WO2004013365A1

WO2004013365A1 - Nonoriented magnetic steel sheet, member for rotary machine and rotary machine

Info

Publication number: WO2004013365A1
Application number: PCT/JP2003/009947
Authority: WO
Inventors: Tadashi Nakanishi; Tishito Takamiya; Masaki Kawano
Original assignee: Jfe Steel Corporation
Priority date: 2002-08-06
Filing date: 2003-08-05
Publication date: 2004-02-12
Also published as: KR20040039438A; JP4718749B2; KR100567239B1; TWI276693B; CN1556869A; JP2004068084A; TW200403346A; CN1277945C

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/cm2 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 × D to 9 × 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

TECHNICAL FIELD The present invention relates to a non-oriented electrical steel sheet used for assembling a rotary machine. The present invention also relates to a rotating machine member and a rotating machine assembled using the above non-oriented electrical steel sheet. BACKGROUND ART To reduce the energy consumption of a rotating machine, it is necessary to increase the magnetic flux density of the iron core of the rotating machine, that is, a rotor (rotor) and a stator (stator), and to reduce iron loss of these iron cores. Is effective. As means for reducing iron loss, means for increasing the electric resistance of the iron core material by increasing the content of Si, Al, Mn, etc., has been generally used. In addition, the method of adding B disclosed in JP-A-58-151453 and the method of adding Ni disclosed in JP-A-3-281758 are known. . Also, there is a method of improving magnetic properties by making the texture of the magnetic steel sheet a crystal grain having a {100} (UVW) orientation preferentially grown, for example, as disclosed in Japanese Patent Application Laid-Open No. 58-181822. It is proposed in the official gazette. By using non-oriented electrical steel sheets manufactured by these means, it is possible to manufacture iron cores with high magnetic flux density and low iron loss. By the way, the non-oriented electrical steel sheet used for the core of the rotating machine is subjected to finish annealing (final annealing) by the steel sheet manufacturer and shipped as a product sheet. Assembled into theta. In this assembling process, after a core plate for a rotor or a core plate for a stator is punched from a steel plate, strain relief annealing is performed as necessary.

A technique has also been proposed to improve the growth of recrystallized grains during the strain relief annealing to obtain even better low iron loss. For example, JP-B-58-55210 and JP-A-8-269532 disclose that the amount of Sol.A1 in a steel sheet is reduced to 0.0010% or less and 0.003% or less, respectively, to reduce fine A1N. Suppressing precipitation improves grain growth during strain relief annealing and reduces low iron loss. The techniques obtained are disclosed. Japanese Patent Application Laid-Open No. 3-24229 also discloses that the amount of Sol. A 1 is reduced to 0.001% or less, and the product of the N and V contents is suppressed to a predetermined value or less. A technique for improving grain growth during annealing and obtaining a low iron loss is disclosed. The JP 7 70719 No. Gazette, 3 ₀ 1. How 1 volume was reduced to 8 111 will be further like to 20ppm or less the amount of Ti + Al, to improve the grain growth property in stress relief annealing Is disclosed.

Furthermore, JP-A-63-195217 and JP-A-7-150248 disclose that, in addition to reducing A1, the composition of inclusions composed of a composite oxide of Si, Al, and Mn is controlled. It is disclosed that by preventing ductility, grain growth during strain relief annealing can be improved and low iron loss can be obtained.

However, even with these technologies, the amount of improvement in iron loss by strain relief annealing is not sufficient. For example, after finish annealing (at the time of shipment), a steel sheet of about 6 W / kg is strain relief-annealed to 5 W / kg. Although it is possible to improve to less than about 4.4 W / kg, it is possible to improve the steel sheet to about 5 W / kg after finish annealing (at the time of shipment). Was difficult. In manufacturing a core for a rotating machine, a rotor core plate and a stator core plate are generally stamped out from the same copper plate by a press in order to maintain a high yield of materials. Then, the rotor core plate and the stator core plate are respectively laminated and assembled into a rotor and a stator.

Of these, the rotor is a rotating member, and is subjected to high stress due to high-speed rotation, so that it must have high strength. In particular, in recent years, in order to increase the efficiency of a rotating machine (motor), a rotor in which a rare-earth magnet is embedded has been developed, and the rotation speed of the rotor has been significantly increased. Therefore, the magnetic steel sheet constituting the rotor is required to have a higher magnetic flux density and strength, for example, a higher yield point (YP) than before. On the other hand, it is important for the stator to have a high magnetic flux density and a low iron loss in order to reduce the size of the rotating machine and save energy. As described above, even if the magnetic steel sheet is used for the same motor, 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 “steel sheet”) are used. Required material), and it is difficult to balance both characteristics. It is difficult. Conventionally proposed technologies, which individually satisfy the characteristics as a rotor material or a stator material, are not directed to satisfy both of these characteristics. DISCLOSURE OF THE INVENTION The present invention discloses that a rotor material and a stator material are simultaneously sampled from the same steel plate while a rotor material has a high magnetic flux density and a high strength, and a stator material has a high V magnetic flux density and a low strength. An object of the present invention is to propose a high magnetic flux density non-oriented electrical steel sheet capable of achieving iron loss, and to further propose a rotating machine member and a rotating machine using the same. The present invention

1. By mass ratio Si: 0.1% ~ 1.2% and Mn: 0.005 ~ 0.30%, C: 0.0005% or less (including 0), Sol. A1: 0 0004% or less (including 0), N: 0. 0030% or less (including 0), containing Fe and unavoidable impurities as the balance and dispersing in the steel sheet to inhibit grain growth and ductile non-metallic inclusions , is deformable non-metallic inclusions with gram growth inhibition) number density (number of inclusions per unit area) force S 1000 / cm ² or less (high magnetic flux density non-oriented electrical steel sheet for rotating turning point is including 0) of .

Here, the term “grain growth-inhibiting ductile nonmetallic inclusions” refers to the average recrystallized grain size (average grain size of recrystallized grains) of a steel sheet among the ductile nonmetallic inclusions, where D is 3 XD to 9XD. Refers to inclusions. Here, the steel sheet refers to the state of the finished annealed product sheet, that is, the steel sheet that has not been subjected to strain relief annealing, and the average recrystallized grain size and the length of ductile nonmetallic inclusions are, of course, the product sheet. It is a value in the state of. In addition, ductile nonmetallic inclusions refer to relatively coarse nonmetallic inclusions that expand relatively easily by rolling (or expand in product sheets, etc.), but do not expand in steel sheets. Are mostly non-metallic inclusions, henceforth simply referred to as ductile inclusions.

It is preferable that the composition of the non-oriented electrical steel sheet substantially consists of the above Si, Mn, Sol. Al, N, the balance of Fe and inevitable impurities.

2. The invention according to the first aspect, further comprising one or two selected from Sb: 0.005% to 0.10% and Sn: 0.005% to 0.2% by mass%. Such a high magnetic flux density non-oriented electrical steel sheet for rotating machines. 3. In mass%? : 0.001% to 0.2% and N i: One selected from 0.001% to 0.2% or

The high magnetic flux density non-oriented electrical steel sheet for a rotating machine according to the invention of the above 1 or 2, further comprising two types.

. 4 Mass ^_0/0 in REM:. 0. 0001% ~ 0 10% and C a:. 0. 0001% ~ 0 one or two species selected from 0.1% further contains any of the above 1 to 3, A high magnetic flux density non-oriented electrical steel sheet for a rotating machine according to the invention.

5. Among the unavoidable impurities, T i, N b and V in mass% are Ti: 0.0020% or less (including 0), b: 0.0050% or less (including 0), and V : The high magnetic flux density non-oriented electrical steel sheet for a rotating machine according to any one of the above-mentioned inventions, which is limited to 0.0060% or less (including 0). .

6. Among the inevitable impurities, S and O are limited by mass% to S: 0.0050% or less (including 0) and O: 0.0100% or less (including 0), respectively. A high magnetic flux density non-oriented electrical steel sheet for a rotating machine according to any one of the inventions of 1 to 5.

7. The average grain size D of the recrystallized grains is 6 μπ! Above: which is ~ 25 m! A high magnetic flux density non-oriented electrical steel sheet for a rotating machine according to any one of the above-described inventions.

8. The rotating machine according to any one of the above-mentioned inventions, wherein the steel sheet is manufactured by at least cold rolling and subsequent finish annealing, and the temperature of the finish annealing is 700 ° C to 800 ° C. High magnetic flux density non-oriented electrical steel sheet. That is, a slab for a non-oriented electrical steel sheet is processed by a conventional method to form a cold-rolled steel sheet having a final thickness, and then subjected to finish annealing at 700 to 800 ° C.

9. The non-oriented electrical steel sheet according to any one of the above-mentioned inventions 1 to 8, wherein the average recrystallized grain size grows twice or more by strain relief annealing at 750 ° C for 2 hours (ie, strain relief annealing). A high magnetic flux density non-oriented electrical steel sheet for rotating machines, characterized by having a crystal grain growth ratio of 2 or more.

10. High magnetic flux density non-oriented electrical steel sheet for rotating machines obtained by subjecting the high magnetic flux density non-oriented electrical steel sheet for rotating machines (product board) according to any one of the above inventions 1 to 9 to strain relief annealing. (Strain relief annealing plate). 11. The high magnetic flux density non-oriented electrical steel sheet for a rotating machine according to the tenth aspect, wherein the temperature of the strain relief annealing is 700 to 800.

That is, the non-oriented electrical steel according to each of the above-mentioned inventions:! To 9 is obtained by processing a slab for a non-oriented electrical steel sheet by a conventional method to obtain a cold-rolled steel sheet having a final thickness of 700 to 800 ° C. Can be subjected to finish annealing, and further subjected to strain relief annealing at 700 to 800, so that the average recrystallized grain size preferably grows to be at least twice the grain size after finish annealing. .

1 2. Above :! A high-flux-density non-oriented electrical steel sheet for a rotating machine according to any one of the above-mentioned inventions, preferably punched and punched out, and then laminated.

13. A high-flux-density non-oriented electrical steel sheet for a rotating machine according to any one of the above-described inventions 1 to 9, preferably a punched and laminated stator member for a rotating machine subjected to strain relief annealing.

1. A rotating machine comprising the same high magnetic flux density non-oriented electrical steel sheet for a rotating machine as the material and having the rotor member according to the above-described invention 12 and the stator member according to the above-described invention 13.

That is, the non-oriented electrical steel sheets according to the inventions of the above:! To 9 can be punched and laminated to form a high-strength rotating machine rotor member. Moreover, after punching and laminating, it can be further subjected to strain relief annealing to obtain a low iron loss rotating machine stator member. Furthermore, a high-performance rotating machine can be obtained using a rotor member and a stator member obtained from the same non-oriented electrical steel sheet. BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 shows the grain growth ratio of the non-oriented electrical steel sheet, that is, the ratio of the average grain size of the steel sheet after strain relief annealing to the average grain size of the steel sheet after finish annealing, and the N of the steel sheet. 4 is a graph showing the relationship with the content using the number of existing non-metallic inclusions inhibiting grain growth as a parameter. BEST MODE FOR CARRYING OUT THE INVENTION First, the present inventors focused on the following points.

(1) The saturation magnetic flux density of non-oriented electrical steel sheets is determined by the iron content (% by mass) of the material. The saturation magnetic flux density decreases when the content of elements other than iron, such as Si and Mn, is high. Inevitable. (2) The magnetic flux density and strength are governed by the crystal grain size of the steel sheet.

(3) As described above, strain relief annealing is performed by the customer, and the annealing may increase the crystal grain size and reduce iron loss. As a result of considering the above, the present inventors have found that the following methods are combined.

(1) High magnetic flux density is ensured by using non-oriented electrical steel sheets with low Si and Mn contents.

(2) The product sheet after finish annealing should have relatively fine grains and high strength, and ensure high crystal grain growth during strain relief annealing.

(3) To ensure strength without performing strain relief annealing in the rotor material, and to achieve low iron loss by grain growth by performing strain relief annealing in the stator material;

With the above combination, the crystal grain size can be appropriately adjusted in the manufacturing process of the rotor and the stator, so that the rotor and the stator can each have required characteristics. The present inventors have further searched for factors governing the growth of the crystal grain size in the strain relief annealing process performed in the process of assembling the stator, and have found that the following methods are combined.

(1) To restrict the upper limit of A1 to a very strict level as an industrial level to suppress fine precipitates such as A1N;

(2) Limit the number density of ductile inclusions dispersed in the steel sheet to a specified value or less in relation to the average grain size of the finish-annealed steel sheet. Finding that it has a dominant effect on grain growth during annealing, and realizing more precise and efficient ductile inclusion control,

It has been found that the combination described above can significantly increase the crystal grain size in the strain relief annealing process (for example, at 750 ° C for about 2 hours) performed in the stator assembly process at the customer. Thus, the present invention has been achieved. Hereinafter, the chemical composition (% by mass) suitable for the magnetic steel sheet of the present invention will be described.

Si: 0.1 to 1.2%

To increase the electrical resistance of the steel sheet and reduce iron loss, it is necessary to contain at least 0.1% of Si. However, when the Si content exceeds 1.2%, the magnetic flux density decreases and the hardness increases. In addition, the workability is inferior. Therefore, the Si content is in the range of 0.1 to 1.2%. Mn: 0.005 to 0.30%

Mn is a component necessary for obtaining good workability in hot rolling, and therefore, it is necessary to contain 0.005% or more. However, when it exceeds 0.30%, the magnetic flux density decreases. Therefore, the content of Mn should be 0.005-0.30%.

C: 0.0050% or less (including 0)

C must be as low as possible to suppress magnetic aging degradation. Further, in order to sufficiently exhibit the effect of improving the texture under the ultralow A1 conditions employed in the present invention, the content must be reduced to 0.0050% or less. However, this reduction of C does not necessarily have to be achieved at the stage of molten steel or slurp, which is the starting material. That is, it may be achieved by the end of finish annealing in the steel sheet manufacturing process. A typical decarburization method is decarburization annealing. When decarburization is performed during the production process, the C content in the starting material is preferably in the range of 0.0050% to 0.1%.

Sol. A1: 0.0004% or less (including 0)

In order to obtain excellent grain growth and magnetic properties, it is necessary to reduce the A1 content of the steel sheet to 0.0004% or less. If the A1 content exceeds 0.0004%, A1N precipitates in the steel sheet, and the magnetic flux density in the finish-annealed product sheet decreases. Further, the recrystallized grain growth during strain relief annealing is also reduced, and the excellent effect of the present invention of remarkably reducing the iron loss value cannot be obtained.

N: 0.0030% or less (including 0)

N combines with A1 to cause the precipitation of nitrides (A1N), and combines with Ti and the like to form various nitrides, thereby reducing the magnetic flux density of finish-annealed products. In addition, it hinders the growth of recrystallized grains during strain relief annealing, which hinders a sufficient decrease in iron loss value. Therefore, it is necessary to reduce the N content to 0.0030% or less. Preferably it is 0.0025% or less. The non-oriented electrical steel sheet of the present invention can be added in addition to the basic composition described above, in addition to Sb, Sn, P, Ni, REM, and Ca according to the properties of the steel sheet. These preferred The high content will be described later. In addition to the above, containing at least one of Cr: 5% or less and Cu: 5% or less does not hinder the effects of the present invention.

Representative examples of other inevitable impurities include Ti, Nb, V, S, and 0, and their preferable ranges will be described later. Further, 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, etc. Unavoidable impurities are also acceptable. The non-oriented electrical steel sheet of the present invention cannot achieve the object of the present invention only by controlling the force composition having the above basic composition. Among the nonmetallic inclusions dispersed in the finish-annealed steel sheet, when the average recrystallized grain size of the steel sheet (finish-annealed product sheet) is D, the ductile inclusion has a length of 3 XD to 9 XD. it is necessary as an object (including 0) m ² or less number density N 1000 (extending '14 nonmetallic inclusions). This ductile non-metallic inclusion having a length of 3 XD to 9 XD is hereinafter defined as a grain growth-inhibiting ductile non-metallic inclusion.

Here, average recrystallization grain size, and measure the number of crystal grains present in the area of 0.5 s Awakening ² of the steel sheet to calculate the average area of crystal grains per unit based on it, the average The diameter used when calculating the diameter of a circle equal to the area was adopted. This average crystal grain size is measured by observing a cross section (so-called L cross section) cut perpendicularly to the width direction of the steel sheet with an optical microscope. The ductile inclusions are rod-shaped inclusions elongated in the rolling direction and inclusions continuously arranged in the rolling direction. When two or more inclusions within a distance of ± 5 ° are aligned in a direction of ± 5 ° with respect to the rolling direction, these inclusions are considered to be connected and regarded as one ductile inclusion. .

The inclusions include isolated circular inclusions in addition to the ductile inclusions. This is a non-ductile inclusion and is not counted as a ductile inclusion. Inclusions were classified as circular if the major axis was less than twice the minor axis, and ductile if greater than twice the minor axis.

Exemplary ductile _{_{_{inclusions, Si0 2, A1 2 0 3}}} , Mn0, CaO or a number thereof; is ^ or Ranaru composite oxide (some, however if the non-ductile depending on the composition). The length of a ductile inclusion refers to the maximum value of the length of a line segment drawn between any two points at the interface between the base metal (matrix structure) and the inclusion, that is, the distance between both ends of the ductile inclusion. (This is the major axis Do). The number of ductile inclusions having a predetermined length was measured by the following procedure.

A cross section perpendicular to the width direction of the steel sheet was polished, and the as-polished surface (without performing any corrosion treatment, etc.) was observed with an optical microscope, and a small area different in color from the ground iron part was identified as an inclusion. The observation field against one sample as 5 Yuzuru ^2, the number of the form deemed extended inclusions having a predetermined length of the inclusions was approved by the measuring, the number per 1 cm ² The number density was converted to the number.

The following is an experiment conducted to investigate the effect of ductile inclusions on grain growth, and the results thereof.

(Experiment 1)

C: 0.002 ° /. , Si: 0.7%, n: 0.2%, Sol. A1: 0.0004% or less, S: 0.002%, remaining unavoidable impurities are the basic components, and N is 0.0010 ~ 0. · Made slabs modified in the range of 0060%.

The resulting slab is 1100. Heated to C, hot rolled to a thickness of 2.3 mm, pickled, cold rolled and finished to a final thickness of 0.35 ram. C, Finished annealing (recrystallization annealing) for 15 seconds to obtain a finished annealed plate (product plate). Adjustment of the amount of ductile inclusions (number density) and the form (length)

(1) Control of oxide amount and composition by changing oxygen content and A1 content,

(2) Controlling the amount of elongation of inclusions by changing the rolling schedule in hot rolling, such as changing the slab thickness

And so on.

The average grain size of the obtained product was measured and the inclusions were observed to measure the length and the number density of the ductile inclusions. Then, 750 for the above products in an argon (Ar) atmosphere. C, annealing for 2 hours (hereinafter simply referred to as “strain relief annealing”) was performed, and the average crystal grain size was measured as in the case of the finish-annealed sheet. The above annealing condition is a condition corresponding to the strain relief annealing at the customer.

Figure 1 shows the ratio of the average grain size of the steel sheet after strain relief annealing to the average grain size of the steel sheet after finish annealing obtained in this way (hereinafter referred to as the “strain relief annealing grain growth ratio” or simply “grain rate”). It is a graph showing the relationship between the growth ratio) and the N content. Here, assuming that the average recrystallized grain size after finish annealing is D, inclusions with a length of 3XD to 9XD (grain growth inhibiting ductile nonmetallic inclusions) Different marks were used depending on the number density. As can be seen from FIG. 1, when the N content is 30 ppra (mass _P pm) or less, the grain growth inhibition ductility If the number density of nonmetallic inclusions is 1000 or less Zcm ² , the strain growth annealing grain growth ratio Becomes 2 or more. However, the number density of grain growth inhibition ductile nonmetallic inclusions, the number of 1000 / cm ² even less, when N content exceeds 0030% 0., or grain growth inhibiting ductile nonmetallic inclusions When the density exceeds 1000 / cm ² , the strain relief annealing crystal grain growth ratio is less than 2.

(Experiment 2)

Similar results can be confirmed from Experiment 2 below. Three slabs, each having the composition shown in Table 1 and having a thickness of 250 mm and consisting of unavoidable impurities, were manufactured.These slabs were machined to a thickness of 25 mm, 50 mm, 100 mm. And 200 mm samples were cut out. Thereafter, these samples were heated to 1070 ° C, hot-rolled to 2.5 mm, pickled, and cold-rolled to a final thickness of 0.5 thigh. Next, the conditions of the finish annealing (recrystallization annealing) of the continuous annealing type were adjusted within the range of 700 to 800 ° C, and the average recrystallized grain size (in the experimental examples and examples, simply referred to as the average grain size). Is 12） m or ある. The obtained product sheet was subjected to strain relief annealing at 750 ° C for 2 hours in an Ar atmosphere. The cross sections perpendicular to the sheet width direction of these product plates (finished annealing plates) and strain relief annealing plates were observed with an optical microscope, and the average crystal grain size was measured. For the product sheet, the number density of the grain growth-inhibiting ductile nonmetallic inclusions was measured. The results are shown in Table 2. As shown in the table, in the sample in which the number density of the grain growth-inhibiting ductile non-metallic inclusions on the product sheet is 1000 ra2 or less, the strain relief annealing crystal grain growth ratio is large.

Steel Chemical composition (mass%)

Symbol C Si Mn Sol. Al N 0 Ti N 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

If the composition is restricted as described above and the number density of the grain growth-inhibiting ductile non-metallic inclusions is appropriately restricted, the average crystal grain size of the steel sheet (iron core material assembled into the stator) after strain relief annealing is determined by the finish annealing. It can be twice or more the size of the subsequent particles. This greatly reduces iron loss in the stator.

On the other hand, by using the rotor in the state of finish annealing, the crystal grains are relatively small. State, and the strength, especially the upper yield point (hereinafter abbreviated as YP), can be kept high. Further, by using the rotor and the stator, a high-performance rotating machine for high-speed rotation can be efficiently assembled. Since the strength level required for the rotor varies depending on the characteristics of the rotating machine, the size of the average crystal grain size, which is a factor controlling the steel sheet strength, is designed according to the required strength level of the rotor. Just fine. However, for a general rotating machine, the average crystal grain size after finish annealing of the steel sheet is preferably 6 to 25 μra. In this case, the strength of the steel sheet is about 200 to 400 MPa in YP and about 100 to 170 in Vickers hardness Hv. Although it does not affect the interpretation of the scope of the right of the present invention, the reason why the strain relief annealing crystal grain growth ratio is controlled by the number density of the grain growth inhibiting ductile non-metallic inclusions is as follows. Conceivable.

First, it is thought that inclusions with the same length as the crystal grain size most hinder grain growth. This is because ductile inclusions exist across one or more grain boundaries, increasing the probability of inhibiting the growth of the grains.

However, when the total amount of non-metallic inclusions present in the magnetic steel sheet is constant, the volume fraction of the steel is considered to be almost constant, so that the crystal grain can be calculated from the Zener equation as shown below. Inclusions that are extremely long compared to the diameter are less likely to inhibit grain growth. In other words, the degree to which the ductile inclusions inhibit the grain growth depends on the length of the inclusions. According to the knowledge of the present inventors, the length of the ductile inclusions is 3 to 9 times the average crystal grain of the finish-annealed sheet. When it is twice, that is, when it is a grain growth-inhibiting ductile nonmetallic inclusion, it becomes the maximum. Therefore, the “strain relief annealing crystal grain growth ratio” is affected by the number density of the ductile inclusions having a length in this range, that is, “grain growth inhibiting ductile nonmetallic inclusions”.

The Zener's equation is the following equation that indicates the inhibitory force I on the growth of the inhibitor.

I = (3/4) X (VX ff X p / r ₀ )

Here, V is the molar volume of the matrix, σ is the grain boundary energy, ρ is the volume fraction of the precipitate, and r ₀ is the average grain radius of the precipitate. As described above, the content of Si, Mn, C, Sol. In addition, by controlling the number density of grain growth-inhibiting ductile non-metallic inclusions to 1,000 or less per cm ² , it is possible to increase the crystal growth rate of strain relief annealing grains, and to achieve a high magnetic flux density suitable for rotating machines. It can be a non-oriented electrical steel sheet. Further, by limiting the contents of Ti, Nb and V in the steel sheet composition, or adding Sb and Sn, the effect can be further improved. This was confirmed by the following experiment.

(Experiment 3)

A steel ingot consisting of the composition shown in Table 3 and consisting of the balance of iron and unavoidable impurities was manufactured.These ingots were heated to 1070 ° C, hot-rolled to 2.5 ram, and pickled. After that, the sheet was finished to a final thickness of 0.5 mm by cold rolling. Next, after finishing annealing (recrystallization annealing) at 800 ° C for 10 seconds to obtain a product plate, the plate was subjected to strain relief annealing at 750 ° C for 2 hours to obtain a strain relief annealed plate. From the obtained product sheet and the strain relief annealing sheet, the same number of samples were cut out in parallel to the rolling direction and perpendicular to the rolling direction, and the magnetic flux density and iron loss were determined in accordance with JIS C 2550. It was measured. The measurement results are shown in Table 3.

The average crystal grain size in each product plate was 10 to 20 tubes. Further, the number density of the grain growth inhibiting ductile nonmetallic inclusions in each product plate was 1,000 / cm ² or less.

Table 3

Chemical composition (mass%)

¾¾p iron loss (

Straightening Straightening C Si Mn Sol. Al N 0 Ti Nb V Sn Sb

MU HI!

11 0.0018 0.90 0.15 0.0001 0.0017 0.0065 0.0024 0.002 0.0010 One-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 ― 5.34.3

15 0.0023 0.90 0.18 0.0001 0.0020 0.0060 0.0015 0.002 0.0020 One-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

21 0.0017 0.90 0.15 0.0001 0.0024 0.0065 0.0003 0.001 0.0010 0.19 5.2 3.7

As can be seen from Table 3, the magnetic properties after strain relief annealing are further improved by limiting Ti to 0.0020% or less, Nb to 0.0050% or less, and the V content to 0.0060% or less. be able to.

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

The reason why the magnetic properties are improved by reducing the amounts of Ti, Nb, and V is not necessarily clear, but is considered as follows. Ti, Nb, and V are both nitride and carbide forming elements, and when these nitrides precipitate finely, it is thought that, similarly to finely precipitated A1N, they have an adverse effect on texture formation and grain growth. Can be Therefore, it is considered that the above harm is prevented by reducing these elements, and as a result, good magnetic properties can be obtained.

It is not clear why the reduction of Ti, Nb, and V affects the magnetic properties after strain relief annealing, but it is considered as follows. If the contents of Ti, Nb and V are large, it is considered that nitrides or carbides partially dissolve during hot-rolled sheet annealing or recrystallization annealing. Then, at the time of strain relief annealing, nitride or carbide precipitates again and hinders the movement of the domain wall. Therefore, it is considered that the iron loss is deteriorated when the amount of each of the above elements is large. Also, it is not clear why the addition of one or two types of Sb or Sn significantly improves the iron loss after strain relief annealing. This is thought to be due to the effect of precipitation and suppression of precipitation and coarsening of precipitates. It should be noted that even with steel in which V and the like have been reduced to the above preferred ranges, some precipitation of V and the like is inevitable. For this reason, it is considered that the effect of adding Sb and Sn is exhibited even in steel with reduced V and the like.

Conventionally, it has been known that in non-oriented electrical steel sheets, Sb or Sn is added to improve the texture and reduce iron loss (for example, Japanese Patent Publication No. 56-54370, JP-A-2000-129409,. Kubota, T. Nagai; J. Mater. Eng. Perform. 1 (1992), p. However, in non-oriented electrical steel sheets in which Al, N, etc. are extremely reduced and ductile inclusions are controlled, the addition of Sb or Sn significantly promotes the iron loss improvement effect in strain relief annealing. Is a phenomenon that was not known before. In this way, the amount of Ti, Nb and V mixed in the hot metal and Si raw material in steel should be limited. Thus, the effect of preventing fine precipitates by reducing the above-mentioned Sol. A1 is further enhanced, and the magnetic properties are further improved. In particular, in a component system in which A1 is reduced as much as possible, it is advantageous to limit the amount of V in addition to the amounts of Ti and Nb. The effect is particularly great in improving iron loss after strain relief annealing. The limitations of the above trace elements are summarized below.

Ti: 0.0020% or less (including 0), b: 0.0050% or less (including 0), and V: 0.0060% or less (including 0)

Ti, Nb, and V form fine nitrides or carbides and inhibit the growth of texture forming crystal grains. In particular, according to the present invention, the tendency is remarkable in non-oriented electrical steel sheets in which the contents of Sol. These elements are respectively Ti: 0.0020% or less, Nb: 0.0050% or less, V: 0.0060 »/. If it is reduced below, the tendency to form nitrides or carbides is suppressed, which contributes to the improvement of iron loss especially after strain relief annealing. Suitable amounts of Sb and Sn are as shown below.

Sb: 0.005-0.10% and Sn: 1 or 2 types selected from 0.005 to 0.2%

Sb and Sn suppress the fine precipitation of nitride and reduce the grain growth inhibiting effect of the nitride, thereby effectively promoting the formation of a texture advantageous in magnetic properties. The effect appears at Sb: 0.005% or more and Sn: 0.005% or more, but exceeds 0.10% and 0.2 ° /, respectively. Above this, the grain growth is rather hindered. In addition to the above, the characteristics of the steel of the present invention can be more effectively exhibited by limiting or adding the following elements.

P: 0.001-0.2% and Ni: 0.001-0.2% 1 or 2 types

If problems such as sagging during punching or a reduction in the space factor of the steel sheet due to an increase in force generated during punching occur, at least one of P and Ni These problems can be avoided by increasing the hardness of the magnetic steel sheet of the present invention by adding. Therefore, these elements can be added as required by the customer within a range that does not impair the electromagnetic characteristics, particularly the magnetic flux density. REM: One or two selected from 0.0001-0.10% and Ca: 0.0001-0.01%

REM and Ca have the effect of increasing (ie reducing) iron loss by coarsening sulfides. Therefore, these elements are expressed in the range of expression of the effect, that is, REM: 0.0001 to 0.10%,

Ca: 0.0001-0. 01 Ca can be added as appropriate.

S: 0.0050% or less (including 0), 0: 0 100% or less (including 0)

If S exceeds 0.0050%, the tendency to form MnS or Cu ₂ S by combining with Mn and Cu of tramp elements (elements mainly mixed from scrap) becomes strong, which hinders grain growth. . On the other hand, if O (oxygen) exceeds 0.0100%, the amount of oxides increases and hinders crystal grain growth. Therefore, it is preferable to limit these elements to the above range. The strength level and iron loss level required for non-oriented electrical steel sheets vary depending on the characteristics of the rotating machine to be manufactured. Therefore, in this effort, it is not necessary to uniformly determine the crystal grain size of the finish-annealed steel sheet. However, the average recrystallized grain size! A value of 6 to 25 / zm is advantageous in that the above-mentioned strain relief annealing grain growth ratio is relatively large, for example, 3 or more. The method for producing the non-oriented electrical steel sheet according to the present invention is not particularly limited. Typically, it can be manufactured by the following process.

First, molten steel adjusted to a suitable component composition is formed into a slab by, for example, a continuous mirror manufacturing method. Then, this is hot-rolled into a hot-rolled sheet. After subjecting this to hot-rolled sheet annealing as needed, it is subjected to one or more cold rolling steps with intermediate annealing as necessary to finish to the final sheet thickness. The obtained cold rolled sheet is subjected to continuous annealing (finish annealing), and then an insulating coating is applied as necessary. When the carbon content of the slab is larger than that of the present invention, decarburizing annealing is appropriately performed after hot rolling. In the present invention, it is important to control the amount of ductile inclusions among the inclusions, and in particular to reduce the number of ductile inclusions whose length relative to the average crystal grain size is within a predetermined range. That is, the amount of the grain growth-inhibiting ductile nonmetallic inclusions is controlled to be 1000 / cm ² or less. Such a con Trolling can be accomplished by any one or combination of the following means.

First, there is a means to reduce the absolute amount of non-metallic inclusions in the slab by reducing the oxygen content.

It is also effective to make the non-metallic inclusions in the slab ductile by increasing the amount of A1 or Mn, or conversely, by reducing the amount of A1 or Mn to make it non-ductile (miniaturized).

In addition, the length of nonmetallic inclusions is adjusted by controlling the manufacturing conditions, especially rolling conditions, to reduce the length of non-metallic inclusions to less than 3 times or more than 9 times the average recrystallized grain size of the finish-annealed steel sheet. You can also be the Lord. For example, the length of the ductile inclusion in the hot-rolled sheet can be adjusted by increasing or decreasing the rolling reduction in hot rolling by increasing or decreasing the slab thickness or the hot-rolled sheet thickness. Also, even if the hot rolling reduction is the same, the length of the ductile inclusion can be changed by increasing or decreasing the rolling reduction in a high-temperature region where the inclusions are stretched. Furthermore, if the cumulative rolling reduction after hot rolling increases, the ductile inclusions become longer, and if the cumulative rolling reduction decreases, the ductile inclusions tend to become shorter. The length of the nonmetallic inclusion can also be adjusted by increasing or decreasing the thickness.

Conversely, the conditions of the finish annealing temperature and soaking time are changed to increase or decrease the average grain size, and as a result, the length of the non-metallic inclusions is reduced to less than three times or more than nine times the average grain size. It can also be the main. In the above manufacturing process, the annealing temperature of the continuous annealing (finish annealing) applied to the cold-rolled sheet cold-rolled to the final sheet thickness was 700 to 800. C is preferable for adjusting the average crystal grain size to 6 to 25 / xm or adjusting the hardness of the steel sheet to an appropriate level, for example, the Vickers hardness (Hv) to 100 to 170. It is preferable that the Vickers hardness be in the above range in order to secure the strength and punching property of the steel sheet. The non-oriented electrical steel sheet thus manufactured can be punched into an iron core for a rotating machine and assembled into a rotor and a stator. At that time, the core material for the rotor and the stator are simultaneously punched from the same steel plate, laminated and assembled into a rotor and a stator member, and then only the stator member is subjected to strain relief annealing to promote grain growth, The iron loss can be reduced. The core material for the rotor is not subjected to strain relief annealing accompanied by grain growth, and maintains high strength. It is better to leave.

The strain relief annealing temperature is preferably in the range of 700 ° C to 800 ° C. The annealing time is preferably about 10 minutes to 3 hours. The conditions of the strain relief annealing are more preferably those in which the strain relief annealing grain growth ratio is 2 or more within the above range, but, for example, the temperature is preferably 750 ° C for about 2 hours in an inert gas atmosphere. desirable. Further, it is preferable to perform the strain relief annealing at a temperature equal to or higher than the finish annealing from the viewpoint of ensuring grain growth. The non-oriented electrical steel sheet subjected to finish annealing is further subjected to a slight strain, for example, a rolling strain of about 0.5 to 5%, punched out, subjected to a strain relief annealing of 700 to 800, and recrystallized. The crystal grain size can be increased to 30 ~: LOO / zm. The steel sheet treated in this way can be used particularly for assembling a stator requiring low iron loss. Suitable strain relief annealing conditions in this case are also as described in the previous paragraph.

(Example)

Hereinafter, embodiments of the present invention will be described more specifically based on examples. (Example 1)

A slab having the component composition shown in Table 4 and comprising the balance of iron and inevitable impurities was produced by a continuous production method. Note that the amounts of Ti, Nb, V, S, and 0 were reduced to the above preferable ranges. After heating these slabs at 1110 ° C for 40 minutes, they were hot rolled into hot rolled sheets with a thickness of 2.5 m. The obtained hot-rolled sheet was pickled, the scale was removed, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.50. Then, by volume ratio, hydrogen: 50% _nitrogen: 50 ° /. In the atmosphere of 780 ° C for 10 seconds. A semi-organic coating solution consisting of dichromate and resin was applied to the resulting annealed plate, and baked at 300 ° C to obtain a product plate.

The amount of grain growth-inhibiting ductile nonmetallic inclusions (number density) was varied by changing the slab thickness and changing the rolling schedule in hot rolling.

A sample was cut out from the obtained product plate, and the magnetic flux density, iron loss, upper yield point (YP), and Vickers hardness (Hv) were measured in accordance with JIS C2550. The upper yield point (ΥΡ) is the average value of the rolling direction and the direction perpendicular to the rolling direction.

Furthermore, the average crystal grain size and the number density of the grain growth inhibiting ductile nonmetallic inclusions were measured. What The measurement was performed on a plane perpendicular to the width direction. Next, the above product plate was subjected to a strain relief annealing at 50 ° C for 2 hours in an argon atmosphere, and then the iron loss and average crystal grain size were measured in the same manner as performed for the product. Furthermore, the strain relief annealing crystal grain growth ratio was calculated. Table 4

Table 5 shows the obtained results. As shown in Tables 4 and 5, those having the component composition and the grain growth-inhibiting ductile nonmetallic inclusion number density according to the present invention have a large strain relief annealing crystal grain growth ratio, and particularly iron loss after strain relief annealing. Value is low. Combined with the relatively high yield point (YP) and high Vickers hardness (Hv) of the product (finished annealing state), the rotor and stator of the rotating machine can be stamped out and manufactured at the same time. It is suitable. Of course, the magnetic flux density is also high enough. In particular, in the invention examples (27, 29) to which Sb and Sn are added, the magnetic properties are significantly improved by the strain relief annealing. Table 5

(Example 2)

A continuous steel slab having the composition shown in Table 6 and having a thickness of 210 and consisting of iron and inevitable impurities was manufactured. At that time, the grain growth inhibition ductile nonmetallic inclusions amount is to fit a range of N 1000 m ² or less by optimizing optimizing the hot rolling condition of slag composition in steelmaking process.

The obtained slap was treated in the same manner as in Example 1 to obtain a product, and tested in the same manner as in Example 1. However, the finish annealing of steel symbol 58 was performed at 680 ° C, and the finish annealing of steel symbol 59 was performed at 850.

Table 7 shows the obtained results. As shown in Table 7, those having the component composition and the average crystal grain size according to the present invention have excellent strain relief annealing crystal grain growth ratio and strength and magnetic properties with excellent deviation, and It is suitable for simultaneous stamping production of rotor and stator.

In addition, controlling the finish annealing temperature to 700 to 800 ° C or controlling the average recrystallized grain size of the product sheet to 6 to 25 m, in particular, increases the strength before strain relief annealing and the strength after strain relief annealing. It can be seen that it is advantageous for achieving both low iron loss values.

Table 7

After strain relief annealing

Product characteristics (before annealing)

Characteristic

Steel 13 Annealing

Average yield yield Vickers Average result Remarks ^W 15/50 ^ΰ 50 ^W 15/50

Crystal grain size Point Hardness Crystal grain size

(W / kg) (Τ) (W / kg) Length ratio

(μπι) (MPa) (Hv) (Aim)

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 L 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

56 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 2003/009947 As described above, according to the present invention, it is possible to provide a non-oriented electrical steel sheet which is extremely suitable for manufacturing a rotor and a stator for a rotating machine.

Further, the non-oriented electrical steel sheet according to the present invention has a feature that it is excellent in so-called recyclability as well as the non-oriented electrical steel sheet. That is, when a conventional iron core material having a high A1 content is recycled to form a motor shaft or the like, the surface oxidation of molten steel proceeds and the viscosity increases. For this reason, the fillability of molten steel in the mold is reduced, and a sound solid may not be obtained. Therefore, although scrap containing A1 is generally considered to have poor recyclability, the non-oriented electrical steel sheet according to the present invention is a low-A1 material, and recyclability for manufacturing is extremely high. Industrial applicability The high magnetic flux density non-oriented electrical steel sheet according to the present invention allows the rotor material and the stator material to be simultaneously sampled from the same steel sheet while providing the rotor material with high magnetic flux density and high strength. In addition, a high magnetic flux density and low iron loss can be imparted to the stator material. As a result, the production efficiency and output characteristics of the rotating machine member and, consequently, the rotating machine can be greatly improved. At the same time, the non-oriented electrical steel sheet according to the present invention is excellent in recyclability at the time of forging, and has improved resilience at the time of recycling punched material scrap.

Claims

The scope of the claims

. 1 Mass ^_0/0 (the same applies hereinafter), S i:.. 0 1% ~ 1 2%, Mn:. Containing 0. 005% ~0 3%, C , A 1, N , respectively C: 0.005% or less (including 0), Sol. A1: 0.0004% or less (including 0), N: 0.0030% or less (including 0), Fe and unavoidable as the balance A non-oriented electrical steel sheet containing impurities and having a number density of 1000 / cm ² or less of inclusions having a length of 3D to 9D with respect to an average grain diameter D of recrystallized grains.

2. The method 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% by mass%. Non-oriented electrical steel sheet.

3. The method according to claim 1, further comprising at least one member selected from the group consisting of: 0.001% to 0.2% and Ni: 0.001% to 0.2% by mass%. Grain-oriented electrical steel sheet.

4. Mass ⁰ /. 2. The non-directional electromagnetic device according to claim 1, further comprising at least one selected from the group consisting of REM: 0.0001% to 0.10% and C a: 0.0001% to 0.01%. steel sheet.

5. Among the inevitable impurities, T i, N and V in mass% are Ti: 0.0020% or less (including 0), Nb: 0.0050% or less (including 0), and V 2. The non-oriented electrical steel sheet according to claim 1, wherein the non-oriented electrical steel sheet is limited to 0.0060% or less (including 0).

6. Among the unavoidable impurities, S and O are limited by mass% to S: 0.0050% or less (including 0) and O: 0.0100% or less (including 0), respectively. Item 1. The non-oriented electrical steel sheet according to item 1.

7. The average grain size D of the recrystallized grains is 6 / Xn! The non-oriented electrical steel sheet according to claim 1, which has a thickness of from 25 to 25 µm.

8. The non-oriented electrical steel sheet according to claim 1, wherein the steel sheet is manufactured by at least cold rolling followed by finish annealing, wherein the temperature of the finish annealing is 700 ° C to 800 ° C. .

9. The non-oriented electrical steel sheet according to claim 1, wherein the average grain size of the recrystallized grains grows twice or more by strain relief annealing at 750 ° C for 2 hours.

10. A non-oriented electrical steel sheet obtained by subjecting the steel sheet according to any one of claims 1 to 9 to stress relief annealing.

11. The non-oriented electrical steel sheet according to claim 10, wherein the temperature of the strain relief annealing is 700 to 800.

1 2. Claim :! A rotating machine rotor member formed by laminating the non-oriented electrical steel sheets according to any one of claims 9 to 9.

13. A stator member for a rotating machine obtained by stacking the non-oriented electrical steel sheets according to any one of claims 1 to 9 and then performing strain relief annealing.

14. A rotating machine having the rotor member according to claim 12 and the stator member according to claim 13 made of the same non-oriented electrical steel sheet.