JPH06128642A - Production of high silicon nonoriented silicon steel sheet extremely excellent in magnetic property - Google Patents

Abstract

PURPOSE:To specify the optimal cold rolling rate at the time of producing a high silicon nonoriented silicon steel sheet by using a cast steel strip solidified by means of the surface of updatedly moving cooling body. CONSTITUTION:In the course where a molten steel, containing >4.0-8.0wt.% Si and <=2.0wt.% Al, for high silicon nonoriented silicon steel sheet is solidified by means of the surface of an updatedly moving cooling body, pickled, cold- rolled, and finish-annealed, cold rooling rate is regulated to 5-<40%. In the case of relatively low cold rolling rate as mentioned above, the texture of a product sheet after finish annealing is sharpened by means of that of columnal crystals. By this method, an ideal texture random cube ([100]<0vw>) for a nonoriented silicon steel sheet can be obtained. Because a high silicon nonoriented silicon steel extremely excellent in magnetic properties can be obtained by this method, this sheet can be a new product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-silicon non-oriented electrical steel sheet having extremely high magnetic flux density and low iron loss.

[0002]

2. Description of the Related Art In recent years, demands for quality improvement of non-oriented electrical steel sheets as magnetic core materials for rotating machines have become stronger from the viewpoint of energy saving. In order to meet this demand, the manufacturers of electromagnetic steel sheets are also conducting research and development to improve the magnetic properties of non-oriented electrical steel sheets, and industrially, a number of them are specified in JIS. Non-oriented electrical steel sheets are manufactured.

In the manufacturing process of non-oriented electrical steel sheets, in order to obtain a product having a low iron loss value, conventionally, the steel is highly purified in its melting stage, the Si content in the steel is increased, and the finishing is performed. In annealing, measures such as taking sufficient temperature and time have been adopted, but in consideration of workability in the post process, conventional S
The upper limit of the content of i was specified to be 4%.

However, when these technical means are used, the iron loss value of the product is low, but there is a problem that the magnetic flux density is low from the viewpoint of texture. Also, S
When i is high as in the claims, in the usual manufacturing method,
In the steps after hot rolling, workability is not practical due to brittleness. In order to overcome this difficulty, methods such as warm rolling and silicon immersion treatment have been devised, but the process becomes complicated and the production cost increases. On the other hand, in recent years, a method of solidifying by a moving and renewing surface of a cooling body has been developed and is beginning to be applied to the field of non-oriented electrical steel sheets. However, in the past, Si% was 4% by weight or less, and the cold rolling rate was 40%.
That was all. When the cold rolling reduction rate is 40% or more, the texture after finish annealing is not only {100} but also {111} plane as the plane index parallel to the steel sheet plane, which is considerably strong.
There was a limit to the improvement of magnetic properties, especially the magnetic flux density.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above problems in the prior art and provides a high silicon non-oriented electrical steel sheet which has a low iron loss in all azimuth directions and an extremely high magnetic flux density. It is an object of the present invention to provide a possible manufacturing method.

[0006]

In order to achieve the above object, the feature of the present invention is that the weight% is 4.0% <
A molten steel consisting of Si ≦ 8.0%, Al ≦ 2.0%, balance Fe and unavoidable impurities (so-called non-transformed steel) is solidified by a moving and renewing cooling body surface to form a cast steel strip,
Then, in the method for producing a non-oriented electrical steel sheet, in which the corresponding cast steel strip is cold-rolled to a predetermined thickness (final sheet thickness) and then finish-annealed, the rolling rate is 5% or more in the cold rolling.
%, And preferably less than 30%, is a method for producing a high-silicon non-oriented electrical steel sheet having extremely excellent magnetic properties.

The present invention will be described in detail below. The present inventors have conducted intensive studies to solve the technical problems in the present invention, and as a result, directly obtain a cast ribbon from molten steel, and by appropriately taking a cold rolling ratio thereafter, after finish annealing. We have succeeded in obtaining a non-oriented electrical steel sheet having a very high magnetic flux density and a good iron loss (low iron loss value).

First, the component system of the present invention will be described. C
Is 0.050% or less, the object of the present invention can be achieved. The non-oriented electrical steel sheet is mainly used in rotating machines, and from the viewpoint of stable magnetic characteristics, it is required that magnetic property deterioration (magnetic aging) does not occur during use of the non-oriented electrical steel sheet. . S is an element that is unavoidably mixed in the melting stage of steel and is combined with Mn to form MnS during cooling after solidification, so S should be 0.0100% or less. N may be 0.010% or less. N is
Similar to S, when rapidly solidified by the moving and renewing surface of the cooling body, it is solid-solved in the steel strip, and AlN,
Precipitates such as MnS are formed, which hinders the growth of recrystallized grains during finish annealing or exhibits a so-called pinning effect that hinders the movement of domain walls when the product is magnetized, which becomes a factor to prevent lower iron loss of the product. Therefore, N ≦ 0.010% should be set.

As is well known in the art, 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%, the workability will be extremely deteriorated and cold rolling will become difficult. But 1
Pickling and cold rolling became possible by applying a warm treatment at 00 ° C. to 300 ° C. and reducing the thickness of the cast slab. For this reason, simply having a high Si content is not a big problem in the production of a high-silicon non-oriented electrical steel sheet. Further, as is well known in the art, since Fe--Si alloy has a very small magnetostriction at 6.5% Si, noise in electric equipment is improved.

Al, like Si, is added to increase the specific resistance of the steel sheet and reduce eddy current loss. For this purpose, a maximum of 2.0% Al has been added to non-oriented electrical steel sheets that have not been transformed so far. Although it is possible in principle to increase the addition amount, the maximum Si content is 2.0% in view of the manufacturing cost because the Si content is already large. M
When the content of n is less than 0.1%, the workability of the product is deteriorated, and n is added to render S harmless. However, if the addition amount of Mn exceeds 2.0%, the magnetic flux density of the product is significantly deteriorated, so Mn ≦ 2.0.
%Must. B is an element that is added as necessary, and is particularly added to render N harmless. N
Therefore, the maximum content is 0.0
05%. N can be made harmless by melting ultra-low nitrogen steel, and in this case, the need for addition is small.

In addition to the above-mentioned components, the present invention is intended to improve the mechanical properties of products, magnetic properties, rust resistance, etc., or for other purposes, P, Ni, Cr, Sb, Sn, Cu.
The effect of the present invention is not impaired even if one or two or more are contained.

Next, the manufacturing process conditions of the present invention will be described. When the cast steel strip obtained by solidifying by the moving and renewing cooling body surface is rolled at a relatively high cold rolling rate, the magnetic flux density is high, but the columnar crystals formed during the solidification process are The recrystallized texture of the product sheet is the same as the steel sheet normal ‖ <111> axial density and the steel sheet normal ‖ <100> axial density, and is an ideal texture for non-oriented electrical steel sheets. is not.

The inventors of the present invention continued their earnest research and found that
At a cold rolling reduction of less than 40% (preferably less than 30%), the recrystallized texture after finish annealing is almost perfect, with the columnar crystals formed during casting as nuclei, {100} <0v.
We found that w> (random cube). The reason for this is not clear yet, but since {100} <0vw> (random cube), which is a columnar crystal texture, is relatively hard to accumulate work strain, the rolling texture also occurs at a slight cold rolling reduction. It is considered that the random cube is preserved as it is, and it is recrystallized and grain-grown at the recrystallization stage during finish annealing (rather, it should be called strain-induced grain boundary migration), and the random cube is sharpened. Also, cold rolling reduction is 5%
If it is less than 5%, the surface quality at the time of casting remains as it is and is not suitable for products. Further, also from the viewpoint of cold rolling property, such a light reduction (5 to 40%,
(Preferably 5 to 30%) is more suitable for actual production than the conventional cold rolling rate of around 70%. In Fig. 1, molten steel of 6.3 wt% ≤ Si ≤ 6.7 wt% is solidified into a cast steel strip by the moving and renewing surface of the cooling body, and then the cast steel strip is cold-rolled to a predetermined thickness. Then, the relationship between the cold rolling rate and the magnetic flux density (B ₅₀ (T)) was shown in the method for manufacturing a non-oriented electrical steel sheet that is finish annealed. Although the product thickness is not constant, it can be seen that an extremely excellent magnetic flux density can be obtained by setting the cold rolling reduction to less than 40%, particularly 30% or less.

It should be noted that it is conceivable that the product is cast with a product thickness. In this case, the surface texture is not suitable for the product as in the case of a cold rolling reduction of less than 5%, and as shown in FIG. The magnetic properties themselves are also not very good.

[0015]

The embodiments of the present invention will be described below. Directly 0.56 m by solidifying the molten steel (comprising the balance Fe and unavoidable impurities) of the ingredients of Table 1 on the surface of the moving cooling body
Steel strips of m, 0.40 mm and 0.25 mm were obtained. afterwards,
It was pickled and cold-rolled to the product thickness shown in Table 1. The cold-rolled steel sheet is degreased and then heated in a continuous annealing furnace to 105
Annealed at 0 ° C for 30 seconds. Then, the magnetic property (average every 22.5 degrees) was measured by the Epstein method. These values were compared with the case of the cold rolling ratio of 40% or more, which is a comparative method (thicknesses of cast slabs are 1.7 mm and 1.05 mm).

[0016]

[Table 1]

A high-silicon non-oriented electrical steel sheet which is solidified by the moving and renewing surface of the cooling body to form a cast steel strip, which is then cold-rolled to a predetermined thickness and then finish-annealed. In the manufacturing method described above, when the rolling rate is set to 5% or more and less than 40% during cold rolling, a high-silicon non-oriented electrical steel sheet having extremely excellent magnetic properties as compared with the case where the cold rolling rate is high is obtained.

FIG. 2 shows the texture of the finished annealed product sheet obtained in the present invention. In this way, a very nice so-called random cube is obtained. It can be said that this is ideal for high silicon non-oriented electrical steel sheets.

[0019]

As described above, according to the present invention,
A non-oriented electrical steel sheet having excellent magnetic properties can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a cold rolling rate and B ₅₀ .

FIG. 2 is a diagram showing a {100} positive electrode dot diagram of a material after finish annealing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hodaka Hodaka No. 1-1 Toibata-cho, Tobata-ku, Kitakyushu, Kitakyushu, Fukuoka Inside Nippon Steel Corporation Yawata Works

Claims (1)

[Claims] 1. A cast steel strip obtained by solidifying a molten steel composed of 4.0% <Si ≦ 8.0% and Al ≦ 2.0% by weight in the balance Fe and unavoidable impurities by a moving and renewing cooling body surface. Then, in the method for producing a high silicon-containing non-oriented electrical steel sheet, in which the corresponding cast steel strip is cold-rolled to a predetermined thickness and then finish-annealed, the rolling ratio is 5% or more and 40% or more in cold rolling.
A method for producing a high-silicon non-oriented electrical steel sheet having extremely excellent magnetic properties, which is characterized by