KR100306155B1 - Method for coating substrate with superior magnetic shielding property - Google Patents

Abstract

PURPOSE: A method is provided to coat a substrate with superior magnetic shielding property using a high magnetic permeability Fe-6.5%Si material as a coating material as a method for giving magnetic shielding property to a material for shielding electromagnetic wave. CONSTITUTION: In a method for coating the surface of a substrate using a spray coating system in which the substrate(2) is perpendicularly mounted onto a holder(1) that is constructed so that it is rotated as being traversed, a spray coating gun(3) is oppositely installed with spaced apart from the substrate(2) in a certain distance, and a spray coating material is supplied between the substrate(2) and the spray coating gun(3), the method for coating a substrate with superior magnetic shielding property comprises the processes of: pretreating the surface of the substrate(2) by shot blasting; and spray coating Fe-6.5%Si powder having a size of 60 to 120 microns as a spray coating material(4) on the surface pretreated substrate, wherein the shot blasting is performed by projecting alumina powder under a pressure of 50 to 60 psi, and the spray coating is performed when a traverse rate and a rotation speed of the holder(1) are 3.0 to 3.5 cm/sec and 110 to 120 rpm respectively in the state that a distance between the spray coating gun(3) and a substrate(2) is 110 to 120 mm, and a pressure of a gas flowing inside the spray coating gun(3) is in the pressure range of 120 to 150 psi in the state that an output of the spray coating gun(3) is impressed in the range of 30 to 35 kw.

Description

Coating method of substrate with excellent magnetic shielding

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of imparting magnetic shielding to a material in order to shield electromagnetic waves, and more particularly to a method of coating a substrate having excellent magnetic shielding property using a high permeability Fe-6.5% Si material as a coating material.

In recent years, as FA and OA equipments are rapidly promoted and distributed, problems such as troubles or malfunctions occur frequently in the signal system of high-precision electronic devices, which are the core of the system. There are a growing number of cases that cause safety accidents. Such cases are often found to be due to the environment in which the control device is installed and used, rather than the defect of the controller itself. In other words, when an operation facility using a large power is installed around the control device, a strong magnetic field generated from the operation device disturbs the signal system of the control device, and this phenomenon is a main cause of malfunction of the control device.

In addition, recent studies on the harmful effects of magnetic fields on the human body have been frequently published in the medical engineering community. As a countermeasure, research on magnetic shielding materials and magnetic field reduction / shielding technologies (magnetic shielding materials development, research report of the Institute of Industrial Science and Technology, 1995; latest magnetic analysis and shielding design and magnetic application technology, Comprehensive Technology Center) 1986) is actively progressing.

Conventionally, Fe-6.5% Si, which is mainly used as a shielding material, is a representative shielding material having a magnetic permeability of about 7 times higher than that of a 3% Si steel sheet, which is a measure of shielding performance. However, when the Si content increases, the workability deteriorates, so there is a disadvantage in that machining is impossible, such as rolling and cutting, and thus it is not easy to use as a shielding material.

In order to improve this problem, NKK has recently developed and proposed a shielding material of Fe-6.5% Si plate, which can be used because it can be machined to a certain extent, but it is expensive (0.1mmt, 9000 won / Kg) and still has a disadvantage in terms of workability compared to the general steel sheet. Therefore, the development of a shielding material that is economical with excellent production cost and excellent shielding is desired.

Accordingly, the present invention has been conducted based on the results of research and experiments to meet the above requirements, and the present invention provides a low permeability and excellent workability by coating a high permeability Fe-6.5% Si material. It is an object of the present invention to provide a material that can be easily manufactured in a complicated shape and has excellent electromagnetic shielding properties.

1 is a schematic view showing a magnetic field shielding material coating apparatus of the present invention.

2 is an exemplary view showing a fastening method for connecting the shielding plate coated by the present invention to a large area.

3 is a graph showing the change of permeability with frequency in the case of spray coating Fe-6.5% Si powder on the substrate surface.

* Explanation of symbols for main parts of the drawings

1 holder 2 substrate

3: warrior spray gun 4: thermal spray

5: main part 6: iron

The present invention for achieving the above object, the substrate 2 is vertically mounted to the holder (1) configured to rotate while reciprocating left and right, facing the substrate 2 at regular intervals and the thermal spray gun (3) In the method for coating the surface of the substrate using a thermal spraying system in which a thermal spray material 4 is supplied between the substrate 2 and the thermal spray gun 3, first, the substrate 2 is shot. Surface pretreatment by blasting, and then to the thermal spraying material (4) to supply a Fe-6.5% Si powder of 120-160μm size to a method of coating a substrate having excellent self-shielding properties to the surface pretreated substrate.

Hereinafter, the present invention will be described in detail.

The present invention is characterized by spraying the Fe-6.5% Si powder on the surface of the substrate by using a plasma spray method of the thermal spray coating method to give electromagnetic shielding, an example of a plasma deposition apparatus for implementing this is shown in FIG. .

As shown in FIG. 1, the plasma thermal spraying device is vertically mounted on a holder 1 configured to rotate while reciprocating from side to side, and is opposed to the substrate 2 at a predetermined interval. (3) is provided, and a thermal spray material 4 is supplied between the substrate 2 and the thermal spray gun 3 to coat the surface of the substrate 2.

In the present invention, before the thermal spray coating using the apparatus as described above, first, the shot blasting treatment, which is a pretreatment process for improving the adhesion between the thermal spray material and the substrate by forming irregularities on the substrate surface. At this time, 240 mesh of alumina powder is projected under a pressure of 50 to 60 psi. If the pressure condition is 50 psi or less, the adhesive layer between the coating layer and the substrate surface is poor and the coating layer is peeled off. It is preferable to project at a pressure of 50-60 psi since it is so severe that it is difficult to coat by deteriorating the adhesive strength between the coating layer and the substrate. In other words, the roughness of the surface of the substrate can be ensured only when the projection pressure of the powder is short during shot blasting, thereby enabling mechanical coupling between the thermal sprayed particles and the substrate. However, if the projection pressure is too high, the surface roughness is so severe that pores exist between the surface of the substrate and the coating layer, the adhesion is weakened, the adhesion by the oxide film is formed, the peeling phenomenon may occur. Since the Fe-Si powder, which is a thermal spraying material of the present invention, has a greater effect of oxidation on adhesion to a substrate than other thermal spraying materials, it is preferable to consider the possibility of deterioration of the adhesive strength of the coating layer due to oxide film formation.

The Fe-6.5% Si-spray powder having a particle size of 60-120 μm was sprayed onto the pretreated substrate, and the Fe-6.5% Si powder was not commercially sold. Produce powder. First, Fe-6.5% Si ingot, which is a master alloy, is manufactured, and then an amorphous ribbon is prepared by rapid cooling, and then pulverized by an attritor. The powder is recovered by sieving to uniformity. The powder recovered by this method is preferably used to select a powder having a particle size of 60-120 μm in consideration of the output of the thermal spraying device and the projection conditions.

On the other hand, the performance of the coating layer formed on the substrate during plasma deposition is generally affected by various spray condition variables such as the output of the plasma gun, the spray distance, the spray angle, and the arc gas pressure. More important. However, there have been no examples of applying Fe-Si powders to plasma spraying, and there is no sufficient data accumulation for optimal conditions. In particular, the conventional thermal spray coating method is mainly used for the wear-resistant coating material such as iron alloy powder, ceramic powder, whereas the powder used in the present invention is Fe-6.5% Si powder, which is a high functional material expressing high permeability characteristics. It was difficult to establish the spraying conditions for the application. Therefore, the present invention after the preliminary experiment by the trial and error method for coating the Fe-6.5% Si powder was devised as follows.

The distance between the spray gun gun 3 and the substrate 2 is preferably 110 to 120 mm in consideration of coating efficiency and loss of powder material in the thermal spraying operation.

The rotational speed and the traverse rate of the substrate holder 1 are preferably 110 to 120 R.P.M and 3 to 3.5 cm / sec, respectively. If the condition is not satisfied, that is, the speed is low, the substrate holder 1 is not sufficiently cooled during thermal spraying, which causes overheating of the substrate temperature and deteriorates the magnetic properties of the coating layer. Too low a coating.

In addition, the output of the spray gun 3 is a major parameter affecting the adhesion strength, fusion efficiency, etc., the plasma generation is not easy when the output of the spray gun 3 is 30kW or less, 35kW or more It is preferable that the output of the spray gun 3 be in the range of 30-35 kW, because there is a tendency to generate pores between the substrate and the coating layer and wear out the components of the spray gun, which is not suitable for coating.

In addition, the plasma gas pressure is set to 120 to 150 psi in order to easily adjust the length of the flame to control the coating speed of the sprayed layer. When the gas pressure is 120 psi or less, the coating speed is so slow that the distance between the substrate and the spraying event is considerably increased. Although it should be short, it is not suitable in terms of coating efficiency, and in case of 150 psi or more, it is preferable to set the pressure range of 120-150 psi because the coating speed of the sprayed layer cannot be controlled and the loss of powder material is uneconomical.

Been coated layer thickness is sprayed on the t ₀ (mm) substrate is used as the thermal spraying condition is preferably in a range obtained by substituting the thickness t ₀ of the substrate below.

Coating layer thickness (㎛) = t ₀ × 200-t ₀ × 600 (where t ₀ is in mm)

If the thickness of the coating layer is less than t ₀ × 200μm, the permeability is poor, and if the thickness of the coating layer is more than t ₀ × 600μm, the permeability is saturated, so there is no meaning of increasing the thickness of the coating layer.

In addition, the substrate has a surface hardness of 100 or more in Vickers hardness number in order to easily form unevenness during the shot blasting process, which is a pretreatment, and to increase the adhesive strength with the thermal spraying material. In order to prevent the deformation of the substrate when spraying, a metal, a nonmetal or a compound thereof having a melting temperature of 500 ° C. or higher is preferable.

On the other hand, the present invention is characterized in that the substrate is processed in a small size in advance and then coated under the above conditions, and then assembled to form a magnetic shield source having a large area or a constant curvature.

In other words, FIG. 2 is specifically described as an example, and the shielding material is coated and then deteriorated in performance so that the sheet material is bonded to both sides of the side connected to each other as shown in FIG. Substrates 5 to 6 are formed to process the substrate to be bonded to each other. Thereafter, by coating a high permeability material on the surface of the plate under the conditions set forth in the present invention, the plate is simply two-dimensionally connected as shown in FIG. In addition to reducing processing overhead and improving productivity, it is also possible to shield large-scale or curved magnetic field sources.

The present invention will be described through the following examples.

Example 1

In order to conduct the magnetic property test after coating, a general rolled steel sheet (rolled steel sheet produced and sold by POSCO) with a thickness of 0.7 mm is processed into a ring shape having an inner diameter of ø33 mm and an outer diameter of ø45 mm before coating. It was. The distance between the thermal spray gun 3 and the substrate 2 was 115 mm, and the left and right reciprocating speed of the holder 7 was 3.3 cm / sec, and the rotation speed was 115 rpm. In addition, Fe-6.5% Si powder (particle size of 100μm or less) was coated so that the coating layer thickness was 300μm under the pressure of the gas flowing therein at 135psi under the output of the spray gun 3 at 33kw. In order to increase the spray angle, the thermal spraying coating was made perpendicular to the substrate. The plasma forming gas during the coating was Ar as the primary gas and H ₂ was immersed in the secondary gas. The thermal spray system (METCO MBN type gun, maximum output 40kW) used in the experiment used a jig designed and manufactured to be firmly fixed on the substrate holder to prevent the ring-shaped substrate from falling during the thermal spraying.

Magnetic properties before and after coating of Fe-6.5% Si powder were measured for each substrate by using B-H Analyer (model name: IWATSU SY-8232). Surface roughness is affected when measuring the magnetic properties, so the coated specimens were polished before the magnetic properties were evaluated to eliminate the influence of the magnetic properties due to the surface condition. The coating thickness after polishing was finally about 200 μm.

In the ring-shaped specimen, the number of primary and secondary coil turns were about 50 times (in case of inner diameter ø 33 mm and outer diameter ø45 mm) according to JIS standard, and two sheets of the same specimen were insulated and laminated to lamination. After evaluating the characteristics, the results are shown in FIG.

On the other hand, for comparative analysis with the coating method of the present invention by changing the RPM and the reciprocation rate (traverse rate) of the substrate to 50 and 1.0cm / sec, respectively, the specimens were prepared by the same method described above, and the magnetic properties were evaluated. The results are shown in FIG. 3 as a comparative example.

As shown in FIG. 3, the permeability of the rolled steel sheet after coating according to the present invention showed an overall increase of about 60% or more, and the permeability was about 1600 in the commercial frequency range of 100 Hz or less. It was found that good magnetic properties were expressed. On the other hand, the comparative example, which is a case out of the spraying conditions, showed almost similar to the permeability before coating, and it was found that the magnetic properties depend on the spraying conditions even with the coating layer having the same thickness. Therefore, if the coating conditions of the present invention are well utilized, the permeability can be further improved according to the selection of the substrate thickness and the ratio of the coating thickness to the substrate thickness.

As described above, the present invention has the effect of applying high Fe-6.5% Si powder to the thermal spray coating to coat the material with a high permeability on the substrate with a low production cost to increase the value of the shielding material. In addition, regardless of the shape of the magnetic field source, it can be shielded by connecting a small board to shield the magnetic field source with large area or curvature, thereby mass-producing a shielding plate that is easy to process and complex shape processing. There is.

Claims (7)

The substrate 2 is vertically mounted on a holder 1 configured to rotate while reciprocating left and right, and is opposed to the substrate 2 at regular intervals to provide a thermal spray gun 3, and the substrate 2 In the method of coating the surface of the substrate by using a thermal spraying system in which the thermal spray material is supplied between the thermal spray gun and the thermal spray gun 3, the surface of the substrate 2 is first pretreated by shot blasting, and then the thermal spraying material 4 is sprayed onto the thermal spraying material 4. A method of coating a substrate having excellent magnetic shielding property by spraying Fe-6.5% Si powder having a size of 60-120 μm to the surface pretreated substrate. 2. The method of claim 1, wherein the shot blast is achieved by projecting alumina powder under a pressure of 50-60 psi. The method of claim 1, wherein the thermal spraying speed of the left and right reciprocating speed of the holder 1 is 3.0-3.5cm / second, and the rotational speed of 110-120mm between the thermal spray gun 3 and the substrate 2 Is 110-120rpm, and the pressure of the gas flowing therein is applied in the range of 120-150psi while the output of the spray gun (3) is applied in the range of 30-35kw. The method according to claim 1, wherein the thickness of the coating layer of the substrate having a thickness of t ₀ (mm) is in a range obtained by substituting the thickness t ₀ of the substrate below. Thickness of the coating layer (mu m) = t ₀ x 200-t ₀ x 600, where the unit of t ₀ is mm. The method of claim 1, wherein the substrate is a metal, a nonmetal, or a compound thereof having a melting temperature of 500 ° C. or more and a surface hardness of 100 or more in Vickers hardness number. 6. The method according to claim 5, wherein the substrate is provided with recesses (5) and convex portions (6) on each side contacting the plate to be coupled to both sides to be connected. The method of claim 6, wherein the substrate is bendable.