JPH05295437A - Production of nonoriented silicon steel sheet excellent in rust resistance - Google Patents

Abstract

(57) [Abstract] [Objective] The present invention is used as a core material for electric equipment,
In particular, it can withstand the use environment where rust resistance is required. Provided is a method for producing a non-oriented electrical steel sheet having both magnetic properties and rust resistance. [Constitution] In the production of non-oriented electrical steel sheet, Si:
2.0% or more and 4.0% or less, Al: 2.0% or less, M
n: 2.0% or less, P: 0.1% or less, Cr: 4.0%
Molten steel containing 13.0% or more of the above is rapidly solidified by the moving and renewing surface of the cooling body so that the average crystal grain size is 0.0
By manufacturing a steel strip having a thickness of 5 mm or more and subjecting this steel strip to cold rolling and finish annealing, a non-oriented electrical steel sheet having excellent rust resistance can be obtained. Especially, cold rolling reduction is 30% or more and 80%
When it is less than the above, a high magnetic flux density is obtained, and when it is 80% or more, a non-oriented electrical steel sheet having a small magnetic anisotropy and excellent rust resistance is obtained.

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 non-oriented electrical steel sheet having excellent magnetic properties, which is used as a core material for electric equipment, and particularly in an environment where rust resistance is required. Can bear. The present invention relates to a method for manufacturing a non-oriented electrical steel sheet having both magnetic characteristics and rust resistance.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for higher efficiency of electric equipment in a global movement to save electricity and energy and to protect the global environment. For this reason, even in non-oriented electrical steel sheets that are widely used for iron core materials such as rotating machines and small and medium-sized transformers, there is an increasing demand for improvement in magnetic properties. In addition to this, recently, with the diversification of electrical equipment, the number of examples of use under severe conditions has increased, and in response to this, the required characteristics for non-oriented electrical steel sheets have become diverse. .. As one of them, the iron core material of the magnet switch is required to have magnetic characteristics equal to or higher than those of the conventional non-oriented electrical steel sheet and have excellent rust resistance.

Conventionally, a high Cr low C ferritic stainless steel represented by 13% Cr steel or 18% Cr steel has been used as the core material required to have such rust resistance.
Further, as disclosed in Japanese Patent Publication No. 39-20644, a material is known in which 11.5 to 20% Cr steel contains Si and Ti. However, with these materials, C
Since a large amount of r is contained, the magnetic flux density is lowered, and there is a problem that it is difficult to obtain magnetic characteristics comparable to those of a normal non-oriented electrical steel sheet.

Therefore, at the same time as reducing the Cr content,
A method for improving the magnetic properties by limiting the content of C, N, S, etc., which are the impurity elements of steel, and making it a high-purity steel,
JP-A-61-272352 and JP-A-63-1.
No. 09143 is disclosed. However, even if the iron loss was improved by these methods, the decrease in the magnetic flux density due to the Cr content was unavoidable.

[0005]

SUMMARY OF THE INVENTION The present invention provides a method for producing a rust-resistant non-oriented electrical steel sheet having rust resistance and excellent magnetic properties.

[0006]

Means for Solving the Problems From the viewpoint of increasing the magnetic flux density of steel containing Cr, the present inventors have conducted detailed experiments and analyzes on manufacturing process conditions from casting of steel to rolling and annealing. And conducted extensive studies.

As a result, steel containing Cr is formed into a steel strip by using rapid solidification, and in that case, cold rolling and finish annealing are performed under the condition that the average crystal grain size of the steel strip exceeds a certain value. It was clarified that it is possible to provide both magnetic properties and rust resistance with a combination.

The present invention has been made on the basis of this new finding, and the gist thereof is, in weight%, Si: 2.0% or more and 4.0% or less, Al: 2.0% or less, Mn: 2 0.0% or less, P: 0.1% or less, Cr: 4.0% or less 13.0%
A molten steel containing the following and the remainder consisting essentially of Fe is rapidly solidified by a moving and renewing cooling body surface to produce a steel strip having an average crystal grain size of 0.05 mm or more, and then cooled to the steel strip. It is a method for producing a non-oriented electrical steel sheet having excellent rust resistance, which is characterized by performing rolling and finish annealing. Further, in the present invention, the cold rolling reduction of the steel strip can be set to 30% or more and less than 80%, and the cold rolling reduction of the steel strip can be set to 80% or more.

The present invention will be described in detail below. First, the reasons for limiting the steel components of the present invention will be described. As is well known, Si is a component having an effect of reducing iron loss, and in order to exhibit this effect, it is necessary to contain Si in an amount of 2.0% or more.
On the other hand, if the content thereof increases, the magnetic flux density decreases, the cold rolling workability deteriorates, and the cost also increases, so the content is made 4.0% or less.

Similar to Si, Al has the effect of increasing electric resistance and reducing iron loss. However, its content is 2.0
%, The magnetic flux density decreases, so 2.0% or less.

Mn also has the effect of increasing electric resistance and reducing iron loss. On the other hand, if the content exceeds 2.0%, the magnetic flux density also decreases, so the content is made 2.0% or less.

P is a component necessary for improving the punchability of the steel sheet, but if it is contained in excess of 0.1%, the steel rather becomes embrittled, and the cold workability and workability deteriorate. Therefore, the content is 0.1% or less.

Cr is a component necessary for providing rust resistance, which is a feature of the present invention. To obtain this effect, 4.
It is necessary to contain 0% or more. On the other hand, when the content thereof increases, the magnetic flux density decreases even with the method of the present invention, so the upper limit is made 13.0%. Fe other than the above components
And unavoidable impurity elements.

Next, the molten steel composed of the above components is rapidly solidified on the surface of the moving cooling body to form a steel strip. It is considered that the steel strip directly obtained by the rapid solidification method is likely to be in a desirable state as the pre-cold rolling crystal structure and texture of the non-oriented electrical steel sheet in combination with the below-described average grain size control. In this case, the steel strip thickness is
It should be determined by the cold rolling reduction rate and the final product thickness described later, but it is usually in the range of 0.5 mm to 5.0 mm.

By the way, the average grain size of the steel strip obtained by rapid solidification must be 0.05 mm or more. If the average grain size of the steel strip is less than 0.05 mm,
The decrease in magnetic flux density due to the inclusion of Cr cannot be improved, and it becomes difficult to provide both rust resistance and magnetic characteristics. The control of the average crystal grain size of the steel strip is performed by selecting the material of the surface of the cooling body to be renewed and the cooling conditions, or after rapid solidification as described in, for example, JP-A-62-240714. This can be done by selecting the cooling conditions for the steel strip.

As described above, the feature of the present invention is that the average crystal grain size obtained by rapid solidification of Cr-containing steel is 0.
By subjecting a steel strip having a thickness of 05 mm or more to cold rolling and finish annealing, it is possible to produce a rust-resistant non-oriented electrical steel sheet having rust resistance and excellent magnetic properties.

By the way, as described at the beginning, the non-oriented electrical steel sheet is used for the iron core material of electric equipment as its application. In this case, the sheet thickness accuracy and shape are strictly required. Therefore, it is necessary for the steel strip obtained by rapid solidification to improve the sheet thickness accuracy and adjust the shape by cold rolling. In particular, when the cold rolling reduction is 30% or more and less than 80%, not only the effect of improving the thickness accuracy and the shape correcting effect but also the magnetic flux density is further increased, which is an extremely excellent magnetic property. ..

When the cold rolling reduction is 80% or more, in addition to the effect of improving the plate thickness accuracy and the shape correcting effect, the magnetic flux density and the iron loss have a characteristic difference between the rolling direction and the direction perpendicular thereto. It also has a desirable effect on the non-oriented electrical steel sheet in terms of the magnetic property of becoming smaller.

[0019]

【Example】

Example 1 Si: 2.2%, Al: 0.3%, Mn: 0.2%, C
r: 6.5%, with the balance substantially consisting of Fe, the molten steel was rapidly solidified by the twin roll method, and the cooling conditions were controlled to control three types of 1.
A 5 mm thick steel strip was formed, then cold rolled to a thickness of 0.5 mm (cold rolling reduction ratio: 66.7%), continuous finish annealing was performed at 1000 ° C. for 30 seconds, and magnetic properties were measured.

In addition, the humidity / simulation of the operating environment when used as the iron core material of the magnet switch
A temperature cycle test was conducted. The test results are shown in Table 1. It is apparent that the present invention makes it possible to manufacture a non-oriented electrical steel sheet having rust resistance and good magnetic properties.

[0021]

[Table 1]

Example 2 Si: 3.1%, Al: 0.6%, Mn: 0.2%, C
A molten steel containing r: 7.9% and the balance substantially consisting of Fe was rapidly solidified by the twin roll method, and as shown in Table 2,
3 types of steel strips with different average grain sizes were prepared, and then 0.
It was cold rolled to a thickness of 5 mm, continuously annealed at 1050 ° C. for 30 seconds, and magnetic properties were measured. At the same time, we also conducted a humidity / temperature cycle test that reproduces the usage environment when used as the core material of a magnet switch.

The test results are also shown in Table 2. According to the present invention, it is understood that it is possible to manufacture a non-oriented electrical steel sheet having rust resistance and excellent magnetic properties. In particular, steel strip No. with a cold rolling reduction of 80% or more. In the case of No. 6, it is also clear that the difference between the magnetic properties in the rolling direction and the direction perpendicular thereto is extremely small.

[0024]

[Table 2]

Example 3 A molten steel containing Si: 2.4%, Al: 0.2%, Mn: 0.2%, and the amount of Cr shown in Table 3 and the balance being substantially Fe was prepared by a twin roll method. It is rapidly solidified to obtain three kinds of steel strips (1.6 mm thickness) with an average crystal grain size of 0.45 to 0.50 mm, and these steel strips are cold rolled to a thickness of 0.5 mm (cold rolling reduction ratio: 6
8.8%), continuous annealing was performed at 980 ° C. for 30 seconds, and the magnetic characteristics were measured.

Humidity / simulation of the operating environment when used as an iron core material of a magnet switch
A temperature cycle test was also conducted. The results are also shown in Table 3
Shown in. According to the present invention, it can be seen that it is possible to manufacture a non-oriented electrical steel sheet having both magnetic characteristics and rust resistance.

[0027]

[Table 3]

[0028]

According to the present invention, a non-oriented electrical steel sheet having rust resistance and excellent magnetic properties can be obtained. With the diversification of electrical equipment, non-oriented electrical steel used as an iron core material It is possible to sufficiently meet a wide range of required characteristics for electromagnetic steel sheets, particularly, severe operating conditions where rust resistance is required, and its industrial effect is extremely large.

Claims (3)

[Claims] 1. By weight%, Si: 2.0% or more and 4.0% or less, Al: 2.0% or less, Mn: 2.0% or less, P: 0.1% or less, Cr: 4. A molten steel consisting of 0% or more and 13.0% or less, the balance being substantially Fe, is rapidly solidified by the moving and renewing surface of the cooling body, and the average crystal grain size is 0.05 mm.
A method for producing a non-oriented electrical steel sheet having excellent rust resistance, comprising producing the steel strip as described above, and then subjecting the steel strip to cold rolling and finish annealing. 2. The method for producing a non-oriented electrical steel sheet excellent in rust resistance according to claim 1, wherein the cold rolling reduction of the steel strip is 30% or more and less than 80%. 3. The method for producing a non-oriented electrical steel sheet having excellent rust resistance according to claim 1, wherein the cold rolling reduction of the steel strip is 80% or more.