JP2697967B2 - Method of forming insulation coating on grain-oriented electrical steel sheet with low core baking excellent in core workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an insulating film on a low-temperature-baked grain-oriented electrical steel sheet having excellent core workability and magnetic properties.

[0002]

2. Description of the Related Art Generally, grain-oriented electrical steel sheets have a Si value of, for example, 2
４4% silicon steel slab is hot-rolled, annealed, and then cold rolled once or twice with intermediate annealing to a final thickness, then decarburized and annealed, and the surface of the steel sheet is mainly made of SiO ₂ After forming an oxide film, apply an annealing separator mainly composed of MgO,
Finish annealing is performed to develop secondary recrystallization having a Goss orientation, further removing impurities such as S and N, and forming a glass coating mainly composed of fiolsterite (Mg ₂ SiO ₄ ). Is applied and baked to obtain a product.

[0003] In order to further improve iron loss, fine linear strain is applied to the surface of a grain-oriented electrical steel sheet at intervals after or before finish annealing so that magnetic domains are subdivided. (JP-A-53-137016,
No. 56-51522). If the linear distortion is made after forming the insulating film, the film may be locally damaged,
A coating agent for an insulating film is applied again for the purpose of rust prevention and insulation, and is baked at a temperature low enough that the effect of improving iron loss due to linear distortion is not lost.

[0004] Grain-oriented electrical steel sheets are mainly used as core materials for transformers and electric equipment. In the manufacture of iron cores, slit, shear or punched materials having a predetermined width are continuously wound or laminated. It is used as a wound iron core or stacked iron core. In the case of a wound core, it is wound into a case after winding, compression molding, and strain relief annealing, and then put into a case after a winding operation called lacing. In the case of a laminated core, the core is mainly assembled by hand and the winding is performed to form a transformer.

[0005] In the above-mentioned production, for example, in the case of a wound iron core, the lubricating property of the coating is good, the winding work and the forming operation can be performed smoothly, and the formed steel sheet has an excellent shape without irregularities on the end face or the lap portion of the formed steel sheet. It is important that In the case of stacked iron cores, in addition to the coating properties such as insulation properties, the insulation coating on the coil surface at the processing stage at the customer must have sufficient strength to prevent peeling and dusting when contacting or shearing under the load of a transfer roll or other load. Required.

[0006] Especially conventional coating tension as the insulating film forming agent for grain-oriented electrical steel sheet, the roller insulating properties, corrosion resistance and the like problems
Idal silica, phosphate and chromate based or phosphorus
Insulating coatings based solely on acid salts are mainly used. In order to prevent the chromium compound and phosphorus compound of this coating component from being powdered in the transformer processing process and the influence on the working environment due to the peeling of the coating, the insulating properties were improved by preventing the powdering and peeling of the insulating coating by improving the coating characteristics. It is desired to develop a coating agent for forming a film and a method of forming a film.

As a means for improving the properties of the coating by improving the insulating coating, for example, Japanese Patent Application Laid-Open No. 61-4773 discloses a method in which a first phosphate such as Al or M is added as a coating agent to ultrafine particles having a particle diameter of 8 nm or less. A technique is disclosed in which a mixture of colloidal silica and one or more of chromic acid and chromate is applied to a steel sheet after finish annealing and baked to improve the slipperiness of the insulating coating. .

[0008] By improving these insulating coatings, the iron loss, magnetostriction and insulating properties of the grain-oriented electrical steel sheet are improved, as well as the lubricating properties of the coatings. As a result, the workability during iron core processing and the powdering and peeling phenomena of the coatings are reduced. The effect of improvement has been obtained. But,
Low iron loss grain-oriented electrical steel sheets that have low iron loss by applying linear distortion to the product with a laser or the like and re-baking the insulation film at low temperature. Therefore, the baking process must be performed at a low temperature such as 500 ° C or less. Therefore, since the film formation is not completed sufficiently with the above-described conventional insulating coating components, the strength (hardness) of the insulating film is not sufficient. Absent.

As a result, the insulating film is easily damaged in a later processing step, causing problems such as contamination of the working environment due to powdering and peeling, and problems such as deterioration of characteristics due to surface defects. For this reason, in the grain-oriented electrical steel sheet with an ultra-low iron loss as in the present invention, as one means for fully exhibiting the characteristics in the manufactured transformer, the core workability by improving the insulating coating is It is important to further improve.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a steel sheet in which a linear strain is applied to a grain-oriented electrical steel sheet by a laser or the like to reduce iron loss, before, after, or both before and after the application of strain. It is an object of the present invention to provide a method for forming an insulating film having good slipperiness, excellent core workability, and free from powdering and peeling when forming an insulating film on a conductive electromagnetic steel sheet.

[0011]

The gist of the present invention is as follows. (1) A silicon steel slab is hot-rolled, and as it is or subjected to hot-rolled sheet annealing, and then cold-rolled once or twice or more with intermediate annealing to a final sheet thickness, and then decarburized annealing. ,
After applying an annealing separating agent and winding it into a strip coil, performing finish annealing, then applying a coating agent for forming an insulating film, and applying optical, mechanical, and chemical Alternatively, in a method of applying a linear strain under conditions such as heat, and then applying an insulating coating agent again and baking at a temperature range of 500 ° C. or less to form an insulating coating, as the insulating coating agent for film formation, CrO ₃ to 10 parts by weight, H ₃ PO ₄ 30~60 parts by weight, MgO, CaO, and 6-16 parts by weight one or more of Al ₂ O ₃ , H ₃ BO ₃ and Na ₂ SiO ₃
0.5 to 5.0 parts by weight or Fe, Ca, Ba, Zn, A
l, Ni, Sn, Cu, Cr, Cd, Nb, Mn, Mo, Ti, W, Bi, Sr, V or Sb oxide, carbide, nitride, sulfide, boride, hydroxide, silica As a colloid solution of salts, carbonates, borates, sulfates, nitrates or chlorides, apply a treating agent containing 1 to 10 parts by weight of one or more of a solution having a particle size of 80 to 500 nm as a solid content. A method for forming an insulating film on a low-temperature-baked grain-oriented electrical steel sheet having excellent core workability, characterized by performing baking treatment. (2) The silicon steel slab is hot-rolled and subjected to annealing as it is or hot-rolled, and then cold-rolled once or twice or more with intermediate annealing to a final thickness, and then decarburized annealing. ,
After applying an annealing separating agent and winding it into a strip coil, performing finish annealing, then applying a coating agent for forming an insulating film, and applying optical, mechanical, and chemical Alternatively, in a method of applying a linear strain under conditions such as heat, and then applying an insulating coating agent again and baking at a temperature range of 500 ° C. or less to form an insulating coating, as the insulating coating agent for film formation, CrO ₃ to 10 parts by weight, H ₃ PO ₄ 30~60 parts by weight, MgO, CaO, and 6-16 parts by weight one or more of Al ₂ O ₃ , H ₃ BO ₃ and Na ₂ SiO ₃
0.5 to 5.0 parts by weight of glycerin, adipic acid and succinic acid.
0.5-5.0 parts by weight and Fe, Ca, Ba, Zn, Al, Ni , Sn, Cu, C
an oxide consisting of r, Cd, Nb, Mn, Mo, Ti, W, Bi, Sr, V or Sb ,
Carbides, nitrides, sulfides, borides, hydroxides, silicates,
As a colloidal solution of carbonate, borate, sulfate, nitrate or chloride, apply a treating agent containing 1 to 10 parts by weight of one or two or more of a solution having a particle size of 80 to 500 nm as a solid content, A method for forming an insulating film on a grain-oriented electrical steel sheet, which is excellent in workability of a core, and is characterized by performing baking treatment.

[0012]

Hereinafter, the present invention will be described in detail. The inventors of the present invention apply the linear strain to a steel sheet surface with a laser or the like at intervals, apply a coating agent for forming an insulating film before and after applying the linear strain, and bake at a low temperature. We examined to solve the problem. As a result, in such a low-temperature baking treatment film, the conventional
Colloidal silica, phosphate and chromate based or
It was found that the film formation did not proceed sufficiently with the phosphate-only coating agent, and the film strength and lubricity could not be obtained.

As a result of studying this measure, chromic acid, Al,
Based on oxides such as Ca and Mg or phosphoric acid based composition ,
It has been found that the composition in which a reducing agent such as glycerin and the coarse particle colloid are added has remarkably good lubricity and significantly increased hardness regardless of low-temperature baking. This coating, lubricity of the insulating coating, corrosion resistance, adhesion and the like is remarkably improved, Hatsuko in processing step, that the formation of free insulation coating of work environment <br/> problems due film peeling can be I found it.

The details will be described below based on experimental data.
Cut out a sample from the coil after finish annealing of high magnetic flux density directional electrical steel sheet with a thickness of 0.23 mm manufactured by a known method,
Strain relief annealing at 850 ° C. × 4 hours was performed to remove the coil set and the strain. Then, after light pickling at 80 ° C. × 20 seconds with 2% H ₂ SO ₄ , a coating agent having a composition consisting of 100 ml of 20% colloidal silica having a particle diameter of 10 nm, 50 ml of 50% primary phosphoric acid Al, and 5 g of chromic anhydride was applied. Coating was performed so that the weight after baking became 5.0 g / m ² , and baking treatment was performed at 800 ° C. for 20 seconds in an N ₂ atmosphere. Next, a linear distortion imparting treatment was performed on the surface of the product plate in a direction perpendicular to the rolling at an interval of 5 mm by laser treatment to improve iron loss characteristics.

An insulating coating agent having the composition shown in Table 1 was applied to the steel sheet so that the weight after baking was 2.5 g / m ² , and a low-temperature baking treatment was performed at 380 ° C. for 20 seconds in the air. A sample was cut out from the obtained product plate, and the lubricity (method A and method B) of the insulating film was measured by the method shown in FIGS. In the method A (FIG. 1), the sample 2 is placed between the sandwiching plates 1-1 and 2-2, a load N is applied by the weight 3, and the force A for pulling out the sample 2 is measured by a spring meter 4, and the sliding friction coefficient is measured. μ to μ (FF)
= A / N.

In the method B (FIG. 2), a steel ball 8 to which a constant load 7 is applied is placed on the insulating film of the sample 2, and the steel ball is reciprocated to make the resistance value received by the steel ball 8 from the insulating film. Was continuously measured by the strain gauge 6. For this measurement,
The load 7 was 100 g, and the diameter of the steel ball 8 was 100 mm.
9 is a recorder, 10 is a chart. In addition, the influence on the corrosion resistance, adhesion, and magnetic properties of the coating was investigated using samples cut separately. The results are shown in Table 3 and FIG.
Shown in

FIG. 3 is obtained by the method of FIG. 2 (method B).
13 shows the charts of Inventive Example 5 and Comparative Example 13. The lubricity deteriorates as the surface resistance increases. Looking at the above results,
Insulating coating agents that do not use fine-particle colloidal silica as the main component as in the present invention have excellent film properties and markedly improved lubricity, etc. Was.

[0018]

[Table 1]

[0019]

[Table 2]

Next, a method for forming an insulating film according to the present invention will be described. The coating material for forming an insulating film in the present invention is, for 10 parts by weight of chromic acid, 30 to 60 parts by weight of phosphoric acid, Al, Ca,
6 to 16 parts by weight of one or more of oxides of Mg, and if necessary, one or more of glycerin, succinic acid, adipic acid, and / or Fe, Ca, Ba having a particle diameter of 80 to 500 nm. , Zn, Al,
It has a composition consisting of 1 to 10 parts by weight as a solid content of a colloid composed of Ni, Sn, Cu, Cr, Cd, Nb, Mn, Mo, Ti, W, Bi, Sr, V, Sb and the like .

CrO ₃ is important for densifying the coating and providing hardness, and for suppressing the hygroscopicity of phosphoric acid and phosphate by reaction with free phosphoric acid and phosphate. If the amount of chromic acid is too large, stickiness may occur due to free chromic acid or the denseness of the film may be impaired. Conversely, if the amount is too small, free phosphoric acid will remain after baking the film, so that it absorbs moisture and generates stickiness and rust.

The oxides of Al, Ca and Mg react with phosphoric acid and chromic acid to form stable compounds. As a result, the film is densified, the insulating property and the film tension are improved, and a film having good adhesion is formed. If the amount is less than 6 parts by weight with respect to 10 parts by weight of CrO _{3, the} amount of free Cr increases and the area where stickiness occurs is widened.
In addition, film properties such as insulation and corrosion resistance are deteriorated. On the other hand, 16
When the amount is more than the weight part, an insoluble portion of the oxide is generated, which impairs the appearance and adhesion, which is not preferable.

[0023] Phosphoric acid reacts with other components to form a phosphoric acid compound, and has a strong action to form a dense glass film.
Has a great influence on lubricity, film tension, etc. Chromic acid 10
If the amount is less than 30 parts by weight, the effect of improving the lubricity is weak, and an insoluble portion of oxides such as Al is generated to impair the film properties. Conversely, if the amount is 60 g or more, a problem such as stickiness due to hygroscopicity occurs due to an increase in free phosphoric acid. Chromic acid, Al, C
The mixing ratio of oxides such as a and Mg and phosphoric acid is strictly controlled in this way.

H ₃ BO ₃ and / or Na ₂ SiO ₃ are added at a ratio of 0.5 to 5.0 parts by weight based on 10 parts by weight of chromic acid. These additions are effective in vitrifying and densifying the film, and at the same time, are effective in lowering the baking film formation temperature. If the addition amount is less than 0.5 parts by weight to 10 parts by weight of chromic acid, such vitrification effect is weak, and if the addition amount is more than 5.0 parts by weight, the hardness of the coating film is reduced, or in the case of Na ₂ SiO ₃ This is not preferred because stickiness occurs.

Glycerin, adipic acid, and succinic acid, which are added as necessary, are effective in lowering the film baking temperature. In the process of improving core loss by controlling magnetic domains by applying linear strain by a laser or the like as in the present invention, the baking temperature is set to a low temperature of 500 ° C. or less to maintain the linear strain. This is very important. CrO ₃ 10 is a reducing agent such as glycerin
It is added in the range of 0.5 to 5.0 g based on parts by weight. If the amount is less than 0.5 part by weight, this effect is small. On the other hand, if it is more than 5.0 parts by weight, the stability of the solution is undesirably reduced.
Further, in this case, a problem of magnetic deterioration occurs because a compressive stress is generated at the time of baking due to an increase in the organic component.

The addition of the colloidal solution of coarse particles should
500 nm, the amount of addition is 1.0 to 10 parts by weight as a solid content with respect to 10 parts by weight of chromic acid. The coarse particle colloid forms fine spherical protrusions on the coating film due to the spherical shape of the particles.
The shape effect and the particles improve the lubricity and hardness of the coating and improve the workability of the iron core. The particle size of the coarse particle colloid is 80 to 500 nm. If the particle diameter is smaller than 80 nm, the effect of improving lubricity is small. In the case of a coating having a relatively small coating amount as in the present invention when the particle diameter is 500 nm or more,
There are problems such as deterioration of the space factor and stability of the coating solution (sedimentation of colloid particles). Most preferred
The particle size is between 100 and 300 nm.

The amount of the coarse particle colloid to be added is 1.0 to 10.0 parts by weight in terms of solid content per 10 parts by weight of chromium oxide. If the amount is less than 1.0 part by weight, the effect of improving lubricity and the like is small. If the amount is more than 10 parts by weight, the space factor is lowered as in the case where the particle diameter is large. The insulating coating agent having these compositions is converted into an aqueous solution, applied to a steel plate by a coating roll or the like, and baked. Drying conditions at this time are baking at a steel sheet temperature of 500 ° C. or less. Atmosphere conditions in this case may be either in an atmosphere gas such as N ₂ or in the air.

The baking temperature is 500 ° C. or less. If the temperature is higher than 500 ° C., the effect of improving iron loss due to linear distortion by laser or the like is reduced by releasing the distortion. Preferably 250-450 ° C
It is. The optimum points for these drying and baking conditions vary depending on the coating composition. Hereinafter, examples will be described.

[0029]

EXAMPLE C in weight%; 0.078%, Si; 3.30%, Mn
0.065%, S; 0.024%, Al; 0.030%, and a balance of silicon steel slab consisting of iron and unavoidable impurities was hot-rolled, annealed, and cold-rolled by a known method to a final thickness of 0.23 mm. Next, after decarburizing annealing in a N ₂ + H ₂ humid atmosphere, an annealing separating agent was applied, and finish annealing was performed at 1200 ° C. × 20 hours to form a glass film. Next, excess MgO is removed by washing with water, and after light pickling, 100 ml of 20% colloidal silica having a particle diameter of 10 mm, 50 ml
% First phosphoric acid Al 55ml, CrO ₃ 6 a known insulating film-forming coating agent consisting g in weight after baking treatment 4.0 g /
m ² , and baked in N ₂ at 810 ° C. for 20 seconds. Thereafter, linear distortion was imparted at intervals of 5 mm in the direction perpendicular to the rolling direction of the steel sheet by laser irradiation, and iron loss improvement treatment was performed.

Next, a coating agent for an insulating film having the composition shown in Table 3 was applied so that the film weight after baking became 2.0 g / m ² , and baked at 380 ° C. for 30 seconds in the air. A sample was cut out from this steel sheet and the film properties were investigated. Table 4 shows the results.

[0031]

[Table 3]

[0032]

[Table 4]

As can be seen from Table 4, according to the method of the present invention, the film properties are excellent and the lubricity, corrosion resistance, etc. are remarkably improved.

[0034]

As described above, according to the present invention, although a coating is formed on the surface of a grain-oriented electrical steel sheet by low-temperature baking, the core workability is remarkably good, and the corrosion resistance and lubricity are excellent. Can be formed.

[Brief description of the drawings]

FIG. 1 shows a method for measuring the lubricity of an insulating film of a sample (A
FIG.

FIG. 2 shows a method for measuring the lubricity of an insulating film of a sample (B
FIG.

FIG. 3 is a diagram showing surface resistance values of an example of the present invention and a comparative example 8.

Continuation of the front page (56) References JP-A-4-272183 (JP, A) JP-A-52-25296 (JP, A) JP-A-61-41778 (JP, A) JP-A-57-203720 (JP, A) , A) JP-A-61-257483 (JP, A) JP-A-1-316424 (JP, A) JP-B-43-7849 (JP, B1) Toshizo Chitani "New Edition Inorganic Chemistry" First Volume First Edition 7th print 40-5-10 Sangyo Tosho Co., Ltd. 367-368

Claims (2)

(57) [Claims] Claims: 1. A silicon steel slab is hot-rolled and subjected to as-is or hot-rolled sheet annealing, and then cold-rolled once or twice or more with intermediate annealing to a final sheet thickness, and then decarburized. After annealing, applying an annealing separating agent, winding it into a strip coil, applying finish annealing, then applying a coating agent for forming an insulating film, and applying optical and mechanical In the method of applying a linear strain under conditions such as thermal, chemical or thermal, and then applying an insulating coating agent again and baking at a temperature range of 500 ° C. or less to form an insulating coating, as the insulating coating agent for an insulating film-forming to be made in respect CrO ₃ 10 parts by weight, H ₃ PO ₄ 30 to 60 parts by weight, MgO, CaO, and Al ₂
6 to 16 parts by weight of one or more of O ₃ , H ₃ BO ₃ and Na ₂ S
0.5 to 5.0 parts by weight of one or both of iO ₃ and Fe, C
a, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nb, Mn, Mo, Ti, W, Bi, Sr, V
Or colloidal solutions of oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, sulfates, nitrates or chlorides composed of Sb , the particles of which are 80 to
One or two or more of a 500 nm solution is 1 to 10
A method for forming an insulating coating on a low-temperature-baked grain-oriented electrical steel sheet having excellent core workability, comprising applying a treating agent mixed in parts by weight and baking. 2. A silicon steel slab is hot-rolled, and as it is or after being subjected to hot-rolled sheet annealing, is subjected to one or two or more cold-rolling steps including intermediate annealing to a final sheet thickness, and then decarburization. Annealing, applying an annealing separator, winding and forming a strip coil, performing a final annealing, then applying a coating agent for forming an insulating film, and applying optical and mechanical A method of applying a linear strain under conditions such as chemical or thermal, and then applying an insulating coating agent again and baking at a temperature range of 500 ° C. or less to form an insulating film. as the insulating coating agent for an insulating film-forming to be made, to CrO ₃ 10 parts by weight, H ₃ PO ₄ 30 to 60 parts by weight, MgO, CaO, and Al ₂
6 to 16 parts by weight of one or more of O ₃ , H ₃ BO ₃ and Na ₂ S
0.5 to 5.0 parts by weight of one or both of iO ₃ and 0.5 to 5.0 parts by weight of one or more of glycerin, adipic acid and succinic acid, and Fe, Ca, Ba, Zn, Al, Ni, S
oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates consisting of n, Cu, Cr, Cd, Nb, Mn, Mo, Ti, W, Bi, Sr, V or Sb , Borate, sulphate, nitrate or chloride as a colloidal solution containing 80 to 500 nm particles.
A method for forming an insulating coating on a low-temperature-baked grain-oriented electrical steel sheet having excellent core workability, comprising applying a treating agent containing 1 to 10 parts by weight of a seed or two or more kinds as a solid content and baking.