KR100515461B1 - Ultra-low iron loss unidirectional silicon steel sheet - Google Patents

Abstract

The present invention relates to an ultra-low iron loss unidirectional silicon steel sheet which is suitable for use as an iron core material of transformers and other electric equipments. At least two layers of ceramic tension coatings made of nitrides and / or carbides on the finished annealed smoothed or grooved surfaces of the unidirectional silicon steel sheet, the coefficient of thermal expansion of the ceramic tension coating is smaller toward the outer layer and the outermost ceramic tension By forming the film so as to have an insulating property, it is possible to obtain a significantly better iron loss and drop ratio compared to the conventional unidirectional silicon steel sheet.

Description

ULTRA-LOW IRON LOSS UNIDIRECTIONAL SILICON STEEL SHEET}

The present invention relates to an ultra-low iron loss unidirectional silicon steel sheet which is suitable for use as an iron core material of transformers and other electric equipments. In particular, on the finished annealed surface of the smoothed unidirectional silicon steel sheet or on the finished annealed surface of the unidirectional silicon steel sheet having a linear concave region, it is made of nitride and / or carbide, and has a small coefficient of thermal expansion toward the outer layer side. It was intended to further improve the iron loss characteristics by forming a ceramic tension coating.

Unidirectional silicon steel sheets are mainly used as iron cores of transformers and other electrical equipment. The unidirectional silicon steel sheet is required to have high magnetic flux density (represented by the value of B ₈ ) and low iron loss (represented by W _17/50 ) as magnetic properties.

In order to improve the magnetic properties of the unidirectional silicon steel sheet, first, it is necessary to align highly the <001> axis of the secondary recrystallized grains in the steel sheet in the rolling direction. Second, it is necessary to reduce as few impurities or precipitates remaining in the final product as possible.

Since the basic manufacturing technology of unidirectional silicon steel sheet by two-stage cold rolling was proposed by N.P.Goss, numerous improvements have been made. As a result of these improvements, the magnetic flux density and iron loss value of the unidirectional silicon steel sheet have been improved over the years.

Particularly representative of the improved technologies include the method described in Japanese Patent Publication No. 51-13469 using Sb and MnSe or MnS as an inhibitor, and Japanese Patent Publication No. 33-4710 using AlN and MnS as an inhibitor; Japanese Patent Application Laid-Open No. 40-15644, Japanese Patent Application Laid-open No. 46-23820, and the like. These methods make it possible to obtain high magnetic flux products having a B ₈ exceeding 1.88 T.

In addition, in order to obtain a product having a high magnetic flux density, Japanese Patent Publication No. 57-14737 discloses a method of compounding Mo in a material, and Japanese Patent Publication No. 62-42968 adds Mo to a material. The method of quenching after the intermediate annealing just before final cold rolling is proposed. By these methods, low iron loss was obtained at a high _magnetic flux density of B ₈ of 1.90 T or more and of W _17/50 of 1.05 W / kg (product thickness: 0.30 mm) or less. However, there is room for improvement for repeated low iron losses.

In particular, the demand for minimizing power loss after the recent energy crisis has increased significantly. Therefore, the iron core material is required to be further improved, and a number of products having a thin plate thickness of 0.23 mm or less have been used for the purpose of minimizing the eddy current loss as much as possible.

In addition to the above metallurgical method, as proposed in Japanese Patent Publication No. 57-2252, a method of irradiating a laser onto a surface of a steel sheet after finishing annealing or a method of irradiating plasma (B. Fukuda, K.Sato, T.Sugiyama, A.Honda and Y. Ito: Proc. Of ASM Con. Of Hard and Soft Magnetic Materials, 8710-008, (USA), (1987)) The method of reducing iron loss by reducing (magnetic segmentation technology) has been developed. This technique significantly reduced the iron loss of unidirectional silicon steel sheets.

However, there has been a drawback that the iron loss improvement effect by magnetic domain segmentation technique by laser irradiation is lost by annealing at high temperature. Therefore, the product by this technique has a problem that the use is limited to the hematite transformer which generally does not require stress relief annealing.

Therefore, as a self-refining technique having an iron loss improvement effect that can withstand stress relief annealing, a linear groove is introduced into the surface of the steel sheet after finishing annealing of the unidirectional silicon steel sheet, and the anti-magnetic effect by the groove is introduced. Application has been industrialized to achieve finer granularity (H. Kobayashi, E. Sasaki, M. Iwasaki and N. Takahashi: Proc. SMM-8., (1987), P. 402).

In addition, the method of forming a groove and subdividing magnetic domains (Japanese Patent Publication No. Hei 8-6140) has also been industrialized by locally performing electrolytic etching on the final cold rolled sheet of unidirectional silicon steel sheet.

Unlike the unidirectional silicon steel sheet, amorphous alloys disclosed in Japanese Patent Application Laid-Open No. 55-19976, Japanese Patent Application Laid-open No. 56-127749, and Japanese Patent Application Laid-open No. Hei 2-3213 are conventional power transformers. It is attracting attention as a material such as high frequency transformer.

As such an amorphous material, very excellent iron loss characteristics can be obtained as compared with a conventional unidirectional silicon steel sheet. However, there are many disadvantages in practical use, such as ① Lack of thermal stability ② Poor drop rate ③ Not easy to cut ④ It is too thin and weak so that the cost of trans assembly is high. Thus, in the present situation, it has not been reached until it is used in large quantities.

On the other hand, the inventor in Japanese Patent Application Publication No. 63-54767 discloses Si, Mn, Cr by dry plating such as CVD, ion plating, ion implantation and sputtering on a unidirectional silicon steel sheet smoothed by polishing. It is disclosed that ultra low iron loss can be obtained by forming one or two or more kinds of tension films selected from nitrides and carbides of Ni, Mo, W, V, Ti, Nb, Ta, Hf, Al, Cu, Zr and B. . This manufacturing method has made it possible to obtain a unidirectional silicon steel sheet having excellent iron loss characteristics as a material such as a power transformer or a high frequency transformer. Nevertheless, it was difficult to say that they are sufficiently responding to the recent demand for low iron loss.

The present invention is advantageous to respond to the recent demand for low iron loss, and an object of the present invention is to propose an ultra-low iron loss unidirectional silicon steel sheet which further reduces the iron loss as compared with the prior art.

Disclosure of the Invention

The inventors have made a fundamental review from various viewpoints in order to respond to the recent demand for low iron loss.

That is, in order to obtain an ultra low iron loss product by forming one or two or more kinds of tension films selected from various nitrides and carbides on the finished annealed surface of the smoothed unidirectional silicon steel sheet in a stable process, We recognized that a fundamental review is necessary from the raw material composition to the final treatment process. In addition, intensive investigations were conducted on the tracking of the texture of the unidirectional silicon steel sheet, the influence of the smoothness of the surface of the steel sheet, and the influence of the final CVD or PVD treatment process.

As a result, the following experiences (1) and (2) were obtained with respect to the case where one layer of ceramic coating was applied. As the representative example of the ceramic film, a TiN film was used.

(1) Finishing of unidirectional silicon steel sheet The ceramic coating coated on the annealed surface has a small degree of iron damage even when formed to a thickness of 1.5 µm or more. In other words, the TiN film having a thickness of 1.5 µm or more can expect only a slight decrease in the drop rate, a decrease in the magnetic flux density, and an iron loss.

(2) The tension of the TiN film (Yuki Iguchi, Kazuhiro Suzuki, Yasuhiro Kobayashi: see Japanese Society of Metals, 60 (1996), pp. 674-678) was 8 to 10 MPa. A magnetic flux density by the film tension can be expected to improve the ΔB ₈ = 0.014 ~ 0.016 T. This is equivalent to an improved Goss orientation density of about 1 °. In this case, the large tension of the TiN film is caused by good adhesion to the unidirectional silicon steel sheet in addition to the addition of the tension specific to the ceramic. Good adhesion was observed by transmission electron microscopy of the TiN cross-section (see Yukio Iguchi: 60 (1996), pp. 781 to 786). A layer with TiN embedded on the surface of a steel was observed as a 10 nm horizontal stripe. It can be seen that. In addition, the 10 nm-thick layer corresponds to the 5-atomic layer of Fe-Fe atoms in the [011] direction of the unidirectional silicon steel sheet. In the simultaneous measurement of the two-layer texture by X-rays of the TiN coating area and the chemical polishing area (see Y. Inokuti: ISIJ International, 36 (1996), P.347 to 352), The ｛200 Fe peak shape of Fe in the polishing region was circular, whereas the ｛200｝ peak shape of Fe in the TiN coating region was elliptical. It is also supported by this observation that the tension is strongly applied in the [100] _si-steel direction of the unidirectional silicon steel sheet.

Moreover, the experience of the following (3) to (6) was obtained regarding the state of one layer of the ceramic film and the steel sheet surface.

(3) In the final cold rolled sheet of unidirectional silicon steel sheet, a groove is formed by local electrolytic etching to form a groove, and after the second recrystallization treatment, the surface of the steel sheet is polished and smoothed, and then the groove is introduced when the TiN ceramic film is coated. In addition to the magnetic domain segmentation caused by the anti-magnetic field effect caused by, the tension loss caused by the ceramic coating effectively reduces the iron loss.

(4) In the case where a concave groove is formed on the surface of the steel sheet before the ceramic coating, the effect of reducing iron loss due to tension in the ceramic coating is greater than that of the silicon steel sheet smoothed by ordinary polishing (Japanese Patent Laid-Open Publication No. 3- 32889). The state is shown in FIG. The solid line in FIG. 1 shows the influence of the tensile tension on the iron loss when the groove is formed. The broken line in FIG. 1 shows the effect of tensile tension on iron loss when smoothed by chemical polishing. In the case where the groove is formed, the degree of reduction in iron loss due to the tensile tension is increased. When the groove is introduced, the occurrence of tension difference affects the groove portion and the non-groove portion on the surface of the silicon steel sheet.

(5) In the case where the ceramic film is coated on the finish-annealed surface of the unidirectional silicon steel sheet having concave grooves, the reduction effect of iron loss is increased compared with the case where the ceramic film is coated on the silicon steel sheet smoothed by ordinary polishing. The state is shown in FIG. Figure 2a shows a magnetic domain formed on the surface of the steel sheet of a conventional unidirectional silicon steel sheet. The magnetization directions of the hatching part and the hatching part are 180 ° to each other. Figure 2b shows a magnetic domain formed on the surface of the steel sheet when a linear groove is introduced into the unidirectional silicon steel sheet. Reference numeral 20 denotes a groove portion, and reference numeral 22 denotes a non-groove portion. It can be seen that the magnetic domains are subdivided as compared with (a) due to the anti-magnetic effect caused by the grooves. Fig. 2C shows a magnetic domain formed on the surface of a steel sheet when a linear groove is introduced into a unidirectional silicon steel sheet and a ceramic tension film is formed. In (c), it can be seen that the domain is further divided. It is more effective to form grooves, to further form a ceramic tension film, and to further subdivide the magnetic domain, and to obtain ultra low iron loss.

(6) In the case where the groove is formed by local electrolytic etching on the final cold rolled sheet of the unidirectional silicon steel sheet, even if the TiN ceramic film is formed without polishing smoothing the surface of the steel sheet after the secondary recrystallization treatment, significant iron loss is achieved. Reduction effect can be exhibited. That is, even in a state in which smooth unevenness is present on the surface by polishing, for example, in a pickling process, a strong tension can be applied to the surface of the silicon steel sheet by coating a ceramic film having a small coefficient of thermal expansion, thereby reducing iron loss. It can be advantageously reduced.

Therefore, the inventor has repeated numerous experiments and studies in order to achieve the desired purpose based on the experiences of (1) to (6). As a result, in any of the silicon steel sheet with the smooth surface and the silicon steel sheet with the linear grooves, the coefficient of thermal expansion of the ceramic tension film formed on the surface of the silicon steel sheet is made smaller toward the outer layer. Recognition was very effective. It was also found that it is preferable to make these ceramic tension films into several types especially.

Hereinafter, the content of the present invention will be described in detail. First, the content of the ceramic film which should be formed on the surface of a silicon steel sheet is shown.

3 (a), (b) and (c), respectively, near (a) the current unidirectional silicon steel sheet, (b) TiN coated unidirectional silicon steel sheet, and (c) the ultra-low iron loss unidirectional silicon steel sheet of the present invention. Compare the cross sections of and show them conceptually.

Current one-way (a), a silicon steel sheet, the coefficient of thermal expansion to form a 13 × 10 ^-6 / K in the metal part 10, based on the coating film 14 whose thermal expansion coefficient is 11 × 10 ^-6 / K in light poster (forsterite) over In addition, an insulating film 16 having a thermal expansion coefficient of 5 × 10 ⁻⁶ / K is further formed thereon, thereby achieving low iron loss and improvement of magnetostriction characteristics. A sulfide or an oxide 12 is formed at the interface between the base iron and the posterlite base coating. In this case, the droplet ratio is about 96.5%.

The TiN coated unidirectional silicon steel sheet of (b) forms a thin TiN film 15 having a thickness of about 1 μm on the base iron 10, and further forms an insulating film 16 thereon. The interface 11 of the base iron and the TiN film is smoothed. In this case, the thermal expansion coefficient of the TiN film is 8 × 10 ^-6 / K, which is lower than that of the posterlite base film: 11 × 10 ^-6 / K. Further improvement of the magnetostrictive properties is possible. In this case, the droplet ratio is improved by about 1% from (a) to about 97.5%.

On the other hand, the ultra-low iron loss silicon steel sheet of this invention of (c) forms the TiN film 15 thinly (0.01-0.5 micrometer) on the surface of a fibrous iron, and its thermal expansion coefficient is very small (3x10 <^-6> / K). An ultra-low iron loss silicon steel sheet having a thin-nitride ceramic coating having a two-layer structure in which an insulating Si ₃ N ₄ (18) was formed to a thickness of 0.3 to 1.5 µm. The interface 11 of the base iron and the TiN film is smoothed. In this case, the spot ratio is about 99%, which is the ultimate silicon steel sheet.

FIG. 4 compares and shows changes in iron loss due to tension in a unidirectional silicon steel sheet having two types of thin nitride-based ceramic coatings shown in FIGS. 3B and 3C. The solid line has shown about FIG. 3C, and the broken line has shown about FIG. 3B. As shown in FIG. 4, the TiN-Si ₃ N ₄ two-layer thin nitride ceramic film is formed according to the present invention of FIG. 3C, as compared to the case where the TiN film is simply formed on the unidirectional silicon steel sheet of FIG. 3B. In the case, it is noted that the change in iron loss due to tension is small. That is, in the case of FIG. 3C, it can be seen that more effective tension is applied to the silicon steel sheet to achieve ultra low iron loss.

Next, the relationship between the state of the surface of a silicon steel sheet and a ceramic film is shown.

In FIG. 5, the result of having investigated the change of iron loss when tension | tensile_strength is applied to the unidirectional silicon steel plate in which surface states differ in various ways is shown.

5, (a)-(e) are the iron loss reduction curves of the following cases, respectively.

(a) On the final cold-rolled sheet surface of the unidirectional silicon steel sheet, a linear concave region having a width of 200 μm and a depth of 20 μm at intervals of 4 mm in a direction substantially perpendicular to the rolling direction is formed, and then finish annealing is performed. (110), Iron loss reduction curve (solid line) when secondary recrystallization of [001] orientation was developed, and then tension was added after chemical polishing of the steel plate surface.

(b) After smoothing the surface after finishing annealing of the unidirectional silicon steel sheet by chemical polishing, a linear concave region having a width of 200 μm and a depth of 20 μm at intervals of 4 mm in a direction substantially perpendicular to the rolling direction on the steel sheet surface. The iron loss reduction curve (dotted and dashed line) at the time of forming a and then adding tension.

(c) On the final cold rolled sheet surface of the unidirectional silicon steel sheet, using a knife at a distance of 4 mm in a direction substantially perpendicular to the rolling direction, using a knife to form a linear concave region, and then subjected to finish annealing, the surface of the steel sheet is chemically polished Iron loss curve (double dashed line) when tension is applied after

(d) After smoothing the surface after finishing annealing of the unidirectional silicon steel sheet by chemical polishing, a linear concave region was formed on the steel plate surface using a knife at intervals of about 4 mm in a direction substantially perpendicular to the rolling direction, followed by tension. Iron loss reduction curve when () is added.

(e) Iron loss reduction curve (dotted line) when tension is added after smoothing the surface after finishing annealing of unidirectional silicon steel sheet by chemical polishing.

As shown in Fig. 5, in the iron loss reduction curves under these tensile tensions, the degree of iron loss reduction of the silicon steel sheet due to the tensile tension is the largest under the conditions of (a) and (b), followed by the conditions of (c) and (d). , (e) is a condition.

Here, in the conditions of FIGS. 5A and 5B, as shown in FIG. 2, since the tension difference near the surface of the steel sheet acts effectively, the reduction degree of iron loss is considered to be the largest.

Hereinafter, the progress and the invention content in which success by the present invention is derived will be described in detail. First, the specific experimental result about a ceramic film is shown.

C: 0.072% by weight (hereinafter simply referred to as%), Si: 3.44%, Mn: 0.085%, Se: 0.023%, Sb: 0.028%, Al: 0.025%, N: 0.0082%, and Mo: 0.013% In addition, the remainder was heat-treated for 4 hours at 1360 DEG C of the silicon steel continuous casting slab having a composition of Fe, and then hot-rolled to obtain a hot rolled sheet having a plate thickness of 2.0 mm. The hot rolled sheet was subjected to homogenization annealing at 980 ° C. for 3 minutes, followed by cold rolling twice with an intermediate annealing at 960 ° C. in the middle to obtain a final cold rolled sheet having a thickness of 0.23 mm. The cold rolled plate was subjected to decarburization and primary recrystallization annealing in 840 ° C. wet hydrogen, and then applied to the surface of the annealing plate by applying an annealing separator slurry containing MgO as a main component. Subsequently, the coating plate was heated up to 1050 ° C. at 8 ° C./h at 850 ° C. to develop secondary recrystallized grains strongly accumulated in a goth orientation on the steel sheet, and then purified in 1220 ° C. dry hydrogen. After removing the surface coating of the annealing plate thus obtained, the surface was smoothed by chemical polishing. Thereafter, TiN (ion plating by HCD method) was formed to a thickness of about 0.2 μm on the surface of the silicon steel sheet, and then Si ₃ N ₄ was further formed to have a thickness of 0.5 μm.

Table 1 shows the results of measuring the magnetic properties of the unidirectional silicon steel sheet.

Table 1 also shows magnetic property values of (2) TiN coated silicon steel sheet and (3) current silicon steel sheet (both after self-segmentation) for comparison.

As it can be seen from Table 1, as compared to _{W 17/50 (W / ㎏) =} 0.80 W / ㎏ of current silicon steel sheet (Comparative Example) of ③, the TiN coated silicon steel sheet ② W _17/50 (W / ㎏ ) Is excellent at 0.62 W / kg.

However, ① the In accordance with the present invention, TiN and Si ₃ N ₄ layer 2 (0.7 ㎛) to form a ceramic film of the silicon steel sheet, W _17/50 (W / ㎏) is improved remarkably to 0.55 W / ㎏. In addition, it is noted that the droplet ratio of ① is 99.0% and is remarkably superior to ② and ③.

As described above, the remarkable improvement of the magnetic properties in the present invention smooths the surface of the unidirectional silicon steel sheet on which the secondary recrystallized grains strongly accumulated in the goth direction are smoothed, and the movement of the magnetic walls is facilitated. This is achieved by forming a two-layer (0.7 μm) ceramic film of TiN + Si ₃ N ₄ on top.

Next, specific experimental results regarding the state of the surface of the silicon steel sheet are shown.

C: 0.074%, Si: 3.35%, Mn: 0.069%, Se: 0.021%, Sb: 0.025%, Al: 0.025%, N: 0.0072% and Mo: 0.012%, and the remainder is substantially composed of Fe. The phosphorus silicon steel continuous casting slab was heated at 1350 ° C. for 4 hours, and then hot rolled to obtain a hot rolled sheet having a thickness of 2.0 mm. The hot rolled sheet was subjected to homogenization annealing at 970 ° C. for 3 minutes, and then subjected to two rolling with an intermediate annealing at 1050 ° C. in the middle to obtain a final cold rolled sheet having a thickness of 0.23 mm. This final cold rolled sheet was then treated as follows.

(1) The surface of this final cold rolled sheet was coated with an etch resist ink containing alkyd resin as a main component by gravure offset printing so that the non-coated portion remained in a line shape having a width of 200 mu m and a spacing of 4 mm almost perpendicular to the rolling direction. Then, it baked at 200 degreeC for 3 minutes. At this time, the resist thickness was 2 micrometers. In this way, electrolytic etching was performed on the steel sheet coated with the etching resist to form a linear groove having a width of 200 µm and a depth of 20 µm, and then immersed in an organic solvent to remove the resist. At this time, the electrolytic etching was performed under conditions of a current density of 10 A / m ² and a treatment time of 20 seconds in a NaCl electrolyte solution.

② For comparison, final cold rolled plates not treated with ① were also prepared.

Subsequently, all of these steel sheets were subjected to decarburization and primary recrystallization annealing in 840 ° C. wet hydrogen, and then, on the surface of the steel sheet, MgO (25%), Al ₂ O ₃ (70%), and CaSiO ₃ (5%) were used. After annealing separator slurry was applied and then annealed at 850 ° C. for 15 hours, the temperature was raised to 1150 ° C. at a rate of 10 ° C./h to develop secondary recrystallized grains strongly concentrated in a goth orientation, and then dried in dry hydrogen at 1200 ° C. Purification was performed.

After removing the surface coating of the annealing plate thus obtained, the surface of the silicon steel sheet was smoothed by chemical polishing. Thereafter, TiN (ion plating by HCD method) was formed to a thickness of about 0.2 µm on the surface of the silicon steel sheet, and then Si ₃ N ₄ was further formed to a thickness of 0.5 µm.

Table 2 shows the results of measuring the magnetic properties of the silicon steel sheet.

Table 2 also shows magnetic property values of the silicon steel sheet coated with only TiN for comparison.

As can be seen from Table 2, when a concave linear groove is formed on the surface of the steel sheet in accordance with ①, and a two-layer ceramic film of TiN (0.2 µm) + Si ₃ N ₄ (0.5 µm) is formed thereon, It is noted that the magnetic flux density is decreased 0.04 to 0.05 T as compared to ② and ③, and the iron loss W _17/50 is significantly reduced to 0.45 W / kg.

As described above, the remarkable improvement of the magnetic properties in the present invention is to form concave linear grooves on the surface of the silicon steel sheet before ceramic coating, and to further subdivide the magnetic domains by applying the anti-magnetic effect by the grooves. It is achieved by forming a two-layer (0.7 μm) ceramic film of TiN + Si ₃ N ₄ on the furnace to more effectively self-fractionate it.

Here, the ceramic film formed on the surface of the silicon steel sheet is selected from nitrides or carbides of Si, Mn, Cr, Ni, Mo, W, V, Ti, Nb, Ta, Hf, Al, Cu, Zr, and B, but There are two important points:

(1) The coefficient of thermal expansion is made smaller toward the outer layer.

(2) The ceramic film of outermost layer is equipped with insulation,

Moreover, it is preferable to make the total thickness of a ceramic film into about 0.3-2 micrometers. The reason for this is that the effect of improving iron loss is small because the tensile effect is small at the film thickness of less than 0.3 mu m, while the drop rate and the magnetic flux density are lowered when the thickness exceeds 2 mu m. As described above, it is needless to say that the present invention is superior in iron loss and droplet ratio as compared with the conventional silicon steel sheet, and is a breakthrough ultra low iron loss unidirectional silicon steel sheet excellent in magnetostriction, heat resistance and insulation.

As the silicon-containing steel which is the raw material of the present invention, all conventionally known component compositions are suitable, but the representative compositions are as follows. All are weight%.

C: 0.01% to 0.08%

If C is less than 0.01%, the suppression of hot rolled texture is insufficient, and large elongated particles are formed, so that the magnetic properties deteriorate. On the other hand, when more than 0.08%, decarburization takes time in a decarburization process, and it is uneconomical. Therefore, it is preferable to set it as about 0.01 to 0.08%.

Si: 2.0% to 4.0%

If Si is less than 2.0%, sufficient electric resistance cannot be obtained, and the eddy current loss chamber increases, resulting in deterioration of iron loss. On the other hand, when it is more than 4.0%, brittle cracking occurs easily at the time of cold rolling. Therefore, it is preferable to set it as about 2.0 to 4.0% of range.

Mn: 0.01% to 0.2%

Mn is an important component for determining MnS or MnSe as a dispersed precipitated phase that governs secondary recrystallization of unidirectional silicon steel sheets. If the amount of Mn is less than 0.01%, the absolute amount of MnS or the like necessary for generating secondary recrystallization is insufficient, causing incomplete secondary recrystallization and increasing surface defects called blisters. On the other hand, if it exceeds 0.2%, even if dissociation of MnS or the like is performed during slab heating or the like, the dispersed precipitated phase precipitated at the time of hot rolling is likely to coarsen, and the optimum size distribution desired as an inhibitor is impaired and the magnetic properties. This is deteriorated. Therefore, it is preferable to make Mn about 0.01 to 0.2%.

S: 0.008% to 0.1%, Se: 0.003% to 0.1%

Both S and Se are preferably 0.1% or less. In particular, it is preferable that S be 0.008 to 0.1%, or Se be 0.003 to 0.1% of range. If they exceed 0.1%, hot and cold workability will deteriorate. On the other hand, if the respective lower limit is not reached, there is no particular effect on the primary particle growth inhibitory function as MnS and MnSe.

In addition, addition of Al, Sb, Cu, Sn, B, and the like which are conventionally known as an inhibitor does not impair the effects of the present invention.

Next, the manufacturing process of the ultra-low iron loss unidirectional silicon steel sheet which concerns on this invention is demonstrated.

In order to first melt the material, not only can an LD converter, an electric furnace, a furnace, and other known steelmaking furnaces be used, but also vacuum melting and RH degassing can be used in combination.

According to the present invention, as a method for adding a small amount of S, Se or other primary grain growth inhibitors contained in the raw material into molten steel, any conventionally known method may be used, for example, at the end of LD converter and RH degassing. Or it can add in molten steel at the time of ingot.

In addition, although the slab manufacturing is advantageous in employing the continuous casting method due to economical and technical advantages such as cost reduction, and further, uniformity in the longitudinal direction of the slab or quality uniformity, it is also possible to use a conventional ingot slab.

The continuous casting slab is heated to a temperature of 1300 ° C. or more in order to dissociate and solidify the inhibitor in the slab. Thereafter, the slab is hot rolled, followed by hot finish rolling to form a hot rolled sheet having a thickness of about 1.3 to 3.3 mm.

Next, the hot rolled sheet is subjected to cold rolling twice with an intermediate annealing in the temperature range of 850 to 1100 ° C. as necessary to obtain a final sheet thickness. In order to obtain a product having low iron loss characteristics with high magnetic flux density, It is necessary to pay attention to the final cold rolling reduction rate (usually about 55 to 90%).

At this time, the upper limit of the product thickness was limited to 0.5 mm from the viewpoint of making the eddy current loss of the silicon steel sheet as small as possible, and the lower limit of the plate thickness was limited to 0.05 mm in order to avoid the damage of hysteresis loss.

In the case of forming a linear groove on the surface of the steel sheet, it is particularly advantageous to finish the final cold rolling to perform the steel sheet having the sheet thickness of the product.

That is, on the surface of the steel sheet before and after the final cold rolled sheet or the secondary recrystallization, a linear concave region having a width of 50 to 500 µm and a depth of 0.1 to 50 µm is formed at intervals of 2 to 10 mm in a direction substantially perpendicular to the rolling direction. It is to let.

Here, limiting the interval of the linear concave region to the range of 2 to 10 mm is uneconomical because the unevenness of the steel sheet is so significant that the magnetic flux density is lowered if it is less than 2 mm, while the magnetic segmentation effect exceeds 10 mm. Because becomes small.

In addition, if the width of the concave region is less than 50 μm, it is difficult to use the semi-magnetic effect. On the other hand, if the width of the concave region exceeds 500 μm, the magnetic flux density is lowered and it is uneconomical. Therefore, the width of the concave region is limited to 50 to 500 μm. .

In addition, if the depth of the concave region does not reach 0.1 μm, the semi-magnetic field effect cannot be effectively used. On the other hand, if the depth of the concave region exceeds 50 μm, the magnetic flux density decreases and it is uneconomical. Therefore, the depth of the concave region is limited to 0.1 to 50 μm.

As a method of forming a linear concave region, an etching process is applied after baking an etching resist on the surface of the final cold rolled sheet, followed by baking, and then the resist is removed. Compared with a method using a laser or the like, it is advantageous in that industrial stability can be performed and tensile loss can be more effectively reduced.

Hereinafter, the typical example of the linear groove formation technique by the said etching is demonstrated concretely.

On the final cold-rolled sheet surface, an etching resist ink mainly composed of alkyd-based resin is applied by gravure offset printing so that the non-coating portion remains in a line shape having a width of 200 mu m and a spacing of 4 mm almost perpendicular to the rolling direction. Thereafter, baking is carried out at 200 ° C. for about 20 seconds. At this time, the resist thickness is about 2 m. In this way, the steel sheet to which the etching resist is applied is subjected to electrolytic etching or chemical etching to form linear grooves having a width of 200 µm and a depth of 20 µm. At this time, the electrolytic etching conditions may be a current density of 10 A / m 2 and a treatment time of about 20 seconds in NaCl electrolyte, and the chemical etching conditions of about 10 seconds of immersion time in HNO ₃ liquid. Subsequently, the resist is removed by immersing in the organic solvent, and the steel sheet is subjected to decarbonization annealing. This annealing aims to remove C, which is harmful when the cold rolled tissue is used as the primary recrystallized structure and also develops secondary recrystallized grains in the {110} <1> orientation during final annealing (also called finishing annealing). It is done. Usually, it is performed in 750-880 degreeC humidified hydrogen.

Final annealing is performed in order to fully develop secondary recrystallized grains in the {110} <1> orientation, and is usually carried out by raising the temperature directly to 1000 ° C. or higher and maintaining the temperature by box annealing. This final annealing is usually performed by applying an annealing separator such as magnesia, and simultaneously forms a base film called posterlite on the surface. In the present invention, however, the annealing separator that does not form such a posterlite base coating is advantageous because the base coating is removed in the next step even if the posterite base coating is formed. That is, annealing separation in which the content ratio of MgO forming the posterlite base coating is reduced (50% or less), and the content ratio of Al ₂ O ₃ , CaSiO _3, etc., which does not form such a coating is high (50% or more) instead I am advantageous. In order to develop the secondary recrystallized structure highly integrated in the {110} <1> orientation in the present invention, it is advantageous to isothermally anneal at a low temperature of 820 ° C. to 900 ° C., but for example, about 0.5 to 15 ° C./h. Sequence annealing of the temperature rise rate of may be sufficient.

After this final annealing, the posterritic base film and the oxide film on the surface of the steel sheet are removed by a known chemical method such as pickling, mechanical methods such as cutting and polishing, or a combination thereof to smooth the surface of the steel sheet.

That is, after removing the various coatings on the surface of the steel sheet, the steel sheet to about 0.4 μm or less in the center line average roughness (Ra) by conventional methods such as chemical polishing such as chemical polishing and electropolishing or buff polishing or a combination thereof. Smooth the surface.

In addition, when forming a linear recessed area on the surface of a silicon steel sheet, the steel plate surface does not necessarily need to be smoothed. Therefore, in this case, there is an advantage in that a sufficient iron loss reduction effect can be exhibited only by pickling, without performing a smoothing process involving an increase in cost. Even so, it does not change that it is advantageous to perform the smoothing treatment.

Subsequently, silicon, Mn, Cr, Ni, Mo, W, V, Ti, Nb, Ta, Hf, Al, Cu, Zr were used on various surfaces such as PVD, CVD, or sputtering on the surface of the silicon steel sheet after the smoothing treatment. And at least two layers of a tension film made of one or two papers selected from nitrides or carbides of B to form a ceramic tension film.

In the formation of such a ceramic tension coating, two points are noted.

(1) The coefficient of thermal expansion decreases toward the outer layer side,

(2) The outermost ceramic coating is provided with insulation

Here, it is preferable to make the sum total of the thickness of such a ceramic tension film into about 0.3-2 micrometers as mentioned above.

In addition, with respect to the formation of the ceramic tension coating film, the ceramic coating film formed in FIG. 3C is shown in the case where it is clearly divided into two layers. In the present invention, the boundary of the ceramic layer does not necessarily need to be so clear. The components of each layer may be in a state where they are diffused into different layers, and the important thing is that the thermal expansion coefficient of the coating may be reduced toward the outer layer side.

1 is a graph showing the relationship between tensile tension and iron loss in unidirectional silicon steel sheets subjected to chemical polishing and groove introduction.

Fig. 2 shows (a) a magnetic domain on the surface of a steel sheet having a secondary recrystallized structure in a goth orientation, (b) a magnetic domain when a linear groove is introduced into the surface of the steel sheet in (a), and (c) the steel surface on the surface of (b). It is a figure which shows the observation result of the magnetic domain when a ceramic tension film is formed in the film.

Fig. 3 is a schematic diagram showing the cross-section of the vicinity of the surface of (a) the current unidirectional silicon steel sheet, (b) TiN coated unidirectional silicon steel sheet, and (c) the ultra low iron loss unidirectional silicon steel sheet of the present invention.

4 is a relationship between tensile tension and iron loss characteristics in a unidirectional silicon steel sheet on which a TiN film is simply formed on a steel plate surface and a unidirectional silicon steel sheet on which a TiN-Si ₃ N ₄ two-layer thin nitride ceramic film is formed according to the present invention. Is a graph.

5 is a graph showing a relationship between tensile tension and iron loss when tension is applied to silicon steel sheets having various surface states.

In order to explain this invention in more detail, it demonstrates according to an Example, and this invention is not limited to these Examples.

(Example 1)

C: 0.073%, Si: 3.42%, Mn: 0.073%, Se: 0.021%, Sb: 0.026%, Al: 0.025%, and Mo: 0.014%, and the remainder is a silicon steel continuous casting which is substantially a composition of Fe. After slab was heat-processed at 1340 degreeC for 4 hours, hot rolling was performed and it was set as the thickness of 1.8 mm hot-rolled sheet. Subsequently, after performing 900 degreeC homogenization annealing, cold rolling was performed twice with the intermediate | middle annealing of 950 degreeC in the middle, and it was set as the final cold rolled plate of thickness 0.23mm. In addition, at the time of rolling, 350 degreeC warm rolling was performed. Thereafter, after decarburization and primary recrystallization annealing was carried out in 820 ° C. wet hydrogen, MgO was slurry-coated on the surface of the steel sheet, followed by secondary recrystallization annealing at 850 ° C. for 50 hours, followed by purified annealing in 1220 ° C. dry hydrogen. . Subsequently, the surface of the steel sheet was smoothed by pickling and chemical polishing, and then two layers of various ceramic coatings were formed using the PVD method and the magnetron sputtering method.

Table 3 shows the results of investigating the magnetic properties of the product thus obtained.

In addition, in Table 3, the results of the investigation of the magnetic properties of the TiN-coated silicon steel sheet and the current silicon steel sheet (both after self-dividing granularity) are also described together.

As can be seen from the table, all of the silicon steel sheet obtained in accordance with the present invention can obtain a much better iron loss value and the dripping rate compared to the conventional material.

(Example 2)

C: 0.074%, Si: 3.46%, Mn: 0.077%, sol.Al: 0.025%, N: 0.0074%, Se: 0.021%, Mo: 0.011%, Cu: 0.21%, and Sb: 0.023%, The remainder is a silicon steel continuous casting slab, which is substantially composed of Fe, is gradually reheated at 1260 ° C. for 40%, and then gradually heated to 1360 ° C. at 1.5 ° C./min and then maintained at this temperature for 4 hours. After hot rolling was carried out to obtain a thickness of 1.8 mm hot rolled sheet.

Subsequently, after homogenization annealing at 1050 ° C, cold rolling was performed twice with an intermediate annealing at 1000 ° C in the middle to obtain a final cold rolled plate having a thickness of 0.23 mm. In addition, at the time of rolling, 300 degreeC warm rolling was performed. Thereafter, after decarburization and primary recrystallization annealing in 840 ° C. wet hydrogen, MgO was slurry-coated on the surface of the steel sheet, and the temperature was elevated to 1080 ° C. at 850 ° C. at 12 ° C./h, followed by secondary recrystallization. Purified annealing was carried out in dry H ₂ .

After that, the surface of the steel sheet was smoothed by pickling and chemical polishing, and then formed into two layers (0.6 µm) of TiN + Si ₃ N ₄ by magnetron sputtering, and then subjected to magnetic granularity treatment. I measured the rate,

W _17/50 = 0.53 W / kg

Droplet ratio = 99.1%

Excellent characteristic value was obtained.

(Example 3)

C: 0.069%, Si: 3.39%, Mn: 0.077%, Se: 0.022%, Sb: 0.025%, Al: 0.020%, N: 0.071%, and Mo: 0.012%, and the remainder is substantially composed of Fe. Phosphorus silicon continuous cast slab was cracked at 1350 ° C. for 5 hours, and then hot rolled to obtain a hot rolled sheet having a thickness of 2.1 mm. Subsequently, after carrying out the uniformized annealing of 950 degreeC, cold rolling was performed twice with the intermediate | middle annealing of 1050 degreeC in the middle, and it was set as the final cold rolled plate of thickness: 0.23 mm. Thereafter, the following three treatments were performed on the surface of the steel sheet.

① On the surface of the final cold rolled sheet, the etching resist ink mainly containing alkyd resin is coated by gravure offset printing so that the non-coating portion remains in a line shape having a width of 200 μm and a spacing of 4 mm almost perpendicular to the rolling direction. And baked at 200 ° C. for about 20 seconds. At this time, the resist thickness was 2 micrometers. In this way, electrolytic etching was performed on the steel sheet to which the etching resist was applied to form a linear groove having a width of 200 µm and a depth of 20 µm, and then immersed in an organic solvent to remove the resist. The electrolytic etching at this time was performed in NaCl electrolyte solution on conditions of current density: 10 A / m <2>, and processing time: 20 second.

Thereafter, decarburization and primary recrystallization annealing was performed in 840 ° C. wet hydrogen, and then, on the surface of the steel sheet, an annealing separator composed of MgO (25%), Al ₂ O ₃ (70%), and CaSiO ₃ (5%) was slurry. After coating and annealing at 850 ° C. for 15 hours, the temperature was raised to 1150 ° C. at a rate of 10 ° C./h to develop secondary recrystallized grains in a goth orientation, and then purified in 1200 ° C. dry hydrogen. .

(2) After decarburizing and primary recrystallization annealing were performed on the final cold rolled sheet in 840 ° C. wet hydrogen, a linear groove was formed on the surface of the decarburization and primary recrystallization annealing plate in the same manner as in (1). Thereafter, slurry annealing separators composed of MgO (25%), Al ₂ O ₃ (70%) and CaSiO ₃ (5%) were applied to the surface of the steel sheet, followed by annealing at 850 ° C. for 15 hours, followed by 10 ° C. / After the temperature was raised to 1150 ° C. at a h rate, the secondary recrystallized grains strongly accumulated in the goth direction were developed, and then purified in 1200 ° C. dry hydrogen.

③ After the decarburization and primary recrystallization annealing was performed in 840 ° C. wet hydrogen in the final cold rolled sheet, the steel sheet after the secondary recrystallization of the (110) [001] orientation was developed by final annealing in the same manner as in ②. After removing the oxide film on the surface and then smoothing the surface by chemical polishing, linear grooves were formed in the same manner as in ① and ②.

Next, two layers of various ceramic films were formed on the surface of the steel sheet by using the PVD method and the magnetron sputtering method.

Table 4 shows the results of investigating the magnetic properties of the product thus obtained.

Table 4 also shows the results of investigating the magnetic properties of the TiN coated silicon steel sheet and the current silicon steel sheet (both after self-fractionation) for comparison.

As can be seen from the table, all of the silicon steel sheets obtained according to the present invention can obtain better iron loss characteristics as compared with the conventional materials.

(Example 4)

A silicon steel continuous casting slab containing C: 0.043%, Si: 3.34%, Mn: 0.068%, Se: 0.020%, Sb: 0.025%, and Mo: 0.012%, the remainder being substantially a composition of Fe at 1330 ° C. After heating for 3 hours, hot rolling was performed to obtain a hot rolled sheet having a thickness of 2.4 mm.

Subsequently, after homogenization annealing of 900 degreeC, cold rolling was performed twice by sandwiching 950 degreeC intermediate annealing, and it was set as the final cold rolled plate of thickness 0.23mm.

After that, the etch resist ink mainly containing alkyd-based resin as a main component was applied to the final cold rolled sheet by gravure offset printing so that the non-coated portion remained in a line shape having a width of 200 占 퐉 and a width of 4 mm almost perpendicular to the rolling direction, and then 200 Baking at about 20 seconds. At this time, the resist thickness was 2 micrometers. In this way, electrolytic etching was performed on the steel sheet to which the etching resist was applied to form a linear groove having a width of 200 µm and a depth of 20 µm, and then immersed in an organic solvent to remove the resist. At this time, the electrolytic etching was performed under conditions of a current density of 10 A / m 2 'and a processing time of 20 seconds in a NaCl electrolyte solution.

Thereafter, decarburization and primary recrystallization annealing is performed in 840 ° C. wet hydrogen, and then, on the surface of the steel sheet, an annealing separator having a composition of MgO (25%), Al ₂ O ₃ (70%) and CaSiO ₃ (5%) is used. After the slurry was applied, secondary recrystallized grains strongly concentrated in the (110) [001] orientation were developed by isothermal annealing at 850 ° C. for 50 hours, and then purified in 1200 ° C. dry hydrogen.

The oxide film on the surface of the silicon steel sheet thus obtained was removed, and then the surface was smoothed by chemical polishing, and then two layers (0.7 μm) of TiN + Si ₃ N ₄ were formed by using magnetron sputtering.

The iron loss and the dripping rate of the product thus obtained were measured,

W _17/50 = 0.49 W / kg

Dripping rate = 98.8%

Excellent characteristic value was obtained.

(Example 5)

A silicon steel continuous casting slab containing C: 0.079%, Si: 3.46%, Mn: 0.086%, Se: 0.022%, Sb: 0.023%, Al: 0.026%, and Mo: 0.012, with the remainder substantially consisting of Fe. Was heated at 1350 ° C. for 3 hours and then hot rolled to obtain a hot rolled sheet having a thickness of 2.2 mm. Subsequently, cold rolling was performed twice with an intermediate annealing in between to obtain a final cold rolled plate having a thickness of 0.23 mm.

After that, the etch resist ink mainly containing alkyd-based resin as a main component was applied to the final cold rolled sheet by gravure offset printing so that the non-coated portion remained in a line shape having a width of 200 占 퐉 and a width of 4 mm almost perpendicular to the rolling direction, and then 200 Baking at about 20 seconds. At this time, the resist thickness was 2 micrometers. In this way, electrolytic etching was performed on the steel sheet to which the etching resist was applied to form a linear groove having a width of 200 µm and a depth of 20 µm, and then immersed in an organic solvent to remove the resist. At this time, the electrolytic etching was performed under conditions of a current density of 10 A / m 2 and a processing time of 20 seconds in a NaCl electrolyte solution.

Thereafter, decarburization and primary recrystallization annealing are performed in 845 DEG C. hydrogen water, followed by MgO (25%), Al ₂ O ₃ (70%), CaSiO ₃ (3%), and SnO ₂ (2%) on the steel sheet surface. After applying slurry annealing separator, which is a composition of, and annealing at 850 ° C. for 15 hours, the temperature was raised to 1100 ° C. at a rate of 10 ° C./h to develop secondary recrystallized grains strongly concentrated in a goth orientation, and then 1200 Purification was carried out in dry hydrogen.

Thereafter, the pickling treatment is performed in 30% HCl (80%) to remove the oxide on the surface of the steel sheet, and then the coil is divided into two parts. The first half of the coil is Si ₃ N ₄ film (0.3) using a magnetron sputtering method. Two layers of AlN film (0.2 mu m thick) were formed. On the other hand, for the latter part of the coil, an AlN film of low purity in the first layer (containing about 1.5% Fe, Ti and Al as impurities in the ceramic film; 0.3 μm thick) using the magnetron sputtering method, and on the second layer thereon Two layers of high purity AlN film (purity of AlN in ceramic film: 99% or more) were formed.

The iron loss and the drip rate of the product thus obtained were measured,

Coil first half W _17/50 = 0.59 W / kg Droplet ratio = 99.1%

Coil second half W _17/50 = 0.58 W / kg Drop rate = 99.2%

Excellent characteristic value was obtained.

(Example 6)

C: 0.072 wt%, Si: 3.35 wt%, Mn: 0.072 wt%, Se: 0.020 wt%, Sb: 0.025 wt%, Al: 0.020 wt%, N: 0.072 wt% and Mo: 0.012 wt% The rest of the material was substantially hot-rolled after the silicon steel continuous casting slab was heated at 1350 ° C. for 4 hours to obtain a hot rolled sheet having a thickness of 2.2 mm. Subsequently, after performing homogenization annealing at 1020 degreeC, cold rolling was performed twice with the intermediate | middle annealing of 1050 degreeC in the middle, and it was set as the final cold rolled plate of thickness 0.23mm.

Subsequently, decarburization and primary recrystallization annealing is performed in 840 ° C. wet hydrogen, and then slurry coated annealing separator having a composition of MgO (20%), Al ₂ O ₃ (70%) and CaSiO ₃ (10%) on the surface of the steel sheet. Subsequently, after annealing at 850 ° C. for 15 hours, the temperature was raised from 850 ° C. to 12 ° C./h to 1180 ° C. to develop secondary recrystallized grains in a goth bearing, followed by purifying in 1220 ° C. dry hydrogen. Was carried out.

After the oxide film on the surface of the silicon steel sheet thus obtained was removed, a smoothing treatment by chemical polishing was performed.

Then, the silicon steel sheet, using a magnetron sputtering process to form a ceramic film 0.6 ㎛ Si ₃ N _4. At this time, the target used for plasma coating was formed as follows.

100 kg of ferrosilicon material was dissolved in a vacuum melting furnace, sheared to 10 mm x 127 mm x 476 mm, and then bonded. This bonding treatment is obtained by plating one side of the Si substrate with Cu, and then attaching it onto the Cu substrate (the magnet can be provided on the back side of the water-cooled Cu substrate) using In to form ferrosilicon. This is done for use as a target. In addition, the main components of this ferrosilicon target contained Si: 91.1%, Fe: 8.2%, Al: 0.09%, Ti: 0.08%, and other trace elements. This ferrosilicon target was inserted into a magnetron sputtering device, and a thin Si ₃ N ₄ of about 0.6 μm was deposited on a silicon steel sheet using a magnetron sputtering method using an operating power of 400 V and a current of 50 A. Coated. At the interface between the silicon steel sheet and the ceramic coating, nitrides of Fe, Al, and Ti, which are impurity elements, were detected, and adhesion was confirmed to be good, and it was also confirmed that the components of Si ₃ N ₄ were changing in the film thickness direction. It was also confirmed that the coefficient of thermal expansion also decreased with the outer layer.

The magnetic properties and adhesion of the product thus obtained are as follows.

① When the smoothing process is performed

Magnetic properties B ₈ : 1.95 T

W _17/50 : 0.58 W / kg

Even if bent 180 ° on a round bar with an adhesive diameter of 10 mm, it does not peel off.

And good.

② In case of pickling treatment

Magnetic properties B ₈ : 1.94 T

W _17/50 : 0.63 W / kg

Even if bent 180 ° on a round bar with an adhesive diameter of 10 mm, it does not peel off.

And good.

(Example 7)

Silicon steel continuous containing C: 0.044% by weight, Si: 3.39% by weight, Mn: 0.073% by weight, Se: 0.020% by weight, Sb: 0.025% by weight, and Mo: 0.012% by weight, with the remainder being substantially a composition of Fe The cast slab was heat-treated at 1340 ° C. for 3 hours and then hot rolled to obtain a hot rolled sheet having a thickness of 2.4 mm. Subsequently, after performing 900 degreeC homogenization annealing, cold rolling was performed twice with the intermediate | middle annealing of 950 degreeC in the middle, and it was set as the final cold rolled plate of thickness 0.23mm.

After that, the etch resist ink mainly containing alkyd-based resin was gravure offset printing on the surface of the final cold-rolled sheet, and the non-coated portion was formed in a line shape having a width of 200 μm in a direction substantially perpendicular to the rolling direction and a gap of 4 mm in the rolling direction. After coating to remain, it was baked at 200 ° C. for about 20 seconds. At this time, the resist thickness was 2 micrometers. In this way, electrolytic etching was performed on the steel sheet to which the etching resist was applied to form a linear groove having a width of 200 µm and a depth of 20 µm, and then immersed in an organic solvent to remove the resist. At this time, the electrolytic etching was performed under conditions of a current density of 10 A / dm 3 and a processing time of 20 seconds in a NaCl electrolyte solution.

Subsequently, after decarburization and primary recrystallization annealing is performed in 840 ° C humid hydrogen, slurry annealing separator having a composition of MgO (25%), Al ₂ O ₃ (70%) and CaSiO ₃ (5%) is applied to the surface of the steel sheet. Subsequently, secondary recrystallized grains which had been integrated into a goth orientation by isothermal annealing at 850 ° C. for 50 hours were developed, and then purified in 1200 ° C. dry hydrogen.

After removing the oxide film on the surface of the silicon steel sheet thus obtained, the surface of the unidirectional silicon steel sheet was smoothed by chemical polishing. Subsequently, Si was formed into a film having a thickness of 0.05 μm using a magnetron sputtering method, and after treatment in a mixed atmosphere of He (50%) + N ₂ (50%) at 1000 ° C. for 15 minutes, colloidal silica ( A tension insulating film (approximately 2 μm thick) formed mainly of colloidal silica) and phosphate was formed and baked at 800 ° C.

The magnetic properties and adhesiveness of the product thus obtained were as follows.

Magnetic properties B ₈ : 1.88 T

W _17/50 : 0.66 W / kg

Even if bent 180 ° on a round bar with 20 mm of adhesion

And good.

The magnetic properties of the product obtained by forming a phosphate-based tension insulating film after forming a very thin, Si-containing nitride and oxide layer on the surface of the steel sheet in the same manner as described above as it was pickled without chemical polishing. And adhesiveness is as follows.

Magnetic properties B ₈ : 1.88 T

W _17/50 : 0.68 W / kg

Even if bent 180 ° on a round bar with 20 mm of adhesion

And good.

In this way, according to the present invention, it is possible to obtain an ultra-low iron loss unidirectional silicon steel sheet which is remarkably superior in iron loss and dripping rate as compared with conventional materials.

Claims (4)

On the finish-annealed surface of the unidirectional silicon steel sheet, it has a ceramic tension coating whose thermal expansion coefficient becomes smaller toward the outer layer side, and the outermost layer of the ceramic tension coating has insulation and is rolled on the finish-annealed surface of the unidirectional silicon steel sheet. Ultra-low iron loss unidirectional silicon having a plate thickness of 0.05 to 0.5 mm with a linear concave region having a width of 50 to 500 μm and a depth of 0.1 to 50 μm at intervals of 2 to 10 mm in a direction substantially perpendicular to the direction. Grater. The ultra-low iron loss unidirectional silicon steel sheet according to claim 1, wherein the finish-annealed surface of the unidirectional silicon steel sheet is smoothed. The ultra-low iron loss unidirectional silicon steel sheet according to claim 1 or 2, wherein the droplet ratio is 98% or more. The ultra-low iron loss unidirectional silicon steel sheet according to claim 1 or 2, wherein the ceramic tension coating is two or more layers made of nitride and carbide or nitride or carbide.