Non-oriented electrical steel with high frequency, low iron loss and excellent fatigue performance and manufacturing method thereof

Abstract

The invention discloses non-oriented electrical steel with high frequency, low iron loss and excellent fatigue performance, which contains Fe and inevitable impurities, and also contains the following chemical elements in percentage by mass: less than or equal to 0.0045% of C, 2.65-3.75% of Si, 0.1-1.04% of Mn, 0.1-1.85% of Al, less than or equal to 0.025% of P, less than or equal to 0.025% of S, less than or equal to 0.025% of P, less than or equal to 0.025% of S, less than or equal to 0.025% The number of Al2O3 inclusions with the size of 2.0 microns or above in the non-oriented electrical steel is not more than 4 / mm < 2 >. Correspondingly, the invention also provides a manufacturing method of the non-oriented electrical steel with high frequency, low iron loss and excellent fatigue performance. The non-oriented electrical steel has the characteristics of excellent high frequency and low iron loss, reduces the motor loss, improves the motor efficiency, has excellent fatigue performance, and can meet the requirement that a motor iron core motor rotor stably runs at a high speed in a range from room temperature to 150 DEG C without deformation and fracture.

Description

Technical Field

[0001] The present invention relates to a steel plate and a method for manufacturing the same, and in particular to a non-oriented electrical steel plate and a method for manufacturing the same. Background Art

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

[0003] Non-oriented silicon steel is an excellent soft magnetic material, widely used in various motor cores such as generators, drive motors, compressors, micro motors, industrial motors, etc.

[0004] For non-oriented silicon steel materials, the material loss should be low, especially the loss above medium frequency. At the same time, it is also hoped that it has excellent fatigue performance to ensure that the motor rotor does not suffer from aging deformation or even the risk of fracture at weak locations such as the magnetic bridge during repeated starting and stopping and high-speed operation.

[0005] Based on this, the Chinese patent document with publication number CN105331879A, publication date February 17, 2016, and titled "A non-oriented silicon steel for high power density motor and production method" disclosed: Si: 3.25-3.45%, Mn: 0.05-0.10%, Sn: 0.04-0.06%, no Al alloy added, and its manufacturing process includes: smelting low Al pure steel and continuous casting into billets, billet heating, hot rolling, normalization, one-time cold rolling, finished product annealing, etc. The obtained finished product has an iron loss P1.0 / 400≤17.0W / kg and a room temperature fatigue limit strength≥400Mpa. Summary of the invention

[0006] One of the purposes of the present invention 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 and low iron loss characteristics to reduce motor loss and improve motor efficiency. At the same time, the non-oriented electrical steel also has excellent high temperature fatigue performance, which can meet the requirements of high-speed and stable operation of motor cores and motor rotors in the range of room temperature to 150°C without deformation or fracture.

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

[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 does not exceed 4 / mm 2 .

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

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

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

[0013] In the non-oriented electrical steel described in the present invention, the chemical composition of the non-oriented silicon steel contains Al. During the RH refining process, aluminum particles or aluminum ingots are added to the ladle for deoxidation. Aluminum will quickly combine with free oxygen in the molten steel to form Al2O3 oxide, which has a high melting point and hard particles. When such inclusions gather and grow to a certain size, and are not floated up and removed, and are retained in the finished steel plate, they will hinder the movement of magnetic domains during the magnetization process of the material, deteriorate the iron loss of the steel plate, and greatly harm the fatigue performance of the material. Moreover, the larger the size of the inclusions and the more there are, the easier it is for the steel plate to produce stress concentration around large-particle Al2O3 inclusions under repeated alternating stress, resulting in microcracks, and the more serious the degradation of fatigue performance. Therefore, the present invention controls the content of Al2O3 inclusions with a size of 2.0μm or more to not exceed 4 / mm 2 .

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

[0015] C: In the non-oriented electrical steel described in the present invention, carbon is an impurity harmful element, which will combine with other alloy elements to form carbide precipitation, deteriorating iron loss. However, since C is an element that must be contained in steel, its content will not be 0. The present invention hopes to control its upper limit, and the lower its content, the better. Therefore, in the non-oriented electrical steel described in the present invention, the mass percentage of C element is controlled to be below 0.0045%. 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 present invention, Si element can significantly increase the resistivity of the steel plate and reduce the iron loss of the material. At the same time, silicon can also improve the high temperature fatigue strength of the steel plate. In order to achieve the fatigue limit S under the condition of 50% survival rate at 150°C ambient temperature, 150The pressure is not less than 330MPa and the iron loss requirement, the silicon content needs to be guaranteed to be above 2.65%, but the Si content should not be too high, otherwise the difficulty of cold rolling processing of the material increases sharply and it is difficult to stably mass produce. Therefore, in the non-oriented electrical steel of the present invention, the mass percentage of Si element is controlled between 2.65-3.75%.

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

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

[0019] Furthermore, the non-oriented electrical steel of the present invention further 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 present invention, in order to further optimize the performance of the non-oriented electrical steel of the present invention, an appropriate amount of Ca element and rare earth elements may be preferably added to the steel. Among them:

[0021] Ca: In the non-oriented electrical steel of the present invention, the Ca element can react with S and O in the steel to generate CaS and CaO with stable structure, improve the morphology and distribution of inclusions in the molten steel, reduce the formation of fine inclusions, and help reduce iron loss. However, when the Ca content is too high, it will lead to the formation of too many oxide inclusions, affecting the surface quality of the steel plate. Therefore, in the non-oriented electrical steel of the present invention, the mass percentage of the Ca element can be controlled between 0.0005% and 0.0060%.

[0022] REM: In the non-oriented electrical steel described in the present invention, rare earth elements are easily combined with harmful elements such as sulfur and oxygen. By adding a proper 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 REM content is too high, it will cause steel defects on the surface of the steel plate and deterioration of magnetic properties. Therefore, in the non-oriented electrical steel described in the present invention, the mass percentage of REM can be controlled between 0.0005% and 0.012%. In some more preferred embodiments, the mass percentage of REM can be controlled between 0.0008% and 0.012%.

[0023] Furthermore, the non-oriented electrical steel of the present invention may also contain at least one of Nb, V, Cu, Mo, Ni, Co, Cr, Sn, Sb and Zr, and the total mass percentage thereof is controlled within a range of 0.0095-1.05%.

[0024] Furthermore, in the non-oriented electrical steel of the present invention, the mass percentage of Sn is 0.0035%-0.25%.

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

[0026] In addition to the Sn element, one or more elements such as Nb, V, Cu, Mo, Ni, Co, Cr, Sb, and Zr may be further added. Among them, Nb, V, and Zr elements can be dissolved into the matrix to improve the strength of the material. Cu, Mo, Ni, Co, and Cr elements increase the resistivity of the material, reduce losses, and also play a certain role in solid solution strengthening. The Sb element is concentrated at the grain boundaries, inhibits oxidation in the steel plate, and improves the favorable texture of the finished annealed structure. In some embodiments, one or more of the above elements can be selected to be added, and the total amount added can be controlled between 0.0095-1.05%.

[0027] Furthermore, among the inevitable impurities of the non-oriented electrical steel of the present invention, P≤0.02%, S≤0.0055%, N≤0.0035%, and Ti≤0.0025%.

[0028] In the non-oriented electrical steel of the present invention, P, S, N and Ti are all impurity elements in the non-oriented electrical steel sheet. Under the condition that technical conditions permit, in order to obtain steel with better performance and better quality, the content of impurity elements in the steel should be reduced as much as possible. Among them:

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

[0030] S: In the non-oriented electrical steel of the present invention, the S element is a harmful impurity element, which will combine with the Mn element to form sulfide, hindering the growth of grains and causing significant deterioration of the iron loss of the steel plate. Therefore, in the non-oriented electrical steel of the present invention, the mass percentage of the S element can be controlled to be less than 0.0055%, and in some more preferred embodiments, the mass percentage of the S element can be controlled to be less than 0.0040%.

[0031] N: In the non-oriented electrical steel of the present invention, when the N content is too high, it will combine with various elements in the steel to form a large number of fine nitrides, hindering the growth of grains and deteriorating magnetic properties. Therefore, in the non-oriented electrical steel of the present invention, the mass percentage of the N element can be controlled to be less than 0.0035%. In some more preferred embodiments, the mass percentage of the N element can be controlled to be less than 0.0030%.

[0032] Ti: In the non-oriented electrical steel of the present invention, the Ti element is a harmful impurity element for the non-oriented silicon steel. It reacts with carbon and nitrogen to precipitate titanium carbide and titanium nitride to pin the grain boundary, hinder the growth of grains in the recrystallization process, and deteriorate the iron loss. Therefore, in the non-oriented electrical steel of the present invention, the mass percentage of the Ti element can be controlled to be less than 0.0025%, and in some more preferred embodiments, the mass percentage of the Ti element can be controlled to be less than 0.0020%.

[0033] Furthermore, the thickness of the non-oriented electrical steel of the present invention is 0.15-0.35 mm.

[0034] Furthermore, the average grain size of the non-oriented electrical steel of the present invention is 45-165 μm.

[0035] In the non-oriented electrical steel of the present invention, when the grain size is too small, although the tensile strength and fatigue strength of the material can be improved, the high-frequency iron loss will be seriously deteriorated. However, when the grain size is too large, the material strength will be reduced, the magnetic domain size will be increased, and the eddy current loss of the material will be increased. Therefore, the non-oriented electrical steel of the present invention controls the average grain size in the steel to be between 45-165μm.

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

[0037] The non-oriented electrical steel of the present invention can obtain excellent iron loss P by reasonable chemical composition design, process control, especially inclusion and grain size control. 10 / 600 Performance, in order to reduce the high-frequency iron loss of non-oriented silicon steel, and is beneficial to reduce the loss of high-speed drive motors, can improve the working efficiency of the motor, save a lot of electricity, and is also conducive to the miniaturization of the motor design and saving materials.

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

[0039] In the non-oriented electrical steel of the present invention, when the fatigue limit S 25 ≥365MPa, and S 25 The fatigue limit S at 150°C 150 Satisfy: 0.80≤S 150 / S 25 When ≤1.0, it can be ensured that the non-oriented electrical steel of the present invention can be made into a high-speed motor rotor core and 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 object of the present 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, and at the same time has excellent fatigue performance, which can meet the requirements of high-speed and stable operation of motor cores and motor rotors in the range of room temperature to 150°C without deformation or fracture.

[0041] Accordingly, in order to achieve the above-mentioned object of the invention, the present invention proposes a method for manufacturing non-oriented electrical steel, which comprises 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 decarburization, 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 meet the relationship: [O] / [C]≤21.5; after adding aluminum material, the circulating air volume V1 and the circulating air volume V0 at the end of decarburization are controlled to meet the following relationship: V1≥V0+12[Al], where [Al] is the aluminum content in the molten steel, and V0≥140Nm 3 / h.

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

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

[0045] In addition, the present invention also achieves the removal of large-sized inclusions by reasonably controlling the circulating air blowing volume during the RH refining process. The key point is that the circulating air blowing volume V0 should be ≥140Nm during the decarburization process and before the end of decarburization. 3 / h, after adding aluminum particles or aluminum ingots, the circulating air volume V1 and V0 meet the relationship: V1≥V0+12[Al], where [Al] is the total Al content in the molten steel (that is, the value before the percentage sign of the Al element mass percentage in the steel grade). The present invention achieves the rapid floating of Al2O3 inclusions with the flow of molten steel to be removed by differentially controlling the circulating air volume at different times during the RH refining process, thereby achieving that the number of Al2O3 inclusions with a size of more than 2.0 μm in the steel plate does not exceed 4 / mm 2 .

[0046] The non-oriented electrical steel and the method for manufacturing the same according to the present invention have the following advantages and beneficial effects:

[0047] The non-oriented electrical steel with high frequency, low iron loss and excellent fatigue performance of the present invention has a fatigue limit S of 50% under the condition of 25°C temperature survival rate. 25 Not less than 365MPa, and the fatigue strength S at 150℃ 150 Satisfying relationship: 0.80≤S 150 / S 25 ≤1.0, thereby ensuring that when the non-oriented electrical steel of the present invention is used to make the 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 fracture.

[0048] The non-oriented electrical steel with high frequency, low iron loss and excellent fatigue performance of the present invention can obtain excellent iron loss P by reasonable chemical composition design, process control, especially the control of inclusions and grain size. 10 / 600 Performance, in order to reduce the high-frequency iron loss of non-oriented silicon steel, and is beneficial to reduce the loss of high-speed drive motors, can improve the working efficiency of the motor, save a lot of electricity, and is also conducive to the miniaturization of the motor design and saving materials. DETAILED DESCRIPTION

[0049] The non-oriented electrical steel and the method for manufacturing the same according to the present invention will be further explained and illustrated below in conjunction with specific embodiments. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present 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 by the following steps:

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

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

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

[0055] (4) Hot rolling: For example, the floor slab heating temperature may be 1180° C., the coil final rolling temperature may be 780° C., and the coiling temperature may be 660° C. to obtain a hot-rolled plate with a thickness of 2.5 mm.

[0056] (5) Normalizing annealing: For example, the normalizing holding temperature may be 980° C., and the holding time may be 10 min.

[0057] (6) Cold rolling to obtain a finished product with a thickness of 0.15-0.35 mm: The steel coil in Example 3 adopts a double cold rolling process, while the other examples and comparative examples adopt a single cold rolling process.

[0058] (7) Final annealing and application of insulating coating: For example, the annealing holding time is 50 seconds. The annealing temperatures in the embodiments and comparative examples are shown in Table 2.

[0059] Table 1 lists the mass percentages of chemical elements in the non-oriented electrical steels of Examples 1-8 and the comparative steel sheets of Comparative Examples 1-5.

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

[0061]

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

[0063] Table 2.

[0064]

[0065]

[0066] In order to verify the implementation effect of the present invention, samples were taken from the final finished products of Examples 1-8 and the comparative steel sheets of Comparative Examples 1-5, and these non-oriented electrical steel sheets were tested, and the test results are listed in the following Table 3. The relevant performance testing methods are as follows:

[0067] Fatigue performance test: The test is carried out in accordance with GB-T 3075-2008 Axial Force Control Method for Fatigue Test of Metallic Materials. The test condition parameters can be set as follows: test environment temperature 25±5℃ and 150±3℃, waveform control according to sine wave, stress ratio R=0.1, test frequency: 50Hz, conditional fatigue limit cycle number is 1.0×10 7 The fatigue limit is calculated based on a survival rate of 50%.

[0068] Statistics of Al2O3 oxide inclusions in non-oriented electrical steel: Statistical analysis was performed using a field emission scanning electron microscope. 20*20mm samples were randomly cut from the base steel plate, ground to 1 / 2 thickness of the steel plate, and mechanically or electrochemically polished. Then, photographs were taken under the backscattered electron image to confirm the presence of Al2O3 oxide inclusions and count the number. More than 20 fields of view were taken continuously, and the number of Al2O3 oxides with a size of more than 2.0μm in the field of view was counted. The unit was "pieces / mm 2 ” Calculate the distribution density.

[0069] Iron loss P 1.0 / 600 (It represents the iron loss value under 1.0T, 600HZ conditions) 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 national standard "GBT6394-2017 Metal Average Grain Size Determination Method" area method, the average grain size is counted. A small sample of 15*20mm is cut from the finished annealed plate, and the cross section in the rolling direction is the observation surface. It is ground and mechanically polished, and the observation surface is etched with nitric acid alcohol solution to show the grain boundary, count the number of grains, and calculate the average grain size.

[0071] Table 3.

[0072]

[0073]

[0074] As can be seen from Table 3, in Examples 1-8 of the present invention, the free oxygen [O] of the molten steel at the end of decarburization in the RH refining process, the carbon content [C] of the molten steel at the end of decarburization, the annular air blowing volume V0 at the end of decarburization, and the annular air blowing volume V1 after adding the aluminum ingot are all within the design range of the present invention, so the number of Al2O3 inclusions with a size of 2.0 μm or more in the obtained non-oriented electrical steel is no more than 4 / mm 2 The average grain size is between 45-165μm, and the fatigue limit at 25℃ is greater than 365MPa, and the fatigue strength S at 150℃ is 150 With S 25 The ratio is between 0.8 and 1.0, and the iron loss P 1.0 / 600 Excellent performance, and all meet P 1.0 / 600 ≤36-([Si]+1.2*[Al]) / 5t, which ensures that the non-oriented electrical steel sheets of each embodiment can reduce motor losses, improve motor efficiency, have excellent fatigue performance, and meet the requirements of high-speed and stable operation of the motor core and motor rotor in the range of room temperature to 150°C without deformation or fracture.

[0075] In contrast, although the chemical composition of Comparative Example 1 is within the range of the present invention, the free oxygen [O] of the molten steel at the end of decarburization in Comparative Example 1 is too high, and the carbon content [C] ratio of the molten steel at the end of decarburization is higher than 21.5, which makes subsequent deoxidation difficult; and after adding the aluminum ingot, a large amount of Al2O3 oxide inclusions are generated, resulting in a large-size Al2O3 oxide particle residue density of 5 pieces / mm in the final product. 2 , the fatigue performance at 25℃ is lower than 365MPa.

[0076] Although the chemical composition of the steels of Comparative Examples 2 and 3 is within the range described in the present invention, the circulating air blowing volume V0 at the end of decarburization and the circulating air blowing volume V1 after adding the aluminum ingot during the RH refining process do not comply with the present invention, resulting in the large-sized Al2O3 generated during the aluminum deoxidation process not being fully floated up and removed, resulting in a high density of inclusions in the finished plate and poor fatigue performance of the product. In addition, the average grain size of the finished plate of Comparative Example 3 is less than 45μm, resulting in further deterioration of iron loss.

[0077] Although the process parameters of the steels of Comparative Examples 4 and 5 are within the scope of the present invention during the RH refining process, the Si or Al content in the chemical composition is low, resulting in low corresponding final fatigue strength and low iron loss P 1.0 / 600 The performance that can be achieved by the present invention cannot be achieved.

[0078] It should be noted that the prior art in the protection scope of the present invention is not limited to the embodiments given in the present application documents. All prior art that does not contradict the scheme of the present invention, including but not limited to prior patent documents, prior public publications, prior public uses, etc., can be included in the protection scope of the present invention.

[0079] In addition, the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0080] It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with the contents disclosed by those skilled in the art from the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A non-oriented electrical steel with high frequency, low iron loss and excellent fatigue performance, comprising Fe and inevitable impurities, characterized in that: It also contains the following chemical elements in the following mass percentages: C≤0.0045%, Si: 2.65-3.75%, Mn: 0.1-1.04%, Al: 0.1-1.85%; The number of Al2O3 inclusions with a size of 2.0 μm or more in the non-oriented electrical steel does not exceed 4 / mm 2 .

2. The non-oriented electrical steel according to claim 1, characterized in that: The mass percentage of each chemical element is: C≤0.0045%, Si: 2.65-3.75%, Mn: 0.1-1.04%, Al: 0.1-1.85%; the balance is Fe and unavoidable impurities.

3. The non-oriented electrical steel according to claim 1 or 2, characterized in that: It also contains at least one of the following elements: Ca: 0.0005-0.006wt%, REM: 0.0005-0.012wt%.

4. The non-oriented electrical steel according to claim 1 or 2, characterized in that: It also contains at least one of Nb, V, Cu, Mo, Ni, Co, Cr, Sn, Sb and Zr, and the total mass percentage of the contents is controlled within the range of 0.0095-1.05%.

5. The non-oriented electrical steel according to claim 4, characterized in that: The mass percentage of Sn is 0.0035%-0.25%.

6. The non-oriented electrical steel according to claim 1 or 2, characterized in that: Among the inevitable impurities, P≤0.02%, S≤0.0055%, N≤0.0035%, and Ti≤0.0025%.

7. The non-oriented electrical steel according to claim 1 or 2, characterized in that: Its thickness is 0.15-0.35mm.

8. The non-oriented electrical steel according to claim 1 or 2, characterized in that: Its average grain size is 45-165μm.

9. The non-oriented electrical steel according to claim 1 or 2, characterized in that: Its iron loss P 1.0 / 600 ≤36-([Si]+1.2×[Al]) / 5t, where t represents the thickness of the steel plate, and its unit parameter is mm. [Si] and [Al] are substituted with the values ​​before the percentage sign of the mass percentage of Si and Al in the steel respectively.

10. The non-oriented electrical steel according to claim 1 or 2, characterized in that: Its fatigue limit S at 25℃ ambient temperature 25 ≥365MPa, and S 25 The fatigue limit S at 150°C 150 Satisfy: 0.80≤S 150 / S 25 ≤1.

0.

11. A method for producing non-oriented electrical steel according to any one of claims 1 to 10, comprising the steps of: smelting, RH refining, casting, hot rolling, normalizing annealing, cold rolling, continuous annealing and insulation coating; characterized in that: In the RH refining step: after decarburization, 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 meet the relationship: [O] / [C]≤21.5; after adding aluminum material, the circulating air volume V1 and the circulating air volume V0 at the end of decarburization are controlled to meet the following relationship: V1≥V0+12[Al], where [Al] is the aluminum content in the molten steel, and V0≥140Nm 3 / h.

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