JP3138282B2 - Aluminum alloy plate for automobile body panel - 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 sheet for use as an automobile body panel, and more particularly to an aluminum alloy sheet for an automobile body panel having excellent press formability.

[0002]

2. Description of the Related Art In general, a body panel for an automobile is manufactured through a process of press-forming, welding, degreasing and forming a steel plate material and then painting the surface. At this time, a lubricating oil is used in the press forming step to facilitate the forming, and a low-viscosity oil called a rust-preventive oil is generally used in general in consideration of the degreasing efficiency in the subsequent step. However,
Aluminum alloy sheets for automobile body panels are inferior in formability to conventional cold-rolled steel sheets, and therefore, depending on the product shape, press cracking may occur even with the use of the above lubricating oil.

In order to prevent such press cracking, it is effective to increase the amount of material flowing into a mold at the time of press molding, and at the stage of trial production, a high-viscosity oil called press oil or polyvinyl chloride is used. (PVC) film may be used. However, the use of high-viscosity press oil reduces the processing capacity of the degreasing process, while the use of polyvinyl chloride film easily breaks and adheres to the mold, necessitating peeling work. This is not an effective means of achieving this.

[0004] The present inventors have reported that alkali metal salts of higher fatty acids are used as components that can provide good lubrication even when low-viscosity oil is used and can be pressed smoothly without impairing spot weldability and degreasing properties. It has been found that the composition is effective, and an aluminum alloy sheet for an automobile body panel having the above components applied to the surface has already been proposed (Japanese Patent Application No. 2-303038).

[0005]

As a result of continuous research on effective surface treatment agents, the present invention shows that, when an alkali metal salt of a low-medium chain fatty acid is used, the same surface lubricity can be obtained even with a smaller coating amount. It has been demonstrated that it can be provided. Accordingly, it is an object of the present invention to provide an aluminum alloy sheet for an automobile body panel having a surface lubricity suitable for press forming without deteriorating spot weldability, degreasing property, and the like.

[0006]

An aluminum alloy plate for an automobile body panel according to the present invention for achieving the above object is provided by an aluminum alloy plate for press forming for use in press forming using a low-viscosity rust-preventive oil. Wherein an alkali metal salt of a low-medium chain fatty acid is applied to the surface in the form of an aqueous solution, and dried to impart surface lubricity.

[0007] Low- and medium-chain fatty acids useful in the present invention include:
Lauric acid, myristic acid or capric acid can be mentioned, and sodium salts or potassium salts are mainly used as alkali metal salts. Therefore, sodium or potassium salts of low- and medium-chain fatty acids selected from lauric acid, myristic acid or capric acid are suitable surface treatment agents for the purpose of the present invention.

These surface treatment agents are usually applied in the form of an aqueous solution to the surface of an aluminum alloy plate using a bar coater or the like, and subsequently subjected to a drying treatment. In the present invention,
The effect of imparting good surface lubricity appears from a small amount of 150 mg / m ^{2 on} the surface after drying. However, lubricity is insufficient when the amount of the surface coating is less than 150 mg / m ^2, on the other hand, 2500
If it exceeds mg / m ² , the spot weldability and the degreasing property decrease. Therefore, the preferred surface coating amount is 150 to 2500 mg / m
It is in the range of ² .

The aluminum alloy sheet for an automobile body panel according to the present invention is supplied as a raw material product in a state where the above-mentioned surface treatment has been performed, and a body panel is formed through steps after press molding. The lubricating oil that is usually applied immediately before press molding may be applied in advance after applying and drying the surface treating agent of the present invention.

[0010] The alkali metal salt of a low- and medium-chain fatty acid applied to the surface of the aluminum alloy plate for an automobile body panel of the present invention imparts excellent lubricating performance with a surface application amount as small as 150 mg / m ² , and provides press formability. It works effectively to improve. Therefore, only by using the ordinary low-viscosity rust-preventive oil at the time of press molding, the molding cracking phenomenon caused by the lack of the moldability of the material itself is effectively reduced, and smooth press molding becomes possible.

The alkali metal salt of a low-medium chain fatty acid used as a surface treatment agent in the present invention does not lower the spot welding property and the degreasing property and does not stain the equipment. In addition, since it does not dissolve in ordinary mineral oil at normal temperature, lubricity is not impaired even when washing with a low-viscosity oil for removing foreign substances attached during handling after shipping.

[0012]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example A 1 mm-thick aluminum alloy plate for an automobile body panel (annealed material having an alloy composition of Al-4.5% Mg-0.3% Cu) was washed with an acidic degreasing agent, and laurin belonging to low and medium chain fatty acids was formed on the upper and lower surfaces thereof. The sodium acid solution (concentration: 2 to 15%) 7
The coating amount was changed using a bar coater, and the coating was dried at room temperature.

Investigation test on lubricating property, spot welding property and degreasing property under both "no oiling" and "with oiling" conditions using the aluminum alloy plate for each automobile body panel subjected to the surface treatment as described above. Was done. Note that the lubricating oil using the anti-rust oil [Yukenkogyo Co. RP-75N), the coating amount 5000 mg / m ² at the time of lubricity of the study, during the degreasing test and spot weldability 400 mg / m ² The oil was applied and the test was performed.

Each performance test was performed according to the following tests and evaluation methods. (1) Lubricity The test apparatus shown in FIG. 1 is set on a crank press with a die cushion, and the die 2 is pushed down to apply a plate holding force H to the material 1 by the die 2 and the plate holder 3. Next, as shown in FIG. At this time, the working force P acting on the punch 4 and the sum (H + P) of the working force P acting on the die 2 and the plate holding force H were measured with a load cell to obtain a chart illustrated in FIG. The plate holding force H and the processing force P at the dead center are read.
A similar test is performed by changing the air pressure of the die cushion, and the relationship between the plate holding force H and the processing force P is determined as shown in FIG. Then, the lubricity is evaluated from the magnitude of the gradient μ (the coefficient of friction) in FIG. Lubricity quality is evaluated according to the following criteria. ○: Slope μ is 0.1 or less □: Slope μ is 0.1 to 0.15 △: Slope μ is 0.15 to 0.2 ×: Slope μ is 0.2 or more

(2) Spot weldability Welding current 23KA, three-phase low frequency type, welding pressure 320kgf,
Spot welding is performed under the conditions of a forge pressure of 920 kgf and a chromium copper electrode (diameter 16 mm), and the spot weldability is evaluated based on the number of continuous welding possible at that time. The number of continuous welds that can be performed is determined based on the tensile shear strength of the welded portion in the continuous welding test.
It is determined by the number of continuous spot welding at 8 kg / point or more and the minimum value is 166 kgf / point or more. Since the contact resistance is increased depending on the surface treatment, the amount of heat generated at the contact portion between the electrode and the material becomes excessive, so that the electrode is damaged more and the number of times of continuous welding is reduced. The quality of spot weldability is evaluated based on the following criteria. ○: The number of continuous welding is 400 or more △: The number of continuous welding is 100 to 400 ×: The number of continuous welding is less than 100

(3) Degreasing The material was added to an alkaline degreasing agent (FCL-4460, manufactured by Nippon Parkerizing Co., Ltd.) and sodium laurate (2 g / l) and a rust preventive oil (RP-75N, manufactured by Yuken Kogyo Co., Ltd.) 0.8 The degreased solution to which g / l has been added is immersed at a temperature of 43 ° C. for 2 minutes.
The degreasing property is evaluated by visually observing the water wettability of both surfaces of the test piece subjected to the immersion treatment and determining the area ratio thereof according to the following criteria. ○: Water wettability 100% △: Water wettability 80% or more ×: Water wettability less than 80%

The results of the above tests (Examples) are shown in Table 1 in comparison with the amount of the applied sodium laurate. For comparison, Table 1 shows, as comparative examples, an example in which sodium oleate was applied to the same aluminum alloy sheet, an example in which acrylic acid polymer used for lubricating steel sheets was applied to the same aluminum alloy sheet, and an untreated example. It was also added.

[0018]

[Table 1]

From Table 1, it can be seen that, in the examples, practical application of lubrication is provided from a coating amount of 150 mg / m ^{2 under} the condition of “with oiling”, and spot welding and degreasing properties are provided up to a coating amount range of 2500 mg / m ² . It is recognized that the results of the present invention are superior to those of the comparative examples.

Similar results were obtained when sodium and potassium salts of myristic acid or capric acid were used as coating components instead of sodium laurate in the examples.

As described above, according to the aluminum alloy plate for an automobile body panel provided by the present invention, the alkali metal salt of a low-medium chain fatty acid applied to the surface exhibits a unique lubricating function, and the amount of application is small. It has the effect of effectively reducing the occurrence of cracks and scratches during pressing without impairing spot weldability and degreasing properties.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an apparatus used for a lubricity test.

FIG. 2 is an explanatory diagram of an apparatus used for a lubricity test.

FIG. 3 is an example of a load chart of a lubricity test.

FIG. 4 shows an evaluation graph of a lubricity test.

[Explanation of symbols]

 Reference Signs List 1 material 2 die 3 plate holder 4 punch

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C10N 30:00 40:24 (72) Inventor Tatsuya Hikita 3-1-1-12 Millennen, Minato-ku, Nagoya-shi, Aichi Sumitomo Light Metal Industries, Ltd. Inside the Technical Research Institute (72) Inventor Hideyuki Utsu 3-1-1-12 Minato-ku, Minato-ku, Nagoya-shi, Aichi Sumitomo Light Metal Industries, Ltd. Technical Research Institute (56) References JP-A-1-153794 (JP, A) 2-298592 (JP, A) JP-A-1-319962 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B05D ⁷ /00-7/24 C10M 101/00-177 / 00 C22C 21/00-21/18

Claims (3)

(57) [Claims] 1. A low-viscosity rust-preventive oil , characterized in that a low-medium chain alkali metal salt of an alkali metal salt is applied to the surface in the form of an aqueous solution and then subjected to a drying treatment to impart surface lubricity.
Aluminum alloy plate for automobile body panel to be used for press forming . 2. The aluminum alloy plate for an automobile body panel according to claim 1, wherein the alkali metal salt of a low-medium chain fatty acid is a sodium or potassium salt of lauric acid, myristic acid or capric acid. 3. The aluminum alloy plate for an automobile body panel according to claim 1, wherein the surface coating amount of the alkali metal salt of a low-medium chain fatty acid is in the range of 150 to 2500 mg / m ² .