JPH0339484A - Formation of insulating film on grain-oriented magnetic steel sheet excellent in workability of iron core and heat resistance - Google Patents

Abstract

PURPOSE:To improve the lubricity of an insulating film and to prevent the seizing of the film in the process for applying and baking a coating agent for foaming an insulating film by specifying the grain diameter of colloidal silica in the coating agent. CONSTITUTION:A silicon-steel slab is hot-rolled, and one cold rolling or >=2 cold rollings including process annealing are then applied to obtain a final thickness. The material is decarburization-annealed, an annealing and separation agent is applied thereon and baked, final finish-annealing is applied, then the coating agent for forming the insulating film is applied and baked, and then heat-flattening is applied to produce the magnetic steel sheet. In this case, the coating agent is obtained by adding 130-250 pts.wt. of one or >=2 kinds among the phosphates of Al, Mg, Ca and Zn and 10-40 pts.wt. of one or >=2 kinds among chromic anhydride, chromate and bichromate to 100 pts.wt. of a colloidal soln. consisting, by weight based on solid, of 50-95% colloidal silica having <=20mum grain diameter and 5-50% colloidal silica having 80-2000mum grain diameter.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for forming an insulating film on a grain-oriented electrical steel sheet. The present invention relates to a method for forming an insulating film on a grain-oriented electrical steel sheet that has excellent workability and improves the magnetic properties of transformer products.

(Prior Art) Grain-oriented electrical steel sheets are produced by hot rolling a silicon steel slab containing, for example, 2 to 4% Si, annealing it, and then cold rolling it once or twice or more with intermediate annealing in between. to obtain the final plate thickness.
Next, after decarburization annealing, an annealing separator containing MgO as the main component is applied, and final annealing is performed to develop secondary recrystallized grains with Goss orientation. Furthermore, impurities such as S and N are removed, and glass It is manufactured by a process in which a film is formed, then a coating liquid for the insulation film is applied, and a baking process is performed to form the insulation film into a final product.

The grain-oriented electrical steel sheets obtained in this way are mainly used as iron core materials for electrical equipment, transformers, etc., and are required to have high magnetic flux density and low iron loss values.

On the other hand, when a magnetic steel sheet with orientation 1 is used as the core of a transformer, the hoop of the grain-oriented magnetic steel sheet is continuously unwound and cut into a predetermined length with a shearing machine, and then sequentially wound and rolled up with a core processing machine. Alternatively, they may be stacked to form wound cores or stacked cores. In the case of wound cores, they are made into transformers by compression molding, strain relief annealing, and winding work called lacing.

In this core manufacturing process, for example, in the case of a wound core,
It is necessary that the winding and forming operations can be carried out smoothly, that the end face of the steel sheet or the lap portion after forming has no unevenness, that the shape is excellent, and that the surface of the steel sheet has good lubricity.

In addition, the fact that there is no seizure between the surface coatings of the steel sheets during strain relief annealing, and the lacing work can be performed smoothly, improves core processing efficiency and prevents the induction of distortion and deterioration of coating performance due to seizure. It is important because To solve these problems, since the properties of the insulation coating on the surface of grain-oriented electrical steel sheets have a large effect, we developed an insulation coating that does not cause seizure between the surface coatings of the steel sheet during strain relief annealing and allows smooth racing work. The development of such a material is strongly desired not only from the viewpoint of processability but also from the standpoint of improving the magnetic properties of transformers.

As a means to improve the workability of such transformer cores, improvements have been made to the coating agents used when forming the insulation film. JP-A No. 61-4773 discloses that a mixture of one or more of primary phosphate, ultrafine colloidal silica with a particle diameter of 8 mμ or less, chromic acid, and chromate is used as a coating agent for finishing annealing. A technique has been disclosed that improves the slipperiness of an insulating film formed on the surface of a steel plate by applying it to a subsequent steel plate (strip) and treating the baking process.

In recent years, improvements in these insulating films have improved the iron loss, magnetostriction, and insulation properties of grain-oriented electrical steel sheets, as well as the film lubricity, and some effects have been obtained.

However, manufacturers who manufacture transformers and other products using grain-oriented electrical steel sheets are increasingly automating and speeding up the processing and forming machines used to process them into iron cores, making processing easier than using the improved insulating film coating agent mentioned above. The current situation is that there is a demand for an insulating film that eliminates the troubles associated with magnetic fields and has further improved magnetic properties.

(Problems to be Solved by the Invention) The present invention provides a oriented type magnetic steel plate which has good slip properties of an insulating film on the surface of a grain-oriented electrical steel sheet, good heat resistance during strain relief annealing, and excellent workability of an iron core. The purpose was to provide a method for forming an insulating film on steel plates.

(Means for Solving the Problems) The gist of the present invention is to hot-roll a silicon steel slab and annealing it, then cold-roll it once or twice or more with intermediate annealing in between to form a final plate. A method for producing a grain-oriented electrical steel sheet, in which the material is decarburized, annealed for decarburization, coated with an annealing separator, then final annealed, coated with a coating agent for forming an insulating film, baked, and then heat flattened. 20m at
- Colloidal solution 1001 (1 part (SiO2 130 to 250 parts by weight of one or more phosphates of AL Mgl Ca, Zn, and 10 to 250 parts by weight of one or more of chromic anhydride, chromate, and dichromate.
A method for forming an insulating film on a grain-oriented electrical steel sheet having excellent workability and heat resistance of an iron core, which comprises applying an insulating film-forming coating agent containing 40 parts by weight and performing baking.

The present invention will be explained in detail below.

In order to solve the above problems, the inventors have conducted various studies on methods of forming an insulating film on grain-oriented electrical steel sheets.

As a result, by controlling the particle size of colloidal silica in the coating agent for forming an insulation film during the coating and baking process, the lubricity (slip property) of the insulation film can be significantly improved. Furthermore, it has been found that the phenomenon of film sticking, which occurs during stress relief annealing, can be significantly improved.

Hereinafter, the present invention will be explained in more detail based on experimental data.

A sample was cut from a strip coil after final finish annealing of a grain-oriented electrical steel sheet with a thickness of 0.23 mm manufactured by a known method, and strain relief annealing was performed at 850°C for 4 hrs to remove the coil set. 80″C at ToSOi
The sample was subjected to light pickling for 10 seconds. For this sample, as shown in Table 1, 15ml1 of colloidal silica having a coarse particle size of 80m5 or more was added.
A coating agent for forming an insulating film based on a solution mixed with fine colloidal silica having a particle size of 1 is applied at a coating density of 4.5 g/m2 after baking, and baked at 850°C for 30 seconds in a N2 atmosphere. The burning has been treated.

A sample was cut out from the product board thus obtained, and the sliding friction coefficient (FF value) of the insulating film was measured by the method shown in FIG. 1 (Method A). That is, the sample 2 is placed between the sandwich plates 1-1 and 1-2.
, apply a load with a weight 3, pull out the sample 2, measure the mold with a spring weigher 4, and calculate the sliding friction coefficient μ as μ(FF
)-F'.

Furthermore, a steel ball with a constant load was slid on the insulating film, and the resistance value that the steel ball received from the surface of the insulating film was measured (Method B).

In addition, separately cut out 3CIX4C11 boards were stacked,
To tighten this to 80Kg/c+s, bind it with pressure and use N2
Strain relief annealing was performed at 850°C for 4 hrs in an atmosphere.
The peeling load of the steel plate was measured by the method shown in FIG. 2, and the sticking property was investigated.

The results are shown in Table 1.

As shown in Table 1, colloidal silica of 80 to 10100O was added to colloidal silica of particle size 15 mQ by weight.
% compounded insulating film forming agent of the present invention and treated with baking, there was a significant improvement in both the FF value by method A, the lubricity by method B, and the staking resistance during strain relief annealing. It was seen.

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

In the present invention, as a coating agent for forming an insulating film, 20
Colloidal silica with a particle size of m, n or less is 50 to 95% by solid weight, and colloidal silica with a particle size of 80 to 2000 m trm is 5 to 50% by solid weight.
100 parts by weight of a colloidal solution consisting of 5iOz, 130 to 250 parts by weight of one or more phosphates of AZ, Mg, Ca, Zn, chromic anhydride, chromate, dichromate. 1 type or 2 or more types of
A coating agent for forming an insulating film is applied in an amount of 0 to 40 parts by weight, and baking is performed.

When carrying out the present invention, colloidal silica having a particle size of 20 m or less is 50 to 95% by solid weight,
In order to obtain a colloidal solution consisting of 5 to 50% solid content of colloidal silica having a particle size of 80 to 2000 mn1, a particle size distribution of 1 which satisfies the above regulations is required.
Different types of colloidal solutions may be prepared, or two or more types of colloidal silica having uniform particle sizes may be mixed to satisfy the above requirements.

Next, the reasons for limiting the conditions in the present invention will be explained.

In the present invention, the application and baking of the coating agent for forming an insulating film is carried out at the processing stage, and the coating agent for forming an insulating film is
A colloidal solution consisting of 50 to 95% by solid weight of colloidal silica having a particle size of n or less and 5 to 50% by weight of solid content of colloidal silica having a particle size of 80 to 2000 m is 100 weight as Stow. '＋
F'g+ Ca.

Use a mixture containing 130 to 250 parts by weight of one or more Zn phosphates and 10 to 40 parts by weight of one or more of chromic anhydride, chromate, and dichromate. ing.

Thus, the key is to mix and disperse an appropriate amount of coarse particles of colloidal silica into fine particles of colloidal silica.

Colloidal silica with a particle size of 20 mfa or less is 50-95% by solid weight, and colloidal silica with a particle size of 80-2000 mpm is 5-5% by solid weight.
In the range of 0%, a remarkable effect of improving the slipperiness of the insulating film appears. The base fine particle colloidal silica is
It is important that the particle size is 20 m or less;
If it exceeds n, the effect of improving iron loss and magnetostriction, which are the basic characteristics of an insulating film, will be reduced, the film will become opaque, and the appearance will be impaired, and other problems will occur, as well as the overall particle size will become coarser. On the contrary, the slipperiness of the film deteriorates.

The particle size of the coarse particles of colloidal silica blended with the fine particles of colloidal silica is 80 to 2000 mirm. If the particle size is less than 80 mμm, the effect of improving lubricity cannot be obtained.On the other hand, if the particle size exceeds 2000 m-, the product may not be laminated even though it has slip properties and heat resistance (state king resistance). This is not preferable because it sometimes causes a decrease in the space factor.

Next, the composition of colloidal silica and phosphate is /V, with respect to 100 parts by weight of colloidal silica as SiO2,
The amount of one or more phosphates of Mg, Ca, and Zn is 130 to 250 parts by weight. This is important when considering the tension effect of the insulating film and the heat resistance of the film. If the blending ratio of phosphate to 100 parts by weight of colloidal silica is less than 130 parts by weight, cracks will occur in the insulating film after formation due to insufficient binder for colloidal silica, and the tensile effect of the insulating film will be lost, which is not preferable. On the other hand, if the blending ratio exceeds 250 parts by weight, the appearance of the film becomes cloudy or the tension effect decreases, and furthermore, the heat resistance during strain relief annealing rapidly deteriorates, so the upper limit is set at 250 parts by weight.
'Limited to quantity.

As the phosphate, one or more of kl, Mg, Ca, and Zn phosphates are used.

As the phosphate, a commercially available 50% solution may be used.
Since the solubility is low and a 50% solution cannot be obtained, the calculated value is 5.
Added to balance 0% solution.

From the perspective of improving the lubricity of the base film, the most preferred phosphate combinations are At-Mg-Ca and Af-C.
a, Mg-Ca.

Chromic anhydride, chromate, and dichromate are blended according to the amount of phosphate.

If the amount is less than 10 parts by weight relative to 130 to 250 parts by weight of phosphate, it will not be the amount necessary to stabilize the free phosphoric acid in the film component by forming CrPOa, etc., and will cause stickiness. On the other hand, 40! ! When the amount exceeds part ii, free chromic acid becomes excessive, and stickiness also occurs in this case.

In the present invention, colloidal silica manufactured in such a way that the particle size is appropriately dispersed at the manufacturing stage is used, or two or more types of fine particle and coarse particle colloidal silica each manufactured separately are used. Any means of mixing to obtain a combination of particle sizes defined in the present invention can be applied.

Next, the insulating film formed by the present invention has lubricity,
The reason for its excellent heat resistance will be explained. Mechanisms for improving the lubricity of the surface of electrical steel sheets include 1) smoothness of the film surface, 2) good lubricity of the film itself, and 3) improvement of point contact from the viewpoint of surface shape effects. It is conceivable that there is a mechanism that allows for smoother sliding.

The method proposed by the present inventors and disclosed in Japanese Unexamined Patent Publication No. 61-4773 is based on the effect 1).

The present invention is based on the point contact brought about by the shape effect in 3). In particular, in the present invention, since a combination of particle sizes of colloidal silica is utilized, the spherical shape of the colloid on the surface of the insulating film produces a remarkable effect. It is assumed that this will result in

FIGS. 3(a) and 3(b) are diagrams showing the relationship between the surface shape and lubricity of a product obtained by applying the present invention. (Act) have been significantly improved.

FIG. 4 shows the relationship between the composition of the coating agent for forming an insulating film (see Table 4) and the lubricity of the product surface.

Sample (a), which does not satisfy the compositional conditions stipulated in the present invention, has become untestable after several tests. 80 as coarse particles
(2) using mg of colloidal silica showed good lubricity although the resistance value gradually increased.

In cases (C) and (d) in which colloidal silica of 300 m5 or 2000 m, n was used as coarse particles, the resistance value showed a low value without changing over time, and had good lubricity.

(Example) C: 0.078%, St: 3.22% in weight%
, MrBo, 068%, S; 0.024%, acid soluble 1'j; 0.032%.

A silicon steel slab consisting of the remainder Fe and unavoidable impurities is hot rolled by a known method, annealed and then cold rolled to a final thickness of 0.295.
It was Peng. Then, after decarburization annealing and application of an annealing separator, 1
Final annealing was performed at 200°C for 20 hours, and the excess zero-order annealing separating agent that had formed a glass film was removed by water washing. After light pickling, the particle size of colloidal silica was adjusted as shown in Table 2. An insulating coating agent containing phosphate and phosphate was applied so that the weight after baking was 4.5 gets”, and 830”C×
The baking process was carried out in NZ for 30 seconds. A sample was cut out from this product board, and the FF value (method A) and lubricity (method B) were measured.
, state king resistance, etc. were investigated. 3rd result
Shown in the table.

(Effects of the invention) According to the invention, the surface of the steel plate has good slipperiness and heat resistance,
It is possible to obtain a grain-oriented electromagnetic steel sheet which has excellent workability of the iron core in transformer manufacture and which also improves the magnetic properties of transformer products.

[Brief explanation of drawings]

Figure 1 shows a means for measuring the sliding friction coefficient of an insulating film (A
Figure 2 (a) and (b) are diagrams showing a method for investigating the sticking property when strain relief annealing is performed after processing an electrical steel sheet into an iron core; Figure 3 (aL
b) is a diagram showing the relationship between the surface shape and lubricity of the product obtained by the present invention, and Figures 4 (a) to (d) are diagrams showing the relationship between the composition of the coating agent for forming an insulating film and the lubricity of the product. FIG. Figure 1 Figure 2 Figure 3 Cb) Ra value calculator

Claims (1)

[Claims] After hot rolling and annealing a silicon steel slab, it is cold rolled once or twice or more with intermediate annealing in between to achieve the final thickness, and this material is decarburized and annealed, coated with an annealing separator, and then final rolled. In a method for producing a grain-oriented electrical steel sheet in which finish annealing is applied, a coating agent for forming an insulating film is applied, a baking treatment is performed, and then heat flattening is performed, colloidal silica having a particle size of 20 mm or less is solid content of 50 to 95%, 80~
Al, Mg, Ca, Z
A coating for forming an insulating film containing 130 to 250 parts by weight of one or more phosphates of n and 10 to 40 parts by weight of one or more of chromic anhydride, chromate, and dichromate. A method for forming an insulating film on a grain-oriented electrical steel sheet, which has excellent workability and heat resistance of an iron core, and is characterized by applying an agent and baking it.