KR20200084491A - Post-treatment coating composition for galvanized steel sheet containing magnesium and steel sheet using the same - Google Patents

Abstract

The present invention relates to a post-treatment composition for a galvanized steel sheet containing magnesium and a high functioning galvanized steel sheet manufactured thereby. A purpose of the present invention is to improve adhesiveness with a post-treatment coating layer and a matrix steel sheet when post-treatment coating is performed after the manufacture of a galvanized steel sheet containing magnesium, and to improve corrosion resistance through the addition of magnesium while preventing a deterioration in processability. To achieve the purpose, the post-treatment composition includes: a matrix cold-rolled steel sheet (10); a magnesium-zinc alloy layer (20) plated on the surface of the matrix cold-rolled steel sheet (10); and a post-treatment coating layer (30) of an organic resin base formed on one or both sides of the cold-rolled steel sheet (10) where the magnesium-zinc alloy layer (20) is formed. The magnesium-zinc alloy layer (20), with respect to the whole composition of the alloy layer, contains 1.1-1.7 wt% of aluminum, 1.1-1.7 wt% of magnesium, and 96.6-97.8 wt% of zinc.

Description

Post-treatment composition of galvanized steel sheet containing magnesium and plated steel sheet produced thereby{POST-TREATMENT COATING COMPOSITION FOR GALVANIZED STEEL SHEET CONTAINING MAGNESIUM AND STEEL SHEET USING THE SAME}

The present invention relates to a post-treatment composition of a zinc-plated steel sheet containing magnesium and a high-function plated steel sheet produced thereby, more specifically, to improve adhesion to a plated steel sheet manufactured in a continuous hot-dip plating process line. It relates to a post-treatment composition of a galvanized steel sheet containing magnesium capable of producing a high-performance galvanized steel sheet excellent in corrosion resistance and processability by applying a post-treatment composition capable of, and a plated steel sheet produced thereby.

In general, the plated steel sheet is provided with a post-treatment coating equipment at the rear end of the continuous galvanizing line to provide a function of temporary rust to form a post-treatment coating layer.

The function of the temporary rust prevention is usually performed by an inorganic post-treatment coating. In this case, there is a disadvantage in that the slip property is lowered during processing due to the thin coating film, resulting in scratch on the surface of the steel sheet.

On the other hand, an organic post-treatment coating is also applied to prevent the slip property from being deteriorated during processing. In this case, there is a disadvantage in that corrosion resistance is deteriorated compared to the post-treatment coating method containing chromium.

In addition, magnesium may be added to improve the corrosion resistance of the steel sheet.

In this case, however, magnesium oxide is formed on the surface of the steel sheet by oxidation in the process of cooling after immersing the steel sheet in the pot.

When the magnesium oxide layer is formed on the surface of the steel sheet in this way, there is a problem in that the adhesion between the steel sheet and the post-treatment coating solution at the time of post-treatment coating is very deteriorated.

The present invention is to solve the above-mentioned problems of the prior art, when the post-treatment coating after the production of hot-dip galvanized steel sheet containing magnesium, the purpose is to improve the adhesion between the steel plate and the post-treated coating layer .

Another object of the present invention is to improve the corrosion resistance by the addition of magnesium, while being able to manufacture a plated steel sheet that does not deteriorate workability.

The zinc-plated steel sheet containing magnesium according to the present invention for achieving the above object is a cold rolled steel sheet; A magnesium-zinc alloy layer plated on the surface of the cold rolled steel sheet; And an organic resin-based post-treatment coating layer formed on one or both sides of the cold-rolled steel sheet on which the magnesium-zinc alloy layer is formed, wherein the magnesium-zinc alloy layer is based on the entire composition of the alloy layer. It is characterized by containing 1.1 to 1.7% by weight of aluminum, 1.1 to 1.7% by weight of magnesium, and 96.6 to 97.8% by weight of zinc.

In addition, the post-treatment composition to form the post-treatment coating layer, based on the post-treatment composition, urethane resin 20 to 30% by weight, acrylic resin 30 to 40% by weight, CO-solvent 1 to 4% by weight, wax 3 to 4 It is characterized by consisting of weight%, wetting agent 0.1 to 0.5% by weight, antifoaming agent 0.05 to 0.1% by weight, chromium compound 1.0 to 3.0% by weight, and the rest being made of water.

In addition, a method of manufacturing a zinc-plated steel sheet containing magnesium according to the present invention includes: (a) pre-processing the cold rolled steel sheet (S10); (B) annealing the cold-rolled steel sheet (S20); (c) plating the base cold rolled steel sheet in a molten zinc plating bath containing magnesium (S30); (d) forming a post-treated coating layer on one or both sides of the magnesium-zinc plated steel sheet (S40), wherein the post-treatment coating layer in the S40 step is 20-30 wt% urethane resin, 30 acrylic resin. ~ 40 wt%, CO solvent 1 ~ 4 wt%, wax 3 ~ 4 wt%, wetting agent 0.1 ~ 0.5 wt%, antifoaming agent 0.05 ~ 0.1 wt%, chromium compound 1.0 ~ 3.0 wt%, the rest to the post-treatment composition consisting of water It is characterized by being formed by drying at 100 to 120° C. after being applied in an amount of 1500 to 3000 mg/m 2.

According to the present invention, when the post-treatment coating after production of the hot-dip galvanized steel sheet containing magnesium, there is an effect that can improve the adhesion between the base steel sheet and the post-treated coating layer.

In addition, there is an effect that it is possible to manufacture a plated steel sheet that does not degrade workability while improving corrosion resistance by the addition of magnesium.

As a result, it is possible to manufacture a hot-dip galvanized steel sheet containing magnesium having high corrosion resistance and processability.

1 is a schematic cross-sectional view of a plated steel sheet coated with a post-treatment composition according to the present invention.
Figure 2 is a flow chart showing the manufacturing process of the high-function plated steel sheet according to the present invention.

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

The galvanized steel sheet containing magnesium according to the present invention, as shown in Figure 1, the cold-rolled steel sheet 10, and the magnesium-zinc alloy layer 20 plated on the surface of the cold-rolled steel sheet 10 , The magnesium-zinc alloy layer 20 is formed on the cold-rolled steel sheet 10 is formed on one side or both sides of the organic resin-based post-treatment coating layer 30.

Various materials may be used as the base cold rolled steel sheet 10.

In addition, the magnesium-zinc alloy layer 20, based on the total composition of the alloy layer, aluminum is 1.1 to 1.7% by weight, magnesium is 1.1 to 1.7% by weight, zinc is preferably contained 96.6 to 97.8% by weight .

And the post-treatment coating layer 30, based on the total composition of the post-treatment solution, urethane resin (Urethane resin) 20 ~ 30% by weight, acrylic resin (Acrylic resin) 30 ~ 40% by weight, CO-solvent (Co -solvent) 1 to 4% by weight, 3 to 4% by weight of wax, 0.1 to 0.5% by weight of wetting agent, 0.05 to 0.1% by weight of antifoaming agent, 1.0 to 3.0% by weight of chromium compound, and the rest being made of water desirable.

In the post-treatment composition, urethane resin and acrylic resin serve as a binder of the composition.

When the content of the urethane resin and the acrylic resin is less than 20% by weight and 30% by weight, the role of the binder decreases, and properties such as corrosion resistance, chemical resistance, blackening resistance, and adhesion decrease.

In addition, when the content of the urethane resin and the acrylic resin exceeds 30% by weight and 40% by weight, respectively, a problem arises in the stability of the solution.

CO-solvent is added to form the coating film smoothly.

When the content of the CO-solvent is less than 1% by weight, the chemical resistance decreases, and when it exceeds 4% by weight, fumes are generated during drying, which causes trouble to work.

Wax is added to improve slip properties during product press and roll forming and to prevent scratches during processing.

When the content of the wax is less than 3% by weight, slip property decreases, and scratching and peeling of the coating film occur during processing.

In addition, when the content of the wax exceeds 4% by weight, there is a problem in processing due to overslip.

Wetting and anti-foaming agents are added to achieve smooth workability and beautiful appearance.

When the content of the wetting agent and the antifoaming agent is less than 0.1% by weight and 0.05% by weight, a roll mark defect in which the shape of the roll is transferred occurs during coating of the roll for painting, and the coating film cannot be properly spread, resulting in craters. ) Occurs and the appearance is not beautiful.

The chromium compound is added to improve corrosion resistance and blackening resistance.

When the content of the chromium compound is less than 1.0% by weight, the physical properties of corrosion resistance and blackening resistance are lowered, and when it exceeds 3% by weight, a solution gelation occurs.

On the other hand, the method of manufacturing a zinc-plated steel sheet containing magnesium according to the present invention, as shown in Figure 2, (a) pre-processing the cold rolled steel sheet 10 (S10); (B) an annealing process (S20) of the cold-rolled steel sheet (10); (c) plating (S30) the molten cold-rolled steel sheet 10 in a molten zinc plating bath containing magnesium; (d) forming a post-treatment coating layer 30 on one or both sides of the magnesium-zinc plated steel sheet (S40).

In addition, the post-treatment coating layer 30 in the step S40, 20 ~ 30% by weight of urethane resin, 30 ~ 40% by weight of acrylic resin, 1 ~ 4% by weight of CO solvent, 3 ~ 4% by weight of wax, wetting agent 0.1 ~ 0.5 Weight%, antifoaming agent 0.05 ~ 0.1% by weight, chromium compound 1.0 ~ 3.0% by weight, the rest is formed by drying at 100 ~ 120 ℃ after being applied in an amount of 1500 ~ 3000 mg / ㎡ by a post-treatment composition consisting of water.

When the adhesion amount of the post-treatment composition is less than 1500mg/m2, corrosion resistance is deteriorated, and when it exceeds 3000mg/m2, the thickness of the post-treatment coating film becomes too thick, resulting in a phenomenon that the coating film peels off during press processing or roll forming. .

Therefore, it is preferable that the adhesion amount of the post-treatment composition is 1500 to 3000 mg/m 2.

In addition, when the drying temperature is less than 100°C, the post-treatment solution is not properly dried, so that the post-treatment solution is deposited on the roll after the post-treatment process, and there is a problem that the physical properties after production are deteriorated.

On the other hand, when the drying temperature exceeds 120°C, fume is excessively generated, thereby reducing workability, and a phenomenon in which the post-treatment solution is burned occurs.

The present inventor evaluated the properties as follows while changing the post-treatment composition on the galvanized steel sheet containing magnesium.

<Adhesive amount>

The adhesion amount of the coating film was evaluated using an XRF instrument.

<appearance>

The appearance was evaluated by the presence or absence of roll marks generated by the rolls of the post-treatment equipment used for coating the post-treatment solution. The roll marks occurred in a vertical line, and were evaluated as 0 points when the roll marks occurred clearly and 5 points when the roll marks were uniformly coated without the roll marks.

<Corrosion resistance>

Corrosion resistance is 5% NaCl in the case of a flat part, 5 points if the occurrence of white rust is less than 5% after 500 hours at 35°C, 4 points if 10%, 3 points if 20%, 2 points if 30%, 1 if 40% or more It was evaluated as a point.

On the other hand, in the case of the processing part, by the Ericsson test method, 6 mm processing, 5% NaCl, after 5 hours at 35°C, the occurrence of white rust is within 5%, 5 points, 10% 4 points, 20% 3 points, 30 It was evaluated as 2 points if it is %, and 1 point when it is 40% or more.

<Moisture resistance>

Moisture resistance was tested with a colorimeter after 120 hours in an environment of 50°C and 90% humidity, 5 points if the before/after measured value satisfies ΔE≤3, 4 points if ΔE is 4 or less, 3 points if ΔE is 5 or less, It evaluated as 2 points when (DELTA)E is 6 or less, and 1 point when (DELTA)E is 7 or more.

In case of lamination, 20Kg _f /cm ² in 50℃ and 90% humidity environment Experimented with a colorimeter after 120 hours under load, 5 points if the before/after measured value is ΔE≤3, 4 points if ΔE is 4 or less, 3 points if ΔE is 5 or less, 2 points if ΔE is 6 or less, When (DELTA)E was 7 or more, it evaluated as 1 point.

<Chemical resistance>

5% alkali and 5% acid were used for chemical resistance, and each was dropped on the surface of a post-treated surface and cured for 5 minutes, and then tested with a color difference meter. Before and after the measured value was evaluated as 5 points when ΔE ≤ 3, 4 points when ΔE is 4 or less, 3 points when ΔE is 5 or less, 2 points when ΔE is 6 or less, and 1 point when ΔE is 7 or more.

<Friction coefficient>

The friction coefficient was measured using Alteck Mobility Tester.

<Coating adhesion>

The flat plate adhesiveness (Cross Cut Test) was evaluated by crossing the surface of the dried post-treated coating surface with a cutter knife at intervals of 1 mm to make 100 divisions, and then compressing and peeling the 3M transparent tape. The number of cells attached without being separated by the transparent tape among the 100 divisions was indicated.

The adhesion of the processed part (Cross Cut Erichsen Test) was evaluated by making 100 graduations on the surface of the post-treated surface in the same manner as the above method, and then performing a 6 mm Erichsen Test, compressing and removing 3M transparent tape. The number of cells attached without being separated by the transparent tape among the 100 divisions was indicated.

<Fingerprint resistance>

The anti-fingerprint property was evaluated by applying petrolatum on the surface of the post-treated surface and measuring the color difference before/after 1 hour using a colorimeter. ΔE ≤ 2 was evaluated as 5 points, ΔE was 3 or less, 4 points, ΔE was 4 or less, 3 points when ΔE was 5 or less, and 1 point when ΔE was 6 or more.

<Boiling water resistance>

When boiling water was heated to 100±3° C., immersed for 5 minutes, then taken out, bent to 0T 180°, and then 3M transparent tape was attached to the bending part and peeled, the peeling and cracking of the processed surface was evaluated. If it did not adhere to the transparent tape, it was evaluated as 5 points, and when peeling and cracking occurred, it was evaluated as 1 point.

Table 1 below shows examples and comparative examples according to the present invention.

Examples and comparative examples of post-treatment compositions Item Urethane/acrylic resin Co-
solvent wax Antifoam Wetting agent Cr compound Example 1 55 3.5 3 0.09 0.4 3 Comparative Example 1 55 0 3 0.08 0.4 3 Comparative Example 2 55 0.9 3.5 0.08 0.4 3 Comparative Example 3 55 6 3 0.09 0.4 3 Comparative Example 4 55 3 One 0.09 0.4 3 Comparative Example 5 55 3 6 0.09 0.4 3

[Table 2] below shows the evaluation results of Examples and Comparative Examples for the post-treatment composition of [Table 1] above.

Evaluation results of Examples and Comparative Examples 1 to 5 Item Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Adhesion amount (mg/㎡) 2000 2000 2000 2000 2000 2000 Exterior 5 5 5 5 5 5 Corrosion resistance reputation 5 3 4 5 5 5 Processing 5 3 4 5 5 5 Moisture resistance Type 5 5 5 5 4 5 Lamination 5 5 5 5 2 5 Chemical resistance alkali 5 One 3 5 5 5 mountain 5 One 3 5 5 5 Coefficient of friction 0.03 0.03 0.03 0.03 0.05 0.01 Adhesion reputation 100/100 80/100 80/100 100/100 100/100 100/100 Processing 100/100 30/100 50/100 100/100 100/100 100/100 Anti-fingerprint 5 4 5 4 4 5 Boiling water resistance 5 3 4 4 4 5

As can be seen from the evaluation results in [Table 2] above, the composition of the post-treatment solution has a great influence on the properties of the plated steel sheet.

[Table 3] below shows the evaluation of physical properties for each amount of the post-treatment composition.

Evaluation of physical properties by adhesion amount of post-treatment composition Item Comparative Example 6 Example 1 Example 2 Comparative Example 7 Adhesion amount (mg/㎡) 1000 2000 1500 5000 Exterior 5 5 5 5 Corrosion resistance reputation 3 5 5 5 Processing 2 5 5 5 Moisture resistance Type 4 5 5 5 Lamination 3 5 5 5 Chemical resistance alkali 4 5 5 5 mountain 4 5 5 5 Coefficient of friction 0.03 0.03 0.03 0.04 Adhesion reputation 100/100 100/100 100/100 100/100 Processing 100/100 100/100 100/100 80/100 Anti-fingerprint 5 5 5 5 Boiling water resistance 5 5 5 5

As can be seen from the above results, when the adhesion amount of the post-treatment coating layer is 1500 mg/m 2 or less, corrosion resistance decreases.

In addition, it can be seen that when the post-treated coating layer is excessively applied, workability and adhesion are deteriorated.

[Table 4] below shows the results of actual processing evaluation after property evaluation.

If it is judged that there is no problem in processing, O, there is no problem in processing, but when a small amount of post-processing peeling occurs or work is possible, but workability is considered to be poor, △, post-processing peeling causes a problem in processing. When abnormal processing is impossible or processing itself is impossible, it is denoted by X.

Actual processing evaluation result Item Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Press processing O X X O △ △ Roll forming O X X O △ X

In Table 2, Comparative Example 5 and Example 1 showed the same numerical values, but Comparative Example 5 exhibited a result that the workability was poor during press forming and that it was not processed due to overslip during roll forming.

In addition, Comparative Example 1 and Comparative Example 2, due to the lack of CO-solvent was poor adhesion, the phenomenon that the post-processing peeling during processing appeared.

In addition, in Comparative Example 4, the post-treatment coating layer was peeled during processing due to the lack of wax components, and in Comparative Example 5, excessive slip caused by excess wax components, and the roll and the material were not processed during roll forming. There was a problem.

Generally, when plating is performed by adding magnesium to a steel sheet, corrosion resistance is improved, but workability is deteriorated.

In addition, when the steel sheet is plated and then subjected to post-treatment coating for rust prevention, a problem occurs in that the adhesion between the plated steel sheet and the post-treatment composition decreases.

However, according to the present invention, the corrosion resistance can be improved by adding magnesium, so that the workability is not reduced.

In particular, by improving the adhesion between the plated steel sheet and the post-treatment composition, it is possible to manufacture a highly functional plated steel sheet excellent in corrosion resistance and workability.

The technical idea of the present invention has been described and illustrated as above, but the present invention is not limited to the configuration and operation as described above. Those of ordinary skill in the art will appreciate that many changes and modifications to the present invention are possible without departing from the scope of the technical spirit described in the claims. Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

10: possession cold rolled steel sheet
20: magnesium-zinc alloy layer (20)
30: post-treatment film layer (30)

Claims (3)

Cold rolled steel sheet 10;
A magnesium-zinc alloy layer 20 plated on the surface of the cold rolled steel sheet 10; And
The magnesium-zinc alloy layer 20 includes an organic resin-based post-treatment coating layer 30 formed on one or both sides of the cold-rolled steel sheet 10,
The magnesium-zinc alloy layer 20,
Based on the total composition of the alloy layer, aluminum is 1.1 to 1.7% by weight, magnesium is 1.1 to 1.7% by weight, zinc is galvanized steel sheet containing magnesium, characterized in that contains 96.6 to 97.8% by weight. The method according to claim 1,
The post-treatment composition for forming the post-treatment coating layer 30,
Based on the total composition of the post-treatment, urethane resin 20 ~ 30 wt%, acrylic resin 30 ~ 40 wt%, CO solvent 1 ~ 4 wt%, wax 3 ~ 4 wt%, wetting agent 0.1 ~ 0.5 wt%, antifoaming agent 0.05 ~ 0.1 Zinc plated steel sheet containing magnesium, characterized in that it consists of weight %, chromium compound 1.0 to 3.0 weight %, and the rest. In the manufacturing method of the galvanized steel sheet containing magnesium,
(a) pre-processing the cold-rolled steel sheet 10 (S10);
(b) annealing the base cold rolled steel sheet 10 (S20);
(c) plating the base cold rolled steel sheet 10 in a molten zinc plating bath containing magnesium (S30);
(d) forming a post-treated coating layer 30 on one or both sides of the magnesium-zinc plated steel sheet (S40),
The post-treatment coating layer 30 in the step S40,
Based on the total composition of the post-treatment, urethane resin 20 ~ 30 wt%, acrylic resin 30 ~ 40 wt%, CO solvent 1 ~ 4 wt%, wax 3 ~ 4 wt%, wetting agent 0.1 ~ 0.5 wt%, antifoaming agent 0.05 ~ 0.1 Weight%, chromium compound 1.0 ~ 3.0% by weight, the rest is coated with an amount of 1500 ~ 3000 ㎎ / ㎡ by a post-treatment composition made of water, and then magnesium is characterized by being formed by drying at 100 ~ 120 ℃ Method for manufacturing galvanized steel sheet.

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