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

Abstract

The present invention relates to a method for manufacturing a non-oriented electrical steel sheet, comprising: a hot rolling step of manufacturing a hot-rolled sheet by hot rolling a slab comprising, in wt%, silicon (Si): 2.8 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.5 wt%, aluminum (Al): 0.5 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.003 wt%, sulfur (S): greater than 0 and less than or equal to 0.002 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, nitrogen (N): greater than 0 and less than or equal to 0.002 wt%, titanium (Ti): greater than 0 and less than or equal to 0.002 wt%, and the remainder being iron (Fe) and unavoidable impurities; a hot rolling annealing step of manufacturing a hot-rolled annealed sheet by hot rolling the hot-rolled sheet; and a cold rolling step of manufacturing a cold-rolled sheet by cold rolling the hot-rolled annealed sheet. A method for manufacturing a non-oriented electrical steel sheet is provided, comprising: a cold rolling annealing step of manufacturing a cold rolling annealed sheet by cold rolling annealing the cold rolling sheet; wherein the cold rolling annealing temperature (T) and the cold rolling annealing time (t) in the cold rolling annealing step satisfy the relationship 1 (3.2 < (T*t0.5) / 1000 < 8.0).

Description

Technology Field

[0001] The present invention relates to a non-oriented electrical steel sheet and a method for manufacturing a non-oriented electrical steel sheet. Background Technology

[0002] Due to policies aimed at reducing carbon dioxide (CO2) emissions to prevent global warming, existing internal combustion engine vehicles are being rapidly replaced by eco-friendly vehicles (hybrid vehicles (HEV), electric vehicles (EV), etc.), particularly electric vehicles (EV).

[0003] In line with the increasing demand for electric vehicles (EVs), the energy conversion efficiency of drive motors for EVs is being improved, and to this end, excellent magnetic properties of motor core materials are required.

[0004] Non-oriented electrical steel sheets used as motor core materials play a role in converting electrical energy into mechanical energy in rotating machinery, and for energy saving, it is important to possess magnetic properties, namely low iron loss and high magnetic flux density.

[0005] The magnetic properties of electrical steel sheets are influenced by the structure of magnetic domains. In this context, a magnetic domain refers to a group of atoms where the magnetic moments of the atoms are aligned in one direction.

[0006] When an external magnetic field is applied, the domain walls, which are the boundaries of the magnetic domains, move, causing the entire steel plate to merge into a single magnetic domain. The movement of the domain walls can be influenced by the magnetic domain structure in the absence of an external magnetic field. The problem to be solved

[0007] Embodiments of the present invention can provide a non-oriented electrical steel sheet with improved magnetic properties and a method for manufacturing the same. means of solving the problem

[0008] One embodiment of the present invention is a method for manufacturing a non-oriented electrical steel sheet, comprising: a hot rolling step of manufacturing a hot-rolled sheet by hot rolling a slab comprising, in wt%, silicon (Si): 2.8 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.5 wt%, aluminum (Al): 0.5 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.003 wt%, sulfur (S): greater than 0 and less than or equal to 0.002 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, nitrogen (N): greater than 0 and less than or equal to 0.002 wt%, titanium (Ti): greater than 0 and less than or equal to 0.002 wt%, and the remainder being iron (Fe) and unavoidable impurities; and a hot rolling annealing step of manufacturing a hot-rolled annealed sheet by hot rolling annealing the hot-rolled sheet. The method comprises: a cold rolling step for manufacturing a cold rolled plate by cold rolling the hot-rolled annealed plate; and a cold rolling annealing step for manufacturing a cold-rolled annealed plate by cold rolling annealing the cold rolled plate; wherein the cold rolling annealing temperature (T) and the cold rolling annealing time (t) in the cold rolling annealing step are given by the relationship 1(3.2 < (T*t 0.5 A method for manufacturing a non-oriented electrical steel sheet satisfying ) / 1000 < 8.0 is provided.

[0009] In this embodiment, the cold rolling annealing temperature may be 950°C to 1100°C.

[0010] In this embodiment, the cold rolling annealing time may be 10s to 70s.

[0011] In this embodiment, the cold rolling annealing step may be performed in an atmosphere having a hydrogen fraction of 20% or more and 100% or less and the remainder being nitrogen.

[0012] In this embodiment, the ND / / of the non-oriented electrical steel sheet <001> The average magnetic domain width of the crystal grains can be 10㎛ to 50㎛.

[0013] In this embodiment, the iron loss (W of the non-oriented electrical steel sheet) 10 / 400 The standard may be 12.5 W / kg or less.

[0014] In this embodiment, the slab may further contain 0.005 wt% to 0.05 wt% of tin (Sn) and antimony (Sb) in total.

[0015] One embodiment of the present invention is a non-oriented electrical steel sheet comprising, in wt%, silicon (Si): 2.8 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.5 wt%, aluminum (Al): 0.5 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.003 wt%, sulfur (S): greater than 0 and less than or equal to 0.002 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, nitrogen (N): greater than 0 and less than or equal to 0.002 wt%, titanium (Ti): greater than 0 and less than or equal to 0.002 wt%, and the remainder being iron (Fe) and unavoidable impurities, wherein the ND / / of the non-oriented electrical steel sheet <001> A non-oriented electrical steel sheet is provided, wherein the average magnetic domain width of the crystal grains is 10㎛ to 50㎛.

[0016] In this embodiment, the non-oriented electrical steel sheet may further contain 0.005 wt% to 0.05 wt% of tin (Sn) and antimony (Sb) in total.

[0017] In this embodiment, the iron loss (W of the non-oriented electrical steel sheet) 10 / 400 The standard may be 12.5 W / kg or less.

[0018] Other aspects, features, and advantages other than those described above will become clear from the specific details, claims, and drawings for implementing the invention below. Effects of the invention

[0019] According to one embodiment of the present invention as described above, the magnetic properties of a non-oriented electrical steel sheet can be improved. Of course, the scope of the present invention is not limited by this effect. Brief explanation of the drawing

[0020] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention. FIG. 2 is an ND / / of a non-oriented electrical steel sheet according to one embodiment of the present invention. <001> This is a diagram schematically illustrating the width of the magnetic domains of the crystal grains. Specific details for implementing the invention

[0021] The present invention is capable of various modifications and may have various embodiments; specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention, and the methods for achieving them, will become clear by referring to the embodiments described below in detail together with the drawings. However, the present invention is not limited to the embodiments disclosed below but can be implemented in various forms.

[0022] In the following embodiments, terms such as first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0023] In the following examples, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0024] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0025] In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, and therefore the present invention is not necessarily limited to what is illustrated.

[0026] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

[0027] In this specification, "A and / or B" indicates the case where it is A, B, or both A and B. And, "at least one of A and B" indicates the case where it is A, B, or both A and B.

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. When describing with reference to the drawings, identical or corresponding components are given the same reference numerals, and redundant descriptions thereof will be omitted.

[0029] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0030] Referring to FIG. 1, a method for manufacturing a non-oriented electrical steel sheet may include a hot rolling step (S100), a hot rolling annealing step (S200), a cold rolling step (S300), and a cold rolling annealing step (S400).

[0031] In the hot rolling step (S100), the slab may be reheated, then hot-rolled at a predetermined finishing rolling temperature, and then cooled and coiled. At this time, in the method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention, the semi-finished product subject to hot rolling may be a slab. The slab in the semi-finished product state can be obtained through a continuous casting process after obtaining molten steel of a predetermined composition through a steelmaking process.

[0032] In one embodiment, the slab may contain silicon (Si), manganese (Mn), aluminum (Al), carbon (C), sulfur (S), phosphorus (P), nitrogen (N), titanium (Ti), the remainder being iron (Fe) and unavoidable impurities. Additionally, the slab may contain at least one of tin (Sn) and antimony (Sb).

[0033] Specifically, the slab may contain, in wt%, silicon (Si): 2.8 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.5 wt%, aluminum (Al): 0.5 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.003 wt%, sulfur (S): greater than 0 and less than or equal to 0.002 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, nitrogen (N): greater than 0 and less than or equal to 0.002 wt%, titanium (Ti): greater than 0 and less than or equal to 0.002 wt%, and the remainder may contain iron (Fe) and unavoidable impurities. Additionally, the slab may contain tin (Sn) and antimony (Sb) in total of 0.005 wt% to 0.05 wt%.

[0034] Silicon (Si) can be an element that increases the resistivity of the manufactured non-oriented electrical steel sheet and lowers iron loss. Silicon (Si) may be included in an amount of 2.8 wt% to 3.8 wt%. If silicon (Si) is included in an amount less than 2.8 wt%, iron loss reduction in the high-frequency region may be insufficient. That is, if silicon (Si) is included in an amount less than 2.8 wt%, it may be difficult to obtain low iron loss. If silicon (Si) exceeds 3.8 wt%, cold rolling performance and punchability may be inferior.

[0035] Manganese (Mn) can increase the resistivity of non-oriented electrical steel sheets manufactured together with silicon and lower iron loss. Additionally, manganese (Mn) can form sulfide inclusions (e.g., MnS) with sulfur (S). Manganese (Mn) may be included in an amount of 0.2 wt% to 0.5 wt%. If manganese (Mn) is included in an amount less than 0.2 wt%, the above-mentioned effects cannot be expected. If manganese (Mn) is included in an amount greater than 0.5 wt%, sulfide inclusions (e.g., MnS) may precipitate finely, which may increase iron loss.

[0036] Aluminum (Al) can increase the resistivity of non-oriented electrical steel sheets manufactured together with silicon, thereby reducing iron loss. Additionally, aluminum (Al) can form nitride inclusions (e.g., AlN) with nitrogen (N). Aluminum (Al) may be included in an amount of 0.5 wt% to 1.5 wt%. If the aluminum (Al) content is less than 0.5 wt%, the low amount of added aluminum (Al) results in insufficient resistivity, which may increase iron loss in the high-frequency range. On the other hand, if the aluminum (Al) content exceeds 1.5 wt%, problems such as nozzle clogging may occur during the continuous casting process.

[0037] Since carbon (C) can form carbides such as TiC and have an adverse effect on magnetism, it may be desirable to have a lower carbon content in the slab (or non-oriented electrical steel sheet). Carbon (C) may be included in an amount greater than 0 and less than or equal to 0.003 wt%. If carbon is included in an amount greater than 0.003 wt%, it may cause self-aging, which can degrade the magnetic properties of the manufactured non-oriented electrical steel sheet. If carbon is included in an amount less than or equal to 0.003 wt%, the self-aging phenomenon may be suppressed.

[0038] Sulfur (S) is an element that can adversely affect magnetism by forming sulfides (e.g., MnS, TiS, etc.), so it may be desirable to have a low sulfur (S) content in the slab (or non-oriented electrical steel sheet). Sulfur (S) may be included in an amount greater than 0 and less than or equal to 0.002 wt%. If sulfur (S) is included in an amount greater than 0.002 wt%, precipitates such as MnS and TiS may be formed, which may increase iron loss and inhibit grain growth.

[0039] Phosphorus (P) is a grain boundary segregation element and can be a component that develops texture. Phosphorus (P) may be included in an amount greater than 0 and less than or equal to 0.015 wt%. If phosphorus (P) is included in an amount greater than 0.015 wt%, grain growth may be inhibited due to the segregation effect, magnetic properties may be degraded, and cold rolling performance may be reduced.

[0040] Nitrogen (N) is an element that can adversely affect magnetism by forming nitrides (e.g., AlN, TiN, etc.), so it may be desirable to have a low nitrogen content in the slab (or non-oriented electrical steel sheet). Nitrogen (N) may be included in an amount greater than 0 and less than or equal to 0.002 wt%. If nitrogen (N) is included in an amount greater than 0.002 wt%, precipitates such as AlN and TiN may be formed, which may increase iron loss and inhibit grain growth.

[0041] Titanium (Ti) can inhibit grain growth by forming fine precipitates such as TiC, TiN, and TiS. Since magnetic properties deteriorate as titanium (Ti) is added, it may be desirable to add titanium (Ti) as low as possible. Titanium (Ti) may be included in an amount greater than 0 and less than or equal to 0.002 wt%. If titanium is included in an amount greater than 0.002 wt%, it can inhibit grain growth by forming fine precipitates such as TiC, TiN, and TiS, and magnetic properties may deteriorate.

[0042] Tin (Sn) and antimony (Sb) can serve as surface precipitation elements that concentrate in the surface layer of the steel sheet to inhibit nitrogen adsorption and nitride formation, thereby reducing iron loss. Tin (Sn) and antimony (Sb) may be included in a total amount of 0.005 wt% to 0.05 wt%. If the sum of the contents of tin (Sn) and antimony (Sb) is less than 0.005 wt%, the effect of inhibiting the formation of the nitride layer may be negligible. If the sum of the contents of tin (Sn) and antimony (Sb) exceeds 0.05 wt%, the grain boundaries may become embrittled, raising concerns about fracture during cold rolling and potentially reducing fatigue resistance.

[0043] In the hot rolling step (S100), the slab can be reheated, and then the reheated slab can be hot-rolled to produce a hot-rolled plate. For example, the slab on which the hot rolling step (S100) is performed can be called a hot-rolled plate.

[0044] In the hot rolling step (S100), the slab may be reheated. At this time, the slab may have a width of 900 mm or more and a thickness of 200 mm to 300 mm. The slab reheating temperature in the hot rolling step (S100) may be 1000°C to 1180°C. If the slab reheating temperature is less than 1000°C, it may be difficult to perform hot rolling. On the other hand, if the slab reheating temperature exceeds 1180°C, AlN may melt and finely reprecipitate in subsequent processes, which may increase iron loss. Therefore, if the slab reheating temperature in the hot rolling step (S100) satisfies 1000°C to 1180°C, a decrease in rollability can be prevented and a deterioration in magnetic properties can be prevented.

[0045] The hot rolling step (S100) can finish rolling the slab at a predetermined finish rolling temperature. At this time, the finish rolling temperature may be 800°C to 900°C.

[0046] In addition, the hot rolling step (S100) may cool the hot-rolled slab to a predetermined coiling temperature (CT) and coil it. At this time, the coiling temperature may be 550°C to 650°C. If the coiling temperature is below 550°C, brittleness increases, and plate breakage may occur during coiling. On the other hand, if the coiling temperature exceeds 650°C, fine AlN may be formed during coiling, which may increase iron loss.

[0047] The thickness of the hot-rolled plate produced through the hot rolling step (S100) may be 1.6 mm to 2.3 mm. At this time, if the thickness of the hot-rolled plate exceeds 2.3 mm, the cold rolling reduction rate increases, which may result in a deterioration of the texture.

[0048] A hot rolling annealing step (S200) may be performed after the hot rolling step (S100). A hot-rolled plate in which the hot rolling annealing step (S200) has been performed may be called a hot-rolled annealed plate. The hot rolling annealing step (S200) may be performed under conditions where the heating rate is 10℃ / s or higher, the holding temperature (e.g., hot rolling annealing temperature) is 900℃ to 1100℃, the holding time (e.g., hot rolling annealing time) is 30s to 90s, and the cooling rate is 20℃ / s or higher. Specifically, in the hot rolling annealing step (S200), the hot rolling plate is heated at a heating rate of 10°C / s or more, the heated hot rolling plate is maintained at a temperature of 900°C to 1100°C (e.g., hot rolling annealing temperature) for a time of 30 s to 90 s (e.g., annealing), and can be cooled at a cooling rate of 20°C / s or more. At this time, the hot rolling annealing step (S200) can be performed in an atmosphere where the nitrogen fraction is 80% to 100% and the remainder is atmospheric.

[0049] A cold rolling step (S300) may be performed after the hot rolling annealing step (S200). The hot-rolled annealed plate after the cold rolling step (S300) may be called a cold-rolled plate. In the cold rolling step (S300), the hot-rolled annealed plate may be cold-rolled with a reduction rate of 84% to 94%. The thickness of the cold-rolled plate after the cold rolling step (S300) may be 0.15mm to 0.30mm.

[0050] A cold rolling annealing step (S400) may be performed after the cold rolling step (S300). A cold rolled plate in which the cold rolling annealing step (S400) has been performed may be called a cold rolling annealing plate. The cold rolling annealing step (S400) may be performed under conditions where the heating rate is 10℃ / s or higher, the holding temperature (e.g., cold rolling annealing temperature) is 950℃ to 1100℃, the holding time (e.g., cold rolling annealing time) is 10s to 70s, and the cooling rate is 10℃ / s or higher. Specifically, in the cold rolling annealing step (S400), the cold rolled sheet is heated at a heating rate of 10°C / s or more, the heated cold rolled sheet is maintained at a temperature of 950°C to 1100°C (e.g., cold rolling annealing temperature) for a time of 10 s to 70 s (e.g., annealing), and can be cooled at a cooling rate of 10°C / s or more. At this time, the cold rolling annealing step (S400) can be performed in an atmosphere equipped with a hydrogen fraction of 20% or more and 100% or less and the remainder being nitrogen. If the hydrogen fraction is less than 20%, nitrogen (N) may penetrate to the surface and form nitrides, which may increase iron loss. If the holding temperature (e.g., cold rolling annealing temperature) is less than 950°C, the size of the magnetic domains decreases rapidly, and the manufactured non-oriented electrical steel sheet may have high iron loss. If the holding temperature (e.g., cold rolling annealing temperature) exceeds 1100℃, it may be difficult to proceed with heat treatment due to problems such as deformation of the steel sheet during the process.

[0051] In one embodiment, a non-oriented electrical steel sheet can be manufactured through a hot rolling step (S100) to a cold rolling annealing step (S400). Additionally, although not illustrated, a coating step for forming an insulating coating layer on the non-oriented electrical steel sheet can be performed after the cold rolling annealing step (S400). By forming an insulating coating layer on the non-oriented electrical steel sheet through the coating step, punchability can be improved and insulation can be ensured.

[0052] The non-oriented electrical steel sheet produced by the aforementioned manufacturing method may contain silicon (Si), manganese (Mn), aluminum (Al), carbon (C), sulfur (S), phosphorus (P), nitrogen (N), titanium (Ti), the remainder being iron (Fe) and unavoidable impurities. Additionally, the non-oriented electrical steel sheet may additionally contain at least one of tin (Sn) and antimony (Sb).

[0053] Specifically, the non-oriented electrical steel sheet may contain, in wt%, silicon (Si): 2.8 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.5 wt%, aluminum (Al): 0.5 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.003 wt%, sulfur (S): greater than 0 and less than or equal to 0.002 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, nitrogen (N): greater than 0 and less than or equal to 0.002 wt%, titanium (Ti): greater than 0 and less than or equal to 0.002 wt%, and the remainder may contain iron (Fe) and unavoidable impurities. Additionally, the non-oriented electrical steel sheet may contain tin (Sn) and antimony (Sb) in total of 0.005 wt% to 0.05 wt%.

[0054] In one embodiment, the non-oriented electrical steel sheet has an iron loss (W) of 12.5 W / kg or less. 10 / 400 It can have a standard). In this case, iron loss (W 10 / 400 ) was measured according to the test method specified in the IEC 60404-2 international standard and can be measured using the Epstein frame test method.

[0055] FIG. 2 is an ND / / of a non-oriented electrical steel sheet according to one embodiment of the present invention. <001> This is a diagram schematically illustrating the width of the magnetic domains of the crystal grains.

[0056] Referring to Fig. 2, the non-oriented electrical steel sheet is ND / / <001> The average magnetic domain width (W) of the crystal grains may be 10 μm to 50 μm. In this case, the average magnetic domain width may correspond to the average of the width of the smallest magnetic domain and the width of the largest magnetic domain within the crystal grain. In this case, the average magnetic domain width may be measured using the Neoark BH-782PI instrument.

[0057] If the size of magnetic domains within non-oriented electrical steel is small, hysteresis loss increases, which can increase the total iron loss. If the size of magnetic domains within non-oriented electrical steel is large, eddy current loss increases, which can increase the total iron loss. Therefore, there may exist an optimal magnetic domain size for non-oriented electrical steel to have low iron loss.

[0058] ND of non-oriented electrical steel sheets <001> As the magnetic domain width of the grains increases, iron loss decreases; however, after reaching the minimum iron loss, iron loss may increase as the magnetic domain width increases. Specifically, the ND / / of non-oriented electrical steel sheets <001> As the magnetic domain width of the grains increases, hysteresis loss decreases and iron loss decreases, but after reaching the minimum iron loss, as the magnetic domain width increases, eddy current loss increases and iron loss may increase. Therefore, there may exist an optimal magnetic domain width for non-oriented electrical steel sheets to have low iron loss.

[0059] ND of non-oriented electrical steel sheets <001> If the average magnetic domain width of the grains is less than 10㎛, iron loss may increase due to hysteresis loss. In addition, non-oriented electrical steel sheets ND / / <001> If the average magnetic domain width of the grains exceeds 50㎛, iron loss may increase due to eddy current losses. ND / / of non-oriented electrical steel sheets <001> When the average magnetic domain width of the grains satisfies 10㎛ to 50㎛, the non-oriented electrical steel sheet can have low iron loss. For example, the ND / / of the non-oriented electrical steel sheet <001> When the average magnetic domain width of the grains satisfies 10㎛ to 50㎛, the non-oriented electrical steel sheet has an iron loss (W) of 12.5 W / kg or less. 10 / 400 Can have a standard.

[0060] The inventors [have] that when the cold rolling annealing temperature (T) and the cold rolling annealing time (t) in the cold rolling annealing step (S400) satisfy the following relationship 1, the ND / / of the non-oriented electrical steel sheet <001> The average magnetic domain width of the grains may be 10㎛ to 50㎛, and the non-oriented electrical steel sheet has an iron loss (W) of 12.5 W / kg or less. 10 / 400 It was confirmed that it has the standard.

[0061] <Relation Equation 1>

[0062] 3.2 < (T*t 0.5 ) / 1000 < 8.0

[0063] In Equation 1, T is the cold rolling annealing temperature (°C) and t is the cold rolling annealing time (s). For example, if the cold rolling annealing temperature (°C) is 1000°C, T can be 1000, and if the cold rolling annealing time (s) is 50s, t can be 50.

[0064] In one embodiment, when the cold rolling annealing temperature (T) in the cold rolling annealing step (S400) satisfies 950°C to 1100°C, the cold rolling annealing time (t) satisfies 10s to 70s, and the cold rolling annealing temperature (T) and the cold rolling annealing time (t) satisfy Equation 1, the ND / / of the non-oriented electrical steel sheet <001> The average magnetic domain width of the grains may be 10㎛ to 50㎛, and the non-oriented electrical steel sheet has an iron loss (W) of 12.5 W / kg or less. 10 / 400 Can have a standard.

[0065] Experimental Example

[0066] The present invention will be explained in more detail below through experimental examples. However, the following experimental examples are intended to explain the present invention more specifically, and the scope of the present invention is not limited by the following experimental examples. The following experimental examples may be appropriately modified or changed by those skilled in the art within the scope of the present invention.

[0067] Table 1 below shows the components of Examples 1 to 12 and Comparative Examples 1 to 11 of the present invention. Examples 1 to 12 and Comparative Examples 1 to 11 may be provided with the components listed in Table 1, and Examples 1 to 12 and Comparative Examples 1 to 11 may include the remainder of iron (Fe) and unavoidable impurities.

[0068] The non-oriented electrical steel sheets of Examples 1 to 12 and Comparative Examples 1 to 11 were manufactured by the following method.

[0069] A slab was prepared having the composition shown in Table 1 and the remainder being iron (Fe) and unavoidable impurities. The slab was then hot-rolled to produce a hot-rolled plate with a thickness of 2.0 mm. At this time, the hot rolling was performed under conditions of a reheat temperature of 1150°C, a finish rolling temperature of 890°C, and a coiling temperature of 640°C.

[0070] The obtained hot-rolled plate was hot-rolled and annealed to produce a hot-rolled annealed plate. At this time, the hot-rolled annealing was performed under conditions of heating rate: 12℃ / s, hot-rolled annealing temperature: 980℃, holding time: 80s, and cooling rate: 30℃ / s.

[0071] The obtained hot-rolled annealed plate was cold-rolled to produce a cold-rolled plate with a thickness of 0.25 mm. At this time, the cold rolling was performed under conditions of a reduction rate of 93%.

[0072] Subsequently, the obtained cold-rolled sheet was subjected to cold-roll annealing and coating to produce a final product (e.g., non-oriented electrical steel sheet). At this time, cold-roll annealing was performed under conditions of a heating rate of 15℃ / s and a cooling rate of 10℃ / s. Cold-roll annealing was carried out in a mixed atmosphere of 40% hydrogen and 60% nitrogen. In addition, cold-roll annealing was performed under the conditions of the cold-roll annealing temperature and holding time (e.g., cold-roll annealing time) listed in Table 2 below.

[0073] ND / / <001> Average domain width of the grain

[0074] Using Neoark's BH-782PI equipment ND / / <001> The average domain width of the grains was measured, and DomainImagingR2 was used as the observation software.

[0075] Specifically, using the equipment and software described above, images were taken in 10 areas with a width x height of 20mm x 20mm, and the spacing of the magnetic domains was measured using ImageJ software for each of the captured images. In addition, the average magnetic domain width was calculated using the width of the smallest and largest magnetic domains measured.

[0076] High frequency iron loss W 10 / 400

[0077] Iron loss (W 10 / 400) was measured according to the test method specified in the IEC 60404-2 international standard, and was measured using the Epstein frame test method.

[0078] Specifically, a specimen (e.g., non-oriented electrical steel sheet) was cut to a length of (300±0.5) mm and a width of (30±0.2) mm to prepare a test specimen for measuring iron loss.

[0079] Half of the test specimens for measuring iron loss during cutting were cut in a direction parallel to the rolling direction (RD, Rolling direction), and the other half were cut in a direction perpendicular to the rolling direction (TD, Transverse direction).

[0080] Afterwards, four times the number of prepared iron loss measurement specimens were prepared and measured after stacking them in a double-overlapping manner. At this time, the iron loss measurement specimens were measured by inserting them into a coil former with the same cut iron loss measurement specimens facing each other.

[0081] Ingredients (wt%) Si Mn Al C S P N Ti Sn 3.5 0.3 0.9 0.0021 0.0017 0.0082 0.0017 0.0015 0.03

[0082] division Cold rolling annealing temperature (°C) Cold rolling annealing time (s) Value of Equation 1 ND / / <001> Average domain width of the grain (㎛) High frequency iron loss W 10 / 400 (W / kg) Example 1 950 30 5.2 26.9 11.94 Example 2 950 60 7.4 45.6 12.34 Example 3 950 70 7.9 49.0 12.45 Example 4 1000 15 3.9 15.9 12.31 Example 5 1000 20 4.5 20.9 12.14 Example 6 1000 30 5.5 29.5 11.86 Example 7 1000 60 7.7 48.2 12.42 Example 8 1050 10 3.3 10.8 12.48 Example 9 1050 30 5.8 32.0 11.89 Example 10 1100 10 3.5 12.5 12.43 Example 11 1100 30 6.0 33.7 11.94 Example 12 1100 50 7.8 49.0 12.45 Comparative Example 1 930 10 2.9 2.2 13.52 Comparative Example 2 930 30 5.1 4.5 13.22 Comparative Example 3 930 60 7.2 5.1 12.88 Comparative Example 4 950 10 3.0 8.2 12.57 Comparative Example 5 950 80 8.5 54.95 12.65 Comparative Example 6 1000 10 3.2 9.9 12.51 Comparative Example 7 1000 70 8.4 54.1 12.62 Comparative Example 8 1050 5 2.3 3.9 12.78 Comparative Example 9 1050 60 8.1 51.6 12.51 Comparative Example 10 1100 5 2.5 4.0 12.75 Comparative Example 11 1100 60 8.5 54.9 12.65

[0083] Referring to Tables 1 and 2, for Examples 1 to 12, when the cold rolling annealing temperature (T) satisfies 950°C to 1100°C and the cold rolling annealing time (t) satisfies 10s to 70s, and the cold rolling annealing temperature (T) and the cold rolling annealing time (t) satisfy Equation 1, the ND / / of the non-oriented electrical steel sheet <001> The average magnetic domain width of the grains is 10㎛ to 50㎛, and the non-oriented electrical steel sheet has an iron loss (W) of 12.5 W / kg or less. 10 / 400 It can be confirmed that it has a standard.

[0084] Comparative Example 1 is a case where the cold rolling annealing temperature (T) is less than 950℃ and the value of Equation 1 is 3.2 or less, wherein the cold rolling annealing temperature (T) is less than 950℃ and the value of Equation 1 is 3.2 or less, ND / / <001> The average domain width of the grains decreases, so ND / / <001> It can be confirmed that the average magnetic domain width of the crystal grains is less than 10㎛ and has an iron loss of more than 12.5 W / kg.

[0085] Comparative Examples 2 and 3 are cases where the cold rolling annealing temperature (T) is less than 950℃, and when the cold rolling annealing temperature (T) is less than 950℃, the cold rolling annealing temperature is too low ND / / <001> The average domain width of the grains decreases, so ND / / <001> It can be confirmed that the average magnetic domain width of the crystal grains is less than 10㎛ and has an iron loss of more than 12.5 W / kg.

[0086] Comparative Examples 4 and 6 are cases where the value of Equation 1 is 3.2 or less, and even if the cold rolling annealing temperature (T) and cold rolling annealing time (t) satisfy the required conditions, the value of Equation 1 is 3.2 or less, ND / / <001> It can be confirmed that the average magnetic domain width of the crystal grains is less than 10㎛ and has an iron loss of more than 12.5 W / kg.

[0087] Comparative Example 5 is a case where the cold rolling annealing time (t) exceeds 70s and the value of Equation 1 is 8.0 or higher, wherein when the cold rolling annealing time (t) exceeds 70s ND / / <001> The average domain width of the grains increases, so ND / / <001> It can be confirmed that the average magnetic domain width of the crystal grains is greater than 50㎛ and has an iron loss of greater than 12.5 W / kg.

[0088] Comparative Examples 7, 9, and 11 are cases where the value of Equation 1 has a value of 8.0 or higher, and even if the cold rolling annealing temperature (T) and cold rolling annealing time (t) satisfy the required conditions, if the value of Equation 1 has a value of 8.0 or higher, ND / / <001> It can be confirmed that the average magnetic domain width of the crystal grains is greater than 50㎛ and has an iron loss of greater than 12.5 W / kg.

[0089] Comparative Examples 8 and 10 are cases where the cold rolling annealing time (t) is less than 10 s and the value of Equation 1 is 3.2 or less, and where the cold rolling annealing time (t) is less than 10 s and the value of Equation 1 is 3.2 or less, ND / / <001> It can be confirmed that the average magnetic domain width of the crystal grains is less than 10㎛ and has an iron loss of more than 12.5 W / kg.

[0090] The present invention has been described with reference to the embodiments illustrated in the drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

Claim 1 A method for manufacturing a non-oriented electrical steel sheet comprises: a hot rolling step of manufacturing a hot-rolled sheet by hot rolling a slab containing, in wt%, silicon (Si): 2.8 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.5 wt%, aluminum (Al): 0.5 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.003 wt%, sulfur (S): greater than 0 and less than or equal to 0.002 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, nitrogen (N): greater than 0 and less than or equal to 0.002 wt%, titanium (Ti): greater than 0 and less than or equal to 0.002 wt%, and the remainder being iron (Fe) and unavoidable impurities; a hot rolling annealing step of manufacturing a hot-rolled annealed sheet by hot rolling the hot-rolled sheet; and a cold rolling step of manufacturing a cold-rolled sheet by cold rolling the hot-rolled annealed sheet. A method for manufacturing a non-oriented electrical steel sheet, comprising: a cold rolling annealing step of cold rolling annealing the cold rolled sheet to produce a cold rolling annealed sheet; wherein the cold rolling annealing temperature in the cold rolling annealing step is 950℃ to 1100℃, and the cold rolling annealing temperature (T) and cold rolling annealing time (t) in the cold rolling annealing step satisfy the following Equation 1. <Equation 1> 3.2 < (T*t 0.5 ) / 1000 < 8.0 In the above relationship 1, T is the cold rolling annealing temperature (°C) and t is the cold rolling annealing time (s). Claim 2 delete Claim 3 A method for manufacturing a non-oriented electrical steel sheet according to claim 1, wherein the cold rolling annealing time is 10s to 70s. Claim 4 A method for manufacturing a non-oriented electrical steel sheet according to claim 1, wherein the cold rolling annealing step is performed in an atmosphere having a hydrogen fraction of 20% or more and 100% or less and the remainder being nitrogen. Claim 5 In claim 1, the ND / / of the above non-oriented electrical steel sheet <001> A method for manufacturing a non-oriented electrical steel sheet, wherein the average magnetic domain width of the crystal grains is 10㎛ to 50㎛. Claim 6 In claim 1, the iron loss (W of the above-mentioned non-oriented electrical steel sheet) 10 / 400 A method for manufacturing non-oriented electrical steel sheets, wherein the standard is 12.5 W / kg or less. Claim 7 A method for manufacturing a non-oriented electrical steel sheet according to claim 1, wherein the slab further comprises 0.005 wt% to 0.05 wt% of tin (Sn) and antimony (Sb) in total. Claim 8 A non-oriented electrical steel sheet comprising, in wt%, silicon (Si): 2.8 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.5 wt%, aluminum (Al): 0.5 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.003 wt%, sulfur (S): greater than 0 and less than or equal to 0.002 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, nitrogen (N): greater than 0 and less than or equal to 0.002 wt%, titanium (Ti): greater than 0 and less than or equal to 0.002 wt%, and the remainder being iron (Fe) and unavoidable impurities, and the ND / / of the non-oriented electrical steel sheet <001> Non-oriented electrical steel sheet having an average magnetic domain width of 10㎛ to 50㎛. Claim 9 In claim 8, the non-oriented electrical steel sheet further comprises 0.005 wt% to 0.05 wt% of tin (Sn) and antimony (Sb) in total. Claim 10 In claim 8, the iron loss (W of the above-mentioned non-oriented electrical steel sheet) 10 / 400 Non-oriented electrical steel sheet with a standard of 12.5 W / kg or less.

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