KR0164960B1 - Zn-sn two layer coated steel sheet and production thereof - Google Patents

Abstract

The present invention relates to a zinc / tin two-layer plated steel sheet excellent in corrosion resistance, adhesion, and solderability and a method of manufacturing the same.

Conventional plating methods are hot-dip galvanizing and electroplating methods, but it is not easy to control the adhesion amount control, plating of material system with high melting point is impossible, deterioration of coating layer occurs, and workability is deteriorated. There is a problem in that operational efficiency is lowered and pollution prevention facilities need to be added.

In order to solve these problems, the present invention produced a zinc / tin two-layer plated steel sheet by a plating method by vacuum deposition.

Description

Zinc / tin two-layer coated steel sheet with good adhesion and solderability and manufacturing method

The present invention relates to a zinc / tin two-layer plated steel sheet excellent in corrosion resistance, adhesion, and solderability and a method of manufacturing the same.

Plating system widely used as an important industrial material to prevent corrosion of steel, such as automobiles, home appliances, building materials, etc., is a zinc-plated system that uses zinc sacrificial anticorrosion as the mainstream. It is widely used throughout. However, zinc has a reddish blue color after 100 hours in the salt spray test even when the coating weight is 100 g / m 2 or more. In order to improve corrosion resistance and other properties, development of various zinc alloy plated steel sheets and two-layer plated steel sheets has been proposed. As the plating method, the hot-dip plating method and the electro-plating method are used, but there are limitations in the combination of the alloy composition and the two-layer plating operation in manufacturing them by the hot-dip plating method and the electro-plating method. The hot dip coating method is not easy to control the adhesion control (patent 20g / ㎡ or less) due to the characteristics of the equipment, and it is impossible to plate the material with high melting point, and deterioration of the coating layer due to alloy layer formation at the interface between the base steel sheet and workability is achieved. This is followed by stabilization in the operating conditions where additional alloying inhibitors are required and material system constraints. In addition, the electroplating method has problems such as manufacturing stability, productivity, economical efficiency in the industrial equipment, a decrease in operating efficiency due to hydrogen generation reaction in aqueous solution, and the need to add pollution prevention facilities.

In order to solve these problems, the present invention focuses on the plating method by vacuum deposition instead of the hot dip plating method and the electroplating method. The plating method by vacuum evaporation can be arbitrarily controlled from thin plating to after plating, so that double-side plating, one-side plating, deviation plating, etc. can be performed continuously, and the composition control of alloy plating and the combination of two-layer plating are also compared with other plating methods. It is easy. However, in the vacuum plating method, adhesion to the steel sheet by iron oxide on the steel sheet is carried out by performing electrolytic degreasing, which is a process of removing oil or other impurities on the steel sheet depending on the material system such as zinc and zinc plating. Not secured. As a method of securing adhesiveness, commonly used methods include reduction annealing in a reducing atmosphere and a brushing unit prior to vacuum plating to remove the iron oxide film to secure the adhesion, but the additional equipment cost The problem of weighted burden and stable role over the entire surface of the base steel sheet has emerged, and this suggests a method of improving the adhesion and coating properties by two-layer plating. In the case of two-layer plating, various coating layers suitable for the required characteristics are selected according to the type and properties of the upper and lower plating material systems coated on the base material, thereby improving corrosion resistance, adhesion, paintability, weldability, and post-treatment. Can be. As a form which can provide corrosion resistance and adhesiveness to a lower layer, and can provide coating property, weldability, heat resistance, and a beautiful appearance to an upper layer, zinc type, aluminum type, tin type, titanium type etc. are mentioned. There a plating system a bi-layer by such methods also improve the adhesion and corrosion resistance of Rooster zinc / tin bi-layer coated steel sheets (Republic of Korea Patent No. 072 752 call), which to secure the adhesion of the tin in the corrosion resistance is also excellent one lower Rooster ^10- A method of removing iron oxide on a steel sheet by performing glow discharge in an argon gas atmosphere of about ² Torr, and performing an additional process by substrate cleaning to secure adhesion, which requires sufficient removal of an oxide film after a certain period of time. There is a problem of deterioration. In the present invention, the tin has a low melting point (232 DEG C), and it is judged that the adhesion can be secured by the formation of an intermetallic compound with iron by heat treatment, and the heat treatment is performed at a constant temperature with tin as the lower layer and zinc as the upper layer. The present invention relates to a zinc / tin two-layer plated steel sheet having improved adhesion and solderability of a plated coating using a method, and a method of manufacturing the same.

Hereinafter will be described the experimental method and its effects and effects of the present invention.

The zinc / tin bilayer film of the present invention is formed under vacuum of ⁵ × 10 ⁻⁵ Torr or less. First, the zinc and tin in grain shape are put in different evaporation sources, and then the substrate is mounted and evacuated until the desired vacuum is achieved by using a vacuum pump.

At this time, the distance between the evaporation source and the substrate is set in advance according to the size of the substrate, and is adjusted so that the difference in thickness of the plating layer is within 5%. Resistance evaporation, induction melting or electron beam heating was used as the evaporation source. Cold rolled steel sheets of 0.8 mm thickness were used, and ultrasonic cleaning using alkaline degreasing and organic solvents was performed before charging into a vacuum chamber. When the degree of vacuum reaches 10 ⁻⁵ Torr or less, the temperature of the substrate is adjusted to 150 to 200 ° C., and an appropriate amount of power is supplied to each evaporation source to degas the evaporation source. After degassing, tin was deposited to a desired thickness in the lower layer, followed by vacuum deposition of zinc at a constant thickness in the upper layer. After the deposition was completed, a heat treatment test was conducted at a constant temperature and time in a heat treatment furnace. Even if the iron oxide on the steel sheet is not removed, adhesion is ensured that tin with low melting point first dissolves during heat treatment to sufficiently prevent pores of the coating film, and is alloyed on the interface by combining with iron on the steel sheet by thermal diffusion. Adhesion was secured by forming a layer, and solderability was improved due to the surface thickening caused by melting of tin. In the zinc / tin two-layer coated steel sheet, the heat treatment temperature is in the range of 400 to 500 ° C., and the total coating amount of the plated coating is 10 g / m 2 or more. When the adhesion amount is less than the limit, the coating property cannot be exhibited by the pores and the adhesion due to the weak formation of the alloy layer is not secured. The alloy layer of tin and iron is generally adhesive according to the degree of the alloy layer. And it is known that it affects the corrosion resistance. When the heat treatment temperature is 400 ℃ or less, the formation of the alloy layer of tin and iron is weak, so that the adhesion is not secured and some burying phenomenon, the heat treatment temperature is above 500 ℃ As a result, the formation of the alloy layer was promoted, resulting in film deterioration, resulting in peeling of the coating film, resulting in a decrease in corrosion resistance. In the case where the alloy layer by heat treatment was not formed, the coating film was completely peeled off, and thus application as a plated steel sheet product was impossible.

In the ion plating method, the evaporation material was ionized using a hot electron emission source and an ionization electrode while evaporating aluminum and manganese, and a voltage of 100 to 1000 V was applied to the substrate.

The present invention not only realizes plating products having much better corrosion resistance and weldability than conventional plating products, but also manufactures a zinc / tin two-layer coating film having excellent adhesion, processability, and solderability in automobiles, home appliances, building materials, and electronic circuit boards. It is expected to be used in products requiring high corrosion resistance, solderability, adhesion and processability.

In the following examples, a zinc / tin two-layer coating film was prepared by the method of the present invention, and its characteristics were investigated. As a comparative material, a zinc single plating product and a tin / zinc two-layer coating product were used. As a property evaluation and comparison, before processing, total adhesion and solderability were tested and the results are shown in Table 1.

Corrosion resistance was compared with initial blue-blue incubation time in 5% NaCl solution, and adhesion evaluation was performed by Ot, 180 ° bend once and peel test by tape. The degree of peeling by was tested. Solderability evaluated the characteristic by spot welding.

The following example is to prepare a zinc / tin bilayer film by the method of the present invention on a low carbon steel sheet to investigate its properties.

Example 1

Alumina coated tungsten bow for tin evaporation, graphite bow for zinc evaporation, substrate temperature of 150 ° C, vacuum degree of evaporation at 10x / m2 at 5x10 ^-5 Torr 10 g / m 2 of zinc as an upper layer was deposited on a low carbon steel sheet of 0.8 × 100 × 150 mm, and then heat-treated at 420 ° C. for 5 minutes.

Example 2

In the same manner as in Example 1 except that the tin deposited 7g / m 2 as the lower layer and zinc 13g / m 2 as the upper layer.

Example 3

The same process as in Example 1 except that 5 g / m 2 of tin was used as the lower layer and 15 g / m 2 of zinc was used as the upper layer.

Example 4

The same process as in Example 1 except that 2 g / m 2 of tin was used as the lower layer and 18 g / m 2 of zinc was used as the upper layer.

Example 5

The same process as in Example 1 except that 10 g / m 2 of tin was used as the lower layer and 10 g / m 2 of zinc was used as the upper layer.

Example 6

The same process as in Example 1 except that 10 g / m 2 of tin was used as the lower layer and 10 g / m 2 of zinc was used as the upper layer.

Example 7

The same process as in Example 1 except that 5 g / m 2 of tin was used as the lower layer and 15 g / m 2 of zinc was used as the upper layer.

Example 8

The same process as in Example 1 except that 2 g / m 2 of tin was used as the lower layer and 18 g / m 2 of zinc was used as the upper layer.

Example 9

The same process as in Example 1 except that 2 g / m 2 of tin was used as the lower layer and 18 g / m 2 of zinc was used as the upper layer.

Comparative Example 1

This product is made by depositing alumina coated tungsten bow as evaporation source and depositing 20g / m2 with substrate temperature of 15 ℃ and vacuum degree of 5x10 ^-5 Torr. .

Comparative Example 2

It is the product when 20g / m2 is deposited with graphite bow as evaporation source for vapor deposition of single metal zinc and substrate temperature is 200 ℃ and vacuum degree during evaporation is 5x10 ^-5 Torr.

Claims (2)

In the zinc / tin two-layer coated steel sheet, the lower layer is a tin plating layer of 5-20 g / m 2, the upper layer is vacuum-deposited with a zinc plating layer of 5-20 g / m 2, and the total plating deposition obtained by heat treatment is 10 g / m 2 or more. Two-layer tin plated steel. In the method of manufacturing a zinc / tin two-layer plated steel sheet, the tin is deposited on the lower layer by vacuum deposition or ion plating at a substrate temperature in the range of room temperature to 300 ° C., and the zinc is deposited on the upper layer, followed by 5 at 400 to 500 ° C. Method of producing a zinc / tin two-layer plated steel sheet to heat-treating for 10 minutes to form a zinc-tin alloy layer.