JP5939190B2 - Electrical steel sheet - Google Patents

Description

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

  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, for example, a magnetic steel sheet, which is a material for a motor core, is processed into a motor core shape by punching, and is then fastened by caulking, welding, etc., and then fixed to a housing or the like by press fitting or shrink fitting. Thus, a motor core is obtained. 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 the Epstein test 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 are contained by weight% in Si: 0.4 to 2.0%, Mn: 0.25 to 1.00%, and S: Control within the range of 0.015-0.035%, the slab heating temperature before hot rolling is as low as 1100-1180 ° C, and the finishing temperature of hot rolling is relatively high, 850-950 ° C, A technique for obtaining a non-oriented electrical steel sheet with good magnetic properties and little deterioration of magnetic properties due to punching 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. This invention is made | formed in view of such a problem, and it aims at providing the electrical steel sheet which was excellent in the high frequency iron loss which suppressed the iron loss deterioration at the time of punching.

  The present inventors diligently studied the above-mentioned problems. As a result, the iron loss at the time of punching was increased by increasing the amount of Si in the steel sheet surface layer, increasing the amount of Cr in the steel, and further reducing the amount of As and Se in the steel. It was revealed that high-frequency iron loss can be reduced in narrow materials that are prone to deterioration.

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 in the steel sheet surface layer portion is 4 to 7%, the average Si amount in the steel plate inner layer portion is 5% or less, contains Cr: 0.3 to 5.0%, and As: 0.01% or less, Se: 0.005% or less, having a component composition consisting of the remainder Fe and inevitable impurities, the Si concentration at which the surface of the plate thickness is higher in the plate thickness direction than the center of the plate thickness It has a gradient, the average Si amount of the steel sheet surface layer part is 0.5 mass% or more higher than the average Si amount of the steel sheet inner layer part, and the ratio of the steel sheet surface layer part thickness is 0.10 to 0.70 of the plate thickness An electrical steel sheet characterized in 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.
[2] The electrical steel sheet according to [1], further containing, by mass%, Mn: 0.5 to 5.0%.
[3] The electrical steel sheet according to [1] or [2], further containing, by mass%, Al: 3% or less.
[4] In any one of the above [1] to [3], one kind selected from Mg: 0.0003 to 0.002% and Sn: 0.01 to 0.5% in mass%. Or the electrical steel sheet characterized by containing 2 types.

  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 Cr content in steel, and iron loss (W10 / 2k). 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). It is a figure which shows the relationship between Mn content and iron loss (W10 / 2k) in Cr addition steel.

  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 = 3.8%, Al = tr. Cr = 0.1%, Mn = tr. As = tr. , Se = tr. The steel made was melted in the laboratory to make an ingot. Thereafter, hot rolling was performed, followed by annealing at 900 ° C. for 30 seconds, pickling, and cold rolling to obtain a cold rolled sheet having a thickness of 0.20 mm. Subsequently, finish annealing at 1000 ° C. × 30 s was performed to obtain a steel sheet having a relatively uniform amount of Si in the thickness direction. From the rolling direction and the perpendicular direction of rolling of the steel plate obtained here, 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. Further, by subjecting the cold-rolled sheet to a silicidation treatment at 1200 ° C. for 10 minutes, the average Si amount of 30% of the sheet thickness (60% of the total sheet thickness) from each surface is 6 .5%, and a steel sheet in which the Si amount in the central part of the plate thickness (the portion of 40% of the plate thickness from the center to the plate thickness) is 4.5% is also produced. Similarly, from the rolling direction and the perpendicular direction of rolling, 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.

  Table 1 shows the results of measuring iron loss (W10 / 2k) by Epstein test according to JIS C2550 for these samples. At this time, about the sample of width 5mm, six sheets were arranged in the width direction and the iron loss was measured by making width 30mm. 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 29.2% in the material (uniform material) in which Si is uniform in the thickness direction after the finish annealing, and in the sample of 5 mm width compared to the sample of 30 mm width. 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 gradient in the plate thickness direction and the surface layer portion is higher than the plate thickness center portion, the iron loss deterioration rate is 6. 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 affected by the compressive stress at the time of punching due to the low magnetostriction of the surface layer part and the fact that tensile residual stress is generated in the steel sheet surface layer part due to the change in the lattice constant due to the siliconization treatment. It may be difficult.

  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 = 2.9%, Al = tr. Cr = 0.1%, Mn = 0.1%, As = tr. , Se = tr. The steel sheet was hot-rolled and then subjected to hot-rolled sheet annealing at 900 ° C. × 30 s. After pickling, the sheet thickness was 0.20 mm by cold 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 ratio of the thickness of the surface layer portion to the total thickness of the steel sheet, and 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% Cr steel) obtained here and the iron loss (W10 / 2k) (circle mark in the figure). The steel sheet inner layer average Si amount was 4.0% in all samples. From this, it can be seen that the higher the average amount of Si in the steel sheet surface layer portion, the lower the iron loss.

  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. Therefore, while focusing on Cr as an element that does not cause embrittlement of the steel sheet while increasing the specific resistance, examination was performed.

  That is, Si = 3.2%, Al = tr. Cr = 2.2%, Mn = 0.1%, As = tr. , Se = tr. The steel sheet was hot-rolled and then subjected to hot-rolled sheet annealing at 900 ° C. × 30 s. After pickling, the sheet thickness was 0.20 mm by cold 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 obtained here (2.2% Cr steel) and the iron loss (W10 / 2k) (Δ mark in the figure). The steel sheet inner layer average Si amount was 4.0% in all samples. The iron loss of 2.2% Cr steel is smaller than that of 0.1% Cr steel, especially when the average Si content of the steel sheet surface layer is 4% or more. I understand that 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 Cr. From this, the average Si amount in the steel sheet surface layer portion is 4% or more, preferably 4.5% or more. On the other hand, when the average Si content in the steel sheet surface layer portion exceeds 7%, punching becomes difficult, so the upper limit is set to 7%.

  Next, the influence of the Cr addition amount was investigated. Si = 3.1%, Al = tr. Cr = 0.1-5.5%, Mn = 0.1%, As = tr. , Se = tr. Then, steel with a large change in Cr content was produced by vacuum melting, hot-rolled, then annealed at 900 ° C. for 30 s, and 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 relationship between the iron loss (W10 / 2k) and the Cr content of the steel sheet. From this, it can be seen that when the Cr content is 0.3% or more, the iron loss is reduced and the iron loss is improved. Note that even if Cr exceeds 5.0%, the cost is unnecessarily increased, so the upper limit of the Cr amount is 5.0%.

  Next, the amount of Si in the inner layer of the steel sheet was examined. Si = 1 to 4.5%, Al = tr., Cr = 2.0%, Mn = 0.1%, As = tr. , Se = tr. After hot rolling, hot rolled sheet annealing at 900 ° C. × 30 s 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 when the steel plate exceeds 5%, the steel plate cracks during punching, and it is impossible to produce an Epstein sample, and the punchability is 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. Al = tr., Cr = 2.1%, Mn = 0.1%, As = tr. , Se = tr. In the same manner as above, the steel material with various Si contents was hot-rolled and then subjected to hot-rolled sheet annealing at 900 ° C. × 30 s. After pickling, the sheet thickness was 0.20 mm by cold rolling. The silicidation time was changed to 1200 ° C. and the silicidation time was changed variously to carry out the silicidation treatment. The average Si content of the steel sheet surface layer portion was 6.2%, the average Si content of the steel plate inner layer portion was 3.1%, and multiple layers. A steel sheet having a ratio of 0.05 to 0.90 was produced. 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. 3 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 0.10 or more. This is because when the multilayer ratio is less than 0.10, that is, when the surface layer portion of the steel sheet, which is the high Si portion of the surface layer, is less than 0.10 in the plate thickness, the amount of the low magnetostrictive portion and the residual portion of the tensile stress is small, and the iron loss deterioration during punching This is thought to be due to the small suppression effect. On the other hand, if the multilayer ratio exceeds 0.70, cracking occurred during punching, so the upper limit is set to 0.70.

  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. Cr = 2.0%, Mn = 0.1%, As = tr. , Se = tr. After hot rolling, hot rolled sheet annealing at 900 ° C. × 30 s was performed, and after pickling, the sheet thickness was 0.20 mm by cold 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 was variously changed so that the steel plate surface layer portion (surface high Si portion) was 30% of the plate thickness (multilayer ratio = 0.30). Adjusted.

  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 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). FIG. 4 shows that the iron loss (W10 / 2k) decreases when 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 is 0.5 mass% or more. 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.

  Here, in the present invention, in order to further reduce the iron loss by adding an element other than Cr, the addition of Mn having a small influence on workability was studied. In order to examine the influence of the Mn addition amount on the iron loss, Si = 4.5%, Al = tr. Cr = 2.1%, As = tr. , Se = tr. And Mn = 0.1 to 4.7%, and a steel with a large change in the amount of Mn is prepared by vacuum melting, hot-rolled and then annealed at 900 ° C. × 30 s, pickled, cooled The sheet thickness was 0.20 mm by hot rolling. Thereafter, a siliconizing treatment at 1200 ° C. for 1 to 20 minutes was performed to make the average Si content of the steel sheet surface layer portion 6.5%. Here, the thickness of the steel plate surface layer portion (surface layer high Si portion) was set to 25% of the plate thickness. 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. 5 shows the relationship between iron loss (W10 / 2k) and Mn content. From this, it can be seen that the iron loss decreases when the Mn amount is 0.5% or more. Thereby, the lower limit of the amount of Mn is set to 0.5%. Even if the Mn amount exceeds 5.0%, the cost is unnecessarily increased, so the upper limit of the Mn amount is 5.0%.

The present invention will be described including the results of the above examination.
First, the component composition of the present invention will be described. The magnetic steel sheet of the present invention is mass%, the average Si content of the steel sheet surface layer portion is 4-7%, the average Si content of the steel plate inner layer portion is 5% or less, and contains Cr: 0.3-5.0%. And As: 0.01% or less, Se: 0.005% or less, and a component composition composed of the remaining Fe and inevitable impurities.

Average Si content of steel sheet surface layer is 4-7%
The average Si content of the steel sheet surface layer greatly affects the iron loss deterioration due to punching. By making the average Si content of the steel sheet surface layer part 4% or more, the iron loss at high frequency is greatly improved as shown in FIG. can do. 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.

Cr: 0.3-5.0%
By setting the Cr content in the steel sheet to 0.3% or more, as shown in FIG. 2, the iron loss at high frequency can be improved. On the other hand, even if the Cr content exceeds 5.0%, the cost is only increased, so the upper limit of the Cr content is 5.0%.

As: 0.01% or less As is an element that is an impurity and is preferably reduced. However, if it exceeds 0.01%, a precipitate is formed and the hysteresis loss is deteriorated. Restrict to 01%. Note that the As amount is preferably 0.003% or less, and more preferably 0.001% or less.

Se: 0.005% or less Se is an impurity and is preferably an element to be reduced. However, if it exceeds 0.005%, precipitates are formed in the same manner as As, leading to deterioration of hysteresis loss. Is restricted to 0.005%. The Se amount is preferably 0.003% or less, and more preferably 0.001% or less.

  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.

Mn: 0.5 to 5.0%
By setting the amount of Mn in the steel sheet to 0.5% or more, the iron loss at high frequency can be improved as shown in FIG. On the other hand, even if the Mn amount exceeds 5.0%, the cost is only increased, so the upper limit of the Mn amount is 5.0%. In the electrical steel sheet of the present invention, an Mn content of less than 0.5% is an impurity.

Al: 3% or less Al is an effective element for increasing the specific resistance. However, if the Al content in the steel sheet exceeds 3%, the material becomes brittle and difficult to punch, so the upper limit of Al content is 3%. And In order to obtain the above effect, Al is preferably added in an amount of 0.7% or more. In the electrical steel sheet of the present invention, an Al content of less than 0.1% is an impurity.

One or two kinds selected from Mg: 0.0003 to 0.002% and Sn: 0.01 to 0.5% Mg: 0.0003% to 0.002%
If Mg is added in an amount of 0.0003% or more, the precipitates are coarsened to reduce the iron loss, and the effect of improving the iron loss can be obtained. Therefore, the lower limit of the Mg amount is set to 0.0003%. On the other hand, even if Mg is added in an amount exceeding 0.002%, the iron loss is not reduced any more and the cost is unnecessarily increased. Therefore, the upper limit of the amount of Mg is set to 0.002%. In the electrical steel sheet of the present invention, an Mg content of less than 0.0003% is an impurity.
Sn: 0.01-0.5%
Sn can prevent oxidation, nitridation, and the like by adding 0.01% or more to improve the magnetic properties of the steel sheet, so the lower limit of Sn content is 0.01%. On the other hand, even if Sn is added in excess of 0.5%, the cost is only increased, so the upper limit of Sn content is 0.5%. In the electrical steel sheet of the present invention, an Sn content of less than 0.01% is an impurity.

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 Of 0.10 to 0.70, that is, the multilayer ratio = 0.10 to 0.70.

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 mass%
As shown in FIG. 4, 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 = 0.10-0.70
By setting the multilayer ratio, which is the ratio of the steel plate surface layer thickness to the plate thickness, to 0.10 or more, as shown in FIG. 3, deterioration of iron loss can be suppressed even with a narrow material of 5 mm. On the other hand, if the multilayer ratio exceeds 0.70, cracking occurs when punching a narrow material, making punching difficult. Therefore, the multilayer ratio is set to 0.10 or more and 0.70 or less.

  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, the magnetic steel sheet of the present invention can be obtained by performing a siliconization 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, about the primary recrystallization which arises in a siliconization process, you may perform the heat processing (primary recrystallization annealing) which produces this separately before a siliconization process.
Moreover, it is good also as an electrical steel sheet of this invention which has a steel plate surface layer part (surface layer high Si part) by performing hot rolling, cold rolling, and finish annealing after bonding the ingot from which a component differs.

  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 about 0.05 mm from the viewpoint of productivity.

  After defoaming in a converter, degassing treatment was performed to adjust to a predetermined component, and casting was performed. Steel slabs having chemical components shown in Tables 2 and 3 were obtained. The amount of Si in the steel slab was appropriately adjusted so that the Si concentration distributions shown in Tables 2 and 3 were obtained after the diffusion treatment described later. 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. Thereafter, pickling was performed, and cold rolling was performed to 0.20 mm to obtain a cold-rolled sheet. Then, finish annealing was performed with a finish annealing temperature of 1000 ° C. and a finish annealing time of 15 s to obtain a magnetic steel sheet having a uniform Si amount in the plate thickness direction (sample No. 1). Further, the above cold-rolled sheet is subjected to a siliconizing treatment under various conditions with a siliconizing temperature of 1200 ° C. and a siliconizing time as shown in Tables 2 and 3, and after the siliconizing treatment, a diffusion treatment is performed at 1200 ° C. for 10 minutes. By performing, the magnetic steel sheet shown in Table 2 and Table 3 was obtained (sample No. 2-50).

  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 Tables 2 and 3. Further, the thickness of the steel sheet surface layer portion thus obtained was determined to calculate the multilayer ratio, and are shown in Tables 2 and 3.

  Further, an Epstein sample having a length of 180 mm, a width of 30 mm, a length of 180 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 magnetic measurement (W10 / 2k) was performed by an Epstein test in accordance with JIS C2550. The above-described iron loss deterioration rate was determined from the results obtained and obtained. The results are shown in Tables 2 and 3. 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. 13, Sample No. In No. 27, the average Si amount in the steel sheet surface layer portion was high, and punching was difficult, and an Epstein sample could not be produced. Therefore, the iron loss was not measured. Sample No. No. 30 has a high average Si amount in the inner layer of the steel plate. 35 has a large multilayer ratio. Since No. 43 had a high Al content, Epstein samples could not be produced due to the occurrence of cracks or cracks when punching the samples, and therefore, iron loss was not measured.

  From Tables 2 and 3, the steel sheet of the present invention has an iron loss deterioration rate of 6.5% or less, a small deterioration in punching property when a narrow material is punched, and the iron loss itself has a frequency of 2 kHz ( The iron loss when the maximum magnetic flux density is 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 (4)

In mass%, the average Si amount in the steel sheet surface layer portion is 4-7%, the average Si amount in the steel plate inner layer portion is 5% or less, contains Cr: 0.3-5.0%, As: 0.01 % Or less, Se: 0.005% or less, having a component composition consisting of the balance Fe and inevitable impurities, and having a Si concentration gradient in the plate thickness direction in which the plate thickness surface has a higher Si concentration than the plate thickness center portion. The average Si amount of the steel sheet surface layer portion is 0.5 mass% or more higher than the average Si amount of the steel plate inner layer portion, and the steel sheet surface layer portion thickness ratio is 0.10 to 0.70 of the plate thickness. Features of 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.
However, a clad electromagnetic steel sheet is excluded as the electromagnetic steel sheet.   Furthermore, it contains Mn: 0.5-5.0% by mass%, The electrical steel sheet of Claim 1 characterized by the above-mentioned.   The electrical steel sheet according to claim 1 or 2, further comprising, by mass%, Al: 3% or less.   Furthermore, it contains 1 type or 2 types chosen from Mg: 0.0003-0.002% and Sn: 0.01-0.5% by the mass%, The Claims 1 thru | or 3 characterized by the above-mentioned. The electrical steel sheet according to any one of the above.

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