JPH11256288A - Silicon steel sheet with low residual magnetic flux density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon steel sheet stably exhibiting low residual magnetic flux density and excellent in the balance of magnetic property among magnetic properties. SOLUTION: The silicon steel sheet with low residual magnetic flux density is obtained by providing a composition containing, by weight, <=0.02% C, 0.05-0.5% Mn, <=0.01% P, <=0.02% S, 0.001-0.06% sol. Al, <=0.01% N, and <=7%, on average, of Si, providing a concentration gradient of Si in a sheet thickness direction, and making the concentration gradient to >=3 wt.%/mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer, a reactor, and a transformer (CT) in which an inrush current due to magnetic bias is a problem.
The present invention relates to a silicon steel sheet having a low residual magnetic flux density used as an iron core of a motor or a motor.

[0002]

2. Description of the Related Art Research has been conducted on silicon steel sheets used for iron cores of transformers, motors and the like to increase the magnetic flux density and reduce iron loss, and materials having a large squareness ratio have been developed.
However, as a result, the residual magnetic flux density becomes large, and in the case of a device such as a transformer, various problems occur due to the magnetic polarization.

The inventors of the present invention have previously found that it is effective to form a Si concentration gradient in the thickness direction to reduce the residual magnetic flux density, which is a cause of magnetic bias, and filed a patent application. (JP-A-9-184051). Also, forming a Si concentration gradient in the thickness direction is disclosed in
No. 27033 to JP-A-62-227036 and JP-A-4-246157.

[0004] However, as disclosed in Japanese Patent Application Laid-Open No. 9-184051, although the residual magnetic flux density certainly decreases, the value of the Si concentration gradient required to achieve a desired low residual magnetic flux density in a silicon steel sheet itself is reduced. Was unknown. For this reason, there is a case where a sufficiently low residual magnetic flux density is not achieved even if a Si concentration gradient is formed, or a case where a low residual magnetic flux density is achieved but iron loss is increased and magnetic permeability is reduced occurs. is there.

On the other hand, JP-A-62-27033 to JP-A-62-227036, and
In 246157, the purpose of forming a Si concentration gradient in the thickness direction of the sheet is to manufacture the silicon by a siliconizing method (CVD method).
5 wt. % Silicon steel sheet production efficiency, iron loss and workability, and no mention is made of low residual density characteristics.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a silicon steel sheet which shows a low residual magnetic flux density stably and has an excellent magnetic property balance. .

[0007]

Means for Solving the Problems The present inventors conducted analysis and experiments on the Si concentration gradient necessary for achieving a desired low residual magnetic flux density. The mechanism of the reduction of the residual magnetic flux density disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 9-184051 has been studied from the magnetic domain structure. The reason for the magnetic domain structure as disclosed therein was analyzed from magnetoelastic energy. As a result, from an energy point of view, it is estimated that the lower residual magnetic flux density due to the Si concentration gradient is attributable to the following reasons.

The distribution of magnetostriction is formed in the thickness direction by the concentration gradient of Si. If there is a distribution in magnetostriction, when magnetized, stress is generated in the surface layer and inside in the thickness direction, and the magnetoelastic energy increases. Since the remanent magnetization is also in a magnetized state, if the remanence is large, it is disadvantageous in terms of energy. Therefore, it is estimated that a magnetostriction distribution, that is, a concentration gradient, results in a magnetic domain structure having a small remanence.

Thus, in order to reduce the residual magnetic flux density,
The value of the Si concentration gradient itself is one of the important factors, and the present invention has ascertained the Si concentration gradient from which a desired low residual magnetic flux density can be obtained based on the results of such studies.

That is, according to the present invention, C ≦ 0.02 wt.
%, 0.05 wt. % ≦ Mn ≦ 0.5 wt. %, P ≦
0.01 wt. %, S ≦ 0.02 wt. %, 0.001
wt. % ≦ sol. Al ≦ 0.06 wt. %, N ≦ 0.
01 wt. % And an average of 7 wt. % Or less, and has a Si concentration gradient in the thickness direction, and the concentration gradient is 3w.
t. % / Mm or more, characterized by having a low residual magnetic flux density. A more preferred range of the Si concentration gradient is 4.5 wt. % / Mm or more.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. As described above, the silicon steel sheet used as the iron core material needs to have a low residual magnetic flux density. Therefore, in the present invention, the concentration gradient of Si in the thickness direction is specified.
That is, as described above, the existence of the Si concentration gradient is presumed to result in a magnetic domain structure having a small residual magnetism, and the value of the Si concentration gradient itself is an important factor in reducing the residual magnetic flux density.

Therefore, it was examined how much the Si concentration gradient required to obtain a desired low residual magnetic flux density. Table 1 shows the results. The concentration gradient (wt.%) Shown in Table 1 was used.
/ Mm) is the Si concentration difference (wt.%) In the thickness direction at the portion where the Si concentration is inclined is the distance (mm) in the thickness direction.
The example is shown in FIG. 1 or FIG. FIG. 1 shows a case where there is a region having a constant Si concentration in the surface layer portion and the central portion of the steel plate, and FIG. 2 shows a case where there is no region having a constant Si concentration.

[0013]

[Table 1]

As shown in Table 1, in order to reduce the residual magnetic flux density to a practical value of 0.4 T or less, a Si concentration gradient of 3 wt.
% / Mm or more. Further, the Si concentration gradient is 4.
5 wt. % / Mm or more, the residual magnetic flux density is 0.3
It becomes a more preferable value of T or less.

The Si concentration gradient value required for lowering the residual magnetic flux density does not largely change even if the product plate thickness changes between 0.05 and 0.65 mm, but the Si concentration gradient value becomes smaller when the plate thickness is small. Large values tend to be required.

In the present invention, the average Si concentration is 7 wt.
% Or less, which is 7 wt. %, The workability is degraded, and component processing becomes impossible.

Next, the reasons for limiting elements other than Si will be described. If C is contained in a large amount, it causes magnetic aging, so the upper limit is 0.02 wt. %. The lower limit is not particularly defined, but from the viewpoint of economical removal, the lower limit is 0.001 wt. % Is preferable.

If Mn is contained in a large amount, the steel sheet becomes brittle, so the upper limit is 0.5 wt. %. However, if the content is too low, breakage and surface flaws are induced in the hot rolling step, so the lower limit is 0.05 wt. %.

P is a preferable element from the viewpoint of magnetic properties. However, when P is contained in a large amount, the workability of the steel sheet is deteriorated. %. The lower limit is not particularly defined, but from the viewpoint of economical removal, the lower limit is 0.001 wt. % Is preferable.

Since S deteriorates workability, its upper limit is 0.02 wt. %. The lower limit is not particularly defined, but from the viewpoint of economical removal, the lower limit is 0.001 wt. % Is preferable.

Sol. A1 also impairs processability, so its upper limit is 0.06 wt. %. On the other hand, the lower limit is 0.001 wt. %.

If N is contained in a large amount, it forms nitrides and deteriorates magnetic properties.
%. The lower limit is not specified, but
Considering current steelmaking technology, practically 0.0001 wt.
% Is the lower limit.

The silicon steel sheet having a concentration gradient of Si according to the present invention can be manufactured by various methods, and the manufacturing method is not limited. For example, chemical vapor deposition (CVD, siliconizing), physical vapor deposition (PVD), cladding technology,
It can be manufactured by plating technology.

As an example, a manufacturing method by the CVD method will be described. First, for example, 3 wt. % Cold rolled steel is manufactured by a normal steel sheet manufacturing process. This coil is CV
D treatment is performed to obtain a steel sheet having a Si concentration gradient. That is, heating to 1100 ° C. or more in a non-oxidizing atmosphere
By reacting with a compound gas, for example, a SiCl ₄ gas, a Si layer having a high Si concentration is formed on the surface. Subsequently, a diffusion process is performed to diffuse a required amount of Si into the inside of the steel sheet, thereby producing a silicon steel sheet having a target average Si amount and a Si concentration gradient.

In the present invention, the average Si means the average value of the Si concentration with respect to the total thickness, and is, for example, a value that can be obtained by chemical analysis with the product thickness. In addition, the maximum and minimum of the Si concentration are determined by EPMA
It can be determined from the Si concentration profile obtained by analysis. Furthermore, the concentration of each element is the concentration in the product. Furthermore, the residual magnetic flux density is a value after a DC excitation of 1.2 T.

[0026]

EXAMPLE The thickness of the composition shown in Table 2 (except for Si, the composition at the time of commercialization; Si is the composition before CVD treatment) is 0.0.
Steel sheets of 5-0.5 mm were manufactured by the usual steel making process. This was subjected to CVD treatment to obtain steel sheets having various Si average concentrations and concentration distributions. Table 3 shows the average Si concentration and the Si concentration gradient at that time. And the residual magnetic flux density of these steel plates was measured. The results are also shown in Table 3.

[0027]

[Table 2]

[0028]

[Table 3]

As shown in Table 3, the Si concentration gradient was 3 w
t. % / Mm or more of the present invention material was confirmed to exhibit a low residual magnetic flux density of 0.4 T or less.

[0030]

As described above, according to the present invention,
It is possible to obtain a silicon steel sheet which shows a low residual magnetic flux density stably and has an excellent balance of magnetic properties.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the definition of a Si concentration gradient in a case where a constant concentration region is provided in a surface layer and a central portion of a steel sheet.

FIG. 2 is a diagram for explaining the definition of a Si concentration gradient when there is no constant concentration region.

Claims (2)

[Claims] 1. The method according to claim 1, wherein C ≦ 0.02 wt. %, 0.05 wt.
% ≦ Mn ≦ 0.5 wt. %, P ≦ 0.01 wt. %, S
≦ 0.02 wt. %, 0.001 wt. % ≦ sol. A
l ≦ 0.06 wt. %, N ≦ 0.01 wt. %
7 wt. % Or less, and has a Si concentration gradient in the thickness direction, and the concentration gradient is 3 wt. % / Mm or more, characterized by having a low residual magnetic flux density. 2. The method according to claim 2, wherein the concentration gradient of Si is 4.5 wt. % / Mm
The silicon steel sheet having a low residual magnetic flux density according to claim 1, characterized in that: