JP2019035116A - Nonoriented electromagnetic steel sheet and method of producing the same - Google Patents

Abstract

To provide a nonoriented electromagnetic steel sheet that can improve iron loss in a low magnetic field and a method of producing the same.SOLUTION: A nonoriented electromagnetic steel sheet contains, in mass%, C: 0.005% or less, Si: 1.0-4.0%, Al: 0.1-0.8%, Mn: 0.01-0.07%, P: 0.02-0.3%, N: 0.005% or less, and S: 0.0012-0.005%, Cu: 0.001-0.5%, Ti: 0.005% or less, and at least one of Sn and Sb: 0.01-0.2% in total, with the balance being Fe and inevitable impurities. The ratio N/Nof a number of copper sulfide Nin inclusions with an equivalent spherical diameter of 0.01-1 μm to a number of the inclusions Nis 0.100 or less.SELECTED DRAWING: None

Description

  The present invention relates to a non-oriented electrical steel sheet and a manufacturing method thereof, and more particularly to a non-oriented electrical steel sheet having improved magnetic properties by controlling the contents of Mn, Al, P, and S within a specific range. .

  Non-oriented electrical steel sheets are used as iron core materials in rotating equipment such as motors and generators and stationary equipment such as small transformers, and play an important role in determining the energy efficiency of electrical equipment.

  Typical properties of the electromagnetic steel sheet include iron loss and magnetic flux density. The lower the iron loss, the better, and the higher the magnetic flux density. This is because, when the magnetic field is induced by applying electricity to the iron core, the energy lost by heat can be reduced as the iron loss is lower. Also, the higher the magnetic flux density is, the larger the magnetic field can be induced with the same energy.

  Therefore, in order to meet the demand for energy saving and environmentally friendly products, a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density and a manufacturing method thereof are required.

  Typical methods for improving iron loss among the magnetic properties of non-oriented electrical steel sheets include a method of reducing the plate thickness and a method of adding an alloy element having a large specific resistance such as Si, Mn, and Al. It has been known.

  However, in the method of reducing the thickness of the non-oriented electrical steel sheet, the sheet thickness is determined according to the characteristics of the product used, and the thinner the sheet thickness, the lower the productivity of the steel sheet and the higher the cost. There is a problem.

  In addition, in the method of adding an alloy element having a large specific resistance such as Si, Mn, and Al, the iron loss is reduced by adding the alloy element, but the saturation magnetic flux density may be reduced and the magnetic flux density may be reduced. There is an inevitable problem.

  On the other hand, when the Si content is 4% or more, the workability is lowered, so that cold rolling becomes difficult and the productivity may be lowered. Further, as Mn, Al and the like are added in a larger amount, the rollability is lowered, the hardness is increased, and the workability may be lowered.

  On the other hand, if fine inclusions are present in the steel sheet, crystal grain growth during annealing is inhibited, and the domain wall movement inhibition action increases, thereby deteriorating iron loss. As the number of fine inclusions contained in the steel sheet increases and the size decreases, the crystal grain growth is inhibited. Therefore, in order to improve crystal grain growth, it is necessary to reduce the number of inclusions and coarsen the inclusions.

  Examples of fine inclusions that inhibit grain growth of non-oriented electrical steel sheets include sulfides such as copper sulfide and manganese sulfide, oxides such as silica and alumina, and nitrides such as aluminum nitride and titanium nitride. Are known. In the following, inclusions mean non-metal precipitates such as oxides, sulfides, and nitrides.

Among these fine inclusions, sulfide dissolves in annealing after rolling and reprecipitates in the cooling process, so the number is large and tends to become fine, so it inhibits crystal grain growth and degrades iron loss. The action to make is great. And, in particular, the non-oriented electrical steel sheet containing Cu effective for controlling the texture and strength of the steel, etc., and the CuS found in the non-oriented electrical steel sheet containing Cu inevitably entering from scrap and ore, For example, copper sulfide such as Cu ₂ S has a deposition initiation temperature as low as about 1000 ° C. to 1100 ° C. as compared with other sulfides such as manganese sulfide which starts deposition at about 1100 ° C. to 1200 ° C. For this reason, compared with other sulfides, copper sulfide dissolves and reprecipitates at a lower temperature in annealing after rolling, so that the number of copper sulfides tends to be larger and finer. Therefore, it is considered that copper sulfide has a larger effect on inhibiting grain growth and deteriorating iron loss than other sulfides.

  Therefore, in order to improve the crystal grain growth of the steel sheet, it is important to make it harmless by reducing or coarsening the number of copper sulfides among fine sulfides. However, it has been considered difficult to completely avoid the formation of fine copper sulfide. For this reason, in the non-oriented electrical steel sheet containing Cu, on the premise that fine copper sulfide exists, a technique for controlling fine copper sulfide within a harmless range has been advanced.

  As a technique for controlling fine copper sulfide within a harmless range, for example, Patent Document 1 controls hot rolling conditions within a specific range on the premise that fine copper sulfide exists. Thus, a technique for improving magnetic properties by controlling the mass ratio and precipitation state of copper sulfide within a specific range is disclosed. In Patent Document 2, by controlling the contents of Mn, Al, P, and S within a specific range, formation of fine inclusions such as copper sulfide is suppressed and coarse inclusions are increased. Thus, a technique for improving magnetic properties by improving crystal grain growth and domain wall mobility is disclosed.

JP 2010-174376 A Special table 2015-508454 gazette

  In the prior art, as described above, it was considered that the sulfide was sufficiently detoxified. In fact, in the above-described conventional steel sheet, the crystal grain growth at a high temperature is good, and the iron loss in a high magnetic field at which a general steel sheet characteristic evaluation is performed is sufficiently improved. However, when the present inventors investigated various characteristics in a practical use environment, it was found that sufficient effects were not obtained particularly when Cu was contained. That is, even if the sulfide is controlled to be detoxified with respect to crystal grain growth, it is suggested that there is room for improvement in iron loss characteristics in an actual use environment in a steel sheet containing Cu. The reason for this is not clear, but is considered as follows. In an actual use environment, the magnetic flux does not flow uniformly in the steel sheet, and a location where the magnetic flux is concentrated locally occurs. Accordingly, there is a region where the magnetic flux is weakened, and the area of the region where the magnetic flux is weakened is larger. For this reason, the characteristic value in a lower magnetic flux density region has a strong influence. And when it contains Cu, as a sulfide, in addition to manganese sulfide, the production | generation ratio of copper sulfide increases, and it is thought that the bad influence of copper sulfide with respect to the iron loss characteristic in a lower magnetic flux density area | region appears. In view of this situation, the inventors set as an issue to improve iron loss in a low magnetic field.

  The present invention has been made in view of the above-described problems, and a non-oriented electrical steel sheet capable of improving iron loss in a low magnetic field by suppressing or avoiding the formation of fine copper sulfide as much as possible, and a method for producing the same The purpose is to provide.

  Based on the situation as described above, the present inventors have conducted intensive research on a method for solving the above-described problems.

  First, when using the above-described technique for controlling fine copper sulfide within a harmless range in a non-oriented electrical steel sheet containing Cu, the present inventors have a high magnetic field (for example, 1.5%). Although iron loss at ~ 1.7T) is improved, there is still room for improvement in iron loss at lower magnetic fields (for example, around 1.0-1.4T), and earnest research on the improvement method Went. As a result, after optimizing the chemical composition of the steel sheet and further controlling the hot-rolled sheet smelting condition within a specific range, it is possible to suppress or avoid the formation of fine copper sulfide as much as possible, We have found that iron loss at low magnetic field is improved.

  Furthermore, as a result of diligent research on this cause, the improvement of iron loss at low magnetic fields realized by suppressing or avoiding the formation of fine copper sulfide as much as possible is the grain growth property realized by detoxification of copper sulfide. It was found that this was due to a phenomenon different from the improvement of iron loss at high magnetic field through the improvement of the magnetic field, mainly due to the drastic improvement in magnetic permeability due to the rapid improvement of domain wall mobility. .

This invention is made | formed based on these knowledge, The summary is C: 0.005% or less, Si: 1.0-4.0%, Al: 0.1-0. 8%, Mn: 0.01 to 0.07%, P: 0.02 to 0.3%, N: 0.005% or less, and S: 0.0012 to 0.005%, Cu: 0.001 -0.5%, Ti: 0.005% or less, and at least one of Sn and Sb: 0.01 to 0.2% in total, with the balance being Fe and inevitable impurities And the ratio N _CuS / N _Tot of the number N _CuS of copper sulfides in the inclusions to the number N _Tot of inclusions having a sphere equivalent diameter of 0.01 to 1 μm is 0.100 or less. It is a non-oriented electrical steel sheet.

  Another gist is the above-mentioned non-oriented electrical steel sheet characterized by not containing copper sulfide having a sphere equivalent diameter of 0.01 to 1 μm.

Another gist is that the contents of Mn, Cu, Al, P, and S have the chemical composition satisfying the following formula (1), and the number of the inclusions to the number N _Tot of the inclusions. Number of sulfides having a sphere equivalent diameter of 0.1 μm or more N _{XS ≧ 0.1 μm} Ratio N _{XS ≧ 0.1 μm} / N _Tot is 0.51 or more, and the average sphere equivalent diameter of the inclusions is 0.00. The non-oriented electrical steel sheet described above, which is 114 μm or more.
3.0 ≦ {([Mn] + [Cu]) / (100 × [S]) + [Al]} / [P] ≦ 70
(1)
(Here, [Mn], [Cu], [Al], [P], and [S] mean the contents [mass%] of Mn, Cu, Al, P, and S, respectively.)

  Furthermore, another gist is a method for manufacturing the above-mentioned non-oriented electrical steel sheet, a hot rolling process for obtaining a hot-rolled steel sheet by subjecting the slab having the above-described chemical composition to hot rolling, and the hot-rolled steel sheet. On the other hand, the average temperature increase rate from 600 ° C. to 800 ° C. is set to 50 ° C./second or more and 800 ° C./second or less, and the temperature is raised to the highest temperature in the temperature range of 800 ° C. or more and 1200 ° C. or less After holding in the zone for 5 seconds or more and 300 seconds or less, hot-rolled sheet smelting and pickling is performed by cooling with an average cooling rate from 800 ° C. to 400 ° C. being 50 ° C./second or more and 800 ° C./second or less. Hot-rolled sheet pure / pickling process to obtain a tempered sheet, cold-rolling process to cold-roll the hot-rolled annealed sheet to obtain a cold-rolled steel sheet, and finish annealing to finish-anneal the cold-rolled steel sheet And a process for producing a non-oriented electrical steel sheet characterized by comprising: It is.

  ADVANTAGE OF THE INVENTION According to this invention, the non-oriented electrical steel plate which can improve the iron loss in a low magnetic field, and its manufacturing method can be provided.

  Hereinafter, the non-oriented electrical steel sheet and the manufacturing method thereof according to the present invention will be described in detail.

A. Non-oriented electrical steel sheet The non-oriented electrical steel sheet of the present invention is, in mass%, C: 0.005% or less, Si: 1.0 to 4.0%, Al: 0.1 to 0.8%, Mn : 0.01-0.07%, P: 0.02-0.3%, N: 0.005% or less, and S: 0.0012-0.005%, Cu: 0.001-0.5 %, Ti: 0.005% or less, and at least one of Sn and Sb: 0.01 to 0.2% in total, with the balance being a chemical composition consisting of Fe and inevitable impurities, The ratio N _CuS / N _Tot of the number N _CuS of copper sulfides in the inclusions to the number N _Tot of inclusions having an equivalent diameter of 0.01 to 1 μm is 0.100 or less.

  Hereinafter, each structure in the non-oriented electrical steel sheet of this invention is demonstrated.

1. Precipitation state of inclusions (1) Precipitation state of copper sulfide a. In non-oriented electrical steel sheet precipitation state invention copper sulfide, the ratio of the number _{N CuS} copper sulfide of the inclusions to the number _{N Tot} inclusions sphere equivalent diameter 0.01 to 1 [mu] m _{N CuS} / N _Tot is 0.100 or less. That is, the formation of copper sulfide having a large effect of deteriorating magnetic properties among inclusions is suppressed or avoided as much as possible. Thereby, deterioration of magnetic characteristics can be effectively suppressed. Particularly in a low magnetic field, the iron loss is improved by improving the magnetic permeability.

  Here, in the present invention, "inclusion sphere equivalent diameter" means the diameter when the inclusion is converted into a sphere, that is, the diameter of a sphere having the same volume as the inclusion, and the precipitation state of the inclusion described later It is calculated | required from the size and shape of the inclusion observed with the observation sample. Needless to say, it is necessary to measure all inclusions having a diameter equivalent to a sphere to be present in the entire observation region. In addition, the sphere equivalent diameter and the number of inclusions can be obtained using image analysis or the like.

In the present invention, it is preferable that copper sulfide having a sphere equivalent diameter of 0.01 to 1 μm is not contained. Because the formation of copper sulfide, which has a large effect of deteriorating magnetic properties among inclusions, is completely avoided, especially in a low magnetic field, the magnetic permeability is remarkably improved, so that the iron loss is remarkably improved. It is.
Here, in the present invention, “copper sulfide having a sphere equivalent diameter of 0.01 to 1 μm is not contained” means that at least 200 inclusions having a sphere equivalent diameter of 0.01 to 1 μm are obtained by the procedure described below. When the type of inclusion is investigated, it means that there is no inclusion judged to be copper sulfide (the number of inclusions judged to be copper sulfide is zero). For example, when the kind of inclusion is determined for 1000 inclusions having a diameter corresponding to a sphere of 0.01 to 1 μm by the procedure described below, it is determined that copper sulfide is one of the 1000 inclusions. It means that the number of inclusions is zero.

b. Presumed mechanism in which the precipitation state of copper sulfide acts In the present invention, the mechanism in which iron loss in a low magnetic field is reduced due to N _CuS / N _Tot being within the above-mentioned range, although there is an unclear part, It is estimated as follows.
In this specification, the present invention is described based on the following estimation mechanism. However, since the estimation mechanism is only an estimation, the effects of the present invention in the future will be May be expressed by different mechanisms. However, the findings thus found do not deny the present invention.

  Fine copper sulfide has been conventionally recognized as an inclusion that has a particularly large effect of reducing the crystal grain growth. When the number density of fine copper sulfide is reduced, the crystal grain growth is improved monotonously. It is considered. This is generally caused by a phenomenon called the pinning effect. When the inclusions are present on the grain boundary, the pinning effect means that there is no grain boundary in the region when considering the interface energy of the grain boundary. Is a phenomenon in which the arrangement of crystal grain boundaries is stabilized and the mobility of crystal grain boundaries is lowered. In steel sheets, if the volume ratio of inclusions containing copper sulfide, etc. is constant, the pinning effect becomes smaller as inclusions become coarser, so conventionally, inclusions, including copper sulfide, etc., should be coarsened. By reducing the pinning effect, the crystal grain growth property is improved and the domain wall mobility is improved.

On the other hand, as described above, the ratio N _CuS / N _Tot of the number N _CuS of copper sulfides in the inclusions to the number N _Tot of inclusions having a sphere equivalent diameter of 0.01 to 1 μm is reduced to 0.100 or less. In the non-oriented electrical steel sheet according to the present invention, the average of the sphere equivalent diameter of the copper sulfide is refined to a range of about 100 nm or less in accordance with the reduction in the ratio N _CuS / N _Tot of the number N _CuS of the copper sulfide. It is estimated that. Therefore, in the non-oriented electrical steel sheet of the present invention, the phenomenon that the iron loss in a low magnetic field is improved is that the above-mentioned pinning effect is reduced because the copper sulfide becomes coarser as the ratio of the copper sulfide is reduced. It is presumed that the cause is not that the copper sulfide itself directly affects the mobility of the domain wall.

  Specifically, since the domain wall has a thickness, when the sphere equivalent diameter of copper sulfide is larger than the thickness of the domain wall, if the domain wall is positioned so that the copper sulfide protrudes on both sides, the domain wall is on both sides of the domain wall. The portion of the copper sulfide that protrudes has a magnetization opposite to that of the ground iron, and also generates a magnetic moment opposite to the domain wall, so that the magnetostatic energy decreases. Thereby, the inhibitory effect to the mobility of the domain wall by copper sulfide increases.

On the other hand, in the non-oriented electrical steel sheet, the thickness of the domain wall is considered to be about 50 to 100 nm. Therefore, according to the reduction of the number N _CuS of copper sulfides N _CuS / N _Tot described above, When the average diameter is refined to a range of about 100 nm or less, the volume of the portion that protrudes from the domain wall disappears rapidly, and the magnetostatic energy does not decrease. For this reason, the inhibitory action to the mobility of the domain wall by copper sulfide reduces rapidly. Therefore, in consideration of such a phenomenon, when the sphere equivalent diameter of copper sulfide is about 100 nm, even if the copper sulfide is coarsened, it does not become harmless. Therefore, the number of copper sulfides N _CuS described above By reducing the ratio N _CuS / N _Tot of the copper sulfide, the average of the sphere equivalent diameter of the copper sulfide is refined to a range of about 100 nm or less so that the copper sulfide does not protrude from the domain wall. Therefore, it is estimated that the inhibitory effect on the mobility of the domain wall by copper sulfide can be reduced. As a result, it is estimated that iron loss in a low magnetic field is reduced.

  Furthermore, taking into account that the reduction in iron loss at low magnetic fields is highly correlated with the increase in permeability at low magnetic fields, this reduction in iron loss at low magnetic fields This is due to a phenomenon different from the improvement of iron loss at high magnetic fields through the improvement of grain growth realized by coarsening, and that copper sulfide itself directly affected the domain wall mobility. Presumed to be the cause.

(2) Precipitation state of other inclusions In the non-oriented electrical steel sheet of the present invention, the contents of Mn, Cu, Al, P, and S have the above-described chemical composition satisfying the following formula (1). The ratio N _{XS ≧ 0.1 μm} of the number N of sulfides having a sphere equivalent diameter of 0.1 μm or more to the number N _Tot of inclusions having a sphere equivalent diameter of 0.01 to 1 μm _. It is preferable that _{1 μm} / N _Tot is 0.51 or more, and the average sphere equivalent diameter of the inclusion is 0.114 μm or more.
3.0 ≦ {([Mn] + [Cu]) / (100 × [S]) + [Al]} / [P] ≦ 70
(1)
(Here, [Mn], [Cu], [Al], [P], and [S] mean the contents [mass%] of Mn, Cu, Al, P, and S, respectively. (Mn, Cu, Al, P, and S content [mass%] may be abbreviated as [Mn], [Cu], [Al], [P], and [S].)

  By appropriately controlling the ratio of the contents of Cu, Mn, and S, the ratio of the number of copper sulfides in the inclusions is controlled in a more preferable range, and not only the characteristics at low magnetic fields are improved. In addition, the saturation magnetic flux density can be increased by reducing the contents of Mn and Al within the range described below, and coarse inclusions can be obtained even when the contents of Mn and Al are reduced within the range described below. Since it can be increased, hysteresis loss can be reduced by improving crystal grain growth. This is because the iron loss in a high magnetic field can be further reduced and the magnetic flux density can be increased.

Hereinafter, the contents of Mn, Cu, Al, P, and S satisfy the above formula (1), and the ratio N _{XS ≧ 0.1 μm} / N _Tot and the average of the equivalent sphere diameters are within the above-mentioned range. Thus, the reason why the above-described effect can be obtained will be described.

  Mn is added to increase the specific resistance and reduce the eddy current loss, but combines with S to form MnS. Similarly, Cu combines with S to form copper sulfide. On the other hand, Al is also added to increase the specific resistance and reduce the eddy current loss in the same manner as Mn, but forms a nitride. Inclusions such as sulfides and nitrides such as MnS and copper sulfide are generally as fine as a sphere equivalent diameter of about 0.05 μm, so the crystal grain growth is reduced and the domain wall mobility is reduced. By doing so, the magnetic characteristics in a high magnetic field are greatly deteriorated (in particular, the hysteresis loss is increased among iron losses). For this reason, it is necessary to coarsen the inclusions in order to minimize the deterioration of the magnetic properties (iron loss).

Generally, it is known that when the contents of Mn, Cu, and Al are decreased, the fine inclusions among the inclusions formed by Mn, Cu, and Al are correspondingly increased. However, when the contents of Mn, Cu, Al, P, and S satisfy the above formula (1), unlike general knowledge, the contents of Mn, Cu, and Al are within the ranges described below. By reducing the number of particles, the formation of fine inclusions can be suppressed and coarse inclusions can be increased. Specifically, as described above, the number N of sulfides having a sphere equivalent diameter of 0.1 μm or more of the inclusions N _{Tot with} respect to the number N _Tot of inclusions having a sphere equivalent diameter of 0.01 to 1 μm _. The ratio N _{XS ≧ 0.1 μm} / N _Tot of _{1 μm} can be set to 0.51 or more, and the average sphere equivalent diameter of the inclusions can be set to 0.114 μm or more. As a result, the content of Mn, Cu, and Al can be reduced to increase the saturation magnetic flux density, and the coarse inclusions can be increased even if the content of Mn, Cu, and Al is reduced. Therefore, by improving the crystal grain growth property, it is possible to reduce the hysteresis loss that has a great influence on the iron loss in a high magnetic field. Thereby, the iron loss in a high magnetic field can be further reduced and the magnetic flux density can be increased.

  ([Mn] + [Cu]) / [S] is important in controlling the type of sulfide, the equivalent sphere diameter, and the number of inclusions among the inclusions. [Al] is important in controlling the precipitation state of nitride among inclusions. Furthermore, P is an element that segregates at the grain boundaries. For this reason, the ratio of ([Mn] + [Cu]) / [S] and [Al] with respect to [P] removes the grain growth inhibitory power of inclusions by coarsening the inclusions. This is considered to have a very large influence on improving the magnetic characteristics in a high magnetic field.

Therefore, the contents of Mn, Cu, Al, P, and S satisfy the above formula (1), and the ratio N _{XS ≧ 0.1 μm} / N _Tot and the average of the equivalent sphere diameters of the inclusions are within the above-mentioned range. Thus, it is considered that the above-described effects can be obtained.

  On the other hand, when the contents of Mn, Cu, Al, P and S do not satisfy the above formula (1) and the above formula (1) is less than 3.0 or exceeds 70, Mn and Al If the content of is reduced within the range described later, formation of fine inclusions cannot be suppressed and the inclusions cannot be coarsened, so that crystal grain growth is suppressed. As a result, it is considered that the effects as described above cannot be obtained.

Although it is described just in case, in the explanation of the above-described formula (1) and the coarsening of sulfide related thereto, explanation including Cu and copper sulfide is given, but in the present invention, the formation of copper sulfide is completely intervened. Since the number ratio N _CuS / N _Tot with the product is suppressed to 0.100 or less, it can be understood that most of the effects described above are due to sulfides (mainly MnS) and nitrides other than copper sulfide. In other words, copper sulfide causes the invention effect through the interaction with the domain wall itself in a low magnetic field as described above, whereas MnS and nitride improve the crystal grain growth as described above. It acts to improve the magnetic properties in a high magnetic field by affecting the mobility of the domain wall via the crystal grain size, and should be interpreted as causing different actions.

(3) Method of investigating the precipitation state of inclusions The number N _Tot of inclusions having a sphere equivalent diameter of 0.01 to 1 μm, the number N _{CuS of} copper sulfides in the inclusions, and the sphere equivalent of the inclusions The number N _{XS ≧ 0.1} μm of sulfides having a diameter of 0.1 μm or more and the average of the equivalent sphere diameters of the inclusions are determined from the type of inclusions present in the steel sheet, the equivalent sphere diameter, and the number. As a method for investigating the type of inclusions, the equivalent sphere diameter, and the number of inclusions, a method of observing a mirror-polished steel plate surface using a SEM (scanning electron microscope) and analyzing it using EDS is used.

a. Method for Creating Sample for Observation of Precipitation State of Inclusions A method for preparing the sample for observation of the precipitation state of inclusions will be described.
In the method for preparing the sample for observation of the precipitation state used by the present inventors, the oxide film such as the scale formed on the steel sheet surface is removed by chemical polishing or mechanical polishing to expose the steel sheet surface, A sample for observation of the precipitation state is prepared by mirror polishing the surface of the steel sheet. When preparing the observation sample, as a mirror polishing method, in order to stably observe inclusions or precipitates that are easily dissolved by moisture, a method of mirror finishing by oil polishing in the final finishing step is used. The investigation of the precipitation state of the inclusions described above is performed by observing the polished surface of the sample for observation of the precipitation state of the inclusions thus prepared.

b. Method of investigating inclusion type, equivalent sphere diameter, and number of inclusions The inclusion type, equivalent sphere diameter, and number of inclusions were determined using the SEM on the polished surface of the sample for observation of the precipitation state of inclusions described above. This is investigated by observing a region selected at random so that the type, the equivalent sphere diameter, and the number of the spheres are not biased. Specifically, after setting the SEM to a magnification at which inclusions with a sphere equivalent diameter of 0.01 μm or more are clearly observed, measure the size, shape, and number of all inclusions present in the observation region. To investigate the sphere equivalent diameter and the number of inclusions having at least 200 sphere equivalent diameters of 0.01 μm to 1 μm. Furthermore, the type of those inclusions is determined using EDS. In this case, for example, the polished surface is measured with a working distance (WD) of 10 mm, an acceleration voltage of 15 kV, and a magnification of 100 to 200000 times.

  In addition, the size and shape of inclusions measured in the observation region of the polished surface of the observation sample are two-dimensional sizes and shapes, whereas the equivalent sphere diameters of inclusions used in the present invention are defined. Is the size in three dimensions. For this reason, when investigating the sphere equivalent diameter of an inclusion as described above, the inclusion circle is a two-dimensional size directly obtained from the size and shape of the inclusion measured as described above. As an equivalent diameter multiplied by 1.27, the equivalent sphere diameter of the inclusion is obtained.

In the present invention, when investigating the type, inclusion equivalent diameter, and number of inclusions present in the steel sheet, it is not only difficult to observe and measure inclusions with an equivalent diameter of less than 0.01 μm. Because of its small influence on magnetic properties, it is not included in the survey. Further, oxides such as SiO ₂ and Al ₂ O ₃ having a sphere equivalent diameter of more than 1 μm are not included in the investigation because they have a small influence on the magnetic properties.

  Further, when all kinds of inclusions are investigated using EDS, the case where S is detected in inclusions by EDX is determined as “sulfide”. Further, even if S is not clearly detected due to the small size of inclusions, other inclusions in which S is clearly detected for inclusions in which Cu, Mn, etc. are detected and O etc. are not detected The inclusions that can be virtually determined to contain S from the form comparison are also determined as “sulfides”. Further, “sulfide” in which Cu is detected by EDX or in which it can be practically determined that Cu is contained is determined as “copper sulfide”.

  It should be noted that “copper sulfide” and “sulfide” in the present invention determined as described above are determined by a simple method that enables practical implementation. Here, the meanings of “copper sulfide” and “sulfide” in the present invention will be described.

  In general, “copper sulfide” or “sulfide” means a specific compound having a determined crystal structure and composition. However, since inclusions containing sulfides such as copper sulfide and manganese sulfide that inhibit crystal grain growth are very fine, it is often difficult to determine their crystal structure and composition. Whether or not the inclusion observed by TEM is copper sulfide whose precipitation state should be specified in the present invention is determined by whether or not the inclusion contains S and Cu. In this case, O, C, etc. may be detected together with S by EDX, and Mn, Ti, etc. may be detected together with Cu, for example. In addition, other elements may be detected. For this reason, for example, it is assumed that Cu is detected due to solid solution of Cu in inclusions that are completely determined to be manganese sulfide from the crystal structure and composition. Therefore, for example, inclusions that are determined to be sulfides only from the intensity ratio of the detected element in EDX are interpreted as various types of inclusions such as oxides or carbides, or oxysulfides or carbon sulfides. It may be possible. Actually, it is often described based on such a judgment not only in patent application specifications but also in academic papers.

  However, in the present invention, it is meaningless to strictly determine the type of inclusion, and it is not practical because much labor is required in practice. Therefore, as described above, the type of inclusion is determined depending on whether S, Cu, or the like is contained. Therefore, in the present invention, “sulfide” means inclusions containing S, and “copper sulfide” means inclusions containing S and Cu. That is, in the present invention, “sulfide” and “copper sulfide” are meant to include inclusions that are not strictly speaking sulfides and copper sulfides from the crystal structure and composition, respectively. In addition, “sulfide” and “copper sulfide” are meant to include inclusions in which the compound name cannot be specified strictly.

2. Next, the chemical composition in the present invention will be described. In the following, the content of each component is a value in mass%.

(1) C
When the C content is large, the austenite region is expanded, the phase transformation interval is increased, and the crystal grain growth of ferrite is suppressed during annealing, which may increase the iron loss. Further, it combines with Ti or the like to form a carbide to deteriorate the magnetic properties, and there is a risk of increasing iron loss due to magnetic aging when using an electric product processed from the final product. For this reason, C content is made into 0.005% or less.

(2) Si
Si is a main element that is added to increase the specific resistance and to reduce the eddy current loss. If the Si content is small, it is difficult to obtain an effect of reducing eddy current loss. If the Si content is large, the steel sheet may be broken during cold rolling, so the content is set to 1.0 to 4.0%.

(3) Al
Al is an element that is unavoidably added to deoxidize steel in the steelmaking process, and is the main element added to increase the specific resistance and reduce the eddy current loss in the same manner as Si. It is an element. For this reason, Al is added in a large amount in order to reduce the iron loss, but when added in a large amount, the saturation magnetic flux density is reduced. Specifically, when the Al content exceeds 0.8%, the magnetic flux density is lowered. On the other hand, even when the contents of Mn, Al, P, and S satisfy the above-described formula (1), when the Al content is less than 0.1%, fine AlN is formed to form crystals. Grain growth is lowered and magnetic properties are lowered. Therefore, the Al content is set to 0.1 to 0.8%.

(4) Mn
Mn is an element that is added to increase the specific resistance and reduce the eddy current loss in the same manner as Si and Al. In order to obtain such an effect, conventionally, the Mn content has been set to 0.1% or more. However, when the Mn content is increased, the saturation magnetic flux density is decreased to decrease the magnetic flux density, and Mn combines with S to form fine MnS, thereby reducing the grain growth and moving the domain wall. In particular, the hysteresis loss is increased in the iron loss by reducing the property. Therefore, the Mn content is set to 0.01 to 0.07% from the viewpoint of increasing the magnetic flux density and reducing the iron loss. Furthermore, from this viewpoint, the Mn content is preferably 0.01 to 0.05%.

(5) P
P increases the specific resistance to lower the iron loss and segregates at the grain boundaries to suppress the formation of {111} texture that is disadvantageous to the magnetic properties, and is advantageous for magnetic properties. Add to promote tissue formation. If the P content exceeds 0.3%, the rolling property deteriorates and the effect of improving the magnetic properties decreases, so the P content is 0.02 to 0.3%.

  Mn is an element that suppresses the formation of ferrite, while P is an element that expands the ferrite phase. By satisfying [Mn] <[P], hot rolling and hot rolling are performed. Since the ferrite phase can be stabilized at the time of pure plate baking, the high-frequency magnetic characteristics can be improved by increasing the texture favorable to the magnetic characteristics.

(6) N
N is an element harmful to magnetic properties that causes problems such as a decrease in crystal grain growth by forming a nitride by strongly bonding with Al or Ti in steel, so it is better to reduce N Good. For this reason, N content shall be 0.005% or less.

(7) S
Since S is an element that forms sulfides such as MnS, CuS, and (Cu, Mn) S composite sulfides harmful to magnetic properties, it is preferable to reduce the content as much as possible. However, if the S content is less than 0.0012%, it is rather disadvantageous for the formation of texture, and the magnetic properties deteriorate, and if it exceeds 0.005%, the magnetic properties deteriorate due to an increase in fine sulfides. Therefore, the S content is set to 0.0012 to 0.005%.

(8) Cu
Cu reacts with S in the same way as Mn to form sulfides. However, the influence of copper sulfide on the magnetic properties of low magnetic fields is larger than that of manganese sulfide, so that the control of the content is particularly important. It is. Even if the content of Cu is small, it is considered that a fine sulfide is formed in the hot rolling process, particularly after the finish rolling, and the iron loss and the magnetic flux density are remarkably deteriorated. For this reason, although it is thought that it is preferable that the Cu content is as low as possible, normally, since C inevitably enters from the raw material and scrap mixed in the manufacturing process in the steel sheet, it is not allowed to contain Cu Have difficulty. Moreover, since the feature of the present invention is the control of copper sulfide, the inclusion of Cu is essential, and if the Cu content is excessively small, the inventive effect does not appear. For this reason, Cu content shall be 0.001% or more. On the other hand, in the present invention, the formation of copper sulfide can be sufficiently suppressed, so that a relatively large amount can be contained. Therefore, the Cu content is set to 0.5% or less. In order to avoid deteriorating the magnetic flux density, the Cu content is preferably 0.3% or less.

(9) Ti
Ti forms fine carbides or nitrides to reduce crystal grain growth. Therefore, as the added amount increases, the texture increases as fine carbides or nitrides increase, and the magnetic properties deteriorate. For this reason, Ti content shall be 0.005% or less.

(10) Sn and Sb
Sn and Sb are elements that segregate at the grain boundaries, and suppress the formation of {111} textures that are disadvantageous to magnetic properties by suppressing the diffusion of nitrogen through the grain boundaries. Promotes the formation of {100} texture that is advantageous to the properties. For this reason, in order to improve a magnetic characteristic, at least 1 sort (s) is added among Sn and Sb. When the content of one of Sn and Sb is added, or the total content of both when Sn and Sb are added exceeds 0.2%, the grain growth property In order to degrade the magnetic characteristics by lowering the thickness, the content is made 0.01 to 0.2%.

(11) Remainder The remainder is Fe and inevitable impurities. Among the inevitable impurities, Nb, Zr, Mo, V, and the like are elements that form carbonitrides. Therefore, it is desirable to reduce them as much as possible, and their contents are preferably 0.01% or less, respectively. . Further, the inevitable impurities include impurities that are inevitably included in each manufacturing process, and examples thereof include Ni and Cr mixed by using scrap as a raw material. Further, if the non-oriented electrical steel sheet of the present invention can obtain the effects of the present invention, the magnetic characteristics can be improved, the mechanical properties such as strength, corrosion resistance, or fatigue characteristics can be improved, or the castability or plateability can be improved. Ni, Cr, W, Co, Mg, Ca, REM, etc. may be contained in place of a part of the remaining Fe for a publicly known purpose such as improving the properties relating to the productivity.

(12) Others It is preferable that the contents of Mn, Cu, Al, P, and S satisfy the above-described formula (1). This is because the iron loss in a high magnetic field can be further reduced and the magnetic flux density can be increased.

3. Non-oriented electrical steel sheet In the non-oriented electrical steel sheet of the present invention, the crystal grain size is preferably 50 to 180 μm. When the crystal grain size increases, it is advantageous because the hysteresis loss in the iron loss decreases, but the eddy current loss in the iron loss increases, so that the crystal grain suitable for minimizing such iron loss. The diameter is thus limited.

  The crystal grain size is obtained by measuring and averaging the diameters of circles of the same area relative to the projected area for a plurality of crystal grains revealed by mirror-polishing a plate thickness section of a steel plate and performing nital etching. Ask.

B. Non-oriented electrical steel sheet manufacturing method The non-oriented electrical steel sheet manufacturing method of the present invention is a non-oriented electrical steel sheet manufacturing method described in the item "A. Non-oriented electrical steel sheet" described above. A hot rolling step in which a hot-rolled steel sheet is obtained by subjecting a slab having a chemical composition to hot rolling, and an average temperature increase rate from 600 ° C. to 800 ° C. is 50 ° C./second or more 800 The average cooling rate from 800 ° C. to 400 ° C. after raising the temperature to 800 ° C. or higher and reaching the highest temperature in the temperature range of 800 ° C. or higher and 1200 ° C. or lower and holding in that temperature range for 5 seconds or longer and 300 seconds or shorter. Hot-rolled sheet tempering and pickling performed by cooling at 50 ° C./second to 800 ° C./second to obtain a hot-rolled sheet baked pure sheet, and the above-mentioned hot-rolled annealed sheet A cold rolling process in which cold rolling is performed to obtain a cold rolled steel sheet; And a finish annealing step for performing finish annealing.

  Hereinafter, the manufacturing method of the non-oriented electrical steel sheet of the present invention will be described focusing on the chemical composition of the slab and each process.

1. Chemical composition The chemical composition of the slab is the chemical composition described in the item “A. Non-oriented electrical steel sheet 2. Chemical composition”. In addition, the chemical composition of the slab is preferably a composition that satisfies the above-described formula (1). This is because, as described above, the ratio of the number of inclusion species and the average of equivalent sphere diameters are controlled within a preferable range.

2. Hot rolling step In the hot rolling step, a hot rolled steel sheet is obtained by hot rolling a slab having the above-described chemical composition.

  The hot rolling conditions are not particularly limited as long as the effects of the present invention can be obtained, and may be general conditions, for example.

  In the hot rolling process, it is preferable to heat the slab having the above-described chemical composition before hot rolling. This is because the above-described ratio of the number of inclusion species and the average of the equivalent sphere diameters are more effectively controlled within a preferable range. In addition, the slab heating conditions are not particularly limited, and may be general conditions, for example, but those that heat the slab to 1200 ° C. or less are preferable. When the heating temperature of the slab exceeds 1200 ° C., inclusions such as AlN and MnS existing in the slab are re-dissolved and then finely precipitated during hot rolling, thereby reducing the grain growth property. This is because the magnetic characteristics are deteriorated.

  The finish rolling is preferably finished in the ferrite phase. Further, the rolling reduction of the hot rolling is not particularly limited as long as the effects of the present invention can be obtained. For example, a general rolling reduction may be used, but the final rolling reduction of the hot rolling is a plate shape. It is preferable to make it 20% or less for correction. Furthermore, it is preferable that the steel sheet after finish rolling is wound at a winding temperature of 700 ° C. or lower and cooled in air.

3. Hot-rolled sheet fired pure / pickling process In the hot-rolled sheet fired pure / pickled process, the hot-rolled steel sheet is subjected to hot-rolled sheet fired pure and pickled to obtain a hot-rolled sheet fired pure plate. Pickling and hot-rolled sheet annealing are in no particular order, and hot-rolled sheet annealing may be performed after pickling, or pickling may be performed after hot-rolled sheet annealing.

The hot-rolled sheet pure condition is that the average temperature increase rate from 600 ° C. to 800 ° C. is 50 ° C./second or more and 800 ° C./second or less, and the temperature is raised to the highest temperature in the temperature range of 800 ° C. or more and 1200 ° C. or less. Then, after maintaining in the temperature range for 5 seconds or more and 300 seconds or less, the average cooling rate from 800 ° C. to 400 ° C. is set to 50 ° C./second or more and 800 ° C./second or less. By setting it as such conditions, it can suppress that copper sulfide reprecipitates in a cooling process, Therefore Formation of fine copper sulfide can be suppressed or avoided as much as possible. For this reason, in the non-oriented electrical steel sheet, the above-described precipitation state of copper sulfide (N _CuS / N _Tot ) is within the range of the present invention, or copper sulfide having a sphere equivalent diameter of 0.01 to 1 μm is not contained. Can be.

  The temperature increase rate is controlled within the above-mentioned specific range because the number of copper sulfide precipitation sites decreases during the temperature increase process when the temperature increase rate in the above temperature range is smaller than the above specific range. This is because, as a result of the coarsening, the overall magnetostatic energy is reduced, so that a problem that the iron loss is deteriorated in a low magnetic field is likely to occur. When the rate of temperature increase is larger than the specific range described above, the number of copper sulfide precipitation sites increases in the temperature increase process, resulting in a fine and large number of sites. This is because the problem of hindering the magnetic field and the high magnetic field characteristics are likely to deteriorate. In addition, the cooling rate is controlled within the specific range described above because, when the cooling rate in the temperature range is smaller than the specific range described above, the copper sulfide re-deposited in the cooling process becomes coarse. This is because the overall magnetostatic energy is lowered and the iron loss in a low magnetic field is worsened. When the cooling rate is larger than the specific range described above, the copper sulfide re-deposited in the cooling process becomes fine and numerous, resulting in deterioration of the iron loss in the low magnetic field and the inhibition of grain growth and the high magnetic field. This is because the characteristics also deteriorate.

  The reason why the temperature range for controlling the rate of temperature increase is from 600 ° C. to 800 ° C. is because the temperature range overlaps with the temperature range where copper sulfide is dissolved. The reason why the temperature range for controlling the cooling rate is from 800 ° C. to 400 ° C. is because it overlaps the copper sulfide precipitation temperature range (nucleation and initial growth stage). The reason why the temperature is maintained in the temperature range of 800 ° C. or higher and 1200 ° C. or lower for 5 seconds or more and 300 seconds or less is to appropriately coarsen the crystal grain size of the hot-rolled steel sheet and ensure the magnetic properties after cold rolling annealing.

  The conditions for pickling are not particularly limited. For example, the main component of the pickling solution is hydrochloric acid, and the temperature is 80 ° C. or higher.

  In the hot-rolled sheet tempering / pickling process, the above-mentioned temperature range of 800 ° C. or higher and 1200 ° C. or lower that is held for a predetermined time for tempering is as follows. When the crystal grain growth is insufficient and the temperature exceeds 1150 ° C., the crystal grain growth becomes excessive and the surface defects of the steel sheet become excessive. Therefore, a temperature range of 850 ° C. or more and 1150 ° C. or less is preferable.

4). Cold rolling step In the cold rolling step, the hot-rolled annealed plate is cold-rolled to obtain a cold-rolled steel plate. If necessary, cold rolling is performed once or two or more times with intermediate annealing.

  The cold rolling conditions and the cold rolling reduction ratio are not particularly limited as long as the effects of the present invention can be obtained, and may be general conditions. In the cold rolling step, it is preferable to set the plate thickness to 0.10 to 0.70 mm by setting the reduction rate of cold rolling to 50 to 95%. This is because the above-described ratio of the number of inclusion species and the average of the equivalent sphere diameters are more effectively controlled within a preferable range.

5. Final annealing process In the final annealing process, the cold-rolled steel sheet is subjected to final annealing.

  The finish annealing conditions are not particularly limited as long as the effects of the present invention can be obtained, and may be general conditions, for example. As the final annealing condition, it is preferable to use a condition in which the maximum ultimate temperature is 800 to 1100 ° C. and the holding time is 1 to 300 seconds as a general continuous annealing condition. When the final annealing temperature is less than 800 ° C., the crystal grain growth is insufficient, and {111} texture that is disadvantageous to the magnetic properties increases, and when it exceeds 1100 ° C., the crystal grain growth becomes excessive and magnetic. This is because the characteristics are deteriorated.

6). Other Steps The method for producing the non-oriented electrical steel sheet of the present invention is not particularly limited as long as it produces the non-oriented electrical steel sheet described in the item “A. Non-oriented electrical steel sheet”. There may be other processes. For example, you may have the insulating film formation process which forms an insulating film by apply | coating a coating liquid to the steel plate surface obtained by finish annealing, and baking after a finishing annealing process. The insulating coating generally imparts insulating properties when electromagnetic steel sheets are laminated and used, and the type of insulating coating is not particularly limited. The insulating coating may be composed of an organic component, may be composed of an inorganic component, or may be composed of both an organic component and an inorganic component. As an inorganic component which comprises an insulating film, bichromic acid-boric acid type | system | group, phosphoric acid type | system | group, a silica type etc. are mentioned, for example. Moreover, as an organic component which comprises an insulating film, resin, such as a general acrylic type, an acrylic styrene type, an acrylic silicon type, a silicon type, a polyester type, an epoxy type, a fluorine type, is mentioned, for example. In consideration of paintability, a preferable resin is an emulsion type resin. An insulating film exhibiting adhesive ability may be formed by heating or pressurizing. Examples of the insulating coating having adhesive ability include acrylic, phenolic, epoxy, and melamine resins. The thickness of the insulating coating is not particularly limited, but is generally 0.05 μm to 2 μm per side. Further, other insulating film forming conditions may be general.

  The present invention is not limited to the embodiment described above. The above-described embodiment is an exemplification, and this embodiment has substantially the same configuration as the technical idea described in the scope of claims of the present invention and exhibits the same function and effect. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described specifically by way of examples. The conditions of the examples are examples adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to the conditions of the examples. The present invention can adopt various conditions as long as the object is achieved without departing from the gist thereof.

  Material No. shown in Table 1 below. The slab having the chemical composition of M01 to M29 was hot rolled under the conditions shown in Table 1 below. Thereby, the material No. Hot rolled steel sheets of M01 to M29 were obtained.

  Subsequently, the material No. M01-M29 hot-rolled steel sheets were subjected to hot-rolled sheet tempering under the conditions shown in Table 2 below. 1 to 44 hot-rolled sheet fired pure plates were obtained. The hot-rolled sheet smelting conditions shown in Table 2 below are the following in a temperature range of 800 ° C. or more and 1200 ° C. or less, with the average temperature increase rate from 600 ° C. to 800 ° C. shown in Table 2 shown below for each sample. After raising the temperature to the maximum temperature shown in Table 2 and holding in the temperature range for the holding time shown in Table 2 below, the average cooling rate from 800 ° C. to 400 ° C. is cooled as shown in Table 2 below. It is a condition.

  Next, the hot-rolled sheet fired pure plate was pickled and then cold-rolled to obtain cold-rolled steel plates having the thicknesses shown in Table 2 below. Further, the cold-rolled steel sheet was subjected to finish annealing under the conditions shown in Table 2 below. 1-44 non-oriented electrical steel sheets were manufactured.

Sample No. For the observation sample of the precipitation state of inclusions prepared from the non-oriented electrical steel sheets 1 to 44, the size, shape, number, and type of all the inclusions existing in the predetermined observation region are measured by the method described above. By determining, 1000 inclusions having a sphere equivalent diameter of 0.01 μm to 1 μm were investigated (N _Tot = 1000), the number of copper sulfides N _CuS among the inclusions, and the inclusions The number N _{XS ≧ 0.1} μm of sulfides having a sphere equivalent diameter of 0.1 μm or more was determined by the above-described method, and N _CuS / N _Tot and N _{XS ≧ 0.1 μm} / N _Tot were calculated. Furthermore, the average [μm] of the equivalent sphere diameters of inclusions having an equivalent sphere diameter of 0.01 to 1 μm was determined.

  Sample No. The crystal grain size of the non-oriented electrical steel sheets A1 to A15 was determined by the method described above.

Furthermore, sample no. For the non-oriented electrical steel sheets A1 to A15, the magnetic flux density B ₅₀ [T] when magnetized at a magnetizing force of 5000 A / m and the iron loss W _15/50 when magnetized at a magnetic flux density of 1.5 T at a frequency of 50 Hz, In addition, the magnetic permeability μ _L [mH / m] at a magnetic flux density of 1.0 T and the iron loss W _L [W / kg] when magnetized at a magnetic flux density of 1.0 T at a frequency of 50 Hz were obtained. These magnetic flux density, iron loss, and magnetic permeability were measured by the Epstein method shown in JIS-C-2550 after cutting a steel plate of each sample into a length of 25 cm. These results are shown in Table 2 below.

As shown in Table 1 and Table 2, in a non-oriented electrical steel sheet manufactured from a hot-rolled steel sheet having a chemical composition containing Cu, a steel sheet having N _CuS / N _Tot of 0.100 or less. _, as compared to steel plates N CuS _{/ N Tot} exceeds 0.100, mu _L is increased, _{W L} tended to be low.

In addition, as shown in Table 1 and Table 2 above, the material No. Sample No. with M02 In the non-oriented electrical steel sheets of 4 to 7, N _CuS / N _Tot becomes closer to “0.000” (a situation in which copper sulfide having a sphere equivalent diameter of 0.01 to 1 μm is not contained), and μ _L increases. will, W _L tended to be low. In addition, the material No. Is sample number M03. The same tendency was also observed in the 8 to 13 non-oriented electrical steel sheets. Furthermore, material No. Sample No. whose M is M04 The same tendency was also observed in the non-oriented electrical steel sheets 14-17.

Moreover, the raw material No. whose chemical composition is within the scope of the present invention. Sample No. manufactured from hot-rolled steel sheets of M02 to M04. In the non-oriented electrical steel sheets of 4 to 17, N _CuS / N _Tot becomes high when either the average heating rate or the average cooling rate in the hot-rolled sheet pure condition is less than 50 ° _C./second. When a tendency was observed and the average rate of temperature increase under hot-rolled sheet sinter conditions was less than 50 ° _C./second , N _CuS / N _Tot exceeded 0.100.

In addition, as shown in Table 1 and Table 2 above, the material No. Sample No. with M02 In the non-oriented electrical steel sheets of 4 to 7, the contents of Mn, Cu, Al, P, and S have a chemical composition satisfying the above formula (1), and N _{XS ≧ 0.1 μm} / N _Tot Steel sheet having an average sphere equivalent diameter of inclusions having a sphere equivalent diameter of 0.01 to 1 μm is 0.114 μm or more compared to a steel sheet that does not satisfy any of these requirements. , W _15/50 was decreased and B ₅₀ was increased. In addition, the material No. Is sample number M03. The same results were obtained for the non-oriented electrical steel sheets of 8 to 13 as well. Sample No. whose M is M04 Similar results were obtained in the non-oriented electrical steel sheets 14-17.

Furthermore, as shown in Table 1 and Table 2 above, the material No. with a Cu content exceeding the upper limit of the present invention. Sample No. manufactured from hot rolled steel sheet of M05. In 18-20 non-oriented electrical steel sheets, N _CuS / N _Tot exceeded 0.100 regardless of whether the hot-rolled sheet annealing conditions were within the preferred range of the present invention.

Claims (4)

In mass%, C: 0.005% or less, Si: 1.0 to 4.0%, Al: 0.1 to 0.8%, Mn: 0.01 to 0.07%, P: 0.02 -0.3%, N: 0.005% or less, and S: 0.0012-0.005%, Cu: 0.001-0.5%, Ti: 0.005% or less, and Sn and Sb Among them, at least one type: containing 0.01 to 0.2% in total, the balance having a chemical composition consisting of Fe and inevitable impurities,
The ratio N _CuS / N _Tot of the number N _CuS of copper sulfides in the inclusions to the number N _Tot of inclusions having a sphere equivalent diameter of 0.01 to 1 μm is 0.100 or less. Electrical steel sheet.   The non-oriented electrical steel sheet according to claim 1, wherein copper sulfide having a sphere equivalent diameter of 0.01 to 1 µm is not contained. The content of Mn, Cu, Al, P, and S has the chemical composition satisfying the following formula (1),
By the number _{N XS ≧ 0.1 [mu] m} ratio _{N XS ≧ 0.1μm} / _{N Tot} sphere equivalent diameter of more than 0.1 [mu] m sulfides of the inclusions to the number _{N Tot} of the inclusions is 0.51 or more Yes,
The non-oriented electrical steel sheet according to claim 1 or 2, wherein an average sphere equivalent diameter of the inclusions is 0.114 µm or more.
3.0 ≦ {([Mn] + [Cu]) / (100 × [S]) + [Al]} / [P] ≦ 70
(1)
(Here, [Mn], [Cu], [Al], [P], and [S] mean the contents [mass%] of Mn, Cu, Al, P, and S, respectively.) It is a manufacturing method of the non-oriented electrical steel sheet according to any one of claims 1 to 3,
A hot rolling step of hot-rolling a slab having the chemical composition according to claim 1 to obtain a hot-rolled steel sheet;
With respect to the hot-rolled steel sheet, the average temperature increase rate from 600 ° C. to 800 ° C. is set to 50 ° C./second or more and 800 ° C./second or less, and the temperature is raised to the highest temperature in the temperature range of 800 ° C. or more and 1200 ° C. or less. Then, after holding in the temperature range for 5 seconds or more and 300 seconds or less, hot-rolled sheet smelting and pickling are performed for cooling at an average cooling rate from 800 ° C. to 400 ° C. at 50 ° C./second or more and 800 ° C./second or less. Hot-rolled sheet baked pure and pickling process to obtain hot-rolled sheet baked pure plate,
A cold rolling step of cold rolling the hot rolled annealed sheet to obtain a cold rolled steel sheet;
A finish annealing step of performing finish annealing on the cold-rolled steel sheet;
A method for producing a non-oriented electrical steel sheet, comprising: