JP2000059086A - Magnetic shielding electromagnetic steel plate superior in magnetic shielding characteristics and corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic shielding steel plate which is superior in magnetic shield characteristics and sufficiently high in corrosion resistance to withstand outdoor use. SOLUTION: An electromagnetic steel plate is formed under the conditions, where a magnetic flux density is above 1.2 T in the direction of rolling when a DC magnetic field 80 A/m is applied on the direction of rolling, the interloper resistance of a film formed on the surface of the electromagnetic steel plate after finish annealing is less than 200 Ωm2/sheet, and furthermore a film whose main component is zinc is formed as thick as 5 to 100 g/m2 on the above film, so that an electromagnetic steel plate which is superior in magnetic shielding properties and corrosion resistance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic shielding steel sheet having excellent magnetic shielding performance and excellent corrosion resistance in a corrosive environment to which building materials are generally exposed. .

[0002]

2. Description of the Related Art Direct current strong magnetic fields in NMR and linear motor cars, various transportation systems, building steel frames and steel plates, high-voltage wires,
The influence of urban magnetic noise (DC, fluctuation, AC magnetic field) from power transmission and distribution equipment on precision equipment and the human body has become a problem. In order to prevent the influence of such a magnetic field, a magnetic shield technique using a ferromagnetic material is used. This involves using a material with high magnetic permeability, that is, magnetic steel sheets, pure iron-based materials, permalloy, etc., to surround the source of the magnetic field and the space where a weak magnetic field is required, concentrate the magnetic flux in the magnetic material, and reduce the weak magnetic field. This prevents the magnetic flux from entering the required space.

[0003] Conventionally, magnetic fields have been regarded as a problem by NMR.
Because of this, it was an indoor device, and the space affected by the magnetic field was limited, so the shielding technology was often used indoors. However, in recent years, the above-mentioned problem of urban magnetic noise has been largely taken up. The characteristics of urban magnetic noise are that the source of the magnetic field is large and difficult to identify, and the space where a weak magnetic field is required is large. For this reason, the case where the magnetic shield is arranged not only indoors but also outdoors is increasing.

In general, in magnetic shields using ferromagnetic materials, inexpensive electromagnetic steel sheets having high shielding performance are often used. Although the shielding performance becomes better as the magnetic permeability increases, there are two types of electrical steel sheets: a non-oriented electrical steel sheet having a uniform in-plane magnetic permeability and a directional electrical steel sheet having a good permeability in the rolling direction. A non-oriented electrical steel sheet can be used when the direction of the target magnetic field changes, and a directional electrical steel sheet can be used when the direction does not change. On the surface of these electromagnetic steel sheets, a film is formed on the assumption that the core is used for a motor or a transformer. These coatings are intended to ensure insulation between steel sheets and, in the case of grain-oriented electrical steel sheets, to impart tension to the steel sheets, and do not have sufficient rust-preventive ability. Further, it was difficult to apply a rust-preventive treatment generally used for building materials, such as hot-dip galvanizing, on these films.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic shielding material having excellent magnetic shielding properties and having excellent corrosion resistance even in a corrosive environment where building materials are generally exposed. .

[0006]

Means for Solving the Problems The present inventors have described the above.
As a result of intensive studies to solve the conventional problems, the shield
A magnetic shielding material that has excellent performance and can withstand outdoor use
Invented. The gist of the present invention is as follows. (1) When a DC magnetic field of 80 A / m is applied in the rolling direction
The magnetic flux density in the rolling direction is 1.2T or more, and after finish annealing
Interlayer resistance of the film formed on the surface is 200Ωcm ^Two/Sheet
An electromagnetic steel sheet as described below, further comprising:
Chromium, nickel, cobalt, iron, with zinc as the main component
Molybdenum, aluminum or magnesium
In total, 5 to 100 g / m of a film containing 0 to 60%^Two Have
Excellent magnetic shielding performance and corrosion resistance
Magnetic steel sheet for magnetic shielding. (2) A grain-oriented electrical steel sheet, and in the manufacturing process,
Forsterite skin formed on steel sheet surface after finish annealing
0.5 g / m film weight^Two Characterized in that:
The magnetic steel sheet for magnetic shielding according to (1).

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, the shielding performance and the magnetic properties of the material will be described.
Assuming that the magnetic shield material is excited to the magnetic flux density Ba by the external magnetic field Ho, the magnetic field leaking inside the shield body is equal to the magnetic field Hi for exciting the material to Ba on the magnetization curve of the material used. This indicates that when the target of the magnetic field after shielding is fixed to, for example, Hi, the necessary thickness and weight of the shielding material decrease as the magnitude of Ba, which is the magnetic flux density with respect to the applied magnetic field Hi, increases. . In the present invention, the material has a magnetic flux density of 1.2 T in the rolling direction when a DC magnetic field of 80 A / m is applied in the rolling direction in order to have an excellent magnetic shielding property and suppress an increase in weight and cost of the shield body. Must be at least.

When the magnetic flux density is 1.2 T or less, the weight of the shield required to obtain the same shielding performance is 1.2 T.
This is because the number increases more rapidly than in the case of T or more. The increase in weight limits the places where the shield can be constructed, necessitates a reinforced frame at the place of installation, and leads to an increase in cost. Next, the surface state of the steel sheet before the rust prevention treatment is performed will be described. An inorganic or semi-organic film is formed on the surface of the non-oriented electrical steel sheet or the grain-oriented electrical steel sheet to ensure insulation between the steel sheets. Since this film alone does not have sufficient corrosion resistance, further rust prevention treatment is required.

However, as mentioned earlier, these coatings
Above, apply anti-corrosion treatment generally used for building materials.
And it was difficult. How to apply rust prevention treatment to such steel sheet
As a result of intensive examination, the interlayer resistance of the film was 200 Ωcm^Two
Efficient coating with rust-prevention ability
I found out what can be formed. Interlayer resistance is 200Ωcm
^TwoNo film for rust prevention is formed with more than / sheets
Was. It also improves the electrical conductivity of the base iron and the coating, and
In order to obtain the corrosion protection effect, the interlayer resistance is 200Ωcm ^Two/Sheet
It is preferable to make the following.

In the case of a grain-oriented electrical steel sheet, a forsterite (Mg ₂ SiO ₄ ) -based primary film formed during the finish annealing process and a phosphate-based secondary film formed by baking treatment are formed on the steel sheet surface. . Also in this case, there is no change in that a film having rustproofing ability can be formed by setting the interlayer resistance of the film to 200 Ωcm ² / sheet or less. Furthermore, the amount of the forsterite primary coating is 0.5 g / m
By setting the ratio to ² or less, the interlayer resistance can be suppressed low, and a film having rust-preventive ability can be efficiently formed.

The rust-preventive film is not particularly limited as long as it is a general film that sacrifices and protects iron, but it is necessary to provide a film having a rust-preventive ability that does not produce red rust for 120 hours in a salt spray accelerated test. . If the film produces red rust within 120 hours, it will rust in a few months in an outdoor environment, causing not only deterioration of appearance but also extreme reduction of magnetic permeability in extreme cases. Will not work. 5-100 coating films containing zinc as a main component and containing 0-60% of chromium, nickel, cobalt, iron and molybdenum
When g / m ^{2 is} formed, this condition is sufficiently satisfied. There is no particular limitation on the method of providing a film, and a technique may be used in which zinc powder is added to the paint and the sacrificial corrosion resistance is used, in addition to electroplating and hot-dip plating.

[0012]

EXAMPLE A grain-oriented electrical steel sheet (thickness 0.35 mm) with a magnetic flux density of 1.65 T in the rolling direction when a DC magnetic field of 80 A / m is applied in the rolling direction, and a non-oriented electrical steel sheet of 1.2 T in the rolling direction (0.35 mm) was cut into a size of 455 mm × 455 mm, and the sheets were overlapped with each other in a rolling direction of a plate to obtain a shield panel. Panels having different thicknesses were prepared by changing the number of plates by an even number. The panel having the same thickness was assembled on a cubic shield box with six panels, a magnetic field was applied from the outside of the shield box with a Helmholtz coil, and a magnetic field sensor was placed at the center of the box to measure the internal magnetic field. Each side was covered with joints by non-oriented electrical steel sheet. The magnetic field is 80 A at the center of the box without the shield box
/ M.

Table 1 shows changes in the weight of the entire shield body and changes in the internal leakage magnetic field when the thickness of the panel is changed.
The table also shows, as a comparative example, the results when non-oriented electrical steel sheets having a magnetic flux density of 1.0 T and 0.72 T in the rolling direction when a DC magnetic field of 80 A / m was applied. In Examples 1 and 2 of the present invention, an internal leakage magnetic field of 10 A / m can be achieved when the total weight of the shield body is 10 kg or less, whereas in Comparative Examples 3 and 4, a total weight of 25 kg is obtained to obtain the same shielding performance. , 30 kg required. In order to obtain a light-weight shield having excellent magnetic shielding performance as a structure, it is necessary to use an electromagnetic steel sheet having a magnetic flux density of 1.2 T or more in the rolling direction.

[0014]

[Table 1]

Next, various surface treatments were performed to evaluate the rust-preventing ability of the shield body, and the adhesion and corrosion resistance of the coating were evaluated. At the time of surface treatment, in order to investigate the influence of the steel sheet surface, various methods of manufacturing the steel sheet, such as annealing conditions, and post-treatment methods after the steel sheet were manufactured, were varied to control the amount of forsterite film formed and the interlayer resistance of the film. As a surface treatment method, electroplating, hot-dip plating, and a baking type coating containing a water-soluble chromic acid compound and zinc powder disclosed in JP-A-7-48678 were used. The composition of the coating to be applied,
The adhesion amount and corrosion resistance of the film were evaluated by changing the amount of adhesion. In addition, the film adhesion was evaluated by the state of peeling with a cellophane tape after OT bending, and the corrosion resistance was evaluated by the presence or absence of red rust after 120 hours of a salt spray test (JIS Z-2371) with a cross cut.

[0016]

[Table 2]

As can be seen from Table 2, after the interlayer resistance of the film formed on the surface in the manufacturing process and the amount of forsterite film were adjusted to appropriate ranges, Examples 1 to 3 were subjected to surface treatment with an appropriate composition and basis weight. In the case of No. 6, a rust-preventive film having sufficient adhesion can be provided, and corrosion resistance that can withstand practical use can be secured. On the other hand, in Comparative Example 7 in which the correlation resistance of the steel sheet and the forsterite film were not controlled in appropriate ranges, it was difficult to secure the adhesion of the rust preventive film, and as a result, sufficient corrosion resistance was not obtained. Further, even when the surface condition of the steel sheet was controlled to an appropriate range, the amount of the rust preventive film to be applied did not fall within the appropriate range. It can be seen that only one can be obtained.

[0018]

As described above, according to the present invention, it is possible to provide a magnetic shielding material having excellent magnetic shielding properties and excellent corrosion resistance even in a corrosive environment where building materials are generally exposed. became.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shuichi Yamazaki 20-1 Shintomi, Futtsu-shi, Chiba F-term in the Technology Development Division of Nippon Steel Corporation (reference) 5E321 AA41 BB60 GG07 GH10

Claims (2)

[Claims] 1. When a DC magnetic field of 80 A / m is applied in the rolling direction, the magnetic flux density in the rolling direction is 1.2 T or more, and the interlayer resistance of the film formed on the surface after finish annealing is 200 Ωc.
An electromagnetic steel sheet of m ² / sheet or less, further comprising 0 to 60% in total of any one of chromium, nickel, cobalt, iron, molybdenum, aluminum, and magnesium with zinc as a main component on the film. 5-100g of film
/ M ^2, an electromagnetic steel sheet for magnetic shielding having excellent magnetic shielding performance and corrosion resistance. 2. The grain-oriented electrical steel sheet according to claim 1, wherein in the manufacturing process, the amount of forsterite film formed on the steel sheet surface after finish annealing is 0.5 g / m ² or less. Magnetic steel sheet for magnetic shielding.