JPH0790604A - Surface treated aluminum alloy sheet excellent in workability, electrical conductivity, spot resistance weldability and corrosion resistance - Google Patents

Abstract

PURPOSE:To form an aluminum alloy without executing oil coating and degreasing stages and impact excellent workability, electrical conductivity and spot resistance weldability thereto by subjecting an aluminum alloy sheet to chromating treatment and thereafter forming an organic resin film layer contg. carbon black and a powdery solid lubricant. CONSTITUTION:On the face of a sheet in which the thickness of an oxidized film on the surface is regulated to <=150Angstrom by picking or the like, a chromate layer of 5 to 50mg/m<2> expressed in terms of metal Cr is formed. Furthermore, on the surface, by using an organic resin mixture contg., to 100 pts. organic resin, 1 to 40 pts.wt. carbon black having >=800m<2>/g specific surface area and 1 to 30 pts.wt. powdery lubricant, a film is formed by 0.1 to 3.0mum as a dry film thickness. The powdery lubricant to be used is constituted of wax and/or fluorocarbon having 0.1 to 10mum average particle diameter, and the average particle diameter is preferably regulated to 1.0 to 10times the dry film thickness of the average particle diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum or aluminum alloy plate which is mainly processed by press forming and is required to have electrical conductivity, spot resistance weldability and corrosion resistance, that is, aluminum for home appliances, office automation equipment, automobiles and the like. The present invention relates to an alloy plate (hereinafter collectively referred to as an aluminum alloy plate including an aluminum plate).

[0002]

2. Description of the Related Art Aluminum alloy plates (including a wide range of aluminum plates) are often press-molded in the manufacturing process of home appliances, office automation equipment, automobile products and the like.

In general, when these press workings are carried out by applying a lubricating oil, there are the following problems. (1) Lubricating oil is often applied by spraying, which causes the lubricating oil to scatter around and deteriorate the working environment. (2) It is necessary to remove the lubricating oil after pressing,
Since a solvent (CFC, 1,1,1-trichloroethane, etc.) is used in this degreasing process and an alkaline cleaner is used, pollution prevention measures are required, resulting in increased costs and a poor working environment.

Under such a background, as a technique capable of omitting the oiling and degreasing steps, a chromate layer is formed on an aluminum alloy plate, and a so-called lubricating resin for forming a resin layer containing a lubricant is further formed thereon. It is suggested to do so. (For example, JP-A-4-268038)

However, the above technique has a serious drawback in that the resin layer is formed on the aluminum alloy plate, so that the conductivity originally possessed by the aluminum alloy plate is impaired. Further, as a technique for improving the conductivity, the technique disclosed in JP-A-63-83172 in which conductive particles are contained in a resin makes it difficult to further improve the conductivity while ensuring processability. It was

[0006]

The above-mentioned drawback of the prior art is that a resin layer having a high resistance value is formed on an aluminum alloy plate in order to improve workability. Usually resin is 10
^{1 5} Omega · cm has a very high volume resistivity of about 10 ^{1 0} even when applied as a thin film having a thickness of about 1μm
Since it exists on the surface of the aluminum alloy plate as a layer having a resistance of Ω or more, this impairs the conductivity and the grounding property.

Further, in the method of improving the conductivity by adding conductive particles to these resin layers, it is necessary to add a large amount of particles in order to obtain sufficient conductivity, resulting in deterioration of workability and resin coating work. There was a problem such as making it difficult.

The present invention provides a surface-treated aluminum alloy sheet which overcomes the above-mentioned drawbacks of the prior art and can be press-formed without oiling and degreasing steps and which has sufficient conductivity (groundability), spot resistance weldability and corrosion resistance. The purpose is to do.

[0009]

As a result of intensive studies to overcome the above-mentioned drawbacks of the prior art, the inventors of the present invention have the smallest effect on workability among the conductive agents added to improve conductivity. The present invention was accomplished by discovering that carbon black is used, and that there is a certain relationship between the specific surface area of carbon black and processability and conductivity.

That is, according to the present invention, on an aluminum alloy substrate whose surface oxide film thickness is adjusted to 150 Å or less,
A chromate layer of 5 to 50 mg / m ^{2 in} terms of metal Cr is formed, and 1 to 4 carbon black having a specific surface area of 800 m ² / g or more is further formed on 100 parts by weight of the organic resin.
An organic resin mixture containing 0 part by weight of the powdered lubricant and 1 to 30 parts by weight of the powdered lubricant as a dry film thickness of 0.01 to 3.
Provided is a surface-treated aluminum alloy plate excellent in workability, conductivity, spot resistance weldability and corrosion resistance, which is characterized by forming an organic resin layer having a thickness of 0 μm.

The powder lubricant has an average particle size of 0.0
It is preferable that the wax and / or fluororesin has a thickness of 1 to 10 μm and the average particle diameter thereof is 1.0 to 10 times the dry film thickness.

[0012]

The present invention will be described in more detail below. The aluminum alloy plate in the present invention means JIS H4000.
The invention broadly includes the aluminum material defined in 1) and aluminum plates and aluminum alloy plates processed by press forming for home appliances, OA equipment, automobiles and the like.

In the present invention, in order to reduce the surface resistance and improve the spot resistance weldability of the above-mentioned aluminum plate, the oxide film thickness on the surface is adjusted to 150 Å or less.
If the oxide film thickness exceeds 150Å, the surface resistance increases and sufficient weldability cannot be obtained.

As the oxide film adjusting treatment, a treatment for removing the surface alumina layer by an alkali etching treatment, a pickling treatment for mainly removing the magnesia layer in an acidic aqueous solution containing a mineral acid, or a treatment for carrying out a pickling treatment after an alkali etching treatment is carried out. Is used to remove most of the oxide layer on the surface.

As the alkali etching treatment and the pickling treatment, a method generally used as a treatment method for aluminum materials may be used, and a commercially available treatment solution may be used. For example, caustic soda, caustic potash, etc. can be used for the alkali etching treatment, and sulfuric acid, nitric acid, hydrofluoric acid, a nitric acid + hydrofluoric acid mixed solution, etc. can be used for the pickling treatment.

Aluminum alloy sheets are generally excellent in corrosion resistance, but the problem of under-coating corrosion on the thread called thread rust poses a problem. Since appearance is deteriorated when thread rust is generated and the commercial value is remarkably reduced, in the present invention, the chromate treatment is performed on the aluminum alloy plate whose oxide film thickness is adjusted to 150 Å or less as described above.

The amount of chromate is 5 mg / m in terms of metal Cr.
^If it is less than ² , the effect of preventing thread rust is insufficient and 50 mg / m ²
If it exceeds the range, the spot resistance weldability deteriorates.
It was 5mg / m ² ~50mg / m ² in terms of r. The chromate treatment method may be any of coating type, reaction type and electrolytic type.

Next, as the organic resin of the resin layer formed on the chromate layer, epoxy resin, alkyd resin, acrylic resin, urethane resin, phenol resin, melamine resin, polyvinyl butyral resin, polyester resin, etc., which have good adhesion One or a mixture or copolymer of two or more thereof is preferable.

If the dry film thickness of these resin layers is less than 0.01 μm, sufficient workability cannot be ensured, and if it exceeds 3.0 μm, it becomes difficult to secure conductivity, so 0.01-3.0.
Limit to μm range. A more preferred range is 0.1
It is 1.0 μm.

Next, the carbon black added to the resin will be described. When the specific surface area is less than 800 m ² / g, it is difficult to secure sufficient processability and conductivity, and the addition amount is 100 parts by weight of the resin. On the other hand, if it is less than 1 part by weight, sufficient workability and conductivity improving effect cannot be obtained, and if it exceeds 40 parts by weight, the cohesive force of the resin is lowered and powdering easily occurs, so that the specific surface area is 800 m ² / G or more, the addition amount is limited to 1 to 40 parts by weight.

As the powdery lubricant added to the resin, it is preferable to use a synthetic wax, a fluororesin or a mixture thereof. Examples of synthetic waxes include polyethylene wax, polypropylene wax, and polybutene wax. Examples of the fluorine-based resin include polytetrafluoroethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin and the like.

The average particle size of these lubricants is 0.01 to 1
It is preferably 0 μm and used in the range of 1.0 to 10 times the dry film thickness. If the average particle size of the lubricant is too small compared to the dry film thickness, the lubricity is insufficient, and if it is too large, the lubricant is likely to fall off and sufficient workability cannot be obtained. A more preferable range is 1.5 to 5 times the dry film thickness. When the amount of addition is less than 1 part by weight with respect to 100 parts by weight of the organic resin, the effect of improving the workability and lubricity is not sufficient, and when the amount is more than 30 parts by weight, the cohesive force of the organic resin is reduced and powdering is performed. Therefore, there is a risk of generating the above-mentioned problem and a risk of decreasing the paint adhesion of the post-coating, so the range is limited to 1 to 30 parts by weight.

[0023]

EXAMPLES The present invention will be specifically described below based on examples. (Example) As a test piece, JIS A5182 plate thickness 1
A mm aluminum alloy plate was used. After steam degreasing the aluminum alloy plate with 1,1,1-trichloroethane, the surface oxide film of the aluminum alloy plate is subjected to the treatments (a) to (d) shown below to be adjusted, and then the roll coater is used. Then, a coating type chromate was applied, dried and baked at 120 ° C., and then treated with a resin. (A) 5% NaOH, 60 ° C., 30 sec (b) 30% HNO ₃ , room temperature, 30 sec (c) 10% H ₂ SO ₄ , room temperature, 30 sec (d) (a) + (b)

The following chromates, organic resins, carbon blacks and lubricants were used in this example. The following tests and evaluations were performed on the obtained samples. The results are shown in Table 1. (Chromate) Coating Chromate: 451 made by Nippon Parkerizing Co., Ltd.
3H

(Organic resin) Epoxy resin; Yuka Shell Epoxy Co., Ltd. Epicoat alkyd resin; Mitsui Toatsu Kagaku Co., Ltd. Urix acrylic resin; Mitsui Toatsu Chemical Co., Ltd. Almatex 749 urethane resin; Mitsui Toatsu Chemical Co., Ltd. Orestar Phenolic resin; Dainippon Ink and Chemicals Inc. Super Beckasite melamine resin; Mitsui Toatsu Chemicals Inc. Uban Butyral resin; Denki Kagaku Kogyo Denka Butyral polyester resin; Mitsui Toatsu Chemicals Almatex P645

Epoxy + acrylic resin is 50 parts by weight of acrylic resin with respect to 100 parts by weight of epoxy resin, epoxy + urethane resin is 100 parts by weight of urethane resin with respect to 100 parts by weight of epoxy resin, and acrylic + urethane resin is 100 parts by weight of acrylic resin. Urethane resin 100 parts by weight
It was made into a weight part.

[0027] (carbon black); Mitsubishi Kasei Co., Ltd. CF9 specific surface area of 60m ² / g; Mitsubishi Kasei Co., Ltd. MA8 137m ² / g; Mitsubishi Kasei Co., Ltd. # 1000 200m ² / g; Mitsubishi Kasei Co., Ltd. # 2400 280m ² / g; Mitsubishi Kasei # 3750 800m ² / g; Mitsubishi Kasei # 3950 1500m ² / g; Ketjen Black EC 800m ² / g; Ketjen Black EC600JD 1270m ² / g; homemade acetylene black 560m ² / g The specific surface area is determined by the nitrogen adsorption method.

(Lubricant) Wax 1 San Nopco SL92 average particle size 27 μm Wax 2 San Nopco SL417 14 μm Wax 3 San Nopco SL530 6 μm Wax 4 San Nopco SL600 1.2 μm Fluororesin 1 Asahi Glass AD1 8 μm Fluorine Resin 2 Lubron 0.2 μm manufactured by Daikin Industries, Ltd.

(Workability Test and Evaluation Method) After Surface Treatment
The workability of the test piece was determined by the plane sliding test (200k
g / cm ², 100 mm / sec) and a height of 33 mmφ
Performs high-speed cylindrical drawing (processing speed 500 mm / sec)
Evaluation based on friction coefficient (μ) and limit reduction ratio (LDR)
did. Evaluation by μ ○: Less than 0.15 △; 0.15 or more and less than 0.2 ×; 0.2 or more Evaluation by LDR ○: 1.96 or more △; 1.90 or more and less than 1.96 ×; Less than 1.90

(Conductivity Test and Evaluation Method) The conductivity was evaluated by measuring the surface resistance value with a surface resistance meter Loresta manufactured by Mitsubishi Yuka. The value was the average of 10 measurements. ○: less than 0.5Ω △; 0.5Ω or more and less than 2Ω ×; 2Ω or more

(Weldability Test and Evaluation Method) Weldability was tested with the following welding machine, electrode and welding conditions. In the evaluation, the effect was judged by either the number of hitting points until welding or the number of hitting points until the nugget diameter fell below 4√t (t: plate thickness), whichever was smaller. (Welding machine) Inverter type DC welding machine (Electrode) ・ Shape: Cone head (CF) type ・ Tip diameter;
0mmφ ・ Material: Cu-Cr (welding condition) ・ Pressure: 150kgf ・ Initial pressurization time: 20/50 seconds ・ Electrification time: 6/50 seconds ・ Holding time: 5/50 seconds ・
Welding current 15 kA ○: 1000 points or more △: 500 or more and less than 1000 points ×; Less than 500 points

(Corrosion resistance test and evaluation method) A test piece (70 × 150) coated with cationic electrodeposition coating, intermediate coating and top coating.
mm), according to the thread rust corrosion test method specified in ASTM D2803, a cross cut scratch reaching the substrate was applied, and a test was performed for 6 weeks, and the length of the thread rust from the cross cut scratch was evaluated. ○: Thread rust length less than 1 mm △: Thread rust length 1 or more and less than 2 mm ×; Thread rust length 2 mm or more

FIG. 1 shows the results of investigation of the relationship between μ and the surface resistance value by varying only the specific surface area of carbon black under the conditions of Inventive Example 1 and investigating the relationship. From this, it is apparent that the slidability and conductivity are remarkably improved when the specific surface area is 800 m ² / g or more.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

As described above, according to the present invention,
By forming a chromate layer and an organic resin layer containing carbon black and a powdery lubricant on the surface of an aluminum alloy plate with a surface oxide film adjusted, the slidability, press workability, conductivity, spot weldability and corrosion resistance are improved. Significantly improved. As a result, the productivity of home appliances, office automation equipment, automobile parts, etc. processed by press molding can be remarkably improved, and the oiling and degreasing steps can be omitted, which is also effective for environmental improvement.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the specific surface area of carbon black and slidability and conductivity.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B32B 27/20 Z 8413-4F (72) Inventor Nobuo Totsuka Kawasaki-machi, Chuo-ku, Chiba-shi, Chiba Prefecture No. 1 Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Koji Uesugi No. 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Mabuchi Masaki Chiba Prefecture Kawasaki Steel Co., Ltd., Chuo-ku, Chiba City, Kawasaki Steel Co., Ltd. (72) Inventor Koichi Hashiguchi, Kawasaki-machi, Chuo-ku, Chiba City, Chiba Prefecture, Kawasaki Steel Co., Ltd. (72) Inventor Namba Emoto Hiro 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Industry Co., Ltd.

Claims (2)

[Claims] 1. On an aluminum alloy substrate whose surface oxide film thickness is adjusted to 150 Å or less, 5 to 50 mg in terms of metal Cr
/ M ² chromate layer is formed, and further 1 to 40 parts by weight of carbon black having a specific surface area of 800 m ² / g or more is contained with respect to 100 parts by weight of the organic resin. Surface treatment excellent in workability, conductivity, spot resistance weldability and corrosion resistance, characterized in that an organic resin layer having a dry film thickness of 0.01 to 3.0 μm is formed with an organic resin mixture containing parts by weight. Aluminum alloy plate. 2. The powdery lubricant has an average particle size of 0.01.
The processability, conductivity, spot resistance weldability and corrosion resistance according to claim 1, which is a wax and / or a fluororesin having a particle size of 10 μm and an average particle size of 1.0 to 10 times the dry film thickness. Excellent surface treated aluminum alloy plate.