JP6724712B2 - Non-oriented electrical steel sheet - Google Patents

Description

The present invention relates to a non-oriented electrical steel sheet.

Recently, global environmental problems have been attracting attention, and demands for energy saving measures have been further increased. Above all, there has been a strong demand in recent years for high efficiency of electric devices. For this reason, even in non-oriented electrical steel sheets that are widely used as iron core materials for motors, transformers, etc., there is an increasing demand for improved magnetic properties. In recent years, the tendency is remarkable in the motors for electric vehicles and hybrid vehicles, and the motors for compressors, in which the efficiency of motors is increasing.

Among the magnetic properties of non-oriented electrical steel sheets, in order to particularly improve high frequency iron loss (that is, reduce high frequency iron loss), alloy elements are added to the steel to increase the electrical resistance of the steel sheet and It is effective to reduce the current loss. Therefore, for example, as disclosed in Patent Document 1 and Patent Document 2 below, an element having an effect of increasing electric resistance such as Si, Al, Mn, or P is added, and magnetic characteristics (iron loss, magnetic flux density Etc.) are being implemented.

JP 2000-129409 A JP, 2005-131993, A

Here, considering the addition of alloying elements with the same content (mass %), Si is an element effective in reducing iron loss because it easily increases electric resistance. Therefore, in the above-mentioned Patent Document 1, the content of Si is varied from 0.1% by mass to 7.0% by mass for study. However, as a result of diligent studies by the present inventors, it became clear that if Si is contained too much, the workability (more specifically, cold rollability) of the non-oriented electrical steel sheet is significantly reduced. ..

Moreover, in the said patent document 2, although iron loss and a magnetic flux density are aimed at improvement by adding P of 0.03 mass%-0.20 mass %, this artificer examined earnestly. As a result, it became clear that if P was contained too much, the workability (more specifically, cold rollability) of the non-oriented electrical steel sheet was significantly reduced.

As described above, it is currently difficult to obtain a non-oriented electrical steel sheet excellent in both cold rolling property and magnetic property by the techniques disclosed in Patent Document 1 and Patent Document 2 described above.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a non-oriented electrical steel sheet capable of improving both cold rolling property and magnetic property. Especially.

In order to solve the above problems, as a result of intensive studies by the present inventors, the content of Al is set to a predetermined value or less, and cold rolling property is less likely to decrease by adding Mn together with Si. The present invention has been completed based on the finding that it is possible to improve both cold rollability and magnetic properties.
The gist of the present invention completed based on the above findings is as follows.

(1) In mass %, C: more than 0% to 0.0050% or less, Si: 3.0% to 4.0%, Mn: 2.0% to 3.3%, P: more than 0% to 0. Less than 0.030%, S: more than 0% to 0.0050% or less, Sol. Al: more than 0% to 0.0040% or less, N: more than 0% to 0.0040% or less, Si-0.5 x Mn: 2.0% or more, the balance being Fe and impurities. , A non-oriented electrical steel sheet having an average crystal grain size of 55 μm to 200 μm.
(2) In addition to part of the balance of Fe, at least one selected from Sn: 0.005% to 0.10% and Sb: 0.005% to 0.10% is further contained. ) Non-oriented electrical steel sheet as described in.

As described above, according to the present invention, in the non-oriented electrical steel sheet, it is possible to improve both cold rolling property and magnetic property.

It is explanatory drawing which showed typically the structure of the non-oriented electrical steel sheet which concerns on embodiment of this invention. It is a flow chart showing an example of a flow of a manufacturing method of a non-oriented electrical steel sheet concerning the embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, constituent elements having substantially the same functional configuration are designated by the same reference numerals, and a duplicate description will be omitted.

(About non-oriented electrical steel sheet)
In order to reduce high-frequency iron loss in non-oriented electrical steel sheets, it is common practice to incorporate alloying elements into the steel to increase the electrical resistance of the steel sheet and reduce eddy current loss. Here, considering the addition of alloying elements with the same content (mass %), Si is an element effective in reducing iron loss because it easily increases electric resistance. However, as a result of the study by the present inventors, it became clear that when the Si content exceeds 4 mass %, the cold rolling property of the non-oriented electrical steel sheet remarkably deteriorates.

Further, although Al is also an alloying element showing an effect of increasing electric resistance like Si, it has been clarified that the cold rolling property is lowered similarly to Si. Further, if the Al content exceeds 2 mass %, the hysteresis loss tends to deteriorate and the magnetic properties tend to deteriorate, and it is difficult to incorporate a large amount of Al as an alloy element.

Therefore, as a result of intensive studies on the method capable of improving both the cold rolling property and the magnetic property, the present inventors have set the content of Al to a predetermined value or less, and the cold rolling property. It was conceived to add Mn together with Si so that the decrease in

Hereinafter, the non-oriented electrical steel sheet according to the embodiment of the present invention will be described in detail with reference to FIG. 1.
FIG. 1 is an explanatory view schematically showing the structure of a non-oriented electrical steel sheet according to an embodiment of the present invention.

The non-oriented electrical steel sheet 10 according to the present embodiment has a base metal 11 containing a predetermined chemical component, as schematically shown in FIG. In addition, the non-oriented electrical steel sheet according to the present embodiment preferably further has an insulating coating 13 on the surface of the base metal 11.

Below, first, the base metal 11 of the non-oriented electrical steel sheet 10 according to the present embodiment will be described in detail.

<Chemical composition of base steel>
The base steel 11 of the non-oriented electrical steel sheet 10 according to the present embodiment is, in mass %, C: more than 0% to 0.0050% or less, Si: 3.0% to 4.0%, Mn: 2.0. % To 3.3%, P: more than 0% to less than 0.030%, S: more than 0% to 0.0050% or less, Sol. Al: more than 0% to 0.0040% or less, N: more than 0% to 0.0040% or less, Si-0.5 x Mn: 2.0% or more, and the balance is Fe and impurities. ..

Further, the base iron 11 of the non-oriented electrical steel sheet 10 according to the present embodiment is further replaced with a part of the remaining Fe, and further Sn: 0.005% to 0.10%, Sb: 0.005% to. It is preferable to contain at least one selected from 0.10%.

Hereinafter, the reason why the chemical composition of the base steel 11 according to the present embodiment is defined as described above will be described in detail. In the following, “%” represents “mass %” unless otherwise specified.

[C: more than 0% to 0.0050% or less]
C (carbon) is an element that is unavoidably contained and causes iron loss deterioration. If the C content exceeds 0.0050%, iron loss deterioration occurs in the non-oriented electrical steel sheet, and good magnetic properties cannot be obtained. Therefore, in the non-oriented electrical steel sheet according to the present embodiment, the content of C is set to 0.0050% or less. The content of C is preferably 0.0040% or less, more preferably 0.0030% or less. The smaller the content of C, the better. However, if the content of C is reduced to less than 0.0005%, the cost will be unnecessarily increased. Therefore, the C content is preferably 0.0005% or more.

[Si: 3.0% to 4.0%]
Si (silicon) is an element that increases the electric resistance of steel, reduces eddy current loss, and improves high frequency iron loss. Moreover, since Si has a large solid solution strengthening ability, it is also an effective element for increasing the strength of the non-oriented electrical steel sheet. Higher strength is necessary from the viewpoint of suppressing deformation and fatigue fracture during high-speed rotation of the motor. In order to fully exert such an effect, it is necessary to contain 3.0% or more of Si. On the other hand, if the Si content exceeds 4.0%, the workability is significantly deteriorated, and it becomes difficult to carry out cold rolling (that is, the cold rollability is deteriorated). Therefore, the Si content is set to 4.0% or less. The Si content is preferably 3.1% or more and 3.9% or less, and more preferably 3.2% or more and 3.8% or less.

[Mn: 2.0% to 3.3%]
Mn (manganese) is an element that is effective for reducing eddy current loss by increasing electric resistance without deteriorating workability of steel and improving high frequency iron loss. Further, Mn is an element that has a smaller solid solution strengthening ability than Si, but can contribute to high strength without degrading workability. In order to fully exert such an effect, it is necessary to contain 2.0% or more of Mn. On the other hand, when the Mn content exceeds 3.3%, the decrease in magnetic flux density becomes remarkable. Therefore, the Mn content is 3.3% or less. The Mn content is preferably 2.1% or more and 3.2% or less, and more preferably 2.2% or more and 3.1% or less.

[P: more than 0% to less than 0.030%]
P (phosphorus) is an element that significantly deteriorates the workability and makes cold rolling difficult in the high alloy steel containing a large amount of Si and Mn, which is the target of the present embodiment. Therefore, the P content is less than 0.03%. The content of P is preferably 0.001% or more and 0.020% or less, and more preferably 0.002% or more and 0.010% or less.

[S: over 0% to 0.0050% or less]
S (sulfur) is an element that is inevitably contained, and is an element that increases iron loss by forming fine precipitates of MnS and deteriorates the magnetic properties of the non-oriented electrical steel sheet. Therefore, the S content needs to be 0.0050% or less. The smaller the S content, the better. However, an attempt to reduce the S content to less than 0.0001% unnecessarily increases the cost. Therefore, the S content is preferably 0.0001% or more. The content of S is preferably 0.0030% or less, more preferably 0.0020% or less.

[Sol. Al: more than 0% to 0.0040% or less]
Al (aluminum) is an element that, when solid-dissolved in steel, increases the electrical resistance of the non-oriented electrical steel sheet to reduce eddy current loss and improve high frequency iron loss. However, in the present embodiment, Mn, which is an element that increases the electric resistance without deteriorating the workability, is positively contained as compared with Al, and is not positively contained. In this case, if the Al content exceeds 0.0040%, fine nitrides are precipitated in the steel to inhibit crystal grain growth during hot-rolled sheet annealing or finish annealing, and deteriorate magnetic properties. Therefore, the content of Al is set to 0.0040% or less. On the other hand, if the content of Al is reduced to less than 0.0001%, the cost is unnecessarily increased. Therefore, the Al content is preferably 0.0001% or more and 0.0030% or less, and more preferably 0.0001% or more and 0.0020% or less.

[N: more than 0% to 0.0040% or less]
N (nitrogen) is an element that is unavoidably contained, and also causes magnetic aging to increase iron loss and deteriorate the magnetic properties of the non-oriented electrical steel sheet. Therefore, the N content needs to be 0.0040% or less. The smaller the content of N, the better. However, if the content of N is reduced to less than 0.0001%, the cost will be unnecessarily increased. Therefore, the N content is preferably 0.0001% or more. The content of N is preferably 0.0001% or more and 0.0030% or less, and more preferably 0.0003% or more and 0.0020% or less.

[Si-0.5 x Mn: 2.0% or more]
The alloying element Si is a ferrite phase promoting element (so-called ferrite former element), while the alloying element Mn is an austenite phase promoting element (so-called austenite former element). Therefore, the metallographic structure of the non-oriented electrical steel sheet changes depending on the contents of Si and Mn, and the non-oriented electrical steel sheet becomes a component system having a transformation point or a component system having no transformation point. I will become. In the non-oriented electrical steel sheet according to the present embodiment, it is required to realize a component system having no transformation point and appropriately increase the average crystal grain size in the base iron. Therefore, the respective contents of Si and Mn are required to satisfy a predetermined relationship so that the component system does not have a transformation point.

Here, empirically, the austenite phase promoting ability of Mn (in other words, the effect of canceling the ferrite phase promoting ability) can be considered to be about 0.5 of the ferrite phase promoting ability of Si. Therefore, the equivalent amount of the ferrite phase promoting ability in the present embodiment can be expressed as “Si-0.5×Mn” based on the Si content.

When the value of Si-0.5xMn is less than 2.0%, the non-oriented electrical steel sheet becomes a component system having a transformation point. As a result, the metallurgical structure of the steel sheet is not a ferrite single phase during high temperature treatment during manufacturing, which may reduce the magnetic properties of the non-oriented electrical steel sheet, which is not preferable. Therefore, the value of Si-0.5 x Mn is set to 2.0% or more. On the other hand, the upper limit of Si-0.5xMn is not particularly specified, but from the range of Si content and Mn content of the non-oriented electrical steel sheet according to the present embodiment, Si-0.5xMn. The value of Mn cannot exceed 3.0%. Therefore, the upper limit of Si-0.5xMn is substantially 3.0%. The value of Si-0.5×Mn is preferably 2.1% or more and 3.0% or less, and more preferably 2.1% or more and 2.9% or less.

[Sn: 0.005% to 0.10%]
[Sb: 0.005% to 0.10%]
Sn (tin) and Sb (antimony) are optional additive elements useful for ensuring low iron loss by segregating on the surface and suppressing oxidation during annealing. Therefore, in the non-oriented electrical steel sheet according to the present embodiment, in order to obtain such an effect, at least one of Sn and Sb is contained in the base metal as an optional additive element in place of a part of the remaining Fe. You may let me. In order to fully exert such effects, the Sn or Sb content is preferably 0.005% or more. On the other hand, when the content of Sn or Sb exceeds 0.10%, the ductility of the base metal may be deteriorated and cold rolling may be difficult. Therefore, the content of Sn or Sb is preferably 0.10% or less. When Sn or Sb is contained in the base metal, the Sn or Sb content is more preferably 0.01% or more and 0.05% or less, respectively.

In the non-oriented electrical steel sheet according to the present embodiment, regarding the content of elements other than the above-mentioned elements, such as Ni (nickel), Cr (chromium), Cu (copper), and Mo (molybdenum), It is not specified. In the non-oriented electrical steel sheet according to this embodiment, even if these elements are contained in an amount of 0.5% or less, the effect of the present invention is not particularly affected. Further, even if Ca (calcium) or Mg (magnesium) is contained in the range of 100 ppm or less in order to promote the crystal grain growth during the finish annealing of the non-oriented electrical steel sheet, the effect of the present invention is not particularly affected. The inclusion of rare earth elements (REM) in the range of 200 ppm or less does not particularly affect the effects of the present invention.

In addition to the above elements, Pb (lead), Bi (bismuth), V (vanadium), As (arsenic), B (boron), and other elements are contained in the range of 0.0001% to 0.0050%. However, this does not impair the present invention.

The chemical composition of the base iron in the non-oriented electrical steel sheet according to this embodiment has been described above in detail.

When the chemical composition of the base iron in the non-oriented electrical steel sheet is to be subsequently measured, various known measurement methods can be used, for example, ICP-MS (inductively coupled plasma mass spectrometry). The law or the like may be appropriately used.

<About the average crystal grain size of base iron>
The average crystal grain size of the base iron 11 in the non-oriented electrical steel sheet 10 according to the present embodiment is 200 μm or less in order to reduce the eddy current loss and the high frequency iron loss. On the other hand, when the average crystal grain size is less than 55 μm, the hysteresis loss becomes large and the iron loss deteriorates. Therefore, the range of the average crystal grain size of the base metal 11 is set to 55 μm to 200 μm. The average crystal grain size of the base iron 11 is preferably 60 μm to 190 μm, and more preferably 65 μm to 180 μm.

When measuring the average crystal grain size, the average cross-sectional area of the crystal grains is obtained by the comparison method or the cutting method described in the JIS G0552 steel ferrite grain size test method, and a circle equivalent to the obtained area is obtained. The diameter may be the average crystal grain size.

<About the thickness of base steel>
The plate thickness (thickness t in FIG. 1) of the base metal 11 in the non-oriented electrical steel sheet 10 according to the present embodiment is 0.40 mm or less in order to reduce eddy current loss and high frequency iron loss. Is preferred. On the other hand, when the plate thickness t of the base metal 11 is less than 0.10 mm, it may be difficult to thread the annealing line due to the small plate thickness. Therefore, the plate thickness t of the base metal 11 in the non-oriented electrical steel sheet 10 is preferably 0.10 mm or more and 0.40 mm or less. The plate thickness t of the base metal 11 in the non-oriented electrical steel sheet 10 is more preferably 0.15 mm or more and 0.35 mm or less.

The base metal 11 of the non-oriented electrical steel sheet 10 according to the present embodiment has been described above in detail.

<About insulation film>
Next, the insulating coating 13 that the non-oriented electrical steel sheet 10 according to this embodiment preferably has will be briefly described.

In order to improve the magnetic properties of the non-oriented electrical steel sheet, it is important to reduce the iron loss, and the iron loss is composed of eddy current loss and hysteresis loss. By providing the insulating coating 13 on the surface of the base metal 11, it is possible to suppress the conduction between the electromagnetic steel sheets laminated as the iron core and reduce the eddy current loss of the iron core. It is possible to further improve various magnetic characteristics.

Here, the insulating coating 13 according to this embodiment is not particularly limited as long as it is used as an insulating coating of a non-oriented electrical steel sheet, and a known insulating coating can be used. As such an insulating coating, for example, a composite insulating coating mainly containing an inorganic substance and further containing an organic substance can be mentioned. Here, the composite insulating coating is mainly composed of, for example, at least one of an inorganic substance such as a metal salt of chromate, a metal salt of phosphoric acid or colloidal silica, a Zr compound, and a Ti compound, in which fine particles of an organic resin are dispersed. It is an insulating film. In particular, from the viewpoint of reducing the environmental load at the time of manufacturing, which has been in increasing demand in recent years, a metal phosphate, a coupling agent of Zr or Ti, or an insulating coating using a carbonate or ammonium salt of these as a starting material. It is preferably used.

Here, the adhesion amount of the insulating coating 13 as described above is not particularly limited, but for example, it is preferable to be about 0.1 g/m ² or more and 2.0 g/m ² or less per one side, and More preferably, it is 0.3 g/m ² or more and 1.5 g/m ² or less. By forming the insulating coating 13 so as to have such an adhesion amount, it becomes possible to maintain excellent uniformity. When the amount of the insulating coating 13 adhered is measured afterwards, various known measuring methods can be used. The amount of the insulating coating 13 adhered is, for example, the non-oriented electrical steel sheet 10 on which the insulating coating 13 is formed is immersed in a hot alkaline solution to remove only the insulating coating 13, and the mass difference before and after the removal of the insulating coating 13 It is possible to calculate from.

<Measurement method of magnetic properties of non-oriented electrical steel sheet>
The non-oriented electrical steel sheet 10 according to the present embodiment has excellent magnetic properties by having the above structure. Here, various magnetic properties exhibited by the non-oriented electrical steel sheet 10 according to the present embodiment include Epstein's method defined in JIS C2550 and single sheet magnetic property measurement method (SST) defined in JIS C2556. ), it is possible to measure.

The non-oriented electrical steel sheet 10 according to the present embodiment has been described above in detail with reference to FIG.

(About manufacturing method of non-oriented electrical steel sheet)
Subsequently, a method for manufacturing the non-oriented electrical steel sheet 10 according to the present embodiment as described above will be briefly described with reference to FIG.
FIG. 2 is a flow chart showing an example of the flow of the method for manufacturing a non-oriented electrical steel sheet according to this embodiment.

In the method for manufacturing the non-oriented electrical steel sheet 10 according to the present embodiment, hot rolling, hot-rolled sheet annealing, pickling, cold rolling, and finishing are performed on the steel ingot having the predetermined chemical composition as described above. Annealing is performed in order. When the insulating coating 13 is formed on the surface of the base metal 11, the insulating coating is formed after the finish annealing. Hereinafter, each step performed in the method for manufacturing the non-oriented electrical steel sheet 10 according to the present embodiment will be described in detail.

<Hot rolling process>
In the method for manufacturing a non-oriented electrical steel sheet according to the present embodiment, first, a steel ingot (slab) having the above chemical composition is heated, and hot rolling is performed on the heated steel ingot to obtain a hot rolled sheet. (Step S101). Here, the heating temperature of the steel ingot when it is subjected to hot rolling is not particularly specified, but is preferably 1050°C to 1300°C, for example. Further, the plate thickness of the hot rolled plate after hot rolling is not particularly specified, but considering the final plate thickness of the base steel, it is preferably about 1.6 mm to 3.5 mm, for example. .. The hot rolling step is preferably completed while the temperature of the steel sheet is in the range of 700°C to 1000°C. The heating temperature of the steel ingot is more preferably 1050°C to 1250°C, and the end temperature of the hot rolling is more preferably 750°C to 950°C.

<Hot rolled sheet annealing process>
After the hot rolling, hot rolled sheet annealing is performed (step S103). In the case of continuous annealing, the hot-rolled steel sheet is annealed by soaking at 750°C to 1200°C for 10 seconds to 10 minutes, for example. Further, in the case of box annealing, the hot-rolled steel sheet is annealed by soaking at 650°C to 950°C for 30 minutes to 24 hours. Although the magnetic properties are inferior to the case where the hot-rolled sheet annealing process is performed, the hot-rolled sheet annealing process may be omitted for cost reduction.

<Pickling process>
After the hot rolled sheet annealing, pickling is performed (step S105). As a result, the scale layer mainly composed of the oxide formed on the surface of the steel sheet by the hot rolled sheet annealing is removed. When the hot rolled sheet annealing is box annealing, the pickling step is preferably performed before the hot rolled sheet annealing from the viewpoint of descaling.

<Cold rolling process>
After the pickling (when the hot-rolled sheet annealing is performed by box annealing, it may be after the hot-rolled sheet annealing step), cold rolling is performed (step S107). In such cold rolling, the scale-removed pickled plate is rolled at a reduction rate such that the final plate thickness of the base metal is 0.10 mm or more and 0.40 mm or less.

<Finishing annealing process>
After the cold rolling, finish annealing is performed (step S109). In the method for manufacturing a non-oriented electrical steel sheet according to this embodiment, the heating process of the finish annealing is rapid heating. By rapidly heating in the temperature rising process, a recrystallized texture advantageous for magnetic properties is formed in the base iron 11, and the average crystal grain size of the base iron 11 described above is realized. Therefore, in the method for manufacturing a non-oriented electrical steel sheet according to this embodiment, such finish annealing is performed by continuous annealing.

Specifically, in the heating process, the average heating rate is set to 1° C./sec to 2000° C./sec, and the atmosphere is a mixture of H ₂ and N ₂ in which the proportion of H ₂ is 10% by volume to 100% by volume. It is preferable to set the atmosphere (that is, H ₂ +N ₂ =100% by volume) and set the dew point of the atmosphere to 30° C. or lower. The average heating rate is more preferably 5°C/sec to 1000°C/sec, the proportion of H _{2 in} the atmosphere is more preferably 20% to 90% by volume, and the dew point of the atmosphere is The temperature is more preferably 20°C or lower, and further preferably 10°C or lower. The above average heating rate may be, for example, direct heating or indirect heating using a radiant tube in the case of heating by gas combustion, or other known heating methods such as electric heating or induction heating. Therefore, it can be realized.

In the soaking process, the soaking temperature is 700° C. to 1100° C., the soaking time is 1 second to 300 seconds, and the atmosphere is H ₂ and N in which the proportion of H ₂ is 10% by volume to 100% by volume. _It is preferable to set the mixed atmosphere of ₂ (that is, H ₂ +N ₂ =100% by volume) and set the dew point of the atmosphere to 20° C. or lower. The soaking temperature is more preferably 750° C. to 1050° C., the proportion of H _{2 in} the atmosphere is more preferably 20% by volume to 90% by volume, and the dew point of the atmosphere is more preferably 10%. ℃ or less, more preferably 0 ℃ or less.

In the cooling process, the average cooling rate is preferably 1°C/sec to 50°C/sec. The average cooling rate is more preferably 5°C/sec to 30°C/sec.

The non-oriented electrical steel sheet 10 according to the present embodiment can be manufactured through the above-described steps.

<Insulating film forming step>
After the finish annealing, an insulating film forming step is carried out if necessary (step S111). Here, the step of forming the insulating coating is not particularly limited, and the coating and drying of the processing liquid may be performed by a known method using the above-described known insulating coating liquid.

The surface of the base metal on which the insulating coating is formed may be subjected to any pretreatment such as degreasing treatment with alkali or pickling treatment with hydrochloric acid, sulfuric acid, phosphoric acid or the like before applying the treatment liquid. Alternatively, the surface may be as it is after finish annealing without performing these pretreatments.

The method for manufacturing the non-oriented electrical steel sheet according to this embodiment has been described above in detail with reference to FIG.

Hereinafter, the non-oriented electrical steel sheet according to the present invention will be specifically described with reference to Examples and Comparative Examples. The examples described below are merely examples of the non-oriented electrical steel sheet according to the present invention, and the non-oriented electrical steel sheet according to the present invention is not limited to the following examples.

(Experimental example 1)
A steel slab containing the composition shown in Table 1 below and the balance being Fe and impurities was heated to 1150° C. and then hot-rolled to a thickness of 2.0 mm. Subsequently, the hot-rolled sheet was annealed at 1000° C. for 40 seconds in a continuous annealing type, and then cold-rolled to a thickness of 0.25 mm, and finish annealing was performed at 1000° C. for 15 seconds. After that, a non-oriented electrical steel sheet was manufactured by further applying a solution containing an acrylic resin emulsion mainly containing metal phosphate and baking it on both sides of the steel sheet to form a composite insulating coating.

Here, the finish annealing was performed in an atmosphere with an atmospheric dew point of −30° C. and an H ₂ ratio of 20%. Further, the average heating rate and the average cooling rate during the finish annealing were set to 20° C./sec and 20° C./sec, respectively.

In Table 1 below, “Tr” means that the corresponding element was not intentionally added. In addition, in Table 1 below, “*” indicates that it is outside the scope of the present invention.

Then, with respect to each manufactured non-oriented electrical steel sheet, the magnetic flux density B ₅₀ and the iron loss W _10/400 were evaluated by the Epstein method specified in JIS C2550. The obtained results are also shown in Table 1 below.

Also, for the base iron of the obtained non-oriented electrical steel sheet, the average cross-sectional area of the crystal grains was obtained by the cutting method described in the JIS G0552 steel ferrite grain size test method, and the diameter of a circle equivalent to the obtained area Was defined as the average crystal grain size. The obtained results are also shown in Table 1 below.

As is clear from Table 1 above, Test Nos. 3 and 4 in which the P content is higher than the range of the present invention and Test No. 12 in which the Si content is higher than the range of the present invention, Since it broke during cold rolling, magnetic measurement could not be performed. Further, Test Nos. 1, 2, 5, 6, 8, 9, 10, and 13 in which the chemical composition and average crystal grain size of the steel sheet are within the scope of the present invention, cold rolling is possible, and iron loss is also excellent. I found out that On the other hand, sol. Test number 7 in which the content of Al deviates from the scope of the present invention to a high degree is sol. It was found that the iron loss was inferior to the test numbers 5 and 6 in the range of the present invention, which had almost the same composition except for Al. Further, it was found that Test No. 11, in which the Mn content and the Si-0.5×Mn content were out of the range of the present invention, had poor core loss and magnetic flux density.

(Experimental example 2)
A steel slab containing the composition shown in Table 2 below and the balance being Fe and impurities was heated to 1160° C. and then hot-rolled to a thickness of 2.0 mm. Subsequently, the hot-rolled sheet was annealed at 1000° C. for 40 seconds by continuous annealing, and then cold-rolled to a thickness of 0.25 mm, and finish annealing was performed for 15 seconds at three soaking temperatures. After that, a non-oriented electrical steel sheet was manufactured by further applying a solution containing an acrylic resin emulsion mainly containing metal phosphate and baking it on both sides of the steel sheet to form a composite insulating coating. Regarding the soaking temperature of finish annealing, test number 14 is 1000°C, test number 15 is 1050°C, and test number 16 is 1120°C.

Here, the finish annealing was performed in an atmosphere with an atmosphere dew point of −20° C. and an H ₂ ratio of 30%. Further, the average heating rate and the average cooling rate during the finish annealing were set to 30° C./sec and 20° C./sec, respectively.

Further, in Table 2 below, “Tr” indicates that the corresponding element was not intentionally added. In addition, in Table 2 below, “*” indicates that it is outside the scope of the present invention.

Then, with respect to each manufactured non-oriented electrical steel sheet, the magnetic flux density B ₅₀ and the iron loss W _10/400 were evaluated by the Epstein method specified in JIS C2550. The obtained results are also shown in Table 2 below.

Also, for the base iron of the obtained non-oriented electrical steel sheet, the average cross-sectional area of the crystal grains was obtained by the cutting method described in the JIS G0552 steel ferrite grain size test method, and the diameter of a circle equivalent to the obtained area Was defined as the average crystal grain size. The obtained results are also shown in Table 2 below.

As is clear from Table 2 above, it was found that test numbers 14 and 15 in which the chemical composition and average crystal grain size of the steel sheet are within the range of the present invention have excellent iron loss. On the other hand, it was found that the test number 16 in which the average crystal grain size was out of the range of the present invention was inferior in iron loss and magnetic flux density.

(Experimental example 3)
A steel slab containing the composition shown in Table 3 below and the balance being Fe and impurities was heated to 1100° C. and then hot-rolled to a thickness of 1.8 mm. Next, the hot-rolled sheet was annealed at 820° C. for 10 hours by a box-annealing type hot-rolled sheet, and then cold-rolled to a thickness of 0.20 mm, and finish annealing was performed at 1000° C. for 15 seconds. After that, a non-oriented electrical steel sheet was manufactured by further applying a solution containing an acrylic resin emulsion mainly containing metal phosphate and baking it on both sides of the steel sheet to form a composite insulating coating.

Here, the finish annealing was performed in an atmosphere with an atmosphere dew point of −15° C. and an H ₂ ratio of 25%. Further, the average heating rate and the average cooling rate during the finish annealing were set to 30° C./sec and 20° C./sec, respectively.

Further, in Table 3 below, “Tr” means that the corresponding element was not intentionally added. In addition, in Table 3 below, “*” indicates that it is outside the scope of the present invention.

Then, with respect to each manufactured non-oriented electrical steel sheet, the magnetic flux density B ₅₀ and the iron loss W _10/400 were evaluated by the Epstein method specified in JIS C2550. The obtained results are also shown in Table 3 below.

Also, for the base iron of the obtained non-oriented electrical steel sheet, the average cross-sectional area of the crystal grains was obtained by the cutting method described in the JIS G0552 steel ferrite grain size test method, and the diameter of a circle equivalent to the obtained area Was defined as the average crystal grain size. The obtained results are also shown in Table 3 below.

As is clear from Table 3 above, it was found that Test No. 17, in which the chemical composition of the steel sheet was within the range of the present invention, showed an excellent iron loss value. On the other hand, in Test No. 18 in which the amount of Mn deviates from the range of the present invention, the magnetic flux density is excellent because the amount of alloy is low, but iron loss, which is the most important characteristic, is inferior. Note that Experimental Example 3 is an experimental example in which the iron loss is smaller because the electromagnetic steel sheet is thinner and the eddy current loss is smaller than in Experimental Examples 1 and 2 above. Referring to Experimental Example 3, it can be seen that the non-oriented electrical steel sheet according to the embodiment of the present invention can obtain an excellent iron loss value regardless of the sheet thickness.

The preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, but the present invention is not limited to these examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

10 Non-oriented electrical steel sheet 11 Base iron 13 Insulating coating

Claims (2)

In mass %,
C: over 0% to 0.0050% or less Si: 3.0% to 4.0%
Mn: 2.0% to 3.3%
P: more than 0% to less than 0.030% S: more than 0% to 0.0050% or less Sol. Al: more than 0% to 0.0040% or less, N: more than 0% to 0.0040% or less,
Si-0.5 x Mn: 2.0% or more, the balance being Fe and impurities,
A non-oriented electrical steel sheet having an average crystal grain size of 55 μm to 200 μm. Instead of part of the remaining Fe,
Sn: 0.005% to 0.10%
Sb: 0.005% to 0.10%
The non-oriented electrical steel sheet according to claim 1, containing at least one selected from the group consisting of:

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