JPH06136449A - Production of low iron loss grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet low in iron loss by irradiating the surface of a grain-oriented silicon steel sheet subjected to finish annealing and thereafter coated with an insulated film with electron beams under specified conditions. CONSTITUTION:The surface of a grain-oriented silicon steel sheet subjected to finish annealing and thereafter coated with an insulating film is applied with continuous or intermittent irradiation by electron beams in such manner that the irradiating width in the rolling direction is regulated to 0.2 to 1.0mm and they stretch zigzag in a direction crossed with the rolling direction with an inclination of <=30 deg.C to the crossed direction at intervals of 2 to 20mm in the rolling direction. At this time, preferably, the electron beam irradiation is executed at 2 to 9J/cm<2> energy density, and it is force-fitted into the film to a depth of about 0.01 to 5mum. As for the generating conditions of the electron beams, preferably, the electron beams with about 0.1 to 0.5mm phi irradiating diameter are applied at spot central intervals of about 50 to 500mum by about 60 to 500KV pressurizing voltage and about <=5mA accelerating flow. In this way, effective domain fractionation can be executed without destroying the film on the steel surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a low iron loss unidirectional silicon steel sheet using electron beam irradiation,
In addition to stabilizing the magnetic domain subdivision effect, the improvement of the magnetostriction when used as a laminated iron core (hereinafter simply referred to as magnetostriction), the noise when used as a transformer (hereinafter simply referred to as noise), and the shape of steel plate Then, this unidirectional silicon steel sheet is advantageously used as a material for an iron core of a transformer or electric equipment.

In a unidirectional silicon steel sheet, secondary recrystallized grains of a product are highly integrated in a Goss orientation, a forsterite coating is formed on the surface of the steel sheet, and an insulating coating having a small thermal expansion coefficient is further formed on the forsterite coating. It is intended to improve the magnetic properties by, for example, applying a tension to the steel sheet by applying the above method, and is manufactured through complicated and various processes that require strict control. Such unidirectional silicon steel sheet is mainly used as an iron core of transformers and other electric devices, and has a high magnetic flux density (represented by B ₈ value) of the product as a magnetic property, and an iron loss (W _{17 /} (Represented by ₅₀ values) is low, and an insulating film with good surface properties is applied. In particular, the demand for reduction of power loss has been remarkably strengthened at the border of the energy crisis, and the need for unidirectional silicon steel sheet with lower iron loss as an iron core material for transformers has been increasing more and more. It is no exaggeration to say that the history of improving iron loss of this unidirectional silicon steel sheet is the history of improving the Goss-oriented secondary recrystallization texture.

[0003]

2. Description of the Related Art As a method for controlling secondary recrystallized grains, Al
A method of preferentially growing secondary recrystallized Goss grains using a primary recrystallized grain growth inhibitor such as N 2, MnS and MnSe, a so-called inhibitor, has been implemented.

On the other hand, various iron loss improving techniques different from the metallurgical means for controlling the secondary recrystallization texture have been developed. That is, Tadashi Ichiyama: Iron and Steel, 69 (1983), P. 89.
5, JP-B-57-2252, JP-B-57-53419,
Japanese Patent Publication No. 58-26405 and Japanese Patent Publication No. 58-26406 disclose lasers, and JP-A-62-96617, JP-A-62-151511, and JP-A-62-151516. JP-A-62-151517 and the like propose an epoch-making method of irradiating plasma on the surface of a steel sheet to introduce local microstrain into the steel sheet to subdivide magnetic domains and reduce iron loss. It is disclosed. However, all of these methods have an energy efficiency as low as 5 to 20%, so that there is a disadvantage in that cost reduction is inevitable in reducing iron loss.

[0005]

Therefore, the inventors of the present invention have proposed a technique for domain division into domains having high energy efficiency.
63-186826, JP-A-2-118022 and JP-A-2-277780. That is, it is a method of locally and intermittently irradiating the surface of a steel sheet with an electron beam generated by a high voltage and a small current in the width direction of the steel sheet intersecting the rolling direction, and press-fitting the coating into the base metal. However, although these methods achieve improvement in magnetic properties, they have a problem that it is difficult to stably produce a steel sheet having quality as a product because of large variations in magnetostriction, noise and steel sheet shape. It is considered that this is because the penetration depth of the electron beam from the surface of the steel sheet to the inside is deeper than in other methods such as laser.

On the other hand, regarding the magnetic domain subdivision by electron beam irradiation, US Pat. Nos. 4,1997,33 and 4,195,750 each describe an energy density of 60 J / in ² or more for a laminated iron core.
It is disclosed that the energy density of 150 to 4000 J / in ² is used for wound iron cores, but no consideration is given to the penetration depth of the electron beam, and the energy density depends on the type of electron beam irradiation device and the irradiation method. The stable production of products is difficult because it changes depending on the situation. An object of the present invention is to solve the above problems and propose a method for stably producing a high quality product.

[0007]

According to the present invention, the irradiation width in the rolling direction of the unidirectional silicon steel sheet coated with an insulating film after finishing annealing is 0.2 to 1.
In the direction intersecting the rolling direction at 0 mm, with respect to the intersecting direction
A method for producing a low iron loss unidirectional silicon steel sheet, characterized in that continuous or intermittent irradiation extending in a zigzag shape with an inclination of 30 ° or less is performed at intervals of 2 to 20 mm. Further, in practice, it is advantageous to use an electron beam having an energy density of ^{2 to} 9 J / cm ² .

FIG. 1 shows an electron beam irradiation apparatus used directly in the present invention. Number 1 in the figure is exhaust port 1
a casing for forming a vacuum chamber including a and 1b,
A high pressure insulator 2, an electron gun 3 for emitting electrons and an electron gun 3 arranged to face the electron gun 3 for accelerating the electrons emitted from the electron gun 3 in a casing 1 having a high vacuum of preferably 10 ⁻² Torr or less. The electron beam 5 is emitted from the anode 4. Further, 6 is a column valve for always maintaining the electron beam generating section in a high vacuum, 7 is a focusing coil for focusing the electron beam 5, and 8 is a traveling direction of the electron beam 5 focused by the focusing coil 7. It is a deflection coil that changes the direction and irradiates a predetermined area of the steel sheet 9. By this deflection coil 8, as shown in FIG. 2 (b), the electron beam is tilted within the irradiation width of 0.2 to 1.0 mm in a direction intersecting with the rolling direction at an angle of 30 ° or less with respect to the intersecting direction. Achieve intermittent irradiation or continuous irradiation that extends in a zigzag shape. This irradiation enables effective magnetic domain subdivision without destroying the coating on the steel sheet.

The electron beam irradiation at this time is preferably performed at an energy density of ² to 9 J / cm ² . And it is preferable to press fit the film to a depth of 0.01 to 5 μm, and the electron beam generation condition for this is that the acceleration voltage is 60
It is preferable to set kV to 500 kV and an acceleration current to 5 mA or less, and it is preferable to further irradiate an electron beam having an irradiation diameter of 0.1 to 0.5 mmφ with a spot center interval of 50 to 500 μm or continuously.

In applying the method of the present invention, the component composition of the grain-oriented silicon steel sheet may be any conventionally known component composition, and the representative compositions are as follows. C: 0.01 to 0.10 wt% Not only the refinement of the structure during hot rolling and cold rolling but also
It is an element useful for the development of Goss orientation, and at least 0.01
Addition of wt% or more is preferable. However, if the content exceeds 0.10 wt%, the Goss orientation is rather disturbed, so the upper limit is preferably 0.10 wt%. Si: 2.0 to 4.5 wt% Increases the specific resistance of steel sheet and effectively contributes to the reduction of iron loss.
If it is less than 0 wt%, not only the resistivity decreases but also α- during the final high-temperature annealing for secondary recrystallization and purification.
The gamma transformation causes the crystal orientation to be randomized, so that a sufficient iron loss improving effect cannot be obtained, and if it exceeds 4.5 wt%, cold ductility is impaired. Therefore, the lower limit is 2.0 wt% and the upper limit is
It is preferably 4.5% by weight. Mn: 0.02 to 0.12 wt% At least 0.02 wt% is required to prevent hot embrittlement, but if it is too much, the magnetic properties deteriorate, so the upper limit is preferably 0.12 wt%.

The inhibitors are roughly classified into MnS and Mn.
There are Se series and AlN series. In case of MnS and MnSe system, S: 0.
At least one of S and Se selected from 005 to 0.06 wt% and Se: 0.005 to 0.06 wt% is an effective element as an inhibitor for controlling the secondary recrystallization of grain-oriented silicon steel sheet. Both require at least about 0.005 wt% from the viewpoint of securing suppression, but if it exceeds 0.06 wt%, the effect is impaired, so it is preferable to set the lower limit to 0.005 wt% and the upper limit to 0.06 wt%. . In the case of AlN system, Al: 0.005 to 0.10 wt% and N: 0.004 to 0.015 wt% Al and N range may be set to the above range for the same reason as in the case of MnS system and MnSe system described above. preferable.

As the inhibitor component, S and S described above are used.
In addition to e and Al, Cr, Mo, Cu, Sn, Ge, Sb, Te, Bi and P are also suitable, and a small amount of each may be contained. The preferred ranges of addition of the above components are Cr, Cu, Sn: 0.01 wt% or more and 0.50 wt% or less, Mo, Ge, Sb, Te, Bi: 0.005 wt% or more, 0.1 wt% or less, P: 0.01 The content is not less than wt% and not more than 0.2 wt%, and these inhibitor components are suitable for both single use and combined use.

[0013]

Next, the present invention will be described based on experimental examples. C: 0.079 wt%, Si: 3.36 wt%, Mn: 0.08 wt%, Mo:
Silicon steel slab containing 0.012wt%, sol.Al: 0.025wt%, Se: 0.019wt%, and Sb: 0.025wt% at 1360 ℃
After 3 hours of heating, it is hot-rolled to a hot-rolled sheet with a thickness of 2.2 mm, and then cold-rolled twice with intermediate annealing at 1050 ° C for 2 minutes to obtain a final cold-rolled sheet with a thickness of 0.23 mm. did. Then, after decarburizing and primary recrystallization annealing in wet hydrogen at 840 ° C, an annealing separator containing MgO as a main component is applied as a slurry on the surface of the steel sheet,
After that, the temperature was raised at 10 ° C / h and annealed at 850 ° C for 15 hours, and then the temperature was raised to 1180 ° C at 12 ° C / h to carry out the secondary recrystallization annealing to obtain the goth-oriented secondary recrystallized grains. After preferential growth,
Purification annealing was performed for 5 hours in dry hydrogen at 1220 ° C. Next, an insulating coating containing phosphate and colloidal silica as main components was formed on the surface of the steel sheet. Then, using the apparatus shown in FIG. 1, an electron beam (voltage: 150 kV, current: 0.9 mA, energy density: 7.1 J / cm ² ) was applied in a direction orthogonal to the rolling direction of the steel sheet at a scanning interval of 6 mm and a scanning speed. Irradiation at 700 cm / s was performed linearly (irradiation width: 0.20 mm) shown in FIG. 2 (a) and zigzag (irradiation width: 0.35 mm) shown in FIG. 2 (b). In the zigzag irradiation, as shown in FIG. 6B, the displacement L in the direction intersecting the rolling direction of the electron beam is kept constant at 0.2 mm while the displacement H in the rolling direction is 0.2 mm. The tilt angle θ with respect to the intersecting direction was changed by changing the tilt angle within the range of mm or less. For comparison, a sample not subjected to magnetic domain refinement treatment was also prepared.

The results of examining the magnetic properties and the shape of the steel sheet thus obtained are shown in FIG. From the figure,
It can be seen that the iron loss improvement amount is large for the steel sheet that is zigzag-irradiated when the inclination angle θ is 30 ° or less, and the iron loss improvement amount decreases when the inclination angle θ exceeds 30 °. Similarly, the amount of change in magnetic flux density also decreases as the tilt angle θ increases. On the other hand, the amount of C warpage, which is the amount of deformation of the steel sheet before and after irradiation in the C direction (direction orthogonal to the rolling direction), decreases as the tilt angle θ increases, and a steel sheet having an excellent shape can be obtained.

Table 1 shows the results of examining the magnetic properties, magnetostriction, noise and steel plate shape of the steel plate obtained in the same manner as above. The tilt angle θ in zigzag irradiation is 1
It was 1.3 °. Here, magnetostriction is evaluated by excitation VA (normally expressed in VA / kg) and noise is evaluated by db, and the evaluation at this time is usually shown by the value at 1.7 T / 50 Hz. These evaluations are the same in the experiments and examples shown below.

[0016]

[Table 1]

As is clear from Table 1, both the samples subjected to the magnetic domain refinement treatment showed a remarkable improvement in the iron loss as compared with the samples not subjected to the magnetic domain refinement treatment, but the same zigzag pattern was observed when the electron beam was linearly irradiated. It can be seen that the magnetostriction, noise, and deterioration in the shape of the steel sheet are remarkable as compared with the case of irradiating in a uniform shape.

Further, the inventors also conducted an experiment on the energy density of the electron beam. That is, the steel sheet with an insulating coating obtained in the same manner as the experiment whose results are shown in Table 1 is
Electron beam (voltage: 150-225
kV, current: 0.5 to 1.50mA, beam diameter: 0.2 to 0.3mm φ)
Irradiating in a zigzag pattern with a scanning interval of 6 mm and an irradiation width of 0.35 to 0.80 mm in a direction orthogonal to the rolling direction of the steel sheet,
The energy density was changed from 1 to 30 J / cm ² .
For comparison, a sample not subjected to magnetic domain refinement treatment was also prepared. The results of examining the magnetic properties, magnetostriction, noise, and steel plate shape of the steel plate thus obtained are shown in FIG. 4, respectively.

As is clear from the figure, when the energy density is 9.0 J / cm ² or less, the magnetic properties, magnetostriction, noise and steel plate shape are all improved, but the iron loss is less than 2.0 J / cm ^2. Deteriorated. Therefore, the energy density is 2.0 to 9.
By setting the range to 0 J / cm ² , all of the magnetic characteristics, magnetostriction, noise and steel plate shape can be further improved.

Disadvantages caused by electron beam irradiation, in particular, are magnetostriction, noise, and deterioration of the shape of the steel sheet, because electron beams have high energy efficiency and the beam can be narrowed down.
This is because the minute strain is deeply dispersed in the steel sheet irradiated with the electron beam. Therefore, by performing electron beam irradiation in a zigzag manner and at an energy density of 2.0 to 9.0 J / cm ² , it is possible to increase the frequency of occurrence of domain wall nuclei that can subdivide 180 ° magnetic domains. As a result, the magnetic domains can be sufficiently subdivided at a lower energy density than that disclosed in the already-known US Pat. Nos. 4,1997,33 and 4,195,750. Further, in the present invention, by providing such an energy density, it is possible for the first time to improve not only magnetic characteristics but also magnetostriction, noise and steel plate shape. Therefore, although the above-mentioned U.S. patents can improve the magnetic characteristics, they have problems in magnetostriction, noise, and the shape of the steel sheet, and it has been impossible to manufacture a product.

[0021]

【Example】

(A) C: 0.042 wt%, Si: 3.48 wt%, Mn: 0.073 wt%,
Mo: 0.012 wt%, Se: 0.020 wt% and Sb: 0.022 wt% (B) C: 0.020 wt%, Cu: 0.2 wt%, Sn: 0.08 wt% and
A silicon steel slab containing Al: 0.024wt% was heated at 1380 ℃ for 4 hours and hot-rolled to a hot rolled sheet with a thickness of 2.2mm.
It was cold rolled twice with an intermediate anneal of 2 min.
The final cold rolled sheet had a thickness of 23 mm. Then, after decarburizing and primary recrystallization annealing in wet hydrogen at 840 ° C, an annealing separator containing MgO as a main component is slurry-coated on the surface of the steel sheet, and then 850
After annealing at 20 ℃ for 20h, the temperature is raised to 1180 ℃ at 8 ℃ / h to preferentially grow Goss-oriented secondary recrystallized grains, and then at 1220 ℃.
Purified annealing was performed for 8 hours in the dry hydrogen. Next, an insulating coating containing phosphate and colloidal silica as main components was formed on the surface of the steel sheet. Then, using the apparatus shown in FIG. 1, an electron beam [voltage: 150 kV, current: 1.6 mA, beam diameter: 0.
25mmφ (by knife edge method), vacuum degree: 5 × 10 ^-4 To
rr] in the direction orthogonal to the rolling direction of the steel sheet, irradiation width: 0.5 mm
And the scanning interval: 6 mm, the irradiation with a zigzag shape with the inclination angle θ of 15.6 ° is performed at an energy density of 6.3 J /
done in cm ² . Table 2 shows the results of examining the magnetic properties, magnetostriction, noise and steel plate shape of the product thus obtained.

[0022]

[Table 2]

[0023]

According to the present invention, good magnetic characteristics,
In particular, a unidirectional silicon steel sheet with a low iron loss can be produced without causing magnetostriction, noise and deterioration of the steel sheet shape,
An excellent product can be stably provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an electron beam irradiation apparatus used in the method of the present invention.

FIG. 2 is a schematic diagram showing an electron beam irradiation procedure.

FIG. 3 is a tilt angle θ in zigzag irradiation of an electron beam
6 is a graph showing the relationship between the magnetic properties and the steel plate shape.

FIG. 4 is a graph showing the relationship between electron beam energy density and iron loss, magnetostriction, noise, and steel plate shape.

[Explanation of symbols]

 1 Casing 1a Exhaust port 1b Exhaust port 2 High-pressure insulator 3 Electron gun 4 Anode 5 Electron beam 6 Column valve 7 Focusing coil 8 Deflection coil 9 Steel plate

Claims (2)

[Claims] 1. A surface of a unidirectional silicon steel sheet coated with an insulating film after finish annealing is irradiated with an electron beam in a direction crossing the rolling direction at an irradiation width of 0.2 to 1.0 mm in the rolling direction. Continuous or intermittent irradiation that extends in a zigzag shape with an inclination of 30 ° or less with respect to the crossing direction
A method for producing a low iron loss unidirectional silicon steel sheet, which is performed at intervals of ~ 20 mm. 2. An electron beam having an energy density of 2 to 9 J
The method according to claim 1, wherein a material having a density of / cm ² is used.