JP2708682B2 - Non-oriented electrical steel sheet having extremely excellent magnetic properties and method for producing the same - Google Patents

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 having a very high magnetic flux density in the entire circumferential direction and a low iron loss, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, demands for quality improvement of non-oriented electrical steel sheets as a magnetic core material for rotating machines have become increasingly stronger from the viewpoint of energy saving. In order to respond to this demand, manufacturers of electrical steel sheets have been working on research and development to improve the magnetic properties of non-oriented electrical steel sheets. Non-oriented electrical steel sheets are manufactured.

[0003] In the production process of non-oriented electrical steel sheets, in order to obtain a product having a low iron loss value, conventionally, it is necessary to purify the steel at the melting stage or to increase the Si content in the steel. Means such as sufficient temperature and time in finish annealing have been adopted. However, when using these technical means, although the iron loss value of the product is low, there is a problem that the magnetic flux density is low, which is said to be caused by the texture of the product plate.

[0004] In order to solve this problem, a so-called self-annealing method in which hot rolling is performed at a high temperature by means of hot rolling, or a method of annealing a hot rolled sheet has been adopted. Furthermore, recently, a method of solidifying a cast steel strip by a cooling body surface to be moved and renewed, and then cold-rolling the cast steel strip to a predetermined thickness, followed by finish annealing to obtain a non-oriented electrical steel sheet. Was developed.
Even in these methods, when the cold rolling reduction is 40% or more, the texture after the final annealing is so-called Goss orientation {110}.
Although the <001> and {111} <112> directions are developed, the magnetic properties in all directions are inferior to the {100} <0vw> direction. Had limitations.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and provides a non-oriented electrical steel sheet having a low iron loss in all directions and a very high magnetic flux density, and a method of manufacturing the same. The purpose is to do.

[0006]

In order to achieve the above object, the present invention provides a non-oriented electrical steel sheet having a thickness of 0.20 mm to 1.20 mm, wherein the structure after primary recrystallization is {100} <0.
vw> {100} having texture and parallel to the rolling surface
It is characterized by having a random cube texture whose surface strength is at least twice as large as the random strength, whereby extremely excellent magnetic properties can be obtained in all circumferential directions. In the above steel plate,
In terms of weight%, Si ≦ 4.0%, Al ≦ 2.0%, other elements which are usually contained in a non-oriented electrical steel sheet, and the balance is made of Fe and impurities are applied. In addition, the present invention provides a method for producing a non-oriented electrical steel sheet having extremely excellent magnetic properties in all circumferential directions, in which Si ≦ 4.0% and Al ≦ 2.0% by weight.
%, Containing the elements normally contained in non-oriented electrical steel sheets, the balance: molten steel consisting of Fe and unavoidable impurities is solidified by the surface of the cooling body to be moved and renewed to form a cast steel strip. In a method of performing finish annealing after cold rolling to a predetermined thickness, the rolling rate is set to 5% or more and less than 40% in cold rolling. The content of the above-mentioned Si and Al is not changed (Si + 2Al)> 2.5% and changed (Si
+ 2Al) ≦ 2.5%.

Hereinafter, the present invention will be described in detail. The inventors have conducted intensive studies to solve the technical problems in the present invention, and as a result, while confirming the existence of a random cube texture that was conventionally called an ideal texture of a non-oriented electrical steel sheet, This random cube was proved to be an ideal texture of a non-oriented electrical steel sheet, and the present invention was completed.

In order to obtain this ideal texture, a random cube, a cast ribbon is obtained directly from molten steel, and then the cold rolling reduction is appropriately set so that the texture in the product after finish annealing is reduced. Thus, a non-oriented electrical steel sheet having extremely high magnetic flux density and good iron loss (low iron loss value) was successfully obtained.

First, the component system of the product targeted by the present invention will be described. In the present invention, specific amounts of Si and Al are contained. However, in order to improve the mechanical properties of the product, magnetic properties, rust resistance, etc. Even if one or more of Mn, P, B, Ni, Cr, Sb, Sn, and Cu are contained in addition to the contained C, N, and S, the effect of the present invention is not impaired. If C is 0.050% or less, the object of the present invention can be achieved. Non-oriented electrical steel sheets are mainly used for rotating machines. From the viewpoint of the stability of magnetic properties, it is required that the magnetic properties do not deteriorate (magnetic aging) during use. Is preferably lower,
It is desirable to make it 0.005% or less. In addition, Japanese Patent Application No. 3
By applying cooling conditions equivalent to the gamma treatment described in JP-A-204419, C can be rendered harmless, so that the allowable range is 0.05.
%.

[0010] N may be 0.010% or less. In the conventional method for producing a non-oriented electrical steel sheet, if N has a large content like S, it temporarily re-dissolves during slab heating of hot rolling, and precipitates such as AlN and MnS during hot rolling. Forming
The so-called pinning effect, which hinders the growth of recrystallized grains during finish annealing or hinders the movement of the domain wall when the product is magnetized, is a factor that hinders the reduction of iron loss in the product. Therefore, the N content is preferably lower, and more preferably 0.005% or less. However, γ according to Japanese Patent Application No. 3-204419
If cooling conditions equivalent to the treatment are applied, N can be rendered harmless, so that N can be allowed up to 0.050%. S is an element that is inevitably mixed in the steel smelting stage. If the content increases, the workability is deteriorated. Therefore, the content should be 0.010% or less, preferably 0.005% or less.
If the same cooling condition as that of the γ treatment according to No. 204419 is applied, S can be made harmless, so that it is allowable to 0.020%.

As is well known, Si is added to increase the specific resistance of the steel sheet and reduce the eddy current loss. If Si is added in excess of 4.0%, workability is extremely deteriorated, making cold rolling difficult, and the use of the present invention is not suitable for mass production. Al, like Si, is added to increase the specific resistance of the steel sheet and reduce eddy current loss. For this purpose, conventional non-oriented electrical steel sheets have a maximum of 2.0% of A
1 has been added. Although it is possible in principle to further increase the amount of addition, the maximum is set to 2.0% in consideration of cold rollability similarly to Si. The above Si and Al are (Si + 2A)
l) is more than 2.5% without transformation and (S
i + 2Al) includes both ranges having transformations of 2.5% or less.

If the content of Mn is less than 0.1%, the processability of the product is deteriorated, and Mn is added to render S harmless. However, the amount of Mn added is
If it exceeds 2.0%, the magnetic flux density of the product is significantly deteriorated, so it is preferable to set Mn ≦ 2.0%. P is added in a range of up to 0.1% in order to improve the punchability of the product. If P ≦ 0.2%, there is no problem from the viewpoint of the magnetic properties of the product. B is added as necessary for detoxification of N. When adding, the balance with the amount of N is necessary, and the maximum content is 0.005.
%. N can be rendered harmless by applying the same cooling conditions as in the gamma treatment described in JP-A-3-204419, or by melting and adding an appropriate amount of Al to an ultra-low nitrogen steel. You may. Other Ni, Cr, S
One, two or more of b, Sn and Cu may be contained as needed, and their contents may be appropriately selected depending on the purpose.

Next, the product of the present invention will be described. In the present invention, the thickness of the product is 0.20 to 1.20 mm. Conventionally, non-oriented electrical steel sheets produced in large quantities have a product thickness of 0.20
1.00 mm. Although the case of less than 0.20 mm is exceptionally used for medium and high frequency regions, in the present invention, the lower limit of the 0.20 mm plate thickness that can be mass-produced is set. That is, the product use at less than 0.20 mm is a region at 400 Hz or higher, and iron loss in this region is largely affected by eddy current loss, and hysteresis loss contributed by texture is small, and the thickness is limited. It is related to the reason. Also, the upper limit is 1.
The reason why the thickness is set to 20 mm is that even if the thickness is further increased, the usefulness of the random cube texture does not change, but it exceeds the current actual processing range, while the iron loss increases, so the current trend of high efficiency and energy saving Therefore, it was set in this range. A preferable range of the product thickness is 0.35 to 0.80 mm which is often used in practical use.

The present invention specifies the {100} plane strength of a product. B _{50 for a} texture with perfect random orientation
Although approximately 83% of the saturation magnetic flux density, the present invention is intended to be obtained the more B _50. That is, $ 10
If the random intensity against 0 ° is further increased than in the case of the perfect random orientation (= 1), an orientation unfavorable for B ₅₀ appears at the same time.
In order to obtain _B50 as described above, it is necessary to reduce the value of {10}
It has been found that the 0 ° plane strength should be doubled or more at random.

A method for obtaining a random cube by secondary or tertiary recrystallization and a method for directly obtaining a random cube by directly and rapidly solidifying molten steel to form a columnar crystal are already known. In the former case, it consumes enormous energy in a broad sense (such as the need for long-time high-temperature annealing during decompression), which is not realistic. In the latter case, it has some significance as energy saving. Is not stable, and
It is very difficult to obtain a product thickness exceeding 20 mm. According to the present invention, a random cube is formed by primary recrystallization without using such a method. A specific manufacturing method for this will be described below.

According to the present invention, the cast steel strip obtained by solidification by the moving and renewing cooling body surface is cold-rolled at an appropriate rolling reduction. When this steel strip is rolled at a relatively high cold rolling reduction, the magnetic flux density increases, but the columnar crystals formed during the solidification process are considerably destroyed at this high rolling reduction, and the recrystallized aggregates of the product sheet The structure is <111> parallel to the steel sheet normal.
The axial density and the <100> axis density parallel to the normal of the steel sheet are almost the same, and it is not an ideal texture for a non-oriented electrical steel sheet. The present inventors have conducted intensive studies and found that when the rolling reduction was set to less than 40% (preferably less than 30%), the columnar crystals formed at the time of casting were used as nuclei to re-process after finish annealing. Crystal texture is almost complete {100}
<0vw> (random cube). The reason for this is not clear yet, but {100} <0vw>, which is a texture of columnar crystals, is relatively difficult to accumulate work strain. This is considered to be due to the fact that it is preserved as it is, and in the recrystallization stage at the time of finish annealing, it recrystallizes and grows, and the random cube is sharpened. In addition, the cold rolling reduction rate is 5%.
If it is less than 10%, it can be seen that the surface properties at the time of casting remain as they are and are not suitable for products. However, in the case of transformed steel and non-transformed steel, the cast steel strip obtained by solidification on the surface of the cooling body to be moved and renewed has different textures at the steel strip surface position and the center position. Interpretation may not always be definitive.

Furthermore, it is conceivable that the casting is performed with the product thickness. In this case, as in the case of the cold rolling reduction of less than 5%, not only the surface properties are not suitable for the product, but also as shown in FIG. The magnetic properties themselves are not very good.

FIG. 1 shows a non-oriented electrical steel sheet which is solidified by the surface of a moving cooling body to form a cast steel strip. In the manufacturing method, the relationship between the cold rolling reduction and the magnetic flux density [B50 (T)] was shown. Although the product thickness is not necessarily 0.50 mm, an extremely excellent magnetic flux density is exhibited by setting the cooling reduction to 5 to 40%.
Hereinafter, embodiments of the present invention will be described.

[0019]

EXAMPLE 1 Molten steel having the components shown in Table 1 (consisting of the balance of Fe and unavoidable impurities) was solidified on the surface of a cooling body to be moved and renewed to obtain steel strips of 0.56 mm and 0.62 mm directly.
Then, it was pickled and cold rolled to a thickness of 0.50 mm. The cold-rolled steel sheet is degreased, and is baked in a continuous annealing furnace.
Annealing was performed at 50 ° C. for 30 seconds in a dry atmosphere of N ₂ : 70%, H ₂ : 30%. Thereafter, the magnetic properties (average at every 22.5 degrees) were measured by the Epstein method. These values are
It was compared with the case of a cold rolling reduction of 40% or more (the thickness of the steel was 2.0 mm and 1.5 mm) which was a comparative method.

[0020]

[Table 1]

A method of manufacturing a non-oriented electrical steel sheet which is solidified by the surface of the cooling body which moves and renews as described above to form a cast steel strip, and then cold-rolls the cast steel strip to a predetermined thickness and then finish-anneals. In the cold rolling, the rolling reduction was 5
% To less than 40%, it is possible to obtain a non-oriented silicon steel sheet having extremely excellent magnetic properties in all circumferential directions as compared with the case where the cold rolling reduction is high. FIG. 2 shows the texture of the product sheet after finish annealing obtained in the example of the present invention. A very nice, so-called random cube is thus obtained. This can be said to be ideal for non-oriented electrical steel sheets.

[0022]

Example 2 Liquid steel of the composition shown in Table 2 (consisting of the balance of Fe and unavoidable impurities) is solidified on the surface of a cooling body to be moved and renewed, and is directly 0.56 mm, 0.62 mm and 0.70 mm.
Steel strip was obtained. Then, it was pickled and cold rolled to a thickness of 0.50 mm. The cold-rolled steel sheet is degreased, and in a continuous annealing furnace at 850 ° C. for 30 seconds, H ₂ : 5%, N ₂ : 95
%, Annealed in a dry atmosphere. Then, the magnetic properties (2
(Average every 2.5 degrees) was measured by the Epstein method.
These values were compared with those of a comparative method where the cold rolling reduction was 40% or more (the thickness of the cast steel was 2.0 mm and 1.5 mm).

[0023]

[Table 2]

As in the first embodiment, the cast steel strip is solidified by the surface of the cooling body to be moved and renewed, and the cast steel strip is cold-rolled at a rolling ratio of 5% or more and less than 40%, so that the cold-rolling rolling ratio is high. As a result, a non-oriented electrical steel sheet having extremely excellent magnetic properties in all circumferential directions can be obtained. FIG. 3 shows the texture of the product sheet after finish annealing obtained in the example of the present invention. Thus, an ideal random cube is obtained.

[0025]

As described above, by cold rolling the steel strip obtained according to the present invention, a product having extremely excellent magnetic properties can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a cold rolling reduction and B ₅₀ (T) in all circumferential directions.

FIG. 2 is a {100} positive electrode spot diagram of the product of the present invention.

FIG. 3 is a {100} positive electrode spot diagram of another product of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Masui 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (72) Inventor Tadashi Nakayama 20-Shintomi, Futtsu-shi, Chiba 1 Nippon Steel Corporation Technology Development Division (72) Inventor Takeaki Takeshita 1-1, Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (56) References 3-24250 (JP, A)

Claims (5)

(57) [Claims] 1. The structure after primary recrystallization is {100} <0v
w> has a texture, and has a {100} plane strength parallel to the rolled surface that is at least twice as large as a random number, a sheet thickness of 0.20 mm to
A non-oriented electrical steel sheet having extremely excellent magnetic properties in all circumferential directions, characterized by having a random cube texture of 1.20 mm. 2. The composition according to claim 1, wherein Si ≦ 4.0% and Al ≦ 2.
2. The non-oriented electrical steel sheet according to claim 1, wherein the non-oriented electrical steel sheet contains 0%, other elements normally contained in the non-oriented electrical steel sheet, and the balance is Fe and impurities. 3. The composition according to claim 2, wherein Si ≦ 4.0% and Al ≦ 2.
0%, and other elements normally contained in non-oriented electrical steel sheets, the remainder: molten steel consisting of Fe and inevitable impurities is solidified by the surface of the cooling body to be moved and renewed to form a cast steel strip, and then the cast steel strip In a method for producing a non-oriented electrical steel sheet, which is cold-rolled to a predetermined thickness and then finish-annealed, the rolling ratio is set to 5% or more and less than 40% during cold rolling. A method for manufacturing non-oriented electrical steel sheets with extremely excellent magnetic properties. 4. The method for producing a non-oriented electrical steel sheet according to claim 3, wherein (Si + 2Al)> 2.5%. 5. The method for producing a non-oriented electrical steel sheet according to claim 3, wherein (Si + 2Al) ≦ 2.5%.