Non-oriented electromagnetic steel sheet and method of manufacturing the same

Abstract

This invention provides a non-directional electromagnetic steel sheet and a method for manufacturing the same. The method includes a hot-rolling step of a steel billet containing a specific alloy composition to obtain a hot-rolled steel sheet with better toughness; and a cold-rolling step of the hot-rolled steel sheet to obtain the non-directional electromagnetic steel sheet. This improves the yield of the non-directional electromagnetic steel sheet, and the resulting non-directional electromagnetic steel sheet has a lower iron loss value.

Description

Technical Field

[0001] This invention relates to a non-directional electromagnetic steel sheet and its manufacturing method, and more particularly to a non-directional electromagnetic steel sheet with low iron loss and high yield and its manufacturing method. Prior Technology

[0002] In recent years, driven by global efforts to conserve energy, reduce carbon emissions, and promote sustainable development, the electric vehicle industry has rapidly emerged and become an important way to reduce carbon dioxide emissions in transportation. Compared to traditional vehicles that use internal combustion engines as their power source, electric vehicles are powered by electric motors. Therefore, to improve the range of electric vehicles, the drive motors typically use non-directional electromagnetic steel sheets with low iron loss characteristics as the core material to reduce energy loss during operation.

[0003] The iron losses of nondirectional electromagnetic steel sheets mainly include hysteresis loss, eddy current loss, and abnormal eddy current loss. Eddy current loss and abnormal eddy current loss are mainly caused by eddy currents generated by electromagnetic induction, and can usually be controlled by adjusting the thickness and resistivity. Hysteresis loss refers to the energy loss required for magnetic domains with different magnetic moments in the material to unify in the same direction during magnetization. It is mainly affected by the internal microstructure of the material, such as precipitates, heterogeneous interfaces like grain boundaries, and grain orientation distribution. In addition, iron losses are also affected by the operating frequency. Eddy current loss is proportional to the square of the operating frequency, so it increases sharply under high-frequency or high-speed operating conditions.

[0004] To reduce eddy current losses in non-directional electromagnetic steel sheets operating at high frequencies, conventional methods involve increasing the silicon and aluminum content in the steel to suppress eddy current generation by increasing resistivity, thereby reducing eddy current losses. However, adding excessive amounts of silicon (e.g., about 3 wt%) and aluminum (e.g., about 0.5 wt% to about 1.5 wt%) can degrade the toughness of the hot-rolled steel sheet, making it prone to brittle fracture or breakage during cold rolling, resulting in poor yield of the non-directional electromagnetic steel sheet. Therefore, conventional techniques cannot simultaneously achieve both good magnetic properties and high yield of non-directional electromagnetic steel sheets.

[0005] In view of this, there is an urgent need to provide a method for manufacturing non-directional electromagnetic steel sheets to improve the above-mentioned shortcomings. Summary of the Invention

[0006] One aspect of the present invention is to provide a method for manufacturing non-directional electromagnetic steel sheets, which involves hot rolling a steel billet containing a specific alloy composition to obtain a hot-rolled steel sheet with better toughness, thereby improving the yield of non-directional electromagnetic steel sheets.

[0007] Another aspect of the present invention is to provide a non-directional electromagnetic steel sheet, which is manufactured using the above method.

[0008] According to the above description of the present invention, a method for manufacturing a non-directional electromagnetic steel sheet is provided. First, a steel billet is provided, wherein based on a weight of 100 wt%, the steel billet comprises 2.8 wt% to 3.8 wt% silicon, 0.3 wt% to 1.6 wt% aluminum, 0.0005 wt% to 0.003 wt% calcium, unavoidable impurities, and a balanced amount of iron, and the composition of the steel billet satisfies the following relationship (1). (1). Next, the steel billet undergoes a hot rolling process to obtain a hot-rolled steel sheet. Then, the hot-rolled steel sheet undergoes a cold rolling process to obtain a non-directional electromagnetic steel sheet.

[0009] According to one embodiment of the present invention, based on the steel billet having a weight of 100 wt%, the steel billet further comprises 0.1 wt% to 0.8 wt% of manganese and 0.01 wt% to 0.06 wt% of antimony.

[0010] According to one embodiment of the present invention, the hot rolling step includes a reheating step of the steel billet to obtain a reheated steel billet; a rolling step of the reheated steel billet to obtain a rolled steel sheet; and a coiling step of the rolled steel sheet to obtain a hot-rolled steel sheet.

[0011] According to one embodiment of the present invention, the rolling temperature of the above-mentioned rolling step is 800°C to 950°C.

[0012] According to one embodiment of the present invention, the winding temperature in the above winding step is 600°C to 750°C.

[0013] According to one embodiment of the present invention, the hot-rolled steel plate contains a variety of media, including aluminum nitride media, aluminum-magnesium oxide media, manganese sulfide media, calcium aluminate media, and calcium sulfide media.

[0014] According to one embodiment of the present invention, the various media in the above-mentioned hot-rolled steel plate satisfy the following relationship (2). (2).

[0015] According to one embodiment of the present invention, before performing the cold rolling step, the above method further includes performing an intermediate annealing treatment on the hot-rolled steel sheet to obtain an intermediate annealed steel sheet, wherein the intermediate annealing temperature of the intermediate annealing treatment is 800°C to 1050°C.

[0016] According to one embodiment of the present invention, the above method further includes performing a final annealing treatment on the non-directional electromagnetic steel sheet, wherein the final annealing temperature of the final annealing treatment is 800°C to 1000°C.

[0017] According to another aspect of the present invention, a non-directional electromagnetic steel sheet is provided, which is manufactured using the above-described method.

[0018] The method for manufacturing non-directional electromagnetic steel sheets according to this invention involves hot rolling a steel billet containing a specific alloy composition to obtain a hot-rolled steel sheet with better toughness. This avoids brittle fracture or strip breakage of the hot-rolled steel sheet during subsequent cold rolling, thereby improving the yield of non-directional electromagnetic steel sheets. Furthermore, the resulting non-directional electromagnetic steel sheets also possess low iron loss magnetic properties. Simple Explanation of the Diagram

[0019] To gain a more complete understanding of the embodiments and advantages of the present invention, please refer to the following description and corresponding drawings. It must be emphasized that the various features are not depicted to scale and are for illustrative purposes only. The relevant drawings are explained below: Figure 1 is a flowchart illustrating a method for manufacturing a non-directional electromagnetic steel sheet according to some embodiments of the present invention. Implementation

[0020] The manufacture and use of embodiments of the present invention are discussed in detail below. However, it will be understood that the embodiments provide many applicable inventive concepts that can be implemented in a wide variety of specific contexts. The specific embodiments discussed are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] Unless otherwise specified, the numerical ranges mentioned in this invention (e.g., 10% to 11% of A) include both upper and lower limits (i.e., 10% ≤ A ≤ 11%). If no lower limit is defined for a numerical range (e.g., less than 0.2% of B, or B below 0.2%), then the lower limit may be 0 (i.e., 0% ≤ B ≤ 0.2%). The terms "around," "about," "approximately," or "substantially" as used in this invention generally mean within 20%, 10%, or 5% of the stated value or range. These terms are used to illustrate and understand this invention, and not to limit it.

[0022] As described above, this invention provides a non-directional electromagnetic steel sheet and its manufacturing method. A hot-rolling step is performed on a steel billet containing a specific alloy composition to obtain a hot-rolled steel sheet with better toughness. This avoids brittle fracture or strip breakage of the hot-rolled steel sheet during subsequent cold rolling, thereby improving the yield of the non-directional electromagnetic steel sheet. Furthermore, the obtained non-directional electromagnetic steel sheet also possesses low iron loss magnetic properties.

[0023] Please refer to Figure 1, which is a flowchart illustrating a method 100 for manufacturing a non-directional electromagnetic steel sheet according to some embodiments of the present invention. First, operation 110 is performed to provide a steel billet. In some embodiments, based on a steel billet weight of 100 wt%, the steel billet contains about 2.8 wt% to about 3.8 wt% silicon, about 0.3 wt% to about 1.6 wt% aluminum, about 0.0005 wt% to about 0.003 wt% calcium, unavoidable impurities, and a balanced amount of iron.

[0024] The addition of silicon helps to increase the resistivity of non-directional electromagnetic steel sheets and reduce their eddy current losses, resulting in non-directional electromagnetic steel sheets with lower iron loss values. However, when the silicon content is too high (e.g., greater than 3.8 wt%), it leads to a deterioration in the toughness of the subsequently produced hot-rolled steel sheet, making it prone to brittle fracture or strip breakage during subsequent cold rolling steps, thus affecting the yield of non-directional electromagnetic steel sheets. Conversely, when the silicon content is too low (e.g., less than 2.8 wt%), the resistivity of the non-directional electromagnetic steel sheet cannot be effectively increased, meaning that the non-directional electromagnetic steel sheet cannot possess the magnetic properties with low iron loss.

[0025] The addition of aluminum helps to increase the resistivity of non-directional electromagnetic steel sheets and reduce their eddy current losses, resulting in non-directional electromagnetic steel sheets with low iron loss values. However, when the aluminum content is too high (e.g., greater than 1.6 wt%), it leads to a deterioration in the toughness of the subsequently produced hot-rolled steel sheet, making it prone to brittle fracture or strip breakage during subsequent cold rolling steps, thus affecting the yield of non-directional electromagnetic steel sheets. Conversely, when the aluminum content is too low (e.g., less than 0.3 wt%), the resistivity of the non-directional electromagnetic steel sheet cannot be effectively increased, meaning that the non-directional electromagnetic steel sheet cannot possess the magnetic properties of low iron loss.

[0026] The addition of calcium promotes the formation of spherical calcium sulfide media by sulfur and calcium, and inhibits the formation of elongated manganese sulfide media by sulfur and manganese. This lowers the brittle transition temperature of the subsequently produced hot-rolled steel sheet and gives it better toughness. It should be noted that the aforementioned "brittle transition temperature" refers to the temperature at which a material transitions from a ductile (tough) state to a brittle state. A lower brittle transition temperature indicates stronger resistance to low-temperature brittleness, i.e., better toughness. Since hot-rolled steel sheets with better toughness are less prone to brittle fracture or strip breakage during subsequent cold rolling, the yield of non-directional electromagnetic steel sheets can be increased.

[0027] Furthermore, calcium can also form calcium aluminate media with aluminum. Both calcium aluminate and calcium sulfide media can serve as nucleation sites for fine precipitates, thereby reducing their dispersion in the matrix and preventing them from hindering or interfering with the subsequent magnetization process. This results in a lower iron loss value for the produced non-directional electromagnetic steel sheet. Therefore, when the calcium content is too low (e.g., less than 0.0005 wt%), it is not only impossible to effectively improve the toughness of hot-rolled steel sheets and increase the yield of non-directional electromagnetic steel sheets, but it is also difficult to produce non-directional electromagnetic steel sheets with low iron loss values. However, when the calcium content is too high (e.g., greater than 0.003 wt%), coarse and unevenly distributed calcium oxide media are easily formed, leading to an increase in the iron loss value of the non-directional electromagnetic steel sheet.

[0028] In some embodiments, the composition of the steel billet satisfies the following relationship (1). (1). When the steel billet does not satisfy the relationship of equation (1), it is impossible to effectively improve the toughness of hot-rolled steel plate and increase the yield of non-directional electromagnetic steel sheet, and it is also difficult to make the non-directional electromagnetic steel sheet have a low iron loss value.

[0029] In some embodiments, the aforementioned steel billet may selectively contain about 0.1 wt% to about 0.8 wt% of manganese and about 0.01 wt% to about 0.06 wt% of antimony. When the steel billet contains manganese within the aforementioned content range, the resulting non-directional electromagnetic steel sheet can have a higher magnetic flux and a lower iron loss value. When the steel billet contains antimony within the aforementioned content range, the resulting non-directional electromagnetic steel sheet can have a higher magnetic flux.

[0030] Generally, unavoidable impurities in the aforementioned steel billet may include elements such as carbon, nitrogen, sulfur, and phosphorus. Carbon, nitrogen, sulfur, and phosphorus readily combine with other elements in the steel billet to form coarse precipitates, leading to an increase in the iron loss value of the non-directional electromagnetic steel sheet. Therefore, in some embodiments, the carbon content is preferably no more than 0.004 wt%, the nitrogen content is preferably no more than 0.003 wt%, the sulfur content is preferably no more than 0.003 wt%, and the phosphorus content is preferably no more than 0.01 wt%.

[0031] Next, as shown in Figure 1, operation 120 is performed to hot-roll the steel billet to obtain a hot-rolled steel sheet. In some embodiments, the hot-rolling step may include a reheating step of the steel billet to obtain a reheated steel billet. In some embodiments, the reheating temperature of the reheating step is from about 1050°C to about 1200°C. When the reheating temperature of the reheating step is controlled within the aforementioned range, the subsequent rolling steps can proceed smoothly, and excessive precipitates can be prevented from re-dissolving at high temperatures and re-precipitating during subsequent cooling, which would increase the iron loss value of the non-directional electromagnetic steel sheet.

[0032] Next, the hot rolling step may include a rolling step on the reheated steel billet after the reheating step to obtain a rolled steel sheet. In some embodiments, the completion rolling temperature of the rolling step is about 800°C to about 950°C. When the completion rolling temperature of the rolling step is controlled within the aforementioned range, the hot-rolled steel sheet can form a stable and sufficiently recrystallized grain structure, which is conducive to the growth of grains in the subsequent magnetically optimized orientation, thereby giving the non-directional electromagnetic steel sheet better magnetic properties.

[0033] Then, the hot rolling step may be included after the rolling step, in which the rolled steel sheet is coiled to obtain a hot-rolled steel sheet. In some embodiments, the coiling temperature of the coiling step is about 600°C to about 750°C. When the coiling temperature of the coiling step is controlled within the aforementioned range, the hot-rolled steel sheet can form a stable and sufficiently recrystallized grain structure, which is conducive to the growth of grains in the subsequent magnetically optimized orientation, thereby giving the non-directional electromagnetic steel sheet better magnetic properties.

[0034] In some embodiments, the hot-rolled steel sheet includes a variety of media, including aluminum nitride media, aluminum-magnesium oxide media, manganese sulfide media, calcium aluminate media, and calcium sulfide media.

[0035] In some embodiments, the various media in a hot-rolled steel sheet may satisfy the following relationship (2). (2). It should be noted that the density of calcium aluminate, the density of calcium sulfide, and the sum of the densities in equation (2) refer to the number of particles larger than 1 μm per unit area (number / cm2). When the various particles in the hot-rolled steel sheet satisfy the relationship in equation (2), it indicates that the hot-rolled steel sheet has sufficient calcium aluminate and calcium sulfide particles, which can effectively improve the stability of the subsequent cold rolling step and magnetization treatment, so that the obtained non-directional electromagnetic steel sheet has a higher yield and a lower iron loss value.

[0036] In some embodiments, the final thickness of the hot-rolled steel sheet is about 1.5 mm to about 2.5 mm. When the final thickness of the hot-rolled steel sheet is controlled within the aforementioned range, it can be combined with the equipment capacity of the hot rolling step and the subsequent cold rolling step to improve the efficiency of subsequent re-rolling to the finished thickness of the non-directional electromagnetic steel sheet.

[0037] Then, as shown in Figure 1, operation 130 is performed to cold roll the hot-rolled steel sheet to obtain a non-directional electromagnetic steel sheet. In some embodiments, the thickness of the non-directional electromagnetic steel sheet is from about 0.15 mm to about 0.5 mm. It should be noted that the thickness of the non-directional electromagnetic steel sheet can be varied according to product specification requirements.

[0038] In some embodiments, the hot-rolled steel sheet may be selectively subjected to intermediate annealing before the cold rolling step to obtain an intermediate-annealed steel sheet. In some embodiments, the intermediate annealing temperature is from about 800°C to about 1050°C. In some embodiments, the intermediate annealing time is from about 100 seconds to about 250 seconds. When the intermediate annealing temperature and intermediate annealing time are controlled within the aforementioned range, it is beneficial to form a moderately coarse recrystallized grain structure, thereby forming crystal nuclei with favorable magnetic orientation after the cold rolling step, so that the resulting non-directional electromagnetic steel sheet has better magnetic properties.

[0039] In some embodiments, after obtaining the non-directional electromagnetic steel sheet, a final annealing treatment may be selectively performed on the non-directional electromagnetic steel sheet. In some embodiments, the final annealing temperature is from about 800°C to about 1000°C. In some embodiments, the final annealing time is from about 60 seconds to about 250 seconds. When the final annealing temperature and final annealing time are controlled within the aforementioned ranges, it is beneficial to form a recrystallized rolled structure and coarsen the grains. This reduces the hysteresis loss of the non-directional electromagnetic steel sheet and gives the obtained non-directional electromagnetic steel sheet better magnetic properties.

[0040] The following examples illustrate the application of the present invention, but they are not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Evaluation methods 1. Methods for determining the density of media

[0041] Hot-rolled steel plates were cut into specimens approximately 20mm × 20mm in size. The surfaces of the specimens were then mechanically ground to remove the oxide layer. Next, the surfaces were polished to obtain the observation specimens. Then, quantitative analysis of various inclusions was performed using an Automated Scanning Probe Exfoliation (ASPEX) instrument. The particle size and chemical composition observed within the specimen matrix were classified and statistically analyzed. Finally, the statistical quantity of each inclusion was converted to the number of inclusions per unit area based on the observed area, which is the inclusion density (number of inclusions / cm²). 2. Method for determining the brittleness transition temperature

[0042] According to the JIS Z2202 standard, Charpy impact tests were conducted on hot-rolled steel plates at different temperatures (room temperature to 200℃) to measure the impact absorption energy of the hot-rolled steel plates at each temperature, and the transition temperature of the hot-rolled steel plates was calculated based on this. 3. Grain size measurement methods

[0043] According to the ASTM E112 standard, non-directional electromagnetic steel sheets were prepared into metallographic samples in which grain boundaries could be clearly observed, and the average grain size of each sample was calculated using the average linear intercept method. 4. Measurement method of iron loss value

[0044] Using a magnetic measurement device conforming to IEC 60404 (brand: Brockhaus Measurements, model: Measuring Unit MPG 200D), the iron loss value (W10 / 400) of a non-directional electromagnetic steel sheet was measured at a test frequency of 400 Hz and a magnetic flux density of 1.0 Tesla.

[0045] Example 1

[0046] First, a steel billet is provided. Based on a weight of 100 wt%, the steel billet of Example 1 contains 3.01 wt% silicon, 0.63 wt% aluminum, 0.16 wt% manganese, 0.0020 wt% calcium, 0.0035 wt% carbon, and 0.0014 wt% sulfur, as shown in Table 1 below. Substituting the aluminum and calcium contents of the steel billet of Example 1 into the above formula (1), the calculated X1 value is 0.52. Next, the steel billet is subjected to a hot rolling step to obtain a hot-rolled steel sheet. The hot rolling step involves reheating the steel billet to obtain a reheated steel billet. The reheating temperature of the reheating step is 1150°C. Next, the reheated steel billet is subjected to a rolling step to obtain a rolled steel sheet. The rolling temperature of the rolling step is 850°C. Then, the rolled steel sheet is subjected to a coiling step to obtain a hot-rolled steel sheet. The coiling temperature of the coiling step is 610°C. The finished thickness of the hot-rolled steel sheet was 2.0 mm. The density of the intermediate material in the hot-rolled steel sheet was then measured, and the results are shown in Table 2 below. Next, the X² value calculated by substituting the density of the calcium aluminate intermediate, the density of the calcium sulfide intermediate, and the sum of the intermediate densities into the above formula (2) was 29.2%. Furthermore, the transition temperature of the hot-rolled steel sheet was measured, and the results are shown in Table 2 below.

[0047] Next, the hot-rolled steel sheet was subjected to intermediate annealing to obtain intermediate-annealed steel sheet. The intermediate annealing temperature was 950℃, and the intermediate annealing time was 200 seconds. Then, the intermediate-annealed steel sheet was cold-rolled to obtain non-directional electromagnetic steel sheet. The thickness of the non-directional electromagnetic steel sheet was 0.25 mm. Next, the non-directional electromagnetic steel sheet was subjected to a final annealing step. The final annealing temperature was 950℃, and the final annealing time was 100 seconds. Afterward, the grain size and iron loss value of the obtained non-directional electromagnetic steel sheet were measured, and the measurement results are recorded in Table 2 below.

[0048] Examples 2, 3 and Comparative Examples 1 to 5

[0049] Examples 2, 3, and Comparative Examples 1 to 5 were manufactured using a similar method to Example 1, except that the alloy composition, densities of various media, and their X1 and X2 values ​​in the steel billet were different. The alloy composition and X1 values ​​are shown in Table 1, and will not be repeated here. Furthermore, since the total silicon and aluminum content in the steel billet affects the transition embrittlement temperature of the hot-rolled steel sheet and the grain size and iron loss value of the non-directional electromagnetic steel sheet, Examples 1, 1, and 2, containing similar total silicon and aluminum content (approximately 3.6 wt%), Examples 2, 3, and 4, containing similar total silicon and aluminum content (approximately 4.1 wt%), and Examples 3 and 5, containing similar total silicon and aluminum content (approximately 4.5 wt%), are compared below.

[0050] The measurement results of various media densities, X2 values, transition embrittlement temperatures, grain size and iron loss values ​​of the hot-rolled steel plates of Examples 2, 3 and Comparative Examples 1 to 5 are recorded in Table 2 below.

[0051] Table 1 Total content of silicon and aluminum (wt%) Silicon (wt%) aluminum (wt%) calcium (wt%) manganese (wt%) carbon (wt%) sulfur (wt%) X1 Example 1 3.64 3.01 0.63 0.0020 0.16 0.0035 0.0014 0.52 Comparative Example 1 3.54 2.97 0.57 0.0003 0.16 0.0034 0.0008 0.90 Comparative Example 2 3.66 3.03 0.63 0.0000 0.14 0.0026 0.0012 1.00 Actual example 2 4.17 3.12 1.05 0.0021 0.18 0.0028 0.0007 0.67 Comparative Example 3 4.17 3.10 1.07 0.0003 0.17 0.0030 0.0010 0.95 Comparative Example 4 4.14 3.08 1.06 0.0007 0.21 0.0032 0.0020 0.88 Actual example 3 4.53 3.17 1.36 0.0018 0.18 0.0035 0.0003 0.77 Comparative Example 5 4.52 3.04 1.48 0.0001 0.18 0.0018 0.0020 0.99

[0052] Table 2 Density of media (number of media / cm2) X2 (%) Brittleness transition temperature (°C) Grain size (μm) Iron loss value W10 / 400 (W / kg) Aluminum nitride Calcium aluminate Aluminum-magnesium oxides Calcium sulfide Manganese sulfide The sum of the densities of matter Example 1 2664 161 734 1240 0 4799 29.2 50 140 12.43 Comparative Example 1 1121 50 1630 4 60 2815 1.9 60 126 12.98 Comparative Example 2 2024 2 1157 2 48 3232 0.1 63 103 12.62 Example 2 2842 301 197 951 0 4291 29.2 65 136 12.05 Comparative Example 3 1479 19 380 7 232 2116 1.2 73 105 12.35 Comparative Example 4 3116 5 539 37 twenty two 3718 1.1 75 112 12.19 Actual example 3 1354 11 57 159 1 1581 10.8 95 119 11.90 Comparative Example 5 2328 3 316 10 117 2773 0.5 115 97 11.88

[0053] As shown in Tables 1 and 2, compared with Comparative Examples 1 to 5, the hot-rolled steel sheets of Examples 1 to 3 have lower brittle transition temperatures, and the non-directional electromagnetic steel sheets of Examples 1 to 3 have larger grain sizes. Therefore, under conditions containing similar total silicon and aluminum content, when the silicon, aluminum, and calcium content in the steel billet is controlled within a specific range, and the composition of the steel billet satisfies the relationship in Equation (1), not only can the brittle transition temperature of the hot-rolled steel sheet be effectively reduced, thus improving the yield of the non-directional electromagnetic steel sheet, but the resulting non-directional electromagnetic steel sheet can also have a larger grain size and a lower iron loss value. Furthermore, when the densities of various media in the hot-rolled steel sheet satisfy Equation (2), the stability of the cold rolling step and magnetization treatment can be further improved, resulting in a higher yield and a lower iron loss value for the resulting non-directional electromagnetic steel sheet.

[0054] Besides the silicon and aluminum content in the steel billet, the carbon content also affects the iron loss value of the resulting non-directional electromagnetic steel sheet. Generally speaking, the higher the carbon content, the higher the iron loss value. As shown in Tables 1 and 2, compared with Comparative Examples 1 and 2, which have similar carbon contents, the non-directional electromagnetic steel sheet of Example 1 has a lower iron loss value, and compared with Comparative Examples 3 and 4, which have similar carbon contents, the non-directional electromagnetic steel sheet of Example 2 also has a lower iron loss value. However, compared with Comparative Example 5, which contains a lower carbon content, the non-directional electromagnetic steel sheet of Example 3, which contains a significantly higher carbon content, still has an iron loss value similar to that of Comparative Example 5. It can be seen that Examples 1 to 3 contain specific silicon, aluminum, and calcium contents, and the composition of the steel billet satisfies Equation (1), thus reducing the iron loss value of the non-directional electromagnetic steel sheet.

[0055] As can be seen from the above embodiments, the manufacturing method of the non-directional electromagnetic steel sheet of the present invention involves hot rolling a steel billet containing a specific alloy composition to obtain a hot-rolled steel sheet with better toughness. This avoids brittle fracture or strip breakage of the hot-rolled steel sheet during subsequent cold rolling, thereby improving the yield of the non-directional electromagnetic steel sheet. Furthermore, the obtained non-directional electromagnetic steel sheet also possesses low iron loss magnetic properties.

[0056] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the art to which this invention pertains may make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0057] 100: Method 110, 120, 130: Operation

[0058] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A method for manufacturing a non-directional electromagnetic steel sheet, comprising: A steel billet is provided, wherein, based on a weight of 100 wt%, the steel billet comprises: 2.8 wt% to 3.8 wt% silicon; 0.3 wt% to 1.6 wt% aluminum; 0.0005 wt% to 0.003 wt% calcium; unavoidable impurities; and a balanced amount of iron, and the composition of the steel billet satisfies the following relationship (1); the steel billet is subjected to a hot rolling step to obtain a hot-rolled steel sheet; and the hot-rolled steel sheet is subjected to a cold rolling step to obtain the non-directional electromagnetic steel sheet.

2. A method for manufacturing a non-directional electromagnetic steel sheet as described in claim 1, wherein, based on a steel billet weight of 100 wt%, the steel billet further comprises: 0.1 wt% to 0.8 wt% manganese; And 0.01 wt% to 0.06 wt% of antimony.

3. A method for manufacturing a non-directional electromagnetic steel sheet as described in claim 1, wherein the hot rolling step includes: The steel billet is subjected to a reheating step to obtain a reheated steel billet; The reheated steel billet is subjected to a rolling step to obtain a rolled steel sheet; and the rolled steel sheet is subjected to a coiling step to obtain the hot-rolled steel sheet.

4. A method for manufacturing non-directional electromagnetic steel sheets as described in claim 3, wherein the rolling temperature of the rolling step is 800°C to 950°C.

5. The method for manufacturing a non-directional electromagnetic steel sheet as described in claim 3, wherein the winding temperature of the winding step is 600°C to 750°C.

6. A method for manufacturing a non-directional electromagnetic steel sheet as claimed in claim 1, wherein the hot-rolled steel sheet comprises a plurality of media, and the media include aluminum nitride media, aluminum-magnesium oxide media, manganese sulfide media, calcium aluminate media, and calcium sulfide media.

7. A method for manufacturing a non-directional electromagnetic steel sheet as described in claim 6, wherein the media in the hot-rolled steel sheet satisfy the following relationship (2), (2).

8. The method for manufacturing a non-directional electromagnetic steel sheet as described in claim 1, further comprising, prior to the cold rolling step: The hot-rolled steel sheet is subjected to an intermediate annealing treatment to obtain an intermediate annealed steel sheet, wherein the intermediate annealing temperature of the intermediate annealing treatment is 800℃ to 1050℃.

9. The method for manufacturing the non-directional electromagnetic steel sheet as described in claim 1 further includes: The non-directional electromagnetic steel sheet is subjected to a final annealing treatment, wherein the final annealing temperature is 800°C to 1000°C.

10. A non-directional electromagnetic steel sheet, which is manufactured using the manufacturing method of the non-directional electromagnetic steel sheet described in any one of claims 1 to 9.

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