JPH062042A - Production of grain-oriented silicon steel sheet with low iron loss for laminated iron core - Google Patents

Abstract

PURPOSE:To surely and stably scan an electron beam and to obtain a high quality product by adopting a beam optical system of single stage diaphragm for electron beam irradiation equipment and also controlling the range of a working distance. CONSTITUTION:The surface of a grain-oriented silicon steel sheet on which an insulating film is formed after finish annealing is irradiated with an electron beam in a direction intersecting a rolling direction. At this time, a beam optical system of single stage diaphragm is adopted for a beam passage from the generation of beam from an electron gun to a deflection coil. Further, the working distance of the beam optical system is set at a value in the range of 300 to 700mm. The working distance means the distance between the center of a focusing coil converging the electron beam and the position of the steel sheet. Because the breakage of the film on the steel sheet due to electron beam irradiation is prevented, the necessity of recoating can be obviated.

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 a unidirectional silicon steel sheet is mainly used as an iron core of a transformer and other electric equipment,
Magnetic flux density of products as magnetic characteristics (represented by B ₈ value)
High, and low iron loss (represented by the W _17/50 value),
Further, it is required to form an insulating film having a good surface property. 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.

[0004]

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 a low energy efficiency of 5 to 20%, so that there is a disadvantage in that cost reduction is inevitable in reducing iron loss.

[0006]

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 magnetic domain subdivision by electron beam irradiation, US Pat. No. 4,1997,33 and US Pat. No. 4,195,750 each describe an energy density of 60 J / in ² or more for a laminated iron core and a wound iron core. Although it is disclosed that the energy density is 150 to 4000 J / in ² , no consideration is given to the penetration depth of the electron beam, and the energy density and the beam diameter vary depending on the type of electron beam irradiation device and the irradiation method. Therefore, stable production of products is difficult.

An object of the present invention is to solve the above problems and propose a method for stably producing high quality products.

[0009]

Means for Solving the Problems The inventors have studied a method for industrially stably performing magnetic domain subdivision of a unidirectional silicon steel sheet for laminated iron cores by electron beam irradiation. It was found that the electron beam must be reliably and stably scanned, and the beam optical system that controls the electron beam focusing and deflection plays an important role in realizing these. Therefore, the current electron beam utilization technology, which is shown in FIG. 1 according to the purpose of use and the purpose of use, was examined in detail.

That is, in order to easily and stably use a finely focused electron beam for a long time, a beam with a three-stage or two-stage aperture shown in the left side of FIG. It was considered optimal to apply an optical system. The filament of the electron gun used in the electron microscope is a thin hairpin (0.1-0.3 mmφ) made of W or a single crystal of LaB _{6 with} a sharp tip, and this method is the best for the purpose of using an extremely thin beam. It is conceivable that the electron beam cannot be used easily and safely, and the high voltage beam, the hairpin filament and the optical system of several stages are adopted to make it a high-speed ultrafine beam. Has a problem in that the insulation coating on the silicon steel sheet is destroyed and it is difficult to secure insulation. Therefore, recoating is required after irradiation, which increases the cost and occupies the space of the silicon steel sheet. There is a disadvantage that the rate drops.

The electron beam used for electron welding, heating and melting shown on the right side of FIG. 1 uses an electron optical system with a single-stage aperture, but the filament of the electron gun used here is thick. Since it is a linear or rod-shaped W filament and has a beam diameter of 0.5 to 10 mmφ, it is not suitable for magnetic domain subdivision processing of a silicon steel sheet.

Therefore, with respect to an electron optical system which can be easily and stably used for electron beam irradiation for a long time, many trial experiments were conducted by returning to the origin. As a result, by using the beam optical system as a single stop and adjusting the working distance, it is possible to obtain an extremely stable magnetic domain subdivision unidirectional silicon steel sheet with excellent magnetic domain characteristics, magnetostriction, noise and steel sheet shape. It was newly found that it can be manufactured.
Also, when the filament of the electron gun was examined, it was found that the ribbon filament is advantageous.

That is, according to the present invention, an electron beam emitted from an electron gun is converged and deflected by a beam optical system on the surface of a unidirectional silicon steel sheet coated with an insulating film after finish annealing to intersect with the rolling direction. A method for producing a low iron loss unidirectional silicon steel sheet for a laminated iron core, characterized in that the beam optical system has a single-stage aperture upon irradiating in a direction, and the working distance thereof is 300 to 700 mm. Is.

Here, the working distance is
As will be described later with reference to FIG. 2, it refers to the distance from the center of the focusing coil 7 that focuses the electron beam 5 to the position of the steel plate 9 (electron beam irradiation plate).

In practice, it is advantageous to use ribbon filaments in the electron gun.

FIG. 2 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 above electron beam generator in a high vacuum, and 7 is an electron beam 5
Is a focusing coil, and 8 is a deflection coil for scanning the focused electron beam 5 in the width direction of the steel plate 9.

This electron beam irradiation apparatus is characterized in that, in the apparatus shown in FIG. 2, a beam optical system with a single-stage aperture is adopted in the beam path from the beam generation of the electron gun 3 to the deflection coil 8, and the acceleration voltage is increased. Is a high voltage of 60 to 500 kV and an accelerating current is a narrow current of 5 mA or less, and the working distance of the beam optical system is in the range of 300 to 700 mm in order to narrow down the electron beam generated and to achieve stable use for a long time. It is essential to set and use. Further, it is preferable to use a ribbon filament for the electron gun 3.

[0018]

Next, the experimental results which are the basis of the present invention will be described. Using the electron beam irradiation device shown in FIG. 2, when irradiating the surface of a unidirectional silicon steel sheet having an insulating coating after finish annealing with an electron beam at intervals of 6 mm at right angles to the rolling direction, the working of the beam optical system was performed.・ The change in iron loss when the distance is changed from 100 mm to 1000 mm is shown in Fig. 3 (a). The electron beam generation conditions at this time were: acceleration voltage: 150 kV, acceleration current: 0.7 mA, and vacuum degree: 3 × 10 ⁻⁴ Torr. Also, FIG. 3 (b)
Is the plate shape (C warpage amount) of the product after electron beam irradiation
Is plotted against working distance. At the same time, Fig. 2 (b) also shows the results of an investigation on whether or not the product after electron beam irradiation needs to be recoated.

As is apparent from FIGS. 3 (a) and 3 (b),
The working distance is in the range of 200 to 700 mm in the area where the magnetic properties of the unidirectional silicon steel sheet are improved, but the area where the amount of C warpage is small and recoating is unnecessary is
It can be seen that the working distance is in the range of 300 mm or more. That is, the working distance is 3
If it is less than 00 mm, the magnetic properties are good, but the amount of C warpage is extremely poor, and it is necessary to recoat the insulating film. This has a working distance of 300mm
If it is less than the above range, the beam diameter becomes too small and the local strain of the steel sheet increases, so that the plate shape of the product deteriorates, and it is considered necessary to recoat the insulating film. Therefore, the working distance is 300
By setting in the range of ~ 700 mm, stable use for a long time becomes possible.

By controlling the working distance in the range of 300 to 700 mm as the electron beam irradiation condition, the coating film on the steel sheet can be press-fitted to a depth of 0.01 to 5 μm. As described above, the electron beam generation condition at this time is preferably such that the acceleration voltage is 60 to 500 kV and the acceleration current is 5 mA or less, but the irradiation energy density is ^{2 to} 9 J / cm ² And the beam diameter generated under these conditions: 0.2 to 0.45
It is preferable to irradiate the electron beam of mm intermittently or continuously with the spot center interval: 50 to 500 μm.

Incidentally, with respect to the application of the method of the present invention, as for the component composition of the grain-oriented silicon steel sheet, any of the conventionally known component compositions is suitable, 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 a useful component for the development of Goss orientation, at least 0.01wt.
It is preferable that the content be at least%. 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 the steel sheet and effectively contributes to the reduction of iron loss.
If the content is less than 0 wt%, not only the resistivity decreases, but also α-γ during the final high-temperature annealing for secondary recrystallization and purification.
The transformation causes randomization of the crystal orientation, so that a sufficient iron loss improving effect cannot be obtained, and if it exceeds 4.5 wt%, cold ductility is impaired. Therefore, it is preferable to set the lower limit to 4.5 wt%.

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 mnS.
There are e type and AlN type. In case of MnS, MnSe system, S: 0.0
At least one selected from 05 to 0.06 wt% and Se: 0.005 to 0.06 wt% S and Se are both effective components as inhibitors that control the secondary recrystallization of grain-oriented silicon steel sheet. Both require at least about 0.05 wt% from the viewpoint of securing suppression, but if it exceeds 0.06 wt%, the effect will be impaired.
The lower limit is preferably 0.005 wt% and the upper limit is preferably 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 ranges are set to the upper limit range for the same reason as in the case of MnS system and MnSe system described above. Preferably.

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
These are also suitable, and may be contained together in small amounts. The preferred addition ranges of the above components are Cr, Cu, Sn: 0.01 wt% or more and 0.5 wt% or less, Mo, Ge, Sb, Te, Bi: 0.005 wt% or more, 0.1 wt% or less, P: 0.01 wt. % Or more and 0.2 wt% or less, and these inhibitor components are suitable for both single use and combined use.

Next, the manufacturing process of the present invention will be described.
The molten steel whose components have been adjusted as described above is made into a slab by continuous casting and then heated at a temperature of 1250 ° C. or higher. This heating is indispensable for dissociation and solid solution of the inhibitor in steel. The heat treated slab is then hot rolled
It is a hot-rolled sheet with a thickness of 1.5 to 3.5 mm. After that, homogenizing annealing is performed, and at least one cold rolling is performed with intermediate annealing interposed therebetween to obtain a final cold-rolled sheet having a thickness of 0.15 to 0.35 mm. After that, the surface of the steel sheet is degreased, and a primary recrystallization annealing that also serves as decarburization is performed in wet hydrogen in the temperature range of 750 to 850 ° C. After that, an annealing separator containing MgO as a main component is slurry-coated on the surface of the steel sheet. After that, the secondary recrystallization annealing is annealed at a temperature of 830 ° C or higher to develop highly integrated secondary recrystallized grains in the Goss orientation. At this time, long-term holding at a constant temperature for 30 to 50 hours or slow heat annealing is adopted. Then, in order to purify the steel sheet, it is annealed at 1150 ° C. or higher for 3 to 10 hours in dry H ₂ . After that, a tension insulating coating containing phosphate and colloidal silica as main components is applied on the surface of the steel sheet. Next, electron beam irradiation is performed on the surface of the steel plate treated in this manner to subdivide magnetic domains.

In the electron beam irradiation process, an electron beam irradiation device of a beam optical system having a one-stage aperture as shown in FIG. 2 is preferably used. Particularly, in the present invention, the working distance of the beam optical system in FIG.
It is indispensable to set it in the range of 300 to 700 mm.

Such electron beam irradiation is usually performed by air
It is carried out using a continuous line of air-to-air system, but batch type is also suitable, and the vacuum degree at that time is recommended to be 5 × 10 ^{-6 to} 5 × 10 ^-2 Torr. To be done.

[0030]

【Example】

(A) C: 0.044 wt%, Si: 3.38 wt%, Mn: 0.066 wt%, Mo:
0.012wt%, Se: 0.018wt% and Sb: 0.023wt% (B) C: 0.068wt%, Si: 3.35wt%, Mn: 0.078wt%, Mo:
0.012wt%, Se: 0.019wt%, Cu: 0.08wt%, Sn: 0.009wt%
And a silicon steel slab containing Al: 0.026wt% are heated at 1350 ℃ for 4 hours, hot rolled into a 2.3mm thick hot-rolled sheet, then 1050 ℃
After performing cold rolling twice with intermediate annealing for 3 minutes at 0.
The final cold rolled sheet had a thickness of 23 mm. Then, after decarburizing and primary recrystallization annealing in wet hydrogen at 835 ° C, an annealing separator containing MgO as a main component is applied on the surface of the steel sheet by slurry, and then 10 ° C.
After performing secondary recrystallization annealing at 850 ° C for 50 hours at a temperature of / h to preferentially grow Goss-oriented secondary recrystallized grains, then perform purification annealing in dry hydrogen at 1220 ° C for 5 hours. . Next, an insulating coating containing phosphate and colloidal silica as main components was formed on the surface of the steel sheet.

Thereafter, using the apparatus shown in FIG. 2, an electron beam [voltage: 150 kV, current: 0.7 mA, working distance: 500 mm, beam diameter: 0.32 mmφ (by knife edge method measurement), vacuum degree: 5 X 10 ^-4 Torr] was irradiated in a zigzag shape in a direction orthogonal to the rolling direction of the steel sheet with an irradiation width of 0.18 mm and a scanning interval of 6 mm. Table 1 shows the results of examining the magnetic properties and the steel sheet shape of the product thus obtained.

[0032]

[Table 1]

[0033]

EFFECTS OF THE INVENTION A unidirectional silicon steel sheet irradiated with an electron beam is cut as it is and used as a transformer material for a laminated iron core, but the coating of the steel sheet according to the present invention is not destroyed by the electron beam irradiation. No recoating required. Further, by using the electron beam irradiation conditions according to the scope of the present invention, the product used for the laminated iron core can have excellent magnetic characteristics and the shape of the steel sheet, and a high-quality laminated steel sheet for the laminated iron core can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a current electron beam utilization technique for each purpose and use.

FIG. 2 is a schematic diagram showing an electron beam irradiation device used in the present invention.

FIG. 3 is a graph showing the relationship between working distance and iron loss or steel plate shape and insulating coating quality.

[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. An electron beam emitted from an electron gun is converged and deflected by a beam optical system onto a surface of a unidirectional silicon steel sheet coated with an insulating film after finish annealing, and irradiated in a direction intersecting the rolling direction. In doing so, the beam optical system has a single-stage aperture and its working distance is
A method for producing a low iron loss unidirectional silicon steel sheet for a laminated iron core, which is characterized in that the thickness is 300 to 700 mm. 2. The manufacturing method according to claim 1, wherein a ribbon-shaped filament is used in the electron gun.