Non-oriented electrical steel sheet and method for producing non-oriented electrical steel sheet

Abstract

A non-oriented electrical steel sheet which contains, in mass%, 0.005% or less of C, 2.00% to 4.50% or less of Si, 0.01% to 5.00% or less of Mn, 0.03% to 5.00% or less of Al, more than 0% and 0.005% or less of the total SE of one or more of S, Se and Te, more than 0% and 0.005% or less of N, and more than 0% and 1.000% or less of P, with the remainder being Fe and impurities, and which satisfies formulae (1) and (2), the standard deviation of the ratio LRD / LTD between the length LRD in the rolling direction and the length LTD in the width direction of a circular hole punched using a substantially circular die is 0.010 or less, and the iron loss W15 / 50 is 2.50 W / kg or less. (Si + Mn + Al) > = 4.5% formula (1) Al / 3 < = Mn formula (2).

Description

Technical Field

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

[0002] This application claims priority based on Tokugan Application No. 2022-157415 filed in Japan on September 30, 2022, the contents of which are incorporated herein by reference. Background Art

[0003] When non-oriented electromagnetic steel sheets are high-grade products, they contain about 2% to 5% Si by mass. At this time, in order to prevent the magnetic properties from being biased toward a specific orientation of the steel sheet, the crystal axis orientation of each crystal is arranged as randomly as possible. Such non-oriented electromagnetic steel sheets are used as core materials for stators and rotors of rotating electrical machines, for example, because of their excellent magnetic properties.

[0004] In addition, various developments have been made to further improve the magnetic properties of such non-oriented electromagnetic steel sheets. In particular, with the demand for energy saving in recent years, further reduction of iron loss is sought. Iron loss is composed of eddy current loss and hysteresis loss. In order to reduce eddy current loss, it is effective to add elements such as Si, Al, and Mn as steel components to increase the inherent resistance.

[0005] Furthermore, when the non-oriented electromagnetic steel sheet is used as a rotating electrical machine, the non-oriented electromagnetic steel sheet is punched into the shape of a stator and a rotor, and then the non-oriented electromagnetic steel sheet is stacked. That is, a plurality of non-oriented electromagnetic steel sheets are stacked when manufacturing a stator and a rotor, and the stacked body is used as a rotating electrical machine. Therefore, it is important that the dimensional accuracy of the steel sheet after punching is excellent and each steel sheet is uniformly formed into a predetermined shape.

[0006] However, if elements such as Si, Al, and Mn are added as steel components, there are technical problems in that the strength of the steel sheet increases and the dimensions of the steel sheet after punching may vary.

[0007] Patent Document 1 discloses a technique for controlling the tension and cooling rate in the cooling process of final annealing to control the variation in rolling, width, and uniform elongation in each direction of 45 degrees.

[0008] Furthermore, Patent Document 2 discloses a technique for improving punching dimensional accuracy by controlling the relationship between yield stress and sheet thickness and the balance of alloy amounts.

[0009] Furthermore, Patent Document 3 discloses a technique of performing skin pass rolling and stress relief annealing after final annealing while controlling the average grain size, the thickness of the internal oxide layer, and the Young's modulus in the rolling direction and / or the width direction.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent No. 6685491

[0013] Patent Document 2: Japanese Patent Application Publication No. 2004-152791

[0014] Patent Document 3: International Publication No. 2020 / 149405 Summary of the invention

[0015] Technical problem to be solved by the invention

[0016] As global environmental issues have intensified in recent years, electrical equipment has been required to be smaller, have higher output, and have higher energy efficiency. Non-oriented electromagnetic steel sheets, which are core materials for motors, have also been required to have lower iron losses.

[0017] In order to further reduce iron loss, high alloying with increased Si, Mn or Al components is effective. When highly alloyed, it is expected that the strength of the steel sheet will increase and the rotation speed of the motor will increase. On the other hand, it is clear that when highly alloyed, the size (punching size) after punching the steel sheet into the shape of a motor is prone to deviation.

[0018] Patent Document 1 discloses a non-oriented electrical steel sheet that can improve roundness during punching by controlling tension and cooling rate in the cooling process of final annealing to reduce anisotropy of uniform elongation.

[0019] Patent Document 2 discloses a thin electromagnetic steel sheet for high-efficiency motors having excellent punching dimensional accuracy and high-frequency magnetic properties by controlling alloy addition conditions and the relationship between the yield stress and the thickness of the steel sheet.

[0020] Patent Document 3 discloses a non-oriented electromagnetic steel sheet that is suitable for a split type stator and has high dimensional accuracy by controlling the average crystal grain size, the internal oxide layer, and the anisotropy of the Young's modulus of the steel sheet.

[0021] However, including Patent Documents 1 to 3, in the prior art, there is no disclosure of a method for reducing the deviation of the blanking dimensions in the rolling direction and the width direction of the steel coil by focusing on the control of the alloy addition amount and the final annealing conditions. In addition, in the prior art, even if the blanking dimensional accuracy is good to a certain extent each time, the blanking dimensional accuracy may sometimes deviate during multiple blanking operations. Moreover, even if the prior art is used flexibly, there may be deviations in the blanking dimensional accuracy in the width direction of the steel coil. That is, in the prior art or the blanking method of the prior art, it is inferred that it is difficult to strictly control the blanking dimensional accuracy within the entire length or width of the steel coil. In particular, when the width of the steel coil is large (for example, a width of 80 mm or more), a deviation in the blanking dimensional accuracy is likely to occur. In the prior art, it is inferred that the deviation in the blanking dimensional accuracy in the width direction of the steel coil has not been completely suppressed.

[0022] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a non-oriented electrical steel sheet having low iron loss and excellent punching dimension accuracy, and a method for producing the same.

[0023] Technical means for solving technical problems

[0024] The gist of the present invention is as follows.

[0025] [1] A non-oriented electrical steel sheet according to one embodiment of the present invention,

[0026] Chemical composition, in mass%, contains

[0027] C: 0.005% or less,

[0028] Si: 2.00% or more and 4.50% or less,

[0029] Mn: 0.01% to 5.00%,

[0030] Al: 0.03% to 5.00%,

[0031] Total SE of one or more of S, Se and Te: more than 0% and less than 0.005%,

[0032] N: more than 0% and less than 0.005%,

[0033] P: higher than 0% and less than 1.000%,

[0034] Cu: 0% or more and 1.0% or less,

[0035] Sn: 0% or more and 1.0% or less,

[0036] Ni: 0% or more and 1.0% or less,

[0037] Cr: 0% or more but less than 1.0%

[0038] Sb: 0% or more and 1.0% or less,

[0039] The remaining part is composed of Fe and impurities, and satisfies equations (1) and (2).

[0040] The rolling direction length L of the round hole after punching using a substantially circular die RD The width length L TD Ratio L RD / L TD The standard deviation is less than 0.010.

[0041] Iron loss W 15 / 50 Below 2.50W / kg,

[0042] (Si+Mn+Al)≧4.5%···Formula (1)

[0043] Al / 3≦Mn···Formula (2).

[0044] [2] The non-oriented electrical steel sheet according to [1] may be

[0045] In terms of mass%, it further comprises

[0046] Ti: 0% or more and 0.0030% or less,

[0047] Nb: 0% or more and 0.0030% or less,

[0048] V: 0% or more and 0.0030% or less,

[0049] Zr: 0% or more and 0.0030% or less

[0050] One or more than one of the groups.

[0051] [3] A method for producing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises:

[0052] A hot rolling step of heating the steel slab having the chemical composition described in [1] or [2] above and hot rolling it to produce a hot-rolled steel sheet;

[0053] A cold rolling step of cold rolling the hot-rolled steel sheet to obtain a cold-rolled steel sheet;

[0054] A final annealing step of performing final annealing on the cold-rolled steel sheet to obtain a final annealed sheet; and

[0055] an insulating film coating step of applying an insulating coating to the final annealed sheet to form an insulating film on the final annealed sheet to obtain an insulating film coated steel sheet;

[0056] In the final annealing process, when the average heating rate of the steel plate in the temperature range of 300° C. to 700° C. is set to Vh (° C. / second), the soaking temperature of the steel plate is set to Tf (° C.), the soaking time of the steel plate is set to tf (seconds), and the average cooling rate of the steel plate in the temperature range of 700° C. to 300° C. is set to Vc (° C. / second), Tf is 750 to 1100° C., tf is 10 to 300 seconds, and the formula (3) is satisfied,

[0057] In the insulating film coating step, the drying temperature Tc (°C) during the insulating coating is 250 to 500°C, and the steel sheet tension is 0.5 to 5.0 kgf / mm 2 ,

[0058] Vh / 4≦Vc≦4Vh···Formula (3).

[0059] [4] The method for producing a non-oriented electrical steel sheet as described in [3] above may be:

[0060] Prior to the cold rolling step, there is a hot rolled sheet annealing step of performing hot rolled sheet annealing on the hot rolled steel sheet to obtain a hot rolled annealed sheet.

[0061] Effects of the Invention

[0062] According to the above aspects of the present invention, it is possible to provide a non-oriented electrical steel sheet having low iron loss and excellent punching dimension accuracy, and a method for producing the same. DETAILED DESCRIPTION

[0063] The inventors of the present invention have conducted intensive studies on the conditions of final annealing, in particular, in order to improve the accuracy of punching dimensions in a non-oriented electrical steel sheet, and have finally found the following findings.

[0064] By controlling the average heating rate of the steel sheet, the soaking temperature and soaking time of the steel sheet, and the average cooling rate of the steel sheet in the final annealing process, and controlling the drying temperature of the insulating coating and the steel sheet tension in the insulating coating process, it is possible to manufacture a non-oriented electrical steel sheet with excellent punching dimensional accuracy.

[0065] The preferred embodiments of the present invention are described in detail below.

[0066] In addition, the present invention is not limited to the structure disclosed in this embodiment, but can be variously modified within the scope of the purpose of the present invention. In addition, in the following numerical limit range, unless otherwise specified, the expression "a to b" for the numerical values ​​a and b means "above a and below b". In the relevant expression, when only the numerical value b is marked with a unit, the unit also applies to the numerical value a. In addition, in the numerical value expressed as "less than" or "higher than", the value is not included in the numerical range.

[0067] <Non-oriented electrical steel sheet>

[0068] Next, the non-oriented electrical steel sheet according to the present embodiment will be described in detail.

[0069] [Chemical composition]

[0070] First, the chemical composition of the base material of the non-oriented electrical steel sheet according to the present embodiment will be described.

[0071] In addition, unless otherwise specified, the description "%" means "mass %".

[0072] In addition, the remainder other than the elements described below is Fe and impurities. Here, the so-called impurities refer to components contained in the raw materials or components mixed in the manufacturing process, and are not components intentionally contained in the base steel plate. In addition, the chemical composition of the steel billet as the material of the non-oriented electrical steel sheet is basically based on the chemical composition of the non-oriented electrical steel sheet.

[0073] C: 0.005% or less

[0074] C is an element that may cause magnetic aging in the final non-oriented electrical steel sheet, so it is not preferred to contain a large amount. Therefore, the C content is 0.005% or less, preferably 0.004% or less. In addition, the lower the C content, the better, and considering the cost, the lower limit can be set to 0.0005% or more.

[0075] Si: 2.00% or more and 4.50% or less

[0076] Si reduces eddy current loss, which is one of the causes of iron loss, by increasing the electrical resistance of the non-oriented electromagnetic steel sheet. When the Si content is less than 2.00%, it is not preferred because it is difficult to fully suppress the eddy current loss of the final non-oriented electromagnetic steel sheet. When the Si content is higher than 4.50%, it is not preferred because the workability decreases. Therefore, the lower limit of the Si content is 2.00% or more, preferably 2.40% or more, more preferably 3.20% or more, and more preferably 3.30% or more. The upper limit of the Si content is 4.50% or less, preferably 4.30% or less, and more preferably 4.10% or less.

[0077] Mn: 0.01% or more and 5.00% or less

[0078] Mn has the same effect of increasing resistance as Si, reducing eddy current loss, which is one of the causes of iron loss. When the content of Mn is less than 0.01%, it is not preferred because the effect of reducing eddy current loss is insufficient. When the content of Mn is higher than 5.00%, it is not preferred because the processability is reduced. Therefore, the lower limit of the Mn content is more than 0.01%, preferably more than 0.05%, and more preferably more than 0.30%. The upper limit of the Mn content is preferably less than 5.00%, preferably less than 4.00%, and more preferably less than 3.50%. The upper limit of the Mn content can also be less than 3.00%, and further set to less than 2.50%.

[0079] Al: 0.03% or more and 5.00% or less

[0080] Al, like Si, has the effect of increasing resistance and reducing eddy current loss, which is one of the causes of iron loss. When the Al content is less than 0.03%, it is not preferred because the effect of reducing eddy current loss is insufficient. When the Al content is higher than 5.00%, it is not preferred because the processability is reduced. Therefore, the lower limit of the Al content is greater than 0.03%, preferably greater than 0.15%, more preferably greater than 0.90%, and the upper limit of the Al content is less than 5.00%, preferably less than 4.00%, and more preferably less than 3.50%. The upper limit of the Al content can also be less than 3.00%, and it is more preferably set to less than 2.00%.

[0081] Total SE of one or more of S, Se and Te: more than 0% and less than 0.0050%

[0082] S, Se and Te form precipitates together with the above-mentioned Mn to reduce hysteresis loss. When the total SE of the S, Se and Te contents is higher than 0.0050%, the precipitation of MnS, MnSe and MnTe becomes excessive, which is not preferred due to the deterioration of hysteresis loss. Therefore, the upper limit of the total SE of the contents of one or more of S, Se and Te is less than 0.0050%, preferably less than 0.0040%, and more preferably less than 0.0030%. The lower limit of the total SE of the contents of one or more of S, Se and Te can be higher than 0% because the lower the better, but from the perspective of reducing costs and the effect of hysteresis loss, it can be set to more than 0.0001%.

[0083] N: higher than 0% and less than 0.0050%,

[0084] N forms AlN together with the above-mentioned Al, which deteriorates the hysteresis loss. When the content of N is higher than 0.0050, the amount of AlN precipitation becomes too much, which is not preferred because the hysteresis loss deteriorates. Therefore, the upper limit of the N content is 0.0050% or less. The lower limit of the N content can be higher than 0% because the lower the better, but from the perspective of reducing costs and hysteresis loss effects, it can be set to 0.0001% or more.

[0085] P: higher than 0% and less than 1.000%

[0086] P has the effect of increasing strength without reducing magnetic flux density. However, when P is contained excessively, the toughness of the steel is impaired and the steel sheet is prone to fracture. Therefore, the upper limit of the P content is 1.000% or less, preferably 0.150% or less, and more preferably 0.120% or less.

[0087] The lower limit of the P content is not particularly limited, but can be set to 0.001% or more in consideration of production cost.

[0088] Cu, Sn, Ni, Cr, or Sb: any one or two or more: each content is 0% or more and 1.0% or less

[0089] In addition to the above elements, it is also possible to further contain an element as an A group element that improves the texture and increases the magnetic flux density, that is, one or more selected from the group consisting of Cu, Sn, Ni, Cr, or Sb. When the A group element is contained, the upper limit of the content of each of the above elements is set to 1.0% or less, preferably 0.3% or less. Since it is arbitrary to contain the A group element, the lower limit of the content of each of the above elements can be set to 0% or more, preferably 0.0005% or more.

[0090] Any one or two or more of Ti, Nb, V, or Zr: each content is 0% or more and 0.0030% or less

[0091] In addition, as B group elements, one or more selected from the group consisting of Ti, Nb, V, or Zr, which is an element that forms precipitates in steel and worsens hysteresis loss, may be further contained. When containing B group elements, the content of each of the above elements is greater than 0% and less than 0.0030%. Regarding B group elements, by setting each content to less than 0.0030%, the grain growth of the manufactured non-oriented electromagnetic steel sheet can be further improved, and the hysteresis loss can be further reduced. Therefore, regarding B group elements, the upper limit of the content of each of the above elements can be set to less than 0.0030%. The lower limit of each content of B group elements is 0% because the lower the better, but from the viewpoint of reducing costs and hysteresis loss effects, it can be set to 0.0001%.

[0092] (Si+Mn+Al)≧4.5%

[0093] Si, Mn, and Al have the effect of increasing resistance and reducing eddy current loss, which is one of the causes of iron loss degradation. Si, Mn, and Al each have the effect of increasing resistance, and composite addition also has an effect, so the total content of Si, Mn, and Al is effective in achieving increased resistance. In order to increase resistance and obtain the effect of sufficiently reducing eddy current loss, the lower limit of the total content of Si, Mn, and Al is 4.50% or more, preferably 4.80% or more, and more preferably 5.00% or more. On the other hand, if the total content of Si, Mn, and Al is too much, it is not preferred due to reduced processability. Therefore, the upper limit of the total content of Si, Mn, and Al is preferably set to less than 10.00%, and more preferably to less than 9.70%.

[0094] Al / 3≦Mn

[0095] When Al / 3 is larger than the Mn content, the punching dimensional accuracy sometimes deviates. Therefore, it is effective for the chemical composition to satisfy the relationship of Al / 3≦Mn. Although the detailed mechanism by which the dimensional accuracy after punching can be improved by satisfying this relationship is unclear, it is inferred as follows. Since Al has a greater effect on increasing the strength of the steel sheet than Mn, it is easily affected by the stress in the final annealing and insulating coating. Therefore, when Al / 3 is larger than the Mn content, for example, it is inferred that strain is likely to remain unevenly in the width direction of the steel coil (the width direction of the plate, i.e., the direction perpendicular to the rolling direction and the plate thickness direction) due to the stress in the plate width direction accompanied by thermal deformation.

[0096] The above chemical composition is the composition of the silicon steel sheet which is the base material of the non-oriented electrical steel sheet of the present embodiment. That is, when the non-oriented electrical steel sheet as the measurement sample has an insulating film on the surface, the insulating film is removed before measurement.

[0097] As a method of removing the insulating film of the non-oriented electrical steel sheet, the following method is mentioned, for example.

[0098] First, the non-oriented electrical steel sheet having an insulating film is immersed in a sodium hydroxide aqueous solution, a sulfuric acid aqueous solution, and a nitric acid aqueous solution in sequence, and then washed. Finally, it is dried with hot air. Thus, a silicon steel sheet after removing the insulating film described later can be obtained.

[0099] The above chemical components can be measured by common analytical methods. For example, ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) can be used for measurement. C and S can be measured by combustion-infrared absorption method, and N can be measured by inert gas fusion-heat conduction method.

[0100] [Punching dimensional accuracy]

[0101] The rolling direction length L of each round hole after punching out the non-oriented electrical steel sheet using a substantially circular die is RD The width length L TD Ratio L RD / L TD The standard deviation is less than 0.010.

[0102] The motor core is manufactured by punching non-oriented electromagnetic steel sheets with a die, and stacking the punched non-oriented electromagnetic steel sheets in the shape of the core to produce the motor core. If there is a deviation in the punching size, the end surface shape of the stacked motor core becomes uneven, and the motor efficiency decreases, which is not preferred. Therefore, the rolling direction length L of the round hole after punching with a roughly circular die is set to RD The width length L TD Ratio L RD / L TD The standard deviation of is set to be 0.010 or less. The numerical value processing in the calculation result of the standard deviation can be based on JIS Z9041-1:1999.

[0103] The die used for punching can be roughly circular. Using the same die, punch out at 5 points in the width direction of the steel coil, and measure the rolling direction length L of each circular hole. RD The width length L TD Ratio L RD / L TD , calculate the standard deviation, and thus be able to evaluate the punching dimensional accuracy.

[0104] Regarding the positions for blanking in the width direction of the steel coil, five positions can be selected approximately equally in the width direction of the steel coil for the non-oriented electromagnetic steel sheet or the sample cut from the non-oriented electromagnetic steel sheet. Regarding the positions for blanking, for example, the obtained sample is divided into five equal parts in the width direction of the steel coil, and the positions are selected in such a way that the vicinity of the center of each area is approximately consistent with the center of the blanking die. The five blanking positions do not need to be arranged in a straight line in the width direction of the steel coil, and the blanking positions can also be changed in the rolling direction in each blanking area.

[0105] The size of the die used for punching is preferably about 1 / 10 of the length of the obtained sample in the width direction of the steel coil, but may be larger or smaller if five locations are punched in the width direction of the steel coil.

[0106] The rolling direction length L of the round hole after punching RD The width length L TD The measuring method is not particularly limited. A caliper may be used, a commercially available shape measuring instrument may be used, or a commercially available image analysis software may be used after recording the shape with a scanner. The rolling direction length L of the circular holeRD The width length L TD It is preferably measured using a digital caliper. The rolling direction length L of the round hole is RD , which indicates the maximum diameter among the diameters parallel to the rolling direction, the so-called width length L of the circular hole TD , which indicates the maximum diameter among the diameters parallel to the width of the steel coil.

[0107] Here, in this specification, the "rolling direction" can also be determined from the rolling pattern on the surface of the non-oriented electromagnetic steel sheet. The rolling pattern can be confirmed using an optical microscope or a scanning electron microscope after removing the insulating film formed on the surface of the non-oriented electromagnetic steel sheet with an alkaline solution or the like. In addition, in this specification, the so-called "coil width direction" is a direction that forms an angle of 90 degrees with the rolling direction determined from the rolling pattern within the steel sheet surface.

[0108] <Magnetic properties of non-oriented electrical steel sheets>

[0109] The non-oriented electrical steel sheet of the present embodiment has excellent magnetic properties.

[0110] The iron loss W of the non-oriented electrical steel sheet of the present embodiment when magnetized at 50 Hz to a magnetic flux density of 1.5 T is 15 / 50 It is 2.50 W / kg or less, preferably 2.40 W / kg or less.

[0111] The magnetic properties of non-oriented electrical steel sheets can be measured by the single sheet magnetic properties test method (Single Sheet Tester: SST) specified in JIS C 2556: 2015. For example, a 55 mm square sample is cut in the rolling direction for the 0° and 90° directions, and the iron loss W when the flux density is 1.5 T at 50 Hz magnetization is calculated for each direction in the rolling direction and the direction perpendicular to the rolling direction. 15 / 50 That's it.

[0112] <Method for producing non-oriented electrical steel sheet>

[0113] Next, a method for producing a non-oriented electrical steel sheet will be described.

[0114] First, a steel billet having the above chemical composition is manufactured. Specifically, the steel billet is formed by casting molten steel adjusted to the chemical composition described above. In addition, the casting method of the steel billet is not particularly limited. In addition, in research and development, even if a steel ingot is formed by a vacuum melting furnace or the like, the same effect as the case of forming a steel billet can be confirmed with respect to the above chemical composition.

[0115] [Hot rolling process]

[0116] Next, the steel slab is heated and hot rolled to obtain a hot rolled steel sheet.

[0117] The billet heating temperature is not particularly limited. The upper limit of the billet heating temperature is not particularly limited.

[0118] On the other hand, there is a case where compounds such as sulfides (S-compounds) and nitrides (N-compounds) that are dissolved again when the steel billet is heated are finely precipitated and the magnetic properties are deteriorated. In order to avoid such deterioration of magnetic properties, the steel billet heating temperature can be set to 1250°C or less, and preferably to 1200°C or less. The lower limit of the steel billet heating temperature is not particularly limited, but can be set to 1000°C or more from the perspective of reducing the equipment load during hot rolling.

[0119] The finishing temperature in hot rolling is preferably set to 700°C to 1000°C. The coiling temperature is preferably set to 500°C to 900°C. The thickness of the hot-rolled steel plate after hot rolling is preferably, for example, 1.5 mm to 3.5 mm. When the thickness of the hot-rolled steel plate is less than 1.5 mm, the shape of the steel plate after hot rolling may sometimes deteriorate. When the thickness of the hot-rolled steel plate is higher than 3.5 mm, the rolling load in the cold rolling process may sometimes increase. In addition, after the hot rolling process (before the cold rolling process), a hot-rolled plate annealing process may be provided as needed, in which the hot-rolled steel plate is annealed to obtain a hot-rolled annealed plate.

[0120] [Pickling process]

[0121] The hot-rolled steel sheet after hot rolling may be pickled. When the pickling process is performed, the pickling solution is not particularly limited, and sulfuric acid or hydrochloric acid may be used. The pickling solution may contain a pickling accelerator or an inhibitor. In addition, for the purpose of promoting the removal of the oxide layer formed on the surface of the hot-rolled steel sheet, crack defects may be introduced into the surface of the hot-rolled steel sheet by shot peening or the like before pickling.

[0122] [Cold rolling process]

[0123] The hot rolled steel sheet is subjected to a single cold rolling, or multiple cold rolling with intermediate annealing, to obtain a cold rolled steel sheet. In addition, in the case of multiple cold rolling with intermediate annealing, the annealing of the hot rolled sheet in the previous stage can be omitted. Among them, in the case of hot rolled sheet annealing, in order to make the steel sheet shape better, the possibility of the steel sheet breaking during cold rolling can be reduced. In addition, before cold rolling, in order to remove the oxide scale attached to the surface of the steel sheet, etc., it is preferred to carry out the above-mentioned pickling. When pickling is carried out, in order to control the precipitates in the thickness direction, it is sufficient to carry out at least one pickling treatment after hot rolling and before final annealing. In the case of multiple cold rolling, it is preferred to carry out pickling treatment before each cold rolling from the viewpoint of reducing the wear of the rollers in the cold rolling. In addition, the thickness of the cold rolled steel sheet after the final cold rolling is not particularly limited, but from the viewpoint of reducing the iron loss, it is preferably 0.35 mm or less, and more preferably 0.30 mm or less. The lower limit of the thickness of the cold rolled steel sheet is not particularly limited, for example, it can be set to 0.10 mm or more.

[0124] In addition, the steel plate can be heat treated at a temperature below 300°C between cold rolling passes, between roll stands, or during rolling. In this case, the magnetic properties of the non-oriented electromagnetic steel sheet finally obtained can be improved. In addition, as mentioned above, the hot-rolled steel plate can also be rolled by more than three cold rollings. However, multiple cold rollings will increase the manufacturing cost, so the hot-rolled steel plate is preferably rolled by one or two cold rollings. Cold rolling can be carried out by a tandem cold rolling mill, or by reverse rolling by a Sendzimir rolling mill or the like. In the case of cold rolling by reverse rolling, the number of passes in each cold rolling is not particularly limited, but from the perspective of manufacturing cost, it is preferably less than 9 times.

[0125] [Final annealing process]

[0126] Next, the cold-rolled steel sheet is subjected to final annealing to obtain a cold-rolled steel sheet.

[0127] Here, the inventors of the present invention have found that the blanking dimensions in the coil rolling direction and the coil width direction differ depending on the heating pattern and insulation coating conditions of the final annealing. In addition, the atmosphere gas composition in the final annealing is not particularly limited.

[0128] In the heating process of the final annealing step, the average heating rate of the cold-rolled steel sheet in the temperature range of 300°C to 700°C is set to Vh (°C / s), the soaking temperature of the cold-rolled steel sheet in the soaking process is set to Tf (°C) and the soaking time is set to tf (s), and the average cooling rate of the cold-rolled steel sheet in the temperature range of 700°C to 300°C in the cooling process is set to Vc (°C / s), Tf is 750 to 1100°C, tf is 10 to 300 seconds, and the following formula (3) is satisfied.

[0129] Vh / 4≦Vc≦4Vh···Formula (3)

[0130] When the temperature increase rate Vc does not satisfy the formula (3), there is a possibility that the punching dimensional accuracy cannot be obtained when the non-oriented electrical steel sheet is produced.

[0131] The detailed mechanism by which the heating pattern in the final annealing step affects the punching dimensional accuracy is not clear, but is inferred as follows.

[0132] The final annealing is usually carried out in a series of steps including heating, soaking and cooling, and the tension of the steel plate controlled in the rolling direction is the same in each process. In addition, the steel plate is transported in the rolling direction by the hearth rollers according to the plate passing speed, but the tension control of the steel plate in the width direction is not implemented. However, the steel plate is thermally deformed in the width direction of the steel coil, expanding in the width direction due to thermal expansion during the heating process, and shrinking in the width direction due to thermal contraction during the cooling process. Here, the deformation of the steel plate in the width direction caused by thermal stress is constrained by the tension of the steel plate in the rolling direction and the friction with the hearth rollers. At this time, if the conditions of the final annealing are not properly controlled, it is considered that the deformation of the steel plate in the width direction of the steel coil becomes uneven.

[0133] That is, when the difference between the heating rate Vh and the cooling rate Vc in the final annealing is too large, that is, when the formula (3) is not satisfied, the difference in the thermal deformation rate in the width direction of the steel coil becomes too large, and the introduced strain becomes uneven depending on the position in the width direction of the steel coil. On the other hand, when the heating rate Vh and the cooling rate Vc are appropriately controlled, that is, when the formula (3) is satisfied, the difference in the thermal deformation rate in the width direction of the steel coil is maintained within an appropriate range, so the introduced strain is suppressed within a certain range depending on the position in the width direction of the steel coil. Part of the strain caused by deformation or constraint at high temperature also remains inside the cold-rolled steel sheet after cooling, generating residual stress, and it is inferred that it affects the dimensional accuracy after punching. Therefore, it is effective that the relationship between the average heating rate Vh and the average cooling rate Vc of the cold-rolled steel sheet in the final annealing satisfies the range of formula (3).

[0134] In addition, the soaking temperature Tf of the cold-rolled steel sheet during the soaking process of the final annealing has a great influence on the iron loss through the grain growth of the cold-rolled steel sheet. When Tf is less than 750°C, the hysteresis loss sometimes deteriorates due to the small grain size of the cold-rolled steel sheet. When Tf is higher than 1100°C, the effect of reducing iron loss sometimes becomes saturated and the equipment load becomes larger. The lower limit of the soaking temperature Tf is above 750°C, preferably above 800°C, and the upper limit of the soaking temperature Tf is below 1100°C, preferably below 1075°C.

[0135] In addition, the soaking time tf of the cold-rolled steel sheet in the soaking process of the final annealing also has a great influence on the iron loss via the grain growth of the cold-rolled steel sheet. When the soaking time tf is less than 10 seconds, the hysteresis loss sometimes deteriorates due to the small particle size of the cold-rolled steel sheet. When the soaking time tf is higher than 300 seconds, the annealing time becomes longer and the productivity deteriorates. The lower limit of the soaking time tf is more than 10 seconds, preferably more than 20 seconds. The upper limit of the soaking time tf is less than 300 seconds, preferably less than 250 seconds.

[0136] As described above, the heating mode of the final annealing is estimated to have an influence on the blanking dimensional accuracy and the iron loss. In addition, it is estimated that when the steel sheet composition is high alloy, the hardness of the steel sheet increases, and therefore these influences are more significant.

[0137] It should be noted that the width of the steel coil during the final annealing is not particularly limited, but it can be set to 80 mm or more, for example. The width of the steel coil can be set to 200 mm or more, or 500 mm or more, or 800 mm or more. Generally, the larger the width of the steel coil, the easier it is for the punching dimensional accuracy to deviate, but according to the non-oriented electromagnetic steel sheet of this embodiment, even if the width of the steel coil becomes larger, the deviation of the punching dimensional accuracy can be suppressed in the entire width range of the steel coil. In addition, electromagnetic steel sheets are usually provided by slitting steel coils into specified widths. According to the non-oriented electromagnetic steel sheet of this embodiment, in the slit electromagnetic steel sheet, the deviation of the punching dimensional accuracy can also be suppressed regardless of the width direction position of the steel coil.

[0138] [Insulation film coating process]

[0139] Next, an insulating coating is applied to the surface of the final annealed sheet after final annealing to form an insulating film. In the insulating film coating step, the drying temperature Tc (°C) of the insulating coating is 250°C to 500°C, and the steel sheet tension is 0.5 kgf / mm. 2 Above 5.0kgf / mm 2 When the drying temperature Tc and the steel sheet tension are out of the above ranges, the punching dimensional accuracy may not be obtained when manufacturing the non-oriented electrical steel sheet.

[0140] Although the detailed mechanism by which the various conditions in the insulation film coating process affect the punching dimensional accuracy is not clear, it is presumed as follows.

[0141] In the insulation coating step, an insulation coating is applied to at least one surface of the final annealed sheet, and then dried to form an insulation coating. Here, in order to maintain the punching dimensional accuracy, after the insulation coating is applied, when the final annealed sheet passes through the drying furnace, it is preferred that the final annealed sheet is flat in the width direction of the steel coil. Therefore, tension is applied to the final annealed sheet in the insulation coating step in the rolling direction. At this time, the steel sheet tension in the rolling direction is higher than 5.0 kgf / mm2 In the case of the final annealing, the steel sheet is deformed unevenly in the width direction of the steel coil, and the punching dimensional accuracy may be deteriorated. On the other hand, the steel sheet tension in the rolling direction is less than 0.5 kgf / mm 2 When the steel sheet is flat in the width direction of the steel coil, the punching dimension accuracy may deteriorate. Therefore, the lower limit of the steel sheet tension in the insulation film coating process is 0.5 kgf / mm 2 Above, preferably 0.7kgf / mm 2 Above, the upper limit of steel plate tension is 5.0kgf / mm 2 Below, preferably 4.0kgf / mm 2 the following.

[0142] In addition, after an insulating film is formed on the final annealed sheet and an insulating film-coated steel sheet is manufactured, the steel sheet is often wound up in a coil shape for shipment. That is, the drying process of the insulating coating is often the final process performed before the steel coil is shipped. Here, when the drying temperature Tc of the insulating coating is higher than 500°C, uneven strain is sometimes generated in the width direction of the steel coil, and the punching dimensional accuracy deteriorates. On the other hand, when the drying temperature Tc is less than 250°C, the drying of the insulating coating sometimes becomes insufficient. Therefore, the lower limit of the drying temperature Tc is above 250°C, preferably above 275°C, and the upper limit of the drying temperature Tc is below 500°C, preferably below 475°C. In addition, when the steel sheet component is a high alloy, the hardness of the steel sheet increases, so it is inferred that these effects become significant.

[0143] The composition of the insulating film is not particularly limited. For example, the insulating film may be an organic film or an inorganic film. Examples of the organic film include polyamine resins; acrylic resins; acrylic styrene resins; alkyd resins; polyester resins; silicone resins; fluororesins; polyolefin resins; styrene resins; vinyl acetate resins; epoxy resins; phenolic resins; polyurethane resins; melamine formaldehyde resins, etc.

[0144] In addition, examples of the inorganic coating include phosphate coatings, aluminum phosphate coatings, and organic-inorganic composite coatings containing the above-mentioned resins.

[0145] The average thickness of the insulating film is not particularly limited, but is preferably 0.1 μm to 10.0 μm as an average film thickness per single surface.

[0146] [Magnetic properties evaluation]

[0147] In addition, the magnetic properties of the electromagnetic steel sheet, such as iron loss, can be measured by a known method. For example, the magnetic properties of the electromagnetic steel sheet can be measured by using a method based on the Epstein test specified in JIS C2550:2011, or a single sheet magnetic property test method (Single Sheet Tester: SST) specified in JIS C2556:2015. In addition, in research and development, when a steel ingot is formed by a vacuum melting furnace, etc., it is difficult to use a test piece of the same size as that of the actual machine. At this time, for example, a test piece of 55 mm wide × 55 mm long can be taken, and the measurement based on the single sheet magnetic property test method can be performed. In addition, in order to obtain the same measurement value as the method based on the Epstein test, the measurement result based on the single sheet magnetic property test method can also be multiplied by a correction coefficient. In this embodiment, the measurement is performed by a measurement method based on the single sheet magnetic property test method.

[0148] An adhesive or the like may be applied on the surface of the non-oriented electrical steel sheet manufactured through the above steps as necessary.

[0149] According to the above steps, the final non-oriented electrical steel sheet can be manufactured. According to the manufacturing method of the present embodiment, a non-oriented electrical steel sheet having excellent magnetic properties can be manufactured.

[0150] Example

[0151] While showing the examples below, a non-oriented electrical steel sheet and a method for manufacturing the same according to an embodiment of the present invention are described in more detail. It should be noted that the examples shown below are only examples of the non-oriented electrical steel sheet and a method for manufacturing the same according to the present embodiment, and the non-oriented electrical steel sheet and a method for manufacturing the same according to the present embodiment are not limited to the examples shown below. The present invention can adopt various conditions within the scope of achieving the purpose of the present invention without departing from the gist of the present invention.

[0152] In the laboratory, alloys (steel No. A1 to A29 and a1 to a12) having the chemical composition described in Table 1 were melted. In addition, in Table 1, the contents of Cu, Sn, Ni, Cr, and Sb are recorded in the column of "A group elements". Similarly, the contents of Ti, Nb, V, and Zr are recorded in the column of "B group elements". In addition, the underlined characters in Table 1 indicate compositions outside the scope of the present invention, and the blank columns indicate that the corresponding element content is 0% in the significant figures (numerical values ​​to the smallest digit) specified in the embodiment, or is less than the lower limit of the component analysis. In addition, the underlined characters in Tables 1 to 4 indicate conditions that are out of the scope of the present invention, manufacturing conditions that are not preferred, or characteristic values ​​that are not preferred.

[0153] After the obtained alloy was hot-rolled to a thickness of 2.0 mm, the hot-rolled sheet was annealed and pickled as described in Table 2 to obtain a pickled sheet. Thereafter, the pickled sheet was cold-rolled to a thickness of 0.3 mm. Next, the obtained cold-rolled sheet was subjected to final annealing and insulation coating to obtain a non-oriented electromagnetic steel sheet with a width of 80 mm. In addition, the width of the through-sheet steel coil in the final annealing was set to 80 mm.

[0154] A test piece 55 mm long in the rolling direction and 55 mm long in the width direction was cut from the non-oriented electrical steel sheet after final annealing by shearing, and the magnetic properties were measured according to the single plate magnetic property test method of JIS C 2556:2015. Here, the magnetic measurement value is set as the average value in the rolling direction and the direction perpendicular to the rolling direction. Here, the iron loss W 15 / 50 The test results were considered acceptable when the iron loss (when the steel sheet was magnetized at 50 Hz to a magnetic flux density of 1.5 T) was 2.50 W / kg or less.

[0155] Then, along the width direction of the obtained non-oriented electrical steel sheet, five positions were punched at equal intervals (interval between the centers of the punching dies: about 16 mm). The circular die is used for punching, and the rolling direction length and width direction length of the round hole after punching are measured with a precision vernier caliper to derive the standard deviation.

[0156] [Table 1]

[0157]

[0158] [Table 2]

[0159]

[0160] At this time, as shown in Table 3, in the combination of steel No. A1 to A29 of the present invention example and manufacturing method No. B11 and B12 of the present invention example, the magnetic properties are excellent and the punching dimensional accuracy also meets the specified range. In addition, the composition of the base steel sheet after the final annealing is the same as the chemical composition described in Table 1.

[0161] On the other hand, in the combination of steel No. a1 to a12 as comparative examples and manufacturing methods No. B11 and B12 as examples of the present invention, magnetic properties and punching dimensional accuracy were poor, and the desired non-oriented electrical steel sheet was not obtained. In addition, marks c3, c5, c7, and c10 caused cold rolling cracks.

[0162] [Table 3]

[0163]

[0164] <Example 2>

[0165] In the laboratory, alloys (steel No. A26 and A27) having the chemical composition described in Table 1 were smelted. After the obtained alloy was hot-rolled to a thickness of 2.0 mm, hot-rolled sheet annealing and pickling were performed according to the description in Table 2 to obtain pickled sheets (manufacturing method No. B1 to B12 and b1 to b8). Thereafter, the pickled sheets were cold-rolled in a manner to a thickness of 0.3 mm. Next, the obtained cold-rolled sheets were subjected to final annealing and insulation coating to obtain non-oriented electromagnetic steel sheets with a width of 80 mm. In addition, the width of the through-sheet steel coil in the final annealing was set to 80 mm.

[0166] A test piece 55 mm long in the rolling direction and 55 mm long in the width direction was cut from the non-oriented electrical steel sheet after final annealing by shearing, and the magnetic properties were measured according to the single plate magnetic property test method of JIS C 2556:2015. Here, the magnetic measurement value is set as the average value in the rolling direction and the direction perpendicular to the rolling direction. Here, the iron loss W 15 / 50 Examples with a value of 2.50 W / kg or less were considered acceptable.

[0167] Then, along the width direction of the obtained non-oriented electrical steel sheet, five positions were punched at equal intervals (interval between the centers of the punching dies: about 16 mm). The circular die is used for punching, and the rolling direction length and width direction length of the round hole after punching are measured with a precision vernier caliper to derive the standard deviation.

[0168] As shown in Table 4, in the combination of the steel No. A26 and A27 of the present invention example and the manufacturing method No. B1 to B12 of the present invention example, the magnetic properties are excellent and the punching dimensional accuracy also meets the specified range. In addition, the composition of the base steel sheet after the final annealing is equivalent to the chemical composition described in Table 1.

[0169] On the other hand, in the combination of steel No. A27 of the present invention and manufacturing methods No. b1 to 8 of the comparative examples, at least one of the magnetic properties and the punching dimensional accuracy deteriorated, and the desired non-oriented electrical steel sheet could not be obtained. In addition, in the combination of steel No. A27 and manufacturing method No. b5, that is, comparative example d5, the insulating film was poorly formed, the magnetic properties could not be measured, and therefore the punching accuracy could not be measured.

[0170] [Table 4]

[0171]

[0172] <Example 3>

[0173] First, a steel billet is prepared and hot-rolled to obtain a hot-rolled steel plate with a thickness of 2.0 mm. The steel billet contains, by mass%, 0.003% C, 3.3% Si, 0.61% Mn, 1.22% Al, 0.0020% S, 0.0020% N, 0.010% P, and the remainder is composed of Fe and impurities.

[0174] Thereafter, the hot-rolled steel sheet was subjected to hot-rolled sheet annealing, pickling and cold rolling according to the conditions B12, b4 and b8 shown in Table 2 to obtain a cold-rolled sheet with a thickness of 0.3 mm. Next, the obtained cold-rolled sheet was subjected to final annealing and insulation coating to obtain a non-oriented electromagnetic steel sheet with a width of 1000 mm. Here, the hot-rolled sheet annealing was carried out at 900°C × 1 minute in an atmosphere of 100% nitrogen. In addition, pickling was carried out by immersing in a pickling solution of 0.07% polyamine and formic acid added to 85°C hydrochloric acid (7.5%) for 30 seconds. In addition, the dew point temperature of the final annealing was set to -40°C. The width of the through-plate steel coil in the final annealing was set to 1000 mm.

[0175] From the non-oriented electrical steel sheet after the final annealing, a test piece was taken according to the method specified in JIS C 2552:2014, and the magnetic properties were measured according to the method specified in JIS C 2550:2011. 15 / 50 Examples with a value of 2.50 W / kg or less were considered acceptable.

[0176] Then, along the width direction of the obtained non-oriented electrical steel sheet, five positions were punched at equal intervals (interval between the centers of the punching dies: about 200 mm). The circular die is punched, and the length in the rolling direction and the width direction of the round hole after punching are measured with a digital caliper to derive the standard deviation.

[0177] As shown in Table 5, in the non-oriented electrical steel sheet obtained under the conditions of the manufacturing method No. B12 of the present invention example, the magnetic properties are excellent and the blanking accuracy also satisfies the prescribed range. In addition, the composition of the mother steel sheet after the final annealing is equivalent to the chemical composition of the steel billet. In this way, in the present invention example, even if the width is large (for example, 1000 mm wide) in which the blanking accuracy deviation is easy to occur, in the case of the non-oriented electrical steel sheet of the present invention example, the deviation of the blanking accuracy can be suppressed in the entire width range of the steel sheet.

[0178] On the other hand, in the case of the marks d1 and d2 obtained under the conditions of the manufacturing methods No. b4 and b8 of the comparative examples, the punching dimensional accuracy was poor and the desired non-oriented electrical steel sheets could not be obtained.

[0179] [Table 5]

[0180]

[0181] Industrial Applicability

[0182] According to the above aspects of the present invention, a non-oriented electrical steel sheet having excellent magnetic properties and punching dimensional accuracy can be provided, and the industrial applicability is high.

Claims

1. A non-oriented electromagnetic steel sheet, characterized in that: Chemical composition, by mass%, contains C: 0.005% or less, Si: 2.00% or more and 4.50% or less, Mn: 0.01% to 5.00%, Al: 0.03% to 5.00%, Total SE of one or more of S, Se and Te: more than 0% and less than 0.005%, N: more than 0% and less than 0.005%, P: higher than 0% and less than 1.000%, Cu: 0% or more and 1.0% or less, Sn: 0% or more and 1.0% or less, Ni: 0% or more and 1.0% or less, Cr: 0% or more but less than 1.0% Sb: 0% or more and 1.0% or less, The remaining part is composed of Fe and impurities, and satisfies equations (1) and (2). (Si+Mn+Al)≧4.5%···Formula (1) Al / 3≦Mn···Formula (2) The rolling direction length L of the round hole after punching using a substantially circular die RD The width length L TD Ratio L RD / L TD The standard deviation is less than 0.

010. Iron loss W 15 / 50 It is below 2.50W / kg.

2. The non-oriented electrical steel sheet according to claim 1, characterized in that: The chemical composition, in mass %, further comprises Ti: 0% or more and 0.0030% or less, Nb: 0% or more and 0.0030% or less, V: 0% or more and 0.0030% or less, Zr: 0% or more and 0.0030% or less One or more of the groups.

3. A method for manufacturing a non-oriented electromagnetic steel sheet, characterized in that: include: A hot rolling process, heating the steel billet having the chemical composition of claim 1 or 2, and hot rolling it to produce a hot-rolled steel sheet; A cold rolling step of cold rolling the hot-rolled steel sheet to obtain a cold-rolled steel sheet; A final annealing step, performing final annealing on the cold-rolled steel sheet to obtain a final annealed sheet; as well as an insulating film coating step of applying an insulating coating to the final annealed sheet to form an insulating film on the final annealed sheet to obtain an insulating film coated steel sheet; In the final annealing process, when the average heating rate of the steel plate in the temperature range of 300° C. to 700° C. is set to Vh (° C. / second), the soaking temperature of the steel plate is set to Tf (° C.), the soaking time of the steel plate is set to tf (seconds), and the average cooling rate of the steel plate in the temperature range of 700° C. to 300° C. is set to Vc (° C. / second), Tf is 750 to 1100° C., tf is 10 to 300 seconds, and the formula (3) is satisfied, Vh / 4≦Vc≦4Vh···Formula (3) In the insulating film coating step, the drying temperature Tc (°C) during the insulating coating is 250 to 500°C, and the steel sheet tension is 0.5 to 5.0 kgf / mm 2 .

4. The method for manufacturing a non-oriented electrical steel sheet according to claim 3, wherein: Prior to the cold rolling step, a hot rolled sheet annealing step is provided to perform hot rolled sheet annealing on the hot rolled steel sheet to obtain a hot rolled annealed sheet.

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