Non-oriented silicon steel with excellent comprehensive performance and manufacturing method therefor

Abstract

Disclosed in the present invention is non-oriented silicon steel, which comprises, in addition to Fe and inevitable impurities, the following chemical elements in percentage by mass: ≤0.0050％ of C, 2.0-4.0% of Si, 0.1-2.0% of Mn, 0.001-2.0% of Al, 0.001-5.0% of Cr, 0.001-5.0% of Ni, and 0.001-2.0% of Cu, wherein the mass percentage contents of the corresponding chemical elements also satisfy 0<3×Si+0.5×Al+0.5×Mn-5×Cu-2.5×Cr-Ni≤13.5％, and each element symbol in the formula represents the mass percentage content of the corresponding element. Further disclosed in the present invention is a method for manufacturing the non-oriented silicon steel. Using the solution of the present invention can obtain non-oriented silicon steel plates with good heat conduction performance and electromagnetic performance and excellent comprehensive performance.

Description

Non-oriented silicon steel with excellent comprehensive performance and manufacturing method thereof Technical Field

[0001] The present invention relates to a steel plate and a manufacturing method thereof, and in particular to a non-oriented silicon steel plate and a manufacturing method thereof. Background Art

[0002] Non-oriented silicon steel sheets are important soft magnetic materials for the manufacture of electric motors and generators. In recent years, with the increasing global demand for energy conservation and environmental protection, the new energy vehicle industry has experienced rapid development, which has also driven the development of non-oriented silicon steel materials for drive motors. The operating conditions of new energy vehicle drive motors are more severe than those of conventional motors. For example, the motor operating temperature is generally 150°C or above. At the same time, the drive motor is restricted by the interior space layout of the vehicle, and its heat dissipation conditions are also more severe. Therefore, the temperature rise of the drive motor during operation and the corresponding cooling are very important issues in the field of drive motor design. In order to reduce the temperature rise of the drive motor, non-oriented silicon steel needs to have better thermal conductivity.

[0003] Furthermore, to improve the efficiency and specific power density of drive motors, higher motor speeds are a key development trend. When the number of pole pairs in the motor's rotating magnetic field remains constant, the motor's speed is proportional to the operating frequency. As the motor's design speed increases, the motor's operating frequency also increases accordingly. Currently, the operating frequency of new energy vehicle drive motors has increased to a medium frequency range of 400 to 2000 Hz. Compared to conventional motors, the losses of non-oriented silicon steel at medium frequencies are far greater than those of conventional motors at 50 to 60 Hz. To reduce the iron loss of non-oriented silicon steel, its resistivity needs to be increased.

[0004] A Chinese patent document, publication number CN104726794A, published on June 24, 2015, and titled "Non-oriented silicon steel sheet and method for manufacturing the same," discloses a non-oriented silicon steel sheet comprising, by weight, 2.0-3.5% Si, 0.5-3.5% Mn, 0.5-3.5% Cr, greater than 0% and less than 0.8% Al, less than 0.004% C, less than 0.004% S, less than 0.004% N, less than 0.004% Ti, and less than 0.004% P.

[0005] A Chinese patent application, CN104294185A, published on January 21, 2015, and titled "A Non-Oriented Silicon Steel for High-Efficiency Motors and Its Production Method," discloses a non-oriented silicon steel for high-efficiency motors. Its chemical composition and weight percentages are as follows: C ≤ 0.0030%, Si: 1.9-2.1%, Mn: 0.28-0.32%, Al: 0.10-0.60%, P: 0.01-0.06%, S ≤ 0.0050%, Cu: 0.10-0.30%, Sb: 0.02-0.05%, and N ≤ 0.0030%. This solution fully utilizes the beneficial effects of each element in physical metallurgy by controlling the total amount of the main alloying elements (Si+Al+Mn) and the content of the auxiliary elements (Cu+P+Sb). The combined effects of (Cu+P+Sb) on the microstructure and magnetic properties of silicon steel were discovered, so (Cu+P) was used to replace part of the (Si+Al) elements in the steel. This not only increased the number of rebends in the normalized steel, but also improved the punchability of the finished steel.

[0006] As can be seen, the solution in the aforementioned patent adds as much Si and Al as possible to the steel to significantly increase the resistivity of the finished steel sheet, thereby reducing iron loss. However, adding a certain amount of P and Cr to the steel also reduces the iron loss of the finished steel sheet, especially at high frequencies. Furthermore, these measures, to a certain extent, limit the increase in the normalizing temperature of the steel sheet and reduce the manufacturability of cold rolling.

[0007] Summary of the Invention

[0008] One of the objectives of the present invention is to provide a non-oriented silicon steel with excellent comprehensive performance, which is obtained by optimizing the chemical composition design of the steel, preferably combining process design, and controlling the reasonable thermal conductivity and resistivity of the non-oriented silicon steel, so as to obtain a non-oriented silicon steel sheet with good thermal conductivity and electromagnetic properties and excellent comprehensive performance.

[0009] In order to achieve the above object, the present invention provides a non-oriented silicon steel, which, in addition to Fe and unavoidable impurities, further contains the following chemical elements in percentage by mass:

[0010] C≤0.0050%, Si: 2.0~4.0%, Mn: 0.1~2.0%, Al: 0.001~2.0%, Cr: 0.001~5.0%, Ni: 0.001~5.0%, Cu: 0.001~2.0%;

[0011] The mass percentage of the chemical elements also satisfies the following: 0<3×Si+0.5×Al+0.5×Mn-5×Cu-2.5×Cr-Ni≤13.5%, wherein the symbols of the elements represent the mass percentage of the corresponding elements.

[0012] In the design concept of traditional non-oriented silicon steel products, there is an inherent contradictory relationship between thermal conductivity and resistivity. For example, simply increasing the content of alloying elements such as Si and Al in steel will lead to a decrease in the thermal conductivity of non-oriented silicon steel and an increase in the resistivity. The inventors found through research that the difference in thermal conductivity of non-oriented silicon steel mainly lies in the strength of the metal bonds therein, while the determining factor of the resistivity of non-oriented silicon steel is the alloy content. Therefore, the present invention defines the element synergistic relationship characteristics by preferentially combining the types and contents of chemical elements contained in non-oriented silicon steel, while balancing the relationship between metal bonds and alloy content: 0<3×Si+0.5×Al+0.5×Mn-5×Cu-2.5×Cr-Ni≤13.5%, so as to effectively control the thermal conductivity and resistivity of non-oriented silicon steel and obtain non-oriented silicon steel with good thermal conductivity and electromagnetic properties (high thermal conductivity and high resistivity).

[0013] Preferably, the present invention further provides a non-oriented silicon steel, the chemical composition of the steel being calculated in percentage by mass:

[0014] C≤0.0050%, Si: 2.0~4.0%, Mn: 0.1~2.0%, Al: 0.001~2.0%, Cr: 0.001~5.0%, Ni: 0.001~5.0%, Cu: 0.001~2.0%; the balance is Fe and unavoidable impurities.

[0015] In the non-oriented silicon steel sheet of the present invention, the design principle of the chemical composition is as follows:

[0016] C: In the non-oriented silicon steel sheet of the present invention, C strongly hinders grain growth in the finished non-oriented silicon steel sheet and easily combines with impurities such as Nb, V, and Ti to form fine precipitates, which increases losses and causes magnetic aging. Therefore, C content must be strictly controlled below 0.0050%. Preferably, the C content in the steel is above 0.0005%, as a content below 0.0005% complicates the manufacturing process required to maintain a low C content.

[0017] Si: In the non-oriented silicon steel sheet of the present invention, Si is an effective element for increasing resistivity and reducing iron loss. In addition, Si has a higher solid solution strengthening ability than other solid solution strengthening elements such as Mn, Al, and Ni. Therefore, Si is the most effective element for achieving both high strength and low iron loss in a balanced manner. If the Si content in the steel is lower than 2.0%, the above-mentioned effects cannot be achieved. Therefore, the Si content is set to be above 2.0%. On the other hand, if the Si content in the steel is too high, the manufacturability, especially the workability, of the non-oriented silicon steel sheet will be reduced. In addition, as described later, by properly controlling the grain structure of the silicon steel sheet, the reduction in workability can be suppressed. However, if the Si content exceeds 4.0%, the cold workability of the non-oriented silicon steel sheet will be reduced. Therefore, the present invention controls the Si content in the steel to be below 4.0%. The preferred Si content is 3.6% or less.

[0018] Mn: In the non-oriented silicon steel sheet of the present invention, Mn increases resistivity. It reacts with the impurity element S to form MnS, which prevents hot brittleness caused by the formation of low-melting-point FeS along grain boundaries. Therefore, the addition of at least 0.1% Mn is necessary. However, an addition exceeding 2.0% will prevent sufficient grain growth during the steel sheet's final annealing, resulting in increased iron loss. Therefore, the present invention limits the Mn content to 0.1-2.00%.

[0019] Al: In the non-oriented silicon steel sheet of the present invention, Al increases resistivity and effectively reduces iron loss. However, Al content above 2.0% significantly reduces the steel's magnetic induction and cold rollability. Al content below 0.001% precipitates fine nitrides in the steel, hindering grain growth during hot-rolled and finish annealing, leading to deterioration of magnetic properties.

[0020] Cr: In the non-oriented silicon steel sheet described herein, Cr improves thermal conductivity and resistivity, while also reducing eddy current loss and high-frequency iron loss. However, a Cr content exceeding 5.0% reduces magnetic flux density, and excessively high metal content increases manufacturing costs. If the Cr content is below 0.001%, controlling the Cr content within a relatively low range significantly increases manufacturing process costs. Therefore, the present invention limits the Cr content to 0.001-5.0%.

[0021] Ni: In the non-oriented silicon steel sheet of the present invention, Ni improves thermal conductivity, solid-solution strengthens the silicon steel, and contributes to increased electrical resistance, thereby reducing iron loss, without reducing saturation magnetic flux density. However, if the Ni content exceeds 5.0%, manufacturing costs increase significantly. If the content is less than 0.001%, the manufacturing process costs of controlling the content within a lower range increase significantly. Therefore, the present invention controls the Ni content to 0.001-5.0%.

[0022] Cu: In the non-oriented silicon steel sheet of the present invention, Cu increases resistivity and thermal conductivity. However, when the Cu content exceeds 2.0%, the magnetic flux density decreases, and the excessively high metal content increases manufacturing costs. When the Cu content is below 0.001%, controlling the content within a low range significantly increases manufacturing process costs. Therefore, the present invention controls the Cu content to 0.001-2.0%.

[0023] Preferably, the non-oriented silicon steel of the present invention further contains 0≤Sn≤0.5wt% and / or 0≤Sb≤0.5wt%.

[0024] In a preferred embodiment of the present invention, at least one of Sn and Sb elements may also be contained. Sn and Sb inhibit oxidation and nitridation during annealing by segregating on the surface of the steel sheet, thereby ensuring that the steel sheet has low iron loss. In addition, these two elements also have the effect of segregating at the grain boundaries, thereby improving the microstructure and increasing the magnetic flux density of the steel sheet. However, if the content of Sn and Sb is excessive, the toughness of the steel will be reduced, making cold rolling difficult. Therefore, the content of Sn and Sb should be less than 0.05%, respectively.

[0025] Unless otherwise specified, the "content" of chemical elements in steel used in the present invention refers to the mass percentage.

[0026] Preferably, the non-oriented silicon steel of the present invention further contains at least one of the following chemical elements:

[0027] 0≤Ca≤0.02wt%;

[0028] 0≤Mg≤0.02wt%;

[0029] 0≤REM≤0.02wt%.

[0030] In a preferred embodiment of the present invention, at least one of Ca, Mg, and REM may also be contained. Ca, Mg, and REM are elements that fix the impurity S as sulfides or oxysulfides, inhibiting the fine precipitation of MnS and other elements, and promoting recrystallization and grain growth during final annealing. However, if the content of Ca, Mg, or REM exceeds 0.02%, excessive sulfides or oxysulfides will form, hindering recrystallization and grain growth during final annealing of the steel sheet. Therefore, in the present invention, the content of each of Ca, Mg, and REM is controlled to 0.02% or less.

[0031] Preferably, in the non-oriented silicon steel of the present invention, the inevitable impurities satisfy at least one of the following in terms of mass percentage: P≤0.20%, S≤0.005%, N≤0.005%, Nb≤0.005%, V≤0.005%, Ti≤0.005%.

[0032] In the present invention, P, S, N, Nb, V, and Ti are all impurity elements. If the process conditions permit, their contents are preferably as low as possible.

[0033] P will segregate along grain boundaries, and a content exceeding 0.20% will aggravate the brittleness of silicon steel sheets. Therefore, in a preferred embodiment of the present invention, the P content is controlled to be below 0.20%.

[0034] S is an element that is detrimental to the magnetic properties of silicon steel. When the S content exceeds 0.005%, it significantly increases the number of harmful inclusions such as MnS and Cu2S, strongly hindering grain growth and deteriorating the magnetic properties of the steel. Therefore, in a preferred embodiment of the present invention, the S content is controlled to below 0.005%.

[0035] When the N content exceeds 0.005%, the precipitation of Nb, V, Ti, Al, etc. will increase significantly, strongly hindering grain growth and deteriorating the magnetic properties of the steel. Therefore, in a preferred embodiment of the present invention, the N content is controlled to 0.005% or less.

[0036] Nb, V, and Ti may combine with carbon or nitrogen to form precipitates (carbides or nitrides). These precipitates can degrade the magnetic properties of the steel sheet. Specifically, these precipitates hinder grain growth during annealing, degrading magnetic properties. Therefore, in a preferred embodiment of the present invention, the Nb, V, and Ti contents are all controlled to below 0.005%.

[0037] Preferably, the chemical composition of the non-oriented silicon steel of the present invention satisfies at least one of the following in terms of mass percentage:

[0038] Si: 2.0-3.6%;

[0039] Al: 0.55~2.0%;

[0040] Cr: 0.04~2.11%;

[0041] Ni: 0.02~2.85%;

[0042] Cu: 0.05~2.0%.

[0043] Preferably, in the non-oriented silicon steel of the present invention, the number of grains with a grain size of 10 μm or more accounts for more than 10%.

[0044] More preferably, the number of grains with a grain size of 10 μm or more accounts for more than 50%.

[0045] Preferably, the thermal conductivity λ of the non-oriented silicon steel of the present invention at 150°C is 150 The resistivity is 10-35W / mK, the resistivity ρ at room temperature is 40-90μΩ·cm, and satisfies: 1000≤λ 150×ρ≤2000. Substitute dimensionless values ​​for calculation. For example, the thermal conductivity λ of non-oriented silicon steel at 150℃ is 150 is 20W / mK, and the resistivity ρ at room temperature is 50μΩ·cm, then λ 150 ×ρ=20×50=1000.

[0046] In order to better describe the actual working conditions of the motor, the thermal conductivity of the non-oriented silicon steel of the present invention is expressed as the thermal conductivity λ at 150°C. 150 Characterization. The inventors found through research that: for permanent magnet synchronous motors, when the value exceeds 1000≤λ 150 When ×ρ≤2000, the desired temperature rise performance of the permanent magnet synchronous motor cannot be obtained.

[0047] Preferably, the temperature rise of the permanent magnet synchronous motor manufactured using the non-oriented silicon steel of the present invention during operation is lower than 125°C.

[0048] Preferably, the iron loss P of the non-oriented silicon steel of the present invention is 10 / 700 ≤50W / kg.

[0049] Another object of the present invention is to provide a method for manufacturing non-oriented silicon steel, by controlling process parameters and adapting the composition ratio of the above-mentioned non-oriented silicon steel, so as to obtain non-oriented silicon steel sheets with good thermal conductivity and electromagnetic properties and excellent comprehensive performance.

[0050] In order to achieve the above object, the present invention provides a method for manufacturing non-oriented silicon steel, which comprises the following steps performed in sequence:

[0051] smelting and casting;

[0052] hot rolling;

[0053] Normalization;

[0054] cold rolling;

[0055] Continuous annealing and application of insulating coatings;

[0056] The continuous annealing temperature is 700-1100°C.

[0057] In the present invention, the continuous annealing temperature is controlled between 700°C and 1100°C because, in order to achieve recrystallization of the steel plate structure, the annealing temperature must be above the recrystallization temperature. Therefore, the present invention controls the lower limit of the continuous annealing temperature to 700°C. There is no specific upper limit for the annealing temperature, but for comprehensive manufacturing cost considerations, the upper limit is 1100°C.

[0058] In a preferred embodiment of the present invention, the cold rolling may adopt a one-time cold rolling process to directly roll the steel to the required thickness of the finished non-oriented silicon steel.

[0059] In another preferred embodiment of the present invention, the cold rolling may be performed by a process of primary cold rolling, intermediate annealing and secondary cold rolling, wherein the cumulative reduction ratio of the secondary cold rolling is 45-75%.

[0060] In this embodiment, the cumulative reduction rate of the secondary cold rolling is controlled to be 45-75% because: the reduction rate of the secondary cold rolling method has a significant impact on the microstructure of the steel plate. In order to improve the microstructure and thus improve the electromagnetic properties, the present invention controls the cumulative reduction rate of the secondary cold rolling to be 45-75%.

[0061] The non-oriented silicon steel of the present invention has the following advantages and beneficial effects:

[0062] The difference in thermal conductivity of the non-oriented silicon steel in the present invention mainly depends on the strength of the metal bonds in the steel, while the determining factor of the resistivity of the non-oriented silicon steel is the content of the alloying elements in the steel. The inventors have found that by combining the types and contents of the chemical elements in the non-oriented silicon steel appropriately, the relationship between the metal bonds and the alloy content in the steel is balanced, thereby effectively controlling the thermal conductivity and resistivity of the non-oriented silicon steel. It is further preferred to combine it with an appropriate manufacturing process, and more preferably to control the thermal conductivity λ of the non-oriented silicon steel at 150°C. 150 The resistivity is 10-35W / mK, the resistivity at room temperature is 40-90μΩ·cm, and 1000≤λ 150 ×ρ≤2000, and finally a non-oriented silicon steel sheet with good thermal conductivity, electromagnetic properties and excellent comprehensive performance is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] FIG1 shows the λ of the non-oriented silicon steel of the present invention. 150 ×ρ and the temperature rise of the permanent magnet synchronous motor made of corresponding non-oriented silicon steel.

[0064] FIG2 shows the metallographic structure of the non-oriented silicon steel according to Example 5 of the present invention. DETAILED DESCRIPTION

[0065] Through research, the inventors discovered that the difference in thermal conductivity of non-oriented silicon steel mainly depends on the strength of the metal bond, while the determining factor of the resistivity of non-oriented silicon steel is the content of alloying elements in the steel. Therefore, by selecting the appropriate combination of the types and contents of chemical elements contained in non-oriented silicon steel and balancing the relationship between metal bonds and alloy content, the thermal conductivity and resistivity of non-oriented silicon steel can be effectively controlled. In order to better describe the actual operating conditions of the motor, the thermal conductivity of non-oriented silicon steel is expressed as the thermal conductivity λ at 150°C. 150 representation.

[0066] In this invention, a permanent magnet synchronous motor was trial-produced using steel plates with different thermal conductivity and resistivity. The main parameters of the motor were: outer diameter 220mm, stack thickness 150mm, rated power 150KW, and maximum torque 350Nm. The temperature rise of the trial-produced permanent magnet synchronous motor was measured, and λ was obtained. 150 The relationship between ×ρ and the temperature rise of the permanent magnet synchronous motor is shown in Figure 1.

[0067] As can be seen from Figure 1, when the value exceeds 1000≤λ 150 When ×ρ≤2000, the expected motor temperature rise performance cannot be obtained.

[0068] The non-oriented silicon steel and the manufacturing method thereof of the present invention will be further explained and illustrated below in conjunction with specific embodiments and the accompanying drawings.

[0069] Examples 1-9 and Comparative Examples 1-6

[0070] Tables 1-1 and 1-2 list the mass percentages of various chemical elements in the non-oriented silicon steel sheets of Example 1-9 and the comparative steel sheets of Comparative Example 1-6. Table 1-1 shows the contents of the main elements in the steel and the calculated relationships between the corresponding element contents, while Table 1-2 shows the contents of other optional elements and exemplary unavoidable impurities in the steel. In conjunction with Tables 1-1 and 1-2, the balance of the steel composition in each Example and Comparative Example is Fe and other unavoidable impurities other than P, S, N, Nb, V, and Ti.

[0071] Table 1-1. (wt%)

[0072] Table 1-2. (wt%)

[0073] The non-oriented silicon steel sheets of Examples 1-9 of the present invention were all prepared by sequentially performing the following steps:

[0074] (1) Molten iron was obtained from a blast furnace according to the composition shown in Tables 1-1 and 1-2, and then subjected to molten iron pretreatment, converter smelting, RH refining and continuous casting to obtain a continuous casting billet with a nominal thickness of 300 mm.

[0075] (2) Heating: heating temperature is 1050°C, holding time is 1.5 hours;

[0076] (3) Finish rolling and coiling: The final rolling temperature of the steel coil is 800°C and the coiling temperature is 625°C to obtain a hot-rolled plate with a thickness of 1.5-2.5 mm;

[0077] (4) Normalizing annealing: annealing temperature is 950℃;

[0078] (5) cold rolling after pickling;

[0079] (6) Continuous annealing and insulating coating; wherein the continuous annealing temperature is 700-1100°C.

[0080] In each example, Examples 6-9 and Comparative Examples 4-6 employed a single cold rolling process; Examples 1-5 employed a single cold rolling + intermediate annealing + double cold rolling process, with the cumulative reduction ratio of the double cold rolling controlled at 45-75%. The remaining steps of Comparative Examples 1-6 were essentially the same as those of the present invention, with the differences listed in the table.

[0081] Table 2 lists the cumulative reduction ratios of secondary cold rolling (not applicable to Examples 6-9 and Comparative Examples 4-6) and continuous annealing temperatures used for comparison of the non-oriented silicon steel sheets of Examples 1-9 and Comparative Examples 1-6.

[0082] Table 2.

[0083] In addition, the present invention also samples the non-oriented silicon steel sheets of Examples 1-9 and the comparative steel sheets of Comparative Examples 1-6, and tests the relevant properties of the steel sheets of each Example and Comparative Example. The results of the observations and relevant performance tests are listed in Table 3. The specific testing methods for the relevant properties are as follows:

[0084] Microstructure inspection: Grain size statistics adopt the area method of "GB / T6394-2017 Metal Average Grain Size Determination Method".

[0085] Iron loss performance test: Based on GB / T10129-2019 electrical steel strip (sheet) medium frequency magnetic property measurement method, the Epstein square circle method is used for iron loss performance test. The test temperature is 20℃ constant temperature test, the sample size is 30mm×300mm, the target mass is 0.25kg, and the test parameters are P 10 / 700 .

[0086] Thermal conductivity test: Use the transient plane heat source method in accordance with GB / T 32064-2015. The test equipment can be Hot Disk TPS2500S.

[0087] Room temperature resistivity test: Test in accordance with GB / T 351-2019.

[0088] Temperature rise test: refer to GB / T 18488.2-2015 Electric vehicle drive motor system Part 2: Test method for testing.

[0089] Table 3 lists the relevant performance test results of the non-oriented silicon steel sheets of Examples 1-9, the comparative steel sheets of Comparative Examples 1-6, and the permanent magnet synchronous motors manufactured from the steel sheets.

[0090] Table 3.

[0091] Note: The “temperature rise” in Table 3 is the temperature rise data of the permanent magnet synchronous motors trial-produced using the steel plates of the corresponding embodiments and comparative examples.

[0092] Figure 2 shows the metallographic structure of the non-oriented silicon steel sheet according to Example 5 of the present invention. As shown in Figure 2 , the number of grains with a grain size of 10 μm or more accounts for more than 50%.

[0093] Combining Table 1, Table 2 and Table 3, it can be seen that in Examples 1 to 9 that meet the design requirements of the present invention, due to the unique composition design and preferred process design of the present invention, the thermal conductivity λ of the final product non-oriented silicon steel sheet at 150°C is 150 The resistivity is 10-35W / mK, the resistivity ρ at room temperature is 40-90μΩ·cm, and satisfies: 1000≤λ 150 ×ρ≤2000, and at the same time has good electromagnetic properties, the finished steel plate iron loss P 10 / 700 The temperature rise of the permanent magnet synchronous motors made of the non-oriented silicon steel in these embodiments is lower than the target value of 125°C.

[0094] However, the comparative steel sheets of Comparative Examples 1-6 do not meet the requirements of the present invention due to one or more of their composition, secondary cold rolling process, and continuous annealing process failing to meet the requirements of the present invention, resulting in their thermal conductivity and resistivity failing to meet the requirements of the present invention. In particular, the temperature rise of the permanent magnet synchronous motors made using the steel sheets of these comparative examples all exceeded the target value of 125°C. This is because the motor generates heat and dissipates heat during operation. Heat generation is closely related to the resistivity of the silicon steel sheet, while heat dissipation is related to the thermal conductivity of the silicon steel sheet. When these two properties of the silicon steel sheet fail to meet the requirements, the heat generated by the silicon steel sheet cannot be dissipated in a timely manner, resulting in an increase in the motor temperature. Excessive temperature rise can seriously affect the performance and operational safety of the motor and must be controlled within an appropriate range.

[0095] It should be noted that 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.

[0096] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therefrom that can be directly derived from or easily conceived by those skilled in the art based on the disclosure of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A non-oriented silicon steel, which contains, in addition to Fe and unavoidable impurities, the following chemical elements in terms of mass percentage: C≤0.0050%, Si: 2.0-4.0%, Mn: 0.1-2.0%, Al: 0.001-2.0%, Cr: 0.001-5.0%, Ni: 0.001-5.0%, Cu: 0.001-2.0%; in, The mass percentage of the chemical elements also satisfies: 0<3×Si+0.5×Al+0.5×Mn-5×Cu-2.5×Cr-Ni≤13.5%, wherein the symbol of each element represents the mass percentage of the corresponding element.

2. The non-oriented silicon steel according to claim 1, characterized in that: The chemical composition of the non-oriented silicon steel is calculated by mass percentage as follows: C≤0.0050%, Si: 2.0-4.0%, Mn: 0.1-2.0%, Al: 0.001-2.0%, Cr: 0.001-5.0%, Ni: 0.001-5.0%, Cu: 0.001-2.0%; the remainder is Fe and other inevitable impurities.

3. The non-oriented silicon steel according to claim 1 or 2, characterized in that: The non-oriented silicon steel further contains 0≤Sn≤0.5wt% and / or 0≤Sb≤0.5wt%.

4. The non-oriented silicon steel according to claim 1 or 2, characterized in that: The non-oriented silicon steel further contains at least one of the following chemical elements: 0≤Ca≤0.02wt%; 0≤Mg≤0.02wt%; 0≤REM≤0.02wt%.

5. The non-oriented silicon steel according to claim 1, characterized in that: The unavoidable impurities satisfy at least one of the following in terms of mass percentage: P≤0.20%, S≤0.005%, N≤0.005%, Nb≤0.005%, V≤0.005%, Ti≤0.005%.

6. The non-oriented silicon steel according to claim 1 or 2, characterized in that: The chemical composition of the non-oriented silicon steel satisfies at least one of the following in terms of mass percentage: Si: 2.0-3.6%; Al: 0.55-2.0%; Cr: 0.04-2.11%; Ni: 0.02-2.85%; Cu: 0.05-2.0%.

7. The non-oriented silicon steel according to claim 1 or 2, characterized in that: In the non-oriented silicon steel, the number of grains with a grain size of more than 10 μm accounts for more than 10%.

8. The non-oriented silicon steel according to claim 7, characterized in that: In the non-oriented silicon steel, the number of grains with a grain size of more than 10 μm accounts for more than 50%.

9. The non-oriented silicon steel according to claim 1 or 2, characterized in that: The thermal conductivity λ of the non-oriented silicon steel at 150°C 150 The resistivity at room temperature is 40 to 90 μΩ·cm and satisfies: 1000 ≤ λ 150 ×ρ≤2000.

10. The non-oriented silicon steel according to claim 1 or 2, characterized in that: The iron loss P of the non-oriented silicon steel 10 / 700 ≤50W / kg.

11. A permanent magnet synchronous motor manufactured using the non-oriented silicon steel as claimed in claim 1 or 2, characterized in that: The temperature rise of the permanent magnet synchronous motor during operation is lower than 125°C.

12. The method for manufacturing non-oriented silicon steel according to any one of claims 1 to 10, characterized in that: The method comprises the following steps performed in sequence: smelting and casting; Hot rolling; Normalization; Cold rolling; Continuous annealing and application of insulating coatings; Wherein, the continuous annealing temperature is 700-1100°C.

13. The method according to claim 12, characterized in that In the cold rolling step, a single cold rolling process is adopted.

14. The method according to claim 12, characterized in that In the cold rolling step, a process of primary cold rolling, intermediate annealing and secondary cold rolling is adopted, wherein the cumulative reduction rate of the secondary cold rolling is 45-75%.

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