JPH1171683A - Grain oriented silicon steel sheet having high-tension insulating coating film and its treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel sheet good in coating film characteristics such as adhesion and having an excellent high-tension coating film by providing an insulating coating film consisting essentially of phosphates, chromates and colloidal silica having a specified glass transition point on the surface and specifying the coating weight. SOLUTION: An insulating coating film is formed with phosphates, chromates and colloidal silica having 950-1200 deg.C glass transition point. By using such colloidal silica, a large tension is imparted to the steel sheet when coated and baked. The insulating coating film weight of the product is controlled to 2.5-7.0 g/m<2> . In the coating film processing soln., 100 pts.wt. of the colloidal silica, expressed in terms of solid, is mixed with 145-225 pts.wt. of the phosphates of Al, Mg and Ca, and 10-45 pts.wt. of the chromate, expressed in terms of CrO3 , is mixed with 100 pts.wt. of the colloidal silica, expressed in terms of solid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet having a high-tensile insulating coating and a method for treating the insulating coating.

[0002]

2. Description of the Related Art Generally, the surface coating of grain-oriented electrical steel sheets is
A forsterite layer called a primary coating formed during high-temperature finish annealing, and a phosphate coating layer formed by applying a treatment liquid mainly containing phosphate and baking during heat flattening of a steel sheet. It is formed from two layers. These insulating coating layers are required to have electrical insulating properties, but in addition to insulating properties, various coating properties such as heat resistance, slip properties, and adhesion are required. One of the important characteristics of the insulating coating of the grain-oriented electrical steel sheet is to impart tension to the steel sheet to improve the magnetic properties of the grain-oriented electrical steel sheet.

[0003] By applying tension to a grain-oriented electrical steel sheet, iron loss of the grain-oriented electrical steel sheet is improved, and this is one of the main causes of noise of a transformer manufactured using the grain-oriented electrical steel sheet as an iron core. It is known that it is also effective in reducing magnetostriction. In addition, processing a grain-oriented electrical steel sheet into an iron core such as a transformer involves going through various manufacturing processes.However, when manufacturing the iron core, heat resistance, slipperiness, and adhesion are inferior. Since the coating peels off during strain relief annealing and the workability deteriorates because the steel sheets cannot be laminated smoothly, it is necessary that the insulating coating of the grain-oriented electrical steel sheet retains these coating properties. .

Japanese Patent Publication No. 53-28375 discloses an insulating coating solution mainly containing a phosphate, a chromate and a colloidal silica having a specific composition on a forsterite coating formed on a steel sheet surface after finish annealing. A method of forming an insulating film having a high tension on the surface of a steel sheet by applying and baking to reduce iron loss and magnetostriction of a grain-oriented electrical steel sheet is disclosed.

[0005] The technology disclosed in the above-mentioned publication has remarkably improved various film characteristics and improved film tension, but energy efficiency and environmental problems have been highlighted in recent years. And reduction of noise. Therefore, the magnetic properties of the grain-oriented electrical steel sheet, which is the iron core material of the transformer, are required to be further improved. Higher tensile strength and higher performance are required, and various methods for improving the film properties have been proposed.

Japanese Patent Application Laid-Open No. 61-41778 discloses an insulation by applying and baking a treatment liquid containing a specific ratio of ultrafine colloidal silica having a particle size of 8 μm or less and primary phosphate and chromate. There is disclosed a method for maintaining high tension of a film and further improving lubricity of the film.

[0007] The technique disclosed in the above publication is to increase the specific force of the colloidal silica by using ultrafine colloidal silica to increase the bonding force, thereby increasing the tension applying force to the steel sheet. Is what you do. According to the technology disclosed in the above publication, high tension is maintained and the lubricating property of the insulating coating is greatly improved. There is a problem that the cost is high, and industrially, there is a demand for an insulating coating treatment technique using a stable and inexpensive colloidal silica.

[0008]

The object of the present invention is to improve the properties of an insulating film formed on the surface by coating and baking on a steel sheet in the final step of manufacturing a grain-oriented electrical steel sheet, thereby improving various properties such as adhesion. It is an object of the present invention to obtain a grain-oriented electrical steel sheet having a good tensile strength and a remarkably superior high-tensile coating as compared with conventional ones.

[0009]

The gist of the present invention is as follows. (1) An insulating coating mainly composed of phosphate, chromate, and a colloidal silica having a glass transition point (Tg point) of 950 ° C. to 1200 ° C. on the surface, and the adhesion amount is 2 to 2.
A grain-oriented electrical steel sheet having a high-strength insulating film characterized by being 7 g / m ² .

(2) On the surface, phosphate, chromate and colloidal silica are the main components, and at least 40% of the total colloidal silica has a glass transition temperature of 950 ° C. to 12%.
A grain-oriented electrical steel sheet having a high-tensile insulating coating, having an insulating coating of colloidal silica at 00 ° C. and an adhesion amount of ² to 7 g / m ² .

(3) C: 0.005% or less, Si:
2.5-7.0%, average grain size is 1-10mm
The surface of a grain-oriented electrical steel sheet having an average deviation of 8 ° or less in the rolling direction from the ideal orientation of (110) [001] in the rolling direction with respect to the ideal orientation of (110) [001], as described in (1) or (2) above. A grain-oriented electrical steel sheet having a high-strength insulating film, characterized by having a coating of (i).

(4) In a method for forming an insulating film by applying a treatment liquid containing phosphate, chromate and colloidal silica as main components to a grain-oriented electrical steel sheet, a glass transition point of 950 ° C. to 1200 ° C and an average particle size of 8 to 20
nm, 100 parts by weight of colloidal silica
45 to 225 parts by weight of phosphate of Al, Mg, Ca
A treatment liquid containing seeds or two or more kinds and 10 to 45 parts by weight of a chromate in terms of CrO _{3 with} respect to 100 parts by weight of the colloidal silica is applied, and 800 ° C. to 1000 ° C.
A method for treating a grain-oriented electrical steel sheet having a high-strength insulating film, characterized by baking at a temperature of less than.

(5) The method for treating a grain-oriented electrical steel sheet having a high-tensile insulating coating according to (4), wherein the colloidal silica contains 100 to 300 ppm of chloride ions.

(6) In a method of forming an insulating film by applying a treatment solution containing phosphate, chromate and colloidal silica as main components to a grain-oriented electrical steel sheet, the method comprises forming at least 40% of the total colloidal silica. Has a glass transition point of 950 ° C. to 1
A colloidal silica having a temperature of 200 ° C. and an average particle diameter of 8 to 20 nm.
A treatment liquid containing 145 to 225 parts by weight of one or more of Al, Mg and Ca phosphates and 10 to 45 parts by weight of chromate in terms of CrO ₃ is applied, and 800 ° C. or more A method for treating a grain-oriented electrical steel sheet having a high-tensile insulating coating, characterized by baking at a temperature of less than 1000 ° C.

(7) C: 0.005% or less, Si:
2.5-7.0%, average grain size is 1-10mm
And (4), (5) or (5) on the surface of the grain-oriented electrical steel sheet having an average deviation of 8 ° or less in the rolling direction from the ideal orientation of (110) [001] in the rolling direction. (6) A method for treating a grain-oriented electrical steel sheet having a high-tensile insulating coating, characterized by performing the treatment described in (6).

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, in order for the insulating coating of the grain-oriented electrical steel sheet to apply tension to the steel sheet, it is necessary that there is a difference in the coefficient of thermal expansion between the steel sheet and the insulating coating. If the thermal expansion coefficient of the insulating coating is lower than that of the steel sheet, the contraction of the steel sheet is larger than that of the insulating coating when the insulating coating is baked. . Therefore, the tensile stress applied to the steel sheet can be further increased by reducing the coefficient of thermal expansion of the insulating coating.

The present inventors have conducted intensive studies to reduce the coefficient of thermal expansion of the insulating coating. As a result, in the insulating coating mainly containing phosphate, chromate, and colloidal silica, the glass transition point of the colloidal silica Greatly affects the coefficient of thermal expansion of the insulating film, and the glass transition temperature is 950 ° C. to 1
It has been found that the coating tension can be remarkably increased by applying the colloidal silica at 200 ° C.

Next, a method of forming an insulating film according to the present invention will be described. In applying the present invention, as the grain-oriented electrical steel sheet after the finish annealing, either a steel sheet having a normal forsterite coating or a steel sheet having no forsterite coating may be used. Regardless of the type of steel sheet used, the surplus annealing separating agent is washed and removed with water, and then pickled and washed with a sulfuric acid bath or the like to perform surface cleaning and surface activation.

In the present invention, the glass transition point is 950.
A treatment liquid for forming an insulating film mainly composed of colloidal silica, phosphate and chromate at a temperature of from 1 to 1200 ° C is used. The first feature of the present invention lies in the glass transition point of the colloidal silica. That is, the glass transition point, which is the thermal property of colloidal silica, is very high, unlike the colloidal silica used for the insulating coating of conventional grain-oriented electrical steel sheets.

Normally, colloidal silica is prepared by converting a sodium silicate solution to 6% of SiO ₂ / Na ₂ O using an ion exchange resin.
A sol of 0 to 30 is formed, followed by aging at a high temperature to promote a polymerization reaction, and further, a dilute sol separately formed by an ion exchange resin is gradually added to form a stable colloidal silica.

Since colloidal silica uses sodium silicate as a raw material, it usually contains a trace amount of sodium. Various factors such as the particle size, specific surface area, and the type and amount of anions added during production are involved in the reactivity of colloidal silica, but the reactivity of colloidal silica also changes depending on the sodium content. It is known that the greater the amount of sodium contained in the colloidal silica, the higher the reactivity of the colloidal silica.

The colloidal silica is added to and mixed with a solution containing phosphate and chromate as a main component to form a treatment solution for an insulating film, and then applied to a steel plate and baked to form an insulating film. In order to form a strong film, colloidal silica with high reactivity is better,
In the past, colloidal silica with a high sodium content was usually used.

However, when the sodium content of the colloidal silica is high, the glass transition temperature tends to decrease, and the glass transition temperature of the colloidal silica usually used for the insulating coating of the grain-oriented electrical steel sheet is lower than 900 ° C. Normal.

The present inventors also examined anions added during the production of colloidal silica, and found that colloidal silica using chloride ions had good reactivity with phosphate. Was.

Next, the reasons for limitation of the present invention will be described. First, a feature of the present invention is that an insulating coating is formed of phosphate, chromate, and colloidal silica having a glass transition point of 950 to 1200 ° C. By setting the glass transition point of the colloidal silica to 950 to 1200 ° C., a significantly higher tension is applied to the steel sheet at the time of coating baking than before. If the glass transition point of the colloidal silica is lower than 950 ° C., a high tension cannot be obtained, which is limited. On the other hand, when the temperature exceeds 1200 ° C., the reaction between the phosphate and the chromate and the colloidal silica is inferior, and the adhesion of the coating is reduced due to cracks in the insulating coating, which is limited.

The amount of insulating coating of the product is 2.5 to 7.0 g / m ^2.
It is. If it is less than 2.5 g / m ^2, it is difficult to obtain a high tension, and the insulating property, corrosion resistance and the like are reduced, and the strength is 7.0 g / m ^2.
If it exceeds, the space factor will be reduced because it will be limited.

Next, the reasons for limiting the manufacturing method of the present invention will be described. First, the mixing ratio of the colloidal silica and the phosphate used in the present invention is 10% in terms of solid content.
0 parts by weight, phosphate 145 of Al, Mg, Ca
225 parts by weight are blended. If the amount is less than 145 parts by weight, the tension effect cannot be sufficiently exhibited. On the other hand, if the content exceeds 225 parts by weight, the excess phosphoric acid content causes a so-called sticking property deterioration during annealing, which is limited.

The mixing ratio of the chromate is 10 to 45 parts by weight in terms of CrO _{3 based} on 100 parts by weight of colloidal silica in terms of solid content. If the amount is less than 10 parts by weight, the sticking property is inferior because the fixing ability of the phosphoric acid is not sufficient. If the amount is more than 45 parts by weight, the treatment liquid is liable to gel, so that the amount is limited.

Next, the baking temperature of the insulating film in the present invention is 800 ° C. or more and less than 1000 ° C. If the baking temperature is less than 800 ° C., sufficient tension is not exhibited, and
If the temperature exceeds 1000 ° C., cracks occur in the coating, and the insulating properties and the like are reduced.

Next, the chlorine ion contained in the colloidal silica solution is preferably 100 to 300 ppm.
If the chlorine ion content is less than 100 ppm, the effect of improving the reactivity is low, and if it is more than 300 ppm, the corrosion resistance of the formed insulating coating tends to decrease, which is limited.

The colloidal silica used in the present invention is:
It is also possible to use a mixture with colloidal silica having a normal glass transition point of around 900 ° C. In this case, the mixing ratio of the colloidal silica used in the present invention must be 40% or more of the total colloidal silica amount. If the compounding ratio is less than 40%, the effect of the present invention cannot be obtained.

Incidentally, the above-mentioned insulating film treatment was carried out according to
No. 8567, manufactured using the technique disclosed in Japanese Patent No. 8567, contains C: 0.005% or less, Si: 2.5 to 7.0%, has an average crystal grain size of 1 to 10 mm, and has a crystal orientation of (1
10) By applying to a grain-oriented electrical steel sheet having an average deviation of 8 ° or less in the rolling direction with respect to the ideal orientation of [001], an effect of further reducing iron loss can be obtained.

[0033]

EXAMPLE Next, an example will be described. [Example 1] A width of 7 cm x a length of 300 cm from the same coil after the final annealing of a grain-oriented electrical steel sheet having a thickness of 0.23 mm
Was cut out, and the annealing separating agent remaining on the surface was removed by washing with water and light acid, leaving a glass film, and then performing strain relief annealing. Next, a phosphate solution was prepared at the compounding ratio shown in Table 1, and then, using a colloidal silica shown in Table 2, an insulating coating treatment solution having a composition shown in Table 3 was applied to a steel sheet so that the coating amount was 4 g / m ^2. After coating and baking, the film properties and magnetic properties were evaluated. Table 4 shows the results.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

Example 2 A molten steel containing 3.25% of Si was cast using the technique disclosed in Japanese Patent Application Laid-Open No. 7-268567, heated to a slab, and then hot-rolled.
After annealing the hot-rolled plate at 00 ° C. for 5 minutes, cold rolling was carried out to form a 0.1 mm.
The thickness was 22 mm. This steel sheet was heated to 850 ° C. at a heating rate of 400 ° C./sec, then decarburized and annealed, an annealing separator was applied, and finish annealing was performed at 1200 ° C. for 20 hours. The same operation as in Example 1 was performed using the same coil having an average particle diameter of 7.5 mm and a crystal orientation having an average deviation of 6.5 ° from the ideal orientation of (110) [001]. Then, using a phosphate solution shown in Table 1 and a colloidal silica shown in Table 2, an insulating coating solution having a composition shown in Table 5 was applied to a steel sheet at a coating amount of 4 g / m ² and baked. The properties and magnetic properties were evaluated. Table 6 shows the results.

[0039]

[Table 5]

[0040]

[Table 6]

As a result of this test, the glass transition point was 950 ° C.
To 1200 ° C., the insulating coating agent using colloidal silica was higher in tension and superior in adhesion than the comparative example, and the effect of improving magnetic properties was good.

[0042]

According to the present invention, it is possible to obtain a grain-oriented electrical steel sheet having a large coating tension applied to the surface of the steel sheet, good adhesion of the iron core material in the production of a transformer, and excellent magnetic properties.

Claims (7)

[Claims] 1. An insulating coating mainly composed of phosphate, chromate, and a colloidal silica having a glass transition point (Tg point) of 950 ° C. to 1200 ° C. A grain-oriented electrical steel sheet having a high-strength insulating coating characterized by a weight of 7 g / m ² . 2. On the surface, phosphate, chromate and colloidal silica are the main components, and at least 40% of the total colloidal silica has a glass transition point of 950 ° C. to 1200 ° C.
A grain-oriented electrical steel sheet having a high-tensile insulating coating, characterized by having an insulating coating which is a colloidal silica of the above, and having an adhesion amount of ² to 7 g / m ² . 3. C: 0.005% or less, Si: 2.5 to
Containing 7.0%, having an average crystal grain size of 1 to 10 mm,
3. The coating according to claim 1 or 2, wherein the grain oriented steel sheet has an average deviation from the ideal orientation of (110) [001] in the rolling direction of 8 ° or less in the rolling direction on the surface of the grain-oriented electrical steel sheet. A grain-oriented electrical steel sheet having a high-tensile insulating coating characterized by the following. 4. A method for forming an insulating film by applying a treatment liquid containing phosphate, chromate and colloidal silica as main components to a grain-oriented electrical steel sheet, wherein the glass transition point is 95%.
145 to 100 parts by weight of colloidal silica having a mean particle size of 8 to 20 nm at 0 to 1200 ° C.
A treatment containing 225 parts by weight of one or more of phosphates of Al, Mg and Ca, and 10 to 45 parts by weight of chromate in terms of CrO _{3 based on} 100 parts by weight of the colloidal silica. A method for treating a grain-oriented electrical steel sheet having a high-tensile insulating coating, comprising applying a liquid and baking at a temperature of 800 ° C. or more and less than 1000 ° C. 5. The colloidal silica has a chlorine ion of 10%.
The method for treating a grain-oriented electrical steel sheet having a high-tensile insulating coating according to claim 4, wherein the content is 0 to 300 ppm. 6. A method for forming an insulating film by applying a treatment liquid mainly containing phosphate, chromate and colloidal silica to a grain-oriented electrical steel sheet, wherein at least 40% of the total colloidal silica is formed. Glass transition point from 950 ° C to 1200
C. and colloidal silica having an average particle diameter of 8 to 20 nm.
A treatment liquid containing 225 parts by weight of one or more of Al, Mg, and Ca phosphates and 10 to 45 parts by weight of chromate in terms of CrO ₃ is applied,
A method for treating a grain-oriented electrical steel sheet having a high-tensile insulating coating, wherein the method comprises baking at a temperature of less than 00 ° C. 7. C: 0.005% or less, Si: 2.5 to
Containing 7.0%, having an average crystal grain size of 1 to 10 mm,
7. The process according to claim 4, 5 or 6, wherein the surface of a grain-oriented electrical steel sheet having an average deviation from the ideal orientation of (110) [001] of 8 ° or less in the rolling direction with respect to the ideal orientation is performed. A method for treating a grain-oriented electrical steel sheet having a high-tensile insulating film, characterized by the above-mentioned.