JP2010185119A - Non-oriented electromagnetic steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-oriented electromagnetic steel sheet with low core loss, which is manufactured without needing to increase Si content in the steel sheet to more than 4 wt.% or use a special facility. <P>SOLUTION: The non-oriented electromagnetic steel sheet has a chemical composition comprising, by mass%, 0.005% or less C, 3.5% or less Si, 3.0% or less sol. Al, 3.5% or less Mn, 0.1% or less P, 0.005% or less S, 0.005% or less N and the balance Fe with impurities; and has such specific resistance ρ (μΩ cm) and spontaneous magnetization Is (T) as to satisfy expression (1); ρ≥58.0 and expression (2); Is≥2.34-0.006×ρ, respectively at room temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-oriented electrical steel sheet suitable for iron core materials for compressor motors such as air conditioners and refrigerators, drive motors such as electric vehicles and hybrid vehicles, and high efficiency motors such as starter generators.

  Due to the need to reduce global warming gas, products that consume less energy are being developed in the fields of automobiles and home appliances. For example, in the automobile field, there are low fuel consumption vehicles such as a hybrid drive vehicle combining a gasoline engine and a motor, and a motor drive electric vehicle. In the field of home appliances, there are high-efficiency air conditioners, refrigerators and the like that consume less electricity annually. The technology common to these is a motor, and it is important to improve the efficiency of the motor. As one of the technologies supporting the high efficiency of the motor, there is a demand for low iron loss of non-oriented electrical steel sheets used as iron core materials.

  2. Description of the Related Art In recent years, motors used in the fields of electric equipment, electric vehicles, and the like have been adopted that have a higher rotational speed than before for the purpose of downsizing while maintaining output. In a magnet motor, a multipolar rotor tends to be used from the viewpoint of improving torque and reducing torque ripple. In such a high rotation speed, multi-pole motor, the frequency of the drive power supply tends to increase as the rotation speed and the number of poles increase. For this reason, non-oriented electrical steel sheets that are materials for motor cores are required to reduce iron loss under high frequency conditions.

As the ratio of eddy current loss to iron loss increases rapidly with increasing frequency, the specific resistance of the steel sheet can be increased by increasing the Si content in the steel as a method of reducing the iron loss under such high frequency conditions. Many methods have been used so far.
For example, Patent Document 1 discloses a method of reducing iron loss by increasing the Si content to over 4 wt% and increasing the specific resistance. In the method disclosed in Patent Document 1, when the Si content is increased to more than 4 wt%, the workability of the steel sheet is rapidly deteriorated and it becomes difficult to produce by rolling. Therefore, in the rolling stage, the Si content is set to less than 4 wt%. In addition, the Si content is increased to more than 4 wt% by performing a siliconization treatment on the rolled steel sheet. However, since special equipment is required for the siliconizing treatment, this method has a problem that the manufacturing cost of the steel sheet is remarkably increased.

JP 2001-254166 A

  The present invention has been made in view of the above-described problems of the prior art, and does not require an increase in the Si content of the steel sheet to more than 4 wt% or the use of special equipment, resulting in low iron loss. The object is to provide a non-oriented electrical steel sheet.

In order to solve the above problems, the present inventors have investigated in detail the relationship between the specific resistance ρ of the steel sheet and the iron loss W _10/400 . As a result, it is difficult to effectively reduce the iron loss under high-frequency conditions simply by increasing the specific resistance of the steel sheet by increasing the Si, Al and Mn contents as proposed previously. It has been found. Further, by further examining in detail, it has been newly found out that it is extremely important to increase the specific resistance and the spontaneous magnetization in order to reduce the iron loss more effectively.
That is, increasing the specific resistance by increasing the contents of Si, Al and Mn is important in reducing the iron loss, but it is not sufficient to reduce the iron loss more effectively. It was clarified that it is important to balance the content of elements so as to increase the spontaneous magnetization.
The gist of the present invention based on such new findings is as follows.

That is, the present invention is mass%, C: 0.005% or less, Si: 3.5% or less, sol. Al: 3.0% or less, Mn: 3.5% or less, P: 0.1% or less, S: 0.005% or less and N: 0.005% or less, with the balance being Fe and impurities Provided is a non-oriented electrical steel sheet having a chemical composition and having a specific resistance ρ (μΩcm) at room temperature and a spontaneous magnetization Is (T) at room temperature satisfying the following formulas (1) and (2): To do.
ρ ≧ 58.0 (1)
Is ≧ 2.34−0.006 × ρ (2)

Since the non-oriented electrical steel sheet of the present invention has low iron loss, it is suitable as a material for an iron core of a motor used in a high-speed rotation region such as an air conditioner or a refrigerator in the automobile field, such as a hybrid car or an electric car in the automobile field, This can contribute to improvement of motor efficiency.
In addition, the non-oriented electrical steel sheet of the present invention can be manufactured by the same manufacturing method as that of the prior art, and does not require special treatment, and thus is excellent in terms of manufacturing cost.

It is a graph which shows the relationship between the iron loss _{W10 / 400} , the specific resistance (rho) in room temperature, and the spontaneous magnetization Is.

  Hereafter, each structure in the non-oriented electrical steel sheet of this invention is demonstrated in detail.

(Chemical composition)
First, the reason for limiting the chemical composition of the steel sheet will be described. “%” Indicating the content of each element means “mass%” unless otherwise specified.

  C is an element that is contained as an impurity and deteriorates magnetic properties. For this reason, C content shall be 0.005% or less. Preferably, it is 0.003% or less.

Si, Al, and Mn are all effective elements for increasing the specific resistance of the steel sheet and reducing the iron loss.
However, since Si is also a solid solution strengthening element, if the Si content is excessive, the steel sheet becomes hard and cold rolling becomes difficult. For this reason, Si content shall be 3.5% or less. Preferably, it is 3.0% or less.
Further, when Al is excessively contained, the magnetic flux density is remarkably lowered. For this reason, sol. Al content shall be 3.0% or less.
Since Mn has a higher alloy cost than Si and Al, an increase in Mn content is economically disadvantageous. For this reason, Mn content shall be 3.5% or less. Preferably it is 2.5% or less.

  In the present invention, the resistivity ρ at room temperature is set to 58.0 μΩcm or more by containing Si, Al, and Mn. However, these elements have the same kind of properties in increasing the specific resistance of the steel sheet. However, it is possible to substitute each other. For this reason, it is not necessary to prescribe | regulate the minimum of content of each element. However, since the upper limit of the content of each element is limited as described above, in order to easily make the specific resistance ρ at room temperature 58.0 μΩcm or more, each of Si, Al, and Mn is 0.1%. It is preferable to contain above.

  P is an element generally contained as an impurity. However, P has an effect of improving the magnetic properties by improving the texture of the non-oriented electrical steel sheet, and therefore may be positively contained. However, since P is also a solid solution strengthening element, if the P content is excessive, the steel sheet becomes hard and cold rolling becomes difficult. Therefore, the P content is 0.1% or less.

  S is contained as an impurity and combines with Mn in the steel to form fine MnS, inhibits the growth of crystal grains during annealing, and degrades the magnetic properties of the non-oriented electrical steel sheet. For this reason, S content shall be 0.005% or less. Preferably it is 0.003% or less.

  N is contained as an impurity and combines with Al to form fine AlN, which inhibits the growth of crystal grains during annealing and deteriorates magnetic properties. For this reason, N content shall be 0.005% or less. Preferably it is 0.003% or less.

(Characteristic)
The non-oriented electrical steel sheet of the present invention has characteristics that the specific resistance ρ (μΩcm) at room temperature and the spontaneous magnetization Is (T) at room temperature satisfy the following formulas (1) and (2).
ρ ≧ 58.0 (1)
Is ≧ 2.34−0.006 × ρ (2)

  Here, the specific resistance ρ at room temperature may be measured by a known four-terminal method. The sample used for measurement may be a non-oriented electrical steel sheet from which the insulating coating on the surface has been removed, or a sample for measuring specific resistance from a hot-rolled sheet or slab.

Further, the spontaneous magnetization Is at room temperature is obtained from the following formula (3). In addition, following formula (3) calculates | requires spontaneous magnetization on the assumption that the spontaneous magnetization of a steel plate is simply diluted with elements other than Fe.
Is = 2.16 × {(density of steel plate) / (density of Fe)}
× {(Fe content (% by mass)) / 100} (3)
In addition, what is necessary is just to measure the density of a steel plate according to JISZ8807.
Further, the content of Fe in the formula (3) is from 100 (mass%) to C, Si, sol. It is set as the value which subtracted each content (mass%) of Al, Mn, P, S, and N.

FIG. 1 shows the contents of Si, Al and Mn as basic components with C: 0.002%, P: 0.01%, S: 0.003% and N: 0.002%, respectively. 0-3.0%, sol. At room temperature, which affects the iron loss W _10/400 of a non-oriented electrical steel sheet having a thickness of 0.30 mm when Al: 0.5 to 5.0% and Mn: 0.2 to 3.1% are changed. It is a graph which shows the influence of specific resistance (rho) and spontaneous magnetization Is at room temperature. In the figure, “◯” indicates the case where W _10/400 <16.5 W / kg, and “X” indicates the case where the iron loss W _10/400 ≧ 16.5 W / kg.
As is apparent from FIG. 1, the iron loss W _10/400 has a correlation with the specific resistance ρ at room temperature and the spontaneous magnetization Is. In _order to reduce the iron loss W _10/400 , first, the ratio of the steel plate at room temperature is It is necessary that the resistance ρ be 58.0 μΩcm or more. That is, it is necessary that the specific resistance ρ at room temperature satisfies the above formula (1). Next, it is not sufficient to simply increase the specific resistance ρ, but it is necessary to increase the specific resistance Is and increase the spontaneous magnetization Is. That is, it is necessary that the specific resistance ρ at room temperature and the spontaneous magnetization Is at room temperature satisfy the above formula (2).

In carrying out the present invention, the above formula (1) may be satisfied by increasing the contents of Si, Al and Mn, which have the effect of increasing the specific resistance of the steel sheet.
The spontaneous magnetization Is at room temperature can be obtained from the above formula (3), but the contents of Si, Al and Mn are much higher than the contents of other alloy elements. The density and Fe content are substantially determined by the Si, Al and Mn contents. Therefore, what is necessary is just to satisfy said Formula (2) by adjusting content of Si, Al, and Mn.
Those skilled in the art can implement these without requiring trial and error, complicated experiments, and the like that exceed expectations.
Note that increasing the spontaneous magnetization Is also leads to an improvement in magnetic flux density, which is preferable from the viewpoint of magnetic characteristics.

(Thickness)
The present invention effectively reduces the iron loss W _10/400 of the steel sheet by satisfying a predetermined relationship between the specific resistance ρ and the spontaneous magnetization Is at room temperature. Not limited. However, since it is preferable that the plate thickness is thinner for reducing iron loss under high-frequency conditions, it is preferable that the thickness be 0.30 mm or less. On the other hand, excessively thinning significantly reduces the productivity of the steel sheet and the motor, so the thickness is preferably 0.10 mm or more, and more preferably 0.20 mm or more.

(Production method)
The non-oriented electrical steel sheet of the present invention can be produced by a general method for producing a non-oriented electrical steel sheet.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be described specifically by way of examples.
In a laboratory vacuum melting furnace, C: 0.002%, Si: 1.0-3.0%, sol. Al: 0.5 to 5.0%, Mn: 0.2 to 3.1%, P: 0.01%, S: 0.003%, N: 0.002%, with the balance being Fe and A steel piece made of impurities was produced.
These steel slabs were kept at a temperature of 1150 ° C. for 30 minutes, and then immediately hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2.2 mm. The obtained hot-rolled steel sheet was pickled and then subjected to hot-rolled sheet annealing that was held at a temperature of 800 ° C. for 4 hours. The obtained cold-rolled steel sheet was subjected to finish annealing at a temperature of 1000 to 1100 ° C. to obtain a non-oriented electrical steel sheet.

The non-oriented electrical steel sheet thus obtained was measured for the density of the steel sheet, the specific resistance ρ at room temperature, the spontaneous magnetization Is at room temperature, and the iron loss W _10/400 .
Table 1 shows the chemical composition, finish annealing temperature, density, specific resistance ρ at room temperature, spontaneous magnetization Is at room temperature, and iron loss W _10/400 .

  As shown in Table 1, steel plate No. 7, 16, 20, 22, and 23 had high iron loss due to low spontaneous magnetization despite having a specific resistance of 58.0 μΩcm or more. Steel plate No. 2 and no. Although No. 24 had high spontaneous magnetization, the specific resistance was less than 58.0 μΩcm, so the iron loss was high.

Claims (1)

% By mass, C: 0.005% or less, Si: 3.5% or less, sol. Al: 3.0% or less, Mn: 3.5% or less, P: 0.1% or less, S: 0.005% or less and N: 0.005% or less, with the balance being Fe and impurities A non-oriented electrical steel sheet having a chemical composition and having a specific resistance ρ (μΩcm) at room temperature and a spontaneous magnetization Is (T) at room temperature satisfy the following formulas (1) and (2):
ρ ≧ 58.0 (1)
Is ≧ 2.34−0.006 × ρ (2)

Images