JP2000169973A - Surface treatment agent for grain-oriented electrical steel sheet containing no chromium and method for producing grain-oriented electrical steel sheet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve corrosion resistance, annealing resistance, and core workability of a tension-containing insulating film for directional magnetic steel sheets of a phosphate-colloidal silica-based material containing no chromium. SOLUTION: In terms of solid content, 1 to 25 parts by weight of a boron compound is contained with respect to 100 parts by weight of one or more kinds of primary phosphates of Al, Mg and Ca and 35 to 70 parts by weight of colloidal silica. A surface treating agent for grain-oriented electrical steel sheets, characterized by that:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming an insulating film for grain-oriented electrical steel sheets, and more particularly to a processing solution containing no chromium and using the same to use it for corrosion resistance, annealing resistance, film tension, and insulation. The present invention relates to a method for forming an insulating film having excellent properties, adhesion, core workability, and the like.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are formed by adding Si, for example, from 2 to 2.
A 4% silicon steel slab is hot-rolled, annealed, and then cold-rolled once or twice or more with intermediate annealing to a final thickness, then decarburized and then annealed mainly with MgO. Applying a separating agent, performing finish annealing to develop secondary recrystallization having Goss orientation, further removing impurities such as S and N, forming a glass film, then applying an insulating film agent, and baking. Heat-flattening treatment is performed to obtain the final product. The grain-oriented electrical steel sheet obtained in this way is mainly used as an iron core material for electrical equipment, transformers and the like, and is required to have a high magnetic flux density and an excellent iron loss.

When a grain-oriented magnetic steel sheet is used as a transformer core, the grain-oriented magnetic steel sheet coil is slit into a predetermined width, and then cut into a predetermined length and stacked to form a piled core or wound. It is processed into a wound iron core. In the case of a wound iron core, it is further transformed into a transformer by performing winding work called racing through compression molding and strain relief annealing.

In the transformer manufacturing process, it is important that cutting, winding, and forming operations can be easily performed. Especially in the production of wound cores, the insulation film has excellent adhesion during cutting and winding molding, and does not impair the working environment such as dusting, and also has excellent winding workability and annealing resistance, and film performance, magnetic properties and workability. It is important not to impair. The surface film of a grain-oriented electrical steel sheet usually consists of a forsterite film usually called a glass film formed during the final annealing and an insulating film to be treated thereon. As a technique for forming the insulating film, Japanese Patent Publication No. 53-28375 discloses the invention of a tension film comprising colloidal silica, a phosphate and a chromium compound, and has been industrialized. Japanese Patent Application Laid-Open No. 61-41778 discloses a treating agent which is excellent in tension imparting property and sliding property, comprising a first phosphate comprising fine colloidal silica having a particle diameter of 8 nm or less and a chromium compound.

In Japanese Patent Application Laid-Open No. 3-39484,
Colloidal silica having a particle size of 20 nm or less with respect to primary phosphates of Al, Mg, Ca, and Zn and a chromium compound,
A technique has been shown in which by mixing 2000 nm of colloidal silica, a uniform projection effect is obtained on the surface of the insulating film to improve winding workability (slipperiness), annealing resistance, and film tension in the winding core processing step. ing.

Further, as a technique for improving heat resistance and slipperiness, Japanese Patent Application Laid-Open No. 4-165082 discloses a phosphate of Al, Mg, Ca, Zn per 100 parts by weight of colloidal silica having a particle size of 50 nm or less as SiO2. 130 to 250 parts by weight of one or more of the following, 10 to 40 parts by weight of one or more of chromic anhydride, chromate, and dichromate, and Fe, Co, Ba, Zn, Al , Ni, Sn,
Cu, Cr, Cd, Nb, Mn, Mo, Si, Ti,
Non-colloidal solids of oxides, carbides, nitrides, sulfides, silicates, carbonates, borates, sulfates, nitrates or chlorides of W, Bi, Sr and having a particle size of 0.5 to 2000 nm There has been proposed a method of forming an insulating film by using a treating agent containing 0.5 to 25 parts by weight of one or more of the above.

[0007] By these techniques, a tensile effect and an improvement in workability of the iron core can be obtained, and a grain-oriented electrical steel sheet having excellent magnetic properties and magnetostrictive properties has been obtained.

[0008]

SUMMARY OF THE INVENTION These insulating films are:
In all cases, a chromium compound has been added and blended in consideration of, for example, moisture absorption after phosphate baking treatment and suppression of film seizure during strain relief annealing. However, in the case where the treatment liquid contains hexavalent chromium using chromic anhydride, chromate or dichromate, there is a problem of a working environment at the time of coating operation and a waste liquid treatment operation. Further, Cr is reduced to trivalent chromium in the film after the baking treatment and is less harmful. However, if powdering occurs in the iron core processing step, there is a possibility of contaminating the working environment.

[0009] As a countermeasure, studies have been made on an insulating film agent containing no chromium compound. Japanese Patent Publication No. 57-963
No. 1 discloses that colloidal silica is selected from the group consisting of 20 parts by weight of SiO2, 10 to 120 parts by weight of Al phosphate, 2 to 10 parts by weight of boric acid, and sulfates of Mg, Al, Fe, Co, Ni and Zn. There has been proposed an insulating film forming method in which a treatment solution containing 4 to 40 parts by weight of one or two kinds in total is baked at 300 ° C. or more. Also, Japanese Patent Application Laid-Open
No. 180064 discloses M ²⁺ 1-xM ³⁺ x (OH) ₂
Disclosed is a treating agent having a solid solution composite hydroxide composition having an average particle diameter of 1 μm or less represented by a general formula of + x-nyAn-y · mH ₂ O.

[0010] These are all technologies capable of exhibiting the effect of film tension, and exhibit their effects as such. However, compared with the conventional chromium-containing insulating film agent, it cannot be said that the film performance is generally sufficiently improved, and further improvement has been desired. The present invention solves environmental problems by having an insulating coating agent composition not containing a chromium compound, and can improve magnetic properties and magnetostriction properties, and does not contain a chromium compound in a conventional phosphate-colloidal silica-based coating. The present invention provides an insulating coating agent for a grain-oriented electrical steel sheet having excellent film performance to solve the problems of poor moisture absorption resistance and annealing resistance in such a case, and a method for producing a grain-oriented electrical steel sheet using the same.

[0011]

The gist of the present invention is as follows, as a composition of an insulating film agent for a grain-oriented electrical steel sheet containing no chromium compound and a method of treating an insulating film. (1) Primary phosphate of Al, Mg, Ca in terms of solid content 10
A surface treatment agent for grain-oriented electrical steel sheets containing no chromium compound, characterized in that it contains 1 to 25 parts by weight of one or more boron compounds based on 0 parts by weight and 35 to 100 parts by weight of colloidal silica. .

(2) In addition to boron, the boron compound is Li,
Na, K, Mg, Mn, Ca, Ba, Sr, Zr, F
e, Co, Ni, Cu, Zn, Al, O, or one or more of them. (1)
The surface treating agent for grain-oriented electrical steel sheets which does not contain a chromium compound according to the above. (3) The silicon steel slab is hot-rolled, cold-rolled once or two or more times with intermediate firing after firing to a final thickness, decarburized annealing, applied with an annealing separating agent, and then subjected to final finish annealing, Next, in the method for producing a grain-oriented electrical steel sheet to which an insulating film agent is applied and subjected to baking treatment and heat flattening, the surface treating agent described in (1) or (2) is applied as an insulating film agent, and then 350 ° C. or higher. A method for producing a grain-oriented electrical steel sheet, comprising performing a baking treatment at a temperature.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have worked on a chromium-free composition in a conventional tension-imparting insulating film mainly containing a phosphate, colloidal silica and a chromium compound. That is, in order to improve the hygroscopicity (stickiness and rust generation) after the film baking treatment and the seizure in the strain relief annealing, which were disadvantages in the case of the composition of only the phosphate and colloidal silica which had been made chromium-free in the conventional composition. We worked on the development of the film composition. As a result, in the tension-imparting film component mainly composed of phosphate and colloidal silica, one of boron compounds
Insulation film that solves the problem of conventional chromium-free by adding seeds or two or more kinds, has excellent corrosion resistance, annealing resistance, adhesion, slipperiness, insulation, etc., and has excellent magnetic properties and magnetostriction properties. The agent and its treatment were successfully completed. The details will be described below.

In applying the surface treatment agent according to the present invention, a finish-annealed grain-oriented electrical steel sheet is used as a starting material, an excess annealing separating agent is removed in a continuous treatment baking line, and after light pickling, the present invention is applied. Is applied to the surface of the steel sheet and a baking treatment is performed. The present invention is first characterized by its film composition. That is, A in solid weight
One or more boron compounds are added in an amount of 1 to 25 parts by weight to a base liquid composed of 100 parts by weight of a primary phosphate of 1, Mg and Ca and 35 to 100 parts by weight of colloidal silica.

Among the boron compounds having an important role, in addition to boron, Li, Na, K, Mg, Mn,
Ca, Ba, Sr, Zr, Fe, Co, Ni, Cu, Z
One or two or more compounds composed of elements selected from n, Al and O are added. As compounds, borate,
Compounds with borides, oxides or other salts are used.

The reason why the surface treating agent of the present invention can prevent the hygroscopicity after the baking treatment and the seizure of the steel sheet during the strain relief annealing is not clear, but is presumed as follows.
Boron and metal elements from the boron compound uniformly dispersed in the solution react with free phosphoric acid generated from the first phosphate during film baking or strain relief annealing to form a more stable phosphate compound. That is, when a conventional chromium compound is blended, Cr has the effect of reacting with free phosphoric acid to produce a very stable compound such as CrPO ₄ .
When the metal element in the organic acid salt reacts with the phosphoric acid in the high temperature range during baking or strain relief annealing, it stabilizes, suppressing decomposition and the fusibility due to the phosphoric acid, and improving the moisture absorption resistance and annealing resistance Conceivable.

Next, the reasons for limiting the surface treatment agent according to the present invention will be described. In the insulating film of the present invention, first,
The ratio of primary phosphate of Al, Mg, Ca and base liquid of colloidal silica is important. Primary phosphate 1 by weight of solids
Colloidal silica should be 35 to 100 parts by weight based on 00 parts by weight. If the amount is less than 35 parts by weight, the surface of the film becomes cloudy and a transparent and glossy film cannot be obtained, the tension effect by the film is lost, and good magnetism and magnetostriction improvement effects cannot be obtained. On the other hand, if it exceeds 100 parts by weight, although the moisture absorption resistance and the annealing resistance are improved, the tension effect of the film is lost, which is not preferable.

The boron compound which is the most characteristic additive of the present invention includes, in addition to boron, Li, Na, K, M
g, Mn, Ca, Ba, Sr, Zr, Fe, Co, N
One or more compounds of the elements selected from i, Cu, Zn, Al and O are added. The amount of the boron compound added is 1 to 100 parts by weight of the first phosphate and 35 to 100 parts by weight of the colloidal silica.
25 parts by weight are blended. If the amount is less than 1 part by weight, P cannot be stabilized by the reaction with free PO ₄ in the film, and the effect of improving the moisture absorption resistance and the annealing resistance cannot be sufficiently obtained. On the other hand, if it exceeds 25 parts by weight, fusion is caused by an excessive boron compound or the treatment solution is destabilized, so that it is limited. A more preferable range of the addition amount is 5 to 5.
15 parts by weight.

These compositions are dispersed in a solvent such as water and applied to a steel sheet. When the boron compound is added, it is desirable to add and mix while stirring the base solution after previously preparing an aqueous solution or dispersion with water or warm water in order to homogenize the reaction with free phosphoric acid. In this case, it is advantageous to sufficiently agitate the base liquid before proceeding to the coating treatment.

The treatment agent adjusted as described above is applied in a continuous line while controlling the application amount using a coating roll or the like. The amount of application is determined by the thickness of the steel sheet to be applied and the purpose of use of the product. In the case of the coating agent of the present invention, if it is ² to 7 g / m ² , a grain-oriented electrical steel sheet excellent in not only the coating performance and appearance but also the magnetic characteristics and magnetostriction characteristics can be obtained.

The steel sheet coated with the insulating film agent is subsequently baked at a temperature of 350 ° C. or higher. When the baking temperature is lower than 350 ° C., the reaction between the first phosphate, colloidal silica and boron compound is not sufficiently performed, and the hygroscopic property remains.
In the case where a magnetic domain refinement treatment such as a laser is performed on a product to obtain an effect of improving magnetic properties, a temperature range of 350 to 450 ° C. is preferable. However, as with ordinary grain-oriented electrical steel sheets, a sufficient tensile effect and corrosion resistance,
To obtain annealing resistance, baking treatment at 750 ° C to 900 ° C is required.

When the agent of the present invention is applied, in addition to the material having a glass film formed by finish annealing, glass formation is prevented by using a glass film formation inhibitor as an annealing separating agent, or the glass film is removed by pickling. It may be applied to so-called glassless materials.

[0023]

<Example 1> A sample was cut out from a 0.23 mm high magnetic flux density oriented magnetic steel sheet coil having a glass film on the surface of the steel sheet subjected to final finish annealing, washed with water, and then strained at 850 ° C x 4 hr. Anneal, then 2%-
Light acid washing was performed at 85 ° C. for 15 seconds in an H ₂ SO ₄ aqueous solution. A coating solution was applied to this sample using a coating roll so that the treating agent solution in which the type and amount of borate were changed as shown in Table 1 was 4.5 g / m ² in weight after drying and baking. 850 ° C. for 30 seconds. Thereafter, a sample was cut out from the product plate and the film properties were investigated. Table 2 shows the results.

[0024]

[Table 1]

[0025]

[Table 2] As a result of this test, in each of the examples of the present invention to which the boron compound of the present invention was added, an excellent improvement effect of corrosion resistance and annealing resistance was obtained, and Comparative Example 3 containing the conventional chromium compound was obtained.
The result was not inferior to. Lubricity is comparative example 3
It was a better result. On the other hand, in the case of Comparative Example 2 in which the boron compound was not added, the corrosion resistance and the annealing resistance, the film tension, and the magnetic properties were extremely poor as compared with the examples of the present invention. Comparative Example 1 with a small amount of borate added
As in Comparative Example 2 where no additive was added, the results were considerably inferior in corrosion resistance, heat resistance and the like.

<Example 2> A sample was cut out from a 0.23 mm-thick magnetic steel sheet having a high magnetic flux density which had been subjected to final finish annealing in the same manner as in Example 1, washed with water at 850 ° C ×
4Hr strain relief annealing is performed, and then 2% -H ₂ SO ₄
Light acid pickling was performed in an aqueous solution at 75 ° C. for 15 seconds. A treating agent in which the type and amount of the boron compound were changed as shown in Table 3 was added to this sample in terms of the weight after drying and baking.
The coating was performed using a coating roll so as to have a concentration of 5 g / m ^2, and a baking treatment was performed at 850 ° C. for 30 seconds. Thereafter, a sample was cut out from the product plate and the film properties were investigated. Table 4 shows the results.

[0027]

[Table 3]

[0028]

[Table 4] As a result of this test, as in Example 1, when the boron compound of the present invention was added, the corrosion resistance and annealing resistance were all excellent, and the magnetic properties were good.
The result was comparable to that. On the other hand, in Comparative Example 1 in which the amount of the boron compound added was too large, the surface of the insulating film was rough and the corrosion resistance and the annealing resistance were slightly inferior. In the case of Comparative Example 2 where no boron compound was added,
Corrosion resistance and annealing resistance were significantly inferior to those of the present invention.

[0029]

According to the present invention, the corrosion resistance of a film after baking is improved by adding a boron compound to a tensile film of a grain-oriented electrical steel sheet containing phosphate-colloidal silica and containing no chromium compound. The effect of remarkable improvement in seizure resistance during strain relief annealing is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for evaluating the seizure of a film in strain relief annealing, in which (a) shows a pressure-bonded state and (b) shows a method for measuring a peeling force.

FIG. 2 is a diagram showing an outline of an apparatus for evaluating film lubricity.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shingo Okada, Inventor 1-1, Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Prefecture Inside Nippon Steel Corporation Yawata Works (72) Inventor, Osamu Tanaka Ogata, Kitakyushu-shi, Fukuoka 46 at Nakahara 59 Nippon Steel Plant Design Co., Ltd. F-term (reference)

Claims (3)

[Claims] 1 to 100 parts by weight of a primary phosphate of Al, Mg and Ca and 35 to 100 parts by weight of colloidal silica in terms of solid content, one or more boron compounds are added in an amount of 1 to 2 parts.
A surface treatment agent for grain-oriented electrical steel sheets containing no chromium compound, which is contained in an amount of 5 parts by weight. 2. The method according to claim 1, wherein the boron compound is Li, N
a, K, Mg, Mn, Ca, Ba, Sr, Zr, Fe,
2. The surface treating agent for grain-oriented electrical steel sheets according to claim 1, wherein the surface treating agent comprises one or more of Co, Ni, Cu, Zn, Al and O. 3. A silicon steel slab is hot-rolled, cold-rolled once or twice or more after intermediate firing to a final thickness, decarburized annealing, coated with an annealing separator, and then final finished annealing. And
Next, in a method for producing a grain-oriented electrical steel sheet, in which an insulating film agent is applied and subjected to baking treatment and heat flattening, the surface treating agent according to claim 1 or 2 is applied as an insulating film agent, and then at a temperature of 350 ° C. or more. A method for producing a grain-oriented electrical steel sheet, comprising performing a baking process.