JPH0543944A - Manufacture of low iron loss grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To manufacture a low iron loss grain-oriented silicon steel sheet having good product properties by positioning the focus of electron beams to the place farther than the surface of a steel sheet in the case the electron beams are perpendicularly made incident on the surface of the steel sheet. CONSTITUTION:The surface of a grain-oriented silicon steel sheet K subjected to finish annealing or after the formation of an insulated film is irradiated with electron beams in such a manner that they scan in a direction crossing the rolling direction of the steel sheet K to manufacture a grain-oriented silicon steel sheet. In this case, the focus of the electron beams is positioned to the place farther than the surface O of the steel sheet K in the case the electron beams are perpendicularly made incident on the surface of the steel sheet K. In this way, the low iron loss grain-oriented silicon steel sheet having good product properties in the breadthwise direction of the steel sheet can stably be obtd. by a simple method.

Description

Detailed Description of the Invention

[0001]

[Industrial application] In unidirectional silicon steel sheets, generally, the secondary recrystallized grains of the product are highly integrated in the Goss direction, and a forsterite coating is formed on the surface of the steel sheet, and thermal expansion is further formed on it. It is an insulating coating with a low coefficient, and is manufactured through complicated and diverse processes that require strict control. Such a unidirectional silicon steel sheet is mainly used as an iron core of transformers and other electric equipment, and has a high magnetic flux density (represented by a B ₈ value) of a product as a magnetic characteristic, and an iron loss (W (Represented by _17/50 value) is low, and further, it is required to have an insulating coating having good surface properties. In recent years, especially as the energy crisis has become a borderline, the demand for reducing power loss has increased remarkably, and the need for unidirectional silicon steel sheets with lower iron loss as an iron core material for transformers has become increasingly important. ing. This invention is
The present invention relates to a method for producing a low iron loss unidirectional silicon steel sheet, which is intended to stably obtain good product characteristics in the steel sheet width direction by a particularly simple method.

[0002]

2. Description of the Related Art In order to improve the iron loss of unidirectional silicon steel sheets, efforts have conventionally been made to improve the goth-oriented secondary recrystallized structure.As a method of controlling such secondary recrystallized grains, AlN, MnS, and MnSe are used. A method of preferentially growing the goth-oriented secondary recrystallized grains by incorporating a primary recrystallized grain growth inhibitor, so-called inhibitor, etc. has been carried out.

Further, in recent years, as a method different from the method for controlling such secondary recrystallization texture, the surface of the steel sheet is irradiated with laser (for example, Tadashi Ichiyama: Iron and Steel, 69 (1983) p. 8).
95, Japanese Patent Publication No. 57-2252, 57-53419, 58-24605,
No. 58-24606), or plasma irradiation (see, for example, JP-A Nos. 62-96617, 62-151511, 62-151516, and 62-151517). An epoch-making method has been proposed in which local microstrain is introduced into the surface to subdivide the magnetic domains, thereby reducing the iron loss. However, all of these methods have energy efficiency of 5 to 5.
Since it is as low as 20%, there is a problem that a significant increase in cost is required to reduce iron loss.

As a method different from the laser irradiation and the plasma irradiation, the inventors have used an accelerating voltage:
Irradiation with an electron beam generated at a high voltage of 65 kV to 500 kV and a low current of 0.01 to 5 mA is disclosed in Japanese Patent Laid-Open No. 63-1.
No. 86826, JP-A-2-118022, and JP-A-2-277780. That is, such an electron beam has the advantages of (1) effective for subdivision of magnetic domains, (2) good energy efficiency, and (3) easy beam scanning and a deep penetration depth. Is particularly advantageous as a means for subdividing the magnetic domains. However, the scanning in the plate width direction in such electron beam irradiation is usually such that the electron beam is focused on one point in the width direction central portion on the surface of the steel plate and the electron beam is deflected in the plate width direction in this state. Met. With such electron beam scanning, sufficient product characteristics can be obtained because the electron beam is exactly focused at the center in the width direction, but the electron beam is defocused at both ends in the width direction, so the electron beam is defocused. However, there was a problem that the irradiation effect was reduced and the irradiation effect was smaller than that in the central part, and the product characteristic improvement effect was reduced.

With respect to such a problem, the above-mentioned Japanese Patent Laid-Open No. 2-118022
In the publication, the inventors of the present invention perform irradiation (dynamic focus method) in the plate width direction of the substrate while appropriately correcting the focal length of the electron beam so that the peak intensity is always the same even if the irradiation region of the electron beam changes. We have proposed an electron beam irradiation method that aims to improve the product characteristics even further, but the method of uniformly irradiating the plate width direction while correcting the focal length of the electron beam is the electron beam irradiation method. It is necessary to change the focal length according to the speed of scanning in the substrate width direction, which requires a dynamic focus control device and the like, which complicates the device and enables stable focus control. I left a problem in a difficult place.

Recently, US Pat.
In No. 0, as a condition for performing such electron beam irradiation on the surface of a silicon steel sheet, an energy density of 60 J / in ² or more was obtained for a silicon steel sheet for a laminated core without strain relief annealing.
On the other hand, 150-
It is disclosed that an energy density of 4000 J / in ² or more is required for each. This method has a large change in energy density depending on the type of electron beam and irradiation method, and is therefore difficult to apply to an actual grain-oriented silicon steel sheet.

[0007]

A low iron loss unidirectional silicon steel sheet which solves the above problems advantageously and has good product characteristics in the steel sheet width direction by a magnetic domain refining method using extremely stable electron beam irradiation. It is an object of the present invention to propose a production method capable of stably obtaining the compound by a particularly simple method.

[0008]

According to the present invention, the surface of a unidirectional silicon steel sheet after finish annealing or after formation of an insulating coating is irradiated with an electron beam while scanning it in a direction transverse to the rolling direction of the steel sheet. In the method for manufacturing a unidirectional silicon steel sheet, the focal point of the electron beam is located farther than the steel sheet surface when the electron beam is perpendicularly incident on the steel sheet surface. It is a manufacturing method of a silicon carbide steel plate.

[0009]

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows an example of an electron beam irradiation apparatus suitable for use in carrying out the method according to the present invention. Number 1 in the figure is exhaust port 1
A casing 2 for forming a vacuum chamber having a and 1b is an electron gun for emitting an electron beam B.
Is a high-voltage insulator 2a, a filament that emits electrons
2b, an anode 2c for accelerating the emitted electrons, and a column valve for constantly keeping the electron beam generating section in a vacuum. Further, 3 is a focusing coil for focusing the electron beam B emitted from the electron gun 2, and 4 is a deflection coil for changing the traveling direction of the focused electron beam and irradiating a predetermined region of the substrate with a symbol B. Represents an electron beam, and K represents a steel plate which is a target plate for electron beam irradiation.

An electron beam pattern according to the present invention using such an apparatus is schematically shown in FIG. The electron beam that has passed through the focusing coil and the deflection coil is focused on the surface of the steel sheet, is deflected from the deflection coil position W in the width direction of the steel sheet K, and is scanned in the width direction of the steel sheet.

Conventionally, when irradiating the steel sheet K with an electron beam, the electron beam is focused on a point O (center in the width direction) on the surface of the steel sheet K, and in this state, the electron beam is deflected in the width direction of the steel sheet. The electron beam was irradiated across the width of the steel sheet. According to the scanning of the electron beam in the width direction of the steel sheet, the electron beam is exactly focused at the point O which is the center of the width direction, so that sufficient product characteristics can be obtained. However, at the points Q and Q ′ at both ends in the width direction, the focus of the electron beam is on the arc indicated by the dotted line U in the figure, so the intensity of the electron beam is reduced and the irradiation effect is at the central portion O.
As a result, the characteristic value significantly changes in the plate width direction.

On the other hand, in the present invention, the focusing of the electron beam is made farther than the normal O point, and the positions of S point and P point shown in the figure are set, for example, on an arc indicated by a solid line T in the figure. By scanning the electron beam in the plate width direction so that it is in focus, uniform irradiation can be performed across the plate width direction, and excellent iron loss can be stably obtained with little variation in the plate width direction. Of.

In this case, if the focal point of the electron beam is located at a distance a little further than the substrate surface (point O in FIG. 1) when the electron beam is perpendicularly incident on the substrate surface, the target plate width is obtained. It enables uniform irradiation across directions. On the other hand, the focus of the electron beam is not placed farther than the surface of the steel plate over the entire width, and in order to obtain good product characteristics, it is necessary that about half the width of the steel plate is far from the focus position of the electron beam. preferable.

The electron beam of the present invention has a voltage of 65.
An electron beam generated at a high voltage of kV to 500 kV and a low current of 5 mA or less is used. Since the electron beam can be narrowed down and the depth of focus of the electron beam is deep, the electron beam is focused at the point S.
By focusing on the point P or the point P, uniform electron beam irradiation in the plate width direction becomes possible.

The present invention will be described below by concrete experiments. C: 0.046 wt%, Si: 3.40 wt%, Mn: 0.072 wt%,
A silicon steel slab containing Se: 0.021 wt%, Sb: 0.026 wt% and Mo: 0.013 wt% and the balance being substantially Fe composition was heated at 1340 ° C for 4 hours and then hot-rolled. Give thickness
It was a 2.4 mm hot rolled sheet. After that, cold rolling was performed twice with intermediate annealing interposed therebetween to obtain a final cold-rolled sheet having a width of 150 mm and a thickness of 0.23 mm. After that, decarburization / primary recrystallization annealing was performed in wet hydrogen at 830 ° C. for 3 minutes, secondary recrystallization annealing was performed at 850 ° C. for 50 hours, and then purification annealing was performed at 1200 ° C. for 5 hours. After that, an insulating film mainly containing phosphate and colloidal silica was applied and formed on the surface of the steel sheet, and then electron beam irradiation was performed toward the surface of the steel sheet by the electron beam irradiation apparatus shown in FIG. The irradiation conditions for this electron beam irradiation are: acceleration voltage: 150 kV, current: 0.6 mA, scanning speed: 0.014 cm / 20 s =
700 cm / s, electron beam spot interval: 6 mm, distance from deflection coil position to steel plate surface: 500 mm, and electron beam focus is at the following four positions, as shown in Fig. 2, namely X point (5 mm from steel plate). Top) O point (on the surface of the steel plate) S point (5 mm below the steel plate) P point (10 mm below the steel plate) The focal length is changed by changing the coil current of the focusing coil 3 in FIG. I went. The magnetic properties of the product plate thus obtained are shown in Table 1 in comparison with the electron beam non-irradiated material.

[0016]

As is clear from Table 1, under the conditions (1) to (4), the effect of electron beam irradiation for domain segmentation is large, and the degree of improvement in iron loss is large in comparison with the comparative example.

Since the electron beam generated with such a high voltage and a low current has a deep depth of focus, its focus is from point O to point S.
The present invention has discovered that it is possible to effectively subdivide magnetic domains in the width direction of the steel sheet when the points are changed to points or P points, that is, when the steel sheet is located on the lower side of the steel sheet. Is completely absent from the conventional publicly known documents.

The present invention is effective for the unidirectional silicon steel sheet subjected to the electron beam irradiation regardless of the presence or absence of the insulating coating. Also, by adopting such a focal position of the electron beam, the beam efficiency to the steel plate is improved,
Further, the characteristic of the product is improved. For example, since the degree of destruction of the insulating coating due to electron beam irradiation is reduced and the plate warpage due to irradiation is also reduced, the plate shape can be improved.

[0020]

EXAMPLE Two kinds of steel plates having different components, namely (a) C:
0.063 wt%, Si: 3.26 wt%, Mn: 0.082 wt%, Al: 0.02
6 wt%, Se: 0.020 wt% and Sb: 0.026 wt%,
The balance is substantially Fe composition, and (b) C: 0.049 wt%, S
i: 3.32 wt%, Mn: 0.069 wt%, Se: 0.021 wt%, Sb:
A hot-rolled sheet containing 0.025 wt% and Mo: 0.012 wt% with the balance being essentially Fe composition was cold-rolled twice with an intermediate annealing at 980 ° C for 3 minutes to obtain a thickness. 0.23mm, width 180m
It was the final cold-rolled sheet of m. After that, decarburization and primary recrystallization annealing were performed in wet hydrogen at 830 ° C for 3 minutes, and then the temperature was raised from 830 ° C at a heating rate of 5 ° C / h to 1050 ° C and the Goss orientation secondary recrystallization was performed. After developing the crystal grains, purification annealing was carried out in dry hydrogen at 1200 ° C. for 5 hours. After that, an insulating film mainly containing phosphate and colloidal silica was applied and formed on the surface of the steel sheet, and then electron beam irradiation was performed toward the surface of the steel sheet by the electron beam irradiation apparatus shown in FIG. The irradiation conditions for this electron beam irradiation are: acceleration voltage: 150 kV, current: 0.7 mA, scanning speed: 1000 cm / s, electron beam spot interval: 7 mm, distance from deflection coil position to steel plate surface: 500 mm. The coil current of the focusing coil 3 in FIG. 1 was adjusted so that the point S (5 mm below the steel plate) shown in FIG. The magnetic properties of the product plate thus obtained are (a): B ₈ = 1.94 (T), W _17/50 = 0.76 (W / kg) (unirradiated material: B ₈ = 1.94 (T), W _{17 / 50 = 0.93 (W / kg)} ) (b): B 8 = 1.92 (T), W 17/50 = 0.77 (W / kg) ( no irradiation _{member: B 8 = 1.92 (T)} , W 17/50 = 0.91 (W / kg)), indicating good magnetic properties. At this time, no broken portion was produced in the insulating film, and the plate shape of the steel plate was good.

[0021]

The method for manufacturing a unidirectional silicon steel sheet according to the present invention is a magnetic domain subdivision method using electron beam irradiation,
Since the focal point of the electron beam is located farther than the steel plate surface when the electron beam is perpendicularly incident on the steel plate surface, a low iron loss unidirectional silicon steel plate having good product characteristics in the width direction is particularly preferable. It can be stably obtained by a simple method.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of an electron beam irradiation apparatus suitable for use in carrying out a method according to the present invention.

FIG. 2 is a schematic diagram showing an electron beam pattern according to the present invention.

[Explanation of symbols]

 1 casing 2 electron gun 3 focusing coil 4 deflection coil B electron beam K steel plate

Claims (1)

[Claims] 1. A unidirectional silicon steel sheet, which comprises irradiating a surface of a unidirectional silicon steel sheet after finish annealing or after formation of an insulating film with an electron beam while scanning the steel sheet in a direction transverse to a rolling direction of the steel sheet. A method of manufacturing a low iron loss unidirectional silicon steel sheet, characterized in that the focus of the electron beam is located farther than the steel sheet surface when the electron beam is perpendicularly incident on the steel sheet surface.