KR100567239B1 - Nonoriented magnetic steel sheet, member for rotary machine and rotary machine - Google Patents

Abstract

Si: 0.1% to 1.2% and Mn: 0.005 to 0.30% by mass ratio, C: 0.0050% or less (including 0), Sol.Al: 0.0004% or less (including 0), N: 0.0030% or less ( The number density of the ductile nonmetallic inclusions dispersed in the steel sheet is limited to 1000 or less (including 0), and the rotor and stator materials are simultaneously taken from the same steel sheet. By applying a high magnetic flux density and high strength in the rotor material and a stress relief annealing in the stator material, a non-oriented electromagnetic steel sheet capable of achieving high magnetic flux density and low iron loss is obtained.

Herein, when the average recrystallized grain size of the finished annealed steel sheet is D, the grain growth inhibiting ductile nonmetallic inclusion refers to an inclusion having a length of 3 x D to 9 x D.

Description

Non-Directed Electromagnetic Steel Sheet, Rotator Member and Rotator {NONORIENTED MAGNETIC STEEL SHEET, MEMBER FOR ROTARY MACHINE AND ROTARY MACHINE}

The present invention relates to a non-oriented electromagnetic steel sheet used for assembling a rotating machine.

The present invention also relates to a rotor part and a rotor assembled using the non-oriented electromagnetic steel sheet.

In order to reduce the energy consumption of the rotor, it is effective to raise the magnetic flux density of the iron core of the rotor, that is, the rotor (rotor) and the stator (stator), and to attain low iron loss of these iron cores. As means for reducing the iron loss, a means for increasing the electrical resistance of the iron core material by increasing the content of Si, Al, Mn and the like has been generally used. In addition to these means, for example, a method of adding B disclosed in JP-A-58-151453, a method of adding Ni disclosed in JP-A-3-281758, and the like are known. In addition, there is a method of improving the magnetic properties by preferentially growing the grain structure of the electromagnetic steel sheet, for example, in the {100} < UVW > direction, for example in Japanese Patent Laid-Open No. 58-. 181822, etc. are proposed. By using the non-oriented electromagnetic steel sheet manufactured by these means, it is possible to manufacture iron cores of high magnetic flux density and low iron loss.

By the way, the non-oriented electromagnetic steel sheet used for the iron core of the rotating machine is finished by annealing (final annealing) by a steel plate manufacturer, and then shipped as a product sheet. ) Is assembled to the rotor and stator of the rotor. In the assembling step, after the iron core plate for the rotor or the iron core plate for the stator is punched out from the steel sheet, stress relief annealing is performed as necessary.

The technique of obtaining the low iron loss which is further excellent by improving the growth property of the recrystallized particle in the said stress relief annealing is also proposed. For example, JP-A-58-55210 and JP-A-8-269532 disclose that the amount of So1.Al in the steel sheet is reduced to 0.0010% or less and 0.003% or less, respectively, to suppress fine AlN precipitation. The technique which improves the grain growth in stress relief annealing and obtains a low iron loss is disclosed. Japanese Unexamined Patent Application Publication No. 3-24229 also improves grain growth in stress relief annealing by reducing the amount of Sol.Al to 0.OO1% or less and suppressing the product of N and V content below a predetermined value. And a technique for obtaining low iron loss. Japanese Patent Laid-Open No. 7-70719 discloses a method for improving grain growth in stress relief annealing, such as reducing the amount of Sol.Al to 8 ppm or less, and further reducing the amount of Ti + Al to 20 ppm or less. have.

In addition, Japanese Patent Application Laid-Open No. 63-195217 or Japanese Patent Laid-Open No. 7-150248 disclose that in addition to low Al, the composition of inclusions made of a composite oxide of Si, Al, and Mn is controlled to soften the inclusions. It is disclosed that the grain growth in the stress relief annealing is improved by preventing the loss, and low iron loss can be obtained.

However, even with these techniques, the amount of improvement of the iron loss by stress relief annealing is not sufficient, for example, after finishing annealing (factory), the steel sheet of about 6 W / kg is stress-annealed to less than 5 W / kg. Although it is possible to improve the degree, it was difficult to improve the degree to less than 4.4 W / kg by stress relief annealing in the steel sheet previously reduced to about 5 W / kg after finishing annealing (shipment).

By the way, in order to manufacture the iron core for a rotating machine, in order to keep the product yield of a material high, generally, the iron core plate for rotors and a stator iron core are punched by a press from the same steel plate. And the iron core plate for rotor and the iron core plate for stator are laminated | stacked, respectively, and it assembles to a rotor and a stator.

Among these, the rotor is a rotating member, and a high stress due to high speed rotation is required, so that the rotor is required to have high strength. In particular, in recent years, in order to raise the efficiency of a rotor (motor), a rotor of a type provided with rare earth magnets has been developed, and the rotational speed of the rotor has been significantly increased. Therefore, for the electromagnetic steel sheet which comprises a rotor, the magnetic flux density and intensity | strength, for example, a higher yield point YP, are calculated | required higher than before. On the other hand, the stator has high magnetic flux density and low iron loss is important for miniaturization and energy saving of the rotor.

Thus, even if it is an electromagnetic steel sheet 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 "stator material") have required characteristics. This is different and it is difficult to make both characteristics compatible. The conventionally proposed technique does not work so as to satisfy both of these characteristics even if the characteristics as the rotor and stator materials are individually satisfied.

The present invention provides a high magnetic flux density and high strength in the rotor material and high magnetic flux density and low iron loss in the stator material while simultaneously taking the rotor material and the stator material from the same steel plate. An object of the present invention is to propose a density non-oriented electromagnetic steel sheet and to propose a rotor member and a rotor using the same.

The present invention,

1.Mad: 0.1%-1.2% and Mn: 0.005-0.30% by mass ratio, C: 0.0050% or less (including 0), Sol.Al: 0.0004% or less (including 0), N: limited to 0.0030% or less (including 0), deformable non-metallic inclusions with grain growth inhibition containing Fe and unavoidable impurities as remainder and dispersed in the steel sheet It is a high magnetic flux density non-oriented electromagnetic steel sheet for rotating machines whose number of inclusions per unit area is 1000 pieces / cm 2 or less (including 0).

Herein, when the average recrystallized grain size (average particle diameter of the recrystallized grains) of the steel sheet is D, the grain-inhibited ductile nonmetallic inclusion refers to an inclusion having a length of 3 x D to 9 x D. Here, the steel sheet refers to the steel sheet in the state of the finished annealed product sheet, that is, the state not being stress annealed, and the average recrystallized grain size and the length of the ductile nonmetallic inclusion are naturally values in the state of the product sheet. In addition, the flexible nonmetallic inclusion refers to a relatively coarse nonmetallic inclusion that increases relatively easily by rolling (or increases on a product plate or the like). However, since most of the elongation in a steel sheet is nonmetallic inclusion, it is simply referred to as a soft inclusion.

In addition, the composition of the non-oriented electrical steel sheet is preferably substantially made of the Si, Mn, C, Sol.A1, N, the balance Fe and unavoidable impurities.

2. The high magnetic flux density non-oriented electromagnetic steel sheet for a rotating machine according to the above 1 item, which further contains one or two selected from Sb: 0.005% to 0.10% and Sn: 0.005% to 0.2% by mass.

3. High magnetic flux density non-directional electrons for rotating machines according to the invention of 1 or 2 above, which further contain one or two selected from P: 0.OO1% to 0.2% and Ni: 0.001% to 0.2% by mass%. Grater.

4. The rotation according to any one of the above 1 to 3, which further contains one kind or two kinds selected from REM: 0.10% to 0.1% and Ca: 0.1% to 0.01% by mass%. High magnetic flux density non-oriented electrical steel sheet.

5. Among the unavoidable impurities, Ti, Nb and V are in mass%, respectively, Ti: 0.OO20% or less (including 0), Nb: 0.0050% or less (including 0), and V: 0.OO60% or less (0 A high magnetic flux density non-oriented electromagnetic steel sheet for a rotating machine according to any one of the above 1 to 4, wherein the high magnetic flux density is not limited thereto.

6. In any of the above inevitable impurities, S and O are each in mass%, S: 0.0050% or less (including 0), and O: 0.0100% or less (including 0). High magnetic flux density non-oriented electromagnetic steel sheet for a rotating machine according to the invention.

7. The high magnetic flux density non-oriented electromagnetic steel sheet according to any one of the above 1 to 6, wherein the average particle diameter D of the recrystallized particles is 6 µm to 25 µm.

8. Steel sheet manufactured by at least cold rolling and subsequent finish annealing, wherein the finish annealing temperature is 700 ° C. to 800 ° C., wherein the high magnetic flux density non-oriented electromagnetic steel sheet for a rotating machine according to any one of the above 1 to 7 is used. . That is, the slab for non-oriented electromagnetic steel sheet is processed by a routine method to form a cold rolled steel sheet having a final sheet thickness, and then finish annealing is performed at 700 to 800 ° C.

9. The non-oriented electrical steel sheet according to any one of the above 1 to 8, wherein the average recrystallized grain size is grown by 2 times or more by stress relief annealing at 750 ° C. for 2 hours (that is, the stress removal annealing crystal grain growth ratio is 2). The high magnetic flux density non-oriented electromagnetic steel sheet for a rotating machine characterized by the above).

10. A high magnetic flux density non-oriented electromagnetic steel sheet (stress relief annealing plate) formed by subjecting a high magnetic flux density non-oriented electromagnetic steel sheet (product plate) to a rotor according to any one of the above 1 to 9 to stress relief annealing. .

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

That is, the non-oriented electromagnetic steel according to each of the inventions 1 to 9 above is treated with a slab for non-oriented electromagnetic steel sheet by a routine method to form a cold rolled steel sheet having a final sheet thickness, and then subjected to finish annealing at 700 to 800 ° C. In addition, stress removal annealing was further performed at 700-800 degreeC here, Preferably, the average recrystallized grain size can also be made to grow more than twice the grain size after finish annealing.

12. The rotor member for rotor which laminates after high punching the high magnetic-density-density non-oriented electromagnetic steel sheet for rotors which concerns on any one of said 1-9.

13. A stator member for a rotor, wherein the high magnetic flux density non-oriented electromagnetic steel sheet for a rotor according to any one of the above 1 to 9 is preferably punched out, laminated, and then subjected to stress relief annealing.

14. A rotor having a rotor member according to the invention of 12 and a stator member according to the invention of 13 according to the invention, which are made of the same high magnetic flux density non-oriented electromagnetic steel sheet for a rotor.

That is, the non-oriented electromagnetic steel sheets according to the above inventions 1 to 9 can be laminated after punching to form a high strength rotor rotor member. In addition, after punching, lamination may be performed again and then stress relief annealing may be used to form a low iron loss rotor stator member. In addition, by using the rotor member and the stator member obtained from the same non-oriented electromagnetic steel sheet, a high performance rotor can be obtained.

Fig. 1 shows the relationship between the ratio of the average grain size of the steel sheet after stress relief annealing to the average grain size of the steel sheet after the non-oriented electrical steel sheet, that is, the finish annealing, and the N content of the steel sheet. It is a graph which shows the number of ductile nonmetallic inclusions as a parameter.

Best Mode for Carrying Out the Invention

EXAMPLE

The present inventors first focused on the following points.

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

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

(3) The stress relief annealing is performed at the demand as described above, and the annealing can increase the grain size and reduce the iron loss.

As a result of considering the above, the present inventors found out the configuration of each of the following methods.

(1) Securing high magnetic flux density by adopting non-oriented electromagnetic steel sheet having low Si content and Mn content,

(2) In the product plate after the finish annealing, it is relatively fine particles, high strength, and high growth of the crystal grains in the stress relief annealing,

(3) In the rotor material, strength is secured without stress relief annealing, and in the stator material, stress relief annealing is performed to realize low iron loss by grain growth.

By the above combination, the grain size can be optimized in the manufacturing process of the rotor and the stator to impart the necessary characteristics to the rotor and the stator, respectively.

The present inventors again explored the factors that govern the growth of grain size in the stress relief annealing process performed in the assembling process of the stator, and found that the following methods were combined.

(1) limiting the upper limit of Al as a strict industrial level to suppress fine precipitates such as AlN;

(2) Limiting the number density of the soft inclusions dispersed in the steel sheet to a predetermined value or less in relation to the average crystal grain size of the finished annealed steel sheet, that is, the grain growth in the stress relief annealing of the soft inclusions in a specific dimensional range. To determine the dominant influence on and to realize more precise and efficient soft inclusion control,

The combination of the above finds that the grain size can be remarkably grown in the stress relief annealing step (for example, about 2 hours at 750 ° C.) performed in the stator assembly process at the demand. Reached.

Hereinafter, the chemical composition (mass%) suitable for the electromagnetic steel sheet of this invention is demonstrated.

Si: 0.1 to 1.2%

In order to increase the electrical resistance of the steel sheet and reduce the iron loss, it is necessary to contain at least 0.1% of Si. However, when Si content exceeds 1.2%, magnetic flux density will fall, hardness will rise, and workability will also deteriorate. Therefore, Si content is taken as 0.1 to 1.2% of range.

Mn: 0.005 to 0.30%

Mn is a component necessary for obtaining good workability at the time of hot rolling, and for that purpose, Mn needs to be contained in 0.05% or more. However, when it exceeds 0.30%, magnetic flux density will fall. Therefore, content of Mn is made into 0.005 to 0.30%.

C: 0.OO50% or less (including 0)

In order to suppress self-aging deterioration, it is necessary to make C as low as possible. Moreover, in order to fully exhibit the improvement effect of an aggregate structure under the ultra-low Alization conditions employ | adopted by this invention, it is necessary to reduce to 0.OO50% or less. However, the reduction of C does not necessarily have to be achieved at the stage of molten steel or slab which is a starting material. That is, in the manufacturing process of the steel sheet, it may be achieved until the end of the finish annealing. Representative decarburization means is decarburization annealing. In addition, when decarburizing in a manufacturing process, it is preferable that the amount of C in a starting material exists in the range of 0.550%-0.1%.

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

In order to obtain excellent grain growth and magnetic properties, it is necessary to reduce the Al amount of the steel sheet to 0.0004% or less. When the Al content is more than 0.004%, AlN precipitates in the steel sheet, and the magnetic flux density decreases in the finished product sheet annealed. Moreover, the recrystallized grain growth property at the time of stress relief | stretch annealing also falls, and the outstanding effect of this invention that remarkably reduces iron loss value cannot be acquired.

N: 0.OO30% or less (including 0)

N combines with Al to cause nitride (AlN) to precipitate, and in combination with Ti to form various nitrides and causes a decrease in magnetic flux density of the finished annealed product. Moreover, recrystallization grain growth at the time of stress relief annealing is inhibited and it becomes a cause which inhibits sufficient fall of an iron loss value. Therefore, it is necessary to reduce N amount to 0.0030% or less. Preferably it is 0.0025% or less.

In addition to the above basic composition, the non-oriented electrical steel sheet of this invention can add at least any of Sb, Sn, P, Ni, REM, and Ca according to the target steel plate characteristic. These suitable contents are demonstrated later. In addition to the above, at least any one of Cr: 5% or less and Cu: 5% or less does not interfere with obtaining the effect of the present invention.

In addition, typical examples of other unavoidable impurities include Ti, Nb, V, S, and 0, and a suitable range thereof will be described later. Also, inevitable impurities such as Cu: 0.2% or less, Cr: 0.08% or less, Zr: 0.005% or less, As: 0.01% or less, Mo: 0.95% or less, and W: 0.95% or less are also acceptable. do.

Although the non-oriented electromagnetic steel sheet of this invention has the above basic composition, only the control of a composition cannot achieve the objective of this invention. Among the nonmetallic inclusions dispersed in the finished annealed steel sheet, when the average recrystallized grain size of the steel sheet (finished annealed product sheet) is D, the number density of the flexible inclusions (ductile nonmetallic inclusions) having a length of 3 × D to 9 × D is It is necessary to be 1000 pieces / cm 2 or less (including 0). This flexible nonmetallic inclusion having a length of 3xD to 9xD is then defined as a grain growth inhibiting flexible nonmetallic inclusion.

Here, the average recrystallized grain diameter measures the number of crystal grains which exist in the area of 0.5 mm <2> of a steel plate, calculates the average area per crystal grain based on it, and calculates the diameter of a circle which is equal to the average area. The diameter at the time of use was adopted. This average grain size is measured by observing a cross section (so-called L section) cut perpendicular to the sheet width direction of the steel sheet with an optical microscope.

The soft inclusions refer to the inclusions in the shape of rods extending in the rolling direction and the inclusions continuously next to the rolling direction. In addition, when two or more inclusions in the distance of 10 micrometers or less are arranged in the direction within 5 degrees with respect to a rolling direction, these inclusions were connected and regarded as one soft inclusion.

Incidentally, the inclusion includes an isolated circular inclusion in addition to the soft inclusion. This is a non-soft inclusion and is not counted for the soft inclusion. When the length of the inclusions is less than twice the short diameter, it is classified as a circular type and when the length exceeds 2 times, it is classified as a soft inclusion.

Representative soft inclusions include SiO ₂ , Al ₂ O ₃ , MnO, CaO, or some of these composite oxides (which may be non-combustible depending on their composition).

The length of a flexible inclusion is the maximum value of the length of the line segment drawn between any two points in the interface between the branch iron and the interposition of the inclusion, that is, the distance between both ends of the flexible inclusion. (This is called Jangkyung). The measurement of the number of the flexible inclusions of predetermined length was made into the following procedure.

The cross section perpendicular to the plate width direction of the steel sheet was polished and the surface of the steel sheet (without being subjected to corrosion treatment, etc.) was observed with an optical microscope, and a small region different in color from the iron part was recognized as an inclusion. The observation field of one sample was 5 mm2, and the number of the types recognized as flexible inclusions of a predetermined length among the inclusions recognized above was measured, and this number was converted into the number per 1 cm 2 to obtain the number density. .

Below, the experiment and the result which were performed in order to investigate the influence on the particle growth property of a flexible inclusion are shown.

Experiment 1

C: 0.002%, Si: 0.7% Mn: 0.2%, Sol.Al: 0.OOO% or less, S: 0.OO2%, residual unavoidable impurities as a basic component, and N in the range of 0.0010% to 0.0060% The slab changed to was prepared.

The resulting slab was heated to 1100 ° C., hot rolled to a thickness of 2.3 mm, then pickled, cold rolled to a final plate thickness of 0.35 mm, and then finished annealing (recrystallization annealing) at 800 ° C. for 15 seconds. It carried out and it was set as the finish annealing board (product board). In addition, adjustment of the amount (number density) and form (length) of flexible inclusions is, for example,

(1) controlling the amount and composition of oxides by changing oxygen content and Al content,

(2) The control was performed by controlling the amount of stretching of the inclusions by changing the slab thickness in hot rolling, such as changing the slab thickness.

For the obtained product, the average grain size was measured, the inclusions were observed, and the length and the number density of the flexible inclusions were measured. Subsequently, the product was annealed at 750 ° C. for 2 hours in an argon (Ar) atmosphere (hereinafter, simply referred to as “stress removal annealing”), and the average crystal grain size was measured as in the finish annealing plate. The annealing condition is a condition corresponding to the stress relief annealing at the demand.

1 shows the ratio of the average grain size of the steel sheet after stress removal annealing to the average grain size of the steel sheet after finish annealing thus obtained (hereinafter referred to as “stress removal annealing crystal grain equipment” or simply “particle equipment”) and N It is a graph showing the relationship between contents. Here, when the average recrystallized grain size after finish annealing was referred to as D, different marks were used depending on the number density of inclusions having a length of 3 x D to 9 x D (referred to as grain growth inhibiting soft nonmetallic inclusions).

As can be seen from FIG. 1, when the N content is 30 ppm (mass ppm) or less, when the number density of the grain growth inhibiting ductile nonmetallic inclusions is 1000 pieces / cm 2 or less, the stress relief annealing crystal grain equipment becomes 2 or more. However, even if the number density of the grain growth inhibiting flexible nonmetallic inclusions is less than 1000 / cm 2, when the N content exceeds 0.0030% or the number density of the grain growth inhibiting flexible nonmetallic inclusions exceeds 1000 / cm 2, the stress The removal annealing crystal grain growth ratio becomes less than two.

Experiment 2

The same result can be confirmed from the following Experiment 2. With the composition shown in Table 1, three slabs having a thickness of 250 mm made of residual iron and unavoidable impurities were manufactured, and the thicknesses were 25 mm, 50 mm, 100 mm and 200 mm samples were cut out, respectively. Then, after heating these samples to 1070 degreeC, it was made into 2.5 mm by hot rolling, and after pickling, it finished by cold rolling to the final board thickness of 0.5 mm. Subsequently, the conditions of the continuous annealing type finish annealing (recrystallization annealing) are adjusted in the range of 700 to 800 ° C, and the average recrystallized grain size (in the experimental examples and examples, only referred to as average grain size) is 12 µm or 14. It was set as a product plate which is 탆.

The obtained product plate was subjected to stress removal annealing at 750 ° C. for 2 hours in an Ar atmosphere. The cross section perpendicular | vertical to the plate width direction of these product boards (finishing annealing board) and the stress relief annealing board was observed with the optical microscope, and the average grain size was measured. In addition, about the product plate, the number density of the grain growth inhibiting ductile nonmetallic inclusions was measured. The results are shown in Table 2. As shown in Table 2, the stress reduction annealing crystal grain growth ratio is large in the sample of which the number density of the grain growth inhibiting ductile nonmetallic inclusions of the product plate is 1000 / cm 2 or less.

TABLE 1

TABLE 2

By limiting the composition and suitably limiting the number density of the ductile nonmetallic inclusions that inhibit grain growth, the average grain size of the steel sheet (iron core material configured in the stator) after the stress relief annealing can be at least twice the particle size after the finish annealing. Can be. As a result, the iron loss in the stator is greatly reduced.

On the other hand, as the rotor is used in the final annealed state, the crystal grains become relatively small, and the strength, in particular, the yield point (hereinafter abbreviated as YP) can be kept high.

Moreover, by using the rotor and the stator, it is possible to efficiently assemble a high performance rotor for high speed rotation.

Since the strength level required for the rotor depends on the characteristics of the rotor, the size of the average grain size, which is a factor governing the steel sheet strength, may be designed in accordance with the required strength level of the rotor. However, if it is a general rotary machine, 6-25 micrometers is suitable for the average grain size after finish annealing of a steel plate. 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.

In addition, although it does not affect the interpretation of the scope of the present invention, the reason why the stress removal annealing crystal grain growth rate is governed by the number density of the grain growth inhibiting ductile nonmetallic inclusions is considered as follows.

First, inclusions of the same length as the crystal grain size are considered to most inhibit grain growth. This is because the soft inclusions exist across one or more grain boundaries, and the probability of inhibiting the growth of the grains increases.

However, if the total amount of nonmetallic inclusions present in the electromagnetic steel sheet is constant, the volume fraction of the steel sheet is considered to be almost constant. Therefore, as indicated by the Zener equation, it is extremely extreme compared to the grain size. As a result, long inclusions are less likely to inhibit particle growth.

In other words, the extent to which the soft inclusions inhibit grain growth depends on the length of the inclusions, and in the inventors' opinion, when the length of the soft inclusions is 3 to 9 times the average crystal grains of the finished annealing plate, that is, the grain growth inhibition When it is a soft nonmetallic inclusion, it is the maximum. Therefore, the "stress removal annealing crystal grain growth ratio" is influenced by the number density of the soft inclusions in this range length, that is, the "particle growth inhibiting soft nonmetallic inclusions".

In addition, Zener Formula is a following formula which shows the particle growth suppression force I of an inhibitor.

I = (3/4) × (V × σ × ρ / r _o )

Where V is the molar volume of the parent phase, σ is the grain boundary energy, ρ is the volume fraction of the precipitate, and r _o is the average particle radius of the precipitate.

As described above, by controlling the contents of Si, Mn, C, Sol.A1 and N of the non-oriented electromagnetic steel sheet, respectively, and again suppressing the number density of the grain growth inhibiting ductile nonmetallic inclusions to 1000 / cm 2 or less, The stress removal annealing crystal grain growth ratio can be increased and it can be set as the high magnetic flux density non-oriented electromagnetic steel sheet suitable for rotating machines. Furthermore, the effect can be further improved by restricting the contents of Ti, Nb and V in the steel sheet composition or by adding Sb and Sn. It was confirmed by the following experiment.

Experiment 3

The steel sheet is formed from the composition shown in Table 3, and the remainder is made of iron and unavoidable impurities, and these steel ingots are heated to 1070 ° C, hot rolled to 2.5 mm, pickled, and then cold rolled to form a final sheet thickness. It finished to 0.5 mm. Subsequently, after finishing annealing (recrystallization annealing) at 800 ° C. for 10 seconds to form a product plate, stress relief annealing was performed at 750 ° C. for 2 hours to obtain a stress relief annealing plate. From the obtained product plate and the stress relief annealing plate, the same number of samples were each taken out in parallel with a rolling direction, and orthogonal to a rolling direction, and magnetic flux density and iron loss were measured based on JISC2550. The measurement results are shown in Table 3.

In addition, the average grain size in each product board was 10-20 micrometers. In addition, the number density of the grain growth inhibitory soft nonmetallic inclusions in each product board was 1000 pieces / cm <2> or less.

TABLE 3

As can be seen from Table 3, the magnetic properties after stress relief annealing can be further improved by restricting Ti to 0.0020% or less, Nb to 0.0050% or less, and V amount to 0.0060% or less.

Furthermore, by adding one or two of Sb or Sn, the iron loss after the stress 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 together are nitrides and carbide forming elements, and when these nitrides are finely precipitated, it is thought that they adversely affect the texture of the formation of the texture and the grain growth like the fine precipitated AlN. For this reason, it is thought that favorable magnetic characteristics can be obtained as a result of preventing said solution by reducing these elements.

It is not clear why the reduction in the amounts of Ti, Nb and V affects the magnetic properties after stress relief annealing, but it is considered as follows. If the content of Ti, Nb and V is high, it is considered that the nitride or carbide partially dissolves during hot rolled sheet annealing or recrystallization annealing. In the stress relief annealing, nitride or carbide again precipitates and inhibits the movement of the magnetic domain wall. Therefore, it is considered that the iron loss is deteriorated when each of the above elements is large.

In addition, the reason why the iron loss after stress relief annealing is greatly improved by adding one or two kinds of Sb or Sn is not clear, but segregation of Sb and Sn affects precipitation behavior such as V and suppresses precipitation. I think it is because coarsening of precipitate occurs. In addition, even in steels in which V and the like are reduced to the appropriate ranges described above, precipitation of V and the like to some extent cannot be avoided. For this reason, it is thought that the effect of adding Sb and Sn is exhibited also in the steel which reduced V etc ..

In addition, conventionally, in the non-oriented electromagnetic steel sheet, it is known to add Sb or Sn in order to improve the texture and reduce iron loss (for example, JP-A-56-54370, JP-A-2000-129409, T. Kubota, T. Nagai; J. Mater. Eng. Perform. 1 (1992), p. 219, etc.). However, in the non-oriented electrical steel sheet in which Al, N, etc. are extremely reduced and ductile inclusions are controlled, it is not known that addition of Sb or Sn significantly promotes the iron loss improvement effect in stress relief annealing. It is a phenomenon.

By limiting the amounts of Ti, Nb, and V mixed in such molten iron and Si raw materials in the steel, the effect of preventing fine precipitates due to the reduction of Sol.Al is further enhanced and the magnetic properties are further improved. This is achieved. In particular, in the component system in which Al is reduced as much as possible, it is advantageous to limit the amount of V in addition to the limitation of the amount of Ti and Nb. The effect is especially great in improving iron loss after stress relief annealing. The limitation of the trace element is summarized as follows.

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 and inhibit formation of aggregates and growth of crystal grains. In particular, according to the invention, Sol. The tendency is remarkable in the non-oriented electrical steel sheet in which the Al and N contents are limited. When these elements are respectively reduced to Ti: 0.0020% or less, Nb: 0.0050% or less, and V: 0.0060% or less, the tendency of nitride or carbide formation is suppressed, which contributes particularly to the improvement of iron loss after stress relief annealing.

In addition, the suitable addition amount of Sb and Sn is as showing below.

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

Sb and Sn suppress the microprecipitation of nitride and at the same time reduce the particle growth inhibiting effect of the nitride, thereby effectively promoting formation of an advantageous texture in magnetic properties. The effect appears at Sb: 0.005% or more and Sn: 0.005% or more, but exceeds 0.10% and inhibits grain growth beyond 0.2%.

In addition to the above, by restricting or adding the following elements, the properties of the inventive steel can be exhibited more effectively.

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

If a problem occurs such as shear droop or crushing at the time of punching, or a decrease in spot ratio of the steel sheet due to a large return force generated at the time of punching, P and These problems can be avoided by raising the hardness of the electromagnetic steel sheet of the present invention by adding at least one of Ni. Therefore, these elements can be added according to the demand of the demand within the range that does not impair the electronic characteristics, especially the magnetic flux density.

One or two selected from REM: 0.0001 to 0.10% and Ca: 0.001 to 0.01%

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

S: 0.0050% or less (including 0), O: 0.0100% or less (including 0)

If S exceeds 0.0050%, the tendency to form MnS or Cu ₂ S in combination with Mn or Cu of the tramp element (primarily an element mixed from scrap) becomes stronger, which hinders crystal grain growth. In addition, when O (oxygen) exceeds 0.0100%, oxides increase, which hinders grain growth. Therefore, these elements are preferably limited within the above range.

The strength level and iron loss level required for the non-oriented electrical steel sheet are changed depending on the characteristics of the rotating machine to be manufactured. Therefore, in the present invention, the grain size of the finished annealed steel sheet need not be determined uniformly. Therefore, setting the average recrystallized grain diameter D to 6 to 25 µm advantageously works to make the stress removal annealing crystal grain growth ratio described above 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 manufacture by the following process.

First, molten steel adjusted to a suitable composition is made into a slab by, for example, a continuous casting method. Then, this is hot rolled to obtain a hot rolled sheet. After performing hot-rolled sheet annealing to this as needed, cold rolling of one or more times is performed between intermediate annealing as needed, and it finishes to a final board thickness. After performing continuous annealing (finishing annealing) on the obtained cold rolled sheet, insulation coating is performed as needed. In addition, when the carbon content of the slab is larger than the components of the present invention, decarburization annealing is appropriately performed after hot rolling.

In the present invention, it is important to control the amount of the soft inclusions in the inclusions and the form of the presence of the inclusions, and in particular, to reduce the soft inclusions whose length to the average grain size falls within a predetermined range. That is, the amount of the grain growth inhibiting ductile nonmetallic inclusion is controlled to 1000 or less / cm 2 or less. Such adjustment can be accomplished by any one or a combination of the following means.

First, there is a means for reducing the absolute amount of nonmetallic inclusions in the slab by reducing the oxygen content.

In addition, a means for softening the nonmetallic inclusions in the slab by increasing the amount of Al and Mn or, on the contrary, by deducting (miniaturizing) by reducing the amount of Al and Mn is also effective.

In addition, the manufacturing conditions, in particular, the rolling conditions may be controlled to adjust the length of the nonmetallic inclusions, and the flexible inclusions may be mainly less than three times or more than nine times the average recrystallized grain size of the finished annealed steel sheet. For example, the length of the flexible inclusion in the hot rolled sheet can be adjusted by increasing or decreasing the reduction ratio of hot rolling by increasing or decreasing the slab thickness or the hot rolled sheet thickness. In addition, even if the hot rolling reduction rate is the same, the length of the flexible inclusion can be changed by increasing or decreasing the reduction rate in a high temperature region where the inclusions are easy to extend whole body. Furthermore, if the cumulative reduction ratio after hot rolling increases, the soft inclusions tend to be long, and when the cumulative reduction ratio decreases, the soft inclusions tend to be short. Therefore, the length of the nonmetallic inclusion may be increased by increasing or decreasing the thickness of the hot rolled sheet. You can also make adjustments.

On the contrary, the average grain size can be increased or decreased by changing the conditions such as the temperature and the cracking time of the finish annealing. As a result, the length of the nonmetallic inclusion can be mainly less than three times or more than nine times the average grain size.

In the above manufacturing process, the annealing temperature of the continuous annealing (finishing annealing) performed on the cold rolled sheet cold rolled to the final sheet thickness is set to 700 to 800 ° C, and the average grain size is adjusted to 6 to 25 µm, Or it is preferable to adjust the hardness of a steel plate to a suitable level, for example, Vickers hardness (Hv) to 100-170. Setting the Vickers hardness Hv to the above range is suitable for securing the strength and punching property of the steel sheet.

The non-oriented electromagnetic steel sheet thus produced can be punched into an iron core for a rotating machine and assembled to a rotor and a stator. At that time, the iron core material for the rotor and the stator are simultaneously punched from the same steel sheet, laminated and assembled to the rotor and the stator member, and then stress relief annealing is performed only on the stator member to promote grain growth and lower the iron loss. Can be. It is preferable that the iron core member for the rotor is not subjected to stress removal annealing due to grain growth, and to maintain high strength.

The stress 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 for the stress relief annealing are more preferably within the above ranges, in which the stress removal annealing crystal grain growth ratio is 2 or more, but is preferably about 750 ° C. for about 2 hours in an inert gas atmosphere. Furthermore, the stress relief annealing temperature is preferably at a temperature higher than the finish annealing temperature from the viewpoint of ensuring particle growth.

In addition, the finish-annealed non-oriented electrical steel sheet again has a slight deformation, for example

A rolling deformation of about 0.5 to 5% is imparted, and after punching, a stress relief annealing of 700 to 800 ° C. is performed, recrystallization is promoted, and the grain size can be grown to 30 to 100 μm. The steel sheet thus treated can be used for assembling a stator, which requires particularly low iron loss. The appropriate stress relief annealing condition in this case is also as described in the shear lock.

(Example)

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described more concretely based on an Example.

(Example 1)

A slab having the composition shown in Table 4 and consisting of iron and unavoidable impurities in the balance was produced by the continuous casting method. In addition, the amounts of Ti, Nb, V, S, and O were reduced to a suitable range of electricity. After heating these slabs for 40 minutes at 1110 degreeC, it hot-rolled and made the hot rolled board of thickness 2.5mm. The obtained hot rolled sheet was pickled, the scale was removed, and then cold rolled to finish the cold rolled sheet having a thickness of 0.50 mm. Then, finish annealing was performed at 780 ° C for 10 seconds in an atmosphere of hydrogen: 50% to nitrogen: 50% at a capacity ratio. The semi-organic coating liquid which consists of dichromate and resin was apply | coated to the obtained finishing annealing board, and it heat-processed at 300 degreeC, and was made into the product board.

In addition, the amount (number density) of the grain growth-retardant ductile nonmetallic inclusions was varied by changing the slab thickness or changing the rolling schedule in hot rolling.

The sample was cut out from the obtained product plate, and the magnetic flux density, iron loss, phase yield point (YP), and Vickers hardness (Hv) were measured based on JIS C2550. In addition, the upper yield point YP was made into the average value of a rolling direction and a rolling right direction.

Furthermore, the average grain size and the number density of grain growth inhibiting ductile nonmetallic inclusions were measured. In addition, the measurement was made about the surface perpendicular | vertical to the width direction.

Subsequently, the product plate was subjected to stress removal annealing at 750 ° C. for 2 hours in an argon atmosphere, and then the iron loss and the average grain size were measured in the same manner as that for the product, and the stress removal annealing crystal grain growth ratio was again calculated. .

TABLE 4

The obtained results are shown in Table 5. As shown in Table 4 and Table 5, having the composition of the composition and the number growth density of the ductile nonmetallic inclusions according to the present invention has a high stress removal annealing crystal grain growth ratio, and therefore a particularly low iron loss value after stress removal annealing. In addition, the upper yield point (YP) and the Vickers hardness (Hv) of the product (finishing annealing state) are matched with relatively high, making it suitable for producing the rotor and the stator by simultaneously punching the rotor. Of course, the magnetic flux density is also high enough. In particular, in the inventive examples (27, 29) in which Sb or Sn is added, the improvement of the magnetic properties by stress relief annealing is remarkable.

TABLE 5

(Example 2)

A continuous casting slab having a thickness of 210 mm having a component composition shown in Table 6 and consisting of iron and unavoidable impurities was produced. At this time, in the steelmaking process, the amount of ductile non-metallic inclusions inhibiting particle growth was accommodated in the range of 1000 / cm 2 or less by optimizing slag composition and optimizing hot rolling conditions.

The obtained slab was processed in the same manner as in the case of Example 1 to obtain a product, and tested in the same manner as in the case of Example 1. However, the finish annealing of the steel symbol 58 was 680 degreeC, and the finish annealing of the steel symbol 59 was 850 degreeC.

The obtained results are shown in Table 7. As shown in Table 7, all of the components having the composition and average grain size according to the present invention have excellent stress relief annealing crystal grain growth ratio and strength and magnetic properties, which are suitable for simultaneous punching of the rotor and stator. It is.

In particular, controlling the finish annealing temperature to 760 to 800 ° C. or controlling the average recrystallized grain size of the product sheet to 6 to 25 μm is compatible with high strength before stress relief annealing and low iron loss value after stress relief annealing. It turns out that it is advantageous to.

TABLE 6

TABLE 7

According to the present invention as described above, it is possible to provide a non-oriented electromagnetic steel sheet which is very suitable for manufacturing a rotor and a stator for a rotor.

Moreover, the non-oriented electromagnetic steel sheet which concerns on this invention has the characteristic that it is excellent in what is called recycling property, without stopping there. That is, when the conventional iron core material with a high Al content is recycled and the shaft of a motor is cast, surface oxidation of molten steel advances and viscosity increases. For this reason, the filling property of molten steel may fall, and a sound casting may not be obtained. Therefore, although the scrap containing Al generally said that the recycling property was insufficient, the non-oriented electrical steel sheet which concerns on this invention is a low Al material, and the recycling property for casting is very high.

[Industry availability]

By using the high magnetic flux density non-oriented electromagnetic steel sheet according to the present invention, the rotor material and the stator material are simultaneously taken from the same steel plate, while the rotor material has high magnetic flux density and high strength, and the stator material has high magnetic flux density and low iron loss. ) Can be given. Thereby, the manufacturing efficiency and output characteristic of a rotating member, and also a rotating machine can be improved significantly. Moreover, the non-oriented electrical steel sheet which concerns on this invention is excellent in the recyclability at the time of casting, and the castability at the time of recycling scrap of a punching material is improved.

Claims (14)

In mass% (similarly below), Si: 0.1%-1.2%, Mn: 0.005%-0.3%, C, Al, N are C: 0.0050% or less, Sol.Al: 0.0004% or less, N: The number density of inclusions having a length of 3D to 9D is limited to 0.OO30% or less and contains Fe and unavoidable impurities as the remainder, and the average particle diameter D of the recrystallized particles is 1000 pieces / cm 2. Non-oriented electromagnetic steel sheet characterized by the following. The method of claim 1, The non-oriented electrical steel sheet 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. The method of claim 1, The non-oriented electrical steel sheet further comprising at least one selected from the group consisting of P: 0.001% to 0.2% and Ni: 0.001% to 0.2% by mass. The method of claim 1, The non-oriented electrical steel sheet further comprising at least one selected from the group consisting of REM: 0.0001% to 0.10% and Ca: 0.0001% to 0.01% by mass. The method of claim 1, The non-oriented electrical steel sheet according to claim 1, wherein Ti, Nb, and V are limited by mass% to Ti: 0.0020% or less, Nb: 0.0050% or less, and V: 0.0060% or less. The method of claim 1, The non-oriented electrical steel sheet according to claim 1, wherein S and O are limited to S: 0.0050% or less, and O: 0.0100% or less in terms of mass%. The method of claim 1, The non-oriented electrical steel sheet, wherein the average particle diameter D of the recrystallized particles is 6 µm to 25 µm. The method of claim 1, A non-oriented electrical steel sheet, which is produced by finish annealing at least 70 ° C. to 800 ° C. after cold rolling. The method of claim 1, Non-oriented electrical steel sheet, characterized in that the growth of recrystallized grains by stress relief annealing is about 2 times the average grain diameter of recrystallized grains is grown by a stress relief annealing at 750 ℃ for 2 hours. The method according to any one of claims 1 to 9, Non-oriented electrical steel sheet, characterized in that the steel sheet is produced by performing a stress relief annealing. The method of claim 10, Non-oriented electrical steel sheet, characterized in that the temperature of the stress relief annealing is 700 ~ 800 ℃. A rotor member for laminating the non-oriented electromagnetic steel sheet according to any one of claims 1 to 9. A stator member for a rotating machine comprising the step of laminating the non-oriented electromagnetic steel sheet according to any one of claims 1 to 9, followed by stress relief annealing. A rotor having a rotor member according to claim 12 and a stator member according to claim 13, which are made of the same non-oriented electromagnetic steel sheet.

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