JPH03130376A - Production of unidirectionally oriented silicon steel sheet excellent in magnetic characteristic - Google Patents

Abstract

PURPOSE:To obtain an unidirectionally oriented silicon steel sheet excellent in flux density and iron loss by removing a nonmetallic material on the surface of a finish-annealed grain-oriented silicon steel sheet, smoothing the surface, then forming a gel thin film in specified thickness and further forming an insulat ing coating film. CONSTITUTION:The nonmetallic material on the steel surface is electrolytically removed with a halide or nitrate. In this case, the surface layer is removed to >=3mum thickness. The surface freed of the nonmetallic material is chemically or electrolytically polished into the smooth surface having <=0.3mum mean rough ness on the center line. A gel thin film layer having 0.1-0.5mum thickness and consisting of a metal alkoxide is then formed on the smoothed surface by the sol-gel method. The gel film is dried at about 100 deg.C, and a phosphate soln., for example, is applied and baked to form an insulating coating film. As a result, the unidirectionally oriented silicon steel sheet excellent in magnetic characteristic is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a grain-oriented silicon steel sheet having extremely good magnetic flux density and iron loss.

(Prior Art) The magnetic properties of a unidirectional silicon steel sheet are defined by magnetic flux density and iron loss, and the magnetic flux density (represented by the magnetic flux density Be(T) at a magnetizing force of 800 A/m) is Higher is desirable, and iron loss (1.7T. Iron loss W of 5011z
+t/s. ) is preferably lower.

In addition, since unidirectional silicon steel sheets are used in a laminated manner, it is necessary to apply an insulating coating to the surface of the steel sheet, and the insulating coating is usually applied during finish annealing at high temperatures in the manufacturing process of grain oriented silicon steel sheets. It consists of a 2N film consisting of a glass-like coating mainly composed of forsterite and a phosphate coating to provide insulation.

Incidentally, in recent years, research has been actively conducted to fully bring out the various properties of various substances through surface modification.

In the field of silicon steel, it has long been well known that a type of surface modification technology that smoothes the surface of a silicon steel sheet can significantly improve iron loss, mainly due to a reduction in hysteresis loss.

That is, if the surface is mirror-finished by removing the glass-like film and the internal oxidation II (subscale) on the surface layer, iron loss can be significantly improved.

However, as mentioned above, the surface of the silicon steel sheet requires insulation, so it cannot be used as a core material in its mirror-finished state, and the phosphate coating described above has poor adhesion to mirror surfaces. Therefore, it was not possible to form a film directly on the mirror surface.

Therefore, various technical devices have been devised to solve these problems.

For example, Japanese Patent Application Laid-Open No. 49-96920 states, ``The surface of the steel sheet is chemically polished or electrolytically polished, and then metal plating such as Zn+Sn+Cu+Nt is applied to the mirror-like surface.
Japanese Patent Publication No. 56-4150 discloses that ``ceramics are vacuum-deposited on a smooth surface obtained by chemical polishing or electrolytic polishing.
application by chemical vapor deposition, sputtering or thermal spraying.

All of these techniques provide a solution to the problem that it is not possible to directly apply an insulating coat such as phosphate to a mirror-polished surface.

(Problem to be Solved by the Invention) However, none of the above methods has been industrialized. This is because, although it is shown in JP-A No. 49-96920 that it is possible to apply a coating while maintaining a smooth surface by applying metal plating,
If this treatment is actually carried out, the metal plating will diffuse into the steel during strain relief annealing performed after processing on silicon steel sheets, which are the iron core material, and will deteriorate the magnetic properties of the silicon steel sheets. Deterioration is also significant and the product value decreases significantly.

On the other hand, with the technology disclosed in Japanese Patent Publication No. 56-4150, vacuum evaporation has problems with productivity because the reaction rate and processing area are limited, and chemical vapor deposition has problems with the reaction rate and film homogeneity. In addition, sputtering has lower productivity than vacuum deposition, and thermal spraying makes it extremely difficult to form a homogeneous thin film, resulting in a significant drop in space factor.

For these reasons, the above method has not been implemented industrially.

Therefore, the present invention has developed a coating method that can uniformly form a highly adhesive insulating film over a wide area without deteriorating the excellent magnetism of the smoothed silicon steel sheet. The purpose of the present invention is to propose a method for producing grain-oriented silicon steel sheets with low iron loss and high magnetic flux density.

(Means for Solving the Problems) In order to overcome the above problems, the inventors worked on the development of a technology to improve the magnetic properties by modifying the surface of grain-oriented silicon steel sheets. By forming a thin gel film with a thickness of 0.1 to 0.5 μm on the surface of a silicon steel plate using the sol-gel method, and then adding an insulating film on top of it, the magnetic properties can be We succeeded in forming an insulating film that is homogeneous and has good adhesion, which is advantageous for the space factor.

That is, this invention involves removing nonmetallic substances from the surface of a grain-oriented silicon steel sheet that has been finish annealed, and then making the surface of the steel sheet a smooth surface with a centerline average roughness of 0.3 μm or less. A patented method characterized by forming a gel thin film with a thickness of 0.1 to 0.5 μm on the surface by a sol-gel method, and further removing an insulating film on this thin film, and a directional structure that has been finish annealed. Non-metallic substances on the surface of the raw steel sheet are removed, and then the surface layer of the steel sheet is removed to a thickness of 3 μm or more by electrolytic treatment using a water-soluble halide or nitrate. A method for producing a unidirectional silicon steel sheet with extremely good magnetic properties, characterized by forming a gel thin film with a thickness of 0.1 to 0.5 μm by a gel method, and further removing an insulating coating on this thin film. It is.

(for production) Next, this invention will be explained in detail in the order of steps.

The grain-oriented silicon steel sheet used in this invention is a steel sheet that has been subjected to secondary recrystallization treatment by a conventionally known method. That is, a steel ingot containing a grain-oriented silicon steel sheet material component is hot rolled, further cold rolled and annealed repeatedly to obtain a predetermined thickness, and then primary recrystallization annealing is performed. Next, an annealing separation material is applied to the surface of the steel plate and secondary recrystallization annealing is performed. Since this invention method improves magnetism by modifying the surface, it goes without saying that it has the effect of improving magnetism regardless of the inhibitor of the material or the manufacturing method such as rolling annealing method.

Incidentally, typical component compositions are as shown below.

C: 0.01 to 0.10 wt% (hereinafter simply referred to as %) C
is an element useful for the development of Goss orientation, which results in uniform refinement of the structure during hot rolling and cold rolling, and has at least 0
．． It is preferable to add 0.01% or more. However, 0.10
If the content exceeds 0.1%, the Goss orientation will be disturbed, so the upper limit is preferably about 0.10%.

Si: 2.0 to 4.5% Si increases the resistivity of the steel sheet and effectively contributes to reducing iron loss, but if it exceeds 4.5%, cold rollability is impaired;
If it is less than 0%, not only will the resistivity decrease, but also randomization of crystal orientation will occur due to α-γ transformation during the final high-temperature annealing performed for secondary recrystallization and purification, resulting in a sufficient iron loss improvement effect. is not obtained, the amount of Si is preferably about 2.0 to 4.5%.

Mn: 0.02-0.12% Mn is at least 0.02% to prevent hot embrittlement
It is preferable to set the upper limit at about 0.12%, since too much content deteriorates the magnetic properties.

Inhibitors include so-called MnS, MnSe, and AIN inhibitors. In the case of MnS and MnSe,
At least one selected from Se, S: o, o
Contains os~0.08%.

Both Se+S are effective elements as inhibitors that control secondary recrystallization of grain-oriented silicon steel sheets.

From the viewpoint of ensuring suppressive power, it is necessary to have at least about 0.005%, but if it exceeds 0.06%, the effect will be impaired, so the lower limit and upper limit are 0.01%, respectively.
It is preferably about 0.08%.

For AIN type, Al 70.005-0.10%, N: 0.00
Regarding the range of 4 to 0.015% AI and N, for the same reason as the above-mentioned MnS, Mn5 (system),
It is set within the above range. Here, the above-mentioned MnS, MnS
The e system and the AIN system can each be used in combination.

In addition to the above-mentioned S, Se, and Al, inhibitor components include Cu, Sn, Cr, Ge+ sb, Mo+
Since Tet Bi and P are also advantageously compatible, they can also be contained together in small amounts. Here, the preferred addition ranges of the above components are Cu, Sn, Cr, respectively.
: 0.01~0.15%, Ge, Sb, Mo,
Te, Bi: 0.005-0.1%, P: 0. ．．
01 to 0.2%, and each of these inhibitor components can be used alone or in combination.

Next, oxides on the surface generated during final annealing are removed to finish the steel plate surface into a smooth surface with a center line average roughness of 0.3 μm or less. At this time, it is necessary to avoid leaving large plastic strain on the surface since this will deteriorate the magnetic properties of the product.

Therefore, to remove the oxide, it is preferable to use pickling, low strain mechanical polishing using an elastic body, or the like. Thereafter, the surface is smoothed to a predetermined roughness by chemical polishing or electrolytic polishing. Here, it is necessary to finish the surface of the steel plate to 0.3 μm Ra or less.

This is because if the surface roughness of the steel plate exceeds 0.3 μm Ra, sufficient reduction in hysteresis loss cannot be obtained.

Also, as a means of smoothing other than chemical polishing and electrolytic polishing,
Electrolytic treatment with a water-soluble halide or nitrate solution may also be used. Here, water-soluble halides are:
HCI, N) I4C1 and various metal chlorides, P+
Water-soluble acids, alkali, alkaline earth and other metal salts, or ammonium salts with Br+ I as an anion, as well as derivatives (BP, salts) or silicon fluorides (SiF6 salts) Of these, it means water-soluble ones. Nitrates also refer to nitrates that are water-soluble. Electrolytic treatment using an aqueous solution of halides or nitrates cannot produce a so-called mirror surface like chemical polishing or electrolytic polishing, but electrolytic treatment that reduces the surface layer to a thickness of 3 μm or more can produce a surface similar to that of a mirror surface. It is possible to obtain the effect of reducing IN.

Afterwards, the surface of the smoothed steel plate is coated with 0% by sol-gel method.
．． A thin gel film layer with a thickness of 1 to 0.5 μl is formed. For example, a metal alkoxide is used as a raw material for the membrane. Metal alkoxides have the general formula M (OR) n. Here, M: metal element, R: alkyl group, respectively. As M, Si, Ti, ^l.

Zr+ Get B+ Lit Na+ Fe, Ga
, Mg, P+ Sb, Sn, Ta and V, and single or multiple metal alkoxides thereof are used. This metal alkoxide is then coated in a sol state onto the surface of the steel plate by spraying or dipping. Further, if the film thickness is less than 0.1 μm, it is difficult to obtain a homogeneous film, and if it exceeds 0.5 μm, cracks will occur in the gel film, leading to deterioration of magnetic properties. It was set to 5 μm.

Next, the gel film is dried at a temperature of about 100° C. 1, and then a phosphate solution, for example, is applied to the surface of the steel plate in order to form an insulating film. Of course, a conventionally known tension-applying insulating film forming solution may be applied, and the application may be performed using either a roll coater or a spray.

The above-mentioned coating film is baked, and at that time, the intermediate dry gel film layer becomes vitrified and becomes a strong binder, and also imparts tension to the surface of the steel sheet.

Note that the dry gel film may be baked prior to insulating coating. The temperature of baking varies depending on the type of metal alkoxide used, but it is not a high temperature in any case. For example, when using Si (OCJs) a, 45
It can be baked by heating at 0°C for 5 minutes.

In addition to the metal alkoxides mentioned above, acetylacetone metal salts, naphthenic acid metal soaps, octylic acid metal soaps, silica-alumina sols, and the like can be used in the sol-gel method.

(Example) Non-metallic substances present on the surface of a finish-annealed grain-oriented silicon W4 plate containing 3.2% St, with MnSe as an inhibitor, were removed by pickling, and then the surface was treated with phosphoric acid. Electrolytic polishing was performed using a mixed acid solution of chromic acid and chromic acid to give a surface roughness of 0.1 μm Ra.

Thereafter, various sol solutions were applied to the obtained polished surface by a dip method and dried at 100°C to form a gel film (suitable example). In addition, as a comparative method, a chromium film with a thickness of approximately 0.8 μm was deposited by electroplating on the polished surface obtained in the same manner as above, and Comparative method A) was applied to the polished surface obtained in the same manner. , TiN by ion blating 1.
A film was formed to a thickness of 0 μm (comparative method B).

Next, a solution containing colloidal silica as a main component of magnesium phosphate was applied onto the film formed under each of the above conditions and baked, thereby breaking a tension-applied insulating film with a thickness of about 1.4 μm. In addition, as a comparative method, we applied an insulating film directly to the same polished surface as above without forming an intermediate film (
Comparative method C). In addition, the insulating coating was removed without applying the above polishing to the surface of the steel plate after finish annealing (conventional method).

The following tests were conducted on the coated m plates obtained according to the above conditions.

First, film adhesion was evaluated by wrapping a steel plate around a cylindrical test rod, stretching it, and examining the minimum diameter (-) of the cylinder without peeling off the film, to evaluate bending adhesion. Incidentally, for conventional grain-oriented silicon steel sheets, it is sufficient if the thickness is 30 or less.

The magnetic property of the steel plate is determined by the iron loss value Wl'l/S. (w/kg)
and Bl(T). Since the magnetic value itself is highly dependent on the magnetic value of the material, the improvement is described in comparison with the conventional method in which an insulating film is applied to the surface that still contains the nonmetallic substance after final annealing. Since the method of this invention improves magnetism by modifying the surface, it goes without saying that it has the effect of improving magnetism regardless of the inhibitor of the material or the manufacturing method such as rolling or annealing. Furthermore, the space factor is determined from the ratio of the calculated thickness and the measured thickness obtained from the weight after the insulation coating is formed.
The variation in the film thickness was measured by measuring the variation in the thickness of a sample having a width of 50 cm.

The results obtained are shown in Table 1.

As can be seen from the table, the method of the present invention makes it possible to efficiently form a homogeneous insulating film with high adhesion and space factor without deteriorating the excellent magnetic properties.

Non-metallic substances present on the surface of a finish-annealed grain-oriented silicon steel sheet containing 3.2% St using Ura-Kokushu AIN as an inhibitor are removed by low-strain mechanical polishing using an elastic polishing roll, Then, the surface of the steel plate was electrolytically treated using an aqueous NaCl solution to remove the surface layer of the steel plate over a thickness of 5 μm. The electrolytic treatment was carried out using a steel plate as an anode and applying a direct current of 50 A/d-.

Although the surface after electrolytic treatment was not a so-called mirror surface, the hysteresis loss was sufficiently reduced.

Next, various sol solutions were applied to this electrolytically treated surface by a dip method and dried at 100'C to form a gel film (suitable example). In addition, as a comparative method, a chromium film with a thickness of about 0.8 μm was formed by electroplating on the treated surface obtained in the same manner as above (Comparative Example D), and on the treated surface obtained in the same manner as above. , TiO by ion blating 1.
A film was formed to a thickness of 0 μm (Comparative Example E).

Next, a solution containing colloidal silica as a main component of magnesium phosphate was applied onto the film formed under each of the above conditions and baked to form a tension-applying insulating film with a thickness of about 1.4 μm. In addition, as a comparative method, we applied an insulating film directly to the same treated surface without forming an intermediate film (
Comparative method F). In addition, the insulating coating was removed without applying the above polishing to the surface of the steel plate after finish annealing (conventional method).

The same tests as in Example 1 were conducted on the coated steel sheets obtained according to the above conditions.

The results obtained are shown in Table 2.

As can be seen from the table, the method of the present invention makes it possible to efficiently form a homogeneous insulating film with high adhesion and space factor without deteriorating the excellent magnetic properties.

1. Non-metallic substances present on the surface of finish-annealed oriented silicon w4'Fi containing 3.2% Si with MnSe as the inhibitor are removed by low strain mechanical polishing using an elastic polishing roll. Then, the surface thereof was subjected to an electrolytic treatment using an aqueous NaCl solution to remove the surface layer of the steel plate over a thickness of 5 μm. The electrolytic treatment uses a steel plate as an anode and is applied at 50A/d-
This was done by applying a direct current of .

Although the surface after electrolytic treatment was not a so-called mirror surface, the hysteresis loss was sufficiently reduced.

Next, various sol solutions were applied to this electrolytically treated surface by a dip method and dried at 100°C to form a gel film. Furthermore, the gel film was vitrified by heating at 500″C (suitable example)
In addition, as a comparative method, a chromium film with a thickness of about 0.8 μm was formed by electroplating on the treated surface obtained in the same manner as above (Comparative Example G), and then on the treated surface obtained in the same manner. On the other hand, Tie is 1,0 by ion brating.
A film was formed to a thickness of μm (Comparative Example H).

Next, a solution containing magnesium phosphate as the main component was applied onto the film formed under each of the above conditions and baked to form a film with a thickness of about 1.2 μm.
A thick tension-applied insulation coating was applied.

In addition, as a comparative method, an insulating film was directly formed on the same treated surface as above without performing intermediate film formation (Comparative method I).
. In addition, the same tests as in Example 1 were conducted on coated steel plates obtained according to the above conditions, in which an insulating coating was formed on the surface of the steel plate after finish annealing without the above-mentioned polishing (conventional method). .

The results obtained are shown in Table 3.

As can be seen from the table, the method of the present invention makes it possible to efficiently form a homogeneous insulating film with high adhesion and space factor without deteriorating the excellent magnetic properties.

(Effects of the Invention) According to this invention, it is possible to significantly improve the iron loss and magnetic flux density of grain-oriented silicon steel sheets, and it is possible to provide products with extremely high industrial value that meet social demands for energy conservation. . Furthermore, since a coating with excellent adhesion and homogeneity can be obtained, it is possible to increase the space factor of the grain-oriented silicon steel sheet, further increasing its industrial value.

Claims (2)

[Claims] 1. After removing non-metallic substances from the surface of a grain-oriented silicon steel sheet that has been finish annealed, the surface of the steel sheet is made smooth with a center line average roughness of 0.3 μm or less, and then a sol is applied onto the surface of the steel sheet. Manufacture of a unidirectional silicon steel sheet with extremely good magnetic properties characterized by forming a gel thin film with a thickness of 0.1 to 0.5 μm by a gel method and further forming an insulating film on this thin film. Method. 2. Non-metallic substances on the surface of a grain-oriented silicon steel sheet that has been finish annealed are removed, and then the surface layer of the steel sheet is electrolytically treated using a water-soluble halide or nitrate.
After removing a thickness of 3 μm or more, a thin gel film with a thickness of 0.1 to 0.5 μm is formed on the surface of the steel plate by a sol-gel method, and an insulating film is further formed on this thin film. A method for manufacturing a unidirectional silicon steel sheet with extremely good magnetic properties.