JPH0849044A - Monoriented silicon steel sheet for electric automobile and its production - Google Patents

Abstract

PURPOSE:To produce a nonoriented silicon steel sheet high in motor efficiency and useful as the motor stock for electric automobiles by specifying the contents of C, Si and Mn in a steel sheet and its sheet thickness and regulating the relationship between its core loss and magnetic flux density into a specified range. CONSTITUTION:A steel slab contg., by weight, <=0.0050% C, 1.0 to 4.5% Si and <=1.5% Mn is subjected to hot rolling and is subjected to cold rolling including process annealing to regulate its sheet thickness to 0.10 to 0.50mm. The cooling after the finish annealing is executed under the conditions of <=0.3kg/mm<2> tension and <=5 deg.C/s<2> cooling rate change. Thus, the nonoriented silicon steel sheet for electric automobiles in which core loss W15/50 in 1.5T and 50Hz and core loss W5/1000 (W/kg) in 0.5T and 1000Hz and magnetic flux density B50 (T) in 5000A/m satisfy the relationship in the inequalities I and II can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oriented electrical steel sheet particularly suitable as a material for a motor of an electric vehicle and a method for producing the same.

[0002]

2. Description of the Related Art Non-oriented electrical steel sheets are widely used as core materials for motors and transformers. In recent years, from the viewpoint of energy saving, there has been a loud call for higher efficiency of electrical equipment, but with this, further reduction of iron loss has been desired for iron core materials.

As means for reducing iron loss of electromagnetic steel sheets, Si, Al
An eddy current loss reduction method by adding a specific resistance increasing element such as is inexpensive and most effective. It is also effective to improve the texture, for example, in Japanese Patent Publication No. 56-22931, by improving the cold rolling conditions, in Japanese Patent Publication No. 58-3027.
By adding Sn, in Japanese Patent Publication No. 57-59293, Sb
This is achieved by adding, respectively.
In addition, since inclusions and precipitates in the steel impede the movement of the domain wall to deteriorate the hysteresis loss, the method disclosed in JP-A-59-7
In Japanese Patent No. 4258, this is achieved by reducing impurities. Further, in JP-A-59-74256, JP-A-60-152628 and JP-A-3-104844, the iron loss is reduced by reducing the number of inclusions.

All of the above methods attempt to reduce iron loss under specific conditions such as W _10/50 or W _15/50 . However, when a motor for an electric vehicle is manufactured by using such an electromagnetic steel sheet, good motor characteristics, particularly good motor efficiency have not always been obtained.

The reason for this is that the motor for an electric vehicle is not driven under a certain driving condition, unlike a normal motor. That is, it is necessary to constantly change the rotation speed of the automobile motor from low-speed rotation to high-speed rotation or vice versa, and the drive frequency and the magnetic flux condition at that time change significantly each time. Therefore, the characteristics of the material under certain conditions, such as W _10/50 (1.0T, 50Hz
It is not possible to evaluate the efficiency of electric vehicle motors only by the iron loss in.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to establish a motor efficiency evaluation method for electric vehicle motors, and to provide a non-oriented electrical steel sheet useful as a material for highly efficient electric vehicle motors based on the method. Where it is.

[0007]

[Means for Solving the Problems] Now, the present inventors not only evaluate the characteristics of materials by the conventional method, but also actually create model motors using various materials, and under the same conditions as driving an electric vehicle. By driving this model motor with and examining efficiency and all other characteristics,
First, the motor efficiency was evaluated. As a result, the total motor efficiency (η _TOT ) is expressed by the following equation η _TOT = 0.5 η ₁₂₀ +0.2 (η ₆₀ + η ₂₄₀ ) +0.05 (η
₃₀ + η ₃₀₀ ) Here, it was clarified that it is represented by the efficiency when driven at η _X : x Hz.

Based on these results, regarding the relationship between the motor efficiency η _TOT and the material characteristics, the magnetic flux density: 0.1 to 2.0 T,
Frequency: A thorough investigation was conducted over a wide range of 10 to 10000 Hz. As a result, 1.5T, 50Hz and 0.5T, 1000Hz
Each iron loss W _15/50, W _5/1000 in (W / kg) and 5
It has been found that if the magnetic flux density B ₅₀ (T) at 000 A / m satisfies a predetermined relationship, an extremely efficient motor for an electric vehicle can be obtained. The present invention is based on the above findings.

[0009]

That is, the present invention has a composition containing C: 0.0050 wt% or less, Si: 1.0 to 4.5 wt%, Mn: 1.5 wt% or less, and a plate thickness of 0.10 mm or more and 0.50 mm or more. mm loss or less, and iron loss W _15/50 and 0.5 at 1.5T, 50Hz
Iron loss at T, _1000Hz W _5/1000 (W / kg) and 5000
The magnetic flux density B ₅₀ (T) at A / m is _expressed by the following formula W _15/50 + (W _5/1000/10 ) ≤ 7.0 W _15/50 + (W _5/1000 / 10) ≤ 62 · B ₅₀ -97 Is a non-oriented electrical steel sheet for electric vehicles, which satisfies the relationship of

Further, according to the present invention, a steel slab having a composition containing C: 0.0050 wt% or less, Si: 1.0 to 4.5 wt%, and Mn: 1.5 wt% or less is hot-rolled once or in intermediate annealing. In order to manufacture a non-oriented electrical steel sheet by a series of steps in which a final plate thickness is obtained by cold rolling including 2 times, the cooling after the finish annealing is performed at a tension of 0.3 kg / mm ² or less, Change in cooling rate: A method for producing a non-oriented electrical steel sheet for electric vehicles, which is performed under the condition of 5 ° C / s ² or less.

Below, the experimental results that form the basis of the present invention will be explained. C: 0.0020 wt%, Si: 0.5-3.5 wt
%, Mn: 0.5 wt% and the balance of which is substantially Fe, by hot rolling and then cold rolling according to a conventional method to obtain various cold-rolled sheets with a thickness of 0.05 to 0.75 mm. A steel plate was obtained. Then, after finishing annealing at 800-1000 ℃ for 1 min, 0.15
Cooling was performed under a tension of ~ 0.3 kg / mm ^{2 at} a cooling rate of 20 to 35 ° C / s and a cooling rate change of 1 to 5 ° C / s ² . A model motor was produced from each of the obtained steel plates, and the results of investigation of the motor efficiency thereof are summarized in relation to the material characteristics and shown in FIG.

As is clear from the figure, the motor efficiency η
_In order to achieve _TOT ≧ 80%, the following formula W _15/50 + (W _5/1000 / 10) ≦ 7.0 W _15/50 + (W _5/1000 / 10) ≦ it is the is investigated it is necessary to satisfy the relationship of 62 · B ₅₀ -97. The reason why the motor efficiency can be evaluated well with the above formula is not clear so far, but 50 Hz is the iron loss representing the low frequency region and 1000 Hz is the high frequency region. It is considered that the relatively high magnetic field is an important factor.

Next, the manufacturing conditions of the non-oriented electrical steel sheet having the WB characteristics as described above were examined. As a result, it was found that the cooling conditions after finish annealing, especially the applied tension and the cooling rate change during cooling, are important for obtaining the desired properties. That is, the applied tension during cooling is 0.
By setting the cooling rate to 3 kg / mm ² or less and the cooling rate change to 5 ° C./s ² or less, the relation of the above equation is satisfied, and thus η
_{It was clarified} that a high motor efficiency of _TOT ≥ 80% can be stably obtained. In this respect, the applied tension during cooling in the past was about 0.2 to 0.5 kg / mm ² , so
It is probable that stable and good motor efficiency was not obtained.

[0014]

In the present invention, the composition of the steel sheet is limited to the above range for the following reason. C: 0.0050 wt% or less C is an unfavorable element in terms of magnetic properties, and when it exceeds 50 ppm, the iron loss is particularly deteriorated, so the content is limited to 50 ppm or less.

Si: 1.0 to 4.5 wt% Si effectively contributes to the reduction of iron loss by increasing the specific resistance, but if the content is less than 1.0 wt%, the effect is poor, while 4.5 wt% If it exceeds the range, cold workability will be deteriorated, so the range was limited to 1.0 to 4.5 wt%.

Mn: 1.5 wt% or less Mn is a useful element which is effective not only for preventing hot rolling cracks but also for increasing the specific resistance and reducing iron loss, but its content is 1.5 wt%. If it exceeds 0.1%, disadvantages such as deterioration of magnetic flux density may occur, so the range is limited to 1.5 wt% or less.

Although the basic components have been described above, in addition, in the present invention, Al, P, Sb, Sn and the like may be contained in the following ranges, if necessary. Al: 1.0 wt% or less Al enhances the specific resistance and effectively contributes to the reduction of eddy current loss, but when it exceeds 1.0 wt%, the magnetic flux density decreases, so
About 1.0 wt% or less is preferable. P: 0.08 wt% or less P, like Al, is a useful element that increases specific resistance and reduces eddy current loss, but if the content exceeds 0.08 wt%, workability deteriorates. It is preferable to add it. Sb: 0.08 wt% or less Sb effectively contributes to the improvement of texture, but if it exceeds 0.08 wt%, grain growth is inhibited, so about 0.08 wt% or less is preferable. Sn: 0.2 wt% or less Sn, like Sb, is a useful element that improves the texture,
If the content exceeds 0.2 wt%, grain growth is inhibited.
% Or less is preferable.

Further, in the present invention, the plate thickness of the steel plate is 0.
It is necessary to limit the range to 10 mm or more and 0.50 mm or less. This is because when the plate thickness exceeds 0.50 mm, the WB balance deteriorates and it becomes difficult to obtain the desired motor efficiency.
If it is less than 0.10 mm, not only the motor core laminating time becomes longer but also the automatic crimping property is deteriorated.

Next, the manufacturing method of the present invention will be described. In producing the slab, either the continuous casting method or the ingot-segmentation method may be used. Then, after heating the slab, hot rolling is performed, if necessary hot-rolled sheet annealing,
Cold rolling is performed once or twice including intermediate annealing to finish to the final plate thickness. After that, about 1 min at 800-1100 ℃
Although the finish annealing is performed to some extent, the cooling step after the soaking treatment in the finish annealing is particularly important in the present invention.

That is, this cooling treatment was performed under a tension of 0.3 kg.
/ mm ² or less, change in cooling rate: 5 ° C / s ² It is important to carry out under the conditions of ² or less. This is because when the changes in the applied tension and the cooling rate deviate from the above ranges, as described above, good motor efficiency cannot be obtained, although the reason is not clear. At this time, the cooling rate is not particularly limited.

[0021]

EXAMPLES Steel slabs having various compositional compositions shown in Table 1 were hot-rolled and then cold-rolled once to obtain a sheet thickness of 0.10 to 0.65 mm.
Cold-rolled sheet. Then, after finishing annealing at 800 to 1000 ° C. for 1 min, it was cooled under various conditions shown in Table 2. Using the obtained steel sheet, 3 phase 6 poles, inverter frequency: 10 to 400 Hz,
Create a model motor with a carrier frequency of 1 to 20 kHz,
The motor efficiency η _TOT was investigated. The obtained results are also shown in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

As described above, the non-oriented electrical steel sheet according to the present invention can be used in a motor for an electric vehicle whose number of revolutions constantly changes, and can ensure a much higher motor efficiency than the conventional one.

[Brief description of drawings]

FIG. 1 is a diagram showing an influence of a WB characteristic of a material on a motor efficiency η _TOT .

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01F 1/16 H02K 1/02 Z (72) Inventor Minoru Takashima 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Address: Steel Research and Development Division, Steel Research Laboratory, Kawasaki Steel Co., Ltd. (72) Inventor Takafumi Obara, Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Corporation Steel Development and Production Division, Steel Research Laboratory (72) Invention Osamu Oyama 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Kawatetsu Techno Research Co., Ltd.

Claims (2)

[Claims] 1. C: 0.0050 wt% or less, Si: 1.0 to 4.5
wt%, Mn: 1.5 wt% or less, the composition is 0.10 mm
Iron loss W above 0.50mm and below 1.5T, 50Hz
_15/50 and 0.5T, iron loss in 1000Hz W _5/1000 (W /
kg) and the magnetic flux density B ₅₀ (T) at 5000 A / m,
For electric vehicles characterized by satisfying the following formula: W _15/50 + (W _5/1000/10 ) ≤ 7.0 W _15/50 + (W _5/1000 / 10) ≤ 62 · B ₅₀ -97 Non-oriented electrical steel sheet. 2. C: 0.0050 wt% or less, Si: 1.0 to 4.5
A steel slab with a composition containing wt% and Mn: 1.5 wt% or less is hot-rolled and then cold-rolled once or twice including intermediate annealing to obtain the final plate thickness, and then subjected to finish annealing. When manufacturing a non-oriented electrical steel sheet by the process described in 1., cooling after finish annealing is performed under conditions of tension: 0.3 kg / mm ² or less and cooling rate change: 5 ° C / s ² or less. Manufacturing method of non-oriented electrical steel sheet for automobiles.