JP2017179485A - Nonoriented electromagnetic steel sheet, motor core and manufacturing method of nonoriented electromagnetic steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented electromagnetic steel sheet with suppressing reduction of magnetic properties, a motor core using the same and a manufacturing method of the nonoriented electromagnetic steel sheet.SOLUTION: There is provided a nonoriented electromagnetic steel sheet containing, by mass%, 0.5%≤Si≤4.0%, 0.2%≤Al≤2.0%, 0.1%≤Mn≤3.0%, 0.010%≤Sn≤0.150%, C≤0.005%, S≤0.010%, N≤0.005% and the balance Fe with impurities and has difference between σand σ, (σ-σ) of 40 MPa≤(σ-σ)≤200 MPa, where σis tensile strength at elongation of the steel of 0.1% and σis tensile strength at elongation of the steel sheet of 0.2%.SELECTED DRAWING: None

Description

  The present invention relates to a non-oriented electrical steel sheet, a motor core, and a method for producing a non-oriented electrical steel sheet.

  In recent years, due to the increase in efforts for global environmental problems, for example, in the fields of automobiles (hybrid cars, electric cars, fuel cell cars, etc.) and household appliances (air conditioners, refrigerators, etc.), products with low energy consumption have spread. Yes. These products use high-efficiency motors that rotate at high speed, and non-oriented electrical steel sheets are used as the material for motor cores of high-efficiency motors (hereinafter, the motor core may be simply referred to as “core”). Yes.

  Non-oriented electrical steel sheets used for the cores of high-efficiency motors are required to have a high saturation magnetic flux density in order to effectively utilize the strength that can withstand high-speed rotation and the reluctance torque. In order to obtain a high saturation magnetic flux density, it is preferable to employ a low alloy non-oriented electrical steel sheet. However, low alloy non-oriented electrical steel sheets have large iron loss and low steel sheet strength. For this reason, low alloy non-oriented electrical steel sheets are not suitable for use in the core of a high-efficiency motor that rotates at high speed.

  Therefore, a highly alloyed steel sheet is required as a non-oriented electrical steel sheet for use in the core of a high efficiency motor. For example, a non-oriented electrical steel sheet that has been made into a high alloy by adding components such as Si, Al, and Mn is effective in that the strength is improved.

On the other hand, when simply applied to a non-oriented electrical steel sheet with increased strength, when applied to the core of a high-efficiency motor, the reduction in torque particularly during motor driving becomes significant. This is considered to be caused by a decrease in Bs (saturation magnetization) due to high alloying.
Therefore, a steel sheet to which P is added is known as a highly alloyed non-oriented electrical steel sheet from the viewpoint of balancing the increase in strength and the decrease in Bs (saturation magnetization).

For example, Patent Document 1, in mass% content of P, not more than 0.30% or more 0.100%, the magnetic flux density is 1.70T or more _{B 50,} no direction yield strength is at least 300MPa An electrical steel sheet is disclosed.

Further, in Patent Document 2, the content of P is% by mass, 0.25% or less, the area ratio of the recrystallized portion is less than 90%, and the tensile strength in the 45 ° direction from the rolling direction is 600 MPa or more, non-oriented electrical steel sheet flux density of 45 ° direction from the rolling direction is not less than 1.68T in B ₅₀ is disclosed.

Japanese Patent No. 3870725 JP 2009-299102 A

  By the way, even if the non-oriented electrical steel sheet containing P simply improves the yield point and the tensile strength, when applied to the core of a high-efficiency motor, the magnetic characteristics are likely to deteriorate.

For example, the non-oriented electrical steel sheets disclosed in Patent Document 1 and Patent Document 2 described above have good strength characteristics and magnetic characteristics, and are suitable for application to high-efficiency motors.
However, studies on higher speed rotation of high-efficiency motors are underway. Therefore, the conventional non-oriented electrical steel sheet to which P is added has a tendency to decrease the magnetic characteristics when applied as a core material of a high-efficiency motor that rotates at a higher speed than a conventional high-efficiency motor. I can see that.

  Thus, the conventional non-oriented electrical steel sheet to which P is added provides sufficient magnetic properties when applied to the core of a high-efficiency motor rotated at a higher speed than the conventional high-efficiency motor. Due to the difficulty, further improvement in magnetic properties has been demanded.

  Accordingly, an object of the present invention is to provide a non-oriented electrical steel sheet in which deterioration of magnetic properties is suppressed even when used as a core of a high-efficiency motor that rotates at high speed. Moreover, the motor core using this non-oriented electrical steel sheet is provided. Furthermore, the manufacturing method of this non-oriented electrical steel sheet is provided.

In view of the above circumstances, the inventors of the present invention have studied the non-oriented electrical steel sheet by paying attention to magnetic characteristics required when applied to the core of a high-efficiency motor that rotates at high speed.
By the way, when a non-oriented electrical steel sheet is applied as a core of a high-efficiency motor that rotates at high speed, the non-oriented electrical steel sheet is deformed because stress due to centrifugal force is applied. On the other hand, when the rotation of the motor stops, the deformation of the non-oriented electrical steel sheet returns. So far, there have been reports on the influence of stress on the magnetic properties of non-oriented electrical steel sheets, in relation to magnetostriction. However, it has not been generally recognized from the viewpoint of improving the efficiency of a high-speed rotating motor by controlling minute deformation behavior (dislocation formation behavior) in the process of transition from an elastic region to a plastic region. Therefore, the present inventors considered that the efficiency of the high-speed rotating motor can be preferably controlled by controlling the deformation of the non-oriented electrical steel sheet in this process, and proceeded with the study. According to the study by the present inventors, it has been found that the deformation behavior of the non-oriented electrical steel sheet in the process of transition from the elastic region to the plastic region affects the magnetic properties. Therefore, the present inventors have further studied the influence of the magnetic characteristics in the above process.

As a result, the present inventors have found that high magnetic properties can be obtained in the non-oriented electrical steel sheet to which Sn is added. Specifically, in a non-oriented electrical steel sheet containing Sn in a mass percentage of 0.010% to 0.150%, the tensile strength at an elongation of 0.1% is σ _A , and the elongation is 0.2. when the tensile strength was sigma _B in%, the difference between the sigma _a and σ _B (σ _B -σ _a) may be in the range of _{40MPa~200MPa (40MPa ≦ (σ B -σ} a) ≦ 200MPa) Thus, the inventors have obtained knowledge that high magnetic characteristics can be secured and deterioration of magnetic characteristics can be suppressed even when applied to a core material of a high-efficiency motor that rotates at high speed. Furthermore, when studies were made to further suppress the deterioration of magnetic characteristics, the relationship of (σ _B −σ _A ) ≧ 600 × Sn _c +35 was satisfied, so that it was used for the core of a high efficiency motor that rotates at high speed. The knowledge that the iron loss at the time of a case can be reduced more was acquired.

In addition, the inventors of the present invention have advanced the study of the production process in producing a non-oriented electrical steel sheet containing Sn in a mass percentage of 0.010% to 0.150%. As a result, in the cooling process of the finish annealing process, the steel sheet is manufactured under the condition that the cooling rate between 80 ° C. and 40 ° C. is 5 ° C./second or more, and the tensile strength is 0.1%. strength sigma _a, and when the tensile strength at elongation of 0.2% was sigma _B, the difference between the sigma _a and σ _B (σ _B -σ _a) is non-directional as the range of 40MPa~200MPa An electrical steel sheet was obtained. Furthermore, in order to further suppress the deterioration of the magnetic properties, the manufacturing process was further examined. In addition to the above cooling rate conditions between 80 ° C. and 40 ° C., in the cooling process of the finish annealing step, By setting the tension between 800 ° C. and 500 ° C. to 4 MPa or less, (σ _B −σ _A ) is in the above range, and (σ _B −σ _A ) ≧ 600 × Sn _c +35 A satisfactory non-oriented electrical steel sheet was obtained. And by obtaining a non-oriented electrical steel sheet by this manufacturing method, the obtained non-oriented electrical steel sheet has high magnetic properties, even when applied to the core material of a high-efficiency motor that rotates at high speed. And the knowledge that the fall of a magnetic characteristic can be suppressed was acquired.

  That is, the present invention has been made based on these findings. That is, the gist of the present invention is as follows.

<1> By mass%
0.5% ≦ Si ≦ 4.0%,
0.2% ≦ Al ≦ 2.0%,
0.1% ≦ Mn ≦ 3.0%,
0.010% ≦ Sn ≦ 0.150%,
C ≦ 0.005%,
S ≦ 0.010%,
N ≦ 0.005%,
And the balance contains Fe and impurity elements,
The difference between σ _A and σ _B (σ _B −σ _A) where σ _A is the tensile strength at 0.1% elongation of the steel sheet and σ _B is the tensile strength at 0.2% elongation of the steel sheet. ) Is a non-oriented electrical steel sheet in which 40 MPa ≦ (σ _B −σ _A ) ≦ 200 MPa.

<2> When the Sn content is Sn _c (mass%), the difference between the σ _A and the σ _B and the relationship of the Sn _c are (σ _B −σ _A ) ≧ 600 × Sn The non-oriented electrical steel sheet according to <1>, which satisfies _c +35.

<3> A motor core that uses the non-oriented electrical steel sheet according to <1> or <2>, and is used for a motor that rotates at a rotational speed of 10,000 rpm or more.

<4> After heating the slab having the chemical composition according to <1>, a hot rolling step of hot rolling,
A hot-rolled sheet annealing step for annealing the steel sheet after the hot rolling;
A cold rolling step of cold rolling the steel plate after the annealing;
Finish annealing in which the steel sheet after cold rolling is finish-annealed and is cooled at a cooling rate of 5 ° C./second or more until the temperature of the steel plate in the finish annealing step is changed from 80 ° C. to 40 ° C. Process,
The method for producing a non-oriented electrical steel sheet according to <1> or <2>.

<5> The method for producing a non-oriented electrical steel sheet according to <4>, wherein the steel sheet is cooled with a tension of 4 MPa or less until the temperature of the steel sheet in the finish annealing step is 850 ° C. to 500 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, even when it is a case where it is a case where it is a case where it is a case where it is used as a core of the highly efficient motor rotated at high speed, the non-oriented electrical steel plate with which the fall of the magnetic characteristic was suppressed can be provided. Moreover, the motor core using this non-oriented electrical steel sheet can be provided. Furthermore, the manufacturing method of this non-oriented electrical steel sheet can be provided.

It is a schematic diagram which shows the stress-strain curve of a non-oriented electrical steel sheet. It is a schematic diagram which shows an example of the structure of the motor core of this invention. It is a schematic diagram which shows the other example of the structure of the motor core of this invention.

Hereinafter, the present invention will be described in detail.
In addition, in this specification, the numerical range represented using "to" means the range which includes the numerical value described before and behind "to" as a lower limit and an upper limit.

<Non-oriented electrical steel sheet>
As a result of research, the present inventors have found that the non-oriented electrical steel sheet has the above configuration, and even when it is used as the core of a high-efficiency motor that rotates at high speed, the decrease in magnetic properties is suppressed. I found. And when the non-oriented electrical steel sheet of this invention was applied as a core of the high efficiency motor which rotates at high speed, it discovered that motor efficiency improved. The reason is not clear, but for example, it is estimated as follows.

In general, deformation of a metal material is classified into an elastic region and a plastic region. However, in a practical material, the boundary between these regions is not clear.
For example, FIG. 1 is a schematic diagram showing a stress-strain curve of a non-oriented electrical steel sheet. As shown in FIG. 1, in the initial region that is deformed when a load is applied to the electrical steel sheet (referred to as “proportional region” in this specification), the relationship between stress and strain is almost completely elastic. It is proportional to (Young's modulus). This proportional range is basically understood as a phenomenon within the range of deformation of the crystal lattice.
However, even in the stress range (elastic range) that is generally considered to be below the yield stress, if the deformation when a load is applied to the non-oriented electrical steel sheet exceeds a certain value, the relationship between stress and strain is This is a region where the deformation proceeds outside the strict proportional relationship with the elastic modulus (referred to herein as the “initial curing region”). In this initial hardening region, it is considered that some new lattice defects are generated. In general, it is natural to consider this as a dislocation, and in this specification, it is assumed that a new dislocation occurs. In the initial hardening region, dislocations are generated due to deformation due to the load. However, except for the load, most of the dislocations move in the direction opposite to the occurrence of the dislocations, and the dislocations disappear.

  By the way, since the core of the motor under high-speed rotation is a centrifugal force that rotates the motor, a part of the non-oriented electrical steel sheet applied to the core is not a little deformed. At that time, a material having a longer “proportional range” can suppress deformation of the non-oriented electrical steel sheet itself applied to the core. In other words, if the load due to centrifugal force is constant, the amount of deformation is small, and the density of dislocations formed is reduced. Lowering the dislocation density reduces the obstacles to the domain wall movement, so that the lowering of the magnetic permeability can be avoided, and as a result, the lowering of the magnetic properties accompanying the high speed rotation is suppressed.

  The present inventors have extensively investigated this phenomenon by changing the kind, amount, and manufacturing method of the additive element. As a result, the non-oriented electrical steel sheet containing Sn in a specific range, although the hardening behavior in the elastic region does not change so much even if the content of Al or Si used as a solid solution strengthening element is increased. For, it was clearly confirmed that the curing behavior in the elastic region changed greatly.

The above phenomenon occurs particularly in connection with the continuation limit of the proportional range. The hardening behavior in the elastic range including the continuation of the proportional range can be expressed by the difference in tensile strength at two points where the amount of strain in the elastic range of the steel sheet is different. In other words, the hardening behavior in the elastic region is close to the continuation limit in the proportional region, that is, the initial hardening has not occurred, or the initial hardening has a small tensile amount σ _A and a large initial hardening has occurred. It is represented by the difference in tensile strength σ _B with the amount of strain.

The tensile strength σ _A may be a value measured in either the proportional range or the initial curing range. In order to clarify the difference in curing behavior within the elastic region, the tensile strength σ _A is close to the initial curing region even within the proportional region, or has a low strain amount close to the proportional region even within the initial curing region. It is good to adopt the value measured in the area. A general non-oriented electrical steel sheet is considered to be appropriate as an index representing a value in this region when the elongation of the non-oriented electrical steel sheet is 0.1%. Therefore, in the non-oriented electrical steel sheet of the present invention, the tensile strength σ _A is defined by the value of the tensile strength at an elongation of 0.1% of the steel sheet.
In addition, the tensile strength σ _B is obtained at least with the amount of strain in the initial hardening region. In general non-oriented electrical steel sheets, it is considered appropriate that the tensile elongation is 0.2% and exceeds the proportional range and is in the initial hardening range. Therefore, in the non-oriented electrical steel sheet of the present invention, σ _B is defined by the value of tensile strength at a tensile elongation of 0.2%.

The above behavior will be schematically described with reference to FIG. In the stress-strain curve of the non-oriented electrical steel sheet shown in FIG. 1, the σ _A and the yield stress of the non-oriented electrical steel sheet of the present invention (indicated as the present invention steel in FIG. 1) are the conventional non-oriented electrical steel sheets. (In FIG. 1, the conventional steel is indicated). However, sigma _B of the present invention steel is higher than that sigma _B of the conventional steels. This indicates that the steel according to the present invention has a larger continuation limit in the proportional range than the conventional steel (that is, the proportional range continues up to a high strain).
From FIG. 1, the material having a continuous behavior in the proportional range corresponding to the steel of the present invention having a high σ _B exceeds the strain amount under a constant stress, particularly in the proportional range, in the initial hardening range where the steel sheet is slightly deformed. It can be understood that the amount of strain in the above range is smaller than that of the conventional steel.

  As a result, when the non-oriented electrical steel sheet of the present invention is applied to a material for a motor core that rotates at a high speed (for example, 10,000 rpm or more), even if a load due to centrifugal force is applied, deformation (specifically) Specifically, deformation in the initial hardening region is suppressed, and the dislocation density is reduced. Therefore, the obstacle of domain wall movement is reduced, and the decrease in magnetic permeability is avoided, and as a result, the decrease in magnetic properties is suppressed.

  In the above description, the “proportional area” and the “initial curing area” have been described. However, it should be noted that the boundary between the “proportional area” and the “initial curing area” is non-directional. It varies depending on the composition and manufacturing method of the heat-resistant electrical steel sheet. In addition, these areas cannot be strictly distinguished. In the present invention, this boundary is not strictly determined and is not necessary.

In the non-oriented electrical steel sheet of the present invention, when the tensile strength at a tensile elongation of 0.1% of the steel sheet is σ _A and the tensile strength at 0.2% of the steel sheet is σ _B , σ _A and σ the difference between _{B (σ B -σ a)} is in the range of 40MPa～200MPa. The fact that σ _B −σ _A is 40 MPa to 200 MPa means that the steel plate has an enhanced hardenability in the elastic region as described above. The higher this value, the higher the speed of the motor that rotates. The effect of suppressing a decrease in magnetic characteristics (decrease in motor efficiency) when applied to the core becomes significant. When σ _B −σ _A is less than 40 MPa, the change in curing behavior in the elastic region is small, and the above effect is not exhibited even when applied to the core of a high-efficiency motor that rotates at high speed.

σ _B −σ _A is preferably 45 MPa or more, and more preferably 50 MPa or more, from the viewpoint of more easily obtaining the above effect. On the other hand, in order to make this value very large, element segregation at the grain boundary is required, and therefore the grain boundary tends to become brittle. For this reason, the upper limit of σ _B −σ _A is set to 200 MPa or less. The upper limit of σ _B −σ _A is preferably 170 MPa or less, and more preferably 120 MPa or less.

Σ _A and σ _B are read from a stress-strain curve obtained by performing a tensile test in accordance with JIS Z2241.

In order for the non-oriented electrical steel sheet of the present invention to satisfy the relationship of 40 MPa ≦ (σ _B −σ _A ) ≦ 200 MPa, for example, the Sn content (mass%) is 0.010% to 0.150%. When the steel plate is finish-annealed, the cooling rate during the cooling process in the finish-annealing process described later until 80 ° C to 40 ° C is preferably 5 ° C / second or more.

The reason for this is not clear, but is considered as follows. In the cooling process in the finish annealing step, when the steel sheet to which Sn is added in the above range is cooled under the above conditions, Sn is segregated in the vicinity of the grain boundary. It is known that a grain boundary becomes a dislocation generation source during deformation, and it is considered that the occurrence of dislocation from the grain boundary is suppressed by the segregation of Sn in the vicinity of the grain boundary. As a result, in the non-oriented electrical steel sheet according to the present invention, the proportional range of the steel sheet increases with the grain boundary segregation of Sn.
Thus, although it is thought that the segregation of Sn exhibits the effect which suppresses generation | occurrence | production of the dislocation from the grain boundary used as a dislocation generation source, on the other hand, C is also known to segregate to a grain boundary like Sn. , C segregation seems to cancel the effect of Sn.
However, by cooling at a cooling rate of 5 ° C./second or more while the temperature of the steel sheet reaches from 80 ° C. to 40 ° C., Sn in the steel is segregated to the grain boundary, but C in the steel is a grain. Segregation to the boundary is suppressed. From the above, it is presumed that the expansion of the proportional range of the steel sheet is related to such a phenomenon.

Moreover, it is preferable that the non-oriented electrical steel sheet of the present invention satisfies the relationship (σ _B −σ _A ) ≧ 600 × Sn _c +35. The non-oriented electrical steel sheet satisfying this relationship was used for the core of a high-efficiency motor that rotates at high speed without causing excessive Sn to remain in the grains while avoiding the problem of grain boundary embrittlement. In this case, the iron loss can be reduced, and the effect of suppressing the deterioration of magnetic properties can be sufficiently obtained. Incidentally, the Sn _c is the content of Sn (mass%).

For the non-oriented electrical steel sheet of the present invention, which satisfies the relation _{(σ B -σ A) ≧ 600} × Sn c +35 (Sn c represents the content of Sn (mass%)), for example, Sn When the steel sheet having a content (mass%) of 0.010% to 0.150% is finish-annealed, the temperature of the steel sheet in the cooling process of the finish annealing process to be described later is between 80 ° C and 40 ° C. In addition to setting the cooling rate to 5 ° C./second or more, it is preferable that the tension until the temperature of the steel sheet in the cooling process in the finish annealing step is 850 ° C. to 500 ° C. is 4 MPa or less. By cooling in this manner, the steel plate contained in the specific range has a greater effect of increasing the value of (σ _B −σ _A ) as the Sn content increases.

The reason for this is considered as follows, for example. In the cooling process in the finish annealing process, the residual strain that can be a trap site for C is introduced appropriately by setting the tension in the rolling direction of the steel sheet to 4 MPa or less until the temperature of the steel sheet reaches 850 ° C. to 500 ° C. Is done. Thereby, segregation of C to the grain boundary is suppressed, excessive Sn does not remain in the grains, and it is considered that the effect obtained by containing Sn in the above range becomes remarkable. On the other hand, when the tension between the temperature of the steel plate from 850 ° C. to 500 ° C. exceeds 4 MPa, excessive residual strain is introduced into the steel plate, and iron loss is not reduced.
And the above-mentioned effect | action is acquired by making the cooling rate until the temperature of the steel plate in the cooling process of a finish annealing process reaches 80 degreeC-40 degreeC or more, and the content of Sn is said above. If it increases within the range, the continuation limit of the proportional range of the steel plate also increases. Therefore, for the above reasons, it is estimated that (σ _B −σ _A ) increases as the Sn content increases.
If it is a non-oriented electrical steel sheet that satisfies the above relationship, it should sufficiently prevent the deterioration of magnetic properties when used in the core of a high-efficiency motor that rotates at high speed while avoiding the problem of grain boundary embrittlement. Can do.

Details of the component composition of the non-oriented electrical steel sheet of the present invention will be described.
In addition, about the component composition of a steel plate, "%" is "mass%".

  The non-oriented electrical steel sheet of the present invention is 0.5% ≦ Si ≦ 4.0%, 0.2% ≦ Al ≦ 2.0%, 0.1% ≦ Mn ≦ 3.0% by mass%. 0.010% ≦ Sn ≦ 0.150%, C ≦ 0.005%, S ≦ 0.010%, N ≦ 0.005%, and the balance is Fe and impurity elements.

(0.5% ≦ Si ≦ 4.0%)
Si increases the electrical resistance of the steel sheet, reduces eddy current loss, and reduces iron loss. Furthermore, the magnetic flux density is improved by making the texture of the steel plate preferable for the electromagnetic steel plate. It is also used to increase the strength of the steel sheet.
In order to obtain these effects, the Si content is 0.5% or more. The Si content is preferably 1.5% or more, and more preferably 2.0% or more.
When there is too much content of Si, the saturation magnetic flux density of a steel plate will fall. Moreover, the crack of the steel plate at the time of cold rolling tends to occur. Therefore, the Si content is 4.0% or less. The Si content is preferably 3.8% or less, and more preferably 3.6% or less.
However, even if Si is increased, the proportional range regarding the hardening behavior in the elastic range does not change so much.

(0.1% ≦ Al ≦ 2.0%)
Al has the effect of increasing the electrical resistance of steel, which is almost the same as that of Si, and can reduce eddy current loss and iron loss. Furthermore, the magnetic flux density is improved by making the texture of the steel plate preferable for the electromagnetic steel plate. It is also used to increase the strength of the steel sheet.
Therefore, the Al content is 0.1% or more. The Al content is preferably 0.15% or more, and more preferably 0.2% or more.
On the other hand, when there is too much content of Al, the saturation magnetic flux density of a steel plate will fall. Therefore, the Al content is set to 2.0% or less. The Al content is preferably 1.5% or less, and more preferably 1.2% or less.
However, even if Al is increased, the proportional range regarding the hardening behavior in the elastic range does not change so much.

(0.1% ≦ Mn ≦ 2.0%)
Mn, like Si, has the effect of increasing the electrical resistance of steel and reducing iron loss. Furthermore, the magnetic flux density is improved by making the texture of the steel plate preferable for the electromagnetic steel plate. Moreover, Mn is advantageous in that the amount of decrease in saturation magnetic flux density of the steel sheet is small. It is also used to increase the strength of the steel sheet. Therefore, the Mn content is 0.1% or more. The Mn content is preferably 0.2% or more, and more preferably 0.5% or more.
If the Mn content is too high, the alloy cost increases, so the Mn content is set to 2.0% or less. The Mn content is preferably 1.8% or less, and more preferably 1.5% or less. However, even if Mn is increased, the proportional range related to the hardening behavior in the elastic range does not change so much.

(0.010% ≦ Sn ≦ 0.150%)
Sn affects the steel texture and increases the magnetic flux density. Further, Sn is an important element for expanding the continuation limit of the proportional range related to the hardening behavior in the elastic range, as described above. For this reason, the content of Sn is limited to 0.010% to 0.150%.
In terms of obtaining the effects of the present invention more effectively, the Sn content is preferably 0.020% or more, and more preferably 0.030% or more. On the other hand, when Sn is excessively contained, the toughness of the steel is impaired, and the steel sheet is easily broken. Therefore, the Sn content is preferably 0.150% or less. More preferably, it is 0.120% or less, More preferably, it is 0.100% or less.

(C ≦ 0.005%)
If the content of C is large, the amount of precipitation of carbides increases, which adversely affects iron loss. Therefore, the C content is preferably 0.005% or less.
Although the lower limit of the C content is not particularly limited, the C content is practically 0.0001% or more in view of industrial purification technology, and 0.0005% or more in consideration of the manufacturing cost.

(S ≦ 0.010%)
If the S content is large, the S content is adversely affected by the increase in sulfides, so the smaller the content, the better. Therefore, the content of S is preferably 0.010% or less.
The lower limit of the S content is not particularly limited. However, considering industrial purification technology, the S content is practically 0.0001% or more, and considering the manufacturing cost, it is 0.0005% or more.

(N ≦ 0.005%)
If the content of N is large, it is preferable that the content is small because the increase in nitrides adversely affects iron loss. Therefore, the N content is preferably 0.005% or less.
Although the lower limit of the N content is not particularly limited, the N content is practically 0.0001% or more in view of industrial purification technology, and 0.0005% or more in consideration of the manufacturing cost.

(Fe and impurity elements)
The balance of the steel sheet is Fe and impurity elements. Further, the inclusion of P, Cr, Cu, Ni, Ti, Nb, Ca, Mg, REM, etc. as optional elements in place of Fe in a known range in the non-oriented electrical steel sheet loses the effect of the present invention. It is not a thing. Here, the impurity element refers to a component contained in the raw material or a component mixed in the manufacturing process and not intentionally included in the steel plate.

<Method for producing non-oriented electrical steel sheet>
Next, the manufacturing method of the non-oriented electrical steel sheet of this invention is demonstrated.
In the electrical steel sheet of the present invention, Sn is added in an amount in the above-mentioned range. As described above, the action of Sn segregated at the grain boundary and the action of suppressing the grain boundary segregation of C are the features of the present invention. Is considered to be one factor that causes the expansion of the continuation limit of the proportional range, but simply adding Sn does not provide the effect of expanding the continuation limit of the proportional range. . A non-oriented electrical steel sheet with an extended continuation limit of the proportional range can be obtained by the following manufacturing method in addition to the steel components.
In addition, if the steel plate which shows the hardening behavior in the elastic region which the non-oriented electrical steel plate of this invention has is obtained, the manufacturing method of the non-oriented electrical steel plate of this invention will be specifically limited. It goes without saying that it is not a thing.

  The non-oriented electrical steel sheet of the present invention is a hot rolling step for heating and rolling the slab having the chemical composition of the non-oriented electrical steel sheet of the present invention, and heat for annealing the steel sheet after the hot rolling. A sheet annealing process, a cold rolling process for cold rolling the steel sheet after the annealing, and a final annealing process for finish annealing the steel sheet after the cold rolling, and the temperature of the steel sheet in the final annealing process is 80 ° C. Until the temperature reaches 40 ° C., a finish annealing step of cooling at a cooling rate of 5 ° C./second or more can be obtained.

The cooling rate until the temperature of the steel sheet is changed from 80 ° C. to 40 ° C. is more preferably 8 ° C./second or more from the viewpoint of further suppressing the decrease in magnetic permeability. On the other hand, the upper limit of the cooling rate is not particularly limited. For example, it is preferably set to 50 ° C./second or less from the viewpoint of productivity.
Examples of the method for obtaining the cooling rate include a method of immersing the steel plate in 20 ° C. cooling water when the temperature of the steel plate reaches 80 ° C.

  In addition, the temperature of the steel sheet in the finish annealing process is from 850 ° C. to 500% in that excessive Sn does not remain in the grains and the iron loss when used in the core of a high-efficiency motor that rotates at high speed is further reduced. It is good to cool with the tension | tensile_strength of 4 Mpa or less (preferably 3 Mpa or less) until it becomes ° C. Although it does not specifically limit as a lower limit of tension | tensile_strength, it is good that it is 1 Mpa or more. This tension represents the tension applied in the rolling direction.

  Hereinafter, manufacturing conditions other than the cooling process of the above-described finish annealing will be described. The manufacturing conditions do not have to be special conditions for obtaining the effects of the present invention, and generally known conditions may be applied. It should be noted that applying a generally known manufacturing method for grain boundary segregation of Sn to promote this may be applied positively to obtain the effects of the present invention.

(Hot rolling process)
A hot rolling process is a process of hot-rolling, for example, after heating the slab which has said chemical composition. Specifically, the steel having the above chemical composition is made into a slab obtained by a general method such as a continuous casting method or a method of rolling a steel ingot, and it is charged in a heating furnace and hot rolled. It is a process to apply. When the slab temperature is high, hot rolling may be performed without charging the heating furnace. By this step, a hot rolled sheet is obtained.
Although the slab heating temperature when performing hot rolling is not particularly limited, it is preferably set to 1000 ° C. to 1300 ° C. from the viewpoint of cost and hot rolling properties. The slab heating temperature is more preferably 1050 ° C to 1250 ° C.
Although each condition when performing hot rolling is not specifically limited, For example, it is good to perform finishing temperature at 800 to 1100 degreeC, and coiling temperature at 500 to 750 degreeC.

(Hot rolled sheet annealing process)
A hot-rolled sheet annealing process is a process of annealing the steel plate (hot rolled sheet) after a hot rolling process. Hot-rolled sheet annealing may be performed by any method of box annealing and continuous annealing.
The conditions for performing hot-rolled sheet annealing are not particularly limited. For example, from the viewpoint of equipment load and manufacturing cost, the annealing temperature is 800 ° C. to 1250 ° C. (preferably 900 ° C. to 1100 ° C.), and the annealing time is 1 second. It is good to set it to -2 hours (preferably 20 seconds-1 hour).
In addition, you may provide the pickling process of pickling the steel plate (hot-rolled board) before annealing, or the steel plate (annealed steel sheet) after annealing a hot-rolled board as needed.

(Cold rolling process)
The cold rolling step is a step of cold rolling the steel plate (annealed steel plate) obtained in the hot rolled sheet annealing step. In the cold rolling step, the annealed steel sheet may be a cold rolled sheet having a predetermined thickness by one cold rolling, or the annealed steel sheet may be predetermined by two or more cold rollings through intermediate annealing. It is good also as a cold-rolled board of the board thickness. The rolling reduction (final cold rolling reduction) in the final cold rolling is preferably 78% or more. Moreover, what is necessary is just to make the plate | board thickness of the cold rolled sheet after completion | finish of cold rolling into the target board thickness, For example, it is good to set it as the range of 0.15 mm-0.50 mm.

(Finish annealing process)
The finish annealing step is a step of finish annealing the steel plate (cold rolled plate) after the cold rolling step. Various conditions in the final annealing process are not particularly defined, but from the viewpoint of load on equipment and manufacturing cost, the final annealing temperature is 850 ° C. to 1100 ° C. (preferably 850 ° C. to 1050 ° C.), and the final annealing time is It is preferably 5 seconds to 5 hours (preferably 10 seconds to 3 hours).

(Other processes)
Even if the manufacturing method of the non-oriented electrical steel sheet of this invention has an insulating film formation process which provides an insulating film on the surface of the steel plate (non-oriented electrical steel sheet) after a final annealing process as needed, for example. Good. Examples of the insulating film include an insulating film made of only an organic component, only an inorganic component, or a mixture of an organic component and an inorganic component. Further, the insulating film may be an insulating film that exhibits adhesive ability by heating and pressurizing. Examples of the material for the insulating film that exhibits adhesive ability include acrylic resin, phenol resin, epoxy resin, and melamine resin.

From the above, since the non-oriented electrical steel sheet obtained by the production method of the present invention has a large continuation limit in the proportional range, even when it is used as the core of a high-efficiency motor that rotates at high speed, the magnetic properties are deteriorated. A non-oriented electrical steel sheet in which is suppressed is obtained.
Therefore, the non-oriented electrical steel sheet of the present invention is suitable as a material for the motor core. Specifically, for example, drive motors mounted on hybrid vehicles, electric vehicles, fuel cell vehicles, etc .; compressor motors such as air conditioners and refrigerators; small generators mounted on motorcycles and home cogeneration systems; It is suitable as a material for the core of a high-efficiency motor that rotates (for example, 10,000 rpm).

<Motor core>
Next, an example of a motor core using the non-oriented electrical steel sheet of the present invention will be described with reference to the drawings.

  FIG. 2 is a schematic diagram showing an example of the structure of the motor core of the present invention. The motor core 100 shown in FIG. 2 is formed as a laminated body 21 in which a plurality of punched plates 11 of non-oriented electrical steel sheets are laminated and integrated. As shown in FIG. 2, the punching plate 11 has four rectangular cutouts 13 for embedding permanent magnets. In addition, although the notch 13 shown in FIG. 2 is formed in four places in the punching board 11, it is not limited to this. When the permanent magnets are embedded in the cutouts 13, the cutouts 13 need only be provided in even numbers so that the adjacent permanent magnets have the opposite magnetic poles.

  FIG. 3 is a schematic view showing another example of the structure of the motor core of the present invention. The motor core 120 shown in FIG. 3 is formed as a laminate 23 in which a plurality of punched plates 15 of non-oriented electrical steel sheets are laminated and integrated. As shown in FIG. 3, the punching plate 15 includes a yoke portion 19 on an arc and a teeth portion 17 projecting radially inward from the inner peripheral wall surface of the yoke portion 19. The yoke portion 19 and the teeth portion 17 are formed on the punching plate 15 at three locations. In addition, although the yoke part 19 and the teeth part 17 which are shown in FIG. 3 are formed in three places in the punching board 11, it is not limited to this. The yoke part 19 and the teeth part 17 should just be provided according to the target number. The motor core 120 shown in FIG. 3 can be used by winding a copper wire coil around the tooth portion 17 of the laminate 23.

  The motor core 100 shown in FIGS. 2 and 3 is described as an example showing the structure of the motor core of the present invention, and the motor core of the present invention is not limited to this.

An example of a method for manufacturing a motor core will be described with reference numerals omitted.
The method for manufacturing the motor core is not particularly limited, and may be manufactured by a manufacturing method that is usually employed industrially. Specifically, for example, first, the non-oriented electrical steel sheet of the present invention is punched into a predetermined shape to produce a predetermined number of punched plates. When the punched plate is punched into a predetermined shape, a concavo-convex portion for stacking and integration is formed.
Next, a punched plate punched into a predetermined shape is laminated with a predetermined number of punched plates and subjected to caulking. By the caulking process, the concavo-convex portions formed on each punched plate are mechanically fitted and fixed to each other, and a laminated body in which the punched plate is integrated is obtained. This obtained laminate is used as a motor core. Or it is good also as a motor core, after giving annealing to this laminated body as needed.

  The motor core using the non-oriented electrical steel sheet of the present invention is preferably used for a motor (high efficiency motor) that rotates at a rotational speed of 10,000 rpm or higher (preferably 15000 rpm or higher). The upper limit of the number of revolutions of the high efficiency motor is not particularly limited, but is preferably 17000 rpm or less from the viewpoint of productivity of the high efficiency motor.

  The present invention is not limited to the above. The above is an exemplification, and any technology that has substantially the same configuration as the technical idea described in the claims of the present invention and has the same operational effects can be used. To be included in the scope.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

A slab having the chemical composition shown in Table 1 is prepared, and this slab is heated at 1150 ° C. Then, finish hot rolling is performed at 820 ° C., winding is performed at 650 ° C., and a hot-rolled steel sheet having a thickness of 2.0 mm is obtained. After pickling of the hot-rolled steel sheet, hot-rolled sheet annealing is performed, and a cold-rolled sheet having a thickness of 0.27 mm is obtained by one cold rolling. A cold-rolled sheet is subjected to finish annealing by holding at 1000 ° C. for 30 seconds, the tension until the temperature of the steel sheet after finishing annealing is changed from 850 ° C. to 500 ° C., and the temperature of the steel sheet after finishing annealing. Cooling is performed under the conditions shown in Table 1 at a cooling rate between 80 ° C. and 40 ° C.
Through the above steps, various non-oriented electrical steel sheets are obtained. Various non-oriented electrical steel sheets are evaluated later.
In Table 1, “FA process” indicates “finish annealing process”.

<Evaluation>
Each evaluation shown below is performed about the obtained non-oriented electrical steel sheet of each example.

(Magnetic properties)
The magnetic properties are evaluated by measuring the following physical properties under the conditions of the single plate characteristics and the characteristics when the tensile strain is 0.2%.
Single plate characteristics (no load): Measured under the conditions of the single plate magnetic property test method (JIS C 2556).
・ Characteristics when 0.2% tensile strain is applied: Use the same equipment as that used for evaluation of single plate characteristics, and add tensile deformation (tensile deformation is 0.2% in the direction parallel to the excitation direction) Measure the magnetic properties in the added state.
Magnetic flux density: B ₅₀ (T) (magnetic flux density at a magnetizing force of 5000 A / m)
Iron loss: W _10/800 (iron loss under conditions of maximum magnetic flux density of 1.0 T and frequency of 800 Hz)

(Mechanical properties)
Σ _A , σ _B , and σ _B −σ _A
The tensile strength (σ _A ) at an elongation of 0.1% and the tensile strength (σ _B ) at an elongation of 0.2% of the non-oriented electrical steel sheet are measured by the method described above. And (sigma) _B- (sigma) _A is calculated | required from each obtained value. The unit is MPa.

  From the evaluation results shown in Table 2, the steel sheet of the invention example has a smaller difference between the magnetic flux density in the single plate characteristics and the magnetic flux density in the characteristics when the tensile strain is 0.2% than the steel sheet of the comparative example. Recognize. In addition, it can be seen that the steel plate of the invention example has a smaller difference between the iron loss in the single plate properties and the iron loss in the properties when the tensile strain is 0.2% than the steel plate of the comparative example. Thereby, it turns out that the steel plate of an invention example suppresses the fall of a magnetic characteristic compared with the steel plate of a comparative example. In addition, although the steel plate 17 has Sn content exceeding 0.150 mass%, since this steel plate becomes brittle, productivity falls. Moreover, it turns out that a magnetic characteristic falls compared with the steel plate of an invention example.

(Evaluation of motor efficiency)
From various non-oriented electrical steel sheets, 30 steel sheets having a size of 300 mm in the rolling direction and a size of 60 mm in the direction orthogonal to the rolling direction are punched out. Then, 30 steel plates are laminated with each other, and a laminate is obtained by caulking. Subsequently, this laminate is annealed at 750 ° C. for 2 hours. And let the laminated body after this annealing be a motor core.
Next, this motor core is incorporated into a 4-pole permanent magnet embedded synchronous motor driven by inverter control, and the motor efficiency is evaluated. The motor efficiency is evaluated for the case of rotating at a rotational speed of 5000 rpm, the case of rotating at a rotational speed of 10,000 rpm, and the case of rotating at a rotational speed of 15000 rpm.
The motor efficiency is a value calculated by a ratio of output electric energy to input electric energy represented by the following formula.
Formula: Motor efficiency = (output electric energy / input electric energy) × 100

  From the evaluation results shown in Table 3, it can be seen that the steel plate of the example has better motor efficiency than the steel plate of the comparative example even when applied to a high-efficiency motor that rotates at high speed.

11, 15 Punched plate 13 Notch 17 Teeth part 19 Yoke part 21, 23 Laminate 100, 120 Motor core

Claims (5)

0.5% ≦ Si ≦ 4.0% by mass%,
0.2% ≦ Al ≦ 2.0%,
0.1% ≦ Mn ≦ 3.0%,
0.010% ≦ Sn ≦ 0.150%,
C ≦ 0.005%,
S ≦ 0.010%,
N ≦ 0.005%,
And the balance contains Fe and impurity elements,
The difference between σ _A and σ _B (σ _B −σ _A where σ _A is the tensile strength at 0.1% elongation of the steel sheet and σ _B is the tensile strength at 0.2% elongation of the steel sheet. ) Is a non-oriented electrical steel sheet in which 40 MPa ≦ (σ _B −σ _A ) ≦ 200 MPa. When the content of the Sn was Sn _c (mass%), the sigma difference between _A and the sigma _B, and the relation of the Sn _c, satisfy _{(σ B -σ A) ≧ 600} × Sn c +35 The non-oriented electrical steel sheet according to claim 1.   A motor core using the non-oriented electrical steel sheet according to claim 1 or 2, wherein the motor core is used for a motor that rotates at a rotational speed of 10,000 rpm or more. A hot rolling step of hot rolling after heating the slab having the chemical composition according to claim 1;
A hot-rolled sheet annealing step for annealing the steel sheet after the hot rolling;
A cold rolling step of cold rolling the steel plate after the annealing;
Finish annealing in which the steel sheet after cold rolling is finish-annealed and is cooled at a cooling rate of 5 ° C./second or more until the temperature of the steel plate in the finish annealing step is changed from 80 ° C. to 40 ° C. Process,
The manufacturing method of the non-oriented electrical steel sheet according to claim 1 or 2, wherein   The method for producing a non-oriented electrical steel sheet according to claim 4, wherein the steel sheet is cooled with a tension of 4 MPa or less until the temperature of the steel sheet in the finish annealing step is 850 ° C to 500 ° C.