloy with a Si content of 8% to 20% is used. The ferrosilicon alloy is heated to a molten state using induction eddy current, and the molten ferrosilicon alloy is sprayed onto the surface of the steel 110 using a spray gun to form a coating layer 120. The thickness of the coating layer 120 is controlled between 0.05 and 0.1 mm, and the resistivity of the coating layer 120 is higher than that of the steel 110.

[0082] Using the above technical solution, the coating layer 120 has a higher resistivity than the steel 110, which can effectively reduce the eddy current loss of the skin surface of the non-oriented silicon steel 100 under high frequency conditions, thereby reducing the total loss of the non-oriented silicon steel 100 under high frequency conditions.

[0083] More specifically, in step S6. Alloy coating, the spray pressure of the high-pressure spray gun is controlled between 180 and 320 bar; step S6. Alloy coating is always carried out in a protective atmosphere.

[0084] Using the above technical solution, step S6. Alloy coating is carried out in a protective atmosphere to prevent oxidation of the ferrosilicon alloy.

[0085] More specifically, the protective atmosphere is nitrogen and / or argon.

[0086] Using the above technical solution, the protective atmosphere here needs to be an inert gas to play an isolation role. If hydrogen is used, it will increase the risk of combustion and explosion. Therefore, nitrogen and / or argon are used.

[0087] More specifically, in step S7, the temperature for applying the insulating coating is 400–580°C, and the curing time is 30–60 seconds.

[0088] By adopting the above technical solution, coating the surface of steel 110 with an insulating coating can ensure that the interlayer resistance of the non-oriented silicon steel 100 is greater than or equal to 300 Ω·mm2. The insulating coating can effectively confine the eddy currents within each non-oriented silicon steel 100 lamination, reduce the eddy current loss of the non-oriented silicon steel 100, and minimize the power loss between the non-oriented silicon steel 100 laminations.

[0089] The non-oriented silicon steel 100 produced by the present invention has a steel material 110 with uniform and coarse equiaxed crystal structure, and a coating layer 120 with a thickness of 0.05 to 0.1 mm on one side surface, with a Si content of 8% to 20%. The resistivity of the coating layer 120 is higher than that of the internal steel material 110, which effectively reduces the eddy current loss of the skin surface of the non-oriented silicon steel 100 under high frequency conditions, thereby reducing the total loss of silicon steel at high frequency. Specific Implementation

[0091] Example 1

[0092] 1) The molten steel after vacuum smelting is continuously cast into a billet with a thickness of 230mm. Electromagnetic stirring is used in the crystallizer during the continuous casting process. The chemical composition of the billet by weight percentage is Si: 3.15%; Als: 0.27%; Mn: 0.18%; C+S+N+Ti: 79ppm, and the content of each element is less than or equal to 28ppm. The remainder is Fe and unavoidable impurity elements.

[0093] 2) The billet is heated in a walking beam furnace to a temperature of 1150℃, and then subjected to 6 passes of rough rolling and 7 passes of finish rolling to a thickness of 2.15mm to obtain a hot-rolled steel plate.

[0094] 3) Hot-rolled steel sheets are normalized at 910℃ for 185 seconds to obtain cold-rolled raw material sheets. The cold-rolled raw material sheets are then surface-cleaned in a turbulent acid bath. After pickling, the cold-rolled raw material sheets are cold-rolled in 6 passes to obtain cold-rolled steel sheets with a target thickness of 0.27mm.

[0095] 4) Cold-rolled steel sheet is annealed at a temperature of 970℃ for 300s to obtain steel 110. The protective atmosphere in the furnace is 40% hydrogen + 60% nitrogen.

[0096] 5) The alloy coating uses a silicon-iron alloy with a Si content of 10%. The silicon-iron alloy, which is induction heated to a molten state, is sprayed onto the surface of steel 110 using an argon spray gun with a pressure of 200 bar. This ensures that the coating process is carried out in an oxygen-free environment. The coating layer 120 has a thickness of 0.08 mm.

[0097] 6) Apply an insulating coating to the surface of coating layer 120 and cure it at 550°C for 48 seconds.

[0098] The non-oriented silicon steel 100 manufactured by the above process has a good bond between the coating layer 120 and the steel 110. The finished non-oriented silicon steel 100 has a P1.5 / 50 of 2.13W / kg, a P1.0 / 400 of 13.7W / kg, and a P1.0 / 1000 of 46.8W / kg.

[0099] Example 2

[0100] 1) The molten steel after vacuum smelting is continuously cast into a billet with a thickness of 230mm. Electromagnetic stirring is used in the crystallizer during the continuous casting process. The chemical composition of the billet by weight percentage is Si: 3.08%; Als: 0.25%; Mn: 0.10%; C+S+N+Ti: 75ppm, and the content of each element is less than or equal to 30ppm. The remainder is Fe and unavoidable impurity elements.

[0101] 2) The billet is heated in a walking beam furnace to a temperature of 1150℃, and then subjected to 6 passes of rough rolling and 7 passes of finish rolling to a thickness of 2.10mm to obtain a hot-rolled steel plate;

[0102] 3) Hot-rolled steel sheets are normalized at 900℃ for 185 seconds to obtain cold-rolled raw material sheets. The cold-rolled raw material sheets are then surface-cleaned in a turbulent acid bath. After pickling, the cold-rolled raw material sheets are cold-rolled in 6 passes to obtain cold-rolled steel sheets with a target thickness of 0.27mm.

[0103] 4) Cold-rolled steel sheet is annealed at a temperature of 970℃ for 300s to obtain steel 110. The protective atmosphere in the furnace is 40% hydrogen + 60% nitrogen.

[0104] 5) The alloy coating uses a silicon-iron alloy with a Si content of 12%. The silicon-iron alloy, which is induction heated to a molten state, is sprayed onto the surface of steel 110 using an argon spray gun with a pressure of 200 bar. This ensures that the coating process is carried out in an oxygen-free environment. The coating layer 120 has a thickness of 0.05 mm.

[0105] 6) Apply an insulating coating to the surface of coating layer 120 and cure it at 540°C for 48 seconds.

[0106] The non-oriented silicon steel 100 manufactured by the above process has a good bond between the coating layer 120 and the steel 110. The finished non-oriented silicon steel 100 has a P1.5 / 50 of 2.14W / kg, a P1.0 / 400 of 13.4W / kg, and a P1.0 / 1000 of 49.7W / kg.

[0107] Example 3

[0108] 1) The molten steel after vacuum smelting is continuously cast into a billet with a thickness of 230mm. Electromagnetic stirring is used in the crystallizer during the continuous casting process. The chemical composition of the billet by weight percentage is Si: 3.26%; Als: 0.21%; Mn: 0.15%; C+S+N+Ti: 80ppm, and the content of each element is less than or equal to 25ppm. The remainder is Fe and unavoidable impurity elements.

[0109] 2) The billet is heated in a walking beam furnace to a temperature of 1150℃, and then subjected to 6 passes of rough rolling and 7 passes of finish rolling to a thickness of 2.15mm to obtain a hot-rolled steel plate.

[0110] 3) Hot-rolled steel sheets are normalized at 910℃ for 185 seconds to obtain cold-rolled raw material sheets. The cold-rolled raw material sheets are then surface-cleaned in a turbulent acid bath. After pickling, the cold-rolled raw material sheets are cold-rolled in 6 passes to obtain cold-rolled steel sheets with a target thickness of 0.27mm.

[0111] 4) Cold-rolled steel sheet is annealed at a temperature of 970℃ for 300s to obtain steel 110. The protective atmosphere in the furnace is 40% hydrogen + 60% nitrogen.

[0112] 5) The alloy coating uses a silicon-iron alloy with a Si content of 17%. The silicon-iron alloy, which is induction heated to a molten state, is sprayed onto the surface of steel 110 using an argon spray gun with a pressure of 200 bar. This ensures that the coating process is carried out in an oxygen-free environment. The coating layer 120 has a thickness of 0.03 mm.

[0113] 6) Apply an insulating coating to the surface of coating layer 120 and cure it at 550°C for 48 seconds.

[0114] The non-oriented silicon steel 100 manufactured by the above process has a good bond between the coating layer 120 and the steel 110. The finished non-oriented silicon steel 100 has a P1.5 / 50 of 2.14W / kg, a P1.0 / 400 of 12.7W / kg, and a P1.0 / 1000 of 45.4W / kg.

[0115] Comparative Example 1

[0116] 1) The molten steel after vacuum smelting is continuously cast into a billet with a thickness of 230mm. Electromagnetic stirring is used in the crystallizer during the continuous casting process. The chemical composition of the billet by weight percentage is Si: 3.30%; Als: 0.25%; Mn: 0.20%; C+S+N+Ti: 88ppm, and the content of each element is less than or equal to 30ppm. The remainder is Fe and unavoidable impurity elements.

[0117] 2) The billet is heated in a walking beam furnace to a temperature of 1150℃, and then subjected to 6 passes of rough rolling and 7 passes of finish rolling to a thickness of 2.20mm to obtain a hot-rolled steel plate;

[0118] 3) Hot-rolled steel sheets are normalized at 910℃ for 185 seconds to obtain cold-rolled raw material sheets. The cold-rolled raw material sheets are then surface-cleaned in a turbulent acid bath. After pickling, the cold-rolled raw material sheets are cold-rolled in 6 passes to obtain cold-rolled steel sheets with a target thickness of 0.27mm.

[0119] 4) Cold-rolled steel sheet is annealed at a temperature of 980℃ for 300s to obtain steel 110. The protective atmosphere in the furnace is 40% hydrogen + 60% nitrogen.

[0120] 5) Apply an insulating coating to the surface of steel 110 and cure it at 550°C for 48 seconds.

[0121] The non-oriented silicon steel 100 manufactured by the above process has the following properties: P1.5 / 50 is 2.23W / kg, P1.0 / 400 is 14.9W / kg, and P1.0 / 1000 is 58.7W / kg.

[0122] As can be seen from Examples 1 to 3 and Comparative Example 1, there is no coating layer 120 in Comparative Example 1, and the Si content in its steel 110 is 3.3%, which is higher than 3.15%, 3.08%, and 3.26% in Examples 1 to 3. However, the finished non-oriented silicon steel 100P1.0 / 1000 in Comparative Example 1 is 58.7 W / kg, which is significantly higher than 46.8 W / kg, 49.7 W / kg, and 45.4 W / kg in Examples 1 to 3. This indicates that the presence of coating layer 120 reduces the iron loss of the finished non-oriented silicon steel 100.

[0123] It should be noted that the iron loss P1.5 / 50 is the total loss measured at a magnetic polarization intensity of 1.5T under an alternating magnetic field with a frequency of 50Hz.

[0124] Iron loss P1.0 / 400 is the total loss measured at a magnetic polarization intensity of 1.0T under an alternating magnetic field with a frequency of 400Hz.

[0125] Iron loss P1.0 / 1000 is the total loss measured at a magnetic polarization intensity of 1.0T under an alternating magnetic field with a frequency of 1000Hz.

[0126] In this invention, high frequency refers to the frequency of alternating current above 400Hz. In the application scenarios of non-oriented silicon steel 100, the highest frequency is generally around 1000Hz.

[0127] The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description and drawings should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of development and significance of the technology and is not intended to limit the present invention or its application areas.

[0128] More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, such as combinations between various embodiments, adaptive changes, and / or substitutions, as would be apparent to those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly as used in the language of the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of this application, which should be considered non-exclusive. Any step listed in any method or process claim may be performed in any order and is not limited to the order set forth in the claims. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given above.

Claims

1. A non-oriented silicon steel, characterized in that: The non-oriented silicon steel includes: steel, a coating layer on the surface of the steel, and an insulating layer on the surface of the coating layer; Wherein, the resistance of the coating layer is greater than that of the steel; The coating is a silicon-iron alloy with a Si content of 8wt%~20wt%; The thickness of the coating layer is 0.05 mm to 0.1 mm; The steel comprises the following chemical composition by weight percentage: Si: 3.0% to 3.6%; Als: 0.20% to 0.60%; Mn: 0.10% to 0.40%; The C, S, N, and Ti contents are all less than 0.003% and the total content of C, S, N, and Ti is less than or equal to 90 ppm; The balance consists of iron and unavoidable impurities.

2. The non-oriented silicon steel according to claim 1, characterized in that: The thickness of the non-oriented silicon steel is less than or equal to 0.3 mm.

3. A method for manufacturing non-oriented silicon steel, characterized in that: The non-oriented silicon steel is the non-oriented silicon steel according to any one of claims 1 to 2; The manufacturing method of the non-oriented silicon steel includes the following steps: S1. Continuous casting; S2. Hot-rolled; S3. Normal heating; S4. Cold rolled; S5. Annealing; S6. Alloy coating; S7. Apply insulating coating.

4. The method for manufacturing non-oriented silicon steel according to claim 3, characterized in that: Step S6. Alloy coating includes: heating the ferrosilicon alloy to a molten state using induction eddy current, and spraying the molten ferrosilicon alloy onto the steel surface using a spray gun to form a coating layer.

5. The method for manufacturing non-oriented silicon steel according to claim 4, characterized in that: Step S6. Alloy coating is performed in a protective atmosphere to prevent oxidation of the ferrosilicon alloy.

6. The method for manufacturing non-oriented silicon steel according to claim 5, characterized in that: The protective atmosphere is nitrogen and / or argon.

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