JP2846489B2 - Aluminum alloy for painting with excellent thread rust resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for coating and is suitable for a coated product used for an automobile body sheet material and the like, and has extremely excellent thread rust resistance even under severe corrosive environment. It relates to an aluminum alloy for painting.

[0002]

2. Description of the Related Art Conventionally, aluminum products manufactured by molding such as automobiles, cars such as electric trains, and cases of home electric appliances, etc., have a predetermined shape after molding in order to improve decorativeness and corrosion resistance. After surface treatment,
Generally, baking is performed. Products that have been baked in this way, under severe corrosive environment during use, due to surface scratches and moisture that penetrates through pinholes of paint, thread-like corrosion between the material Al or Al alloy and the coating film, so-called Yarn rust may occur, causing a problem in appearance, and significantly impairing the product value. Since the occurrence of this thread rust is affected by the type of the material, the method of preparing the base material before coating, the type of coating, etc.
Although attempts have been made to prevent rust corrosion by improving the chemical composition, structure, and manufacturing process of the material, it has not been completely solved at present. By the way, conventionally, as aluminum alloys used for these baking coatings,
2030 (Al-Cu), 600 for automotive panels
9, 6010 (Al-Mg-Si based), 5182 (Al
-Mg), and 5182 for yarn rust resistance;
6010 etc. are said to be relatively excellent. However, car body sheet materials are used in snowfall areas.
Since a snow melting agent such as CaCl ₂ is often sprayed on roads as a deicing agent, the corrosive environment has become more severe and the warranty period of automobile manufacturers has been extended. Therefore, development of a material having more excellent yarn rust resistance is required.

[0003]

[0004]

In order to develop an aluminum material for coating which can achieve the above-mentioned object, the present inventor has made various adjustments to the chemical composition of aluminum in order to improve the frustration resistance of conventional aluminum materials. Here, an aluminum material having excellent thread rust resistance and usable for vehicles such as automobiles and trains, and cases for home electric appliances, etc., has been found. 0.5 to 10.0%, Cr is 0.001 to 0.15%, T
Aluminum for coating excellent in thread rust resistance, comprising 0.001 to 0.15% of i, 0.01 to 0.18% of Cu, and less than 0.1% of Mn, with the balance being Al and its impurities. Alloy. That is, the present invention improves the strength and rust resistance by adding Mg to Al, improves the corrosion resistance of the alloy by adding Cr, eliminates the directionality of rust by adding Ti, and adds Cu. Thus, the strength after baking is increased, and the amount of Mn is regulated to prevent the overall corrosion.

[0005]

The reasons for limiting the chemical components in the present invention are as follows. Mg imparts strength and has a high effect of improving yarn rust resistance. At 5.5%, sufficient mechanical performance cannot be obtained. To obtain high mechanical performance as a molding material, 5.5 is required.
%, And at the same time, if Mg exceeds 5.5%, the rust resistance is remarkably improved.
It is an essential condition to exceed 5.5%. Mg is
If it exceeds 10%, the strength is high, but the stress corrosion cracking resistance is deteriorated, which is not preferable. Therefore, Mg is 5.5
% And up to 10% is preferred. Cr has a high effect of improving the corrosion resistance. If it is less than 0.001%, there is no effect of improving the corrosion resistance. If it exceeds 0.15%, a huge intermetallic compound is formed, which impairs the formability and simultaneously reduces the rust resistance. It is not preferable because it impairs. Therefore, the Cr content is in the range of 0.001 to 0.15%. Ti has an effect of eliminating the directionality of yarn rust growth and improves formability. Ti has the effect of refining the crystal grains, but if it is less than 0.001%, the effect is not obtained. If it exceeds 0.15%, a coarse Al-Ti-based metal compound is formed. It is not preferable because the property is deteriorated. Therefore, the amount of Ti is set in the range of 0.001 to 0.15%.

Since Cu reduces the rust resistance, it is desirable that Cu be as small as possible for a high quality rust resistant aluminum material for coating. However, Cu is an element that imparts strength, and particularly produces an effect of improving the strength after baking, but if less than 0.01%, the effect is not obtained. Cu is 0.1
If it exceeds 8%, pitting corrosion is particularly likely to occur, and the rust resistance is significantly impaired. Therefore, the Cu content is set in the range of 0.01 to 0.18%. Since Mn enhances the overall corrosiveness, it is desirable that Mn be as small as possible in a high-quality aluminum material for coating with thread-rust resistance. Therefore, the amount of Mn is 0.1
%.

Further, in the present invention, with respect to other elements such as impurities, for example, Fe, Si, Zn, Be, Zr, etc., in order to have excellent yarn rust resistance, the allowable content thereof is such that the Mg content is increased. However, in the case of the same Mg content, the corrosion resistance and the rust resistance are degraded as the content of other elements increases, so that high-quality rust-resistant aluminum materials for coating have other elements. It is desirable to have less. Therefore, the content ranges of the other elements are preferably less than 0.2%.

[0008]

An embodiment of the present invention will be described below.
A 50 mm thick ingot of an Al alloy having the chemical components shown in Table 1 was homogenized at 500 ° C. for 4 hours.
Perform hot rolling to a thickness of 5 mm between 80 and 280 ° C,
Further, cold rolling was performed to a thickness of 1 mm. This 1mm
A thick aluminum alloy plate is rapidly heated to 520 ° C.
After holding for 2 seconds, the material quenched in water was used as a test material.
The yarn rust test on the obtained test material was performed in the following manner. Preparation of test piece 70 × 150 mm test piece → degreasing → surface conditioning → zinc phosphate treatment → cationic electrodeposition coating (170 ° C. × 30 minutes baking) →
Middle coat (140 ° C × 30 minutes) → Top coat (140 ° C × 30 minutes) Corrosion test Using a sharp edge on the painted surface, as shown in Fig. 1, two pieces each of length and width parallel to the aluminum base, 25mm long The test piece with a linear scratch (total length 100 mm) was subjected to a salt water spray test (according to JIS Z 2371) for 24 hours → a wet test (40 ° C, 60 to 85% RH) for 240 hours, for a total of 1344 hours. Evaluation of thread rust resistance As shown in FIG. 1, in the case where thread rust 2 was generated from a portion where an artificial scratch 1 was formed, the evaluation was made based on the maximum length of the thread rust and the number of occurrences of thread rust, blisters and the like.

[0009]

[Table 1]

As is clear from Table 1, the alloys of the present invention all have excellent rust resistance. On the other hand, all of the comparative examples having the chemical components outside the range of the present invention have poor rust resistance. In particular, when there are many cu (No. 10, 13, 14)
It can be seen that the rust resistance is poor. Alternatively, it can be seen that even when the cu addition amount is small, when the Mn is large (No. 12), the rust resistance is poor.

[0011]

As described in detail above, according to the present invention, by appropriately adjusting the additive components, an aluminum alloy having excellent rust resistance can be obtained, which has industrially remarkable effects. is there.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view for explaining a procedure of a thread rust test method and a situation of occurrence of thread rust.

[Explanation of symbols]

 1 artificial wound 2 yarn rust

──────────────────────────────────────────────────続 き Continued on the front page (72) Kunihiko Kishino, Inventor Furukawa Aluminum Industry Co., Ltd. 2-6-1 Marunouchi, Chiyoda-ku, Tokyo (56) References JP-A-1-219139 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) C22C 21/06

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein Mg is added in an amount of more than
%, 0.001 to 0.15% of Cr, and 0.1% of Ti.
001 to 0.15%, Cu is 0.01 to 0.18
% And Mn of less than 0.1%, with the balance being Al and its impurities, an aluminum alloy for coating excellent in thread rust resistance.