KR100554740B1 - Manufacturing method of electro galvanized steel sheet with phosphate coating - Google Patents

Abstract

Provided is a method for manufacturing an electrogalvanized steel sheet having a phosphate coating.

In the present invention, after immersing an electrogalvanized steel sheet in a phosphate treatment solution, washing with water and drying to produce an electrogalvanized steel sheet formed with a phosphate coating, the amount of phosphate deposited on the surface of the electrogalvanized steel sheet, 3.0 ~ Zn ⁺² ions containing 5.1 g / l to 8.0 g / l so as to be 5.0 g / m ² , the free acidity and acidity are in the range of 0.3 to 2.0 pt and 5 to 15 pt, and Ni and Mn are The present invention relates to a method for producing a galvanized steel sheet having excellent workability and degreasing property, which is immersed in a phosphate treatment solution not included.

Galvanized steel sheet, phosphate solution, degreasing, phosphate coating

Description

A method for manufacturing a electro-galvanized steel sheet having the phosphated film formed thereon}

The present invention relates to a method for producing an electro-zinc plated steel sheet having a phosphate coating capable of improving the degree of processing when forming a galvanized steel sheet, and more particularly, a phosphate solution in which the galvanized steel sheet does not contain Ni and Mn ions. The present invention relates to a method for producing an electro-zinc plated steel sheet having improved workability and degreasing properties by coating phosphate on the surface thereof by dipping in phosphate.

In general, a galvanized steel sheet for automobiles is formed with a phosphate coating to improve the processability during molding. Conventional iron phosphate-based and manganese-phosphate-based phosphate treatment solutions have been used as phosphate solutions to form the phosphate coating. Recently, a small amount of nickel and manganese were added to the conventional phosphate-zinc phosphate treatment solution to obtain a fine crystal size. The film adhesion is improved by making it uniform.

As described above, examples of the prior art in which Ni and Mn are added to the phosphoric acid solution include the inventions disclosed in Japanese Patent Application No. Hei 11-337301 and Korean Patent Application 1997-3802. For example, in the Korean patent application, in the method of manufacturing a phosphate-treated electrogalvanized steel sheet, a phosphate treatment solution containing 1000 to 3000 ppm zinc, 50 to 300 ppm nickel, and 300 to 2000 ppm manganese is prepared for each ion content composition ratio. To prepare the concentration of the solution in the range of 1.5 ~ 5.0%; Forming a coating layer on the surface adjustment agent treatment layer pretreated in the steel sheet so as to have a coating deposition amount in a range of 0.5 to 3.0 g / m ₂ by using a temperature of the phosphate treatment solution in a range of 40 to 70 ° C .; The manufacturing method of electro galvanized steel sheet is shown.

These technologies used Ni, Mn-containing phosphoric acid solution to secure the coating amount required to improve processability and corrosion resistance, but Ni and Mn formed a passivation film on the surface of the steel sheet, and due to inadequate zinc ion content, There has been a problem that oily deterioration and paint blister deteriorate accordingly and its application to the steel sheet for automobiles is difficult.

Accordingly, the present invention is to solve the problems of the prior art described above, by improving the coating amount by adjusting the concentration of the Zn ion component in the phosphate treatment solution for forming the phosphate coating, and by eliminating the addition of Ni, Mn It is an object of the present invention to provide a method for producing a plated steel sheet having a phosphate coating which can be applied to a steel sheet for automobiles by preventing passivation coating.

Hereinafter, the present invention will be described.

In order to improve the workability of the automotive galvanized steel sheet, the coating amount is essential. In the related art, the coating amount was determined by adjusting the Ni and Mn components. However, as described above, the Ni and Mn components in the phosphate treatment solution form a passivation film in the steel sheet, which deteriorates the degreasing properties during automobile degreasing, and thus the coating property is also worsened, making it difficult to use.

Therefore, the present invention has been repeated many experiments and studies to solve this problem, as a result, phosphate having excellent adhesion by appropriately adjusting the concentration of zinc ions and acidity of the solution without adding Ni and Mn to the phosphate treatment solution It is to find that the film can be formed and to present the present invention.

Therefore, the present invention, after immersing the electro-galvanized steel sheet in a phosphate treatment solution, and washed with water and dried to produce an electro-galvanized steel sheet formed with a phosphate coating,

The galvanized steel sheet is composed of Zn ^{+ 2} ions 5.1 g / l to 8.0 g / l such that the amount of phosphate attached to the surface thereof is 3.0 to 5.0 g / m ² , and the free acidity and acidity are The present invention relates to a method for producing a galvanized steel sheet having excellent workability and degreasing property, which is in the range of 0.3 to 2.0 pt and 5 to 15 pt, and is immersed in a phosphate treatment solution containing no Ni and Mn.

 Hereinafter, the present invention will be described in detail.

The present invention can be applied irrespective of the type of steel sheet as long as it is a phosphate treated steel sheet formed by phosphoric acid treatment after surface-adjusting the steel sheet coated with zinc. When the phosphate coating treatment is performed on these steel grades, the coating amount is determined by the phosphate solution ion composition and its acidity. As a result, the processability and degreasing property are determined.

In the case of the present invention, when the phosphate treatment is performed on the base material on which the electrogalvanized layer is formed, it is required to attach the phosphate film in the range of 3.0 g to 5.0 g / m 2 in order to improve the degreasing property, which means that the phosphate coating amount is 3.0. If it is out of the range of ~ 5.0g / ㎡, degreasing properties of the automobile company deteriorates and the paint blister deteriorates.

Therefore, in the present invention, it is very important to manage the composition of the phosphate treatment solution in order to secure the proper coating amount.

That is, in the present invention, as described above, in order to form a phosphate film on the galvanized steel sheet, the phosphate treatment solution should be a Ni, Mn-free solution without Ni, Mn added. When Ni and Mn are present in the phosphate treatment solution, a passivation film is formed, and thus, the removal of these components is necessary. However, when the removal of these components is performed, it is difficult to secure the coating amount.

In other words, in the present invention, it is possible to secure the film deposition amount by removing Ni and Mn ions in the phosphate treatment solution and adding Zn ⁺² ions in an appropriate concentration, and removing the passive film in the film by Ni, Mn-free. It is possible to manufacture a product with improved coating performance by improving the degreasing during yarn processing.

Therefore, the phosphate treatment solution of the present invention is formulated to contain a concentration of 5.1 to 8.0 g / l of Zn ⁺² ions, and its free acidity and acidity are in the range of 0.3 to 2.0 pt and 5 to 15 pt, including Ni and Mn. It is characterized by not being.

In the present invention, Zn ^{+ 2} ions are the main components of the phosphate treatment solution, and the amount of coating may vary depending on the concentration thereof.

In the present invention, the concentration of such Zn ⁺² ions is limited to 5.1 to 8.0 g / l. If the concentration is less than 5.1g / l, it is impossible to secure the coating weight of 3.0g ~ 5.0g / ㎡, and the workability is deteriorated.If the concentration exceeds 8.0g / l, the amount of phosphate coating is also decreased. Because I bet.

In addition, in the present invention, the free acidity of the phosphate treatment solution is managed in the range of 0.3 to 2.0 pt. When the free acidity is low, the film forming reaction becomes difficult in the passage of time in the continuous line. This is because steel sheet performance is rather deteriorated.

After immersing the galvanized steel sheet in the phosphate treatment solution thus prepared, the immersed steel sheet is washed with water and dried in a conventional manner to produce an electro-zinc plated steel sheet.

When the phosphate film is formed on the lead-plated steel sheet using the phosphate treatment solution of the present invention as described above, the passivation film is formed on the surface of the steel sheet by the Ni and Mn components, thereby effectively preventing degreasing property. Phosphate coating galvanized steel sheet excellent in degreasing properties can be produced.

Hereinafter, the present invention will be described in detail through examples.

(Example)

When the film is formed on the galvanized steel sheet using the phosphate treatment solution prepared as in the present invention, it satisfies the coating deposition amount of 3.0 ~ 5.0g / ㎡, thereby producing a plated steel sheet excellent in workability and degreasing properties In order to confirm that the following experiment was carried out.

That is, after cutting a large number of galvanized steel sheets having a zinc deposition amount of 20 g / m 2 to 300 x 300 mm, surface adjustment was performed for 2 seconds using 40 ° C Ti solution (PL-Z), which is usually used before phosphate coating. . Each of the steel sheets surface-adjusted as described above was immersed in the phosphate treatment solution prepared as shown in Table 1, then washed with water and dried to form a phosphate film on the surface. At this time, the acidity of the treatment solution was carried out under the conditions of free acidity 1.0, which is an appropriate management range, and acidity 10pt.

Phosphoric acid film adhesion amount, processability, degreasing property and coating performance of each steel sheet thus produced were measured, and the results are also shown in Table 1.

In this experiment, the amount of phosphate coating was measured by wet analysis, and the processability was applied to the conventionally used Eriksen processing limit. In addition, degreasing performance was evaluated by degreasing at about 60 ° C. by spraying for about 20 to 25 seconds using a degreasing solution (NaOH) commonly used by automobile companies. The paintability was carried out using the electrodeposition coating of the automobile company, and the coating properties were evaluated through the hot water test (Cross Cut 1 x 1mm) and the salt water temperature test (Tape peeling test).

On the other hand, the Eriksen threshold, which is the workability index, indicates that the higher the numerical value, the better the workability, and the higher the degreasing ratio in the degreasing treatment after degreasing. And paint peelability is an experimental value of tape peeling, which means that the lower the value, the better the result.

Phosphate Treatment Solution Glass Top (Computational) Phosphate Coating Amount Degreasing (%) Machinability (Ericsen limit value: mm) Peelability of Coating (mm) Inventive Example One -Ni, Mn free -Zn ⁺² ions: 5.1 g / l 1.0 (10.0) 3.05 g 80.5 9.4 0.31 2 -Ni, Mn free -Zn ⁺² ions: 7.0 g / ℓ 1.0 (10.0) 3.99g 82.8 9.6 0.29 3 -Ni, Mn free -Zn ⁺² ions: 8.0 g / l 1.0 (10.0) 4.98 g 82.3 9.5 0.350 Comparative example One -Ni, Mn free -Zn ⁺² ions: 3.0 g / l 1.0 (10.0) 2.8 g 49.8 8.9 2.8 2 -Ni, Mn free -Zn ⁺² ions: 5.0 g / l 1.0 (10.0) 2.99g 79.5 9.1 1.01 3 -Ni, Mn free -Zn ⁺² ion: 8.1g / ℓ 1.0 (10.0) 5.05 g 76.5 9.1 1.10 4 -Ni, Mn free -Zn ⁺² ions: 9.0 g / l 1.0 (10.0) 2.55g 43.3 8.4 2.32 5 -Ni, Mn free -Zn ⁺² ions: 10.0 g / ℓ 1.0 (10.0) 1.49 g 36.5 7.5 2.35 Conventional example One -Ni: 7 g / l or less-Mn: 2 g / l or less-Zn ⁺² ions: 0.5 to 5.0 g / l 1.0 (10.0) 0.5-3.0 g 5.0-37.0 7.1-8.4 1.7-3.0

As shown in Table 1, in the examples (1 to 3) of the present invention using a phosphate treatment solution in which Zn ⁺² ion concentration was controlled to 5.1 g / L to 8.0 g / L and Ni and Mn were not added, It can be seen that the coating amount of phosphate coating can be controlled within the scope of the present invention, so that it is possible to manufacture an electro-zinc plated steel sheet capable of securing workability and degreasing property and greatly improving paint peelability.

On the contrary, Comparative Examples (1 to 2) having a lower concentration of Zn ⁺² ions than the present invention generally improved the degreasing property, but generally did not reach the degreasing level (80%) required by the automobile company. It can be seen that the workability (Erichsen limit) and paint peeling property are insufficient due to the decrease, and even in Comparative Examples (3 to 5) where the concentration of Zn ^{+ 2} ions is higher than that of the present invention, the deposition rate of phosphate film is lowered to obtain a steel sheet having excellent physical properties. It can be seen that.

In addition, the conventional example using a phosphate treatment solution containing Ni, Mn and the concentration of Zn ⁺² controlled at 0.5 to 5.0 g / l is very bad with 5 to 37% degreasing property. Phosphoric acid adhesion was decreased due to the formation of Mn passivation film and the decrease of Zn ⁺² concentration.

As described above, the present invention can optimally maintain the amount of phosphate coating adhering to the surface of the steel sheet by appropriately controlling the composition of the phosphate treatment solution and its zinc ion concentration, ensuring workability, and degreasing properties and Phosphate-coated electrogalvanized steel sheet with excellent paintability can be produced effectively.

Claims (1)

In immersing an electrogalvanized steel sheet in a phosphate treatment solution, washing with water and drying to produce an electrogalvanized steel sheet having a phosphate coating, The galvanized steel sheet is composed of Zn ^{+ 2} ions 5.1 g / l to 8.0 g / l such that the amount of phosphate attached to the surface thereof is 3.0 to 5.0 g / m ² , and the free acidity and acidity are A method for producing a galvanized steel sheet having excellent workability and degreasing property, which is in the range of 0.3 to 2.0 pt and 5 to 15 pt, and is immersed in a phosphate treatment solution containing no Ni and Mn.