KR102161480B1 - Thermoplastic powder coating method for spring of vehicle - Google Patents

Abstract

The present invention relates to a thermoplastic powder coating and a method of painting a vehicle spring using the same, and a spring subjected to shot peening and zinc phosphate pretreatment is put into a hot air preheating furnace to preheat above the curing temperature of the powder coating, and powder coating on the preheated spring When powder coating is carried out, the powder coating is immediately cured and dried by natural cooling, so a separate curing drying furnace can be eliminated, shortening the production time of the spring, and coating defects through reheating when coating defects occur through thermoplastic powder coatings. It relates to a method of painting a spring for a vehicle using a thermoplastic powder coating that can easily calibrate and reduce the manufacturing cost of the spring.

Description

Coating method of vehicle spring using thermoplastic powder coating{THERMOPLASTIC POWDER COATING METHOD FOR SPRING OF VEHICLE}

The present invention relates to a thermoplastic powder paint and a method of painting a vehicle spring using the same, and more particularly, a spring subjected to shot peening and zinc phosphate pretreatment is introduced into a hot air preheating furnace to preheat above the curing temperature of the powder paint, and preheated. Powder coating is applied to the spring so that the powder coating is immediately cured and dried by natural cooling during powder coating, so a separate curing drying furnace can be eliminated, shortening the production time of the spring, and reheating when coating defects occur through thermoplastic powder coating. It relates to a coating technology that can reduce the manufacturing cost of the spring by easily correcting the coating defect through.

In general, various coatings are performed in all industrial fields to prevent corrosion of products or to give them a shape. Accordingly, various coating methods exist. Typical examples include a coating method using a mixture of solvent and paint, and powder coating without using a solvent. Particularly, since powder coating does not use solvents, there are few problems of environmental pollution, and by not using volatile solvents, there is less risk of fire, and a predetermined film thickness can be obtained with one application, reducing the coating process. It has good workability and is easy to automate because it does not require mixing work of thinner (solvent) and paint, and it is economical and widely used because unused paint can be reused after recovery.

For this reason, powder coating is widely used as a method of coating metal products including vehicle springs.

The conventional method is a pretreatment step (S20) in which the surface of the spring, which is a metal that has been subjected to the shot peening treatment through the shot peening step (S10), is pretreated with a zinc phosphate film treatment, and the surface of the spring, which is metal, is dried. It consists of a manual drying step (S30) for, a powder coating step (S40) of powder coating the surface of a metal spring, and a hardening drying step (S50) of curing and drying the coating of the metal spring surface in a hardening drying furnace.

When the powder coating is finished, a hardening drying step (S50) passing through a hardening drying furnace is performed. In this step, painting hardening is performed under conditions in which the surface temperature of the spring is maintained for 10 minutes or more in a preset temperature range.

However, in the case of painting through the conventional powder coating process, the water-drying step (S30) of removing moisture from the metal surface after pretreatment of zinc phosphate and the hardening drying step (S50) passing for a long time of 1 hour or more after powder coating are used. As a result, defective products such as reduced productivity, increased cost for maintaining temperature for each process, reduced space utilization due to wide space use, and reduced coating quality (adherence, gloss, appearance) due to lack of temperature maintenance time due to power failure or line stop. There are problems that can arise.

In addition, since conventional powder coating coatings have thermosetting properties, when the surface of the spring is poorly coated, the coating must be completely removed and then powder coating must be performed again, thereby increasing the cost and time required for repainting.

Republic of Korea Patent Publication No. 10-1557632 (Name of invention: Vehicle spring coating method, 2015. 10. 06. Announcement)

In the embodiment of the present invention, when the spring is painted, the spring subjected to shot peening and zinc phosphate pretreatment is put into a hot air preheating furnace and powder coating is performed on the preheated spring, so that the powder coating is immediately cured and dried by natural cooling. , It is possible to eliminate a separate hardening drying furnace, shortening the production time of the spring while reducing the manufacturing cost of the spring.

In an embodiment of the present invention, it is an object of the present invention to reduce the cost and time required for modification of the painted surface when a powder coating failure of a spring occurs.

According to an embodiment of the present invention, a shot peening step (S1) of performing shot peening on the surface of a molded and heat-treated spring, after the shot peening step, a pretreatment step of performing a zinc phosphate coating treatment on the surface of the spring ( S2), water quality drying step of passing the spring through a water quality drying furnace (S3), preheating step of heating the spring (S4), and powder coating of powder coating the surface of the spring using a thermoplastic powder coating after passing through the preheating step Step (S5), after passing through the powder coating step, natural drying step (S6) of drying the spring in the air; And an inspection step of inspecting the surface coating condition of the spring after the natural drying step of the thermoplastic powder coating is completed, and a reheating step of improving the coating condition of the thermoplastic powder coating by performing reheating when determining defective coating, wherein the preheating step includes 120 In a hot air preheating furnace formed at a temperature of ℃ to 180 ℃, the surface of the spring is heated to a temperature of 100°C or higher with radiant heat from a heating wire heater and hot air using a fan, and the thermoplastic powder coating is a polyethylene resin of 55% to 70% by weight Wow, 3.0% by weight of wax, 1.0% by weight antioxidant, and 2.0% to 3.0% by weight of pigment are included, and even if the curing drying step is omitted, it is possible to paint and cure the spring in the air.

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According to an embodiment of the present invention, by preheating the spring by putting it into the hot air preheating furnace, and applying powder coating to the preheated spring, the powder paint is rapidly cured on the spring surface and dried by natural cooling. In addition, there is an effect of shortening the production time of the spring while reducing the manufacturing cost of the spring.

According to an embodiment of the present invention, by performing powder coating of the spring using a thermoplastic powder coating, the coating defect is corrected through heating without the need to remove the paint and repaint when a coating defect occurs. There is an effect that can save time and cost.

According to an embodiment of the present invention, since a hot air heater and a fan are installed on a wall surface of the hot air preheating furnace to heat the spring with hot air, there is an effect of reducing the installation space of the preheating process line.

According to an embodiment of the present invention, in the case of using a hot air preheating furnace, since heating can be simultaneously generated while passing a plurality of springs through the heating furnace, there is an effect of improving production efficiency compared to preheating through conventional resistance heating. have.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

It will be described in detail focusing on the parts necessary to understand the operation and operation according to the present invention.

While describing the embodiments of the present invention, descriptions of technical contents that are well known in the technical field to which the present invention pertains and are not directly related to the present invention will be omitted.

This is to more clearly convey the gist of the present invention by omitting unnecessary description.

In addition, in describing the constituent elements of the present invention, different reference numerals may be assigned to constituent elements of the same name according to the drawings, and the same reference numerals may be denoted even in different drawings.

However, even in this case, it does not mean that the corresponding component has different functions according to the embodiment, or that it has the same function in different embodiments, and the function of each component is the corresponding embodiment. It should be determined based on the description of each component in

In addition, the technical terms used in the present specification should be interpreted in the meaning generally understood by those of ordinary skill in the technical field to which the present invention belongs, unless otherwise defined in this specification. It should not be construed as a meaning or an excessively reduced meaning.

In addition, the singular expression used in the present specification includes a plurality of expressions unless the context indicates otherwise.

In the present application, terms such as “consisting of” or “comprising” should not be construed as necessarily including all of the various elements or various steps described in the specification, and some of the elements or some steps are included. It should be construed that it may not be, or may further include additional components or steps.

Hereinafter, a configuration and operation method according to each embodiment according to the present invention will be described.

The main object of the vehicle spring coating method according to an embodiment of the present invention refers to a stabilizer bar, coil spring, and leaf spring used for vehicle suspension, but furthermore, it is related to the shape of the product. It can be any spring without it, and the spring supplied to the painting process is a spring supplied through the molding process and tempering (heat treatment) process in the previous step.

Specifically, the method of painting a spring for a vehicle according to an embodiment of the present invention includes a preheating step (S4), a powder coating step (S5), and a natural drying step (S6), further comprising a water drying step (S3). It may include, may further include a pre-treatment step (S2), may further include a shot peening step (S1).

First, by applying a compressive residual stress to the spring through the shot peening step (S1) in which shot peening is performed on the surface of the spring that has been subjected to the forming and heat treatment steps, the durability fatigue life is significantly increased than that of the spring before shot peening, and then phosphoric acid The pretreatment step (S2) of performing the zinc coating treatment is performed to clean the foreign matter on the surface of the shot-peened spring, and at the same time, the pretreated zinc phosphate particles are evenly coated on the spring surface.

After that, there is a preheating step (S4). In the preheating step (S4), the spring is moved to the hot air preheating furnace using a spring moving means, and the spring is 5M long, and a hot air preheating furnace that forms a temperature range of 120°C to 180°C. By passing through, the spring is heated using the radiant heat of the hot wire heater provided on the wall of the hot air preheating furnace and the hot air generated by the operation of the fan.

Since the hot air preheating furnace transmits the radiant heat of the hot wire heater provided on the wall and the hot air using a fan to the spring, the spring moving inside the hot air preheating furnace can be rapidly heated, and moisture on the spring surface in the preheating step (S4) As the internal and surface temperature of the spring is rapidly increased while removing the material, the thermoplastic powder coating applied to the spring surface is rapidly cured immediately after passing through the subsequent powder coating step (S5) or in the air drying step (S6). The elapsed time in the drying step can be shortened.

That is, the preheating step (S4) can shorten the time of about 30 minutes passing through the conventional water drying furnace, and the time required while passing through the hardening drying furnace in the conventional hardening drying step can be shortened by 1 hour or more.

Here, the water cutting drying step (S3) is carried out between the pretreatment step (S2) and the preheating step (S4), and in the water cutting drying step (S3), the spring is moved to the water cutting drying furnace using a spring moving means, and then the spring is By passing through the drying furnace, moisture on the surface of the spring is removed, preventing poor appearance and lifting, swelling, or deterioration of coating adhesion due to contact with moisture during powder coating.

However, since the spring can also perform the function of the water cutting drying step S3 while going through the preheating step S4, the water cutting drying step S3 may be omitted.

When the preheating step (S4) is finished, it is directly connected to the powder coating step (S5), and if the spring is injected directly from the hot air preheating furnace into the powder coating machine in the powder coating step (S5), the powder coating machine is sprayed on the surface of the spring. The thermoplastic powder paint is sprayed, and the hardening of the painted surface occurs rapidly by preheating of the spring.

At this time, if the spring is preheated to a temperature equal to or higher than the melting point of the thermoplastic powder coating, the curing of the thermoplastic powder coating does not occur. Therefore, the preheating must be performed at a temperature below the melting point of the thermoplastic powder coating, and the preheating temperature is 120℃~180. It is preferable to form within the range of °C.

When the powder coating step (S5) is completed, the natural drying step (S6) of drying the spring in the air is performed, and the natural drying step (S6) does not require a separate hardening drying furnace unlike the hardening drying step in the conventional spring painting process. However, since the thermoplastic powder paint is applied to the surface of the heated spring during the preheating step (S4) and begins to melt and cure, the powder in the powder coating step (S5) even if the curing drying step of the conventional spring coating method is omitted. After painting, it is possible to perform paint hardening of the spring in the atmosphere without any additional process.

[Table 1] is a chart comparing the conventional coating method and the coating method of the present invention.

division Prior art The present invention Number of paintings 1 time Painting method spray Number of heat treatment 1 time Painting temperature Room temperature 120℃~180℃ Curing time 40 minutes to 1 hour 0 minutes Hardening furnace length 70M to 74 meters 0M

In addition, [Table 2] shows detailed chemical components of the thermoplastic powder coating of the present invention.

division Detailed chemical composition Prior art The present invention Suzy Epoxy resin 45% to 55% by weight - Polyethylene resin - 55% to 70% by weight Hardener Phenol type-A 15% to 20% by weight - Filler Calcium carbonate (CaCO3) 20% to 30% by weight - additive WAX, etc. 1.0% by weight 3.0% by weight or less Antioxidant - 1.0% by weight or less Pigment Carbon black 0.5% to 1.0% by weight 2.0% to 3.0% by weight

As shown in Table 2, the thermoplastic powder coating according to an embodiment of the present invention includes 55% to 70% by weight of polyethylene resin, 3.0% by weight or less wax, 1.0% by weight or less antioxidant, and 2.0% to 3.0% by weight % Pigments are included.

In the method of painting a spring for a vehicle according to an embodiment of the present invention, a spring subjected to shot peening and zinc phosphate pre-treatment when painting the spring is preheated by putting it into a hot air preheating furnace to generate rapid hardening of the thermoplastic powder paint, and then dry it by a natural cooling method. Therefore, it is possible to eliminate the conventional hardening drying furnace, shorten the production time of the spring, while reducing the manufacturing cost of the spring.

In the vehicle spring coating method according to an embodiment of the present invention, when the natural drying step of the thermoplastic powder coating is completed, an inspection step (S7) of inspecting the surface coating condition of the spring and reheating is performed upon determination of coating defects. The reheating step (S8) to improve the painting condition is sequentially carried out. Unlike conventional powder coatings having thermosetting properties, powder coating of the spring is performed using thermoplastic powder coatings, and when coating defects occur, the paint is removed and repainted. By making it possible to correct coating defects through heating without need, it is possible to reduce the time and cost required for correcting coating defects.

In addition, by applying the preheating step (S4) to the powder coating process of the spring, at least the hardening and drying step is eliminated after pretreatment of zinc phosphate, thereby reducing the heat treatment time of the entire process by 40 minutes to 1 hour or more compared to the conventional one, thereby dramatically increasing productivity. I can.

In addition, the installation space of the preheating process line can be reduced because the hot air preheating furnace heats the spring by installing a hot wire heater and a fan on the wall.

In addition, in the case of using a hot air preheating furnace, since heating can be simultaneously generated while passing a plurality of springs through the heating furnace, it is possible to improve production efficiency compared to preheating through conventional resistance heating.

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Although the embodiments of the present invention have been described with reference to the above, those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features.

Therefore, the embodiments described above should be understood as illustrative and non-limiting in all respects, and the scope of the present invention described in the detailed description is indicated by the claims to be described later, and the meaning of the claims and It should be construed that all changes or modifications derived from the scope and equivalent concepts are included in the scope of the present invention.

S1: shot peening step S2: pretreatment step
S3: water drying step S4: preheating step
S5: Powder coating step S6: Natural drying step
S7: reheating step S8: inspection step

Claims (5)

A shot peening step (S1) of performing shot peening on the surface of the molded and heat-treated spring;
After passing through the shot peening step, a pretreatment step (S2) of performing a zinc phosphate coating treatment on the surface of the spring;
Water quality drying step of passing the spring through the water quality drying furnace (S3);
Preheating step of heating the spring (S4);
After the preheating step, a powder coating step (S5) of powder coating the surface of the spring using a thermoplastic powder coating;
After passing through the powder coating step, natural drying step (S6) of drying the spring in the air; And
Including; an inspection step of inspecting the surface coating condition of the spring after the natural drying step of the thermoplastic powder coating is completed, and a reheating step of improving the coating condition of the thermoplastic powder coating by performing reheating when determining defective coating;
In the preheating step, the surface of the spring is heated to a temperature of 100° C. or higher with radiant heat of a hot wire heater and hot air using a fan in a hot air preheating furnace formed at a temperature of 120° C. to 180° C.,
The thermoplastic powder coating contains 55% to 70% by weight of polyethylene resin, 3.0% by weight of wax, 1.0% by weight of antioxidant, and 2.0% to 3.0% by weight of pigment,
A method of coating a spring for a vehicle using a thermoplastic powder coating, characterized in that coating curing of the spring in the atmosphere is possible even if the curing drying step is omitted. delete delete delete delete