KR20060083021A - Method for producing lubricated inorganic solution compositions and galvanized steel sheet coated thereof, having a good formability and weldability - Google Patents

Abstract

In the present invention, 3 to 15 parts by weight of fine particles of zinc oxide are added to 40 to 70 parts by weight of pure water as a lubricant, and 0.2 to 5 parts by weight of hydrophilic surfactant is added to the wetting agent and mixed evenly in an aqueous solution. In order to improve lubricity, 1 to 5 parts by weight of polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride, and polyvinyl butyral, which are polyvinyl compounds, are added in an amount of 1 to 5 parts by weight. It is essential to prepare a lubricating solution composition in which a turbid solution is dispersed by adding at least 5 parts by weight of sodium phosphate to 5 to 20 parts by weight, followed by dissolution and dispersing, and finally adding pure water so that the solid content is 10 to 30%. Shall be.

In addition, the lubricated solution prepared in the present invention is coated on a galvanized steel sheet so as to have an adhesion amount of 800 to 1300 mg / m 2 after drying, and a galvanized steel sheet having excellent workability and weldability by being baked in a steel sheet temperature of 60 to 200 ° C It is a main point to provide a surface treatment method.

Description

Process for producing lubricated inorganic solution compositions and galvanized steel sheet coated etc, having a good formability and weldability             

1 is a graph showing the molding ratio according to the lubricant content.

2 is a graph showing the molding ratio according to the lubricant adhesion amount.

The present invention relates to a method for producing a metal oxide-based lubricating solution composition excellent in surface lubricity and weldability to a galvanized steel sheet, in particular a hot dip galvanized steel sheet, and a method for treating a hot dip galvanized steel sheet using the same.

Hot-dip galvanized steel or alloyed hot-dip galvanized steel sheet, which is increasingly used as a steel sheet for automobiles, has an excellent corrosion resistance due to the sacrificial anticorrosion effect of the zinc alloy layer present on the surface. . However, these hot-dip galvanized steel sheets are difficult to use for parts requiring deep drawing since cracking occurs during press working.

Therefore, when the hot-dip galvanized steel sheet is used for parts requiring deep processing, steel sheets having higher elongation must be used as materials or lubricated steel sheets. However, in the case of using high-strength high-strength steel, the manufacturing cost is significantly increased as compared to the case of using the general steel, resulting in a product price increase. On the other hand, when lubricating the steel sheet has advantages in terms of cost because it can produce the effect using high grade steel using ordinary steel.

However, the conventional lubricating solution includes a wax-based lubricant and various additives based on the polymer resin. In this case, the surface-treated lubricant during the welding of the automobile body is oxidized under high temperature and high pressure welding conditions to form carbides, which adhere to the welding rod. Adhered carbides can disrupt the flow of current and ultimately shorten the life of the electrode.

Therefore, the present invention has been devised to replace various additives, such as a conventional organic polymer resin-based wax-based lubricants, such as inorganic zinc oxide powder of the fine particles to solve the above problems. In the case of replacing the inorganic fine particles, the lubricant powder does not burn during welding, which does not shorten the welding rod life and thus does not reduce the continuous weldability. In addition, the lubricating solution according to the present invention has a good adhesion and film-repellency, the film is removed in the degreasing process after welding the car body, the method of producing a high lubricating conductivity chromium-free steel plate excellent in weldability and workability does not affect the coating process afterwards It is an object of the present invention to provide.

Therefore, in the present invention, 3 to 15% by weight of fine particles of zinc oxide are added to 40 to 70% by weight of pure water as a lubricant, and 0.2 to 5% by weight of hydrophilic surfactant is added to the wetting agent and mixed evenly so as to be stable in an aqueous solution. In order to improve lubricity, 1 to 5% by weight of polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride, and polyvinyl butyral are added at 1 to 5% by weight. 5 to 20% by weight of one or more of the polymerized sodium phosphate is added by dissolving and mixing to dissolve the turbid solution to ensure stability and finally to add a pure water to prepare a lubricated solution composition so that the solid content is 10 to 30% Let's make a point.

In addition, the coated lubricating solution of the present invention is coated on a steel sheet so that the adhesion amount is 800 ~ 1300mg / m ² after drying, and by baking the steel sheet temperature in the range of 60 ~ 200 ℃ by excellent surface workability and weldability galvanized steel sheet surface treatment The main idea is to provide a method.

Hereinafter, the present invention will be described in more detail.

In preparing the lubricating solution of the present invention, as described above, first, 3 to 15% by weight of fine particles of zinc oxide powder are added to 40 to 70% by weight of pure water. Zinc oxide powder is used as a lubricant and usually uses nano-size ultrafine particles. When the zinc oxide powder is added below 3%, the effect of improving surface lubricity is insignificant. When the zinc oxide powder is added above 15%, the effect of improving the lubricity is not increased by partial aggregation of particles. It is preferable.

After the lubricant is added, 0.2 to 5% by weight of the hydrophilic surfactant is added and mixed sufficiently so that the lubricant powder is evenly dispersed in the aqueous solution. Since the particles of the lubricant powder are nano-sized particles, when the surfactant is added at 0.2% or less, the agglomeration of the particles may cause poor lubricity and stains on the surface of the coating film. Adhesion may be degraded and overall physical properties may fall.

Meanwhile, in order to improve lubricity and dispersibility, which are very important factors in the lubricating agent solution, polyvinyl-based additives are added in an amount of 1 to 5% by weight. As the polyvinyl-based additive, at least one of polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride, and polyvinyl butyral is selected. If the polyvinyl-based additives are added in less than 1%, the solution stability is lowered. If the polyvinyl additive is added in excess of 5%, it is an organic additive.

After the treatment, a phosphate-based additive is added in an amount of 5 to 20% by weight for the purpose of improving corrosion resistance, dispersibility and adhesion. As the phosphate additive, at least one selected from potassium pyrophosphate, sodium pyrophosphate, sodium phosphate tribasic, and sodium hexameter phosphate is selected. When the phosphate-based additive is added in less than 5%, the adhesion of the coating film is lowered, and when added in excess of 20%, the solution stability is lowered, so it is preferable to manage in the range of 5 to 20%.

After mixing all of these additives, the turbid solution is dispersed to ensure stability, and finally, pure water is added to dilute the solids to 10 to 30% of the conventional lubricating solution according to the present invention.

The present invention is coated with a lubricating solution prepared as described above by a roll coating to a dry adhesion amount based on 800 ~ 1300mg / m ² , and by drying it at a steel sheet temperature 60 ~ 200 ℃ temperature alloying melting excellent workability and weldability Galvanized steel sheet can be produced. As a result of repeated experiments, when the dry adhesion amount was less than 800 mg / m ^{2, the} effect of improving surface lubricity was not large. When the dry adhesion amount was greater than 1300 mg / m ² , the lubricity was rather deteriorated. In addition, if the surface coating steel sheet drying temperature is less than 60 ℃, the lubricating solution is not dried enough to ensure the physical properties, if the temperature is higher than 200 ℃ may change the properties of the steel sheet itself to manage in the range of 60 ~ 200 ℃ desirable. However, the steel sheet surface drying temperature is selected in an appropriate range depending on the type of lubricant, the surfactant, the coating amount of the lubricating solution based on the above-mentioned additives and dry weight.

Hereinafter, embodiments of the present invention will be described in detail.

(Example 1)

First, the relationship between the dry weight (mg / m ² ) and the molding ratio of the lubricant content (%) and the molding ratio (%) of the material steel sheet according to the application and drying of the lubricating solution was investigated. In the preparation of lubricating agent, add 50 parts by weight of zinc oxide powder to 1 to 19 parts by weight of pure water, add 4 parts by weight of surfactant, 2 parts by weight of polyvinyl butyral, and 18 parts by weight of sodium pyrophosphate to make solid content 24%. Dilution with pure water produced a lubricant. The relationship between lubrication agent content (%) and molding ratio (%) is shown. 1 is shown. In addition, the coating coating by changing the dry adhesion amount of the lubricating agent prepared in the range 300 ~ 1700mg / m ² , and evaluated the workability, it is shown in Figure 2 the results. 1 and 2, it can be seen that the lubricant has the lowest molding ratio at 13% and 1100 mg / m ² , respectively, and the moldability is improved. Based on the above results, 13% of the lubricant and 1100 mg / m ² of the dry coating weight were used as the standard. .

(Example 2)

13% by weight of zinc oxide powder was added as a lubricant to 50% by weight of pure water, and a surfactant, polyvinyl butyral as a polyvinyl additive, and sodium pyrophosphate as a phosphate additive were added in the amounts shown in Table 1, respectively. Dilution with pure water to 24% yielded Inventive Example No. 1-No. 8 and Comparative Example No. 1-No. 6.

The lubrication solution prepared as above, zinc coating weight 45g / m ^2, thickness 0.7㎜t, processing is applied so that the NQ-grade materials dried coating weight 1100mg / m ² on the steel sheet made by the air-cooling and dried at 60 ℃ and coating properties as follows: Was evaluated and the results are shown in Table 1 below.

The steel sheet produced by applying, coating, and drying the solution of the above-described composition of Table 1 was tested for physical properties as follows.

[Processability] The workability evaluation was performed by drawing cups and then drawing cups to determine the molding ratio. Molding ratio is defined by the following equation.

Forming ratio = (maximum punch load of lubricated steel sheet / maximum punch load of unlubricated steel sheet) x100 (%)

Workability evaluation (double-circle): Molding ratio less than 93%, (circle): Molding ratio less than 95%, (triangle | delta): Molding ratio less than 98%, X: Molding ratio 98% or more

[Weldability] The weldability evaluation was performed by a stationary spot welder to evaluate the continuous weldability under conditions of 8 kA, 250 kgf, and 14 cycles of pressing force. The size of the nugget formed every 100 RBI intervals was measured, and the time when the diameter fell below 4√t was set as the value of continuous weldability.

Continuous weldable RBI: ◎: 1000 RBI or more, ○: 700 RBI or more, △: 300 RBI or more, X: 300 RBI or less

[Film removal property] The film removal property was evaluated by immersing the steel plate in a degreased liquid stirred for 3 minutes while drying the A, B materials of Samyang Chemical (trade name: Galardoclean 4292L) and heating to 55 ° C, and measured by a color difference meter (Minolta). Was compared with that of an unlubricated hot dip galvanized steel sheet. At this time, the color difference is evaluated by ΔL value.

Film release evaluation (ΔL) ◎: less than 1, ○: less than 2, △: less than 3, X: 3 or more

[Surface Appearance] The surface appearance was evaluated by visual observation and touch.

Surface appearance evaluation ◎: No stain at all, ○: Some stain, △: The stain is clearly visible, X: The stain is touched when the stain is touched by hand

Solution Stability Solution stability was evaluated by an immersion test. The immersion test was evaluated by pouring 1 L of lubricating solution into the measuring cylinder, leaving it to stand for 1 hour, and then reading the volume of the settled solids.

Solution stability (double-circle): Less than 10 mL, (circle): Less than 50 mL, (triangle | delta): Less than 100 mL, X: More than 100 mL

TABLE 1

division   Surfactants(%)   Poly vinyl system (%) Phosphate salt (%) Machinability Weldability Membrane Surface appearance  Solution stability  Remarks     Inventive Example (1) No. One 4 4 18 ◎ ○ ◎ ◎ ◎ No. 2 4 4 6 ◎ ○ ◎ ◎ ◎ No. 3 4 2 18 ◎ ◎ ◎ ◎ ◎ No. 4 4 2 6 ◎ ◎ ◎ ◎ ○ No. 5 One 4 18 ◎ ○ ○ ○ ◎ No. 6 One 4 6 ○ ○ ◎ ○ ◎ No. 7 One 2 18 ◎ ◎ ◎ ○ ◎ No. 8 One 2 6 ○ ◎ ◎ ○ ○    Comparative Example (2) No. One 3 3 2 ◎ ○ ◎ △ △ No. 2 3 3 25 ◎ ○ △ ○ ○ No. 3 3 10 14 ◎ △ ○ ○ ○ No. 4 3 0.5 14 ○ ○ ○ △ △ No. 5 0.2 3 14 Ⅹ ○ ○ △ △ No. 6 10 3 14 △ ○ ○ ◎ ○

The results obtained by analyzing and evaluating the results of Table 1 by comparing the invention examples with the comparative examples are as follows.

Invention Example No.1-No.8

After preparing a solution composition of the present invention in which a surfactant, a polyvinyl-based additive, and a phosphate-based additive were mixed in the condition range of the present invention, the product coated on the steel sheet was evaluated, and showed excellent physical properties as shown in Table 1 above. . Among them, No. 3 samples showed excellent results over all of the physical properties, and No. 5 and No. 6 samples showed relatively poor weldability and surface appearance.

[Comparative Example No.1-No.2]

When 2% of pyrophosphate, a phosphate-based additive, was added below the condition range, the dispersibility of the lubricating solution could not be secured, and the surface appearance and solution stability did not meet the standards. Due to the adhesion of the phosphate-based additives, the lubricating film was not completely removed during degreasing, indicating poor film removal properties.

[Comparative Example No.3-No.4]

When the polyvinyl-based additive polyvinyl butyral is added in excess of 10%, the content of organic matter increases, which causes continuous weldability defects. When the content is less than 0.5%, the dispersibility is poor and the surface appearance and solution stability are poor. It was inferior.

[Comparative Example No. 5-No. 6]

When a small amount of the surfactant was added at 0.2%, the dispersion of the lubricant powder was not properly achieved, resulting in inferior processability and poor surface appearance and solution stability. When the surfactant was added in excess of 10%, the lubricant powder partially coagulated and showed poor workability.

According to the present invention, an efficient lubricating solution and a steel sheet capable of deep processing coated with this solution were obtained. As described above, excellent physical properties in workability, weldability, film removal, surface appearance, and the like were obtained.

Claims (2)

In the method for producing a lubricating solution for improving workability and weldability of an alloy galvanized steel sheet, 3 to 15 parts by weight of fine particles of zinc oxide powder, 0.2 to 5 parts by weight of a hydrophilic surfactant, and polyvinyl A lubricating solution composition prepared by dissolving and mixing 1 to 5 parts by weight of a system additive and 5 to 20 parts by weight of a phosphate additive and adding pure water thereto so that a solid content is 10 to 30% of a conventional solid content. After applying the lubricating solution of claim 1 to the plated steel sheet so that the lubricant adhesion amount after drying to 800 ~ 1300mg / ㎡, the baking treatment at the steel plate temperature 60 ~ 200 ℃ characterized in that the excellent workability and weldability of the plated steel sheet Manufacturing method.

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