KR101630974B1 - Plating Steel Sheet and Steel Sheet Coated With Composite Resin and Manufacturing Method for the same - Google Patents

Abstract

Provided is a steel sheet coated with a composite resin, which is a cured product of a steel plate coating composition. The steel sheet coated with a composite resin comprises: a steel plate; a plating layer which is formed at least on one side of the steel plate and has a crater rate of 15% or less, the amount of plated product of 20 to 60 g/m^2, and degree of alloying of 7 to 15%; and a coating layer which is formed on the plating layer, and includes a urethane-acrylic dendrimer resin. The steel plate coated with the composite resin has excellent fuel resistance, corrosion resistance, and deep welding properties.

Description

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

Coated steel sheet, a composite-resin-coated steel sheet and a manufacturing method thereof.

Steel, which is mainly used for fuel tanks for automobiles, is cold-rolled steel sheets of Al-Si hot-dip galvanized, Zn-Ni galvanized steel sheets or Zn-Sn galvanized steel sheets. These plated steel sheets have a disadvantage in that they are plated with expensive metals to provide excellent quality but have a high manufacturing cost.

On the other hand, a resin-based galvanized steel sheet comprising a polymer resin as a main component is excellent in fuel resistance and corrosion resistance, but has a disadvantage in that the coating surface has an insulating property and thus has poor welding characteristics. Conventionally, in order to improve the weldability, metal particles were mixed with the polymer resin composition to improve the conductivity. However, such a technique has a disadvantage in that the film thickness is increased, the manufacturing cost is high, the workability is poor, and powder is generated at the time of processing, resulting in additional defects.

A technique of applying an expensive zinc-tin alloy hot-dip galvanized steel sheet has been commercialized, but it is not only expensive but also has a disadvantage in that it has poor fuel resistance and corrosion resistance in seam resistance. Moreover, recently, as the use amount of various kinds of fuels such as biofuels is increased, the use environment of the fuel tank is getting worse and it is necessary to develop a steel plate having better fuel resistance.

An object of the present invention is to provide a steel sheet excellent in fuel resistance, corrosion resistance and seam weldability by producing a coated steel sheet having a crater fraction of 15% or less and coating with a composite resin containing a urethane-acryl dendrimer resin.

According to an embodiment of the present invention, there is provided a coated steel sheet having a crater fraction of 15% or less, an amount of plating adhered of 20 to 60 g / m 2, and an alloy degree of 7 to 15%.

According to another embodiment of the present invention, And a coating layer formed on at least one surface of the steel sheet and having a crater fraction of 15% or less, a plating adhesion amount of 20 to 60 g / m 2 and an alloy degree of 7 to 15%, and a coating layer formed on the plating layer, Provides a composite resin coated steel sheet which is a cured product of a steel sheet coating composition.

The steel sheet coating composition may contain 15 to 100 parts by weight of a curing agent, 10 to 70 parts by weight of a metal silicate, and 5 to 50 parts by weight of a titanium compound, based on 100 parts by weight of a urethane-acryl dendrimer resin and a urethane-acryl dendrimer resin.

The curing agent may be at least one of a melamine-based curing agent and an aziridine-based curing agent.

The melamine-based curing agent may be melamine, butoxymethylmelamine, hexamethoxymethylmelamine and trimethoxymethylmelamine.

The metal silicate may be at least one of lithium polysilicate, sodium polysilicate, potassium polysilicate, and colloidal silica.

The titanium compound may be at least one of titanium carbonate, isopropyl ditriethanol aminotitanate, lactic acid titanium chelate, and titanium acetylacetonate.

The coating layer may have a dry film thickness of 0.1 to 2.0 mu m.

The coating layer may have an adhesion amount of dry film of 0.1 to 2.0 g / m < ² >.

According to an embodiment of the present invention, there is provided a method of manufacturing a steel sheet, comprising the steps of: dipping a steel sheet in a plating bath; controlling a plating adhesion amount to 20 to 50 g / m ^2; and controlling the alloying temperature to 460 to 520 ° C, , And the alloyed coated steel sheet has a crater fraction of 15% or less.

According to another embodiment of the present invention, there is provided a method of manufacturing a steel sheet, comprising the steps of: dipping a steel sheet in a plating bath; controlling a plating adhesion amount to 20 to 50 g / m ² ; Preparing a galvannealed steel sheet having an alloying degree of 7 to 13% by controlling the alloying temperature to 460 to 520 캜; A method for manufacturing a composite resin-coated steel sheet, comprising the steps of: coating a steel sheet coating composition on the recycled galvanized steel sheet; and curing the coated steel sheet to form a coating layer, wherein the galvanealed steel sheet has a crater fraction of 15% .

The steel sheet coating composition may contain 15 to 100 parts by weight of a curing agent, 10 to 70 parts by weight of a metal silicate, and 5 to 50 parts by weight of a titanium compound, based on 100 parts by weight of a urethane-acryl dendrimer resin and a urethane-acryl dendrimer resin.

The coating can be carried out by any one of the methods selected from roll coating, casting, screen printing, spraying, gravure coating and deposition.

The coating layer may be formed at a temperature of 80 to 200 DEG C based on the steel sheet temperature.

The coating layer can be controlled to have a dry film thickness of 0.1 to 2.0 mu m.

The coating layer can be controlled to have a dry film adhesion amount of 0.1 to 2.0 g / m < ² >.

In the present invention, a steel sheet produced by coating a composite resin containing a urethane-acryl dendrimer resin with a crater fraction of 15% or less in the coating layer has an excellent effect on fuel resistance, corrosion resistance and core weldability.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a chemical structural formula of a wollastonite acryl dendrimer.
2 is a chemical structural formula of an isyridine curing agent.
3 is a SEM image of the plating layer of Example 6 and Comparative Example 1. Fig.
4 is a photograph of the surface of the hot-dip galvanized steel sheet of Example 6 and Comparative Example 1 after the corrosion resistance evaluation.
5 is a photograph of the surface of the cup product of Example 6 and Comparative Example 1 after the evaluation of fuel resistance.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention is intended to provide a coated steel sheet, a composite resin coated steel sheet and a manufacturing method thereof which are inexpensive and excellent in weldability and fuel resistance.

According to an embodiment of the present invention, there is provided a coated steel sheet having a crater fraction of 15% or less, an amount of plating adhered of 20 to 60 g / m 2, and an alloy degree of 7 to 15%.

If the crater fraction of the plated steel sheet exceeds 15%, the curing temperature of the coating layer becomes high and the energy efficiency may be lowered. If the coated amount is less than 20 g / m ² , it is difficult to secure corrosion resistance and fuel resistance, The insulating property is increased and the weldability is deteriorated. If the degree of alloying of the plated steel sheet is less than 7%, it is difficult to ensure sufficient corrosion resistance and fuel resistance, while if it exceeds 15%, the corrosion resistance and fuel resistance are improved but the insulation property is increased and the weldability is deteriorated.

According to another embodiment of the present invention, And a coating layer formed on at least one surface of the steel sheet and having a crater fraction of 15% or less, a plating adhesion amount of 20 to 60 g / m 2 and an alloy degree of 7 to 15%, and a coating layer formed on the plating layer, Provides a composite resin coated steel sheet which is a cured product of a steel sheet coating composition.

Also, the steel sheet coating composition may contain 15 to 100 parts by weight of a curing agent, 10 to 70 parts by weight of a metal silicate, and 5 to 50 parts by weight of a titanium compound, based on 100 parts by weight of a urethane-acryl dendrimer resin and a urethane- .

The urethane-acryl dendrimer resin has a large number of reactors as shown in the chemical formula shown in FIG. 1, and can be cured at a low temperature, reacts with a curing agent to form a dense three-dimensional network structure, and exhibits excellent characteristics in fuel resistance and corrosion resistance .

The content of the Wangan-acrylic dendrimer resin is preferably 5 to 20% by weight based on the total steel sheet coating composition. When the content is less than 5% by weight, the effect of fuel resistance is poor. When the content is more than 20% by weight, It is difficult to exhibit the effect of corrosion resistance.

It is preferable that the curing agent is at least one selected from a melamine curing agent and an arylidine curing agent having excellent reactivity, and the melamine curing agent may be melamine, butoxymethylmelamine, hexamethoxymethylmelamine and trimethoxymethylmelamine. In addition, the dwelling jidin curing agents can be represented by the chemical formula of FIG. 2, the R 2 groups are _{-H, -CH 3, -CH 2 CH} 3, -CH 2 CH 2 CH 3, -CH 2 OH or -CH ₂ CH ₂ OH.

The content of the curing agent is preferably 15 to 100 parts by weight based on 100 parts by weight of the cyanine-acrylic dendrimer resin. If the content is less than 15 parts by weight, the curing reaction of the dried coating may not be perfect, If the amount is more than 100 parts by weight, a side reaction may occur due to an excessive amount of a curing agent, which may deteriorate the workability of the coating film.

The metal silicate is an inorganic composition, unlike the urethane-acrylic dendrimer resin and the curing agent, which is an organic composition, and can improve the corrosion resistance of the dried coating. The metal silicate may be, but is not limited to, one or more selected from lithium polysilicate, sodium polysilicate, potassium polysilicate, and colloidal silica. The content of the metal silicate is preferably 10 to 70 parts by weight based on 100 parts by weight of the urethane-acrylic resin. If the amount is less than 10 parts by weight, the effect of corrosion resistance is insufficient. When the amount of the metal silicate is more than 70 parts by weight, But the coating can become rough.

The inorganic composition may further comprise a titanium compound. The titanium compound can improve the corrosion resistance of the dried coating film and has an advantage that the corrosion resistance against the processed part is improved even if a small amount of the titanium compound is added. The titanium compound may be at least one selected from titanium carbonate, isopropyl di-triethanol aminotitanate, titanium lactate lactate, and titanium acetylacetonate.

The content of the titanium compound is preferably 5 to 50 parts by weight based on 100 parts by weight of the urethane-acryl dendrimer resin. If the amount is less than 5 parts by weight, the effect of corrosion resistance is insufficient. When the amount is more than 50 parts by weight, Is undesirably increased.

If the dry film thickness is less than 0.1 탆, it is difficult to secure sufficient corrosion resistance and fuel resistance due to the thin coating film thickness. If the thickness exceeds 2.0 탆, the coating layer may have corrosion resistance The fuel property is improved, but the insulating property is increased and the weldability is deteriorated.

The coating layer preferably has an adhesion amount of from 0.1 to 2.0 g / m ^{2. When} the coating film adhesion amount is less than 0.1 g / m ² , it is difficult to secure corrosion resistance and fuel resistance. When the coating film adhesion amount exceeds 2.0 g / m ^2, The weldability deteriorates, which is not preferable.

According to another embodiment of the present invention, there is provided a method for manufacturing a steel sheet, comprising the steps of: dipping a steel sheet in a plating bath; controlling a plating adhesion amount to 20 to 50 g / m ^2; and controlling the alloying temperature to 460 to 520 ° C, , And the alloyed coated steel sheet has a crater fraction of 15% or less.

In order to obtain a hot-dip coated steel sheet having a low crater fraction, the steel sheet is immersed in a plating bath to be plated, and then the amount of plating adhered can be controlled to 20 to 50 g / m ² using an air knife. When the alloying temperature is controlled at 460 to 520 ° C after controlling the amount of plating, the Zn-Fe alloying degree may be 7 to 13%. The galvannealed steel sheet passes through a skin pass mill, Can be made uniform. The coated steel sheet produced by this method may have a low crater fraction, and more specifically, a crater fraction of 15% or less.

According to another embodiment of the present invention, there is provided a method of manufacturing a steel sheet, comprising the steps of: dipping a steel sheet in a plating bath; controlling a plating adhesion amount to 20 to 50 g / m ² ; Preparing a galvannealed steel sheet having an alloying degree of 7 to 13% by controlling the alloying temperature to 460 to 520 캜; A method for manufacturing a composite resin-coated steel sheet, comprising the steps of: coating a steel sheet coating composition on the recycled galvanized steel sheet; and curing the coated steel sheet to form a coating layer, wherein the galvanealed steel sheet has a crater fraction of 15% . The critical meaning of the numerical range of the plating adhesion amount, alloy degree and crater fraction of the plated steel sheet is as described above.

The steel sheet coating composition may contain 15 to 100 parts by weight of a curing agent, 10 to 70 parts by weight of a metal silicate, and 5 to 50 parts by weight of a titanium compound, based on 100 parts by weight of a urethane-acrylic dendrimer resin and a urethane-acryl dendrimer resin. Critical significance of the characteristics and content of the compound contained in the composition is as described above.

The coating is not limited thereto, but can be carried out by any one method selected from roll coating, casting, screen printing, spraying, gravure coating and immersion, among which the roll coating method is most preferred.

The coating layer is preferably formed at a temperature of 80 to 200 DEG C based on the steel sheet temperature. If the curing drying temperature is less than 80 DEG C, the curing reaction between the organic composition and the inorganic composition is insufficient, If the temperature is higher than 200 ° C, the crosslinking reaction of the curing agent is excessively increased and the coating film becomes hard and the processability is deteriorated.

The coating layer can be controlled in a dry film of 0.1 to 2.0 μm thickness of the coating layer, the dry film coating weight can be controlled in the range of 0.1 to 2.0 g / m ^2. The critical significance of the dry film thickness and the dry film coat adherence is as described above.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

The cold-rolled steel sheet is passed through an alkali degreasing, a pickling process, and an annealing process in order, and is immersed in a zinc pot for hot-dip galvanizing. The galvanized steel sheet controlled the amount of galvanized deposit through an air knife and controlled the alloying temperature in the alloying furnace. Table 1 shows the plating adhesion amount, the alloying temperature, the degree of alloying and the crater fraction of the plated layer of the molten plated steel sheet.

Thereafter, a steel sheet coating composition was prepared comprising 10 wt% of urethane acryl dendrimer, 5 wt% of aziridine curing agent, 5 wt% of lithium polysilicate, and 2 wt% of isopropyl ditriethanol aminotitanate. The composition further includes a small amount of alcohol, a leveling agent and a defoaming agent to improve the properties of the solution. The steel sheet coating composition was coated on the steel sheet by roll coating and then cured and dried at a steel sheet temperature of 100 ° C and then cooled to obtain a composite resin coated steel sheet having a dry coat thickness of 0.7 g / m ² and a dry coat thickness of 1.0 μm .

The corrosion resistance, fuel resistance and seam weldability of the composite resin coated steel sheet thus prepared were evaluated. The evaluation results are shown in Table 1.

≪ Evaluation of corrosion resistance &

The corrosion resistance was evaluated by the area of the green rust generated on the surface of the steel sheet after 1,000 hours when the coating was applied only with the composite resin at a salt pressure of 5% and a spray pressure of 1 kg / cm ² at 35 ° C. 4 is a photograph of the surface of a hot-dip galvanized steel sheet after corrosion resistance evaluation of Example 6 and Comparative Example 1. Fig.

◎: Corrosion area is 0% ○: Corrosion area is not more than 5%

?: Corrosion area 5 to 30% X: corrosion area 30% or more

≪ Evaluation of fuel resistance &

The evaluation of fuel resistance was evaluated as the fuelability of accelerated gasoline, deteriorated diesel, ethanol mixed gasoline and biodiesel. The test specimens were filled with cups (Blank size: 115 × 115 mm; Cup size, Punch diameter: 50 mm, Drawing height: 30 mm, Punch R = Die R = 6R) Respectively. 5% of pure gas and 20 ppm of formic acid were added to the gasoline fuel composition and allowed to stand for 1000 hours while shaking at a rate of 60 cycles per minute at 60 DEG C, and then the corrosion state of the steel sheet was evaluated. In the diesel fuel composition, 5% of pure water and 20 ppm of formic acid were shaken at a rate of 60 cycles per minute at 90 ° C., and the corrosion state of the steel sheet was evaluated after leaving for 8 weeks. The evaluation criteria are as follows. 5 is a photograph of the surface of the cup product after the fuel resistance evaluation.

◎: Corrosion area is 0% ○: Corrosion area is not more than 5%

?: Corrosion area 5 to 30% X: corrosion area 30% or more

<Evaluation of seam weldability>

The seam weldability was evaluated by using Ironman (Inverter DC Seam welder) to maintain constant strength without pressure at 4 kN, welding speed of 6 mpm, energization time of 33 ms and dwell time of 10 ms. The evaluation criteria were evaluated by welding current range.

?: 1.5 kA or more?: 1.0 to 1.5 kA or less?: 1.0 kA or less

On the other hand, the fraction (%) of the plated layer crater was calculated by dividing the cross-sectional area of the plated layer by 5 mm in width after measuring the cross-sectional area of the plating layer. 3 is a photograph showing SEM images of cross-section of the plating layer of Example 6 and Comparative Example 1. Fig.

division Plating layer properties Fuel resistance Corrosion resistance Core weldability Plating adhesion amount (g / m ² ) Alloying temperature (캜) Alloying degree (%) Crater fraction (%) Deteriorated gasoline Deteriorated diesel Bioethanol Biodiesel Example 1 30.0 465 8.5 8.5 ◎ ◎ ◎ ◎ ◎ ◎ Example 2 30.0 475 10.3 9.5 ◎ ◎ ◎ ◎ ◎ ◎ Example 3 30.0 495 12.5 10.8 ◎ ◎ ◎ ◎ ◎ ◎ Example 4 30.0 515 13.7 12.5 ◎ ◎ ◎ ◎ ◎ ◎ Example 5 40.0 465 7.2 7.6 ◎ ◎ ◎ ◎ ◎ ◎ Example 6 40.0 475 9.4 8.4 ◎ ◎ ◎ ◎ ◎ ◎ Example 7 40.0 495 11.5 10.5 ◎ ◎ ◎ ◎ ◎ ◎ Example 8 40.0 515 13.1 11.4 ◎ ◎ ◎ ◎ ◎ ◎ Example 9 50.0 465 6.8 7.4 ◎ ◎ ◎ ◎ ◎ ◎ Example 10 50.0 475 9.2 8.5 ◎ ◎ ◎ ◎ ◎ ◎ Example 11 50.0 495 11.1 9.2 ◎ ◎ ◎ ◎ ◎ ◎ Example 12 50.0 515 13.2 9.5 ◎ ◎ ◎ ◎ ◎ ◎ Comparative Example 1 30.0 500 11.5 15.3 △ △ △ △ △ ◎ Comparative Example 2 40.0 500 12.3 16.5 △ △ △ △ △ ◎ Comparative Example 3 50.0 500 13.2 18.6 △ △ △ △ △ ◎

As shown in Table 1, Examples 1 to 12, in which the crater fraction is 15% or less, are superior in both fuel resistance and corrosion resistance as compared with Comparative Examples 1 to 3.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (16)

delete Steel plate;
A plating layer formed on at least one surface of the steel sheet and having a crater fraction of 15% or less, a plating adhesion amount of 20 to 60 g / m 2, and an alloy degree of 7 to 15%
The coating layer formed on the plating layer
/ RTI &gt;
The coating layer is a cured product of the steel sheet coating composition,
The steel sheet coating composition comprises 15 to 100 parts by weight of a curing agent, 10 to 70 parts by weight of a metal silicate, and 5 to 50 parts by weight of a titanium compound, based on 100 parts by weight of a urethane-acryl dendrimer resin and a urethane-
Composite resin coated steel plate for fuel tank.
delete The composite resin-coated steel sheet for a fuel tank according to claim 2, wherein the curing agent is at least one of a melamine-based curing agent and an aziridine-based curing agent.
The composite resin-coated steel sheet for a fuel tank according to claim 4, wherein the melamine-based curing agent is melamine, butoxymethylmelamine, hexamethoxymethylmelamine, and trimethoxymethylmelamine.
The composite resin-coated steel sheet for a fuel tank according to claim 2, wherein the metal silicate is at least one of lithium polysilicate, sodium polysilicate, potassium polysilicate, and colloidal silica.
The composite resin-coated steel sheet for a fuel tank according to claim 2, wherein the titanium compound is at least one of titanium carbonate, isopropylditriethanolaminititanate, lactic acid titanium chelate, and titanium acetylacetonate.
The composite resin-coated steel sheet for a fuel tank according to claim 2, wherein the coating layer has a dry film thickness of 0.1 to 2.0 μm.
The composite resin-coated steel sheet for a fuel tank according to claim 2, wherein the coating layer has a dry film adhesion amount of 0.1 to 2.0 g / m ² .
delete Immersing a steel sheet in a plating bath:
Controlling the plating adhesion amount to 20 to 50 g / m ² ;
Preparing a galvannealed steel sheet having an alloying degree of 7 to 13% by controlling the alloying temperature to 460 to 520 캜;
Coating the steel sheet coating composition on the alloyed coated steel sheet and
A step of curing the coated steel sheet to form a coating layer
/ RTI &gt;
The steel sheet coating composition comprises 15 to 100 parts by weight of a curing agent, 10 to 70 parts by weight of a metal silicate, and 5 to 50 parts by weight of a titanium compound, based on 100 parts by weight of a urethane-acrylic dendrimer resin and a urethane-
The alloyed coated steel sheet has a crater fraction of 15% or less
Method for manufacturing a composite resin coated steel sheet for a fuel tank.
delete 12. The method of claim 11, wherein the coating is performed by any one of the methods selected from roll coating, casting, screen printing, spraying, gravure coating and deposition.
12. The method of claim 11, wherein the coating layer is formed at a temperature of 80 to 200 DEG C based on a steel sheet temperature.
12. The method of claim 11, wherein the coating layer is controlled to have a dry film thickness of 0.1 to 2.0 占 퐉.
12. The method of claim 11, wherein the coating layer is controlled to have a dry film adhesion amount of 0.1 to 2.0 g / m &lt; ² &gt;.

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