JPH0814016B2 - High frequency non-oriented electrical steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a material for electric products generally used for motors and small transformers, especially in a high frequency region, 400H.
The present invention relates to a non-oriented electrical steel sheet which is effective for use at z or higher.

The fields of application include, for example, motors for vacuum cleaners, small transformers such as fluorescent lights for intelligent buildings, various motors, motors and lighting equipment for airplanes and cabins, and robot control motors.

[Conventional technology]

This field of application is a field that has recently begun to receive attention rapidly,
It is effective for improving the energy efficiency of electrical equipment and strict position control of precision motors, but with a frequency of 400H
z or more is needed. Therefore, unlike the so-called commercial frequency of 50 to 60 Hz used for conventional electrical steel sheets, 400 Hz
We have to focus on the above 700 Hz, for example, but we have not yet manufactured and sold the optimum steel plate in this area. For example, the highest grade non-oriented electrical steel sheet is Si
A 3%, 1% Al plate having a thickness of 0.35 mm and a crystal grain size of about 150 μm is commercially available. Although it has excellent magnetic properties at 50 Hz, it does not have satisfactory properties at high frequencies.

As a conventional idea, it is generally known that the eddy current loss in the total iron loss increases as the frequency increases. It has been said that this eddy current loss W _e is calculated by the following known equation (1) as a classical eddy current loss equation.

Here _{^{W e = 0.1645B 2 f 2 d}} 2 / ρD, B: maximum magnetic flux density (T) f: Frequency (Hz, cycles / sec) d: thickness (mm) ρ: specific resistance (μΩ-cm) D : Density (g / cm ³ ) In other words, in order to reduce the eddy current loss, there are methods such as decreasing the design magnetic flux density B, reducing the plate thickness d, and increasing the Si content etc. to increase the specific resistance ρ. I know there is.

Therefore, if this approach is taken, for example, if the iron loss W _5/700 at 700 Hz and 0.5T is to be 12 W / kg or less, Si6.5%
There is a means to make the plate thickness 0.15 mm. However, this method has a problem of cold rolling rupture on the manufacturing side and cracking at the customer's punching, and was industrially impossible. Furthermore,
There was a serious quality problem that the magnetic flux density B _5/700 at a magnetizing force of 700 Hz and 500 A / m was only about _0.05T . For general electric equipment, a magnetic flux density of about 1.0 T is required as a magnetization characteristic, and iron loss is also required to be good at the same time.

[Problems to be Solved by the Invention]

In view of the above points, an object of the present invention is to provide an electrical steel sheet having excellent iron loss and magnetic flux density in a high frequency region of 400 Hz or higher at the same time by an industrial method.

[Means for solving the problem]

The present invention, the total amount of Si and Al is 2.0 ~ 4.0%, C0.005% or less, Mn1% or less, S0.01% or less, N0.01% or less, the balance is iron and unavoidable impurities Magnetic steel sheet having a plate thickness of 0.10 to 0.25 mm and an average crystal grain size of 5 to 5
Iron loss W _{5/700 of} 60 μm is 12 W / kg or less, magnetic flux density B
_Frequency 400Hz with excellent magnetic characteristics of _5/700 of 1.0T or more
The gist is the high-frequency non-oriented electrical steel sheet used above.

Si and Al are effective for increasing the specific resistance of the steel sheet,
It is a commonly used ingredient because it is inexpensive. As is well known
Since the effects of Si content and Al content on the specific resistance are almost equivalent,
When the amount of Si + Al is small, the iron resistance is deteriorated because the specific resistance is not sufficient. On the other hand, as is well known, Si and Al have almost the same atomic weight and have an equivalent effect of reducing the number of Fe atoms per unit weight. If Si + Al is too large, the amount of ferromagnetic Fe decreases, and the magnetic flux density deteriorates.

Further, the plate thickness has a great effect to reduce the eddy current loss. If it exceeds 0.25 mm, the iron loss is insufficient, and if it is less than 0.10 mm, it is industrially difficult to manufacture due to problems such as rolling ability and breakage.

The effect of the crystal grain size is a characteristic of the present invention, which is not predicted from the conventional classical eddy current loss calculation formula,
It has a very important meaning for the magnetic characteristics around 700 Hz. That is, if the iron loss and the magnetic flux density of the magnetic characteristics at a high frequency are simultaneously satisfied, for example, if the iron loss W _5/700 is 12 W / kg or less and the magnetic flux density B _5/700 is 1.0 T or more, the crystal grains are We must take advantage of the diameter effect.

The reasons for limiting the constituent features of the present invention will be described in detail below.

1 and 2 show the effect of the crystal grain size on the product in a 0.20 mm thick non-oriented electrical steel sheet. First
Fig. 2 shows the iron loss, and Fig. 2 shows the effect on the magnetic flux density. The size of the crystal grain size was controlled by the temperature of the final annealing.
As shown in the figure, B _5/700 is good when the amount of Si + Al is 1.5%, but the region of the crystal grain size where W _5/700 is _less than 12 W / kg is narrowly limited. Further, if the amount of Si + Al is 3% within the range of the present invention, both W _5/700 and B _5/700 are satisfied in a wide range of crystal grain sizes of 5 to 60 μm. Furthermore, when Si + Al content is 4.5%, W
_5/700 is good, but B5 / ₇₀₀ with a value of 1.0T or more can be obtained only slightly. The reason why the magnetism deteriorates when the crystal grain size is 20 μm or less is probably due to internal stress. If the crystal grain size is less than 5 μm, unrecrystallized grains remain, so that the magnetism remarkably deteriorates. Also, magnetic deterioration is recognized at 40 μm or more, which is probably because {100} of easy magnetization is reduced.

Therefore, Si + Al satisfying both W _5/700 and B _5/700
The amount is 2.0 to 4.0%, and the crystal grain size is 5 to 60 μm.

Conventionally, the crystal grain size of a high grade non-oriented electrical steel sheet was 100 to 200 μm. This is because the iron loss at the commercial frequency of 50 to 60 Hz is the best at this grain size.

Regarding the measurement method, the crystal grain size was measured by counting the number of crystal grains appearing on the corroded surface by the cutting method. The magnetic measurement was performed by JIS C 2550 audio iron loss test, and the size of the test piece was 30 mm width × 300 mm length, half was the rolling direction, and half was the direction perpendicular to the rolling direction.

Next, the effect of the plate thickness is shown in FIGS. 3 and 4.
The material shown in Fig. 3 has a Si + Al content of 2.0% and a plate thickness of 0.1-0.
The size was changed to 5 mm and the crystal grain size was adjusted to 3 types. As shown in FIG. 3, when the crystal grain size is 50 to 55 μm in the range of the present invention, the iron loss W _5/700 is 12 W / kg in the plate thickness range of 0.1 to 0.25 mm.
Can be cut stably. However, a crystal grain of 90 μm or more cannot stably cut 12 W / kg.

Fig. 4 shows that the amount of Si + Al is 4.0%, and similarly for the magnetic flux density, B _5/700 of 1.0T or more can be stably obtained in the plate thickness range of _0.1 to 0.25 mm. 50 of the present invention
Only ~ 55μm material.

FIG. ₅ is a graph showing the crystal grain size at which the iron loss W ₅ has the best value, which was examined with Si + Al of 3.0% and a plate thickness of 0.15 mm.
As can be seen from the figure, the best crystal grain size becomes smaller as the frequency increases. 6 above 400 Hz, which is the subject of the present invention
A particle size of 0 μm or less is suitable. Further, in FIG. 6, similarly, the crystal grain size at which the magnetic permeability μ _{10 of} 1.0 T is the best value is plotted. It can be seen that it is necessary to reduce the crystal grain size as the frequency becomes higher.

Next, the mechanism of the effect of the crystal grain size will be described.
At the conventional frequency of 50 Hz, the iron loss of about 150 μm is the minimum. However, at high frequencies, the eddy current occupies a large proportion, and inside the steel sheet, the magnetic flux induced by the skin effect becomes small. The present inventors have found that at frequencies above 400 Hz, the smaller the crystal grain size, the higher the magnetic permeability. However, when the magnetic permeability is high, the skin effect is strong and the eddy current loss is reduced. Therefore, at 400 Hz or higher, especially at 700 Hz, the iron loss was good when the crystal grain size was 5 to 60 μm.

In the manufacturing method, first, the composition of molten steel is adjusted. The total weight% of Si and Al is 2.0 to 4.0%. If C is 0.005% or less, there is no problem of magnetic aging and there is no need to decarburize later, but if it exceeds 0.005%, it is necessary to perform decarburization annealing later so as to be less than that. Mn is in the normal range for non-oriented electrical steel sheets, that is, 1% or less. S and N are elements that deteriorate the magnetic properties, and are limited to 0.01% or less, respectively, as in a normal non-oriented electrical steel sheet. This molten steel is cast and ordinary hot rolling is performed. Next, hot-rolled sheet annealing may be performed for the purpose of improving the texture of the product, but it is not essential. Further, cold rolling is performed once or twice with an intermediate anneal to obtain a plate thickness of 0.10 to 0.25 mm, and then a final primary recrystallization anneal is performed. This recrystallization annealing must be strictly controlled so that the crystal grain size is 5 to 60 μm. The temperature at this time depends on the presence or absence of the grain growth suppressing element, but is 650
A temperature of ~ 900 ° C is suitable.

The casting may be performed by rapid solidification with twin rolls, and the hot rolling may be omitted.

〔Example〕

 Examples of the present invention will be specifically described below.

Adjust the weight% of Si and Al as shown in Table 1, and add C0.002
%, Mn 0.30%, S0.006%, N0.005% molten steel was continuously cast into a slab and hot rolled into a 2.5 mm thick hot rolled sheet. This is cold rolled and then continuously annealed to apply an insulating film.
Baking was carried out to manufacture an electromagnetic steel plate having a plate thickness shown in Table 1. At this time, the soaking time was set to 30 seconds and the temperature was changed to 650 to 950 ° C. to obtain the crystal grain size in Table 1. The product was subjected to magnetic measurement at a high frequency of 700 Hz.

In Experiment Nos. 1 to 4, the plate thickness and the crystal grain size were made almost the same, and the effect of the components was observed. Steel plates that deviated from the lower and upper limits of the components of Experiment Nos. 1 and 4 respectively showed iron loss. The magnetic flux density falls outside the range of the present invention. This phenomenon is especially 0.25 mm, which is the upper limit of the plate thickness.
Then, the crystal grain size comes out in a severe case close to the lower limit of the present invention.

Experiment Nos. 5 to 7 are for examining the effect of the plate thickness.
Although it was 2.1% and the crystal grain size was about 57 to 59 μm, the iron loss was out of the range of the present invention at the plate thickness of 0.26 mm in Experiment No. 5. Experiment Nos. 6 and 7 having plate thicknesses within the range of the present invention have characteristic values satisfying both iron loss and magnetic flux density.

Experiment Nos. 8 to 10 also show the effect of the plate thickness.
At 0.26 mm, the magnetic flux density is out of the range of the present invention. This is Si +
This is a tendency when the Al amount is 4.0%, which is the upper limit.

In Experiment Nos. 11 to 16, the influence of the crystal grain size was investigated. Experiment No.
At the final annealing temperature of 650 ° C of No. 11, recrystallization was not completed and there were unrecrystallized parts, but the magnetic properties were very poor. In addition, Experiment Nos. 12 to 14 having a crystal grain size of 7 to 58 μm within the range of the present invention showed good characteristic values. In Experiment Nos. 15 and 16 in which the thickness exceeds 60 μm, the iron loss is out of the range of the present invention.

From these experimental facts, W _5/700 and B _5/700 are respectively
The total amount of Si and Al that can secure magnetic properties of 12 W / kg or less and 1.0 T or more is 2.0 to 4.0%, and the thickness range is
It can be seen that the grain size must be 0.10 to 0.25 mm and the crystal grain size must be within the range of the present invention.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a non-oriented electrical steel sheet having excellent magnetic properties at a high frequency of 400 Hz or higher.

[Brief description of drawings]

Figure 1 shows the effect of grain size and composition on iron loss. FIG. 2 shows the influence of the crystal grain size and composition on the magnetic flux density. FIG. 3 shows the influence of the plate thickness and the crystal grain size on the iron loss. FIG. 4 shows the influence of the plate thickness and the crystal grain size on the magnetic flux density. FIG. 5 shows the crystal grain size that gives the best iron loss value for each frequency. FIG. 6 shows the crystal grain size that gives the best value of magnetic permeability for each frequency.

Claims (1)

[Claims] 1. The total amount of Si and Al is 2.0 to 4.0%, C0.005% or less, Mn1% or less, S0.01% or less, N0.01% or less, and the balance is iron and inevitable impurities. A grain-oriented electrical steel sheet having a plate thickness of 0.10 to 0.25 mm and an average crystal grain size of 5 to 5 mm.
Iron loss W _{5/700 of} 60 μm is 12 W / kg or less, magnetic flux density B
_Frequency 400Hz with excellent magnetic characteristics of _5/700 of 1.0T or more
The high frequency non-oriented electrical steel sheet used above.