JPS61238918A - Formation of insulating film superior in laser beam irradiating property on grain oriented magnetic steel sheet - Google Patents

Abstract

PURPOSE:To decrease iron loss and to improve heat resistance, insulating property of insulating film, by coloring insulating film to improve the light absorbance, at improving iron loss characteristic by irradiating laser beam to grain oriented magnetic steel sheet on which insulating film due to coated liquid is baked. CONSTITUTION:Silicon steel slab contg. 2-4% Si is hot rolled, the plate is then annealed, cold rolled or subjected to >=two times cold rolling contg. intermediate annealing to the final sheet thickness. This is decarburization annealed, then annealing separator agent composed mainly of MgO is coated thereon and finish annealed to manufacture silicon steel sheet. In this case, oxide film contg. SiO2 formed by decarburization annealing and glass film due to annealing separator agent are formed. Next, at forming insulating film due to phosphate contg. Cr salt, insulating film liquid incorporated with coloring agent made of metal oxide is coated and baked. At decreasing iron loss by dividing magnetic domain finely by laser beam irradiation, insulating film absorbing the laser beam uniformly by colored film at superior absorbance, and superior in heat resistance, insulating property is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming an insulating film with excellent laser irradiation properties for improving the core loss characteristics of grain-oriented electrical steel sheets.

[Conventional technology]

Grain-oriented electrical steel sheets are produced by hot-rolling a silicon steel material containing, for example, 2.0 to 4.0% St, and then annealing it and cold-rolling it once, or cold-rolling it two or more times with intermediate annealing in between to form the final sheet. It is made into a thick cold-rolled plate, then decarburized and annealed, coated with an annealing separator containing MgO as the main component, final annealed to develop secondary recrystallized grains with Goss orientation, and further treated with S, N, etc. Impurities are removed and a glass film is formed. Next, a coating liquid for an insulating film is applied and baked to form an insulating film.

Nowadays, there is a strong demand for energy conservation, and in order to further improve the iron loss characteristics of grain-oriented electrical steel sheets, for example,
As described in Japanese Patent No. 8-26410, a steel plate on which an insulating film is formed is irradiated with a laser beam to introduce minute strain and subdivide the magnetic domains.

By the way, the glass film before applying the insulation coating liquid and performing the baking treatment depends on the degree of oxidation of the atmospheric gas during the decarburization annealing process,
Effects of temperature, time, etc., hydration amount of annealing separator, reactivity, etc.
Alternatively, the amount and uniformity of the glass film formed may be affected by the atmospheric conditions between the coil plates during the final annealing process, resulting in inconveniences such as color unevenness and thickness unevenness.

After the glass film has been formed, the coil (steel plate) is light pickled, and an insulation film is formed by performing an insulation coating treatment as described in Japanese Patent Publication No. 53-28735, for example.
If unevenness occurs in the glass film due to the pre-process conditions as described above, the unevenly formed portions will remain uneven in color tone even after the insulation film is formed.

[Problem that the invention seeks to solve]

When trying to improve the iron loss characteristics of a steel plate by laser irradiation, if there is unevenness in the color of the glass film within the steel plate, the absorption rate of light will vary within the steel plate, and the laser irradiation will cause the light to be absorbed. There is a difference in the minute strain caused by That is, there may be locations where microstrains are not introduced or locations where microstrains are excessively introduced, and the improvement in iron loss characteristics may not be uniform within the steel sheet.

The present invention improves laser irradiation properties by improving the light absorption of an insulating film when irradiating a grain-oriented electrical steel sheet with a laser to introduce minute strain and refining magnetic domains to improve core loss characteristics. The first objective is to improve the heat resistance and insulation properties of the insulating film compared to the conventional ones.

[Means for solving problems]

The inventors of the present invention aimed to improve the laser irradiation properties in order to uniformly improve the iron loss characteristics over the entire steel sheet by laser irradiation, even if uneven areas such as color unevenness inevitably occur in the glass coating of grain-oriented electrical steel sheets. We conducted experiments on a method for forming an excellent insulating film.

As a result, by adding a coloring agent that colors the insulation film to the coating liquid, and applying the coating liquid to the steel plate and baking it, the laser absorption rate improves and becomes uniform, eliminating the problem caused by uneven parts of the glass film. It was discovered that an insulating film with excellent laser irradiation properties could be formed.

The present invention has been made based on such knowledge, and the gist thereof is to form an insulating film on a grain-oriented electrical steel sheet:
Primary phosphates such as Al + Mg, Ca + Zn,
One or two of chromic anhydride, chromate, and dichromic acid
A coloring agent that increases the light absorption rate of the insulating film is added to a coating liquid containing colloidal silica or more if necessary, and the coating liquid is applied to a grain-oriented electrical steel sheet and baked. The present invention provides a method for forming an insulating film with excellent laser irradiation properties.

The present invention will be explained in detail below.

When performing laser irradiation treatment, it is desirable that the color tone of the insulating film in the longitudinal direction and width direction of the steel sheet be uniform.

As a means to solve this problem, there are methods by controlling decarburization annealing during glass film formation, annealing separation agents, and final annealing conditions, but these methods are very difficult industrially and have limitations.

In the present invention, as a solution to this problem, a coloring agent that increases the light absorption rate of the insulating film is added to the coating liquid, thereby covering the uneven parts of the glass film and improving the light absorption rate compared to conventional coatings. By obtaining a uniform insulating film, the laser irradiation effect is made uniform and the effect is enhanced.

In forming an insulating film on a grain-oriented electrical steel sheet in the present invention, it is not necessary to specify the steel composition of the grain-oriented electrical steel sheet and the manufacturing conditions before forming the insulation film. For example, a grain-oriented electrical steel sheet contains 2.0 to 4.0% Si and A (l N+ MnS) as an inhibitor.

MnSe, BN+CuzS, etc. are used, and Cu is added as necessary.

Silicon steel slag containing elements such as Sn, Cr, Ni, Mo, and Sb is hot-rolled, annealed, and cold-rolled once or twice or more with annealing in between to obtain the final thickness, and then decarburized. It is manufactured by annealing, applying an annealing separator mainly composed of MgO, and finishing annealing.

A glass film is formed on the grain-oriented electrical steel sheet by a reaction between an oxide film containing SiO2 formed by decarburization annealing and an annealing separator during final annealing.

Next, an insulating film is formed on this grain-oriented electrical steel sheet, and the coating liquid is one or more of primary phosphates such as aluminum phosphate, magnesium phosphate, calcium phosphate, zinc phosphate, or anhydrous. Contains one or more of chromic acid, chromate, and dichromate.

Colloidal silica is also included if necessary.

a coloring agent that colors the insulating film and increases light absorption in the liquid;
For example, TlX0yt MnX0.005x>y. +C
uxOy.

Add MoxOy etc.

The amount added is f41. For 100 parts by weight of primary phosphates such as Mg, Ca, Zn, etc., 20 to 80 parts by weight of 5 ints of colloidal silica and one or two of chromic anhydride, chromates, and dichromates. The above is C
10 to 48 parts by weight of rO3 and 0.1 parts of colorant
It is preferable to mix up to 20 parts by weight.

If the coating liquid is applied to a steel plate and baked at a temperature of 350°C or higher, for example, even if the glass film exhibits color unevenness on the steel plate, it will be eliminated and the light absorption rate will be reduced. A good and uniform insulation film is formed.

Coloring agent added to the coating liquid in the present invention, for example, Ti
Ti, which is an oxide of 0. is the x value is 0.5 for the y value
As it gets bigger, it becomes black.X"")'
(Tie) exhibits true black color.

By blending this coloring agent TixOy (0,5x>y) into the coating liquid, it is dispersed in the coating liquid in a colloidal form and forms a uniform black insulating film when coated and baked on the rope. Form. Therefore, during laser treatment, the effect of increasing the light absorption rate and making it uniform is produced.

At this time, Ti, 0. Although the particle size is not particularly defined, ultrafine particles of 0.2 μm or less are desirable. This is because it is easy to disperse in a colloidal form in the coating liquid and does not have a negative effect on the space factor and the tension effect of the film. In addition to improving laser processability, the addition of Ti and O also improves heat resistance (sticking), insulation, and the like.

Such an action is caused by Mnz with coloring action of 0,5x>y.
Oy + CLIxOy,? It is also found in colorants such as '1oXO.

〔Example〕

Actual status ■C: 0.075%, Si: 3.20%, Mn: 0.07
8%, Al: 0.028%, S: 0.025%, Cu:
Silicon steel slag containing Sn: 0.10% and Sn: 0.07% was hot-rolled, hot-rolled plate annealed, and cold-rolled to 0.2251 by a known method.
Made it thick.

Next, a steel plate on which a glass film was formed was obtained by decarburization annealing, application of an annealing separator, and final finish annealing.

As an insulating coating on this finish-baked pure steel plate,
After applying the coating composition shown in the table at a coating amount of 5 g/rrr, baking treatment was performed at 800°C for 30 seconds, and the magnetic properties and light absorption rate of the steel plate were measured in the length direction and width direction.

Next, as laser treatment, CO□ laser was irradiated under constant conditions at 5N intervals in the direction perpendicular to the rolling direction, and the magnetic properties at this time were measured.

The results are shown in Table 2.

Margins below Table 1 Table 2 Large table 1ul A cold-rolled sheet prepared in the same manner as in Example 1 was decarburized and annealed, and an annealing separator was applied.Atmospheric gas (N225% + H275% ) for (1) completely wet gas and (2) moderately wet (800
The annealing was performed at a temperature of +10°C. As a result, under the condition (1), the glass coating on the steel sheet has a thin, whitish, non-uniform appearance, whereas under the condition (2), a good glass coating with a uniform gray-black color is obtained. In the coating liquid applied and baked on this steel plate in Example 1, C, E,
After coating and baking G, the magnetic properties were measured. Next, it was subjected to laser irradiation treatment in the same manner as in Example 1, and its magnetic properties were measured.

These results are shown in Table 3.

Table 3: Table 3: When TiO is added to the coating solution, the laser treatment effect is large even when the glass film is formed with an uneven appearance, whereas when TiO is not added, when the glass film is formed unevenly. Otherwise, the laser treatment effect was weak and good results could not be obtained.

Claims (1)

[Claims] 1. A grain-oriented electrical steel sheet characterized in that a coloring agent that increases the light absorption rate of the insulation film is added to the coating liquid when coating the grain-oriented electrical steel sheet and baking it to form an insulation film. A method for forming an insulating film with excellent laser irradiation properties.