KR102170061B1 - 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-performance plated steel sheet manufactured thereby, wherein when the post-treatment coating is performed after the manufacture of a hot-dip galvanized steel sheet containing magnesium, the base steel sheet and the post-treated coating layer and The purpose of this is to improve the adhesion of the material and improve the corrosion resistance by the addition of magnesium while preventing the workability from deteriorating.
To this end, the present invention, the holding cold-rolled steel sheet 10; A magnesium-zinc alloy layer 20 plated on the surface of the cold-rolled steel sheet 10; And an organic resin-based post-treatment coating layer 30 formed on one or both surfaces of the cold-rolled steel sheet 10 on which the magnesium-zinc alloy layer 20 is formed, and the magnesium-zinc alloy layer 20 Silver, based on the total composition of the alloy layer, characterized in that it contains 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.

Description

Post-treatment composition of galvanized steel sheet containing magnesium and plated steel sheet manufactured therefrom {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 galvanized steel sheet containing magnesium and a high-performance plated steel sheet manufactured thereby, and more particularly, to improve the adhesion of the coated steel sheet to the plated steel sheet manufactured in a continuous hot dip plating process line. It relates to a post-treatment composition for a galvanized steel sheet containing magnesium capable of producing a high-functional coated steel sheet having excellent corrosion resistance and workability by applying a possible post-treatment composition, and a coated steel sheet manufactured thereby.

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

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

On the other hand, in order to prevent slip property from deteriorating during processing, an organic post-treatment coating is sometimes applied, and in this case, there is a disadvantage in that corrosion resistance is lowered compared to the inorganic post-treatment coating method containing chromium.

In addition, magnesium is sometimes added to improve the corrosion resistance of the steel sheet.

However, in this case, magnesium oxide is formed on the surface of the holding steel plate by oxidation during cooling after the holding steel plate is immersed in the pot.

In this way, when the magnesium oxide layer is formed on the surface of the holding steel sheet, there is a problem that the adhesion between the holding steel sheet and the post-treatment coating liquid is very deteriorated during post-treatment coating.

Korean Patent Application Publication No. 10-2017-0076258 (2017.07.04.) Korean Patent Application Publication No. 10-2015-0075183 (2015.07.03.)

The present invention is to solve the above problems of the prior art, and when post-treatment coating is performed after the manufacture of a hot-dip galvanized steel sheet containing magnesium, it is an object of the present invention to improve the adhesion between the base steel sheet and the post-treated coating layer. .

Another object of the present invention is to make it possible to manufacture a plated steel sheet that does not deteriorate workability while improving corrosion resistance by the addition of magnesium.

The galvanized steel sheet containing magnesium according to the present invention for achieving the above object comprises: a cold-rolled steel sheet; A magnesium-zinc alloy layer plated on the surface of the base cold-rolled steel sheet; And a post-treatment coating layer of an organic resin base formed on one or both surfaces 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 total composition of the alloy layer, It is characterized in that it contains 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 forming the post-treatment coating layer is based on the post-treatment composition, based on the post-treatment composition, 20 to 30% by weight of urethane resin, 30 to 40% by weight of acrylic resin, 1 to 4% by weight of CO-solvent, and 3 to 4 of wax. It is characterized in that it consists of weight%, wetting agent 0.1 ~ 0.5% by weight, antifoaming agent 0.05 ~ 0.1% by weight, chromium compound 1.0 ~ 3.0% by weight, the rest is made of water.

In addition, the method of manufacturing a galvanized steel sheet containing magnesium according to the present invention includes the steps of: (a) pre-treating 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-treatment coating layer on one or both sides of the magnesium-zinc plated steel sheet (S40), and the post-treatment coating layer in the step S40 is 20 to 30% by weight of urethane resin, 30% by weight of acrylic resin. ~ 40% by weight, CO solvent 1 ~ 4% by weight, wax 3 ~ 4% by weight, wetting agent 0.1 ~ 0.5% by weight, antifoaming agent 0.05 ~ 0.1% by weight, chromium compound 1.0 ~ 3.0% by weight, the rest is water It is characterized in that it is formed by coating in an amount of 1500 to 3000 mg/m 2 and then drying at 100 to 120°C.

According to the present invention, when the post-treatment coating is performed after the manufacture of a hot-dip galvanized steel sheet containing magnesium, there is an effect of improving the adhesion between the base steel sheet and the post-treated coating layer.

In addition, the addition of magnesium has an effect of manufacturing a plated steel sheet that improves corrosion resistance and does not deteriorate workability.

This makes it possible to manufacture a high-functional magnesium-containing galvanized steel sheet having excellent corrosion resistance and workability.

1 is a schematic cross-sectional view of a plated steel sheet to which a post-treatment composition according to the present invention is applied.
Figure 2 is a flow chart showing the manufacturing process of the high-performance 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 FIG. 1, includes a cold-rolled steel sheet 10, a magnesium-zinc alloy layer 20 plated on the surface of the cold-rolled steel sheet 10, and , And an organic resin-based post-treatment coating layer 30 formed on one or both surfaces of the cold-rolled steel sheet 10 on which the magnesium-zinc alloy layer 20 is formed.

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

In addition, the magnesium-zinc alloy layer 20 preferably contains 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, based on the total composition of the alloy layer. .

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 ~ 4% by weight, wax (Wax) 3 ~ 4% by weight, wetting agent (wetting agent) 0.1 ~ 0.5% by weight, antifoaming agent 0.05 ~ 0.1% by weight, chromium compound 1.0 ~ 3.0% by weight, the rest is 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, respectively, the role of the binder decreases, and physical properties such as corrosion resistance, chemical resistance, blackening resistance, and adhesion are decreased.

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

CO-solvent is added to form a smooth coating.

When the content of the CO-solvent is less than 1% by weight, chemical resistance is deteriorated, and when it exceeds 4% by weight, fume is generated during drying, which interferes with the operation.

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

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

In addition, when the content of the wax exceeds 4% by weight, a problem occurs in processing due to excessive slip.

Wetting agents and antifoaming agents are added to realize 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, respectively, a roll mark defect in which the shape of the roll is transferred during roll coating for painting occurs, and the coating film cannot be spread properly, causing 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 deteriorated, and when it exceeds 3% by weight, the solution is gelled.

Meanwhile, a method of manufacturing a galvanized steel sheet containing magnesium according to the present invention includes the steps of: (a) pre-treating the cold-rolled steel sheet 10 (S10); (b) annealing the 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-treatment coating layer 30 on one or both surfaces of the magnesium-zinc plated steel sheet (S40).

In addition, the post-treatment coating layer 30 in the S40 step is 20 to 30% by weight of urethane resin, 30 to 40% by weight of acrylic resin, 1 to 4% by weight of CO solvent, 3 to 4% by weight of wax, 0.1 to 0.5% wetting agent It is formed by applying in an amount of 1500 to 3000 mg/m 2 by weight %, antifoaming agent 0.05 to 0.1 weight %, chromium compound 1.0 to 3.0 weight %, and the remainder in an amount of 1500 to 3000 mg/m2 with water and then drying at 100 to 120°C.

When the adhesion amount of the post-treatment composition is less than 1500 mg/m 2, the corrosion resistance decreases, and when the amount of the post-treatment composition exceeds 3000 mg/m 2, the thickness of the post-treatment coating becomes too thick, causing the coating film to peel off during press processing or roll forming. .

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

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

On the other hand, when the drying temperature exceeds 120° C., fume is generated excessively, resulting in reduced workability and burning of the post-treatment solution.

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

<Attachment amount>

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

<Appearance>

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

<corrosion resistance>

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

On the other hand, in the case of the processed part, according to the Ericsson test method, 5 points if the occurrence of white rust after 120 hours at 6 mm processing, 5% NaCl, 35°C is within 5%, 4 points if 10%, 3 points if 20%, and 30 If it is %, it was evaluated as 2 points, and if it was 40% or more, it was evaluated as 1 point.

<Moisture resistance>

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

In the case of lamination, 20Kg _f /cm ² at 50℃ and 90% humidity After 120 hours with a load applied, the experiment was performed with a colorimeter, and if the measured value before/after ΔE ≤ 3, 5 points, 4 points when ΔE is 4 or less, 3 points when ΔE is 5 or less, and 2 points when ΔE is 6 or less, If ΔE was 7 or more, it was evaluated as 1 point.

<Chemical resistance>

For chemical resistance, 5% alkali and 5% acid were used, and each was dropped on the surface of the post-treated coating surface, cured for 5 minutes, and then tested with a colorimeter. If the measured values before and after ΔE ≤ 3, 5 points, 4 points if ΔE is 4 or less, 3 points if ΔE is 5 or less, 2 points if ΔE is 6 or less, and 1 point if ΔE is 7 or more.

<Friction coefficient>

The coefficient of friction was measured using the Alteck Mobility Tester.

<Coating film adhesion>

Flat plate adhesion (Cross Cut Test) was evaluated by crimping the dried post-treated painted surface at intervals of 1 mm with a cutter knife to make 100 scale compartments, and then compressing the 3M transparent tape and removing it. Out of 100 scale cells, the number of cells attached without being separated by a transparent tape is indicated.

The cross cut Erichsen test was evaluated in the same manner as in the above method, after making 100 graduations on the surface of the post-treated coating surface and then conducting the 6 mm Erichsen test, and then pressing and removing the 3M transparent tape. Out of 100 scale cells, the number of cells attached without being separated by a transparent tape is indicated.

<fingerprint resistance>

Fingerprint resistance was evaluated by applying petrolatum to the surface of the post-treated coating surface and measuring the color difference before/after 1 hour using a color difference meter. If ΔE≤2, it was evaluated as 5 points, if ΔE was 3 or less, 4 points, if ΔE was 4 or less, 3 points, if ΔE was 5 or less, 2 points, and if ΔE was 6 or more, it was evaluated as 1 point.

<Naeboiling Mercury>

For boiling water resistance, pure water was heated to 100 ± 3°C, immersed for 5 minutes, taken out, and bent at 0T 180°, and when a 3M transparent tape was attached and removed on the bending part, peeling and cracking of the processed surface were evaluated. The evaluation was made as 5 points if not stained on the transparent tape, and 1 point if peeling and cracking occurred.

[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 part 5 3 4 5 5 5 Moisture resistance Sheet 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 part 100/100 30/100 50/100 100/100 100/100 100/100 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 physical properties of the plated steel sheet.

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

Evaluation of 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 part 2 5 5 5 Moisture resistance Sheet 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 part 100/100 100/100 100/100 80/100 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 is deteriorated.

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

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

If it is judged that there is no problem in processing, O, if there is no problem in processing, but a small amount of post-treatment peeling occurs, or if it is judged that the work is possible but workability is poor, When abnormal processing is impossible or when processing itself is impossible, it is marked with an X.

Actual machining 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 exhibited the same numerical values, but Comparative Example 5 showed a result of poor workability during press processing and not being processed due to excessive slip during roll forming processing.

In addition, Comparative Examples 1 and 2 showed a phenomenon in which post-treatment peeled off during processing due to poor adhesion due to lack of CO-solvent.

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

In general, when magnesium is added to the steel sheet to be plated, corrosion resistance is improved, but there is a disadvantage of lowering workability.

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

However, according to the present invention, it is possible to improve the corrosion resistance by the addition of magnesium and prevent the workability from deteriorating.

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

Although the technical idea of the present invention has been exemplarily described and illustrated above, the present invention is not limited to the configuration and operation as described above. Those of ordinary skill in the art will appreciate that a number of changes and modifications can be made to the present invention without departing from the scope of the technical idea described in the claims. Accordingly, all such appropriate changes and modifications and equivalents should be considered to be within the scope of the present invention.

10: cold rolled steel sheet
20: magnesium-zinc alloy layer 20
30: post-treatment coating layer 30

Claims (3)

delete Base cold rolled steel sheet 10;
A magnesium-zinc alloy layer 20 plated on the surface of the cold-rolled steel sheet 10; And
And an organic resin-based post-treatment coating layer 30 formed on one or both surfaces of the cold-rolled steel sheet 10 on which the magnesium-zinc alloy layer 20 is formed,
The magnesium-zinc alloy layer 20,
In the galvanized steel sheet containing magnesium 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, based on the total composition of the alloy layer,
The post-treatment composition for forming the post-treatment coating layer 30,
Based on the total post-treatment composition, 20 to 30% by weight of urethane resin, 30 to 40% by weight of acrylic resin, 1 to 4% by weight of CO solvent, 3 to 4% by weight of wax, 0.1 to 0.5% by weight of wetting agent, 0.05 to 0.1 of antifoam A galvanized steel sheet containing magnesium, characterized in that the weight%, the chromium compound 1.0 ~ 3.0% by weight, the rest is made of water. In the method of manufacturing a galvanized steel sheet containing magnesium,
(a) pre-treating the base cold-rolled steel sheet 10 (S10);
(b) annealing the 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) including the step (S40) of forming a post-treatment coating layer 30 on one or both sides of the magnesium-zinc plated steel sheet,
The post-treatment coating layer 30 in the step S40,
Based on the total post-treatment composition, 20 to 30% by weight of urethane resin, 30 to 40% by weight of acrylic resin, 1 to 4% by weight of CO solvent, 3 to 4% by weight of wax, 0.1 to 0.5% by weight of wetting agent, 0.05 to 0.1 of antifoam Magnesium-containing, characterized in that it is formed by drying at 100 to 120°C after applying in an amount of 1500 to 3000 mg/m 2 by weight%, 1.0 to 3.0% by weight of chromium compounds, and the remainder by a post-treatment composition consisting of water Manufacturing method of galvanized steel sheet.

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