JPH04244262A - Powder coating method and powder coated article - Google Patents

Abstract

PURPOSE:To form a gloss coating layer having a smooth surface to a substrate by coating the substrate with a powder in two or more parts and differentiating the curing speeds of the powder at respective coating times. CONSTITUTION:A powder of a first layer is applied to the surface of a substrate composed of a metal and the substrate is gradually heated to cure the coated powder to form a coating layer 2 and, subsequently, the powder is applied on the surface of the first coating layer 2 and the substrate 1 is suddenly heated to cure the coated powder to form a second coating layer 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating method for coating powder on the surface of a metal substrate and to powder-coated articles.

0002

[Prior Art] Magnetic parts such as choke coils used in electronic circuit devices are made by coating a base material made of wound or laminated magnetic thin metal plates with an insulating resin to form a coating layer. is used.

[0003] Conventionally, in order to apply powder to the substrate of this magnetic component, the substrate is first preheated to a predetermined temperature, then the powder is applied to the surface of the substrate, and then the substrate is heated and applied. A method has been adopted in which a coating layer is formed by curing powder.

[0004] In order to apply powder to a substrate, a method is used in which the substrate is immersed in the powder placed in a powder bath, or a method in which the powder is sprayed onto the surface of the substrate.

[0005]

[Problem to be solved by the invention] In magnetic parts,
The surface of the coating is required to be smooth and glossy both in terms of appearance and product properties.

However, in conventional magnetic parts, fine protrusions or pores exist on the surface of the coating layer formed on the surface of the base material, so that it may not be possible to obtain a good product that meets the above conditions. .

The present invention has been made based on the above-mentioned circumstances, and aims to provide a powder coating method capable of obtaining a coating layer with a smooth and glossy surface, and a powder-coated article having this coating layer. shall be.

[0008]

[Means and Effects for Solving the Problems] The inventors of the present invention have solved the problem of fine protrusions or pores occurring on the surface of the powder coating layer formed on the surface of the base in conventional magnetic components. I have conducted various research.

[0009] As a result, it has been found that one of the causes of deterioration of the surface of the coating layer is the heating method used when heating the substrate in order to harden the powder applied to the surface of the substrate.

[0010] At least when the substrate is rapidly heated to harden the powder, the powder particles are sufficiently melted and a coating layer with a smooth surface can be obtained. However, the base of the magnetic component is formed by winding or laminating thin metal plates, and air exists between each thin metal plate. Moreover, when powder is applied to the surface of the base, the gaps between the respective thin metal plates are sealed. Therefore, when the substrate is rapidly heated during powder curing, the air present between the metal thin plates is rapidly heated, expands, and blows out through the coating layer to the outside. As a result, pores are formed on the surface of the coating layer.

[0011] In order to avoid the generation of pores, the heating rate of the substrate is slowed down, so that the air existing inside the substrate is gradually heated and does not escape through the powder to the outside. However, the powder hardens before the particles are sufficiently melted.
After curing, unmelted particles remain and semicircular convex portions are formed on the surface of the coating layer.

Based on the results of these observations, the occurrence of the above phenomenon can be prevented by applying the powder to the substrate in two or more times and varying the speed of curing the powder during each application. I found out that it can be done.

The present invention has been made based on this knowledge.

[0014] The powder coating method of the present invention is a method for coating powder on the surface of a metal substrate, in which at least a first layer of powder is applied to the surface of the substrate, and the substrate is gradually heated. The applied powder is cured to form a first coating layer, and then the outermost powder is applied at least on the surface of the previous coating layer of the outermost coating layer, and the substrate is rapidly heated. The second coating layer is formed by curing the applied powder.

That is, by slowing down the curing speed of the powder applied to at least the first layer, the air existing inside the substrate is prevented from expanding and escaping through the powder to the outside, and the coating layer prevents the air from expanding. is sealed inside the base. Then, the powder applied to at least the outermost layer is rapidly heated to obtain a coating layer with a smooth surface. At this time, the air existing inside the substrate is sealed by the first powder coating layer and does not escape through the coating layer to the outside. Therefore, by powder coating, a coating layer having a smooth and glossy surface without pores or protrusions can be formed.

Further, the powder coated article of the present invention comprises:
Applying powder to the surface of at least a substrate made of metal, applying powder to the surface of a first coating layer formed by curing and containing unmelted particles, and at least a coating layer preceding the outermost coating layer; It is characterized by comprising an outermost coating layer that is formed by hardening and has no unmelted particles.

[0017] The powder-coated article of the present invention also includes at least a first coating layer, which is formed by coating and curing powder on the surface of a substrate made of metal, and has fine protrusions on the surface; It is characterized by comprising an outermost coating layer which is formed by applying powder to the surface of the coating layer preceding the outermost coating layer and curing it.

That is, the powder-coated article of the present invention seals air inside the substrate with the first coating layer, and also accelerates the curing speed of the powder coated on the top surface, resulting in a smooth surface. This makes it possible to form a second coating layer that is free of pores. Further, since the fine convex portions are present on the surface of the first coating layer, the second coating layer is reliably bonded to the first coating layer. Thus, it is possible to obtain a powder coated article with a coating layer that is free of pores and has a smooth, glossy surface.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, as shown in FIG. 1, a thin plate 1a made of, for example, an amorphous magnetic alloy is wound in a toroidal shape, and the surface of the base 1 is coated with powder of an insulating resin, such as an epoxy resin. This method is applied to the case where insulating resin powder is coated on the surface of a substrate in a layered magnetic component.

First, as shown in FIG. 2, a first layer of powder is applied to the surface of a substrate 1 to form a first coating layer 2.

[0022] The method of coating this powder will be explained. First, the base 1 is preheated. This preheating temperature is set to a temperature that does not impair the magnetic properties of the amorphous magnetic alloy thin plate 1a constituting the base body 1. For example, it is 140-150°C. If this preheating temperature is too low, resin adhesion will be insufficient.
On the other hand, if the temperature is too high, the surface properties of the resin after curing will be good, but the magnetic properties of the magnetic alloy thin plate will deteriorate, making it impossible to obtain a magnetic component with the intended properties, so the above temperature is preferable.

Next, powder is applied to the surface of the substrate 1. As a coating method, for example, a method is employed in which the substrate 1 is immersed in powder contained in a container. The coating thickness is relatively thin, about 35% of the total coating layer thickness including the first coating layer and the first coating layer. For example, it is 0.2 mm. Finally, the substrate 1 is heated to harden the applied powder to form the first coating layer 2. In this case, the method of heating the substrate 1 is to gradually raise the heating temperature to a predetermined curing temperature over time. That is, the curing speed of the powder is slowed down and the powder is cured in stages. For example, starting from a temperature of 80°C, the temperature is raised to 120°C over 60 minutes. The maximum value of the curing temperature is set to a temperature that does not impair the magnetic properties of the amorphous magnetic alloy thin plate 1a.

As a result, the air existing between the thin plates 1a of the base body 1 does not expand rapidly and escape through the first coating layer 2 to the outside, and the first coating layer 2 prevents the air between the thin plates 1a confined between. In addition, the entire powder particles are not sufficiently melted and unmelted particles remain, and the presence of these unmelted particles causes the first coating layer 2 to melt.
Many fine semicircular convex portions appear on the surface.

Next, as shown in FIG. 2, powder is applied to the surface of the first coating layer 2 to form a second coating layer 3.

[0026] The method of coating this powder will be explained. First, the base 1 is preheated. The preheating temperature is set to a temperature that does not impair the magnetic properties of the amorphous magnetic alloy thin plate 1a constituting the substrate 1, as in the case of the first layer of powder coating. For example 1
The temperature is 40-150°C. Next, powder is applied to the surface of the first coating layer 2. As a coating method, for example, a method is employed in which the substrate 1 is immersed in powder contained in a container. The coating thickness is approximately 65% of the total coating layer thickness including the first coating layer 2 and the second coating layer 3. For example, it is 0.3 mm. Finally, the second coating layer 3 is formed by heating the substrate 1 and curing the applied powder. In this case, the method of heating the substrate 1 is to rapidly raise the heating temperature to a predetermined curing temperature in a short period of time. That is, the curing speed of the powder is increased to cause it to harden rapidly. For example, starting from a temperature of 80°C, the temperature is raised to 120°C within 10 minutes. The maximum value of the curing temperature is set to a temperature that does not impair the magnetic properties of the amorphous magnetic alloy thin plate 1a.

As a result, the entire powder particles are sufficiently melted, and the surface of the second coating layer 3 is smooth and glossy. Furthermore, since the air existing between the amorphous magnetic alloy thin plates 1a of the base 1 is sealed in the first coating layer 2, this air cannot escape through the second coating layer 3. Therefore, no pores are formed in the second coating layer 3.

[0028] Therefore, a high-quality coating layer having a smooth and glossy surface without pores or irregularities can be formed on the substrate 1.

In addition, the magnetic component of this example has a high-quality coating layer with a smooth and glossy surface formed by the combination of the first coating layer 2 and the second coating layer 3. That is, this magnetic component seals the air inside the base 1 with the first coating layer 2, and then accelerates the melting and hardening speed of the powder applied to the surface of the first coating layer 2, thereby creating a good surface. This makes it possible to form a second coating layer 3 having a In addition, since there are thin convex portions on the surface of the first coating layer 2, the second coating layer 3 reliably covers the first coating layer 2.
is combined with

Although the present invention is effective when powder is applied to a substrate made of laminated thin plates as in the above embodiment, it is not limited thereto, but is effective when applying powder to various powder-coated articles. can be effectively applied to

Furthermore, the coating layer of the present invention is not limited to two layers, but three or more coating layers may be formed.

[0032]

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide a powder coating method that provides a coating layer with a smooth and glossy surface, and a powder-coated article having this coating layer. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a powder coated article showing one embodiment of the present invention.

FIG. 2 is an enlarged view showing a coating layer of a powder coated article.

[Explanation of symbols]

1...Base, 2...First coating layer, 3...First coating layer.

Claims (3)

[Claims] 1. A method of coating a powder on the surface of a metal substrate, wherein a first layer of powder is applied to at least the surface of the substrate, and the substrate is gradually heated to harden the applied powder. to form a first coating layer, and then apply the powder of the outermost layer on the surface of at least the preceding coating layer of the outermost coating layer, and the powder applied by rapidly heating the substrate. A powder coating method characterized by curing to form the outermost coating layer. 2. A first coating layer formed by coating and curing powder on the surface of at least a substrate made of metal and containing unmelted particles, and at least a coating layer preceding the outermost coating layer. 1. A powder-coated article comprising an outermost coating layer formed by applying and curing powder and containing no unmelted particles. 3. A first coating layer formed by coating and curing powder on the surface of at least a metal substrate and having fine convexities on the surface, and at least a coating layer preceding the outermost coating layer. A powder-coated article characterized by comprising a smooth outermost coating layer formed by coating and curing powder on the surface.