JPH06116738A - Aluminum material excellent in spot resistance weldability, corrosion resistance, and workability - Google Patents

Abstract

PURPOSE:To provide an aluminum material excellent in spot weldability, corrosion resistance, and workability. CONSTITUTION:This aluminum material has, as a first layer, a layer of aluminum oxide and/or aluminum hydroxide of 0.01-5mum thickness formed by heating the surface of the aluminum material in warm water, warm aqueous solution, or saturated aqueous water. Further, on the above layer, a second layer prepared by forming a solid lubricating film containing 0.05-40wt.%, in total, of 0.05-30wt.% of inorganic lubricating grains and/or 0.05-20wt.% of organic lubricating grains so that coating weight becomes (0.1 to 5)g/m<2> per side is provided. By this method, the aluminum material excellent in spot resistance weldability, corrosion resistance, and workability can be obtained.

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 material mainly used as a lightweight material for automobiles, and particularly to an aluminum material excellent in spot weldability and workability.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of global environmental problems, in particular, measures against global warming by CO _2, etc., weight reduction of automobile bodies has been actively promoted in order to improve fuel consumption of automobiles. Aluminum alloys have been in the spotlight in terms of material reliability, workability, recycling, etc., and these are now being applied to inner and outer plates of automobile bodies.

[0003]

However, the aluminum material conventionally used for such an automobile body has the following problems. Poor weldability Most of the aluminum alloy sheets are spot welded when assembled into automobile bodies, but aluminum alloy sheets have extremely poor spot weldability, especially electrode life compared to steel sheets, resulting in a significant decrease in vehicle body production efficiency. Is the current situation.

That is, in spot resistance welding of an aluminum alloy plate, a welding phenomenon is likely to occur, and the number of welding spots at which an appropriate nugget can be obtained with the same electrode is extremely short, so that proper nugget cannot be performed before welding occurs. The electrode shape is frequently adjusted before dressing or replaced with a new electrode, which has a great influence on the welding efficiency, and by extension, the production efficiency of the automobile body.

Since aluminum alloys have only recently been put to practical use in mass-produced products with spot resistance weldability such as automobiles, there are very few proposals for appropriate means for solving the above problems. However, for example, JP-A-6
Japanese Unexamined Patent Publication No. 0-187483 provides an improved method by controlling the thickness of the oxide film on the aluminum plate joint surface by anodizing. Further, although it is not intended to be applied to an aluminum alloy plate for automobiles, it is disclosed in, for example, JP-A-5353.
-6252, JP-A-53-48954, JP-A-53
No. 48955 discloses Z on the aluminum joint surface.
An improved method by interposing n, Ti and a stainless steel thin film is disclosed in Japanese Patent Application Laid-Open No. 57-4389 as Cr, N.
An improved method by applying i, Cu, Ag plating is disclosed.

However, the improvement method by controlling only the anodized film is not practical because uniform treatment is difficult and its effect is unstable. Further, the improvement method by interposing Zn, Ti, and stainless steel thin films is difficult to apply to automobiles, and the improvement method by applying Cr, Ni, Cu, Ag plating is the adhesion of these platings to an aluminum alloy. Is extremely bad and not practical.

Workability is poor Further, aluminum has a serious drawback that it has a small elongation and is soft as compared with a steel sheet, and is apt to cause galling of the mold, resulting in poor press workability. SPCC as a representative of steel plate
For example, the elongation is 45% and the r value is 1.4.
Reaches 2.15, while aluminum alloy plate has JI
Taking SA 5182 as an example, elongation is 30%, r value is 0.7.
And the LDR reaches only 1.8. As described above, the formability of the aluminum alloy sheet is remarkably inferior, so that the application of the aluminum alloy sheet to an automobile body is greatly restricted. That is, as an example of application of the aluminum alloy plate to a vehicle body panel, it is limited to a lightly processed member such as a hood, and it is impossible to apply it to a more complicated member accompanied by heavy working.

Poor Corrosion Resistance When an accelerated durability test is performed in a harsh environment after painting, filiform corrosion is likely to occur, which not only impairs the aesthetic appearance but also causes functional problems when advanced. Will occur.

The present invention overcomes the drawbacks of the above-mentioned aluminum materials, and greatly improves the electrode life during spot resistance welding, that is, continuous spotting property, corrosion resistance and press formability, compared with conventional aluminum materials, and is industrially easy. The purpose is to provide an aluminum material that can be manufactured economically.

[0010]

First, the improvement of spot weldability is based on the following knowledge. That is,
When spot resistance welding is repeatedly performed on an aluminum alloy plate using the same copper-based electrode, the current-carrying diameter at the electrode tip expands with the dot, and the nugget diameter also decreases due to the decrease in the current density in the plate. Finally, although the life of the electrode is extended, the aluminum alloy plate is characterized in that the expansion speed of the electrode tip diameter is significantly higher than that of the steel plate. Therefore, paying attention to such a phenomenon,
As a result of diligent examination of the cause, in the case of continuous spot welding of an aluminum alloy plate, molten aluminum adheres to the current-carrying part of the electrode tip, and its oxide deposits together with the spot.
This forms an insulating layer, and finally sparks occur between the electrode and this insulating layer, at which time the electrode is damaged like a worm and the insulating oxide film on the surface of the aluminum alloy plate at the joint surface It has been found that it inhibits rapid welding. It was found that such a peculiar phenomenon of the aluminum alloy plate promotes the enlargement of the electrode tip diameter and the electrode life is extremely deteriorated.

Further, the occurrence of such a spark on the electrode surface side,
It was found that the poor welding on the joining surface side is promoted by the nonuniformity of the oxide film layer on the surface of the as-rolled aluminum material.

Therefore, it is important to control the film thickness of the aluminum oxide and / or hydroxide layer on the surface of the aluminum material, and in the present invention, it is defined as 0.01 to 5 μm. It is possible to secure better weldability by adjusting the thickness of the electrode contact surface side to be ⅔ or less of that of the spot welding joint surface side.

Regarding the corrosion resistance after coating, the thread rust that usually occurs in the coating material of an aluminum body originates from a defective portion of the coating film such as a scratch on the surface, and in a corrosive environment where chlorine is present. At this time, corrosive substances reached the aluminum base,
The main cause is corrosion of the aluminum substrate. Therefore, it is important to form a film capable of obtaining a strong anticorrosion effect on the aluminum base material. From this point as well, in the present invention, the film thickness of the aluminum oxide and / or hydroxide is 0.01 to 5 μm. Sufficient corrosion resistance was able to be obtained by controlling to.

On the other hand, regarding press formability, it is essentially important to improve the elongation of aluminum.
We have found that even the same material can improve the formability by improving the lubricity of the surface, and as a measure to improve the lubricity, it is necessary to coat a solid lubricating film containing a powdered semi-lubricant. It turned out to be very effective.

That is, according to the present invention, in order to achieve the above object, the surface of the aluminum material as the first layer is formed by heating the surface of the aluminum material in hot water, a hot aqueous solution or saturated steam and has a thickness of 0.01 μm to 5 μm. Having a layer of aluminum oxide and / or aluminum hydroxide,
In addition, 0.05 to 30% by weight of inorganic lubricating particles and / or 0.05 to 20% by weight of organic lubricating particles are added to 0.0 in total.
Spot resistance weldability, corrosion resistance and processing, characterized in that it has a second layer formed by forming a solid lubricating coating containing 5 to 40% by weight so as to have an attached amount of 0.1 to 5 g / m ^{2 on} one surface. An aluminum material having excellent properties is provided.

The solid lubricating coating of the second layer is preferably a coating containing a precoat wax or an acrylic resin copolymer as a main component, which can be easily removed by an alkaline degreasing treatment.

Particularly, the inorganic lubricating particles have an average particle size of 20 μm.
m or less of molybdenum disulfide and / or boron nitride powder, the organic lubricating particles are waxes having an average particle diameter of 20 μm or less and a melting point of 70 ° C. or more, and these lubricating powders are uniformly dispersed in a solid lubricating film. It is preferable to apply it.

[0018]

The present invention will be described in more detail below. The aluminum material in the present invention broadly includes aluminum materials such as aluminum and aluminum alloys, and its form is arbitrary such as plate material, bar material and can material.

In the present invention, the geometric structure of the oxide film formed by heating the above-mentioned aluminum material in hot water, hot aqueous solution or saturated steam depends on the processing conditions and is not particularly limited.

Aluminum oxide and / or aluminum oxide
Luminium hydroxide is usually Al₂O ₃ , AlOOH, Al (OH)
₃ , Etc., is formed with water of crystallization attached, but with this film
The presence or absence of crystal water does not cause any particular problem. Also, film formation
Pretreatment of the treatment does not need to be performed.
Film formation process may be performed, but usually aluminum production
For the purpose of removing the heterogeneous film formed during the process, acid,
Etching in Lucari, Smut in acid solution (insoluble
It is desirable to appropriately remove the degradable residue). This
These are usually used for alkali etching and pickling.
This is the method used to treat aluminum materials.
Alternatively, a commercially available processing solution can be used.

In the present invention, the thickness of the first layer is 0.01
When the thickness is less than 0.01 μm, the desired electric resistance cannot be obtained, the weldability is deteriorated, and the anticorrosion effect on the aluminum base becomes insufficient, resulting in poor corrosion resistance. If it exceeds 5 μm, the electric resistance becomes too large and welding becomes impossible. Also, by adjusting the film thickness on the electrode contact surface side to 2/3 or less of the spot welding surface side, it is possible to prevent the occurrence of sparks on the electrode surface side and the prevention of aluminum welding on the electrode surface. It has a great effect.

On the other hand, the solid lubricating film formed as the second layer is made of a precoat wax or an acrylic resin copolymer containing inorganic lubricating particles and / or organic lubricating particles. As the inorganic lubricating particles, for example, molybdenum disulfide, boron nitride powder, or a mixture of two or more thereof is used. If the amount of these mixtures is too small, the lubricating effect will be small, and if they are excessive, the viscosity of the oil will be increased and the coating operation will be inconvenient. Also,
Particles having an average particle size of more than 20 μm have poor dispersibility and deteriorate the uniformity after oiling. As the organic lubricating particles, either synthetic wax or natural wax may be used. However, if the wax has a melting point of less than 70 ° C, the viscosity under extreme pressure becomes too small and the lubricating effect is not sufficient, so the melting point should be 70 ° C or more. Good. Further, the addition amount and the average particle size are each 0.05 to 30% by weight and the average particle size is 2 for the same reason as the above inorganic lubricating particles.
It was limited to 0 μm or less. When the inorganic lubricating particles and the organic lubricating particles are used in combination, the limit of the amount added increases to 40% by weight, but if the amount is more than that, the coating work will be inconvenient, so the amount is limited to 0.05 to 40% by weight.

[0023]

EXAMPLES The present invention will be specifically described below based on examples. (Example) JIS A 51 having a thickness of 1 mm, which is a typical aluminum alloy used as a material for automobiles
82 (Al-0.3% Mn-4.5% Mg) alloy plate, first the aluminum alloy plate surface was steam degreased with 1,1,1 trichloroethane, then etching with a commercially available alkaline detergent, water washing, Smut removal by nitric acid pickling and water washing were performed, and oxidation treatment was performed by the method shown in Table 1.

Next, using a commercially available precoat wax, Caolule W-2 (manufactured by Kao Corporation) as a base,
The above-mentioned alloy plate (1 mm × 100 mm) was heated to 60 ° C. and melted, and inorganic lubricating powder and / or organic lubricating powder was added to and mixed with the molten wax, which was heated to 60 ° C. in molten wax prepared in the ratio shown in Table 2.
X200) was immersed and pulled up, and then air-cooled and dried. The coating amount was arbitrarily adjusted by adjusting the dipping / pulling rate and the air cooling / drying rate. The weight of the plate after coating and the weight of the plate after degreasing / washing were measured. In addition, the lubricating powder was crushed in advance with a ball mill to adjust the particle size. The particle size was measured by forming the lubricating coating on a glass plate and observing directly with an optical microscope.

Next, a commercially available alkali-soluble polymer lubricating coating agent Millbond MC-560J (manufactured by NOF CORPORATION) was used as a base, and an inorganic lubricating powder and / or an organic lubricating powder was added and mixed in Table 2 at the same time. Show. Since this agent is a water-based paint, it was difficult to uniformly disperse it for a long time depending on the type of wax, but immediately after strong stirring the alloy plate was dip coated and dried to obtain a uniformly dispersed film. It was The drying was carried out by hot air drying at 80 ° C., and the coating amount was adjusted by changing the amount of water added to the coating solution. The coating amount is measured and the lubricant powder is prepared in the same manner as described above.

The following waxes were used in Table 2. Wax 1 San Nopco SN Wax 22-SF Wax 2 San Nopco SL 506 Wax 3 Yasuhara Yushi Kogyo Arrow Wax Wax 4 Same as above Wax stirring and grinding time shortened Wax 5 Nippon Oil Co., Ltd. PO Wax H-10 Pretreatment chemicals Alsoft 108, Desmut N-
20 is a commercially available pretreatment liquid for aluminum plates, which is manufactured by Okuno Chemical Industries Co., Ltd.

(Workability Test and Evaluation Method) The workability of the aluminum alloy plate after the surface treatment was punched to 70 mmφ, and each sample was high speed cylindrical drawn with a diameter of 33φ (processing speed 5
00 mm / sec), and a crack that could not be processed was defective (×
(Marked), the one that has been bitten but can be processed normally (△),
Good that can be processed with almost no galling (○)
Was judged as.

(Welding Test and Evaluation Method) The electrode life of the aluminum alloy plate after the coating treatment was evaluated using an inverter DC welding machine under the following electrodes and welding conditions. The number of dots or nugget diameter before welding is 4√t
The effect was judged by the smaller number of RBIs, whichever is smaller than (t: plate thickness). The evaluation criteria are poor (x) when the number of hit points is less than 500, normal (△) from 500 to 1000, and good (◯) from 1000 to 1500.
Exceeding the point was rated as excellent (◎). (Electrode) ・ Shape: Cone truncated cone (CF) type ・ Tip diameter: 5.0 mmφ ・ Material: Cr-Cu (welding condition) ・ Pressure: 150 kgf ・ Initial pressurization time: 20/50 seconds ・ Electrification time: 6/50 seconds ・ Holding time: 5/50 seconds ・ Welding current: 15 kA

(Corrosion resistance after coating) From the coil after treatment to 70
A test piece of × 150 mm was cut out, degreased with a weak alkaline degreasing agent at 43 ° C for 2 minutes, washed with water, and then surface-adjusted with a colloidal titanium-based solution at room temperature for 30 seconds. In this state, a chemical conversion treatment was performed at 43 ° C. for 2 minutes with a commercially available zinc-phosphorus treatment solution. afterwards,
After washing with water and drying, a sample was prepared by undercoating by cationic electrodeposition coating, followed by intermediate coating by spraying and topcoating. The total coating thickness at this time is 10
It was 0 μm.

A cross-cut reaching the aluminum substrate was put on the surface of this sample, salt water spray according to JIS Z2371 was carried out for 24 hours, and after that, it was left in a wet atmosphere of 50 ° C. × 95% RH for 2000 hours, and then generated from the cross-cut portion. The maximum length of thread rust was measured. Judgment was made such that the thread rust length of 4 mm or more was poor (x), 2 to 4 mm was normal (◯), and 2 mm or less was good (⊚).

Inventive examples and comparative examples are summarized in Table 3. As is clear from Tables 1 to 3, it can be seen that the present invention is extremely effective in improving spot weldability and workability of aluminum alloy sheets.

On the other hand, in Comparative Example 1, the oxide and / or hydroxide layer was too thin and the weldability and corrosion resistance were poor, and in Comparative Examples 2 to 4, the lubricating powder addition amount was small, so that sufficient workability was obtained. I can't get it. In Comparative Examples 5 to 7, 9 and 10, the amount of lubricating powder added was too large and the weldability deteriorated. In Comparative Example 8, the coating amount was too small and sufficient workability could not be obtained. Comparative Example 11
Has too much adhesion and impairs weldability. Comparative Example 12
Has a poor weldability because the oxide and / or hydroxide layer is too thick.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

[0037]

[Table 5]

[0038]

As described above, according to the present invention, a solid lubricating coating containing an oxide and / or hydroxide layer formed on the surface of an aluminum plate or an aluminum alloy plate and containing powdery lubricating particles on the surface thereof. By forming
Spot resistance weldability and press workability are significantly improved. As a result, it can be expected that the productivity of welded structures such as those for automobile parts processed by press forming and spot weldability will be remarkably improved and the stability of quality will be improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Totsuka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Headquarters (72) Inventor Koji Uesugi Chuo-ku, Chiba-shi, Chiba Kawasaki-cho No. 1 Kawasaki Steel Co., Ltd., Technical Research Division (72) Inventor Naoki Nishiyama No. 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Toshio Tani Tokyo 2-6-1, Marunouchi, Chiyoda-ku, Furukawa Aluminum Co., Ltd. (72) Inventor, Motohiro Namba 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Co., Ltd.

Claims (4)

[Claims] 1. A layer of an aluminum oxide and / or aluminum hydroxide having a thickness of 0.01 μm to 5 μm, which is formed by heating the surface of an aluminum material in warm water, a warm aqueous solution or saturated steam as the first layer. Have,
In addition, 0.05 to 30% by weight of inorganic lubricating particles and / or 0.05 to 20% by weight of organic lubricating particles are added to 0.0 in total.
Spot resistance weldability, corrosion resistance and processing, characterized in that it has a second layer formed by forming a solid lubricating coating containing 5 to 40% by weight so as to have an attached amount of 0.1 to 5 g / m ^{2 on} one surface. Aluminum material with excellent properties. 2. The spot resistance weldability according to claim 1, wherein the solid lubricant film of the second layer is a film containing a precoat wax or an acrylic resin copolymer as a main component, which can be easily removed by an alkaline degreasing treatment. Aluminum material with excellent corrosion resistance and workability. 3. The spot resistance weldability, corrosion resistance and workability according to claim 1, wherein the inorganic lubricating particles in the second layer are molybdenum disulfide and / or boron nitride powder having an average particle size of 20 μm or less. Excellent aluminum material. 4. The organic lubricating particles in the second layer have an average particle size of 2
An aluminum material having excellent spot resistance weldability, corrosion resistance and workability according to any one of claims 1 to 3, which is a wax having a melting point of 70 ° C or higher and a melting point of 0 µm or lower.