JPH0432517A - Production of grain-oriented silicon steel sheet reduced in iron loss - Google Patents

Abstract

PURPOSE:To press locally an insulating film into a base metal and to reduce the iron loss of a silicon steel sheet by irradiating a finish-annealed grain oriented silicon steel sheet having an insulating film with at least two electron beams dissimilar in acceleration energy along the width direction of this steel sheet. CONSTITUTION:After finish annealing is applied to a grain oriented silicon steel sheet, e.g., a forsterite film h2 is formed on the above steel sheet and also an insulating film h1 is further formed on the above. Subsequently, the resulting coated steel sheet is irradiated with an electron beam A which has high voltage and small electric current and also has relatively narrow beam diameter and penetrates deeply into the steel sheet, by which local and recessed minute melted regions are formed in the interface between the film and the base metal and simultaneously the film is pressed into these regions to fractionize a magnetic domain. Then, the above sheet is irradiated with an electron beam B of low voltage and small electric current, by which strain in the forsterite film or the insulating film can be released and deterioration in magnetic properties due to the presence of strain can be avoided, and further, iron loss can be advantageously reduced.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method of manufacturing a unidirectional silicon steel sheet with low iron loss, and in particular to a method for locally removing a film formed on the surface of the steel sheet into a base metal. By introducing local strain that is press-fitted into the core, the magnetic domain is subdivided and the iron loss is further reduced.

(Prior technology) Unidirectional silicon steel sheets have secondary recrystallized grains of the product highly concentrated in the Goss orientation, and a forsterite film on the surface of the steel sheet, which has a small coefficient of thermal expansion. It is coated with an insulating film and is manufactured through a complex and diverse process that requires strict control.

These unidirectional silicon steel sheets are mainly used as cores for transformers and other electrical equipment, and their magnetic properties include high magnetic flux density (represented by the value B).
It is required to have low iron loss (represented by the value W+7/!l) and to have an insulating film with good surface quality.

In particular, in the wake of the energy crisis, demand for reduced power loss has become significantly stronger, and the need for unidirectional silicon steel sheets with lower iron loss as core materials for transformers has become increasingly important. There is.

Now, it is no exaggeration to say that the history of improving iron loss in unidirectional silicon steel sheets is the history of improving the Goss orientation secondary recrystallization texture. As a method for controlling such secondary recrystallized grains, a primary recrystallized grain growth inhibitor such as AIN, MnS, and MnSe is used to control the Goss orientation
Methods have been implemented to preferentially grow secondary recrystallized grains. However, such methods have reached their limits with current production means, and it is extremely difficult to make any further improvements, and even if some improvement is recognized, the effect of improving iron loss is small compared to the effort. The situation is such that.

On the other hand, a method that is completely different from these methods of controlling the secondary recrystallization texture is the method of irradiating the steel plate surface with a laser (Masashi Tsuchiyama: Tetsu to Hagane, 69 (1983), p. 895, Japanese Patent Publication No. 57-2252, same). No. 57-53419, No. 58-2
4605, 58-24606) or plasma irradiation (see JP-A-62-96617, JP-A-62451-511, JP-A-62-151516, and JP-A-151517). An innovative iron loss reduction method has been proposed that introduces strain to subdivide magnetic domains and thereby reduce iron loss. By the way, the steel sheet obtained through this method has the disadvantage that local microstrains disappear when heated to a high temperature range, so it cannot be used as a material for wound core transformers, which is subjected to high-temperature strain relief annealing. Ta.

As a method of not deteriorating iron loss even if such high-temperature strain relief annealing is performed, for example, a method of forming grooves or serrations on the surface of a finish annealed plate (Japanese Patent Publication No. 50-3
No. 5679, JP-A-59-28525 and JP-A No. 59-1
97520), a method for forming a defective region or a different thickness in a forsterite film (Japanese Unexamined Patent Publication No. 60-9
No. 2479, No. 60-92480, No. 60-9248
1, Japanese Patent Publication No. 60-258479), a method of forming different compositional regions in the base steel, forsterite, or tensile insulation film of a steel plate (Japanese Patent Application Laid-Open No. 60-103124, Japanese Patent Publication No. 60-258479).
0-103182), etc. However, these methods have not been industrially adopted because the process is complicated and the iron loss improvement effect is small, and the manufacturing cost is high.

Note that Japanese Patent Publication No. 1-36970 proposes an electron beam annealing method in which two or more electron beams with different beam acceleration energies are irradiated; However, it was not a solution that would help reduce iron loss in unidirectional silicon steel sheets.

(Problems to be Solved by the Invention) The purpose of the present invention is to propose a new method in which the iron loss, which has been reduced by subdividing magnetic domains by introducing local strain, does not deteriorate even when strain relief annealing is applied. shall be.

(Means for Solving the Problems) This invention provides an insulating coating that is formed on a unidirectional silicon steel plate that has been subjected to finish annealing, and then continuously (linearly) or discontinuously coats the unidirectional silicon steel plate along the width direction of the steel plate. When locally press-fitting the insulating film into the base metal of the steel plate by irradiating an electron beam (in a dotted manner), at least two types of electron beams having different acceleration energies are irradiated as the electron beam. This is a method for manufacturing a silicon steel sheet with unidirectional iron loss.

Electron beams with different acceleration energies that can be applied in this invention include electron beams generated with high voltage and small current, electron beams generated with low voltage and large current, etc., where high voltage is 65 to 500 KV. A range of 10 to 64 KV is particularly preferred.

(Function) In this invention, after a forsterite film and an insulating film are formed on a finish-annealed unidirectional silicon steel plate, the beam diameter is relatively small and the beam penetrates deeply into the plate. A high-voltage, low-current electron beam is irradiated, and then a low-voltage, high-current electron beam with a large beam diameter and a relatively shallow penetration depth into the steel plate is irradiated. When irradiated with a high-voltage, small-current electron beam, a micro-dissolved region of local concave portions is formed at the interface of the base metal, and at the same time, the above-mentioned coating is press-fitted into that region, thereby creating a demagnetizing field. Aim to subdivide magnetic domains. On the other hand, irradiation with a low-voltage, small-current electron beam releases strain in the forsterite film or insulating film, thereby avoiding deterioration of magnetic properties due to the presence of the strain. Here, the local strain formed by the high-voltage, small-current electron beam does not disappear even after subsequent strain-relief annealing (in addition, the strain generated in the film is also relaxed, and therefore the unidirectionality is reduced). The iron loss of silicon steel sheets is advantageously reduced.

By subdividing the magnetic domains using an electron beam ordered at high voltage and low current, the iron loss does not deteriorate even when high temperature heat treatment such as strain relief annealing is performed, because a press-fit region is formed in the base steel. , which creates a small hole that creates a demagnetizing field.

FIG. 1 shows a cross section of a main part of a steel plate when electron beam irradiation is performed in accordance with the above-described order, and FIG. 2 shows an electron beam irradiation apparatus suitable for carrying out the present invention. In Fig. 2, number 1 is an electron beam irradiation system that generates a high-voltage, small-current electron beam A, 2 is an electron beam irradiation system that generates a low-voltage, large-current electron beam B, and 1a and 2a are electron beams. The electron guns 1a and 2a each consist of filaments lb and 2b, Wehnelt lc and 2c, and anodes ld and 2d. In addition, le and 2e are load resistances, I
f and 2f are blanking electrodes useful when performing intermittent electron beam irradiation; 3 and 4 are converging lenses that converge the electron beams A and B emitted from the electron guns 1a and 2a, respectively; 5 and 6 are converging lenses This is a deflection coil for scanning the electron beam focused by the lens 3.4 along the width direction of a silicon steel plate covered with a coating h (forsterite coating + insulation coating, etc.).

When irradiating an electron beam, it is preferable to first irradiate the electron beam A generated at a high voltage and a small current, and then irradiate the electron beam B generated at a low voltage and a large current.
If more effective irradiation is desired, irradiation can be performed simultaneously.

Further, the number of times of electron beam irradiation is not limited to two, but can be increased as necessary.

As the silicon-containing steel used in this invention, those having conventionally known compositions are advantageously suitable, but typical compositions are as follows.

C: 0.01 to 0.10 ivt% (hereinafter simply expressed as %)
C is an element useful not only for uniform refinement of the structure during hot rolling and cold rolling, but also for the development of Goss orientation, and for this purpose, it is preferably contained at least 0.01%. However, if the content exceeds 0.10%, the Goss orientation will be disturbed, so the upper limit is preferably about 0.10%.

Si: 2.0-4.5% Si increases the resistivity of the steel sheet and effectively contributes to reducing iron loss, but if Si exceeds 4.5%, cold rollability is impaired,
On the other hand, if it is less than 2.0%, not only the specific resistance decreases, but also 2.0%.
During the final high temperature annealing for the next recrystallization and purification, α−
The T-transformation causes randomization of crystal orientation, and a sufficient iron loss improvement effect cannot be obtained. Therefore, the Si content is 2.0
It is preferable to set it to about 4.5%.

Mn: 0.02-0.12% Mn is at least 0.02% to prevent hot embrittlement
It is necessary to contain a certain amount, but if it is too large, the magnetic properties will be deteriorated, so the upper limit is preferably about 0.12%.

As inhibitors, so-called MnS, MnS
There are e-type and AIN-type. In the case of MnS and MnSe, at least one selected from Se and S is contained in a range of 0.005 to 0.06%.

Both Se and S are effective elements as inhibitors that control secondary recrystallization of grain-oriented silicon steel sheets. From the perspective of securing suppressive power, it is necessary to have at least 0.005%, but if it exceeds 0.06%, the effect will be impaired, so the upper and lower limits should be 0.005% each.
, is preferably about 0.06%.

For AIN type, Al: 0.005-0.10%
, N: 0.004 to 0.015%, the range of A1 and N is also the same as the above-mentioned MnSMnS
The above range was set for the same reason as in the case of e series.

Note that the above inhibitors can be used in combination.

In addition to the above-mentioned components, Cu5n, Ge, Sb, Mo, Te, Bi, and P are also advantageously suitable as inhibitors, so they can also be contained in small amounts. Here, the preferred addition range of the above components is 0.01 to 0.1 for Cu, Sn, and Cr, respectively.
5% Ge.

0.005~ for Sb+ Mo, Te, B+
0.1%, P is about 0.01 to 0.2%, and each of these inhibitor components can be used alone,
Can be used in combination.

Table 1 shows the results of investigating the magnetic properties of a unidirectional silicon steel sheet in an experiment in which the steel sheet was manufactured according to the present invention.

The steel plate used in this experiment had C: 0.044%,
Si: 3.39%, Mn: 0.068%, Se
: 0.020%, 5b=0.025%, Mo:
A silicon steel slab containing 0.012% and the remainder substantially Fe was heated at 1360°C for 4 hours, then hot rolled into a 2.4M thick hot rolled sheet, and further heated at 970°C for 3 hours. Cold rolled twice with intermediate annealing for 0.2 min.
A final cold-rolled plate with a thickness of 0 mm was obtained, and after decarburization and primary recrystallization annealing was performed in wet hydrogen at 825°C, M was applied on the surface of the fence plate.
An annealing separator mainly composed of nO was applied as a slurry, and then secondary recrystallization annealing was performed at 850°C for 50 hours to preferentially grow Goss-oriented secondary recrystallized grains, and then at 1200°C.
The steel sheet was subjected to purification annealing in soft hydrogen for 5 hours, and an insulating film containing phosphate and colloidal silica as main components was formed on the surface of the steel sheet. irradiated with an electron beam.

1. Accelerating voltage: 150 KV, accelerating current: 1.5m
A, Beam diameter: 0.13mm, 5m in the longitudinal direction of the steel plate
Irradiate parallel to the width direction of the copper plate at m intervals (electron beam A in Figure 2).

2. Accelerating voltage: 150 KV, accelerating current: 1.5m
A, Beam diameter: O, 13mm, Irradiation parallel to the width direction of the steel plate at intervals of 5 cylinders in the longitudinal direction of the steel plate, followed by acceleration voltage: 15KV, Acceleration voltage: 150mA, Beam diameter =
Irradiate parallel to the width direction of the steel plate at a beam of 90 m (electron beam A+B in Figure 2).

3. Irradiate parallel to the width direction of the steel plate with accelerating voltage: 15 KV, accelerating current 150 mA, beam diameter: 90 mm (second
Electron beam B) in the figure.

4. No electron beam irradiation.

Table-1 As is clear from Table-1, the conditions No.
It is noteworthy that in No. 2, the iron loss is significantly improved. Irradiation with an electron beam generated at a high voltage and small current creates a concave shape due to the melting of the substrate interface and the press-in of the film, while the electron beam generated at a low voltage and large current creates a concave shape. It is thought that the strain in the area was removed, and as a result, the magnetic properties, especially the iron loss properties, were improved.

In this invention, a hatch-type vacuum device can be used for electron beam irradiation, but a differential pressure device that maintains a high vacuum inside by connecting multiple casings to block the atmosphere may also be used. It is best to continuously guide the silicon steel plate to the surface and irradiate it with an electron beam. Irradiation with an electron beam is effective even on one side of a steel plate, but
Both sides may be irradiated.

(Example) C: 0.76%, Si: 3.38%, Al:
0.028%, S2 0.025%, Cu: 0.06
%, Sn: 0.05% (No, 1) or C:
0.044%, Si: 3.41%, Mn: 0.
072%, Se: 0.025%, Sb: 0.025
%, Mo: 0.013% (No, 2), respectively, and the remainder was substantially made of Fe on a finish annealed plate (0.20 mm thick) with a forsterite film of Sisuzaki, as shown in Fig. 2 above. Applying an apparatus having the configuration shown in , the annealed plate was irradiated with an electron beam in parallel to the width direction, and strain relief annealing was performed under the condition of Nα2 in Table 1. The magnetic properties of each steel plate were investigated. The results are shown below for comparison.

Note that the electron beam irradiation conditions for No. 1 steel plate are acceleration voltage: 150 KV, acceleration current: 1.3
mA, beam diameter of 0.15, beam spot center spacing: 300 μm, scanning interval: 5 mm, a high voltage, small current electron beam is intermittently irradiated along the width direction of the steel plate, followed by accelerating voltage. : 15 KV, accelerating current: 150 mA, this is an example of electron beam irradiation with a beam diameter of 70 ant, and the acceleration voltage for the steel plates 1, No., and 2 is 15 KV.

This is an example in which an electron beam is irradiated with an accelerating current of 150 mA and a beam diameter of 70 mm.

Copper plate Nα1: Be = 1.93T, WI7/So
=0.76W/kg Steel plate Nα2: Be =1.9
0T WI,/S. -0.77 W/kg (Effects of the Invention) Thus, according to the present invention, the magnetic domains are subdivided by introducing local strain that locally presses the film formed on the surface of the unidirectional silicon steel sheet into the base steel. In order to achieve this, at least two types of electron beams with different acceleration energies are irradiated, so even if strain relief annealing is performed, this local strain will not disappear, and the strain generated in the film will also be alleviated. Therefore, further reduction in iron loss can be expected.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a steel plate when irradiated with an electron beam according to the present invention. FIG. 2 is an explanatory diagram of the configuration of an electron beam irradiation apparatus suitable for use in the present invention. 1.2...Electron beam irradiation system la, 2a...electron gun Ib, 2b...filament lc, 2c...Wehnelt ld, 2d...anode le, 2e...load resistance if, 2f ...Blanking electrode 3.4...Focusing lens 5.6...Deflection coil P
...Power supply h...Coating A, B...Electron beam hl...Insulating coating K...Mesh plate h2...Forsterite coating Figure 1

Claims (1)

[Claims] 1. After forming an insulating film on a unidirectional silicon steel plate that has been subjected to finish annealing, the insulating film is formed by continuously or intermittently irradiating the steel plate with an electron beam along the width direction. A method for producing a low core loss unidirectional silicon steel sheet, which comprises irradiating at least two types of electron beams with different acceleration energies as the electron beam when locally press-fitting into the base metal of the steel sheet.