JPH11286786A - Equipment for producing ultralow core loss grain-oriented silicon steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equipment for producing a grain-oriented silicon steel sheet markedly excellent in core loss extremely inexpensively compared to a conventional case and also with high productivity. SOLUTION: As a treating equipment forming a tensile insulating film on the surface of a grain-oriented silicon steel sheet subjected to finish annealing, a pretreating tank 1 composed of a chloride bath essentially consisting of SiCI4 , a primary heat treating furnace 2 in which drying and heat treatment are executed after that, a substrate treating tank 3 in which the surface of the silicon steel sheet subjected to the pretreatment is coated with a treating soln. in which a trace amt. of inorganic compd. contg. one or >=two kinds selected from Si, Fe, Al and B is added to a diluted soln. obtd. by diluting a coating soln. for a tensile insulating film essentially consisting of phosphate and colloidal silica with water, a secondary heat treating furnace 4 in which drying and heat treatment are executed after that, a tensile insulating film coating tank 5 in which the surface of the silicon steel sheet where the substrate film has been formed is coated with a coating soln. for a tensile insulating film essentially consisting of phosphate and colloidal silica and an annealing furnace 6 in which drying and backing treatment are executed after that are arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facility for manufacturing an ultra-low iron loss unidirectional silicon steel sheet, and more particularly to a method for forming a tension insulating film on a surface of a silicon steel sheet which has been subjected to finish annealing. By effectively improving the adhesion to a silicon steel sheet, it is intended to further improve iron loss characteristics at low cost.

[0002]

BACKGROUND ART grain oriented 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, it is necessary to first align the <001> axis of the secondary recrystallized grains in the steel sheet in the rolling direction, and secondly, to make the final It is necessary to minimize impurities and precipitates remaining in the product.

[0004] For this reason, since NPGoss proposed a basic manufacturing technique by two-stage cold rolling of a grain-oriented silicon steel sheet, a number of improvements have been made to the technique, and the magnetic flux density and the density of the grain-oriented silicon steel sheet have been improved. Iron loss values have improved over the years. Among them, the most typical ones are Sb and MnSe or
JP-B-51-13469 using MnS as an inhibitor, and JP-B-33-4710 and JP-B-40-156 using AlN and MnS as inhibitors.
The method according to 44 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] Apart from this, significant improvements have also been made from the standpoint of insulating coatings on unidirectional silicon steel sheets. That is,
The silicon steel sheet currently on the market is designed to reduce iron loss and improve magnetostriction by applying tension to the steel sheet by utilizing the difference in the coefficient of thermal expansion between the steel sheet and the insulating film of the forsterite-based undercoat. ing. As a typical method of forming an insulating film, a method using a coating solution containing aluminum phosphate, colloidal silica and chromic anhydride as main components disclosed in Japanese Patent Publication No. 53-28375, and Japanese Patent Publication No. 56-28375. No. 52117 discloses a co-polymer containing magnesium phosphate, colloidal silica and chromic anhydride as main components.
A method using a kink solution is used.

[0008] 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 the grain-oriented silicon steel sheet 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 regard, as a domain refining technique capable of withstanding strain relief annealing, a linear groove is introduced into the surface of a steel sheet after finish annealing of a unidirectional silicon steel sheet, and the demagnetizing effect by the groove is applied to the magnetic domain. 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 sheet of 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,
Amorphous alloys are receiving attention as materials for ordinary power transformers and high-frequency transformers. However, such an amorphous material can provide extremely excellent iron loss characteristics as compared with a normal unidirectional silicon steel sheet, but lacks thermal stability, has a low space factor, and is easy to cut. However, since it is too thin and brittle, there are many practical disadvantages such as a large increase in the cost of assembling the transformer, so that it has not been used in large quantities at present.

[0011] In addition, Japanese Patent Publication No. 52-24499 discloses that a forsterite undercoat formed after finish annealing of a silicon steel sheet is removed, the steel sheet surface is polished, and then the metal surface is plated with metal. A method has been proposed. However, this method has a disadvantage that although a low iron loss can be obtained at a low temperature, the metal is diffused into the silicon steel sheet when subjected to a high temperature treatment, so that the iron loss is rather deteriorated.

In this regard, the inventors have previously disclosed in Japanese Patent Publication No. 63-54767 and the like, as solutions to the above disadvantages.
Si, Mn, Cr, Si, Mn, Cr, etc. are applied on a grain-oriented silicon steel sheet by dry plating (PVD) such as CVD, ion plating and ion implantation.
Ni, Mo, W, V, Ti, Nb, Ta, Hf, Al, Cu, Zr and B
It has been disclosed that an ultra-low iron loss can be obtained by forming one or two or more kinds of tension films selected from nitrides and carbides. 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.

Therefore, the present inventors have made a fundamental reexamination from all viewpoints in order to further reduce iron loss as compared with the prior art. That is, the inventor formed one or two or more kinds of tension films selected from various nitrides and carbides on the surface of a grain-oriented silicon steel sheet smoothed in a stable process to form an ultra-low iron loss. In order to obtain a product of the following, from the recognition that a fundamental review from the raw material composition of the unidirectional silicon steel sheet to the final processing step is necessary, from tracking the texture of the silicon steel sheet, Smoothness of steel sheet surface and final CVD and P
Intensive studies were conducted up to the VD processing step. as a result,
The following findings were obtained.

(1) Even if a thin film of 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. In other words, a TiN film having a thickness of 1.5 μm or more can only expect a slight improvement in iron loss, but rather causes a decrease in space factor and magnetic flux density. (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 addition of tension specific to ceramic. That is, in the transmission electron microscope observation of the cross section of TiN (see Iguchi, Y .: Journal of the Japan Institute of Metals, 60 (1996), pp. 781-786), horizontal stripes of 10 nm are observed, which are caused by the [011] -Corresponds to a 5-atomic layer of Fe atoms. (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 shape of the {200} peak of Fe in the TiN coating region is elliptical, and the silicon steel sheet 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)
At 10 MPa, an improvement in magnetic flux density of about 0.014 to 0.016 T can be expected. (This is equivalent to increasing the degree of Goss orientation integration by about 1 °.)

The above is new findings on ceramic coating. Further, the following findings concerning the surface condition of the ceramic film and the steel sheet have been obtained. (5) When the final cold-rolled silicon steel sheet is subjected to local electrolytic etching to form grooves, and after the secondary recrystallization treatment, the steel sheet surface is smoothed by polishing and then coated with a TiN ceramic film In addition, in addition to the magnetic domain segmentation caused by the demagnetizing field effect caused by the introduced grooves, the core loss is effectively reduced by the addition of tension by the ceramic coating. (6) The effect of reducing iron loss by tension when a concave groove is formed on the surface of a steel sheet before ceramic coating is greater than that of a silicon steel sheet smoothed by ordinary polishing (Japanese Patent Publication No. 3-32889). Gazette). That is, when grooves are introduced, different tension acts on the surface of the silicon steel sheet, and the degree of reduction in iron loss due to tensile tension increases. (7) When the ceramic film is coated on the silicon steel plate having the concave grooves, the effect of reducing iron loss is more effective than the case where the ceramic film is smoothed by ordinary polishing and coated with the ceramic film. (For example, see Japanese Patent Publication No. 63-35686) That is, a linear groove is introduced, and the magnetic domain is subdivided by applying the demagnetizing effect of the groove. It is more effective to subdivide the main magnetic domain, and an ultra-low iron loss can be obtained. (8) If grooves are formed by performing local electrolytic etching on the final cold-rolled sheet of silicon steel sheet, the surface of the steel sheet after the secondary recrystallization treatment is not smoothed by polishing and the TiN ceramic Even when a film is formed, a considerable iron loss reduction effect is exhibited. In other words, even when the surface is not smoothed by polishing, for example, even when there are small irregularities on the surface due to pickling treatment or the like, a strong tension is applied to the surface of the silicon steel sheet by coating the ceramic film having a small coefficient of thermal expansion. It is possible to add, and thereby the iron loss can be advantageously reduced.

Therefore, based on the above-mentioned new findings, the inventor repeated numerous experiments and studies in order to achieve the intended purpose, and as a result, introduced a silicon steel sheet having a smooth surface and linear grooves. Regardless of the silicon steel sheet, it is possible to reduce the iron loss by using a plurality of types of ceramic tension coatings formed on the surface of the silicon steel sheet, and reducing the coefficient of thermal expansion of the ceramic tension coating as it goes outward. Was found to be extremely effective, and based on this, a unidirectional silicon steel sheet with extremely low iron loss was newly developed (Japanese Patent Application No. 9-328042).
Specification).

The thus obtained grain-oriented silicon steel sheet has an extremely thin ceramic film having excellent adhesion and a tensile film, and is capable of achieving not only an ultra-low iron loss but also an insulating property. Moreover, since it has an excellent space factor, it can be said that it is an ideal silicon steel sheet.

However, in order to form such a dense ceramic film, processing under a high plasma atmosphere in a vacuum is indispensable. In such a method, high-speed formation of the ceramic film cannot be performed. Because of its low property, there is a problem in that the cost increases when industrialized.

In addition, separately from this, recently, Patent No. 26624
Nos. 82 and 2664326 each propose a low iron loss unidirectional silicon steel sheet having improved coating adhesion and iron loss by forming a composite film of Al oxide-B oxide on the surface of a smoothed steel sheet. Was done. However, the iron loss value W _17/50 of the silicon steel sheet by this method is 0.77 to
It is only about 0.83 W / kg, and it cannot be said that there is still room for improvement with this ultimate iron loss value despite the small product plate thickness. Further, the composite ceramic film of Al oxide-B oxide based on this method is compared with a ceramic film formed using vacuum plasma.
Inferior in terms of denseness and smoothness, the insulating coating of this unidirectional silicon steel sheet has insufficient chemical stability and corrosion resistance,
Improvements in water resistance have been pointed out.

Then, based on the above-mentioned new findings, the inventors again examined the surface condition of the silicon steel sheet and the ceramic tension film formed on the surface. As a result, prior to forming a tension insulating film mainly composed of phosphate and colloidal silica on the surface of the silicon steel sheet, the coating solution for the tension insulating film is diluted with water, and After thinly applying a treatment liquid containing an inorganic compound containing one or more selected from Fe, Si, Al and B, and attaching a small amount of an inorganic compound containing Fe or the like to the surface of the steel sheet, When a short-time heat treatment is performed in a non-oxidizing atmosphere, an ultra-thin film basically having the same film component as the tensile insulating film is formed and is present in the film.
The inorganic compound containing Fe etc. changes into nitride / oxide such as Fe with high activity, and this is firmly fixed on the steel sheet surface.As a result, the ultra-thin film is formed on the steel sheet surface with high adhesion, On the other hand, since this ultra-thin film is of the same quality as the tensile insulating film formed thereon, its adhesion is also very good. As a result, the tensile insulating film has much better adhesion than before. It has been found that a coating can be formed on the surface of a steel sheet, and thus a unidirectional silicon steel sheet having extremely low iron loss can be manufactured with good productivity and at low cost, and is disclosed in Japanese Patent Application No. 10-43238. In the disclosure.

Further, as a result of continuing research on the above-mentioned technology, as described above, Fe, Si, Al and B
After forming an ultra-thin undercoat with finely dispersed nitride / oxide such as, it is also possible to finely disperse a small amount of Si nitride / oxide in the tensile insulation coating that is formed by layering on it. It has been found that it is more advantageous for improving the adhesiveness and thus the iron loss characteristics, and disclosed in Japanese Patent Application No. 10-43239.

Further, as a result of continuing these development studies, an ultra-thin undercoating in which nitrides and oxides such as Fe, Si, Al and B are finely dispersed as described above is formed on the surface of the steel sheet. Prior to this, it was found that immersion in an aqueous solution of chloride containing SiCl ₄ as a main component to slightly dissolve the surface of the ground iron was more effective in improving the adhesion and, consequently, the iron loss characteristics. -74274.

[0023]

SUMMARY OF THE INVENTION The present invention proposes a facility for producing an ultra-low iron loss unidirectional silicon steel sheet suitable for producing the above-described ultra-low iron loss unidirectional silicon steel sheet. The purpose is to:

[0024]

That is, the present invention relates to a treatment equipment for forming a tension insulating film on the surface of a unidirectional silicon steel sheet which has been subjected to finish annealing, comprising a chloride bath containing SiCl ₄ as a main component. Heat treatment furnace for performing a heat treatment in a dry and non-oxidizing atmosphere, and a tension insulating coating mainly composed of phosphate and colloidal silica on the surface of the silicon steel sheet after the pretreatment. Base treatment tank for applying a treatment liquid containing a small amount of an inorganic compound containing one or more selected from Si, Fe, Al and B in a diluting liquid obtained by diluting a coating solution for water with water and then drying And a second heat treatment furnace for performing heat treatment in a non-oxidizing atmosphere, and a tension insulation for applying a coating solution for a tension insulation film containing phosphate and colloidal silica as a main component to the surface of the silicon steel sheet on which the base film is formed. Coating A production facility for an ultra-low iron loss unidirectional silicon steel sheet, comprising: a heating tank and a subsequent annealing furnace for performing a baking treatment in a dry and non-oxidizing atmosphere.

[0025] In the present invention, the surface of the finish-annealed unidirectional silicon steel sheet is placed in a direction intersecting the rolling direction by 2 to 10 mm.
It is advantageous to provide a linear concave region having a width of 50 to 500 μm and a depth of 0.1 to 50 μm at intervals of. Further, in the present invention, the surface of the annealed grain-oriented silicon steel sheet is a surface that has been subjected to a smoothing treatment, is not subjected to such smoothing treatment, and is a surface that has been subjected to an acid pickling treatment. Is also good.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. FIG. 1 schematically shows a preferred example of a production facility according to the present invention. In the figure, reference numeral 1 denotes a pretreatment tank, 2 denotes a first heat treatment furnace, 3 denotes a base treatment tank, 4 denotes a second heat treatment furnace, and 5 denotes A tension insulating film coating tank, and 6 is an annealing furnace.

Now, as shown in FIG.
First, a silicon steel sheet whose surface oxide has been removed by pickling or a silicon steel sheet whose surface has been further smoothed by electrolytic polishing or the like is first introduced into the pretreatment tank 1 to slightly melt the surface of the steel sheet. The reason for such pre-treatment is that
This is because by dissolving the components to some extent, the activity of the surface of the base iron is increased, and the adhesion to the ultra-thin base coat formed thereafter is improved. For this purpose, the pretreatment tank 1
It is important to use a chloride bath containing SiCl ₄ as a main component. Here, as chlorides other than SiCl ₄ , MgCl ₂ , C
aCl ₂ , SrCl ₂ , BaCl ₂ etc. are suitable, but if they are trace amounts, TiCl ₃ , ZrCl ₄ , NbCl ₅ , TaCl ₅ , CrCl ₃ , CoCl ₃ , NiCl
₂ , CuCl ₂ , ZnCl ₂ , TlCl _{3 and the} like can also be used. The concentration of chloride may be about 0.5 to 300 cc per liter, and the bath temperature and immersion time are 80 to 100 ° C, respectively.
About 3 to 5 seconds are preferable.

In some cases, after the finish annealing, the surface may be directly guided to the pretreatment tank 1 without performing a smoothing treatment such as removal of an oxide on the surface or electrolytic polishing. In this case, the pretreatment is a so-called pretreatment. This corresponds to the pickling treatment. Instead of immersing the silicon steel sheet in the chloride bath, such a chloride aqueous solution may be sprayed or sprayed on the steel sheet surface.

Then, after drying in the first heat treatment furnace 2, heat treatment is performed in a non-oxidizing atmosphere. The heating means is not particularly limited, but a radiant tube is particularly suitable, and a treatment temperature and a treatment time of about 900 to 1000 ° C. and about 1 to 100 seconds are sufficient.

Thereafter, the solution is guided to a base treatment tank 3 and a treatment liquid for forming a base coat is applied to the surface of the steel sheet. This treatment solution for forming the undercoat film contains a trace amount of an inorganic compound containing one or more selected from Fe, Si, Al and B in a diluent obtained by diluting a coating solution for a tension insulating film with water. It has been added. Here, as a coating solution for a tension insulating film mainly containing phosphate and colloidal silica,
For example, as disclosed in JP-B-53-28375, colloidal silica: 4 to 16% by weight, aluminum phosphate: 3 to 24% by weight
%, Chromic anhydride and / or chromate: 0.2-4.
Coating liquid containing 5 wt%, colloidal silica: 7 to 24 wt% as disclosed in JP-B-56-52117,
Magnesium phosphate: 5 to 30 wt% (however, the molar ratio of magnesium phosphate to colloidal silica: 20/80 to 30 /
70), and, if necessary, a coating liquid to which chromic anhydride, chromate and / or dichromate: 0.01 to 5% by weight is advantageously applied.

The dilution of the coating solution is about 1 to 60%, preferably 10 to 20% (for example, 15 to 20%).
It is preferable to dilute the solution to the extent that 100 to 1000 cc of the coating solution is dissolved in a 00 cc aqueous solution). That is, in order to form an undercoat film that is firmly adhered to the base iron, it is necessary to convert inorganic compounds such as Fe, Si, Al and B contained in the undercoat treatment solution into nitrides and oxides. However, if the concentration of the base treatment liquid is too high, the treatment atmosphere at that time (preferably a mixed gas atmosphere of N ₂ (50%) + H ₂ (50%))
This is because it is difficult to convert an inorganic compound into a nitride / oxide properly, and it is effective to dilute with an appropriate amount of water in order to effectively promote the nitridation / oxidation.

Further, the amount of the inorganic compound containing one or more selected from the group consisting of Fe, Si, Al and B in the diluent is about 5 to 500 g per liter of the inorganic compound. (About 0.001 to 0.5 mol / l). The reason is that if the amount of these inorganic compounds is too small, the effect cannot be exhibited, while if the amount is too large, not only is it not economical but also the coating properties deteriorate. Here, among the various inorganic compounds described above, FeCl ₃ , Fe (N
O ₃ ) ₃ etc. are SiCl ₄ , Na ₂ Si
O ₃ , SiO _2, etc. are inorganic compounds containing Al such as AlCl ₃ , Al
(NO ₃ ) ₃ , AlPO _4, etc. are H ₃ B as inorganic compounds containing B
O ₃ , Na ₂ B ₄ O ₇ etc. are particularly advantageously suited.

The bath temperature of the base treatment tank is 50 to 100 ° C.
And the immersion time is desirably about 1 to 100 seconds. The coating amount of the undercoating liquid is preferably in a 0.01 to 0.5 g / m ² approximately, by the heat treatment was coated the amount of this extent, ultimately to 0.001 to 3.0 [mu] m about suitable thickness Thus, an extremely thin undercoating can be obtained.
Further, regarding the coating method of the treatment liquid, in addition to the immersion treatment described above, a coating method using a normal roll coater or the like, a method of directly spraying or spraying the treatment liquid on the surface of the steel sheet, and a known method such as an electrolytic treatment method Can also be used.

Next, after drying in the second heat treatment furnace 4, heat treatment is performed for a short time in a non-oxidizing atmosphere to form an extremely thin undercoat. In this way, after a small amount of an inorganic compound containing Fe, Si, Al, B, etc. is attached to the surface of the steel sheet, and then subjected to a short-time heat treatment in a non-oxidizing atmosphere, the tension insulating film is basically formed. An ultra-thin film is formed which has the same film component as that described above, and is present in the film.
The inorganic compound containing Fe etc. is changed into nitride / oxide such as Fe with high activity, and this is firmly fixed on the steel sheet surface. As a result, the ultra-thin film is formed on the steel sheet surface with high adhesion. It is.

As the heating means, as in the case of the first heat treatment furnace 2, a radiant tube is particularly advantageously applied, but is not limited thereto. The treatment atmosphere is preferably an N-containing non-oxidizing atmosphere in order to promote nitriding, and for example, a (N ₂ + H ₂ ) mixed gas atmosphere and an ammonia-containing (NH ₃ + H ₂ ) mixed atmosphere are particularly suitable. . The processing temperature is preferably about 200 to 1100 ° C (preferably about 500 to 900 ° C), and the processing time is about 1 to 100 minutes (preferably about 3 to 30 minutes).

Thereafter, the solution is guided to a tension insulating film coating tank 5 to apply a coating solution for a tensile insulating film containing colloidal silica and phosphate as main components on the surface of the above-mentioned ultra-thin base film according to a conventional method. In annealing furnace 6, 5
Bake at a temperature of about 100 to 1000 ° C and apply a tension insulating coating (0.5
(About 5 μm thick). Examples of the coating liquid for the above-mentioned tension insulating film include a coating liquid mainly containing colloidal silica, aluminum phosphate, chromic anhydride and the like, which is disclosed in the above-mentioned JP-B-53-28375. The coating solution disclosed in JP-A-56-52117, which contains colloidal silica, magnesium phosphate, chromic anhydride and the like as main components, is advantageously suitable. As the annealing atmosphere, a nitrogen atmosphere is particularly preferable.

Here, since the above-mentioned ultra-thin base film and the tensile insulating film formed thereon are of the same quality, their adhesion is extremely high, and as a result, the adhesion is much higher than in the past. This makes it possible to coat a tensile insulating film having excellent resistance on the surface of the steel sheet, and thus to obtain a unidirectional silicon steel sheet having extremely low iron loss with good productivity and at low cost.

[0038]

The silicon-containing steel used as the material of the present invention is compatible with any of the conventionally known component compositions, but typical compositions are as follows. C: 0.01 to 0.08 wt% If the content of C is less than 0.01 wt%, the suppression of hot rolled texture is insufficient and large elongated grains are formed, thereby deteriorating the magnetic properties. Since it takes a long time to decarburize in the charcoal process and is not economical, it is preferable to set the content to about 0.01 to 0.08 wt%.

Si: 2.0 to 4.0 wt% If the content of Si is less than 2.0 wt%, sufficient electric resistance cannot be obtained, so that eddy current loss increases and iron loss deteriorates.
If the content is more than wt%, brittle cracks are likely to occur during cold rolling, so it is preferable to be in the range of about 2.0 to 4.0 wt%.

Mn: 0.01 to 0.2 wt% Mn is an important component that determines MnS or MnSe as a dispersed precipitation phase that affects secondary recrystallization of a grain-oriented silicon steel sheet. If the amount of Mn is less than 0.01% by weight, the absolute amount of MnS or the like necessary for causing secondary recrystallization becomes insufficient, causing incomplete secondary recrystallization and increasing the number of surface defects called blisters. On the other hand, if the content exceeds 0.2 wt%, 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 is likely to be coarse, and the optimal size distribution desired as an inhibitor is impaired. Therefore, Mn is preferably set to about 0.01 to 0.2 wt%.

S: 0.008 to 0.1 wt%, Se: 0.003 to 0.1
wt% S and Se are each 0.1 wt% or less, and S is 0.0
Preferably, the content of Se is in the range of 08 to 0.1 wt%, and the content of Se is in the range of 0.003 to 0.1 wt%. The reason is that if these contents exceed 0.1 wt%, 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. It is. In addition, even if Al, Sb, Cu, Sn, B and the like which are conventionally known as inhibitors are added in combination, the effect of the present invention is not hindered.

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 smelt the raw material, not only an LD converter, an electric furnace, an open hearth furnace, and other known steelmaking furnaces can be used, but also vacuum melting and RH degassing can be used together.

According to the present invention, S, Se contained in the raw material
Alternatively, as a method of adding a small amount of 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 continuously cast slab is heated to a temperature of 1300 ° C. or more in order to dissociate and form a solid solution of the inhibitor in the slab. 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, the hot-rolled sheet is subjected to hot-rolled sheet annealing (also referred to as homogenizing annealing) in a temperature range of about 850 to 1100 ° C. as necessary, and then is subjected to one or two cold-pressing steps including intermediate annealing. Rolling is performed to obtain a final thickness, but in order to obtain a product having high magnetic flux density and low iron loss, attention must be paid to the final cold rolling rate (normally 55 to 90%). At this time, the upper limit of the product thickness is 0.5 from the viewpoint of minimizing the eddy current loss of the silicon steel sheet.
mm, and the lower limit of the plate thickness was limited to 0.05 mm in order to avoid the adverse effect of hysteresis loss.

When forming a linear groove on the steel sheet surface,
It is particularly advantageous to carry out the process on a steel sheet which has finished the final cold rolling and has a product thickness. That is, on the surface of the final cold-rolled sheet or the steel sheet before and after the secondary recrystallization, the width: 50 to 500 μm, the depth: 0.1 at intervals of 2 to 10 mm in a direction crossing the rolling direction.
That is, a linear concave region of about 50 μm is formed. Here, the interval between the linear concave regions is limited to the range of 2 to 10 mm. If it is less than 2 mm, the unevenness of the steel sheet is too remarkable, the magnetic flux density is lowered and it is not economical. This is because the conversion effect is reduced. If the width of the concave region is less than 50 μm, it will be difficult to use the demagnetizing effect, while if it exceeds 500 μm, the magnetic flux density will decrease and it will not be economical, so the width of the concave region will be in the range of 50 to 500 μm. Limited to. Furthermore, if the depth of the concave region is less than 0.1 μm, the demagnetizing effect cannot be effectively used.
If the thickness exceeds 50 μm, the magnetic flux density decreases and it becomes not economical. Therefore, the depth of the concave region is limited to the range of 0.1 to 50 μm. In addition, the forming direction of the linear concave region is optimally set to a direction perpendicular to the rolling direction, that is, the sheet width direction, but substantially the same effect can be obtained as long as it is within ± 30 ° with respect to the sheet width direction. .

Further, as a method of forming the linear concave region,
On the surface of the final cold-rolled sheet, an etching resist is applied by printing, after baking, an etching process is performed, and then the method of removing the resist is compared with a method using a conventional knife edge or a laser, This is advantageous in that it can be carried out industrially stably, and that iron loss can be more effectively reduced by tensile tension.

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 / dm 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 (hereinafter 50%), CaO not to form a Kakaru replace _{film, Al 2 O 3, CaSiO 3} , high content of SiO ₂ or the like (50% The annealed separator described above is 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, or a mechanical method such as cutting or polishing, or a combination thereof. Is smoothed. That is, after removing various coatings on the steel sheet surface, chemical polishing,
The surface of the steel sheet is smoothed to a center line average roughness Ra of about 0.4 μm or less by a conventional method such as chemical polishing such as electrolytic polishing or mechanical polishing such as buff polishing or a combination thereof.

It is not always necessary to smooth the surface of the silicon steel sheet. Therefore, in this case, there is an advantage that a sufficient iron loss reducing effect can be exerted only by the pickling treatment without performing the smoothing treatment accompanied by the cost increase. Although,
It is still advantageous to perform the smoothing process. At this stage, a concave groove can be introduced into the surface of the steel sheet. The grooves may be introduced by the same method as that used for the surface of the final cold-rolled sheet or the steel sheet before and after the secondary recrystallization.

Next, a unidirectional silicon steel sheet having excellent film adhesion and, consequently, excellent iron loss characteristics is produced by leading the production line shown in FIG. 1 and performing a predetermined treatment.

[0055]

An embodiment in which an ultra-low iron loss oriented silicon steel sheet is manufactured using the manufacturing line shown in FIG. 1 will be described below. Example 1 C: 0.076 wt%, Si: 3.43 wt%, Mn: 0.071 wt%, Se:
0.020 wt%, Sb: 0.025 wt%, Al: 0.020 wt%, N: 0.
A continuously cast slab of silicon steel containing 072 wt% and Mo: 0.012 wt%, with the balance being substantially Fe, was heated at 1350 ° C. for 5 hours and then hot-rolled to a thickness of 2.2 mm. Hot rolled sheet. Then, after subjecting to homogenization annealing at 1000 ° C, 1050 ° C
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, after decarburization and primary recrystallization annealing in 840 ° C wet H ₂ , MgO (10%), CaO (20%
%), Al ₂ O ₃ (40%), SiO ₂ (30%), and a slurry of an annealing separating agent.Then, after annealing at 850 ° C. for 15 hours, 850 ° C.
After 12 ° C. / h speed was heated to 1100 ° C. In the not develop secondary recrystallized grains strongly integrated in the Goss orientation from ° C., of 1220 ° C. dry H ₂
Purification processing was performed inside.

After removing the oxide film on the surface of the silicon steel sheet thus obtained, (A) a smoothing treatment by chemical polishing,
(B) An acid pickling treatment with 10% HCl was carried out, and the solution was led to the equipment shown in FIG. 1 to carry out the following treatment. First, in the pretreatment tank 1, it is immersed for 3 seconds in an aqueous solution of 80 ° C. in which SiCl ₄ (20 cc / l) is dissolved.
Heat treatment was performed at 900 ° C. for 3 seconds in a mixed gas of ₂ (50%) + H ₂ (50%). Thereafter, in the base treatment tank 3, a diluting solution (100 cc / cm 2) obtained by diluting a coating solution for a tensile insulating film containing magnesium phosphate and colloidal silica as main components with distilled water.
l) contains SiCl ₄ (20 cc / l), AlPO ₄ (10 g / l) and H ₃ BO ₄ (10 g / l
l) was immersed for 2 seconds in a treatment solution (80 ° C) to which composite addition of l) was performed, and then guided to a _second heat treatment furnace, where the mixture was heated at 900 ° C, 5% in a mixed gas of N ₂ (93%) and H ₂ (7%). Heat treatment was applied for a second. Thereafter, in a tension insulating film coating tank 5, a coating solution for a tensile insulating film containing magnesium phosphate and colloidal silica as main components is applied using a ringer roll, and then guided to an annealing furnace 6 for baking at 800 ° C. Process,
A 1.5 μm thick tensile insulation coating was applied.

The magnetic properties and adhesion of the product thus obtained were as follows. (A) smoothing processing alms was when magnetic properties _{B 8: 1.93 T W 17/50:} 0.65 W / kg adhesion diameter: even if the 180 ° bending on a 15mm round bar peeling without a good Was. (B) Magnetic properties when subjected to pickling treatment _{B 8: 1.92 T W 17/50:} 0.68 W / kg adhesion diameter: even if the 180 ° bending on a 15mm round bar peeling without a good Was.

Example 2 C: 0.073 wt%, Si: 3.46 wt%, Mn: 0.071 wt%, Se:
0.019 wt%, Sb: 0.023 wt%, Al: 0.019 wt%, N: 0.
A continuously cast silicon steel slab containing 073 wt% and Mo: 0.013 wt%, with the balance being substantially Fe, was subjected to a heat treatment at 1350 ° C. for 5 hours and then hot-rolled to a thickness of 2.0 mm. Hot rolled sheet. After 980 ° C uniform annealing, 1020 ° C
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 subjected to gravure offset printing so that the non-applied portion has a width of approximately 200 μm in a direction substantially perpendicular to the rolling direction, and a distance between the rolling directions of 4 mm. And then baked at 200 ° C. for about 20 seconds. At this time, the resist thickness was 2 μm. By subjecting the steel sheet coated with the etching resist in this way to electrolytic etching, the width: 200 μm and the depth:
A 20 μm linear groove was formed and then immersed in an organic solvent to remove the resist. The electrolytic etching at this time is
In a Cl electrolyte, the current density was 10 A / dm ² , and the treatment time was 20 seconds.

Then, after decarburization and primary recrystallization annealing in wet H ₂ at 850 ° C., MgO (5%), CaO (25%), Al ₂ O
₃ (30%), CaSiO ₃ (10%) and SiO ₂ (30%) were applied by slurry coating with an annealing separator, and then annealed at 850 ° C for 15 hours. After increasing the temperature to 1050 ° C at a high speed to develop secondary recrystallized grains strongly integrated in Goss orientation,
Purification was performed in dry H ₂ at ° C. After removing the oxide film on the surface of the silicon steel sheet thus obtained, the steel sheet surface was smoothed by chemical polishing, and then led to the equipment shown in FIG. 1 for the following treatment.

First, in the pretreatment tank 1, SiCl ₄ (20 cc)
/ l) is immersed in an aqueous solution at 80 ° C for 3 seconds, and then introduced into a first heat treatment furnace 2 at 900 ° C in a mixed gas of N ₂ (50%) + H ₂ (50%). Heat treatment was performed for 3 seconds. Then, in the undercoating tank 3, SiCl ₄ (20c / l) was added to a diluent (100cc / l) obtained by diluting a coating solution for a tension insulating film mainly composed of aluminum phosphate and colloidal silica with distilled water.
c / l), AlPO ₄ (10 g / l) and H ₃ BO ₄ (10 g / l) were immersed in a treatment solution (80 ° C.) for 2 seconds, and then introduced into a second heat treatment furnace, ₂ (93%) + H ₂ (7%) mixed gas at 900 ℃,
Heat treatment was performed for 5 seconds. Thereafter, in a tension insulating film coating tank 5, a coating solution for a tensile insulating film containing aluminum phosphate and colloidal silica as main components is applied using a ringer roll, and then guided to an annealing furnace 6 for baking at 800 ° C. After the treatment, a 1.5 μm-thick tensile insulating film was formed.

The magnetic properties and adhesion of the product thus obtained were as follows. Magnetic properties _{B 8: 1.91 T W 17/50:} 0.58 W / kg adhesion diameter on 10mm round bar 180 ° bend without peeling even if the were good. Thereafter, the product was subjected to strain relief annealing at 800 ° C. for 3 hours, and the magnetic properties were as follows. Thus, it can be seen that the silicon steel sheet withstands strain relief annealing.

[0062]

As described above, according to the present invention, a grain-oriented silicon steel sheet having excellent iron loss characteristics can be obtained at extremely low cost and with high productivity as compared with the prior art.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a production line for a grain-oriented silicon steel sheet according to the present invention.

Claims (4)

[Claims] Claims: 1. A treatment facility for forming a tensile insulating coating on the surface of a unidirectional silicon steel sheet which has been finish-annealed, comprising: a pretreatment tank comprising a chloride bath containing SiCl ₄ as a main component; A first heat treatment furnace for performing heat treatment in a non-oxidizing atmosphere, and a diluting solution obtained by diluting a coating solution for a tension insulating film mainly containing phosphate and colloidal silica with water on the surface of the pre-treated silicon steel sheet. A base treatment tank for applying a treatment liquid containing a trace amount of an inorganic compound containing one or more selected from Si, Fe, Al and B, and then performing a heat treatment in a dry and non-oxidizing atmosphere A second heat treatment furnace, a tension insulating film coating bath for applying a coating solution for a tension insulating film containing phosphate and colloidal silica as a main component to the surface of the silicon steel sheet on which the base film is formed, and then drying the tank. Manufacturing equipment ultra-low iron loss grain oriented silicon steel sheet, characterized in that in a non-oxidizing atmosphere and comprises a furnace for performing the baking process. 2. The method according to claim 1, wherein the surface of the finish-annealed unidirectional silicon steel sheet is oriented in a direction intersecting the rolling direction.
At intervals of 10 mm, width: 50-500 μm, depth: 0.1-50 μm
An ultra-low iron loss unidirectional silicon steel sheet manufacturing facility characterized by having a linear concave region of: 3. The production facility for an ultra-low iron loss unidirectional silicon steel sheet according to claim 1, 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 1 or 2, wherein the surface of the finish-annealed unidirectional silicon steel sheet has not been subjected to a smoothing treatment and is a surface as it is in an pickling treatment. production equipment.