JPH05154447A - Precoated aluminum plating steel sheet excellent in working for building material - Google Patents

Abstract

PURPOSE:To improve scratch resistance in a roll forming work of a hot dip aluminized steel sheet for building material and to improve press moldability in a press molding work. CONSTITUTION:The hot dip aluminized steel sheet is coated by 0.5-4.5mu in dried coating film thickness with a clear coating material, into which a wax of 0.1-3% in weight ratio to dried coated film is added, after chromate treated. As a result, scratch resistance in the roll forming work and press moldability in the press molding work is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated aluminum-plated steel sheet for building materials, which has improved scratch resistance and formability during various processes such as roll forming and pressing.

[0002]

2. Description of the Related Art Aluminized steel sheets have been developed from conventional heat-resistant parts for household appliances and fire wall materials, which utilize the excellent heat resistance characteristics, to the recently more excellent corrosion resistance and weather resistance characteristics. As the building materials for exterior such as roofing materials and wall materials are expanding, they are being used in large quantities. Among them, it is often used as a roofing material, taking advantage of the silver-white appearance unique to hot-dip aluminum plated steel sheets. Aluminum-plated steel sheets are generally formed into various product shapes by bending and bending with various processing methods such as roll forming.At that time, the aluminum-plated layer is picked up and attached to the forming machine to From the problem of deterioration of corrosion resistance and surface appearance,
As described in Japanese Examined Patent Publication No. 63-12141, "After the surface of the aluminum-plated steel sheet has been chromate-treated in advance, a transparent resin paint (clear paint) is applied to a thickness of 5 to 15 .mu.m.
The development of "aluminized steel sheet that prevents aluminum from adhering to dry forming machines" is also underway. However, since the aluminum plating layer itself is soft, there is a problem that the plating layer is flawed and red rust is generated from the flawed part in a building material product that requires a complicated shape or harsh processing after roll molding was there. Further, there is a problem that such a flaw and red rust often occur in the press forming method which has a larger frictional force than the roll forming method.

[0003]

Therefore, as a result of pursuing the cause of such a problem from a molding method, a coating method, a coating material, etc., the present inventors found that the conventional transparent resin coating has insufficient lubrication function. I found out that there is something. The present invention is to improve the lubrication function of the transparent resin paint based on this knowledge, while maintaining the appearance unique to aluminum plating, the object is to provide an aluminum plated steel sheet excellent in corrosion resistance and formability, The gist of this is that a chromate-treated film is applied to the surface of an aluminum-plated steel sheet, and a transparent resin coating containing 0.1 to 3.0% of wax in a weight ratio of the coating film after drying is 0.5 to
It is a coated aluminum-plated steel plate for building materials with a workability of 4.5 μm.

The present invention will be described in detail below. Chromate coating is applied to the surface of pure aluminum-plated steel sheet manufactured by the usual aluminum plating method after cleaning the surface of the steel sheet or aluminum alloy-plated steel sheet to which other components such as Si and Mg are selectively added little by little. .. The chromate film has the effect of improving the corrosion resistance and the coating adhesion, and the adhesion amount is, as shown in Table 1, 5 to 50 mg /
Stable improvement in corrosion resistance (white rust occurrence rate after 10 days of SST) is shown in the range of m ² . Further, in the present invention, a transparent resin coating material containing wax is applied in a thickness of 0.5 to 4.5 μm on the coating film having the surface characteristics of the aluminized steel sheet improved by attaching such a chromate coating film. The transparent resin coating is applied to maintain a lubricating oil function when processing a chromate-coated aluminum plated steel sheet and to maintain a good appearance after processing.Alkyd-based, acrylic-based, polyester-based, silicon-modified Various synthetic resin paints such as urethane and fluorine are used. With such a single type of synthetic resin coating, it is not possible to obtain the lubricating performance that satisfies the above-mentioned severe processing, so in order to improve the lubricating performance,
Contains wax. As the wax, various synthetic lubricating oils such as polyethylene type, olefin type and polypropylene type are used, and the amount thereof is 0.1 to 3.0% in the coating film weight ratio after drying as shown in FIG. That is, if the wax content is less than 0.1%, the effect of improving the lubricity is small. On the contrary, if the content of wax exceeds 3.0%, the effect of improving the lubricity reaches the saturation range, and further effect is recognized. I can't. Among synthetic lubricating oils, polyethylene-based oils have the feature that after coating, they move to the surface of the coating film and the surface of the coating film is covered with polyethylene fine particles to further enhance the lubricating effect.

Further, as described above, even if the transparent resin coating film containing the wax has any thickness, the object of the present invention cannot be stably obtained. That is, for the transparent resin coating film, as shown in FIG.
A thin coating film of less than 1 has a problem that the lubrication effect required at the time of press molding is insufficient, the coating film or plating layer in the lower layer portion is destroyed, and corrosion resistance is significantly impaired. Further, a thick coating film having a thickness of more than 4.5 μ reaches the saturated region in the effect of improving the lubricity. In the present invention, the thickness of the transparent resin coating film is the coating film (5 to 15 μm thick) of the conventional coated aluminum-plated steel plate as described above.
The fact that it is made thinner compared to the above is due to the effect of containing wax in the transparent resin paint.

By applying the wax-added clear coating in the present invention to a hot-dip aluminized steel sheet, when it is used as a building material such as a roofing material, the plated surface is prevented from being scratched during roll forming, and roll formability is remarkably improved.
Furthermore, it is now possible to provide coated aluminum plated steel sheets with excellent corrosion resistance and appearance characteristics. Next, examples will be described.

[0007]

[Example] An aluminum-plated steel plate having a plate thickness of 0.5 mm, a plate width of 914 mm, and a plating amount of 200 g / m ² was used, on which chromic acid (CrO ₃ ) 30 g / l, phosphoric acid (H ₃ P 2
Chromate treatment was performed by immersing in O ₄ ) 10 g / l liquid (normal temperature). The amount of deposited chromium was adjusted to 20 mg / m ² . A powdery polyethylene wax was added to coil coat 289 (acrylic resin) of a transparent resin paint (manufactured by Kawakami Paint Co., Ltd.) in an amount of 0.6% by weight based on the amount of the dry film to give a film thickness of 0.51, 24. 5 μ was applied and baked and dried at 200 ° C.
The roof material shown in FIG. 4 was subjected to roll forming and pressing. In addition, as a comparative example, after the same pretreatment was performed, the coil coat 28 was added without adding polyethylene wax.
The same processing was carried out for the case where 7 μ of 9 was applied.
The results are shown in Table 1. From the results shown in Table 1, it can be seen that press moldability is improved by adding wax to the coating film.

[0008]

[Table 1]

<Test Method> SST (salt spray test) Specimen size: 70 × 150 mm, the end face is paraffin-sealed, and the white rust rate (area ratio) is evaluated according to JIS Z2371. Using a property tester, a drawing test was performed by changing the sample diameter with a wrinkle-pressed 200 kg and a punch diameter of 50 mm, and the maximum diameter without cracking of the sample was obtained and the ratio to the punch diameter was evaluated as the limiting drawing ratio. .. Appearance The appearance was visually evaluated according to the following criteria. ◎ Almost no change ○ Slightly yellow coloring △ Quite yellow coloring × remarkable coloring.

[0010]

As described above, by applying the wax-added clear coating of the present invention to the hot-dip aluminized steel sheet, when it is used as a building material such as a roofing material, the plated surface is scratched during roll forming. It was possible to obtain a coated aluminum-plated steel sheet which was excellent in prevention and roll forming workability, and which was excellent in corrosion resistance and appearance characteristics.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a chromium deposition amount in a chromate treatment of an aluminum-plated steel sheet and SST corrosion resistance after clear coating (4 μ) and appearance.

FIG. 2 is a diagram showing the influence of the amount of polyethylene wax added in a clear coating film on press moldability.

FIG. 3 is a diagram showing the effect of clear coating film thickness on press formability.

FIG. 4 shows a processed shape obtained by processing a building material by an actual machine.

Front page continuation (72) Inventor Katsumasa Kido 1 Aze, Wakamatsu Ward, Kitakyushu City, Fukuoka Prefecture Tokai Steel Co., Ltd. Wakamatsu Factory (72) Inventor Matsui Iwane 1 Aze, Wasematsu Ward, Kitakyushu, Fukuoka Prefecture Tokai Steel Wakamatsu Factory

Claims (1)

[Claims] 1. A transparent resin paint containing a chromate-treated film on the surface of an aluminum-plated steel sheet, and containing 0.1 to 3.0% of wax in a weight ratio of the dried film on the transparent resin paint.
A coated aluminum-plated steel sheet for building materials with excellent workability characterized by being coated with a thickness of 4.5μ.