JP2000169972A - Chromium-free surface treating agent for grain oriented silicon steel sheet, and manufacture of grain oriented silicon steel sheet using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve environmental problems and to improve magnetic properties by providing a composition of insulation coating agent which contains one or >=2 oxide colloidal substances in specific weight percentages based on primary phosphates of Al, Mg, and Ca and colloidal silica in respectively specified weight percentages expressed in terms of solids and is free from chromium compounds. SOLUTION: One or more oxide colloidal substances are contained in an amount of 0.3-15 pts.wt. based on 100 pts.wt. primary phosphates of Al, Mg, and Ca and 35-100 pts.wt. colloidal silica. It is preferable that, in this surface treating agent for silicon steel sheet, one or >=2 kinds among the compounds composed of any of Mg, Ca, Ba, Sr, Zr, Fe, Mn, Co, Ni, Cu, Zn, Al, Si, and B are used as the oxide colloidal substances and also the oxide colloidal substances of 0.1-5 μm particle size are used and chromium compounds are not contained. By adding the oxide colloidal substances, the corrosion resistance of film after baking and the seizure resistance at stress relief annealing can be improved.

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, insulation. The present invention relates to a method for forming an insulating film on a grain-oriented electrical steel sheet having excellent properties, adhesion, core workability, and the like.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are made of, for example, Si
% Silicon steel slab is hot-rolled and 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 an agent, finish annealing to develop secondary recrystallization with Goss orientation, further removing impurities such as S and N, forming a glass film, then applying an insulating film agent, baking and heating The product is flattened and finished. 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 iron core or wound. It is made 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 has excellent coating 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, the inventors of the present invention have disclosed in Patent Publication No. 53-28375 the invention of a tension film comprising colloidal silica, a phosphate and a chromium compound, and have been industrialized. Japanese Unexamined Patent Publication (Kokai) No. 61-41778 discloses a treating agent having excellent 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, A
Colloidal silica having a particle size of 20 nm or less and a particle size of 80 to 2 with respect to the primary phosphate and the chromium compound of l, Mg, Ca, Zn.
By mixing 000 nm colloidal silica,
There is disclosed a technique for obtaining a uniform projection effect on the surface of an insulating film to improve winding workability (slipperiness), annealing resistance, and film tension in a winding core processing step.

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:
A chromium compound has been added and blended in consideration of, for example, the hygroscopicity after the film baking treatment with phosphate and the 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 coating after baking, and is less harmful. However, if dusting occurs in the iron core processing step, there is a possibility that the working environment may be contaminated.

[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 20 parts by weight of SiO ₂ , 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 liquid 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 contains a chromium compound in a conventional phosphate-colloidal silica-based coating. Provided are an insulating coating agent for a grain-oriented electrical steel sheet having excellent coating performance that solves the problems of poor moisture absorption resistance and annealing resistance when not performed, and a method for manufacturing a grain-oriented electrical steel sheet using the same.

[0011]

SUMMARY OF THE INVENTION The present invention has the following constitution as an insulating coating agent composition containing no chromium compound and an insulating coating treatment method. (1) Primary phosphate of Al, Mg, Ca in terms of solid content 10
With respect to 0 parts by weight and 35 to 100 parts by weight of colloidal silica, one or more kinds of oxide colloidal substances are added in an amount of 0.1 to 0.2 parts by weight.
A surface treatment agent for grain-oriented electrical steel sheets containing no chromium compound, comprising 3 to 15 parts by weight. (2) Mg, Ca, B as an oxide colloidal substance
a, Sr, Zr, Fe, Mn, Co, Ni, Cu, Z
The surface treating agent for grain-oriented electrical steel sheets containing no chromium compound according to (1), wherein one or more of compounds comprising any one of n, Al, Si and B are used. (3) A surface for a grain-oriented electrical steel sheet containing no chromium compound according to any one of (1) and (2), wherein an oxide colloidal substance having a particle size of 0.1 to 5 μm is used. Processing agent. (4) The silicon steel slab is hot-rolled, cold-rolled once after annealing, or twice or more with intermediate annealing in between to obtain the final thickness, decarburized annealing, coated with an annealing separator, and then subjected to final finishing annealing. Then, in a method for producing a grain-oriented electrical steel sheet which is applied with an insulating film agent and subjected to baking treatment and heat flattening, the surface treating agent according to any one of (1) to (3) is applied as the insulating film agent. And baking at 350 ° C. or higher.

[0012]

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 coating composition. As a result, by adding one or more colloidal oxides to the tension-imparting coating component mainly composed of phosphate and colloidal silica, the conventional problem of chromium-free can be solved and corrosion resistance can be improved. An insulating coating agent having excellent annealing resistance, adhesiveness, slipperiness, insulating properties, etc., and excellent magnetic properties and magnetostriction properties, and a processing method thereof have been successfully completed. The details will be described below.

In applying the surface treating 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. The liquid is applied to the surface of the steel sheet and a baking process is performed. The present invention is first characterized by its coating composition. That is, in terms of solid content, Al, M
One or more colloidal oxides are added in an amount of 0.3 to 15 parts by weight to a base solution composed of 100 parts by weight of a primary phosphate of g and Ca and 35 to 100 parts by weight of colloidal silica. Oxide colloidal materials having this important role include Mg, Ca, Ba, Sr, Zr, Fe, M
One or two or more of any of n, Co, Ni, Cu, Zn, Al, Si and B are added.

According to the present invention, moisture absorption and distortion removal after the baking treatment are performed.
The reason why the seizure of steel sheet during annealing can be prevented is clear.
Is not estimated, but is estimated as follows. Disperse evenly in the solution
Fine particles of the oxide colloidal material are
Phosphoric acid generated from primary phosphate during annealing and strain relief annealing
To produce a more stable phosphate compound. That is,
When conventional chromium compounds are blended, Cr becomes free phosphorus.
CrPO by reacting with acid _FourA very stable compound like
Metal elements that make up the oxide so that it has an action to generate
Reacts with phosphoric acid at high temperatures during baking and strain relief annealing.
And minimize the presence of free phosphoric acid. That
As a result, suppressing the decomposition of phosphate and the fusibility due to phosphoric acid content,
It is considered to improve moisture absorption resistance and annealing resistance. This place
In general, such reactions are unlikely to occur with ordinary oxide powder.
On the other hand, colloidal materials show extremely significant reactivity,
It contributes to stabilization of free phosphoric acid.

It is considered that by controlling the contact area by fine projections on the surface of the insulating film formed by the colloidal oxide material, an effect of improving the image sticking property can be obtained. Next, the reasons for limitation of the present invention will be described. In the insulating film of the present invention, first, Al, M
The ratio of the primary phosphate of g and Ca to the base liquid of colloidal silica is important. Colloidal silica should be 35 to 100 parts by weight based on 100 parts by weight of the first phosphate in terms of solid content. 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, the moisture absorption resistance and the annealing resistance are improved, but the tension effect of the coating film is lost, which is not preferable.

The colloidal oxide material which is the most characteristic additive of the present invention includes Mg, Ca, Ba, S
r, Zr, Fe, Mn, Co, Ni, Cu, Zn, A
One or two or more of the elements 1, 1, and B are added. The addition amount of these oxide colloidal substances is 100 parts by weight of primary phosphate and colloidal silica 35.
0.3 to 15 parts by weight is blended with respect to 100 parts by weight of the base liquid. If the amount is less than 0.3 part by weight, the stabilization of P due to the reaction between free PO ₄ in the coating and the metal element and the effect of suppressing seizure during annealing due to the effect of the surface shape of the particles cannot be obtained, and the moisture absorption resistance and the annealing resistance are not obtained. This is limited because the effect of improving the property cannot be sufficiently obtained. On the other hand, if the amount exceeds 15 parts by weight, the film tension is reduced and the appearance is deteriorated due to excessive colloidal particles. If the added amount is in the range of 0.3 to 15 parts by weight, the appearance, corrosion resistance, and annealing resistance are excellent,
An insulating film with excellent adhesion and core workability can be obtained.

The particle diameter of the colloidal substance is preferably 0.1 to 5.0 μm. The smaller the particle size, the better the reactivity with free phosphoric acid, but at the same time, the cohesiveness is increased, so that a colloid having excellent dispersibility cannot be obtained. If the particle diameter is 0.1 μm or more, a good colloid is obtained, but it is preferably 0.5 μm or more. On the other hand, when the particle diameter is 5 μm or more, the reactivity with free phosphoric acid is reduced, and the surface unevenness is too large to cause a decrease in the space factor, which is limited.

The addition amount and the particle size are appropriately adjusted depending on the thickness of the product and the purpose of use. In particular, in the case of a material having a small thickness, the effect of the thickness and the surface roughness of the insulating film on the space factor is relatively large. In addition, when adding the colloidal oxide, gradually add the colloidal oxide while stirring the base solution in order to suppress agglomeration, or sufficiently disperse it in advance using a mixer, colloid mill, ultrasonic stirring device or the like. After that, it is preferable to uniformly disperse in the base liquid by gradually adding and blending. In particular, when using particles having a particle size of 1 μm or more,
Since the stability in a solution is lower than that of a normal colloid, it is necessary to sufficiently stir or disperse the solution even after the addition when storing or applying the solution, and to use the solution while suppressing coagulation and sedimentation.

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 magnetic properties and magnetostriction properties as well as coating properties and appearance can be obtained.

The steel sheet coated with the treating agent continues to be 35
The baking process is performed at 0 ° C. or higher. Baking temperature is 3
If the temperature is lower than 50 ° C., the reaction between the first phosphate, colloidal silica and the organic acid salt is not sufficiently performed, and the hygroscopicity 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, in order to obtain a sufficient tensile effect, corrosion resistance, and annealing resistance by utilizing a difference in thermal expansion during a baking process as in a normal grain-oriented electrical steel sheet, a baking process at 750 ° C. to 900 ° C. is necessary. is there.

In applying the agent of the present invention, 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.

[0022]

<Example 1> A sample was cut out from a high magnetic flux density directional magnetic steel sheet coil having a thickness of 0.23 mm having a glass coating on the surface of a 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 treating agent obtained by adding a solution in which the type and amount of the oxide colloidal substance were changed as shown in Table 1 was added to this sample,
After applying using a coating roll so that the weight after drying and baking would be 5 g / m ² , 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 2 shows the results
Shown in

[0023]

[Table 1]

[0024]

[Table 2] As a result of this test, when the oxide colloidal substance of the present invention was added, an excellent improvement effect of corrosion resistance and annealing resistance was obtained, and the result was comparable to Comparative Example 2 in which a Cr compound was added. Met. In addition, the lubricating property was superior to those to which the Cr compound was added and the comparative examples to which no colloidal substance was added. Further, in the film tension and the magnetic characteristics of the present invention, the same results as those obtained by the prior art with the addition of the Cr compound were obtained. <Example 2> A sample was cut out from a high magnetic flux density oriented magnetic steel sheet coil having a thickness of 0.23 mm which had been subjected to final finish annealing in the same manner as in Example 1, washed with water, and then subjected to a strain relief annealing at 850 ° C x 4 hr, and thereafter 7 in _2% -H 2 SO ₄ aqueous solution
Light pickling was performed at 5 ° C. for 15 seconds. To this sample, a coating roll was prepared by changing the type, particle size and amount of the colloidal oxide as shown in Table 3 so that the weight after drying and baking was 4.5 g / m ^2. After the application, 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.

[0025]

[Table 3]

[0026]

[Table 4] As a result of this test, when the oxide colloidal substance of the present invention was added in the same manner as in Example 1, the corrosion resistance and the annealing resistance were all excellent, and the magnetic properties were good. The result was comparable to 3. On the other hand, in the case of Comparative Example 1 in which the amount of the colloidal substance was too large, although the annealing resistance was excellent, the space factor and the magnetic properties were extremely poor. In Comparative Example 2 in which no oxide colloid was added, the corrosion resistance and the annealing resistance were considerably inferior to those of the present invention.

[0027]

According to the present invention, in a tensile coating of a grain-oriented electrical steel sheet based on phosphate-colloidal silica and containing no chromium compound, by adding an oxide colloidal substance, the corrosion resistance of the coating after baking is improved. Performance is improved,
A remarkable improvement in seizure resistance during strain relief annealing can be obtained.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a method for evaluating the seizure property 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, Fukuoka Prefecture Inside Nippon Steel Corporation Yawata Works (72) Inventor, Kimihiko Sugiyama Tobata-ku, Kitakyushu-shi, Fukuoka 1-1 Nippon Steel Corporation Yawata Works (72) Inventor Haru Tanaka F-term 4K026 AA03 AA22 BA03 at 59 Nippon Plant Design Co., Ltd., 46 Ohara Nakahara, Tobata-ku, Kitakyushu-shi, Fukuoka BB04 BB05 BB10 CA16 CA18 CA23 CA24 CA41 DA15 EA07 EA17 EB11 4K033 AA02 HA03 JA01 JA04 LA01 TA01 TA03 UA04

Claims (4)

[Claims] 1. One or two or more oxide colloidal substances are added in an amount of 0.3 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. A surface treatment agent for grain-oriented electrical steel sheets containing no chromium compound, comprising 15 parts by weight. 2. Mg, C as an oxide colloidal substance
a, Ba, Sr, Zr, Fe, Mn, Co, Ni, C
2. The surface treating agent for grain-oriented electrical steel sheets containing no chromium compound according to claim 1, wherein one or more of compounds comprising any one of u, Zn, Al, Si and B are used. 3. An oxide colloidal substance having a particle diameter of 0.1 to 5 μm is used.
A surface treating agent for grain-oriented electrical steel sheets which does not contain the chromium compound described in the above. 4. A silicon steel slab is hot-rolled and cold-rolled once after annealing or two or more times with intermediate annealing to a final thickness,
4. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein said decarburizing annealing is performed, said annealing separating agent is applied, said final finishing annealing is performed, and then said insulating film is applied, and baking treatment and heat flattening are performed. A method for producing a grain-oriented electrical steel sheet, comprising applying the surface treatment agent according to any one of the above, and then performing a baking treatment at a temperature of 350 ° C. or more.