Non-oriented silicon steel with excellent overall performance and its manufacturing method

Abstract

The present invention discloses a non-oriented silicon steel containing, in addition to Fe and unavoidable impurities, the following chemical elements in mass percent: 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%, and Cu: 0.001-2.0%, where the mass percent contents of the corresponding chemical elements further satisfy the following: 0<3×Si+0.5×Al+0.5×Mn-5×Cu-2.5×Cr-Ni≦13.5%, where each element symbol represents the mass percent content of the corresponding element. The present invention also discloses a method for producing the non-oriented silicon steel. By using the solution of the present invention, a non-oriented silicon steel sheet with good thermal conductivity, electromagnetic properties, and excellent overall performance can be obtained.

Description

[Technical Field]

[0001] Technical Field The present invention relates to a steel sheet and a manufacturing method thereof, and more particularly to a non-oriented silicon steel sheet and a manufacturing method thereof. [Background technology]

[0002] Background technology Non-oriented silicon steel is an important metallic soft magnetic material used in motors and generators. In recent years, the increasing global demand for energy conservation and environmental protection has led to rapid development of the new energy vehicle industry, simultaneously promoting the development of non-oriented silicon steel for drive motors. The operating conditions of drive motors in new energy vehicles are worse than those of conventional motors. For example, the motor's operating temperature is generally above 150°C. At the same time, the drive motor is limited by the vehicle's interior space layout, further worsening its heat dissipation requirements. Therefore, the temperature rise of drive motors during operation and the corresponding cooling are of great importance in the field of drive motor design. To limit the temperature rise of drive motors, non-oriented silicon steel requires better thermal conductivity.

[0003] Additionally, increasing motor speeds has become an important development trend to improve the operating efficiency and specific power density of traction motors. For a given number of pole pairs in the motor's rotating magnetic field, motor speed is directly proportional to its operating frequency. As motor speed designs increase, the operating frequency of the motor also increases accordingly. Currently, the operating frequency of traction motors for new energy vehicles has been raised to the intermediate frequency range of 400 to 2,000 Hz. Compared to conventional motors, the loss of non-oriented silicon steel at intermediate frequencies is much greater than the loss of conventional motors at power frequencies of 50 Hz or 60 Hz. To reduce the iron loss of non-oriented silicon steel, the electrical resistivity of the steel must be improved.

[0004] A Chinese patent document entitled "Non-oriented silicon steel sheet and manufacturing method thereof" with publication number CN104726794A and publication date June 24, 2015, discloses a non-oriented silicon steel sheet containing the following by weight: Si: 2.0 to 3.5%, Mn: 0.5 to 3.5%, and Cr: 0.5 to 3.5%, Al: more than 0% and not more than 0.8%, C: 0.004% or less, S: 0.004% or less, N: 0.004% or less, Ti: 0.004% or less, and P: 0.004% or less.

[0005] A Chinese patent publication, Publication Number CN104294185A, entitled "Non-oriented Silicon Steel for High-Efficiency Motors and Its Manufacturing Method," published on January 21, 2015, discloses a non-oriented silicon steel for high-efficiency motors. The chemical composition by weight percent is 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 the physical metallurgy by controlling the total amount of the main alloying elements (Si, Al, Mn) and the amounts of the auxiliary elements (Cu, P, and Sb). It has been discovered that the elements (Cu+P+Sb) have a combined effect on the structure and magnetic properties of silicon steel. Therefore, the elements (Cu+P) are used to replace part of the elements (Si+Al) in the steel, which can improve the reverse bending number of the normalized sheet on the one hand and the punching performance of the finished sheet on the other hand.

[0006] It can be seen that the solution of the above patent adds Si and Al elements to the steel as much as possible to significantly improve the electrical resistivity of the finished steel sheet, thereby further reducing iron loss. However, adding a certain amount of P and Cr elements to the steel can also reduce the iron loss of the finished steel sheet, especially the iron loss at high frequencies. Furthermore, these measures to a certain extent limit the increase in the normalizing temperature of the steel sheet and reduce the cold rolling manufacturability. Summary of the Invention [Means for solving the problem]

[0007] Summary of the Invention One of the objects of the present invention is to provide a non-oriented silicon steel with excellent overall performance, which can be achieved by optimizing the chemical composition design, preferably in combination with the steel process design, to rationally control the thermal conductivity and electrical resistivity of the non-oriented silicon steel, thereby obtaining a non-oriented silicon steel sheet with excellent overall performance in terms of good thermal conductivity and electromagnetic performance.

[0008] 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 mass %: 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%; wherein the chemical elements in mass % further satisfy: 0<3×Si+0.5×Al+0.5×Mn−5×Cu−2.5×Cr−Ni≦13.5%, where each element symbol in the formula represents the mass % of the corresponding element.

[0009] The design principles of conventional non-oriented silicon steel products inherently contradict each other between thermal conductivity and electrical resistivity. For example, simply increasing the content of alloying elements such as Si and Al decreases the thermal conductivity of non-oriented silicon steel while increasing its electrical resistivity. The inventors' research has revealed that the difference in thermal conductivity of non-oriented silicon steel is primarily due to the strength of the metallurgical bond within it, while the alloy content is a key factor in its electrical resistivity. Therefore, the present invention optimizes the combination of chemical elements and their content in non-oriented silicon steel, while simultaneously balancing the relationship between the metallurgical bond and the alloy content. The element synergy characteristic is defined as: 0<3×Si+0.5×Al+0.5×Mn-5×Cu-2.5×Cr-Ni≦13.5%, thereby effectively controlling the thermal conductivity and electrical resistivity of non-oriented silicon steel and achieving good thermal conductivity and electromagnetic performance (high thermal conductivity and high electrical resistivity).

[0010] Preferably, the present invention further provides a non-oriented silicon steel, the chemical composition of which is, in mass %, C≦0.0050%, Si: 2.0 to 4.0%, Mn: 0.1 to 2.0%, Al: 0.001 to 2.0%, Cr: 0.001 to 5.0%, Ni: 0.001 to 5.0%, Cu: 0.001 to 2.0%, and the balance is Fe and unavoidable impurities.

[0011] In the non-oriented silicon steel sheet of the present invention, the design principle of the chemical composition is as follows: C: In the non-oriented silicon steel sheet of the present invention, C significantly inhibits 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 increase loss and cause magnetic aging. Therefore, it must be strictly controlled to 0.0050% or less. Preferably, the C content in the steel is 0.0005% or more. If the content is less than 0.0005%, the manufacturing process becomes complicated to control the content within a low range.

[0012] Si: In the non-oriented silicon steel sheet of the present invention, Si is an element effective in increasing electrical resistivity and reducing iron loss. Furthermore, 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 balancing high strength and low iron loss. If the Si content in the steel is less than 2.0%, the above effects cannot be achieved. Therefore, the Si content is set to 2.0% or more. On the other hand, if the Si content in the steel is too high, the manufacturability, particularly the workability, of the non-oriented silicon steel sheet is reduced. Note that, as described below, it is possible to suppress the deterioration of workability by appropriately controlling the crystal grain structure of the silicon steel sheet. However, if the Si content exceeds 4.0%, the cold workability of the non-oriented silicon steel sheet is reduced. Therefore, in the present invention, the Si content in the steel is controlled to 4.0% or less. Preferably, the Si content is 3.6% or less.

[0013] Mn: In the non-oriented silicon steel sheet of the present invention, Mn can improve electrical resistivity and react with the impurity element S to form MnS, which can prevent thermal embrittlement caused by the formation of FeS, which has a low melting point, along grain boundaries. Therefore, the addition of Mn element must be 0.1% or more. However, if the addition amount exceeds 2.0%, the crystal grains do not grow sufficiently during the final annealing of the steel sheet, which results in increased iron loss of the non-oriented silicon steel sheet. Therefore, in the present invention, the Mn content is controlled to 0.1 to 2.00%.

[0014] Al: In the non-oriented silicon steel sheet of the present invention, Al is an element that increases the electrical resistivity and effectively reduces the iron loss of the steel. However, if the Al content exceeds 2.0%, the magnetic induction of the steel will decrease significantly, and the rollability of the cold rolling will decrease significantly. However, if the Al content is less than 0.001%, fine nitrides will precipitate in the steel, which will inhibit grain growth during annealing of the hot-rolled sheet and the finished product, resulting in deterioration of the magnetic properties.

[0015] Cr: In the non-oriented silicon steel sheet of the present invention, Cr can improve thermal conductivity, increase electrical resistivity, reduce eddy current loss, and reduce high-frequency iron loss. However, if the Cr content exceeds 5.0%, the magnetic flux density decreases and the metal content increases, resulting in higher manufacturing costs. If the Cr content is below 0.001%, the manufacturing process costs increase significantly due to the need to control the Cr content to a low range. Therefore, in the present invention, the Cr content is controlled to 0.001 to 5.0%.

[0016] Ni: In the non-oriented silicon steel sheet of the present invention, Ni improves thermal conductivity and simultaneously solid-solution strengthens the silicon steel, promoting an increase in the electrical resistivity of the silicon steel and reducing iron loss without reducing saturation magnetic flux density. However, if the Ni content exceeds 5.0%, the manufacturing cost increases significantly. If the Ni content falls below 0.001%, the manufacturing process cost increases significantly due to the need to control the Ni content to a low range. Therefore, in the present invention, the Ni content is controlled to 0.001 to 5.0%.

[0017] Cu: In the non-oriented silicon steel sheet of the present invention, Cu can increase electrical resistivity and improve thermal conductivity. However, if the Cu content exceeds 2.0%, the magnetic flux density decreases and the manufacturing cost increases due to the high metal content. If the Cu content is below 0.001%, the manufacturing process cost increases significantly due to the need to control the Ni content to a low range. Therefore, in the present invention, the Cu content is controlled to be 0.001 to 2.0%.

[0018] Preferably, the non-oriented silicon steel of the present invention further contains 0≦Sn≦0.5 wt% and / or 0≦Sb≦0.5 wt%.

[0019] In a preferred embodiment of the present invention, the non-oriented silicon steel may further contain at least one of Sn and Sb. Sn and Sb ensure low iron loss of the steel sheet by inhibiting oxidation and nitridation during annealing due to surface segregation of the steel sheet. These two elements also have the effect of segregating at grain boundaries, thereby improving the microstructure of the steel sheet and increasing its magnetic flux density. However, excessive Sn and Sb contents can reduce the toughness of the steel, which can make cold rolling of the steel difficult. Therefore, the Sn and Sb contents should each be 0.05% or less.

[0020] Unless otherwise specified, the "content" or "amount" of a chemical element in the steel of the present invention means mass %.

[0021] Preferably, the non-oriented silicon steel of the present invention further contains at least one of the following chemical elements: 0≦Ca≦0.02wt%; 0≦Mg≦0.02wt%; 0≦REM≦0.02wt%.

[0022] In a preferred embodiment of the present invention, the non-oriented silicon steel may also contain at least one of Ca, Mg, and REM. Ca, Mg, and REM are elements that fix impurity S as sulfides or sulfur oxides, suppress the fine precipitation of MnS, and promote recrystallization and grain growth during final annealing. However, if the Ca, Mg, and REM contents exceed 0.02%, excessive sulfides or sulfur oxides are formed, which inhibits recrystallization and grain growth during final annealing of the steel sheet. Therefore, in the present invention, any one of Ca, Mg, and REM is controlled to 0.02% or less.

[0023] Preferably, the unavoidable impurities in the non-oriented silicon steel of the present invention satisfy at least one of the following in mass percent: P≦0.20%, S≦0.005%, N≦0.005%, Nb≦0.005%, V≦0.005%, Ti≦0.005%.

[0024] In the present invention, P, S, N, Nb, V, and Ti are all impurity elements. If process conditions permit, it is expected that the contents of these elements will be as low as possible.

[0025] P accumulates along grain boundaries. If the content exceeds 0.20%, the brittleness of the silicon steel sheet increases. Therefore, in some preferred embodiments of the present invention, the P content is controlled to 0.20% or less.

[0026] S is an element that is harmful to the magnetic properties of silicon steel. If the S content exceeds 0.005%, the number of harmful inclusions such as MnS and CuS will increase significantly, which will significantly hinder the grain growth of the steel and deteriorate the magnetic properties of the steel. Therefore, in some preferred embodiments of the present invention, the S content is controlled to be 0.005% or less.

[0027] If the N content exceeds 0.005%, the precipitates of N, such as Nb, V, Ti and Al, will increase significantly, which will significantly inhibit the grain growth of the steel and deteriorate the magnetic properties of the steel. Therefore, in some preferred embodiments of the present invention, the N content is controlled to be 0.005% or less.

[0028] Nb, V, and Ti can combine with carbon and nitrogen to form precipitates (carbides and nitrides). These precipitates deteriorate the magnetic properties of steel sheets. Specifically, these precipitates hinder grain growth during annealing and deteriorate the magnetic properties. Therefore, in some preferred embodiments of the present invention, the contents of Nb, V, and Ti are controlled to 0.005% or less.

[0029] Preferably, the chemical composition of the non-oriented silicon steel of the present invention satisfies at least one of the following: 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%.

[0030] Preferably, in the non-oriented silicon steel of the present invention, the proportion of crystal grains having a grain size of 10 μm or more exceeds 10%.

[0031] More preferably, the proportion of crystal grains with a grain size of 10 μm or more exceeds 50%.

[0032] Preferably, the non-oriented silicon steel of the present invention has a thermal conductivity λ at 150 ° C. of 10 to 35 W / mK. 150 and electrical resistivity ρ at room temperature of 40 to 90 μΩ·cm, and: 1000≦λ 150 ×ρ≦2000. Calculations are performed by substituting dimensionless values. For example, the thermal conductivity λ of non-oriented silicon steel at 150°C is 20 W / mK. 150 and electrical resistivity ρ at room temperature of 50 μΩ cm, λ 150 ×ρ=20×50=1000.

[0033] In order to better represent the actual operating conditions of the motor, the thermal conductivity performance of the non-oriented silicon steel of the present invention is measured by the thermal conductivity λ at 150 °C. 150 The inventors have studied and found that 1000≦λ150 It was found that the desired temperature rise performance of the permanent magnet synchronous motor could not be obtained when the range of ×ρ≦2000 was exceeded.

[0034] Preferably, the temperature rise during operation of a permanent magnet synchronous motor manufactured from the non-oriented silicon steel of the present invention is less than 125°C.

[0035] Preferably, the core loss of the non-oriented silicon steel of the present invention is P 10 / 700 ≦50W / kg.

[0036] Another object of the present invention is to provide a method for producing non-oriented silicon steel, in which process parameters are controlled to match the above composition ratio of the non-oriented silicon steel, thereby obtaining a non-oriented silicon steel sheet having excellent overall performance in terms of good thermal conductivity and electromagnetic performance.

[0037] To achieve the above object, the present invention provides a method for producing non-oriented silicon steel, comprising the following steps in order: smelting and foundry; Hot rolling; Tempering; Cold rolling; Continuous annealing and application of insulating coating; Here, the temperature of the continuous annealing is 700 to 1100°C.

[0038] In the present invention, the annealing temperature must be higher than the recrystallization temperature to achieve recrystallization of the steel sheet structure, and therefore the continuous annealing temperature is controlled to 700 to 1100°C. Based on this, the lower limit of the continuous annealing temperature is required to be controlled to 700°C. The upper limit of the annealing temperature is not particularly limited. However, taking into consideration the overall manufacturing cost, the upper limit of the annealing temperature is 1100°C.

[0039] In some preferred embodiments of the present invention, cold rolling can use a single cold rolling process to directly roll the non-oriented silicon steel to the finished thickness.

[0040] In another preferred embodiment of the present invention, the cold rolling can use a process of a first cold rolling process, intermediate annealing and a second cold rolling process, wherein the cumulative reduction rate of the second cold rolling is 45 to 75%.

[0041] 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 has a significant effect on the microstructure of the steel sheet. In the present invention, the cumulative reduction rate of the secondary cold rolling is controlled to be 45-75% in order to improve the microstructure and thereby the electromagnetic performance.

[0042] The non-oriented silicon steel of the present invention has the following advantages and beneficial effects: The difference in thermal conductivity of non-oriented silicon steel mainly depends on the strength of the metallurgical bond in the steel, while the important factor in the electrical resistivity of non-oriented silicon steel is the content of alloying elements in the steel. The inventors have found that by appropriately combining the type and content of chemical elements in non-oriented silicon steel, the relationship between the metallurgical bond and the alloying content in the steel can be balanced, thereby effectively controlling the thermal conductivity and electrical resistivity of non-oriented silicon steel. Furthermore, an appropriate manufacturing process is preferably used. More preferably, the non-oriented silicon steel has a thermal conductivity λ at 150°C of 10 to 35 W / mK. 150 and electrical resistivity ρ at room temperature of 40 to 90 μΩ·cm, and 1000≦λ 150 ×ρ≦2000. Finally, a non-oriented silicon steel sheet with excellent overall performance in terms of good thermal conductivity and electromagnetic properties is obtained. [Brief explanation of the drawings]

[0043] [Figure 1] FIG. 1 shows the relationship between λ150×ρ of the non-oriented silicon steel of the present invention and the temperature rise of a permanent magnet synchronous motor manufactured using the corresponding non-oriented silicon steel. [Figure 2] FIG. 2 shows a graph of the metallographic structure of the non-oriented silicon steel of Example 5 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0044] Detailed Description of the Embodiments The inventors have conducted research and found that the difference in thermal conductivity of non-oriented silicon steel is mainly dependent on the strength of the metallurgical bond, while the important factor in its electrical resistivity is the alloy content in the steel. Therefore, the thermal conductivity and electrical resistivity of non-oriented silicon steel can be effectively controlled by selecting the appropriate combination of the types and contents of chemical elements contained in the non-oriented silicon steel and balancing the relationship between the metallurgical bond and the alloy content. To better represent the actual operating conditions of a motor, the thermal conductivity performance of non-oriented silicon steel is measured by the thermal conductivity λ at 150°C. 150 can be characterized by

[0045] In this study, a permanent magnet synchronous motor was fabricated using steel sheets with different thermal conductivities and electrical resistivities. The motor's main parameters were an outer diameter of 220 mm, lamination thickness of 150 mm, rated power of 150 kW, and maximum torque of 350 Nm. The temperature rise of the prototype permanent magnet synchronous motor was measured, and λ 150 The relationship between ×ρ and the temperature rise of a permanent magnet synchronous motor is shown in Figure 1.

[0046] As can be seen from Figure 1, 1000 ≤ λ 150 If the range of ×ρ≦2000 is exceeded, the expected temperature rise performance of the motor cannot be obtained.

[0047] The non-oriented silicon steel and its manufacturing method described in the present invention will be further described and illustrated in the specification by means of specific examples and drawings.

[0048] Examples 1 to 9 and Comparative Examples 1 to 6 Tables 1-1 and 1-2 show the amount of each chemical element in the non-oriented silicon steel sheets of Examples 1 to 9 and the comparative steel sheets of Comparative Examples 1 to 6, in terms of mass %. Table 1-1 shows the calculated values ​​of the contents of the major elements and the relationships between the corresponding elements in the steel. Table 1-2 shows the contents of other optional elements and exemplary unavoidable impurities contained in the steel. The balance of the steel components in each Example and Comparative Example is Fe and unavoidable impurities excluding P, S, N, Nb, V, and Ti.

[0049] [Table 1-1]

[0050] [Table 1-2]

[0051] The non-oriented silicon steel sheets of Examples 1 to 9 of the present invention were all manufactured through the following steps in order: (1) Molten iron was obtained in a blast furnace from the components shown in Table 1-1 and Table 1-2, and then the molten iron was subjected to preliminary treatment, converter smelting, RH refining, and continuous casting in that order to obtain a continuously cast billet with a nominal thickness of 300 mm. (2) Heating: the heating temperature was 1050°C, and the holding time was 1.5 hours; (3) Finish rolling and coiling: The final rolling temperature of the steel coil was 800°C, and the coiling temperature was 625°C. Hot-rolled sheets with thicknesses of 1.5-2.5 mm were obtained; (4) Normalizing annealing: The annealing temperature was 950°C; (5) Cold rolling after pickling; (6) Continuous annealing and application of insulating coating; here, the continuous annealing temperature was 700-1100°C.

[0052] In each example, Examples 6 to 9 and Comparative Examples 4 to 6 employed a single cold rolling process; Examples 1 to 5 employed a process of primary cold rolling + intermediate annealing + secondary cold rolling, where the cumulative reduction rate of the secondary cold rolling was controlled to 45 to 75%. The other steps of Comparative Examples 1 to 6 were substantially the same as those of the examples of the present invention. The differences between them are shown in the table.

[0053] Table 2 shows the cumulative reduction ratios and continuous annealing temperatures of the secondary cold rolling (not applied to Examples 6 to 9 and Comparative Examples 4 to 6) used in the non-oriented silicon steel sheets of Examples 1 to 9 and Comparative Examples 1 to 6.

[0054] [Table 2]

[0055] Furthermore, the non-oriented silicon steel sheets of Examples 1 to 9 and the comparative steel sheets of Comparative Examples 1 to 6 were sampled and tested for each relevant property of the steel sheets of the Examples and Comparative Examples. The results obtained from the relevant property tests and observations are shown in Table 3. The specific test methods for the relevant properties are as follows:

[0056] Microstructure detection: Grain size statistics are inspected by the area method of "GB / T6394-2017 Method for determining the average grain size of metals".

[0057] Iron loss performance test: Based on GB / T10129-2019 "Method for measuring the medium-frequency magnetic properties of electromagnetic steel strips (sheets)", the iron loss performance test was carried out using the Epstein square method. The test was carried out at a constant temperature of 20°C. The sample size was 30mm x 300mm. The target mass was 0.25kg. The test parameters were P 10 / 700 It was.

[0058] Thermal conductivity test: The test was carried out according to GB / T 32064-2015 by the transient plane heat source method. A hot disk TPS2500S was used as the test equipment.

[0059] Electrical resistivity test at room temperature: measured according to GB / T 351-2019.

[0060] Temperature rise test: Measured in accordance with GB / T 18488.2-2015 Electric vehicle drive motor systems - Part 2: Test methods.

[0061] Table 3 shows the results of relevant performance tests of the non-oriented silicon steel sheets of Examples 1 to 9 and the comparative steel sheets of Comparative Examples 1 to 6, as well as the permanent magnet synchronous motors manufactured from these steel sheets.

[0062] [Table 3]

[0063] Note) "Temperature rise" in Table 3 shows the temperature rise data of the permanent magnet synchronous motors prototyped using the corresponding steel sheets of the examples and comparative examples.

[0064] 2 is a graph showing the metal structure of the non-oriented silicon steel of Example 5 of the present invention. As shown in FIG. 2, the percentage of the number of crystal grains having a grain size of 10 μm or more exceeds 50%.

[0065] By combining Tables 1, 2, and 3, in Examples 1 to 9 that meet the design requirements of the present invention, the final non-oriented silicon steel sheet obtained by the unique composition design and optimized process design of the present invention has a thermal conductivity λ of 10 to 35 w / mK at 150 ° C. 150 and electrical resistivity ρ at room temperature of 40 to 90 μΩ·cm, and λ ≦ 1000 150 ×ρ≦2000, and obtain better electromagnetic performance, and the iron loss P 10 / 700 It can be seen that the temperature rise is ≦50 W / kg. All of the permanent magnet synchronous motors manufactured using the non-oriented silicon steel of these examples have a temperature rise that is lower than the target value of 125° C.

[0066] However, the thermal conductivity and electrical resistivity of the comparative steel sheets of Comparative Examples 1 to 6 did not meet the requirements of the present invention because at least one of their composition, secondary cold rolling process, and continuous annealing process was not satisfied. In particular, the permanent magnet synchronous motors manufactured using these comparative steel sheets all had a temperature rise higher than the target value of 125°C. This is due to the generation and dissipation of heat during motor operation. The heat generation condition is closely related to the electrical resistivity of the silicon steel sheet, while the heat dissipation condition is related to the thermal conductivity of the silicon steel sheet. If these two properties of the silicon steel sheet do not meet the requirements, the heat released by the silicon steel sheet cannot be conducted in time, resulting in a temperature rise in the motor. If the temperature rise is too high, it will have a significant impact on the performance and operational safety of the motor and must be controlled within an appropriate range.

[0067] It should be noted that the combinations of the technical features in this application are not limited to the combinations described in the claims of this application or the combinations described in the specific embodiments of this application, and all technical features described in this application can be freely combined in any way as long as they are not inconsistent with each other.

[0068] It should also be noted that the above examples are merely specific embodiments of the present invention, and obviously the present invention is not limited to the above examples, and all similar changes or modifications that can be directly derived or easily associated by those skilled in the art from the disclosure of the present invention shall fall within the protection scope of the present invention.

Claims

1. Non-oriented silicon steel containing, in addition to Fe and unavoidable impurities, the following chemical elements in mass %: 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%; wherein the chemical elements in mass % further satisfy: 0<3×Si+0.5×Al+0.5×Mn−5×Cu−2.5×Cr−Ni≦13.5%, where each element symbol in the formula represents the mass % of the corresponding element.

2. 2. Non-oriented silicon steel according to claim 1, characterized in that the chemical composition in mass % is: 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 being Fe and unavoidable impurities.

3. 3. The non-oriented silicon steel according to claim 1, further containing 0≦Sn≦0.5 wt% and / or 0≦Sb≦0.5 wt%.

4. 3. Non-oriented silicon steel according to claim 1 or 2, characterized in that it 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 mass%: P≦0.2%, S≦0.005%, N≦0.005%, Nb≦0.005%, V≦0.005%, Ti≦0.005%.

6. 3. The non-oriented silicon steel according to claim 1, characterized in that the chemical composition satisfies at least one of the following in mass%: 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. 3. The non-oriented silicon steel according to claim 1, wherein the proportion of crystal grains having a grain size of 10 μm or more in the non-oriented silicon steel is 10% or more.

8. 8. The non-oriented silicon steel according to claim 7, wherein the proportion of crystal grains having a grain size of 10 μm or more in the non-oriented silicon steel is 50% or more.

9. Thermal conductivity λ at 150°C of 10 to 35W / mK 150 and an electrical resistivity ρ at room temperature of 40 to 90 μΩ cm, and: 1000≦λ 150 3. The non-oriented silicon steel according to claim 1, wherein xρ≦2000 is satisfied.

10. Iron loss is P 10／700 3. The non-oriented silicon steel according to claim 1, wherein the non-oriented silicon steel satisfies ≦50 W / kg.

11. 3. A permanent magnet synchronous motor manufactured using the non-oriented silicon steel according to claim 1, wherein the temperature rise of the permanent magnet synchronous motor during operation is less than 125°C.

12. The method for producing non-oriented silicon steel according to any one of claims 1 to 10, characterized in that it comprises the following steps in order: smelting and foundry; Hot rolling; Tempering; Cold rolling; Continuous annealing and application of insulating coating; Here, the temperature of the continuous annealing is 700 to 1100°C.

13. 13. The method of claim 12, wherein the cold rolling step uses a single cold rolling process.

14. 13. The method according to claim 12, wherein the cold rolling step uses a process of first cold rolling, intermediate annealing and second cold rolling, and the cumulative reduction rate of the second cold rolling is 45-75%.

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