JPH0740527B2 - Directional electrical steel sheet subjected to magnetic domain control treatment and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a grain-oriented electrical steel sheet in which magnetic domains are controlled by a glass in a perforation, and in particular, magnetic domain control that does not disappear even when strain relief annealing is performed. The present invention relates to a treated grain-oriented electrical steel sheet and a method for manufacturing the same.

(Prior Art) Among grain-oriented electrical steel sheets, those having a crystal orientation as close as possible to the Goss orientation and a relatively large crystal grain size of several millimeters or more have excellent magnetic characteristics other than iron loss such as magnetic flux density. There is. The main reason for the comparatively poor iron loss characteristics of grain-oriented electrical steel sheets whose crystal orientation is close to the Goss orientation and whose crystal grain size is relatively large is that in the case of the above-oriented material, the magnetic domain becomes relatively large. As a countermeasure against this problem, magnetic domain subdivision technology such as laser processing has already been devised in this field (Japanese Patent Publication No.
-2252 publication).

Therefore, when manufacturing a wound core transformer using a grain-oriented electrical steel sheet, the steel sheet must be bent, which causes strain on the material and inevitably deteriorates the magnetic properties. Generally, pre-annealing is performed to remove the strain and recover the magnetism.

In the conventional magnetic subdivision processing method such as laser treatment, internal strain is given to the finally annealed steel sheet by a laser or the like, and thus such internal strain disappears by performing the above-mentioned strain relief annealing.

(Problems to be Solved by the Invention) The present invention solves the problem of the prior art that the iron loss becomes relatively low when the magnetic induction characteristics of the grain-oriented electrical steel sheet are high by the magnetic domain control process, and the grain orientation electromagnetic If there is no choice but to perform strain relief annealing for steel plate shaping reasons,
It is intended to provide a magnetic subdivision technique in which strain is not lost even if strain relief annealing is performed.

(Means and Actions for Solving Problems) The grain-oriented electrical steel sheet according to the present invention has a structure in which substantially triangular pyramid-shaped perforations are formed in a point sequence formed on the surface of the grain-oriented electrical steel sheet obtained in a normal process. The magnetic domain control treatment is performed by having a glass containing stellite as a main component, and the magnetic domain control treatment method according to the present invention is obtained in a normal manufacturing process of grain-oriented electrical steel sheet, cold The surface of the rolled plate or decarburized annealed plate is perforated in a dot sequence, and then a coating containing MgO as a main component is applied, and then secondary recrystallization annealing is performed to form forsterite on the surface of the secondary recrystallization annealed plate. Thus, a glass containing forsterite as a main component is buried in the perforations. Hereinafter, the present invention will be described in detail with reference to the drawings.

In FIG. 1, "1" is a grain-oriented electrical steel sheet having a secondary recrystallized structure grown by a normal treatment, and 2 is a surface coating containing forsterite as a main component formed in the final annealing step. The grain-oriented electrical steel sheet 1 according to the present invention has substantially triangular pyramid-shaped perforations 3 formed in dots on its surface.
Has micropores forsterite 4 inside.
On the surface portion of the grain-oriented electrical steel sheet 1 in contact with the micropores forsterite 4, the surface oxide layer 5 mainly composed of Fe-Si may be formed by oxidation during formation of the glass film. Since the linear expansion coefficient of forsterite, which is the main component of the above glass, is much smaller than that of the Fe-Si matrix 6 of the steel sheet 1, in the process of quenching to room temperature after finish annealing at a high temperature of 1000 ° C or higher. When the forsterite contracts in the perforations 3, a tensile stress is applied to the Fe-Si matrix 6, so that local stress is generated around the perforations 3. Further, the internal oxide layer 5 also has a difference in linear expansion coefficient from that of the Fe-Si matrix 6 as compared with the forsterite, but since it is composed of an oxidative component, a local strain is generated at the root 5a in the above quenching process. Due to the internal stress generating action of the glass containing forsterite as a main component as described above, a minute magnetic domain having a direction different from the magnetic domain unique to the secondary recrystallization is generated.

The anisotropic magnetic domain has a surface coating 2 having a small coefficient of linear expansion.
Since the surface tension is applied by the formation of
Many 0 ° magnetic domains expand and the magnetic domains are subdivided.
By subdividing the magnetic domains, the iron loss of the grain-oriented electrical steel sheet having a high magnetic flux density can be improved, and even if the original magnetic domain is relatively large due to the high magnetic flux density, a product having excellent iron loss can be obtained. . Furthermore, the subdivided magnetic domains formed in this way are not caused by the displacement due to the existing lattice defects or strain as in the conventional magnetic domain subdivision technology. Since it is in a deflected state due to solid inclusions, the effect does not disappear even if stress relief annealing is performed thereafter.

The most effective perforation in the present invention is a diameter of 10 μm to 1 mm,
It has a substantially triangular pyramid shape in which a depth of 3 to 100 μm and a spacing of 10 μm to 20 mm are perforated.

In the present invention, the lower limit of the diameter of the holes of the perforations 3 is set to 10 μm, it is difficult to perforate holes having a diameter smaller than this in an industrially practical range, and the upper limit is set to 1 mm. This is because if it exceeds, iron loss improvement due to magnetic domain subdivision generated by the holes is not performed. The lower limit of the depth of the holes 3 is set to 3 μm because the thickness of the surface oxide layer 5 of the ordinary electromagnetic steel sheet coating is 2 to 3 μm, and the effect of the present invention is 3 μm or more. is there. Also, the upper limit is 100μ
The reason for setting m is as follows.

The cross-sectional area occupancy rate of the iron core passing through the magnetic flux is an important factor that is measured as the space factor in the case of a transformer, but usually the space factor can be regarded as an allowable error range if it fluctuates within 1%. A range in which the cross-sectional area of the hole was 1% or less was determined, and this was set as the upper limit of the depth.

Next, the lower limit of the distance between the perforations 3 (d-see FIG. 2) is 10 μm.
The reason is that the minimum diameter of the holes is 10 μm, and the densest condition in which the outer diameters of the holes are in contact is 10 μm, so this was made the lower limit. Moreover, the upper limit of 2 mm is set as a condition for further subdividing this because the magnetic domain width is about 2 mm in the case of the material having the best orientation.

A preferred specific example of the dot-like array form, pitch and spacing of the perforations 3 on the surface of the grain-oriented electrical steel sheet according to the present invention will be described with reference to FIG.

In the present invention, the preferable pitch (t) of the point sequence of the perforations 3 is set to
The lower limit is set to 10 μm to 20 mm under the condition of being in contact with the minimum pore diameter of 10 μm, and is set to 20 mm or less in order to improve the magnetic properties, particularly the iron loss value. Note that the pitch (t) is not a regular pitch, but may be a combination of a pitch of 0.5 to 2 mm and a pitch of 3 to 15 mm, for example. Further, the preferable angle (θ) formed by the perforations 3 arranged in a dot shape with respect to the rolling direction (RD) is
45 ° C to 90. With the above angle, the material iron loss value can be improved and the transformer iron loss value can be reduced.

Hereinafter, the method according to the present invention will be described.

Ordinary electromagnetic steel sheet manufacturing process, namely, steel making, hot rolling, hot rolled sheet annealing, cold rolling process to produce a cold rolled sheet,
Next, the cold-rolled sheet is irradiated with a pulse laser to form a point array of minute perforations. Next, after decarburizing and annealing the cold-rolled sheet with the minute perforations formed to remove the oxide film formed on the surface layer, magnesia coating is applied at a normal basis weight, followed by finish annealing under normal conditions. To do. Further, when forming the above-mentioned point train of minute perforations on the surface of the decarburized and annealed plate, the finish annealing is performed under a heat treatment condition sufficient to remove the oxide film formed on the surface of the decarburized and annealed plate.

The above-mentioned perforation is carried out by pulsed laser light irradiation, but a pulse intensity of 10 to 300 mJ / Pulse is suitable for practical use. In addition to laser light, holes may be formed by means of electric discharge machining, electron beam, or other mechanical means.

(Example) Hereinafter, the present invention will be described based on examples.

Example 1 Plate thickness 0.225 mm obtained in a normal grain-oriented electrical steel sheet manufacturing process
Laser irradiation was performed on the cold-rolled sheet of No. 1 under the following conditions.

Laser pulse intensity: 150mJ / Pulse Laser irradiation direction: 90 ° to rolling direction Laser irradiation pitch: 5mm Micro perforation: Diameter 0.08mm, depth 0.02mm, interval 0.5mm N: 25 for the above cold rolled sheet % ・ DP65 ℃ atmosphere 850 ℃ × 120
After decarburizing and annealing for 2 seconds, the oxide film was also removed during the decarburizing and annealing, and then an annealing separator containing MgO as a main component was applied and finish annealing was performed at 1200 ° C for 20 hours.

The magnetic flux density B ₈ of the grain-oriented electrical steel sheet thus manufactured is 1.90.
T, iron loss (W _17/50) was 0.84 W / kg. In addition, when observing the cross section of the grain-oriented electrical steel sheet with a 400x optical microscope,
It was confirmed that minute perforations with a substantially triangular pyramid shape were formed, and a glass containing forsterite as a main component was formed inside the perforations. Also, when the surface of the grain-oriented electrical steel sheet was observed with a scanning electron microscope, it was confirmed that a large number of 180 ° magnetic domains in which the magnetic domains found in the ordinary secondary recrystallized structure were subdivided were elongated in the rolling direction. It was

The above finish annealed steel sheet was subjected to strain relief annealing at 850 ° C. for 4 hours.

The iron loss values are shown below, together with the comparison machine of the same lot not subjected to the laser irradiation.

Example 2 A cold-rolled sheet having a plate pressure of 0.225 mm obtained in a normal process was decarburized and annealed, and then the decarburized and annealed sheet was irradiated with laser under the following conditions.

Laser pulse intensity: 100mJ / Pulse Laser irradiation direction: 70 ° to rolling direction Laser irradiation pitch: Combination of 0.5mm and 6mm Micro perforation: Diameter 0.06mm, depth 0.02mm, interval 0.5mm Above decarburized annealing plate 850 ℃ in N: 25% ・ DP60 ℃ atmosphere
After pre-annealing for 120 seconds to remove the oxide film formed during decarburization annealing, an annealing separator containing MgO as a main component was applied and finish annealing was performed at 1200 ° C for 20 hours.

The magnetic flux density B ₈ of the grain-oriented electrical steel sheet thus manufactured is 1.91.
T, iron loss 8 (W _17/50) was 0.79W / kg.

By the same method as in Example 1, it was confirmed that substantially triangular pyramid-shaped minute perforations, formation of glass containing forsterite as a main component, and subdivision of magnetic domains were confirmed. After that, 850 ℃ on the steel plate
A standard strain relief annealing was performed for 4 hours. The iron loss value of the obtained material is shown below together with the iron loss value of the comparative material of the same lot not subjected to the laser irradiation.

(Effect of the Invention) According to the magnetic domain control means of the present invention, the effect does not disappear even after the stress relief annealing is performed, so that it can be used as a material for a wound core transformer, and its industrial value is enormous.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view of a magnetic domain control treated steel according to the present invention, and FIG. 2 is an explanatory view for explaining an arrangement of point-like perforations of the magnetic domain control treated steel according to the present invention. 1 ... Grain-oriented electrical steel sheet, 2 ... Surface coating, 3 ... Perforation, 4 ... Micropore forsterite.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuro Kuroki 1-1-1 Edamitsu, Hachimanto-ku, Kitakyushu, Fukuoka Prefecture, Nippon Steel Corporation Production Technology Laboratory (72) Inventor Takashi Kobayashi Yawatahigashi, Kitakyushu, Fukuoka Kuedaemitsu 1-1-1 Production Engineering Laboratory, Nippon Steel Corporation (56) References JP-A-57-152423 (JP, A) JP-A-60-114519 (JP, A)

Claims (5)

[Claims] 1. A diameter of 10 μm to 1 mm perforated on the surface of a grain-oriented electrical steel sheet obtained in a normal process, a depth of 3 to 100 μm and an interval of 10 μm.
A grain-oriented electrical steel sheet that has been subjected to a magnetic domain control process, characterized by having a glass containing forsterite as a main component inside a perforation in the shape of a triangular pyramid with a dot array of ~ 2 mm. 2. The grain-oriented electrical steel sheet according to claim 1, wherein the dot sequence is in an angle range of 90 ° to 45 ° with respect to the rolling direction and the pitch is 10 μm to 20 mm. 3. A diameter of 10 μm to 1 m on the surface of a cold-rolled plate or a decarburized annealed plate obtained by a normal production process of grain-oriented electrical steel sheet.
m, depth of 3 ~ 100μm, almost triangular pyramidal hole 10μm ~ 2mm
To form a forsterite on the surface of the secondary recrystallized annealed plate, after applying a coating containing MgO as the main component, and then forming a forsterite on the surface of the secondary recrystallized annealed plate.
A method of manufacturing a grain-oriented electrical steel sheet subjected to a magnetic domain control process, characterized in that a glass containing forsterite as a main component is formed in the perforations. 4. The method according to claim 3, wherein the dot sequence is in the angle range of 90 ° to 45 ° with respect to the rolling direction and the pitch is 10 μm to 20 mm. 5. The method according to claim 3, wherein the hole is formed by irradiating with a laser beam.