KR101720130B1 - Coated Steel Sheet of Different Kind of Metal and Manufacturing Method Thereof - Google Patents

Abstract

The present invention relates to a steel sheet coated with a dissimilar metal bonded material and a method of manufacturing the same, and a method of manufacturing a coated steel sheet by applying a specific paint on the surface of a dissimilar metal bonded material, And to improve durability such as wettability and corrosion resistance.
In order to achieve the above object, the present invention provides a dissimilar metal bonding material obtained by joining two or more materials selected from a metal or a metal alloy and joining them, wherein the dissimilar metal bonding material is formed by joining the A metal (10) (10), the bonding of the B metal (20) and the A metal (10), the bonding of the A metal (10), the B metal (20) and the C metal (30) And a top coat film layer formed on the undercoat film layer, wherein the top coat film layer is formed on one surface of the dissimilar metal bonding material.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated steel sheet,

The present invention relates to a steel sheet coated with a dissimilar metal bonding material and a method for producing the same, and more particularly, to a steel sheet coated with a specific coating material on a surface of a dissimilar metal bonding material to impart physical properties to the steel sheet and to provide durability such as moisture resistance and corrosion resistance The present invention relates to a coated steel sheet of a dissimilar metal bonded material and a method of manufacturing the same.

In general, plated steel sheets are widely used as a substrate for coated steel sheets.

The coated steel sheet is obtained by plating zinc (Zn), aluminum (Al), or an alloy thereof on the surface of the steel sheet. When the coated steel sheet is used as the base of the coated steel sheet, the corrosion resistance and surface appearance are excellent.

In addition to the above-described coated steel sheet, aluminum, aluminum alloy (Al Alloy), and stainless steel (STS) are also used as the material of the coated steel sheet.

Painted steel sheets using these materials are widely used in construction interior / exterior materials such as roofing materials and panel materials, and household appliances such as washing machines and refrigerators, but their use is still limited.

    On the other hand, heterogeneous metal bonding materials, which are currently attracting attention in various industrial fields, are formed by bonding two or more different metals in order to overcome the physical limitations of a single metal, and simultaneously satisfy two or more physical characteristics .

Recently, as the limit of performance improvement of single metal has been pointed out, the use of materials capable of satisfying the functions exceeding the characteristic limits of existing materials, reliability, processability and the like is gradually increasing.

These dissimilar metal bonded materials are used in a variety of industrial fields such as aerospace, automobiles, structural materials, building materials, and kitchen utensils.

    However, if such a dissimilar metal bonding material is directly used, the metal surface is directly exposed to the outside, so that the durability of the material is lowered and the aesthetic function is lowered.

In addition, the conventional dissimilar metal bonding materials can not improve durability such as moisture resistance and corrosion resistance, and thus are difficult to apply to various fields.

Disclosure of Invention Technical Problem [8] The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method and apparatus for applying a specific paint on the surface of a dissimilar metal bonding material, And to improve durability such as corrosion resistance.

Another object of the present invention is to improve the appearance of the appearance and to obtain an additional variety of functions, and to improve the marketability of the differentially coated steel sheet.

It is still another object of the present invention to provide a coated steel sheet excellent in physical properties as compared with a coated steel sheet using a single metal or a metal alloy.

According to another aspect of the present invention, there is provided a dissimilar metal bonding material comprising two or more materials selected from a metal or a metal alloy and joining them, B metal bonding, bonding of the A metal, the B metal and the A metal, bonding of the A metal and the B metal and the C metal, and the undercoat formed on one surface of any one of the above- A coating layer, and an upper coating layer formed on the lower coating layer.

It is further characterized in that it further comprises a chemical conversion coating layer formed between the metal or metal alloy layer and the undercoating layer.

Further, it is characterized by further comprising a clear coating film layer formed on the upper surface of the upper coat layer.

The undercoating layer preferably comprises 20 to 70% by weight of at least one selected from the group consisting of a polyester resin, a urethane resin, an epoxy resin and a fluoride resin. .

The undercoat layer has a thickness of 2.0 to 10.0 mu m.

The top coat layer may be formed of one or more selected from the group consisting of polyester resin, polyolefin resin, urethane resin, fluoride resin and epoxy resin in an amount of 20 to 70 By weight.

The upper coating layer has a thickness of 5.0 to 50.0 mu m.

The chemical conversion coating layer is characterized by containing 5.0 to 20.0% by weight of at least one metal selected from the group consisting of chromium (Cr), zirconium (Zr), silicon (Si) and titanium (Ti).

The deposition amount of the chemical conversion coating layer is 20 to 120 mg / m 2 on a one-side basis.

The clear coating film layer may contain 20 to 70% by weight of at least one selected from the group consisting of an acrylic resin, a melamine resin, a polyolefin resin, a polyester resin and a fluoride resin .

Further, the clear coating film layer has a thickness of 5.0 to 30.0 mu m.

According to another aspect of the present invention, there is provided a method for manufacturing a coated steel sheet of a dissimilar metal bonded material, comprising the steps of: (a) (S10) preparing a dissimilar metal bonding material to which a metal or metal alloy is bonded; (b) applying a primer coating composition to one surface of the dissimilar metal bonding material and drying the primer at a temperature of 180 to 260 ° C to form a primer coating layer (S30); (c) coating the top coat composition on one surface of the dissimilar metal bonding material having the undercoat layer formed thereon, and then drying the PMT under a condition of 180 to 260 ° C to form a top coat layer (S40) .

Also, before the step (S30) of forming the undercoat layer, the chemical treatment liquid is applied to one or both surfaces of the dissimilar metal bonded material, and the PMT is dried at a temperature of 60 to 130 DEG C to form a chemical conversion coating layer (S20).

After the upper coating layer is formed (S40), a clear paint is applied to one surface of the dissimilar metal bonding material having the upper coating layer formed thereon, and then the PMT is dried under the condition of 180 to 260 deg. C to form the clear coating layer The method comprising the steps of:

The solution of the above-mentioned problems does not list all the features of the present invention. The various features of the present invention and the advantages and effects thereof can be understood in detail by the following specific embodiments.

According to the present invention, by applying a specific paint on the surface of the dissimilar metal bonding material, it is possible to improve the durability such as moisture resistance and corrosion resistance by imparting the physical performance of the coated steel sheet while maintaining the advantages of the dissimilar metal .

In addition, the aesthetics of the appearance can be improved and various additional functions can be obtained, and the commerciality of the dissimilar metal-coated steel sheet can be improved.

In addition, there is an effect that it is possible to obtain a coated steel sheet excellent in physical properties as compared with a coated steel sheet using a single metal or a coated steel sheet.

1 is a schematic cross-sectional view of a conventional dissimilar metal bonded material having an A metal / B metal junction structure.
2 is a schematic cross-sectional view of a conventional dissimilar metal bonded material having an A metal / B metal / A metal junction structure.
3 is a schematic cross-sectional view of a conventional dissimilar metal bonded material having an A metal / B metal / C metal junction structure.
4 is a flowchart showing a process for manufacturing a coated steel sheet of a dissimilar metal bonded material according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a coated sheet of a dissimilar metal bonded material according to the present invention and a method for producing the same will be described in detail.

A dissimilar metal bonded material according to the present invention is a dissimilar metal bonded material obtained by joining two or more materials selected from a metal or a metal alloy and joining them, wherein the dissimilar metal bonding material is composed of an A metal (10) and a B metal (20 , Bonding of the A metal 10 and the B metal 20 to the A metal 10 and bonding of the A metal 10 to the B metal 20 and the C metal 30 A lower coating layer formed on one surface of any one of the dissimilar metal bonding materials, and an upper coating layer formed on the lower coating layer.

As the method for producing the dissimilar metal bonding material, a rolling method, an explosive bonding, a diffusion bonding, a friction bonding, a laser bonding, a casting, a resistance welding and the like can be used. Considering productivity and economical efficiency, it is preferable to use the rolling method.

The thickness of the dissimilar metal bonding material is preferably 0.2 mm to 3.0 mm. If the thickness of the material is less than 0.2 mm, it is difficult to withstand the tensile force applied to the material during the production of the coated steel sheet. If the thickness exceeds 3.0 mm, it is difficult to impart sufficient tension.

The undercoat layer is formed on the surface of the dissimilar metal bonding material and provides adhesion to the overcoating layer to be described later, thereby improving the corrosion resistance and workability of the coated steel sheet.

The undercoat layer preferably contains 20 to 70 wt% of at least one selected from the group consisting of polyester resin, urethane resin, epoxy resin and fluoride resin, The remainder of the resin may be a pigment and other additives.

As the above-mentioned additives, UV absorbers, antifoaming agents, smoothing agents, and extinction agents are preferably used, but are not limited thereto.

The thickness of the undercoat layer is preferably 2.0 to 10.0 mu m.

If the thickness of the undercoat layer is less than 2.0 占 퐉, corrosion resistance of the coated steel sheet may be deteriorated. If the thickness exceeds 10.0 占 퐉, the workability and adhesion of the coated steel sheet may be deteriorated.

The upper coating layer is formed on the lower coating layer to realize various colors and to impart functionalities such as chemical resistance, coating film hardness, corrosion resistance, moisture resistance and weather resistance to the coated steel sheet.

Wherein the top coat layer comprises 20 to 70 wt% of at least one selected from the group consisting of polyester resin, polyolefin resin, urethane resin, fluoride resin and epoxy resin, And the balance other than the resin may be a pigment and other additives.

As the additive, a defoaming agent, a smoothing agent, and a light extinction agent are preferably used, but are not limited thereto.

The thickness of the top coat layer is preferably 5.0 to 50.0 mu m.

If the thickness of the top coat layer is less than 5.0 占 퐉, the physical properties such as chemical resistance, coating film hardness, corrosion resistance, moisture resistance, and weather resistance are reduced and the function of the coated steel sheet can not be sufficiently exhibited.

On the other hand, when the thickness of the upper coat layer exceeds 50.0 탆, there is a high possibility that the workability and heat resistance of the coated steel sheet are lowered, and the coating film boiling phenomenon occurs during the drying process.

Further, a chemical conversion coating layer may be further formed between the dissimilar metal bonding material and the undercoating layer.

The chemical conversion coating layer serves to improve the adhesion between the dissimilar metal bonding material and the undercoating layer and to improve the corrosion resistance of the coated steel sheet.

It is preferable that the chemical conversion coating layer contains 5.0 to 20.0 wt% of at least one metal selected from the group consisting of chromium (Cr), zirconium (Zr), silicon (Si) and titanium (Ti) The remainder may be a solvent, an inorganic compound, a surface tension adjusting agent, distilled water and a crosslinking agent.

The deposition amount of the chemical conversion coating layer is preferably 20 to 120 mg / m 2 on a one-side basis.

If the deposition amount of the chemical conversion coating layer is less than 20 mg / m 2, the effect is not sufficient. If the deposition amount exceeds 120 mg / m 2, the corrosion resistance of the coated steel sheet may be deteriorated.

Further, a clear coating film layer may be further formed on the top coat layer.

The clear coating layer imparts hue and gloss to the final product and protects the appearance of the final product from external environmental conditions such as chemical and mechanical friction.

The clear coating film layer may contain 20.0 to 70.0 wt% of at least one selected from the group consisting of an acrylic resin, a melamine resin, a polyolefin resin, a polyester resin and a fluoride resin, And the balance other than the resin may be a pigment and other additives.

As the additive, UV absorbers, antifoaming agents, smoothing agents, and extinction agents may be used, but are not limited thereto.

The thickness of the clear coat layer is preferably 5.0 to 30.0 mu m.

If the thickness of the clear coat layer is less than 5.0 mu m, the function of protecting the appearance of the coated steel sheet is deteriorated. If the thickness exceeds 30.0 mu m, the workability and gloss of the coated steel sheet are adversely affected.

Hereinafter, a method for manufacturing a coated steel sheet of dissimilar metal bonded material, which is another aspect of the present invention, will be described with reference to FIG.

First, a dissimilar metal bonding material in which two or more metals are bonded is prepared (S10), and foreign substances such as scale and dust remaining on the surface are removed.

The dissimilar metal bonding material is composed of an A metal 10 and a B metal 20 (see FIG. 1), an A metal 10 and a B metal 20, an A metal 10 (see FIG. 2) 10, the bonding of the B metal 20 and the C metal 30, but is not limited thereto.

The dissimilar metals may be joined by rolling, explosion bonding, diffusion bonding, friction bonding, laser bonding, casting, resistance welding, or the like. Since these bonding methods are well known in the art, a detailed description thereof will be omitted.

Subsequently, the undercoating composition is coated on one surface of the dissimilar metal bonding material, and dried under conditions of PMT (Peak Metal Temperature) of 180 to 260 ° C to form a lower coating layer (S30).

Here, the PMT means the highest temperature that the steel sheet receives during the drying process. If the PMT is less than 180 ° C, the undercoating layer is not completely dried, and the appearance of the product may be adversely affected.

On the other hand, if the PMT exceeds 260 캜, the resin component in the undercoat layer may be deformed, resulting in defects in the appearance of the final product.

Therefore, the PMT at the time of forming the undercoating layer is preferably maintained at 180 to 260 캜.

Also, when the PMT is above 300 캜, an intermetallic compound may be generated at the interface between dissimilar metals. For example, at the Al / Mg and Cu / Al interfaces, an intermetallic compound is produced even at a relatively low temperature of about 300 ° C.

The above-mentioned intermetallic compound generally has a high hardness and is fragile, causing peeling between the dissimilar metals and deteriorating the mechanical properties of the dissimilar metal bonding material.

Further, before the step (S30) of forming the undercoat layer, the chemical treatment liquid may be applied to one or both surfaces of the dissimilar metal bonded material and the PMT may be dried at 60 to 130 ° C to further form the chemical conversion coating layer (S20).

At this time, if the PMT is less than 60 ° C, the adhesion is decreased, whereas if it exceeds 130 ° C, the curing reaction does not occur but only the heat is lost.

Therefore, the PMT at the time of forming the chemical conversion coating layer is preferably maintained at 60 to 130 캜.

Subsequently, the top coat composition is applied to one surface of the dissimilar metal bonding material having the undercoat layer formed thereon, and then dried at a temperature of 180 to 260 ° C to form a top coat layer (S40).

If the PMT is less than 180 ° C., the top coat layer may not be completely dried to adversely affect the appearance of the product. If the PMT is higher than 260 ° C., the resin component in the top coat layer may be deformed, Thereby generating defects.

Therefore, the PMT at the time of forming the top coat layer is preferably maintained at 180 to 260 캜.

After the upper coating layer is formed (S40), a clear paint is applied to one surface of the dissimilar metal bonding material on which the upper coating layer is formed, and then the PMT is dried at 180 to 260 deg. C to form a clear coating layer (Step S50).

If the PMT is less than 180 ° C., the clear coating layer may not be completely dried to adversely affect the appearance of the product. On the other hand, if the PMT is higher than 260 ° C., the resin component in the clear coating layer may be deformed, Thereby generating defects.

Therefore, it is preferable to maintain the PMT at the time of forming the clear coat layer at 180 to 260 캜.

On the other hand, the method of applying the chemical conversion treatment liquid, the undercoating composition, the top coat composition and the clear paint is not particularly limited.

For example, the coating may be applied by a roll coating method in the case of contact type or by a die coating method in the case of non-contact type.

As the means for drying the paint, it is preferable to use a device capable of controlling a heat source such as an infrared ray heater using an infrared ray, an induction heater, and a hot oven, It does not.

Hereinafter, an experimental example of the present invention will be described. The following experimental examples are intended to illustrate the practice of the present invention, and thus the present invention is not limited thereto.

< Experimental Example>

A stainless steel (austenitic STS 304) material having a thickness of 0.3 mm and an aluminum alloy (Al 1050) having a thickness of 0.55 mm were prepared as a dissimilar metal bonding material, and the dissimilar metals were bonded by rolling.

Thereafter, the undercoating composition (30 wt% of polyester resin, 5 wt% of epoxy resin, 15 wt% of pigment, 40 wt% of solvent and 10 wt% of other additives) was applied to the surface of the dissimilar metal bonding material, Lt; 0 &gt; C to form an undercoat layer having a dry film thickness of 5.0 mu m.

Subsequently, a top coat composition (containing 50 wt% of polyester resin, 10 wt% of melamine resin, 20 wt% of pigment, 15 wt% of solvent and 5 wt% of other additives) was coated on the surface of the alloy- Thereafter, the resultant was dried under the conditions of PMT 232 ° C to form an upper coat layer having a dry film thickness of 20.0 μm, to produce a coated steel sheet (Inventive Example 1) of a dissimilar metal bonded material.

On the other hand, for comparison with the above-mentioned example 1, a coated steel sheet (Comparative Example 1) was prepared by preparing a general zinc-plated coated steel sheet and forming a lower coat layer and an upper coat layer on the surface thereof under the same conditions as in Inventive Example 1 Then, the properties were compared and evaluated.

<Hardness>

Place the test plate horizontally and fix it with one hand. With the remaining one hand, gently wrap 4 ~ 6 pieces of gauze and rub the film surface vertically with a proper amount of solvent (METHYL ETHYL KETONE) The test was terminated and the number of times until this time was measured.

The degree of hardening was comparable to that of a general zinc-plated steel sheet (Comparative Example 1) and a steel sheet coated with dissimilar metals (Inventive Example 1).

<Processability>

Test specimens were prepared according to EN 23270; 1991 test method, and then subjected to 180-degree T-bending using a vise. At this time, a tape having a length of about 75 mm was adhered to the processing region using a transparent adhesive tape, and the processability was evaluated by peeling the tape at a uniform rate of 60 degrees from 0.5 to 1 second.

Both zinc plated steel sheets and coated steel sheets with different metals showed excellent results.

<Sea water, etc.>

The temperature of the hot water bath was maintained at 95 ~ 100 ℃, and after 1 hour, the specimens were taken out from the hot water bath and rinsed with water.

Good results were obtained for both general galvanized steel sheets and coated steel sheets.

<Adhesion>

After the test plate was fixed on a flat surface, the adhesion was evaluated by holding a coin at a 30-45 degree angle on the test plate and scoring it over 20 mm.

Both zinc plated steel sheets and coated steel sheets with different metals showed excellent results.

<Acid resistance>

The sections were completely protected with reagents and tape to withstand the duration of the test, the 5% HCl reagent was added to the beaker, and the test plate was fully immersed so as not to contact the beaker. After 24 hours, the test piece was taken out and washed with water and dried.

Good results were obtained for both general galvanized steel sheets and coated steel sheets.

<Alkali resistance>

The cut surfaces were fully protected with reagents and tape to withstand the test period, the 5% aOH reagent was added to the beaker, and the test plate was fully immersed so as not to contact the beaker, and after 24 hours, it was taken out and washed with water and dried.

Good results were obtained for both general galvanized steel sheets and coated steel sheets.

<Pencil hardness>

The test plate was fixed to the pencil hardness tester, and the pencil was cut so that the end was smooth and the angle was sharpened so that the core was exposed to about 3 mm, and the pencil was bound to the hardness tester at an angle of about 45 degrees.

Then, a load of 1 kg was applied, and the line was repeatedly drawn 5 times so as to have a length of 20 mm or more, and the test area was erased with an eraser and observed with the naked eye.

The hardness of pencil was equal to that of ordinary galvanized coated steel sheet and coated steel sheet with dissimilar metal bonding.

<Corrosion resistance>

The test was conducted according to the salt spray test standard according to ASTM D B1117. The cut surface of the test piece was covered with a tape and protected, and the flat portion was cut with a cutter. After 2000 hours, the degree of occurrence of white rust and blister in the flat portion of the test piece was observed.

Good results were obtained for both general galvanized steel sheets and coated steel sheets.

<Moisture resistance>

The conditions of the wet tester were set at a temperature of 49 1 캜 and a relative humidity of 95% or higher. The test piece was fixed on a sample holder and maintained for 2000 hours, and the degree of occurrence of blister was observed.

Good results were obtained for both general galvanized steel sheets and coated steel sheets.

[Table 1] summarizes the above experimental results.

 Experimental results of painted steel sheet of ordinary galvanized coated steel sheet and dissimilar metal bonded material division General galvanized steel plate
(Comparative Example 1) Dissimilar metal bonded material coated steel plate
(Inventive Example 1) Degree of hardening 50 times 50 times Processability ◎ ◎ Abdominal aquatic ○ ○ Attachment ◎ ◎ Acid resistance ○ ○ My alkalinity ○ ○ Pencil hardness F F Corrosion resistance ○ ○ Moisture resistance ○ ○  △ Normal, ○ Good, ◎ Excellent

As shown in Table 1, the physical properties of the coating film formed on the coated steel sheet of the dissimilar metal bonded material according to the present invention were found to be equivalent to the physical properties of the coating film formed on the conventional zinc coated steel sheet.

That is, it can be confirmed that the performance of the coated metal sheet of the present invention produced through the PCM (Pre Coated Metal) process is the same as that of the conventional zinc coated steel sheet.

Further, in order to compare the mechanical properties, the same general zinc-plated coated steel sheet as above (Comparative Example 2) was prepared and its mechanical properties were evaluated.

The tensile test was carried out using a Universal Materials Testing Machine (UNITED, US / SSTM). The tensile specimen had a gauge length of 15 mm and a width of 3.4 mm. The crosshead speed at both ends of the specimen was maintained at 0.9 mm / And the strain rate was 1 × 10 ^-3 / sec.

[Table 2] below summarizes the results of the tensile test described above.

 Tensile test results of painted steel sheets of ordinary galvanized steel sheets and dissimilar metal bonded materials division General galvanized steel plate
(Comparative Example 2) Dissimilar metal bonded material coated steel plate
(Inventive Example 1) The tensile strength 360Mpa 360Mpa Strain 45% 45% Yield strength 320Mpa 320Mpa

[Table 2] As can be seen from the tensile test results, the mechanical properties of the coated steel sheet of the dissimilar metal bonded material (Inventive Example 1) prepared through the PCM process were comparable to those of the conventional general zinc-coated steel sheet (Comparative Example 2) Respectively.

From the above test results, it can be seen that the coated steel sheet of the dissimilar metal bonded material according to the present invention possesses the characteristics of the conventional galvanized coated steel sheet while maintaining the excellent mechanical properties possessed by the dissimilar metal bonded material.

10: A metal
20: B metal
30: C metal

Claims (18)

1. A coated steel sheet made of two or more kinds of metal materials or metal alloys,
The dissimilar metal bonding material may be,
A metal 10 and a B metal 20 are bonded to each other by a flat plate bonding of the A metal 10 and the B metal 20 and the A metal 10, C metal 30 in a flat plate-like manner by any one of the methods,
A lower coating layer formed on one surface of any one of the dissimilar metal bonding materials;
A chemical conversion coating layer formed between the metal or metal alloy layer and the undercoat layer,
An upper coating film layer formed on the lower coating film layer,
And a clear coating film layer formed on an upper surface of the top coat layer,
The undercoat layer may be,
(20 to 70 wt%) selected from the group consisting of a polyester resin, a urethane resin, an epoxy resin and a fluoride resin, and the thickness of the undercoat layer is 2.0 - 10.0 占 퐉,
Wherein the top coat layer comprises:
And 20 to 70% by weight of at least one member selected from the group consisting of a polyester resin, a polyolefin resin, a urea resin, a fluoride resin and an epoxy resin, The thickness of the layer is 5.0 to 50.0 탆,
Wherein the chemical conversion coating layer comprises
Wherein the coating layer contains at least one metal selected from the group consisting of chromium (Cr), zirconium (Zr), silicon (Si) and titanium (Ti) in an amount of 5.0 to 20.0% by weight, / M &lt; 2 &
The clear coating film layer
And 20 to 70% by weight of at least one member selected from the group consisting of an acrylic resin, a melamine resin, a polyolefin resin, a polyester resin and a fluoride resin, And the thickness of the layer is 5.0 to 30.0 占 퐉. delete delete delete delete delete delete delete delete delete delete A method of manufacturing a coated steel sheet of a dissimilar metal bonded material in which two or more plate-like materials made of a metal or a metal alloy are bonded to each other,
(a) preparing (S10) a dissimilar metal bonding material consisting of two or more metals or metal alloys;
(b) applying a primer coating composition to one surface of the dissimilar metal bonding material and drying the primer at a temperature of 180 to 260 ° C to form a primer coating layer (S30);
(c) forming an upper coat layer by forming a top coat layer composition on the one surface of the dissimilar metal bonding material having the undercoat layer formed thereon, and drying the resultant at a temperature of 180 to 260 ° C under a PMT (Peak Metal Temperature) The method comprising the steps of:
A step of applying a chemical liquor to one or both surfaces of the dissimilar metal bonded material and drying the PMT at a temperature of 60 to 130 ° C to form a chemical lacquer coating layer S20 (S20) before forming the undercoat layer Further comprising:
After the upper coating layer is formed (S40), a clear paint is applied to one surface of the dissimilar metal bonding material having the upper coating layer formed thereon, and then the PMT is dried at 180 to 260 ° C to form a clear coating layer Further comprising:
The undercoat layer may be,
And 20 to 70% by weight of at least one member selected from the group consisting of a polyester resin, a urethane resin, an epoxy resin and a fluoride resin,
Wherein the top coat layer comprises:
And 20 to 70% by weight of at least one member selected from the group consisting of a polyester resin, a polyolefin resin, a urea resin, a fluoride resin and an epoxy resin,
Wherein the chemical conversion coating layer comprises
Wherein the alloy contains 5.0 to 20.0 wt% of at least one metal selected from the group consisting of chromium (Cr), zirconium (Zr), silicon (Si), and titanium (Ti)
The clear coating film layer
And 20 to 70% by weight of at least one member selected from the group consisting of an acrylic resin, a melamine resin, a polyolefin resin, a polyester resin and a fluoride resin. (METHOD FOR MANUFACTURING COATED STEEL SHEET).
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