JP2654862B2 - Method for forming insulation film on grain-oriented electrical steel sheet with excellent core workability and dust resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming an insulating film on a grain-oriented electrical steel sheet having excellent core workability and dust resistance.

(Prior Art) A grain-oriented electrical steel sheet is formed by hot rolling a silicon steel slab containing, for example, 2 to 4% of Si, annealing, and then performing cold rolling once or twice or more with intermediate annealing. As the final thickness,
Next, decarburizing annealing, applying an annealing separator containing MgO as a main component, applying finish annealing to develop secondary recrystallized grains having Goss orientation, further removing impurities such as S, N, and glass coating Is formed, and then a coating liquid for an insulating film is applied, followed by baking treatment to form an insulating film, thereby obtaining a product.

Further, for the purpose of lowering iron loss, fine linear strain is applied to the surface of the grain-oriented electrical steel sheet at intervals after or before finish annealing to separate magnetic domains ( For example, JP-A-53-137016, JP-A-56-51
No. 522).

If the linear distortion is performed after the formation of the insulating film, the film may be damaged. Therefore, the insulating film is treated again for the purpose of rust prevention.

By the way, grain-oriented electrical steel sheet is mainly used as a core material for transformers and electric equipment. After being cut into lengths and shapes, the cores are sequentially wound or laminated by an iron core processing machine to form a wound iron core or a laminated iron core. In the case of a wound core, it is formed into a transformer by performing winding work called racing through compression molding and strain relief annealing.

In the case of a laminated core, the core is assembled manually and the winding operation is performed to form a transformer, but usually, the strain relief annealing is not performed.

In the manufacture of iron cores, for example, in the case of wound iron cores, the lubrication of the coating is good, so that winding and forming work can be performed smoothly, and the shape and shape of the steel sheet end surface and lap part are excellent without forming irregularities. In addition, in the case of a laminated core, the insulating film formed on the surface of the steel sheet does not become dust when it comes into contact with a transfer roll or the like under a load or shears, and the slipperiness of the film is appropriate. It is required to be performed smoothly.

Furthermore, in the case of a wound iron core, there is no seizure between the surface coatings of the steel sheet during the strain relief annealing, and the lacing work can be performed smoothly. Important from a point of view. Since these properties are greatly affected by the properties of the insulating film of the grain-oriented electrical steel sheet, it is strongly desired to develop an insulating film having excellent properties.

As means for improving the workability of the iron core of the transformer, improvement of a coating agent for forming an insulating film has been studied. For example, Japanese Patent Application Laid-Open No. 61-4773 discloses that as a coating agent, one or two of ultrafine colloidal silica having a particle diameter of 8 μm or less, chromic acid, and chromate are added to a first phosphate.
There is disclosed a technique for improving the slip property of an insulating film by applying a mixed liquid composed of at least one kind to a steel sheet after finish annealing and performing a baking treatment.

By improving these insulating films, the lubricity of the film has been improved along with the iron loss, magnetostriction, and insulating properties of the grain-oriented electrical steel sheet, and a certain effect has been obtained.

However, in grain-oriented electrical steel sheets that have been subjected to linear strain to reduce iron loss and have an insulating film formed again, the baking temperature of the insulating film cannot be sufficiently increased in order to secure the linear strain. It is necessary to print. As a result, the film strength becomes insufficient, the insulating film is easily scratched, and dusting of the film may be observed. Although the magnetic properties of the grain-oriented electrical steel sheet have been advanced, it is important to further improve the workability of the steel core of the steel sheet insulating film as one of the requirements for sufficiently exhibiting the properties in a manufacturing transformer. It is.

(Problems to be Solved by the Invention) The present invention relates to a grain-oriented electrical steel sheet in which a linear strain is applied to reduce iron loss, before or after the application of the linear strain, or both before and after. It is an object of the present invention to provide a method for forming an insulating film, which has good slipperiness and excellent core workability, and is capable of dusting or forming an insulating film.

(Means for Solving the Problems) The gist of the present invention is that a silicon steel slab is hot-rolled and annealed as necessary, and a single or intermediate annealing is performed.
Cold rolling more than twice to the final thickness, decarburizing annealing,
After applying the annealing separator, finish annealing, apply an insulating film coating agent to the steel sheet after the finish annealing, and perform baking treatment,
A method in which fine linear strain is applied to the surface of a steel sheet at intervals, and then an insulating film coating agent is applied again to form a baked insulating film, wherein 100 parts by weight of colloidal silica having a particle size of 50 nm or less (as SiO ₂₎ ), 130 to 300 parts by weight of one or more of Al, Mg, Ca, Zn phosphates, and chromic anhydride, chromate,
10 to 100 parts by weight of one or more dichromates and Fe, Ca, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, Mn, Mo, Si, Ti,
W, Bi, Sr, V oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, nitrates or chlorides, the particle size of which is 100 to 2000 nm An insulating coating agent obtained by adding 0.5 to 25 parts by weight of one or more of the non-colloidal solids to a steel sheet before, after, or both before and after the application of the linear strain. A method for forming an insulating film on a grain-oriented electrical steel sheet having excellent core workability and dust resistance, characterized by forming a baked insulating film.

 Hereinafter, the present invention will be described in detail.

The present inventors apply linear strain to a steel sheet surface at intervals, and apply an insulating film coating agent before and after applying the linear strain to form a baked insulating film. When non-colloidal solids of 100 to 2000 nm are added, they are dispersed uniformly, and these form small rounded protrusions on the formed insulating film. A film is formed, which is hard to be scratched and does not generate dust.

 The present invention will be described in detail based on experimental data.

A sample was cut out from a strip coil of grain-oriented electrical steel sheet subjected to finish annealing by a known method, and strain relief annealing was performed by 83
After removing the coil set at 0 ° C for 5 hours, 2% H ₂ S
A sample that had been subjected to light acid washing at 80 ° C. for 8 seconds with O ₄ was used as a sample. As shown in Table 1, this sample was coated with an insulating film coating agent in which 234 parts by weight of Al phosphate was blended with 100 parts by weight of colloidal silica having a particle diameter of 10 nm.
m, 2 parts by weight of a non-colloidal SiO ₂ powder of 1200 nm was added and mixed, mixed with water and stirred, applied as a coating solution to a steel sheet, applied after baking to 4.0 g / m ^2, and N _Two
A baking treatment was performed at 860 ° C. for 30 seconds in an atmosphere. Thereafter, fine linear strain was applied to the steel sheet surface by laser irradiation at intervals of 10 mm in the direction perpendicular to the rolling direction. Thereafter, an insulating film coating solution was applied again and baked at 400 ° C.

A sample was cut out from the obtained product plate, and the coefficient of sliding friction (FF value) of the insulating film was measured by the method (method A) shown in FIG. The measuring method is as follows. A sample 2 is placed between the sandwiching plates 1-1 and 1-2, a load N is applied by a heavy load 3, and a force A for extracting the sample 2 is obtained.
Is measured with a spring meter 4, and the sliding friction coefficient μ, μ (FF)
= A / N.

In addition, a steel ball with a constant load was repeatedly slid on the insulating film, and at that time, the resistance value received by the steel ball from the insulating film was continuously measured, and the presence or absence of flaws in the insulating film was investigated (lubrication). Sex, B method).

Further, a 3 cm x 4 cm sample cut separately was laminated, and this was bundled at a tightening pressure of 90 kg / cm ² and 860 in an N ₂ atmosphere.
The steel sheet was subjected to strain relief annealing at 3 ° C. × 3 hours, and the peeling load of the steel sheet was measured by the method shown in FIG. 2 (b) to investigate the sticking property. The results are shown in Table 1.

As shown in Table 1, coating and baking of an insulating coating agent containing 2 parts by weight of non-colloidal SiO ₂ having a particle size of 250 nm or 1200 nm has a low FF value and excellent lubricity. There is no flaw generation, high dusting resistance, and good sticking resistance during strain relief annealing.

 Next, a method for forming an insulating film according to the present invention will be described.

The composition of the coating agent for forming an insulating film is as follows: 100 parts by weight of colloidal silica having a particle size of 50 nm or less (as SiO ₂ ), Al,
130 to 300 parts by weight of one or more of Mg, Ca and Zn phosphates and 10 to 100 parts by weight of one or more of chromic anhydride, chromate and dichromate. ing. The colloidal silica needs to be fine particles of 50 nm or less in order to reduce iron loss and magnetostriction and to improve the slip property of the film.

The phosphates of Al, Mg, Ca, and Zn have the effect of preventing the stickiness of the film and improving the slipperiness.In addition, when the insulating film as the object of the present invention is formed again, the dusting of the film is reduced. It has an effect of preventing it, and in order to exhibit this effect, it is required to be 130 parts by weight or more based on 100 parts by weight of the colloidal silica. On the other hand, if the amount is large, the film becomes soft, and the film is apt to be damaged. The phosphates of Al, Mg, Ca and Zn are selectively blended, and one or more of them are blended.

One or more of chromic anhydride, chromate and dichromate are blended to stabilize the film formation. However, if the amount is less than 10 parts by weight, the film becomes sticky.
It must be at least 10 parts by weight. On the other hand, if this amount is increased, the amount of free chromic acid becomes excessive, so that even when recoating and forming a film at a low temperature, the amount is less than 100 parts by weight because of stickiness.

Fe, Ca, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, Mn, Mo, Si, Ti, W, B
Non-colloidal solids of i, Sr, V oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, nitrates or chlorides are added. The solid material is formed by dispersing fine convex spheres on the surface of the film to enhance slipperiness and has a particle diameter of 100 nm or more in order to prevent film dusting. On the other hand, if the particle size increases, the space factor of the film decreases, so that the particle size is set to 2000 nm or less. When the particle diameter is about 5 to 100 nm, the solids agglomerate to form the convex sphere on the film surface. In addition, if the amount of the non-colloidal solid is small, the effect of improving the slip property cannot be obtained,
In order to prevent such a phenomenon and enhance the slipperiness, it is necessary to add 0.5 parts by weight or more to 100 parts by weight of the colloidal silica. On the other hand, if the amount increases, the space factor of the film decreases, so the upper limit is 25 parts by weight.

The insulating film coating agent having the above composition is in the form of an aqueous solution, applied to a steel sheet and baked to form an insulating film, but before or after forming a linear strain that subdivides magnetic domains in the steel sheet and reduces iron loss. It is used for formation of any one of the insulating films. The same effect can be obtained by applying the insulating film coating agent according to the present invention before and after the application of the linear strain.

 Next, examples will be described.

(Example 1) C: 0.083%, Si: 3.23%, Mn: 0.068%, S: 0.024% by weight
%, Sol. Al: 0.029%, the balance being a steel slab consisting of iron and unavoidable impurities was hot-rolled by a known method, then annealed and then cold-rolled to a final sheet thickness of 0.220 mm. Then, after decarburizing annealing, after applying an annealing separator, finish annealing at 1200 ° C × 20 hours,
A glass film was formed. Then, the excess annealing separating agent was removed by washing with water, and after light acid washing, an insulating coating agent in which the particle size and phosphate of colloidal silica were adjusted as shown in Table 2 was 4.5 g / m 2 after baking. ² and baked in an N ₂ atmosphere at 850 ° C. for 30 seconds. However, the specific gravity of 20% colloidal silica is 1.12 g / cc, and the specific gravity of phosphate (50%) is 1.
45g / cc. Thereafter, linear strain was applied at 10 mm intervals in the direction perpendicular to the rolling axis of the steel sheet by laser irradiation. Thereafter, an insulating coating agent having a composition shown in No. 7 of Table 2 was applied by a known method so that the total weight after baking was 4.5 g / m ² , and then the coating was performed at 400 ° C. for 30 seconds in an N ₂ atmosphere. Was subjected to a baking treatment.

A sample is cut out from the obtained steel sheet, and the FF value, lubricity,
The occurrence of flaws and sticking resistance were investigated. The results are shown in Table 2.

(Example 2) C: 0.083%, Si: 3.23%, Mn: 0.068%, S: 0.024% by weight
%, Sol. Al: 0.029%, the balance being a steel slab consisting of iron and unavoidable impurities was hot-rolled by a known method, then annealed and then cold-rolled to a final sheet thickness of 0.220 mm. Then, after decarburizing annealing, after applying an annealing separator, finish annealing at 1200 ° C × 20 hours,
A glass film was formed. Then, the excess annealing separating agent was removed by washing with water, and after washing with light acid, a known method of Table 3 was used.
An insulating film coating agent having the composition shown in No. 5 was applied so that the weight after baking became 4.0 g / m ² , and baking treatment was performed in an N ₂ atmosphere at 850 ° C. for 30 seconds. Then, a linear strain is applied at 10 mm intervals in the direction perpendicular to the rolling axis of the steel sheet by laser irradiation, and as shown in Table 3, the coating film of the insulating coating in which the particle size of the colloidal silica and the phosphate have been adjusted is baked. the coating is a 4.5 g / m ² by weight, and then 400 ° C. × 30 seconds N ₂
The baking treatment was performed in an atmosphere. However, the specific gravity of 20% colloidal deer is 1.12 g / cc and the specific gravity of phosphate (50%) is 1.45 g / cc
And

A sample is cut out from the obtained steel sheet, and the FF value, lubricity,
The occurrence of flaws and sticking resistance were investigated. The results are shown in Table 3.

(Effects of the Invention) According to the present invention, there is provided an insulating film which has excellent slipperiness and heat resistance of a steel sheet, is less likely to have scratches on the film surface, has excellent dust resistance, and has excellent workability of an iron core in transformer production. A grain-oriented electrical steel sheet is obtained.

[Brief description of the drawings]

FIG. 1 shows a means (A) for measuring the sliding friction coefficient of an insulating film.
FIGS. 2 (a) and 2 (b) are diagrams showing a method of investigating the sticking property when performing strain relief annealing after processing an electromagnetic steel sheet into an iron core, and FIG. FIG. 4 is a diagram showing a layered state of a sample in strain relief annealing in the investigation of sticking property in FIG. 4, and FIG. 6 (b) is a diagram showing an aspect of measuring a state of interlaminar seizure after strain relief annealing.

Continuation of the front page (56) References JP-A-52-25296 (JP, A) JP-A-61-41778 (JP, A) JP-A-57-203720 (JP, A) JP-A-43-7849 (JP) , B1)

Claims (1)

(57) [Claims] 1. A silicon steel slab is hot-rolled and annealed as required, and cold-rolled one or more times with an intermediate anneal in between to obtain a final sheet thickness, decarburized annealing, and an annealing separator. After finish annealing, apply an insulating film coating agent to the steel sheet after the finish annealing and perform a baking treatment, apply fine linear strain to the steel sheet surface at intervals, and then again apply the insulating film coating agent. A method of forming a baked insulating film by applying a coating of one or more of phosphates of Al, Mg, Ca, Zn to 100 parts by weight (as SiO ₂ ) of colloidal silica having a particle size of 50 nm or less. Up to 300 parts by weight, and 10 to 100 parts by weight of one or more of chromic anhydride, chromate and dichromate, and F
e, Ca, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, Mn, Mo, Si, Ti, W, Bi, S
r, V oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, nitrates or chlorides, non-colloidal with a particle size of 100 to 2000 nm An insulating film coating agent obtained by adding 0.5% to 25% by weight of one or more of the solids of the above is applied to a steel sheet before and / or after the application of the linear strain, and a baked insulating film is formed. A method for forming an insulating film on a grain-oriented electrical steel sheet having excellent core workability and dust resistance, characterized by being formed.