High-frequency low-iron loss and excellent fatigue performance of non-oriented electrical steel and its manufacturing method

Abstract

The application discloses a kind of high-frequency low iron loss and excellent fatigue performance non-oriented electrical steel, it contains Fe and inevitable impurities, it also contains the following each chemical element with mass percentage content as follows: C≤0.0045%, Si: 2.65-3.75%, Mn: 0.1-1.04%, Al: 0.1-1.85%;The number of Al2O3 inclusions in the non-oriented electrical steel with size 2.0 μm above is not more than 4 / mm 2 Correspondingly, the application also provides a kind of high-frequency low iron loss and excellent fatigue performance non-oriented electrical steel manufacturing method.The non-oriented electrical steel has excellent high-frequency low iron loss characteristics, reduces motor loss, improves motor efficiency, while having excellent fatigue performance, can meet motor core motor rotor in the range of room temperature to 150 DEG C high-speed stable operation, does not occur deformation, fracture.

Description

TECHNICAL FIELD

[0001] The present application relates to a steel sheet and a manufacturing method thereof, and more particularly, to an non-oriented electrical steel sheet and a manufacturing method thereof. BACKGROUND

[0002] With the rapid development of new energy vehicle market, the requirements for energy saving and environmental protection of various types of electric machines are getting higher and higher, especially the high-speed electric machines and new energy vehicle driving motors, which are constantly developing towards high efficiency, miniaturization and low loss.

[0003] Non-oriented silicon steel is an excellent soft magnetic material, which is widely used in various electric machine cores such as generators, driving motors, compressors, micro and small electric machines, and industrial electric machines.

[0004] For non-oriented silicon steel material, the material loss is low, especially the loss above medium frequency, and at the same time, it is also desired to have excellent fatigue performance to ensure that the magnetic bridge and other weak positions do not occur aging deformation or even risk of rupture during repeated start-stop and high-speed operation of the motor rotor.

[0005] Based on this, the Chinese patent document with publication number CN105331879A and publication date of February 17, 2016, entitled "Non-oriented silicon steel for high power density electric machine and production method" discloses that Si: 3.25-3.45%, Mn: 0.05-0.10%, Sn: 0.04-0.06%, without adding Al alloy, and its manufacturing process includes: low Al pure steel smelting and continuous casting into billet, billet heating, hot rolling, normalizing, primary cold rolling method, finished product annealing, etc. The obtained finished product has a core loss P1.0 / 400≤17.0W / kg and a room temperature fatigue limit strength≥400Mpa. SUMMARY

[0006] One of the purposes of the present application is to provide a non-oriented electrical steel with high frequency low iron loss and excellent fatigue performance. The non-oriented electrical steel has excellent high frequency low iron loss characteristics to reduce the loss of the electric machine and improve the efficiency of the electric machine, and at the same time, the non-oriented electrical steel also has excellent high temperature fatigue performance, which can meet the stable high-speed operation of the motor rotor of the electric machine core in the range of room temperature to 150℃ without deformation or rupture.

[0007] In order to achieve the above-mentioned purpose, the present application provides a non-oriented electrical steel with high frequency low iron loss and excellent fatigue performance, which contains Fe and inevitable impurities, and in addition, contains the following chemical elements in mass percentage:

[0008] C≤0.0045%, Si: 2.65-3.75%, Mn: 0.1-1.04%, Al: 0.1-1.85%;

[0009] The number of Al2O3 inclusions with a size of 2.0 μm or more in the non-oriented electrical steel is not more than 4 per mm 2 .

[0010] Correspondingly, the application also provides a non-oriented electrical steel with high frequency, low iron loss and excellent fatigue performance, the mass percentage of each chemical element being:

[0011] C≤0.0045%, Si: 2.65-3.75%, Mn: 0.1-1.04%, Al: 0.1-1.85%; the balance being Fe and inevitable impurities;

[0012] The number of Al2O3 inclusions with a size of 2.0 μm or more in the non-oriented electrical steel is not more than 4 per mm 2 .

[0013] In the non-oriented electrical steel of the application, the non-oriented silicon steel chemical composition contains Al, and in the RH refining process, aluminum particles or aluminum ingots are added to the ladle for deoxidation treatment. Aluminum will rapidly combine with free oxygen in the molten steel to form Al2O3 oxide, which has a high melting point and hard particles. When such inclusions grow to a certain size and are not removed by floating, they remain in the finished steel plate, which will hinder the magnetic domain motion during material magnetization and deteriorate the iron loss of the steel plate, causing great harm to the fatigue performance of the material. Moreover, the larger the size and the more the number of inclusions, the more likely it is to produce stress concentration around large-particle Al2O3 inclusions under the action of repeated alternating stress, resulting in micro-cracks and more serious deterioration of fatigue performance. Therefore, the content of Al2O3 inclusions with a size of 2.0 μm or more is controlled to be not more than 4 per mm 2 .

[0014] In the non-oriented electrical steel of the application, the design principles of each chemical element are as follows:

[0015] C: In the non-oriented electrical steel of the application, carbon is a harmful impurity element that will combine with other alloying elements to form carbides and deteriorate the iron loss. However, since C is an element that must be contained in steel, its content cannot be 0, and the application aims to control its upper limit and desirably have a lower content. Therefore, in the non-oriented electrical steel of the application, the mass percentage of C element is controlled to be below 0.0045%, and in some more preferred embodiments, the mass percentage of C element can be controlled to be below 0.0030%.

[0016] Si: In the non-oriented electrical steel of the application, the Si element can significantly increase the resistivity of the steel plate and reduce the material iron loss, and silicon can also improve the high-temperature fatigue strength of the steel plate. In order to achieve a fatigue limit S 150No less than 330MPa and iron loss requirements, the silicon content needs to ensure more than 2.65%, but the Si content should not be too high, otherwise the material cold rolling processing difficulty increases sharply, it is difficult to stable batch production.Therefore, in the non-oriented electrical steel described in the application, the mass percentage content of Si element is controlled between 2.65-3.75%.

[0017] Mn: In the non-oriented electrical steel described in the application, Mn element is an element that increases the electrical resistivity of the material, and can form MnS with S element in the steel to improve the morphology of precipitates in the steel, so it is necessary to add more than 0.1% of Mn element. When the addition amount exceeds 1.04%, the hardness of the strip steel increases, which is not conducive to cold rolling. Therefore, in the non-oriented electrical steel described in the application, the mass percentage content of Mn element is controlled between 0.1-1.04%.

[0018] Al: In the non-oriented electrical steel described in the application, Al element can increase the electrical resistivity of the material and reduce the iron loss. In order to achieve the effect of the application, more than 0.1% of Al element can be added. However, when the AL addition amount exceeds 1.85%, the production difficulty increases, and a large amount of aluminum oxide is generated during the steelmaking process, which on the one hand deteriorates the performance of the finished product, and on the other hand easily causes the water gap to be blocked, affecting the generation. Therefore, in the non-oriented electrical steel described in the application, the mass percentage content of Al element is controlled between 0.1-1.85%.

[0019] Further, the non-oriented electrical steel described in the application also contains at least one of the following elements: Ca: 0.0005-0.006wt%, REM: 0.0005-0.012wt%.

[0020] In the above technical solution of the application, in order to further optimize the performance of the non-oriented electrical steel described in the application, the steel can also preferably add appropriate amount of Ca element and rare earth element. Among them:

[0021] Ca: In the non-oriented electrical steel described in the application, Ca element can react with S and O in the steel to form CaS and CaO with stable structure, improve the morphology and distribution of inclusions in the molten steel, reduce the formation of fine inclusions, and is beneficial to reduce the iron loss. However, when the Ca content is too high, too much oxide inclusions will be formed, which will affect the surface quality of the steel plate. Therefore, in the non-oriented electrical steel described in the application, the mass percentage content of Ca element can be controlled between 0.0005%-0.0060%.

[0022] REM: In the non-oriented electrical steel described in the present application, rare earth elements are easy to combine with harmful elements such as sulfur and oxygen. By adding an appropriate amount of rare earth elements, the molten steel can be purified, the growth of fine inclusions can be promoted, and the recrystallized grain structure of the finished steel plate can be improved. However, when the content of REM is too high, it will cause defects on the surface of the steel plate and deterioration of the magnetic properties. Therefore, in the non-oriented electrical steel described in the present application, the mass percentage of REM can be controlled between 0.0005% and 0.012%, and in some more preferred embodiments, the mass percentage of REM can be controlled between 0.0008% and 0.012%.

[0023] Further, the non-oriented electrical steel described in the present application can also contain at least one of Nb, V, Cu, Mo, Ni, Co, Cr, Sn, Sb, Zr, and the total mass percentage of these elements is controlled between 0.0095% and 1.05%.

[0024] Further, in the non-oriented electrical steel described in the present application, the mass percentage of Sn is between 0.0035% and 0.25%.

[0025] Sn: In the non-oriented electrical steel described in the present application, Sn elements can be segregated at grain boundaries, inhibit oxidation in the steel plate, and improve the beneficial texture of the finished annealing structure, but excessive addition can lead to an increase in surface defects of the steel. Therefore, in the non-oriented electrical steel described in the present application, the mass percentage of Sn elements can be controlled between 0.0035% and 0.25%, and in some more preferred embodiments, the mass percentage of Sn elements can be controlled between 0.0065% and 0.25%.

[0026] In addition to Sn elements, one or more of the following elements can be further added: Nb, V, Cu, Mo, Ni, Co, Cr, Sb, Zr. Among them, Nb, V, Zr elements can be solid-solved in the matrix to improve the strength of the material. Cu, Mo, Ni, Co, Cr elements increase the resistivity of the material, reduce the loss, and also have a certain solid solution strengthening effect. Sb elements segregate at grain boundaries, inhibit oxidation in the steel plate, and improve the beneficial texture of the finished annealing structure. In some embodiments, one or more of the above elements can be selected for addition, and the total amount of addition can be controlled between 0.0095% and 1.05%.

[0027] Further, in the inevitable impurities of the non-oriented electrical steel described in the present application, P≤0.02%, S≤0.0055%, N≤0.0035%, Ti≤0.0025%.

[0028] In the non-oriented electrical steel described in the present application, the P element, the S element, the N element and the Ti element are all impurity elements in the non-oriented electrical steel plate, and the content of the impurity elements in the steel should be reduced as much as possible to obtain a steel material with better performance and quality under the condition of technical requirements.

[0029] P: In the non-oriented electrical steel described in the present application, the P element is easy to segregate at the grain boundary, increasing the brittleness of the material. Therefore, in the non-oriented electrical steel described in the present application, the mass percentage content of the P element can be controlled to be below 0.02%, and in some more preferred embodiments, the mass percentage content of the P element can be controlled to be below 0.015%.

[0030] S: In the non-oriented electrical steel described in the present application, the S element is a harmful impurity element, which can combine with the Mn element to form sulfide, hinder grain growth, and cause significant deterioration of the iron loss of the steel plate. Therefore, in the non-oriented electrical steel described in the present application, the mass percentage content of the S element can be controlled to be below 0.0055%, and in some more preferred embodiments, the mass percentage content of the S element can be controlled to be below 0.0040%.

[0031] N: In the non-oriented electrical steel described in the present application, when the content of the N element is too high, a large amount of fine nitrides will be formed by combining with various elements in the steel, hindering grain growth and deteriorating magnetic properties. Therefore, in the non-oriented electrical steel described in the present application, the mass percentage content of the N element can be controlled to be below 0.0035%, and in some more preferred embodiments, the mass percentage content of the N element can be controlled to be below 0.0030%.

[0032] Ti: In the non-oriented electrical steel described in the present application, the Ti element is a harmful impurity element for non-oriented silicon steel, which reacts with carbon and nitrogen to precipitate titanium carbide and titanium nitride, pinning the grain boundary and hindering grain growth during the recrystallization process, thereby deteriorating the iron loss. Therefore, in the non-oriented electrical steel described in the present application, the mass percentage content of the Ti element can be controlled to be below 0.0025%, and in some more preferred embodiments, the mass percentage content of the Ti element can be controlled to be below 0.0020%.

[0033] Further, the thickness of the non-oriented electrical steel described in the present application is 0.15-0.35mm.

[0034] Further, the average grain size of the non-oriented electrical steel described in the present application is 45-165μm.

[0035] In the non-oriented electrical steel described in this invention, while a small grain size can improve the tensile strength and fatigue strength of the material, it also severely degrades high-frequency iron loss. However, an excessively large grain size reduces the material's strength, increases the magnetic domain size, and leads to increased eddy current losses. Therefore, the non-oriented electrical steel of this invention controls the average grain size in the steel to be between 45-165 μm.

[0036] Furthermore, the iron loss P of the non-oriented electrical steel described in this invention... 1.0 / 600 ≤36-([Si]+1.2×[Al]) / 5t, where t represents the thickness of the steel plate, with the unit parameter being mm, and [Si] and [Al] are substituted into the values ​​before the percentage signs of the mass percentage content of Si and Al in the steel, respectively.

[0037] The non-oriented electrical steel described in this invention, through reasonable chemical composition design and process control, especially the control of inclusions and grain size, can achieve excellent iron loss P. 10 / 600 The performance is improved to reduce the high-frequency iron loss of non-oriented silicon steel, which is also beneficial to reduce the loss of high-speed drive motors, improve motor efficiency, save a lot of power, and also facilitate the miniaturization of motor design and save materials.

[0038] Furthermore, the fatigue limit S of the non-oriented electrical steel described in this invention at an ambient temperature of 25°C... 25 ≥365MPa, and S 25 The fatigue limit S150 at 150℃ satisfies: 0.80 ≤ S 150 / S 25 ≤1.0.

[0039] In the non-oriented electrical steel described in this invention, the fatigue limit S at an ambient temperature of 25°C is... 25 ≥365MPa, and S 25 The fatigue limit S at 150°C 150 Satisfy: 0.80≤S 150 / S 25 When the value is ≤1.0, it can be guaranteed that after the non-oriented electrical steel of the present invention is made into a high-speed motor rotor core, it can operate stably for a long time in the operating temperature range of room temperature to 150°C without sudden failure, deformation, or even breakage.

[0040] Another objective of this invention is to provide a method for manufacturing non-oriented electrical steel with high frequency, low iron loss, and excellent fatigue performance. The non-oriented electrical steel obtained by this method has excellent high frequency and low iron loss characteristics, as well as excellent fatigue performance, which can meet the requirements of high-speed stable operation of motor core and motor rotor in the range of room temperature to 150°C without deformation or breakage.

[0041] Correspondingly, in order to achieve the above-mentioned purposes, the present application provides a manufacturing method of non-oriented electrical steel, comprising the steps of smelting, RH refining, casting, hot rolling, normalizing annealing, cold rolling, continuous annealing and insulating coating; wherein:

[0042] In the RH refining step: after the decarburization is completed, the ratio of the free oxygen content [O] in the molten steel to the carbon content [C] in the molten steel at this time is controlled to satisfy the relationship: [O] / [C]≤21.5; after the aluminum material is added, the circulating blowing amount V1 is controlled to satisfy: V1≥V0+12[Al], wherein [Al] is the aluminum content in the molten steel, and V0≥140 Nm 3 / h.

[0043] In order to obtain the non-oriented electrical steel with high frequency and low iron loss and excellent fatigue performance, in addition to the above-mentioned chemical composition and grain structure design, the present application also controls the harmful Al2O3 inclusions in the steel through process means, wherein:

[0044] In the RH refining decarburization process, the KTB oxygen lance is used to blow oxygen into the vacuum chamber to react with CO gas and molten steel. During this process, the decarburization reaction needs to be strictly controlled according to the ratio of free oxygen and carbon in the molten steel, so that the blown oxygen is used for decarburization, and the increase of free oxygen in the molten steel is avoided, so as to control the oxygen content of the molten steel at the end of decarburization within a controllable range, otherwise, it will directly lead to the difficulty of subsequent aluminum deoxidization and produce a large amount of Al2O3 oxide inclusions. After the decarburization is completed in the RH refining process, the ratio of the free oxygen content [O] in the molten steel to the carbon content [C] in the molten steel at this time is controlled to satisfy the relationship: [O] / [C]≤21.5.

[0045] In addition, the present application also removes the large-sized inclusions by reasonably controlling the circulating blowing amount in the RH refining process, and the key points are that the circulating blowing amount V0 before the end of the decarburization process is ≥140 Nm 3 / h, after the aluminum particles or aluminum ingots are added, the circulating blowing amount V1 and V0 satisfy the relationship: V1≥V0+12[Al], wherein [Al] is the total Al content in the molten steel (that is, the value before the mass percentage of Al element in the steel is substituted). The present application realizes the rapid floating of Al2O3 inclusions with the molten steel by the differential control of the circulating blowing amount at different times in the RH refining process, so as to realize that the number of Al2O3 inclusions with a size of more than 2.0 μm in the steel plate is not more than 4 / mm 2 .

[0046] The non-oriented electrical steel and the manufacturing method thereof have the following advantages and beneficial effects:

[0047] The non-oriented electrical steel with high frequency, low iron loss, and excellent fatigue performance described in this invention exhibits a fatigue limit Sf under a 50% survival rate at 25°C. 25 Not less than 365 MPa, and the fatigue strength S at 150℃. 150 Satisfying the relation: 0.80≤S 150 / S 25 ≤1.0, thereby ensuring that when the high-speed motor rotor core is made of the non-oriented electrical steel described in this invention, it can operate stably for a long time in the operating temperature range of room temperature to 150°C, without sudden failure, deformation or breakage.

[0048] The high-frequency, low-iron-loss, and fatigue-resistant non-oriented electrical steel described in this invention, through rational chemical composition design and process control, especially the control of inclusions and grain size, can achieve excellent iron loss P. 10 / 600 The performance is improved to reduce the high-frequency iron loss of non-oriented silicon steel, which is also beneficial to reduce the loss of high-speed drive motors, improve motor efficiency, save a lot of power, and also facilitate the miniaturization of motor design and save materials. Detailed Implementation

[0049] The non-oriented electrical steel and its manufacturing method described in this invention will be further explained and described below with reference to specific embodiments. However, such explanation and description do not constitute an undue limitation on the technical solution of this invention.

[0050] Examples 1-8 and Comparative Examples 1-5

[0051] The non-oriented electrical steels of Examples 1-8 and Comparative Examples 1-5 were prepared using the following steps:

[0052] (1) Blast furnace molten iron undergoes molten iron pretreatment and converter smelting.

[0053] (2) Decarburization, deoxidation, and alloying treatments are carried out in RH refining: After decarburization, the ratio of free oxygen content [O] in the molten steel to carbon content [C] in the molten steel at this time is controlled to meet the following relationship: [O] / [C]≤21.5; After adding aluminum, the circulating air volume V1 and the circulating air volume V0 at the end of decarburization are controlled to meet the following condition: V1≥V0+12[Al], where [Al] is the aluminum content in the molten steel, and V0≥140Nm 3 / h. Table 2 shows the specific process parameters for this step in each embodiment and comparative example.

[0054] (3) After refining, the molten steel is continuously cast to obtain a continuously cast slab, the chemical element composition of which is shown in Table 1.

[0055] (4) Hot rolling: exemplary slab heating temperature can be 1180 °C, finishing temperature of the steel coil can be 780 °C, coiling temperature can be 660 °C, and a 2.5 mm thick hot-rolled plate is obtained.

[0056] (5) Normalizing annealing: exemplary normalizing holding temperature can be 980 °C, holding time can be 10 min.

[0057] (6) Cold rolling to obtain a finished product with a thickness of 0.15-0.35 mm: among them, the steel coil of Example 3 adopts a two-step cold rolling process, and the steel coils of the other examples and comparative examples adopt a one-step cold rolling process.

[0058] (7) Final annealing and coating with insulating coating: exemplary annealing holding time is 50 s. The annealing temperature in each example and comparative example is shown in Table 2.

[0059] Table 1 lists the mass percentage of each chemical element of the non-oriented electrical steel of Examples 1-8 and the comparative steel plates of Comparative Examples 1-5.

[0060] Table 1. (wt%, the balance is Fe and unavoidable impurities other than P, S, N, Ti)

[0061]

[0062] Table 2 lists the specific process parameters of the non-oriented electrical steel of Examples 1-8 and the comparative steel plates of Comparative Examples 1-5 in each step of the manufacturing process.

[0063] Table 2.

[0064]

[0065]

[0066] In order to verify the implementation effect of the present application, the final finished product of the non-oriented electrical steel of Examples 1-8 and the comparative steel plates of Comparative Examples 1-5 are sampled respectively, and the non-oriented electrical steel plates are tested, and the test results obtained are listed in Table 3 below. Among them, the relevant performance test means are as follows:

[0067] Fatigue performance test: according to GB-T 3075-2008 Metal Materials Fatigue Test Axial Force Control Method, the test condition parameters can be set as follows: test environment temperature 25±5 °C and 150±3 °C, sinusoidal wave control waveform, stress ratio R=0.1, test frequency: 50 Hz, conditional fatigue limit cycle number is 1.0×10 7 , and the fatigue limit is calculated according to the survival rate of 50%.

[0068] Statistical analysis of Al2O3 oxide inclusions in non-oriented electrical steel: Statistical analysis was performed using field emission scanning electron microscopy (FET). 20*20mm samples were randomly cut from the base steel plate, ground to half the plate thickness, and then mechanically or electrochemically polished. The samples were then photographed under backscattered electron microscopy to confirm the presence and number of Al2O3 oxide inclusions. At least 20 fields of view were continuously photographed, and the number of Al2O3 oxide inclusions larger than 2.0μm in each field of view was counted, expressed as "inclusions / mm". 2 The distribution density was calculated.

[0069] Iron loss P 1.0 / 600 (It represents the iron loss value under the conditions of 1.0T and 600HZ) Test: Based on the square circle method of the standard "GB / T10129-2019 Measurement Method of Medium Frequency Magnetic Properties of Electrical Steel Strip (Sheet)".

[0070] Grain size detection: According to the area method in the national standard "GBT6394-2017 Method for Determination of Average Grain Size of Metals", the average grain size is counted. A 15*20mm small sample is cut from the finished annealed plate, and the cross-section in the rolling direction is used as the observation surface. After grinding and mechanical polishing, the observation surface is etched with nitric acid alcohol solution to reveal the grain boundaries. The number of grains is counted, and the average grain size is calculated.

[0071] Table 3.

[0072]

[0073]

[0074] As can be seen from Table 3 above, in Examples 1-8 of the present invention, the chemical composition, the free oxygen [O] in the molten steel at the end of decarburization in the RH refining process, the carbon content [C] in the molten steel at the end of decarburization, the circulating air volume V0 at the end of decarburization, and the circulating air volume V1 after adding aluminum ingots are all within the design range of the present invention. Therefore, the number of Al2O3 inclusions with a size of 2.0 μm or larger in the obtained non-oriented electrical steel does not exceed 4 inclusions / mm. 2 Their average grain size is between 45-165 μm, and their fatigue limit at 25℃ is greater than 365 MPa, while their fatigue strength S at 150℃ is... 150 With S 25 The ratios are all between 0.8 and 1.0, while the iron loss P 1.0 / 600 Excellent performance, and all meet P requirements. 1.0 / 600 The formula ≤36-([Si]+1.2*[Al]) / 5t ensures that the non-oriented electrical steel plates in each embodiment can reduce motor losses and improve motor efficiency, while also having excellent fatigue performance. Furthermore, it ensures that the motor core and rotor can operate stably at high speed within the range of room temperature to 150°C without deformation or breakage.

[0075] By contrast, although the chemical composition of Comparative Example 1 is within the range described in the present application, the free oxygen [O] of the molten steel at the end of decarburization of Comparative Example 1 is too high, the ratio of the carbon content [C] of the molten steel at the end of decarburization is higher than 21.5, leading to difficulty in subsequent deoxidization; and after adding aluminum ingots, a large amount of Al2O3 oxide inclusions are generated, leading to the density of the large-size Al2O3 oxide particle residues in the final product reaching 5 pieces / mm 2 The fatigue performance at 25°C is lower than 365 MPa.

[0076] Although the steel grades of Comparative Example 2 and Comparative Example 3 have chemical compositions within the range described in the present application, the circulation gas blowing amount V0 at the end of decarburization during RH refining and the circulation gas blowing amount V1 after adding aluminum ingots do not comply with the present application, leading to insufficient floating removal of large-size Al2O3 generated during the aluminum deoxidization process, resulting in high inclusion density of the finished plate and poor fatigue performance of the product, and the average grain size of the finished plate of Comparative Example 3 is less than 45 μm, leading to further deterioration of the iron loss.

[0077] Although the steel grades of Comparative Example 4 and Comparative Example 5 have process parameters within the range of the present application during RH refining, the Si or Al in the chemical composition is low, leading to low final fatigue strength, high iron loss P 1.0 / 600 and unable to achieve the performance that can be achieved by the present application.

[0078] It should be noted that the scope of protection of the present application is not limited to the embodiments given in the present application file, and all prior art, including but not limited to prior patent documents, prior published publications, prior public use, etc., that are not contradictory to the scheme of the present application, can be included in the scope of protection of the present application.

[0079] In addition, the combination of the technical features in the present case is not limited to the combination of the claims in the present case or the combination of the embodiments described in the present case, and all the technical features described in the present case can be freely combined or combined in any way, unless contradictory to each other.

[0080] It should also be noted that the above-mentioned embodiments are only specific embodiments of the present application. Obviously, the present application is not limited to the above-mentioned embodiments, and similar changes or modifications that can be directly derived or easily thought of by those skilled in the art from the disclosure of the present application should all be within the scope of protection of the present application.

Claims

1. An non-oriented electrical steel having high frequency and low iron loss and excellent fatigue properties, characterized in that, each of the chemical elements is contained in an amount of 0.0005-0.006wt%, C≤0.0045%, Si: 2.65-3.75%, Mn: 0.1-1.04%, Al: 0.1-1.85%; the balance being Fe and inevitable impurities; The number of Al2O3 inclusions having a size of 2.0 μm or more in the non-oriented electrical steel is not more than 4 per mm 2 The average grain size in the non-oriented electrical steel is 45-165 μm. The iron loss P of the non-oriented electrical steel 1.0 / 600 ≤ 36 - ([Si] + 1.2 x [Al]) / 5t, where t represents the thickness of the steel sheet, the unit of which is mm, [Si] and [Al] represent the numerical values before the mass percentage of Si and Al in the steel is substituted into the percentage symbol; the fatigue limit S at an ambient temperature of 25°C 25 ≥ 365 MPa, and S 25 at a temperature of 150°C 150 satisfies: 0.80 ≤ S 150 / S 25 ≤ 1.

0.

2. The non-oriented electrical steel of claim 1, wherein, it further contains at least one of the following elements: Ca: 0.0005-0.006wt%, REM: 0.0005-0.012wt%.

3. The non-oriented electrical steel of claim 1, wherein, it further contains at least one of Nb, V, Cu, Mo, Ni, Co, Cr, Sn, Sb, Zr, and the total amount of the mass percentage of each of the elements is controlled to be 0.0095-1.05%.

4. The non-oriented electrical steel of claim 3, wherein, the mass percentage of Sn is 0.0035%-0.25%.

5. The non-oriented electrical steel of claim 1, wherein, in the inevitable impurities, P≤0.02%, S≤0.0055%, N≤0.0035%, Ti≤0.0025%.

6. The non-oriented electrical steel of claim 1, wherein, the thickness is 0.15-0.35mm.

7. A manufacturing method of the non-oriented electrical steel according to any one of claims 1-6, comprising the steps of smelting, RH refining, casting, hot rolling, normalizing annealing, cold rolling, continuous annealing and insulating coating; characterized in that: In the RH refining step: after the decarburization is finished, the ratio of the free oxygen content [O] in the molten steel to the carbon content [C] in the molten steel at this time is controlled to satisfy the relationship: [O] / [C]≤21.5; after the aluminum material is added, the circulation blowing amount V1 is controlled to satisfy: V1≥V0+12[Al], wherein [Al] is the aluminum content in the molten steel, and V0≥140 Nm 3 / h.

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