JP2007204787A - Electrical steel sheet for permanent magnet motor and permanent magnet motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrical steel sheet for a permanent magnet motor as an iron core material for a magnet motor used from a low output region including a no-load region to a high output region, the steel sheet enabling a no-load loss and a loss when being rotated by external force to be reduced, and to provide a permanent magnet motor obtained by using the electrical steel sheet. <P>SOLUTION: The magnet motor is obtained by using a nonoriented electrical steel sheet and a permanent magnet. The nonoriented electrical steel sheet first contains 0.1 to 4.5 mass% Si. Then, the steel sheet has magnetic characteristics satisfying all of J100≥1.75T-(1)J10/J100≤0.80-(2)W20≤3.0W/kg-(3) (wherein, J100: magnetic polarization in a magnetizing force of 10,000 A/m, J10: magnetic polarization in a magnetizing force of 1,000 A/m, and W20: core loss when being magnetized under 2,000 A/m and 50 Hz). As one embodiment of the nonoriented electrical steel sheet, the nonoriented electrical steel sheet in which the ratio of the X-ray reflecting surface intensity in the ä111} plane orientation to the random aggregated structure intensity is 3.5 to 9.0, and also, the average crystal grain size is ≥45 μm can be cited. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electromagnetic steel plate for a permanent magnet motor and a permanent magnet motor used in an electric vehicle or the like.

Conventionally, main development issues in non-oriented electrical steel sheets for motor cores have mainly been improvement of magnetic permeability and reduction of iron loss.
By increasing the magnetic permeability of the iron core material, the torque of the motor is improved. This is because the attractive force and the repulsive force between the armature and the magnetic pole increase with the increase of the magnetic flux density of the iron core. For this reason, in the development of non-oriented electrical steel sheets, development has been carried out with the goal of further increasing the magnetic flux density at a magnetizing force of 5000 A / m called B50. One way to increase B50 is to reduce alloying elements. However, in this case, there is a drawback that the iron loss is deteriorated due to an increase in eddy current loss. On the other hand, an effective improvement of B50 is to improve the texture by increasing the orientation that is advantageous to the permeability characteristics such as {100} plane orientation and reducing the structure harmful to the permeability characteristics such as {111} plane orientation. Known as a method. And the improvement of the magnetic permeability in conventional electromagnetic steel sheet development has been performed mainly by the improvement of this texture (for example, patent document 1).
With the development of such conventional iron core materials, non-oriented electrical steel sheets that achieve a B50 of about 1.7 T while the iron loss W15 / 50 is 2.5 W / kg are currently being developed.

  On the other hand, permanent magnets, which are the magnetic poles of magnet motors, have made great strides in recent years, and very strong magnets such as Sm-Co magnets and Nd-Fe-B rare earths have been developed and put to practical use. It has become. When such a strong magnet is used, the iron core is magnetized to a high magnetic flux density by the magnetomotive force of the magnet even when no current is passed through the armature.

Furthermore, in recent years, motor applications that require not only the low output range but also the output characteristics of the high output range, such as drive motors and EPS motors for electromagnetic vehicles and hybrid electric vehicles, have emerged. Characteristics are becoming more important. In such a motor, the maximum magnetic flux density reached under actual use conditions is higher than that of the conventional motor, and the magnetic flux density of the iron core reaches a region exceeding the B50 value.
In a motor that also requires the output characteristics in the high output range, increasing the magnet strength in order to obtain a high output increases the iron loss at no load or light load. And when an operation mode changes frequently, it leads to the fall of average efficiency. In addition, there is a problem that a motor operated in a magnetic saturation region makes it difficult to control current and torque due to a decrease in inductance in a high magnetic field region.
On the other hand, there is a case where it is necessary to take measures to reduce the volume of the rare earth magnet in order to reduce the adverse effect caused on the iron core side due to the dramatic progress of the magnet strength. In such a case, as a method of compensating for the reduced torque, there is a method of using the reluctance torque together with the magnet torque. However, the higher the utilization rate of the reluctance torque, there is a problem that the gap between the rotor and the stator needs to be reduced, and the control becomes more difficult due to magnetic saturation.
JP 7-188871 A

  In view of such circumstances, the present invention relates to a core material for a magnet motor that is used from a low output range including a no load range to a high output range, and reduces the loss when rotating with no load loss or external force. It is an object of the present invention to propose an electromagnetic steel plate for a permanent magnet motor and a permanent magnet motor using the electromagnetic steel plate.

In order to solve the above-mentioned problems, the inventors have investigated and studied in detail a method for solving the problem of increasing no-load loss in a motor used in a magnetic flux density region near a saturation value. As a result, the following knowledge was obtained and the present invention was completed. In the following, the magnetic flux density is referred to as “B”, and the magnetic polarization is referred to as “J”. The magnetic flux density is an amount that governs the actual motor torque, and has a relationship of B = J + μ ₀ H (μ ₀ is the vacuum permeability, and H is the magnetizing force). Here, J is an amount corresponding to the magnetization of the material. Since the difference between B and J is large in the high magnetization force region, B and J are distinguished from each other and J is used as a material factor.

  (1) In order to improve the loss in the no-load region while ensuring the torque in the high output region (high magnetic field region), it is better to lower the magnetic flux density when magnetized only with the magnet. This is because an increase in magnetic flux density inevitably increases iron loss. On the other hand, in order to obtain a desired output when a high output is required, it is necessary to reach a sufficiently high magnetic flux density when the motor coil is energized. For this purpose, the magnetic flux density generated by the magnetomotive force of the magnet is limited to a low value as in the development guidelines for conventional magnetic steel sheets, and not high in all magnetization regions. Ideally, the magnetic flux density is obtained. Here, even if the magnetic flux density in the low magnetic field region is reduced, the torque will not be significantly reduced unless the maximum magnetic flux density at high output is reduced. However, there are portions / instants where the magnetic flux density is low in position and time inside the iron core, and a decrease in permeability in a low magnetic field region may cause a slight torque decrease. Such a decrease in torque can be compensated by increasing the magnet strength or increasing the current value.

  (2) Iron loss during rotation due to external force is not iron loss specified by magnetic flux density (for example, iron loss W15 / 50 of maximum magnetic flux density 1.5T, frequency 50Hz), but iron specified by magnetizing force The loss should be less than a certain value. This is because when the rotor is rotated by an external force, the magnetic flux density changes according to the magnet strength, unlike the case where the magnetic flux density is defined by the torque or control voltage as in the case of driving. It is suitable to evaluate by the iron loss under the condition that is constant.

  (3) Furthermore, in order to obtain a magnetic steel sheet with a low magnetic field density reduced while maintaining a high magnetic field density, a certain amount of {111} plane orientation, which was previously considered disadvantageous for magnetic properties, is used. It has been found that it is effective to increase, and at the same time, it is possible to obtain a desired magnetization curve while reducing the iron loss by increasing the crystal grain size.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] A non-oriented electrical steel sheet containing Si in an amount of 0.1 to 4.5 mass% and having magnetic properties satisfy the following formulas (1) to (3):
J100 ≧ 1.75T ――― (1)
J10 / J100 ≦ 0.80 ――― (2)
W20 ≦ 3.0W / kg ――― (3)
However, J100: Magnetic polarization at a magnetizing force of 10000 A / m, J10: Magnetic polarization at a magnetizing force of 1000 A / m, W20: Iron loss when magnetized at 2000 A / m, 50 Hz.
[2] Non-oriented electrical steel sheet containing 0.1 to 4.5 mass% of Si, the ratio of the X-ray reflecting surface strength of {111} plane orientation to the random texture strength is 3.5 or more and 9.0 or less, and the average crystal A magnetic steel sheet for a permanent magnet motor, wherein the particle diameter is 45 μm or more.
[3] A magnet motor using a non-oriented electrical steel sheet and permanent magnet containing 0.1 to 4.5 mass% of Si, wherein the magnetic properties of the non-oriented electrical steel sheet are expressed by the following equations (1) to (3). A permanent magnet motor characterized by satisfying.
J100 ≧ 1.75T ――― (1)
J10 / J100 ≦ 0.80 ――― (2)
W20 ≦ 3.0W / kg ――― (3)
However, J100: Magnetic polarization at a magnetizing force of 10000 A / m, J10: Magnetic polarization at a magnetizing force of 1000 A / m, W20: Iron loss when magnetized at 2000 A / m, 50 Hz.
[4] A magnet motor using a non-oriented electrical steel sheet and permanent magnet containing 0.1 to 4.5 mass% of Si, and a random set of X-ray reflecting surface strengths in the {111} plane orientation of the non-oriented electrical steel sheet A permanent magnet motor characterized in that the ratio to the tissue strength is 3.5 or more and 9.0 or less, and the average crystal grain size is 45 μm or more.

  In the present specification, “%” indicating the component of steel is “% by mass”.

According to the present invention, it is possible to reduce the loss in the case of being rotated by no-load loss or external force. Therefore, when the electromagnetic steel sheet of the present invention is used from a low output to a high output range, the motor iron loss is reduced, and a highly efficient motor can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail together with the reasons for limitation.

First, the electromagnetic steel sheet for a permanent magnet motor of the present invention is a non-oriented electrical steel sheet, and is mass% and contains Si in an amount of 0.1 to 4.5%.
Si 0.1% or more and 4.5% or less
Si is a component element that contributes to reducing iron loss by reducing eddy current loss by increasing electrical resistivity. If the Si content is less than 0.1%, the above effect cannot be obtained. On the other hand, if the content exceeds 4.5%, workability such as rollability is remarkably deteriorated. Therefore, the Si content is 0.1% or more and 4.5% or less.

  Other components are not particularly limited, but for the purpose of further improving performance, the following conditions are preferable.

  Since C has a problem of magnetic aging, it is preferably 0.02% or less.

  P is an element effective for increasing the strength of the steel sheet, but if added over 0.2%, central segregation during casting is likely to occur, and the steel sheet becomes brittle and cold rollability is reduced. It is preferable to make it 2% or less.

  Mn is an element effective for preventing red heat brittleness during hot rolling, and is preferably contained at 0.05% or more. On the other hand, if it exceeds 3%, the magnetic flux density is lowered.

  Al, like Si, is an element effective for increasing the specific resistance, and is preferably contained at 0.1% or more. On the other hand, if it exceeds 3%, the saturation magnetization is lowered and the castability is also lowered.

Further, in addition to the above components, Cu, Sb, Sn, B, Ni, Cr, Co and the following known magnetic property improving elements are shown for the purpose of improving the magnetic properties within the range not impairing the object of the present invention. REM can be added alone or in combination.
Cu: 0.5 to 4%,
Sb: 0.005 to 0.05%,
Sn: 0.005 to 0.1%,
B: 0.0002 to 0.002%,
Ni: 0.1 to 5%,
Co: 0.2-3% and REM: 0.001-0.01%
In addition, Cr lowers the electrical resistivity, which is advantageous for reducing iron loss. However, if the added amount is excessive, the saturation magnetization is lowered, so it is desirable to make it 8% or less.

  The electrical steel sheet used in the present invention is composed of the above components and further satisfies the following formulas (1) to (3) as magnetic characteristics. This is the most important requirement in the present invention. By satisfying the following formula, it is possible to reduce the loss when no load loss or external force is applied when used as a permanent magnet motor. It is possible to use from a low output range including a no-load range to a high output range.

J100 ≧ 1.75T-(1) However, J100: Magnetic polarized magnet motor with magnetizing force of 10000 A / m reaches a magnetic flux density of around 5000 to 10,000 A / m as the magnetizing force in the DC magnetization curve at high output. Therefore, in order to ensure the torque under the high output driving condition, it is necessary to set the magnetic polarization at a magnetizing force of 10000 A / m to a certain value or more. Based on the above, J100 is specified to be 1.75T or higher. Here, J100 is appropriately measured by the Epstein test method with a sample of about 500 g with half amount L direction and half amount C direction, depending on the maximum value in DC magnetic test or AC magnetic test below 50 Hz. It is better to measure.

J10 / J100 ≦ 0.80-(2) However, J10: the magnetic polarization formula (2) at a magnetizing force of 1000 A / m is a fundamental part of the present invention. J100 assumes a value about the maximum value of magnetic polarization that the iron core can reach when the motor is operated at high output, and J10 specifies magnetic polarization in a low magnetic field region. By limiting J10 to a value equal to or less than the coincidence value with respect to J100, the saturation phenomenon of magnetization starts from the low magnetic field region, and an excessive increase in magnetic flux density in the low magnetic field region is prevented. Reducing inductance drop in magnetic field. When J10 / J100 exceeds 0.80, the magnetic flux density in the low magnetic field region increases excessively, increasing the loss at no load and light load, and increasing the permeability change from the low magnetic field region to the high magnetic field region. Make the inductance drop in the high magnetic field region remarkable. Therefore, in the present invention, J10 / J100 ≦ 0.80. In order to obtain the above effect more effectively, it is desirable that J10 / J100 ≦ 0.70.
In the above, the ratio J10 / J100 of the magnetic polarization J10 at a magnetizing force of 1000 A / m and the magnetic polarization J100 at 10,000 A / m is defined. This is because, in the magnetization curve of a non-oriented electrical steel sheet, the increase in magnetic flux density decreases near the magnetizing force of 1000 A / m, and magnetic saturation begins to occur. It is an indicator.

  Note that J100 and J10 are appropriately measured by the Epstein test method with a sample of about 500g with the half amount in the L direction and the half amount in the C direction. The maximum value in a DC magnetic test or an AC magnetic test of 50Hz or less It is better to measure by.

W20 ≦ 3.0W / kg-(3) However, W20: 2000A / m, iron loss when magnetized at 50Hz As mentioned above, when no load or light load and the motor is rotated by external force In the magnet motor, a loss occurs due to the magnet magnetizing the iron core. In order to suppress the occurrence of iron loss due to the magnetization of the iron core when there is no load, as specified above, J10 should be lowered and the iron loss when magnetized with a constant magnetizing force should be kept low. good. Furthermore, by setting the iron loss near 2000 A / m to 3.0 W / kg or less, it is possible to reduce the iron loss when the magnet motor is rotated by an external force. Therefore, in the present invention, W20 ≦ 3.0 W / kg. Note that W20 ≦ 3.0 W / kg can be achieved by optimizing the crystal grain size, for example.

  As one embodiment of the present invention for obtaining the non-oriented electrical steel sheet, the ratio of the {111} plane orientation X-ray reflecting surface strength to the random texture strength is 3.5 or more and 9.0 or less, and the average Examples include non-oriented electrical steel sheets having a crystal grain size of 45 μm or more. Hereinafter, this point will be described in detail.

In order to achieve J10 / J100 ≦ 0.80, which is the above formula (2), the ratio of {111} plane orientation X-ray reflecting surface strength to random texture strength is 3.5 or more and 9.0 or less. It is preferable that the surface orientation {111} having an effect of reducing is appropriately included. Conventionally, it has been desirable to reduce the orientation that adversely affects such magnetization as much as possible. However, the present invention appropriately includes such orientation, contrary to the conventional knowledge. Is the first finding that it is advantageous to appropriately include the surface orientation {111} in a magnet motor that places importance on high output characteristics. In order to obtain such an effect, the ratio of {111} plane orientation to random intensity is set to 3.5 or more. On the other hand, when it exceeds 9.0, J100 which is the above formula (1) decreases and falls below 1.75T. Therefore, the ratio of the {111} plane orientation X-ray reflecting surface strength to the random texture strength is set to 3.5 or more and 9.0 or less. When the texture changes in the plate thickness direction, the above range is defined by the average value of all plate thicknesses.

In order to reduce the iron loss when the crystal grain size is 45 μm or more and no load is applied, it is effective to reduce the magnetic flux density (or magnetic polarization) of the iron core in this state. However, as long as a permanent magnet is used for the field, this cannot be eliminated. Therefore, we focused on reducing the iron loss of the material itself. And when the iron loss of the material itself was actually reduced, it was confirmed that the iron loss at no load and light load was reduced. As a technique for reducing the iron loss of the material itself, it is effective to increase the crystal grain size. In order to achieve W20 ≦ 3.0 W / kg while keeping the {111} plane orientation within the above range, the crystal grain size needs to be 45 μm or more as the average crystal grain size. The average crystal grain size is defined by the following equation as an equivalent circle diameter, where N is the number of crystal grains observed in a sufficiently wide cross section (area S).

  In producing the non-oriented electrical steel sheet of the present invention composed of the above, first, in a converter or an electric furnace, the steel melted in the above-described predetermined component is subjected to continuous rolling or split rolling after ingot forming. To make a steel slab. Next, the obtained slab is hot-rolled, subjected to hot rolling hill annealing as necessary, and subjected to cold rolling or warm rolling twice or more sandwiching one or intermediate annealing to obtain a product thickness. Annealing and then aging treatment. Furthermore, at any stage after finish annealing, an insulating coating is applied and baked as necessary.

  In the present invention, regarding the material of the appropriate component, considering the characteristics of the above-mentioned J10, J100 and W20, each of the above characteristics satisfies the formulas (1) to (3) according to the component, or finish annealing It is necessary to determine each of the above process conditions so that the later electrical steel sheet satisfies predetermined texture strength and crystal grain size. In particular, by changing the annealing temperature of hot-rolled sheet annealing, intermediate annealing, finish annealing, etc., satisfying the above formulas (1) to (3), or the electrical steel sheet after finish annealing has a predetermined texture strength, crystal grains It is preferable to determine whether the diameter is satisfied and to determine each annealing temperature.

  In applying the electromagnetic steel sheet of the present invention to a magnet motor, it is effective to use it in a portion where the amount of iron loss generated by the alternating magnetic flux is large. That is, it is preferable to use a rotor steel plate for a brush type motor and a stator steel plate for a brushless DC motor. In addition, application to the iron core part other than the above does not disturb the effect of the present invention.

  A silicon steel slab containing Si: 3.0%, Mn: 0.5%, Al: 0.3% as the main components is manufactured and hot rolled into a 2.5 mm hot rolled sheet, and then hot rolled under the conditions shown in Table 1. Sheet annealing was performed. Subsequently, after cold rolling to a plate thickness of 0.35 mm, finish annealing was performed under the conditions shown in Table 1, and an insulating coating was further applied to obtain a test material. About 500 g of an Epstein test piece was cut out in half from the rolling direction and the direction perpendicular to the rolling from the obtained test material, and magnetic measurement was performed based on JIS C2550. In addition, a motor core was manufactured from the electromagnetic steel sheet as the test material, and after making a brushless DC motor using a rare earth magnet (distributed wound rare earth magnet IPM, rated output 300 W), no-load loss was measured. The results obtained as described above are shown in Table 1 together with the conditions.

  From Table 1, it can be seen that a motor with a low no-load loss is obtained in the example of the present invention. In particular, when J10 / J100 is set to 0.70 or less, it can be seen that even lower no-load loss is obtained. On the other hand, in the comparative example, any one or more of J100 ≧ 1.75T, J10 / J100 ≦ 0.80, W20 ≦ 3.0W / kg is off, and a random set of X-ray reflecting surface intensities in {111} plane orientation Since any one or more of the ratio to the tissue strength and the average crystal grain size are also outside the scope of the present invention, the no-load loss is high.

  For example, the present invention can be used for motor applications that also require output characteristics in a high output range, such as electric motors, drive motors for hybrid electric vehicles, and EPS motors.

Claims (4)

An electromagnetic steel sheet for permanent magnet motors, which is a non-oriented electrical steel sheet containing Si in an amount of 0.1 to 4.5 mass% and whose magnetic properties satisfy the following formulas (1) to (3).
J100 ≧ 1.75T ――― (1)
J10 / J100 ≦ 0.80 ――― (2)
W20 ≦ 3.0W / kg ――― (3)
However, J100: Magnetic polarization at a magnetizing force of 10000 A / m, J10: Magnetic polarization at a magnetizing force of 1000 A / m, W20: Iron loss when magnetized at 2000 A / m, 50 Hz.   It is a non-oriented electrical steel sheet containing 0.1 to 4.5 mass% of Si, the ratio of the X-ray reflecting surface strength of {111} plane orientation to the random texture strength is 3.5 or more and 9.0 or less, and the average grain size is A magnetic steel sheet for a permanent magnet motor, characterized by being 45 μm or more. It is a magnet motor using a non-oriented electrical steel sheet containing 0.1 to 4.5 mass% Si and a permanent magnet, and the magnetic properties of the non-oriented electrical steel sheet satisfy the following formulas (1) to (3): A feature of permanent magnet motor.
J100 ≧ 1.75T ――― (1)
J10 / J100 ≦ 0.80 ――― (2)
W20 ≦ 3.0W / kg ――― (3)
However, J100: Magnetic polarization at a magnetizing force of 10000 A / m, J10: Magnetic polarization at a magnetizing force of 1000 A / m, W20: Iron loss when magnetized at 2000 A / m, 50 Hz.   It is a magnet motor using a non-oriented electrical steel sheet and permanent magnet containing 0.1 to 4.5 mass% of Si, with respect to the random texture strength of the X-ray reflecting surface strength of {111} plane orientation of the non-oriented electrical steel sheet A permanent magnet motor having a ratio of 3.5 to 9.0 and an average crystal grain size of 45 μm or more.