JP5326441B2 - Motor core and motor core material - Google Patents

Description

The present invention relates to a motor core and a motor core material used for, for example, a home air conditioner compressor motor, a hybrid electric vehicle motor, and the like.

For example, a variable speed operation is performed in a home air conditioner compressor motor, and the maximum frequency is about 200 to 400 Hz. Therefore, it is used in a state where a carrier frequency of several kHz is superimposed by PWM control or the like.
In addition, drive motors and generators of hybrid electric vehicles that have been rapidly spreading recently are also driven at a frequency of several kHz from the viewpoint of high output and miniaturization.
Therefore, a non-oriented electrical steel sheet used as the core material of such a motor is required to have a low high-frequency iron loss, and a high grade electrical steel sheet with Si + Al = 3-4% is used. Has been.

By the way, in a compressor motor, shrink fitting is performed for core fastening, and the motor core is used in a state where a compressive stress of about 100 MPa is applied. In addition, a resin mold or the like is also applied to the drive motor of the hybrid electric vehicle, and compressive stress is applied to the motor core.
It is known that when an electrical steel sheet is used under such a compressive stress, the magnetic characteristics are greatly deteriorated. In view of the above, a material with little iron loss deterioration under a compressive stress is demanded.
For example, in Patent Document 1, Si = 2.6 to 4%, specific resistance is 50 to 75 × 10 ⁻⁸ Ωm, and crystal grain size is 60 to 165 μm as an improvement in iron loss characteristics under compressive stress. Non-oriented electrical steel sheets are disclosed. However, even if the material of Patent Document 1 is used, the amount of iron loss deterioration due to the application of compressive stress is not significantly different from that of the conventional material, and there is a demand for a material having low stress dependency.
Japanese Patent No. 4023183

  The present invention has been made in view of such circumstances, and an object thereof is to provide a motor core and a motor core material using a material having low high-frequency iron loss even under compressive stress.

  In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, it was found that the deterioration of iron loss can be suppressed even under compressive stress by using a multilayer material with an increased Si content in the surface layer portion.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] The surface layer part is composed of a steel sheet containing 4% to 7%, Al: 3% or less, and the balance Fe and unavoidable impurities, and the inner layer part is mass% and Si: 4% or less. Al: 3% or less, and using a multi-layered material made of steel sheet as the balance Fe and inevitable impurities as the iron core, the ratio of the thickness of the surface layer portion of the multi-layered material to the total thickness is 0.1 to 0.7 The featured motor core.
[2] The motor core according to [1], wherein in the multilayer material, the amount of inclusions having a diameter of 5 μm or more in the surface layer portion is 30 pieces / mm ² or less.
[3] The surface layer part is composed of a steel sheet that includes Si: 4 to 7%, Al: 3% or less, with the balance being Fe and inevitable impurities, and the inner layer part is mass% and Si: 4% or less. Al: 3% or less, a multi-layer motor core material composed of the remaining Fe and inevitable impurities, wherein the ratio of the surface layer thickness to the total thickness is 0.1 to 0.7.
[4] The motor core material according to [3], wherein an amount of inclusions having a diameter of 5 μm or more in the surface layer portion is 30 pieces / mm ² or less.
In addition, in this specification,% which shows the component of steel is mass% altogether.

According to the present invention, a motor core and a motor core material excellent in iron loss characteristics can be obtained.
Since the motor core of the present invention has little iron loss deterioration even under compressive stress, an air conditioner compressor motor, a hybrid EV drive motor, an EV drive motor, and an FCEV drive motor in which a compressive stress is applied to the core material by a resin mold or the like It becomes possible to reduce the iron loss of the high-frequency rotating machine of the high-speed generator.

The motor core in the present invention is obtained by punching into a predetermined shape using a multilayer material satisfying the following (1) to (3) as an iron core.
(1) The surface layer part is composed of a steel sheet that includes, by mass%, Si: 4 to 7%, Al: 3% or less, and the balance Fe and inevitable impurities,
(2) The inner layer part is composed of a steel sheet that includes, by mass%, Si: 4% or less, Al: 3% or less, the remaining Fe and inevitable impurities,
(3) The ratio of the surface layer thickness to the total thickness is 0.1 to 0.7.
As described above, the present invention is characterized in that a multilayer material having an increased Si amount in the surface layer portion is used as the material constituting the motor core. This is the most important requirement in the present invention. By using such a multilayer material as an iron core, a motor core having excellent iron loss characteristics can be obtained. The present invention is particularly effective when used under compressive stress.

  The present invention is directed to a multilayer material having a three-layer structure of surface layer-inner layer-surface layer in the plate thickness direction, and the surface layer portion refers to a layer including the steel plate surface. On the other hand, the inner layer portion is a central portion in the thickness direction excluding the surface layer portion. Here, the interface between the surface layer portion and the inner layer portion refers to the following region. That is, when the Si concentration gradient is measured in the steel plate thickness direction by EPMA, a rapid change in the Si concentration distribution occurs at the boundary between the surface layer portion and the inner layer portion. The position at which this rapid concentration change of Si is seen is taken as the interface. However, when the interface is not uniquely determined due to Si diffusion or the like, the interface starts at a position where the Si concentration becomes 90 when the Si concentration on the surface is 100. On the other hand, the end of the interface is a position where the Si concentration becomes 110 when the central Si concentration is 100.

Next, details of the present invention will be described based on experimental results.
First, the magnetic properties under compressive stress are investigated.
A steel with Si = 2.50%, Al = 0.50% and O = 0.020% was melted in the laboratory to obtain an ingot. After that, hot rolling and hot-rolled sheet annealing at 900 ° C x 30s were performed to make the plate thickness 0.25mm, followed by finish annealing at 1000 ° C x 30s, and a single plate with a length of 180mm and a width of 30mm along the rolling direction. A sample was made. A compressive stress of 100 MPa was applied in the longitudinal direction of the single plate, and the sample was excited in the stress loading direction to investigate the magnetic properties. For comparison, the stressless magnetic properties were also investigated.
As a result, the iron loss under compressive stress was W3 / 5k = 169 W / kg, and the iron loss without stress was W3 / 5k = 65 W / kg. From this result, it is understood that the iron loss is deteriorated by about 2.6 times by applying the compressive stress.
In order to investigate this cause, when iron loss separation was performed, both hysteresis loss and eddy current loss increased due to the application of compressive stress. In particular, it was revealed that the deterioration ratio of eddy current loss was large. As for the cause of the deterioration of hysteresis loss, the steel sheets as described above have positive magnetostriction, so when the steel sheet is magnetized, the steel sheet will stretch in the magnetization direction, but compressive stress is applied to the magnetization direction. If this is done, the steel sheet cannot be stretched, magnetization becomes difficult, and iron loss is considered to have increased. On the other hand, the cause of the increase in eddy current loss is not clear, but it may be due to some change in the magnetic domain structure.

By the way, it is known that when the steel plate is excited in a high frequency range exceeding 1 kHz, the magnetic flux is concentrated only on the surface layer portion of the steel plate due to the skin effect. Therefore, it is considered that the iron loss deterioration can be suppressed if the stress applied to the surface layer portion can be reduced by any method when compressive stress is applied.
Therefore, the magnetic properties under compressive stress were investigated by changing the mechanical and magnetic properties by producing materials with different surface layer and inner layer components.

First, the influence of the Si content in the surface layer will be examined.
Steel with Si = 3.0%, Al = 0.20% and O = 0.0018% used for the inner layer, and steel with Al = 0.2% and O = 0.0018% used for the surface layer and Si varied from 3.0 to 6.5% After melting and making each ingot, lamination is performed so that the multilayer ratio (surface layer thickness / total thickness) is 0.3, and then hot rolling and hot-rolled sheet annealing at 900 ° C x 30s are performed to prevent sheet breakage. Therefore, warm rolling was performed at 250 ° C., and the plate thickness was set to 0.25 mm. Thereafter, finish annealing at 1000 ° C. × 30 s was performed to produce a single plate sample having a length of 180 mm and a width of 30 mm along the rolling direction. The obtained single plate was subjected to a compressive stress of 100 MPa in the longitudinal direction, and the sample was excited in the stress load direction to investigate the magnetic characteristics.
The obtained results are shown in FIG. 1 as the relationship between the Si amount in the surface layer portion and the iron loss W3 / 5k. FIG. 1 shows that the iron loss is reduced when the Si content in the surface layer is 4% or more. The cause of this is not clear, but it is thought that the stress at the surface layer portion of the steel sheet becomes relatively low due to the multi-layering, and the magnetic domain structure change which is undesirable for eddy current loss is less likely to occur.
From the above, the Si content in the surface layer portion is 4% or more, preferably 4.5% or more. On the other hand, when the Si content exceeds 7%, it is difficult to prevent sheet breakage even if warm rolling is performed, so the upper limit of the Si content in the surface layer portion is 7%.

Next, the amount of Si in the inner layer will be examined.
Steel with Si = 5.40%, Al = 0.30% and O = 0.0018% used for the surface layer part, and steel with Al = 0.2% and O = 0.0017% used for the inner layer part and Si varied from 1.0 to 5.0% After melting and making each ingot, lamination is performed so that the multilayer ratio (surface layer thickness / total thickness) is 0.3, and then hot rolling and hot-rolled sheet annealing at 900 ° C x 30s are performed to prevent sheet breakage. Therefore, warm rolling was performed at 250 ° C., and the plate thickness was set to 0.25 mm. Thereafter, finish annealing at 1000 ° C. × 30 s was performed, a single plate sample having a width of 30 mm and a length of 180 mm was cut out, a compressive stress of 100 MPa was applied in the magnetization direction, and the magnetic characteristics were evaluated in the same manner as described above.
The results obtained from the above are shown in FIG. 2 as the relationship between the Si amount in the inner layer and the iron loss W3 / 5k. FIG. 2 shows that the iron loss increases when the Si content in the inner layer exceeds 4%. This is considered to be because the difference in Si between the surface layer and the inner layer is reduced, so that the effect of multi-layering is reduced and a magnetic domain structure change which is undesirable for eddy current loss occurs.
From the above, the Si content in the inner layer is made 4% or less. The lower limit is preferably 2% or more, more preferably 2.5% or more from the viewpoint of iron loss.

Next, the multilayer ratio will be examined.
Ingot made by melting steel with Si = 5.30%, Al = 0.20% and O = 0.0018% used for the surface layer and steel with Si = 3.3%, Al = 0.2% and O = 0.0017% used for the inner layer. In order to prevent sheet breakage, it is laminated so that the multilayer ratio (surface layer thickness / total thickness) is 0.05 to 0.9, followed by hot rolling and hot-rolled sheet annealing at 900 ° C. × 30 s. Warm rolling was performed at a temperature of 0.25 mm. Thereafter, finish annealing at 1000 ° C. × 30 s was performed, and the magnetic characteristics of the material obtained as described above were evaluated in the same manner as in the above experiment.
The results obtained as described above are shown in FIG. 3 as the relationship between the multilayer ratio and the iron loss W3 / 5k. FIG. 3 shows that the iron loss is reduced when the multilayer ratio is 0.1 to 0.7. This is probably because when the surface high Si part is less than 0.1 or more than 0.7, the effect of the multi-layering is reduced, and the magnetic domain structure changes unfavorably for eddy current loss and the iron loss is increased.
From the above, the multilayer ratio is 0.1 to 0.7.

When manufacturing or processing such a multilayer material having a high Si content in the surface layer portion, there is a problem that it is easily broken. For example, when a material having a multilayer structure in the ingot stage is hot-rolled and cold-rolled, a large tensile force acts on the surface layer in the coil bending and unbending processes, so that the material is easily cracked. In addition, there is a risk of cracking because the coil is bent and unbent during the machining of the motor core. Therefore, when the material in which such a crack occurred was observed, it was found that the frequency of occurrence of the crack due to coarse inclusions was larger than that of a material that is difficult to break. Therefore, the relationship between coarse inclusions and cracks was investigated.
Steel with Si = 5.5%, Al = 0.50%, O = 0.0018% used for the surface layer part, and steel with Si = 3.5%, Mn = 0.30%, Al = 0.5%, O = 0.0017% used for the inner layer part Each was melted to form an ingot, and then bonded so that the multilayer ratio (surface layer thickness / total thickness) was 0.3. At this time, in order to change the amount of coarse inclusions in the surface layer portion, the deoxidation time at the time of melting the surface steel was variously changed. Thereafter, hot rolling was performed to obtain a sheet thickness of 2 mm, 900 ° C. × 30 s hot-rolled sheet annealing was performed, the hot-rolled annealed sheet was bent to an angle of 45 ° at 40 ° C., a bending test was performed, and the number of bendings was measured.
The results obtained above are shown in FIG. 4 as the relationship between the amount of inclusions having a diameter of 5 μm or more and the number of bendings. Here, the inclusions were observed by using an optical microscope, observing 20 fields of view at 200 ×, and determining the size and quantity. The reason why inclusions of 5 μm or more are targeted is that inclusions smaller than that do not affect the bendability. FIG. 4 shows that the number of bending increases when the number of inclusions is 30 / mm ² or less.
From the above, the amount of inclusions with a diameter of 5 μm or more in the steel sheet surface layer portion is 30 pieces / mm ² or less.

Next, the reasons for limiting other components will be described.
Al: 3% or less
Al is an effective element for increasing the specific resistance, but if it exceeds 3%, the magnetic flux density decreases as the saturation magnetic flux density decreases. Therefore, the upper limit is 3%. Although a lower limit is not prescribed | regulated, it is preferable that it is 0.01% or more from a viewpoint of deoxidation.
O: 0.01% or less (preferable range)
O content is preferably 0.01% or less because inclusions increase when the content is large and the material is easily cracked.
This patent provides a material with low iron loss in a high frequency range, and is preferably applied to a motor used at a frequency of 1 kHz or higher. The frequency mentioned here includes a case where the carrier frequency is 1 kHz or more in addition to the fundamental frequency, and is effective also in such a case.

Next, the manufacturing method of the motor core material of this invention is demonstrated.
In the present invention, it is important to change the amount of Si in the surface layer portion and the inner layer portion. For this purpose, for example, materials having different components are blown in a converter, the molten steel is degassed and adjusted to a predetermined component, and subsequently cast into a slab, and then a predetermined multilayer ratio is obtained. Thus, the steel plate of the surface layer portion and the steel plate of the inner layer portion are bonded together. After that, the slab is hot-rolled in a normal manner, and then made into a predetermined sheet thickness by two or more cold or warm rolling sandwiched between one cold or warm rolling or intermediate annealing, By performing the finish annealing, the multilayer material of the present invention can be obtained. Here, the finishing temperature and the coiling temperature at the time of hot rolling do not need to be specified in particular, and may be normal. Moreover, although hot-rolled sheet annealing after hot rolling may be performed, it is not essential.
Moreover, it is also possible to use as a multilayer material by making a steel plate into a multilayer structure. For example, in order to set the surface layer portion to Si: 4 to 7% and the inner layer portion to Si: 4% or less, the finish annealing plate can be subjected to Si siliconization treatment.
When performing the siliconization treatment to the finish annealed plate, it is necessary to perform the siliconization and diffusion treatment at a high temperature, so that the crystal grains become coarse and the material is easily broken. For this reason, when performing a siliconization process, it is preferable to take Al and 0.01% or more, and to take the technique of suppressing the grain growth at the time of a siliconization process.
The thickness of the plate is not particularly specified, but is 0.35 mm or less, more preferably 0.2 mm or less from the viewpoint of reducing high-frequency iron loss. The lower limit is preferably 0.05 mm or more from the viewpoint of productivity.

  Thus, the motor core material of the present invention is obtained. And the motor core of this invention is obtained by using this as an iron core, and the motor core of this invention is suitable especially when used under a compressive stress. As described above, the iron loss usually deteriorates about 2.6 times by applying a compressive stress of 100 MPa equivalent to shrink fitting. On the other hand, by using the material of the present invention, it is possible to reduce the iron loss by 10% or more (iron loss deterioration ratio 2.3 times or less) compared to the conventional material, which can contribute to the improvement of the motor efficiency. Here, if the iron loss improvement allowance of the part to which compressive stress is applied is less than 10%, the efficiency improvement rate of the motor is small, and the material improvement allowance is covered by manufacturing variations, etc. More than 10% of the material.

  The steel shown in Table 1 was blown in a converter and then degassed to adjust to a predetermined component and then cast into a slab. Subsequently, the obtained slabs were laminated so as to have a multilayer ratio shown in Table 2, the outer periphery was welded, heated at 1140 ° C. for 1 hour, and hot rolled to a thickness of 2.0 mm. The hot rolling finishing temperature was 800 ° C. The coiling temperature was 610 ° C., and after coiling, hot rolled sheet annealing at 900 ° C. × 30 s was performed. Thereafter, pickling was performed, and annealing was performed under the finish annealing conditions shown in Table 2.

A single plate sample with a length of 180 mm from the rolling direction is cut out from the specimen obtained as described above, and a compressive stress of 100 MPa is applied in the longitudinal direction. Measured.

Moreover, the bending test was done using the said test material. The bending test was evaluated by bending and unbending the hot-rolled annealed plate at an angle of 45 ° at 40 ° C.
Further, the amount of inclusions of 5 μm or more was determined as follows.
Inclusion amount of 5 μm or more Using an optical microscope, 20 fields of view were observed at 200 ×, and the results of counting the amount of the circle equivalent diameter of 5 μm or more that can be clearly distinguished from inclusions were listed together with the components and manufacturing conditions. It is shown in 2.

  From Table 2, it can be seen that by setting the components of the surface layer and the inner layer and the multilayer ratio within the range of the present invention, a steel sheet having low iron loss and no cracking during sheet passing can be obtained. In particular, it can be seen that the iron loss characteristics under a compressive stress of 100 MPa are even better than the comparative example. In the present invention, the iron loss value W3 / 5k under a compressive stress of 100 MPa is 2.3 times or less than the iron loss value W3 / 5k under no stress, which is optimal as a motor core used under a compressive stress. I understand.

  Air conditioning compressor motor, hybrid EV drive motor, EV drive motor, FCEV drive motor, and high-speed generator high-speed generator that compressive stress is applied to the core material by using the motor core with excellent iron loss characteristics of the present invention It can be used for a variety of purposes, mainly in the machine.

It is a figure which shows the relationship between surface layer Si amount and an iron loss. It is a figure which shows the relationship between inner layer Si amount and iron loss. It is a figure which shows the relationship between a multilayer ratio and an iron loss. It is a figure which shows the relationship between the number of inclusions 5 micrometers or more, and the bending frequency.

Claims (2)

The surface layer part is composed of a steel sheet that includes Si: 4 to 7%, Al: 3% or less, with the balance being Fe and inevitable impurities, and the inner layer part is mass%, Si: 4% or less, Al: comprises 3%, using a multilayered material consisting of a steel plate is a balance of Fe and inevitable impurities as a core, Ri ratio 0.1-0.7 der to total thickness of the surface layer portion thickness of said plurality layer-type material , motor core amount of inclusions or more in diameter 5μm in the surface layer portion, characterized in der Rukoto 30 / mm ² or less. The surface layer part is composed of a steel sheet that includes Si: 4 to 7%, Al: 3% or less, with the balance being Fe and inevitable impurities, and the inner layer part is mass%, Si: 4% or less, Al: comprises 3%, a multilayered motor core material balance consisting of Fe and unavoidable impurities, Ri total ratio thickness 0.1-0.7 der of the surface layer portion thickness, diameter of at least 5μm in the surface layer portion motor core material interposed amount is characterized in der Rukoto 30 / mm ² or less.

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