JPH0997991A - How to join magnetic shield materials - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent magnetic shielding effect by flame spraying a flame spraying material made of metal having the maximum relative magnetic permeability of a specific value or more to the gap between the connecting parts of the magnetic shielding material, and connecting the shielding materials. SOLUTION: As the metal source of a flame spraying material, metal having the maximum relative magnetic permeability of 1000 or more is used. As a flame spraying method, a gas flame spraying, or a plasma flame spraying can be used. The droplet of the flame spraying material of melted or semimelted state is injected from a flame spraying nozzle, the material is sprayed to the gap generated between connecting members to solidify the droplet. The solidified layer is sequentially deposited and filled in the gap between the connecting members. When the material is sprayed to the gap between the members, if the sprayed material is not solidified in the gap but sprayed through the gap, the spraying side is sealed up to prevent the spraying through of the material. Thus, particularly in the alternating magnetic field of 5MHz or less, excellent magnetic shielding effect 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 method of preventing leakage of magnetic flux generated at a joint portion of a magnetic shield material when constructing a magnetic shield room and joining other magnetic shield members.

[0002]

2. Description of the Related Art Electroencephalographs, CT scanners, precision measuring instruments such as nuclear magnetic resonance devices, and other precision electrical equipment are home electric appliances, O
When exposed to the leakage magnetic flux generated from the A equipment or the like, the measurement accuracy often deteriorates or malfunction occurs. Therefore, when precise measurement control is required, it has been attempted to enclose these precision devices with a magnetic shield material and perform the measurement control in a shielded room that shields an external magnetic field. Further, it is considered that the house is magnetically shielded from the fear that the alternating magnetic field radiated from the power transmission line or the like is harmful to the living body.

[0003]

When the object to be shielded is large, it is necessary to join the magnetic shield material. For the above-mentioned magnetic shielding, a thin plate such as silicon steel or permalloy is usually used as a magnetic shield material. Then, for joining these thin plate members, fastening with rivets, bolts and nuts, spot welding and the like are performed. However, according to these joining methods, since an overlapping portion is required at the joining portion, it is necessary to use a large amount of expensive magnetic shield material, which is not only uneconomical, but also causes leakage of magnetic flux from the gap between the overlapping portions. It is difficult to prevent.

According to welding, a gap is not formed at the above-mentioned joint portion, which is satisfactory as a magnetic shield, but there are problems such as processing of deformation of a thin plate caused by welding and welding cost. . The present invention has been made in view of the above circumstances, and an object thereof is to provide an economical method for joining magnetic shield materials having an excellent magnetic shield effect.

[0005]

In order to achieve the above object, in the method for joining magnetic shield materials of the present invention, the magnetic material to be joined is a magnetic material having a maximum relative magnetic permeability of 1000 or more. It is characterized in that the shield material is sprayed and bonded in the gap between the bonded portions.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for joining magnetic shield materials of the present invention, the joint portions of the magnetic shield materials to be joined are arranged according to the joining mode, and in this state, the gaps formed between the joining members are filled with the thermal spray material. Then, the joining member is joined. The mode of joining may be either butt joining in which the end faces of the joined portions are placed in abutment with each other, or lap joining in which the joined portions are placed in an overlapping manner.

As the thermal spraying method, any of the thermal spraying methods such as gas thermal spraying and plasma thermal spraying can be used. The molten or semi-molten spray droplets of the spray material are ejected from the spray nozzle, and the spray material is blown into the gap formed between the joining members to solidify the droplets. By sequentially depositing this solidified layer, the gap between the joining members is filled. When the thermal spray material is blown into the gap between the joining members and the thermal spray material solidifies in the gap and blows through the gap without stopping, the blow-through side is provided with a seal to prevent the thermal spray material from passing through.

In the present invention, a metal having a maximum relative magnetic permeability of 1000 or more is used as the metal source. The metal source is processed into a powder, wire, or the like suitable as a thermal spray material, and is provided for thermal spraying. The maximum relative permeability in the present invention is
It is the value obtained in the state where the magnetic ingot is appropriately magnetic annealed as necessary. The maximum relative magnetic permeability of the metal source is set to 1000 or more because the maximum relative magnetic permeability is 10 or more.
5M by using a metal of 00 or more as a metal source
This is because the shielding effect in the low frequency alternating magnetic field of Hz or less can be exhibited, and when the metal having the maximum relative magnetic permeability of less than 1000 is used, the shielding effect in the low frequency alternating magnetic field of 5 MHz or less decreases.

[0009]

[Example] A PC permalloy thin plate having a thickness of 0.5 mm was bent to form a thickness of 0.5 mm, an outer diameter of 50 mm, and a length of 150.
It was molded into a cylindrical shape of mm. At this time, the joint portion of the plates was made parallel to the axis of the cylinder. As the joining state of the plates,
The experiment was conducted mainly with the joints of the plates abutting each other, but for some of the experiments, the joints of the plates were superposed with each other.

In the case of butt joining, the butt portion has a width of 1 m.
I took a gap of m. Then, a wood piece having a thickness of 3 mm and a width of 5 mm was attached to the inside of the cylinder with an adhesive so as to close the gap. As a result, the cylindrical shape is maintained and a seal is provided to prevent blowout during thermal spraying. In the case of lap joining, the lap width was 5 mm. As the thermal spray material, metal powders produced from various metals shown in Table 1 by a gas atomization method (water atomizing method) were used. Further, a PC permalloy wire having a diameter of 1 mm was manufactured and an experiment was conducted using this as a thermal spray material.

[0011]

[Table 1]

The maximum relative magnetic permeability of the metal used as the thermal spray material was determined as follows. That is, a ring-shaped test piece having an outer diameter of 10 mm, an inner diameter of 6 mm, and an axial length of 2.0 mm was carved out from an ingot obtained by remelting a metal powder used as a thermal spraying material and solidifying the metal powder, and exposing it in an argon atmosphere. Magnetic annealing was performed under the conditions shown in 1. The magnetic characteristics of the ring-shaped test piece subjected to the magnetic annealing were measured according to the DC magnetic characteristic test defined in JIS C 2531, and the maximum relative magnetic permeability was determined from the result. The maximum relative magnetic permeability values obtained for each metal are shown in Table 1.

Thermal spray materials shown in Table 1 were sprayed onto the joints of the cylinders to prepare test pieces for measuring magnetic shield characteristics. Thermal spraying was performed as follows. Metal powder is charged into a high-speed combustion gas flame to melt the metal powder, and this is sprayed from a spray nozzle by the spraying force of the combustion gas flame (gas spraying method). Thermal spraying was performed by arranging the cylindrical gap portion facing the thermal spray nozzle, and forming a thermal spray layer in the cylindrical gap portion to fill the gap. Further, thermal spraying was performed using a plasma flame instead of the above-mentioned combustion gas flame (plasma thermal spraying method), and a thermal spray layer was similarly formed in the gap portion of the cylinder to fill the gap.

As a comparative example, a test body was also produced by welding the PC permalloy while filling the gap of the PC permalloy cylindrical joint with the filler metal by the TIG welding method using the filler metal as the filler metal. The magnetic shield characteristics were measured using the test piece manufactured as described above.
The magnetic shield characteristics were measured using the device shown in FIG.
That is, a pair of Helmholtz coils 1 wound in a ring shape,
2 is used as a magnetic field source, and an exciting current is supplied to the Helmholtz coils 1 and 2 from a power supply device 6 including an oscillator 3, an amplifier 4 and an ammeter 5 to form an even alternating magnetic field in the middle of the Helmholtz coils 1 and 2. The sample 7 for magnetic shield characteristic measurement is arranged in this alternating magnetic field. Outer diameter 1 in the hollow part of the specimen 7
A search coil 8 having a length of 5 mm and a length of 4 mm is inserted. The leakage flux passing through the sample 7 is measured by the voltage measuring device 9 as the output voltage Ei of the search coil 8. Further, the output voltage Eo of the search coil 8 when the sample 7 is not placed is measured. The shield effect S was obtained from these values by the following equation (1).

S = 20 log (Eo / Ei) (1) The maximum magnetic field strength of the alternating magnetic field is set to 1 gauss and the frequency of the oscillator 3 is variously changed to obtain the shield effect S.
Shown in Table 3 shows the results of obtaining the shield effect S by varying the maximum magnetic field strength with the frequency of the alternating magnetic field set to 50 Hertz.

[0016]

[Table 2]

[0017]

[Table 3]

According to Tables 2 and 3, the examples of the present invention showed excellent magnetic shielding effect comparable to welding. In the examples of the present invention, the shielding effect is less likely to decrease even with an alternating magnetic field having a low frequency, and it can be seen that the shielding effect is superior to the comparative material, particularly in an alternating magnetic field of 5 MHz or less. Further, in the case of the comparative example to which welding is applied, it is necessary to shape the test body because the test body is deformed by the strain due to heat. However, in the example of the present invention, the deformation due to the bonding hardly occurred.

[0019]

As described above, according to the present invention, an excellent magnetic shield effect is exhibited especially in an alternating magnetic field of 5 MHz or less, and the deformation at the time of joining is small as compared with the joining by the welding method, and it is excellent. Bonding with magnetic shield effect is possible. According to the method of the present invention, since the deformation at the time of joining is small, the number of steps for removing the deformation after the joining can be saved, and the magnetic shielding property of the material is less likely to be damaged by the strain applied in the step of removing the deformation. Further, since the thermal spraying method is used in the method of the present invention, it is possible to obtain an economic effect that the bonding work can be efficiently performed even for a large structure.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a magnetic shield characteristic measuring device using a Helmholtz coil.

[Explanation of symbols]

 1, 2 Helmholtz coil 3 Oscillator 4 Amplifier 5 Ammeter 6 Power supply device 7 Specimen 8 Search coil 9 Voltage measuring instrument

Claims (1)

[Claims] 1. A magnetic shield material, characterized in that a thermal spray material using a metal having a maximum relative magnetic permeability of 1000 or more as a metal source is sprayed and bonded in a gap between the bonding portions of the magnetic shield materials to be bonded. Joining method.