JP2003226948A - Nonoriented silicon steel sheet and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical nonoriented silicon steel sheet which has excellent caulking properties even in the case of a sheet thickness of ≤0.4 mm, and can secure prescribed high frequency magnetic properties, and to provide a production method therefor. <P>SOLUTION: The steel sheet has a steel composition containing ≤0.01% C, ≤3.0% Si, 0.1 to 2.5% Mn, ≤0.01% S, ≤3.0% acid soluble Al, ≤0.2% P and ≤0.004% N. The number of MnS and inclusions compounded with MnS, or CaS and inclusions compounded with CaS having dimensions of 0.5 to 5 μm in the steel is ≤30 pieces/mm<SP>2</SP>. The thickness of an insulation film provided on the surface of the steel sheet, and consisting only of an organic resin or obtained by compounding an organic resin and inorganic components is controlled to 0.05 to 0.4 μm on the average value per mm<SP>2</SP>, and further, its sheet thickness is controlled to 0.15 to 0.4 mm. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same. More specifically, the present invention mainly relates to a high-efficiency motor excellent in high frequency magnetic characteristics (
Examples: Hermetic motors used in air conditioner compressors, spindle motors used in personal computer hard disks, main motors and starter generators in hybrid and electric vehicles, high-speed rotary motors used in vacuum cleaners and vacuum pumps, etc. The present invention relates to a non-oriented electrical steel sheet having excellent high-frequency magnetic properties and automatic crimping properties used for a multi-pole motor such as a servo motor, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Non-oriented electrical steel sheets are used for motors and small transformers, but in recent years, there has been a demand for reduction of CO ₂ , nitrogen oxides, etc. emitted from thermal power plants or automobiles due to environmental and energy problems. Has been. As a method of reducing such exhaust gas, high efficiency of the motor is required in order to reduce power consumption, and by combining an electric vehicle driven by an electric motor instead of the engine of the vehicle or an engine and an electric motor A hybrid electric vehicle with reduced power consumption is being developed.

In the prior art, for example, a magnetic steel sheet used as an iron core in an induction motor having a low efficiency in a hermetic motor of a compressor for an air conditioner is JIS C255.
It was about 50A1300 specified in 2. Although such a steel sheet has a poor iron loss, it has a low Si content and a relatively thick sheet thickness of 0.5 mm, so it has good automatic crimping ability, and the binding force of the core crimped by the superhard automatic crimping die is , 40MP per caulking
There was about a, and it was firmly fixed. However, an increase in the Si content leads to a decrease in the elongation of the steel sheet, and it becomes difficult to form the caulking projections, so an increase in the Si content is disadvantageous to the caulking property.

However, synchronous motors that use permanent magnets have become the mainstream along with higher motor efficiency, and a large amount of Si is included to improve efficiency, and the plate thickness is 0.35 mm, 0.27 mm or to reduce high frequency iron loss. The mainstream is the use of thin electrical steel sheets with a thickness of 0.2 mm.

[0005] These electromagnetic steel sheets are, for example, electromagnetic steel sheets such as 35A230 specified in JIS C2552. Since the coating film thickness of these products is usually about 0.5 µm, the binding force per caulking point is It is reduced to about 10MPa and the cohesion is weak. Furthermore, if the plate thickness is reduced to 0.27 mm, the contact area of the caulking projections will be further reduced, so the caulking strength will be further reduced and increasing the binding force with a small contact area will be an important issue. It was The thinner the plate is, the more inevitable the binding force will be.

On the other hand, in the use of micromotors such as spindle motors mainly used in hard disks of personal computers, thin electromagnetic steel plate ST-20 (0.2 mm) according to the Electrical Manufacturers' Association standard.
Sheet thickness) is mainly used. These thin electromagnetic steel sheets have magnetic characteristics specified, but formability, especially automatic caulking property, is not mentioned, and the film thickness is 0.5 μm or more. Moreover, although these micromotors are manufactured by the caulking method, the caulking core is further hardened with resin, so a caulking strength of about 5 MPa per caulking point is sufficient, and caulking ability has been emphasized until now. There wasn't.

In recent years, however, the use of these 0.2 mm electromagnetic steel sheets and thinner electromagnetic steel sheets for large motors used in electric vehicles and the like has made crimpability important. However, since the crimpability of such a thin plate is significantly deteriorated, from the point of practicality, it is necessary to satisfy the contradictory characteristics of reducing the plate thickness and securing the crimpability at the same time.

Regarding the non-oriented electrical steel sheet excellent in automatic crimping property, S: 0.01% in Japanese Patent No. 2742688 is disclosed.
It has been proposed to provide an insulating coating having a thickness of 0.1 to 0.3 μm on the following silicon steel sheet, but this is aimed at improvement by focusing on the relationship between the insulating coating and caulking property.

The binding force after pressing when the automatic crimping by the press is performed is expressed by the pushing force when the wedge is pushed between the bound cores and the binding is released, which is the evaluation of the automatic crimping property. This is one indicator to do. Normally, this binding force is required to be 8 kgf / mm ² (78.4 MPa) or more.
In the above patent, the binding force was 12 kgf / mm ² (117 MPa) at maximum.

[0010]

However, in the above patent, in order to improve the caulking property, S: 0.01% or less and the thickness of the insulating film is 0.1 to 0.3 μm. Is 4% in consideration of rollability
Although the following is set, in the practical example, Si: 0.2 to
As 0.5%, the magnetic properties are not sufficiently improved, and the thickness of the plate is not mentioned. For example, it is predicted that the binding force will be significantly reduced when the thickness is reduced to 0.5 mm or less. There is room for

As a result of the subsequent research, in order to make the technique proposed in the above patent even more practical,
Further improvements in magnetic properties, especially high-frequency magnetic properties, and caulking properties are required, and for that purpose, from the aspect of the steel composition, the form of inclusions, and the form of the electrical steel sheet itself. It was found that it is necessary to study from a comprehensive viewpoint.

An object of the present invention is to provide a crimping property which is practically sufficient even if the plate thickness is 0.4 mm or less, for example 0.2 mm or less, and is capable of ensuring a predetermined high frequency magnetic characteristic. It is another object of the present invention to provide a further improved non-oriented electrical steel sheet and a manufacturing method thereof.

[0013]

In order to solve such a problem, the inventors of the present invention have conducted various studies and have developed a thin non-oriented electrical steel sheet excellent in both high frequency magnetic characteristics and caulking property and a method for producing the same. The inventors have found the present invention and have reached the present invention.

It is known to reduce the plate thickness in order to improve the high-frequency characteristics. Even in the non-oriented electrical steel sheet according to the present invention, the plate thickness is in the range of 0.15 mm to 0.4 mm. It was found that there are two important points in order to improve the crimping property in the thin region having a good high frequency characteristic. It was also found that one of them contributes to the improvement of high frequency magnetic properties and has a synergistic effect.

Generally, when a thin electromagnetic steel sheet having a thickness of 0.4 mm or less is bound by automatic crimping, the contact cross-sectional area of the protrusion is small, so that the crimping strength is low. Although the above-mentioned Japanese Patent No. 2742688 describes that the caulking force is weakened by the sliding effect of MnS, the S-based inclusion is not limited to the case of MnS alone, but also the complex inclusion in which MnS is precipitated in the oxide. Many of them have complicated forms such as Ca, inclusions such as CaS and complex compounds thereof, and the behavior of these complex inclusions was not clear.

By the way, in the lamination of the electromagnetic steel plates by caulking, first, a protrusion is formed, and then the protrusion of the next steel plate to be laminated is fitted into the protrusion to bind them together. Therefore, the soundness of the protrusion body when the protrusion is formed is important. Usually, in an electromagnetic steel sheet having an insulating coating on its surface, the coating component slightly wraps around the body of the protrusion, and when the coating contains a resin, the resin has a lubricating action, which causes a decrease in the binding force.

When the caulking projection is round and flat, the body has a sound diaphragm surface, and when the V or round V type has a notch, the shearing surface ratio of the notch is large. Will be improved.

According to the knowledge of the present inventors, not only the slip effect of MnS described in the above-mentioned Japanese Patent No. 2742688 but also the S-type inclusions among the inclusions in the steel are reduced by this reduction. The surface integrity is impaired, the contact area is reduced, and the caulking strength is lowered.
In the present invention, the caulking property is improved by controlling the size and amount of the S-based inclusions, which cannot be taught from the above patent publication.

Further, if the size of the inclusions becomes large, it becomes easy to "crack" at the time of cutting by a press, and the ratio of the fracture surface becomes high. This tendency is due to the size of inclusions being 5μ, for example.
It becomes remarkable when m exceeds a certain value.

The caulking is supported by the frictional force of the shearing surface, not the fracture surface, and the reduction of the shearing surface leads to the reduction of the caulking force. On the other hand, in terms of magnetic properties, thin electromagnetic steel sheets with a thickness of 0.15 mm to 0.4 mm have a small sheet thickness, so that the surface energy increases during the recrystallization process, making it difficult to grow crystal grains. Therefore, it has been found that when "there are many S-based inclusions", the growth of crystal grains is hindered during the finish annealing and the high frequency magnetic properties deteriorate, but the magnetic properties can be improved by controlling the S-based inclusions.

The surface insulating coating usually contains an organic resin in order to improve punchability, but the above-mentioned Patent No. 27
As described in Japanese Patent No. 42688, this organic resin wraps around the contact surface of the caulking projection, and the wrapping resin acts as a lubricant, and the binding force becomes weak. In the case of thin electrical steel sheets, the ratio of the coating thickness to the shearing surface of the protrusion is large, so the amount of wrapping around is also large, and the caulking and binding force tends to decrease further, so it is important to control the film thickness. I found that.

The present invention has been completed based on such various findings, and the gist of the invention is as follows. (1) Mass%, C: 0.01% or less, Si: 3.0% or less, Mn:
0.1% or more and 2.5% or less, S: 0.01% or less, acid-soluble Al: 3.
It has a steel composition containing 0% or less, P: 0.2% or less, and N: 0.004% or less, and is an inclusion in the steel, which is an inclusion compounded with MnS and MnS or an inclusion compounded with CaS and CaS. 30 pieces / mm ^{2 with a} size of 0.5 μm or more and 5 μm or less
In the following steel sheets, the surface of the steel sheet has an insulating coating composed of only organic resin or a composite of organic resin and inorganic component, and the thickness of the insulating coating is 0.05 μm or more 0.4 mm on average per 1 mm ^2.
Non-oriented electrical steel sheet with a thickness of 0.15 mm or more and 0.4 mm or less, which is μm or less.

(2) The fragrance-free electrical steel sheet according to the above (1), wherein the steel composition comprises the balance Fe and inevitable impurities. (3) Molten steel having the steel composition described in (1) or (2) above is solidified by continuous casting into a slab, held at 500 ° C or higher, inserted into a heating furnace, and heated at a temperature of 900 ° C or higher and 1300 ° C or lower. After hot rolling, hot-rolled sheet is annealed at 600 ℃ ~ 1100 ℃, or cold-rolled as-rolled once or twice or more with intermediate annealing to obtain the final thickness. 0.15 mm or more
After finishing to 0.4 mm or less and then finishing annealing by continuous annealing at 700 ° C to 1150 ° C, a surface insulating film made of an organic resin or a composite of an organic resin and an inorganic material has an average value per 1 mm ^{2 of} thickness. A method for manufacturing a non-oriented electrical steel sheet, which comprises forming on the surface of the steel sheet at 0.05 μm or more and 0.4 μm or less.

(4) When adjusting the composition at the molten steel stage, S
The Ca-based desulfurizing agent was added to remove S in the steel from the system to the outside of the system with a Ca content of 0.01% or less.
Refluxing was performed until the content became 001% or less, and the inclusions in the final product steel compounded with MnS and MnS and S-based inclusions compounded with CaS and CaS had a size of 0.5.
The method for producing a non-oriented electrical steel sheet according to the above (3), characterized in that the control is performed so that the number of those having a size of μm or more and 5 μm or less is 30 pieces / mm ² or less.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the steel composition, inclusions, plate thickness, and insulating coating thickness of the electromagnetic steel sheet of the present invention as described above are shown below. In the present specification, "%" indicating the steel composition is "mass%" unless otherwise specified.
Is.

Steel composition: When C exceeds 0.01%, magnetic aging occurs and the magnetic properties are deteriorated.
% Or less. It is preferably 0.005% or less.

Si is an essential element for improving the magnetic properties, but if it is contained in excess of 3.0%, cold rolling becomes difficult and the caulking property deteriorates, so it was made 3.0% or less. It is preferably 2.9% or less. The lower limit of Si is not particularly limited, but in order to secure magnetic properties, it is preferably 0.05
%, More preferably 0.1% or more.

Mn is an element effective for improving magnetic properties,
If it is less than 0.1%, there is no effect, while if it exceeds 2.5%, cold rolling becomes difficult, so the content was made 2.5% or less.
It is preferably 0.2% or more and 1.5% or less.

On the contrary, the addition of S deteriorates the magnetic properties, so S was made 0.01% or less. It is preferably 0.005% or less. Acid soluble Al is limited to 3.0% or less, but the presence of Al in steel is important for improving magnetic properties,
If the content of Al exceeds 3.0%, the hardness significantly increases, and cold rolling becomes difficult. Preferably 0.2% or more 2.
The presence of P of 5% or less is important for improving the mechanical properties for securing punchability, but if it is contained in excess of 0.2%, it causes fracture during cold rolling, so 0.2% is included.
% Or less. Further, if it is less than 0.005%, the effect becomes small, so it is preferably made 0.005% or more.

N is detrimental to the magnetic properties and is combined with Al to form AlN, resulting in finer crystal grains and deterioration of the magnetic properties, so N was made 0.0040% or less. In the present invention, the balance of the steel composition is Fe and inevitable impurities, but when desulfurization treatment using a Ca-based desulfurizing agent is performed in the stage of melting, Ca is included as one of the inevitable impurities, and preferably , Its amount is less than 0.001% as CaS. Other inevitable impurities include Ti, V, Zr, Nb, Sb, Sn, B, Cr and N.
The total content of i, Mo, etc. may be 1.0% or less.

Regarding the product plate thickness, if the plate thickness is less than 0.15 mm, it becomes difficult to bind by caulking, while if it exceeds 0.4 mm, the high frequency iron loss increases remarkably, so 0.15 mm or more and 0.4 m
It was set to m or less.

Regarding the form of inclusions, if there are many MnS and CaS-based inclusions, the ratio of shear planes will be reduced by press working, the contact area between steel sheets will be small, and fine cracking will occur in the case of caulking projections in the form of a drawing. It was found that the contact area was decreased and the caulking force was decreased. It was found that among these inclusions, large inclusions having a size of 0.5 μm or more and 5 μm or less dominate the shear ratio and the microcracks at the origin of the inclusions. It was found that the tendency was remarkable when the number of such S-type inclusions such as large MnS and CaS exceeded 30 / mm ² , and in the present invention, the number of such large inclusions was determined to be good. 30 pieces / mm ² or less in order to obtain good properties. It is preferably 15 / mm ² or less.

Although the steel sheet according to the present invention is coated with an insulating coating, it has been found that the coating contains an organic resin component and wraps around the sheared surface during press working.
It has been found that this wraparound coating acts as a lubricating action on the contact surface between the steel plates in the caulking portion and reduces the caulking force.

It was found that when the coating film thickness is 0.4 μm or less on the cut surface of the steel plate having a product plate thickness of 0.15 mm to 0.4 mm, the caulking force does not significantly decrease due to the wraparound.
Coating thickness is 0.4 μm due to good caulking
Below. On the other hand, if the coating film thickness is less than 0.05 μm, a stable coating cannot be manufactured, so the film thickness lower limit is 0.
It was set to 05 μm. It is preferably 0.15 to 0.35 μm.

In producing the non-oriented electrical steel sheet according to the present invention, molten steel having a predetermined steel composition is melted by a conventional means, and a slab is obtained by an appropriate means such as a continuous casting method or an ingot method. The slab thus obtained is subjected to hot rolling and cold rolling according to the present invention.

In the production of molten steel, first, the components of molten steel obtained by a usual blast furnace method or electric furnace method are adjusted in a torpedo car, a hot metal desulfurization furnace, a converter or a secondary refining furnace. There is no problem if the predetermined steel composition of the present invention is achieved by the conventional component adjusting means. For example, in the case of a high S content, in order to eliminate S in the steel from the system by Ca until S reaches a specified amount. For example, Ca-based desulfurizing agents such as CaO or CaSi are added at the time of vacuum secondary refining, and the generated CaS is refluxed in the vacuum degassing tank until it becomes 0.001% or less in the steel. MnS and MnS composites, or CaS and CaS composite S-based inclusions with a size of 0.5 μm or more and 5 μm or less
The size and amount of S-type inclusions are controlled so that the number is 0 / mm ² or less.

According to the present invention, in order to reduce the inclusions in the steelmaking, the inclusions are levitated by performing sufficient reflux in the secondary refining, and ultra-large inclusions exceeding 5 microns are produced in the product. It is preferable to eliminate it completely.

The molten steel whose steel composition has been adjusted in this way is solidified into slabs by ordinary continuous casting, held at 500 ° C. or higher, inserted into a heating furnace, and heated at a temperature of 900 ° C. or higher and 1180 ° C. or lower.

By reheating at a low temperature in this way, the re-dissolution of the complex inclusions of MnS and MnS and the complex inclusions of CaS and CaS is prevented, and the generation of fine precipitates of 0.5 μm or less is reduced as much as possible. .

In the present invention, hot rolling may be carried out by a conventional means and is not particularly limited. For example, a slab having the above-mentioned steel composition is heated at a temperature of 1300 ° C. or lower and ordinary hot rolling is carried out. Heating temperatures above 1300 ° C cause MnS in the steel to melt and lead to deterioration of magnetic properties. In order to secure the rollability, the temperature is preferably 1100 ° C to 1250 ° C. After hot rolling, hot-rolled sheet annealing may be performed as the case may be.

After hot rolling, in order to improve magnetic properties, 600 ° C. to 1100 ° C., preferably 600 ° C. to 10 ° C.
Perform hot-rolled sheet annealing at 00 ℃, or cold-roll one time with hot rolling or at least two times with intermediate annealing to finish the final sheet thickness from 0.15mm to 0.4mm. . If the hot-rolled sheet annealing temperature is less than 600 ℃
When the temperature exceeds ℃, the crystal grains are appropriately coarsened, causing troubles such as breakage during cold rolling.

Following the cold rolling, finish annealing is performed by continuous annealing at 700 ° C to 1150 ° C. If the finish annealing temperature is less than 700 ° C, a sufficient recrystallized structure cannot be obtained, magnetic properties become poor, and hardness increases. However, if the temperature exceeds 1150 ° C, the crystal grains become extremely coarse and cracks occur during motor core punching, resulting in poor workability. Therefore, the finish annealing temperature is 1150 ° C.
Below.

After the finish annealing, in order to improve the punching property and the insulating property, a surface insulating film made of an organic resin containing an inorganic binder or a composite of an organic resin and an inorganic material has a thickness of 1
The average value per mm ² is 0.05 μm or more and 0.4 μm or less. The coating thickness should be 0.05 μm to 0.4 μm to obtain sufficient crimping force. The film thickness is calculated as an average value per 1 mm ² , because the area related to caulking is 1 mm ² or more.

The coating method of such an organic coating is not limited to a roll coater type or a curtain flow type. For example, in the case of a roll coater type, in the case of a type in which a pickup roll and a metering roll are directly contacted with an applicator roll. The film thickness is controlled by controlling the rotational speed difference (circumferential speed ratio) and the contact pressure between the applicator roll and the steel plate, and the continuous coil thickness meter measures the total coil length from 0.05 to 0.4 μm per 1 mm ^2. Control the thickness.
Alternatively, in the case of the curtain flow type coater, the film thickness is controlled by controlling the discharge amount of the coating liquid and the line speed of the steel plate.

The film thickness at this time is measured and controlled by a continuous film thickness meter using an infrared thickness meter. In the present invention, the composition of the insulating coating itself is not particularly limited, but the organic resin is exemplified by one kind or a mixture of two or more kinds such as acrylic resin, phenol resin, polystyrene resin, vinyl acetate resin and organic silicon resin. To be done. If necessary, one or more inorganic substances such as chromate, phosphate, colloidal silica, alkaline earth metal salt and the like may be further added thereto. Further, conventional boric acid or the like may be used.

The effects of controlling the S-type inclusions in the present invention are as follows. Preventing magnetic properties due to inclusions, especially deterioration of iron loss,

The crimping property is improved, and even for a thin plate of 0.5 mm or less, the crimping strength (bonding force) is of a degree practically sufficient.
However, in the past, for example, in the above-mentioned Japanese Patent No. 2742688, the binding force is at least 7
It is said that 8.4 MPa is required, but this refers to large equipment using electromagnetic steel sheets with a thickness of 0.5 mm or more, and a thin steel sheet with a thickness of 0.4 mm or less, which is the subject of the present invention. It has been proved that the caulking strength (coalescing force) of at least 40 MPa is sufficient in the case of a device in which is used, together with the miniaturization of the device itself, and

For controlling S-based inclusions,
This is possible by adopting the practical operating conditions that have been implemented in the past, and there is also a practical significance in that new capital investment is not required.

Next, the function and effect of the present invention will be described more specifically by way of examples.

[0050]

(Example) (Example 1) After tapping from the converter, vacuum refining with a ladle was performed, at which time a Ca-based desulfurizing agent was added to the molten steel, and reflux was performed in an RH vacuum tank. Molten steel having the chemical composition shown in 1 was melted. Heating slabs of each steel composition under the conditions shown in the same table, hot rolling, after pickling, after annealing the hot rolled sheet and then cold rolling, after finishing the sheet thickness in the table, Continuous annealing was performed at the temperature shown in the table, and after recrystallization annealing, a surface insulation film (coating) consisting of acrylic resin emulsion, magnesium chromate, and boric acid was formed to a film thickness of 0.
A target of 2 μm was formed on the surface of the steel sheet by the roll coater method.

The magnetic characteristics are 25 cm type audible frequency Epstein test, and the iron loss when the carrier frequency is 3 kHz by the PWM (pulse width modulation) of the non-sinusoidal wave, the excitation frequency is 50 Hz and 400 Hz, and the magnetic flux density is 1.5 T is JIS. It was measured according to the method of C2550. Iron loss W15 / 50 is 3 W / kg or less, W10 / 400 is 40 W / k
Each g or less was regarded as good.

The thickness of the surface coating layer was measured by the FIB method (focused ion beam method, Focused Ion Beam method). According to JIS G0555, the measurement of inclusions is EDX for inclusions with a size of 0.5 μm or more and 5 μm or less.
Only MnS, CaS and their composite inclusions were selected by the method and their numbers were measured.

The caulking strength is such that a ring having an inner diameter of 33 mm and an outer diameter of 45 mm is caulked at four points (4 mmφ round flat type, cut and raised plate thickness 80
%, Indentation amount 90% of plate thickness) The upper and lower surfaces were bonded to a tensile test metal fitting with a cyanoacrylate adhesive, and the tensile strength was measured with a tensile tester, that is, the caulking strength by the tensile method. A crimping strength of 30 MPa or more was considered good.

Separately from this, after crimping at four points as described above, a wedge is pushed between the bound rings, the pushing force when the bundle is released is measured, and this is determined as the crimping strength by the wedge method. did. This is to evaluate the same characteristic as the caulking strength by the above-mentioned tensile method, but it can be said that the wedge method has a larger variation and the tensile method is more suitable.

[0055]

[Table 1]

FIG. 1 is a graph showing the relationship between the shear ratio and the size of inclusions in the test material of this example. this is,
When the size of inclusions increases, when cutting with a press,
The ratio of the fracture surface increases because it becomes easy to "crack". This tendency becomes remarkable when the size of inclusions exceeds a certain value.
The size of μm was the rough boundary.

The caulking is supported by the frictional force of the shearing surface, not the fracture surface, and the reduction of the shearing surface leads to the reduction of the caulking force. The binding force measured by the wedge method according to the present invention was about 40 MPa or more.

FIG. 2 shows the relationship between the caulking strength and the plate thickness of the S-type steel inclusions (MnS, CaS and their composites) having a size of 0.5 to 5 μm, which are classified by the number.
However, in the case of FIG. 2, the thickness of the insulating film was 0.25 μm.

As can be seen from these results, in the conventional case, it was predicted that the caulking strength would drastically and drastically decrease when the plate thickness became thinner than 0.5 mm (indicated by a black square in the figure). By controlling the S-based inclusions according to the present invention, it is possible to sufficiently secure the caulking strength of 40 MPa or more even if the plate thickness is 0.4 mm or less. It is a caulking strength that is well tolerated in equipment.

According to the present invention, the value of 0.
It can be seen that there is a significant difference in inclusion control even in the range where the crimping binding force is conventionally insufficient for plates thinner than 5 mm, particularly 0.15 to 0.4 mm. Of course, the plate thickness is 0.15 ~
It goes without saying that the magnetic properties, especially the high frequency properties, are significantly improved by setting the thickness to 0.4 mm.

[0061]

As described above, according to the present invention, it is possible to obtain a non-oriented electrical steel sheet which not only has improved high-frequency magnetic properties due to a thin steel sheet but also has excellent automatic caulking properties. In particular, it can be seen that a non-oriented electrical steel sheet useful for a large motor for electric vehicles, which is attracting attention today, can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the size of inclusions and the shear ratio, obtained in the examples.

FIG. 2 is a graph showing the relationship between the caulking strength and the plate thickness depending on the size of S-based inclusions.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C21D 9/46 501 C21D 9/46 501B C22C 38/06 C22C 38/06 F term (reference) 4K013 AA04 BA05 CE01 EA25 4K033 AA01 CA09 EA01 FA01 FA13 HA01 HA03 JA01 LA04 RA02 SA03 TA03

Claims (4)

[Claims] 1. Mass%, C: 0.01% or less, Si: 3.0%
Below, Mn: 0.1% or more and 2.5% or less, S: 0.01% or less, acid-soluble Al: 3.0% or less, P: 0.2% or less, N: 0.004% or less. Of MnS and inclusions mixed with MnS, or inclusions mixed with CaS and CaS and having a size of 0.5 μm or more and 5 μm or less in a steel plate of 30 pieces / mm ² or less, only the organic resin on the steel plate surface or It has a composite insulation film of organic resin and inorganic components, and the thickness of the insulation film is 0.05 per 1 mm ² on average.
Thickness of 0.15 mm or more and 0.4 mm or less, and plate thickness of 0.15 mm or more and 0.4 mm
The following non-oriented electrical steel sheets. 2. The non-oriented electrical steel sheet according to claim 1, wherein the steel composition comprises the balance Fe and unavoidable impurities. 3. Molten steel having the steel composition according to claim 1 or 2 is solidified by continuous casting to form a slab, which is held at 500 ° C. or higher and inserted into a heating furnace and heated at a temperature of 900 ° C. or higher and 1300 ° C. or lower. Hot-rolled sheet is annealed at 600 ℃ ~ 1100 ℃ after hot rolling, or cold-rolled once as hot-rolled or twice or more with intermediate annealing between them to obtain the final thickness of 0. .
Finish 15mm above 0.4mm or less, and then after the finish annealing in a continuous annealing 700 ° C. to 1150 ° C., the organic resin or the surface insulation film made of a composite of organic resin and inorganic its thickness per 1 mm ² 0.05 μm or more on average 0.4 μm
A method for manufacturing a non-oriented electrical steel sheet, which comprises forming the steel sheet surface below. 4. When the composition is adjusted in the molten steel stage, S is
A Ca-based desulfurizing agent was added to remove S in the steel from the system to 0.01% or less by Ca, and the generated CaS was 0.00
Refluxing was performed until the content became 1% or less, and inclusions in the final product steel mixed with MnS and MnS, CaS and
The size of the S-based inclusion, which is a complex with CaS, is 0.5 μ
4. The method for producing a non-oriented electrical steel sheet according to claim 3, wherein the number of those having a size of m or more and 5 μm or less is controlled to 30 pieces / mm ² or less.