JP3009578B2 - Method for producing grain-oriented electrical steel sheet having excellent film properties and insulating film treating agent therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating film treating agent for grain-oriented electrical steel sheets having good heat resistance, excellent workability of an iron core in a transformer manufacturing process, and good film and magnetic properties of a transformer product. And a method for forming a high-strength insulating film having film characteristics using the same.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets contain, for example, 2 to 4% of Si.
After hot rolling and annealing the silicon steel slab to be contained, the final thickness is obtained by cold rolling once or twice or more with annealing, then primary recrystallization by decarburization annealing and formation of an oxide layer on the steel sheet surface After that, an annealing separator containing MgO as a main component is applied, and a final finish annealing is performed to develop secondary recrystallization having a Goss orientation and remove impurities such as S and N, and at the same time, to form a glass film. Then, a coating agent for an insulating film is applied, dried and baked, and a film is formed to produce a final product. The grain-oriented electrical steel sheet thus obtained is mainly used as a core material for electrical equipment, transformers and the like, and is required to have a high magnetic flux density and a low iron loss value. On the other hand, when the grain-oriented electrical steel sheet is used as the core of a transformer, the hoop slit into a predetermined size is cut into a predetermined length by a shearing machine while being continuously unwound, and is sequentially wound by a core processing machine or Stacked into a wound core or stacked core. Generally, in the case of a wound iron core, after performing a winding operation called lacing through compression molding and strain relief annealing, it is put into a case to be a transformer. In the case of a laminated core, the core is laminated as needed after strain relief annealing, and then wound to form an iron core.

[0003] In this iron core manufacturing process, for example, in the case of a wound iron core, winding and forming operations can be carried out smoothly, and no irregularities are formed on the end face of the steel sheet or the lap portion of the formed core, and the shape is excellent. It is important that the surface of the steel sheet has excellent slipperiness and scratch resistance. In addition, during annealing, it is important to be able to perform lacing work without seizure between the steel sheet coatings from the viewpoint of improving iron core processing efficiency, preventing the induction of distortion in the steel sheet due to seizure and preventing the deterioration of coating performance. is there.
These problems are greatly affected by the properties of the insulating coating of the grain-oriented electrical steel sheet. Therefore, as described above, high-speed winding is easy during strain relief annealing, there is no seizure of the insulating coating on the steel sheet surface, the lacing work can be performed smoothly, and the coating tension for improving iron loss, magnetostriction, etc. There is a strong demand for the development of an insulating film having excellent corrosion resistance and adhesion.

[0004] As a means for improving the workability of the transformer core and the magnetic properties, a coating material for forming an insulating film has been improved. JP-A-61-41778 discloses that as a coating agent, a first phosphate is mixed with one or more kinds of ultrafine silica having a particle diameter of 8 nm or less, chromic acid or chromate after finish annealing. A technique for improving the slipperiness of an insulating film formed on the surface of a steel sheet by applying it to a steel sheet and baking it is disclosed.

Japanese Patent Application Laid-Open No. Hei 3-207868 discloses colloidal silica 5 having a particle size of 50 nm or less as an insulating coating agent.
Fe, Cu, Ba, Zn, Al, Ni, S with 0 to 98% by weight (as SiO ₂ ) and 10 to 40 parts by weight of one or more of chromate, chromate and dichromate.
n, Cu, Cr, Nd, Mn, Mo, Si, Ti, W,
Oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, nitrates of Bi, Sr, V, etc.
A mixture containing 2 to 50% of one or more colloidal substances having a particle diameter of 80 to 3000 nm and containing a chloride and a chromate is applied to the mixture and baked. There has been proposed a method for forming an insulating coating on a grain-oriented electrical steel sheet having excellent workability, heat resistance, and tension imparting property, which is characterized by being treated.

The former is intended to improve the smoothness and seizure by smoothing the surface with ultrafine colloidal silica and improving the fixing force of free phosphoric acid by increasing the particle surface area. The latter is intended to improve the slipperiness, scratch resistance and seizure resistance during annealing by the spherical projection effect of the surface formed by fine and coarse particles of the colloidal substance and the composite phosphate. All of these have achieved a certain effect.

[0007]

In each of these prior arts, phosphate, colloidal silica and chromate are used as the main components as insulating coating components. Basically, the film tension is determined by the ratio of colloidal silica and phosphate, and there is a limit in improving the film tension. There is a need for further improvements with respect to the seizure of the coating during the strain relief annealing caused by the phosphate and the problem of contamination of the working environment of the iron core due to the chromate.

[0008]

Means for Solving the Problems The inventors of the present invention have devised that a film formed by the conventional phosphate, colloidal silica, and chromate-based treatment liquids as described above decomposes the film components during strain relief annealing. In addition to the fact that seizure is likely to occur due to the fusion reaction, the work environment is contaminated by chromate and phosphate substances when the coating agent is peeled off during bending and molding,
For grain-oriented electrical steel sheets, consider the development of a coating agent with a new composition, focusing on the fact that further improvement in the tension of the insulating coating will lead to improvements in iron loss characteristics and magnetostriction characteristics that cause transformer noise. did. As a result, the composite metal hydroxide of the divalent and trivalent metals provides the effect of lowering the melting point, which has not been obtained conventionally with the sol of a simple oxide substance, and has a very good high tension at a low temperature in a short time. The inventors have found that an insulating film can be formed, and have completed the present invention.

That is, the gist of the present invention is as follows:
(4). _{^{(1) M 2+ 1-x}} M 3+ x (OH) 2 + x-ny A ny · mH 2 O
An insulating film treating agent for grain-oriented electrical steel sheets, characterized by having a composition of a solid solution type composite metal hydroxide having an average particle diameter of 1 μm or less represented by the following general formula: _{^{(2) M 2+ 1-x}} M 3+ x (OH) 2 + x-ny A ny · mH 2 O
Of boric acid, acetic acid, oxalic acid, formic acid, phosphoric acid, silicic acid, chromic acid, boric acid, acetic acid with respect to 100 parts by weight of a solid solution type composite metal hydroxide composition material having an average particle diameter of 1 μm or less represented by the following general formula: Insulating film treatment for grain-oriented electrical steel sheets, characterized in that the composition is one to 50 parts by weight of one or more of salts, oxalates, formates, phosphates, silicates, and chromates. Agent. (3) After the final annealing, the treating agent according to (1) is applied to the grain-oriented electrical steel sheet after the completion of the secondary recrystallization by a weight of 1 to 5 after baking.
A method for producing a grain-oriented electrical steel sheet having excellent coating characteristics, comprising applying 5 g / m ² and baking at a temperature of 400 to 1200 ° C. (4) After the final annealing, the treating agent according to (2) is applied to the grain-oriented electrical steel sheet after the completion of the secondary recrystallization by a weight of 1 to 5 after baking.
A method for producing a grain-oriented electrical steel sheet having excellent coating characteristics, comprising applying 5 g / m ² and baking at a temperature of 400 to 1200 ° C. However, in the above items (1) and (2), M ²⁺ ; divalent metal M ³⁺ such as Be, Mg, Ca, Ba, Sr, Sn, Mn, Fe, Co, Ni, Cu, Zn; , Fe, Cr, Co, in , B, Ga, 3 -valent metals such as Ti ^{a n-; OH -, F -} , Cl -, Br -, CO 3 2-, SO 4 2-, SiO 3 2-, ^{_{HPO 4 2-, CrO 4 2-,}} (CH 3 COO) 2 2-, Fe (CN) 6 3-, n -valent anion, such as _{HBO 3 0 <x <1.0 0} <y <2.0 m The number of molecules of interlayer water Hereinafter, the content of the present invention will be described in detail. The types of the inorganic compounds used in the present invention are as follows. In the present invention, a composite hydroxide composed of a divalent metal element and a trivalent metal element is applied and baked on a steel sheet as a sol-like aqueous solution. The form of the hydroxide substance is M 2 ⁺ _{1 -x} M ³⁺ _x
(OH) represented by the ^{_{2 + x-ny A ny ·}} mH 2 O. The divalent metal element applied to the basic composition M 2 ⁺ _{1 -x} M ³⁺ _x (OH) _{2 + x-ny} is Be, Mg, Ca, Ba, Sr, Sn, Mn, F
e, Co, Ni, Cu, Zn, etc., and trivalent metal elements include Al, Fe, Cr, Co, In, B, Ga, T
i.

The crystal structure of these materials is brucite [M
g (OH) ₂ ] is a layered structure composed of two kinds of layers, a similar positively charged basic layer and a negatively charged intermediate layer composed of anions and interlayer water. These include those in which a divalent hydroxide is dissolved in a trivalent hydroxide at the same time. The amount of positive charge is determined depending on the amount of substitution. This positive charge is neutralized by the anion in the intermediate layer to maintain electrical neutralization as the whole crystal. The remaining space occupied by anions in the middle layer is filled with interlayer water.

[0011] Production of a composite metal hydroxide used in the present invention is an alkali is added to the example M ^2+, M ^3+, and A ^n- mixture,
It is obtained by a method in which the reaction is carried out while maintaining the pH at about 7 or more. As such a substance, for example, a solid solution of a divalent hydroxide in a trivalent hydroxide, a solid solution of a trivalent hydroxide in a divalent hydroxide, or both of them. Is used. In these solid-solution type composite metal hydroxide materials, the effects of the anion material and the interlayer water act synergistically mainly due to solid solution, and secondarily, such that the single oxide material cannot be obtained. High reactivity and low melting point can be obtained. For this reason, a high-tensile insulating film is formed even under conditions of low temperature and short-time baking.

Further, since these coating agent materials are predominantly low-thermal-expansion components as compared with conventional phosphate-colloidal silica-chromic acid-based coatings, they can be used in conventional coating agents. There is a feature that a very large tension can be obtained.
The particle size of the composite hydroxide material of the present invention is 1 μm or less. This is because in the baking step, it is important to form a film by a low-temperature and short-time baking treatment when applying a coating agent. For this reason, a particle diameter larger than 1 μm is disadvantageous to high-speed film forming. is there.

The composition of the treating agent used in the present invention is as follows. In the present invention, the effect of lowering the melting point of the composite hydroxide substance is obtained by the anionic group. However, boric acid, acetic acid,
One or more of oxalic acid, formic acid, phosphoric acid, silicic acid, chromic acid, borate, acetate, oxalate, formate, phosphate, silicate, and chromate are composite hydroxide substances 100 It is desirable to mix it in a ratio of 0.5 to 50 parts by weight with respect to parts by weight. By the addition of these substances, the formation of the insulating film at a lower temperature and in a shorter time proceeds, and the adhesion of the film to the steel sheet is improved. If the compounding ratio is less than 0.5 part by weight based on 100 parts by weight of the composite hydroxide material, such an effect becomes extremely small. On the other hand, if it exceeds 50 parts by weight, the film tension may decrease, or excess boric acid, acetic acid, oxalic acid, formic acid, phosphoric acid, silicic acid, chromic acid, borate, acetate, oxalic acid garden, formate, phosphate may be used. , Silicates and chromates cause problems such as stickiness of the coating surface due to hygroscopicity and a decrease in heat resistance, and are also limited by the occurrence of seizure during strain relief annealing.

Next, the application amount of the above-mentioned treating agent will be described.
The amount of the insulating film formed on the surface of the electromagnetic steel sheet is suitably in the range of 1.0 to 5.0 g / m ² in terms of the weight after baking. 1g /
If it is less than m ^2, it is difficult to obtain sufficient film tension, corrosion resistance, insulation properties, and the like. In particular, it is disadvantageous when processing to an electromagnetic steel sheet having no glass coating. In the coating agent composition of the present invention, when the adhesion amount is in the range of 1.0 to 5.0 g / m ² , the plate thickness is 0.23.
When applied to a thickness of 0.5 mm, a film having a high tension of 0.5 to 3.0 kg / m ² can be obtained, and good film characteristics such as corrosion resistance and insulation can be obtained. If the adhesion amount is 5.0 g / m ² or more, the space factor may decrease and the adhesion may decrease due to high tension, and the improvement in iron loss due to the tension effect may be saturated with the adhesion amount near 5 g / m ^2. It is unnecessary because it is disadvantageous in terms of cost.

Further, conditions for applying and baking the above-mentioned treating agent will be described. As a method of applying and baking the treatment liquid, the treatment liquid is diluted to an appropriate concentration with water in a continuous line, applied in a predetermined amount by a roll coater, and subjected to baking at 400 to 1200 ° C. for a short time. If the baking temperature is lower than 400 ° C., it takes a long time to melt the composite hydroxide, so that there is a problem that it cannot withstand industrial use. Further, the thermal expansion of the steel sheet during baking is insufficient, and the effect of the film tension is reduced. On the other hand, when the temperature is 1200 ° C. or more, it is difficult to control the elongation of the steel sheet in baking in a continuous furnace, so that the temperature is limited. Preferably 750-950
° C.

The treating agent of the present invention is applied to a grain-oriented electrical steel sheet which has been subjected to final finish annealing. In this case, there are three cases. The first is for coating on a glass coating after final annealing, the second is for coating a glass coating with another insulating coating agent, and the third is removal of these coatings by pickling etc. This is an application to a so-called glassless material in which the formation of a glass film is prevented by controlling the conditions of an annealing separator or final annealing. In these applications, it is good to apply after performing light pickling or the like as a pretreatment in order to obtain uniform coating properties of the coating, but it is not limited thereto. The film formation is performed by controlling the application amount of the film material, the heat cycle of the baking treatment, and the like according to these uses.

In the present invention, a composite hydroxide material of fine particles composed of a divalent or trivalent metal element as a coating component and, if necessary, boric acid, borate, phosphoric acid, phosphate or the like as a low melting point agent. By adding and applying an aqueous solution, 40
A short-time baking process is performed at 0 to 1200 ° C. to form an insulating film. The coating thus obtained can form a dense insulating coating having excellent heat resistance, insulation properties, corrosion resistance, and the like.
Further, in the present invention, a composite hydroxide sol such as Mg or Al is used as a main component. In the present invention, depending on the selection of the additive, a chromate compound is not used at all, and a phosphoric acid compound is almost used, such as a phosphate, a chromate, and a colloidal silica-based film used for a conventional insulating film. Since the composition of the coating can be reduced, the coefficient of thermal expansion of the coating to be formed is small, and a remarkable high tension can be obtained. Further, in this case, it is possible to realize a coating film having no problem of working environment contamination due to peeling of the coating film in the iron core processing step using a chromium compound or the like.

Another great effect of the composite hydroxide is stabilization of an anionic substance and additives. When the composite hydroxide is not used, even if the baking temperature and time for vitrification are sufficient and the vitrification is completed, free phosphoric acid, boric acid, and the like caused by the anionic substance and the additive and moisture absorption of these salts can be reduced. It cannot be sufficiently suppressed, and it is difficult to improve corrosion resistance and seizure resistance. Although the reason is not clear, the composite hydroxide has an effect of extremely reducing the hygroscopicity and seizure, and the composite material has a large effect of stabilizing the film component.

[0019]

【Example】

Example 1 A cold-rolled coil of a 0.23 mm high magnetic flux density grain-oriented electrical steel sheet treated by a known method was N ₂ 25%
Decarburization annealing was performed at 850 ° C. for 120 seconds in a wet atmosphere of + H ₂ 75% to perform decarburization and oxide film formation. Next, as an annealing separator, a powder having a composition comprising 100 parts by weight of MgO, 5 parts by weight of TiO ₂ , and 0.3 parts by weight of Na borate was applied. Next, final finishing annealing was performed at 1200 ° C. for 20 hours, and a secondary recrystallization and purification were performed, and a glass coating was formed on the steel sheet surface to obtain a starting material.

This coil is washed with water to remove excess MgO on the surface.
And 2% H ₂ SO ₄ in a continuous line, liquid temperature 80 ° C.
After light acid washing for 10 seconds, an aqueous solution containing a composite metal hydroxide having the chemical composition shown in Table 1 and a certain amount of BO ₃ ^3- as an anion substance is baked to a weight of 4 g / m ^2. And baked at 850 ° C. for 60 seconds.
Table 2 shows the results of the film properties and magnetic properties at this time.

[0021]

[Table 1]

[0022]

[Table 2]

As a result, all of the compositions according to the present invention formed a high-tensile, glossy, transparent glassy film, and the adhesion of the film was good. On the other hand, in the case of the comparative example using Al (OH) ₃ without using the composite hydroxide sol, vitrification did not occur, and the coating film adhesion and the iron loss improving effect were remarkably inferior to those of the present invention. In addition, the magnetic properties of the obtained products were also improved in accordance with the film tension. In each case, the iron loss was remarkably improved, and those using no conventional phosphate-colloidal silica system or composite hydroxide as comparative materials were used. Good characteristics were obtained as compared with.

Example 2 A sample obtained in the same manner as in Example 1
The coil after the final annealing was washed with light acid in a continuous line, and as a coating agent disclosed in JP-A-61-4773, 25 ml of 50% Al phosphate, 25 ml of 50% Mg phosphate, and 2 particles having a particle diameter of 6 nm were used.
A treatment agent comprising 100 ml of 0% colloidal silica was applied so that the weight after baking was 3.5 g / m ² ,
A baking process was performed at 25 ° C. for 25 seconds.

An aqueous solution containing a composite metal hydroxide having a chemical composition as shown in Table 3 and an anionic substance and metaboric acid and boric acid as an additive was used as an aqueous solution, and the weight after baking was 4.0 g / m 2. the coating is a ^2, 860 ° C. ×
A baking process was performed for 45 seconds. Table 4 shows the results of the film properties and magnetic properties of the product thus obtained.

[0026]

[Table 3]

[0027]

[Table 4]

As a result, when boric acid or metaboric acid was added to the composite metal hydroxide material of the present invention, good characteristics were obtained in each case. In other words, the film properties are high tension,
A uniform glassy film with good adhesion was formed, excellent in corrosion resistance and seizure resistance during SRA, and the effect of improving iron loss was remarkable. On the other hand, in Comparative Examples in which the composite hydroxide was not used, vitrification was insufficient in all cases, the corrosion resistance and seizure resistance were considerably inferior in the film properties, and the tensile strength was small.

[0029]

According to the present invention, a grain-oriented electrical steel sheet having good heat resistance and high film tension can be produced.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-36284 (JP, A) JP-A-59-205708 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00 C21D 8/12

Claims (4)

(57) [Claims] 1. M 2 ⁺ _{1 -x} M ³⁺ _x (OH) _{2 + x-ny} A ^n- _y.
An insulating film treating agent for grain-oriented electrical steel sheets, characterized by having a solid solution type composite metal hydroxide composition having an average particle size of 1 μm or less represented by a general formula of mH ₂ O. However, M ²⁺ ; divalent metal such as Be, Mg, Ca, Ba, Sr, Sn, Mn, Fe, Co, Ni, Cu, Zn, etc. M ³⁺ ; Al, Fe, Cr, Co, In, B, Ga, 3-valent metal a ^n- such as ^{Ti; OH -, F -, Cl} -, Br -, CO 3 2-, SO 4 2-, SiO 3 2-, HPO 4 2-, CrO 4 2-, ( N-valent anions such as CH ₃ COO) ₂ ²⁻ , Fe (CN) ₆ ³⁻ and HBO ₃ 0 <x <1.00 0 <y <2.0 m; number of molecules of interlayer water 2. M ²⁺ _1-x M ³⁺ _x (OH) _{2 + x-ny} A ^n- _y ·
With respect to 100 parts by weight of a solid solution type composite metal hydroxide composition material having an average particle diameter of 1 μm or less represented by a general formula of mH ₂ O, boric acid, acetic acid, oxalic acid, formic acid, phosphoric acid, silicic acid, chromic acid,
Grain-oriented electrical steel sheet having a composition comprising 1 to 50 parts by weight of one or more of borate, acetate, oxalate, formate, phosphate, silicate and chromate. Insulating coating treatment agent. However, M ²⁺ ; divalent metal such as Be, Mg, Ca, Ba, Sr, Sn, Mn, Fe, Co, Ni, Cu, Zn, etc. M ³⁺ ; Al, Fe, Cr, Co, In, B, Ga, 3-valent metal a ^n- such as ^{Ti; OH -, F -, Cl} -, Br -, CO 3 2-, SO 4 2-, SiO 3 2-, HPO 4 2-, CrO 4 2-, ( N-valent anions such as CH ₃ COO) ₂ ²⁻ , Fe (CN) ₆ ³⁻ and HBO ₃ 0 <x <1.00 0 <y <2.0 m; number of molecules of interlayer water 3. Exit final annealing, the grain-oriented electrical steel sheet after the secondary recrystallization _{^{completion, M 2+ 1-x M 3+}} x (OH) 2 + x-ny A n-
_A treating agent having a solid solution type composite metal hydroxide composition having an average particle diameter of 1 μm or less represented by a general formula of _y · mH ₂ O is applied in an amount of 1 to 5 g / m ² by baking weight, and 400 to 1200 ° C
A method for producing a grain-oriented electrical steel sheet having excellent coating properties, characterized by performing baking treatment in the range described above. However, M ²⁺ ; divalent metal such as Be, Mg, Ca, Ba, Sr, Sn, Mn, Fe, Co, Ni, Cu, Zn, etc. M ³⁺ ; Al, Fe, Cr, Co, In, B, Ga, 3-valent metal a ^n- such as ^{Ti; OH -, F -, Cl} -, Br -, CO 3 2-, SO 4 2-, SiO 3 2-, HPO 4 2-, CrO 4 2-, ( N-valent anions such as CH ₃ COO) ₂ ²⁻ , Fe (CN) ₆ ³⁻ and HBO ₃ 0 <x <1.00 0 <y <2.0 m; number of molecules of interlayer water 4. Exit final annealing, the grain-oriented electrical steel sheet after the secondary recrystallization _{^{completion, M 2+ 1-x M 3+}} x (OH) 2 + x-ny A n-
_With respect to 100 parts by weight of a solid solution type composite metal hydroxide composition material having an average particle diameter of 1 μm or less represented by a general formula of _y · mH ₂ O, boric acid, acetic acid, oxalic acid, formic acid, phosphoric acid, silicic acid, chromic acid , Borate, acetate, oxalate, formate, phosphate,
1 to 50 parts by weight of one or more silicates and chromates are blended with the treating agent in an amount of 1% by weight after baking.
To 5 g / m ² was applied, the production method of the grain-oriented electrical steel sheet having excellent coating properties, characterized in that the baking in a range of 400 to 1200 ° C.. However, M ²⁺ ; divalent metal such as Be, Mg, Ca, Ba, Sr, Sn, Mn, Fe, Co, Ni, Cu, Zn, etc. M ³⁺ ; Al, Fe, Cr, Co, In, B, Ga, 3-valent metal a ^n- such as ^{Ti; OH -, F -, Cl} -, Br -, CO 3 2-, SO 4 2-, SiO 3 2-, HPO 4 2-, CrO 4 2-, ( N-valent anions such as CH ₃ COO) ₂ ²⁻ , Fe (CN) ₆ ³⁻ and HBO ₃ 0 <x <1.00 0 <y <2.0 m; number of molecules of interlayer water