CN1520464A - Nonoriented electromagnetic steel sheet - Google Patents

Abstract

The present invention provides a non-oriented electrical steel sheet containing: 0-0.010% of C; at least one of Si and Al in a total amount of 0.03% to 0.5%, or more than 0.5% to 2.5%; 0.5% or less of Mn; 0.10% or more to 0.26% or less of P; 0.015% or less of S; and 0.010% or less of N, on a mass percentage basis, wherein the non-oriented electrical steel sheet has excellent dimensional accuracy during a punching step. When the Si content is low, the non-oriented electrical steel sheet has the excellent balance between high magnetic flux density and low core loss. When the Si content is medium or high, the non-oriented electrical steel sheet has the excellent balance between high magnetic flux density and high strength.

Description

Non-oriented electromagnetic steel sheet and method for producing same

Technical Field

The present invention relates to a non-oriented electrical steel sheet used as an iron core material for electric appliances. In particular, the present invention relates to a non-oriented electrical steel sheet which is required to have both high punching dimensional accuracy and high magnetic flux density and is suitable as an iron core material for a reluctance motor, an embedded magnet type DC brushless motor, or the like, which is required to have a high strength, and a method for producing the same.

Background

Non-oriented electrical steel sheets are soft magnetic materials mainly used as iron core materials for electric appliances such as motors and transformers. In order to improve efficiency and reduce size of these electric appliances, an electrical steel sheet is required to have a low iron loss and a high flux density. In the field of electric motors, improvement of magnetic properties of electromagnetic steel sheets of core materials, that is, reduction of iron loss and increase of magnetic flux density, is advanced, and replacement of a synchronous motor with higher efficiency and higher performance are rapidly advanced from a conventional asynchronous AC induction motor as well as an electric motor itself.

Synchronous motors are generally classified into DC brushless motors of surface magnet type (SPM) and interior magnet type (IPM), reluctance motors of reluctance torque generated by the apparent polarity of the magnetism of a rotor and a stator, and the like. In the case of a reluctance motor, the amount of torque generated depends on the shapes of the rotor and stator, the gap between the rotor and stator, and the magnetic flux density of the material. Therefore, the core material for the reluctance motor is required to have high magnetic homogeneity and high die cutting accuracy, and is more important than other motors.

Further, as the frequency conversion progresses, the number of poles tends to increase at the same time as the high-speed rotation is performed in order to improve the motor efficiency, torque, and the like. These are factors for increasing the operating frequency, and therefore, it is becoming necessary to improve not only the magnetic properties at the conventional commercial frequency (50 to 60Hz) but also the magnetic properties in the high frequency range of 400Hz or more for the non-oriented electrical steel sheet as a motor material.

Conventionally, various attempts have been made to improve the magnetic flux density and the iron loss of the non-oriented electrical steel sheet as described above.

In order to reduce the iron loss of a non-oriented electrical steel sheet, a method of increasing the Si content is common, and for example, Si is added to the highest-grade non-oriented electrical steel sheet by about 3.5 mass%. However, as the Si content increases, the magnetic flux density is also reduced while the iron loss is surely reduced.

On the other hand, in a low-grade non-oriented steel sheet, a high magnetic flux density can be obtained because the Si content is controlled, but there is a problem that the iron loss is high.

As a method for improving the iron loss of such low Si steel, japanese patent application laid-open No. 62-267421 proposes a technique for reducing and detoxifying inclusions, which are factors inhibiting the growth of crystal grains, by limiting the amount of impurities, so-called C, S, N and O, in a non-oriented electrical steel sheet having an Si content of 0.6 mass% or less and an Al content of 0.15 to 0.60 mass%, thereby promoting the growth of crystal grains and achieving a low iron loss. However, since the grain growth of these low Si steels involves a decrease in strength, there are problems such as a sag in the die cutting surface during the die cutting process and a significant decrease in the die cutting performance due to a large burr.

Further, as a method for improving the punching formability by adjusting the hardness of the low-Si steel, there is a technique of adding P in an amount of about 0.08 to 0.1 mass%, and for example, in japanese unexamined patent publication No. 56-130425, a technique of improving the punching formability by adding P less than 0.2 is disclosed. Further, as a technique for efficiently adding P to a low-Si steel, Japanese unexamined patent publication No. 2-66138 discloses a method for improving magnetic properties by the effect of polymerization of Al and P by adding 0.1 to 0.25 mass% of P to an Al-added steel containing Al in the range of 0.1 to 1.0 mass% and controlling the amount of Si to 0.1 mass% or less.

However, in these techniques, improvement of the punching formability by adding P is only aimed at controlling the sag of the steel sheet by adjusting the hardness, and no consideration is given to the dimensional accuracy after punching.

On the other hand, in the embedded magnet type DC brushless motor, punching accuracy and high magnetic flux density are required from the viewpoint of high torque and miniaturization, but further, in order to be suitable for high-speed rotation of the rotor or to prevent separation of the embedded magnet, it is necessary to maintain high strength of the electromagnetic steel plate. As described above, high-grade Si steel is also advantageous from the viewpoint of strength, but it is desired to achieve low Si from the viewpoint of magnetic flux density, and both strength and magnetic flux density are difficult to achieve.

Disclosure of Invention

As described above, the high magnetic flux density and the low iron loss in the non-oriented electrical steel sheet are common characteristics desired for all uses of the non-oriented electrical steel sheet such as various motors and transformers, and particularly, the high magnetic flux density and the high dimensional accuracy are important factors in the operation principle of the material, particularly, the material for the reluctance motor type non-oriented electrical steel sheet.

However, a non-oriented electrical steel sheet having excellent magnetic properties, i.e., high magnetic flux density and low iron loss, and having punching properties, particularly dimensional accuracy in punching, has not been found. Further, in addition to these properties, a non-oriented electrical steel sheet satisfying the strength requirements required for an embedded magnet type DC brushless motor or the like has not been found.

Further, in addition to these magnetic properties and punching properties, it is not found that a non-oriented electrical steel sheet which can cope with high-speed rotation and high-frequency shift accompanying multi-polarization of a recent motor is also available.

The present invention has been made in view of the above-described state of the art, and an object thereof is to provide a core material for a motor, a rotor, or the like, and particularly,

a non-oriented electrical steel sheet having a magnetic balance of high magnetic flux density to low iron loss which is most suitable, and yet excellent in punching dimensional accuracy, as an iron core material of a reluctance motor having particularly high magnetic flux density and high dimensional accuracy, and,

an electromagnetic steel sheet having both high magnetic flux density, high-speed rotation of a rotor, and prevention of scattering of embedded magnets, which are important high-strength characteristics, and punching accuracy,

and an advantageous manufacturing method.

Hereinafter, for convenience, a steel in which the sum of Si and Al is about 0.03 mass% or more and 0.5 mass% or less will be referred to as a low Si steel, and a steel in which the sum of Si and Al exceeds 0.5 mass% will be referred to as a medium to high Si steel.

As a result of earnest studies to achieve the above object, the present inventors have found that not only excellent magnetic properties with high magnetic path density and low iron loss can be obtained but also punching dimensional accuracy can be remarkably improved by reducing the amounts of Si and Al to a low Si steel grade to essentially obtain a steel with a high saturation magnetic flux density, adjusting the average crystal grain size to a predetermined range, and adding an appropriate amount of P. Further, it is also found that the total of Si and Al is controlled in the range of 0.5 mass% or more to about 2.5 mass%, and that addition of a proper amount of P can improve the effect of dimensional accuracy of punching accuracy and greatly improve strength while maintaining magnetic flux density, thereby achieving an unprecedented balance between magnetic properties and strength.

The present invention is based on the above findings.

That is, the gist of the present invention is as follows.

1. A non-oriented electrical steel sheet having excellent magnetic properties and punching accuracy, characterized by comprising, in mass%,

C：0～0.010％

si and/or Al: 0.03% to 0.5% in total,

mn: the content of the active ingredients is less than 0.5 percent,

p: more than 0.10 percent and less than 0.26 percent,

s: less than 0.015% and

n: 0.010% or less

The balance being Fe and inevitable impurities, and

average crystal particle size: 30 to 80 μm.

2. The non-oriented electrical steel sheet having excellent magnetic properties and punching accuracy as set forth in the above item 1, wherein the steel sheet further comprises, in mass percent

Sb and/or Sn: the total content is less than 0.40%.

3. The non-oriented steel sheet having excellent magnetic properties and punching accuracy according to 1 or 2 above, wherein the steel sheet further comprises, in mass percent

Ni: 2.3% or less.

4. The non-oriented steel sheet having excellent magnetic properties and punching accuracy according to 1, 2 or 3, wherein the steel sheet has a thickness of 0.35mm or less.

5. An electromagnetic steel sheet excellent in magnetic characteristics and punching accuracy, characterized by containing, in mass percentage, an electromagnetic steel sheet

C：0～0.010％，

Si and/or Al: 0.5 to 2.5 percent in total,

mn: the content of the organic acid is less than 0.5,

p: more than 0.10 percent and less than 0.26 percent,

s: less than 0.015% of the total weight of the composition,

n: 0.010% or less, and, if necessary

Ni: less than 2.3%, and,

satisfies an index P represented by the following formula_A：

P_A＝-0.2×Si+0.12×Mn-0.32×Al+0.5×Ni²+0.10×Ni+0.36……(1)

(wherein the unit of the content of each element is% by mass; the same applies to the formula (2))

And the content of P is in such a relationship that,

P≤P_A，

or, an index P represented by the following formula_F：

P_F＝-0.34×Si+0.20×Mn-0.54×Al+0.24×Ni²+0.28×Ni+0.76…(2)，

P_F≤0.26

In the above-mentioned manner, the first and second,

the balance being Fe and unavoidable impurities.

6. The non-oriented steel sheet having excellent strength, magnetic properties and punching accuracy as set forth in the above 5, wherein the steel sheet further comprises

Sb and/or Sn: the total content is less than 0.40%.

In the above steel grades, as the minor element, Ca: 0.01% or less, B: 0.005% or less, Cr: 0.1% or less, Cu: 0.1% or less, Mo: 0.1% or less of at least one of the above compounds.

7. A method for producing a non-oriented steel sheet having magnetic properties and punching accuracy, characterized in that a slab comprising the above-mentioned composition of any one of 1 to 3 is hot-rolled under conditions of a heating temperature of an austenite single-phase region and a coil winding temperature of 650 ℃ or less, then is subjected to a descaling treatment, then is subjected to a cold rolling for 1 time or 2 times or more including an intermediate annealing, and then is subjected to a final annealing in a ferrite single-phase region of 700 ℃ or more.

8. A method for producing a non-oriented steel sheet having magnetic properties and punching accuracy, characterized in that a steel sheet comprising the above-mentioned components of any one of 1 to 3 is hot-rolled, then the hot-rolled sheet is annealed under conditions of a heating temperature of an austenite single-phase region and a coil winding temperature of 650 ℃ or less, and when the Ni content is 0% (no addition) to 1.0 mass%, the hot-rolled sheet is annealed in a ferrite single-phase region or Ac of 900 ℃ or more₃In the austenite single-phase region of not less than the above point, and when the Ni content exceeds 1.0 mass% and is not more than 2.3 mass%, Ac is included₃In an austenite single phase region of more than one point, then subjected to descaling, and then subjected to 1-time or 2-time or more cold annealing including intermediate annealingAfter rolling, final annealing is performed in a ferrite single-phase region of 700 ℃ or higher.

9. A method for producing a non-oriented steel sheet having excellent strength, magnetic properties and punching accuracy, characterized in that the above-mentioned 5 or 6 steel slab is hot-rolled at a hot-rolling heating temperature of 1000 to 1200 ℃ and a hot-rolling coiling temperature of 650 ℃ or less, then is descaled, and then is cold-rolled 1 time or 2 times or more including intermediate annealing, and then is finish-annealed.

In the method for producing an electrical steel sheet of the above 9, hot rolling may be followed by hot-rolled sheet annealing.

In the method for producing an electrical steel sheet of any one of 7, 8, or 9, the treatment for forming an insulating coating may be performed after the final annealing.

Drawings

FIG. 1 is a graph showing the influence of Si content and P content on the relationship between yield strength and piercing diameter.

Fig. 2 is a graph showing the influence of the Si content and the P content relating to the relationship between the yield strength and the die cutting anisotropy.

FIG. 3 is a graph showing the influence of Si content and P content on the relationship between the average crystal grain size and the punching diameter.

FIG. 4 is a graph showing the influence of the Si content and the P content on the relationship between the average crystal grain size and the die cutting anisotropy.

FIG. 5 is a graph showing the influence of the Si content and the P content on the relationship between the average crystal grain size and the iron loss.

FIG. 6 is a graph showing the influence of the Si content and the P content on the relationship between the average crystal grain size and the magnetic flux density.

Fig. 7 is a graph showing the influence of the Si content and the P content on the relationship between the iron loss and the magnetic flux density.

Fig. 8 is a graph showing the influence of the Si content and the P content related to the generation of lamellar cracks.

Fig. 9 is a graph showing the influence of the Si content and the Ni content related to the generation of lamellar cracks.

FIG. 10 is a graph showing the influence of Si content and Ni addition on the relationship between P content and piercing diameter.

FIG. 11 is a graph showing the influence of the addition of Ni and the Si content, which relates to the relationship between the P content and the die cutting anisotropy.

Fig. 12 is a graph showing the influence of the P content relating to the relationship between the tensile strength and the magnetic flux density.

Fig. 13 is a graph showing a relationship between the sheet thickness and the high-frequency iron loss.

Fig. 14 is a graph showing a relationship between the sheet thickness and the magnetic flux density.

Detailed Description

The experimental results leading to the present invention are explained below. All of the following compositional percentages are expressed as "% by mass".

[ experiment 1]

First, in order to clarify the relationship between the steel composition and the blanking dimensional accuracy of a non-oriented electrical steel sheet, a steel sheet having a composition of C: 0.0016-0.0028%, Mn: 0.20 to 0.22%, Al: 0.0007-0.0014%, N: 0.0012-0.0022% and Sb: 0.03% of a substantially constant composition as a basic composition, and steels in which the P content was 0.02% and the Si content was varied from 0.03 to 1.49%, and steels in which the Si content was 0.11% and the P content was varied from 0.02 to 0.29% were respectively smelted in a laboratory. Then, these steels were heated at 1100 ℃ for 60min, and then hot-rolled to a thickness: 2mm, the coil was kept warm at 600 ℃ for 2 hours, and then naturally cooled. Then, the hot rolled sheet was annealed at 900 ℃ for 6 seconds, pickled, and cold rolled to a sheet thickness: after 0.5mm, final annealing is performed at various temperatures of 700 to 900 ℃ to change the grain size of the recrystallized grains. Thereafter, the final annealed plate was coated with an average film thickness: a0.6 μm semi-organic insulating film was used to prepare a baked sample for a punching test.

The average crystal grain size is an equivalent circle diameter obtained by observing a cross section in the thickness direction parallel to the rolling direction and by the Jeffries method.

Die cutting test, using diameter: a circular mold of 21mm was used, and the gap was 8% of the plate thickness. The punching diameter (inner diameter) in the 4 directions forming angles of 0 DEG, 45 DEG, 90 DEG and 135 DEG with the rolling direction was measured, and the average diameter of the 4 points was obtained, and the difference between the maximum diameter and the minimum diameter of the 4 points was measured as an index of the punching anisotropy.

The obtained results are shown in fig. 1 and 2, in which the relationship between the yield strength (YP) obtained from tensile test pieces (JIS No.5) cut in the rolling direction is shown.

As is clear from fig. 1 and 2, all the soft materials having a low YP tend to have a large difference in punching diameter with respect to the die diameter, and the punching diameter approaches the die size as the YP increases, thereby improving the dimensional accuracy. This is considered to be an effect of suppressing collapse deformation at the time of punching due to an increase in strength as conventionally known.

However, it should be noted here that the samples whose strength is adjusted by adding P exhibit excellent dimensional accuracy even in the same level of strength as the conventional electromagnetic steel sheets whose strength varies due to the variation in the amount of Si, and the dimensional difference from the die can be controlled even in a low YP region (fig. 1).

Further, in the steel with the changed Si content, the die cutting diameter is close to the die with the strength increase, and as shown in fig. 2, the anisotropy exhibited by the difference between the maximum diameter and the minimum diameter is still large. On the other hand, in the steel having an increased strength due to an increase in the amount of P, the anisotropy of the die-cut shape is also improved.

These relationships are adjusted to the relationship with the average grain size of the final annealed sheet, and fig. 3 and 4 show the relationship.

As is clear from fig. 3 and 4, the steel with the Si content changed is inferior in blanking dimensional accuracy and blanking anisotropy when the grain size is large, and the steel with 0.13% or more of P added thereto is superior in blanking dimensional accuracy and blanking anisotropy even when the grain size is large.

The reason why the die cutting dimensional accuracy and die cutting anisotropy are effectively improved by containing a certain amount or more of P is not clear in detail, but,

(1) the strength is increased by adding P, the collapse deformation during punching is relieved,

(2) the effect of accelerating the fracture limit at the time of punching is accelerated by the addition of a suitable amount of P, which is a known embrittling element for steel, and

(3) the {100} < uvw > orientation tends to increase in the structure of the final annealed structure due to the addition of P, and this is considered to be a result of a combined action such as an effect of alleviating anisotropy.

Next, the results of the magnetic field studies will be described.

The inventors have made detailed studies on the relationship between the production conditions and the magnetic properties by using a steel having a high magnetic flux density as a material by limiting the contents of Si and Al, which reduce the saturation magnetic flux density and improve the iron loss, as much as possible.

Fig. 5 shows the plate thickness for each steel material: 0.5mm samples, the grain size of the final annealed sheets and the iron loss (W) in the commercial frequency domain were investigated_15/50: a frequency of 50Hz and a maximum magnetic flux density of 1.5T).

As is clear from the figure, low Si is disadvantageous in terms of the reduction of electric resistance, but since the iron loss increases depending on the crystal grain size, the iron loss can be stably reduced by making the grain size 30 μm or more. Further, it was confirmed that, when the electric resistance is reduced as low Al, similarly, it is effective to reduce the iron loss by making the particle size to about 30 μm or more.

However, in the case of a low-grade non-oriented electrical steel sheet made of low-Si and Al according to the present invention, the average grain size of the final annealed sheet is generally limited to about 15 to 25 μm. This is because, as shown in the example of 0.11% Si-0.07% P steel (● prints in the figure) in fig. 3 and 4, deterioration of punching formability due to strength reduction becomes remarkable when crystal grains are grown.

On the other hand, the steel with a higher P content can maintain good punching dimensional accuracy even if the average crystal grain size is about 30 μm or more.

Fig. 6 shows the relationship between the average crystal grain size and the magnetic flux density in each steel, and fig. 7 shows the results of examining the relationship between the iron loss and the magnetic flux density. Here, B₅₀The magnetic flux density was 5000A/m.

The sample containing Si improved the iron loss but the magnetic flux density was significantly reduced. In contrast, the sample containing P can maintain a high magnetic flux density even after the iron loss is improved by the growth of crystal grains.

However, P is an embrittlement element, and when P is added in a large amount as in the present invention, defects such as edge cracking and delamination occur mainly in the cold rolling step. The present inventors have studied and confirmed the fact that when the temperature at the time of heating the slab in the hot rolling process is in the ferrite/austenite coexisting region, P is distributed between ferrite grains and austenite grains, and segregation of P occurs significantly in the ferrite grains, thereby promoting embrittlement of the steel. In order to prevent such embrittlement, it is important in the production of the steel sheet of the present invention that the heating temperature of the slab used for hot rolling be changed to an austenite single-phase region (or ferrite single phase if possible).

Further, since P is a ferrite-forming element, it has an effect of narrowing the austenite single-phase region in the vicinity of the billet heating temperature, but in the range of the composition of the low Si steel, the billet heating temperature can be set to 1000 to 1200 ℃.

As described above, it is clear that the addition of P of about 0.1% or more to the low Si steel is very effective. Therefore, a method of effectively adding P also to a steel sheet containing 0.5% or more of Si is discussed.

[ experiment 2]

Smelting as C: 0.0013-0.0026, Mn: 0.18 to 0.23%, Al: 0.0001-0.0011%, N: 0.0020 to 0.0029% of a substantially stable component, heating various steels with Si content changed to 0.60 to 2.42 and P content changed to 0.04 to 0.29% at 1100 ℃ for 60 minutes, hot rolling to 2mm thickness, pickling, and cold rolling to 0.50mm thickness. As a result, a sheet-like fracture parallel to the sheet surface occurs in the steel sheet after rolling depending on the steel composition, and a defect occurs. The results are shown in FIG. 8.

After analyzing the lamellar fracture-occurring portion by EPMA transformation, it was observed that the fracture-occurring portion was a P-segregated or enriched portion. Therefore, the inventors have studied the P segregation condition in detail and found that P is distributed in the ferrite phase and concentrated in the 2-phase region, which is the ferrite and austenite phases, during the heating of the steel sheet (slab) in the hot rolling.

That is, it was found that in the medium to high steel regions, the austenite single phase region is further narrowed because of a large amount of Si and Al which are ferrite-forming elements, and as a result, the ferrite/austenite 2 phase region is likely to be formed at a conventional heating temperature.

When P exceeds 0.26%, layer fracture occurs even under any composition condition.

Therefore, steels having various amounts of Si, Mn, Al, and P were produced using a research facility, and the conditions for suppressing the segregation of P so as not to cause rolling defects in a temperature range of about 1000 to 1200 ℃. The above-mentioned billet heating temperature is a temperature suitable from the viewpoint of stabilizing the precipitation of carbides, nitrides, sulfides, etc. present in the steel.

First, under the condition that the billet heating temperature is in the austenite single-phase region or the ferrite single-phase region, since segregation due to phase partitioning does not occur, it is considered that if the value of the addition amount P is less than a predetermined amount, the lamellar fracture can be avoided. From the above experiment, it was necessary to reduce the amount of P added to about 0.26% or less.

Therefore, first, the conditions under which medium-to-high Si steel becomes an austenite single phase were examined.

As a result, in the steel containing more than 0.5% of Si + Al, if the amount of P added is,

P≤P_A', wherein

P_A’＝-0.2Si+0.12Mn-0.32Al+0.36……(1)’

(the contents of Si, Mn, Al and P are expressed in% by mass.)

In the austenite single-phase region. Therefore, if the above condition is satisfied and P is limited to about 0.26%, embrittlement by P can be suppressed.

Then, the conditions under which the medium-to-high Si steel became a ferrite single phase were examined, and the amount of P added was the same

If the number of the first-time period is greater than the second-time period,

P≤P_F', wherein

P_F’＝-0.34Si+0.20Mn-0.54Al+0.76……(2)’

(the contents of Si, Mn, Al and P are expressed in% by mass.)

In the ferrite single-phase domain. Therefore, if this condition is satisfied and P is limited to about 0.26%, embrittlement by P can be suppressed.

Then, when heating of the billet in the austenite single-phase region or the ferrite single-phase region was difficult, conditions for suppressing the segregation of P were investigated. When a distribution of P concentration is generated in the ferrite/austenite 2 phase region, P concentration in the ferrite phaseDegree also becomes the above-mentioned P_F', but the results of the investigation showed that P is equal to P_F' to about 0.26 or less, embrittlement by P can be avoided.

The conditions for preventing embrittlement in the 2-phase region and for preventing embrittlement in the ferrite single-phase region are summarized as P.ltoreq.0.26% and P_F'. ltoreq.0.26.

By summarizing the above relationship, the condition for avoiding embrittlement by P is such that P is not more than about 0.26%, and P is not more than P_A' or P_F'. ltoreq.0.26.

From the above results, it was found that when the amount of P added is within about 0.26%, and the conditions of heating in the austenite single phase or ferrite single phase region during hot rolling heating can be made such that defects such as layer cracking after cold rolling are eliminated, and further, even under the conditions of heating in the ferrite/austenite 2 phase, the composition having a low P distribution to the ferrite phase and high Si and Al contents can be made.

Further, various single-phase structure steels have been studied in which P is added in an amount of about 0.1% or more and becomes austenite or ferrite in a slab heating temperature range (around 1000 to 1200 ℃ C.) during hot rolling.

As a result, the addition of Ni, which is an element suitable for improving magnetic properties and securing strength, is also effective for the purpose of enlarging the austenite region in the vicinity of the hot rolling temperature in the P-added steel.

[ experiment 3]

Investigation was performed with C: 0.0013-0.0026%, Mn: 0.18 to 0.23%, Al: 0.0007-0.0013%, N: 0.0014-0.0025% and P: a cold-rolled steel sheet having a basic composition of approximately constant components of 0.16 to 0.18% and a state of occurrence of a layer fracture was obtained by rolling a sample having an Si content of 0.95 to 2.44% and an Ni content of 0 to 2.20% to 0.50mm in the same manner as in experiment 2. The results are shown in FIG. 9.

The 1.1-1.5% Si steel which is broken when Ni is not added can be cold rolled without breaking by adding Ni. On the other hand, it is found that the 1.95% Si steel and the 2.4% Si steel rolled without Ni addition are broken by the increase of Ni, and therefore the effect of Ni also has an appropriate range.

When the effect of Ni addition is expanded from the above formula, it is found that the amount of P added is about 0.26% or less in the steel containing Si + Al of more than 0.5%, and if it is

P≤P_AWherein

P_A＝-0.2Si+0.12Mn-0.32Al+0.05Ni²In the range of +0.10Ni +0.36 … … (1), the billet heating temperature is 1000 to 1200 ℃ in the austenite single phase region, and if it is in the austenite single phase region

P_FLess than or equal to about 0.26, and

P_F＝-0.34Si+0.20Mn-0.54Al+0.24Ni²+0.28Ni+0.76≤P……(2)

in the range of (3), the concentration of P is reduced even in the 2-phase domain or the ferrite single-phase domain, and embrittlement due to P can be avoided in any case.

In the above 2 formulae, the contents of Si, Mn, Al, P and Ni are expressed by mass%. Furthermore, P_FAnd P_AIn the technical sense of (1), with the aforementioned P_F' and P_A' same.

[ experiment 4]

The cold-rolled steel sheets rolled to 0.50mm in experiments 2 and 3 were subjected to finish annealing, and then coated with a semi-organic insulating film having an average thickness of 0.6 μm and baked. These samples were subjected to a die cutting test by the method described in experiment 1, and die cutting diameters and anisotropy thereof were examined, and the results are shown in fig. 10 and 11. According to these figures, even in the case of the steel containing Si + Al in an amount of more than 0.5%, the steel containing P.gtoreq.0.10% always exhibits excellent punching dimensional accuracy. Here, the amount of Ni added to the Ni-added steel varies from 0.38 to 2.20%.

Further, the magnetic flux density B of these samples was measured₅₀Relation to tensile Strength TSShown in fig. 12. Here, TS was obtained by a tensile test as in experiment 1, and the magnetic flux density was also measured by the method of experiment 1.

The steel containing about 0.1% or more of P exhibits excellent B content as compared with conventional medium to high Si content (i.e., Si + Al > 0.5%) electrical steel sheets₅₀-TS balancing. In particular, as the amount of P added increases, TS increases but the magnetic flux density does not decrease and tends to increase. This is because the strengthening of a steel sheet by addition of an alloy element other than Si or Al ferromagnetic bodies, which is generally performed for a conventional electrical steel sheet, is one of the properties that is associated with the decrease in magnetic flux density.

These characteristics are suitable for rotor materials of various rotating machines (motors, generators) such as DC brushless motors and reluctance motors which are required for high-torque, small-size, and high-speed rotation of motors.

From the above findings, as conditions for compatibility of excellent magnetic flux density and punching dimensional accuracy, the average crystal grain size of the final annealed sheet is defined in the following range in the case of Si, Al, P, and Ni contents in the steel, and further in the case of low Si steel. In the case of low-Si steel, the total of 1 or 2 types of Si and Al: about 0.03 to 0.5%.

Since Si and Al have a deoxidizing effect when added to steel, they are used alone or in combination as a deoxidizing agent. To exert the effect, it is necessary that Si and Al be each alone or the total of both be about 0.03% or more. Further, Si and Al also have the effect of increasing the resistivity to improve the iron loss, but on the other hand, they cause a decrease in the saturation magnetic flux density, so that the upper limit thereof is set to 0.5%. In the case of medium to high Si steels, the total of 1 or 2 types of Si and Al: 0.5% over to about 2.5%

When the mechanical strength and the low iron loss are important as well as the excellent dimensional accuracy, the total amount of Si + Al may be more than 0.5%. As described above, in the case of the medium to high Si steel, a material having a high die-cutting diameter and a strength-magnetic flux density balance can be obtained by the effect of the addition of P as compared with the conventional low P medium to high Si steel. However, if the total amount of Si + Al exceeds 2.5%, it is difficult to perform ordinary cold rolling by the method of the present invention, and therefore the range is defined as 0.5% to about 2.5%.

p: more than about 0.10% and less than about 0.26%

P, which is an especially important element in the present invention. P has a function of adjusting the hardness of the material according to its high solid solution strengthening ability, as is known from the past. Particularly, low Si and low Al steel sheets are inherently soft, but in the present invention, it is necessary to reduce the average grain size to about 30 μm or more for the purpose of reducing the iron loss, and therefore the steel sheets may be further softened. P, improvement of the blanking property of the steel sheet of the present invention, and suppression of the increase of the indentation and the burr caused by the insufficient strength of the steel sheet are essential elements. In addition to such an increase in material strength, the punching dimensional accuracy is improved by a combined action of accelerating the fracture limit at the time of punching, suppressing the total deformation amount at the time of punching, increasing the {100} < uvw > orientation in the structural structure of the final annealed sheet, improving the anisotropy, and the like.

Further, the steel sheet has a property that the magnetic flux density is not lowered although the strength of the steel sheet is increased, and this effect is exerted also in medium to high Si steel.

To exert these effects, P needs to be contained by about 0.10 or more. On the other hand, P is originally an embrittlement element for steel, and if added excessively, it is liable to cause edge fracture and layer fracture, thereby deteriorating the manufacturability. In this regard, in the present invention, by devising the manufacturing method or adding Ni, it is possible to manufacture high P-added steel which has been difficult in the past. However, if the content exceeds about 0.26%, it is difficult to produce the P-added steel even by the production method of the present invention, and therefore the amount of P is set to a range of about 0.10 to about 0.26%.

Ni: about 2.3% or less (optionally added)

Ni is effectively added because it has an effect of not only improving the structural structure of steel and increasing magnetic flux density, but also increasing the electrical resistance of steel and reducing the iron loss, and an effect of improving the strength of steel by solid solution strengthening and suppressing indentation at the time of punching.

Further, since Ni is an austenite forming element, Ni has an effect of expanding an austenite region (γ loop in a state diagram) in the vicinity of an appropriate slab heating temperature of 1000 to 1200 ℃. In particular, steel having a composition in which the Si + Al content is more than 0.5% is effective for increasing the operation stability. When this effect is flexibly applied, rolling instability caused when P is positively added as an embrittlement element in the present invention can be greatly improved. That is, the stable manufacturing point of high-quality steel is to control excessive P segregation during hot rolling, and an effective method thereof is to avoid the slab heating temperature from becoming the ferrite/austenite phase region. If the total content of Si and Al exceeds 0.5%, the phases are easily separated into 2 phases at the slab heating temperature, but in such Si and Al composition, the austenite single phase can be formed at the slab heating time due to the γ domain expansion effect of Ni.

However, if the Ni content exceeds about 2.3%, the ferrite (a) → austenite (γ) transformation start temperature decreases, so that austenite transformation may occur in the final annealing, resulting in a decrease in magnetic flux density. Further, in the low Si steel, it is difficult to secure an average grain size of about 30 μm or more at a low finish annealing temperature equal to or lower than the transformation temperature, and thus the iron loss is also deteriorated. Therefore, Ni content is 2.3% or less. When Ni is added, about 0.50% or more is preferably added.

In low Si steel, the average grain size of the final annealed sheet: in order to obtain good iron loss characteristics in the low-Si, low-Al non-oriented electrical steel sheet of the present invention, the average grain size of the final annealed sheet must be about 30 μm or more, as shown in FIG. 5. However, such an effect of improving the iron loss cannot be expected even if the grain size exceeds about 80 μm, and since the steel according to the present invention is a phase-change steel and the ferrite single-phase region suitable for recrystallization annealing is in the range of approximately 700 to 900 ℃, which is a low temperature as compared with a ferrite single-phase steel made of high Si, the excessive grain growth is disadvantageous in terms of productivity of a continuous short-time annealing facility, and therefore 80 μm is set as an upper limit.

Further, in the medium to high Si steel, since a low iron loss is easily obtained by an upward effect of electric resistance according to the alloy, the particle diameter is not limited intentionally, and may be in a normal range. Generally about 20 to 200 μm.

Then, the present inventors have studied a method for improving magnetic properties in a high frequency range, which has recently been emphasized, in association with high-speed rotation of a motor, an increase in the number of poles, and the like. As a result, the reduction in sheet thickness is effective, and the effect is particularly remarkable in low Si steel. Experiments to derive the results are described below.

[ experiment 5]

FIG. 13 shows the results of examining the plate thickness dependence of the iron loss at 400Hz for the 0.11% Si-0.18% P steel, the 0.95% Si-0.02% P steel, and the 2.0% Si-0.5% Al steel.

As shown in the figure, it is found that the eddy-current loss is reduced by the reduction of the plate thickness in any of the samples, and therefore, the high-frequency iron loss tends to be improved, and the effect of improving the high-frequency iron loss by the reduction of the plate thickness is more remarkable in the low-Si steel.

However, the thickness reduction of the non-oriented electrical steel sheet has been mainly performed at 0.50mm, and the above thickness reduction is applied only to a part of high-grade steel sheets having a high content of Si and Al as resistivity elements, and no product example has been found in which the non-oriented electrical steel sheet having a small content of Si and Al is applied.

Fig. 14 shows the results of an examination of the plate thickness dependence of the magnetic flux density of these blanks.

As shown in the figure, when the sheet thickness is reduced, the magnetic flux density tends to be slightly reduced, but the reduction is extremely small, and in any sheet thickness, the term of the low Si steel has an extremely high magnetic flux density. In particular, for applications such as drive motors for Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV), high-speed rotating reluctance motors have been studied, and in such applications, high magnetic flux density and low iron loss at high frequencies are considered important.

As shown in fig. 13, the effect of reducing the sheet thickness becomes remarkable when it becomes about 0.35mm or less, and more remarkable when it becomes about 0.30mm or less. Further, the lower limit of the plate thickness is not set because the thinner the plate thickness is, the more advantageous the eddy current loss is, but on the other hand, the more the number of steps of the magnetic core is increased to increase the cost, and the disadvantage that the overlapping of the laminated magnetic cores becomes difficult, etc., and therefore, it is desirable to set the lower limit to about 0.10mm in the case of general production.

The reasons for limiting the components other than Si, Al, P, and Ni in the present invention will be described below.

C: 0 to about 0.010%

C is an element that deteriorates the magnetic properties (iron loss) with time after the steel sheet is produced by the aging effect, and the C content is limited to 0.010% or less because the C content becomes significant when it exceeds about 0.010%. In the present invention, the C amount includes the case where the C amount is substantially zero (smaller than the analysis limit value), because the smaller the C amount is, the better the aging characteristics are.

Mn: about 0.5% or less

Mn and S are fixed as MnS, and have an effect of suppressing embrittlement in hot rolling caused by FeS. Furthermore, increasing resistivity improves iron loss as the Mn content increases. On the other hand, however, since an increase in the Mn content causes a decrease in the magnetic flux density, the upper limit of the Mn content is set to about 0.5%.

S: about 0.015% or less

S is an inevitable impurity, and when precipitated as FeS as described above, it not only causes hot rolling brittleness, but also deteriorates grain growth when precipitated as fine particles, so it is more advantageous to reduce the iron loss as much as possible. Further, since the iron loss is remarkably deteriorated when the S content exceeds about 0.015%, the upper limit thereof is set to about 0.015%. However, since S also has an effect of improving the shear surface shape at the time of punching, the degree of reduction is determined according to the application.

N: about 0.010% or less

N is an inevitable impurity, and is limited to about 0.010% or less because it deteriorates and inhibits grain growth of iron loss when AlN is finely precipitated.

While the essential components and the inhibiting components have been described above, in the present invention, the following elements may be appropriately contained as the magnetic component to be improved.

Sb and/or Sn: about 0.40% or less in total

Sb and Sn are localized in grain boundaries, and have an effect of improving magnetic flux density and iron loss by suppressing the generation of recrystallization nuclei from {111} orientation of the grain boundaries during recrystallization of steel. To obtain such an effect, the total content is required to be about 0.01% in either case of using alone or in combination. However, the effect of the excess content is saturated, and on the contrary, the content exceeding 0.40% causes breakage at the time of cold and hot rolling after embrittlement, so that the total content is required to be about 0.40% or less in both cases of use alone and use in combination.

Further minor, included elements are explained.

In the present invention, S, which is a deoxidizer and is present as an impurity, may be made to contain Ca in a range of about 0.01% or less as an element that effectively traps together with Mn. Further, about 0.005% or less of B and about 0.1% or less of Cr may be added to relieve oxidation and nitridation at the time of the straightening annealing.

In addition, the effect of the present invention is not impaired even if an element known as Cu or Mo is added as an element that does not deteriorate the magnetic properties, but the content of each element is preferably about 0.1% or less from the viewpoint of the addition cost.

For other components, carbonitride forming elements such as Ti, Nb, V, etc. may be allowed to contain a small amount, but the rare condition is advantageous for maintaining low iron loss.

In the medium to high Si, as described above, when the composition is designed to be a single phase of either the austenite phase or the ferrite phase or a 2-phase state of austenite/ferrite at the slab heating temperature, the distributed concentration amount of P to the ferrite phase in which P is easily concentrated is suppressed, and excessive local segregation of P is suppressed, so that the high P-containing steel can be stably manufactured.

Specifically, in order to suppress excessive local segregation of P at a plate heating temperature (about 1000 to 1200 ℃) suitable for stabilizing precipitation of carbides, nitrides, sulfides and the like present in steel,

index P represented by the following formula_A：

P_A＝-0.2Si+0.12Mn-0.32Al+0.05Ni²+0.10Ni+0.36……(1)

And P content, whether or not

P≤P_AEither the first or the second substrate is, alternatively,

an index P represented by the following formula_F：

P_F＝-0.34Si+0.20Mn-0.54Al+0.24Ni²+0.28Ni+0.76≤P…(2)

Is composed of

P_FLess than or equal to about 0.26

(the unit of Si, Mn, Al, Ni, P is% by mass.)

And more preferably. Where P is_AIn order to experimentally find a term of P content which is an upper limit of an austenite single phase in a temperature range of about 1000 to 1200 ℃ in various Si, Mn, Al, Ni compositions, P_FThe term of the P content which is the lower limit of the ferrite single phase is experimentally obtained.

Next, the production conditions of the present invention will be described.

The molten steel adjusted to have the appropriate composition is melted by a converter refining method, an electric furnace melting method, or the like, and then a billet is produced by a continuous casting method or a block-by-block rolling method.

This billet is then heated and subjected to hot rolling. Here, the billet heating temperature is preferably about 1000 to 1200 ℃. As described above, the phase state during billet heating is extremely important for suppressing excessive local segregation of P.

P is a ferrite-forming element and therefore has the effect of reducing the austenite single phase region in the vicinity of the billet heating temperature, but in the case of low Si steel, the billet heating temperature can be about 1000 to 1200 ℃ in the composition range of the present invention, and the austenite single phase is obtained. In the case of medium-to high-Si steels, if P.ltoreq.P is satisfied_AThe component (b) can be an austenite single phase at a billet heating temperature of about 1000 to 1200 ℃. Further, when the steel is a medium-to-high Si steel, P is satisfied_FWhen the composition is less than or equal to about 0.26, the ferrite phase is transformed into a ferrite/austenite coexisting region, and the segregation degree of P in the ferrite phase is maintained only at a level at which embrittlement is avoided. When heating is performed in a ferrite single-phase region, the ferrite single-phase region can be produced without layer fracture if the P content is within about 0.26%.

The coil coiling temperature after hot rolling is an important factor for ensuring the manufacturability of high-P steel in the present invention. That is, when the coil coiling temperature is high, iron phosphide (Fe) is generated during coil cooling₃P), the bendability and the drawability of the hot rolled sheet are reduced, and therefore, it is required to wind the sheet at as low a temperature as possible at a coil winding temperature of about 650 ℃ or less, preferably about 600 ℃ or less, and more preferably about 550 ℃ or less. Further, a method of cooling the coil at an accelerated speed by immersing the coil after winding in a water tank, or by spraying water or the like is also effective.

The hot-rolled coil is descaled by a method such as pickling and then subjected to cold rolling, but hot-rolled sheet annealing may be performed to further improve the magnetic properties.

Here, the total of the Si content and the Al content is 0.5% or less, and in the low Si steel, the annealing temperature of the hot-rolled sheet is preferably set so as to avoid the ferrite/austenite coexisting region (2-phase region). This is because it is difficult to grow crystal grains in the 2-phase region annealing, and the magnetic properties such as magnetic flux density cannot be improved. Hereinafter, the annealing temperature of the hot rolled sheet suitable for the low Si steel will be described with respect to the Ni content.

When Ni is not added to steel or Ni is less than 1.0% and Ni content is small, the non-oriented electrical steel sheet can be annealed in a ferrite single-phase region of about 900 ℃ or higher as in the case of annealing a hot-rolled sheet in a near-normal state. The annealing temperature may be set to a higher temperature so as to be in an austenite single-phase region (desirably around 1050 to 1100 ℃) which is not lower than the Ac3 point. It is important to avoid annealing in the phase domain which is the intermediate domain of both (especially around 950 ℃).

On the other hand, when the Ni content is large, the austenite formation temperature during annealing is lowered, and thus the phase becomes 2 phase region at an annealing temperature of about 900 ℃, and the magnetic flux density can be lowered. However, annealing at 900 ℃ or lower in the ferrite single-phase region is insufficient in grain growth property, and thus a sufficient magnetic flux density cannot be obtained. Therefore, the annealing conditions for the hot-rolled sheet in such a composition analysis are limited to an austenite single-phase region (desirably around 1050 to 1100 ℃) of the Ac3 point or higher.

In the case of medium to high Si steels, since low iron loss is easily obtained even with fine particles as described above, grain growth during annealing is less important than that of low Si steels. Therefore, the annealing temperature of the hot rolled sheet is not limited intentionally, but is preferably in the range of 700 to 1100 ℃.

Then, the obtained coil was descaled and then rolled 1 time in cold rolling or warm rolling, or rolled 2 times or more in cold rolling (or warm rolling) with intermediate annealing interposed therebetween, thereby completing the predetermined sheet thickness.

Then, final annealing is performed, but when the steel is low Si, such final annealing is performed in a ferrite single phase domain of 700 ℃ or more. The reason for this is that when the final annealing temperature is less than 700 ℃, it is difficult to stably grow the average grain size to about 30 μm or more, and when austenite is generated in excess of the ferrite single-phase region, the structure deteriorates, resulting in deterioration of the magnetic flux density and the iron loss.

In the case of medium to high Si steels, the final annealing temperature is not limited to a specific value because the grain growth during annealing is less important than that of low Si steels as described above, but is preferably in the range of 700 to 1100 ℃.

The structure of a steel sheet formed in advance by heating and water-cooling in various temperature ranges in the ferrite single-phase temperature range or the austenite single-phase temperature range of the hot-rolled sheet and the cold-rolled sheet can be determined by observation with an optical microscope or the like. Alternatively, as another method, the method may be according to Thermo-Calc^TMEtc. are estimated in advance by the calculation state diagram obtained by the thermodynamic calculation software.

After the final annealing, an insulating film can be added as in a general non-oriented electrical steel sheet. The method of adding is not particularly limited, but a method of applying the treatment liquid and then baking the applied treatment liquid is preferable.

The obtained coil stock is cut into a desired size and dimension, punched into shapes of the motor stator and the rotor by a user, and laminated to form a product. Or, according to specific conditions, after punching, performing deformation correction annealing (usually 750 ℃ multiplied by 1-2 h) to obtain the product.

(examples)

[ example 1]

Molten steel having a composition shown in table 1 was cast in a laboratory, and then hot rolled to have a thickness: 30mm of plate stock. Then, the steel sheet was heated at 1100 ℃ for 60min, and then hot-rolled to a sheet thickness: 2mm, uniformly heated at 600 ℃ for 2 hours, and then cooled in air. Then, the hot-rolled sheet was annealed at 950 ℃, pickled, cold-rolled to a thickness of 0.50mm (1-time cold rolling), and final annealed at various temperatures of 700 to 900 ℃ to change the recrystallized grain size to various values. Further, in the cold rolling, since steel J having a P content exceeding the range of the present invention undergoes many layer fractures parallel to the sheet surface during the cold rolling, the following treatment was stopped and no evaluation was performed.

No.56 to 59 were obtained by cold rolling with 2 cold rolling methods including intermediate annealing at 800 ℃ after hot rolling without hot-rolled sheet annealing.

Then, the final annealed plate obtained was fabricated with the average film thickness: a sample of a semi-organic insulating film of 0.6 μm was used for various tests.

Die cutting test, using diameter: 21mm phi was performed by using a circular mold, and the gap was 8% of the plate thickness. The diameter (inner diameter) of the punched circle in the 4 directions at angles of 0 °, 45 °, 90 °, and 135 ° to the rolling direction was measured, and the average diameter of the 4 points was determined. The difference between the maximum diameter and the minimum diameter at 4 points was taken out and used as an index of die cutting anisotropy.

Magnetic properties were measured according to the Ebbstein method using test pieces of a rectangular shape cut at 180mm × 30mm at 0 ° and 90 ° to the rolling direction.

The yield stress (YP) was measured by a tensile test at a speed of 10mm/min using a JIS5 test piece cut parallel to the rolling direction, and the upper yield point was used.

The results are shown in tables 2 and 3.

TABLE 1

Number of steel	Composition of ingredients (mass%)
										C	Si	Al	Mn	S	P	N	Sb	Sn
	A	0.0027	0.03	0.0008	0.21	0.0040	0.02	0.0015	0.030										＜0.001
B										0.0026	0.10	0.0008	0.22	0.0035	0.02	0.0020	0.032	＜0.001
	C	0.0019	0.53	0.0012	0.22	0.0023	0.02	0.0018	0.030										＜0.001
D										0.0019	0.95	0.0007	0.20	0.0033	0.02	0.0012	0.030	＜0.001
	E	0.0022	1.48	0.0014	0.21	0.0041	0.02	0.0022	0.033										＜0.001
F										0.0016	0.11	0.0015	0.20	0.0074	0.07	0.0019	0.030	＜0.001
	G	0.0017	0.11	0.0008	0.21	0.0036	0.13	0.0022	0.031										＜0.001
H										0.0023	0.11	0.0011	0.22	0.0022	0.18	0.0014	0.030	＜0.001
	I	0.0028	0.11	0.0006	0.22	0.0075	0.25	0.0018	0.031										＜0.001
J										0.0016	0.11	0.0014	0.21	0.0060	0.29	0.0016	0.032	＜0.001

TABLE 2

No.	Number of steel	Particle size (. mu.m)	B50(T)	W15/50(W/kg)	YP(MPa)	Punching diameter (mm)	Punching diameter Max-min (mum)	Remarks for note
									123456	A″″″″″	11.320.528.231.942.861.3	1.8181.8111.8071.8041.7971.785	9.796.855.905.455.094.62	311243214204182160	20.97920.96320.95920.95720.95220.950	172128292534	Comparative example "", FIGS
789101112	B″″″″″	10.820.326.831.546.278.2	1.8081.8061.8011.7961.7861.775	10.236.855.995.524.944.50	322249223210183152	20.98120.96820.96120.95920.95420.945	161418192326	Comparative example "", FIGS
									1314151617	C″″″″	9.316.033.659.478.9	1.7861.7821.7711.7641.757	10.957.575.224.434.25	375305236198183	20.98520.98020.97020.96420.957	914131731	Comparative example ""
181920212223	D″″″″″	12.223.527.242.855.564.9	1.7721.7671.7641.7581.7541.746	8.575.885.544.564.254.20	368297284249233224	20.99020.97720.97620.96820.96420.962	151214121516	Comparative example "", FIGS
									2425262728	E″″″″	18.226.831.745.666.8	1.7551.7521.7491.7411.726	6.485.204.684.183.90	361324310284261	20.99020.98620.98320.98020.976	1615131417	Comparative example ""

TABLE 3

No.	Number of steel	Particle size (. mu.m)	B50(T)	W15/50(W/kg)	YP(MPa)	Punching diameter (mm)	Punching diameter Max-min (mum)	Remarks for note
									2930313233	F″″″″	8.626.533.452.059.7	1.8131.8111.8091.8021.797	11.805.995.454.774.75	377246227196188	20.98920.97520.97320.96620.960	711101416	Comparative example ""
343536373839	G″″″″″	11.316.226.533.643.875.2	1.8171.8151.8141.8121.8081.804	9.697.705.955.404.954.45	363320271252233201	20.99520.99320.98920.98820.98620.984	856457	Comparative example "" inventive example "
									4041424344454647	H″″″″″″	11.314.823.025.635.640.256.877.6	1.8221.8191.8191.8191.8161.8141.8131.811	9.668.106.346.025.265.054.624.41	384351305295269260237220	20.99520.99620.99520.99420.99320.93320.99220.991	34564436	Comparative example "" inventive example ""
48495051525354	I″″″″″″	10.813.526.832.540.856.460.5	1.8261.8241.8211.8201.8181.8171.816	9.938.555.775.154.944.594.53	420391321305288267263	20.99420.99520.99620.99420.99320.99420.992	3454544	Comparative example "" inventive example "
									55	J	No evaluation of fracture due to Cold Rolling						Comparative example
5657	B″	19.839.4	1.7841.761	7.985.22	260199	20.96520.953	1621	Comparative example
									5859	H″	18.235.6	1.7951.816	7.815.26	335269	20.99320.993	64	Comparative example inventive example

In steels A to F (Nos. 1 to 33, 56 and 57) in which the P content does not satisfy the suitable range of the present invention and the strength varies depending on the Si amount and the change in the grain size, the die cutting diameter tends to approach the metal gauge with an increase in YP, but the anisotropy of the die cutting dimension, which is represented by the difference between the maximum diameter and the minimum diameter, is relatively large at 10 to 20 μm. Further, if the amount of Si increases, there is a problem that the magnetic flux density decreases.

On the other hand, as in the steels G to H containing P of 0.10 or more in low Si and Al compositions according to the present invention, good die cutting diameters can be obtained even when YP is a low value of 350MPa or less, and anisotropy of die cutting dimensions is small. In addition, from the aspect of magnetic properties, the average grain size of these steels is controlled to be 30 μm or more (No.37, 38, 39, 44, 45, 46, 47, 51, 52, 53, 54, 59), and stable low iron loss and high magnetic flux density can be obtained.

[ example 2]

Molten steels having compositions shown in table 4 were cast in a laboratory, and then hot rolled in the same manner as in example 1 to have thicknesses: after hot rolling of 3mm, annealing the plate at 1100 ℃ for 30s, pickling and cold rolling to a thickness of 0.50 mm. Then, final annealing is performed at various temperatures of 700 ℃ or higher and the ferrite single-phase region to change the recrystallized grain size to various values.

Then, a sample coated with a semi-organic insulating film as in example 1 was prepared and subjected to various tests.

The results obtained are shown in Table 5.

Here, steels K to M were deoxidized with Al that reduced Si, and the group of steels N, O and the group of steels Q, R were melted into a state in which the influence of Ni addition could be evaluated.

TABLE 4

Number of steel	Composition of ingredients (mass%)
											C	Si	Al	Mn	S	Ni	P	N	Sb	Sn
	K	0.0011	0.01	0.32	0.25	0.0032	-	0.05	0.0020	＜0.001											0.044
L											0.0009	0.01	0.33	0.24	0.0039	-	0.16	0.0021	＜0.001	0.046
	M	0.0019	0.02	0.31	0.22	0.0018	-	0.24	0.0024	＜0.001											＜0.001
N											0.0033	0.21	0.23	0.15	0.0028	-	0.16	0.0012	0.060	＜0.001
	O	0.0024	0.21	0.24	0.18	0.0016	1.23	0.16	0.0018	0.055											＜0.001
P											0.0088	0.35	0.0011	0.35	0.0046	-	0.05	0.0031	＜0.001	＜0.001
	Q	0.0082	0.34	0.0007	0.33	0.0040	-	0.19	0.0019	＜0.001											＜0.001
R											0.0080	0.35	0.0011	0.33	0.0051	0.95	0.19	0.0018	＜0.001	＜0.001

TABLE 5

No	Number of steel	Particle size (. mu.m)	B50(T)	W15/50(W/kg)	YP(MPa)	Punching diameter (mm)	Punching diameter Max-min (mum)	Remarks for note
									12	K″	36.161.3	1.7771.769	4.954.27	211177	20.95920.950	1826	Comparative example
345	L″″	26.534.247.0	1.7891.7851.785	5.574.984.47	283262240	20.98220.98520.982	879	Comparative examples inventive examples
									678	M″	12.535.270.2	1.7771.7741.768	8.634.884.06	396294250	20.99520.99120.992	689	Comparative examples inventive examples
91011	N″″	28.736.258.1	1.7861.7851.779	5.384.894.26	289270239	20.99020.98920.989	899	Comparative examples inventive examples
									12131415	O″″″	6.822.732.148.2	1.8071.8031.8031.797	12.965.284.373.70	484329299270	20.99520.99220.99220.995	2237	Comparative example invention exampleExamples of the invention
161718	P″″	43.060.472.0	1.7681.7661.769	4.884.504.38	218197187	20.96620.95920.961	161821	Comparative example
									192021	Q″″	18.444.875.1	1.7661.7661.775	6.994.764.29	348273243	20.98720.97720.984	788	Comparative examples inventive examples
222324	R″″	22.639.756.8	1.7781.7841.781	5.073.753.30	359313290	20.99020.99220.991	455	Comparative examples inventive examples

The steel satisfying the present invention has excellent punching dimensional accuracy, reduced punching anisotropy, and excellent magnetic properties, and has a mean particle diameter of 30 μm or more. In particular, comparison of steel N and steel O, and steel Q and steel R, respectively, confirmed that the magnetic flux density was significantly improved in steel O and steel R to which Ni was added.

[ example 3]

Molten steels having compositions shown in steel F of table 1, steel N of table 4, and steel O were melt-cast in a laboratory, and then were hot-rolled in the same manner as in example 1 to obtain thicknesses: after hot rolling a plate with the thickness of 2mm, annealing the hot rolled plate at 1100 ℃ for 30s, pickling, and cold rolling to obtain the plate with the thickness of 0.50-0.2 mm. Then, final annealing is performed at various temperatures of 700 ℃ or higher and in a ferrite single-phase region to control the recrystallized grain size to 35 to 45 μm.

Then, a sample coated with a semi-organic insulating film as in example 1 was prepared and subjected to various tests. In addition, the high frequency core loss in 400Hz was investigated for these samples.

The results obtained are also shown in Table 6.

TABLE 6

No.	Number of steel	Plate thickness (mm)	Particle size (. mu.m)	B50(T)	W15/50(W/kg)	W15/400(W/kg)	YP(MPa)	Punching diameter (mm)	Punching diameter Max-min (mum)	Remarks for note
											123	F″″	0.500.350.20	38.237.142.8	1.8071.8041.803	4.843.783.41	1719858	217219209	20.96820.98320.989	141211	Comparative example ""
456	N″″	0.500.350.20	42.037.941.3	1.7851.7831.783	4.483.393.08	1417142	259267261	20.98820.99320.995	875	Examples of the invention "
											789	O″″	0.500.350.20	37.443.535.2	1.8021.7971.798	3.863.052.78	894829	288277292	20.99220.99520.995	434	Examples of the invention "

As the thickness of the plate becomes thinner, the iron loss tends to be remarkably improved particularly in high frequencies. Further, die cutting dimensional accuracy also tends to be improved as the sheet thickness is reduced, but steel N, O satisfying the composition range of the present invention is superior to comparative steel F. Further, the steel of the present invention is excellent in anisotropy of die-cut dimension at any thickness.

[ example 4]

Molten steel having a composition shown in table 7 was cast in a laboratory, soaked at 1150 ℃ for 1 hour, and then hot rolled to form a thin slab.

The resulting thin slabs were heated to a temperature (SRT) shown in table 8 and held for 1 hour, then hot-rolled to 2.0mm, subjected to coil treatment at 580 ℃. Then, a part of the steel was removed, and hot-rolled sheet annealing was performed under the conditions shown in table 8. Then, after acid pickling, cold rolling was performed to 0.50 mm.

In the cold rolling, workability in the cold rolling was evaluated based on the state of the sheet during the cold rolling and the results of observation of the cross-sectional structure after the cold rolling. The steels (W, Z, a, c, d, k, and 1) having a high P (. gtoreq.0.10%) and not satisfying the composition range of the present invention, and the steel (W, Z, a, c, d, k, and 1) having a composition range satisfying the present invention, in the items (Nos. 25 and 26) having a slab heating temperature (SRT) or a hot rolling Coiling Temperature (CT) outside the range of the present invention, many cracks parallel to the sheet surface were observed, and the steel was separated into layers during the drawing in some of the samples (Nos. 5, 19, and 25), and the subsequent rolling was difficult. From these results, it was difficult to perform stable production in the industry, and therefore, these samples were not subjected to subsequent treatments and evaluations.

Then, after final annealing was performed on the cold-rolled sheet at various temperatures of 700 ℃ or higher, the same semi-organic insulating film as in example was applied, and then, various tests were performed. Here, the strength was evaluated by cutting a JIS No.5 test piece in parallel with the direction of compression and elongation, and drawing the piece at a drawing rate of 10mm/s to obtain a Tensile Strength (TS). The results are shown in Table 8.

TABLE 7

Steel No	Steel composition	C％	Si％	Al％	Mn％	S％	Ni％	P％	N％	Sb％	Sn％	PA	PA≥P	PF	PF≤0.26	The judgment result of formula (II)
																	S	Comparative steel	0.0018	0.60	0.0010	0.18	0.0041	0.00	0.05	0.0022	＜0.001	＜0.001	0.261	OK	0.591	NG	OK
T	Invention steel	0.0011	0.60	0.0011	0.19	0.0033	0.00	0.13	0.0032	＜0.001	＜0.001	0.262	OK	0.593	NG	OK
																	U	Invention steel	0.0014	0.60	0.0006	0.22	0.0028	0.00	0.19	0.0015	＜0.001	＜0.001	0.266	OK	0.600	NG	OK
V	Invention steel	0.0032	0.60	0.0005	0.18	0.0032	0.00	0.26	0.0018	＜0.001	＜0.001	0.261	OK	0.592	NG	OK
																	W	Comparative steel	0.0031	0.63	0.0006	0.19	0.0041	0.00	0.29	0.0021	＜0.001	＜0.001	0.257	NG	0.585	NG	NG
X	Comparative steel	0.0011	1.02	0.0010	0.19	0.0032	0.00	0.04	0.0018	＜0.001	0.023	0.178	OK	0.451	NG	OK
																	Y	Invention steel	0.0011	1.00	0.0011	0.21	0.0032	0.00	0.15	0.0020	＜0.001	0.036	0.185	OK	0.461	NG	OK
Z	Comparative steel	0.0011	0.98	0.0004	0.19	0.0032	0.00	0.21	0.0022	＜0.001	0.025	0.187	NG	0.465	NG	NG
																	a	Comparative steel	0.0011	1.01	0.0006	0.18	0.0032	0.00	0.25	0.0025	＜0.001	0.032	0.179	NG	0.452	NG	NG
b	Comparative steel	0.0019	1.52	0.0009	0.20	0.0050	0.00	0.04	0.0019	0.018	0.002	0.080	OK	0.283	NG	OK
																	c	Comparative steel	0.0025	1.54	0.0011	0.19	0.0041	0.00	0.12	0.0012	0.022	＜0.001	0.074	NG	0.274	NG	NG
d	Comparative steel	0.0016	1.48	0.0008	0.22	0.0028	0.00	0.17	0.0031	0.023	＜0.001	0.090	NG	0.300	NG	NG
																	e	Invention steel	0.0018	1.63	0.0007	0.18	0.0019	0.00	0.19	0.0026	0.019	＜0.001	0.056	NG	0.242	OK	OK
f	Invention steel	0.0024	1.60	0.0006	0.18	0.0032	0.00	0.25	0.0014	0.022	＜0.001	0.061	NG	0.252	OK	OK
																	g	Comparative steel	0.0008	2.18	0.25	0.20	0.0008	0.00	0.03	0.0018	＜0.001	0.035	-0.132	NG	-0.076	OK	OK
h	Invention steel	0.0011	2.20	0.26	0.18	0.0004	0.00	0.13	0.0022	0.002	0.036	-0.142	NG	-0.092	OK	OK
																	i	Invention steel	0.0016	2.11	0.25	0.18	0.0013	0.00	0.19	0.0021	＜0.001	0.034	-0.120	NG	-0.056	OK	OK
j	Invention steel	0.0017	2.08	0.27	0.19	0.0017	0.00	0.24	0.0035	＜0.001	0.032	-0.120	NG	-0.055	OK	OK
																	k	Comparative steel	0.0024	2.11	0.27	0.22	0.0023	0.00	0.29	0.0028	＜0.001	0.035	-0.122	NG	-0.059	OK	OK
l	Comparative steel	0.0026	1.50	0.0010	0.20	0.0032	0.50	0.18	0.0026	＜0.001	0.022	0.146	NG	0.489	NG	NG
																	m	Invention steel	0.0033	1.45	0.0005	0.19	0.0015	1.09	0.16	0.0021	0.002	0.021	0.261	OK	0.894	NG	OK
n	Invention steel	0.0036	1.56	0.0010	0.19	0.0032	1.57	0.17	0.0019	＜0.001	0.021	0.351	OK	1.296	NG	OK
																	o	Invention steel	0.0038	1.50	0.0006	0.21	0.0022	2.13	0.19	0.0025	＜0.001	0.026	0.525	OK	1.978	NG	OK

TABLE 8

No	Steel No	Steel composition	Remarks for note	SRT(℃)	CT(℃)	Annealing temperature (. degree.C.) of hot rolled sheet	B50(T)	YP(MPa)	TS(MPa)	Punching diameter (mm)	Punching diameter max-min (mum)	Whether or not to manufacture	PA	PA≥P	PF	PF≤0.26
																	1	S	Comparative steel	Comparative example	1150	520	900	1.775	227	348	20.969	16	○	0.261	OK	0.591	NG
2	T	Invention steel	Examples of the invention	1150	520	900	1.774	260	382	20.988	5	○	0.262	OK	0.503	NG
																	3	U	Invention steel	Examples of the invention	1150	520	900	1.776	286	410	20.991	6	○	0.266	OK	0.600	NG
4	V	Invention steel	Examples of the invention	1150	520	900	1.777	315	439	20.993	5	○	0.261	OK	0.592	NG
																	5	W	Comparative steel	Comparative example	1150	520	900	-	-	-	-	-	Fracture of laminae	0.257	NG	0.585	NG
6	X	Comparative steel	Comparative example	1150	550	900	1.762	255	370	20.968	12	○	0.178	OK	0.451	NG
																	7	Y	Invention steel	Examples of the invention	1150	550	900	1.764	297	415	20.992	5	○	0.185	OK	0.461	NG
8	Z	Comparative steel	Comparative example	1150	550	900	-	-	-	-	-	Fracture of laminae	0.187	NG	0.465	NG
																	9	a	Comparative steel	Comparative example	1150	550	900	-	-	-	-	-	Fracture of laminae	0.179	NG	0.452	NG
10	b	Comparative steel	Comparative example	1150	550	1100	1.733	291	400	20.974	15	○	0.080	OK	0.283	NG
																	11	c	Comparative steel	Comparative example	1150	550	1100	-	-	-	-	-	Fracture of laminae	0.074	NG	0.274	NG
12	d	Comparative steel	Comparative example	1150	550	1100	-	-	-	-	-	Fracture of laminae	0.090	NG	0.300	NG
																	13	e	Invention steel	Examples of the invention	1150	550	1100	1.735	360	470	20.993	4	○	0.056	NG	0.242	OK
14	f	Invention steel	Examples of the invention	1150	550	1100	1.733	383	494	20.992	3	○	0.061	NG	0.252	OK
																	15	g	Comparative steel	Comparative example	1150	580	1000	1.703	338	444	20.990	15	○	-0.132	NG	-0.076	OK
16	h	Invention steel	Examples of the invention	1150	580	1000	1.708	382	489	20.995	5	○	-0.142	NG	-0.092	OK
																	17	i	Invention steel	Examples of the invention	1150	580	1000	1.709	400	509	20.996	3	○	-0.120	NG	-0.056	OK
18	j	Invention steel	Examples of the invention	1150	580	1000	1.704	419	530	20.994	3	○	-0.120	NG	-0.055	OK
																	19	k	Comparative steel	Comparative example	1150	580	1000	-	-	-	-	-	Fracture of laminae	-0.122	NG	-0.059	OK
20	l	Comparative steel	Comparative example	1150	550	1100	-	-	-	-	-	Fracture of laminae	0.146	NG	0.489	NG
																	21	m	Invention steel	Examples of the invention	1150	550	1100	1.742	353	465	20.996	3	○	0.261	OK	0.894	NG
22	n	Invention steel	Examples of the invention	1150	550	1100	1.748	372	483	20.995	4	○	0.351	OK	1.296	NG
																	23	o	Invention steel	Examples of the invention	1150	550	1100	1.751	383	495	20.996	4	○	0.525	OK	1.978	NG
24	Y	Invention steel	Examples of the invention	1100	550	なし	1.754	312	416	20.990	6	○	0.185	OK	0.461	NG
																	25	Y	Invention steel	Comparative example	1250	550	550	-	-	-	-	-	Fracture of laminae	0.185	OK	0.461	NG
26	Y	Invention steel	Comparative example	1150	700	700	-	-	-	-	-	Fracture of laminae	0.185	OK	0.461	NG

The steels (2 to 4, 7, 13, 14, 16 to 18, and 21 to 24) containing P in an amount of 0.1% or more as a component in the range of the present invention all showed excellent punching dimensional accuracy. That is, in the steels (No.1, 6, 10 and 15) in which the P addition amount is not more than 0.1%, although the die cutting diameter tends to be improved as the Si + Al amount increases, the anisotropy of the die cutting diameter is large. On the one hand, it was found that the anisotropy of the die-cut diameter and the die-cut diameter of the steel of the present invention was excellent together. Further, these inventive steels have high strength despite having the same or higher magnetic flux density as that of comparative steels having a P content of not more than 0.1%, and have an excellent strength-magnetic flux density balance.

[ example 5]

Melting steels having the compositions shown in steel M, steel N, and steel O in Table 4 in a laboratory? After casting, the steel sheet was hot-rolled to have a thickness: 30mm thin slab. Then, the steel was heated at each temperature (SRT) shown in table 9 for 60 minutes, and then hot-rolled to a sheet thickness: 2mm, and was kept at each temperature (CT) shown in Table 9 for 1 hour by soaking for each coil, and then was cooled in air. Then, a part of the steel was removed, and hot-rolled sheet annealing was performed at each temperature shown in table 9 for 60 seconds.

The obtained hot-rolled steel sheet was subjected to a bending test at room temperature (23 ℃ C.). Bending test A test piece of 100mm X30 mm was taken from a hot-rolled sheet in the longitudinal direction of rolling, and the bending test of 15mm bending radius repeated in accordance with JIS-C2550 was performed. The number of cracks before the hot-rolled sheet surface was cracked is shown in Table 9.

Further, the structure (phase) of the hot-rolled sheet at the time of annealing was examined by the following method at the time of heating the slab. Each of the thin slabs and the hot rolled plates was kept at a predetermined temperature (shown in Table 9) for a predetermined time (slab heating: 1 hour, annealing; 60 seconds), and then the slab was quenched with water to freeze the structure at the time of heating, and the phase was identified by observation of the structure with an optical microscope. The results are shown in Table 9.

The hot-rolled sheet was pickled and then cold-rolled to a thickness of 0.50mm (1 cold-rolling), and whether cold-rolling defects (lamellar fracture) due to embrittlement occurred was evaluated. For the cold-rolled sheet in which the layer fracture did not occur, final annealing was performed at various temperatures as shown in table 9, and then, samples coated with the same semi-organic insulating film as in example 1 were produced and provided for various tests.

The results are shown in Table 9.

TABLE 9

No	Steel No	Steel composition	Remarks for note	SRT(℃)	Texture of the blank when heated	CT(℃)	Annealing temperature (. degree. C.) of hot rolled sheet	Annealed structure of hot rolled plate	Number of hot rolled plate bends	Whether or not to manufacture	Final annealing temperature (. degree. C.)	Particle size (. mu.m)	B50(T)	W15/50(W/kg)	YP(MPa)
																1	M	Invention steel	Comparative example	1250	α+γ	520	Is free of	-	4	Fracture of laminae	-	-	-	-	-
2	M	Invention steel	Examples of the invention	1150	Gamma single phase	520	Is free of	-	30	○	800	46.2	1.765	4.47	275
																3	M	Invention steel	Examples of the invention	1050	Gamma single phase	520	Is free of	-	28	○	800	38.2	1.762	4.75	288
4	M	Invention steel	Comparative example	950	α+γ	520	Is free of	-	5	Fracture of laminae	-	-	-	-	-
																5	M	Invention steel	Comparative example	1150	Gamma single phase	720	900	Alpha single phase	3	Reduced bendability	850	45.1	1.762	6.83	288
6	N	Invention steel	Examples of the invention	1150	Gamma single phase	620	900	Alpha single phase	17	○	850	55.2	1.764	4.31	242
																7	N	Invention steel	Comparative example	1150	Gamma single phase	550	960	α+γ	20	○	850	53.8	1.736	4.33	244
8	N	Invention steel	Examples of the invention	1150	Gamma single phase	550	1100	Gamma single phase	22	○	850	52.1	1.768	4.36	246
																9	N	Invention steel	Comparative example	1150	Gamma single phase	500	900	Alpha single phase	27	○	670	16.0	1.766	7.38	345
10	O	Invention steel	Examples of the invention	1100	Gamma single phase	600	1100	Gamma single phase	26	○	800	36.5	1.777	4.12	290
																11	O	Invention steel	Examples of the invention	1100	Gamma single phase	600	1000	Gamma single phase	33	○	800	38.5	1.780	4.02	286
12	O	Invention steel	Comparative example	1100	Gamma single phase	550	900	α+γ	28	○	800	32.6	1.733	4.34	298
																13	O	Invention steel	Comparative example	1100	Gamma single phase	550	800	Alpha single phase	24	○	800	36.8	1.733	4.10	289

In the steel composition (low Si steel) of the present invention, when the production conditions of the present invention are satisfied (nos. 2, 3, 6, 8, 10 and 11), a steel sheet can be produced without problems despite the high P addition, and the performance is also good.

On the other hand, it was found that when the slab heating temperature of the present invention is 2-phase region (nos. 1 and 4), cold rolling defects are likely to occur due to defects caused by embrittlement, and it is difficult to produce the slab. Further, when the coil coiling temperature is higher than 650 ℃ (No.5), the workability of the hot-rolled sheet is lowered, and the iron loss of the electrical steel sheet obtained is also lowered. Further, when the hot-rolled sheet annealing temperature is in the 2-phase region (nos. 7 and 12), and when the hot-rolled sheet degradation is performed in the α single-phase region in the steel to which more than 1.0 mass% of Ni is added (No.3), the magnetic flux density of the resulting electrical steel sheet decreases. Further, the final annealing temperature is insufficient when the recrystallized grain size is 30 μm or more under the production conditions of the present invention (No.9), and the magnetic properties are deteriorated.

Possibility of industrial utilization

Thus, according to the present invention, it is possible to stably obtain a non-oriented electrical steel sheet having excellent magnetic properties with high magnetic flux density and low iron loss and having high punching dimensional accuracy, and a non-oriented electrical steel sheet having higher strength.

The non-oriented electrical steel sheet of the present invention is suitable for core materials of various electric motors, and is particularly suitable for core materials of reluctance motors, which require high dimensional accuracy and high magnetic flux density, and embedded magnet type brushless motors, which require a high strength.

Claims (11)

1. A non-oriented electrical steel sheet characterized by comprising, in mass%,

C：0～0.010％，

at least 1 of Si and Al: 0.03% to 0.5% in total,

mn: the content of the active ingredients is less than 0.5 percent,

p: more than 0.10 percent and less than 0.26 percent,

s: less than 0.015% and

n: the content of the active carbon is less than 0.010 percent,

the balance being Fe and inevitable impurities, and

average crystal particle size: 30 to 80 μm.

2. The non-oriented electrical steel sheet according to claim 1, wherein the steel sheet further comprises, in mass%,

at least 1 of Sb and Sn: the total content is less than 0.40%.

3. The non-oriented electrical steel sheet according to claim 1 or 2, wherein the steel sheet further comprises, in mass%,

ni: 2.3% or less.

4. The non-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the steel sheet further comprises, in mass%,

ca: 0.01% or less, B: less than 0.005 percent,

Cr: 0.1% or less, Cu: less than 0.1 percent of,

Mo: less than 0.1%

At least one of (1).

5. The non-oriented electrical steel sheet according to any one of claims 1 to 4, wherein the steel sheet has a thickness of 0.35mm or less.

6. A non-oriented electrical steel sheet characterized by comprising, in mass%,

C：0～0.010％，

at least 1 of Si and Al: more than 0.5 and 2.5% in total,

mn: the content of the active ingredients is less than 0.5 percent,

p: more than 0.10 percent and less than 0.26 percent,

s: less than 0.015% of the total weight of the composition,

n: less than 0.010%, and,

if necessary, Ni: the content of the active ingredients is less than 2.3%,

the balance of Fe and inevitable impurities, and satisfies,

P≤P_Aand P_FA relationship of ≦ 0.26 for at least one aspect,

wherein,

P_A＝-0.2Si+0.12Mn-0.32Al+0.05Ni²+0.10Ni+0.36……(1)

P_F＝-0.34Si+0.20Mn-0.54Al+0.24Ni²+0.28Ni+0.76……(2)

here, the unit of the content of each element is mass%.

7. The non-oriented electrical steel sheet according to claim 6, wherein the steel sheet further comprises, in mass%,

at least 1 of Sb and Sn: the total content is less than 0.40%.

8. The non-oriented electrical steel sheet according to claim 6 or 7, wherein the steel sheet further comprises, in mass%,

ca: 0.01% or less, B: less than 0.005 percent,

Cr: 0.1% or less, Cu: less than 0.1 percent of,

Mo: less than 0.1%

At least one of (1).

9. A method for producing a non-oriented electrical steel sheet, characterized in that, in the case of the steel slab having the composition according to any one of claims 1 to 4,

hot rolling is carried out under conditions that the heating temperature is in an austenite single-phase region and the coil coiling temperature is 650 ℃ or less,

then, after descaling treatment, cold rolling is performed 1 time or 2 times or more including intermediate annealing, and then final annealing is performed in a ferrite single-phase region of 700 ℃ or more.

10. A method for producing a non-oriented electrical steel sheet, characterized in that, in the case of the steel slab having the composition according to any one of claims 1 to 4,

after hot rolling is performed under conditions in which the heating temperature is in the austenite single phase region and the coil coiling temperature is 650 ℃ or less,

when Ni is not added or the Ni content is 1.0 mass% or less, hot-rolled sheet annealing is performed at any temperature of a ferrite single-phase region of 900 ℃ or higher or an austenite single-phase region of Ac3 point or higher,

when the Ni content exceeds 1.0 mass% and is 2.3 mass% or less, hot-rolled sheet annealing is performed in an austenite single-phase region of Ac3 point or more,

then, after the descaling treatment, the cold rolling is carried out for 1 time or more than 2 times including intermediate annealing,

the final annealing is performed in the above ferrite single-phase domain at 700 ℃.

11. A method for producing a non-oriented electrical steel sheet, characterized in that, in the case of the steel slab having the composition according to any one of claims 6 to 8,

hot rolling at a heating temperature of 1000 to 1200 ℃ and a coil coiling temperature of 650 ℃ or lower,

the hot rolled sheet is annealed as required,

then, after the descaling treatment, the cold rolling is carried out for 1 time or more than 2 times including intermediate annealing,

and carrying out final annealing.

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