JP3270680B2 - Magnetic shielding material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic shield material, and more particularly, to a magnetic shield material formed by cold working such as a motor case.

[0002]

2. Description of the Related Art In an electric device, a magnetic shielding material is mounted inside or outside the device separately from a case or a cover in order to shield a leakage magnetic flux. For example, audio equipment,
In small motors used for OA equipment, VTRs, and the like, a magnetic shielding material is attached to the motor to shield leakage magnetic flux. In recent years, the size has been further reduced, and strict processing has been required for the magnetic shield material to be mounted.

[0003] As the performance required for the magnetic shield material,
Magnetic shielding properties, beautiful appearance and corrosion resistance. In order to enhance the magnetic shielding property, it is effective to increase the magnetic permeability. In steel, the crystal grain size is increased, and as the content of Si and Al increases, the magnetic permeability increases. Therefore, from the viewpoint of magnetic shielding properties, the use of directional silicon steel having high magnetic permeability is effective. Also, beautiful appearance,
Generally, a paint is applied to the surface to improve corrosion resistance.

If a steel material having high magnetic permeability can be used for a case or a cover of an electric device, it can also serve as a magnetic shielding material, and it is not necessary to separately mount a magnetic shielding material. However, since the case and the cover are subjected to a cold working with a high strength such as a drawing process or a bending process, a steel material having a high magnetic permeability, for example, a directional silicon steel plate, has low workability, and cracks and breaks occur, which is severe. There were problems that the molding process could not be tolerated, the forsterite film formed on the surface was easily peeled off, the coating film was easily peeled off, and the magnetic shielding property was deteriorated with the processing.

To solve the above problem, for example, Japanese Patent Laid-Open No.
No. 26 discloses that a steel containing 4.5% or less in total of Si and / or Al is made into a steel sheet having a recrystallized structure having a crystal grain size of 30 μm or less, then subjected to cold working, and then subjected to a heat treatment to reduce the crystal grains. A method for manufacturing a magnetic shield material to be coarsened has been proposed. However, in this method, the recrystallization annealing is performed after the cold working, so that the annealing efficiency is reduced and the productivity is deteriorated.

Japanese Unexamined Patent Publication (Kokai) No. 5-239694 proposes a grain-oriented silicon steel sheet for magnetic shielding having excellent coating adhesion. This steel plate is characterized in that the thickness of the forsterite coating on the ground iron is limited and the paint is applied directly on the coating. Oriented silicon steel sheets are usually provided with a forsterite coating and a vitreous coating for imparting tensile stress in the rolling direction to improve iron loss. However, since the vitreous coating is harmful to paint adhesion, the vitreous coating is not applied to the silicon steel sheet for magnetic shielding described in JP-A-5-239694. In the absence of a vitreous coating, the state of stress on the paint surface will have a significant effect on the state of stress of the ground iron. As a result, depending on the state of contact between the steel sheets or the state of contact with the jig at the time of forming, strain may be introduced into the surface layer of the ground iron, the magnetic permeability may be reduced, and the magnetic shielding property may be deteriorated.

[0007]

DISCLOSURE OF THE INVENTION The present invention advantageously solves the above problems, and proposes a magnetic shield material excellent in workability, in which the peeling of the coating film and the decrease in magnetic permeability are small even when the work is performed. With the goal.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the peeling of the coating film and the forsterite film and the decrease in the magnetic permeability that occur during the processing of the coated grain-oriented electrical steel sheet. It was found that the coating properties, especially the basis weight and the coefficient of friction of the film had a great influence. First, a description will be given of experimental results on which the present invention is based.

The present inventors assumed that a magnetic shield material to be wound around a small motor was used. The effects of the basis weight and the coefficient of friction were examined. A forsterite film having a thickness of about 2 μm was formed on the surface of the grain-oriented electrical steel sheet used. 8
A flattening anneal of 00 ° C. × 2 min was performed. Magnetic properties after _{annealing, W 17/50: 0.95~1.00W / kg,} B 8: was 1.85～1.86T.

Next, an epoxy resin paint was applied on the forsterite film of the magnetic steel sheet and baked at 200 ° C. The viscosity of the epoxy resin paint is changed by changing the compounding ratio of the epoxy resin and the curing agent, and the compounding ratio of the diluted thinner,
Alternatively, the coating conditions (specifically, the peripheral speed and the plate speed of the coating roll are changed) are changed, and a test piece is prepared in which the weight per unit area of the coating film and the friction coefficient are changed. The shielding properties were investigated.

In the corrosion resistance test, a 5% hydrochloric acid solution (liquid temperature: 35) was applied to the surface of each coated steel sheet having a basis weight of 0.5 to 5 g / m ² with a static friction coefficient (μ) of 0.2. ± 1 ℃)
Spraying was performed at a flow rate of ２2 ml / hr, and the occurrence of rust was observed. The corrosion resistance was evaluated by the number of days required until rusting occurred. From the results of the corrosion resistance test shown in FIG. 1, it can be seen that when the basis weight of the coating film is less than 2 g / m ² , the number of days required for rusting is short and the corrosion resistance is deteriorated.

In the bending resistance test, a coated steel sheet having a static friction coefficient of 0.2 was used, and each coated steel sheet having a basis weight of 1 to 10 g / m ² was wound around a round bar having a different diameter. The maximum round bar diameter at which peeling is observed is determined, and the bending resistance is evaluated. From the results shown in FIG. 2, it can be seen that when the basis weight of the coating film exceeds 8 g / m ² , the bending diameter increases, and the bending workability deteriorates.

Then, the coated steel sheet having a basis weight of the coating film of 6 g / m ² and a friction coefficient of 0.1 to 0.65 was changed to 20 mmφ.
The appearance of the coating film when it was wound around a round bar and unwound was visually observed, and the occurrence rate of peeling of the coating film is shown in FIG. FIG. 3 shows that when the coefficient of friction of the coating film exceeds 0.4, the occurrence rate of coating film peeling increases, and the bending resistance deteriorates.
When the friction coefficient of the coating film exceeds 0.4, the coating film is peeled off even by rubbing between steel plates.

In the magnetic shielding test, the basis weight of the coating film was 6
g / m ² , and each coated steel sheet with the friction coefficient changed to 0.1 to 0.65 was wound around a round bar of 25 mmφ five times and formed.
As shown in FIG. 5, the sample was divided and the magnetic field of the permanent magnet 1 was cut off by the sample 2, and the Gaussian measuring device 3, the conducting wire 4, and the meter 5 were used.
Was used to measure the strength of the magnetic field. The magnetic shielding property was evaluated from the measured magnetic field strength. The strength of the magnetic field of the permanent magnet is 500 A / m. FIG. 4 shows the measurement results. From FIG. 4, it can be seen that when the coefficient of friction of the coating film exceeds 0.4, the strength of the measured magnetic field increases, and the magnetic shielding properties deteriorate. This is probably because the higher the coefficient of friction of the coating film, the more the shear strain introduced into the surface layer of the ground iron during the forming process or the rubbing of the steel sheets, etc., and the lower the magnetic permeability.

From the above experimental results, the characteristics of the coating film of the magnetic shielding material made of the grain-oriented electrical steel sheet coated with the coating material are considered from the viewpoints of the magnetic shielding property, the bending resistance, and the corrosion resistance.
In particular, they have obtained new knowledge that it is important to regulate the friction coefficient and the basis weight. The present invention has been made based on the above findings. That is, the present invention relates to a magnetic shield material comprising a grain-oriented electrical steel sheet having a forsterite film, wherein the surface of the film is coated with an epoxy resin.
Paint, acrylic resin paint and polyester resin paint
A magnetic shield material with excellent workability, characterized in that a coating film having a friction coefficient of 0.4 or less is formed by applying one kind selected from the group consisting of ² to 8 g / m ^2. Oh Ru.
In addition, the present invention, the surface of the grain-oriented electrical steel sheet having a forsterite film, No. 4 Ford cup measurement 30-150
Epoxy resin paint, acrylic resin paint, or polyester resin paint with a viscosity of
This is a method for producing a magnetic shield material having excellent workability, characterized in that the magnetic shield material is coated and baked so that the basis weight of the coating film is ² to 8 g / m ² or less.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic shield material of the present invention is a grain-oriented electrical steel sheet having a forsterite film. Although the composition of grain-oriented electrical steel sheet is not particularly limited, Si: 2.8 ~
Silicon steel sheets containing 3.4% are preferred. Si is an effective element for improving the magnetic shielding property. However, if it exceeds 3.4%, the cold workability deteriorates, and if it is less than 2.8%, the effect is not recognized. A range of 3.4% is desirable.

Further, in addition to Si, it is preferable to contain Al: 10 ppm or less in order to enhance the magnetic shielding property. A
l: Exceeding 10 ppm causes a decrease in magnetic flux density. In addition, if necessary, S, Sn, Se, Mo, Sb, Mn
Etc. can also be added in trace amounts. In melting the base material, any known method such as a converter and an electric furnace can be used. The molten steel whose composition has been adjusted is preferably made into a slab by continuous casting, ingot-bulking method, and then to a final thickness by hot rolling and cold rolling.

After the steel sheet rolled to the final thickness is subjected to decarburizing annealing, an annealing separator mainly composed of MgO is applied to the surface and finish annealing is performed. As a result, a forsterite film is formed on the surface, and secondary recrystallized grains having a uniform orientation are formed, so that excellent magnetic properties are obtained. The forsterite film is preferably 3 μm or less from the viewpoint of workability. The magnetic shield material desirably has a high magnetic permeability, and preferably has a magnetic permeability of at least 0.01 H / m at 100 A / m.

[0021] The grain-oriented electrical steel sheet with the forsterite coating is desirably subjected to flattening annealing, and then a paint is applied on the forsterite coating to form a coating. The paint is preferably an epoxy resin paint, an acrylic resin paint or a polyester resin paint. The epoxy resin paint contains an epoxy resin, a curing agent, an inorganic pigment, and a solvent as main components. As the epoxy resin, a high molecular weight bisphenol A type epoxy resin is preferable. Alternatively, those modified with polyester, urethane, fatty acid or the like may be used. As the curing agent, an alicyclic modified amine, an aliphatic amine, a dicyandiamide-based curing agent, an imidazole-based curing agent, or the like is used. As the inorganic pigment, silica, titanium oxide, mica, or the like is appropriately used. On the surface of the inorganic pigment,
Chemical treatment such as aluminum-silica treatment, silane coupling treatment, and phosphate treatment may be performed.

The acrylic resin paint may be either a thermoplastic acrylic paint or a thermosetting acrylic paint. In the thermoplastic acrylic resin paint, nitrocellulose may be used as a curing agent. Further, a vinyl resin may be mixed. The polyester-based resin paint uses an unsaturated polyester resin, a styrene monomer, paraffin, hydroquinone, and cobalt octoate as a main component, and a methyl ethyl ketone peroxide solution as a curing agent.

In the present invention, a coating material is applied on the forsterite film, and a coating film having a coefficient of friction (static) of 0.4 or less on the surface of the coating film after coating is formed. When the coefficient of friction of the coating film exceeds 0.4, the magnetic shielding property and the peeling property of the coating film are deteriorated. It is considered that the higher the coefficient of friction of the coating film, the greater the introduction of shear strain to the surface of the ground iron due to rubbing or the like due to the contact between steel sheets during winding forming, resulting in a decrease in magnetic permeability.

The change in the coefficient of friction of the coating film surface can be achieved by changing the viscosity of the paint, winding tension, baking conditions, and the amount of inorganic pigment added. The viscosity of the paint can be changed by changing the compounding ratio of the epoxy resin and the curing agent or the compounding ratio of the diluted thinner. Thinner for dilution is
Those containing toluene as a main component and containing ethyl acetate, butyl acetate, amine acetate and the like are preferable.

The coefficient of friction and the basis weight of the coating film can be changed by a combination of the viscosity of the coating material and the application conditions. In order to keep the coefficient of friction of the coating film at 0.4 or less, the viscosity of the coating material should be No. 4 Ford cup measurement for 30 to 150 seconds, and the baking condition should be 180 ° C.
It is desirable to set it to 250 ° C. 2-8 g / m ² of a coating having a friction coefficient of 0.4 or less on the forsterite coating surface
Form.

If the basis weight of the coating film is less than 2 g / m ² , coating unevenness tends to occur, rust is generated from a thin portion of the coating film, and the corrosion resistance is deteriorated. On the other hand, if the basis weight exceeds 8 g / m ² , the bending resistance deteriorates. For this reason, the basis weight of the coating film is ^{2 to} 8 g / m ^2.
Range. In addition, when the coefficient of friction is within the range of the present invention, the basis weight is a sufficient basis weight that does not cause deterioration of the magnetic shielding property even when the steel plates come into contact with each other.

[0025]

[Example] C: 0.04%, Si: 3.2%, Al: 5ppm, Se:
Molten steel containing 0.02% and Mn: 0.07% was formed into a slab by continuous casting, and then a steel sheet having a thickness of 0.23 mm was formed by cold rolling including hot rolling and intermediate annealing. 8
After decarburizing annealing at 00 ° C, an annealing separator containing MgO as a main component is applied to the surface, and finish annealing is performed at 1200 ° C for 5 hours.
A grain-oriented electrical steel sheet was used. On this steel plate, a 2 μm thick forsterite film was formed, and B ₈ : 1.90 T,
W _17/50 : had magnetic properties of 0.90 W / kg.

The coatings shown in Table 1 were applied to the surface of the grain-oriented electrical steel sheet by a roll coater, and were baked under the conditions shown in Table 1 to form coating films having different basis weights and different friction coefficients shown in Table 1. After the coating was applied, it was wound into an 8-12 ton coil. The coating films having different friction coefficients were obtained by changing the viscosity of the paint, the baking conditions, and the winding tension as shown in Table 1.

With respect to the grain-oriented electrical steel sheet with a coating film, the corrosion resistance, bending workability, magnetic shielding property, and coating film peeling property were evaluated. In addition, five test pieces were collected for each test, and the test was performed. The test results are shown as average values and are shown in Table 1.

[0028]

[Table 1]

The corrosion resistance was determined by spraying a 5% hydrochloric acid solution (liquid temperature: 35 ± 1 ° C.) at a flow rate of 1 to 2 ml / hr on the surface of the coated steel sheet, and observing the occurrence of rust. The evaluation was based on the number of days required for occurrence. In the bending resistance test, a steel plate with a coating film was wound around round bars having different diameters, the maximum round bar diameter at which peeling of the coating film was recognized was determined, and the bending resistance was evaluated.

In the magnetic shielding test, the coated steel sheet was wound around a round bar having a diameter of 20 mm 7 times and formed, then divided into two samples, and the magnetic field of the permanent magnet 1 was applied to the sample 2 as shown in FIG.
And the strength of the magnetic field was measured using a measuring device consisting of a Gaussian measuring device 3, a conducting wire 4, and a meter 5. The magnetic shielding property was evaluated from the measured magnetic field strength. The strength of the magnetic field of the permanent magnet is 500 A / m.

[0031] The coating film peeling test was conducted using a steel sheet having a thickness of 20 mm.
Visually observe the appearance of the coating film when wound around a φ round bar 7 times and formed and rewound. If no peeling is observed,
When the peeled area was 1% to 5%, the evaluation was Δ, and when the peeled area was 5% or more, the evaluation was ×. Each of the examples of the present invention is excellent in corrosion resistance, bending work resistance, coating film peeling resistance, and magnetic shielding properties, and has excellent performance as a magnetic shielding material.

In the comparative examples out of the range of the present invention, the magnetic shielding property and the peeling resistance of the film are deteriorated.

[0033]

According to the present invention, it is possible to provide a magnetic shield material excellent in workability with little peeling of a coating film and a decrease in magnetic permeability even when severe molding is performed, and a grain-oriented electrical steel sheet is used. Therefore, it is possible to provide a magnetic shield material having a high magnetic shield property and excellent workability, and further to provide a magnetic shield material for a motor whose size is reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the basis weight of a coating film and corrosion resistance.

FIG. 2 is a graph showing a relationship between a basis weight of a coating film and bending resistance.

FIG. 3 is a graph showing the relationship between the coefficient of friction of a coating film and the releasability of the coating film.

FIG. 4 is a graph showing a relationship between a coefficient of friction of a coating film and a magnetic shielding property.

FIG. 5 is an explanatory diagram showing a test method of a magnetic shielding property.

[Explanation of symbols]

 1 Permanent magnet 2 Sample 3 Gauss measuring device 4 Conductor 5 Meter

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-24779 (JP, A) JP-A-4-2779 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86 H05K 9/00

Claims (2)

(57) [Claims] 1. A magnetic shielding material comprising a grain-oriented electrical steel sheet having a forsterite coating, wherein an epoxy resin coating, an acrylic resin coating, and a
A magnetic shielding material excellent in workability, characterized in that a coating film having a friction coefficient of 0.4 or less is formed in a thickness of ² to 8 g / m ² by applying one selected from polyester resin paints . 2. A surface of a grain-oriented electrical steel sheet having a forsterite film is coated with an epoxy resin paint, an acrylic resin paint, or a polyester resin paint having a viscosity of 30 to 150 seconds as measured by a No. 4 Ford cup. Coefficient is
A method for producing a magnetic shield material having excellent workability, wherein the magnetic shield material is coated and baked so that the coating weight per unit area is ² to 8 g / m ² or less.