JP2000144345A - Silicon steel, its production, production of rolled silicon steel sheet and electric apparatus provided with the silicon steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the electrical resistivity of steel and to reduce eddy current loss therein by allowing it to contain oxides of La. SOLUTION: The preferable range of the content of La in the steel is 0.05 to 2.0 wt.%. On the other hand, the preferable range of the content of Si is 3 to 10 wt.%. As to the production of the steel, La and an Fe-Si compd. are melted by a high-frequency melting method or the like to make an ingot of an Fe-Si-La compd., which is subjected to coarse crushing and pulverizing to form into the powder of an Fe-Si-La compd. Next, this powder is sintered by using an ordinary powder metallurgical method to form La-contg. sintered silicon steel. This silicon steel has a structure in which La oxides 32 are precipitated into the grain boundaries of Fe-Si compd. crystal grains 30. For increasing its workability in cold rolling, the average crystal grain size of the silicon steel before the cold rolling is preferably controlled to η300 μm. Moreover, the sintering can be executed under the conditions of temp.: 1000 to 1150 deg.C, time: 1 to 5 hr and atmosphere: inert gas or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a sintered silicon steel and a method for producing the same. In particular, the present invention relates to a sintered silicon steel having high electric resistivity ρ and excellent magnetic properties and exhibiting good cold-rollability, and a method for producing the same. The sintered silicon steel and the rolled silicon steel sheet of the present invention are widely used for applications such as iron cores of transformers and rotating machines, magnetic shield materials, and electromagnets.

[0002]

2. Description of the Related Art One of high magnetic permeability materials (soft magnetic materials) is F.
There is an e-Si alloy (silicon steel), and its magnetic permeability becomes maximum when the Si content is about 6 wt%. However, as the amount of Si replacing Fe increases, the silicon steel hardens and becomes brittle. Therefore, it is difficult to roll the silicon steel unless the Si content is suppressed to 3 wt% or less.

For the purpose of improving workability, a method has been proposed in which magnetic impurities such as Mn and Ni are added to a molten mass of silicon steel (K. Narita and M. Enokizono: IEEE. Trans. Magn. 1).
4 (1978) 258). The addition of the magnetic impurities makes the average crystal grain of the molten mass finer, so that the workability of the silicon steel is improved and rolling becomes possible. However, since the added magnetic impurities degrade the magnetic properties of the silicon steel sheet, this method has not been widely used.

[0004] After the molten mass in which the Si content is suppressed to 3 wt% is rolled in accordance with a conventional process, the molten mass is subjected to CVD (Chemic).
al. Vapor Deposition), a method of impregnating rolled silicon steel sheet with Si has been proposed (Y. Takada, M. Abe, S. et al.
Masuda and J. Inagaki: J. Appl. Phys. 64 (1988) 5367).
According to this method, since the Si content is increased after the rolling, it is possible to finally obtain a rolled silicon steel sheet having a Si content of 6.5 wt%. However, the use of the CVD method increases the production cost of silicon steel sheets.

The inventor of the present application has invented a method of making it possible to cold-roll even a silicon steel having a Si content of 3 wt% or more by refining the crystal grains of the sintered silicon steel. No. 165981. In this method, the average crystal grain size of the sintered silicon steel is set to 300 μm or less,
Thereby, cold rolling of sintered silicon steel is realized.

[0006]

The conventional silicon steel has the problem that, besides the poor workability, the electrical resistivity ρ is relatively low. If the electric resistivity ρ is low, eddy current loss increases, which is not preferable as a soft magnetic material. The eddy current loss increases as the oscillation frequency of the applied alternating magnetic field increases. In recent years, there is a strong demand for a soft magnetic material that operates with a low loss even in a high frequency region. When the content of Si is increased, the electrical resistivity ρ of silicon steel increases, but silicon steel sheets that can be used in a high frequency range of several kHz or more have not been put to practical use.

The present invention has been made in view of the above points, and a main object of the present invention is to provide a sintered silicon having sufficiently increased electric resistivity ρ and reduced eddy current loss without deteriorating magnetic properties. To provide steel. Another object of the present invention is to
It is to provide high workability to such a sintered silicon steel having excellent electrical and magnetic properties.

[0008]

The silicon steel according to the present invention comprises:
It is characterized by containing an oxide of La.

It is preferable that the La oxide is precipitated at a crystal grain boundary.

[0010] The content of La is preferably in the range of 0.05 wt% to 2.0 wt%.

[0011] Si content is 3.0 wt% to 10 wt%
It is preferably within the range of

The silicon steel has a crystal grain size of 10 to 300 μm.
In the case of, various processes including a plastic deformation process are facilitated. When the crystal grain size of the silicon steel is made sufficiently large by heat treatment (annealing), the magnetic properties as a soft magnetic material are improved.

In the method for producing silicon steel according to the present invention, a step of preparing a powder of a silicon steel containing La and sintering the powder so that at least a part of La is La oxide at a crystal grain boundary. Forming a precipitated sintered silicon steel.

Another method for producing silicon steel according to the present invention is described in
preparing a silicon steel ingot containing a, a step of precipitating the La oxide at crystal grain boundaries by repeatedly hot rolling or hot forging the ingot, and performing a heat treatment. And a step. It is preferably formed from silicon steel powder containing La. Here, “silicon steel containing La” means “L
a silicon oxide containing an oxide ”.

The method for producing a rolled silicon steel sheet according to the present invention
A step of preparing a powder of a silicon steel having a content of 3.0 wt% to 10 wt% and containing La, and sintering the powder so that at least a part of La is obtained. The method includes a step of forming a sintered silicon steel precipitated at a crystal grain boundary as a La oxide, a step of rolling the sintered silicon steel, and a step of heat-treating the sintered silicon steel.

The step of preparing a powder of silicon steel containing La can include not only the step of producing such powder by itself, but also the step of purchasing the powder.

The sintered silicon steel has a La content of 0.05 watts.
It is preferably in the range from t% to 2.0 wt%.

Preferably, the average grain size of the sintered silicon steel before the rolling step is 300 μm or less.
The lower limit of the average crystal grain size is, for example, 10 μm.

An electric device according to the present invention includes a coil for forming a magnetic field, a soft magnetic member arranged in the magnetic field and magnetized, and means for supplying a current to the coil. The soft magnetic member is made of silicon steel containing La oxide. Such electric devices widely include a high-frequency transformer, a motor, an actuator, an MRI, a current sensor, and the like.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The inventor of the present application has made various attempts to obtain silicon steel having a good rolling workability while containing a high concentration of Si of 3.0 wt% or more and having a high electric resistivity ρ. Was conducted. As a result, they have found that by sintering the silicon steel powder to which La is added, it is possible to produce a silicon steel having small eddy current loss and excellent magnetic properties.

The sintered silicon steel of the present invention to which La is added (hereinafter referred to as “La sintered silicon steel”) contains La oxide (La ₂ O ₃ ) precipitated at the crystal grain boundaries. I understood. The grain boundary phase of conventional silicon steel is formed of Fe, Si, and their oxides, but the grain boundary phase of La sintered silicon steel is formed of La oxide having high insulating properties. As a result, it was found that the electrical resistivity ρ of the La sintered silicon steel was higher than that of the conventional silicon steel.

The ionic radius of La ³⁺ (1.22 Å) is larger than the ionic radius of Fe ³⁺ (0.67 Å) or the ionic radius of Si ⁴⁺ (0.39 Å). For this reason, it is considered that La hardly forms a solid solution in the matrix of the silicon steel, but easily precipitates at the crystal grain boundaries by sintering, and forms La oxide at the grain boundaries. In this specification, “La oxide” refers to
It is not limited to La ₂ O ₃ but also broadly includes non-stoichiometric La oxide.

Although La ³⁺ ions are rare earth element ions, they do not have a magnetic moment, so they do not function as magnetic impurities and do not deteriorate the magnetic properties of La sintered silicon steel. Rather, it has also been found that the addition of La contributes to lowering the coercive force because the average crystal grains of the sintered silicon steel are coarsened in the annealing step.

FIG. 1 shows the relationship between the La content and the electric resistivity ρ when the Si content is 6.5 wt%. As can be seen from FIG. 1, La sintered silicon steel is La
It shows a high electrical resistivity ρ at a level several times to nearly 10 times that of a sintered silicon steel without addition.

FIG. 2 shows the relationship between the La content, the average crystal grain size after sintering, and the coercive force iHc when the Si content is 6.5 wt%. As can be seen from FIG. 2, the La sintered silicon steel of the present invention has a larger average grain size than the sintered silicon steel without La added, and exhibits excellent magnetic properties.

The preferred range of the La content in the sintered silicon steel is 0.05 wt% to 2.0 wt%. If the La content is less than 0.05 wt%, the amount of La oxide precipitated at the grain boundaries becomes insufficient, and the effect of increasing the electrical resistivity hardly appears. On the other hand, if the La content exceeds 2.0 wt%, the workability of the sintered silicon steel decreases, and it becomes difficult to produce a silicon steel sheet by cold rolling. From the viewpoint of increasing the electric resistivity or the specific resistance, a more preferable range of the La content is 1.0 wt% to 2.0 wt%.
Further, the most preferable range for the La content is 1.2 w
t% to 1.5 wt%.

On the other hand, a preferable range of the Si content is 3.0 wt% to 10 wt% from the viewpoint of improving magnetic properties.
From the viewpoint of further improving the electric and magnetic properties, a more preferable range of the Si content is 5.0 wt%.
８8.0 wt%. However, if emphasis is placed on obtaining a silicon steel having a high electric resistivity ρ, the Si content may be less than 3.0 wt% as long as the La content is within an appropriate range.

La sintered silicon steel does not need to be processed into a plate shape, but can be processed into various shapes. Further, it may be powdered. In the present specification, sintered silicon steel processed into a plate shape by rolling may be referred to as “sintered silicon steel sheet” for convenience, but the term “sintered silicon steel” is not limited to bulk silicon steel, Silicon steel or rolled silicon steel sheet in a state processed into the shape described above is widely included.

As is clear from the above description, the La sintered silicon steel of the present invention is obtained by adding Si and La to Fe as the main component, but other impurity elements are added for various purposes. Is also good. For example, Ti, Al,
When a small amount of V or the like is added, there is an advantage that the average crystal grain size of the rolled silicon steel is more easily coarsened in an annealing step performed after rolling the La sintered silicon steel.

[Raw Materials] First, La and an Fe-Si compound are melted by a high-frequency melting method or the like, and the Fe-Si compound is melted.
-Produce an ingot of the La compound. After coarsely pulverizing the ingot, a pulverizing step using a jet mill or the like is further performed to obtain a powder of the Fe—Si—La compound. Instead, a gas atomized powder of an Fe—Si—La compound may be used. The powder of the Fe—Si—La compound is sintered after being mixed with the Fe powder.

Examples of the Fe—Si compound mixed with La include a β phase Fe ₂ Si compound, an ε phase FeSi compound,
It is preferable to use an FeSi ₂ compound in the ζβ phase. This is because any of these phases is liable to be brittle fracture and easily forms fine powder.

The composition of the Fe—Si—La compound before being pulverized is adjusted so as to easily cause brittle fracture. Especially Si
The content is preferably set in the range of 20 wt% to 51 wt%, and the La content is preferably set to less than 11 wt%. If the contents of La and Si are too large, cracks and cracks are likely to occur in the sintered body during the subsequent cold rolling, and the magnetic properties also deteriorate.

The average particle size of the Fe—Si—La compound powder is adjusted to fall within the range of 3 to 100 μm. If the average grain size is out of this range, cracks and cracks are likely to occur during cold rolling, and the magnetic properties are also deteriorated. When the average particle size is less than 3 μm, the sintered body becomes hard or brittle during sintering because the powder itself contains a large amount of oxygen, and when the average particle size exceeds 100 μm, the sintered body tends to become porous, This is because the consolidation density decreases.

It is preferable to use carbonyl iron powder as the Fe powder. Carbonyl iron powder may be a commercially available product. However, it is preferable to use a powder having a particle size of 3 to 10 μm and having as small an oxygen content as possible. The amount of oxygen contained in the powder in a state where the Fe powder and the Fe-Si-La compound powder are mixed is preferably as small as possible, and is preferably at most 3000 ppm or less.

[Production of Sintered Body (Rolled Material)] Next, the above-mentioned mixed powder is sintered using a usual powder metallurgy technique, and La
Forming containing sintered silicon steel. As a powder metallurgy method,
For example, a metal injection molding method or a powder molding method can be used. Alternatively, a method in which the mixed powder is formed into a slurry by a slip cast molding method or the like and then molded, and a method of sintering at a predetermined temperature may be used, or a hot molding method such as hot pressing or plasma sintering may be used. Good.

As shown in FIG. 3A, La sintered silicon steel has La oxide 3 at the grain boundaries of Fe—Si compound crystal grains 30.
2 has a precipitated structure.

The Fe—Si—La compound powder is very easily oxidized because it contains La and Si. When a binder is used for molding, oxidation and carbonization are particularly likely to occur, so that atmosphere control during debinding and sintering is essential. The oxygen content and the carbon content in the La sintered silicon steel are desirably 4000 ppm or less and 200 ppm or less, respectively. This is because the oxidized and carbonized sintered body becomes hard and brittle.
If the oxygen content and the carbon content exceed the above upper limits, cracks and cracks may occur during cold rolling, and the magnetic properties after annealing may be significantly reduced.

In order to enhance the workability of cold rolling, it is preferable that the average crystal grain size of the La sintered silicon steel before rolling is 300 μm or less. If the average crystal grain size exceeds 300 μm, the cold-rolled state deteriorates.

The temperature, time and atmosphere of the sintering process vary depending on the components of the mixed powder, the molding density, and the like.
For example, the following conditions may be selected. That is, sintering temperature: 1000 ° C. to 1150 ° C., sintering time: 1 to 5 hours,
Atmosphere: Inert gas, hydrogen gas or vacuum conditions can be employed. In order to further increase the electrical resistivity ρ, the sintering temperature for normal silicon silicon steel is set to 100 ° C.
The sintering is preferably performed at a temperature as low as about ° C. This is because grain boundary precipitation of the La oxide is promoted.

During sintering, the deformation of the sintered silicon steel is suppressed,
It is preferred to keep the parallelism below 0.5 mm. Here, the parallelism means "the amount of warpage" of the sintered silicon steel per 50 mm in length. Parallelism is 0.5m
If it is worse than m, cracks and cracks are likely to occur in the sintered silicon steel during cold rolling.

[Rolling] Since silicon steel is harder and brittle than other metals, the roll diameter for cold rolling and its peripheral speed are finely adjusted by the thickness before rolling and its parallelism. There is a need to. When the sheet thickness before rolling is large and parallelism is poor, it is necessary to perform rolling at a small roll diameter and at a low peripheral speed. On the other hand, when the plate thickness is small and the parallelism is good, this condition is considerably relaxed. In the case of hot rolling, since the silicon steel is easily plastically deformed, the conditions of the roll diameter and the peripheral speed are greatly relaxed as compared with the conditions of the cold rolling.

The average particle size of the sintered silicon steel before rolling is 300 μm.
m or less, the plate thickness is 5 mm or less, and the parallelism is 0.5 mm or less, the roll diameter is 60 mm or less, and the roll peripheral speed is 60 mm or less.
A condition of not more than mm / sec is preferable. Under such conditions, cold rolling can be performed without an annealing step during the cold rolling and without cracks and cracks. When the thickness of the sintered body before rolling is 1 mm or less, it is preferable to perform rolling with a roll having a smaller roll diameter. By doing so, rolling efficiency and thickness dimensional accuracy are improved, and cracks and cracks are less likely to occur.
When the La content exceeds 2 wt%, L
Since the ceramic layer of the oxide a is excessively increased, cracks and cracks occur during rolling regardless of the roll diameter and the roll peripheral speed.

The La sintered silicon steel rolled by the above method can be subsequently processed into various shapes by a cutting machine or a punching machine.

Since the rolled sintered silicon steel according to the present invention is a grain-oriented silicon steel sheet, it has higher magnetic permeability and magnetic flux density than non-oriented silicon steel sheet. Moreover, the rolled sintered silicon steel of the present invention has a feature that the (100) plane has a texture, unlike a normal oriented silicon steel sheet having the (110) plane as a texture.

[Annealing (Heat Treatment)]
Usually, in order to prevent cracks and cracks during rolling, an annealing step is always performed after the rolling step is repeated several times. L
Annealing of the sintered silicon steel sheet has the effect of increasing the electrical resistivity ρ after the completion of rolling and reducing the coercive force, in addition to the effect of preventing cracks and cracks during rolling. This is because the annealing promotes the precipitation of La oxide at the crystal grain boundaries, and the crystal grains of the silicon steel sheet are also coarsened. As a result, the electrical resistivity ρ further increases, and the crystal grain boundaries that hinder domain wall movement decrease, so that the coercive force also decreases.

The La sintered silicon steel after annealing is shown in FIG.
As shown in (b), F grown more than before annealing.
It has a structure in which more La oxide 32 precipitates at the grain boundaries of the e-Si compound crystal grains 30.

The annealing temperature depends on the rolling ratio and the sintering temperature of the sintered body before rolling (here, “rolling ratio” is (1−sheet thickness after rolling / sheet thickness before rolling) × 100.
[%]). The annealing temperature is La
It is also affected by the content and the Si content. When silicon steel sintered at a relatively low temperature (for example, 1000 to 1100 ° C.) is rolled at a rolling reduction of about 70 to 90%, a preferable range of the annealing temperature is 1200 to 130.
0 ° C. On the other hand, a relatively high temperature (for example, 115
When the silicon steel sintered at 0 to 1250 ° C. is rolled at a rolling rate of about 50 to 70%, a preferable range of the annealing temperature is 1150 to 1250 ° C. If the annealing temperature is too high, the crystal grains grow abnormally, and the silicon steel becomes very brittle. Conversely, if the annealing temperature is too low, the precipitation of La oxides and the growth of crystal grains become insufficient, so that the electrical resistivity ρ and the magnetic properties are not sufficiently improved. The annealing time is appropriately selected within a range of, for example, 1 to 5 hours.

According to the present invention, the precipitation of La oxides and the growth of crystal grains are simultaneously performed sufficiently by annealing, so that the electrical resistivity ρ of La sintered silicon steel is several times greater than in the case where La is not added. The grain size increases to about 10 to 10 times, and the grains grow to an average grain size of about 0.5 to 3 mm. Also,
The magnetic characteristics of La sintered silicon steel are characteristics close to those of a normal ingot material.

The La sintered silicon steel of the present invention is widely used for various uses of existing soft magnetic materials. For example, in addition to being used for a magnetic material piece (pole piece) forming an end of an electromagnet or a permanent magnet, it is also suitably used for applications such as a yoke material for MRI, a transformer, a motor, and a yoke.

An embodiment of the present invention will be described below.

[0051]

EXAMPLES (Example 1) In this example, Fe-Si-La compound powder having the components and average particle sizes shown in Table 1 below was used as a raw material powder for La sintered silicon steel. This F
First, the e-Si-La compound powder was prepared using Fe-
After melting the Si compound and La by high frequency melting to produce an alloy ingot, the ingot is coarsely pulverized,
Then, it was produced by jet mill pulverization.
Carbonyl iron powder having the components and average particle size shown in Table 1 was used as the Fe powder.

[0052]

[Table 1] Note that β, ε, and Δβ shown in the column of compounds in Table 1 are F
The type of the crystal phase of the eSi compound is shown.

Next, the Fe—Si—La compound powder and Fe
The powder and the powder were blended at the ratio shown in Table 2 and then mixed with a V-cone.

[0054]

[Table 2] In addition, the raw material No. of Table 2 8 and 9 do not contain La and are used in comparative examples.

Table 3 below shows each of the mixed powders thus obtained.
The PVA (polyvinyl alcohol) binder, water, and a plasticizer were added in the amounts shown in Table 1 to form a slurry.
This slurry was granulated with nitrogen gas under the set conditions of a hot air inlet temperature of 100 ° C. and an outlet temperature of 75 ° C. using a completely hermetic spray dryer. The average particle size of the granulated powder was about 80 μm.

[0056]

[Table 3] Next, the granulated powder was pressed at a pressure of 2 ton using a compression press.
/ Cm ² . Table 4 shows the dimensions of the compact.
Thereafter, sintering was performed in a vacuum and in hydrogen under the binder removal conditions and sintering temperature conditions shown in Table 4 to obtain a sintered body having the dimensions shown in Table 5. Table 5 below shows the residual oxygen content, residual carbon content, average crystal grain size, and relative density of the sintered body.

[0057]

[Table 4]

[0058]

[Table 5] First, a sintered body having the dimensions shown in Table 5 above was rolled at a roll peripheral speed of 60 mm / sec using a two-stage roll of 60φ at a rolling reduction of 50 mm.
%, And further cold-rolled to 0.10 mm at the same roll peripheral speed by a 20φ four-stage roll. After rolling, a ring of 20φ × 10φ × 0.1t and 10
Annealing was performed after punching out a flat plate of × 10 × 0.1 t.

Table 6 below shows the evaluation results of the rolling state, the annealing temperature, the average crystal grain size of the rolled silicon steel sheet, the DC magnetic characteristics, the DC electrical resistivity ρ, and the measured density. The symbol “◎” in the column of the rolling state indicates very good, and the symbol “○” indicates good. The symbol “△” indicates that cracks occurred on the end face of the rolled sheet, and the symbol “×” indicates that cracks occurred on the entire surface.

In Table 6, “Adequacy” means that when the Si content is 3.0 wt%, the electric resistivity ρ is 3.0 × 10 ⁻⁷ Ω.
Those with m or more were evaluated as “suitable”, and those with less than m were evaluated as “bad”. When the Si content was 6.5 wt%, those having an electrical resistivity ρ of 9.0 × 10 ⁻⁷ Ωm or more were evaluated as “suitable”, and those having an electrical resistivity of less than 9.0 × 10 ⁻⁷ Ωm were evaluated as “fail”.

[0061]

[Table 6] In Table 6 above, the results of the property evaluation of the ingots of silicon steel with a Si content of 3.0 wt% and the ingots of silicon steel with a Si content of 6.5 wt% are described as comparative examples.

Table 6 shows the following.

1. Sample No. having a thickness before rolling of 10 mm. Sample No. 5 having a La content of 2.4 wt%. 9,
Sample No. with a parallelism of 0.63 before rolling. 12 is
In all cases, cracks occurred during rolling. As described above, in order to ensure excellent rolling workability, the thickness of the sintered silicon steel before rolling is 5 mm or less, the La content is 2.0 wt% or less,
The parallelism is preferably 0.5 or less.

2. The sintered silicon steel of the comparative example to which La was not added (samples N0.11 and 13) had a relatively lower electric resistivity and a lower coercive force (iHc) than the example having the same Si content. high.

3. Sample No. inferior to the rolled state It can be seen that the examples of the present invention except for Nos. 5 and 9 have excellent magnetic properties equivalent to ordinary ingots, and have higher electrical resistivity p than ordinary ingots. The evaluation of the above examples was performed on the assumption that a sintered silicon steel sheet was manufactured by cold rolling, but the method for processing a sintered silicon steel sheet of the present invention is not necessarily limited to this. Since the electrical resistivity and the coercive force of the sintered silicon steel of the present invention are improved by the addition of La, the sintered silicon steel may be sufficiently used for processing by a method other than cold rolling. In that case, sample N
Even if the thickness and parallelism of the sintered body are unsuitable for the cold rolling process as in 0.5 and 12, excellent electrical and magnetic properties can be obtained without problems according to other processing methods. Can demonstrate. The crystal grain size of the silicon steel before processing was set to 300 μm.
By adjusting the value to m or less, there is an advantage that not only the rolling workability is improved but also other processes involving plastic deformation (for example, bending and punching) are easily performed.

The La-containing silicon steel which has not been subjected to the sintering process does not exhibit a high electric resistivity by itself, but is used as a raw material of the Fe-Si-La compound powder. There is an application that is used in the manufacture of steel.

Although the present invention has been described with reference to an example in which a silicon steel containing La oxide is formed from powder by sintering, a silicon steel having an increased electric resistivity can be obtained by the following method. . That is, Fe-Si-La
Compounds or by dissolving the _{Fe-Si-La 2 O 3} , performs ingot forging. Thereafter, the ingot is repeatedly subjected to hot rolling or hot forging, and La
Disperse ₂ O ₃ . Thereafter, annealing is performed to grow crystal grains and reduce coercive force.

[0068]

According to the present invention, it is possible to provide a sintered silicon steel and a rolled silicon steel sheet having high electric resistivity ρ and excellent magnetic properties. In particular, it has characteristics that are particularly preferable as a material of a member that requires low eddy current loss even with a high-frequency alternating magnetic field, such as a magnetic core of a high-frequency transformer.

Further, the workability is improved by adjusting the grain size of the sintered silicon steel, and cold rolling is also possible, so that it can be used in a wide range of fields.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the electrical resistivity ρ of a sintered silicon steel and the La content when the Si content is 6.5 wt%.

FIG. 2 is a graph showing the average crystal grain size of sintered silicon steel and the relationship between iHc and La content when the Si content is 6.5 wt%.

FIG. 3A is a cross-sectional view schematically illustrating a structure of a sintered La sintered silicon steel according to the present invention before rolling, and FIG. 3B is a cross-sectional view schematically illustrating a structure after annealing. is there.

[Explanation of symbols]

 Reference Signs List 30 Fe-Si compound crystal grains 32 La oxide precipitated

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/02 C22C 38/02 H01F 1/16 H01F 1/16 A (72) Inventor Tsunekazu Saigo Osaka Prefecture 2-15-17 Egawa, Shimamoto-cho, Mishima-gun Sumitomo Special Metals Co., Ltd., Yamazaki Works (72) Inventor Masao Nomi 2--15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture F-term, Yamazaki Works, Sumitomo Special Metals Co., Ltd. Reference) 4K017 AA04 BA06 BB01 BB08 BB09 BB16 BB17 CA07 DA02 EA03 EB00 4K033 CA10 FA00 HA00 QA02 5E041 AA02 AA19 CA01 HB05 HB11 NN01 NN06

Claims (10)

[Claims] 1. A silicon steel containing an oxide of La. 2. The silicon steel according to claim 1, wherein the La oxide is precipitated at a crystal grain boundary. 3. The silicon steel according to claim 1, wherein the content of La is in a range of 0.05 wt% to 2.0 wt%. 4. The Si content is from 3.0 wt% to 10 wt%.
%. The silicon steel according to claim 1, which is in the range of up to%. 5. A step of preparing a powder of a silicon steel containing La, and sintering the powder so that at least a part of La is precipitated on a crystal grain boundary as a La oxide. Forming a silicon steel. 6. A step of preparing an ingot of a silicon steel containing La, and a step of depositing the La oxide on crystal grain boundaries by subjecting the ingot to repeated hot rolling or repeated hot forging. And a step of performing a heat treatment. 7. The Si content is from 3.0 wt% to 10 wt%.
%, And a step of preparing a powder of a silicon steel containing La in a range of up to%, and sintering the powder so that at least a part of La precipitates as La oxide at a crystal grain boundary. A method for producing a rolled silicon steel sheet, comprising: a step of forming a sintered silicon steel sheet; a step of rolling the sintered silicon steel sheet; and a step of heat-treating the sintered silicon steel sheet. 8. The sintered silicon steel having a La content of 0.1 watts.
The method for producing a rolled silicon steel sheet according to claim 7, wherein the content is in a range from t% to 2.0 wt%. 9. The method for producing a rolled silicon steel sheet according to claim 7, wherein an average crystal grain size of the sintered silicon steel before the rolling step is 300 μm or less. 10. An electric apparatus comprising: a coil for forming a magnetic field; a soft magnetic member arranged in the magnetic field and magnetized; and means for supplying a current to the coil, wherein the soft magnetic member is An electric device characterized by being formed from silicon steel containing La oxide.