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

Abstract

Provided is a non-oriented electromagnetic steel sheet which, despite having high strength, has excellent magnetic properties and superior punching workability. The non-oriented electromagnetic steel sheet of the present invention has a TS higher than 580 MPa and satisfies formula (1) when P120 / Fe700, which is the ratio of a peak-to-peak value P120 of P near electron energy of 120eV to a peak-to-peak value Fe700 of Fe near electron energy of 700 eV in an Auger differential spectrum obtained in a grain boundary region of a fracture surface, is defined as [P]GB, and when P120 / Fe700, which is the ratio of P120 to Fe700 of an Auger differential spectrum obtained in the intragrain region of the fracture surface, is defined as [P]IG. A difference ΔS between TS and YP is equal to or less than 110 MPa, and an average crystal grain diameter D (μm) satisfies formula (2).　Formula (1): [P]GB / [P]IG>2.0. Formula (2): D≦100-15×[P]GB / [P]IG+1500 / TS.

Description

[Technical Field]

[0001] This disclosure relates to non-oriented electrical steel sheets and methods for manufacturing the same. [Background technology]

[0002] Non-oriented electrical steel sheets are widely used as motor cores. Motor cores include the stator (stationary part) and the rotor (rotor part). The stator and rotor require different characteristics. The stator requires excellent magnetic properties (low iron loss and high magnetic flux density). On the other hand, while magnetic properties are required for the rotor, high strength is particularly important for the following reason. In recent years, motors for electric vehicles and hybrid vehicles have been designed to increase motor output by increasing the motor rotation speed. As a result, the load on the rotor during motor operation has increased. Therefore, high strength is required for the rotor. Consequently, non-oriented electrical steel sheets, which are the material for motor cores such as stators and rotors, require high strength and excellent magnetic properties.

[0003] Non-oriented electrical steel sheets with high strength and excellent magnetic properties are proposed in Japanese Patent Publication No. 2008-050686 (Patent Document 1). In Patent Document 1, high strength and excellent magnetic properties are achieved by appropriately adjusting the chemical composition. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-050686 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Incidentally, when manufacturing motor cores from non-oriented electrical steel sheets, punching is performed on the non-oriented electrical steel sheets. If the strength of the non-oriented electrical steel sheet is high, it becomes difficult to punch out the desired shape during punching, and the dimensional accuracy of the material after punching may decrease. Furthermore, when the non-oriented electrical steel sheet is pressed into the die by the punching punch, burrs occur on the edges of the material after processing. Motor cores are manufactured by laminating multiple plate-shaped motor core materials punched from non-oriented electrical steel sheets. If burrs occur on the motor core material after processing, it may become difficult to laminate the motor core materials with high precision. Therefore, even when non-oriented electrical steel sheets have high strength, excellent punching properties are required that can improve the dimensional accuracy of the shape of the material after punching and suppress the occurrence of burrs.

[0006] The purpose of this disclosure is to provide a non-oriented electrical steel sheet and a method for manufacturing the same that can be obtained even with high strength, while also having excellent magnetic properties and excellent punching processability. [Means for solving the problem]

[0007] The non-oriented electrical steel sheet of the present disclosure contains, by mass %, Si: 3.2 to 4.5%, Mn: 0.3 to 3.5%, sol.Al: 0.2 to 2.0%, C: 0.0010 to 0.0030%, N: more than 0% and 0.0050% or less, O: more than 0% and 0.0200% or less, P: more than 0% and 0.100% or less, S: more than 0% and 0.0030% or less, Ti: more than 0% and 0.0030% or less, Mo: 0 to 0.100%, Cr: 0 to 1.000%, Ni: 0 to 0.50%, Cu: 0 to 0.50%, B: 0 to 0.0010%, Zn: 0 to 0.0050%, Ga: 0 to 0.0050%, Ge: 0 to 0.0050%, As: 0 to 0.0100%, Sn: 0 to 0.20%, Sb: 0 to 0.10%, Ca: 0 to 0.0050%, La: 0 to 0.0050%, Ce: 0 to 0.0050%, Nd: 0 to 0.0010%, Mg: 0 to 0.0030%, and the balance consists of Fe and impurities, and the tensile strength TS is higher than 580 MPa. In the grain boundary region of the fracture surface of the non-oriented electrical steel sheet, elemental analysis is performed by Auger electron spectroscopy to obtain the Auger differential spectra of Fe and P, and the peak-to-peak value Fe of Fe in the vicinity of an electron energy of 700 eV of the obtained Auger differential spectrum 700 The ratio of the peak-to-peak value P of P in the vicinity of an electron energy of 120 eV to 120 is defined as P 120 / Fe 700 and denoted as [P] GB In the intragranular region of the fracture surface of the non-oriented electrical steel sheet, elemental analysis is performed by Auger electron spectroscopy to obtain the Auger differential spectra of Fe and P, and the peak-to-peak value Fe of Fe in the vicinity of an electron energy of 700 eV of the obtained Auger differential spectrum 700 The ratio of the peak-to-peak value P of P in the vicinity of an electron energy of 1²0 eV to 120 is defined as P 120 / Fe 700 and denoted as [P] IG At this time, the non-oriented electrical steel sheet satisfies formula (1). Further, in the non-oriented electrical steel sheet, the difference ΔS between the tensile strength TS and the yield strength YP is 110 MPa or less, and the average crystal grain size D (μm) satisfies formula (2). [P] GB / [P] IG>2.0 (1) D≦100-15×[P] GB / [P] IG +1500 / TS (2) Here, the value of the tensile strength TS (MPa) is substituted for TS in equation (2).

[0008] The method for manufacturing non-oriented electrical steel sheets according to this disclosure comprises a hot rolling step, a cold rolling step, and a finish annealing step. In the hot rolling step, a hot-rolled steel sheet is produced by hot rolling a slab having the above-mentioned chemical composition. In the cold rolling step, a cold-rolled steel sheet is produced by cold rolling the hot-rolled steel sheet. In the finish annealing step, finish annealing is performed on the cold-rolled steel sheet. In the finish annealing step, the cold-rolled steel sheet is annealed at a maximum attainable temperature T1 of 950°C or less, and the tension TE1 applied to the cold-rolled steel sheet during annealing is 0.15 to 0.80 kgf / mm². 2 Furthermore, during the cooling of the cold-rolled steel sheet after annealing, the average cooling rate CR1 in the temperature range of 700-500°C is set to 20°C / second or less, and the maximum tension TE2 applied to the cold-rolled steel sheet in the temperature range of 200°C or less during the cooling of the cold-rolled steel sheet after annealing is set to TE1 + 0.15 kgf / mm². 2 The above and 0.40 kgf / mm 2 That concludes this section. [Effects of the Invention]

[0009] The non-oriented electrical steel sheet of this disclosure provides excellent magnetic properties and excellent die-cutting properties, even at high strength. The method for manufacturing the non-oriented electrical steel sheet according to the present invention can produce the above-mentioned non-oriented electrical steel sheet. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is an SEM image of the fracture surface of the non-oriented electrical steel sheet of this embodiment. [Figure 2] Figure 2 is an enlarged view of the grain boundary region in Figure 1. [Figure 3] Figure 3 shows an example of Auger differential spectra of Fe and P obtained by elemental analysis of the grain boundary region in Figure 2 using Auger electron spectroscopy. [Figure 4] Figure 4 is an enlarged view of the portion of the ring-shaped sample in the L-direction cross-section, including the cut end face, during the punching processability evaluation test in the example. [Modes for carrying out the invention]

[0011] The inventors investigated non-oriented electrical steel sheets with high strength and excellent magnetic properties from the perspective of chemical composition, in order to manufacture a rotor with the excellent strength required for a rotor and a stator with the excellent magnetic properties required for a stator from a single non-oriented electrical steel sheet. As a result, the inventors determined that the composition, in mass%, is as follows: Si: 3.2-4.5%, Mn: 0.3-3.5%, sol.Al: 0.2-2.0%, C: 0.0010-0.0030%, N: greater than 0% and less than or equal to 0.0050%, O: greater than 0% and less than or equal to 0.0200%, P: greater than 0% and less than or equal to 0.100%, S: greater than 0% and less than or equal to 0.0030%, Ti: greater than 0% and less than or equal to 0.0030%, Mo: 0-0.100%, Cr: 0-1.000%, Ni: 0-0.50%, Cu: 0-0.50%, B: 0-0.0010%, Zn: 0 It was considered that a non-oriented electrical steel sheet having a chemical composition of ~0.0050%, Ga:0~0.0050%, Ge:0~0.0050%, As:0~0.0100%, Sn:0~0.20%, Sb:0~0.10%, Ca:0~0.0050%, La:0~0.0050%, Ce:0~0.0050%, Nd:0~0.0010%, Mg:0~0.0030%, with the remainder being Fe and impurities, would have a tensile strength higher than 580 MPa while also possessing excellent magnetic properties.

[0012] Therefore, the inventors further investigated means for achieving excellent punching processability in non-oriented electrical steel sheets having the above-mentioned chemical composition. As a result, the inventors obtained the following findings.

[0013] In non-oriented electrical steel sheets with a tensile strength higher than 580 MPa, punching was performed and the shear surface was observed. In non-oriented electrical steel sheets with a tensile strength of 580 MPa or less, the shear surface after punching mainly consisted of ductile fracture surfaces. In contrast, in the shear surface after punching of non-oriented electrical steel sheets with a tensile strength higher than 580 MPa, the proportion of brittle fracture surfaces was increased compared to the shear surface after punching of non-oriented electrical steel sheets with a tensile strength of 580 MPa or less. Furthermore, in the brittle fracture surfaces, the proportion of intragranular fracture surfaces (cleavage fracture surfaces) was higher than that of intergranular fracture surfaces. Cleavage propagates along the cleavage surface ((100) surface). The cleavage surface does not necessarily exist along the cutting direction. Therefore, the crack propagates with irregularities, and the dimensional accuracy of the shear surface shape decreases. On the other hand, when cleavage fracture and intergranular fracture are mixed, compared to the case of cleavage fracture alone, the fracture surface closer to the target cutting position is selected and cut. Therefore, deviations in the cutting position are reduced, and the dimensional accuracy of the shear surface is improved.

[0014] Based on the above findings, the inventors hypothesized that increasing the proportion of grain boundary fracture surfaces during punching of non-oriented electrical steel sheets with a tensile strength higher than 580 MPa would improve the dimensional accuracy of the shear surface, and consequently, improve punching workability. Furthermore, the inventors hypothesized that increasing the amount of P segregation at grain boundaries would increase the proportion of grain boundary fracture surfaces during punching. Therefore, the inventors investigated the relationship between the amount of P segregation at grain boundaries and punching workability. As a result, the inventors found that [P], an index of P concentration in the grain boundary region, which can be determined by Auger electron spectroscopy as described later, is GB And, [P] is an indicator of P concentration in the intragranular region. IG We found that excellent punching processability can be obtained by satisfying equation (1). [P] GB / [P] IG >2.0 (1)

[0015] However...P] GB / [P] IGEven when equation (1) was satisfied, burring was still observed on the shear surface after punching. Therefore, the inventors further investigated means to suppress burring caused by punching. As a result, the inventors obtained the following findings.

[0016] In punching processes, fracture occurs through elastic deformation and plastic deformation. Even if the amount of P segregation at grain boundaries can be increased to increase the proportion of grain boundary fracture during punching, it is not possible to eliminate the plastic deformation before fracture. This plastic deformation remains as sagging. Therefore, the inventors investigated means to suppress plastic deformation when intragranular fracture occurs. Plastic deformation occurs from the time an external force of yield strength YP or greater is applied to the steel sheet until an external force of tensile strength TS or greater is applied and the steel sheet fractures. Therefore, the inventors considered that in a non-oriented electrical steel sheet having the above chemical composition, plastic deformation can be suppressed by reducing the difference ΔS between tensile strength TS and yield strength YP. As a result of further investigation, [P] GB / [P] IG The inventors have found that by setting the ratio to a value greater than 2.0 and the difference ΔS between the tensile strength TS and the yield strength YP to 110 MPa or less, excellent dimensional accuracy after punching is achieved, the occurrence of shear deformation is sufficiently suppressed, and excellent punching processability is obtained.

[0017] As described above, the chemical composition is [P] GB / [P] IG If the ratio is set higher than 2.0, and the difference ΔS between the tensile strength TS and the yield strength YP is 110 MPa or less, excellent punching workability can be obtained even for high-strength non-oriented electrical steel sheets with a tensile strength TS exceeding 580 MPa. However, in such non-oriented electrical steel sheets, toughness was sometimes low. When non-oriented electrical steel sheets are used as rotors, not only high strength but also excellent toughness is required. Therefore, the inventors further investigated means to obtain excellent toughness. As a result, the inventors obtained the following findings.

[0018] [P] shows the amount of P segregation at grain boundaries in non-oriented electrical steel sheets. GBThe higher the [P] value, and the higher the tensile strength TS of the non-oriented electrical steel sheet, the more likely the toughness of the non-oriented electrical steel sheet is to decrease. Therefore, the average grain size D (μm) of the non-oriented electrical steel sheet is [P] GB The size should be determined according to the tensile strength TS. In this case, appropriate toughness may be obtained.

[0019] Therefore, the inventors have determined that the average grain size D and [P] GB Furthermore, the relationship between tensile strength TS and toughness was investigated. As a result, the inventors determined that if the average grain size D satisfies equation (2), the chemical composition of the non-oriented electrical steel sheet is used, and the tensile strength TS is increased to more than 580 MPa, [P] GB / [P] IG We found that even when the ratio is set higher than 2.0, and the difference ΔS between tensile strength TS and yield strength YP is 110 MPa or less, excellent toughness can be obtained. D≦100-15×[P] GB / [P] IG +1500 / TS (2) Here, the value of the tensile strength TS (MPa) is substituted for TS in equation (2).

[0020] The non-oriented electrical steel sheet of this embodiment was completed based on the above technical concept, and its gist is as follows.

[0021] The non-oriented electrical steel sheet of the first composition has the following composition by mass%, Si: 3.2-4.5%, Mn: 0.3-3.5%, sol.Al: 0.2-2.0%, C: 0.0010-0.0030%, N: greater than 0% and less than or equal to 0.0050%, O: greater than 0% and less than or equal to 0.0200%, P: greater than 0% and less than or equal to 0.100%, S: greater than 0% and less than or equal to 0.0030%, Ti: greater than 0% and less than or equal to 0.0030%, Mo: 0-0.100%, Cr: 0-1.000%, Ni: 0-0.50%, Cu: 0- The composition is 0.50%, B: 0~0.0010%, Zn: 0~0.0050%, Ga: 0~0.0050%, Ge: 0~0.0050%, As: 0~0.0100%, Sn: 0~0.20%, Sb: 0~0.10%, Ca: 0~0.0050%, La: 0~0.0050%, Ce: 0~0.0050%, Nd: 0~0.0010%, Mg: 0~0.0030%, with the remainder being Fe and impurities, and the tensile strength TS is higher than 580 MPa. Elemental analysis was performed by Auger electron spectroscopy in the grain boundary region of the fracture surface of the non-oriented electrical steel sheet to obtain the Auger differential spectra of Fe and P, and the peak-to-peak value of Fe near an electron energy of 700 eV in the obtained Auger differential spectrum was determined. 700 The peak-to-peak value of P near an electron energy of 120 eV for the given value. 120 P is the ratio of 120 / Fe 700 [P] GB This is defined as follows: Elemental analysis is performed by Auger electron spectroscopy in the intragranular region of the fracture surface of the non-oriented electrical steel sheet to obtain the Auger differential spectra of Fe and P, and the peak-to-peak value of Fe near an electron energy of 700 eV of the obtained Auger differential spectrum is determined. 700 The peak-to-peak value of P near an electron energy of 120 eV for the given value. 120 P is the ratio of 120 / Fe 700 [P] IG This is defined as follows. In this case, the non-oriented electrical steel sheet satisfies equation (1). Furthermore, the difference ΔS between the tensile strength TS and the yield strength YP in the non-oriented electrical steel sheet is 110 MPa or less, and the average grain size D (μm) satisfies equation (2). [P] GB / [P] IG>2.0 (1) D≦100-15×[P] GB / [P] IG +1500 / TS (2) Here, the value of the tensile strength TS (MPa) is substituted for TS in equation (2).

[0022] The second non-oriented electrical steel sheet is the same as the first non-oriented electrical steel sheet, with mass% being: Mo: 0.001~0.100%, Cr: 0.001~1.000%, Ni: 0.01~0.50%, Cu: 0.01~0.50%, B: 0.0001~0.0010%, Zn: 0.0001~0.0050%, Ga: 0.0001~0.0050%, Ge: 0.0001~0.0 It contains one or more elements selected from the group consisting of 0.50%, As: 0.0001-0.0100%, Sn: 0.01-0.20%, Sb: 0.01-0.10%, Ca: 0.0001-0.0050%, La: 0.0001-0.0050%, Ce: 0.0001-0.0050%, Nd: 0.0001-0.0010%, and Mg: 0.0001-0.0030%.

[0023] A method for manufacturing a non-oriented electrical steel sheet of the first configuration is a method for manufacturing a non-oriented electrical steel sheet of the first or second configuration, comprising a hot rolling step, a cold rolling step, and a finish annealing step. In the hot rolling step, a hot-rolled steel sheet is produced by hot rolling a slab having the chemical composition of the first or second configuration. In the cold rolling step, a cold-rolled steel sheet is produced by cold-rolling the hot-rolled steel sheet. In the finish annealing step, finish annealing is performed on the cold-rolled steel sheet. In the finish annealing step, the cold-rolled steel sheet is annealed at a maximum temperature T1 of 950°C or less, and the tension TE1 applied to the cold-rolled steel sheet during annealing is 0.15 to 0.80 kgf / mm 2 Furthermore, during the cooling of the cold-rolled steel sheet after annealing, the average cooling rate CR1 in the temperature range of 700-500°C is set to 20°C / second or less, and the maximum tension TE2 applied to the cold-rolled steel sheet in the temperature range of 200°C or less during the cooling of the cold-rolled steel sheet after annealing is set to TE1 + 0.15 kgf / mm². 2 The above and 0.40 kgf / mm 2 That concludes this section.

[0024] The non-oriented electrical steel sheet according to this embodiment will be described in detail below.

[0025] [Features of the non-oriented electrical steel sheet of this embodiment] The non-oriented electrical steel sheet of this embodiment satisfies the following features 1 to 5. (Feature 1) The chemical composition, in mass%, is as follows: Si: 3.2-4.5%, Mn: 0.3-3.5%, sol.Al: 0.2-2.0%, C: 0.0010-0.0030%, N: greater than 0% and less than or equal to 0.0050%, O: greater than 0% and less than or equal to 0.0200%, P: greater than 0% and less than or equal to 0.100%, S: greater than 0% and less than or equal to 0.0030%, Ti: greater than 0% and less than or equal to 0.0030%, Mo: 0-0.100%, Cr: 0-1.000%, Ni: 0-0.50%, C The composition is as follows: u: 0-0.50%, B: 0-0.0010%, Zn: 0-0.0050%, Ga: 0-0.0050%, Ge: 0-0.0050%, As: 0-0.0100%, Sn: 0-0.20%, Sb: 0-0.10%, Ca: 0-0.0050%, La: 0-0.0050%, Ce: 0-0.0050%, Nd: 0-0.0010%, Mg: 0-0.0030%, and the remainder consists of Fe and impurities. (Feature 2) The tensile strength TS is higher than 580 MPa. (Feature 3) Elemental analysis of the grain boundary region of the fracture surface of non-oriented electrical steel sheet was performed by Auger electron spectroscopy to obtain the Auger differential spectra of Fe and P, and the peak-to-peak value of Fe near an electron energy of 700 eV of the obtained Auger differential spectrum was determined. 700 The peak-to-peak value of P near an electron energy of 120 eV for the given value. 120 P is the ratio of 120 / Fe 700 [P] GB This is defined as follows. Furthermore, elemental analysis of Fe and P was performed by Auger electron spectroscopy in the intragranular region of the fracture surface to obtain the Auger differential spectra, and the peak-to-peak value of Fe near an electron energy of 700 eV of the obtained Auger differential spectrum was determined. 700 The peak-to-peak value of P near an electron energy of 120 eV for the given value.120 P is the ratio of 120 / Fe 700 [P] IG This is defined as follows: In this case, [P] GB and [P] IG This satisfies equation (1). [P] GB / [P] IG >2.0 (1) (Feature 4) The difference ΔS between the tensile strength TS and the yield strength YP is 110 MPa or less. (Feature 5) The average crystal grain size D (μm) satisfies equation (2). D≦100-15×[P] GB / [P] IG +1500 / TS (2) Here, the value of the tensile strength TS (MPa) is substituted for TS in equation (2). Features 1 through 5 are explained below.

[0026] [(Feature 1) Regarding chemical composition] The chemical composition of the non-oriented electrical steel sheet of this embodiment contains the following elements. Unless otherwise specified, "%" in the chemical composition of the non-oriented electrical steel sheet refers to mass percent.

[0027] Si: 3.2~4.5% Silicon (Si) increases the resistivity of steel sheets and reduces eddy current losses. Furthermore, Si dissolves into the steel sheet, increasing the strength of non-oriented electrical steel sheets. If the Si content is less than 3.2%, the above effects are not sufficiently obtained. On the other hand, if the Si content exceeds 4.5%, the punching processability of non-oriented electrical steel sheets decreases. Therefore, the Si content is between 3.2% and 4.5%. The preferred lower limit for the Si content is 3.3%, and more preferably 3.4%. The preferred upper limit for the Si content is 4.4%, and more preferably 4.3%.

[0028] Mn: 0.3~3.5% Manganese (Mn) increases the resistivity of steel sheets and reduces eddy current losses. If the Mn content is less than 0.3%, the above effect is not sufficiently obtained. On the other hand, if the Mn content exceeds 3.5%, the magnetic flux density of the steel decreases. Therefore, the Mn content is between 0.3% and 3.5%. The preferred lower limit for the Mn content is 0.4%, and more preferably 0.5%. The preferred upper limit for the Mn content is 3.4%, more preferably 3.2%, and even more preferably 3.0%.

[0029] sol.Al: 0.2~2.0% Aluminum (sol.Al) increases the resistivity of steel sheets and reduces eddy current losses. If the sol.Al content is less than 0.2%, the above effect is not sufficiently obtained. On the other hand, if the sol.Al content exceeds 2.0%, the magnetic flux density of the steel decreases. Therefore, the sol.Al content is between 0.2% and 2.0%. The preferred lower limit for the sol.Al content is 0.3%, and more preferably 0.4%. The preferred upper limit for the sol.Al content is 1.5%, more preferably 1.0%, and even more preferably 0.5%. In this specification, sol.Al means acid-soluble Al.

[0030] C: 0.0010~0.0030% Carbon (C) fixes dislocations in steel sheets, increasing their yield strength. If the C content is less than 0.0010%, the above effect is not sufficiently obtained. On the other hand, if the C content exceeds 0.0030%, fine carbides precipitate in the steel sheet, degrading iron loss. Therefore, the C content is between 0.0010% and 0.0030%. The preferred lower limit of the C content is 0.0012%, more preferably 0.0014%, and even more preferably 0.0016%. The preferred upper limit for the C content is 0.0028%, more preferably 0.0026%, and even more preferably 0.0024%.

[0031] N: More than 0% and less than 0.0050% Nitrogen (N) is inevitably present. Therefore, the N content is greater than 0%. N forms nitrides in the steel sheet, degrading iron loss. Consequently, the N content is greater than 0% but less than or equal to 0.0050%. It is preferable that the N content be as low as possible. However, excessive reduction of the N content increases manufacturing costs. Therefore, from the viewpoint of industrial productivity, the preferred lower limit of the N content is 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%. The preferred upper limit for the N content is 0.0040%, and more preferably 0.0030%.

[0032] O: More than 0% and less than 0.0200% Oxygen (O) is inevitably present; that is, the O content is greater than 0%. O forms oxides in the steel plate, degrading iron loss and magnetic flux density. Therefore, the O content is greater than 0% but less than or equal to 0.0200%. A low oxygen content is preferable. However, excessive reduction of the oxygen content increases manufacturing costs. Therefore, from the viewpoint of industrial productivity, the preferred lower limit of the oxygen content is 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%. The preferred upper limit for the O content is 0.0150%, and more preferably 0.0100%.

[0033] P: More than 0% and less than 0.100% Phosphorus (P) is inevitably present. Therefore, the P content is greater than 0%. P enhances the punching processability of high-strength, non-oriented electrical steel sheets. However, if the P content exceeds 0.100%, the steel sheet becomes brittle, reducing its workability, and cracking may occur during cold rolling. Therefore, the P content is between 0% and 0.100%. A lower P content is preferable. However, excessive reduction of the P content increases manufacturing costs. Therefore, from the viewpoint of industrial productivity, the preferred lower limit of the P content is 0.001%, more preferably 0.005%, even more preferably 0.008%, and even more preferably 0.010%. The preferred upper limit for the P content is 0.090%, more preferably 0.080%, and even more preferably 0.070%.

[0034] S: More than 0% and less than 0.0030% Sulfur (S) is inevitably present. Therefore, the S content is greater than 0%. S degrades iron loss by generating MnS. Consequently, the S content is greater than 0% but less than or equal to 0.0030%. A low sulfur (S) content is preferable. However, excessive reduction of the S content increases manufacturing costs. Therefore, from the viewpoint of industrial productivity, the preferred lower limit of the S content is 0.0001%, more preferably 0.0003%, and even more preferably 0.0005%. The preferred upper limit for the S content is 0.0028%, more preferably 0.0025%, more preferably 0.0022%, and still more preferably 0.0020%.

[0035] Ti: more than 0% and less than 0.0030% Titanium (Ti) is inevitably present; that is, the Ti content is greater than 0%. Ti forms carbonitrides, increasing the strength of non-oriented electrical steel sheets through precipitation strengthening. However, if the Ti content exceeds 0.0030%, excessive carbonitride formation occurs, degrading the magnetic properties. Therefore, the Ti content is between 0% and 0.0030%. A low Ti content is preferable. However, excessive reduction of the Ti content increases manufacturing costs. Therefore, the preferred lower limit of the Ti content is 0.0001%, more preferably 0.0003%, and even more preferably 0.0005%. The preferred upper limit for the Ti content is 0.0028%, more preferably 0.0026%, and even more preferably 0.0024%.

[0036] The remainder of the chemical composition of the non-oriented electrical steel sheet in this embodiment consists of Fe and impurities. Here, impurities are those that are introduced during the industrial production of the non-oriented electrical steel sheet from raw materials such as ore, scrap, or the manufacturing environment. The content of these impurities is acceptable as long as it does not adversely affect the non-oriented electrical steel sheet in this embodiment.

[0037] [Optional element] The chemical composition of the non-oriented electrical steel sheet of this embodiment may further contain, in place of a portion of Fe, one or more elements selected from the group consisting of Mo: 0-0.100%, Cr: 0-1.000%, Ni: 0-0.50%, Cu: 0-0.50%, B: 0-0.0010%, Zn: 0-0.0050%, Ga: 0-0.0050%, Ge: 0-0.0050%, As: 0-0.0100%, Sn: 0-0.20%, Sb: 0-0.10%, Ca: 0-0.0050%, La: 0-0.0050%, Ce: 0-0.0050%, Nd: 0-0.0010%, and Mg: 0-0.0030%. These elements will be described below.

[0038] [Group 1: Mo, Cr, Ni, and Cu] The chemical composition of the non-oriented electrical steel sheet of this embodiment may further contain, in place of some of the Fe, one or more elements selected from the group consisting of Mo: 0-0.100%, Cr: 0-1.000%, Ni: 0-0.50%, and Cu: 0-0.50%. All of these elements increase the strength of the steel sheet.

[0039] Mo: 0~0.100% Molybdenum (Mo) is an optional element and does not need to be present. In other words, the Mo content may be 0%. If it is present, that is, if the Mo content is greater than 0%, Mo forms carbides, increasing the strength of the non-oriented electrical steel sheet through precipitation strengthening. Even if only a small amount of Mo is present, the above effect can be obtained to some extent. However, if the Mo content exceeds 0.100%, excessive carbides are formed, degrading the magnetic properties. Therefore, the Mo content should be between 0 and 0.100%. The preferred lower limit of the Mo content is 0.001%, more preferably 0.005%, even more preferably 0.010%, and even more preferably 0.015%. The preferred upper limit for the Mo content is 0.090%, more preferably 0.080%, and even more preferably 0.070%.

[0040] Cr: 0~1.000% Chromium (Cr) is an optional element and does not need to be included. In other words, the Cr content may be 0%. If it is included, that is, if the Cr content is greater than 0%, Cr increases the strength of the non-oriented electrical steel sheet. Also, Cr has a high affinity for carbon (C). Therefore, in the temperature range where phosphorus (P) diffuses easily (500-700°C), Cr fixes carbon and suppresses carbon segregation at grain boundaries. As a result, phosphorus becomes more likely to segregate at grain boundaries. Even if only a small amount of Cr is included, the above effects can be obtained to some extent. However, the effect saturates when the Cr content exceeds 1.000%. Therefore, the Cr content is between 0 and 1.000%. The preferred lower limit of the Cr content is 0.001%, more preferably 0.005%, more preferably 0.010%, more preferably 0.015%, more preferably 0.020%, more preferably 0.050%, and more preferably 0.100%. The preferred upper limit for the Cr content is 0.800%, more preferably 0.600%, and even more preferably 0.550%.

[0041] Ni: 0~0.50% Nickel (Ni) is an optional element and does not need to be included. In other words, the Ni content may be 0%. If it is included, that is, if the Ni content is greater than 0%, Ni increases the strength of the non-oriented electrical steel sheet. Even if only a small amount of Ni is included, the above effect can be obtained to some extent. However, if the Ni content exceeds 0.50%, the steel sheet becomes brittle and its workability decreases. Therefore, the Ni content is between 0% and 0.50%. The preferred lower limit for the Ni content is 0.01%, more preferably 0.05%, and even more preferably 0.10%. The preferred upper limit for the Ni content is 0.45%, more preferably 0.40%, and even more preferably 0.35%.

[0042] Cu: 0~0.50% Copper (Cu) is an optional element and does not need to be included. In other words, the Cu content may be 0%. If it is included, that is, if the Cu content is greater than 0%, Cu increases the strength of the non-oriented electrical steel sheet. Even if only a small amount of Cu is included, the above effect can be obtained to some extent. However, if the Cu content exceeds 0.50%, the steel sheet becomes brittle and its workability decreases. Therefore, the Cu content is between 0% and 0.50%. The preferred lower limit for the Cu content is 0.01%, more preferably 0.05%, and even more preferably 0.10%. The preferred upper limit for the Cu content is 0.45%, more preferably 0.40%, and even more preferably 0.35%.

[0043] [Group 2: B, Zn, Ga, Ge, and As] The chemical composition of the non-oriented electrical steel sheet of this embodiment may further contain, in place of a portion of Fe, one or more elements selected from the group consisting of B: 0-0.0010%, Zn: 0-0.0050%, Ga: 0-0.0050%, Ge: 0-0.0050%, and As: 0-0.0100%.

[0044] B: 0~0.0010% Boron (B) is an optional element and may not be present. In other words, the B content may be 0%. If it is present, that is, if the B content is greater than 0%, B forms nitrides, which inhibit recrystallization during finish annealing. Therefore, the B content is between 0 and 0.0010%. Excessive reduction of the B content increases manufacturing costs. Therefore, from the viewpoint of industrial productivity, the preferred lower limit of the B content is 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%. The preferred upper limit for the B content is 0.0009%, more preferably 0.0008%, and even more preferably 0.0007%.

[0045] Zn: 0~0.0050% Zinc (Zn) is an optional element and does not need to be included. In other words, the Zn content may be 0%. If it is included, that is, if the Zn content is greater than 0%, there is no particular problem as long as the Zn content is 0.0050% or less. Excessive reduction of the Zn content increases manufacturing costs. Therefore, from the viewpoint of industrial productivity, the preferred lower limit of the Zn content is 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%. The preferred upper limit for the Zn content is 0.0020%, more preferably 0.0010%, and even more preferably 0.0005%.

[0046] Ga: 0~0.0050% Gallium (Ga) is an optional element and does not need to be included. In other words, the Ga content may be 0%. If it is included, that is, if the Ga content is greater than 0%, there is no particular problem as long as the Ga content is 0.0050% or less. Excessive reduction of the Ga content increases manufacturing costs. Therefore, from the viewpoint of industrial productivity, the preferred lower limit of the Ga content is 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%. The preferred upper limit for the Ga content is 0.0020%, more preferably 0.0010%, and even more preferably 0.0005%.

[0047] Ge: 0~0.0050% Germanium (Ge) is an optional element and does not need to be included. In other words, the Ge content may be 0%. If it is included, that is, if the Ge content is greater than 0%, there is no particular problem as long as the Ge content is 0.0050% or less. Excessive reduction of the Ge content increases manufacturing costs. Therefore, from the viewpoint of industrial productivity, the preferred lower limit of the Ge content is 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%. The preferred upper limit for the Ge content is 0.0020%, more preferably 0.0010%, and even more preferably 0.0005%.

[0048] As: 0~0.0100% Arsenic (As) is an optional element and does not need to be included. In other words, the As content may be 0%. If it is included, that is, if the As content is greater than 0%, there is no particular problem as long as the As content is 0.0100% or less. Excessive reduction of the As content increases manufacturing costs. Therefore, from the viewpoint of industrial productivity, the preferred lower limit of the As content is 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%. The preferred upper limit for the As content is 0.0070%, more preferably 0.0050%, and even more preferably 0.0030%.

[0049] [Group 3: Sn and Sb] The chemical composition of the non-oriented electrical steel sheet of this embodiment may further contain, in place of a portion of Fe, one or more elements selected from the group consisting of Sn: 0-0.20% and Sb: 0-0.10%. All of these elements reduce the iron loss of the non-oriented electrical steel sheet.

[0050] Sn: 0~0.20% Tin (Sn) is an optional element and may not be present. In other words, the Sn content may be 0%. If it is present, that is, if the Sn content is greater than 0%, Sn segregates on the surface of the steel sheet and suppresses oxidation and nitriding during finish annealing. Sn further improves the texture of the steel sheet and increases the magnetic flux density. This reduces iron loss in non-oriented electrical steel sheets. Even if only a small amount of Sn is present, the above effects can be obtained to some extent. However, if the Sn content exceeds 0.20%, the steel sheet becomes brittle and its workability decreases. Therefore, the Sn content is between 0 and 0.20%. The preferred lower limit for the Sn content is 0.01%, more preferably 0.03%, and even more preferably 0.05%. The preferred upper limit for the Sn content is 0.18%, more preferably 0.16%, and even more preferably 0.15%.

[0051] Sb: 0~0.10% Antimony (Sb) is an optional element and may not be present. In other words, the Sb content may be 0%. If it is present, i.e., if the Sb content is greater than 0%, Sb, like Sn, segregates on the surface of the steel sheet and suppresses oxidation and nitriding during finish annealing. Sb also improves the texture of the steel sheet and increases the magnetic flux density. This reduces iron loss in non-oriented electrical steel sheets. Even a small amount of Sb can provide some of the above effects. However, if the Sb content exceeds 0.10%, the steel sheet becomes brittle and its workability decreases. Therefore, the Sb content is between 0 and 0.10%. The preferred lower limit for the Sb content is 0.01%, and more preferably 0.02%. The preferred upper limit for the Sb content is 0.08%, more preferably 0.06%, and even more preferably 0.05%.

[0052] [Group 4: Ca, La, Ce, Nd, and Mg] The chemical composition of the non-oriented electrical steel sheet of this embodiment may further contain, in place of a portion of Fe, one or more elements selected from the group consisting of Ca: 0-0.0050%, La: 0-0.0050%, Ce: 0-0.0050%, Nd: 0-0.0010%, and Mg: 0-0.0030%. All of these elements promote grain growth during finish annealing.

[0053] Ca: 0~0.0050% Calcium (Ca) is an optional element and may not be present. In other words, the Ca content may be 0%. If it is present, that is, if the Ca content is greater than 0%, Ca combines with S during the casting of molten steel to form coarse precipitates, which are coarse sulfides and / or coarse oxysulfides. The particle size of these coarse precipitates is about 1-2 μm. These coarse sulfides adsorb fine inhibitors such as MnS, TiN, and AlN, which have a particle size of about 100 nm and are formed on the steel sheet during the manufacturing process after casting. This suppresses the inhibition of grain growth by inhibitors during finish annealing. Therefore, it promotes grain growth during finish annealing. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. Even if only a small amount of Ca is present, the above effect can be obtained to some extent. However, if the Ca content exceeds 0.0050%, excessive coarse precipitates will be formed. In this case, recrystallization and grain growth during the finish annealing process will be inhibited. Therefore, the Ca content should be between 0 and 0.0050%. The preferred lower limit for the Ca content is 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%. The preferred upper limit for the Ca content is 0.0045%, more preferably 0.0040%, and even more preferably 0.0035%.

[0054] La: 0~0.0050% Lanthanum (La) is an optional element and does not need to be present. In other words, the La content may be 0%. If it is present, that is, if the La content is greater than 0%, La, like Ca, forms coarse precipitates and suppresses the inhibition of grain growth by inhibitors during finish annealing. Therefore, grain growth is promoted during finish annealing. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. Even if only a small amount of La is present, the above effect can be obtained to some extent. However, if the La content exceeds 0.0050%, excessive coarse precipitates will be formed. In this case, recrystallization and grain growth during the finish annealing process will be inhibited. Therefore, the La content should be between 0 and 0.0050%. The preferred lower limit of the La content is 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%. The preferred upper limit for the La content is 0.0045%, more preferably 0.0040%, and even more preferably 0.0035%.

[0055] Ce: 0~0.0050% Cerium (Ce) is an optional element and does not need to be included. In other words, the Ce content may be 0%. If it is included, that is, if the Ce content is greater than 0%, Ce, like Ca, forms coarse precipitates and suppresses the inhibition of grain growth by inhibitors during finish annealing. Therefore, grain growth is promoted during finish annealing. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. Even if only a small amount of Ce is included, the above effect can be obtained to some extent. However, if the Ce content exceeds 0.0050%, excessive coarse precipitates will be formed. In this case, recrystallization and grain growth during the finish annealing process will be inhibited. Therefore, the Ce content should be between 0 and 0.0050%. The preferred lower limit of the Ce content is 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%. The preferred upper limit for the Ce content is 0.0045%, more preferably 0.0040%, and even more preferably 0.0035%.

[0056] Nd: 0~0.0010% Neodymium (Nd) is an optional element and does not need to be included. In other words, the Nd content may be 0%. If it is included, that is, if the Nd content is greater than 0%, Nd, like Ca, generates coarse precipitates and suppresses the inhibition of grain growth by inhibitors during finish annealing. Therefore, grain growth is promoted during finish annealing. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. Even if only a small amount of Nd is included, the above effect can be obtained to some extent. However, if the Nd content exceeds 0.0010%, excessive coarse precipitates will be formed. In this case, recrystallization and grain growth during the finish annealing process will be inhibited. Therefore, the Nd content should be between 0 and 0.0010%. The preferred lower limit of the Nd content is 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%. The preferred upper limit for the Nd content is 0.0008%, more preferably 0.0006%, and even more preferably 0.0004%.

[0057] Mg: 0~0.0030% Magnesium (Mg) is an optional element and may not be present. In other words, the Mg content may be 0%. If it is present, that is, if the Mg content is greater than 0%, Mg, like Ca, forms coarse precipitates and suppresses the inhibition of grain growth by inhibitors during finish annealing. Therefore, grain growth is promoted during finish annealing. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. Even if only a small amount of Mg is present, the above effect can be obtained to some extent. However, if the Mg content exceeds 0.0030%, excessive coarse precipitates will be formed. In this case, recrystallization and grain growth during the finish annealing process will be inhibited. Therefore, the Mg content should be between 0 and 0.0030%. The preferred lower limit of the Mg content is 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%. The preferred upper limit for the Mg content is 0.0020%, more preferably 0.0015%, and even more preferably 0.0010%.

[0058] [Method for measuring the chemical composition of non-oriented electrical steel sheets] The chemical composition of the non-oriented electrical steel sheet of this embodiment can be measured by a well-known component analysis method in accordance with JIS G0321:2017. Specifically, chips are collected from the steel sheet using a drill. The collected chips are dissolved in acid to obtain a solution. Elemental analysis of the chemical composition is performed on the solution using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry). The C and S content is determined by a well-known high-frequency combustion method (combustion-infrared absorption method). The N content is determined using a well-known inert gas melting-thermal conductivity method. The O content is determined using a well-known inert gas melting-infrared absorption method.

[0059] Furthermore, the elemental content of each element shall be rounded to the minimum digit of the elemental content specified in this embodiment, based on the significant figures defined in this embodiment. Rounding means truncating the fractional part if it is less than 5, and rounding up if it is 5 or more.

[0060] [(Feature 2) Tensile strength TS] In this embodiment, the non-oriented electrical steel sheet has a tensile strength TS higher than 580 MPa. In other words, the non-oriented electrical steel sheet of this embodiment has high strength. The preferred lower limit of the tensile strength TS of the non-oriented electrical steel sheet in this embodiment is 585 MPa, and more preferably 590 MPa. The upper limit of the tensile strength TS is not particularly limited. However, if feature 1 is satisfied, the upper limit of the tensile strength TS is, for example, 850 MPa.

[0061] [Measurement methods for tensile strength (TS) and yield strength (YP)] The tensile strength TS and yield strength YP of the non-oriented electrical steel sheet of this embodiment are measured by the following method. A JIS No. 5 tensile test specimen, as specified in JIS Z 2241:2011, is taken from the non-oriented electrical steel sheet. A tensile test specimen is taken. Using the taken tensile test specimen, a tensile test is performed at room temperature and atmospheric pressure in accordance with JIS Z 2241:2011 to obtain the yield strength YP (MPa) and tensile strength TS (MPa). In this embodiment, the average grain size D of the non-oriented electrical steel sheet is fine enough to satisfy feature 5. Therefore, the upper yield point can be observed in the stress-strain curve obtained by the above tensile test. Accordingly, the yield strength YP is taken as the upper yield point.

[0062] [(Feature 3) Regarding the amount of P segregation at grain boundaries] In the non-oriented electrical steel sheet of this embodiment, the index of P concentration at grain boundaries is [P] GB And, [P] is an indicator of the P concentration within the grain. IG We define and as follows: [P] GB : The grain boundary region of the fracture surface of non-oriented electrical steel sheet is analyzed by Auger electron spectroscopy to obtain the Auger differential spectrum. In the obtained Auger differential spectrum, the peak-to-peak value of Fe near an electron energy of 700 eV is determined. 700 This is defined as follows. Furthermore, the peak-to-peak value of P near an electron energy of 120 eV is defined as P 120 This is defined as Fe 700 P for 120 P is the ratio of 120 / Fe 700 [P] GB This is how it is defined. [P] IG : The intragranular region of the fracture surface of a non-oriented electrical steel sheet is analyzed by Auger electron spectroscopy to obtain the Auger differential spectrum. In the obtained Auger differential spectrum, the peak-to-peak value of Fe near an electron energy of 700 eV is determined. 700 This is defined as follows. Furthermore, the peak-to-peak value of P near an electron energy of 120 eV is defined as P 120 This is defined as Fe 700P with respect to 120 The ratio of P 120 / Fe 700 is defined as [P] IG . Note that the vicinity of EN (eV) (EN is the numerical value of electron energy) means the range of EN ± 5%. Also, the peak-to-peak value of P means the difference value between the maximum peak and the minimum peak of P in the vicinity of EN (eV). The peak-to-peak value of Fe means the difference value between the maximum peak and the minimum peak of Fe in the vicinity of EN (eV).

[0063] [P] defined as above GB , and [P] IG satisfies the following formula (1). [P] GB / [P] IG > 2.0 (1)

[0064] [P] GB / [P] IG means the ratio of the P concentration at the grain boundary to the P concentration within the grains in the non-oriented electrical steel sheet. That is, [P] GB / [P] IG becomes an index of the amount of P segregation at the grain boundary. In the non-oriented electrical steel sheet of this embodiment, the amount of P segregation at the grain boundary is increased so that [P] GB / [P] IG is higher than 2.0. As a result, grain boundary fracture is likely to occur during punching. Consequently, excellent punching workability is obtained.

[0065] [P] GB / [P] IG The preferable lower limit of is 2.1, more preferably 2.2, still more preferably 2.3, and still more preferably 2.5. [P] GB / [P] IG The preferable upper limit of is 5.0. In this case, an appropriate amount of grain boundary fracture occurs during punching. Therefore, even better punching workability is obtained. [P] GB / [P] IG The preferable upper limit of is 4.9, more preferably 4.8.

[0066] [[P] GB and [P] IG [Measurement Method] [P] GB and [P] IG It can be measured by the following method. Multiple rough sample pieces measuring 18 mm L × 4 mm W × thickness T (L is the length in the rolling direction, W is the width, and T is the thickness) are taken from a non-oriented electrical steel sheet. A notch is cut into the center of each rough sample piece in the length direction to form a notch extending in the width direction. The prepared test pieces are used as test pieces for Auger electron spectroscopy peak measurement.

[0067] A specimen for Auger electron spectroscopy peak measurement is placed in an Auger electron spectrometer and cooled with liquid nitrogen. After cooling, the specimen is fractured to form a fracture surface. Using a scanning electron microscope (SEM), 10 observation areas of the obtained fracture surface are observed at 2000 to 10000x magnification, and one intergranular fracture surface and one intragranular fracture surface are selected from each observation area.

[0068] Figure 1 shows an example of an SEM image obtained by observation at 3000x magnification using an SEM. Referring to Figure 1, when a circular judgment field VF with a diameter of 3 μm is placed in the observation area, the region 10 (corresponding to the cleavage fracture surface) in which no river pattern is observed within the judgment field VF is determined to be the grain boundary region 10. On the other hand, the region 20 in which a river pattern is observed within the judgment field VF is determined to be the intragranular region 20. When determining that the judgment field VF is a grain boundary region 10, a region is selected in which the river pattern is not substantially observed throughout the entire judgment field FV (i.e., a region that is substantially smooth overall, where no pattern is observed). Similarly, when determining that the judgment field VF is an intragranular region 20, a region is selected in which the river pattern is uniformly observed throughout the entire judgment field FV (i.e., a region in which smooth regions and regions with river patterns do not coexist, and where the river pattern is substantially present overall).

[0069] Elemental analysis by Auger electron spectroscopy is performed on one selected grain boundary region and one intragranular region within each observation area. Specifically, as shown in Figure 2, elemental analysis is performed on any 1.0 μm × 1.0 μm measurement area 100 within the determination field VF, which is determined to be a grain boundary region 10, to obtain the differential spectra of Auger electrons for P and Fe.

[0070] An example of the obtained Auger electron differential spectrum is shown in Figure 3. In the Auger electron differential spectrum, the main peak of Fe appears at an electron energy of around 700 eV. Therefore, the peak-to-peak value, which is the difference between the maximum and minimum peaks of Fe near 700 eV, is used for Fe 700 This is defined as follows. In addition, in the Auger electron differential spectrum, the main peak of P appears near an electron energy of 120 eV. Therefore, the peak-to-peak value of P near 120 eV is defined as P 120 This is defined as follows. And the obtained Fe 700 and P 120 Based on P 120 / Fe 700 To determine P at the grain boundary fracture surface in each observation region. 120 / Fe 700 We find the following 10 P values. 120 / Fe 700 The arithmetic mean of [P] GB Let's assume that.

[0071] Similarly, elemental analysis is performed on any 1.0 μm × 1.0 μm measurement area within the determination field VF, which is determined to be an intragranular region 20 in each observation area, to obtain the differential spectra of Auger electrons of P and Fe. Then, based on the obtained Auger electron differential spectra, P 120 / Fe 700 Determine the following: In the intragranular region within each observation area, P 120 / Fe 700 We find the following 10 P values. 120 / Fe 700 The arithmetic mean of [P] IG Let's assume that.

[0072] For elemental analysis using Auger electron spectroscopy, the primary beam acceleration voltage is set to 10 kV.

[0073] [(Feature 4) Difference between tensile strength TS and yield strength YP] In the non-oriented electrical steel sheet of this embodiment, the difference ΔS between the tensile strength TS and the yield strength YP is 110 MPa or less.

[0074] The smaller the difference ΔS, the more the plastic deformation leading to fracture can be suppressed. In this case, the amount of burr during punching can be reduced. As a result, excellent punching workability can be obtained. In this embodiment, the amount of P segregation at the grain boundaries is increased while strain aging by C is promoted. This raises the upper yield point in the stress-strain curve of the non-oriented electrical steel sheet, thereby increasing the yield strength YP. As a result, the difference ΔS between the tensile strength TS and the yield strength YP is kept below 110 MPa.

[0075] A preferred upper limit for the difference ΔS is 105 MPa, more preferably 100 MPa, even more preferably 95 MPa, and even more preferably 90 MPa.

[0076] [(Feature 5) Regarding the average crystal grain size D] In the non-oriented electrical steel sheet of this embodiment, the average grain size D further satisfies equation (2). D≦100-15×[P] GB / [P] IG +1500 / TS (2) Here, the value of the tensile strength TS (MPa) is substituted for TS in equation (2).

[0077] If non-oriented electrical steel sheets satisfy characteristics 1 to 4, they can achieve excellent punching workability despite having high strength. However, non-oriented electrical steel sheets satisfying characteristics 1 to 4 may experience a decrease in toughness due to embrittlement. [P] shows the amount of P segregation at the grain boundaries of non-oriented electrical steel sheets. GB The higher the value of [P], and the higher the tensile strength TS of the non-oriented electrical steel sheet, the more likely the toughness of the non-oriented electrical steel sheet is to decrease. Therefore, in the non-oriented electrical steel sheet of this embodiment, the average grain size D is set to [P]GB / [P] IG The size shall be determined according to the tensile strength TS. Here, FN is defined as follows: FN = 100 - 15 × [P] GB / [P] IG +1500 / TS If the average grain size D is less than or equal to FN, then [P] GB / [P] IG Furthermore, the average grain size D is sufficiently small compared to the tensile strength TS. Therefore, excellent toughness is obtained.

[0078] [Method for measuring average crystal grain size D] The average grain size D is determined by the following method: The cross section (L section) of the non-oriented electrical steel sheet parallel to the rolling direction is used as the observation surface. After mirror polishing the observation surface, etching is performed on the mirror-polished observation surface using Nital solution. Three arbitrary locations on the etched observation surface are observed at 100x magnification using an optical microscope, and photographic images of the observation field are generated. If the thickness of the non-oriented electrical steel sheet is t (mm), the observation field is rectangular, consisting of the sides in the thickness direction and the sides in the rolling direction, and is t mm × t mm. Using the photographic images, the average grain size (μm) at each field of view area is determined by the sectioning method in accordance with JIS G 0551:2013 "Steel - Microscopic test method for grain size". The arithmetic mean of the three obtained average grain sizes is taken as the average grain size D (μm).

[0079] [Regarding the effects of the non-oriented electrical steel sheet of this embodiment] The non-oriented electrical steel sheet of this embodiment satisfies features 1 to 5. Therefore, despite its high strength, the non-oriented electrical steel sheet of this embodiment offers excellent punching properties. Furthermore, the non-oriented electrical steel sheet of this embodiment also offers excellent toughness.

[0080] [Manufacturing method for non-oriented electrical steel sheets] An example of a method for manufacturing non-oriented electrical steel sheets according to this embodiment will be described. The method for manufacturing non-oriented electrical steel sheets according to this embodiment includes the following steps. (Process 1) Hot rolling process (Process 2) Hot-rolled sheet annealing process (Process 3) Cold rolling process (Step 4) Finish annealing process Note that the hot-rolled sheet annealing process is optional. In other words, the hot-rolled sheet annealing process may be omitted. The following describes each process.

[0081] [(Process 1) Hot Rolling Process] In the hot rolling process, a slab is hot-rolled to produce a hot-rolled steel sheet. The slab has the chemical composition described above. The slab is manufactured by a well-known method. For example, a slab is manufactured by continuous casting using molten metal with the chemical composition described above.

[0082] Hot rolling is performed on the prepared slab. The various conditions during hot rolling are not particularly limited. The manufacturing conditions during hot rolling are not particularly limited. The slab heating temperature is, for example, 1000°C to 1300°C. The finish rolling temperature is, for example, 800°C to 1100°C. The coiling temperature is, for example, 500°C to 800°C.

[0083] [(Process 2) Hot-rolled sheet annealing process] The hot-rolled sheet annealing process is optional. In other words, the hot-rolled sheet annealing process may or may not be performed. If performed, the hot-rolled sheet annealing process involves annealing the hot-rolled steel sheet. The hot-rolled sheet annealing may be box annealing or continuous annealing. The annealing conditions in the hot-rolled sheet annealing process are not particularly limited. The annealing temperature is, for example, 900 to 1100°C. The annealing time is, for example, 1 second to 10 hours. If necessary, a well-known pickling treatment may be performed on the steel sheet before and / or after annealing in the hot-rolled sheet annealing process.

[0084] [(Process 3) Cold Rolling Process] In the cold rolling process, cold rolling is performed on hot-rolled steel sheets produced in the hot rolling process, or on hot-rolled steel sheets after the hot-rolled sheet annealing process, to produce cold-rolled steel sheets. Cold rolling may be performed once or multiple times. If cold rolling is performed multiple times, intermediate annealing may be performed after each cold rolling and before the next cold rolling.

[0085] [(Step 4) Finish annealing process] Non-oriented electrical steel sheets are manufactured by performing finish annealing on cold-rolled steel sheets produced through a finish rolling process. In finish annealing, the cold-rolled steel sheets, which have been finished to their final thickness, are annealed to recrystallize and grow crystal grains. Finish annealing is carried out using a continuous annealing furnace equipped with a heating zone, a soaking zone, and a cooling zone from upstream to downstream. The continuous annealing furnace may also be equipped with an insulating coating and coating drying device downstream of the cooling zone. The finish annealing process satisfies the following conditions 1 to 4. (Condition 1) Annealing is performed at a maximum temperature T1 of 950℃ or lower. (Condition 2) The tension TE1 applied to the cold-rolled steel sheet during annealing is 0.15 to 0.80 kgf / mm². 2 Let's assume that. (Condition 3) During cooling after annealing, the average cooling rate CR1 in the temperature range of 700-500°C should be 20°C / second or less. (Condition 4) During cooling after annealing, the maximum tension TE2 applied to the cold-rolled steel sheet in the temperature range of 200°C or below is TE1 + 0.15 kgf or more and 0.40 kgf / mm². 2 That concludes this section. Conditions 1 through 4 will be explained below.

[0086] [(Condition 1) Regarding the maximum temperature T1 reached] The maximum temperature T1 is set to 950°C or lower. If the maximum temperature T1 exceeds 950°C, the grain boundary migration speed during grain growth increases, and the amount of P segregation at the grain boundaries decreases due to the drag effect. In addition, the grains become excessively coarse, and the average grain size D no longer satisfies equation (2). Therefore, the maximum temperature T1 is 950°C or lower. The lower limit of the maximum temperature T1 can be any known temperature. For example, the lower limit of the maximum temperature T1 is 800°C.

[0087] [(Condition 2) Regarding the tension TE1 during finish annealing] The tension TE1 applied to the cold-rolled steel sheet during finish annealing suppresses meandering of the steel sheet as it passes through the casing. The tension TE1 is 0.15 kgf / mm². 2 If the above conditions are met, the meandering of the steel plate during transit can be sufficiently suppressed. On the other hand, if the tension TE1 is too high, residual strain introduced into the steel sheet during high-temperature annealing may remain, potentially degrading the iron loss. Furthermore, the difference ΔS between the tensile strength TS and yield strength YP of non-oriented electrical steel sheets exceeds 110 MPa. Therefore, the upper limit of the tension TE1 should be set to 0.80 kgf / cm². 2 The preferred upper limit for tension TE1 is 0.50 kgf / mm². 2 And more preferably 0.35 kgf / mm 2 be.

[0088] [(Condition 3) Regarding the average cooling rate CR1] In the finish annealing process, the cold-rolled steel sheet is cooled after finish annealing. The temperature range of 700-500°C during cooling is a temperature range in which phosphorus (P) easily diffuses and segregates at grain boundaries. Therefore, the cooling rate in the 700-500°C range is kept as slow as possible, and the residence time in this temperature range is extended. This allows P to diffuse sufficiently at the grain boundaries, increasing the amount of P segregation at the grain boundaries.

[0089] If the average cooling rate CR1 is 20°C / second or less, the cooling rate between 700°C and 500°C is sufficiently slow, and sufficient residence time in the 700°C-500°C range can be ensured. As a result, [P] GB / [P] IG The result will be higher than 2.0.

[0090] [(Condition 4) Regarding the maximum tension TE2 in the temperature range of 200℃ or below] In the cooling zone of a continuous annealing furnace, multiple bridle rolls and conveyor rolls are arranged. Beyond the cooling zone, the furnace is divided into several zones from upstream to downstream. The multiple bridle rolls are positioned to apply different tensions to the cold-rolled steel sheets in each zone. In addition to the bridle rolls, the tension of the steel sheets before and after the conveyor rolls in the cooling zone can also be changed (adjusted) by the conveyor rolls.

[0091] During cooling after finish annealing, in multiple zones within the temperature range of 200°C or below, the maximum tension TE2 among the one or more tensions applied to the cold-rolled steel sheet is set to TE1 + 0.15 kgf / mm². 2 The above and 0.40 kgf / mm 2 This concludes the explanation. In the temperature range below 200°C, the substitutional element P does not move, but the interstitial element C does. Therefore, if high tension can be applied to the cold-rolled steel sheet in the temperature range below 200°C, solid-solution C will adhere to the dislocations introduced by the tension. This can further accelerate the strain aging of C.

[0092] Therefore, the maximum tension TE2 applied to cold-rolled steel sheets in the temperature range of 200℃ or below is TE1 + 0.15 kgf / mm 2 The above and 0.40 kgf / mm 2 This concludes the explanation. In this case, the strain aging of C can be sufficiently accelerated. As a result, the difference ΔS between the tensile strength TS and the yield strength YP of the non-oriented electrical steel sheet becomes 110 MPa or less.

[0093] As mentioned above, the tension for all periods (zones) in the temperature range below 200°C is TE1 + 0.15 kgf / mm². 2 The above and 0.40 kgf / mm 2 It is not necessary to exceed the above. The maximum tension TE2 applied during at least part of the period (zone) in the temperature range below 200°C is TE1 + 0.15 kgf / mm 2 The above and 0.40 kgf / mm 2 The above should suffice. Therefore, the maximum value of the tension TE2 applied to cold-rolled steel sheets in the temperature range of 200°C or below should be TE1 + 0.15 kgf / mm². 2 The above and 0.40 kgf / mm 2 That concludes this section. Furthermore, while there is no particular upper limit to the maximum tension TE2, considering the normal equipment capacity, the upper limit of the maximum tension TE2 is 1.00 kgf / mm². 2 That is the case.

[0094] [Other processes] In the manufacturing method described above, a coating process may be performed after the finish annealing process. In the coating process, an insulating coating is applied to the surface of the non-oriented electrical steel sheet after finish annealing. The type of insulating coating is not particularly limited. The insulating coating may be made of organic components, inorganic components, or a mixture of organic and inorganic components.

[0095] The non-oriented electrical steel sheet of this embodiment can be manufactured by the manufacturing method described above. However, the manufacturing method of the non-oriented electrical steel sheet of this embodiment is not particularly limited, as long as it satisfies features 1 to 5. [Examples]

[0096] Non-oriented electrical steel sheets having the chemical compositions shown in Tables 1-1 and 1-2 were manufactured by the following method.

[0097] [Table 1-1]

[0098] [Table 1-2]

[0099] Hot rolling was performed on a slab (steel billet) to produce a hot-rolled steel sheet with a thickness of 2.0 mm. The slab heating temperature was 1000°C to 1300°C. The finish rolling temperature was 800°C to 1100°C. The coiling temperature was 500°C to 800°C. Hot-rolled steel sheets were then subjected to hot-rolled sheet annealing by uniform heating at 1000°C for 1 minute. Cold-rolled steel sheets with a thickness of 0.25 mm were then produced by cold-rolling the annealed steel sheets.

[0100] The manufactured cold-rolled steel sheets underwent finish annealing. The annealing temperature T1 (°C) and tension TE1 (kgf / mm²) during the finish annealing were specified. 2 ), average cooling rate CR1 (°C / sec), and tension TE2 (kgf / mm²) 2 The results are shown in Table 2. The non-oriented electrical steel sheets for each test number were manufactured using the above manufacturing process.

[0101] [Table 2]

[0102] [Evaluation Test] The following evaluation tests were conducted on the non-oriented electrical steel sheets for each test number. (Test 1) Chemical composition measurement test (Test 2) Tensile strength TS and yield strength YP measurement test (Exam 3) [P] GB and [P] IG Measurement test (Test 4) Measurement test of average crystal grain size D (Test 5) Magnetic properties evaluation test (Test 6) Punching processability evaluation test (Test 7) ​​Toughness evaluation test The following explains Exams 1 through 7.

[0103] [(Test 1) Chemical Composition Measurement Test] The chemical composition of the non-oriented electrical steel sheets for each test number was determined in accordance with the method described in the above-mentioned [Method for Measuring the Chemical Composition of Non-Oriented Electrical Steel Sheets]. As a result, the chemical composition of the non-oriented electrical steel sheets for each test number was as shown in Tables 1-1 and 1-2.

[0104] [(Test 2) Tensile strength TS and yield strength YP measurement test] The tensile strength TS (MPa) and yield strength YP (MPa) of the non-oriented electrical steel sheets for each test number were determined in accordance with the method described in the above-mentioned [Measurement Method for Tensile Strength TS and Yield Strength YP]. The obtained tensile strength TS (MPa) and yield strength YP (MPa) are shown in Table 3. Furthermore, the difference ΔS (=TS-YP) is shown in the "ΔS (MPa)" column in Table 3.

[0105] [Table 3]

[0106] [(Exam 3)[P] GB and [P]IG [Measurement test] The above [[P] GB and [P] IG In accordance with the method described in [Measurement Method], the [P] of the non-oriented electrical steel sheet for each test number GB and [P] IG We sought [P]. GB / [P] IG This is shown in Table 3.

[0107] [(Test 4) Measurement test of average crystal grain size D] The average grain size D (μm) of the non-oriented electrical steel sheet for each test number was determined in accordance with the method described in [Method for Measuring Average Grain Size D] above. The obtained average grain size D (μm) is shown in Table 3. In Table 3, the "FN" column contains the FN value (=100-15×[P]). GB / [P] IG This indicates +1500 / TS).

[0108] [(Test 5) Magnetic Properties Evaluation Test] The magnetic flux density B is determined by the following method. 50 and iron loss W 5 / 1000 They sought it. [Magnetic flux density B 50 [Measurement Method] For each test number of non-oriented electrical steel sheet, half of the Epstein test specimens (14 each) were used in the rolling direction (L direction) and the direction perpendicular to the rolling direction (C direction) to measure the magnetic flux density B 50 The magnetic flux density B at 5000 A / m was measured. Specifically, from each test number of non-oriented electrical steel sheet, half of the Epstein test specimens extending in the L direction and half of the Epstein test specimens extending in the C direction were cut out in accordance with JIS C 2550-1 (2011). The electrical steel strip test method in accordance with JIS C 2550-1 (2011) and 2550-3 (2011) was performed on the cut Epstein test specimens to measure the magnetic flux density B at 5000 A / m, which is the average of the L and C directions. 50 The magnetic flux density B was measured. 50 (T) is shown in Table 3.

[0109] [Iron loss W 5 / 1000 [Measurement Method] The magnetic flux density B mentioned above 50 Similar to the measurement method, Epstein test specimens were prepared. The electrical steel strip test method in accordance with JIS C 2550-1(2011) and 2550-3(2011) was performed on the Epstein test specimens to obtain the average iron loss W at 1000 Hz and 0.5 T in the L direction (rolling direction) and the C direction (direction perpendicular to the rolling direction). 5 / 1000 The iron loss (W / kg) was measured. 5 / 1000 Table 3 shows the values ​​(W / kg).

[0110] [(Test 6) Punching Processability Evaluation Test] The punching processability of the non-oriented electrical steel sheets for each test number was evaluated in the following test. From the non-oriented electrical steel sheets for each test number, ring-shaped samples with an inner diameter of 90 mm and an outer diameter of 100 mm were punched out using a die with a clearance of 20 μm.

[0111] Dimensional accuracy was evaluated using the following method. First, the inner and outer diameters of the punched ring-shaped sample were determined using a dimensional measuring instrument. Using the measured inner diameter, the maximum deviation between the measured inner diameter and a perfect circle (90 μm) was determined (the maximum difference between the measured inner diameter and a perfect circle). Furthermore, using the measured outer diameter, the maximum deviation between the measured outer diameter and a perfect circle (100 mm) was determined. If both the maximum deviation of the inner diameter and the maximum deviation of the outer diameter were 20 μm or less, it was judged that excellent dimensional accuracy had been obtained (indicated as "E (Excellent)" in the "Dimensional Accuracy" column of the "Punching Processability" column in Table 3). On the other hand, if either the maximum deviation of the inner diameter or the maximum deviation of the outer diameter exceeded 20 μm, it was judged that excellent dimensional accuracy had not been obtained (indicated as "B (Bad)" in the "Dimensional Accuracy" column of the "Punching Processability" column in Table 3).

[0112] The amount of sagging was evaluated using the following method. A ring-shaped sample was cut into an L-shaped cross section. The cut ring-shaped sample was embedded in resin, and the L-shaped cross section was polished. After polishing, the cut end face portions of the inner circumferential surface (inner diameter) and the outer circumferential surface (outer diameter) of the L-shaped cross section were observed under an optical microscope at a magnification of 100x. Figure 4 is an enlarged view of the portion of the ring-shaped sample including the cut end face in the L-shaped cross section. Referring to Figure 4, the intersection position P1 between the sagging portion 20 and the cut end face 30 was identified. For both the inner and outer circumferential surfaces, if the distance t1 in the thickness direction from the surface 10 of the ring-shaped sample to the intersection position P1 was within the range of 1 / 4 of the thickness t0 (i.e., the thickness of the non-oriented electrical steel sheet) from the surface 10, it was determined that the amount of sagging was sufficiently suppressed (indicated as "E (Excellent)" in the "Amount of Sagging" column of the "Dangling Processability" column in Table 3). On the other hand, if the distance t1 on at least one of the inner and outer surfaces exceeds the range from the surface 10 to a position 1 / 4 of the plate thickness t0 (i.e., the plate thickness of the non-oriented electrical steel sheet), it was determined that the amount of sagging could not be sufficiently suppressed (indicated as "B (Bad)" in the "Amount of Sagging" column of the "Drillability" column in Table 3).

[0113] Excellent punching performance was determined when excellent dimensional accuracy was achieved and the amount of burr was sufficiently suppressed.

[0114] [(Test 7) ​​Toughness Evaluation Test] The toughness of the non-oriented electrical steel sheets for each test number was evaluated by fatigue testing. Specifically, fatigue test specimens were taken from the non-oriented electrical steel sheets for each test number, with the L direction as the longitudinal direction. The fatigue test specimens were 30 mm wide and 180 mm long, and the parallel section located in the center of the longitudinal direction of the fatigue test specimen was 15 mm wide and 35 mm long. The end faces of the parallel section and the R section of the fatigue test specimen were polished with 600-grit emery paper.

[0115] Using the fatigue test specimens described above, the following fatigue tests were conducted at room temperature and in air. In the fatigue tests, a single-sided stress (tensile-tensile) with a stress ratio of 0.05 was used, and the frequency was set to 20 Hz. The stress amplitude at which fracture did not occur after 2 million cycles was defined as the fatigue strength (MPa).

[0116] [Evaluation Results] Referring to Tables 1-1, 1-2, 2, and 3, the non-oriented electrical steel sheets for test numbers 1-49 satisfied features 1-5. Therefore, the magnetic flux density B 50 It is 1.55T or more, and iron loss W 5 / 1000 The load was 20.0 W / kg or less. Furthermore, excellent punching properties were obtained. In addition, the fatigue strength was 420 MPa or higher, indicating excellent toughness.

[0117] In tests 50 and 51, the annealing temperature was too high. As a result, the average grain size D did not satisfy equation (2). Consequently, the fatigue strength was less than 420 MPa, and sufficient toughness was not achieved.

[0118] In test number 52, the tension TE1 applied to the cold-rolled steel sheet during finish annealing was too high. As a result, the difference ΔS exceeded 110 MPa. Consequently, the amount of sagging could not be sufficiently suppressed, and excellent dimensional accuracy could not be obtained. In addition, iron loss W 5 / 1000 The (W / kg) ratio was high.

[0119] In tests 53 and 54, the average cooling rate CR1 was too fast. Therefore, [P] GB / [P] IG The value was less than 2.0. As a result, in the punching processability evaluation test, the maximum deviation of the inner diameter and / or the maximum deviation of the outer diameter exceeded 20 μm, and excellent dimensional accuracy could not be obtained.

[0120] In tests 55-57, the tension TE2 was too low. As a result, the difference ΔS exceeded 110 MPa. Consequently, the amount of sagging could not be sufficiently suppressed, and excellent punching performance could not be obtained.

[0121] Preferred embodiments of the present invention have been described above, but the present invention is not limited to such embodiments. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the ideas described in the claims, and these will naturally also fall within the technical scope of the present invention.

Claims

1. Non-oriented electrical steel sheet, In mass percent, Si: 3.2-4.5%, Mn: 0.3 to 3.5%, Sol. Al: 0.2–2.0%, C: 0.0010-0.0030%, N: more than 0% and less than 0.0050%, O: more than 0% and less than 0.0200%, P: more than 0% and less than 0.100%, S: more than 0% and less than 0.0030%, Ti: more than 0% and less than 0.0030%, Mo: 0-0.100%, Cr: 0-1.000%, Ni: 0 to 0.50%, Cu: 0 to 0.50%, B: 0 to 0.0010%, Zn: 0 to 0.0050%, Ga: 0 to 0.0050%, Ge: 0 to 0.0050%, As: 0 to 0.0100%, Sn: 0-0.20%, Sb: 0 to 0.10%, Ca: 0-0.0050%, La: 0 to 0.0050%, Ce: 0 to 0.0050%, Nd: 0 to 0.0010%, Mg: 0-0.0030%, and, The remainder consists of Fe and impurities. The tensile strength TS is higher than 580 MPa. Elemental analysis of the grain boundary region of the fracture surface of the non-oriented electrical steel sheet was performed by Auger electron spectroscopy to obtain the Auger differential spectra of Fe and P, and the peak-to-peak value of Fe near an electron energy of 700 eV of the obtained Auger differential spectrum was determined. ７００ The peak-to-peak value of P near an electron energy of 120 eV for P. １２０ P is the ratio of １２０ / Fe ７００ [P] ＧＢ Defined as, Elemental analysis is performed by Auger electron spectroscopy in the intragranular region of the fracture surface of the non-oriented electromagnetic steel sheet to obtain the Auger differential spectra of Fe and P, and the peak-to-peak value Fe of Fe near an electron energy of 700 eV in the obtained Auger differential spectrum ７００ The ratio of the peak-to-peak value P of P near an electron energy of 120 eV to １２０ is defined as P １２０ / Fe ７００ When defined as [P] ＩＧ it satisfies formula (1), The difference ΔS between the tensile strength TS and the yield strength YP is 110 MPa or less. The average crystal grain size D (μm) satisfies equation (2), Non-oriented electrical steel sheet. [P] ＧＢ / [P] ＩＧ >2.0 (1) D≦100-15×[P] ＧＢ / [P] ＩＧ +1500 / TS (2) Here, the value of the tensile strength TS (MPa) is substituted for TS in equation (2).

2. A non-oriented electrical steel sheet according to claim 1, In mass percent, Mo: 0.001-0.100%, Cr: 0.001-1.000%, Ni: 0.01-0.50%, Cu: 0.01 to 0.50%, B: 0.0001 to 0.0010%, Zn: 0.0001 to 0.0050%, Ga: 0.0001-0.0050%, Ge: 0.0001 to 0.0050%, As: 0.0001 to 0.0100%, Sn: 0.01-0.20%, Sb: 0.01 to 0.10%, Ca: 0.0001-0.0050%, La: 0.0001 to 0.0050%, Ce: 0.0001 to 0.0050%, Nd: 0.0001 to 0.0010%, and, Contains one or more selected from the group consisting of Mg: 0.0001 to 0.0030%. Non-oriented electrical steel sheet.

3. A method for manufacturing a non-oriented electrical steel sheet according to claim 1 or claim 2, A hot rolling step for producing a hot-rolled steel sheet by performing hot rolling on a slab having the chemical composition described in claim 1 or claim 2, A cold rolling process to produce a cold-rolled steel sheet by cold-rolling the aforementioned hot-rolled steel sheet, The system includes a finish annealing step in which finish annealing is performed on the cold-rolled steel sheet, In the aforementioned finish annealing process, The cold-rolled steel sheet is annealed at a maximum temperature T1 of 950°C or less. The tension TE1 applied to the cold-rolled steel sheet during annealing is 0.15 to 0.80 kgf / mm ２ year, During the cooling of the cold-rolled steel sheet after annealing, the average cooling rate CR1 in the temperature range of 700 to 500°C is set to 20°C / second or less. During the cooling of the cold-rolled steel sheet after annealing, the maximum tension TE2 applied to the cold-rolled steel sheet in a temperature range of 200°C or less is TE1 + 0.15 kgf / mm². ２ The above and 0.40 kgf / mm² ２ That concludes this section. A method for manufacturing non-oriented electrical steel sheets.

Images