JP3176646B2 - Manufacturing method of non-oriented electrical steel sheet for high frequency - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for electric products generally used for motors and small transformers.
In particular, it is a non-oriented electrical steel sheet that is effective for use in a high frequency region, that is, 400 Hz or higher.

In this field, for example, motors for vacuum cleaners, motors for inverter type air conditioners and refrigerators, small transformers such as fluorescent lamps for intelligent buildings, various motors, motors and lighting devices for airplanes, motors for robot control, and more. Are motors for medical blood centrifuges.

[0003]

2. Description of the Related Art The above-mentioned field of use is a field that has recently started attracting attention, and is effective for improving the energy efficiency of electric equipment and for strict position control of precision motors.
A frequency of 400 Hz or more has been required. For this reason, the so-called commercial frequency 5 used for the conventional electromagnetic steel sheet is used.
Unlike 0 to 60 Hz, research must be focused on 400 Hz or more, for example, 700 Hz, but a steel sheet optimal for this region has not yet been manufactured and sold. For example, as the highest grade non-oriented electrical steel sheet, those having a sheet thickness of about 0.35 mm and a crystal grain size of about 150 μm are commercially available as Si: about 3% and Al: about 1%. It has excellent magnetic properties at 50 Hz, but does not have satisfactory properties at high frequencies.

[0004] As a conventional idea, it is known that as the frequency increases, the ratio of the eddy current loss in the total iron loss increases. Conventionally, it has been generally known that it is effective to reduce the plate thickness and increase the specific resistance in order to reduce the eddy current loss.

[0005] However, there is a limit to the cold rolling ability in reducing the sheet thickness, and Si or A is not effective in increasing the specific resistance.
There is a problem in production, for example, there is a limit to the amount of l from the viewpoint of brittleness, and it is disadvantageous in terms of cost. For this reason, conventionally, a technique for mass production at relatively low cost for high frequency has been desired from the market.

[0006] In addition to the composition and the plate thickness, known as the effect of the crystal grain size, for example, The Physics of Meta
ls and Metallography vol.
35 (1973), No. 100 on pages 4,168-172
It was known that coarse grains of ~ 500 [mu] m minimize iron loss. However, in the high-frequency region, the iron loss remarkably deteriorates with such a crystal grain size.

[0007]

In view of the above, there is provided a product of a non-oriented electrical steel sheet having excellent magnetic properties in a high frequency region as disclosed in Japanese Patent Application No. 2-15755. did. The contents are as follows. That is, Si
And Al total 2.0-4.0%, C ≦ 0.005%
A non-oriented electrical steel sheet containing
0.25 mm, the average crystal grain size of the steel sheet is 5 to 60 μm, 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 high-frequency non-oriented electrical steel sheet used above. The idea of the present invention lies particularly in the crystal grain size. Although the effect of the crystal grain size is a new finding that cannot be predicted from the conventional classical eddy current loss calculation formula, it has a very important meaning for the magnetic characteristics of 400 Hz or more. In other words, it has been shown that in order to improve the magnetic characteristics at high frequencies, conventional coarse grains must be used and fine grains must be used.

Further, the invention described in Japanese Patent Application No. 2-15755 discloses the manufacturing method shown in the embodiment.
That is, the total amount of Si and Al is 2.0 to 4.0%, and C:
0.002%, Mn: 0.30%, S: 0.006%,
N: Continuously cast molten steel of 0.005% to form a slab, hot-rolled into a hot-rolled sheet having a thickness of 2.5 mm, cold-rolled, and then subjected to continuous annealing at a temperature of 650 to 950 ° C.
This is a method of manufacturing by applying and baking an insulating film. In this manufacturing process, there is a steel sheet having excellent high-frequency magnetic characteristics, but there is a problem that a fold-like shape defect called ridging occurs in a product steel sheet. If there is ridging, laminating this steel sheet on the motor core will significantly reduce the space factor, and will lose commercial value. For this reason, there has been a serious problem that the yield drops as a production side.

In order to solve the above problems, the present inventors have reviewed the entire manufacturing process from the origin, and as a result, by purifying steel components and promoting recrystallization during hot rolling,
We have developed a non-oriented electrical steel sheet that completely prevents the occurrence of ridging when the annealing of the hot-rolled coil is omitted, and further applies the above-mentioned grain size effect to further improve high frequency magnetic properties. That is, an object of the present invention is to provide a technique for producing a non-oriented electrical steel sheet having excellent high frequency characteristics at a high and stable yield.

[0010]

In order to achieve the above object, the gist of the present invention is that the weight ratio of C ≦ 0.
005%, Si: 2.0 to 4.0%, Mn: 0.1 to
1.5%, P ≦ 0.1%, S ≦ 0.005%, Sol.
When hot rolling a steel slab containing Al: 0.1-1.5% and N ≦ 0.003%, the finishing temperature is 930 ° C.-
The temperature was adjusted to 1050 ° C., and then cold-rolled after pickling,
A method for producing a high-frequency non-oriented electrical steel sheet, characterized by a sheet thickness of 5 to 0.30 mm, followed by continuous annealing at a temperature of 650 to 900 ° C.

Hereinafter, the reasons for limitation of the present invention will be described in detail. C: If it exceeds 0.005%, there is a problem of magnetic aging, so the content is made 0.005% or less. Si: There is an element effective for increasing the specific resistance,
If it is less than 2.0%, the specific resistance is insufficient, and if it exceeds 4.0%, there is a risk of brittleness. Therefore, the content is set to 2.0 to 4.0%. Mn: Controls the form of sulfide. If less than 0.1%, Mn
The upper limit is set to 1.5%, since increasing the amount of S precipitates and is harmful to the movement of the domain wall. P: This also increases the specific resistance, but if too large, it becomes brittle, so the upper limit is made 0.1%. S: It is a harmful element. The upper limit is set to 0.005% in order to prevent the movement of the domain wall and deteriorate the high-frequency magnetic characteristics and at the same time generate ridging. This ridging occurs because S impurities suppress recrystallization after completion of hot-rolling finish rolling described below. Sol. Al: an element effective for increasing the specific resistance, if less than 0.1%, this effect is insufficient, and if too large, there is a problem of addition cost, so the upper limit is made 1.5%. N: This is also a harmful element. The upper limit is set to 0.003% in order to hinder the movement of the domain wall, degrade the high-frequency magnetic characteristics and simultaneously generate ridging. This ridging occurs because N impurities suppress recrystallization after the completion of hot-rolling finish rolling described below. Although other elements are not particularly limited, for example, B, Sn, Sb, etc. can be added for the purpose of improving the texture, but are not adopted in the present invention because of the problem of addition cost.

[0012] In order to contain these elements, the components are adjusted by steel making and continuously cast to produce a slab. Next, hot rolling is performed.
Slab heating temperature is carried out at the usual 950-1280 ° C,
The coil is wound by rough rolling and finish rolling. At this time, the finish rolling end temperature (hereinafter, referred to as finish temperature) is important and is 930.
C. to 1050 C. are required. Because, at a temperature lower than 930 ° C., <110> ± θ //
This is because when the fiber texture of the RD develops and the hot-rolled coil annealing is omitted, a shape defect such as a stripe pattern on the tatami mat surface called ridging appears in the final product. On the other hand, if the finishing temperature is too high, the crystal grain size tends to be large in the final product, and it is difficult to obtain the desired crystal grain of 60 μm or less.
Or lower, preferably 1000 ° C. or lower. There is no particular restriction on the winding temperature, but the temperature exceeds 770 ° C.
The temperature is preferably 770 ° C. or lower, because the oxide layer becomes thicker in the self-annealing region and the productivity in the next pickling line deteriorates. The thickness of the hot-rolled coil is desirably about 1.6 to 2.5 mm from the viewpoint of the cold-rolling rate and the product texture.

The hot rolled coil is subjected to cold rolling without annealing the hot rolled coil after the surface scale of the steel sheet is removed in a usual pickling process. Conventionally, for a high-grade non-oriented electrical steel sheet, annealing of a hot-rolled coil has been performed for a long time.
The reason for this is that the grains of the hot-rolled sheet grow to reduce the number of crystal grain boundaries, and the number of <111> -oriented (hard-magnetization) grains coming out of the old grain boundaries during primary recrystallization after cold rolling is reduced. The magnetic properties were improved by the method. However, when trying to reduce the product crystal grain size, which is a feature of the present invention, when the hot-rolled coil is annealed, recrystallization nuclei after cold rolling are reduced, and the crystal grain size of the product tends to increase. And the purpose of the invention cannot be achieved. Therefore, annealing of the hot-rolled coil should be omitted.

The finish thickness in cold rolling is 0.15 to 0.30 mm. The high-frequency characteristics are improved as the product thickness becomes thinner. However, if the product thickness is excessively thin, cold rolling breakage is apt to occur, and it is easy to break even in continuous annealing in the next step. If it exceeds 0.30 mm, the high frequency characteristics are unsatisfactory.

The temperature of the subsequent continuous annealing is important, and the annealing temperature is 900 to 115, which is a conventional high-grade non-oriented electrical steel sheet.
Do not use 0 ° C. The average crystal grain size is 5-60
μm is appropriate, and the temperature is set in view of this particle size, and the temperature is 650 to 900 ° C. The reason is that recrystallization is not completed below 650 ° C., so that the rolled structure remains in the steel sheet, and this internal stress hinders the movement of the domain wall and deteriorates the magnetic properties. When the temperature exceeds 900 ° C., the crystal grain size becomes 60 μm.
m and the object cannot be achieved. The soaking time for annealing is not particularly limited, but within 5 minutes is appropriate from the viewpoint of productivity. Hereinafter, examples of the present invention will be specifically described.

[0016]

【Example】

[Example-1] A slab was manufactured by continuous casting while changing various components of molten steel. The slab was heated at 1120 ° C., the finishing temperature was set at 940 ° C., and then cooled with water and wound at 700 ° C. The hot-rolled coil of 2.5 mm thickness is pickled to a thickness of 0.1 mm.
It was cold rolled to a thickness of 15 mm. This was subjected to continuous annealing at 680 ° C. for 90 seconds in a mixed atmosphere of H ₂ + N ₂ , and an insulating film was applied and baked to obtain a product. The product was subjected to punching and winding on a ring-shaped specimen, and then the magnetic properties were measured. The maximum value of the magnetic flux density at 700 Hz was 500 A.
/ M is the maximum magnetic flux density. Table 1 shows the details of the experiment and the results.

[0017]

[Table 1]

As described above, Si and Sol. When the Al is less than the range of the present invention, the high frequency iron loss is unsatisfactory. Further, each of Mn, S, and N outside the range of the present invention has a large amount of fine precipitates, so that high-frequency magnetic characteristics deteriorate. In coils with many impurities, ridging occurred in part and the yield was reduced. As a result, the samples satisfying the scope of the present invention exhibited excellent iron loss and excitation characteristics at a high frequency of 700 Hz.

Example 2 A slab containing the chemical components shown in Table 2 was cast. An experiment was conducted in which this slab was heated at 1210 ° C. × 20 minutes soak to change the finishing temperature.
° C. All hot rolled coils were 1.9 mm thick, pickled and cold rolled to 0.20 mm thick. 780 ° C x 1
A continuous annealing for 5 seconds was performed in a H ₂ + N ₂ mixed atmosphere, and an insulating film was applied and baked to obtain a product. The product was subjected to punching winding on a ring-shaped sample piece, and the magnetic properties were measured in the same manner as in Example-1. Table 3 shows the details of the experiment and the results.

[0020]

[Table 2]

[0021]

[Table 3]

As shown in Table 3, when the finishing temperature is lower than 930 ° C., ridging occurs. On the other hand, if the temperature exceeds 1050 ° C., the crystal grains of the product become large and the magnetic properties deteriorate.

Example 3 A slab containing the chemical components shown in Table 4 was cast. The slab was heated at 1050 ° C. for 20 minutes soaking so that the finishing temperature was 990 ° C. and the winding temperature was 700 ° C. All hot rolled coils were 1.8 mm thick, pickled and cold rolled to 0.20 mm thick. This is the temperature of continuous annealing ×
During the soaking time, the atmosphere was dry mixed with 40% H ₂ + 60% N ₂ , and an insulating film was applied and baked to obtain a product. The product was subjected to punching and winding on a ring-shaped specimen, and then the magnetic properties were measured. Table 5 shows the details of the experiment and the results.

[0024]

[Table 4]

[0025]

[Table 5]

If the continuous annealing temperature is lower than 650 ° C., the rolled structure remains on the steel sheet and the magnetism is poor. On the other hand, when the temperature exceeds 900 ° C., coarse grains grow and the magnetic properties deteriorate. Experiment No. in which the continuous annealing temperature is within the range of the present invention. Shows excellent magnetic properties at 700 Hz. No ridging was observed in any of these steel sheets. The iron loss at 50 Hz was good for the sample, but poor for the other samples.

[0027]

As described above, according to the present invention, there is provided a technique for producing a non-oriented electrical steel sheet having excellent magnetic properties at a high frequency of 400 Hz or more at a high and stable yield.

──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Takashi Muneda 1 Fujimachi, Hirohata-ku, Himeji-shi, Hyogo Nippon Steel Corporation Hirohata Works (58) Field surveyed (Int. Cl. ⁷ , DB name) ) C21D 8/12 C22C 38/00 303

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein C ≦ 0.005% by weight, Si:
2.0-4.0%, Mn: 0.1-1.5%, P ≦ 0.
1%, S ≦ 0.005%, Sol. Al: 0.1-1.
When hot rolling a steel slab containing 5% and N ≦ 0.003%, the finishing temperature is set to 930 ° C. to 1050 ° C., then, after pickling, cold rolling is performed to obtain a 0.15 to 0.30 mm plate. A method for producing a high-frequency non-oriented electrical steel sheet, comprising: performing annealing at a temperature of 650 to 900 ° C.