WO1993013231A1

WO1993013231A1 - Non-oriented electromagnetic steel sheet having very good magnetic characteristics and method of manufacturing the same

Info

Publication number: WO1993013231A1
Application number: PCT/JP1992/001663
Authority: WO
Inventors: Tomoji Kumano; Takeshi Kubota; Hiroaki Masui; Takeaki Takeshita; Kenji Kosuge
Original assignee: Nippon Steel Corporation
Priority date: 1991-12-27
Filing date: 1992-12-18
Publication date: 1993-07-08
Also published as: JPH05306438A; JP2708682B2

Abstract

A non-oriented electromagnetic steel sheet having random cubes and very good magnetic characteristics in the full circumferential direction; and a method of manufacturing such steel sheets. A non-oriented electromagnetic steel sheet 0.20-1.20 mm in thickness having a {100} <Ovw> texture after the completion of a primary recrystallization operation, and random cubes in which the strength of a {100} surface, which is parallel to a rolled surface, with respect to the random cubes is two times as high as that of a conventional steel sheet of this kind; and a method of manufacturing non-oriented electromagnetic steel sheets, having the steps of solidifying molten steel, which contains mainly Si « 4.0 % and Al « 2.0 %, by the surface of a cooling body which is renewed as it is moved, and setting a cold rolling rate to not lower than 5 % and lower than 40 % in an acid washing step, a cold rolling step and a finish-annealing step. By this method, random cubes {100} <Ovw> which are practically ideal are formed, and a product having very good magnetic characteristics in the full circumferential direction is easily obtained.

Description

Description Non-oriented electrical steel sheet with extremely excellent magnetic properties and its manufacturing method

The present invention relates to a non-oriented electrical steel sheet having extremely high magnetic flux density in all circumferential directions and low iron loss, and a method for manufacturing the same.

Background technology

In recent years, the demand for improved quality of non-oriented electrical steel sheets as magnetic core materials for rotating machines has become increasingly stronger from the viewpoint of energy saving. In order to respond to this demand, research and development for improving the magnetic properties of non-oriented electrical steel sheets have been promoted on the one side of the production of electrical steel sheets.

Numerous non-oriented electrical steel sheets specified in JIS are manufactured.

In the production process of non-oriented electrical steel sheets, to obtain products with low iron loss values, it is necessary to purify conventional steel at the melting stage, increase the Si content in steel, Means such as sufficient temperature and time have been adopted in finish annealing. However, when using these technical means, the iron loss value of the product is low, but there is a problem that the magnetic flux density is low, which is said to be due to the texture of the product plate. In order to solve this problem, take up at high temperature by hot rolling and keep it warm. So-called self-annealing or annealing of hot-rolled sheet has been adopted. Furthermore, recently, the cooling and cooling body surface is moved and renewed to solidify into a green strip, and then the cold-rolled steel strip is cold-rolled to a predetermined thickness, and then subjected to finish annealing to form a non-oriented electrical steel sheet. A way to get it was developed. Even with these methods, when the cold rolling reduction is above, the texture after the final annealing becomes the so-called Goss orientation {1101 <001> or (1111 <112>), but the U001 <Gv _ff > orientation Since the magnetism in the entire circumferential direction is inferior to that of, the improvement of the magnetic properties of the entire circumference, especially the improvement of the magnetic flux density, is limited.

Disclosure of the invention

An object of the present invention is to provide a non-oriented electrical steel sheet having a low iron loss in all circumferential directions and an extremely high magnetic flux density, and a method for manufacturing the same.

BRIEF DESCRIPTION OF THE FIGURES

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

FIG. 2 is a (1001 positive electrode spot diagram) of the product of the present invention.

3 is a (100) positive electrode spot diagram of another product of the present invention.

The present invention relates to a non-oriented electrical steel sheet having a thickness of 20 strokes to 1.20 pieces, in which the structure after primary recrystallization has a U0D1 <0vw> texture and the {100} plane strength parallel to the rolling plane. It is characterized by having a random cube texture that is at least twice as large as the random azimuthal strength, thereby providing extremely excellent magnetic characteristics in all circumferential directions. Property is obtained.

The above steel sheet shall contain, by weight%, Si ≤ 4.0%, A ≤ 2. Q%, and other elements normally contained in non-oriented electrical steel sheets, with the balance being Fe and impurities.

In addition, the present invention provides, in weight%, S i ≤ ^ Λ%, A II ≤ 2.0%. The molten steel containing other elements normally contained in non-oriented electrical steel sheets, the balance being Fe and unavoidable impurities, A non-directional electromagnetic process comprising a step of solidifying with the surface of a cooling body to be moved and renewed into a steel strip, a step of cold-rolling the steel strip to a predetermined thickness, and a step of finish annealing. The method for producing a steel sheet is characterized in that the cold rolling is performed at a rolling reduction of 5% or more and less than 40%.

The content of S i and A above can be either (S i + 2 A)> 2.5% without transformation or (S i + 2 A) ≤ 2.5% with transformation. Cases can also be targeted.

Hereinafter, the present invention will be described in detail.

The inventors have conducted intensive studies to solve the technical problems of the present invention, and as a result, have confirmed the existence of a random cube base structure, which has been conventionally regarded as an ideal texture of non-oriented electrical steel sheets. At the same time, it was proved that this random cube was an ideal base structure of non-oriented electrical steel sheets, and the present invention was completed.

In order to obtain this ideal texture, the random cube is obtained by directly forming a thin steel strip from molten steel and then appropriately setting the cold rolling rate, thereby assembling the product after finish annealing. The structure can be controlled, and as a result, a non-oriented electrical steel sheet with extremely high magnetic flux density and low iron loss value has been successfully obtained.

First, the component system of the product targeted by the present invention will be described.

In the present invention, a specific amount of Si and A is contained. Even if one or more of Mn, P, B, Ni, Cr, Sb, Sn, and Cu are contained in addition to the normally contained C, N, and S, the effect of the present invention is impaired. Not.

If C is 0.50% 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 stabilization of magnetic properties, it is required that the magnetic properties do not deteriorate (magnetic aging) during use. The C content is preferably as low as possible, and is desirably 0.005% or less.

The present inventors control the cooling rate of the non-oriented electrical steel sheet having the phase transformation during the cooling transformation (r → n) (hereinafter referred to as “a treatment”), so that the magnetic flux density is extremely high and the iron loss value is reduced A method for producing low non-oriented electrical steel sheets was proposed.

In the present invention, if cooling conditions equivalent to the y treatment are applied, C can be made harmless, so that the allowable range can be made up to 0.05%.

N may be (L 010% or less. Conventional non-directional electromagnetic In the steel sheet manufacturing method, when N has a high content like S, it temporarily re-dissolves during slab heating during hot rolling, and precipitates such as A £ N and MnS are formed during hot rolling. However, 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 as low as possible and is set to 0.005% or less. However, if cooling conditions equivalent to the y treatment are applied, N can be rendered harmless, so that up to 0.050% is acceptable.

S is an element that is inevitably mixed in the steel smelting stage. If the content increases, the workability deteriorates, so the content should be 0.001% or less, preferably 0.005% or less, but if cooling conditions equivalent to 7 treatments are applied, S Can be made harmless, so that up to 0.020% is acceptable.

As is well known, Si is added to increase the specific resistance of a steel sheet and reduce eddy current loss. If Si is added in excess of 4.0%, workability will be extremely deteriorated, making cold rolling difficult and unsuitable for mass production.

Similar to Si, S is also added to increase the specific resistance of the steel sheet and reduce eddy current loss. For this purpose, up to 2.0% of A is conventionally added to non-oriented electrical steel sheets. Although it is possible in principle to further increase the amount of addition, the maximum is set to 2.0% in consideration of cold rolling properties like Si.

, * »

The above S i .Ai includes both the range where (31 + 28) is more than 2.5% without transformation and the range where (S i + 2A ^) is less than or equal to 2.5%. _N If the content of Mn is less than 0.1%, the processability of the product deteriorates. It is also added to make S harmless. However, when the addition amount of Mn exceeds 2.0%, the magnetic flux density of the product is significantly deteriorated, so that Mn is preferably set to 2.0%.

P is added in a range of up to 0.1% in order to improve the punchability of the product. If Ρ ≤ 0.2%, there is no problem from the viewpoint of the magnetic properties of the product.

Β is added as necessary to detoxify Ν. When added, it is necessary to balance with the amount of Ν, and the maximum content should be 0.005%. Since N can be rendered harmless by applying the same cooling conditions as in the treatment with iron, melting the ultra-low nitrogen steel and adding an appropriate amount of N, it is not necessary to add N in this case.

In addition, Ni, Cr, Sb, Sn and Cu may contain one or more of them as necessary, and their contents are appropriately selected depending on the purpose.

Next, the product of the present invention will be described. ◎

The present invention reduces the product thickness to 0.2! ) To 1.20 hidden. The product thickness of non-oriented electrical steel sheets conventionally produced in large quantities is 0.20 to 1. DO. Batadais with a height of less than 0.20 are also exceptionally used for medium and high frequency regions. However, in the present invention, the lower limit of the plate thickness is 0.20 images that can be mass-produced.

In other words, the product application below 0.20 mm is in the region above QHz, where iron loss is largely affected by eddy current loss and hysteresis loss contributed by texture is small. This is related to the reason for limiting the thickness. In addition, the upper limit of 1.20 is stated. 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. On the other hand, the increase in iron loss is contrary to the current trend of high efficiency and energy saving. The preferred range of product thickness is 0.35 to 0.80, which is often used in practice.

The present invention specifies the UI plane strength of the product. In the case of a texture having a perfect random orientation, is about 83% of the saturation magnetic flux density. However, the present invention seeks to obtain B larger than that. That is, if the anti-random strength of {1 001 is increased from the case of perfect random orientation (= 1), disadvantageous orientations will appear at the same time. In order to obtain B, which is equal to or more than%, the strength of the {1001 plane parallel to the rolling surface may be set to at least twice the random orientation strength.

There are already known methods for obtaining random cupe by secondary or tertiary recrystallization, and for directly obtaining a random cube by directly solidifying molten steel to form columnar crystals. In the former case, energy in a broad sense (requiring long-time high-temperature annealing during decompression, etc.) is enormously consumed, which is not practical. In the latter case, it has some significance as energy savings, but the shape of the product is not stable, and it is very difficult to obtain a product thickness exceeding 0.20 sq.m.

In the present invention, a random cube is formed by primary recrystallization regardless of such a method. Specific manufacturing for this The method is described below.

According to the present invention, a cast steel strip obtained by being solidified by a moving and renewed 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 broken at this high rolling reduction. As a result, the recrystallized texture of the product sheet is approximately the same as the <111> axial density parallel to the steel sheet normal and the <100> glaze density parallel to the steel sheet normal, making it ideal for non-oriented electrical steel sheets. It is not a simple texture.

The present inventors have conducted intensive studies and found that when the cold rolling reduction was set to less than 40% (preferably, less than 30%), the columnar crystals formed at the time of fabrication were used as nuclei, and after finish annealing. The recrystallized texture of was found to be almost perfect {ii <0vw> (random cube).

The reason for this is not clear yet, but U00I <0 ^>, which is a texture of columnar crystals, is relatively unlikely to accumulate work strain. It is considered that the cubes are preserved as they are, and during the recrystallization stage during the final annealing, they recrystallize and grow, and the random cubes become sharper. Ο

On the other hand, if the rolling reduction is less than 5%, the surface properties at the time of fabrication remain and are not suitable for products. Therefore, 5% or more

Ό o

However, at the stage of the transformed steel and the non-transformed steel, the solidified belt obtained by solidification on the surface of the cooling body that moves and renews Since the central position has different textures, the above interpretation may not always be definitive.

In addition, it is conceivable that the product is manufactured 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 the magnetic properties as shown in Fig. 1 The characteristics themselves are not so good.

Figure 1 shows the production of a non-oriented electrical steel sheet which is solidified by the moving and renewed cooling body surface to form a 铸 steel strip, and then cold rolled to a predetermined thickness and then finish-annealed. In the method, the relationship between the cold rolling reduction and the magnetic flux density [B (T)] was shown. Although the product thickness is not necessarily 0.50 mm, an extremely excellent magnetic flux density is shown by setting the cold rolling reduction to 5 to 40%.

Example 1

The molten steel of the components shown in Table 1 (consisting of the balance Fe and unavoidable impurities) is directly solidified on the surface of the cooling body to be renewed.

0.56 and 0,62 strokes of steel strip were obtained. Thereafter, it was pickled and cold rolled to a thickness of 0.50. Degreased rolled steel sheet cold 30 seconds 1 050 ° C in a continuous annealing furnace, N 2%: 70%, H 2%: were annealed at 30% dry棼囲air.

After that, the magnetic properties (average at every 22.5 degrees) were measured by the Epstein-Lead method. These values were compared with those of the comparative method where the cold rolling reduction was 40% or more (steel thickness was 2.0 turns and 1.5 nmi).

Chemical composition (% by weight) Thickness (mm) Cold

All-around characteristics Category Rolling rate

C S i Mn P S N Piece Product (%)

The present invention 0.0069 2, 9 0.22 0, 019 0.0018 0.26 0.0036 0.56 0.50 11 2.57 The present invention 0.0069 2.9 0.22 0, 019 0.0018 0, 26 0, 0036 0.62 0.50 19 2.39 1J36 Comparative material 0.0050 3.0 0.2 \ 0.018 0, 0008 0.29 0.0030 2.0 0, 50 15 3.50 1.648 Specific drawn material 0, 0050 3.0 0, 21 0.018 0.0008 0, 29 0.0030 1.5 0.50 6? 3.40 1.6

(Note) Iron loss w: W / kg. Magnetic flux density B, ₀ : T

The magnetic properties are the circumferential properties (rolling direction, 22. direction, 45 degree direction, 67.5 direction, 90 ° ^ direction, 112.5 direction, 135 degree direction, average of 8 directions of 15U degree direction, each angle from the cold rolling direction Angle).

In the method for manufacturing a non-oriented electrical steel sheet, the solidified steel strip is solidified by the surface of the cooling body that moves and renews in this manner, and then the steel strip is cold-rolled to a predetermined thickness and then finish-annealed. When the rolling reduction is 5% or more and less than 40% in the cold rolling, a non-oriented silicon steel sheet having extremely excellent magnetic properties in all circumferential directions can be obtained 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 is ideal for non-oriented electrical steel sheets.

Example 2

The molten steel of the composition shown in Table 2 (consisting of the balance Fe and unavoidable impurities) is solidified on the surface of the cooling body that moves and renews to obtain steel strips of 0.56 recitation, 0.62 0 and 0.70 咖. Was. Then, it was pickled and cold rolled to the thickness of 50). The cold-rolled steel sheet was degreased and annealed in a continuous annealing furnace at 850 ° C. for 30 seconds in a dry atmosphere of H 2: 5% and N ₂ : 95%.

After that, the magnetic properties (average at every 22.5 degrees) were measured by the Epstein-Lead method. These values were compared with the case of a cold rolling reduction of 40% or more, which is a comparative method (铸 steel thickness of 2.0 strokes and 1.5 recitations). Table 2

Chemical composition (weight%) Thickness (face) Cold all-around properties

CS i M ri PSN piece product (%) Wl 5 /-QD -50 Present invention 0.0040 0.30 0.19 0.068 0.0040 0.0018 0, 0017 0, 56 0.50 11 4, T6 1.845 The present invention 0.0029 1.14 0.27 0 '020 0.0039 0.0014 0.0026 0.62 0.50 19 4.20 1.835 The present invention 0, 0045 0.30 0, 31 0 '101 0.0030 0.394 0.0014 0.70 0.50 29 ί 50 1.821 Comparative material 0.0040 0, 30 0.19 0, 068 0.0040 0.0018 0.0017 2. 0 0.50 75 6, 43 1.753 Comparative material 0.0029 1.14 0.2? 0, 020 0.0039 0, 0014 0.0026 1.5 0.50 67 4.29 1.124

(Note) iron loss w: W / kg,贿密degree B 5 _0: T

The magnetic properties are all-around properties (rolling direction, 22, 5 direction, 45 direction, 67.51 ^ direction, 90 degree direction, 112.5 direction, 135 degree direction, average of 8 directions of 15 U degree direction, each angle is cold Angle from the rolling direction).

In this way, as in Example 1, the forged steel strip solidified by the cooling body surface to be moved and renewed is cold-rolled at a rolling ratio of 5% or more and less than 40%. A non-oriented electrical steel sheet having extremely excellent magnetic properties in all circumferential directions as compared with a case where the rolling reduction is high can be obtained.

FIG. 3 shows the texture of the product sheet after finish annealing obtained in the example of the present invention. Thus, a random cup that can be said to be ideal has been obtained.

Industrial applicability

By cold rolling the strip obtained by the present invention, a product having extremely excellent magnetic properties can be obtained.

Claims

The scope of the claims

1. Sheet thickness D. 20 ~ ~ In a 2Gmm non-oriented electrical steel sheet, the structure after primary recrystallization has a 〖01 〈«texture, and the strength of the U001 plane parallel to the rolling surface is random. A non-directional electromagnetic steel sheet with extremely excellent magnetic properties characterized by being at least twice the azimuthal strength.

2. By weight%, S i ≤ 4.0%, A ≤ ≤ 2.0. Other claims that include elements normally contained in non-oriented electrical steel sheets, the balance being Fe and impurities The non-oriented electrical steel sheet according to item 1, wherein

3. By weight%, Si ≤ 4.0%, AA ≤ 2.0%, and other elements normally contained in non-oriented electrical steel sheets. The balance: molten steel consisting of Fe and unavoidable impurities. Production of a non-oriented electrical steel sheet comprising a step of solidifying the surface of a cooling body to be moved and renewed into a forged steel strip, and a step of cold-rolling the forged steel strip to a predetermined thickness, followed by finish annealing. A method for producing a non-oriented electrical steel sheet having extremely excellent magnetic properties, characterized in that a cold rolling reduction ratio is 5% or more and less than 40%.

4. The method according to claim 3, wherein the forged steel strip has (S i +2)> 2.5%.

5. The method according to claim 3, wherein the steel strip is (Si + 2Ai) 2.5%.