JPH0765108B2 - Iron loss reduction method of unidirectional silicon steel sheet by electron beam irradiation - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a unidirectional silicon steel sheet having a low iron loss, and in particular, subdividing a magnetic domain by press-fitting a coating on the surface of the steel sheet into base iron. It is intended to reduce iron loss by measuring.

(Prior Art) In a unidirectional silicon steel sheet, secondary recrystallized grains of a product are highly integrated in a Goss orientation, and a forsterite coating is formed on the surface of the steel sheet, and a thermal expansion coefficient is small on the forsterite coating. It is an insulating coating, and requires complicated control,
It is manufactured through various processes.

Such a unidirectional silicon steel sheet is mainly used as an iron core of a transformer or other electric equipment, and has a high magnetic flux density (represented by a B ₁₀ value) of a product as a magnetic property, and an iron loss (W _17/50). (Represented by value) is low, and further, it is required to have an insulating coating having good surface properties.

In particular, the demand for reduction of power loss has been remarkably increased at the border of the energy crisis, and the need for a unidirectional silicon steel sheet having a lower iron loss as an iron core material for a transformer is becoming more and more important.

Now, the history of iron loss improvement in unidirectional silicon steel sheet is Goss orientation 2
It is no exaggeration to say that this is the history of improvement in secondary recrystallization texture. As a method for controlling such secondary recrystallized grains, a method for preferentially growing secondary recrystallized grains of Goss orientation using a primary recrystallized grain growth inhibitor such as AlN, MnS and MnSe, a so-called inhibitor is implemented. ing.

On the other hand, a method completely different from the method for controlling these secondary recrystallization textures, that is, laser irradiation on the surface of a steel sheet {Tadashi Ichiyama: Iron and Steel, 69 (1983), P.895, JP-B-57-2252, ibid. Five
7-53419, 58-24605, 58-24606, respectively} or plasma irradiation {Japanese Patent Laid-Open No. 62-96617, 62-151
No. 511, No. 62-151516, and No. 62-151517), an epoch-making method has been proposed in which local microstrain is introduced to subdivide magnetic domains and thereby reduce iron loss. However, the steel sheet obtained by these methods has a drawback that it cannot be used as a material for a wound core transformer that is subjected to high temperature strain relief annealing because minute strain disappears when heated to a high temperature range.

A method has been proposed in which iron loss does not deteriorate 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. 50-35).
679, JP-A-59-28525 and JP-A-59-197520), a method of forming fine recrystallized grain regions on the surface of a finish annealed plate (see JP-A-56-130454), forsterite Method of forming a different thickness or defective region in a porous coating
-92479, 60-92480, 60-92481 and 60-2
58479), a method of forming a different composition region in a base iron, a forsterite coating or a tension insulating coating (see JP-A-60-103124 and 60-103182). is there.

However, all of these methods have not been industrially adopted because the effect of reducing iron loss is small in spite of the complicated process and the manufacturing cost is high.

Therefore, the inventor has developed a method in which the effect of magnetic domain subdivision does not disappear even if strain relief annealing is performed by press-fitting the coating film on the surface of the steel plate into the base metal by using electron beams to subdivide the magnetic domains. However, it was previously proposed in the specification of Japanese Patent Application No. 1-257578.

(Problems to be Solved by the Invention) The present invention relates to an improvement in the above-described process of press-fitting a coating film on the surface of a steel sheet into a base metal by an electron beam, and proposes a method of more effectively and surely performing this process. To aim.

(Means for Solving the Problem) The present invention relates to a unidirectional silicon steel sheet that has undergone finish annealing.
An electron beam generated by a high voltage and a small current is scanned in a direction transverse to the rolling direction of the steel sheet, and the coating on the surface of the steel sheet is locally pressed into the base metal to form a minute press-fit region. Scanning is intermittently stopped at intervals of 20 μs or less, the electron beam is irradiated in spots while this scanning is stopped, and a minute press-fitting area is introduced in a dotted line. Unidirectionality by electron beam irradiation. This is a method for reducing iron loss of silicon steel sheets.

Here, the micro press-fitting region is advantageous in that the press-fitting portion of the steel plate surface extends to the coating on the back surface of the steel plate through the base iron,
On the back surface of the steel sheet having such a minute press-fitted region introduced, minute protrusions corresponding to the press-fitted portions on the steel sheet surface are formed.

The unidirectional silicon steel sheet targeted by the present invention is also suitable if it has a forsterite coating on its surface or has an insulating coating formed on the forsterite coating.

In addition, in order to prevent the loss of iron loss improvement effect due to the magnetic domain refinement due to the fine press-fitting region obtained by press-fitting the forsterite coating and the insulating coating in the microregion in the width direction of the steel plate deeply inside the base steel, even by strain relief annealing. For the first time, it becomes possible only by using a high voltage and small current electron beam (hereinafter referred to as EB). That is, when EB with high voltage and small current is used, the penetrating power in the depth direction is stronger than that of other methods such as laser, plasma, mechanical method, etc., and it penetrates in the narrowest width. In addition, it is possible to push the base coating and the insulating coating into the base metal without disappearing.

Further, as the silicon-containing steel which is the material of the present invention, any of the conventionally known component compositions are suitable, and the representative compositions are as follows.

C: 0.01 to 0.10% C is an element useful not only for uniform refinement of the structure during hot rolling and cold rolling but also for development of Goss orientation, and at least
Addition of 0.01% or more is preferable. However, if the content exceeds 0.10%, the Goss orientation is rather disordered, so the upper limit is preferably about 0.10%.

Si: 2.0 to 4.5% Si increases the resistivity of the steel sheet and effectively contributes to the reduction of iron loss, but if it exceeds 4.5%, the cold ductility is impaired, while if it is less than 2.0%, the resistivity decreases. However, during the final high temperature annealing performed for secondary recrystallization and purification, the α-γ transformation causes random crystallographic orientation, and a sufficient iron loss improving effect cannot be obtained. Therefore, the Si content is 2.0 to 4.5%. It is preferably about the same. Mn: 0.02 to 0.12% Mn needs to be at least about 0.02% in order to prevent hot embrittlement, but if it is too much, the magnetic properties deteriorate, so the upper limit is preferably set to about 0.12%.

As the inhibitor, there are so-called MnS, MnSe type and AIN type. In the case of MnS and MnSe, at least one selected from Se and S: 0.005 to 0.06% Se and S are all effective elements as inhibitors that control the secondary recrystallization of grain-oriented silicon steel sheets. is there. From the viewpoint of securing the suppression power, at least about 0.005% is required, but if it exceeds 0.06%, the effect is impaired, so the lower and upper limits are preferably set to about 0.01% and 0.06%, respectively.

In the case of the AlN type, Al: 0.005 to 0.10%, N: 0.004 to 0.015% The range of Al and N is set to the above range for the same reason as in the case of the above-mentioned MnS and MnSe type. The above-mentioned MnS, MnSe-based and AlN-based can be used together.

As the inhibitor component, in addition to the above S, Se, Al, Cu, S
Since n, Cr, Ge, Sb, Mo, Te, Bi, P, etc. are also advantageously suited, a small amount of each can be included. Here, the preferred addition range of each of the above components is Cu, Sn, Cr: 0.01
~ 0.15%, Ge, Sb, Mo, Te, Bi: 0.005-0.1%, P: 0.01-0.2
%, And each of these inhibitor components can be used alone or in combination.

(Operation) Next, the present invention will be described in detail based on experimental examples.

C: 0.068wt% (hereinafter simply referred to as%), Si: 3.48%, Mn: 0.079
%, Se: 0.020%, Sb: 0.026%, Mo: 0.013%, the balance is a silicon steel slab consisting essentially of Fe, heated at 1360 ° C, and hot-rolled to a hot-rolled sheet with a thickness of 2.4 mm. After that, cold rolling was performed twice with intermediate annealing at 980 ° C. for 120 minutes to obtain a final cold-rolled sheet having a thickness of 0.20 mm. Then, after decarburizing primary recrystallization annealing in wet hydrogen at 825 ° C, an annealing separator containing MgO as a main component is slurry-coated on the surface of the steel sheet, and then at 850 ° C for 50 hours for 2 hours.
After performing secondary recrystallization annealing to preferentially grow Goss-oriented secondary recrystallized grains, purification annealing was performed in dry hydrogen at 1200 ° C. for 5 hours. Next, after forming an insulating coating mainly composed of phosphate and colloidal silica on the steel plate surface, 0.12 mmφ EB generated at 150 kV, 1.2 mA was applied in the direction perpendicular to the rolling direction according to the following conditions. Irradiation was performed by scanning, and this irradiation was performed in the rolling direction at intervals of 8 mm, and then strain relief annealing was performed at 800 ° C. for 3 hours. As a comparison, the same experiment was performed even when EB irradiation was not performed.

Note: Scanning speed: 15 m / min to scan both sides of the steel plate to form a linear micro press-fit area Scan speed: 5 m / min to scan both sides of the steel plate to form a linear micro press-fit area Scan speed: 10 m / 100 μs for every 30 μs scanning at min
Stop and form point-like micro-press-fit areas linearly on both sides of the steel plate at intervals of 300 μm Scanning speed: 7 m / min, stop for 100 μs every 10 μs scan, and point-like micro-press-fit areas 300 μm on both sides of the steel plate Formed linearly at intervals Scanning speed: 12 m / min, 100 μs every 30 μs scanning
Stopping and forming dot-like micro press-fitting areas on one side of the steel plate in zigzag at 250 μm intervals Scanning speed: 8 m / min, stopping for 100 μs every 15 μs scanning, and dot-like micro press-fitting areas 250 μm on one side of steel plate Table 1 shows the magnetic properties of the thus-obtained strain-relief annealed steel sheets formed in zigzag at intervals.

As is clear from the table, EB is higher than that of the steel plate not irradiated with EB.
The iron loss W _{17/50 of the} steel sheet irradiated with is significantly improved to _0.07 to 0.15 W / Kg. This is because the forsterite coating and the insulating coating on the surface of the steel sheet were pressed into the base iron (secondary recrystallized grains having Goss orientation) in the depth direction in the minute region, and thus effective magnetic domains were obtained even after strain relief annealing. It acts as a subdivision nucleus, and it is possible to subdivide magnetic domains.

It can also be seen that the improvement in iron loss depends on the EB irradiation conditions. Irradiation condition with intermittent EB scanning ~
Improved the iron loss value compared with and under continuous scanning. In particular, the improvement of the iron loss in the steel sheet according to the irradiation conditions and is extremely large with W _{17/50 of 0.14} to 0.15 W / kg.

Irradiation conditions and are characterized in that the time interval from the stop of an EB scan to the next stop (hereinafter referred to as the stop time interval) is short compared to the irradiation conditions ~, and the stop time of the EB scan It is considered that by shortening the interval, damage to the base metal matrix other than the stop position of the EB scanning can be reduced, so that it is possible to effectively improve the iron loss.

Next, FIG. 1 shows the result of examination on the relationship between the stop time interval and the iron loss when the EB scan stop interval was changed under the above-mentioned EB irradiation conditions. The other conditions are the same as those in the above experiment.

From the figure, when the EB scan stop time interval is set to a short time of 20 μs or less, the iron loss improvement rate at W _17/50 can be extremely increased to 0.15 W / kg.

Here, in order to stop the EB scanning at a predetermined time interval and irradiate the EB in a spot-like manner, the deflection voltage of the EB may be changed by adopting an amplifier having a large capacity, but the stop time interval is 5 μs or less. It is difficult to make it short. Therefore, if a speed-up capacitor is added to the deflection coil circuit, the stop time interval can be shortened to 10 μs or less. At that time, the rising shape of the deflection voltage of EB should gradually rise without overshooting. In addition, it is important to choose the speed-up capacitor capacity.

Since the EB penetrating force in the plate thickness direction (depth direction) of a silicon steel plate increases at an acceleration voltage of 65 kV or more where a large amount of X-rays are usually generated, the acceleration voltage should be set to maximize the effect of the present invention. It is important to use with high (65 to 500 kV) and small accelerating current (0.001 to 5 mA), which increases the penetrating power of the silicon steel sheet in the plate thickness direction. Further, in order to efficiently subdivide the magnetic domains, it is preferable to make the irradiation region have a size of 0.5 mmφ or less by using EB having a small diameter. Furthermore, after this EB irradiation, an insulating coating may be applied on top of this to increase the insulation on the EB irradiation trace, but this will increase the cost, so it is possible to exhibit a sufficient insulating effect even if it is not usually applied. .

Further, the steel sheet according to the present invention can be used for a laminated iron core or a wound iron core, but when it is used for a laminated iron core material, it is necessary to introduce a fine microstrain as compared with a wound iron core material, so that the EB irradiation condition is current. Is preferably small and the inter-scan distance is wide. On the other hand, the EB irradiation condition when used for wound core materials is that the current is slightly increased and the inter-scan distance is narrowed to promote the introduction of minute strain on the steel plate surface so that the characteristics do not deteriorate even if strain relief annealing is performed. Preferably.

(Example) Example 1 (A) C: 0.069%, Si: 3.39%, Al: 0.029%, S: 0.030
%, Cu: 0.1%, Sn: 0.05% or (B) C: 0.042%, Si: 3.29%, Mn: 0.068%, Se: 0.020
%, Sb: 0.026%, Mo: 0.016%, and the balance is made of Fe, and the balance is made of Fe. Forsterite film-coated finished annealed sheet (0.20 mm thick), using the EB equipment, the direction perpendicular to the rolling direction. The EB irradiation was performed by stopping at a predetermined time interval when scanning the EB. The EB irradiation conditions were accelerating voltage: 150 kV, accelerating current: 1.0 mA, beam diameter: 0.11 mm, beam spot center distance: 300 μm and scanning distance: 9 mm, and stopped for 110 μs every 15 μs scanning. .

When the treated product was subjected to strain relief annealing at 800 ° C. for 2 hours, its magnetic properties were as shown below.

_{(A) B 10 = 1.95T,} W 17/50 = 0.73W / kg (B) B 10 = 1.92T, W 17/50 = 0.57W / kg ( Effect of the Invention) According to the present invention, stress relief annealing It is possible to provide a unidirectional silicon steel sheet in which iron loss does not deteriorate and a method for stably producing the silicon steel sheet.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the EB scan stop time interval and the iron loss improvement degree.

Claims (1)

[Claims] 1. A unidirectional silicon steel sheet that has been subjected to finish annealing,
An electron beam generated by a high voltage and a small current is scanned in a direction transverse to the rolling direction of the steel sheet, and the coating on the surface of the steel sheet is locally pressed into the base metal to form a minute press-fit region. Scanning is intermittently stopped at intervals of 20 μs or less, the electron beam is irradiated in spots while this scanning is stopped, and a minute press-fitting area is introduced in a dotted line. Unidirectionality by electron beam irradiation. A method for reducing iron loss in silicon steel sheets.