JPH11131252A - Ultralow core loss grain-oriented silicon steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To furthermore reduce core loss in a steel sheet compared to the conventional case and regulating it to ultralow one, on the smoothened surface of a grain-oriented silicon steel sheet with specified sheet thickness subjected to finish annealing, by forming a ceramic tensile coating film of plural layers of nitride or carbide in such a manner that the thermal expansion coefficient is made smaller as it goes to the external layer side. SOLUTION: In a grain-oriented silicon steel sheet with 0.05 to 0.5 mm sheet thickness subjected to finish annealng, on the surface in which linear recessed regions of 50 to 500 μm width and 0.1 to 50 μm depth are formed at 2 to 10 mm interval in the approximately rectangular direction to the smoothened or rolling direction, a ceramic tensile coating film of >= two layers composed of nitride and/or carbide is formed. Moreover, as for the ceramic tensile coating film, its thermal expansion coefficient is made smaller as it goes to the external layer side, and the ceramic tensile coating outermost layer is, e.g. composed of Si3 N4 having insulating properties. Preferably, the ceramic tensile coating film is formed by ion plating or the like, its coating thickness is made thin, and the occupying volume ratio thereof is regulated to >=98%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-low iron loss unidirectional silicon steel sheet suitable for use as a core material for transformers and other electric appliances, and more particularly to a surface or wire of a smoothed silicon steel sheet. By further forming two or more layers of a ceramic tension coating made of a nitride and / or carbide on the surface of a silicon steel sheet having a concave region having the shape of a circle, iron loss characteristics are further improved.

[0002]

BACKGROUND ART unidirectional silicon steel sheet is mainly being used as transformer cores and other electrical equipment, (represented by ₈ value B) flux density as the magnetization characteristic is high, the iron loss (W
_17/50 ) is required to be low.

In order to improve the magnetic properties of a grain-oriented silicon steel sheet, first, <001> of secondary recrystallized grains in the steel sheet is required.
The shaft needs to be highly aligned in the rolling direction, and second, it is necessary to minimize impurities and precipitates remaining in the final product.

[0004] For this reason, since NPGoss proposed a basic manufacturing technique by two-stage cold rolling of a unidirectional silicon steel sheet, a number of improvements were made to the manufacturing technique, and the magnetic flux of the unidirectional silicon steel sheet was increased. Density and core loss values have improved over the years. Among them, the most typical one is the one using Sb and MnSe or MnS as an inhibitor.
JP-B-33-4710 and JP-B-40, which use AlN and MnS as inhibitors.
The method according to -15644 JP and Sho 46-23820 Patent Publication, according to these methods B ₈ is now the product is obtained having a high magnetic flux density exceeding 1.88T.

In order to obtain a product having a higher magnetic flux density, Japanese Patent Publication No. 577-14737 discloses a method in which Mo is added to a material in a complex manner.
In Japanese Patent Publication No. 62-42968, Mo is added to the material in a complex manner, and then the quenching treatment is applied after intermediate annealing immediately before the final cold rolling, so that B ₈ has a high magnetic flux density of 1.90 T or more. And iron loss W _17/50 is 1.05 W / kg (product thickness: 0.30m
m) It is disclosed that the following low iron loss can be obtained, but there is still room for improvement in sufficiently reducing iron loss.

[0006] In particular, the demand for minimizing the power loss as much as possible after the energy crisis of more than ten years ago has been remarkably increased, and with this, further improvement in the use of iron core materials is desired. Therefore, for the purpose of minimizing the eddy current loss, a large number of products having a thickness of 0.23 mm or less (9 mil) or less have been used.

[0007] All of the above-mentioned techniques are mainly metallurgical techniques, but apart from these methods, Japanese Patent Publication No. 57-2252
Irradiation of laser or plasma on the surface of the steel sheet after finish annealing as proposed in Japanese Patent Publication (B. Fukuda, K. Sato,
T.Sugiyama, A.Honda and Y.Ito: Proc. Of ASM Con.
of Hard and Soft Magnetic Materials, 8710-008, (US
A), (1987)), and a method for reducing iron loss by artificially reducing the magnetic domain width by 180 ° (magnetic domain refinement technology) was developed. With the development of this technology, the iron loss of unidirectional silicon steel sheets has been significantly reduced. However, this technique has a disadvantage that it cannot withstand annealing at high temperatures, and has a problem that its application is limited to a laminated iron core transformer that does not require strain relief annealing.

In this respect, as a magnetic domain refining technique capable of withstanding strain relief annealing, a linear groove is introduced into the surface of a unidirectional silicon steel sheet after finish annealing, and a magnetic domain is applied by utilizing the demagnetizing field effect of the groove. Has been industrialized to subdivide the technology (H. Kobayashi,
E.Sasaki, M.Iwasaki and N.Takahashi: Proc.SMM-
8., (1987), P.402). Separately, a method has been developed in which a final cold-rolled unidirectional silicon steel sheet is subjected to local electrolytic etching to form grooves and subdivide magnetic domains (Japanese Patent Publication No. 8-6140). Has been industrialized.

Further, apart from the above-described method for producing a silicon steel sheet, as disclosed in JP-B-55-19976, JP-A-57-127749 and JP-A-2-3213, Crystalline alloys have been receiving attention as materials for ordinary power transformers and high-frequency transformers. In such an amorphous material, extremely excellent iron loss characteristics can be obtained as compared with a normal unidirectional silicon steel sheet, but it lacks thermal stability, has a low space factor, and is not easily cut. However, since they are too thin and brittle, there are many practical disadvantages, such as a large increase in the cost of assembling transformers. Therefore, at present, they have not been used in large quantities.

[0010] In this regard, the present inventors have previously disclosed in Japanese Patent Publication No. 63-54767 and the like, for solving the above disadvantages.
Si, Mn, Cr, Ni, Mo, Si, Mn, Cr, Ni, Mo, etc. were applied on the grain-oriented silicon steel sheet by dry plating such as CVD, ion plating and ion implantation.
An ultra-low iron loss can be obtained by forming one or two or more tension films selected from nitrides and carbides of W, V, Ti, Nb, Ta, Hf, Al, Cu, Zr and B. Has been disclosed. This manufacturing method has made it possible to obtain extremely excellent iron loss characteristics as a material for power transformers and high frequency transformers, but nevertheless, it has sufficiently responded to recent demands for low iron loss. It was hard to be there.

[0011]

SUMMARY OF THE INVENTION The present invention advantageously meets the above-mentioned demands, and proposes an ultra-low iron loss unidirectional silicon steel sheet which realizes a further reduction in iron loss as compared with the prior art. With the goal.

[0012]

Means for Solving the Problems The inventor has made fundamental reexaminations from all viewpoints in order to respond to the above demands. That is, the inventor has applied one or more tension coatings selected from various nitrides and carbides on the surface of a unidirectional silicon steel sheet smoothed in a stable process to form an ultra-low iron. Recognizing that a fundamental review from the raw material composition of the unidirectional silicon steel sheet to the final processing step is necessary to obtain a product with loss, the texture of the silicon steel sheet From the pursuit to the smoothness of the steel sheet surface and the final CVD and PVD processing steps, intensive studies were repeated. As a result, the following findings were obtained.

(1) Even if a thin film of a ceramic (a TiN film is used as a representative example) coated on a silicon steel sheet is formed to a thickness of 1.5 μm or more, the degree of improvement in iron loss is reduced. That is, a TiN film having a thickness of 1.5 μm or more can be expected to have only a small improvement in the space factor, magnetic flux density, and iron loss. (2) In this case, the role of TiN is more important in the role of adhesion to the silicon steel sheet, in addition to the application of tension specific to ceramics. In other words, transmission electron microscope observation of the cross section of TiN
(Ichio Iguchi: Journal of the Japan Institute of Metals, 60 (1996), P.781-786
10), horizontal stripes of 10 nm were observed, which corresponded to five atomic layers of Fe—Fe atoms in the [011] direction of the silicon steel sheet. (3) Simultaneous measurement of texture of two layers by X-ray in TiN coating area and chemical polishing area (Y. Inokuti: ISIJ Internationala)
l, 36 (1996), pp. 347-352).
The {200} peak shape is circular. However, the {200} peak shape of Fe in the TiN coating region is elliptical, and the silicon steel plate is strongly tensioned in the [100] _si-steel direction. (4) Tension of TiN thin film (Ichio Iguchi, Kazuhiro Suzuki, Yasuhiro Kobayashi:
Journal of the Japan Institute of Metals, 60 (1996), p.674-678)
10 MPa, this is the magnetic flux density difference ΔB ₈ = 0.014 to 0.016 T
Can be expected to improve. (This is equivalent to increasing the degree of Goss orientation integration by about 1 °.)

The above is new knowledge on ceramic coating. Further, the following knowledge has been obtained on the surface condition of the ceramic film and the steel sheet. (5) Grooves were formed by performing local electrolytic etching on the final cold-rolled silicon steel sheet, and the steel sheet surface after the secondary recrystallization treatment was smoothed by polishing and then coated with a TiN ceramic film. In this case, in addition to the magnetic domain segmentation caused by the demagnetizing field effect caused by the introduced grooves, the iron loss can be effectively reduced by applying tension by the ceramic coating. (6) The effect of reducing iron loss by tension when a concave groove is formed on the steel sheet surface before ceramic coating is greater than that of a silicon steel sheet smoothed by ordinary polishing (Japanese Patent Publication No. 3-32889). Reference and FIG. 1). That is, when grooves are introduced, different tension acts on the surface of the silicon steel sheet, and the degree of reduction of iron loss due to tensile tension increases. (7) When a ceramic film is coated on a silicon steel plate having a concave groove, the effect of reducing iron loss is more effective than when the ceramic film is smoothed by ordinary polishing and coated with a ceramic film. In other words, as schematically shown in FIG. 2, a linear groove is introduced (FIG. 2B), the magnetic domain is subdivided by applying the demagnetizing effect of the groove, and a ceramic tension coating is formed (FIG. 2B). In FIG. C), it is more effective to subdivide the 180 ° main magnetic domain, and an ultra-low iron loss can be obtained. (8) When grooves are formed by performing local electrolytic etching on the final cold-rolled silicon steel sheet, the surface of the steel sheet after the secondary recrystallization treatment is not smoothed by polishing, Even when a ceramic film is formed, a considerable iron loss reducing effect is exhibited. In other words, even if the surface is not smoothed by polishing, for example, even if there are small irregularities on the surface due to pickling treatment or the like, a strong tensile force is applied to the surface of the silicon steel sheet by coating the ceramic film having a small coefficient of thermal expansion. Can be added, whereby the iron loss can be advantageously reduced.

Therefore, based on the above-mentioned new findings, the inventor repeated numerous experiments and studies to achieve the desired object, and as a result, introduced a silicon steel plate having a smooth surface and linear grooves. In any of the silicon steel sheets described above, it is necessary to use a plurality of types of ceramic tension coatings formed on the surface of the silicon steel sheets, and to further reduce the coefficient of thermal expansion of the ceramic tension coatings as they go outward. It was found that it was extremely effective in achieving the expected purpose. The present invention is based on the above findings.

That is, according to the present invention, the thickness is 0.05 to 0.5.
mm having two or more ceramic tension coatings of nitride and / or carbide on the smoothed surface of a finish-annealed unidirectional silicon steel sheet, the ceramic tension coating comprising:
An ultra-low iron loss unidirectional silicon steel sheet (first invention) characterized in that its coefficient of thermal expansion decreases toward the outer layer side and the outermost ceramic tension coating has insulating properties.

Further, according to the present invention, a linearly annealed silicon steel sheet having a thickness of 0.05 to 0.5 mm is linearly formed at an interval of 2 to 10 mm in a direction substantially perpendicular to the rolling direction,
The steel plate has a linear concave region having a width of 50 to 500 μm and a depth of 0.1 to 50 μm, and further has two or more ceramic tension coatings made of nitride and / or carbide on the surface of the steel sheet. The ceramic tension coating is an ultra-low iron loss unidirectional silicon steel sheet (second invention) characterized in that the coefficient of thermal expansion decreases toward the outer layer side, and the outermost ceramic tension coating has insulating properties. is there.

In the second aspect of the present invention, the surface of the annealed finish-oriented silicon steel sheet is a surface that has been subjected to a smoothing treatment, but is a surface that has not been subjected to a smoothing treatment and that has not been subjected to a pickling treatment. Or any of them. In the first and second aspects of the present invention, it is advantageous to reduce the film thickness so that the space factor is 98% or more.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the process leading to the success of the present invention and the contents of the invention will be specifically described.
FIGS. 3 (a), (b) and (c) show (a) the current unidirectional silicon steel sheet, (b) the TiN-coated unidirectional silicon steel sheet, and (c) the ultra-low iron loss of the present invention, respectively. The cross section near the surface of the unidirectional silicon steel sheet is compared and shown schematically. The figures in parentheses in each figure show the space factor, and the numbers in each figure show the coefficient of thermal expansion (10 ^-6 / K). (A) The current unidirectional silicon steel sheet is a forsterite undercoat with a thermal expansion coefficient of 11 × 10 ⁻⁶ / K on a silicon steel sheet with a thermal expansion coefficient of 13 × 10 ⁻⁶ / K. And an insulating film having a thermal expansion coefficient of 5 × 10 ⁻⁶ / K is further formed thereon to reduce iron loss and improve magnetostriction characteristics. The space factor of the silicon steel sheet in this case is about 96.5%. Also, the TiN-coated unidirectional silicon steel sheet of (b)
A thin TiN film with a thickness of about 1 μm was formed on a silicon steel sheet, and an insulating film was formed thereon.
In this case, the thermal expansion coefficient of the TiN coating is 8 × 10 ⁻⁶ / K, which is lower than the thermal expansion coefficient of the forsterite base coating: 11 × 10 ⁻⁶ / K, and a stronger tension can be applied to the silicon steel sheet. Further, it is possible to further reduce iron loss and improve magnetostriction characteristics. In this case, the space factor of the silicon steel sheet is about 97.5%, which is improved by about 1%. On the other hand, the ultra-low iron loss silicon steel sheet of the present invention (c) has a thin TiN (0.01 to 0.5
μm) and a coefficient of thermal expansion of 3 × 10 ⁻⁶ /
Si ₃ N ₄ (0.3 to 1.
This is an ultra-low iron loss silicon steel sheet having a thin nitride ceramic coating with a two-layer structure and a thickness of 5 μm. In this case, the space factor of the silicon steel sheet is about 99%, which can be said to be the ultimate silicon steel sheet.

FIG. 4 shows a comparison of changes in iron loss due to tension of a silicon steel sheet having two types of thin nitride-based ceramic coatings shown in FIGS. 5 (a) and 5 (b). As shown in FIG. 4, the TiN-Si ₃ N according to the present invention of (b) is compared with the case where the TiN film is simply formed on the silicon steel sheet of (a).
_{4 If} two layers of thin nitride ceramic coating are applied,
It is noted that the change in iron loss due to tension is small. That is, in the case of (b), it can be seen that ultra-low iron loss is achieved because more effective tension is applied to the silicon steel sheet.

Next, the above-described first invention will be described with reference to specific experimental examples. C: 0.072 wt% (hereinafter simply indicated as%), Si: 3.44%, M
n: 0.085%, Se: 0.023%, Sb: 0.028%, Al: 0.025
%, N: 0.0082% and Mo: 0.013%, with the balance being 1360.
After 4 hours of heat treatment at ℃, hot-rolled to achieve a thickness of 2.0
mm hot rolled sheet. This hot-rolled sheet was subjected to uniform annealing at 980 ° C. for 3 minutes, and then twice rolled with intermediate annealing at 960 ° C. to obtain a final cold-rolled sheet having a sheet thickness of 0.23 mm. afterwards,
After decarburization and primary recrystallization annealing in 840 ° C wet hydrogen,
The surface of the steel sheet was coated with an annealing separator containing MgO as the main component, and the temperature was raised from 850 ° C to 1050 ° C at a rate of 8 ° C / h to develop secondary recrystallized grains that were strongly integrated in the Goss orientation. Thereafter, a purification treatment was performed in dry hydrogen at 1220 ° C.

After removing the surface coating of the product thus obtained, smoothing the surface of the silicon steel sheet by chemical polishing, TiN (ion plating by HCD method) of about 0.2 μm was applied on the silicon steel sheet surface. After forming the thickness, Si ₃ N ₄ was further formed thereon to a thickness of 0.5 μm. Table 1 shows the results of measuring the magnetic properties of the silicon steel sheet at this time. Table 1 shows, for comparison, TiN-coated silicon steel sheet,
The magnetic properties of the existing silicon steel sheets (all after magnetic domain refinement) are also shown.

[0023]

[Table 1]

[0024] Table 1 as apparent from the compared to _{W 17/50 (W / kg) =} 0.80 W / kg for the current silicon steel sheet (comparative material), the TiN coated silicon steel sheet of W _{17 / 50} (W / kg) 0.62 W /
kg and excellent. However, according to the first invention of T
The _W17 / ₅₀ (W / kg) of a silicon steel sheet coated with a two-layer (0.7 μm) ceramic coating of iN and Si ₃ N ₄ has improved remarkably to 0.55 W / kg. In this case, the space factor is 99.0%.
It is noted that the and are much better than.

As described above, the remarkable improvement of the magnetic properties in the first invention is achieved by smoothing the surface of a silicon steel sheet having developed secondary recrystallized grains strongly integrated in the Goss orientation to facilitate the movement of the domain wall, Furthermore, two layers of TiN + Si ₃ N ₄ (
0.7 .mu.m) of ceramic coating.

The above is the content of the ceramic film to be formed on the surface of the silicon steel sheet. Next, the relationship between the surface state of the silicon steel sheet and the ceramic film will be described. FIG.
The results of investigations on changes in iron loss when tension is applied to silicon steel sheets having various surface conditions are shown below. In the figure,
(a) to (e) are the following iron loss reduction curves, respectively. (a) On the surface of the final cold-rolled unidirectional silicon steel sheet, at a distance of 4 mm in a direction substantially perpendicular to the rolling direction and at a width of 200 μm.
After forming a linear concave region with a depth of 20 μm and then subjecting it to finish annealing to develop secondary recrystallization in the (110) [001] orientation, a tension is applied after the steel plate surface is chemically polished. The iron loss reduction curve (solid line). (b) After the surface of the unidirectional silicon steel sheet after finish annealing is smoothed by chemical polishing, the width is 200 μm and the depth is 20 μm on the steel sheet surface at intervals of 4 mm in a direction substantially perpendicular to the rolling direction.
The iron loss reduction curve (dot-dash line) when a linear concave region is formed and then tension is applied. (c) On the surface of the final cold-rolled unidirectional silicon steel sheet, a linear concave area is formed using a knife at intervals of 4 mm in a direction substantially perpendicular to the rolling direction, and then subjected to finish annealing. After doing
Iron loss reduction curve (two-dot chain line) when tension is applied after chemical polishing of the steel sheet surface. (d) After the surface of a unidirectional silicon steel sheet after finish annealing is smoothed by chemical polishing, a linear concave area is formed on the steel sheet surface at a distance of 4 mm in a direction substantially perpendicular to the rolling direction using a knife. And iron loss reduction curve (three-dot chain line) when tension is applied. (e) Iron loss reduction curve (dotted line) when tension is applied after smoothing the surface of a unidirectional silicon steel sheet after finish annealing by chemical polishing.

As shown in the figure, in the iron loss reduction curves under these tensile tensions, the degree of iron loss reduction of the silicon steel sheet by the tensile tension is the largest under the conditions of (a) and (b), and then (c) ) And (d), and (e). Here, under the conditions of (a) and (b), as shown in FIG. 2, since the different tension near the steel sheet surface acts effectively,
It is considered that the degree of reduction in iron loss is the largest.

Next, the above-described second invention will be described with reference to specific experimental examples. C: 0.074%, Si: 3.35%, Mn: 0.069%, Se: 0.021
%, Sb: 0.025%, Al: 0.025%, N: 0.0072% and
A continuous cast silicon steel slab containing Mo: 0.012%, with the balance being substantially Fe, was heated at 1350 ° C for 4 hours.
Hot rolling was performed to obtain a hot-rolled sheet having a sheet thickness of 2.0 mm. After subjecting this hot rolled sheet to homogenizing annealing at 970 ° C for 3 minutes, 1050 ° C
Was rolled twice, with intermediate annealing being performed, to obtain a final cold-rolled sheet having a sheet thickness of 0.23 mm.

Thereafter, the final cold-rolled sheet was processed as follows. On the surface of the final cold-rolled sheet, an etching resist ink containing an alkyd-based resin as a main component is subjected to gravure offset printing so that a non-applied portion has a width of approximately 200 at right angles to the rolling direction.
The coating was performed so as to remain linearly at a distance of 4 mm, and then baked at 200 ° C. for 3 minutes. At this time, the resist thickness was 2 μm. By performing electrolytic etching on the steel sheet coated with the etching resist in this way,
A linear groove having a width of 200 μm and a depth of 20 μm was formed, and then immersed in an organic solvent to remove the resist. At this time, the electrolytic etching was performed in a NaCl electrolyte at a current density of 10 A / m ² ,
Processing time: 20 seconds. For comparison, a final cold-rolled sheet not subjected to the above treatment was also prepared.

Thereafter, each of these steel sheets was heated to 840 ° C.
After decarburization and primary recrystallization annealing in wet hydrogen, the steel sheet surface has an MgO (25%), Al ₂ O ₃ (70%), CaSiO ₃ (5%) component annealing separator Slurry and then 8
After annealing at 50 ° C for 15 hours, the temperature was raised to 1150 ° C at a rate of 10 ° C / h to develop secondary recrystallized grains strongly integrated in the Goss orientation, and then purified in dry hydrogen at 1200 ° C. did.

After the surface coating of the product thus obtained was removed, the surface of the silicon steel sheet was smoothed by chemical polishing, and TiN (ion plating by the HCD method) of about 0.2 μm was applied on the surface of the silicon steel sheet. After forming the thickness, Si ₃ N ₄ was further formed thereon to a thickness of 0.5 μm. Table 2 shows the results of measuring the magnetic properties of the silicon steel sheet at this time. Table 2 also shows, for comparison, magnetic property values of a silicon steel sheet coated only with TiN.

[0032]

[Table 2]

As is clear from Table 2, a concave linear groove was formed on the surface of the steel sheet in accordance with
When a two-layer ceramic coating of 2 μm) + Si ₃ N ₄ (0.5 μm) was applied, the magnetic flux density was reduced by 0.04 to _{0.05 T} as compared with the previous case, but the iron loss W _17/50 was 0.45 W / kg. It is noteworthy that the number has been significantly reduced.

As described above, the remarkable improvement of the magnetic characteristics in the second invention is achieved by forming a concave linear groove on the surface of a silicon steel sheet before ceramic coating, and applying the demagnetizing effect of the groove to the magnetic domain. After performing the subdivision is achieved by further effectively perform the domain refining by further made two layers of TiN + Si ₃ N ₄ ceramic coating (0.7 [mu] m) to be formed thereon.

The ceramic coating formed on the surface of the silicon steel sheet is made of Si, Mn, Cr, Ni, Mo, W, V, Ti, Nb, Ta,
It is selected from nitrides or carbides of Hf, Al, Cu, Zr and B. What is important here is that the thermal expansion coefficient decreases as it goes to the outer layer side. It is to provide.

In this case, the total thickness of the ceramic coating is preferably about 0.3 to 2 μm. This is because if the film thickness is less than 0.3 μm, the effect of improving iron loss is small because the tensile effect is small, while if it exceeds 2 μm, the space factor and the magnetic flux density decrease.

As described above, the present invention is not only excellent in iron loss and space factor, but also excellent in magnetostriction, heat resistance and insulation, as compared with conventional silicon steel sheets. Ultra low iron loss unidirectional silicon steel sheet.

[0038]

The silicon-containing steel used as the material of the present invention is compatible with any of the conventionally known component compositions, but the typical compositions are as follows.

C: 0.01 to 0.08 If C is less than 0.01%, the suppression of hot rolled texture is insufficient and large elongated grains are formed, so that the magnetic properties are degraded. Since it is not economical because decarburization takes a long time, it is preferable to be 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, so eddy current loss increases and iron loss deteriorates.
%, Brittle cracks are likely to occur during cold rolling.
It is preferable to be in the range of about 2.0 to 4.0%.

Mn: 0.01 to 0.2% Mn is an important component that determines MnS or MnSe as a dispersed precipitation phase which affects secondary recrystallization of a unidirectional silicon steel sheet. When the amount of Mn is less than 0.01%, the absolute amount of MnS or the like necessary for causing secondary recrystallization becomes insufficient, causing incomplete secondary recrystallization and increasing surface defects called blisters. On the other hand, if it exceeds 0.2%, even if dissociated solid solution of MnS or the like is performed in slab heating or the like, the dispersed precipitate phase precipitated during hot rolling tends to be coarse, and the optimal size distribution desired as an inhibitor is impaired. Since the magnetic properties are degraded, it is preferable that Mn be about 0.01 to 0.2%.

S: 0.008 to 0.1%, Se: 0.003 to 0.1% Both S and Se are 0.1% or less, especially S is 0.008 to 0.1%.
% Or Se is preferably in the range of 0.003 to 0.1%. The reason is that if these contents exceed 0.1%, the hot and cold workability deteriorates, and if they do not reach the lower limits, respectively, there is no particular effect on the primary grain growth suppressing function as MnS and MnSe. is there. In addition, even if Al, Sb, Cu, Sn, B and the like conventionally known as inhibitors are added in combination,
It does not prevent the effect of the present invention.

Next, the manufacturing process of the ultra-low iron loss unidirectional silicon steel sheet according to the present invention will be described. First, in order to melt the raw material, it is possible to use not only a LD converter, an electric furnace, an open hearth furnace, and other known steelmaking furnaces but also vacuum melting and RH degassing.

According to the present invention, S,
As a method for adding a small amount of Se or another primary grain growth inhibitor to molten steel, any conventionally known method may be used. For example, LD converter, RH degassing at the end of molten steel or at the time of ingot casting Can be added. In slab production, it is advantageous to use the continuous casting method because of economic and technical advantages such as cost reduction and uniformity of components or quality in the slab longitudinal direction. It does not hinder.

The continuous cast slab is heated to a temperature of 1300 ° C. or higher in order to dissociate the inhibitor in the slab and form a solid solution. Thereafter, the slab is subjected to hot rough rolling and then hot finish rolling to form a hot rolled sheet having a thickness of usually about 1.3 to 3.3 mm.

Next, if necessary, the hot-rolled sheet is subjected to two cold rolling steps with intermediate annealing in the temperature range of 850 to 1100 ° C. to obtain a final sheet thickness. It is necessary to pay attention to the final cold rolling rate (usually about 55 to 90%) to obtain a product having characteristics. At this time, from the viewpoint of minimizing the eddy current loss of the silicon steel sheet, the upper limit of the product thickness is 0.5 mm,
In order to avoid the adverse effect of hysteresis loss,
Limited to 0.05mm.

According to the second aspect of the present invention, when a linear groove is formed on the surface of the steel sheet, it is particularly advantageous to perform the processing on the steel sheet which has been subjected to the final cold rolling to have a product thickness. That is,
On the surface of the final cold-rolled sheet or the steel sheet before and after the secondary recrystallization, at an interval of 2 to 10 mm in a direction substantially perpendicular to the rolling direction, width: 50 to 50
A linear concave region having a depth of 500 μm and a depth of 0.1 to 50 μm is formed. Here, the reason why the interval between the linear concave regions is limited to the range of 2 to 10 mm is that if it is less than 2 mm, the unevenness of the steel sheet becomes too remarkable, the magnetic flux density decreases, and it is not economical.
This is because if it exceeds 10 mm, the effect of magnetic domain refining becomes small. If the width of the concave region is less than 50 μm, it is difficult to utilize the demagnetizing effect.On the other hand, if it exceeds 500 μm, the magnetic flux density decreases and it is not economical.
Limited to the range of 50-500 μm. Furthermore, if the depth of the concave region is less than 0.1 μm, the demagnetizing field effect cannot be effectively used.On the other hand, if it exceeds 50 μm, the magnetic flux density decreases and it is not economical. It was limited to the range of 0.1 to 50 μm.

As a method of forming the linear concave region, a method of applying an etching resist to the surface of the final cold-rolled sheet by printing, baking, applying an etching treatment, and then removing the resist, has conventionally been used. This method is advantageous in that it can be carried out industrially stably and that iron loss can be more effectively reduced by tensile tension, as compared with the method using a blade edge of a knife or a laser.

Hereinafter, a typical example of the above-described linear groove forming technique by etching will be specifically described. An etching resist ink containing an alkyd resin as a main component is gravure offset printed on the surface of the final cold-rolled sheet so that the non-applied portion remains linearly at a right angle to the rolling direction with a width of 200 μm and a spacing of 4 mm in a line. After applying, bake at 200 ° C for about 20 seconds. At this time, the resist thickness is about 2 μm.
The steel plate coated with the etching resist in this way,
By performing electrolytic etching or chemical etching, a linear groove having a width of 200 μm and a depth of 20 μm is formed.
Next, the resist is removed by immersion in an organic solvent. The electrolytic etching conditions at this time are as follows:
10 A / m ² , treatment time: about 20 seconds, and chemical etching conditions: immersion time in HNO ₃ solution: about 10 seconds.

Next, the steel sheet is subjected to decarburization annealing. This annealing makes the cold rolled structure the primary recrystallized structure,
{110} <00 in final annealing (also called finish annealing)
1) For the purpose of removing harmful carbon when secondary recrystallized grains having an orientation are developed, the process is performed in, for example, 750 to 880 ° C. in wet hydrogen.

The final annealing is performed to sufficiently develop secondary recrystallized grains having a {110} <001> orientation.
Usually, it is carried out by immediately raising the temperature to 1000 ° C. or higher by box annealing and maintaining the temperature. This final annealing is usually performed by applying an annealing separating agent such as magnesia, and a base coat called forsterite is simultaneously formed on the surface. However, in the present invention, even if a forsterite undercoat is formed, an annealing separator that does not form such a forsterite undercoat is more advantageous because the undercoat is removed in the next step. That is, to reduce the content ratio of MgO to form a forsterite base coating (50%), behalf Kakaru coating a not formed Al ₂ O _3, CaSiO high content of such ₃ (50%) were the annealing separator Agents are advantageous.

In the present invention, in order to develop a secondary recrystallized structure highly integrated in the {110} <001> orientation, it is advantageous to carry out the constant annealing at a low temperature of 820 ° C. to 900 ° C. For example, slow annealing at a heating rate of about 0.5 to 15 ° C./h may be used.

After this purification annealing, the forsterite undercoat or oxide film on the surface of the steel sheet is removed by a known chemical method such as pickling, a mechanical method such as cutting or polishing, or a combination thereof. Is smoothed. That is, after removing various coatings on the surface of the steel sheet, the center line average roughness Ra is 0.4 μm or less by a conventional method such as chemical polishing such as chemical polishing, electrolytic polishing, mechanical polishing such as buff polishing, or a combination thereof. Smooth the steel sheet surface to the extent.

In the case where a linear concave region is formed on the surface of a silicon steel sheet according to the second invention, the surface of the steel sheet does not necessarily need to be smoothed. Therefore, in this case, there is an advantage that a sufficient iron loss reduction effect can be exhibited only by the pickling treatment without performing the smoothing treatment accompanied by the cost increase. Nevertheless, in the second invention, it is still advantageous to perform the smoothing process.

Next, on the surface of the silicon steel sheet after the smoothing treatment, Si, Mn, Cr, Ni, Mo, W, V, Ti, Nb, T are formed by using various methods such as PVD, CVD or sputtering.
A ceramic tension coating is formed by forming at least two layers of a tension coating consisting of one or more selected from nitrides or carbides of a, Hf, Al, Cu, Zr and B. In forming such a ceramic tension coating, it should be noted that the thermal expansion coefficient is reduced toward the outer layer side as described above, and the outermost ceramic coating is provided with insulating properties. Here, the total thickness of the ceramic tension coating is preferably about 0.3 to 2 μm as described above.

Regarding the formation of the above-mentioned ceramic tension film, the case where the formed ceramic film is clearly divided into two layers is shown in FIGS. 3 (c) and 5 (b) described above. In this case, the boundaries of the ceramic layers do not necessarily need to be clearly defined as described above, and the components of each layer may be in a state of being mutually diffused into other layers. Should be smaller as it goes to the outer layer side.

[0057]

【Example】

Example 1 C: 0.073%, Si: 3.42%, Mn: 0.073%, Se: 0.021
%, Sb: 0.026%, Al: 0.025% and Mo: 0.014%, with the balance being substantially Fe, silicon steel continuous cast slabs were heated at 1340 ° C for 4 hours. Rolling was performed to obtain a hot-rolled sheet having a thickness of 1.8 mm. Then, after performing uniform annealing at 900 ° C, insert intermediate annealing at 950 ° C2
Cold rolling was performed twice to obtain a final cold rolled sheet having a thickness of 0.23 mm. In the rolling, warm rolling at 350 ° C. was performed.
Then, after performing decarburization and primary recrystallization annealing in 820 ° C wet hydrogen, apply MgO slurry on the steel sheet surface,
After performing the secondary recrystallization annealing at 850 ° C. for 50 hours, the annealing was performed in dry hydrogen at 1220 ° C.

Next, after the surface of the steel sheet was smoothed by pickling and chemical polishing, two layers of various ceramic coatings were formed by PVD and magnetron sputtering, followed by magnetic domain refining. Table 3 shows the results of an investigation on the magnetic properties of the product thus obtained. Table 3 also shows, for comparison, the results of a study on the magnetic properties of the TiN-coated silicon steel sheet and the existing silicon steel sheet (both after magnetic domain refinement).

[0059]

[Table 3]

As is clear from the table, all of the silicon steel sheets obtained according to the present invention have more excellent iron loss values and space factors as compared with conventional materials.

Example 2 C: 0.074%, Si: 3.46%, Mn: 0.077%, sol.
025%, N: 0.0074%, Se: 0.021%, Mo: 0.011%,
A silicon steel continuous cast slab containing 0.21% Cu and 0.023% Sb, with the balance substantially consisting of Fe, at 1260 ° C
After 40% repressurizing, the temperature is slowly raised to 1360 ° C. at a rate of 1.5 ° C./min, followed by soaking at 4 ° C., followed by hot rolling to a thickness of 1.8 mm. It was a rolled sheet. Then, after uniform annealing at 1050 ° C., cold rolling was performed twice with intermediate annealing at 1000 ° C. to obtain a final cold-rolled sheet having a thickness of 0.23 mm. In the rolling, warm rolling at 300 ° C. was performed. Then, after decarburization and primary recrystallization annealing in 840 ° C wet hydrogen, apply MgO slurry on the steel sheet surface,
After the temperature was increased from 1080 ° C. to 1080 ° C. at a temperature increasing rate of 12 ° C./h for secondary recrystallization, annealing was performed in dry H ₂ at 1220 ° C.

Thereafter, the surface of the steel sheet is smoothed by pickling and chemical polishing, and then the magnetron sputtering method is used.
The iron loss and space factor of the product after the formation of two layers (0.6 μm) of TiN + Si ₃ N ₄ and subjected to magnetic domain refinement were measured. W _17/50 = 0.53 W / kg _Space factor = An excellent characteristic value of 99.1% 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
A continuously cast silicon steel slab containing Mo: 0.012%, with the balance being substantially Fe, is subjected to soaking at 1350 ° C for 5 hours, hot-rolled, and hot-rolled to a thickness of 2.1 mm. Board.
Next, after performing uniform annealing at 950 ° C., the steel sheet was subjected to two cold rollings with intermediate annealing at 1050 ° C. to obtain a final cold-rolled sheet having a thickness of 0.23 mm.

Thereafter, the following three treatments were performed on the steel sheet surface. On the surface of the final cold-rolled sheet, the non-applied part is almost perpendicular to the rolling direction with a gravure offset printing of an etching resist ink containing an alkyd resin as a main component. Width: 200 μm
, Spacing: 4mm
Bake at 200 ° C. for about 20 seconds. At this time, the resist thickness was 2 μm. The steel sheet coated with the etching resist in this manner is subjected to electrolytic etching to obtain a width:
A linear groove having a thickness of 200 μm and a depth of 20 μm was formed, and then immersed in an organic solvent to remove the resist. The electrolytic etching at this time was performed in a NaCl electrolytic solution under the conditions of a current density of 10 A / m ² and a processing time of 20 seconds. Then, after decarburization and primary recrystallization annealing in wet hydrogen at 840 ° C, MgO (2
5%), Al ₂ O ₃ (70%), CaSiO ₃ (5%) Annealed separating agent is applied by slurry, then annealed at 850 ° C for 15 hours, then at 1150 ° C at a rate of 10 ° C / h. Temperature to 1200 ° C after developing secondary recrystallized grains strongly integrated in Goss orientation
In pure hydrogen. After the final cold-rolled sheet was subjected to decarburization / primary recrystallization annealing in 840 ° C wet hydrogen, linear grooves were formed on the surface of the decarburized / primary recrystallization annealing sheet in the same manner as described above. . Thereafter, an annealing separator having a component composition of MgO (25%), Al ₂ O ₃ (70%), and CaSiO ₃ (5%) was applied to the surface of the steel sheet by slurry, and then 850%.
After annealing at 15 ° C for 15 hours, the temperature was raised to 1150 ° C at a rate of 10 ° C / h to develop secondary recrystallized grains strongly integrated in the Goss orientation, and then purified in dry hydrogen at 1200 ° C. . The final cold-rolled sheet is subjected to decarburization and primary recrystallization annealing in wet hydrogen at 840 ° C., and secondary annealing (110) [001] is developed by final annealing in the same manner as above. After removing the oxide film on the surface of the steel sheet, and then smoothing the surface by chemical polishing, a linear groove was formed in the same manner as described above.

Next, two layers of various ceramic coatings 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 investigation on the magnetic properties of the products thus obtained. Table 4 shows, for comparison, TiN coated silicon steel sheet and existing silicon steel sheet.
The results of examining the magnetic properties of each (after magnetic domain refinement) are also shown.

[0066]

[Table 4]

As is clear from the table, each of the silicon steel sheets obtained according to the present invention has much more excellent iron loss characteristics as compared with conventional materials.

Example 4 C: 0.043%, Si: 3.34%, Mn: 0.068%, Se: 0.020
%, Sb: 0.025% and Mo: 0.012%, with the balance being 13%.
After heating at 30 ° C. for 3 hours, hot rolling was performed to obtain a hot-rolled sheet having a thickness of 2.4 mm. Then, after uniform annealing at 900 ℃, 950 ℃
Was subjected to two times of cold rolling with intermediate annealing being carried out to obtain a final cold-rolled sheet having a thickness of 0.23 mm. Then, on the surface of the final cold-rolled sheet, an etching resist ink containing an alkyd resin as a main component is gravure offset printed, and the non-applied part remains linearly at a right angle to the rolling direction with a width of 200 μm and an interval of 4 mm in a linear manner. After baking, it was baked at 200 ° C. for about 20 seconds. At this time, the resist thickness was 2 μm. The steel plate coated with the etching resist in this manner was subjected to electrolytic etching 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 a NaCl electrolytic solution under the conditions of a current density of 10 A / m ² and a processing time of 20 seconds. After that, decarburization and primary recrystallization annealing are performed in 840 ° C wet hydrogen,
Next, MgO (25%), Al ₂ O ₃ (70%), CaSiO
₃ After applying an annealing separator having a composition of (5%) as a slurry, it was kept at 850 ° C for 50 hours by holding annealing (110).
After developing secondary recrystallized grains which were strongly integrated in the [001] orientation, they were purified in dry hydrogen at 1200 ° C.

The oxide film on the surface of the silicon steel sheet thus obtained was removed, the surface was smoothed by chemical polishing, and a two-layer (0.7 μm) of TiN + Si ₃ N ₄ was coated by magnetron sputtering. Done. When the iron loss and the space factor of the product thus obtained were measured, excellent characteristic values of _W17 / ₅₀ = 0.49 W / kg space factor = 98.8% were obtained.

Example 5 C: 0.079%, Si: 3.46%, Mn: 0.086%, Se: 0.022
%, Sb: 0.023%, Al: 0.026% and Mo: 0.012%, with the balance being substantially Fe, the silicon steel continuous cast slab was heated at 1350 ° C for 3 hours, and then hot rolled. This was a hot rolled sheet having a thickness of 2.2 mm. Then, cold rolling was performed twice with intermediate annealing therebetween to obtain a final cold-rolled sheet having a thickness of 0.23 mm.
Then, on the surface of the final cold-rolled sheet, an etching resist ink containing an alkyd-based resin as a main component is subjected to gravure offset printing so that the non-applied portion has a width of approximately 200 perpendicular to the rolling direction.
The coating was performed so as to remain linearly at a distance of 4 mm and baked at 200 ° C. for about 20 seconds. At this time, the resist thickness was 2 μm. By performing electrolytic etching on the steel sheet coated with the etching resist in this manner, a linear groove having a width of 200 μm and a depth of 20 μm is formed,
Then, the resist was immersed in an organic solvent to remove the resist. At this time, the electrolytic etching was performed at a current density of 10 A /
m ² , treatment time: 20 seconds. Thereafter, decarburization and primary recrystallization annealing were performed in 845 ° C. wet hydrogen, and then MgO (25%), Al ₂ O ₃ (70%), CaSiO ₃ (3%) and SnO ₂ (2 %), And after annealing at 850 ° C for 15 hours, the temperature was raised to 1100 ° C at a rate of 10 ° C / h, and the secondary recrystallized grains strongly integrated in the Goss orientation After the development of, a purification treatment was performed in dry hydrogen at 1200 ° C.

Then, after the oxide on the steel sheet surface was removed by performing pickling treatment in 30% HCl (80%), the coil was divided into two parts, and the first half of the coil was divided by magnetron sputtering. Si ₃ N ₄ film (0.3μm thickness) and AlN film
(0.2 μm thickness) were formed into two layers. On the other hand, for the latter half of the coil, a low-purity AlN film (as an impurity in the ceramic coating) was used as the first layer using magnetron sputtering.
Fe, Ti and Al content approx. 1.5%; 0.3 μm thickness), 2nd
Two layers of a high-purity AlN film (AlN purity in the ceramic film: 99% or more) were formed thereon. The iron loss and space factor of the product thus obtained were measured. The first half of the coil W _17/50 = 0.59 W / kg The space factor = 99.1% The second half of the coil W _17/50 = 0.58 W / kg The space factor = An excellent characteristic value of 99.2% was obtained.

[0072]

As described above, according to the present invention, it is possible to obtain an ultra-low iron loss unidirectional silicon steel sheet having a much better iron loss and space factor than conventional materials.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between tensile strength and iron loss of a unidirectional silicon steel sheet subjected to a chemical polishing treatment and a groove introduction treatment.

FIG. 2 shows (a) an ordinary Goss orientation secondary recrystallization structure, (b) a magnetic domain pattern when a linear groove is introduced into this structure, and (c) a case where a ceramic tension coating is further applied. It is.

FIG. 3 shows cross sections near the surface of (a) the current unidirectional silicon steel sheet, (b) the TiN-coated unidirectional silicon steel sheet, and (c) the ultra-low iron loss unidirectional silicon steel sheet of the present invention. FIG. 3 is a schematic diagram showing a comparison.

FIG. 4 is a graph showing the relationship between tensile tension and iron loss characteristics.

FIG. 5 shows (a) a unidirectional silicon steel sheet in which a TiN film is simply formed on a silicon steel sheet, and (b) TiN-Si ₃ N according to the present invention.
FIG. 4 is a schematic diagram showing a cross section near the surface of a unidirectional silicon steel sheet coated with _four thin nitride ceramic coatings.

FIG. 6 is a graph showing the relationship between tensile strength and iron loss when tension is applied to silicon steel sheets having various surface states.

Claims (5)

[Claims] 1. The method according to claim 1, wherein a nitride and / or a nitrided steel sheet are coated on a smoothed surface of a finish-annealed unidirectional silicon steel sheet having a thickness of 0.05 to 0.5 mm.
Alternatively, it has two or more ceramic tension coatings made of carbide, and the ceramic tension coating has a smaller thermal expansion coefficient toward the outer layer side, and the outermost ceramic tension coating has an insulating property. Ultra low iron loss unidirectional silicon steel sheet. 2. A linearly formed silicon steel sheet having a thickness of 0.05 to 0.5 mm and having a thickness of 0.05 to 0.5 mm, formed linearly at an interval of 2 to 10 mm in a direction substantially perpendicular to the rolling direction, at a width of 50 to 50 mm. 500 μm
, Having a linear concave area of 0.1 to 50 μm depth, and further having, on the surface of the steel sheet, two or more ceramic tension coatings made of nitride and / or carbide, and the ceramic tension coating is An ultra-low iron loss unidirectional silicon steel sheet, wherein the coefficient of thermal expansion decreases toward the outer layer, and the outermost ceramic tension coating has insulating properties. 3. The ultra-low-loss unidirectional silicon steel sheet according to claim 2, wherein the surface of the finish-annealed unidirectional silicon steel sheet is a surface subjected to a smoothing treatment. 4. The ultra-low iron loss unidirectional silicon steel sheet according to claim 2, wherein the surface of the finish-annealed unidirectional silicon steel sheet is an as-picked surface that is not subjected to a smoothing treatment. 5. The space factor according to claim 1, wherein the space factor is 98.
% Ultra-low iron loss unidirectional silicon steel sheet.