Non-oriented electrical steel sheet and method for producing same

Abstract

The purpose of the present invention is to provide a non-oriented electrical steel sheet which has excellent magnetic characteristics and excellent punching workability even when the non-oriented electrical steel sheet has high strength. The non-oriented electrical steel sheet of the present invention has TS higher than 580 MPa, and has [P] GB as the ratio P120 / Fe700 of the peak-to-peak value P120 of P in the vicinity of electron energy of 120 eV in Auger differential spectrum obtained in the grain boundary region of the fracture surface to the peak-to-peak value Fe700 of Fe in the vicinity of electron energy of 700 eV, where P120 / Fe700 is the ratio of P120 to Fe700 of the peak-to-peak value P120 of P in the vicinity of electron energy of 120 eV in Auger differential spectrum. When P120 / Fe700 is defined as [P] IG, the ratio of P120 to Fe700 in an Auger differential spectrum obtained in the intra-grain region of the fracture surface, i.e., P120 / Fe700, satisfies formula (1), the difference [Delta] S between TS and YP is 110 MPa or less, and the average crystal grain diameter D ([mu] m) satisfies formula (2). [P] GB / [P] IG > 2.0 (1) D < = 100-15 * [P] GB / [P] IG + 1500 / TS (2)

Description

Technical Field

[0001] The present disclosure relates to a non-oriented electrical steel sheet and a method for producing the same. Background Art

[0002] Non-oriented electromagnetic steel sheets are widely used as motor cores (iron cores). The motor core is a stator as a fixed part or a rotor as a rotating part. Different properties are required for the stator and the rotor. The stator is required to have excellent magnetic properties (low iron loss and high magnetic flux density). On the other hand, the rotor is also required to have magnetic properties, but high strength is particularly required for the following reasons. In recent years, designs have been made to increase the motor output by increasing the motor speed in motors used in electric vehicles or hybrid vehicles. Due to this, the load applied to the rotor as a rotating part increases during the operation of the motor. Therefore, high strength is required for the rotor. As a result, high strength and excellent magnetic properties are required for non-oriented electromagnetic steel sheets such as stators and rotors, which are raw materials for motor cores.

[0003] Japanese Patent Application Laid-Open No. 2008-050686 (Patent Document 1) proposes a non-oriented electrical steel sheet having high strength and excellent magnetic properties. In Patent Document 1, high strength and excellent magnetic properties are achieved by appropriately adjusting the chemical composition.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-050686 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] However, when manufacturing motor cores from non-oriented electromagnetic steel sheets, the non-oriented electromagnetic steel sheets are subjected to a punching process. If the strength of the non-oriented electromagnetic steel sheets increases, it may be difficult to punch them into the desired shape during punching, and the dimensional accuracy of the blanked raw material may decrease. In addition, when the non-oriented electromagnetic steel sheets are pressed into a die by a punching punch, the edges of the processed raw material may collapse. The motor core is manufactured by stacking multiple sheets of plate-shaped motor core materials punched from non-oriented electromagnetic steel sheets. If the processed motor core material collapses, it may be difficult to stack the motor core materials with high precision. Therefore, even when the strength of the non-oriented electromagnetic steel sheets is high, excellent punching workability is required to improve the dimensional accuracy of the shape of the blanked material and to suppress the occurrence of collapse.

[0009] An object of the present disclosure is to provide a non-oriented electrical steel sheet that can obtain excellent magnetic properties even with high strength and excellent punching workability, and a method for producing the same.

[0010] Technical means for solving technical problems

[0011] The non-oriented electrical steel sheet disclosed herein comprises, in mass%, 3.2-4.5% Si, 0.3-3.5% Mn, 0.2-2.0% sol. Al, 0.0010-0.0030%, 0.0050% N, 0.0200% O, 0.100% P, 0.030% S, 0.0030% Ti, 0.0030% Mo, 0.100% Cr, 0.0010% Ni, and 0.0050% Ni. 0%, 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%, Mg: 0~0.0030%, and the remainder is composed of Fe and impurities, and the tensile strength TS is higher than 580MPa. Elemental analysis was performed on the grain boundary region of the fracture surface of the non-oriented electrical steel sheet by Auger electron spectroscopy to obtain the Auger differential spectrum of Fe and P. The peak-to-peak value P of P around the electron energy of 120 eV in the obtained Auger differential spectrum was calculated. 120 The peak-to-peak value of Fe near the electron energy of 700 eV is 700 The ratio of P 120 / Fe 700 Defined as [P] GB Elemental analysis was performed on the intragranular region of the fracture surface of the non-oriented electrical steel sheet using Auger electron spectroscopy to obtain the Auger differential spectrum of Fe and P. The peak-to-peak value P of P near the electron energy of 120 eV in the obtained Auger differential spectrum was calculated. 120 The peak-to-peak value of Fe near the electron energy of 700 eV is 700 The ratio of P 120 / Fe 700 Defined as [P] IGIn this case, the non-oriented electrical steel sheet satisfies the formula (1). Furthermore, 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 grain size D (μm) satisfies the formula (2).

[0012] [P] GB / [P] IG >2.0 (1)

[0013] D≦100-15×[P] GB / [P] IG +1500 / TS (2)

[0014] Here, the numerical value of the tensile strength TS (MPa) is substituted into TS in the formula (2).

[0015] The manufacturing method of the non-oriented electromagnetic steel sheet disclosed in the present invention includes a hot rolling process, a cold rolling process, and a final annealing process. In the hot rolling process, the steel billet having the above-mentioned chemical composition is hot rolled to produce a hot-rolled steel sheet. In the cold rolling process, the hot-rolled steel sheet is cold rolled to produce a cold-rolled steel sheet. In the final annealing process, the cold-rolled steel sheet is subjected to final annealing. In the final annealing process, the cold-rolled steel sheet is annealed at a maximum reaching temperature T1 below 950°C, and the tension TE1 applied to the cold-rolled steel sheet during annealing is set to 0.15 to 0.80 kgf / mm 2 When the cold-rolled steel sheet after annealing is cooled, the average cooling rate CR1 in the temperature range of 700-500°C is set to 20°C / s or less. When the cold-rolled steel sheet after annealing is cooled, the maximum tension TE2 applied to the cold-rolled steel sheet in the temperature range below 200°C is set to TE1+0.15kgf / mm. 2 Above and 0.40kgf / mm 2 above.

[0016] Effects of the Invention

[0017] The non-oriented electrical steel sheet disclosed herein has excellent magnetic properties and excellent punching workability even at high strength. The method for producing a non-oriented electrical steel sheet of the present invention can produce the above-mentioned non-oriented electrical steel sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is an SEM image of a fracture surface of the non-oriented electrical steel sheet according to the present embodiment.

[0019] Figure 2 yes Figure 1 Magnified view of the grain boundary area.

[0020] Figure 3 It shows the Figure 2An example of the Auger differential spectra of Fe and P obtained by performing elemental analysis of the grain boundary region in using Auger electron spectroscopy.

[0021] Figure 4 This is an enlarged view of a portion including a cut end surface in an L-direction cross section of a ring-shaped test piece in a punching workability evaluation test in Examples. DETAILED DESCRIPTION

[0022] In order to produce a non-oriented electrical steel sheet that has both the excellent strength required for a rotor and the excellent magnetic properties required for a stator from a single non-oriented electrical steel sheet, the inventors of the present invention have studied non-oriented electrical steel sheets with high strength and excellent magnetic properties from the perspective of chemical composition. As a result, the inventors of the present invention have determined that a non-oriented electrical steel sheet having the following chemical composition, in 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 0.0050%, O: greater than 0% and less than 0.0200%, P: greater than 0% and less than 0.100%, S: greater than 0% and less than 0.0030%, Ti: greater than 0% and less than 0.00 30% or less, 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%, Mg: 0-0.0030%, and the remainder is Fe and impurities.

[0023] Therefore, the inventors of the present invention further studied means for achieving excellent blanking workability in the non-oriented electrical steel sheet having the above-mentioned chemical composition. As a result, the inventors of the present invention obtained the following findings.

[0024] A non-oriented electromagnetic steel sheet with a tensile strength higher than 580 MPa was punched and its shear surface was observed. In a non-oriented electromagnetic steel sheet with a tensile strength lower than 580 MPa, the shear surface after punching was dominated by ductile fracture surfaces. In contrast, the proportion of brittle fracture surfaces increased in the shear surface after punching of a non-oriented electromagnetic steel sheet with a tensile strength higher than 580 MPa compared to the shear surface after punching of a non-oriented electromagnetic steel sheet with a tensile strength lower than 580 MPa. Furthermore, in the brittle fracture surface, the proportion of intragranular fracture surfaces (cleavage fractures) was higher than that of grain boundary fracture surfaces. Cleavage developed along the cleavage fracture surface ((100) plane). Cleavage fractures do not necessarily exist along the cutting direction. Therefore, cracks developed along with unevenness, and the dimensional accuracy of the shape of the shear surface was reduced. On the other hand, compared with the case of only cleavage failure, in the case of a mixture of cleavage failure and grain boundary failure, a fracture close to the cutting target position was selected and cut. Therefore, the deviation of the cutting position is reduced and the dimensional accuracy of the sheared surface is improved.

[0025] Based on the above findings, the inventors of the present invention considered that when blanking non-oriented electrical steel sheets with a tensile strength higher than 580 MPa, by increasing the proportion of grain boundary fracture surfaces, the dimensional accuracy of the sheared surface can be improved, and as a result, the blanking workability can be improved. Furthermore, the inventors of the present invention also considered that if the amount of P segregation at the grain boundaries is increased, the proportion of grain boundary fracture surfaces during blanking can be increased. Therefore, the inventors of the present invention studied the relationship between the amount of P segregation at the grain boundaries and the blanking workability. As a result, it was found that the P concentration index at the grain boundary region, namely [P], obtained by the Auger electron spectroscopy method described later, GB [P] is an indicator of the P concentration in the intra-grain region. IG When the formula (1) is satisfied, excellent punching workability is obtained.

[0026] [P] GB / [P] IG >2.0 (1)

[0027] However, even if [P] GB / [P] IG Even when equation (1) is satisfied, edge collapse is still observed in the sheared surface after punching. Therefore, the inventors of the present invention have further studied means for suppressing edge collapse caused by punching. As a result, the inventors of the present invention have obtained the following findings.

[0028] In the blanking process, fracture occurs through elastic deformation and plastic deformation. Although the proportion of grain boundary destruction during blanking can be increased by increasing the amount of P segregation at the grain boundaries, the plastic deformation before fracture cannot be eliminated. This plastic deformation remains as edge collapse. Therefore, the inventors of the present invention have studied means for suppressing plastic deformation when intragranular destruction occurs. Plastic deformation occurs after an external force greater than the yield strength YP is applied to the steel sheet until an external force greater than the tensile strength TS is applied and the steel sheet breaks. Therefore, the inventors of the present invention believe that in the non-oriented electromagnetic steel sheet having the above-mentioned chemical composition, if the difference ΔS between the tensile strength TS and the yield strength YP is reduced, plastic deformation can be suppressed. Furthermore, the inventors of the present invention have found through further research that by making [P] GB / [P] IG When the value exceeds 2.0 and the difference ΔS between the tensile strength TS and the yield strength YP is 110 MPa or less, the dimensional accuracy after punching is excellent, and the occurrence of edge collapse on the sheared surface is sufficiently suppressed, thereby achieving excellent punching workability.

[0029] If the above chemical composition is set, [P] GB / [P] IG If the tensile strength TS is higher than 2.0 and the difference ΔS between the tensile strength TS and the yield strength YP is kept below 110 MPa, even high-strength non-oriented electrical steel sheets with tensile strength TS exceeding 580 MPa can achieve excellent blanking workability. However, such non-oriented electrical steel sheets sometimes suffer from reduced toughness. When non-oriented electrical steel sheets are used in rotors, they require not only high strength but also excellent toughness. Therefore, the inventors of the present invention have also conducted research on means to achieve excellent toughness. As a result, the inventors of the present invention have obtained the following findings.

[0030] [P] represents the amount of P segregation at the grain boundaries of the non-oriented electrical steel sheet GB 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 will decrease. Therefore, the average crystal grain size D (μm) of the non-oriented electrical steel sheet is set to [P] GB And the size corresponding to the tensile strength TS. In this case, there is a possibility of obtaining appropriate toughness.

[0031] Therefore, the inventors of the present invention aimed to determine the average crystal particle size D, [P] GB As a result, the inventors of the present invention found that if the average crystal grain size D satisfies the formula (2), even if the chemical composition of the non-oriented electrical steel sheet is set to be higher than 580 MPa, [P] GB / [P] IGExcellent toughness can also be obtained when the value is higher than 2.0 and the difference ΔS between the tensile strength TS and the yield strength YP is set to 110 MPa or less.

[0032] D≦100-15×[P] GB / [P] IG +1500 / TS (2)

[0033] Here, the numerical value of the tensile strength TS (MPa) is substituted into TS in the formula (2).

[0034] The non-oriented electrical steel sheet of the present embodiment is completed based on the above technical ideas, and its purpose is as follows.

[0035] The non-oriented electrical steel sheet of the first configuration comprises, in mass%, 3.2-4.5% Si, 0.3-3.5% Mn, 0.2-2.0% sol. Al, 0.0010-0.0030%, 0.0050% N, 0.0200% O, 0.100% P, 0.030% S, 0.0030% Ti, 0.0030% Mo, 0.100% Cr, 0.0010% Ni, and 0.5% Ni. 0%, 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%, Mg: 0~0.0030%, and the remainder is composed of Fe and impurities, and the tensile strength TS is higher than 580MPa. Elemental analysis was performed on the grain boundary region of the fracture surface of the non-oriented electrical steel sheet by Auger electron spectroscopy to obtain the Auger differential spectrum of Fe and P. The peak-to-peak value P of P around the electron energy of 120 eV in the obtained Auger differential spectrum was calculated. 120 The peak-to-peak value of Fe near the electron energy of 700 eV is 700 The ratio of P 120 / Fe 700 Defined as [P] GB Elemental analysis was performed on the intragranular region of the fracture surface of the non-oriented electrical steel sheet using Auger electron spectroscopy to obtain the Auger differential spectrum of Fe and P. The peak-to-peak value P of P near the electron energy of 120 eV in the obtained Auger differential spectrum was calculated. 120The peak-to-peak value of Fe near the electron energy of 700 eV is 700 The ratio of P 120 / Fe 700 Defined as [P] IG In this case, the non-oriented electrical steel sheet satisfies the formula (1). Furthermore, 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 grain size D (μm) satisfies the formula (2).

[0036] [P] GB / [P] IG >2.0 (1)

[0037] D≦100-15×[P] GB / [P] IG +1500 / TS (2)

[0038] Here, the numerical value of the tensile strength TS (MPa) is substituted into TS in the formula (2).

[0039] The non-oriented electrical steel sheet of the second constitution is the non-oriented electrical steel sheet of the first constitution, and contains, in mass%, 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: 0.0001-0.0050%, and Cu: 0.0001-0.0050%. At least one selected from the group consisting of: 1 to 0.0050%, As: 0.0001 to 0.0100%, Sn: 0.01 to 0.20%, Sb: 0.01 to 0.10%, Ca: 0.0001 to 0.0050%, La: 0.0001 to 0.0050%, Ce: 0.0001 to 0.0050%, Nd: 0.0001 to 0.0010%, and Mg: 0.0001 to 0.0030%.

[0040] The method for manufacturing a non-oriented electromagnetic steel sheet of the first constitution is a method for manufacturing a non-oriented electromagnetic steel sheet of the first or second constitution, comprising a hot rolling process, a cold rolling process and a final annealing process. In the hot rolling process, a steel billet having the chemical composition of the first or second constitution is hot rolled to manufacture a hot-rolled steel sheet. In the cold rolling process, the hot-rolled steel sheet is cold rolled to manufacture a cold-rolled steel sheet. In the final annealing process, the cold-rolled steel sheet is subjected to final annealing. In the final annealing process, the cold-rolled steel sheet is annealed at a maximum reaching temperature T1 below 950°C, and the tension TE1 applied to the cold-rolled steel sheet during annealing is set to 0.15 to 0.80 kgf / mm. 2When the cold-rolled steel sheet after annealing is cooled, the average cooling rate CR1 in the temperature range of 700-500°C is set to 20°C / s or less. When the cold-rolled steel sheet after annealing is cooled, the maximum tension TE2 applied to the cold-rolled steel sheet in the temperature range of 200°C or less is set to TE1+0.15kgf / mm. 2 Above and 0.40kgf / mm 2 above.

[0041] Next, the non-oriented electrical steel sheet according to the present embodiment will be described in detail.

[0042] [Features of the non-oriented electrical steel sheet according to the present embodiment]

[0043] The non-oriented electrical steel sheet of the present embodiment satisfies the following characteristics 1 to 5.

[0044] (Feature 1)

[0045] The chemical composition is calculated by mass as follows: Si: 3.2-4.5%, Mn: 0.3-3.5%, sol.Al: 0.2-2.0%, C: 0.0010-0.0030%, N: higher than 0% and lower than 0.0050%, O: higher than 0% and lower than 0.0200%, P: higher than 0% and lower than 0.100%, S: higher than 0% and lower than 0.0030%, Ti: higher than 0% and lower than 0.0030%, 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%, Mg: 0~0.0030%, and the remainder is composed of Fe and impurities.

[0046] (Feature 2)

[0047] The tensile strength TS is higher than 580 MPa.

[0048] (Feature 3)

[0049] Elemental analysis was performed on the grain boundary region of the fracture surface of the non-oriented electrical steel sheet by Auger electron spectroscopy to obtain the Auger differential spectra of Fe and P. The peak-to-peak value P of P around the electron energy of 120 eV in the obtained Auger differential spectrum was calculated. 120 The peak-to-peak value of Fe near the electron energy of 700 eV is700 The ratio of P 120 / Fe 700 Defined as [P] GB In addition, the Auger electron spectroscopy was used to perform elemental analysis in the intragranular region of the fracture surface to obtain the Auger differential spectra of Fe and P. The peak-to-peak value P of P near the electron energy of 120 eV in the obtained Auger differential spectrum was calculated. 120 The peak-to-peak value of Fe near the electron energy of 700 eV is 700 The ratio of P 120 / Fe 700 Defined as [P] IG At this time, [P] GB and [P] IG Satisfies formula (1).

[0050] [P] GB / [P] IG >2.0 (1)

[0051] (Feature 4)

[0052] The difference ΔS between the tensile strength TS and the yield strength YP is 110 MPa or less.

[0053] (Feature 5)

[0054] The average crystal grain size D (μm) satisfies the formula (2).

[0055] D≦100-15×[P] GB / [P] IG +1500 / TS (2)

[0056] Here, the numerical value of the tensile strength TS (MPa) is substituted into TS in the formula (2).

[0057] Next, features 1 to 5 will be described.

[0058] [(Feature 1) Chemical composition]

[0059] The chemical composition of the non-oriented electrical steel sheet of the present embodiment contains the following elements: It should be noted that "%" in the chemical composition of the non-oriented electrical steel sheet means mass % unless otherwise specified.

[0060] Si: 3.2-4.5%

[0061] Silicon (Si) increases the inherent resistance of steel sheets and reduces eddy current losses. Si also forms a solid solution in the steel sheet, increasing the strength of non-oriented electrical steel sheets. If the Si content is less than 3.2%, these effects are not fully achieved. On the other hand, if the Si content exceeds 4.5%, the blanking workability of the non-oriented electrical steel sheet decreases. Therefore, the Si content is preferably between 3.2% and 4.5%.

[0062] The lower limit of the Si content is preferably 3.3%, more preferably 3.4%.

[0063] The upper limit of the Si content is preferably 4.4%, more preferably 4.3%.

[0064] Mn: 0.3-3.5%

[0065] Manganese (Mn) increases the inherent resistivity of steel sheets and reduces eddy current losses. A Mn content of less than 0.3% does not fully achieve these effects. On the other hand, a Mn content exceeding 3.5% reduces the magnetic flux density of the steel. Therefore, the Mn content is preferably between 0.3% and 3.5%.

[0066] The lower limit of the Mn content is preferably 0.4%, more preferably 0.5%.

[0067] The upper limit of the Mn content is preferably 3.4%, more preferably 3.2%, and even more preferably 3.0%.

[0068] sol.Al: 0.2~2.0%

[0069] Aluminum (sol.Al) increases the inherent resistivity of steel sheets and reduces eddy current losses. A sol.Al content of less than 0.2% does not fully achieve these benefits. On the other hand, a sol.Al content exceeding 2.0% reduces the magnetic flux density of the steel. Therefore, the sol.Al content is preferably between 0.2% and 2.0%.

[0070] The preferred lower limit of the sol.Al content is 0.3%, more preferably 0.4%.

[0071] The upper limit of the sol.Al content is preferably 1.5%, more preferably 1.0%, and further preferably 0.5%.

[0072] In this specification, sol.Al means acid-soluble Al.

[0073] C: 0.0010~0.0030%

[0074] Carbon (C) fixes dislocations in the steel sheet, increasing its yield strength. A C content of less than 0.0010% does not fully achieve this effect. On the other hand, a C content exceeding 0.0030% causes fine carbides to precipitate in the steel sheet, degrading iron loss. Therefore, the C content is preferably between 0.0010% and 0.0030%.

[0075] The lower limit of the C content is preferably 0.0012%, more preferably 0.0014%, and further preferably 0.0016%.

[0076] The upper limit of the C content is preferably 0.0028%, more preferably 0.0026%, and further preferably 0.0024%.

[0077] N: more than 0% and less than 0.0050%

[0078] Nitrogen (N) is inevitably contained. That is, the N content is higher than 0%. N forms nitrides in the steel sheet, which deteriorates the iron loss. Therefore, the N content is higher than 0% and lower than 0.0050%.

[0079] The N content is preferably as low as possible. However, excessive reduction in the N content increases manufacturing costs. Therefore, from the perspective of industrial productivity, the lower limit of the N content is preferably 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%.

[0080] The upper limit of the N content is preferably 0.0040%, more preferably 0.0030%.

[0081] O: more than 0% and less than 0.0200%

[0082] Oxygen (O) is inevitably contained. That is, the O content is higher than 0%. O forms oxides in the steel sheet, deteriorating iron loss and magnetic flux density. Therefore, the O content is set to be higher than 0% and not more than 0.0200%.

[0083] The O content is preferably as low as possible. However, excessive reduction in the O content increases production costs. Therefore, from the perspective of industrial productivity, the lower limit of the O content is preferably 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%.

[0084] The upper limit of the O content is preferably 0.0150%, more preferably 0.0100%.

[0085] P: higher than 0% and less than 0.100%

[0086] Phosphorus (P) is inevitably present. Specifically, the P content is higher than 0%. P improves the blanking workability of high-strength non-oriented electrical steel sheets. However, if the P content exceeds 0.100%, the steel sheet becomes brittle, workability decreases, and sometimes cracks during cold rolling. Therefore, the P content is preferably higher than 0% and lower than 0.100%.

[0087] The P content is preferably as low as possible. However, excessive reduction in the P content increases manufacturing costs. Therefore, from the perspective 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%.

[0088] The upper limit of the P content is preferably 0.090%, more preferably 0.080%, and further preferably 0.070%.

[0089] S: more than 0% and less than 0.0030%

[0090] Sulfur (S) is inevitably contained. That is, the S content is higher than 0%. S generates MnS, which deteriorates iron loss. Therefore, the S content is higher than 0% and less than 0.0030%.

[0091] The S content is preferably as low as possible. However, excessive reduction in the S content increases manufacturing costs. Therefore, from the perspective of industrial productivity, the lower limit of the S content is preferably 0.0001%, more preferably 0.0003%, and even more preferably 0.0005%.

[0092] The upper limit of the S content is preferably 0.0028%, more preferably 0.0025%, even more preferably 0.0022%, and further preferably 0.0020%.

[0093] Ti: more than 0% and less than 0.0030%

[0094] Titanium (Ti) is inevitably contained. That is, the Ti content is higher than 0%. Ti forms carbonitrides, which improve the strength of non-oriented electrical steel sheets through precipitation strengthening. However, if the Ti content exceeds 0.0030%, excessive carbonitride formation deteriorates the magnetic properties. Therefore, the Ti content is set to be higher than 0% and less than 0.0030%.

[0095] The Ti content is preferably as low as possible. However, excessively low Ti content increases manufacturing costs. Therefore, the lower limit of the Ti content is preferably 0.0001%, more preferably 0.0003%, and even more preferably 0.0005%.

[0096] The upper limit of the Ti content is preferably 0.0028%, more preferably 0.0026%, and further preferably 0.0024%.

[0097] The remainder of the chemical composition of the non-oriented electrical steel sheet of this embodiment consists of Fe and impurities. Impurities are those that enter the non-oriented electrical steel sheet during industrial production, such as from raw material ores and scrap, or from the manufacturing environment. The content of these impurities is permitted within a range that does not adversely affect the non-oriented electrical steel sheet of this embodiment.

[0098] [Any element]

[0099] The chemical composition of the non-oriented electrical steel sheet of the present embodiment may further contain 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%, in place of a portion of Fe. These elements will be described below.

[0100] [Group 1: Mo, Cr, Ni and Cu]

[0101] The chemical composition of the non-oriented electrical steel sheet of this embodiment may further contain 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%, replacing part of Fe. These elements can improve the strength of the steel sheet.

[0102] Mo: 0~0.100%

[0103] Molybdenum (Mo) is an optional element and may not be included. That is, the Mo content may be 0%. When included, i.e., when the Mo content exceeds 0%, Mo forms carbides and improves the strength of the non-oriented electrical steel sheet through precipitation strengthening. The aforementioned effects can be achieved to a certain extent as long as Mo is included, even in small amounts.

[0104] However, if the Mo content exceeds 0.100%, carbides are excessively generated, deteriorating the magnetic properties. Therefore, the Mo content is set to 0 to 0.100%.

[0105] The lower limit of the Mo content is preferably 0.001%, more preferably 0.005%, even more preferably 0.010%, and further preferably 0.015%.

[0106] The upper limit of the Mo content is preferably 0.090%, more preferably 0.080%, and even more preferably 0.070%.

[0107] Cr: 0~1.000%

[0108] Chromium (Cr) is an optional element and may not be present. That is, the Cr content may be 0%. When present, i.e., when the Cr content is higher than 0%, Cr improves the strength of the non-oriented electrical steel sheet. Furthermore, Cr has a high affinity for carbon. Therefore, in the temperature range (500-700°C) where phosphorus easily diffuses, it fixes carbon and suppresses its segregation at grain boundaries. As a result, phosphorus easily segregates at grain boundaries. The aforementioned effects can be achieved to a certain extent by simply including Cr, even in small amounts.

[0109] However, if the Cr content exceeds 1.000%, the effect is saturated. Therefore, the Cr content is 0 to 1.000%.

[0110] The lower limit of the Cr content is preferably 0.001%, more preferably 0.005%, even more preferably 0.010%, further preferably 0.015%, further preferably 0.020%, further preferably 0.050%, further preferably 0.100%.

[0111] The upper limit of the Cr content is preferably 0.800%, more preferably 0.600%, and even more preferably 0.550%.

[0112] Ni: 0-0.50%

[0113] Nickel (Ni) is an optional element and does not need to be included. That is, the Ni content can be 0%. When included, that is, when the Ni content exceeds 0%, Ni improves the strength of the non-oriented electrical steel sheet. The aforementioned effects are achieved to a certain extent as long as Ni is included, even in small amounts. However, if the Ni content exceeds 0.50%, the steel sheet becomes brittle and workability decreases. Therefore, the Ni content is set to 0-0.50%.

[0114] The lower limit of the Ni content is preferably 0.01%, more preferably 0.05%, and even more preferably 0.10%.

[0115] The upper limit of the Ni content is preferably 0.45%, more preferably 0.40%, and even more preferably 0.35%.

[0116] Cu: 0-0.50%

[0117] Copper (Cu) is an optional element and does not need to be included. That is, the Cu content can be 0%. When included, that is, when the Cu content exceeds 0%, Cu improves the strength of the non-oriented electrical steel sheet. The aforementioned effect is achieved to a certain extent as long as Cu is included, even in small amounts. However, when the Cu content exceeds 0.50%, the steel sheet becomes brittle and workability decreases. Therefore, the Cu content is set to 0-0.50%.

[0118] The preferred lower limit of the Cu content is 0.01%, more preferably 0.05%, and even more preferably 0.10%. The preferred upper limit of the Cu content is 0.45%, more preferably 0.40%, and even more preferably 0.35%.

[0119] [Group 2: B, Zn, Ga, Ge and As]

[0120] The chemical composition of the non-oriented electrical steel sheet of the present embodiment may further contain one or more 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%, in place of a portion of Fe.

[0121] B: 0~0.0010%

[0122] Boron (B) is an optional element and may not be present. That is, the B content may be 0%. If present, i.e., if the B content exceeds 0%, B forms nitrides, which hinder recrystallization during final annealing. Therefore, the B content is 0 to 0.0010%.

[0123] Excessive reduction in the B content increases production costs. Therefore, from the viewpoint of industrial productivity, the lower limit of the B content is preferably 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%.

[0124] The upper limit of the B content is preferably 0.0009%, more preferably 0.0008%, and even more preferably 0.0007%.

[0125] Zn: 0~0.0050%

[0126] Zinc (Zn) is an optional element and may not be contained. That is, the Zn content may be 0%. When it is contained, that is, when the Zn content is higher than 0% and the Zn content is 0.0050% or less, no particular problem occurs.

[0127] Excessive reduction in the Zn content increases production costs. Therefore, from the perspective of industrial productivity, the lower limit of the Zn content is preferably 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%.

[0128] The upper limit of the Zn content is preferably 0.0020%, more preferably 0.0010%, and even more preferably 0.0005%.

[0129] Ga: 0~0.0050%

[0130] Gallium (Ga) is an optional element and may not be contained. That is, the Ga content may be 0%. When contained, that is, when the Ga content is higher than 0%, no particular problem will occur as long as the Ga content is 0.0050% or less.

[0131] Excessive reduction in Ga content increases production costs. Therefore, from the perspective of industrial productivity, the lower limit of Ga content is preferably 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%.

[0132] The upper limit of the Ga content is preferably 0.0020%, more preferably 0.0010%, and even more preferably 0.0005%.

[0133] Ge: 0~0.0050%

[0134] Germanium (Ge) is an optional element and may not be contained. That is, the Ge content may be 0%. When it is contained, that is, when the Ge content is higher than 0% and the Ge content is 0.0050% or less, no particular problem occurs.

[0135] Excessive reduction in the Ge content increases production costs. Therefore, from the perspective of industrial productivity, the lower limit of the Ge content is preferably 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%.

[0136] The upper limit of the Ge content is preferably 0.0020%, more preferably 0.0010%, and even more preferably 0.0005%.

[0137] As: 0~0.0100%

[0138] Arsenic (As) is an optional element and may not be contained. That is, the As content may be 0%. When it is contained, that is, when the As content is higher than 0% and the As content is 0.0100% or less, no particular problem occurs.

[0139] An excessive reduction in the As content increases production costs. Therefore, from the perspective of industrial productivity, the lower limit of the As content is preferably 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%.

[0140] The upper limit of the As content is preferably 0.0070%, more preferably 0.0050%, and even more preferably 0.0030%.

[0141] [Group 3: Sn and Sb]

[0142] The chemical composition of the non-oriented electrical steel sheet of this embodiment may further contain one or more elements selected from the group consisting of Sn: 0-0.20% and Sb: 0-0.10% in place of a portion of Fe. These elements reduce the iron loss of the non-oriented electrical steel sheet.

[0143] Sn: 0~0.20%

[0144] Tin (Sn) is an arbitrary element and may not be contained. That is, the Sn content may be 0%. When contained, that is, when the Sn content is higher than 0%, Sn segregates to the surface of the steel sheet, suppressing oxidation and nitridation during the final annealing. Sn further improves the texture of the steel sheet and increases the magnetic flux density. As a result, the iron loss of the non-oriented electromagnetic steel sheet is reduced. As long as a small amount of Sn is contained, the above-mentioned effect can be obtained to a certain extent. However, when the Sn content exceeds 0.20%, the steel sheet becomes brittle and the workability is reduced. Therefore, the Sn content is 0 to 0.20%.

[0145] The lower limit of the Sn content is preferably 0.01%, more preferably 0.03%, and even more preferably 0.05%.

[0146] The upper limit of the Sn content is preferably 0.18%, more preferably 0.16%, and even more preferably 0.15%.

[0147] Sb: 0~0.10%

[0148] Antimony (Sb) is an arbitrary element and may not be contained. That is, the Sb content may be 0%. When contained, that is, when the Sb content is higher than 0%, Sb, like Sn, segregates to the surface of the steel sheet and suppresses oxidation and nitridation during the final annealing. Sb further improves the texture of the steel sheet and increases the magnetic flux density. As a result, the iron loss of the non-oriented electromagnetic steel sheet is reduced. As long as Sb is contained, even in a small amount, the above-mentioned effect can be obtained to a certain extent. However, when the Sb content exceeds 0.10%, the steel sheet becomes brittle and the workability is reduced. Therefore, the Sb content is 0 to 0.10%.

[0149] The lower limit of the Sb content is preferably 0.01%, more preferably 0.02%.

[0150] The upper limit of the Sb content is preferably 0.08%, more preferably 0.06%, and even more preferably 0.05%.

[0151] [Group 4: Ca, La, Ce, Nd and Mg]

[0152] The chemical composition of the non-oriented electrical steel sheet of this embodiment may further contain 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%, in place of a portion of Fe. These elements promote grain growth during final annealing.

[0153] Ca: 0~0.0050%

[0154] Calcium (Ca) is an optional element and may not be present. That is, the Ca content may be 0%. When present, i.e., when the Ca content is higher than 0%, Ca combines with S during casting of the molten steel, forming coarse precipitates in the form of coarse sulfides and / or coarse oxysulfides. The particle size of the coarse precipitates is approximately 1 to 2 μm. During the manufacturing process after the casting step, the coarse sulfides adsorb fine inhibitors such as MnS, TiN, and AlN, which have a particle size of approximately 100 nm and are generated in the steel sheet. This suppresses the growth hindrance of grains due to the inhibitors during the final annealing. Therefore, the final annealing promotes grain growth. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. The aforementioned effects can be achieved to a certain extent by simply containing Ca, even in small amounts.

[0155] However, if the Ca content exceeds 0.0050%, coarse precipitates are excessively formed, which hinders recrystallization and grain growth in the final annealing step. Therefore, the Ca content is 0 to 0.0050%.

[0156] The lower limit of the Ca content is preferably 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%.

[0157] The upper limit of the Ca content is preferably 0.0045%, more preferably 0.0040%, and even more preferably 0.0035%.

[0158] La: 0~0.0050%

[0159] Lanthanum (La) is an optional element and may not be present. That is, the La content may be 0%. When present, i.e., when the La content exceeds 0%, La, like Ca, forms coarse precipitates, suppressing the growth retardation of grains caused by the inhibitor during final annealing. Therefore, final annealing promotes grain growth. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. The aforementioned effects can be achieved to a certain extent by simply including La, even in small amounts.

[0160] However, if the La content exceeds 0.0050%, coarse precipitates are excessively formed, which hinders recrystallization and grain growth in the final annealing step. Therefore, the La content is 0 to 0.0050%.

[0161] The lower limit of the La content is preferably 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%.

[0162] The upper limit of the La content is preferably 0.0045%, more preferably 0.0040%, and even more preferably 0.0035%.

[0163] Ce: 0~0.0050%

[0164] Cerium (Ce) is an optional element and does not need to be included. That is, the Ce content can be 0%. When included, that is, when the Ce content is higher than 0%, Ce forms coarse precipitates, similar to Ca, and suppresses the growth retardation of grains caused by the inhibitor during final annealing. Therefore, grain growth is promoted during final annealing. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. The above-mentioned effects can be achieved to a certain extent by including Ce, even in small amounts.

[0165] However, if the Ce content exceeds 0.0050%, coarse precipitates are excessively formed, which hinders recrystallization and grain growth during the final annealing step. Therefore, the Ce content is 0 to 0.0050%.

[0166] The lower limit of the Ce content is preferably 0.0001%, more preferably 0.0005%, and even more preferably 0.0010%.

[0167] The upper limit of the Ce content is preferably 0.0045%, more preferably 0.0040%, and even more preferably 0.0035%.

[0168] Nd: 0~0.0010%

[0169] Neodymium (Nd) is an optional element and does not need to be included. That is, the Nd content can be 0%. When included, that is, when the Nd content exceeds 0%, Nd forms coarse precipitates similar to Ca, suppressing the inhibitor's inhibition of grain growth during final annealing. Therefore, grain growth is promoted during final annealing. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. The aforementioned effects can be achieved to a certain extent by including Nd, even in small amounts.

[0170] However, if the Nd content exceeds 0.0010%, coarse precipitates are excessively formed, which hinders recrystallization and grain growth in the final annealing step. Therefore, the Nd content is 0 to 0.0010%.

[0171] The lower limit of the Nd content is preferably 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%.

[0172] The upper limit of the Nd content is preferably 0.0008%, more preferably 0.0006%, and even more preferably 0.0004%.

[0173] Mg: 0~0.0030%

[0174] Magnesium (Mg) is an optional element and may not be present. That is, the Mg content may be 0%. When present, i.e., when the Mg content exceeds 0%, Mg forms coarse precipitates, similar to Ca, and suppresses the growth retardation of grains caused by the inhibitor during final annealing. Therefore, grain growth is promoted during final annealing. As a result, the magnetic properties of the non-oriented electrical steel sheet are improved. The aforementioned effects can be achieved to a certain extent by including Mg, even in small amounts.

[0175] However, if the Mg content exceeds 0.0030%, coarse precipitates are excessively formed, which hinders recrystallization and grain growth during the final annealing step. Therefore, the Mg content is 0 to 0.0030%.

[0176] The lower limit of the Mg content is preferably 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%.

[0177] The upper limit of the Mg content is preferably 0.0020%, more preferably 0.0015%, and even more preferably 0.0010%.

[0178] [Method for measuring chemical composition of non-oriented electrical steel sheets]

[0179] The chemical composition of the non-oriented electrical steel sheet of this embodiment can be measured using a known component analysis method based on JIS G 0321:2017. Specifically, a drill is used to remove chips from the steel sheet. The chips are dissolved in acid to obtain a solution. The solution is subjected to ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) to perform elemental analysis of the chemical composition. The C and S contents are determined using the known high-frequency combustion method (combustion-infrared absorption method). The N content is determined using the known inert gas fusion-heat conduction method. The O content is determined using the known inert gas fusion-infrared absorption method.

[0180] It should be noted that the content of each element is the value obtained by rounding off the mantissa of the measured value according to the significant figures specified in the present embodiment to the lowest digit of the content of each element specified in the present embodiment. In addition, rounding means that if the mantissa is less than 5, it is discarded, and if the mantissa is more than 5, it is carried.

[0181] [(Feature 2) Tensile Strength TS]

[0182] In the non-oriented electrical steel sheet of the present embodiment, the tensile strength TS is higher than 580 MPa. That is, the non-oriented electrical steel sheet of the present embodiment has high strength.

[0183] The preferred lower limit of the tensile strength TS of the non-oriented electrical steel sheet of the present embodiment is 585 MPa, more preferably 590 MPa.

[0184] The upper limit of the tensile strength TS is not particularly limited. However, when characteristic 1 is satisfied, the upper limit of the tensile strength TS is, for example, 850 MPa.

[0185] [Measurement method of tensile strength TS and yield strength YP]

[0186] 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 piece specified in JIS Z 2241:2011 is collected from the non-oriented electrical steel sheet. The tensile test piece is then collected. Using the collected tensile test piece, a tensile test is conducted 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). It should be noted that in the non-oriented electrical steel sheet of this embodiment, the average crystal grain size D is sufficiently fine to satisfy Feature 5. Therefore, the upper yield point can be observed in the stress-strain curve obtained by the tensile test. Therefore, the yield strength YP is defined as the upper yield point.

[0187] [(Feature 3) Regarding the amount of P segregation at grain boundaries]

[0188] In the non-oriented electrical steel sheet of the present embodiment, [P], which is an index of P concentration at the grain boundary, is defined as follows: GB [P] is an indicator of the P concentration in the grains. IG .

[0189] [P] GB :

[0190] The grain boundary region of the fracture surface of the non-oriented electrical steel sheet was 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 the electron energy of 700 eV is defined as Fe 700 In addition, the peak-to-peak value of P near the electron energy of 120 eV is defined as P 120 . 120 Relative to Fe 700 The ratio is P 120 / Fe 700 Defined as [P]GB .

[0191] [P] IG :

[0192] The intra-grain region of the fracture surface of the non-oriented electrical steel sheet was 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 the electron energy of 700 eV was defined as Fe 700 In addition, the peak-to-peak value of P near the electron energy of 120 eV is defined as P 120 . 120 Relative to Fe 700 The ratio is P 120 / Fe 700 Defined as [P] IG .

[0193] The term "EN (eV)" (EN is the electron energy) refers to the range of ±5% of EN. The peak-to-peak value of P refers to the difference between the maximum and minimum peaks of P around EN (eV). The peak-to-peak value of Fe refers to the difference between the maximum and minimum peaks of Fe around EN (eV).

[0194] As defined above, [P] GB , and [P] IG The following formula (1) is satisfied.

[0195] [P] GB / [P] IG >2.0 (1)

[0196] [P] GB / [P] IG Indicates 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 It is an indicator of the amount of P segregation at the grain boundaries. In the non-oriented electrical steel sheet of this embodiment, the amount of P segregation at the grain boundaries is increased so that [P] GB / [P] IG When the ratio is higher than 2.0, grain boundary fracture is easily induced during blanking, resulting in excellent blanking workability.

[0197] [P] GB / [P] IG The preferred lower limit of is 2.1, more preferably 2.2, even more preferably 2.3, and further preferably 2.5.

[0198] [P]GB / [P] IG The preferred upper limit of is 5.0. In this case, grain boundary destruction occurs appropriately during blanking. Therefore, further excellent blanking workability is obtained. [P] GB / [P] IG The preferred upper limit is 4.9, more preferably 4.8.

[0199] [[P] GB and [P] IG Determination method of

[0200] [P] GB and [P] IG It can be measured by the following method.

[0201] From non-oriented electrical steel sheets, multiple rough test specimens measuring 18 mm L x 4 mm W x thickness T (L represents the length in the rolling direction, W represents the width, and T represents the thickness) were used. Each rough test specimen was notched in the center of the longitudinal direction, forming a notch extending across the width of the sheet. These test specimens were used for measuring Auger electron spectroscopy peaks.

[0202] Place the test piece for measuring Auger electron spectroscopy peaks in an Auger electron spectrometer and cool it with liquid nitrogen. Cut the cooled test piece to create a fracture surface. Observe ten random observation areas within the resulting fracture surface using a scanning electron microscope (SEM) at magnifications of 2000-10000x. Within each observation area, select one grain boundary fracture surface and one intragranular fracture surface.

[0203] Figure 1 This is an example of an SEM image obtained by observation at 3000 times magnification using an SEM. Figure 1 When a circular judgment field VF having a diameter of 3 μm is arranged in the observation area, a region 10 (equivalent to a cleavage fracture) in which no reverse pattern is observed within the judgment field VF is judged to be a grain boundary region 10. On the other hand, a region 20 in which a reverse pattern is observed within the judgment field VF is judged to be an intra-grain region 20.

[0204] When the determination field VF is determined to be the grain boundary region 10, a region in which substantially no reverse pattern is observed throughout the determination field FV (i.e., a region in which no pattern is observed and the entire region is substantially smooth) is selected. Similarly, when the determination field VF is determined to be the intra-grain region 20, a region in which a reverse pattern is uniformly observed throughout the determination field FV (i.e., a region in which smooth regions and regions with reverse patterns are not mixed and the reverse pattern is substantially present as a whole) is selected.

[0205] Elemental analysis based on Auger electron spectroscopy was performed on one selected grain boundary region and one intra-grain region in each observation region. Figure 2 As shown, elemental analysis is performed on an arbitrary measurement region 100 of 1.0 μm×1.0 μm within the determination field VF determined to be the grain boundary region 10 , and the Auger electron differential spectra of P and Fe are obtained.

[0206] Figure 3 An example of the obtained Auger electron differential spectrum is shown in FIG. 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, the difference between the maximum peak and the minimum peak of Fe near 700 eV, is defined as the Fe peak-to-peak value. 700 In addition, in the Auger electron differential spectrum, the main peak of P appears near the electron energy of 120eV. Therefore, the peak-to-peak value of P near 120eV is defined as P 120 Moreover, according to the obtained Fe 700 and P 120 , find P 120 / Fe 700 In the grain boundary fracture surface of each observation area, P 120 / Fe 700 . And, the 10 P 120 / Fe 700 The arithmetic mean of is set as [P] GB .

[0207] Similarly, elemental analysis is performed on an arbitrary 1.0 μm×1.0 μm measurement area within the judgment field VF determined to be the intra-granular region 20 in each observation region to obtain the Auger electron differential spectra of P and Fe. 120 / Fe 700 In the intra-grain region of each observation area, P 120 / Fe 700 And, the 10 P 120 / Fe 700 The arithmetic mean of is set as [P] IG .

[0208] In the elemental analysis by Auger electron spectroscopy, the primary beam acceleration voltage was set to 10 kV.

[0209] [(Characteristic 4) Difference between tensile strength TS and yield strength YP]

[0210] In the non-oriented electrical steel sheet of the present embodiment, further, the difference ΔS between the tensile strength TS and the yield strength YP is 110 MPa or less.

[0211] The smaller the difference ΔS, the more plastic deformation leading to fracture can be suppressed. This reduces the amount of edge collapse during blanking. As a result, excellent blanking workability is achieved. In this embodiment, the amount of P segregation at grain boundaries is increased, and strain aging due to C is promoted. This increases the upper yield point of 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 suppressed to 110 MPa or less.

[0212] The upper limit of the difference ΔS is preferably 105 MPa, more preferably 100 MPa, even more preferably 95 MPa, and further preferably 90 MPa.

[0213] [(Feature 5) About average crystal grain size D]

[0214] In the non-oriented electrical steel sheet of the present embodiment, the average crystal grain size D further satisfies the formula (2).

[0215] D≦100-15×[P] GB / [P] IG +1500 / TS(2)

[0216] Here, the numerical value of the tensile strength TS (MPa) is substituted into TS in the formula (2).

[0217] When non-oriented electrical steel sheets satisfy characteristics 1 to 4, they have excellent blanking properties despite high strength. However, in non-oriented electrical steel sheets satisfying characteristics 1 to 4, toughness may be reduced due to embrittlement. [P], which indicates the amount of P segregation at grain boundaries in non-oriented electrical steel sheets GB 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 will decrease. Therefore, in the non-oriented electrical steel sheet of this embodiment, the average crystal grain size D is set to [P] GB / [P] IG Here, FN is defined as follows.

[0218] FN=100-15×[P] GB / [P] IG +1500 / TS

[0219] If the average crystal grain size D is less than FN, then relative to [P] GB / [P] IGAs well as the tensile strength TS, the average crystal grain size D is sufficiently small. Therefore, excellent toughness is obtained.

[0220] [Method for measuring average crystal particle size D]

[0221] The average crystal grain size D is obtained by the following method. A cross section (L cross section) parallel to the rolling direction of the non-oriented electrical steel sheet is set as the observation surface. After the observation surface is mirror-polished, the mirror-polished observation surface is etched with a nitric alcohol solution. An optical microscope is used to observe any three locations of the etched observation surface at a magnification of 100 times to generate a photographic image of the observation field. When the thickness of the non-oriented electrical steel sheet is set to t (mm), the observation field is a rectangular shape consisting of the sides in the thickness direction and the sides in the rolling direction, and is set to tmm×tmm. Using the photographic image, the average crystal grain size (μm) in each field of view area is obtained by the cutting method in accordance with JIS G 0551:2013 "Steel - Microscopic test method for crystal grain size". The arithmetic average of the three average crystal grain sizes obtained is taken as the average crystal grain size D (μm).

[0222] [Effects of the non-oriented electrical steel sheet according to the present embodiment]

[0223] The non-oriented electrical steel sheet of this embodiment satisfies characteristics 1 to 5. Therefore, the non-oriented electrical steel sheet of this embodiment has excellent blanking workability despite its high strength. Furthermore, the non-oriented electrical steel sheet of this embodiment also has excellent toughness.

[0224] [Method for producing non-oriented electrical steel sheet]

[0225] An example of a method for producing a non-oriented electrical steel sheet according to the present embodiment will be described. The method for producing a non-oriented electrical steel sheet according to the present embodiment includes the following steps.

[0226] (Process 1) Hot rolling process

[0227] (Process 2) Hot-rolled plate annealing process

[0228] (Project 3) Cold Rolling Process

[0229] (Process 4) Final annealing process

[0230] The hot-rolled sheet annealing step is an optional step. That is, the hot-rolled sheet annealing step can also be omitted. Each step will be described below.

[0231] [(Process 1) Hot rolling process]

[0232] In the hot rolling process, the steel slab is hot-rolled to produce hot-rolled steel sheet. The steel slab has the chemical composition described above. The steel slab is produced using a known method. For example, the steel slab is produced by continuous casting using molten steel having the chemical composition described above.

[0233] The prepared steel slab is hot rolled. The various conditions for hot rolling are not particularly limited. The various manufacturing conditions for hot rolling are not particularly limited. The steel slab heating temperature is, for example, 1000°C to 1300°C. The finishing rolling temperature is, for example, 800°C to 1100°C. The coiling temperature is, for example, 500°C to 800°C.

[0234] [(Process 2) Hot-rolled sheet annealing process]

[0235] The hot-rolled plate annealing process is an optional process. That is, the hot-rolled plate annealing process may be implemented or not. When implemented, the hot-rolled steel plate is annealed in the hot-rolled plate annealing process. Hot-rolled plate annealing may be box annealing or continuous annealing. The annealing conditions in the hot-rolled plate 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. In addition, as needed, the steel plate before annealing in the hot-rolled plate annealing process and / or the steel plate after annealing may be subjected to a well-known pickling treatment.

[0236] [(Process 3) Cold Rolling Process]

[0237] In the cold rolling process, the hot-rolled steel sheet produced in the hot rolling process, or the hot-rolled steel sheet after the hot-rolled steel sheet annealing process, is cold-rolled to produce the cold-rolled steel sheet. Cold rolling can be performed once or multiple times. When cold rolling is performed multiple times, intermediate annealing may be performed after the cold rolling process and before the next cold rolling process.

[0238] [(Step 4) Final Annealing Step]

[0239] The cold-rolled steel sheet produced by the final rolling process is subjected to final annealing to produce non-oriented electrical steel sheet. During final annealing, the cold-rolled steel sheet, after being processed to its final thickness, is annealed to recrystallize and promote grain growth. Final annealing is performed using a continuous annealing furnace equipped with a heating zone, a soaking zone, and a cooling zone extending from upstream to downstream. Furthermore, the continuous annealing furnace may be equipped with equipment for insulating coating and coating drying downstream of the cooling zone. The final annealing process must meet the following conditions 1 to 4.

[0240] (Condition 1)

[0241] Annealing is performed at a maximum reaching temperature T1 of 950° C. or lower.

[0242] (Condition 2)

[0243] The tension TE1 applied to the cold-rolled steel sheet during annealing is set to 0.15 to 0.80 kgf / mm. 2 .

[0244] (Condition 3)

[0245] During cooling after annealing, the average cooling rate CR1 in the temperature range of 700 to 500° C. is set to 20° C. / second or less.

[0246] (Condition 4)

[0247] During cooling after annealing, the maximum tension TE2 applied to the cold-rolled steel sheet in the temperature range of 200°C or less is set to TE1+0.15kgf or more and 0.40kgf / mm 2 above.

[0248] Conditions 1 to 4 are described below.

[0249] [(Condition 1) Regarding the maximum temperature T1]

[0250] The maximum temperature T1 is set to be below 950°C. When the maximum temperature T1 exceeds 950°C, the grain boundary migration speed during grain growth increases, and the amount of P segregation to the grain boundary is reduced due to the drag effect. In addition, there is also the effect that the grains are too coarse and the average crystal grain size D cannot satisfy formula (2). Therefore, the maximum temperature T1 is set to be below 950°C. The lower limit of the maximum temperature T1 can be a well-known temperature. The lower limit of the maximum temperature T1 is, for example, 800°C.

[0251] [(Condition 2) Regarding the tension TE1 during final annealing]

[0252] The tension TE1 applied to the cold-rolled steel sheet during final annealing suppresses meandering of the steel sheet during the sheet passing process. The tension TE1 is 0.15 kgf / mm 2 In the above case, meandering of the steel plate during the plate passing can be sufficiently suppressed.

[0253] On the other hand, if the tension TE1 is too high, the strain introduced into the steel sheet during high-temperature annealing may remain, causing the iron loss to deteriorate. Furthermore, the difference ΔS between the tensile strength TS and the yield strength YP of the non-oriented electrical steel sheet exceeds 110 MPa. Therefore, the upper limit of the tension TE1 is set to 0.80 kgf / cm 2 The upper limit of the tension TE1 is preferably 0.50 kgf / mm. 2 , more preferably 0.35kgf / mm 2 .

[0254] [(Condition 3) Regarding the average cooling rate CR1]

[0255] In the final annealing step, the cold-rolled steel sheet is cooled after the final annealing. The temperature range of 700-500°C during cooling is where phosphorus diffuses and easily segregates at grain boundaries. Therefore, the cooling rate at 700-500°C is minimized, and the dwell time in the 700-500°C temperature range is prolonged. This allows phosphorus to fully diffuse into grain boundaries, increasing the amount of phosphorus segregated at the grain boundaries.

[0256] When the average cooling rate CR1 is 20°C / s or less, the cooling rate at 700-500°C is sufficiently slow, and a sufficient retention time at 700-500°C can be ensured. As a result, [P] GB / [P] IG Higher than 2.0.

[0257] [(Condition 4) Regarding the maximum tension TE2 in the temperature range of 200°C or less]

[0258] The cooling zone of a continuous annealing furnace is equipped with multiple tensioning rollers or transfer rollers. The cooling zone is divided into multiple zones from upstream to downstream. These tensioning rollers are positioned so that different tensions can be applied to the cold-rolled steel sheet in each zone. Furthermore, the tension of the steel sheet before and after the transfer rollers can be varied (adjusted) not only by the tensioning rollers but also by the transfer rollers within the cooling zone.

[0259] During cooling after final annealing, in multiple regions of the temperature range below 200°C, the maximum tension TE2 among one or more tensions applied to the cold-rolled steel sheet is set to TE1 + 0.15 kgf / mm 2 Above and 0.40kgf / mm 2 Above. In the temperature range below 200°C, although P, a substitutional element, does not migrate, C, an intrusive element, does. Therefore, if high tension can be applied to the cold-rolled steel sheet in the temperature range below 200°C, the solid-solution C will be fixed at the dislocations introduced by the tension. This can further promote the strain aging of C.

[0260] Therefore, the maximum tension TE2 applied to the cold-rolled steel sheet in the temperature range below 200°C is set to TE1 + 0.15 kgf / mm 2 Above and 0.40kgf / mm 2 In this case, the strain aging of C can be sufficiently promoted. 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.

[0261] Furthermore, as described above, it is not necessary to set the tension to TE1 + 0.15 kgf / mm in all periods (regions) of the temperature range below 200°C. 2 Above and 0.40kgf / mm 2The maximum tension TE2 applied at least partially during the period (region) of the temperature range below 200°C is TE1 + 0.15 kgf / mm. 2 Above and 0.40kgf / mm 2 Therefore, the maximum value of the tension TE2 applied to the cold-rolled steel sheet in the temperature range below 200°C is set to TE1 + 0.15 kgf / mm 2 Above and 0.40kgf / mm 2 above.

[0262] The upper limit of the maximum tension TE2 is not particularly limited, but considering the general equipment capacity, the upper limit of the maximum tension TE2 is 1.00 kgf / mm. 2 .

[0263] [Other processes]

[0264] In the above-described manufacturing method, a coating step may be performed after the final annealing step. In the coating step, an insulating coating is applied to the surface of the non-oriented electrical steel sheet after the final annealing. The type of insulating coating is not particularly limited. The insulating coating may be composed of an organic component, an inorganic component, or a mixture of organic and inorganic components.

[0265] The non-oriented electrical steel sheet of the present embodiment can be manufactured by the above-mentioned manufacturing method. In addition, the manufacturing method of the non-oriented electrical steel sheet of the present embodiment is not particularly limited as long as it satisfies characteristics 1 to 5.

[0266] Example 1

[0267] Non-oriented electrical steel sheets having the chemical compositions shown in Table 1-1 and Table 1-2 were manufactured by the following method.

[0268] [Table 1-1]

[0269] Table 1-1

[0270]

[0271] [Table 1-2]

[0272] Table 1-2

[0273]

[0274] Hot rolling is performed on steel slabs (steel sheets) to produce 2.0 mm thick hot-rolled steel sheets. The slab heating temperature is 1000°C to 1300°C. The finishing rolling temperature is 800°C to 1100°C. The coiling temperature is 500°C to 800°C. The hot-rolled steel sheets are then annealed at 1000°C for 1 minute. After the annealing, the sheets are cold rolled to produce 0.25 mm thick cold-rolled steel sheets.

[0275] The manufactured cold-rolled steel sheets were subjected to final annealing. Table 2 shows the annealing temperature T1 (°C), the tension TE1 (kgf / mm 2 ), average cooling rate CR1 (°C / sec), and tension TE2 (kgf / mm 2 According to the above manufacturing process, non-oriented electrical steel sheets of various test numbers were manufactured.

[0276] [Table 2]

[0277] Table 2

[0278]

[0279] [Evaluation test]

[0280] The following evaluation tests were performed on the non-oriented electrical steel sheets of each test number.

[0281] (Test 1) Chemical composition determination test

[0282] (Test 2) Tensile Strength TS and Yield Strength YP Measurement Test

[0283] (Test 3) [P] GB and [P] IG Determination test

[0284] (Test 4) Test for measuring average crystal particle size D

[0285] (Test 5) Magnetic properties evaluation test

[0286] (Test 6) Punching workability evaluation test

[0287] (Test 7) ​​Toughness evaluation test

[0288] Next, Tests 1 to 7 will be described.

[0289] [(Test 1) Chemical composition determination test]

[0290] The chemical composition of the non-oriented electrical steel sheet for each test number was determined according to the method described in the [Method for measuring the chemical composition of non-oriented electrical steel sheet]. The chemical composition of the non-oriented electrical steel sheet for each test number is shown in Tables 1-1 and 1-2.

[0291] [(Test 2) Tensile Strength TS and Yield Strength YP Measurement Test]

[0292] The tensile strength TS (MPa) and yield strength YP (MPa) of the non-oriented electrical steel sheet for each test number were determined using the method described in the [Method for Measuring Tensile Strength TS and Yield Strength YP] above. The obtained tensile strength TS (MPa) and yield strength YP (MPa) are shown in Table 3. The "ΔS (MPa)" column in Table 3 shows the difference ΔS (= TS - YP).

[0293] [Table 3]

[0294] Table 3

[0295]

[0296] [(Test 3)[P] GB and [P] IG Determination test of

[0297] According to the above [[P] GB and [P] IG The [P] of the non-oriented electrical steel sheet of each test number was obtained by using the method described in [Measurement method of] GB and [P] IG The obtained [P] is shown in Table 3. GB / [P] IG .

[0298] [(Test 4) Test for measuring average crystal particle size D]

[0299] The average crystal grain size D (μm) of the non-oriented electrical steel sheet of each test number was determined by the method described in the [Method for measuring the average crystal grain size D] above. The obtained average crystal grain size D (μm) is shown in Table 3. In addition, the "FN" column in Table 3 shows the FN value (=100-15×[P] GB / [P] IG +1500 / TS).

[0300] [(Test 5) Magnetic properties evaluation test]

[0301] The magnetic flux density B is obtained by the following method: 50 and iron loss W 5 / 1000 .

[0302] [Magnetic flux density B 50 Determination method of

[0303] In the non-oriented electrical steel sheets of each test number, half of the Epstein test pieces in the rolling direction (L direction) and the direction perpendicular to the rolling direction (C direction) were used (14 pieces each) to measure the magnetic flux density B 50Specifically, from the non-oriented electrical steel sheets of each test number, half of each of the Epstein test pieces extending in the L direction and the Epstein test pieces extending in the C direction were cut out in accordance with JIS C 2550-1 (2011). The cut Epstein test pieces were subjected to the electrical steel strip test method based on JIS C 2550-1 (2011) and 2550-3 (2011), and the average magnetic flux density B at 5000 A / m in the L and C directions was measured. 50 The obtained magnetic flux density B is shown in Table 3. 50 (T).

[0304] [Iron loss W 5 / 1000 Determination method of

[0305] With the above magnetic flux density B 50 Epstein test pieces were prepared in the same manner as in the measurement method. The Epstein test pieces were subjected to the electrical steel strip testing method based on JIS C 2550-1 (2011) and 2550-3 (2011), and the iron loss W at 1000 Hz and 0.5 T was measured as the average in the L direction (rolling direction) and the C direction (direction perpendicular to the rolling direction). 5 / 1000 (W / kg). The obtained iron loss W is shown in Table 3. 5 / 1000 (W / kg).

[0306] [(Test 6) Punching workability evaluation test]

[0307] The blanking workability of the non-oriented electrical steel sheet of each test number was evaluated in the following test: A ring-shaped specimen having an inner diameter of 90 mm and an outer diameter of 100 mm was blanked out from the non-oriented electrical steel sheet of each test number using a die with a gap of 20 μm.

[0308] Regarding dimensional accuracy, evaluation is performed according to the following method. First, the inner diameter and outer diameter of the punched ring sample are obtained using a dimension measuring device. Using the measured inner diameter, the maximum deviation of the measured inner diameter from a perfect circle (90 μm) (the maximum value of the difference between the measured inner diameter and the perfect circle) is obtained. Furthermore, using the measured outer diameter, the maximum deviation of the measured outer diameter from a perfect circle (100 mm) is obtained. When the maximum deviation of the inner diameter and the maximum deviation of the outer diameter are both less than 20 μm, it is judged that excellent dimensional accuracy is obtained (recorded as "E (Excellent)" in the "Dimensional Accuracy" column of the "Blanking Processability" column in Table 3). On the other hand, when either the maximum deviation of the inner diameter or the maximum deviation of the outer diameter exceeds 20 μm, it is judged that excellent dimensional accuracy is not obtained (recorded as "B (Bad)" in the "Dimensional Accuracy" column of the "Blanking Processability" column in Table 3).

[0309] The amount of edge collapse was evaluated using the following method. A ring-shaped specimen was cut from the L-direction cross section. The cut ring specimen was embedded in resin and the L-direction cross section was polished. The cut end surface of the inner circumference (inner diameter) and the cut end surface of the outer circumference (outer diameter) of the polished L-direction cross section were observed using an optical microscope at a magnification of 100x. Figure 4 This is an enlarged view of the portion including the cut end surface in the L-direction cross section of the ring-shaped specimen. Figure 4 , the intersection position P1 of the edge collapse portion 20 and the cut end surface 30 is determined. For either the inner or outer peripheral surface, if the distance t1 in the sheet thickness direction from the surface 10 of the ring specimen to the intersection position P1 is within the range from the surface 10 to a position 1 / 4 of the sheet thickness t0 (i.e., the sheet thickness of the non-oriented electrical steel sheet), the edge collapse is determined to be sufficiently suppressed (recorded as "E (Excellent)" in the "Amount of Edge Collapse" column of the "Blanking Workability" column in Table 3). On the other hand, if the distance t1 exceeds the range from the surface 10 to a position 1 / 4 of the sheet thickness t0 (i.e., the sheet thickness of the non-oriented electrical steel sheet) for at least one of the inner or outer peripheral surface, the edge collapse is determined to be insufficiently suppressed (recorded as "B (Bad)" in the "Amount of Edge Collapse" column of the "Blanking Workability" column in Table 3).

[0310] When excellent dimensional accuracy was obtained and the amount of flange collapse was sufficiently suppressed, it was determined that excellent punching workability was obtained.

[0311] [(Test 7) ​​Toughness evaluation test]

[0312] The toughness of the non-oriented electrical steel sheets of each test number was evaluated through fatigue testing. Specifically, fatigue test specimens were prepared from each non-oriented electrical steel sheet, with the L direction as the longitudinal direction. The fatigue test specimens were 30 mm wide and 180 mm long, with the parallel portion located in the center of the longitudinal direction measuring 15 mm wide and 35 mm long. The parallel portion and the rounded portion of the fatigue test specimens were polished with 600-grade sandpaper.

[0313] The following fatigue test was conducted using the above fatigue test specimens at room temperature in the atmosphere. The fatigue test was conducted using a pulsation (tension-tension) with a stress ratio of 0.05 and a frequency of 20 Hz. The fatigue strength (MPa) was defined as the stress amplitude at which no fracture occurred after 2 million repetitions.

[0314] [Evaluation results]

[0315] Referring to Table 1-1, Table 1-2, Table 2 and Table 3, the non-oriented electrical steel sheets of test numbers 1 to 49 satisfy characteristics 1 to 5. Therefore, the magnetic flux density B 50 More than 1.55T, iron loss W 5 / 1000The heat release rate is 20.0 W / kg or less. Furthermore, excellent punchability is achieved. Furthermore, fatigue strength is 420 MPa or more, achieving excellent toughness.

[0316] In test numbers 50 and 51, the annealing temperature was too high. Therefore, the average grain size D did not satisfy the formula (2). Therefore, the fatigue strength was less than 420 MPa, and sufficient toughness was not obtained.

[0317] In test number 52, the tension TE1 applied to the cold-rolled steel sheet during the final annealing was too high. Therefore, the difference ΔS exceeded 110 MPa. Therefore, the edge collapse could not be sufficiently suppressed, and excellent dimensional accuracy was not obtained. In addition, the iron loss W 5 / 1000 (W / kg) high.

[0318] In test numbers 53 and 54, the average cooling rate CR1 was too high. Therefore, [P] GB / [P] IG Therefore, in the punching workability 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 was not obtained.

[0319] In test numbers 55 to 57, the tension TE2 was too low. Therefore, the difference ΔS exceeded 110 MPa. Therefore, the amount of edge collapse could not be sufficiently suppressed, and excellent blanking workability could not be obtained.

[0320] While the preferred embodiments of the present invention have been described above, the present invention is not limited to these examples. It should be understood by those skilled in the art that various modifications or amendments can be readily envisioned within the scope of the concepts described in the scope, and these modifications naturally fall within the technical scope of the present invention.

Claims

1. A non-oriented electromagnetic steel sheet, In terms of mass%, Si: 3.2-4.5%, Mn: 0.3-3.5%, 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: higher 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: 0-0.50%, 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%, Mg: 0 to 0.0030%, and The rest is composed of Fe and impurities. Tensile strength TS is higher than 580MPa, Elemental analysis was performed on the grain boundary region of the fracture surface of the non-oriented electrical steel sheet by Auger electron spectroscopy to obtain the Auger differential spectrum of Fe and P. The peak-to-peak value P of P near the electron energy of 120 eV in the obtained Auger differential spectrum was calculated. 120 Peak-to-peak Fe relative to the electron energy around 700 eV 700 The ratio of P 120 / Fe 700 Defined as [P] GB , Elemental analysis was performed on the intra-granular region of the fracture surface of the non-oriented electrical steel sheet by Auger electron spectroscopy to obtain the Auger differential spectrum of Fe and P. The peak-to-peak value P of P near the electron energy of 120 eV in the obtained Auger differential spectrum was calculated. 120 Peak-to-peak Fe relative to the electron energy around 700 eV 700 The ratio of P 120 / Fe 700 Defined as [P] IG When , it satisfies formula (1), [P] GB / [P] IG >2.0 (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 formula (2), D≦100-15×[P] GB / [P] IG +1500 / TS (2) Here, the numerical value of the tensile strength TS (MPa) is substituted into TS in the formula (2).

2. The non-oriented electrical steel sheet according to claim 1, In mass%, it contains 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: 0.0001~0.0050%, 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: At least one selected from the group consisting of 0.0001 to 0.0030%.

3. A method for producing a non-oriented electrical steel sheet, the method for producing a non-oriented electrical steel sheet according to claim 1 or 2, comprising: A hot rolling step of hot rolling the steel slab having the chemical composition of claim 1 or claim 2 to produce a hot-rolled steel plate; a cold rolling process of cold-rolling the hot-rolled steel sheet to produce a cold-rolled steel sheet; as well as a final annealing step of performing final annealing on the cold-rolled steel sheet; In the final annealing step, Annealing the cold-rolled steel sheet at a maximum reaching temperature T1 below 950° C. The tension TE1 applied to the cold-rolled steel sheet during annealing is set to 0.15 to 0.80 kgf / mm. 2 , When the cold-rolled steel sheet after annealing is cooled, the average cooling rate CR1 in the temperature range of 700 to 500° C. is set to 20° C. / second or less. When the cold-rolled steel sheet is cooled after annealing, the maximum tension TE2 applied to the cold-rolled steel sheet in the temperature range below 200°C is set to TE1+0.15kgf / mm 2 Above and 0.40kgf / mm 2 above.

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