KR950004783B1 - Zn-al alloy coating steel sheet - Google Patents

Abstract

The plated steel strip has good corrosion resistancl and adherence by applying vacuum evaporation of zinc and aluminum. The manufacturing method of zinc-aluminum plated steel strip comprises (A) electro-degreasing the cold rolled steel strip with thickness of 0.8 mm; and (B) degasing in the vacuum chamber; (C) heating evaporating sources of zinc and aluminum.

Description

Zinc-Aluminum Alloy Coated Steel Sheets

The present invention relates to a zinc-aluminum alloy plated steel sheet excellent in corrosion resistance, adhesion and workability.

As a representative method of preventing corrosion of steel products, galvanized steel sheets using sacrificial corrosion resistance of zinc have been widely used. In particular, galvanized steel sheet is widely used in automobiles and general home appliances in terms of economics and productivity. Conventional hot dip galvanizing and electroplating are used as the plating method. However, these two methods are difficult to control the amount of coating during double-sided and single-sided plating, and plating of material with high melting point is impossible. There is a problem that the alloy layer is formed to deteriorate the processing layer and to further secure the pollution prevention facility and pollution. In order to improve these problems and various properties of the plating material, a vacuum plating method, which is a method of easily plating various plating materials in a vacuum container, has recently emerged as a means for solving the problems. In the vacuum plating method, electrolytic degreasing only to remove oil or other impurities on the steel sheet is performed, and due to the effect of iron oxide present on the steel sheet when the vacuum plating is applied, it does not adhere well to the steel sheet or easily falls off, resulting in poor adhesion. When the iron oxide was removed, good adhesion was shown.

In order to remove the iron oxide to secure the adhesion of zinc, heating the plated material in an anoxic atmosphere, degreasing it in a reducing atmosphere containing hydrogen after degreasing, and brushing unit before vacuum plating There is a method to install and remove, in this case, the iron oxide film is removed to secure the adhesion, but there is a disadvantage that the economic efficiency is lowered due to the burden of additional equipment costs.

In recent years, as rust-preventing regulations become more stringent, Zn-Fe, Zn-Ni, Zn-Mn, Zn-Co, etc. by electroplating methods or Zn-Al, Zn-Al-Si, Zinc-based alloy plating products such as Zn-Al-Mg and Zn-Al-Sn have been developed.

However, the products by the electroplating method may be peeled off after processing (Zn-Ni, Zn-Co), or easily red blue (Zn-Fe) or hydrogen generated during plating, resulting in low current efficiency resulting in lower economic efficiency. (Zn-Mn) and the like, and the hot-dip galvanized products also have problems such as an alloy phase at the interface portion, poor workability or an oxide film on the surface, resulting in poor chemical conversion and poor coating adhesion. The present invention, in the production of zinc-aluminum alloy plated steel sheet by vacuum deposition on a steel sheet subjected to the degreasing, which is easy to solve this problem, the aluminum content in the thickness of 5 ~ 20g / m ² to be prepared by 23 to 75% and the adhesion and It relates to a zinc-aluminum alloy plated steel sheet characterized by securing corrosion resistance.

Hereinafter, the present invention will be described.

The zinc-aluminum alloy film of the present invention was produced under vacuum of 5 × 10 ⁻⁵ Torr or less. First, the granular zinc and aluminum are put in different evaporation sources in a vacuum container, 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 distance between the evaporation source and the substrate is set in advance according to the size of the substrate, and the deviation of the plating layer thickness and the aluminum content is adjusted to be within 5%. As a substrate, a cold rolled steel sheet having a thickness of 0.8 mm was used, and the steel sheet was cleaned by electrolytic degreasing before vacuum plating.

When the vacuum degree is 10 ^-5 Torr or less, the temperature of the substrate is adjusted, and an appropriate amount of power is supplied to each evaporation source to degas the evaporation source. After the degassing, the zinc and aluminum alloy films of the desired weight% are made by adjusting the evaporation source of zinc and aluminum to the already set evaporation rate, where zinc is graphite in consideration of the reactivity with the evaporation source, the easiness of evaporation, and the life of the evaporation source. For the bow and aluminum, a titanium boron boron nitride boat made of a titanium boride (TiB ₂ ) and a boron nitride (BN) compound was used. By forming an appropriate weight% of zinc and aluminum alloy film, aluminum is reduced during deposition of iron oxide, a major oxide present on the surface of steel sheet, which is a major factor that determines the adhesion of plating film. By forming the (Oxide-bonding) layer, it is considered that adhesion is secured even without removing the iron oxide on the cold rolled steel sheet subjected to electrolytic stripping. In the zinc-aluminum alloy coating, the weight of aluminum is 23 to 75%, and the total adhesion of the coating is 5 to 20 g / m ² . Limiting the weight and adhesion of aluminum below is that the adhesion of the aluminum is less than 23%, the adhesion is remarkably poor, and if it is 75% or more, the adhesion is secured, but when the corrosion progresses, the zinc oxide layer of the corrosion product is sufficiently This is because the black surface of the aluminum film is inherently unprotected due to the inability to protect the surface of the film, and the corrosion product of zinc does not sufficiently protect the intergranular corrosion between the grains of zinc-aluminum alloy film as the amount of aluminum increases. The adhesion amount of zinc is limited to 5 to 20 g / m ² because when the adhesion amount is less than this, corrosion resistance is poor and it is insufficient to protect the steel sheet.

In the following examples, a vacuum-coated zinc-aluminum film was prepared by the method of the present invention, and its characteristics were investigated. As a comparative material, a vacuum-coated zinc and aluminum single plated product, and an electric and hot dip zinc plated product were used. Characteristic evaluation and comparison were tested for corrosion resistance and adhesion, and the results are shown in Table 1.

Corrosion resistance was compared by the initial red blue development time in 5% NaCl solution, and adhesion was evaluated by performing a peel test by tape after 180 ° Ot bending once.

Example 1

For the graphite boat for the zinc evaporation, aluminum evaporation boride, titanium (TiB _2), we used a diboride of titanium, boron nitride boat producing a boron nitride (BN) with the compound as the evaporation source, and a substrate temperature of 200 ℃, during evaporation The degree of vacuum of this product is that when the film is evaporated at the same time by opening the shutter at 5 × 10 ^-5 Torr, aluminum is 23% by weight and deposited on the cold rolled steel plate subjected to electrolytic degreasing with the deposition amount of 20 g / m ² .

[Examples 2-3]

Same as Example 1, but in the case of a product with the weight of aluminum 50, 75%, respectively.

[Comparative Examples 1 and 2]

Same as Example 1, but in the case of the product with the aluminum weight of 5, 15%.

Comparative Example 3

In the deposition of metal zinc, the graphite bow was used as the evaporation source and the deposition temperature was 20g / m ² at the substrate temperature of 200 ° C and the degree of vacuum during evaporation at 5 × 10 ^-5 Torr. In the case of products.

[Comparative Example 4]

On it TiB3, cold-rolled steel sheet using BN boat to the evaporation source and by the amount of deposition at 300 ℃ the substrate temperature, the vacuum degree of 5 × 10 ^-5 Torr during evaporation to 20g / m ² via an I liberation but as depositing metal aluminum In the case of a deposited product.

[Comparative Example 5]

This is the case of 20g / m ² coated single metal zinc on cold rolled steel plate by electroplating method.

Comparative Example 6

It is the case that 40g / m ² coated single metal zinc on the cold rolled steel plate by hot dip plating method.

The present invention is expected to be able to be used in products requiring corrosion resistance and adhesion in automobiles, home appliances, building materials, etc. by manufacturing a zinc alloy film having excellent adhesion after degreasing in the pretreatment process.

TABLE 1

Claims (1)

In a zinc-aluminum alloy plated steel sheet in which a zinc-aluminum alloy plated layer is vacuum plated on a steel plate subjected only to degreasing, a deposition amount of a zinc-aluminum alloy plated layer of 23 to 75% by weight of aluminum and the remaining zinc is zinc. 5 ~ 20g / m ² of zinc-aluminum alloy coated steel sheet.