JPS5836051B2 - Processing method for electrical steel sheets - Google Patents

Description

[Detailed Description of the Invention] Does the present invention have excellent magnetic properties and insulation properties? The present invention relates to a method for stably manufacturing magnetic steel sheets.

Examples of electromagnetic steel sheets include non-oriented electromagnetic steel sheets used in rotating machines such as motors, and grain-oriented electromagnetic steel sheets used in transformers and the like.

Non-oriented electrical steel sheet is a pure iron-based silicon steel sheet containing silicon of 1 or 3.5 or less, and after pickling a hot coil,
It is manufactured by repeating cold rolling and annealing one or two times to make the axis of easy magnetization random with respect to the rolling direction, and then applying an insulation coating treatment.

On the other hand, grain-oriented electrical steel sheets are generally manufactured as follows.

That is, it contains 2.5 to 4.0 silicon, and A#N, MnS, BN, Se*CuSs as an inhibitor.
A hot coil containing a predetermined amount of one or more of the elements forming Sb etc. is pickled, cold rolled and annealed once or twice, and then (11o) (001
) In order to selectively grow crystals with an orientation of 1
Finish annealing is performed at 000-1200°C.

In the case of a batch type finish annealing in which coils are subjected to final annealing, refractory oxides such as magnesha, silica, alumina, titanium oxide, and calcium oxide are used as annealing separators to prevent seizure.

In this case, using an annealing separator containing magnesia as a main component will prevent seizure and at the same time cause the silica on the surface of the steel plate to react with magnesia, forming forsterite (2MgO-
A glass film containing Si02) as a main component is formed.

This glass coating is not only effective as an insulating coating, but also has a smaller coefficient of thermal expansion than steel plates, and is effective in reducing iron loss and magnetostriction by applying tension to the steel plate during cooling. The mainstream is the production of grain-oriented electrical steel sheets.

The electromagnetic steel sheet that has been subjected to secondary recrystallization through finish annealing to form a glass film is then subjected to an insulating film treatment after removing excess magnesia, for example
As shown in Publication No. 268, magnesium phosphate treatment liquid and Special Publication No. 531? As shown in Publication No. 8375, a colloidal silica aluminum phosphate-chromic acid treatment solution is applied, and at the same time as the film is baked, flattening is carried out to remove curls and make the steel plate flat. ing.

In this case, if the film is baked at a high temperature of 70,000°C or higher, the film turns into glass and is effective in improving iron loss by applying tension to the steel plate during cooling. A film that has the effect of reducing the tension is called a tension film).

It is an object of the present invention to provide a method for improving iron loss that is more excellent than the improvement in iron loss due to tension caused by a glass film and a baked film of 7000C or higher as described above.

In order to achieve this object, the present invention basically uses a laser beam to irradiate the surface of the electrical steel sheet having the above-mentioned tension coating to form laser marks locally on the surface of the steel sheet. The present invention provides a combination technology in which the subsequent insulation coating treatment is carried out in a temperature range in which the laser beam irradiation effect imparted to the steel sheet does not disappear.

The best result can be obtained by performing the laser beam irradiation treatment to the extent that laser marks are generated on the surface of the steel sheet.

It is desirable that these laser marks be absent from the viewpoint of insulation and voltage resistance, but according to the studies of the present inventors, laser beam irradiation treatment is performed from a tension coating applied to a steel plate.
If an insulating film of a predetermined thickness is then applied, iron loss can be improved without reducing insulation properties and voltage resistance.

In this case, if the insulating film is baked at a high temperature after laser beam irradiation, the iron loss improving effect of laser beam irradiation will gradually disappear.

For this reason, in the present invention, the insulation coating treatment performed after the laser beam irradiation treatment is performed in a temperature range where the iron loss improving effect of the laser beam irradiation does not disappear.

The specific temperature of the plate at the time of baking the film varies slightly depending on the laser beam irradiation conditions, etc., but it is preferably 600'C or less.

The present applicant has already disclosed in Japanese Patent Application No. 55-7000 that after irradiating an electrical steel sheet with a glass coating and an electrical steel sheet with a glass coating, an insulating coating is baked at a temperature that does not eliminate the iron loss improvement effect of the laser beam irradiation. proposed a method to improve insulation and voltage resistance deterioration caused by laser beam irradiation marks.

According to this proposal, since the effect of improving iron loss by laser beam irradiation is large, it is effective even when the above-mentioned tension coating is not provided.

However, as a result of a more detailed study, the inventors of the present invention found that if a tension film treatment can be performed even after laser beam irradiation treatment, an even greater effect of improving iron loss can be obtained. As a result of careful consideration of the possibility of application, we focused on the fact that the baking temperature can be set arbitrarily before the laser beam irradiation treatment. It was a success.

In fact, if a tension coating is actually formed on the surface of an electrical steel sheet and a laser beam irradiation treatment is performed on the surface, the iron loss will be dramatically improved due to the synergistic effect of the laser beam irradiation treatment on the tension coating. be.

This will be explained with reference to FIG. 1, which shows the influence of a tension film on the surface of an electrical steel sheet on laser irradiation.

Click the button on the diagram and the curve ■ indicates only glass coating, ■ indicates tension coating,
■: Glass film + laser beam irradiation, ■: Tension film +
Figure 3 shows laser beam irradiation (method of the present invention).

The laser beam irradiation conditions are (i) energy density 1
7 J/ffl, (11) point trace diameter 0.2 mm,
(1ii) Trace distance is 0.3 mm, (JV) L direction interval is 5 mm.

The insulation film was baked at 500°C (plate temperature) after laser beam irradiation.

As is clear from Figure 1, when a tension film is formed on the glass film at the same time as flattening (see curve ■), the iron loss improves compared to when only the glass film is used (see curve ■). Irradiate the laser beam on the top (see curve ■)
Compared to the case where the glass film is irradiated with a laser beam (see curve ■), the iron loss is improved by 0.05 to 0.07,
It was found that very good iron loss could be obtained.

That is, the inventors observed the magnetic domain structure using a scanning electron microscope (SEM) based on the results shown in FIG.
We obtained the findings shown in the figure.

Figure 2a shows 180 without tension film (glass film).
0 magnetic domain structure is shown.

When a tension film is applied to this, the magnetic domain structure becomes as shown in FIG. 2b.

As is clear from this result, FIG. 2b corresponds to the fact that the magnetic domains are more segmented than in FIG. 2a, and the iron loss value decreases due to the tension effect shown in FIG.

On the other hand, when the sample shown in FIG. 2a is irradiated with a laser, the magnetic domain structure becomes as shown in FIG. 2C.

As is clear from this figure, the magnetic domain width in Figure 2C is the same as Figure 2B.
It can be seen that it is more segmented.

Therefore, when laser irradiation is applied to an electrical steel sheet provided with a tension coating as in the present invention, the magnetic domain structure becomes even more fragmented as shown in Figure 2d, and as a result, as shown in Figure 1. As shown, it can be seen that the effect of reducing iron loss has increased dramatically.

Also, in Figure 3, the iron loss of the electrical steel sheet with a tension coating is wl7.
/50 is 1. The value of 0 5 w/lv was reduced to 0.921 by performing the laser beam irradiation treatment.

However, the iron loss after insulation coating treatment changes greatly depending on the temperature (plate temperature) during the subsequent insulation coating treatment.
In this example, it was found that when the plate temperature exceeds 600°C, the effect deteriorates extremely.

Among these, the best method is to perform the baking process at a board temperature of 550°C or less, which allows the iron loss of the final product after the insulation coating to be equal to or lower than that after the laser beam irradiation process. becomes.

The laser beam irradiation used in carrying out the present invention is not limited in any way; for example, continuous linear irradiation,
Either point irradiation, broken line irradiation, etc. may be used.

Further, in order to improve the magnetic properties in the rolling direction L, the irradiation direction on the electrical steel sheet should be irradiated at an angle of 20° or less from the perpendicular direction C, which will increase the iron loss.

On the other hand, in order to improve iron loss in the direction perpendicular to the rolling direction, the rolling direction is preferable.

Now, to show one application example when using a pulsed laser beam, in order to improve the iron loss in the rolling direction, the energy density P is 0.01 to 1000 J/(1), and the laser beam diameter d is 0. The traces of 01 to 1 are irradiated so that the center distance of the traces is 0.01 to 2 mm in the direction perpendicular to the rolling direction, and further, a trace row of 1 to 30 mm is formed in the rolling direction.

In order to form a trace array of 1 to 30 mm in the rolling direction, the irradiation may be performed approximately perpendicular to the rolling direction, in a sawtooth shape, or in a sine wave shape, depending on the optical system used.

The time width of the laser pulse is 1 ns to 100 ms.

On the other hand, when irradiating with a continuous laser beam, the laser beam diameter is 0.01 to 1 m.
The trace of m has an energy density P of 0.01 to 1000 J/
Leh so that it becomes d? - just scan the beam.

The difference between pulsed irradiation and continuous irradiation is that the former forms a series of trace points, whereas the latter forms continuous traces; other specifications are the same.

Further, the surface to be irradiated may be either one or both sides, but single-sided irradiation is industrially more advantageous.

One of the implementation steps of the method of the present invention is to coat an electrical steel sheet with an annealing separator containing magnesia as a main component.
Finished at 12,000G and annealed at high temperature to form forsterite (2
A glass film whose main component is Mgo-SiO2) is formed.

This coil is flattened at a temperature of 700 to 900°C to remove curls, and at the same time a tension film is applied and baked to apply tension to the steel plate. After that, it is subjected to laser beam irradiation treatment, and then the plate temperature is 600°C. Below, preferably 550
This method performs insulation coating treatment at temperatures below ℃.

The tension film treatment carried out simultaneously with flattening in the present invention can withstand baking at temperatures above 700°C and impart tension to the steel plate upon cooling. processing solution containing colloidal silica, phosphate, and chromate based processing solution described in JP-A No. 52-25296, and processing containing magnesium ion, phosphoric acid, silica, and chromium ion described in U.S. Pat. No. 580449. Although a treatment liquid such as liquid is used, the treatment liquid is not limited to the above-mentioned treatment liquid as long as it can apply tension to the steel plate.

Next, after laser beam irradiation treatment, the plate temperature is 6
The main treatment liquid used to perform insulation coating treatment at temperatures below 00°C is a treatment liquid containing one or more of phosphoric acid and chromate, as well as colloidal silica, colloidal alumina, methane oxide, and boric acid. Some contain one or more compounds added.

In addition, as reducing agents for chromic acid, organic compounds such as polyhydric alcohols and glycerin, water-soluble,
Or emulsion resin, high resistance, 1μ for improved workability
1 of an organic compound such as an organic resin powder having a particle size of
A species or two or more species can be included.

In addition to this, it is also possible to form an insulating film by irradiating with unexpected radiation or the like.

Although the above description has mainly been given to the case of grain-oriented electrical steel sheets, the present invention can also be applied to other non-oriented electrical steel sheets.

Next, an example will be explained.

Example I Si3. O%, C0.003%, Mn 0.0 7 5
%, AlO. Unidirectional electrical steel sheet containing 03% (
0.30m plate thickness) was manufactured by the following process.

After the hot coil is cold-rolled and annealed once, magnesia is applied and dried, wound into a coil, and final high-temperature annealing is performed at 1150°C for secondary recrystallization, after which excess magnesia is removed and a glass film is formed. A magnetic steel sheet having the following properties was obtained.

Divide this coil into two, one coil is 850℃×70
At the same time as flattening, treatment liquid A was applied and baked.

The amount of application is 4. ! 11/m'' (material of the present invention).

The other coil was subjected to only flattening at 850° C. for 70 seconds to serve as a comparative material.

Samples were taken from the unidirectional electrical steel sheet obtained in this way, and the following B and C treatments were applied to the inventive material, and D, E, and F treatments were applied to the comparative material, and various properties were tested. I did it.

Invention material A treatment: Burning the tension film at the same time as flattening? process:
Pulsed laser beam irradiation treatment after A treatment (1) Laser irradiation conditions (I) Energy density = 17 J/dω Point-like trace diameter: 0.2 un (II) Center-to-center distance of dot-like marks in C direction: 0.3 mmtV)
Interval in trace row L direction: 5 mm Insulating coating treatment after C treatment 2 B treatment (1) Insulating coating treatment α) Treatment liquid 20 colloidal silica 1 00 cc 50% aluminum phosphate 6 0 cc chromic anhydride
6g Boric acid 2g ω Baking temperature (board temperature) 500,600,700,8
00'C (I[I) Application amount 1. ! li'/m" Comparative material D treatment: 11 flattening E treatment: Laser beam irradiation treatment after D treatment Laser irradiation conditions are the same as B treatment F treatment: Insulation coating treatment after E treatment Insulation coating treatment solution, baking temperature is C Same as treatment, coating amount was 3 g/m''. Table 1 shows the results carried out as described above.

Example 2 Using the same sample as in Example 1, the following treatments were performed and various characteristics were tested.

Invention material A treatment: A treatment of Example 1 (flattening and applying a tension film at the same time) G treatment 2 Continuous laser beam irradiation after A treatment (1) Laser irradiation conditions α) Power: 2. OW ω Irradiation trace width: 0.2mm ■) Interval between trace rows in the L direction: 5mm ■) Irradiation speed: 200mm/sec H treatment 20 Insulation film treatment after treatment α) Treatment liquid is the same as C treatment Baking temperature 500'C (Plate temperature) ([I) Application amount 0. 8 g/m” Comparative material D treatment: D treatment of Example 1 (residue of flattening) ■Treatment: Continuous laser beam irradiation (I) after D treatment
Laser irradiation conditions Same K treatment as C treatment: ■ After treatment, insulating coating treatment solution, baking temperature, same coating amount as H treatment 3. 9/m'' The results of the above tests are shown in Table 2.

As is clear from Tables 1 and 2, materials with a tensile coating baked in the same way as flattening can have better iron loss than flattening alone, and furthermore, both materials When irradiated with a beam, the electrical steel sheet with the tension coating of the present invention has a greater improvement in core loss.
Furthermore, by baking the insulating film at a temperature of 600° C. or lower, sufficient insulation properties can be obtained in the residue 1 while maintaining the laser beam irradiation effect.

[Brief explanation of drawings]

Figure 1 is a diagram showing the effects of tension coating and laser beam irradiation on iron loss improvement, Figure 2 a''-d are scanning electron micrographs showing the magnetic domain structure of the steel sheet, and Figure 3 is the insulation coating baking temperature. FIG. 3 is a diagram showing the relationship between iron loss and iron loss.

Claims (1)

[Claims] 1. Forming a tension film on the surface of an electromagnetic steel sheet and irradiating it with a laser beam to create laser irradiation marks,
A method for treating an electrical steel sheet, characterized in that the insulation coating treatment is then performed in a warm region where the laser beam irradiation effect does not disappear. 2. The method according to claim 1, wherein the insulation coating treatment is performed in a temperature range where the board temperature does not exceed 600°C.