Intermediate frequency low iron loss high strength non-oriented electrical steel sheet and manufacturing method thereof

Abstract

The application discloses a kind of medium frequency low iron loss high-strength non-oriented electrical steel sheet, it contains Fe and inevitable impurities, in addition it also contains the following mass percentage content of each chemical element: C≤0.0035%, Si: 3.0~4.0%, Mn: 0.1~2.0%, Al: 0.1~2.0%, 0 The application also provides a manufacturing method of the medium frequency low iron loss high-strength non-oriented electrical steel sheet. The medium frequency low iron loss high-strength non-oriented electrical steel sheet has high strength and medium frequency low iron loss.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of steel plate and its manufacturing method, and more particularly to a kind of non-oriented electrical steel plate and its manufacturing method. BACKGROUND

[0002] Non-oriented electrical steel plate is an important metal soft magnetic material for manufacturing electric motor and generator. In recent years, in order to improve the work efficiency and specific power density of driving motor, motor speed-up is an important development trend. With the increase of motor design speed, the centrifugal force of non-oriented silicon steel when driving motor operates also increases accordingly. In order to ensure the safety of motor under high speed rotation, higher requirements are put forward for the strength of non-oriented silicon steel. At the same time, since the pole pair number of motor rotating magnetic field is constant, the motor speed is proportional to the working frequency, so the increase of motor speed also brings the increase of motor working frequency. The working frequency of new energy automobile driving motor has been increased to the medium frequency level of 400-2000 Hz. Compared with the 50 / 60 Hz power frequency used in ordinary motor, the loss of non-oriented silicon steel under medium frequency working condition is much larger than that under power frequency.

[0003] In order to improve the strength of non-oriented electrical steel, generally solid solution strengthening, precipitation strengthening, grain refinement and other methods are adopted.

[0004] For example, the Japanese patent document with publication number JP 2011099163A and publication date May 19, 2011 proposes a manufacturing method of high-strength non-oriented silicon steel, which has the following component characteristics: C≤0.02%, Si: 1.6-3.0%, Mn≤1.0%, Al: 0.1-3.0%, Ni≤2.0%, Cu: 1.0-3.0%, which comprehensively applies the solid solution and precipitation of Ni and the precipitation strengthening effect of Cu to improve the mechanical strength.

[0005] For example, the Japanese patent document with publication number JP 2013044009A and publication date March 4, 2013 proposes a manufacturing method of non-oriented silicon steel for rotor, which has the following component characteristics: C≤0.01%, Si: 1.0-3.0%, Mn: 0.05-2.0%, Al: 0.1-2.0%, S+As+Nb+Ti+V+Zr+N≤0.018, which strongly inhibits the recrystallization process of silicon steel through carbonitride precipitates of Ti, Nb, V, Zr and other elements, so as to achieve the purpose of refining grains and improving mechanical strength.

[0006] However, in the case that the existing technology uses these strengthening mechanisms to make the steel plate reach high strength, the electromagnetic performance of non-oriented electrical steel will be reduced. In addition, solid solution strengthening increases the strength before rolling, which makes the rolling more difficult.

[0007] Therefore, it is desirable to provide an oriented electrical steel sheet with high strength and low core loss at medium frequency. SUMMARY

[0008] One of the objects of the present application is to provide an oriented electrical steel sheet with high strength and low core loss at medium frequency, which has both high strength and low core loss at medium frequency by optimizing the chemical composition design and process design of the steel.

[0009] To achieve the above object, the present application provides an oriented electrical steel sheet with high strength and low core loss at medium frequency, which contains Fe and inevitable impurities, and further contains each chemical element in the following mass percentage:

[0010] C≤0.0035%, Si: 3.0-4.0%, Mn: 0.1-2.0%, Al: 0.1-2.0%, 0

[0011] Further, it satisfies Si+Al+Cr-0.5×Ni-0.5×Mn≤2.5, wherein the numerical values of each chemical element before the percentage sign of the mass percentage are substituted.

[0012] Correspondingly, the present application also provides an oriented electrical steel sheet with high strength and low core loss at medium frequency, which contains each chemical element in the following mass percentage:

[0013] C≤0.0035%, Si: 3.0-4.0%, Mn: 0.1-2.0%, Al: 0.1-2.0%, 0

[0014] Further, it satisfies Si+Al+Cr-0.5×Ni-0.5×Mn≤2.5, wherein the numerical values of each chemical element before the percentage sign of the mass percentage are substituted.

[0015] The content design principle of each chemical element of the oriented electrical steel sheet with high strength and low core loss at medium frequency according to the present application is as follows:

[0016] C: C strongly hinders the grain growth of the finished steel strip, easily combines with impurities such as Nb, V, Ti, etc. to form fine precipitates, thereby causing loss increase and magnetic aging. Based on this, the content of C is strictly controlled below 0.0035%.

[0017] Si: Si is an effective element for increasing resistivity and reducing iron loss. Compared with other solid solution strengthening elements such as Mn, Al, and Ni, Si has a higher solid solution strengthening capacity. In the present application, Si can balance high strength and low iron loss. If the Si content is 3.0% or less, the above effects cannot be obtained. On the other hand, if the Si content is too high, the manufacturability, particularly the processability of the electrical steel sheet, is reduced. In addition, by appropriately controlling the grain structure of the electrical steel sheet, the reduction in processability can be suppressed. However, if the Si content exceeds 4.0%, the cold workability is reduced. Therefore, the present application controls the Si content to be 3.0 to 4.0%. Further preferably, the upper limit of the Si content can be controlled to be 3.5%.

[0018] Mn: Mn can increase the resistivity and react with S to form MnS, thereby preventing the formation of low-melting-point FeS along the grain boundaries, which causes thermal embrittlement. Therefore, the present application adds 0.1% or more of Mn, and if the Mn content exceeds 2.0%, the grains do not sufficiently grow during final annealing, resulting in an increase in iron loss. Therefore, the present application controls the Mn content to be 0.1 to 2.0%.

[0019] Al: Al is an element that increases the resistivity and effectively reduces the iron loss of the steel. In the present application, if the Al content is less than 0.1%, it does not effectively reduce the iron loss. However, when the Al content is higher than 2.0%, the magnetic induction of the steel is significantly reduced, and the cold rolling workability is significantly reduced. Based on this, the present application controls the Al content to be 0.1 to 2.0%.

[0020] Cr: Cr can increase the resistivity, reduce the eddy current loss, and reduce the high-frequency iron loss. However, in the present application, if the Cr content exceeds 2.0%, the magnetic flux density is reduced, and the cost is increased. Based on this, the present application controls the Cr content to be 0 < Cr ≤ 2.0%.

[0021] Ni: In the present application, Ni can solid solution strengthen the electrical steel and increase the resistivity of the electrical steel, thereby reducing the iron loss without reducing the saturation magnetic flux density. However, if the Ni content exceeds 5.0%, the cost is significantly increased. Based on this, the present application controls the Ni content to be 0 < Ni ≤ 5.0%.

[0022] In addition, the chemical elements in the present application need to meet: Si+Al+Cr-0.5xNi-0.5xMn≤2.5. Wherein Si, Al, Cr are ferrite forming elements, and Ni and Mn are austenite forming elements, when the above condition is met, ferrite-austenite phase transformation can be generated. The phase transformation can promote the refinement and homogenization of the average grain size on the one hand, and the smaller and uniform grain size can not only improve the processability of the electrical steel material, but also improve the mechanical strength of the finished electrical steel plate. At the same time, during the ferrite-austenite phase transformation, N will enrich in the austenite because the solubility of N in the austenite is greater than that in the ferrite, thereby reducing the formation of harmful inclusions AlN in the ferrite, and finally stably producing high-strength non-oriented electrical steel plates with excellent magnetic properties. When Si+Al+Cr-0.5xNi-0.5xMn>2.5, the desired effect of combining magnetic properties and strength in the present application cannot be obtained.

[0023] Further, in the unavoidable impurities of the medium-frequency low-iron-loss high-strength non-oriented electrical steel plate described in the present application, P≤0.1%, S≤0.003%, and N≤0.002%.

[0024] The unavoidable impurities in the present application are mainly P, S, and N, and it is desirable to have as low a content as possible under the technical conditions. Among them:

[0025] P will segregate along the grain boundaries, and a content exceeding 0.10% will increase the brittleness of the electrical steel plate, so in some embodiments, the P content is limited to 0.1% or less.

[0026] S is a harmful element to the magnetic properties of silicon steel, and a content exceeding 0.003% will greatly increase the amount of harmful inclusions such as MnS and Cu2S, strongly hindering grain growth and deteriorating the magnetic properties of the steel, so in some embodiments of the present application, the S content is controlled to be 0.003% or less.

[0027] In some embodiments of the present application, a content of N exceeding 0.002% will greatly increase the precipitates of Nb, V, Ti, Al, etc. of N, strongly hindering grain growth and deteriorating the magnetic properties of the steel, so the upper limit of the N content is controlled to be 0.002%.

[0028] Further, the medium-frequency low-iron-loss high-strength non-oriented electrical steel plate described in the present application also contains Sn≥0.003% and / or Sb≥0.003%, and Sn+Sb≤0.3%.

[0029] In some embodiments of the present application, Sn and / or Sb can be further added to improve the texture of the steel and increase the magnetic induction of the steel. However, when the total amount of the two additives exceeds 0.3%, the surface segregation effect will reduce the uniformity of the grains and deteriorate the magnetic properties of the steel.

[0030] Further, the grain size of the medium frequency low iron loss high strength non-oriented electrical steel sheet according to the present application is 20-160 μm.

[0031] Further, the medium frequency low iron loss high strength non-oriented electrical steel sheet according to the present application has an iron loss P 10 / 400 ≤ 13.25 W / kg, and a yield strength ≥ 460 MPa and a tensile strength ≥ 600 MPa.

[0032] Another object of the present application is to provide a manufacturing method of a medium frequency low iron loss high strength non-oriented electrical steel sheet, and the non-oriented electrical steel sheet manufactured by the method has both high strength and medium frequency low iron loss.

[0033] Based on the above-mentioned objects, the present application further provides a manufacturing method of a medium frequency low iron loss high strength non-oriented electrical steel sheet as described above, which comprises the steps of: smelting and casting; hot rolling; normalizing; cold rolling; continuous annealing; insulating coating; wherein in the step of hot rolling, the heating temperature of the slab is controlled to be 1000-1200 °C.

[0034] Further, in the step of continuous annealing of the manufacturing method according to the present application, the annealing temperature is controlled to be 900-1100 °C.

[0035] In some embodiments of the present application, one cold rolling is adopted in the step of cold rolling.

[0036] In some other embodiments of the present application, one cold rolling + intermediate annealing + two cold rollings are adopted in the step of cold rolling.

[0037] The medium frequency low iron loss high strength non-oriented electrical steel sheet and the manufacturing method thereof according to the present application have the following advantages and beneficial effects:

[0038] The general high-silicon non-oriented electrical steel does not have ferrite-austenite phase transition in the whole production process, while the present application takes the ferrite-austenite phase transition of high-silicon non-oriented electrical steel as a necessary condition, utilizes the advantageous factor that it can effectively promote grain size refinement and homogenization, and improves the processability and mechanical strength of non-oriented silicon steel. The resistivity of the electrical steel is improved by higher alloy content to obtain medium frequency low iron loss. By selecting appropriate hot rolling heating temperature and final product annealing temperature based on alloy composition, the medium frequency low iron loss high strength non-oriented electrical steel sheet is finally obtained.

[0039] In some embodiments, the iron loss P 10 / 400 ≤ 13.25 W / kg, and the yield strength is ≥ 460 MPa and the tensile strength is ≥ 600 MPa. DETAILED DESCRIPTION

[0040] The medium-frequency low-iron-loss high-strength non-oriented electrical steel plate and the manufacturing method thereof according to the present application will be further explained and described in connection with specific examples, however, the explanation and description does not constitute undue limitation on the technical solutions of the present application.

[0041] Examples 1-10 and Comparative Examples 1-7

[0042] Table 1 lists the mass percentage of each chemical element in the medium-frequency low-iron-loss high-strength non-oriented electrical steel plate of Examples 1-10 and the comparative steel plate of Comparative Examples 1-7.

[0043] Table 1. (wt%, the balance being Fe and other inevitable impurities except P, S and N)

[0044]

[0045] Note: I = Si + Al + Cr - 0.5 x Ni - 0.5 x Mn in Table 1, wherein each chemical element is substituted by the value before the mass percentage symbol.

[0046] The medium-frequency low-iron-loss high-strength non-oriented electrical steel plate of Examples 1-10 according to the present application is prepared by the following step process:

[0047] (1) After the molten iron in the blast furnace is sequentially subjected to molten iron pretreatment, converter smelting, RH refining and continuous casting, a continuous casting billet is obtained, and the chemical element ratio of the continuous casting billet in each example is shown in Table 1.

[0048] (2) Hot rolling: the slab is heated to a temperature of 1000-1200℃, and then rolled;

[0049] (3) Normalization;

[0050] (4) Primary cold rolling, or primary cold rolling + intermediate annealing + secondary cold rolling; when intermediate annealing is used, the intermediate annealing temperature is 800-1000℃;

[0051] (5) Continuous annealing: the continuous annealing temperature is 900-1100℃;

[0052] (6) Insulating coating.

[0053] It should be noted that the manufacturing process of Comparative Examples 1-7 is basically the same as that of each example of the present application, but the specific process parameters do not conform to the present application.

[0054] Table 2 lists the specific process parameters of the manufacturing method of the medium-frequency low-iron-loss high-strength non-oriented electrical steel plate of Examples 1-10 and the comparative steel plate of Comparative Examples 1-7.

[0055] Table 2.

[0056]

[0057] In addition, the medium-frequency low-loss high-strength non-oriented electrical steel sheets of Examples 1-10 and the comparative steel sheets of Comparative Examples 1-7 were sampled, and the grain detection and related performance tests were performed on the samples of the steel sheets of the Examples and Comparative Examples, and the test results are listed in Table 3, and the related test means are described as follows:

[0058] Grain detection: The grain size was determined by the intercept method using a longitudinal cross-section microstructure photo of the sample at a magnification of 50 times.

[0059] Iron loss performance test: Based on the national standard GB / T 3655-2022, the iron loss performance test was performed by the Epstein square method, the test temperature was 20℃ constant temperature test, the sample size was 30mm×300mm, the longitudinal and transverse samples were each half, the target mass was 0.5kg, and the test parameters were P 10 / 400 .

[0060] Tensile property test: Based on the national standard GB / T228.1-2021, the yield strength and tensile strength performance tests were performed by room temperature tensile test, the test temperature was 20℃, and the longitudinal JIS5# standard tensile sample was used.

[0061] Table 3 lists the performance test results of the medium-frequency low-loss high-strength non-oriented electrical steel sheets of Examples 1-10 and the comparative steel sheets of Comparative Examples 1-7.

[0062] Table 3.

[0063]

[0064] It can be seen from Tables 1, 2 and 3 that in Examples 1-6 which meet the design requirements of the present application, the iron loss P 10 / 400 is less than 13.25W / kg, and the yield strength is greater than 460MPa and the tensile strength is greater than 600MPa, achieving the balance of high strength and medium-frequency low iron loss.

[0065] It should be noted that the combination of the technical features in the present case is not limited to the combination mode described in the claims of the present case or the combination mode described in the specific embodiments, and all the technical features described in the present case can be freely combined or combined in any way, unless contradictory to each other.

[0066] It should also be noted that the above examples are only specific embodiments of the present application. Obviously, the present application is not limited to the above examples, and similar changes or modifications made directly from the disclosure of the present application or easily thought of by those skilled in the art should all fall within the scope of protection of the present application.

Claims

1. A medium frequency low iron loss high strength non-oriented electrical steel sheet, characterized in that: The mass percentage of each chemical element is: C≤0.0035%, Si: 3.0-4.0%, Mn: 0.1-2.0%, Al: 0.1-2.0%, 0<Cr≤2.0%, 0<Ni≤5.0%; the balance is Fe and unavoidable impurities; It also satisfies: Si+Al+Cr-0.5×Ni-0.5×Mn≤2.5, where each chemical element is substituted into the value before the percentage sign of its mass percentage content; The grain size of the high-strength non-oriented electrical steel sheet is 20 to 160 μm; The iron loss P of the high strength non-oriented electrical steel sheet 10 / 400 ≤13.25W / kg.

2. The medium frequency low iron loss high strength non-oriented electrical steel sheet according to claim 1, characterized in that: Among the inevitable impurities, P ≤ 0.1%, S ≤ 0.003%, and N ≤ 0.002%.

3. The medium frequency low iron loss high strength non-oriented electrical steel sheet according to claim 1, characterized in that: It also contains Sn≧0.003% and / or Sb≧0.003%, and Sn+Sb≦0.3%.

4. The medium frequency low iron loss high strength non-oriented electrical steel sheet according to claim 1, characterized in that: Its yield strength is ≥460MPa and its tensile strength is ≥600MPa.

5. The method for manufacturing a medium frequency low iron loss high strength non-oriented electrical steel sheet according to any one of claims 1 to 4, comprising the steps of: smelting and casting; hot rolling; normalizing; cold rolling; continuous annealing; and insulating coating; characterized in that: In the hot rolling step, the heating temperature of the slab is controlled to be 1000-1200°C.

6. The manufacturing method according to claim 5, wherein: In the continuous annealing step, the annealing temperature is controlled to be 900-1100°C.

7. The manufacturing method according to claim 5, wherein: In the cold rolling step, one-time cold rolling is employed.

8. The manufacturing method according to claim 5, wherein: In the cold rolling step, one cold rolling + intermediate annealing + two cold rolling are adopted.

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