JP6123234B2 - Electrical steel sheet - Google Patents

Description

  The present invention relates to a magnetic steel sheet having a low high-frequency iron loss, which is suitable for a motor core such as an air conditioner compressor motor or a drive motor for a hybrid electric vehicle.

  In recent years, home air conditioner compressor motors have been operated at a variable speed, and the maximum frequency is about 200 to 400 Hz. Therefore, it is used in a state where a carrier frequency of several kHz is superimposed by PWM control or the like. In addition, hybrid electric vehicle drive motors and electric vehicle drive motors, which have been rapidly spreading recently, are driven at a frequency of several kHz from the viewpoint of high output and miniaturization. Low losses are required.

Here, the electromagnetic steel sheet, which is the material for the motor core, is processed into a motor core shape by punching, and then tightened by caulking, welding, etc., and after being wound, it is fixed to the housing by press-fitting or shrink fitting. And a motor core. For this reason, the electromagnetic steel sheet is subjected to various processing strains, and iron loss and the like are greatly increased after processing the motor core as compared with the magnetic characteristics of the material measured by Epstein or the like.
For example, regarding punching distortion, when measuring magnetic properties in the Epstein test, the test material is measured by shearing into a strip-shaped test piece having a width of 30 mm, but the motor core is 5 mm even with a relatively large tooth width. This is about 2 mm for a small motor. Here, the longer the cumulative length of the punched end face relative to the punched iron core area, the greater the effect of distortion on the entire iron core.In the case of the teeth width as described above, the motor core iron loss is reduced to the material iron loss by punching. It will increase by about 30 to 50%. For this reason, there is a need for an electrical steel sheet that has low iron loss deterioration due to punching.

  In order to solve such a problem, for example, in Patent Document 1, Si, Mn, and S include Si: 0.4 to 2.0%, Mn: 0.25 to 1.00%, and S: 0.015. Controlled to a range of ~ 0.035%, the slab heating temperature before hot rolling is set to a low temperature, the finishing temperature of hot rolling is set to a relatively high temperature, there is little deterioration in magnetic properties due to punching, and the magnetic properties are good A technique for obtaining a non-oriented electrical steel sheet is disclosed. This technique is intended to suppress iron loss deterioration at the time of punching by precipitating coarse MnS in the steel sheet and reducing the shear resistance at the time of punching.

JP-A-8-246052

However, as in the technique of Patent Document 1, when trying to reduce the shear resistance at the time of punching by precipitating coarse precipitates in the steel sheet, the amount of precipitates in the steel sheet is inevitably increased. There was a problem that iron loss of a certain electromagnetic steel sheet itself was high.
The present invention has been made in view of such problems, and an object of the present invention is to provide an electrical steel sheet excellent in high-frequency iron loss that suppresses iron loss deterioration during punching.

  The present inventors diligently studied the above-mentioned problems. As a result of increasing the amount of Si in the surface layer of the steel sheet, increasing the amount of Mn in the steel, and reducing the amount of As, a narrow material that easily causes iron loss deterioration during punching. It became clear that the high-frequency iron loss in can be reduced.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] In mass%, the average Si amount of the steel sheet surface layer portion is 4% or more and 7% or less, the average Si amount of the steel plate inner layer portion is 5% or less, Mn: more than 0.5% and containing 5% or less, Si: As: 0.002% or less, Se: 0.002% or less, having a component composition composed of the remaining Fe and inevitable impurities, and having a plate thickness surface with a Si concentration higher than the plate thickness center portion in the plate thickness direction The average Si amount in the steel sheet surface layer portion is 0.5 mass% or more higher than the average Si amount in the steel plate inner layer portion, and the thickness ratio of the steel plate surface layer portion is 0.1 to 0. 7 is an electrical steel sheet.
Here, the steel plate surface layer portion is a steel plate portion having a Si concentration equal to or higher than the average Si amount of the total thickness of the steel plate, and the steel plate inner layer portion is a steel plate portion having a Si concentration less than the average Si amount of the total thickness of the steel plate. It is.
[2] The electrical steel sheet according to [1], further containing, by mass, Al: 3% or less.
[3] The electrical steel sheet according to [1] or [2], further containing Mg: 0.0003% to 0.002% by mass.

  According to the present invention, it is possible to obtain a material whose characteristic deterioration due to punching is small, and iron loss of a motor having a narrow tooth width such as an air conditioner compressor motor, a drive motor for a hybrid electric vehicle, a drive motor for an electric vehicle, and an information equipment motor. There is an advantage that it can be reduced.

It is a figure which shows the relationship between the average Si amount of a steel plate surface layer part, and an iron loss (W10 / 2k). It is a figure which shows the relationship between Mn content in steel, and iron loss (W10 / 2k). It is a figure which shows the relationship between As content and steel loss (W10 / 2k) in steel. It is a figure which shows the relationship between a multilayer ratio and iron loss (W10 / 2k). It is a figure which shows the relationship between the difference of the average Si amount of a steel plate surface layer part, the average Si amount of a steel plate inner layer part, and an iron loss (W10 / 2k).

  The present invention will be described in detail based on experimental results. In addition, in this specification, unless otherwise indicated,% display regarding a component means the mass%.

First, the deterioration of magnetic characteristics due to punching was investigated.
In mass%, Si = 3.9%, Al = tr. , Mn = 0.1%, As = 0.0001%, Se <0.0005% steel was melted in the laboratory to obtain an ingot. Thereafter, hot rolling is performed, followed by hot-rolled sheet annealing at 900 ° C. × 30 s. After pickling, the sheet is cold-rolled to form a cold-rolled sheet having a thickness of 0.20 mm, followed by finish annealing at 1000 ° C. × 30 s. A steel sheet having a relatively uniform amount of Si in the thickness direction was obtained. An Epstein sample having a length of 180 mm and a width of 30 mm and an Epstein sample having a length of 180 mm and a width of 5 mm were produced by punching from the rolling direction and the direction perpendicular to the rolling direction of the steel plate obtained here. Further, by subjecting the cold-rolled sheet to a silicidation treatment at 1200 ° C. for 10 minutes, the average amount of Si in the 30% portion of the plate thickness from the surface is 6.5%, A steel plate having a Si content of 4.5% from the top and the bottom) was also prepared. Similarly, from the rolling direction and the direction perpendicular to the rolling, an Epstein sample having a length of 180 mm and a width of 30 mm, and a length of 180 mm and a width of 5 mm Epstein samples were made by stamping.

  Table 1 shows the results of measuring iron loss (W10 / 2k) by Epstein test according to JIS C2550 for these samples. At this time, for a sample having a width of 5 mm, six sheets were arranged in the width direction and measured as a width of 30 mm. By measuring in this way, five shear portions are included in the width of 30 mm of the sample, so that it is possible to evaluate the influence on the iron loss characteristics by the punching process. In addition, the iron loss (W10 / 2k) of Table 1 is the iron loss (W10 / 2k) calculated | required using the rolling direction sample and the rolling perpendicular direction sample for every half amount. Further, the iron loss deterioration rate (%) = {((iron loss of 5 mm width material) − (iron loss of 30 mm width material)) / (iron loss of 30 mm width material)} × 100 is shown in Table 1. From the results shown in Table 1, the iron loss deterioration rate is 28.9% for a material (uniform material) in which Si is uniform in the thickness direction after finish annealing, and for a sample with a width of 5 mm compared to a sample with a width of 30 mm. It can be seen that the iron loss is increased by about 30%. This is considered to be because the compressive stress remains in addition to the plastic deformation occurring at the end face of the steel sheet by punching.

  On the other hand, in the material (surface high Si material) in which the silicon content is increased by applying a silicon concentration treatment to provide a Si concentration gradient in the plate thickness direction and making the surface layer portion higher than the plate thickness center portion, the iron loss deterioration rate is 5. It can be seen that the influence of the punching width is smaller than that of the uniform material. In the case of the 30 mm width sample, the iron loss of the uniform material and the surface high Si material is almost the same level, but in the case of the 5 mm width sample, the surface high Si material has a significantly lower iron loss than the uniform material. That is, it can be seen that the iron loss deterioration due to punching is suppressed by a steel plate in which a Si concentration gradient is provided in the plate thickness direction and the surface layer portion of the plate thickness is made higher than the central portion of the plate thickness. The cause of this is not clear, but it is less susceptible to compressive stress during punching due to low magnetostriction in the surface layer and due to tensile residual stress in the steel sheet surface due to changes in the lattice constant due to the siliconization treatment. It is thought that it became.

Next, the influence of the Si amount in the steel sheet surface layer portion was investigated. Hereinafter, the steel plate surface layer portion is a steel plate portion having a Si concentration equal to or higher than the average Si amount of the total thickness of the steel plate. Moreover, the steel plate part which has Si concentration less than the average Si amount of the total thickness of a steel plate was made into the steel plate inner layer part.
Si = 3.0%, Al = tr. , Mn = 0.1%, As = 0.0001%, Se <0.0005%, hot-rolled, then hot-rolled sheet annealed at 900 ° C. × 30 s, pickled, cold The plate thickness was set to 0.20 mm by rolling. Thereafter, a silicon immersion treatment at 1200 ° C. for 1 to 20 minutes was performed to change the amount of Si in the surface layer portion of the steel sheet. Here, the thickness of the steel sheet surface layer portion (total thickness of both surface layer portions of the steel plate) is 25% of the total plate thickness, that is, 1000 ° C. after the siliconization treatment so that the multilayer ratio is 0.25. The processing time of the diffusion process performed in was adjusted in various ways. The multilayer ratio is the multilayer ratio = (total thickness of both surface layer portions of the steel sheet) / (total thickness of the steel sheet).

  Further, here, the thickness of the steel sheet surface layer portion is obtained by determining the Si concentration distribution in the plate thickness direction of the steel plate by EPMA, and from this concentration distribution, the average Si amount of the total plate thickness is obtained, and the average Si of the total plate thickness is obtained. The average Si amount of the steel sheet surface layer portion, which is the average of the Si amount of the steel sheet surface layer portion, was determined using a portion having a Si concentration equal to or greater than the amount as the steel sheet surface layer portion.

  Further, from the steel plate thus obtained, an Epstein sample having a length of 180 mm and a width of 5 mm was produced by punching from the rolling direction and the direction perpendicular to the rolling direction, and the iron loss (W10 / 2k) was measured in the same manner as described above.

  FIG. 1 shows the relationship between the average Si content of the steel sheet surface layer portion of the steel sheet (0.1% Mn steel) obtained here and the iron loss (W10 / 2k). The steel sheet inner layer average Si amount was 3.2% in all samples. From this, it can be seen that the iron loss is reduced when the average Si content of the steel sheet surface layer portion is 4% or more. From this, the average Si content of the steel sheet surface layer portion is 4% or more, preferably 4.5% or more. In addition, since punching becomes difficult when the average Si amount of the steel sheet surface layer portion exceeds 7%, the upper limit is 7%.

  Incidentally, in order to further reduce the high-frequency iron loss of a steel sheet having a Si concentration gradient in the thickness direction, it is effective to increase the specific resistance of the steel sheet. Si is an element that increases the specific resistance of the steel sheet. However, when Si is further increased, the material becomes very brittle, and it is difficult to punch the motor. Then, it examined paying attention to Mn as an element which does not embrittle a steel plate, raising a specific resistance.

  That is, Si = 3.0%, Al = tr. , Mn = 2.0%, As = 0.0001%, Se <0.0005%, hot-rolled, then hot-rolled sheet annealed at 900 ° C. × 30 s, pickled, cold The plate thickness was set to 0.20 mm by rolling. Thereafter, a silicon immersion treatment at 1200 ° C. for 1 to 20 minutes was performed to change the amount of Si in the surface layer portion of the steel sheet. Here, the treatment time of the diffusion treatment performed at 1000 ° C. after the siliconization treatment is varied in the same manner as described above so that the thickness of the steel plate surface layer portion is 25% of the plate thickness (multilayer ratio = 0.25). And adjusted. Moreover, the average Si amount of the steel sheet surface layer portion was determined in the same manner as described above.

  From the steel plate thus obtained, an Epstein sample having a length of 180 mm and a width of 5 mm was produced by punching from the rolling direction and the direction perpendicular to the rolling, and the iron loss (W10 / 2k) was measured in the same manner as described above. FIG. 1 shows the relationship between the average Si content of the steel sheet surface layer portion of the steel sheet (2.0% Mn steel) obtained here and the iron loss (W10 / 2k). The steel sheet inner layer average Si amount was 3.2% in all samples. It can be seen that the 2.0% Mn steel has a smaller iron loss than the 0.1% Mn steel, and in particular, the average Si content of the steel sheet surface layer portion is 4% or more, and the iron loss is particularly greatly reduced by the addition of Mn. The reason for this is not clear, but it is thought that the iron loss drop has increased due to the combined effect of Si and Mn.

Next, the influence of Mn addition amount was investigated.
Si = 3.0%, Al = tr. , As = 0.0001%, Se <0.0005%, Mn = 0.1-5%, steel with greatly changed Mn content was vacuum melted, hot rolled, and then hot rolled at 900 ° C. × 30 s The plate was annealed, pickled, and then cold-rolled to a thickness of 0.20 mm. Thereafter, a siliconization treatment at 1200 ° C. for 10 minutes was performed to make the average Si content of the steel sheet surface layer portion 6.5%. In addition, the average Si amount of the steel sheet surface layer portion was determined in the same manner as described above. Moreover, the treatment time of the diffusion treatment performed at 1000 ° C. after the siliconization treatment is varied in the same manner as described above so that the thickness of the steel plate surface layer portion is 25% of the plate thickness (multilayer ratio = 0.25). Changed and adjusted.
From the steel plate thus obtained, an Epstein sample having a length of 180 mm and a width of 5 mm was produced by punching from the rolling direction and the direction perpendicular to the rolling, and the iron loss (W10 / 2k) was measured in the same manner as described above. FIG. 2 shows the effect of Mn content on iron loss (W10 / 2k). This shows that the iron loss decreases when the Mn content exceeds 0.5%. In addition, when Mn exceeds 5%, the effect of Mn addition is saturated and the cost is unnecessarily increased, so the upper limit of the amount of Mn is 5%.

  Next, in order to investigate the production stability of Mn added steel, 2.5% Mn steel was melted in 10 charges in the laboratory among the steels shown in FIG. When the steel sheet was prepared and the iron loss was evaluated in the same manner as in the case where the influence of the Mn addition amount was investigated, two charges with a high iron loss were recognized. In order to investigate this cause, the microstructure of the steel sheet was observed with a scanning electron microscope (SEM). As a result, MnAs precipitates were observed at grain boundaries in the material having a high iron loss. Although precipitation of MnAs is not recognized in a normal electromagnetic steel sheet, it is assumed that MnAs is likely to precipitate in a material having a high Mn content as in this study.

Therefore, the influence of the As amount on the iron loss was investigated.
Si = 3.1%, Al = tr. , Mn = 2.5% and Mn = 0.1%, As = 0.004-0.0026%, Se <0.0005% steel was vacuum melted and after hot rolling, 900 ° C. × 30 s Hot-rolled sheet annealing was performed, and after pickling, the sheet thickness was 0.20 mm by cold rolling. Thereafter, a siliconization treatment at 1200 ° C. for 10 minutes was performed, and the average Si content of the steel sheet surface layer portion was set to 6.5%. Here, the treatment time of the diffusion treatment performed at 1000 ° C. after the siliconization treatment is varied in the same manner as described above so that the thickness of the steel plate surface layer portion is 25% of the plate thickness (multilayer ratio = 0.25). And adjusted.

  From the steel plate thus obtained, an Epstein sample having a length of 180 mm and a width of 5 mm was produced by punching from the rolling direction and the direction perpendicular to the rolling, and the iron loss (W10 / 2k) was measured in the same manner as described above. FIG. 3 shows the effect of As on iron loss. In Mn = 0.1% steel, no increase in iron loss is observed even if As exceeds 0.002%, but in Mn = 2.5% steel, iron loss increases when As exceeds 0.002%. I understand that For this reason, the upper limit of As is set to 0.002%. In addition, since As is contained as an impurity in Mn ore and Si ore, it is desirable to use high-purity ore.

Next, the amount of Si in the inner layer of the steel sheet was examined.
Using steel with Si = 1 to 4.5%, Al = tr., Mn = 2.0%, As = 0.0001%, Se <0.0005%, after hot rolling, 900 ° C. × 30 s Hot-rolled sheet annealing was performed, and after pickling, the sheet thickness was 0.20 mm by cold rolling. Thereafter, a siliconization treatment at 1200 ° C. for 1 to 20 minutes was performed to set the average Si amount in the steel sheet surface layer portion to 6% and to change the Si amount in the inner layer portion of the steel plate.
About the steel plate obtained in this manner, when the Epstein sample with a length of 180 mm and a width of 5 mm was punched, a steel plate with an average Si amount of 5% in the steel plate inner layer part could be produced by punching, It was found that with steel plates exceeding 5%, the plate cracked during punching, and it was impossible to produce an Epstein sample, and the punchability was poor. For this reason, the Si content in the inner layer of the steel sheet is set to 5% or less.

Next, the multilayer ratio was examined.
A steel material in which Al = tr., Mn = 2.0%, As = 0.0001%, Se <0.0005% and various Si contents were changed to 900 ° C. after hot rolling in the same manner as described above. X30s hot-rolled sheet annealed, pickled, cold rolled to a thickness of 0.20mm, silicidation time was changed in various ways, and the average Si content of steel sheet surface layer = 6% A steel sheet was prepared so that the average Si amount in the inner layer of the steel sheet was 3% and the multilayer ratio was 0.05 to 0.9.
About the steel plate thus obtained, an Epstein sample having a length of 180 mm and a width of 5 mm was produced by punching from the rolling direction and the direction perpendicular to the rolling, and the iron loss (W10 / 2k) was measured in the same manner as described above.

  FIG. 4 shows the relationship between the multilayer ratio and the iron loss (W10 / 2k). This shows that the iron loss is reduced when the multilayer ratio is 0.1 or more. This is presumably because when the surface high Si portion is less than 0.1 in thickness, the amount of the low magnetostriction portion and the residual portion of the tensile stress is small, and the effect of suppressing iron loss deterioration during punching is small. On the other hand, if the multilayer ratio exceeds 0.7, cracking occurred during punching, so the upper limit is set to 0.7.

Next, the influence of the difference between the average Si amount in the surface layer portion and the average Si amount in the inner layer portion was examined.
Si = 4.5%, Al = tr. , Mn = 2.0%, As = 0.0001%, Se <0.0005%, hot-rolled, annealed at 900 ° C. for 30 s, pickled, cold-rolled Thus, the plate thickness was set to 0.20 mm. Thereafter, a silicon immersion treatment at 1200 ° C. for 1 to 20 minutes was performed to change the amount of Si in the surface layer portion of the steel sheet. Here, the steel plate surface layer portion was adjusted by varying the treatment time of the diffusion treatment performed at 1000 ° C. after the siliconization treatment so that the surface thickness of the steel plate was 30% (multilayer ratio = 0.3).

About the steel plate thus obtained, an Epstein sample having a length of 180 mm and a width of 5 mm was produced by punching from the rolling direction and the direction perpendicular to the rolling, and the iron loss (W10 / 2k) was measured in the same manner as described above.
FIG. 5 shows the relationship between the difference between the average Si amount in the steel sheet surface layer portion and the average Si amount in the steel plate inner layer portion and the iron loss (W10 / 2k). As shown in FIG. 5, the iron loss (W10 / 2k) decreases as the difference between the average Si amount in the steel sheet surface layer portion and the average Si amount in the steel plate inner layer portion decreases, and when this difference is 0.5 mass% or more, the iron loss (W10 / 2k) is stable and low. This is considered to be because tensile stress was generated in the surface layer portion of the steel sheet by increasing the Si difference, thereby suppressing iron loss deterioration during narrow width shearing.

The present invention will be described including the above experimental results.
First, the component composition of the present invention will be described. The electrical steel sheet of the present invention has an average Si amount of 4% or more and 7% or less of the steel sheet surface layer part, an average Si content of the steel sheet inner layer part of 5% or less, and Mn: more than 0.5% and containing 5% or less, As: 0.002% or less, Se: 0.002% or less, and has a component composition consisting of the remaining Fe and inevitable impurities.

The average Si amount of the steel sheet surface layer portion is 4% or more and 7% or less. The average Si amount of the steel plate surface layer portion greatly affects the iron loss deterioration due to punching, and the average Si amount of the steel plate surface layer portion is 4% or more. As shown in the above, iron loss at high frequencies can be greatly improved. On the other hand, when the average Si content of the steel sheet surface layer portion exceeds 7%, punching becomes difficult. Therefore, the average Si amount in the steel sheet surface layer portion is 4% or more and 7% or less.

When the average Si amount in the inner layer portion of the steel sheet is 5% or less and the average Si amount in the inner layer portion of the steel sheet exceeds 5%, as described above, it becomes difficult to punch, for example, when a narrow material is punched. Therefore, the average Si amount in the inner layer of the steel sheet is 5% or less.
The Si content of the steel sheet of the present invention, that is, the average Si content of the total thickness is preferably about 4% to 6.5% from the viewpoint of improving the iron loss.

Mn: More than 0.5% and not more than 5% By making the amount of Mn in the steel sheet more than 0.5%, the iron loss at high frequency can be improved as shown in FIG. On the other hand, even if the amount of Mn exceeds 5%, the effect of adding Mn is saturated and only the cost is increased.

As: 0.002% or less As is an impurity, but MnAs tends to precipitate in the steel sheet of the present invention having a high Mn content, and iron loss deteriorates when MnAs is precipitated. Even in a magnetic steel sheet having a high Mn amount as in the present invention, as shown in FIG. 3, by setting the As amount to 0.002% or less, iron loss deterioration due to As can be suppressed. Is restricted to 0.002%.

Se: 0.002% or less Se is an impurity. When the Mn content is 0.5% or less, there is no problem, but when the Mn content exceeds 0.5%, the amount of Se in the steel sheet. If it exceeds 0.002%, MnSe is formed and the iron loss increases, so the upper limit of the Se amount is regulated to 0.002%. The upper limit of the Se amount is more preferably 0.001%.

  The above is the basic composition of the electrical steel sheet of the present invention, and the balance is Fe and inevitable impurities. In the present invention, the following elements can be appropriately contained in addition to the above component composition.

Al: 3% or less Since Al is an element effective for increasing the specific resistance, addition of 0.1% or more is preferable. On the other hand, if the Al content in the steel sheet exceeds 3%, the material becomes brittle and punching becomes difficult, so the upper limit of the Al content is 3%.

Mg: 0.0003% or more and 0.002% or less Addition of 0.0003% or more of Mg coarsens sulfide-based precipitates and reduces iron loss. On the other hand, even if added over 0.002%, the iron loss is not further reduced, and the cost is unnecessarily increased. Therefore, it is preferable to add Mg with the Mg amount in the range of 0.0003 to 0.002%.

Next, the Si distribution of the electrical steel sheet according to the present invention will be described.
The electromagnetic steel sheet of the present invention has a Si concentration gradient in which the surface of the plate thickness is higher than the center of the plate thickness in the plate thickness direction, and the average Si amount of the steel plate surface layer portion is equal to the average Si amount of the steel plate inner layer portion. Compared to 0.5% by mass or more, that is, (average Si amount of steel sheet surface layer part) − (average Si amount of steel sheet inner layer part) ≧ 0.5% by mass, and the ratio of the steel sheet surface layer part thickness is the plate thickness 0.1 to 0.7, that is, the multilayer ratio = 0.1 to 0.7.

As shown in Table 1, the thickness surface of the plate thickness surface has a higher Si concentration than the central portion of the plate thickness. As shown in Table 1, the plate thickness surface has a uniform Si concentration distribution in the plate thickness direction. Has a Si concentration gradient in which the Si concentration is higher than that of the center portion of the plate thickness, so that iron loss deterioration due to punching can be suppressed. Therefore, the electrical steel sheet of the present invention has a Si concentration gradient in which the Si surface has a higher Si concentration than the central part of the plate thickness.

(Average amount of Si in steel plate surface layer portion) − (Average amount of Si in steel plate inner layer portion) ≧ 0.5%
As shown in FIG. 5, the iron loss (W10 / 2k) is stably reduced by setting the difference between the average Si amount of the steel sheet surface layer portion and the average Si amount of the steel plate inner layer portion to 0.5 mass% or more. be able to. Therefore, (average Si amount of steel plate surface layer portion) − (average Si amount of steel plate inner layer portion) ≧ 0.5 mass%.

Multilayer ratio = 0.1-0.7
By setting the multilayer ratio, which is the ratio of the steel sheet surface layer thickness to the plate thickness, to 0.1 or more, as shown in FIG. 4, it is possible to suppress the deterioration of iron loss even with a narrow material of 5 mm. On the other hand, if the multilayer ratio exceeds 0.7, cracking occurs when punching a narrow material, making punching difficult. Therefore, the multilayer ratio is 0.1 to 0.7.

Next, the manufacturing method of the electrical steel sheet of this invention is demonstrated. In addition, the manufacturing method which obtains the steel plate of this invention is not limited to the manufacturing method demonstrated below.
In the present invention, it is important to change the amount of Si in the surface layer portion and the inside, and as a technique for that purpose, for example, steel is blown in a converter, the molten steel is degassed and adjusted to a predetermined component, and subsequently After casting into a slab, it is hot-rolled by a normal method, and then a predetermined sheet thickness is obtained by one or more cold or warm rollings or two or more cold or warm rollings with intermediate annealing. Then, finish annealing is performed. Subsequently, the surface high Si steel of the present invention can be obtained by performing a siliconizing treatment. Here, the finishing temperature and the coiling temperature at the time of hot rolling need not be specified, and may be normal conditions. Moreover, although hot-rolled sheet annealing after hot rolling may be performed, it is not essential.
Moreover, after bonding ingots having different components, surface high Si steel may be obtained by performing hot rolling, cold rolling, and finish annealing.

  In addition, although it does not prescribe | regulate especially about the plate | board thickness of the electromagnetic steel plate of this invention, it is preferable to set it as 0.35 mm or less from a viewpoint of a core loss reduction, More preferably, it is 0.2 mm or less. The lower limit is preferably 0.05 mm from the viewpoint of productivity.

  The steel shown in Table 2 was used, and after defoaming in a converter, it was degassed and then cast to a predetermined component and cast into a steel slab. The steel slab was heated at 1140 ° C. for 1 hr and then hot rolled to a thickness of 2.0 mm. The hot rolling finishing temperature was 800 ° C. The winding temperature was 610 ° C., and after winding, 900 ° C. × 30 s hot-rolled sheet annealing was performed. Then, pickling was performed, cold rolling to 0.20 mm was performed, and then a steel plate shown in Table 2 was obtained by performing a siliconizing treatment under various conditions. The diffusion treatment after the siliconization treatment was performed at 1200 ° C. for 10 minutes.

  About the obtained steel sheet, the concentration distribution of Si in the steel sheet was investigated by the above-described method, the steel sheet surface layer part and the steel sheet inner layer part were specified, and the average Si amount of each layer was obtained, and the average Si of the steel sheet surface layer part was determined. The difference between the amount and the average amount of Si in the inner layer of the steel sheet was determined. The results are shown in Table 2. Further, the thickness of the surface layer portion of the steel sheet thus obtained was determined to calculate the multilayer ratio, and Table 2 shows.

  Further, an Epstein sample having a length of 180 mm, a width of 30 mm and a width of 5 mm was cut out from the rolling direction and the direction perpendicular to the rolling direction of the obtained steel sheet, and subjected to magnetic measurement (W10 / 2k) by an Epstein test in accordance with JIS C2550. From the obtained results, the aforementioned iron loss deterioration rate was obtained. The results are shown in Table 2. Here, the iron loss (W10 / 2k) is an iron loss (W10 / 2k) obtained by using half of the rolling direction sample and the rolling perpendicular direction sample. Sample No. 14 has a high average Si content in the surface layer portion of the steel sheet. No. 17 has a high average Si content in the inner layer of the steel plate. No. 22 has a large multilayer ratio. No. 30 is an example having a high Al content. However, when a sample having a width of 5 mm was punched out, an Epstein sample could not be prepared due to the occurrence of cracks or cracks, and therefore iron loss was not measured.

  From Table 2, the steel sheet of the present invention has an iron loss deterioration rate of 4.7% or less, and the punching property deterioration when punching a narrow material is small, and the iron loss itself has a frequency of 2 kHz (maximum magnetic flux density). The iron loss at the time of 1.0 T) is 112.0 W / kg or less in the case of 30 mm width and 116.0 W / kg or less in the case of 5 mm width.

Claims (3)

In mass%, the average Si content of the steel sheet surface layer portion is 4% or more and 7% or less, the average Si content of the steel plate inner layer portion is 5% or less, contains Mn: more than 0.5% and 5% or less, As: 0 0.002% or less, Se: 0.002% or less, having a component composition of the balance Fe and unavoidable impurities, and a Si concentration gradient in which the surface of the plate thickness is higher in the plate thickness direction than the plate thickness center portion The average Si amount of the steel sheet surface layer portion is 0.5% by mass or more higher than the average Si amount of the steel sheet inner layer portion, and the ratio of the steel sheet surface layer portion thickness is 0.1 to 0.7 of the plate thickness. An electrical steel sheet characterized by that.
Here, the steel plate surface layer portion is a steel plate portion having a Si concentration equal to or higher than the average Si amount of the total thickness of the steel plate, and the steel plate inner layer portion is a steel plate portion having a Si concentration less than the average Si amount of the total thickness of the steel plate. It is.
However, a clad electromagnetic steel sheet is excluded as the electromagnetic steel sheet.   The electrical steel sheet according to claim 1, further comprising, by mass%, Al: 3% or less.   Furthermore, it contains Mg: 0.0003% or more and 0.002% or less by mass%, The electrical steel sheet of Claim 1 or 2 characterized by the above-mentioned.

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