CN1277945C - Nonoriented magnetic steel sheet, member for rotary machine and rotary machine - Google Patents

Abstract

A nonoriented magnetic steel sheet which has a chemical composition in mass % wherein contents of Si and Mn are 0.1 to 1.2 % and 0.005 to 0.30 %, respectively, and the contents of C, Sol.Al and N are limited to 0.0050 % or less, 0.0004 % or less, and 0.0030 % or less, respectively, all including 0 %, and has a number density of grain growth inhibiting ductile non-metallic inclusions dispersed in the steel sheet of 1000 pieces/cm<2> or less including 0, wherein a grain growth inhibiting ductile non-metallic inclusion means an inclusion contained in a steel sheet having been subjected to finishing annealing which has a length of 3 x D to 9 x D, D representing an average particle diameter of re-crystallized grains in the steel sheet. The nonoriented magnetic steel sheet allows the production, from one steel sheet, of a rotor material exhibiting a high magnetic flux density and a high strength and a stator material exhibiting a high magnetic flux density and a low iron loss after it is subjected to strain removing annealing.

Description

Non-oriented electrical steel sheet, component for rotating machine, and rotating machine

technical field

The present invention relates to a non-oriented electrical steel sheet for use in rotating machine assemblies. The present invention also relates to a component for a rotating machine and a rotating machine assembled using the non-oriented electrical steel sheet.

Background technique

In order to reduce the energy consumption of the rotating machine, it is effective to increase the magnetic flux density of the iron cores of the rotating machine, that is, the rotor and the stator, and at the same time reduce the iron loss of these iron cores. As a measure to reduce iron loss, it is generally possible to increase the content of Si, Al, Mn, etc. to increase the resistance of the core material. In addition to these measures, known methods include, for example, the method of adding B disclosed in JP-A-58-151453, the method of adding Ni disclosed in JP-A-3-281758, and the like. There is also a method of improving magnetic properties by preferentially growing crystal grains having, for example, {100}<UVW> orientation in the aggregate structure of an electrical steel sheet, such as the method proposed in JP-A-58-181822. By using the non-oriented electrical steel sheet manufactured according to these measures, it is possible to manufacture an iron core with high magnetic flux density and low iron loss.

The non-oriented electrical steel sheet used for the iron core of the rotating machine is finished annealed (final annealed) by the steel sheet manufacturer, and after being shipped as a product plate, it is assembled into the rotor and stator of the rotating machine at a downstream manufacturer. In this assembling step, after stamping out a steel plate into a core plate for a rotor or a core plate for a stator, stress relief annealing is performed as necessary.

Among the disclosed technologies, there is also a technology for further reducing iron loss by improving the growth of recrystallized grains in such stress relief annealing. For example, in Japanese Patent Publication No. 58-55210 and Japanese Unexamined Publication No. 8-269532, etc., the following technology is proposed: the amount of Sol.Al in the steel plate is reduced to 0.0010% or less and 0.003% or less respectively, and the precipitation of fine AlN Suppression is performed to improve particle growth in stress relief annealing, thereby reducing iron loss. In addition, the following technology is proposed in the Japanese Patent Application Publication No. 3-24229: the amount of Sol.Al is reduced to below 0.001%, and the product of the content of N and V is controlled below the specified value, which can also be used in stress relief annealing. The growth of particles is improved, thereby reducing iron loss. In Japanese Patent Laid-Open Publication No. 7-70719, the following methods are proposed: reduce the amount of Sol.Al to below 8 ppm, and then control the amount of Ti+Al to below 20 ppm, etc., so as to improve the particle growth in stress relief annealing .

Furthermore, in JP-A-63-195217 and JP-A-7-150248, it is proposed to control the composition of inclusions formed by Si, Al, and Mn composite oxides on the basis of reducing Al. , to prevent the inclusions from extending, it is possible to improve the particle growth in stress relief annealing and reduce iron loss.

However, even with these techniques, the iron loss caused by stress-relief annealing cannot be improved sufficiently. Even so, it is difficult to improve it to below 4.4W/kg by stress relief annealing for the steel plate which is reduced to about 5W/kg after finished annealing (at the time of delivery).

However, in the manufacture of iron cores for rotating machines, in order to maintain a high material yield, generally, a core plate for a rotor and a core plate for a stator are punched out from the same steel plate by a punching machine. Next, these core plates for the rotor and core plates for the stator are respectively laminated and assembled into the rotor and the stator.

Among them, the rotor is a rotating part, which is subject to high stress due to high-speed rotation, and therefore must have high strength. In particular, in recent years, in order to improve the efficiency of rotating machines (motors), rotors with embedded rare earth magnets have been developed, and the rotational speed of the rotors has been significantly increased. Therefore, the magnetic flux density and strength of the electromagnetic steel sheet constituting the rotor, such as the upper yield point (YP), are required to be higher than before. On the other hand, it is important for the stator to have a high magnetic flux density and low iron loss for the miniaturization and energy saving of the rotating machine.

In this way, even if it is the electromagnetic steel sheet used for the same motor, the required properties of the steel sheet used for assembling the rotor (hereinafter referred to as "rotor material") and the steel sheet used for assembling the stator (hereinafter referred to as "stator material") are the same. It is difficult to satisfy both characteristics at the same time. The conventionally disclosed technology satisfies the characteristics of the rotor material and the stator material separately, but does not simultaneously satisfy the characteristics of both of them.

Contents of the invention

The purpose of the present invention is to provide a high magnetic flux density non-directional electrical steel sheet, from which the rotor material and the stator material can be cut at the same time, and the rotor material can have high magnetic flux density and high strength, and the stator material can have High magnetic flux density and low iron loss, and also provide a component for a rotating machine and a rotating machine using the steel plate.

The invention is

1. High magnetic flux density non-oriented electrical steel sheets for rotating machines, of which:

Contain Si at a mass ratio of 0.1% to 1.2% and Mn at 0.005 to 0.30%; limit C to below 0.0050% (including 0); limit Sol.Al to below 0.0004% (including 0); limit N to 0.0030 % or less (including 0); the rest contains Fe and unavoidable impurities; the number density (number) of ductile non-metallic inclusions (deformable non-metallic inclusions with grain growth inhibition) dispersed in the steel plate of inclusions per unit area) below 1000/cm ² (including 0).

Here, the ductile non-metallic inclusions that inhibit grain growth mean that, among the ductile non-metallic inclusions, when the average recrystallized grain size (average grain size of recrystallized grains) of the steel sheet is D, the length is 3×D～9×D inclusions. In addition, the steel plate here refers to the state of the product plate after the finished annealing, that is, the steel plate in the state without stress relief annealing, and the average recrystallization grain size and the length of the ductile non-metallic inclusions also refer to the The value in the state of the product board. In addition, ductile non-metallic inclusions refer to relatively coarse non-metallic inclusions that are relatively easy to expand by rolling (or already expanded in product plates, etc.), but generally non-metallic inclusions that expand in steel sheets , therefore, hereinafter referred to as ductile inclusions.

In addition, the composition of the above-mentioned non-oriented electrical steel sheet is preferably composed of Si, Mn, C, Sol.Al, N, the rest of Fe, and unavoidable impurities.

2. The high-flux-density non-oriented electrical steel sheet for rotating machines according to the invention of the above-mentioned 1, which further contains one or more selected from Sb in an amount of 0.005% to 0.10% by mass and Sn in an amount of 0.005% to 0.2%. 2 kinds.

3. The high-flux-density non-oriented electrical steel sheet for rotating machines according to the invention of 1 or 2 above, which further contains 1 selected from P and 0.001% to 0.2% of Ni in mass %. species or 2 species.

4. The high-flux-density non-oriented electrical steel sheet for rotating machines according to any one of the above 1 to 3 inventions, further comprising 0.0001% to 0.10% by mass of REM and 0.0001% to 0.01% of Ca 1 or 2 of your choice.

5. The high-flux-density non-oriented electrical steel sheet for rotating machines according to any one of the above 1 to 4 inventions, wherein: among the above-mentioned unavoidable impurities, Ti is limited to 0.0020% or less (including 0), limit Nb to below 0.0050% (including 0), and limit V to below 0.0060% (including 0).

6. The high-flux-density non-oriented electrical steel sheet for rotating machines according to any one of the above 1 to 5 inventions, wherein: among the above-mentioned unavoidable impurities, S is limited to 0.0050% or less by mass % (including 0), limit O below 0.0100% (including 0).

7. The high-flux-density non-oriented electrical steel sheet for rotating machines according to any one of the inventions 1 to 6 above, wherein the average grain diameter D of the recrystallized grains is 6 μm to 25 μm.

8. The high-flux-density non-oriented electrical steel sheet for rotating machines according to any one of the inventions of 1 to 7 above, wherein: the steel sheet is a steel sheet manufactured by at least cold rolling followed by finish annealing, and the finish annealing The temperature ranges from 700°C to 800°C. That is, a slab for a non-oriented electrical steel sheet is processed by a usual method to produce a cold-rolled steel sheet having a final thickness, and then finished annealed at 700°C to 800°C.

9. A high-flux-density non-oriented electrical steel sheet for a rotating machine, characterized in that the non-oriented electrical steel sheet according to any one of the above-mentioned 1 to 8 inventions is annealed at 750°C for 2 hours to make the average The recrystallized grain size grows to be more than 2 times (that is, the grain growth ratio of the stress-relieving annealing is 2 or more).

10. High-flux-density non-oriented electrical steel sheet for rotating machines (stress-relief annealed sheet), which is applied to the high-magnetic-flux-density non-oriented electrical steel sheet (product sheet) for rotating machines according to any one of the above 1 to 9 inventions Manufactured by stress relief annealing.

11. The high-flux-density non-oriented electrical steel sheet for rotating machines according to the invention of 10 above, wherein the stress relief annealing temperature is 700°C to 800°C.

That is, the non-oriented electrical steel sheet according to each of the above 1 to 9 inventions can be produced by treating a slab for an isotropic electrical steel sheet by a usual method to produce a cold-rolled steel sheet having a final thickness, and then It is subjected to finish annealing at 700°C to 800°C, and it is preferable to grow the average recrystallized grain size to be at least twice the grain size after finish annealing.

12. A rotor member for a rotating machine, which is obtained by laminating the high magnetic flux density non-oriented electrical steel sheet for a rotating machine according to any one of the above 1 to 9 inventions, preferably after punching.

13. A stator part for a rotating machine, preferably, the high-flux-density non-oriented electrical steel sheet for a rotating machine according to any one of the inventions 1 to 9 above is stamped and laminated, and then subjected to stress relief annealing. production.

14. A rotating machine comprising the rotor member of the above-mentioned 12th invention and the stator member of the above-mentioned 13th invention, which are made of a high magnetic flux density non-oriented electrical steel sheet for the same rotating machine.

That is, the non-oriented electrical steel sheet according to each of the above 1 to 9 inventions can be punched out and then laminated to form a high-strength rotating machine rotor member. In addition, by performing stress relief annealing after punching and lamination, it is possible to produce a low iron loss rotating machine stator part. Furthermore, a high-performance rotating machine can be realized by using the rotor member and the stator member obtained from the same non-oriented electrical steel sheet.

Description of drawings

Figure 1 uses the number of ductile non-metallic inclusions that hinder particle growth as a parameter to show the particle growth ratio of non-oriented electrical steel sheets, that is, the average grain size of the steel sheet after stress relief annealing versus the steel sheet after finished annealing The graph of the relationship between the ratio of the average grain size and the N content of the steel plate.

Detailed ways

The present inventors first noticed the following points.

(1) The saturation magnetic flux density of the non-oriented electrical steel sheet is determined by the iron content (mass%) of the raw material. If the content of elements other than iron, such as Si or Mn, is high, the saturation magnetic flux density will decrease. inevitable.

(2) The magnetic flux density and strength are determined by the crystal grain size of the steel sheet.

(3) As mentioned above, stress relief annealing is performed at a downstream manufacturer, and by this stress relief annealing, the crystal grain size can be increased and iron loss can be reduced.

In consideration of the above-mentioned points, the present inventors found a combination of the following methods.

(1) Use non-oriented electrical steel sheets with low Si content and low Mn content to ensure high magnetic flux density;

(2) In the product plate after finished annealing, high strength is obtained with relatively fine particles, and the growth of crystal particles in stress relief annealing is highly ensured;

(3) For the rotor material, the strength is ensured without stress relief annealing; for the stator material, the stress relief annealing is carried out to make the particles grow to achieve low iron loss;

With the above-mentioned combination, the crystal grain size can be equalized in the manufacturing process of the above-mentioned rotor and stator, and the required characteristics can be imparted to the rotor and the stator respectively.

The inventors of the present invention further studied the factors governing the growth of the crystal grain size in the stress-relief annealing step performed in the assembly process of the stator, and found a combination of the following methods.

(1) Limit the upper limit of Al very strictly according to the industrial level, and suppress the fine precipitates such as AlN;

(2) According to the relationship with the average grain size of the steel plate after finished annealing, the number density of the ductile inclusions dispersed in the steel plate is limited below the specified value, that is, the ductile inclusions in a specific size range are Crystallization grain growth in stress relief annealing has a dominant influence, resulting in more compact and effective control of ductile inclusions;

Therefore, according to the above combination, the crystal grain size can be significantly grown in the stress relief annealing process (for example, 2 hours at 750°C) performed in the stator assembly process of the downstream manufacturer. the invention.

Next, the chemical composition (mass %) of the electrical steel sheet suitable for the present invention will be described.

Si: 0.1 to 1.2%

In order to increase the electrical resistance of the steel sheet and reduce the iron loss, at least 0.1% of Si must be contained. However, if the Si content exceeds 1.2%, the magnetic flux density decreases, the hardness increases, and the workability also deteriorates. Therefore, the Si content is set in the range of 0.1 to 1.2%.

Mn: 0.005～0.30%

In order to obtain good workability during hot rolling, Mn is an essential component, and therefore must be contained in an amount of 0.005% or more. However, if it exceeds 0.30%, the magnetic flux density will decrease. Therefore, the Mn content is set at 0.005 to 0.30%.

C: 0.0050% or less (including 0)

In order to suppress deterioration of magnetic aging, it is necessary to reduce C as much as possible. In addition, in order to fully exert the effect of improving the microstructure under the extremely low Al reduction conditions used in the present invention, it must be reduced to 0.0050% or less. However, this reduction in C does not necessarily have to be achieved at the stage of the starting material, ie molten iron or slab. That is, it can be achieved before finishing annealing in the manufacturing process of the steel plate. A representative decarburization measure is decarburization annealing. In addition, when decarburization is performed during the manufacturing process, it is preferable that the amount of C in the starting material is in the range of 0.0050% to 0.1%.

Sol.Al: less than 0.0004% (including 0)

In order to obtain good grain growth and magnetic properties, the Al content of the steel sheet must be reduced to 0.0004% or less. If the Al content exceeds 0.0004%, AlN will be precipitated in the steel plate, and the magnetic flux density in the product plate after finished annealing will decrease. In addition, the recrystallized grain growth property in the stress relief annealing process is also reduced, so that the good effect of the present invention of significantly reducing the iron loss value cannot be obtained.

N: 0.0030% or less (including 0)

N combines with Al to cause the precipitation of nitrides (AlN), and furthermore, combines with Ti and the like to form various nitrides, which causes a decrease in the magnetic flux density of the product after finish annealing. It also inhibits the growth of recrystallized grains in the stress relief annealing process, which prevents sufficient reduction of the iron loss value. Therefore, it is necessary to reduce the N content to 0.0030% or less. Preferably it is 0.0025% or less.

In the non-oriented electrical steel sheet of the present invention, in addition to the above-mentioned basic composition, at least one of Sb, Sn, P, Ni, REM, and Ca may be added according to the target steel sheet properties. Appropriate contents of these will be described later. In addition to the above, even if at least one of Cr: 5% or less and Cu: 5% or less is contained, the effect of the present invention will not be inhibited.

In addition, Ti, Nb, V, S, and O are representative examples of other unavoidable impurities, and their appropriate ranges will be described later. In addition, unavoidable impurities such as Cu: 0.2% or less, Cr: 0.08% or less, Zr: 0.005% or less, As: 0.01% or less, Mo: 0.005% or less, W: 0.005% or less are allowed.

The non-oriented electrical steel sheet of the present invention has the above-mentioned basic composition, but the object of the present invention cannot be achieved only by controlling the composition. Among the non-metallic inclusions dispersed in the steel plate after finish annealing, when the average recrystallized grain size of the steel plate (product plate after finish annealing) is set to D, it is necessary to make the elongation with a length of 3×D～9×D The number density of permanent inclusions (ductile non-metallic inclusions) is below 1000/cm ² (including 0). Hereafter, such ductile non-metallic inclusions with a length of 3×D to 9×D are defined as ductile non-metallic inclusions hindering particle growth.

Here, the average recrystallized grain size means that the number of crystal grains present in an area of 0.5 ^mm2 of the steel plate is measured, and the average area corresponding to one crystal grain is calculated from this, and the average area corresponding to the average area is calculated. After equalizing the diameter of the circle, that diameter is used. The average crystal grain size is measured by observing a cross-section (so-called L cross-section) perpendicular to the sheet width direction of the steel sheet by observing it with an optical microscope.

Ductile inclusions refer to rod-shaped inclusions extending along the rolling direction and inclusions arranged continuously in the rolling direction. In addition, when two or more inclusions present within a distance of 10 μm are aligned in a direction within ±5° from the rolling direction, these inclusions are regarded as one continuous ductile inclusion.

In addition, in addition to the above-mentioned ductile inclusions, there are isolated round inclusions among the inclusions. These are non-ductile inclusions and are not counted among ductile inclusions. Inclusions are classified as round inclusions when the major diameter is less than twice the minor diameter, and as ductile inclusions when it exceeds twice the minor diameter.

Typical ductile inclusions include SiO ₂ , Al ₂ O ₃ , MnO, CaO, or composite oxides composed of some of them (here, depending on the composition, they may also be non-ductile).

The length of the ductile inclusions refers to the maximum value of the length of the lead segment between any two points at the interface between the ferrite (parent phase structure) and the inclusions, that is, the distance between the two ends of the ductile inclusions (take it as the long diameter). The number of ductile inclusions with a predetermined length is measured according to the following procedure.

A section perpendicular to the width direction of the steel plate is ground, and the ground surface (without corrosion treatment, etc.) is observed with an optical microscope, and a small area different in color from the ferrite part is identified as an inclusion. The observation field of view for one sample is set to 5mm ² , and among the inclusions determined according to the above, the number of ductile inclusions identified as belonging to the specified length is detected, and the number is converted to more than 1 cm ² The number of , as the number density.

Experiments were carried out to investigate the effect of ductile inclusions on particle growth. Next, this experiment and its results will be described.

(Experiment 1)

C: 0.002%, Si: 0.7%, Mn: 0.2%, Sol.Al: less than 0.0004%, S: 0.002%, and other unavoidable impurities are used as basic components, and N is changed in the range of 0.0010 to 0.0060%. of slabs.

The finished slab is heated to 1100°C, hot-rolled to a thickness of 2.3mm, then pickled and cold-rolled, and processed to a final thickness of 0.35mm, and then finished annealing at 800°C for 15 seconds (again Crystallization annealing) to make finished annealed boards (product boards). In addition, the amount (number density) and shape (length) of ductile inclusions can be adjusted by, for example, the following methods:

(1) Control the amount and composition of oxides by changing the oxygen content and Al content;

(2) The elongation of inclusions is controlled by changing the thickness of the slab and changing the rolling schedule in hot rolling.

For the finished product, the average crystal grain size was measured, and inclusions were observed, and the length and number density of ductile inclusions were measured. Next, the above product was annealed at 750° C. for 2 hours in an argon (Ar) atmosphere (hereinafter referred to as “stress relief annealing”), and the same average grain size as that of the finished degraded plate was measured. In addition, the above annealing conditions are equivalent to the stress relief annealing conditions used by downstream manufacturers.

Fig. 1 shows the ratio of the average grain size of the steel sheet after stress relief annealing to the average grain size of the finished annealed steel sheet made by the above method (hereinafter referred to as "stress relief annealing crystal grain growth ratio" or "for short" The graph of the relationship between the particle growth ratio") and the N content. Here, when D is the average recrystallized grain size after finish annealing, the corresponding number density of inclusions with a length of 3×D to 9×D (called ductile non-metallic inclusions that hinder grain growth) , with different tokens.

It can be seen from Figure 1 that when the N content is below 30ppm (mass ppm), if the number density of ductile non-metallic inclusions hindering particle growth is below 1000/ ^cm2 , the growth ratio of stress-relieving annealed crystal grains will be above 2 . However, even if the number density of ductile non-metallic inclusions hindering particle growth is less than 1000/cm ² and the N content exceeds 0.0030%, or the number density of ductile non-metallic inclusions hindering particle growth exceeds 1000 grain/cm ² , the growth ratio of stress-relief annealing crystal grains is less than 2.

(experiment 2)

The same result was also obtained from Experiment 2 below. Three slabs with a thickness of 250 mm having the composition shown in Table 1 and the remainder being iron and unavoidable impurities were made. After these slabs were machined, they were cut into 25 mm, 50 mm, 100 mm and 200 mm thick slabs respectively. sample. Thereafter, these samples were heated to 1070° C., hot-rolled to 2.5 mm, and then cold-rolled to a final plate thickness of 0.5 mm after pickling. Next, adjust the conditions of the continuous annealing-type finish annealing (recrystallization annealing) to the range of 700 to 800°C, and make an average recrystallized grain size (referred to as the average grain size in the experimental examples and examples) of 12 μm or 14 μm. product board.

The finished product plate was subjected to stress relief annealing at 750° C. for 2 hours in an Ar atmosphere. The cross-sections perpendicular to the sheet width direction of these product sheets (finished annealed sheets) and stress-relieving annealed sheets were observed with an optical microscope, and the average crystal grain diameters were measured. In addition, for product boards, the number density of ductile non-metallic inclusions that inhibit particle growth was measured. The results are shown in Table 2. As shown in the table, in the samples whose number density of ductile non-metallic inclusions hindering grain growth is less than 1000/cm ² , the growth ratio of stress-relieving annealed crystal grains is large.

Table 1 steel mark Chemical composition (mass%) C Si mn Sol.Al N o Ti Nb V 1 0.0027 0.50 0.27 0.0003 0.0015 0.0090 0.0003 0.002 0.0010 2 0.0021 0.50 0.23 0.0003 0.0019 0.0085 0.0004 0.002 0.0010 3 0.0026 0.60 0.22 0.0001 0.0018 0.0070 0.0003 0.001 0.0010

Table 2 steel mark Slab Thickness (mm) Average grain size Stress Relief Annealing Crystal Grain Growth Ratio Number density of ductile non-metallic inclusions hindering particle growth (pieces/cm ² ) Remark Before stress relief annealing (μm) After stress relief annealing (μm) 1 25 12 50 4.2 0.3 Invention example 50 34 2.8 61 Invention example 100 twenty two 1.8 1012 comparative example 200 17 1.4 3581 comparative example 2 25 46 3.8 0.7 Invention example 50 36 3.0 65 Invention example 100 26 2.2 811 Invention example 200 19 1.6 2778 comparative example 3 25 47 3.9 0.3 Invention example 50 43 3.6 19 Invention example 100 26 2.2 286 Invention example 200 twenty two 1.8 1024 comparative example 1 25 14 50 3.7 0.3 Invention example 50 32 2.4 42 Invention example 100 26 2.0 828 Invention example 200 16 1.2 3731 comparative example 2 25 44 3.1 0.5 Invention example 50 34 2.4 35 Invention example 100 28 2.0 657 Invention example 200 twenty two 1.6 2824 comparative example 3 25 50 3.6 0.1 Invention example 50 43 3.1 11 Invention example 100 31 2.2 220 Invention example 200 twenty three 1.6 1038 comparative example

As mentioned above, by restricting the composition and appropriately restricting the number density of ductile non-metallic inclusions that hinder particle growth, the average crystallinity of the steel plate (the core material that makes up the stator) after stress relief annealing can be reduced. The particle diameter is more than twice the particle diameter after the above-mentioned finish annealing. This greatly reduces the iron loss in the stator.

On the other hand, since the rotor is used in the finished annealed state, the crystal grains are relatively small, and it is possible to maintain high strength, especially a high upper yield point (hereinafter referred to as YP).

Furthermore, by using the above-mentioned rotor and stator, it is possible to efficiently assemble a high-performance rotating machine for high-speed rotation.

The strength level required by the rotor varies with the characteristics of the rotating machine. Therefore, the average crystal grain size that plays a dominant role in the strength of the steel plate can be designed according to the strength level required by the rotor. However, for a general rotary machine, the average grain size of the steel plate after finish annealing is 6-25 μm is more appropriate. In this case, the strength of the steel sheet is about 200-400 MPa in YP and about 100-170 in Vickers hardness Hv.

In addition, it does not affect the interpretation of the scope of rights of the present invention, but the mechanism by which the number density of ductile non-metallic inclusions that hinder grain growth dominates the growth ratio of stress-relieved annealed crystal grains is considered to be as follows.

First, it is considered that the inclusions having the same length as the crystal grain diameter hinder the grain growth most. The reason for this is that ductile inclusions exist in such a way as to cut off one or two or more crystal grain boundaries, and there is a high probability of hindering the growth of the crystal grains.

However, when the total amount of non-metallic inclusions present in the electrical steel sheet is constant, it can be considered that the volume ratio occupied in the steel is approximately constant. Therefore, according to the Zener formula, compared with the crystal grain size Extremely long inclusions are less likely to hinder particle growth.

In other words, the extent to which ductile inclusions hinder particle growth varies with the length of the inclusions. According to the findings of the present inventors, when the length of ductile inclusions is 3 to 9 times the average crystal grains of the finished annealed sheet, In other words, this level reaches the maximum in the case of ductile non-metallic inclusions that hinder particle growth. Therefore, the number density of ductile inclusions with a length in this range, that is, "ductile non-metallic inclusions hindering particle growth", has an impact on the "stress relief annealing crystal grain growth ratio".

In addition, Zener's formula represents the inhibitory force I of an obstacle on particle growth, which is the following formula.

I=(3/4)×(V×σ×ρ/r ₀ )

Here, V is the molar volume of the parent phase, σ is the grain boundary energy, ρ is the volume ratio of the precipitates, and _r0 is the average particle radius of the precipitates.

As mentioned above, the contents of Si, Mn, C, Sol.Al, and N in the non-oriented electrical steel sheet are controlled separately, and the number density of ductile non-metallic inclusions that hinder particle growth is controlled at 1000/cm ² or less, the growth ratio of stress-relieved annealed crystal grains can be increased, and a high-flux-density non-oriented electrical steel sheet suitable for rotating machines can be produced. In addition, the effect can be further enhanced by limiting the content of Ti, Nb, and V in the composition of the steel sheet, or by adding Sb, Sn. This can be confirmed by the following experiments.

(Experiment 3)

Steel ingots having the composition shown in Table 3 and the remainder being iron and unavoidable impurities were produced. After heating these ingots to 1070°C, they were hot-rolled to a thickness of 2.5mm, and then cold-rolled starting from pickling Processed to a final plate thickness of 0.5mm. Next, finish annealing (recrystallization annealing) was performed at 800°C for 10 seconds to produce a product plate, and stress relief annealing was performed at 750°C for 2 hours to produce a stress relief annealed plate. Cut the same number of samples from the finished product plate and the stress-relieving annealed plate respectively parallel to the rolling direction and perpendicular to the rolling direction, and measure the magnetic flux density and iron loss according to JIS C 2550. The measurement results are shown in Table 3 together.

In addition, the average crystal grain size in each product board was 10 to 20 μm. In addition, the number density of ductile non-metallic inclusions that inhibit particle growth in each product sheet was 1000/cm ² or less.

table 3 steel mark Chemical composition (mass%) Iron loss(W/kg) C Si mn Sol.Al N o Ti Nb V sn Sb Before stress relief annealing After stress relief annealing 11 0.0018 0.90 0.15 0.0001 0.0017 0.0065 0.0024 0.002 0.0010 - - 6.7 6.1 12 0.0017 0.90 0.17 0.0002 0.0022 0.0060 0.0006 0.006 0.0020 - - 6.2 5.8 13 0.0025 0.90 0.16 0.0001 0.0021 0.0065 0.0010 0.001 0.0065 - - 6.4 5.9 14 0.0019 0.90 0.17 0.0002 0.0015 0.0070 0.0009 0.004 0.0020 - - 5.3 4.3 15 0.0023 0.90 0.18 0.0001 0.0020 0.0060 0.0015 0.002 0.0020 - - 5.2 4.2 16 0.0021 0.90 0.17 0.0001 0.0017 0.0055 0.0004 0.003 0.0050 - - 5.1 4.2 17 0.0018 0.90 0.15 0.0002 0.0015 0.0055 0.0006 0.001 0.0010 - 0.01 5.2 3.8 18 0.0018 0.90 0.17 0.0001 0.0022 0.0055 0.0005 0.002 0.0010 0.01 - 5.3 3.7 19 0.0022 0.90 0.17 0.0001 0.0013 0.0060 0.0004 0.001 0.0020 0.02 0.03 5.2 3.6 20 0.0024 0.90 0.19 0.0002 0.0015 0.0065 0.0004 0.002 0.0020 - 0.08 5.2 3.7 twenty one 0.0017 0.90 0.15 0.0001 0.0024 0.0065 0.0003 0.001 0.0010 0.19 - 5.2 3.7

Table 3 shows that the magnetic properties after stress relief annealing can be further improved by limiting Ti to less than 0.0020%, limiting Nb to less than 0.0050%, and limiting V to less than 0.0060%.

Furthermore, by adding one or both of Sb and Sn, the iron loss after stress relief annealing can be greatly improved.

The mechanism of improving the magnetic properties by reducing the amounts of Ti, Nb, and V is not completely clear, but the following is considered. It is considered that Ti, Nb, and V are all nitride and carbide forming elements, and if these nitrides are finely precipitated, as with finely precipitated AlN, they will adversely affect the formation of the aggregate structure and the growth of crystal grains. Therefore, it is considered that by reducing these elements to prevent the occurrence of the above disadvantages, good magnetic properties can be obtained as a result.

The mechanism of the effect of reducing the amount of Ti, Nb, and V on the magnetic properties after stress relief annealing is not very clear, but the following views are available. It is considered that when the content of Ti, Nb, and V is high, nitrides or carbides are partially dissolved in solid solution during hot-rolled sheet annealing and recrystallization annealing. Next, during stress relief annealing, nitrides or carbides are precipitated again, hindering the movement of magnetic domain walls. Therefore, if there are many of the above-mentioned elements, the iron loss will be increased.

In addition, adding one or both of Sb and Sn can greatly improve the iron loss after stress relief annealing. The mechanism is not very clear, but it can be considered that this is due to the segregation of Sb and Sn on V, etc. The precipitation behavior is affected, so that the precipitation is inhibited or the precipitates become coarse. In addition, even in steels in which V and the like are reduced to the above-mentioned appropriate ranges, precipitation of V and the like is unavoidable to some extent. Therefore, it can be considered that addition of Sb and Sn is effective even for steel in which V and the like are lowered.

In addition, in conventional non-oriented electrical steel sheets, it is known to add Sb and Sn in order to improve the composite structure and reduce iron loss (for example, JP-A-56-54370, JP-A-2000-129409 , T. Kubota, T. Nagai; J. Mater. Eng. Perform. l (1992), p.219, etc.). However, in a non-oriented electrical steel sheet in which Al, N, etc. are extremely reduced and ductile inclusions are controlled, it is a phenomenon that has not been understood until now that the addition of Sb and Sn significantly promotes the iron loss improvement effect in stress relief annealing .

In this way, the amount of Ti, Nb, and V mixed in the molten iron and Si raw materials is limited, and the effect of preventing fine precipitates caused by the above-mentioned decrease in Sol.Al is further improved, and at the same time, it further improves magnetic properties. In particular, in a composition system in which Al is reduced as much as possible, it is advantageous to add a restriction on the amount of V in addition to restrictions on the amounts of Ti and Nb. In particular, it is very effective in improving iron loss in stress relief annealing. The restrictions on the above trace elements are summarized below.

Ti: 0.0020% or less (including 0); Nb: 0.0050% or less (including 0); and V: 0.0060% or less (including 0)

Ti, Nb, and V form fine nitrides or carbides, thereby hindering the formation of aggregated structures and the growth of crystal grains. Especially in the non-oriented electrical steel sheet according to the present invention, where the restrictions on Sol, Al and N are low, this tendency is quite remarkable. Reducing these elements to Ti: 0.0020% or less, Nb: 0.0050% or less, V: 0.0060% respectively, the tendency to form nitrides or carbides will be suppressed, especially beneficial to improve the iron loss after stress relief annealing.

In addition, appropriate addition amounts of Sb and Sn are as follows.

One or two types selected from Sb: 0.005 to 0.10% and Sn: 0.005 to 0.2%

Sb and Sn suppress the fine precipitation of nitrides and reduce the inhibitory effect of the nitrides on particle growth, thus effectively promoting the formation of aggregates with good magnetic properties. This effect is exhibited when Sb: 0.005% or more and Sn: 0.005% or more, but if they exceed 0.10% and 0.2%, respectively, particle growth will be hindered.

In addition to the above, the characteristics of the steel of the present invention can be exhibited more effectively by limiting or adding the following elements.

One or two types selected from P: 0.001 to 0.2% and Ni: 0.001 to 0.2%

Indentation and breakage will occur during punching, and the abnormality generated during punching will increase, reducing the area occupancy of the steel plate, etc. When these problems occur, add at least one of P and Ni to make this These problems can be avoided by improving the hardness of the invented electrical steel sheet. Therefore, these elements can be added according to the requirements of downstream manufacturers within the range that is not harmful to the electromagnetic properties, especially the magnetic flux density.

One or two kinds selected from REM: 0.0001 to 0.10% and Ca: 0.0001 to 0.01%

REM and Ca have the effect of coarsening sulfide and improving iron loss performance (that is, reducing iron loss). Therefore, these elements can be appropriately added within the range in which these elements function, that is, REM: 0.0001 to 0.10%, and Ca: 0.0001 to 0.01%.

S: below 0.0050% (including 0); O: below 0.0100%

If S exceeds 0.0050%, it tends to combine with Mn and impurity elements (mainly elements mixed in from scrap) Cu to form MnS and Cu ₂ S, which will hinder the growth of crystal grains. Also, if O (oxygen) exceeds 0.0100%, oxides increase, thereby hindering the growth of crystal grains. Therefore, it is preferable to limit these elements within the above-mentioned ranges.

The strength level and iron loss level required for the non-oriented electrical steel sheet vary depending on the characteristics of the rotating machine to be manufactured. Therefore, in the present invention, it is not necessary to uniformly define the grain size of the steel sheet after finish annealing. However, if the average recrystallized grain size D is in the range of 6-25 μm, the aforementioned stress-relieving annealing crystal grain growth ratio will be relatively large, for example, 3 or more, thus exerting a favorable effect.

There is no particular limitation on the method of manufacturing the non-oriented electrical steel sheet of the present invention described above. It can be produced according to the following typical processes.

First, according to, for example, a continuous casting method, molten iron prepared with an appropriate composition is formed into a slab. Next, it is hot-rolled to make a hot-rolled sheet. If necessary, hot-rolled sheet annealing is performed, and then cold rolling is performed more than once, and during this period, intermediate annealing is performed as necessary to obtain a final plate thickness. After performing continuous annealing (finish annealing) on the finished cold-rolled steel sheet, insulation coating is performed as necessary. Also, when the carbon content of the slab is higher than that of the composition of the present invention, appropriate decarburization annealing is performed after hot rolling.

In the present invention, it is important to control the amount and existing form of ductile inclusions among inclusions, especially to reduce ductile inclusions whose average crystal grain diameter length is within a predetermined range. That is, the ductile non-metallic inclusions that hinder the growth of particles are controlled below 1000/cm ² . This control can be achieved according to any one or combination of the following methods.

The first is to reduce the absolute amount of non-metallic inclusions in the slab by reducing the oxygen content.

In addition, it is also effective to make the non-metallic inclusions in the slab ductile by increasing the amount of Al and Mn, and conversely, to lose ductility (miniaturization) by reducing the amount of Al and Mn.

In addition, the length of non-metallic inclusions can be adjusted by controlling the manufacturing conditions, especially the rolling conditions, so that the average recrystallized grain size of the finished annealed steel plate can be less than 3 times or more than 9 times the ductile inclusions. things account for the majority. For example, the length of the ductile inclusions in the hot-rolled sheet can be adjusted by increasing or decreasing the hot-rolling reduction rate by increasing or decreasing the thickness of the slab or the thickness of the hot-rolled sheet. Also, even if the hot rolling rolling ratio is the same, the length of the ductile inclusions can be changed by increasing or decreasing the rolling ratio in the high-temperature region where the inclusions tend to elongate. Furthermore, if the cumulative rolling ratio after hot rolling is increased, the ductile inclusions will become longer, and if the cumulative rolling ratio is reduced, the ductile inclusions will be shortened. Adjust the length of non-metallic inclusions by increasing or decreasing the thickness of the hot-rolled plate or the increase or decrease of the product plate thickness.

Conversely, change the annealing temperature and soaking time of the finished product to increase or decrease the average grain size. As a result, the length of most ductile inclusions can be less than 3 times the average recrystallization grain size or exceed the average recrystallization grain size. 9 times the particle size.

In addition, in the above-mentioned manufacturing process, it is preferable to set the annealing temperature of the continuous annealing (finish annealing) of the cold-rolled steel sheet cold-rolled to the final plate thickness at 700-800° C. to adjust the average grain size to 6 ~25 μm, or adjust the hardness of the steel plate to an appropriate level, for example, adjust the Vickers hardness (Hv) to 100-170. Setting the Vickers hardness within the above-mentioned range is advantageous in securing the strength and punchability of the steel sheet.

The non-oriented electrical steel sheet produced in this way is punched into iron cores for rotating machines, and can be assembled into rotors and stators. In this process, the iron core materials for the rotor and stator are punched out from the same steel plate at the same time, laminated separately, and assembled into the rotor and stator parts, and only the stator is subjected to stress relief annealing to promote particle growth, thereby reducing its Iron loss. It is preferable not to perform stress-relief annealing accompanying particle growth on the iron core member for the rotor so as to maintain high strength.

The stress relief annealing temperature is preferably in the range of 700 to 800°C. In addition, the annealing time is preferably 10 minutes to 3 hours. Stress relief annealing conditions are more preferably within the above-mentioned range such that the stress relief annealing crystal grain growth ratio becomes 2 or more, for example, in an inert gas atmosphere, preferably at 750° C. for 2 hours. In addition, the stress relief annealing temperature is a temperature higher than the finish annealing temperature, but it is preferable from the viewpoint of ensuring particle growth.

In addition, the non-oriented electrical steel sheet after finished annealing undergoes slight deformation, such as 0.5-5% rolling deformation, and after punching, implements stress-relief annealing at 700-800°C, which can promote recrystallization and make crystallization The particle size grows to 30-100 μm. In this way, the treated steel plate can be used in the assembly of the stator requiring extremely low iron loss. The stress-relief annealing conditions described in the preceding paragraph are also suitable for this case.

Example

Hereinafter, the embodiments of the present invention will be described more specifically based on examples.

Example 1

A slab having the composition shown in Table 4 and the remainder being iron and unavoidable impurities was produced by the continuous casting method. In addition, the amounts of Ti, Nb, V, S, and O are reduced to the above-mentioned appropriate ranges. These slabs were heated at 1110° C. for 40 minutes, and then hot-rolled to obtain 2.5 mm hot-rolled sheets. The produced hot-rolled plate is pickled, descaled, and cold-rolled to produce a cold-rolled steel plate with a plate thickness of 0.50 mm. Next, finish annealing was performed at 780° C. for 10 seconds in an atmosphere having a capacity ratio of hydrogen:50% to nitrogen:50%. The semi-organic coating solution composed of dichromate and resin is coated on the finished annealed board, and fired at 300°C to make a product board.

In addition, the amount (number density) of ductile non-metallic inclusions that inhibit particle growth varies with changes in the thickness of the slab and changes in the rolling schedule during hot rolling.

Samples were cut out from the produced product boards, and the magnetic flux density, iron loss, upper yield point (YP) and Vickers hardness (Hv) were measured in accordance with JIS C 2550. In addition, the upper yield point (YP) is the average value of the rolling direction and the direction perpendicular to the rolling direction.

In addition, the average crystal grain size and the number density of ductile non-metallic inclusions inhibiting grain growth were detected. In addition, the measurement was performed on the surface perpendicular to the width direction.

Next, in an argon atmosphere, after performing stress relief annealing on the above-mentioned product plate at 750°C for 2 hours, as in the previous product, the iron loss and average grain size were measured, and the stress relief annealing crystal grain growth rate was also calculated. Compare.

Table 4 steel mark Chemical composition (mass%) Slab Thickness (mm) C Si mn Sol.Al N Sb, Sn twenty one 0.0032 0.75 0.25 0.0003 0.0025 - 200 twenty two 0.0031 0.80 0.25 0.0004 0.0024 - 200 twenty three 0.0031 0.55 0.26 0.0002 0.0021 - 200 twenty four 0.0032 0.75 0.25 0.0002 0.0017 - 280 25 0.0037 0.80 0.27 0.0003 0.0021 - 280 26 0.0028 0.55 0.25 0.0004 0.0022 - 280 27 0.0031 0.55 0.26 0.0004 0.0021 Sb: 0.007 200 28 0.0030 0.55 0.24 0.0004 0.0022 Sb: 0.007 280 29 0.0029 0.55 0.25 0.0004 0.0020 Sn: 0.008 200 30 0.0029 0.55 0.24 0.0004 0.0019 Sn: 0.008 280

The obtained results are shown in Table 5. As shown in Table 4 and Table 5, the samples having the composition of the present invention and the number density of ductile non-metallic inclusions that hinder particle growth have a large growth ratio of crystal grains after stress relief annealing, so especially the samples after stress relief annealing Iron loss value is low. Combined with the relatively high upper yield point (YP) and Vickers hardness (Hv) of the finished product (finished annealed state), it becomes a material suitable for simultaneously punching and making rotors and stators of rotary machines. Also, the magnetic flux density is sufficiently high. In addition, especially in the inventive examples (27, 29) in which Sb and Sn were added, the magnetic properties were significantly improved after stress relief annealing.

Example 2

A continuously cast slab having a thickness of 210 mm having the composition shown in Table 6, the remainder being iron and unavoidable impurities was produced. In this process, by properly adjusting the composition of the slab in the steelmaking process and adjusting the rolling conditions, the amount of ductile non-metallic inclusions that hinder particle growth is kept below 1000 pieces/cm ² .

As in the case of Example 1, the produced slabs were treated to produce products and tested. The finish annealing of steel mark 58 is carried out at 680°C, and the finish annealing of steel mark 59 is carried out at 850°C.

The obtained results are shown in Table 7. As shown in Table 7, the samples with the composition and average grain size of the present invention all have good stress relief annealing crystal grain growth ratio and strength and magnetic properties, so they are suitable for simultaneous punching and manufacturing of rotary machines. materials of the rotor and stator.

It also shows that especially controlling the annealing temperature of the finished product at 700-800°C, or controlling the average recrystallization grain size of the product plate at 6-25 μm, is beneficial to the high strength before stress-relief annealing and the low iron loss value after stress-relief annealing All are beneficial.

Table 6 steel mark Chemical composition (mass%) C Si mn Sol.Al N S o Ti Nb V other elements 31 0.0039 0.75 0.38 0.0003 0.0027 0.0045 0.0085 0.0004 0.002 0.0020 32 0.0034 0.30 0.25 0.0002 0.0023 0.0030 0.0070 0.0003 0.001 0.0020 33 0.0030 0.55 0.20 0.0001 0.0017 0.0025 0.080 0.0003 0.004 0.0025 34 0.0022 0.30 0.25 0.0001 0.0022 0.0035 0.0050 0.0004 0.003 0.0035 35 0.0045 1.06 0.27 0.0003 0.0015 0.0030 0.0060 0.0005 0.002 0.0025 36 0.0028 0.90 0.25 0.0004 0.0021 0.0040 0.0090 0.0006 0.003 0.0030 37 0.0025 0.36 0.19 0.0003 0.0014 0.0020 0.0060 0.0005 0.004 0.0035 38 0.0023 0.95 0.25 0.0002 0.0018 0.0015 0.0050 0.0004 0.002 0.0030 39 0.0040 1.10 0.27 0.0002 0.0023 0.0013 0.0040 0.0003 0.002 0.0040 40 0.0027 1.10 0.28 0.0001 0.0024 0.0022 0.0070 0.0006 0.004 0.0020 Sb: 0.008 41 0.0020 1.15 0.25 0.0002 0.0021 0.0035 0.0050 0.0004 0.002 0.0040 Sb: 0.061 42 0.0025 0.95 0.26 0.0001 0.0016 0.0040 0.0045 0.0004 0.002 0.0010 Sn: 0.010 43 0.0036 0.85 0.20 0.0002 0.0025 0.0035 0.0070 0.0004 0.003 0.0040 Sn: 0.150 44 0.0025 0.50 0.19 0.0001 0.0022 0.0025 0.0075 0.0003 0.003 0.0050 Sb: 0.52, Sn: 0.048, P: 0.080, Ni: 0.050 45 0.0026 0.30 0.11 0.0002 0.0017 0.0022 0.0060 0.0003 0.003 0.0015 P: 0.018 46 0.0038 0.28 0.09 0.0001 0.0029 0.0023 0.0040 0.0004 0.005 0.0015 Ni: 0.22 47 0.0043 0.55 0.25 0.0002 0.0029 0.0020 0.0035 0.0003 0.002 0.0010 P: 0.040, Ni: 0.151 48 0.0038 0.75 0.40 0.0003 0.0028 0.0045 0.0060 0.0004 0.002 0.0020 49 0.0033 0.80 0.24 0.0005 0.0023 0.0030 0.0065 0.0004 0.001 0.0020 50 0.0031 0.55 0.18 0.0001 0.0035 0.0025 0.0080 0.0003 0.004 0.0020 51 0.0045 1.05 0.28 0.0003 0.0016 0.0060 0.0065 0.0004 0.002 0.0020 52 0.0029 0.90 0.24 0.0004 0.0022 0.0045 0.0110 0.0009 0.003 0.0030 53 0.0025 0.35 0.21 0.0003 0.0013 0.0019 0.0065 0.0024 0.004 0.0040 54 0.0022 0.95 0.26 0.0002 0.0019 0.0015 0.0050 0.0004 0.006 0.0030 55 0.0040 1.10 0.27 0.0002 0.0022 0.0015 0.0045 0.0004 0.002 0.0060 56 0.0045 1.00 0.24 0.0003 0.0018 0.0060 0.0050 0.0004 0.002 0.0020 REM: 0.01 57 0.0040 1.05 0.26 0.0003 0.0017 0.0060 0.0040 0.0004 0.002 0.0020 Ca: 0.001 58 0.0040 1.10 0.28 0.0010 0.0080 0.0055 0.0110 0.0004 0.003 0.0060 59 0.0040 1.00 0.23 0.0001 0.0017 0.0015 0.0040 0.0003 0.002 0.0020 60 0.0014 0.60 0.22 0.0001 0.0014 0.0015 0.0038 0.0002 0.001 0.0020 Sn: 0.015, P: 0.07 61 0.0026 0.55 0.23 0.0002 0.0015 0.0017 0.0038 0.0002 0.001 0.0020 Sb: 0.01, Ni: 0.10 62 0.0038 0.55 0.20 0.0001 0.0020 0.0015 0.0045 0.0003 0.001 0.0030 Sb: 0.007, Sn: 0.006, Ca: 0.001, REM: 0.005 63 0.0037 0.65 0.25 0.0001 0.0011 0.0018 0.0050 0.0002 0.001 0.0020 Sn: 0.030, Ca: 0.002 64 0.0022 0.60 0.21 0.0001 0.0018 0.0018 0.0043 0.0003 0.000 0.0010 So: 0.035, REM: 0.02 65 0.0025 0.12 0.24 0.0002 0.0013 0.0016 0.0051 0.0002 0.001 0.0020 Sb: 0.007, Sn: 0.010 66 0.0010 0.60 0.22 0.0001 0.0021 0.0013 0.0041 0.0002 0.001 0.0020 Sn: 0.015 67 0.0012 0.60 0.19 0.0001 0.0010 0.0019 0.0035 0.0002 0.000 0.0010 Sn: 0.020

Table 7 steel mark Product properties (before stress relief annealing) Properties after stress relief annealing Stress Relief Annealing Crystal Grain Growth Ratio Remark W _15/50 (W/kg) B ₅₀ (T) Average grain size (μm) Surrender point (MPa) Vickers hardness (Hv) W _15/50 (W/kg) Average grain size (μm) 31 5.3 1.75 14 292 107 4.1 61 4.5 Invention example 32 5.4 1.76 15 294 104 4.3 56 3.8 Invention example 33 5.6 1.76 14 300 106 4.1 61 4.3 Invention example 34 5.9 1.76 14 295 107 4.7 53 3.8 Invention example 35 5.2 1.74 14 298 103 4.1 48 3.5 Invention example 36 5.3 1.75 14 302 104 3.8 55 3.8 Invention example 37 5.7 1.76 15 292 103 4.8 48 3.2 Invention example 38 5.6 1.74 14 301 107 3.9 48 3.5 Invention example 39 5.2 1.75 13 294 102 3.8 55 4.1 Invention example 40 5.1 1.74 14 298 107 3.6 58 4.1 Invention example 41 5.1 1.74 13 293 105 3.9 54 4.0 Invention example 42 5.2 1.75 14 297 108 3.7 59 4.2 Invention example 43 5.3 1.75 15 295 104 3.9 59 3.9 Invention example 44 5.5 1.76 15 328 127 3.9 59 3.9 Invention example 45 5.8 1.76 16 311 123 4.6 50 3.2 Invention example 46 5.8 1.76 14 305 116 4.5 52 3.6 Invention example 47 5.9 1.75 13 331 133 4.5 56 4.4 Invention example 48 6.5 1.72 10 303 108 5.9 20 1.9 comparative example 49 6.8 1.71 10 313 110 6.1 19 1.9 comparative example 50 6.9 1.71 10 307 110 6.1 15 1.4 comparative example 51 5.8 1.73 11 311 113 4.8 28 2.5 Invention example 52 5.8 1.73 12 307 114 4.8 30 2.5 Invention example 53 6.2 1.74 13 305 111 5.1 33 2.5 Invention example 54 6.0 1.74 13 308 115 4.9 30 2.3 Invention example 55 5.9 1.73 12 311 109 4.8 25 2.1 Invention example 55 5.3 1.73 14 297 103 4.2 45 3.2 Invention example 57 5.4 1.73 13 295 100 4.5 46 3.5 Invention example 58 8.7 1.76 5 341 132 6.2 14 2.8 Invention example 59 4.9 1.73 30 272 95 4.4 50 1.7 Invention example 60 5.4 1.75 14 330 131 3.7 63 4.5 Invention example 61 5.5 1.74 14 315 120 3.9 59 4.2 Invention example 62 5.2 1.74 15 295 106 3.7 65 4.3 Invention example 63 5.2 1.76 14 304 109 3.8 60 4.3 Invention example 64 5.3 1.75 14 305 107 3.9 58 4.1 Invention example 65 5.6 1.75 15 301 105 4.0 61 4.1 Invention example 66 5.2 1.74 14 297 108 3.7 60 4.3 Invention example 67 5.2 1.74 14 298 108 3.6 61 4.4 Invention example

As described above, the present invention can provide a non-oriented electrical steel sheet that is extremely suitable for manufacturing rotors and stators for rotating machines.

In addition, the non-oriented electrical steel sheet of the present invention is not limited thereto, but also has good so-called reproducibility characteristics. That is, if the existing iron core material with high Al content is regenerated, and the shaft of the motor is cast, etc., the surface oxidation of molten iron will occur, and the viscosity will increase. Therefore, the fillability of the molten iron in the mold is reduced, and sometimes a perfect casting cannot be produced. Thus, generally Al-containing steel scrap lacks reproducibility, but the non-oriented electrical steel sheet of the present invention is a low-Al material and has high casting reproducibility.

Industrial Applicability

According to the high magnetic flux density non-directional electrical steel sheet of the present invention, the rotor material and the stator material can be cut from the same steel sheet at the same time, and the rotor material has high magnetic flux density and high strength, and the stator material has high magnetic flux density and low Iron loss. This greatly improves the manufacturing efficiency and output characteristics of the components for the rotary machine and the rotary machine related thereto. Furthermore, the non-oriented electrical steel sheet of the present invention has good casting reproducibility, and the castability at the time of recycling scrap iron and steel which is a blanking material is improved.

Claims (15)

1. A non-oriented electrical steel sheet containing Si: 0.1% to 1.2% and Mn: 0.005 to 0.3% in mass % (hereinafter the same), and restricting C, Al, N, and O to C: 0.0050% or less ( containing O), Sol.Al: 0.0004% or less (containing O), N: 0.0030% or less (containing O), and O: 0.0100% or less (containing O), as the rest contains Fe and unavoidable impurities. The average grain size D of crystal grains, and the number density of inclusions with a length of 3D to 9D are below 1000/cm ² . 2. The non-oriented electrical steel sheet according to claim 1, further comprising at least one selected from the group consisting of Sb: 0.005% to 0.10% and Sn: 0.005% to 0.2% in mass%. 3 . The non-oriented electrical steel sheet according to claim 1 , further comprising at least one selected from the group consisting of P: 0.001% to 0.2% and Ni: 0.001% to 0.2% in mass%. 4 . The non-oriented electrical steel sheet according to claim 1 , further comprising at least one selected from the group consisting of REM: 0.0001% to 0.10% and Ca: 0.0001% to 0.01% in mass%. 5. The non-oriented electrical steel sheet according to claim 1, wherein among the unavoidable impurities, Ti, Nb, and V are limited to Ti: 0.0020% or less (including O), and Nb: 0.0050% in mass %, respectively. Below (including O), and V: 0.0060% or below (including O). 6. The non-oriented electrical steel sheet according to claim 1, wherein among the unavoidable impurities, S is limited to S: 0.0050% or less (including O) in mass %. 7. The non-oriented electrical steel sheet according to claim 1, wherein the average grain diameter D of the recrystallized grains is 6 μm to 25 μm. 8. The non-oriented electrical steel sheet according to claim 1, wherein the number density of the inclusions with a length of 3D to 9D relative to the average grain diameter D of recrystallized grains is 0.1 pieces/cm ² or more. 9 . The non-oriented electrical steel sheet according to claim 1 , which is a steel sheet produced by at least cold rolling followed by finish annealing, the temperature of the finish annealing being 700° C. to 800° C. 9 . 10. A non-oriented electrical steel sheet characterized by being the steel sheet according to claim 1, wherein the average grain size of recrystallized grains is doubled or more by stress relief annealing at 750° C. for 2 hours. 11. A non-oriented electrical steel sheet obtained by subjecting the steel sheet according to any one of claims 1 to 10 to stress relief annealing. 12. The non-oriented electrical steel sheet according to claim 11, wherein a temperature of the stress relief annealing is 700°C to 800°C. 13. A rotor member for a rotating machine obtained by laminating the non-oriented electrical steel sheet according to any one of claims 1 to 10. 14. A stator member for a rotary machine, obtained by laminating the non-oriented electrical steel sheet according to any one of claims 1 to 10, and then performing stress relief annealing. 15. A rotating machine comprising the rotor member according to claim 13 and the stator member according to claim 14, which use the same non-oriented electrical steel sheet as a material.

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